FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
“JOINING STRUCTURE AND JOINING METHOD THEREOF”
NSK LTD., a Corporation of Japan, 6-3, Ohsaki 1-chome, Shinagawaku,
Tokyo 141-8560, Japan;
The following specification particularly describes the invention and the manner in which it is to
be performed.
- 2 -
DESCRIPTION
JOINING STRUCTURE AND JOINING METHOD THEREOF
5 Technical Field
[0001]
The present invention relates to a joining structure and
a joining method thereof, and particularly, relates to a
joining structure formed by crimping joint of a shaft member
10 and a thin-walled cylindrical member, and to a joining method
thereof.
Background Art
[0002]
15 Heretofore, a pipe joint described in Patent Literature
1 has been mentioned as a joining structure, which fits a
thin-walled cylindrical member to a shaft member such as a
solid shaft or a hollow shaft, crimps the thin-walled
cylindrical member to then fix the thin-walled cylindrical
20 member to the shaft member.
As shown in FIG. 14, in the pipe joint of Patent
Literature 1, a connecting pipe 103 (thin-walled cylindrical
member) is fitted to an outer circumference of a second pipe
102 (shaft member) fitted to an outer circumference of a first
25 pipe 101. Then, a plurality of spots in an axial length
direction of the connecting pipe 103 is crimped at crimped
portions 104a and 104b.
- 3 -
In the connecting pipe 103, a wall thereof is gradually
thinned from one end thereof to other end thereof, and a crimp
ratio of the crimped portion 104a on a thin-wall side is set
smaller than a crimp ratio of the crimped portion 104b on a
5 thick-wall side. As a result, the second pipe 102 is
prevented from falling out by the crimped portion 104b having
a larger crimp ratio. Meanwhile, cutoff of the second pipe
102, which is caused by a tensile stress, is prevented by the
crimped portion 104a having a smaller crimp ratio.
10
Citation List
Patent Literature
[0003]
PTL 1: JP H11-325360 A
15
Summary of Invention
Technical Problem
[0004]
However, in the joining structure described in Patent
20 Literature 1, it has been extremely difficult to ensure
joining strength in a rotation direction (circumferential
direction) of the shaft member and the thin-walled
cylindrical member.
For example, in a case of reducing a diameter of the
25 thin-walled cylindrical member and crimp-joining the
thin-walled cylindrical member to the shaft member, both
thereof are joined to each other by frictional force of
contact surfaces of both thereof. However, in such a joined
- 4 -
state, since springback of the thin-walled cylindrical member
has been present, it has been difficult to appropriately
control a contact surface pressure between the thin-walled
cylindrical member and the shaft member, and it has been
5 difficult to ensure the joining strength.
In particular, in a case where the shaft member and the
thin-walled cylindrical member are made of raw materials such
as steel and aluminum, which are different from each other,
then in the joining of these shaft member and thin-walled
10 cylindrical member, it is conceived that looseness occurs due
to a linear expansion coefficient difference between the two
members depending on an atmospheric temperature.
[0005]
Moreover, there is also a method of fixing the rotation
15 direction by providing the shaft member side with a groove
parallel to the axial direction and crimping the thin-walled
cylindrical member to the groove; however, also in this method,
a gap sometimes occurs between the groove and the thin-walled
cylindrical member due to the springback of the thin-walled
20 cylindrical member. As a result, a backlash in the rotation
direction has sometimes occurred in the joining of the shaft
member and the thin-walled cylindrical member.
In this connection, the present invention has been made
by focusing on the problem mentioned above, and it is an object
25 of the present invention to provide a joining structure
capable of suitably obtaining the joining strength of the
members which compose the joining structure, and to provide
a joining method thereof.
- 5 -
Solution to Problem
[0006]
A certain embodiment of a joining structure for achieving
5 the above-described object includes: a shaft member; and a
thin-walled cylindrical member that fits an inner
circumferential surface thereof to an outer circumferential
surface of the shaft member,
wherein the thin-walled cylindrical member has: a first
10 crimped portion, in which an axially intermediate portion is
reduced in diameter in a radial direction, and is crimped
along a first V-shaped groove provided on the circumferential
surface of the shaft member; and a second crimped portion,
in which an end surface is folded radially inward, and is
15 crimped along a second V-shaped groove provided on the
circumferential surface of the shaft member.
Here, in the above-described joining structure, the
second V-shaped groove may form a cross-sectional shape
asymmetric in the axial direction, in which a raise angle on
20 an end portion side receiving the thin-walled cylindrical
member may be larger than a raise angle on an opposite side
to the end portion.
