[Designation of Document] SPECIFICATION
[Title of the Invention] BATTERY CAN FOR STORAGE BATTERY
[Technical Field]
[0001]
The present invention relates to a battery can for a storage battery, which is
provided with a score groove type safety valve. Particularly, the battery can for a
storage battery is suitably used for an industrial use and an in-vehicle use.
Priority is claimed on Japanese Patent Application No. 2011-104422, filed on
May 9, 2011, the content of which is incorporated herein by reference.
[Background Art]
[0002]
Recently, an assembled battery for an industrial use and an in-vehicle use,
which uses a high-output battery, has been spreading quickly. In the assembled
battery that is used for these purposes, there is a demand for continuing high
performance (battery characteristics) over a long period of 10 to 15 years.
Accordingly, there is a demand for individual batteries used in the assembled battery to
have, for example, the following performance.
First, even when the assembled battery is used under harsh conditions over a
long period of 10 to 15 years, there is a demand that deterioration in performance of an
individual battery be small. Furthermore, the performance of the assembled battery in
which a number of batteries are connected is greatly affected by battery performance of
one battery having the lowest performance in the assembled battery. Thus, a variance
in the battery performance of the individual batteries, which occurs due to deterioration
of the battery performance during a long period of use, is demanded to be small. In
addition, there is a demand for the individual batteries to secure satisfactory corrosion
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resistance for a long period of time.
[0003]
As a technology in the related art, for example, the following Patent
Documents 1 to 5 are exemplary examples.
Patent Document 1 discloses a thionyl chloride lithium battery that is used as
a battery for an electronic apparatus. In this thionyl chloride lithium battery, a thin
groove portion is provided at a part of a battery lid or a battery case, and a trapezoidal
groove (score) on an inner side of a can is shown as a thin groove portion. In Patent
Document 1, in a case where inner pressure increases during abnormality in a battery,
the thin groove portion is allowed to be ruptured at low pressure, whereby the thin
groove portion is used as a safety valve.
[0004]
Patent Document 2 discloses a square-type sealed battery having a thin groove
portion along a width direction of a sealing lid. The thin groove portion has a Vshaped
cross-section, and is formed by press working.
[0005]
Patent Document 3 discloses a cylindrical storage battery in which a rupture
valve is formed in a diaphragm that is inversed due to an increase in inner pressure and
blocks a current. In the cylindrical storage battery, a groove, which has a V-shaped
cross-section and which is constituted by a combination of a circular curve positioned
at a surface opposite to a surface of the diaphragm to which the inner pressure is
applied, and a straight line of which one end intersects the circular curve and the other
end is located on an outer periphery side of the diaphragm in relation to the circular
curve, is formed as the rupture valve. In addition, in the cylindrical storage battery, a
groove having a U-shaped cross-section is formed in a surface of the diaphragm to
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which the inner pressure is applied and which corresponds to the position at which the
groove having the V-shaped cross-section is formed. In the straight groove, the depth
on the other end side is shallower than the depth on the one end side. Furthermore,
the depth of the groove having the U-shaped cross-section is shallower than the depth
of the groove having the V-shaped cross-section.
[0006]
Patent Document 4 and Patent Document 5 disclose an easy-open can lid that
is opened by rupturing an opening formed in a can lid of a can body so the contents can
be taken out, and a production method thereof. The easy-open can lid is different
from the battery can in the technical field, and is used as a can lid for a beverage can or
a food can. A resin-coated steel sheet is applied as a material of the can lid.
[0007]
In the assembled battery (storage battery) for industrial use and in-vehicle use,
which uses a high-output battery, there is a demand for a battery can capable of
satisfying the characteristics necessary for the battery. The present inventors have
found that it is necessary to consider the following performance for the battery can.
For example, performance stability of a safety valve during a long period of
use is necessary for the battery can. Factors deteriorating the performance stability
are as follows: a pressure variation in a battery can due to repetition of charging and
discharging (that is, fatigue of the safety valve), and an effect by the contents such as
an electrolytic solution (that is, corrosion of the safety valve). In addition, with
regard to an individual battery can when being used as an assembled battery, it is
necessary for the battery can to have a small variance in a valve opening pressure of
the safety valve (that is, uniformity in performance of the safety valve).
[0008]
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However, the thionyl chloride lithium battery that is a primary battery does
not perform charging and discharging, and thus in the battery can disclosed in Patent
Document 1, it is not necessary to consider fatigue resistance of the safety valve. In
addition, the primary battery for an electronic apparatus hardly ever constitutes an
assembled battery, and thus a demand for uniformity in performance of the safety valve
with respect to a plurality of batteries is not so high. Accordingly, in Patent
Document 1, an expensive stainless steel sheet or nickel steel sheet, which has high
corrosion resistance, is used, and a trapezoidal score groove is formed in one surface
(inner surface of a battery) of the sheet in such a manner that the valve opening
pressure may be adjusted by changing a width of the score groove.
[0009]
In addition, in the square-type battery for portable apparatuses, which is
disclosed in Patent Document 2, a life cycle of the apparatuses that are used is short,
and is frequently shorter than 10 years, and thus a demand for the fatigue resistance
with respect to the safety valve or uniformity in performance of the safety valve with
respect to a plurality of batteries is not so high. Accordingly, in Patent Document 2, a
V-shaped thin groove portion is used as the safety valve in order to progress a crack
from the thin groove portion.
[0010]
In Patent Document 3, the storage battery has a battery can in which a rupture
valve is ruptured after inversion of the diaphragm, and to realize this function, a
rupture valve is configured by a groove having a V-shaped cross-section, and a Ushaped
groove which is opposite to the groove having a V-shaped cross-section.
Accordingly, in the storage battery disclosed in Patent Document 3, a demand for the
fatigue resistance with respect to the rupture valve or uniformity in performance of the
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safety valve with respect to a plurality of batteries is not so high.
[0011]
In the easy-open can (hereinafter, referred to as an EOE can) disclosed in
Patent Document 4 and Patent Document 5, a structure of the can lid is different from
that of a portion of the battery can which is provided with a safety valve, and
particularly, a can opening mechanism itself is completely different from a mechanism
of the battery can provided with the safety valve.
[0012]
That is, in Patent Document 4 and Patent Document 5, a large force is caused
to operate on a local point of a score contour by a tab that functions as a lever, the one
local point of the score contour is opened, and then the majority of the score contour is
opened by pushing force of the tab. In this manner, in Patent Document 4, a can lid
having a mechanical opening function is used. Accordingly, with regard to a
mechanical function of opening a can and can opening characteristics that are
necessary, the can lid is basically different from the battery can provided with the
safety valve.
[0013]
A difference between a can opening technology in the field of beverage can,
and a valve opening technology of the battery can will be described below.
[0014]
The safety valve of the battery can is reliably opened at a point of time at
which irmer pressure generated during charging reaches a predetermined designed
inner pressure, and the battery can itself is prevented from being ruptured. When the
designed inner pressure of the safety valve is too high, the battery inner pressure
increases too much, and thus the battery can is apt to be ruptured. On the other hand.
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when the designed inner pressure of the safety valve is too low, the safety valve is
opened during charging, and thus an assembled battery itself is broken. Accordingly,
it is necessary to limit the upper limit of an amount of charge, and thus the
performance of the assembled battery is greatly limited.
[0015]
On the other hand, the beverage can uses a method (a technical field in which
a can opening mechanism is completely different from a mechanism of the safety valve
of the battery can) in which force is focused on one point of the score portion by a
component called a tab functioning as a lever to allow large force to operate so as to
open the can. Accordingly, performance necessary for this method (that is,
performance of the beverage can) includes durability against an impact, easiness of can
opening, and mass productivity. With regard to the durability against an impact, for
example, even when a can into which contents are put is dropped several times at a
height of approximately 1 m, it is necessary for the durability to have a level at which a
score portion is not opened by deformation of the can due to the dropping and the
contents do not flow out. This level is sufficiently lower than a level necessary for
the battery can, and thus a remaining score thickness (Min value) may be made to be
small to the limit of a level necessary for the durability against an impact. In addition,
with regard to the easiness of the can opening, it is necessary to set the upper limit of
can opening power to a remaining score thickness level capable of being opened by the
tip of a finger of human. The can opening power has a variation depending on kinds
of cans, makers, and the like, and has a large margin within a setting range of the can
opening power (a technical field having a margin for the setting of the remaining score
thickness). Accordingly, in the beverage can, the can opening power may vary in an
individual beverage can, and it is not necessary to increase the processing accuracy to a
certain degree of the battery can to increase mass productivity.
[0016]
In addition, with regard to the safety valve of the battery can, it is necessary
for the score portion of the safety valve not to be fatigue-broken under conditions in
which large inner pressure is repetitively applied to the battery can at all times over 10
to 15 years, and it is necessary for the safety valve to be opened at a point of time at
which inner pressure set as valve opening pressure is loaded. On the other hand, in
the beverage can, the repetitive load itself is not present. Accordingly, the technical
field of the beverage can is a technical field in which it is not necessary to consider
fatigue strength to which the present inventors give attention.
[0017]
Accordingly, the technology of the beverage can does not have the same
technical idea as the battery can which endures a repetitive stress load over a long
period of time, and which is reliably opened at a point of time at which a
predetermined loaded inner pressure is applied.
[0018]
Also, as disclosed in Patent Document 5, in a case where the bottom of the
score groove has a curvature, large can-opening-power is necessary, and thus can
opening properties decrease. Accordingly, in this case, it is necessary to extremely
decrease the remaining score thickness.
[0019]
In addition, in the safety valve of the battery can, it is necessary for the valve
opening pressure itself not to be too much lower than a set value, and not to be too
much higher than the set value, that is, it is necessary for a variance in an absolute
value of the valve opening pressure of a number of battery cans to be small.