[0007]
Moreover, in the above-described joining structure, the
25 second crimped portion may be formed only on a part in a
circumferential direction of the end surface of thin-walled
cylindrical member, or the second crimped portions may be
formed at an equal interval.
- 6 -
Furthermore, in the above-described joining structure,
a material of the shaft member and a material of the
thin-walled cylindrical member may be different metals each
other.
5 Moreover, in the above-described joining structure, it
is preferable that a lap margin of the second V-shaped groove
and the thin-walled cylindrical member be equal to or less
than a thickness of the thin-walled cylindrical member.
[0008]
10 Moreover, a certain embodiment of a joining method of
a joining structure, which fits a shaft member and a
thin-walled cylindrical member to each other so that an outer
circumferential surface of the shaft member and an inner
circumferential surface of the thin-walled cylindrical
15 member can abut against each other, includes:
a first crimped portion forming step of forming a first
crimped portion by reducing an axially intermediate portion
of the thin-walled cylindrical member in a radial direction,
the first crimped portion being crimped along a first V-shaped
20 groove provided on a circumferential surface of the shaft
member; and
a second crimped portion forming step of forming a second
crimped portion by folding an end surface of the thin-walled
cylindrical member radially inward in a state where the
25 thin-walled cylindrical member covers a second V-shaped
groove, the second crimped portion being crimped along a
second V-shaped groove provided on the circumferential
surface of the shaft member.
- 7 -
Here, in the above-described joining method of a joining
structure, the second crimped portion may be formed only on
a part in a circumferential direction of the end surface of
thin-walled cylindrical member, or the second crimped
5 portions may be formed at an equal interval.
Advantageous Effects of Invention
[0009]
In accordance with the present invention, there can be
10 provided: the joining structure capable of suitably obtaining
the joining strength of the members which compose the joining
structure; and the joining method thereof.
Brief Description of Drawings
15 [0010]
FIG. 1 is a perspective view showing a configuration in
a certain embodiment of a joining structure;
FIG. 2 is a partial cross-sectional view showing the
configuration in the certain embodiment of the joining
20 structure;
FIG. 3 is a partial cross-sectional view of a main portion,
showing the configuration in the certain embodiment of the
joining structure;
FIG. 4 is a partial cross-sectional view showing a state
25 before a second crimped portion forming step in a certain
embodiment of a joining method of the joining structure;
FIG. 5 is a partial cross-sectional view of the main
portion, showing the state before the second crimped portion
- 8 -
forming step in the certain embodiment of the joining method
of the joining structure;
FIGS. 6A to 6C are views showing steps in the certain
embodiment of the joining method of the joining structure:
5 FIG. 6A is a view showing the state before the second crimped
portion forming step; FIG. 6B is a view showing a state of
the second crimped portion forming step; and FIG. 6C is a view
showing a state after the second crimped portion forming step;
FIGS. 7A and 7B are partial cross-sectional views showing
10 a joining method by a second crimped portion in the certain
embodiment of the joining method of the joining structure:
FIG. 7A is a view showing the state before the second crimped
portion forming step; and FIG. 7B is a view showing the state
after the second crimped portion forming step;
15 FIGS. 8A and 8B are partial cross-sectional views showing
the joining method by the second crimped portion in the
joining method of the joining structure: FIG. 8A is a view
showing a state before the second crimped portion forming step
in a mode where a thin-walled cylindrical member does not
20 cover a second V-shaped groove; and FIG. 8B is a view showing
the state after the second crimped portion forming step;
FIG. 9 is a perspective view showing a configuration in
another embodiment of the joining structure;
FIG. 10 is a perspective view showing the configuration
25 in the other embodiment of the joining structure;
FIGS. 11A and 11B are partial cross-sectional views
showing a configuration of a first crimped portion in the
other embodiment of the joining structure: FIG. 11A shows a
- 9 -
case where a raise angle of a first V-shaped groove is 45°;
and FIG. 11B shows a case where the raise angle of the first
V-shaped groove is 60° and 30°;
FIG. 12 is a graph showing joining strength in a rotation
5 direction of a shaft member and the thin-walled cylindrical
member, in which a relative torque between the shaft member
and the thin-walled cylindrical member is shown on a vertical
axis, and a relative angle between the shaft member and the
thin-walled cylindrical member is shown on a horizontal axis;
10 FIG. 13A is a partial cross-sectional view showing a
positional relationship between the second V-shaped groove
and the thin-walled cylindrical member at a time of joining
the same; and FIG. 13B is a graph showing joining strength
in the rotation direction of the shaft member and the
15 thin-walled cylindrical member; and
FIG. 14 is a partial cross-sectional view showing a
configuration of a conventional joining structure.
Description of Embodiments
20 [0011]
A description is made below of embodiments of a joining
structure according to the present invention and a joining
method thereof with reference to the drawings.
(Joining structure)
25 FIG. 1 is a perspective view showing a configuration in
a certain embodiment of a joining structure according to the
present invention. Moreover, FIG. 2 is a partial
cross-sectional view showing the configuration in the certain
- 10 -
embodiment of the joining structure according to the present
invention. Furthermore, FIG. 3 is a partial cross-sectional
view of a main portion, showing the configuration in the
certain embodiment of the joining structure according to the
5 present invention.
As shown in FIG. 1 to FIG. 3, a joining structure 1 of
this embodiment includes: a shaft member 10; and a thin-walled
cylindrical member 20 that fits an inner circumferential
surface thereof to an outer circumferential surface of the
10 shaft member 10.
In the shaft member 10, a plurality of V-shaped grooves
11 is provided in an axial direction around an entire
circumferential surface thereof. These V-shaped grooves 11
are provided, for example, in order of a first V-shaped groove
15 11A and a second V-shaped groove 11B from an end portion of
the shaft member 10, which receives the thin-walled
cylindrical member 20.
[0012]
The thin-walled cylindrical member 20 includes: a first
20 crimped portion 21, in which an axially intermediate portion
is reduced in diameter in a radial direction, and is crimped
along the first V-shaped groove 11A of the shaft member 10;
and a second crimped portion 22, in which an end surface 20a
is folded radially inward, and is crimped along the second
25 V-shaped groove 11B of the shaft member 10. In this
embodiment, each of the first crimped portion 21 and the
second crimped portion 22 is provided around the entire
circumferential surface of the thin-walled cylindrical
- 11 -
member 20. Note that processing for the first crimped portion
is not limited to processing by mechanical crimping, and the
first crimped portion just needs to be a constriction portion,
which is formed by a diameter reduction method by
5 electromagnetic force, and the like, and roughly goes along
the first V-shaped groove.
Moreover, preferably, the second V-shaped groove 11B
forms a cross-sectional shape asymmetric in the axial
direction, in which a raise angle of an end side that receives
10 the thin-walled cylindrical member 20 is set larger than a
raise angle of an opposite side to the above-described end
portion (refer to FIGS. 7A and 7B).
[0013]
(Joining method of joining structure)
15 Next, a description is made of a joining method of the
joining structure shown in FIGS. 1 to 3.
FIG. 4 is a partial cross-sectional view showing a state
before a second crimped portion forming step in the certain
embodiment of the joining method of the joining structure.
20 Moreover, FIG. 5 is a partial cross-sectional view of the main
portion, showing a state before the second crimped portion
forming step in the certain embodiment of the joining method
of the joining structure.
Moreover FIGS. 6A to 6C are views showing steps in the
25 certain embodiment of the joining method of the joining
structure: FIG. 6A is a view showing the state before the
second crimped portion forming step; FIG. 6B is a view showing
a state of the second crimped portion forming step; and FIG.
- 12 -
6C is a view showing a state after the second crimped portion
forming step. Furthermore, FIGS. 7A and 7B are partial
cross-sectional views showing a joining method by a second
crimped portion in the certain embodiment of the joining
5 method of the joining structure: FIG. 7A is a view showing
the state before the second crimped portion forming step; and
FIG. 7B is a view showing the state after the second crimped
portion forming step.
[0014]
10 The joining method of the joining structure of this
embodiment includes a first crimped portion forming step and
the second crimped portion forming step after fitting the
shaft member 10 and the thin-walled cylindrical member 20 so
that the outer circumferential surface of the shaft member
15 10 and the inner circumferential surface of the thin-walled
cylindrical member 20 can abut against each other.

As shown in FIG. 4, the first crimped portion forming
step is a step of forming the first crimped portion 21 by
20 reducing the diameter of the axially intermediate portion of
the thin-walled cylindrical member 20 fitted to the shaft
member 10 and crimping the intermediate portion along the
first V-shaped groove 11A of the shaft member 10.
[0015]
25
Moreover, as shown in FIG. 5, the second crimped portion
forming step is a step of forming the second crimped portion
22 by folding the end surface 20a of the thin-walled
- 13 -
cylindrical member 20 radially inward of the thin-walled
cylindrical member 20 and crimping the end surface 20a along
the second V-shaped groove 11B of the shaft member 10 in a
state where the thin-walled cylindrical member 20 covers the
5 second V-shaped groove 11B.