Furthermore, since an assembled battery is designed in such a manner that the valve
opening pressure is common to all of assembled batteries that are produced, it is
necessary for individual battery cans used in all of the assembled batteries to have a
small variance in the valve opening pressure of the safety valve of the battery can. As
mentioned above, with regard to the battery can, accuracy (reproducibility) of the
safety valve of the individual battery can is a very important technical field. However,
the beverage can belongs to a technical field having no such technical idea.
[0020]
As mentioned above, the valve opening technology of the battery can is
completely different from the can opening technology of the beverage can.
[Prior Art Document]
[Patent Document]
[0021]
[Patent Document 1] Japanese Unexamined Patent Application, First
Publication No. S59-79965
[Patent Document 2] Japanese Registered Utility Model No. 2585726
[Patent Document 3] Japanese Patent No. 4346637
[Patent Document 4] Japanese Patent No. 3893198
[Patent Document 5] Japanese Unexamined Patent Application, First
Publication No. 2000-233247
[Disclosure of the Invention]
[Problem that the Invention is to solve]
[0022]
The invention is to provide a battery can for a storage battery (particularly, for
an industrial use and an in-vehicle use) which is provided with a safety valve in which
a variance in valve opening pressure of a score groove portion of an individual battery
can is small, and the valve opening pressure of the score groove portion scarcely
decreases by deterioration of the battery can with the passage of time (for example,
over 10 to 15 years) due to fatigue or corrosion. Accordingly, the problem of the
battery can for a storage battery is completely different from the technical problem
disclosed in the prior art documents.
[Means for Solving the Problems]
[0023]
To provide a battery can in which the above-described problem is solved, the
present inventors have made various examinations on a mechanical function of stably
opening the battery can, and valve opening characteristics necessary for valve opening,
and they have accomplished the invention. The gist of the invention is as follows.
[0024]
(1) According to a first aspect of the invention, there is provided a battery can
for a storage battery. The battery can includes a tubular can body portion having a
first end and a second end, a can bottom portion that is continuous to the can body
portion so as to cover the first end of the can body portion, and a can lid portion that is
continuous to the can body portion so as to cover the second end of the can body
portion when constituting a battery. A safety valve having a first score groove portion
and a second score groove portion that are opposite to each other in a cross-sectional
view in a sheet thickness direction is provided to an inner surface and an outer surface
of any one of the can bottom portion, the can body portion, and the can lid portion.
When viewed from a cross-section that is perpendicular to an extension direction of the
first score groove portion, the first score groove portion and the second score groove
portion have a first score groove bottom portion and a second score groove bottom
10
portion, which have a radius of curvature R and a relative clearance of 0.045 mm to
0.150 mm, respectively. The radius of curvature R is more than 0.20 mm and is equal
to or less than 1.20 mm. Any one of the can bottom portion, the can body portion,
and the can lid portion, which has the safety valve, is constituted by a plated steel sheet
having a steel sheet portion in which the content of C is limited to 0.040% by mass or
less and the content of S is limited to 0.020% by mass or less, and tensile strength TS
is 400 MPa or less, and a plate layer formed on the steel sheet portion.
[0025]
(2) In the battery can for a storage battery according to (1), the plated steel
sheet may be subjected to score processing by a press forming method.
[0026]
(3) In the battery can for a storage battery according to (1), after the steel
sheet portion is subjected to the score processing by the press forming method, the
plated layer may be formed on a surface of the steel sheet portion.
[0027]
(4) According to a second aspect of the invention, there is provided a battery
can for a storage battery. The battery can includes a tubular can body portion having
a first end and a second end, a can bottom portion that is continuous to the can body
portion so as to cover the first end of the can body portion, and a can lid portion that is
continuous to the can body portion so as to cover the second end of the can body
portion when constituting a battery. A safety valve having a first score groove portion
and a second score groove portion that are opposite to each other in a cross-sectional
view in a sheet thickness direction is provided to an inner surface and an outer surface
of any one of the can bottom portion, the can body portion, and the can lid portion.
When viewed from a cross-section that is perpendicular to an extension direction of the
11
first score groove portion, the first score groove portion and the second score groove
portion have a first score groove bottom portion and a second score groove bottom
portion, which have a radius of curvature R and a relative clearance of 0.055 mm to
0.150 mm, respectively. The radius of curvature R is 0.30 mm to 1.20 mm. Any
one of the can bottom portion, the can body portion, and the can lid portion, which has
the safety valve, is constituted by a plated steel sheet having a steel sheet portion in
which the amount of C is limited to 0.100% by mass or less and the amount of S is
limited to 0.030%) by mass or less, and tensile strength TS is 400 MPa or less, and a
plate layer formed on the steel sheet portion.
[0028]
(5) In the battery can for a storage battery according to (4), the plated steel
sheet may be subjected to score processing by a press forming method.
[0029]
(6) In the battery can for a storage battery according to (5), after the steel
sheet portion is subjected to the score processing by the press forming method, the
plated layer may be formed on a surface of the steel sheet portion.
[0030]
(7) In the battery can for a storage battery according to any one of (1) to (6),
the plated layer may be Ni plating.
[0031]
(8) In the battery can for a storage battery according to any one of (1) to (3),
the radius of curvature R may be 0.30 mm to 1.20 mm.
[0032]
(9) In the battery can for a storage battery according to (8), the plated layer
may be Ni plating.
12 -
[0033]
(10) According to a third aspect of the invention, there is provided a battery
can for a storage battery. The battery can includes a tubular can body portion having
a first end and a second end, a can bottom portion that is continuous to the can body
portion so as to cover the first end of the can body portion, and a can lid portion that is
continuous to the can body portion so as to cover the second end of the can body
portion when constituting a battery. A safety valve having a first score groove portion
and a second score groove portion that are opposite to each other in a cross-sectional
view in a sheet thickness direction is provided to an inner surface and an outer surface
of any one of the can bottom portion, the can body portion, and the can lid portion.
When viewed from a cross-section that is perpendicular to an extension direction of the
first score groove portion, the first score groove portion and the second score groove
portion have a first score groove bottom portion and a second score groove bottom
portion, which have a radius of curvature R and a relative clearance of 0.045 mm to
0.150 mm, respectively. The radius of curvature R is more than 0.20 mm and is equal
to or less than 1.20 mm. Any one of the can bottom portion, the can body portion,
and the can lid portion, which has the safety valve, is constituted by a stainless steel
sheet in which the amount of C is limited to 0.040% by mass or less and the amount of
S is limited to 0.020% by mass or less, and tensile strength TS is 400 MPa or less.
[0034]
(11) In the battery can for a storage battery according to (10), the stainless
steel sheet may be subjected to score processing by a press forming method.
[0035]
(12) In the battery can for a storage battery according to (10) or (11), the
radius of curvature R may be 0.30 mm to 1.20 mm.
» -13
[Advantage of the Invention]
[0036]
According to the aspects of the invention, it is possible to provide a battery
can for a storage battery which is provided with a safety valve in which a variance in
valve opening pressure of a score groove portion of an individual battery can is small,
and the valve opening pressure of the score groove portion scarcely decreases by
deterioration of the battery can with the passage of time (for example, over 10 to 15
years) due to fatigue or corrosion. Accordingly, an industrial value is significantly
high.
Particularly, in the battery can for a storage battery according to (1) to (12), a
decrease in the valve opening pressure of the score groove portion by fatigue caused by
a repetitive variation in inner pressure (repetitive stress) which is loaded on the battery
can over a long period of time (10 to 15 years) may be effectively suppressed.
In addition, in the battery can for a storage battery according to (1) to (9), a
decrease in the valve opening pressure of the score groove portion, which is caused by
pitting or the like of the score groove portion in the anticorrosive plated steel sheet
having a plate layer such as Ni plating, may be effectively suppressed.
[Brief Description of the Drawing]
[0037]
FIG. 1 is a graph illustrating a relationship between a radius of curvature R
and valve opening pressure.
FIG. 2 is a graph illustrating a relationship between the radius of curvature R
and an index of soundness of a Ni plated layer (average elongation rate of the Ni plated
layer).
FIG. 3 A is a schematic perspective diagram illustrating a battery can
- 14 -
according to an embodiment of the invention.
FIG. 3B is a schematic perspective diagram illustrating a battery can
according to a modification example of the embodiment.
FIG. 3C is a schematic perspective diagram illustrating a battery can
according to a modification example of the embodiment.
FIG. 3D is a schematic perspective diagram illustrating a battery can
according to a modification example of the embodiment.
FIG. 3E is a schematic perspective diagram illustrating a battery can
according to a modification example of the embodiment.
FIG. 3F is a schematic perspective diagram illustrating a battery can
according to a modification example of the embodiment.
FIG. 4 is a schematic longitudinal cross-sectional diagram of the battery can
according to the embodiment.
FIG. 5A is a schematic partial cross-sectional diagram illustrating an example
of a score groove portion of the battery can according to an embodiment of the
invention.
FIG. 5B is a schematic partial cross-sectional diagram illustrating an example
of the score groove portion of the battery can according to the embodiment of the
invention.
FIG. 6A is an explanatory diagram illustrating a radius of curvature R and a
remaining score thickness d in FIG. 5A.
FIG. 6B is an explanatory diagram illustrating a radius of curvature R, a
remaining score thickness d, and a groove opening degree 0' in FIG. 5B.
FIG. 7A is an explanatory diagram illustrating stress concentration in a case of
forming a trapezoidal score groove by press working.
- 15
FIG. 7B is an explanatory diagram illustrating stress dispersion in a case of
forming an arc-shaped score groove by the press working.
[Best Mode for Carrying Out the Invention]
[0038]
Hereinafter, the invention will be described in detail.
[0039]
The present inventors have carried out an examination on a score groove type
safety valve of a battery can for a storage battery (particularly, for an industrial use and
an in-vehicle use) in which a variance in valve opening pressure of a score groove
portion of an individual battery can is small, and the valve opening pressure of the
score groove portion scarcely decreases by deterioration of the battery can with the
passage of time due to fatigue or corrosion. Here, the decrease in the valve opening
pressure of the score groove portion by the deterioration of the battery can with the
passage of time due to fatigue is caused by a repetitive variation in inner pressure
(repetitive stress) which is loaded on the battery can over a long period of time (10 to
15 years). In addition, the decrease in the valve opening pressure of the score groove
portion by the deterioration of the battery can with the passage of time due to corrosion
is caused by pitting or the like of the score groove portion in the anticorrosive plated
steel sheet having a plate layer such as Ni plating.