Here, in the second crimped portion forming step, as
shown in FIG. 5, the thin-walled cylindrical member 20 before
folding the end surface 20a radially inward is fitted to the
outer circumference of the shaft member 10 to a range of
10 completely covering the first V-shaped groove 11A provided
on the shaft member 10, and from this state, is folded
following compression. In such a way, a stress in a
compression direction remains between the first crimped
portion 21 and the second crimped portion 22.
15 [0016]
Moreover, the second crimped portion forming step is
performed by using a die 30 as shown in FIGS. 6A to 6C. The
die 30 is a member that forms an annular shape, in which an
inner circumferential surface 31 is composed by including:
20 a large-diameter portion 31A having an inner diameter
substantially equal to an outer diameter of the thin-walled
cylindrical member 20; a small-diameter portion 31B having
an inner diameter substantially equal to an inner diameter
of the thin-walled cylindrical member 20a; and a tapered
25 surface 31C that connects these to each other. Note that the
large-diameter portion 31A, the small-diameter portion 31B,
the tapered surface 31C and connection portions thereamong
are composed of a smooth curved surface.
- 14 -
In the second crimped portion forming step, first, as
shown in FIG. 6A, for the shaft member 10 and the thin-walled
cylindrical member 20 after the first crimped portion forming
step, an axial direction of the die 30 and the axial direction
5 of the shaft member 10 and the thin-walled cylindrical member
20 are matched with each other, and the die 30 is set.
[0017]
Next, as shown in FIG. 6B, in order that the
large-diameter portion 31A can abut against the outer
10 circumferential surface of the thin-walled cylindrical
member 20, and that the small-diameter portion 31B can abut
against the outer circumferential surface of the shaft member
10, the die 30 is fitted to the shaft member 10 and the
thin-walled cylindrical member 20, and the shaft member 10
15 and the thin-walled cylindrical member 20 are inserted
through the die 30 until the end portion 20a is caught by the
tapered surface 31C.
Next, as shown in FIG. 6C, from a state where the end
portion 20a is caught by the tapered surface 31C, the die 30
20 is pushed onto the thin-walled cylindrical member 20 in an
orientation from the second V-shaped groove 11B of the shaft
member 10 toward the first V-shaped groove 11A thereof, and
the end surface 20a of the thin-walled cylindrical member 20
is folded radially inward (inside of the second V-shaped
25 groove 11B).
[0018]
Here, a description is made in detail of functions in
an event of folding the end surface 20a of the thin-walled
- 15 -
cylindrical member 20 radially inward (inside of the second
V-shaped groove 11B). FIG. 7A shows a state before the end
surface 20a of the thin-walled cylindrical member 20 is folded
radially inward of the thin-walled cylindrical member 20 in
5 a state where the thin-walled cylindrical member 20 covers
the second V-shaped groove 22. Moreover, FIG. 7B shows a
state after the end surface 20a is folded radially inward of
the thin-walled cylindrical member 20. As shown in FIG. 7A,
in the state before the end surface 20a is folded radially
10 inward of the thin-walled cylindrical member 20, the first
crimped portion 21, which is reduced in diameter and crimped,
floats off from the first V-shaped groove 11A by springback.
In this state, a contact surface pressure between the first
V-shaped groove 11A and the first crimped portion 21 of the
15 thin-walled cylindrical member 20 is low, and joining force
generated thereby becomes small.
[0019]
Accordingly, in this embodiment, as shown in FIG. 7B,
the end surface 20a of the thin-walled cylindrical member 20
20 is folded radially inward (inside of the second V-shaped
groove 11B) while being compressed, whereby such a one-side
side surface of the first crimped portion 21, which has
floated off by the springback, is tightly brought into surface
contact with a side surface of the first V-shaped groove 11A,
25 and turns to a state of ensuring the contact surface together
with the second crimped portion 22.
At this time, as mentioned above, the thin-walled
cylindrical member 20 is folded while being compressed,
- 16 -
whereby a suitable surface pressure is generated on each of
the contact surfaces, thus making it possible to obtain the
joining strength.
[0020]
5 Moreover, a description is made below of a reason why
it is preferable that the thin-walled cylindrical member 20
be in the state of covering the second V-shaped groove 11B
in the event of folding the end surface 20a radially inward
of the thin-walled cylindrical member 20.