The present inventors have carried out the following examination, and they
have found that it is possible to provide a battery can for a storage battery with a
satisfactory score groove type safety valve.
[0040]
First, the present inventors have carried out various examinations on a cause
of a variance in valve opening pressure of the score groove portion of an individual
16 -
battery can, and they have found the following (1-a) to (1-e) with respect to the score
groove portion capable of reducing the variance in the valve opening pressure.
[0041]
(1-a) In a trapezoidal blade edge and a triangular blade edge, for example, as
shown in FIG. 7A, strain is focused on a local point. Therefore, the shape of the
blade edge has a great effect on the degree and distribution of an amount of process
strain in the vicinity of a score groove bottom portion 5c 1 processed by the distal
portion of the blade edge. Accordingly, the degree and distribution of the process
strain in the vicinity of the score groove bottom portion 5c 1 greatly vary due to a
variance in the shape of the blade edge (for example, a variance in the shape of the
blade edge for each tool (the blade edge)). As a result, the valve opening pressure of
the score groove portion 5c of an individual battery can greatly varies.
Furthermore, the distal portion of the blade edge has a comer, and thus the
blade edge is abraded due to repetitive score processing, and the shape of the blade
edge has a tendency to vary. Accordingly, due to a variance in the shape of the blade
edge, the valve opening pressure has a tendency to vary.
In addition, even when the blade edge has an arc shape, when a radius of
curvature R of the score groove bottom portion (hereinafter, referred to as a radius of
curvature R) is 0.20 mm or less, the blade edge has a tendency to be abraded during the
score processing, and thus the valve opening pressure has a tendency to vary.
In addition, when the radius of curvature R exceeds 1.20 mm, an amount of
metal flow, which occurs when a worked portion of the can is extruded due to the
formation of a score groove during the score processing, increases too much.
Accordingly, strain occurs on a surface which is subjected to the score processing, and
thus the valve opening pressure varies.
- 17 -
As described above, to sufficiently suppress the variance of the valve opening
pressure, the radius of curvature R is set to be more than 0.20 mm and equal to or less
than 1.20 mm. In addition, when the radius of curvature R is within a range of more
than 0.20 mm and 1.20 mm or less, even when the radius of curvature R of an inner
surface of the can and the radius of curvature R of an outer surface of the can are not
equal to each other, the variance in the valve opening pressure may be sufficiently
suppressed. In a case of further suppressing the abrasion of the blade edge to fiarther
reliably suppress the variance in the valve opening pressure, it is preferable that the
radius of curvature R be 0.30 mm or more.
[0042]
(1-b) From results of comparison between a double-sided score and a singlesided
score, it can be seen that there is a difference in the variance of the valve opening
pressure. In the double-sided score, the maximum amount of strain in the vicinity of
the score groove bottom portion is reduced, and thus nonuniformity of the score groove
portion may be improved, and the variance in the valve opening pressure may be
sufficiently suppressed. However, in the single-sided score, the above-described
characteristics of the score groove portion may not be improved, and thus the
suppression of the variance in the valve opening pressure is not sufficient.
Accordingly, in addition to the setting of the radius of curvature R to more than 0.20
mm and 1.20 mm or less, the score groove portion is made to be present in both the
inner surface and the outer surface of the can.
[0043]
(1-c) Furthermore, for example, as shown in FIG. 7B, when the radius of
curvature R in the double-sided score is set to be more than 0.20 mm, not only the
amount of strain in the vicinity of the score groove bottom portions Sal and 5b 1 may
- 18
be reduced due to dispersed stress, but also a variation rate (deterioration with the
passage of time) of the radius of curvature R of the blade edge due to abrasion of the
blade edge is suppressed. Accordingly, the lifespan of the blade edge of a die may be
increased. In addition, when the radius of curvature R exceeds 0.20 mm, since a
change of the valve opening pressure due to a change of the radius of curvature R is
small, a change (variance) of the valve opening pressure due to the abrasion of the
blade edge of the die scarcely occurs.
In FIGS. 7A and 7B, to illustrate a stress state in an easily understandable
manner, hatching of a cross-section is omitted.
[0044]
(1-d) In a steel sheet used in the battery can, when the amount of C is limited
to 0.040% by mass or less, the amount of S is limited to 0.020% by mass or less, and
tensile strength TS is limited to 400 MPa or less, defects inside the steel sheet which
occur due to score processing strain are reduced, and thus a decrease in ductility of
ferrite may be suppressed. Examples of the defects inside the steel sheet include a
cavity that may be formed at a boundary between FesC and MnS, and ferrite, or a
microcrack that occurs due to a hard characteristic of the steel sheet itself. In addition,
in a steel sheet in which a decrease in ductility of ferrite due to the score processing is
suppressed, when the radius of curvature R of the double-sided score exceeds 0.20 mm,
even when the remaining score thickness d is made as small as 0.045 mm, stable valve
opening pressure may be obtained. Accordingly, the remaining score thickness d may
be made as small as 0.045 mm. Thus, the battery can is applicable to a use in which
relatively low valve opening pressure is necessary. Particularly, to obtain more stable
valve opening pressure after making the remaining score thickness d as small as
possible, it is preferable that the radius of curvature R of the double-sided score be
19 -
0.30 mm or more.
[0045]
(1-e) On the other hand, in a case of providing a score groove type safety
valve in which the radius of curvature R is 0.30 mm to 1.20 mm, and the remaining
score thickness d is 0.055 mm to 0.150 mm, microcracks that occur in the vicinity of
the score groove bottom portion may be greatly reduced. Thereby, when the score
groove portion is formed in such a manner that the radius of curvature R becomes 0.30
mm or more, and the remaining score thickness d becomes 0.055 mm or more, with
regard to a component composition of the steel sheet, the amount of C may be reduced
to 0.100% by mass or less and the amount of S may be reduced to 0.030% by mass or
less, and with regard to strength characteristics of the steel sheet, the tensile strength
TS may be mitigated to 400 MPa or less.
In addition, when the remaining score thickness d exceeds 0.150 mm, the
valve opening pressure becomes too high, and thus the safety valve does not
appropriately function as a safety valve of a storage battery for an industrial use and an
in-vehicle use.
[0046]
Next, with regard to suppression of a decrease in the valve opening pressure
of the score groove portion by deterioration of the battery can with the passage of time
due to fatigue, the present inventors have found the following (2-a) to (2-e).
(2-a) In a score groove portion that is subjected to the score processing with a
trapezoidal blade edge and a triangular blade edge, inner pressure is repetitively
focused on a surface of the score groove portion, and as a result, fatigue breaking
occurs at low inner pressure. Furthermore, in the case of a trapezoidal score or a
triangular score, since large process strain is applied to the vicinity of the score groove
- 20 -
bottom portion formed by the blade edge, microcracks occur at the periphery of the
inclusions and the like in the steel sheet, and propagation of fatigue cracks becomes
fast, and thus fatigue-resistant strength greatly deteriorates. In a score groove portion
in which the radius of curvature R is more than 0.20 mm and equal to or less than 1.20
mm, stress is not focused too much on a local point of the score groove portion, and
thus the fatigue-resistant strength of the score groove portion increases, and thus the
fatigue breaking is not likely to occur. Accordingly, to secure very good fatigueresistant
characteristics against a load caused by a variation of inner pressure over a
long period of time, the radius of curvature R of the score groove portion is set to be
more than 0.20 mm and equal to or less than 1.20 mm. In a case of fiirther improving
the fatigue resistance, it is preferable that the radius of curvature R be 0.30 mm or
more.
[0047]
(2-b) In the double-sided score, since severe process strain is dispersed to both
surfaces of the steel sheet during the score processing, microcracks may be greatly
reduced during the score processing, and thus the fatigue characteristics may be further
improved.
(2-c) When the radius of curvature R in the double-sided score is set to be
more than 0.20 mm and equal to or less than 1.20 mm, local stress serving as an origin
of fatigue is greatly mitigated, and thus the fatigue resistance is improved.
(2-d) In a case where the radius of curvature R of the score groove bottom
portion is more than 0.20 mm and equal to or less than 0.30 mm, and the remaining
score thickness d is 0.045 mm to 0.055 mm, when all conditions, in which the amount
of C in the steel sheet is 0.040% by mass or less, the amount of S in the steel sheet is
0.020% by mass or less, and the tensile strength TS of the steel sheet is 400 MPa or
21
less, are not satisfied, microcracks that occur at a boundary between FesC and MnS,
and ferrite may not be reduced. In this case, a fatigue propagation velocity is high,
and fatigue-resistant characteristics deteriorate, and thus the valve opening pressure of
the safety valve decreases along with an operation time of the battery. Accordingly,
in a case where the radius of curvature R is more than 0.20 mm and equal to or less
than 0.30 mm, and the remaining score thickness is 0.045 mm to 0.055 mm, the
amount of C in the steel sheet is limited to 0.040% by mass or less, the amount of S in
the steel sheet is limited to 0.020% by mass or less, and the tensile strength TS of the
steel sheet is limited to 400 MPa or less.
[0048]
(2-e) On the other hand, in a case of providing a score groove type safety
valve in which the radius of curvature R is 0.30 mm to 1.20 mm, and the remaining
score thickness is 0.055 mm to 0.150 mm, microcracks that occur in the vicinity of the
score groove bottom portion may be greatly reduced. Thereby, when the score
groove portion is formed in such a manner that the radius of curvature R becomes 0.30
mm or more, and the remaining score thickness d becomes 0.055 mm or more, with
regard to a component composition of the steel sheet, the amount of C may be reduced
to 0.100% by mass or less and the amount of S may be reduced to 0.030% by mass or
less, and with regard to strength characteristics of the steel sheet, the tensile strength
TS may be mitigated to 400 MPa or less.