10 FIGS. 8A and 8B are partial cross-sectional views showing
the joining method by the second crimped portion in the
joining method of the joining structure: FIG. 8A is a view
showing a state before the second crimped portion forming step
in a mode where the thin-walled cylindrical member does not
15 cover the second V-shaped groove; and FIG. 8B is a view showing
the state after the second crimped portion forming step.
As shown in FIGS. 8A and 8B, when the end portion 20a
is folded from a state where the thin-walled cylindrical
member 20 does not completely cover the second V-shaped groove
20 11B to allow partial exposure of the second V-shaped groove
11B, then the stress in the compression direction does not
remain between the first crimped portion 21 and the second
crimped portion 22, and the first crimped portion 21 is also
left in the state of floating off by the springback. That
25 is to say, in such a state, it is apprehended that the contact
surface between the shaft member 10 and the thin-walled
cylindrical member 20 may not be suitably ensured, resulting
- 17 -
in an occurrence of a decrease and dispersion of the joining
strength.
[0021]
(Other embodiments)
5 FIG. 9 and FIG. 10 are perspective views showing
configurations in other embodiments of the joining structure.
Moreover, FIGS. 11A and 11B are partial cross-sectional views
showing configurations of the first crimped portion in the
other embodiments of the joining structure: FIG. 11A shows
10 a case where a raise angle of the first V-shaped groove is
45°; and FIG. 11B shows a case where a raise angle of the first
V-shaped groove is 60° and 30°. Note that, in the description
of this embodiment, a description of a duplicate
configuration with that of the above-mentioned embodiment is
15 omitted.
As shown in FIG. 9 and FIG. 10, in this embodiment, second
crimped portions 23 are formed not on an entire circumference
of the end surface 20a of the thin-walled cylindrical member
20 but only on a part in a circumferential direction of the
20 end surface 20a. It is preferable that the second crimped
portions 23 in such a mode be formed at an equal interval in
the circumferential direction of the thin-walled cylindrical
member 20.
[0022]
25 For example, as shown in FIG. 9, a circumferential width
dimension of one second crimped portion 22 may be set at
approximately 5% of a dimension of an entire circumference
of the thin-walled cylindrical member 20, and such second
- 18 -
crimped portions 23 thus formed may be formed at an equal
interval on three spots in the circumference direction of the
thin-walled cylindrical member 20. Moreover, as shown in FIG.
10, the circumferential width dimension of one second crimped
5 portion 23 may be set at approximately 8% of the dimension
of the entire circumference of the thin-walled cylindrical
member 20, and such second crimped portions 23 thus formed
may be formed at an equal interval on four spots in the
circumference direction of the thin-walled cylindrical
10 member 20.
Here, in a case where the second crimped portion 22 is
formed on the entire circumference of the end surface 20a of
the thin-walled cylindrical member 20 as in the
above-mentioned embodiment (refer to FIG. 1), the stress that
15 remains between the first crimped portion 21 and the second
crimped portion 22 sometimes becomes excessive depending on
structure of the joining structure 1. Such an excessive
stress in the inside of the thin-walled cylindrical member
20 causes creep under an environment of a high temperature.
20 [0023]
Moreover, in a case where a material of the shaft member
10 and a material of the thin-walled cylindrical member 20
are different from each other, repeated strain amplitude
sometimes occurs in the thin-walled cylindrical member 20 due
25 to a thermal expansion difference between the shaft member
10 and the thin-walled cylindrical member 20. Therefore, it
is necessary to control the stress between the first crimped
portion 21 and the second crimped portion 22 (23) to be
- 19 -
constant. It is also possible to control the above-described
stress by controlling a compression amount of the thin-walled
cylindrical member 20 (that is, an engagement margin of a
shoulder portion of the second V-shaped groove 11B and the
5 end surface 20a of the thin-walled cylindrical member 20);
however, in this case, it is necessary to strictly control
the above-described engagement margin, and a tremendous load
is required for controlling tolerances of the respective
components.
10 [0024]
Accordingly, in this embodiment, the plurality of second
crimped portions 23 is partially formed on the end surface
20a, and even in the joining structure 1 having such a
configuration, appropriate joining strength can be obtained
15 by adjusting the stress caused by the second crimped portions
23. Moreover, the second crimped portions 23 are partially
formed, whereby such compression force generated between the
first V-shaped groove 11A and the second V-shaped groove 11B
can be prevented from becoming excessive even if the
20 above-described engagement margin becomes large.
[0025]
Moreover, in this embodiment, as shown in FIGS. 11A and
11B, a cross-sectional shape of the first V-shaped groove 11A,
which goes along the axial direction, is made asymmetric in
25 a similar way to the second V-shaped groove 11B, whereby the
joining strength of the joining structure 1 may be controlled.
For example, as shown in FIG. 11A, the cross-sectional shape
of the first V-shaped groove 11A, which goes along the axial
- 20 -
direction, usually has raise angles (45°) symmetric in the
axial direction. In contrast, as shown in FIG. 11B, the
cross-sectional shape of the first V-shaped groove 11A, which
goes along the axial direction, may be formed as a
5 cross-sectional shape asymmetric in the axial direction, and
a raise angle θ on the end portion 20a side that receives the
thin-walled cylindrical member 20 may be larger than a raise
angle δ on an opposite side to the end portion 20a. For
example, these raise angles θ and δ are 60° and 30°,
10 respectively.
Here, a depth dimension of the first V-shaped groove 11A
is substantially equal to a thickness of the thin-walled
cylindrical member 20 no matter which the cross-sectional
shape in the axial direction may be a symmetric shape or an
15 asymmetric shape.
[0026]
Meanwhile, a depth dimension of the second V-shaped
groove 11B is set smaller than the thickness of the
thin-walled cylindrical member 20. This is in order to
20 sufficiently press-fit the thin-walled cylindrical member 20
into the second V-shaped groove 11B in an event of forming
the second crimped portion 22 by using the die 30 (refer to
FIG. 6) as mentioned above, and when the depth dimension of
the second V-shaped groove 11B is larger than the thickness
25 of the thin-walled cylindrical member 20, a gap is generated
between the second V-shaped groove 11B and the thin-walled
cylindrical member 20, whereby it sometimes becomes difficult
to obtain the joining strength of the joining structure 1.
- 21 -
As shown in FIGS. 11A and 11B, the cross-sectional shape
of the first V-shaped groove 11A, which goes along the axial
direction, is formed symmetric in the axial direction (that
is, a groove side surface is formed into a tapered shape),
5 whereby a contact area between a side surface of the first
V-shaped groove 11A and the shaft member 10 can be largely
ensured. Moreover, as shown in FIG. 11B, when the raise angle
δ on the opposite side to the end portion 20a is reduced, the
suitable joining strength can be obtained by a wedge effect.
10 [0027]
Moreover, the above-described embodiment may be used for
a torque sensor that detects torque generated in a rotation
shaft. As such a torque sensor, a torque sensor having such
a configuration as below is mentioned (for example, refer to
15 JP H11-248562 A). That is to say, the above-described torque
sensor includes: a first rotation shaft and a second rotation
shaft, which are disposed coaxially with each other, and are
coupled to each other through a torsion bar; and a cylindrical
member, which is made of a conductive and non-magnetic
20 material, and is integrated with the second rotation shaft
in a rotation direction so as to surround an outer
circumferential surface of the first rotation shaft.
[0028]
Moreover, a surrounded portion of the first rotation
25 shaft, which is surrounded by at least the cylindrical member,
is formed of a magnetic material, and a groove extended in
the axial direction is formed on the surrounded portion.
Furthermore, in the cylindrical member, a window is formed
- 22 -
so that an overlapping state thereof with the groove can
change in response to a relative rotation position thereof
to the first rotation shaft. Then, the torque is detected
based on an inductance of a coil disposed so as to surround
5 a portion of the cylindrical member, in which the window is
formed.
In the torque sensor having such a configuration, there
has been room for consideration of the matter that holding
force of the cylindrical member for the rotation shafts is
10 varied due to a temperature, and a rotation direction position
and axial position of the cylindrical member with respect to
the rotation shafts are shifted as a result that the holding
force decreases, cause a decrease of detection accuracy.
[0029]
15 Accordingly, the joining structure of the present
invention and the joining structure thereof are employed for
the torque sensor having the above-described configuration,
whereby a torque sensor can be provided, which can prevent
the decrease of the detection accuracy, can perform
20 high-accuracy torque detection with a simple structure, and
in addition, can achieve miniaturization of the device.
FIG. 12 is a graph showing the joining strength in the
rotation direction of the shaft member 10 and the thin-walled
cylindrical member 20, in which a relative torque between the
25 shaft member 10 and the thin-walled cylindrical member 20 is
shown on a vertical axis, and a relative angle between the
shaft member 10 and the thin-walled cylindrical member 20 is
shown on a horizontal axis.