[0049]
Next, with regard to suppression of a decrease in the valve opening pressure
of the score groove portion by deterioration of the battery can with the passage of time
due to corrosion, the present inventors have found the following results (3-a) to (3-c).
(3-a) In a score groove portion that is subjected to the score processing with a
#
- 22
trapezoidal blade edge and a triangular blade edge, process strain is focused on a local
point of the score groove portion, and as a result, strong shear strain occurs at a Ni
plate layer, and the Ni plate layer is partially broken due to the shear strain.
Accordingly, pitting progresses from the broken portion of the Ni plated layer. On the
other hand, when using a circular blade edge capable of forming a score groove portion
in which the radius of curvature R is more than 0.20 mm and is equal to or less than
1.20 mm, the partial breakage of the plated layer due to shearing may be suppressed.
Accordingly, the decrease in the valve opening pressure in the Ni plated layer of the
score groove portion due to pitting or the like may be sufficiently suppressed.
(3-b) In the double-sided score, an amount of the process strain of the Ni
plated layer is greatly reduced, and thus the soundness of the Ni plated layer is further
improved.
(3-c) When the radius of curvature R in the double-sided score is set to be
more than 0.20 mm, local strain during the score processing is mitigated, and thus the
soundness of the Ni plated layer is improved and pitting is suppressed. Accordingly,
satisfactory fatigue resistance may be obtained. Furthermore, when the radius of
curvature R becomes 0.30 mm or more, a safety valve in which more satisfactory
soundness of the Ni plated layer and more satisfactory fatigue-resistant characteristics
are secured may be obtained.
[0050]
In addition, in the battery can for a storage battery, when a soft stainless steel
sheet in which the amount of C is limited to 0.040% by mass or less, the amount of S is
limited to 0.020% by mass or less, and the tensile strength TS is limited to 400 MPa or
less is used for the battery can, it is not necessary to consider the findings of (3-a) to
(3-c). However, in consideration of the findings of (1-a) to (1-e), and (2-a) to (2-e), a
- 23
battery can is configured to be provided w^ith the score groove type safety valve having
the score groove portion, in which the radius of curvature R is more than 0.20 mm and
equal to or less than 1.20 mm, and the remaining score thickness d is 0.045 mm to
0.150 mm, on both surfaces of the stainless steel sheet. In this case, it is possible to
provide a battery can for a storage battery in which the local stress serving as an origin
of fatigue is greatly mitigated, and which is satisfactory in stability of the valve
opening pressure, valve opening characteristics, fatigue resistance, and corrosion
resistance under a harsh environment.
[0051]
Here, a portion of the battery can, to which the double-sided score processing
type safety valve is provided, is not particularly limited, and may be a can lid flat
portion (can lid portion), a can bottom flat portion (can bottom portion), or a can side
wall portion (can body portion) as long as the double-sided score may be formed.
[0052]
FIG. 1 shows a relationship between the radius of curvature R and the valve
opening pressure, and FIG. 2 shows a relationship between the radius of curvature R
and an index of soundness of a Ni plated layer (average elongation rate of the Ni plated
layer). In FIGS. 1 and 2, characteristics of the safety valve are evaluated by the
following method.
ANi plated steel sheet (sheet thickness = 0.50 mm) in which the amount of C
is 0.002% by mass, the amount of S is 0.007% by mass, and the tensile strength TS is
310 MPa is dravra to prepare a cylindrical can (a can body portion and a can bottom
portion). A score having curvature (roundness) at a front end (score groove bottom
portion) with a score contour (f) of 25.5 mm is formed in both a front surface and a rear
surface of the can bottom (can bottom portion) of the cylindrical can to prepare a
- 24 -
safety valve in which the remaining score thickness is 100 )am. Then, a can lid (can
lid portion) is attached to the cylindrical can, and then the resultant battery can is
sealed. Inner pressure is loaded to the battery can to open the valve, and the
relationship between the radius of curvature R and the valve opening pressure is
examined. In addition, in a case where the radius of curvature R is 0 mm (that is, a
triangular score), elongation of the Ni plated layer is focused on a local point too much,
and thus an average elongation rate of the Ni plated layer may not be evaluated. Here,
the average elongation rate AL of the Ni plated layer is evaluated by the following
expression (Expression 1) after observing a cross-sectional structure of the scoreprocessed
score groove portion to measure an original line length LO of the Ni plated
layer which corresponds to the score groove portion before the score processing, and a
line length LI of the Ni plated layer which corresponds to the score groove portion
after the score processing.
AL = (LI - L0)/L0 X 100 (Expression 1)
[0053]
As shown in FIG. 1, when the radius of curvature R is changed from zero
(triangular score) to 0.2 mm, the valve opening pressure significantly decreases, and
when the radius of curvature R reaches 0.3 mm, the valve opening pressure decreases
to the lowest loaded inner pressure level, and satisfactory valve opening characteristics
may be obtained. When the radius of curvature R is 0.3 mm to 1.0 mm, stable valve
opening characteristics at the minimum valve opening pressure may be obtained, and
thus this radius of curvature R is more preferable. When the radius of curvature R is
1.0 mm to 1.2 mm, the valve opening pressure gradually increases along with an
increase in the radius of curvature R, and when the radius of curvature R reaches 1.2
mm, the valve opening pressure reaches an appropriate limit. When the radius of
- 25 -
curvature R exceeds 1.2 mm, the valve opening pressure rapidly increases along with
an increase in the radius of curvature R.
[0054]
Furthermore, the present inventors have found that a relationship between the
radius of curvature R and the valve opening pressure as shown in FIG. 1 has the same
tendency as a relationship between the radius of curvature R and stability of the valve
opening pressure, and a relationship between the radius of curvature R and fatigue
strength.
[0055]
A relationship between an average elongation rate of the Ni plated layer and
the radius of curvature R, which has a great effect on the soundness of the Ni plated
layer, is shown in FIG. 2. When the radius of curvature R is within a range of more
than 0 and 0.2 mm or less, the average elongation rate of the Ni plated layer is
significantly reduced, and when the radius of curvature R exceeds 0.2 mm, the average
elongation rate of the Ni plated layer sufficiently decreases, and thus the soundness of
the Ni plated layer may be secured. When the radius of curvature R further increases,
the average elongation rate of the Ni plated layer gradually decreases, and thus the
soundness of the Ni plated layer is improved. In addition, when the soundness of the
Ni plated layer is improved, the pitting of the Ni plated layer may be decreased, and
thus an abnormal decrease in the valve opening pressure due to the pitting is not likely
to occur. Accordingly, the durability of the battery can itself is also improved. Also,
when the radius of curvature R is 0.3 mm or more, the average elongation rate of the
Ni plated layer may be reduced by 200% or less, and thus the radius of curvature R is
more preferably 0.3 mm or more.
[0056]
#
26
Hereinafter, a battery can for a storage battery (hereinafter, referred to simply
as "battery can") according to an embodiment of the invention will be described in
detail. In addition, in the specification and drawings, the same reference numerals
will be given to components having substantially the same functional configuration,
and a redundant description thereof will be omitted here.
[0057]
FIG. 3 A shows a schematic perspective diagram of the battery can according
to the embodiment. As shown in FIG. 3 A, the battery can 1 includes a tubular can
body portion 2 having two ends 2a and 2b (a first end 2a and a second end 2b), a can
bottom portion 3 that is continuous to the can body portion 2 so as to cover the end 2a
of the can body portion 2, and a can lid portion 4. In the battery can 1, when a battery
is assembled, the battery can 1 seal the battery in such a manner that the can lid portion
4 is provided to be continuous to the can body portion 2 so as to cover the end 2b of
the can body portion 2 as shown in FIG. 3 A.
[0058]
Besides, as shown in FIG. 3A, the battery can 1 includes a score groove type
safety valve 5 at the can bottom portion 3. In a case where the battery is configured
using the battery can 1, and pressure inside the battery can 1 is abnormally raised, the
safety valve 5 is opened to prevent the battery can itself from being ruptured.
[0059]
FIG. 4 shows a schematic longitudinal cross-sectional diagram of the battery
can according to the embodiment, which is cut to pass through the central axis of the
battery can 1 shown in FIG. 3A. Also, FIG. 5A shows a partial schematic diagram
illustrating an enlarged view of broken-line portion A in FIG. 4. As shown in FIG.
5A, the safety valve 5 is constituted by a score groove portion 5a (first score groove
- 27 -
portion 5a) in an inner surface of the can bottom portion 3, and a score groove portion
5b (second score groove portion 5b) in an outer surface of the can bottom portion 3.
In this manner, the safety valve 5 includes the score groove portions 5a and 5b in the
inner surface and the outer surface of the can bottom portion 3, and the score groove
portions 5a and 5b are disposed to be opposite to each other in a cross-section view in
a sheet thickness direction (that is, in a groove depth direction). In addition, when
viewed from a cross-section that is perpendicular to an extension direction (a direction
perpendicular to a groove width direction and the groove depth direction) of the score
groove portions 5a and 5b, the score groove portions 5a and 5b have score groove
bottom portions 5al and 5bl which have a radius of curvature R. Besides, here, a
groove shape that faces to the extension direction of the score groove portions 5a and
5b is the same in each case.
[0060]
In addition, the can bottom portion 3 provided with the safety valve 5 (that is,
a portion provided with the safety valve) is formed from a plated steel sheet 3 c having
a steel sheet portion 3 a (an original sheet portion for plating) in which the amount of C
and the amount of S that is an unavoidable impurity are limited, and which has a
tensile strength TS, and plated sheets 3b on a surface of the steel sheet portion 3a. In
this case, the radius of curvature R and a range of a distance (that is, remaining score
thickness) d between the score groove bottom portions 5al and 5bl are determined in
accordance with the amount of C and the amount of S, and the tensile strength TS of
the steel sheet portion 3 a.