- 23 -
Note that, in FIG. 12, a broken line shows an evaluation
result when the thin-walled cylindrical member 20 is reduced
in diameter and crimped to the V-shaped grooves 11 provided
on the shaft member 10. Moreover, a solid line in FIG. 12
5 shows an evaluation result of the joining structure 1 of the
embodiment shown in FIGS. 8A and 8B.
Here, the joining structure taken as an evaluation target
is one in which the aluminum-made thin-walled cylindrical
member 20 with a plate thickness of less than 1 mm is joined
10 to the steel-made shaft member 10 with an outer diameter of
φ27 mm. Moreover, this evaluation is a result of applying
torque to the joined portions (first crimped portion 21 and
second crimped portion 22) until a relative torsion angle
after removing the torque reaches a prescribed amount.
15 [0030]
As shown in FIG. 12, there was obtained a result that
a difference of approximately two times occurred in the
applied torque until the relative torsion angle reached θ
depending on whether the end portion of the thin-walled
20 cylindrical member 20 was folded. That is to say, in
accordance with the joining structure of this embodiment, it
becomes possible to enhance reliability of the joined
portion.
FIG. 13A is a partial cross-sectional view showing
25 positional relationships between the V-shaped grooves 11
(first V-shaped groove 11A and second V-shaped groove 11B)
and the thin-walled cylindrical member 20 in a similar way
to FIGS. 7A and 7B and FIGS. 8A and 8B. Moreover, FIG. 13B
- 24 -
is a graph showing the joining strength in the rotation
direction of the shaft member and the thin-walled cylindrical
member. Specifically, FIG. 13B is a graph showing the joining
strength in the rotation direction of the shaft member 10 and
5 the thin-walled cylindrical member 20, in which the relative
torque between the shaft member 10 and the thin-walled
cylindrical member 20 is shown on a horizontal axis, and the
relative angle between the shaft member 10 and the thin-walled
cylindrical member 20 is shown on a horizontal axis.
10 [0031]
In FIG. 13A, a broken line shows an evaluation result
of the joining structure 1 in which a lap margin (engagement
margin) △ of the shoulder portion of the second V-shaped
groove 11B and the end surface 20a of the thin-walled
15 cylindrical member 20 is folded from a state of “△ = t/5 (t
is a thickness of the thin-walled cylindrical member 20)”.
Moreover, a solid line in FIG. 13 shows an evaluation result
of the joining structure 1 in which the lap margin △ is folded
from a state equivalent to that of the thickness t of the
20 thin-walled cylindrical member 20.
As shown in FIG. 13, it is confirmed that the joining
structure having a larger lap margin tends to obtain higher
joining strength. This is derived from a difference in stress
generated between the second crimped portion 22 and the second
25 V-shaped groove 11B, and illustrates that the joining
strength can be adjusted within a predetermined range by
adjusting the lap margin.
- 25 -
Note that, when the above-described lap margin is folded
from a state of being set at a fixed amount or more, such a
malfunction sometimes occurs that the thin-walled
cylindrical member 20 is buckled before being folded toward
5 the inside of the second V-shaped groove 11B, the load applied
to the first crimped portion 21 becomes excessive, and desired
holding force cannot be obtained. Based on this fact, it is
preferable that the above-described lap margin be set at the
wall thickness t of the thin-walled cylindrical member 20 or
10 less.
[0032]
As described above, in accordance with the certain
embodiment of the present invention, when the shaft member
10 and the thin-walled cylindrical member 20 are crimp-joined
15 to each other, the first crimped portion 21 is provided in
the intermediate portion of the thin-walled cylindrical
member 20, and in addition, the second crimped portion 22
obtained by folding the end surface 20a of the thin-walled
cylindrical member 20 radially inward is provided therein.
20 Then, the formation of the second crimped portion 22 is
performed while compressing the thin-walled cylindrical
member 20, whereby the stress in the compression direction
remains in the inside of the thin-walled cylindrical member
20 (that is, between the first crimped portion 21 and the
25 second crimped portion 22), and as reaction force thereof,
the surface pressure is generated on the contact surface
between the shaft member 10 and the thin-walled cylindrical
member 20.
- 26 -
By this contact surface pressure, suitable frictional
force is generated between the shaft member 10 and the
thin-walled cylindrical member 20, and the joining strength
in the rotation direction can be obtained.
5 [0033]
Moreover, even in the case where the material of the shaft
member 10 and the material of the thin-walled cylindrical
member 20 are different from each other, for example, even
in the case where the materials are steel and aluminum,
10 respectively, then in accordance with this embodiment, the
stress in the compression direction remains between the first
crimped portion 21 and the second crimped portion 22.
Accordingly, if an expansion difference remains within a
fixed range even if the expansion difference occurs due to
15 the change of the atmospheric temperature, then complete
loosening of the crimp joining of the thin-walled cylindrical
member 20 to the shaft member 10 is extremely rare.
As above, the description has been made of the joining
structure and the joining method thereof; however, the
20 joining structure according to the present invention and the
joining method thereof are not limited to the above-described
embodiments, and are modifiable in various ways without
departing from the spirit of the present invention. For
example, detailed conditions such as the shape of the V-shaped
25 grooves, the shape of the second crimped portion and the
number of the second crimped portions are alterable within
a range where the functions of the present invention are
exerted.
- 27 -
Reference Signs List
[0034]
1 JOINING STRUCTURE
5 10 SHAFT MEMBER
11A FIRST V-SHAPED GROOVE
11B SECOND V-SHAPED GROOVE
20 THIN-WALLED CYLINDRICAL MEMBER
20a END PORTION
10 21 FIRST CRIMPED PORTION
22 SECOND CRIMPED PORTION
23 SECOND CRIMPED PORTION
- 28 -
CLAIMS
1. A joining structure comprising:
a shaft member; and
5 a thin-walled cylindrical member configured to fit an
inner circumferential surface of the thin-walled cylindrical
member to an outer circumferential surface of the shaft
member,
wherein the thin-walled cylindrical member includes: a
10 first crimped portion, in which an axially intermediate
portion is reduced in diameter in a radial direction, and is
crimped along a first V-shaped groove provided on the outer
circumferential surface of the shaft member; and a second
crimped portion, in which an end surface is folded radially
15 inward, and is crimped along a second V-shaped groove provided
on the outer circumferential surface of the shaft member.
2. The joining structure according to claim 1,
wherein the second V-shaped groove has a cross-sectional
20 shape asymmetric in the axial direction, in which a raise
angle on an end portion side receiving the thin-walled
cylindrical member is larger than a raise angle on an opposite
side to the end portion.
25 3. The joining structure according to either one of
claims 1 and 2, wherein the second crimped portion is formed
only on a part in a circumferential direction of the end
surface of thin-walled cylindrical member.
- 29 -
4. The joining structure according to claim 3,
wherein the second crimped portions are formed at an equal
interval in the circumferential direction of the end surface
5 of thin-walled cylindrical member.
5. The joining structure according to any one of
claims 1 to 4, wherein a material of the shaft member and a
material of the thin-walled cylindrical member are made of
10 different metals each other.
6. The joining structure according to any one of
claims 1 to 5, wherein a lap margin of the second V-shaped
groove and the thin-walled cylindrical member is equal to or
15 less than a thickness of the thin-walled cylindrical member.
7. A joining method of a joining structure, which
fits a shaft member and a thin-walled cylindrical member to
each other so that an outer circumferential surface of the
20 shaft member and an inner circumferential surface of the
thin-walled cylindrical member can abut against each other,
the joining method comprising:
a first crimped portion forming step of forming a first
crimped portion by reducing an axially intermediate portion
25 of the thin-walled cylindrical member in a radial direction,
the first crimped portion being crimped along a first V-shaped
groove provided on a circumferential surface of the shaft
member; and
- 30 -
a second crimped portion forming step of forming a second
crimped portion by folding an end surface of the thin-walled
cylindrical member radially inward in a state where the
thin-walled cylindrical member covers a second V-shaped
5 groove, the second crimped portion being crimped along a
second V-shaped groove provided on the circumferential
surface of the shaft member.
8. The joining method of a joining structure
10 according to claim 7, wherein the second crimped portion
forming step forms the second crimped portion only on a part
in a circumferential direction of the end surface of
thin-walled cylindrical member.
15 9. The joining method of a joining structure
according to claim 8, wherein the second crimped portion
forming step forms the second crimped portions at an equal
interval in the circumferential direction of the end surface
of thin-walled cylindrical member.
20
- 31 -
ABSTRACT
Provided are: a joining structure capable of suitably
obtaining joining strength between components which compose
5 the joining structure; and a joining method thereof. For this
purpose, a joining structure (1) includes: a shaft member
(10); and a thin-walled cylindrical member (20) that fits an
inner circumferential surface thereof to an outer
circumferential surface of the shaft member (10).
10 The thin-walled cylindrical member (20) has: a first crimped
portion (21), in which an axially intermediate portion is
reduced in diameter in a radial direction, and is crimped to
the shaft member (10); and a second crimped portion (22), in
which an end surface (20a) is folded radially inward, and is
15 crimped to the shaft member (10).