[0061]
With regard to the steel sheet portion 3 a of the can bottom portion 3 which is
provided with the safety valve 5, in a case where the amount of C is limited to 0.040%
28
by mass or less, the amount of S is limited to 0.020% by mass or less, and the tensile
strength TS is 400 MPa or less, the radius of curvature R is more than 0.20 mm and
equal to or less than 1.20 mm, and preferably 0.30 mm to 1.20 mm. In addition, in
this case, the remaining score thickness d is 0.045 mm to 0.150 mm.
Here, to secure strength necessary for the battery, for example, the steel sheet
portion 3a may contain 0.0010% to 0.040% of C. Besides, to reduce the production
cost of the plated steel sheet 3 c by reducing the refining cost of the steel sheet portion
3a, the steel sheet portion 3a may contain 0.0005% to 0.020%) of S.
[0062]
With regard to the steel sheet portion 3 a of the can bottom portion 3 which is
provided with the safety valve 5, in a case where the amount of C is limited to 0.100%)
by mass or less, the amount of S is limited to 0.030%) by mass or less, and the tensile
strength TS is 400 MPa or less, the radius of curvature R is more than 0.30 mm and
equal to or less than 1.20 mm. In addition, in this case, the remaining score thickness
d is 0.055 mm to 0.150 mm.
Here, to secure strength necessary for the battery, for example, the steel sheet
portion 3a may contain 0.0010%) to 0.100%) of C. Besides, to reduce the production
cost of the plated steel sheet 3c by reducing the refining cost of the steel sheet portion
3a, the steel sheet portion 3a may contain 0.0005%) to 0.030%) of S.
Also, the lower limit of the tensile strength TS is not particularly limited as
long as the lower limit is a strength necessary for a battery that is used, but for example,
the lower limit may be 290 MPa.
[0063]
Furthermore, to lengthen the lifetime of the battery by raising the valve
opening pressure as long as a safe and stable battery output is possible even when inner
29 -
pressure is relatively increased, it is preferable that the remaining score thickness d be
0.060 mm or more, more preferably 0.080 mm or more or 0.085 mm or more, and still
more preferably 0.090 mm or more or 0.100 mm or more.
Besides, to further reduce the cost of the battery can by further lengthening
the lifetime of a blade edge, it is more preferable that the radius of curvature R be 0.40
mm or more. To further reliably suppress the process strain that may occur by the
score processing, it is preferable that the radius of curvature R be 1.00 mm or less.
[0064]
For example, in the embodiment, the score groove bottom portions 5al and
5b 1 which have the radius of curvature R as shown in FIGS. 5 A and 5B may be
provided to the bottoms of the score groove portions 5a and 5b, respectively. Here,
the radius of curvature R and the remaining score thickness d in FIGS. 5 A and 5B are
defined as shown in FIGS. 6A and 6B, respectively. In the score groove portions 5a
and 5b, the score groove bottom portions 5a 1 and 5b 1 are portions having the radius of
curvature R. Accordingly, in FIG. 5A, the score groove portions 5a and 5b, and the
score groove bottom portions 5al and 5b 1 are consistent with each other. In FIG. 5B,
parts of the score groove portions 5a and 5b correspond to the score groove bottom
portions 5al and 5bl. In FIGS. 6A and 6B, to illustrate each dimension in an easily
understandable manner, hatching of a cross-section is omitted.
[0065]
In a case of FIG. 5 A, to make the score processing possible, it is preferable
that an angle a (a value of -90° or more and less than 90° in which counter-clockwise
rotation with the sheet thickness direction made as a reference is defined as positive
rotation) made by a tangential line of each end of the score groove bottom portions 5al
and 5b 1 and a sheet thickness direction (that is, the depth direction of the score groove
- 30
portion) of the can bottom portion 3 (that is, a portion of the battery can 1 which is
provided with the safety valve 5) be 0° or more. In addition, in a case of mitigating
the process strain in the vicinity of the score groove portions 5a and 5b as much as
possible, the angle a is preferably 45° or less, more preferably 40° or less, and still
more preferably 30°. Besides, the score groove shape in FIG. 5A and the score
groove shape in FIG. 5B may be changed in accordance with the angle a.
[0066]
In a case of FIG. 5B, to mitigate the process strain in the vicinity of the score
groove portions 5 a and 5 b, two remaining portions (hereinafter, referred to as score
groove upper portions 5a2 and 5b2), which are present on both sides of the score
groove bottom portions 5al and 5bl, of the score groove portions 5a and 5b preferably
have a predetermined angle in an opening direction of the score groove portions 5 a and
5b. For example, to mitigate the process strain in the vicinity of the score groove
portions 5 a and 5 b, with regard to the score groove upper portions 5a2 and 5b2 on one
side, an angle 9' (hereinafter, referred to as groove opening degree 9') made by a
straight line connecting one end and the other end of the score groove upper portions
5a2 and 5b2, and a sheet thickness direction (that is, the depth direction of the score
groove portion) of the can bottom portion 3 (that is, a portion of the battery can 1
which is provided with the safety valve 5) is preferably 20° or more, and more
preferably 22.5° or more. In this case, stress that is applied to the Ni plating may be
dispersed, and thus the soundness of the Ni plating is improved, and thus the thickness
of the Ni plating may be reduced. In a case where the score groove upper portions
5a2 and 5b2 are present, the groove opening degree 9' may be 45° or less or 40° or less
to secure continuity between the score groove bottom portions 5al and 5bl, and the
score groove upper portions 5a2 and 5b2.
- 31
[0067]
In addition, a processing procedure when forming the score groove portions
5a and 5b in the plated steel sheet 3c is not particularly limited, but both prior plating
and post plating may be applied to the processing procedure.
That is, the plated steel sheet (corresponding to the plated steel sheet 3c) may
be directly subjected to the score processing by a press forming method. In this case,
a battery can, which is satisfactory in stability of the valve opening pressure, valve
opening characteristics, and soundness of the plated layer 3b, may be provided at a low
cost without considering adhesive properties of the plating in the score processed
portions.
Besides, the plated layer 3b may be formed on a surface of a steel sheet
(corresponding to the steel sheet portion 3 a, a steel sheet for post plating) after the steel
sheet is subjected to the score processing by a press forming method. In this case, a
battery can, which is satisfactory in stability of the valve opening pressure and the
valve opening characteristics, may be provided without considering deterioration of
corrosion resistance due to the processing.
Moreover, a soft stainless steel sheet (stainless steel sheet having tensile
strength of 400 MPa or less) may be used in place of the plated steel sheet 3c. In this
case, passivation film on a surface of the stainless steel sheet has the same function as
the plated layer 3b, and thus it is not necessary for the surface of the stainless steel
sheet to be plated. Accordingly, the stainless steel sheet may be directly subjected to
the score processing by the press forming method. In this case, a battery can, which
is satisfactory in stability of the valve opening pressure, valve opening characteristics,
and corrosion resistance under a harsh environment, may be provided without
considering deterioration of corrosion resistance due to processing. In addition, in a
- 32 -
case where the soft stainless steel sheet is used, an outermost surface on an inner side
of the battery can 1 (the can body portion 2, the can bottom portion 3, and the can lid
portion 4) is preferably constituted by the soft stainless steel sheet from the viewpoint
of corrosion resistance.
[0068]
Also, the kind of the plated layer 3b is also not particularly limited, and may
be determined in accordance with a material accommodated in the battery (for example,
an electrolytic solution) or an operating environment of the battery. For example, it is
preferable that the plated layer 3b includes a Ni plated layer having particularly
satisfactory corrosion resistance in an organic solvent. In this case, a strike plating
that improves plating adhesiveness may be included between the Ni plated layer and
the steel sheet portion 3a, and the Ni plated layer may contain components of the strike
plating. Particularly, in a case where it is necessary for a surface to have corrosion
resistance, or in a case where it is necessary to avoid mixing of impurities into the
electrolytic solution, it is preferable that the outermost surface of the plated steel sheet
3 c (on an inner side of the battery can 1 (the can body portion 2, the can bottom
portion 3, and the can lid portion 4)) be constituted by the Ni plated layer.
[0069]
Here, in a case of applying the Ni plated steel sheet to the battery can, after Ni
plating is performed on a surface of a cold-rolled steel sheet, annealing is preferably
performed for softening so as to improve workability of the Ni plated layer and for
generation of a Ni-Fe mutual diffusion layer so as to improve adhesiveness in an
interface between the Ni plated layer and the steel sheet (iron). In addition, the Ni
plated steel sheet is not particularly limited as long as workability during the score
processing is secured, and Ni plating of various alloys such as Ni-P, Ni-Sn, and Ni-Cu
33 -
may be applied. That is, the Ni plated layer or the Ni plated diffusion layer may
contain an alloy element such as P, Sn, and Cu as a selective element. Besides, in a
case where the soft stainless steel sheet is applied to the battery can, the kind of
stainless steel sheet is not particularly limited as long as the amount of C is 0.040% by
mass or less, the amount of S is 0.020% by mass or less, and the tensile strength TS is
400 MPa or less. The sheet thickness of the Ni plated steel sheet, the steel sheet for
the post Ni plating, and the soft stainless steel sheet is not particularly limited, but the
sheet thickness may be 0.20 mm to 0.80 mm in consideration of a balance between the
strength and the cost. Particularly, in a case where strength is necessary, it is
preferable that the sheet thickness be 0.30 mm or more, more preferably 0.35 mm or
more or 0.40 mm or more, and still more preferably 0.45 mm or more. On the other
hand, it is preferable that the sheet thickness be 0.75 mm or less to reduce the cost as
much as possible.
[0070]
It is not necessary to limit the above-described production conditions of the Ni
plated steel sheet, the steel sheet for the post Ni plating, and the soft stainless steel
sheet except for the above component compositions (the amount of C and the amount
of S), and the tensile strength TS as long as these steel sheets are suitable for drawing
of the battery can for a storage battery. In a case where the Ni plated steel sheet is
subjected to the score processing, the blade edge is smooth, and thus damage to the Ni
plated layer scarcely occurs. However, in this case, since the Ni plated layer is
stretched and becomes thin during the score processing, the Ni plated layer may be set
to be slightly thicker than necessary. In addition, for example, the thickness (basis
weight) of the plated layer (Ni plated layer) may be controlled to 0.2 )a,m to 5.0 )u,m.
[0071]
- 34
As a modification example of the embodiment, for example, the battery can
may have a structure as shown in FIGS. 3B to 3F.
That is, as shown in FIGS. 3B and 3D, the battery can 1 may be provided with
the safety valve 5 at the can lid portion 4, and as shown in FIG. 3E, the battery can 1
may be provided with the safety valve 5 at the can body portion 2. In addition, the
shape of the battery can 1 is not particularly limited, and the battery can 1 may be a
square can as shown in FIGS. 3C to 3E, or may have a special shape as shown in FIG.
3F. Also, the shape (a shape in a plan view) of the safety valve 5 which is viewed
from an upper side of the safety valve 5 is not particularly limited, and may be
determined depending on a structure (disposition of a positive electrode and a negative
electrode, and the like) inside the battery can in a case of constituting a battery. For
example, in a case where the safety valve is provided to the can bottom portion 3 or the
can lid portion 4, the safety valve may be disposed in such a manner that the center of
the circular safety valve matches the center of the can bottom portion 3 or the can lid
portion 4 as shown in FIG. 3A.
[0072]
As described above, in the embodiment (including the modification example),
the battery can 1 may be provided with the safety valve 5 having the score groove
portions 5a and 5b in both of the inner surface and the outer surface (in the inner
surface and the outer surface, respectively) of any one of the can bottom portion 3, the
can body portion 2, and the can lid portion 4.
In addition, when a positive electrode, a negative electrode, and an electrolyte
(for example, a separator containing the electrolyte) are accommodated in the battery
can 1 according to the embodiment, a storage battery, which includes the battery can 1
according to the embodiment, the positive electrode, the negative electrode, and the
35
electrolyte, may be provided.
[0073]
Accordingly, the battery can according to the embodiment may be applied as a
battery can for a storage battery in which satisfactory stability of the valve opening
pressure, satisfactory valve opening characteristics, and satisfactory corrosion
resistance under a harsh environment are necessary. Particularly, the battery can for a
storage battery may be suitably applied as a battery can for an industrial use (for
example, a fixed apparatus), and an in-vehicle use.
That is, in the battery can according to the embodiment, a variance in the
valve opening pressure of the score groove portion of an individual battery can may be
reduced. In addition, in the battery can of the embodiment, a decrease in the valve
opening pressure of the score groove portion by fatigue caused by repetitive variation
of inner pressure (repetitive stress) which is loaded on the battery can over a long
period of time (10 to 15 years) may be almost prevented. Furthermore, in the battery
can according to the embodiment, fracture or cracking of the Ni plated layer, which
accompanies the score processing, scarcely occurs, and pitting of the score groove
portion, and the like may be suppressed. Accordingly, a decrease in the valve
opening pressure of the score groove portion may be almost prevented.
[Examples]
[0074]
Hereinafter, an effect of the invention will be described with reference to
examples.
[0075]
Cast pieces (steel) which contain chemical components shown in steel A to
steel E, and steel G to steel H in Table 1 were prepared, and hot rolling and cold rolling
- 36
were performed under normal conditions to prepare steel sheets (steel). In addition,
with respect to steel sheets other than a soft stainless steel sheet (steel F), Ni plating
was performed before can production or after can production. In a case where the Ni
plating was performed before the can production (prior plating), Ni plating, annealing,
and temper rolling were performed with respect to the steel sheet to produce a Ni
plated steel sheet, and battery cans (cylindrical can and square can) were prepared from
the Ni plated steel sheet. On the other hand, in a case where the Ni platijig was
performed after the can production (post plating), battery cans were prepared directly
from a steel sheet (raw steel sheet) to which the Ni plating was not applied. Similarly,
a battery can was prepared directly from a soft stainless steel sheet containing chemical
components shown in steel F. Inner pressure was applied to the battery cans to
evaluate valve opening characteristics of the respective battery cans. Here, the
remainder other than the chemical components shown in Table 1 includes iron and
other unavoidable impurities.
[0076]
[Table 1]
Steel
A
B
C
D
E
F
G
H
I
Chemical component (% by mass)
C
0.035
0.002
0.002
0.005
0.060
Si
0.01
0.01
0.01
0.01
0.01
Mn
0.25
0.10
0.12
0.20
0.20
P
0.008
0.008
0.009
0.007
0.010
S
0.007
0.004
0.015
0.005
0.022
sol.Al
0.045
0.035
0.034
0.045
0.041
N
0.0022
0.0028
0.0022
0.0027
0.0032
Ti
-
0.015
0.035
Tr.
-
Nb
-
0.018
0.013
0.022
-
B
-
0.0003
0.0004
Tr.
-
C (0.002% by mass) - S (0.007% by mass) - ferrite-based soft stainless steel
0.150
0.003
0.002
0.01
0.80
0.01
0.15
2.20
0.35
0.010
0.085
0.011
0.015
0.010
0.028
0.045
0.040
0.048
0.0027
0.0020
0.0025
-
0.020
0.005
0.018
0.018
0.025
-
0.0010
0.0004
TS
(MPa)
335
310
307
365
330
380
375
410
315
[0077]
In Table 1, "sol. Al" represents soluble Al. In addition, "Tr." represents that
the amount of a detected chemical component was small to a degree at which
determination of the quantity was impossible. Also, "-" represents that a chemical
- 37
component was not detected during determination.
[0078]
In Table 1, test steel A to test steel E, and test steel I are ultralow-carbon steel,
and test steel F is an ultralow C-ferrite based soft stainless steel sheet which is sold on
the market. In addition, in the steel A, the amount of C is 0.035% by mass, the
amount of S is 0.007%) by mass, and the tensile strength TS is 335 MPa. In the steel
B, the amount of C is 0.002%) by mass, the amount of S is 0.004% by mass, and the
tensile strength TS is 310 MPa. In the steel C, the amount of C is 0.002% by mass,
the amount of S is 0.015%) by mass, and the tensile strength TS is 307 MPa. In the
steel D, the amount of C is 0.005%) by mass, the amount of S is 0.005%o by mass, and
the tensile strength TS is 365 MPa. In the steel E, the amount of C is 0.060% by mass,
the amount of S is 0.022% by mass, and the tensile strength TS is 330 MPa. In the
steel F, the amount of C is 0.002% by mass, the amount of S is 0.007%o by mass, and
the tensile strength TS is 380 MPa. In the steel I, the amount of C is 0.002% by mass,
the amount of S is 0.028%) by mass, and the tensile strength TS is 315 MPa.
[0079]
In Table 1, the test steel G and test steel H are high low-carbon steel, and
high-strength steel sheet, respectively. In the steel G, the amount of C is 0.150%) by
mass and is more than 0.100%) by mass. In the steel H, the tensile strength TS is 410
MPa, and is more than 400 MPa. Here, an underline in Table 1 represents that the
amount of C, the amount of S, and the tensile strength TS are not sufficiently limited.
[0080]
In addition, in the invention, there is no limitation to the steel sheets, and it is
not necessary to particularly limit other conditions of the steel sheets as long as
conditions in which the amount of C is 0.100%) by mass or less, the amount of S is
- 38
0.030% by mass or less, and the tensile strength TS is 400 MPa or less are satisfied.
Therefore, in the invention, Ni plated steel sheets which are produced by steel-making,
hot rolling, cold rolling, Ni plating, annealing, and temper rolling which are commonly
performed, steel sheets to which the Ni plating is not applied (that is, a steel sheet in
which the Ni plating is not performed before can production, and the Ni plating is
performed after the can production), or a soft stainless steel sheet may be applied, and
it is not necessary to particularly regulate a method of producing a steel sheet.
[0081]
Besides, it is not necessary to particularly limit dying conditions of the battery
can, and a dying method thereof, and normal conditions of producing a battery can for
a storage battery may be applied as long as the radius of curvature R and the remaining
score thickness d can be sufficiently controlled.
Battery cans provided with a score groove type safety valve were produced
under conditions shown in Table 2 using steel A to steel I shown in Table 1. Inner
pressure was applied to the battery cans, and as valve opening characteristics, stability
of the valve opening power, valve opening characteristics, and soundness of the Ni
plated layer (excluding post plating and soft stainless steel sheet) were evaluated.
The score groove type safety valve was provided to a can bottom portion in circular
cans of test Nos. 1 to 22, and 25 to 28, a can lid portion in the square can of test No. 23,
and a can side wall portion (can body portion) in the square can of test No. 24,
respectively. In test Nos. 1 to 26, the safety valve was a double-sided score, and in
test Nos. 27 and 28, the safety valve was a single-sided score.
[0082]
A variance in a can opening time when the number of cycles n during
charging and discharging was increased, deterioration of fatigue strength when
39
repetitive inner pressure was loaded, an extent of an effect on valve opening
characteristics by abrasion of a die, and the like were comprehensively evaluated, and
stability of the valve opening power was evaluated by three grades including not good
(NG in Table 2), good (G in Table 2), and very good (VG in Table 2).
[0083]
Valve opening pressure that is necessary when the battery can is applied for an
industrial use and an in-vehicle use was comprehensively evaluated, the valve opening
characteristics being evaluated by three grades including not good (NG in Table 2),
good (G in Table 2), and very good (VG in Table 2).
[0084]
A degree of damage of the plated layer of the score groove portion was
evaluated by SEM (scanning electron microscopy), EPMA (electron probe X-ray
microanalysis), and the like, and the soundness of the Ni plated layer was evaluated by
three grades including not good (NG in Table 2), good (G in Table 2), and very good
(VG in Table 2). However, in sample Nos. 12, 18, and 26, post plating was
performed, and thus evaluation was not performed ("-" in Table 2). In addition, in
sample No. 19, a soft stainless steel sheet was used, and thus evaluation was not
performed ("-" in Table 2).
[0085]
- 40 -
[Table 2]
Test
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Steel
A
B
B
B
A
B
B
B
B
B
B
B
B
B
C
D
E
E
F
G
H
I
B
B
B
B
Ni plating
Kind of plating
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Post plating
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Post plating
None
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Prior plating
Post plating
Outer/1
nner
urn
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
2/2
Dimensions of battery can
Shape
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Circular
Square
Square
Circular
Circular
mm
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
40
*1
*1
40
40
Can
height
mm
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
130
130
115
115
Score shape
Contour
mm
(t)25.5
(|)25.5
(1)25,5
(|)25.5
<|)25.5
(j)25.5
(t)25.5
(|)25.5
(|)25.5
25.5
(|)25.5
(|)25.5
25.5
(|)25.5
(t)25.5
(1)25.5
(t)25.5
(1)25.5
of safety valve
Shape of distal end
inner/outer mm
Trapezoidal 0.3
W/0.3 W
Trapezoidal 0.3
W/0.3 W
Triangular OR/OR
0.15R/0.15R
0.50 R/0.50 R
0.25 R/0.25 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.65 R/0.65 R
0.80 R/0.80 R
0.50 R/0.50 R
1.50R/I.50R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.50 R
0.50 R/0.80 R
0.60 R/0.90 R
Distal
end
0°
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
Remaining
thickness
Hm
50
50
50
50
50
50
45
50
140
60
60
60
60
30
80
80
70
60
60
50
50
50
60
60
60
60
Evaluation result *2
Stability
NG
NG
NG
NG
G
G
G
VG
VG
VG
VG
VG
NG
NG
VG
VG
VG
VG
VG
NG
NG
NG
VG
VG
VG
VG
Valve opening
characteristic
G
G
G
G
G
G
VG
VG
G
VG
VG
VG
NG
VG
VG
VG
VG
VG
VG
VG
NG
G
VG
VG
VG
VG
Soundness
NG
NG
NG
NG
G
G
G
G
VG
VG
VG
-
VG
NG
VG
VG
VG
-
-N
G
NG
G
VG
VG
VG
-
Remarks
Conventional
Example
Conventional
Example
Conventional
Example
Comparative
Example
Example
Example
Example
Example
Example
Example
Example
Example
Comparative
Example
Comparative
Example
Example
Example
Example
Example
Example
Comparative
Example
Comparative
Example
Comparative
Example
Example
Example
Example
Example
wmKmmmmm
41 #
27
28
B
B
Prior plating
Prior plating
2/2
2/2
Circular
Circular
40
40
115
115
4)25.5
(1)25.5
Flat/trapezoidal 0.3
W
Flat/triangular 0 R
60
60
50
50
NG
NG
NG
G
NG
NG
Conventional
Example
Conventional
Example
*1 Length of short side x Length of long side: 40 mm x 100 mm.
*2 NG: Not Good, G: Good, VG: Very Good.
42 -
[0086]
In test No. 1, a cross-sectional shape of the score groove of the safety valve
was a trapezoidal shape, and a lower width of the score groove was 0.3 mm (0.3 W).
Also, in test No. 2, a cross-sectional shape of the score groove of the safety valve was a
trapezoidal shape, and a lower width of the score groove was 0.3 mm (0.3 W). In test
No. 3, a cross-sectional shape of the score groove of the safety valve was a triangular
shape, and a lower width of the score groove was 0 mm. These test Nos. 1, 2, and 3
were double-sided scores of a score groove type in the related art, and the stability of
the valve opening power and the soundness of the Ni plated layer were evaluated as
failure (NG).
[0087]
In test No. 4, the radius of curvature R of the score groove bottom portion was
0.15 mm (that is, 0.20 mm or less), and thus the stability of the valve opening
characteristics and the soundness of the Ni plated layer were not sufficient (NG).
[0088]
In test No. 5, a Ni plated steel sheet of the steel A in which the amount of C
was 0.035% by mass, and the amount of S was 0.007%) by mass was used as a test steel
sheet, the radius of curvature R of the score groove bottom portion was 0.50 mm, and
the remaining score thickness d was 50 ]xm, and thus the stability of the valve opening
characteristics, the valve opening characteristics, and the soundness of the Ni plated
layer were good (G).
[0089]
In test Nos. 6, 7, 8, 9, 10, and 11, a Ni plated steel sheet of the steel B in
which the amount of C was 0.002% by mass, and the amount of S was 0.004%) by mass
was used as a test steel sheet, the radius of curvature R of the score groove bottom
- 43 -
portion was 0.25 mm to 0.80 mm, and the remaining score thickness d was 45 )U.m to
140 [im, and thus in Nos. 6, 7, 8, and 9, the stability of the valve opening power, the
valve opening characteristics, and the soundness of the Ni plated layer were good (G)
or very good (VG). In Nos. 10 and 11, all of the stability of the valve opening power,
the valve opening characteristics, and the soundness of the Ni plated layer were very
good (VG).
[0090]
In test No. 12, a steel sheet for post plating of the steel B in which the amount
of C was 0.002% by mass, and the amount of S was 0.004% by mass was used as a test
steel sheet, the radius of curvature R of the score groove bottom portion was 0.50 mm,
and the remaining score thickness d was 60 \xm, and thus the stability of the valve
opening power and the valve opening characteristics were very good (VG), and the
corrosion resistance was also secured by a post plating treatment.
[0091]
In test Nos. 13 and 14, a Ni plated steel sheet of the steel B in which the
amount of C was 0.002%) by mass, and the amount of S was 0.004% by mass was used
as a test steel sheet. Among these, in test No. 13, since the radius of curvature R of
the score groove bottom portion was 1.50 mm (that is, 1.20 mm or more), the stability
of the valve opening power, and the valve opening pressure were not good (NG). In
test No. 14, since the remaining score thickness d was 30 nm, the stability of the valve
opening power and the soundness of the Ni plated layer were not good (NG).
[0092]
In test No. 15, a Ni plated steel sheet of the steel C in which the amount of C
was 0.002%o by mass, and the amount of S was 0.015%) by mass was used as a test steel
sheet, the radius of curvature R of the score groove bottom portion was 0.50 mm, and
- 44
the remaining score thickness d was 80 fxm, and thus the stability of the valve opening
power, the valve opening characteristics, and the soundness of the Ni plated layer were
very good (VG).
[0093]
In test No. 16, a Ni plated steel sheet of the steel D in which the amount of C
was 0.005% by mass, and the amount of S was 0.005%) by mass was used as a test steel
sheet, the radius of curvature R of the score groove bottom portion was 0.50 mm, and
the remaining score thickness d was 80 |am, and thus the stability of the valve opening
power, the valve opening characteristics, and the soundness of the Ni plated layer were
very good (VG).
[0094]
In test No. 17, a Ni plated steel sheet of the steel E in which the amount of C
was 0.060%) by mass, and the amount of S was 0.022% by mass was used as a test steel
sheet, the radius of curvature R of the score groove bottom portion was 0.50 mm, and
the remaining score thickness d was 70 \xm, and thus the stability of the valve opening
power, the valve opening characteristics, and the soundness of the Ni plated layer were
very good (VG).
[0095]
In test No. 18, a Ni plated steel sheet of the steel E in which the amount of C
was 0.060% by mass, and the amount of S was 0.022% by mass was used as a test steel
sheet, the radius of curvature R of the score groove bottom portion was 0.50 mm, and
the remaining score thickness d was 60 |um, and thus the stability of the valve opening
power, the valve opening characteristics, and the soundness of the Ni plated layer were
very good (VG).
[0096]
- 45
In test No. 19, a ferrite-based low C stainless steel sheet in which the tensile
strength TS was 380 MPa, the amount of C was 0.002%) by mass, and the amount of S
was 0.007% by mass was used as a test steel sheet, the radius of curvature R of the
score groove bottom portion was 0.50 mm, and the remaining score thickness d was 60
|j,m, and thus the stability of the valve opening power, and the valve opening
characteristics were very good (VG).
[0097]
In test No. 20, a Ni plated steel sheet of the steel G in which the amount of C
was 0.150% by mass (that is, more than 0.100% by mass) was used as a test steel sheet,
and thus the stability of the valve opening power and the soundness of the Ni plated
layer were not good (NG). In test No. 21, a Ni plated steel sheet of the steel H in
which the amount of C was 0.003% by mass, and the amount of S was 0.010%) by mass,
but the tensile strength TS was 410 MPa (that is, more than 400 MPa) was used as a
test steel sheet, and thus the stability of the valve opening power, valve opening
characteristics, and the soundness of the Ni plated layer were not good (NG). In test
No. 22, a Ni plated steel sheet of the steel 1 in which the amount of C was 0.002% by
mass, the amount of S was 0.028%) by mass, and the tensile strength TS was 315 MPa
was used as a test steel sheet, but the remaining score thickness d was 50 |am with
respect to a relatively high amount of S (0.020%) to 0.030%), and thus the stability of
the valve opening power was not good (NG).
[0098]
In test Nos. 23 and 24, large-sized square battery cans of 40 mm x 100 mm x
130 mm (height) were prepared using a Ni plated steel sheet of the steel B in which the
amount of C was 0.002% by mass, and the amount of S was 0.004% by mass as a test
steel sheet, and a safety valve in which the radius of curvature R of the score groove
•
- 46 -
bottom was 0.50 mm and the remaining score thickness d was 60 p.m was provided to
the large-sized battery cans. The safety valve was provided to a can lid portion in No.
23, and a can side wall portion (can body portion) in No. 24. In Nos. 23 and 24, the
stability of the valve opening power, the valve opening characteristics, and the
soundness of the Ni plated layer were very good (VG).
[0099]
In test No. 25, a Ni plated steel sheet of the steel B in which the amount of C
was 0.002%) by mass, and the amount of S was 0.004% by mass was used as a test steel
sheet, the radius of curvature R of the score groove in an inner surface of the can was
0.50 mm, the radius of curvature R of the score groove in an outer surface of the can
was 0.80 mm, and the remaining score thickness d was 60 |j,m. In the test No. 25, the
radii of curvature R of the score grooves in the inner and outer surfaces of the can were
different from each other, but the stability of the valve opening power, the valve
opening characteristics, and the soundness of the Ni plated layer were very good (VG).
[0100]
In test No. 26, a steel sheet for post plating of the steel B in which the amount
of C was 0.002% by mass, and the amount of S was 0.004%) by mass was used as a test
steel sheet, the radius of curvature R of the score groove in an inner surface of the can
was 0.60 mm, the radius of curvature R of the score groove in an outer surface of the
can was 0.90 mm, and the remaining score thickness d was 60 |4,m. In test No. 26, the
radii of curvature R of the score grooves in the inner and outer surfaces of the can were
also different from each other, but the stability of the valve opening power and the
valve opening characteristics were very good (VG), and the corrosion resistance was
also secured by a post plating treatment.
[0101]
#
In test No. 27, a cross-sectional shape of the score groove of the safety valve
was a trapezoidal shape, and a lower width of the score groove was 0.3 mm (0.3 W).
In test No. 28, a cross-sectional shape of the score groove of the safety valve was a
triangular shape, and a lower width of the score groove was 0 mm. These test Nos.
27 and 28 were single-sided scores of a score groove type in the related art, and the
stability of the valve opening pressure and the soundness of the Ni plated layer were
evaluated as failure (NG).
In addition, in these test Nos. 27 and 28, the score groove was formed only in
the outer surface of the can, and the inner surface (a surface opposite to the score
groove) of the can had a flat shape. Also, in test Nos. 27 and 28, a Ni plated steel
sheet of the steel B in which the tensile strength TS was 310 MPa, the amount of C was
0.002% by mass, and the amount of S was 0.004% by mass was used as a test steel
sheet.
[0102]
In addition, distal end 0 in Table 2 is an angle made by two portions
(extension lines of these two portions) of a die which correspond to score groove upper
portions, and in a score groove portion having score groove upper portions as shown in
FIG. 5B, the groove opening degree 9' corresponds to 0.5 times of the distal end G.
[0103]
As is clear from the above-described results, in the battery can for a storage
battery which is provided with the score groove type safety valve according to the
invention, a variance in the valve opening pressure of the score groove portion of an
individual battery can is small, and the valve opening pressure of the score groove
portion scarcely decreases by deterioration of the battery can with the passage of time
(for example, 10 to 15 years) due to fatigue or corrosion. Accordingly, even when
48
inner pressure is repetitively loaded on the battery can over a long period of time (10 to
15 years), in the battery can for a storage battery which is provided with the score
groove type safety valve according to the invention, the valve opening pressure
scarcely decreases due to fatigue of the score groove portion. In addition, even when
the prior plating is performed, in the battery can for a storage battery which is provided
with the score groove type safety valve according to the invention, the valve opening
pressure scarcely decreases due to pitting of the score groove portion.
[0104]
Hereinbefore, the preferred examples of the invention have been described,
but the invention is not limited to these examples. Addition, omission, substitution,
and other modifications of configuration may be made within a range not departing
from the gist of the present invention. The present invention is not limited by the
above-described description, and is limited only by the attached claims.
[Industrial Applicability]
[0105]
It is possible to provide a battery can for a storage battery which is provided
with a score groove type safety valve in which a variance in valve opening pressure of
a score groove portion of an individual battery can is small, and valve opening pressure
of the score groove portion scarcely decreases by deterioration of the battery can with
the passage of time due to fatigue or corrosion.
[Description of Reference Numerals and Signs]
[0106]
1: BATTERY CAN (BATTERY CAN FOR STORAGE BATTERY)
2: CAN BODY PORTION (CAN SIDE-WALL PORTION)
2a: END (FIRST END)
#
- 49 -
2b: END (SECOND END)
3: CAN BOTTOM PORTION (CAN BOTTOM)
3a: STEEL SHEET PORTION (STEEL SHEET)
3b: PLATED LAYER (PLATING)
3c: PLATED STEEL SHEET
4: CAN LID PORTION (CAN LID)
5: SAFETY VALVE
5a, 5b: SCORE GROOVE PORTION
Sal, Sbl: SCORE GROOVE BOTTOM PORTION
Sa2, 5b2: SCORE GROOVE UPPER PORTION
R: RADIUS OF CURVATURE
d: REMAINING SCORE THICKNESS
e': GROOVE OPENING DEGREE

ORIGINAL ''^'^M^ ^ ^ « m '
[Designation of Document] CLAIMS 3 0 OCT 2015
[Claim 1]
A battery can for a storage battery, comprising:
a tubular can body portion having a first end and a second end;
a can bottom portion that is continuous to the can body portion so as to cover
the first end of the can body portion; and
a can lid portion that is continuous to the can body portion so as to cover the
second end of the can body portion when constituting a battery,
wherein a safety valve having a first score groove portion and a second score
groove portion that are opposite to each other in a cross-sectional view in a sheet
thickness direction is provided to an inner surface and an outer surface of any one of
the can bottom portion, the can body portion, and the can lid portion,
when viewed from a cross-section that is perpendicular to an extension
direction of the first score groove portion, the first score groove portion and the second
score groove portion have a first score groove bottom portion and a second score
groove bottom portion, which have a radius of curvature R and a relative clearance of
0.045 mm to 0.150 mm, respectively,
the radius of curvature R is more than 0.20 mm and is equal to or less than
1.20 mm, and
any one of the can bottom portion, the can body portion, and the can lid
portion, which has the safety valve, is constituted by a plated steel sheet having a steel
sheet portion in which the amount of C is limited to 0.040% by mass or less and the
amount of S is limited to 0.020% by mass or less, and a tensile strength TS is 400 MPa
or less, and a plate layer formed on the steel sheet portion.
[Claim 2]
ORIGINAL - ^ ' - 9 3 6 8 ffiil 3 '
3 0 OCT m '
The battery can for a storage battery according to Claim 1,
wherein the plated steel sheet is subjected to score processing by a press
forming method.
[Claim 3]
The battery can for a storage battery according to Claim 1,
wherein after the steel sheet portion is subjected to the score processing by the
press forming method, the plated layer is formed on a surface of the steel sheet portion.
[Claim 4]
A battery can for a storage battery, comprising:
a tubular can body portion having a first end and a second end;
a can bottom portion that is continuous to the can body portion so as to cover
the first end of the can body portion; and
a can lid portion that is continuous to the can body portion so as to cover the
second end of the can body portion when constituting a battery,
wherein a safety valve having a first score groove portion and a second score
groove portion that are opposite to each other in a cross-sectional view in a sheet
thickness direction is provided to an inner surface and an outer surface of any one of
the can bottom portion, the can body portion, and the can lid portion,
when viewed from a cross-section that is perpendicular to an extension
direction of the first score groove portion, the first score groove portion and the second
score groove portion have a first score groove bottom portion and a second score
groove bottom portion, which have a radius of curvature R and a relative clearance of
0.055 mm to 0.150 mm, respectively,
the radius of curvature R is 0.30 mm to 1.20 mm, and
any one of the can bottom portion, the can body portion, and the can lid
ORIGINAL .s..iS'S£B^lO
3 0 OCT ZUI6
portion, which has the safety valve, is constituted by a plated steel sheet having a steel
sheet portion in which the amount of C is limited to 0.100% by mass or less and the
amount of S is limited to 0.030%) by mass or less, and a tensile strength TS is 400 MPa
or less, and a plate layer formed on the steel sheet portion.
[Claim 5]
The battery can for a storage battery according to Claim 4,
wherein the plated steel sheet is subjected to score processing by a press
forming method.
[Claim 6]
The battery can for a storage battery according to Claim 4,
wherein after the steel sheet portion is subjected to the score processing by the
press forming method, the plated layer is formed on a surface of the steel sheet portion.
[Claim 7]
The battery can for a storage battery according to any one of Claims 1 to 6,
wherein the plated layer is Ni plating.
[Claim 8]
The battery can for a storage battery according to any one of Claims 1 to 3,
wherein the radius of curvature R is 0.30 mm to 1.20 mm.
[Claim 9]
The battery can for a storage battery according to Claim 8,
wherein the plated layer is Ni plating.
[Claim 10]
A battery can for a storage battery, comprising:
a tubular can body portion having a first end and a second end;
a can bottom portion that is continuous to the can body portion so as to cover
ORIGINAL 53 -
' ^ IWI
the first end of the can body portion; and
a can lid portion that is continuous to the can body portidB si as TO'coTCTTOe
second end of the can body portion when constituting a battery,
wherein a safety valve having a first score groove portion and a second score
groove portion that are opposite to each other in a cross-sectional view in a sheet
thickness direction is provided to an inner surface and an outer surface of any one of
the can bottom portion, the can body portion, and the can lid portion,
when viewed from a cross-section that is perpendicular to an extension
direction of the first score groove portion, the first score groove portion and the second
score groove portion have a first score groove bottom portion and a second score
groove bottom portion, which have a radius of curvature R and a relative clearance of
0.045 mm to 0.150 mm, respectively,
the radius of curvature R is more than 0.20 mm and is equal to or less than
1.20 mm, and
any one of the can bottom portion, the can body portion, and the can lid
portion, which has the safety valve, is constituted by a stainless steel sheet in which the
amount of C is limited to 0.040% by mass or less and the amount of S is limited to
0.020% by mass or less, and a tensile strength TS is 400 MPa or less.
[Claim 11]
The battery can for a storage battery according to Claim 10,
wherein the stainless steel sheet is subjected to score processing by a press
forming method.
[Claim 12]
The battery can for a storage battery according to Claim 10 or 11,
wherein the radius of curvature R is 0.30 mm to 1.20 mm.