[Name of Document] Specification
[Title of the Invention] METHOD OF PRODUCING L-SHAPED
PRODUCT
[Field of the Invention]
[ 0 0 0 1 ]
The present invention relates to a method of
producing an L-shaped product, and in particular to a
method of producing an L-shaped member, which has a hatshaped
cross section, from a blank sheet of metal. In
particular, the L-shaped member is used for a lower front
pillar of an automobile having a monocoque body.
[Background Art]
[0002]
A frame structure of an automobile having a
monocoque body is formed by joining a plurality of frame
parts, produced by stamping sheet metal. A reinforcement
of a lower front pillar, joined to the frame members such
as an outer reinforcement of a side sill, comprises an Lshaped
member having an L-shaped flat top wall, side
walls extending along the edges of the top wall and
flanges connected to the side wall. When such an Lshaped
product is produced by stamping a blank sheet of
metal, there are problems such as generation of wrinkles
in the top wall and cracks in an inside flange of the Lshaped
product.
[0003]
If such an L-shaped product is formed by a drawing
process, generation of wrinkles can be avoided. In
drawing, however, it is necessary to provide a blank with
30 a relatively large margin, which results in lower yield
rate and higher production cost.
[0004]
Further, for drawing processes, it is necessary to
use a blank of relatively high extensibility, whereby a
35 blank for drawing is made of a relatively low-strength
material. Thus, in order to increase the collision
performance of automobiles, a relatively thick blank is
required, which results in an increase in the weight of
the frame structure, and thus higher material cost.
[0005]
Various bending methods have been proposed for
producing a component having uniform cross section such
as simple hat-shaped cross section, or Z-shaped cross
section as described in Patent Publications 1-4.
However, Patent Publications 1-4 do not disclose a method
of producing a more complicated L-shaped member described
above.
[Prior Art Documents]
[Patent Publication]
[0006]
Patent Publication 1: Japanese Unexamined Patent
Application Publication No. 2003-103306
Patent Publication 2: Japanese Unexamined Patent
Application Publication No. 2004-154859
Patent Publication 3: Japanese Unexamined Patent
Application Publication No. 2006-015404
Patent Publication 4: Japanese Unexamined Patent
Application Publication No. 2008-307557
[Summary of the Invention]
[Problem to be solved by the Invention]
[0007]
Thus, the present invention is directed to solve the
above-described problem of the prior art, and therefore,
the object of the present invention is to provide a
method of producing an L-shaped product by stamping a
blank having a relatively small margin, as compared with
conventional drawing process, without generation of
cracks and/or wrinkles. Another object of the present
invention is to provide a method of producing a
satisfactory L-shaped product by using a blank made of a
high tensile strength steel sheet having lower
extensibility as well as a steel sheet having high
extensibility and low strength.
[Means for solving the Problem]
[0008]
In order to obtain the above-described object,
according to the present invention, there is provided a
method of producing an L-shaped product which includes an
5 L-shaped flat top wall having first and second legs
connected to each other so as to define inside and
outside edges, an inside wall extending along and
connected to the inside edge of the top wall and forming
a first angle relative to the top wall, and an outside
wall extending along and connected to the outside edge of
the top wall and forming a second angle relative to the
top wall, each of the inside and outside walls being
terminated by a flange substantially parallel to the top
wall, the method comprising the steps of:
providing sheet metal material; providing a drawing
die assembly; and stamping the sheet metal material with
the drawing die assembly to produce an intermediate
product which includes an L-shaped flat top wall having
first and second legs corresponding to the first and
second legs of the L-shaped flat top wall of the L-shaped
product, and inside and outside walls corresponding to
the inside and outside walls of the completed L-shaped
product, and flanges corresponding to the flanges of the
completed L-shaped product;
wherein the intermediate product includes a first
region adjacent to a free end of the first leg and an
opposite second region adjacent to the second leg, and
wherein, in the first region, the angle between each of
the inside and outside walls relative to the top wall of
the intermediate product substantially coincide with the
first and second angles of the completed L-shaped
product, and wherein, in the second region, the angle
between each of the inside and outside walls relative to
the top wall gradually increases toward the second leg;
the method further comprising the steps of:
providing a bending die assembly; stamping the
intermediate product by the bending die assembly to
produce the completed L-shaped product.
[Effect of the Invention]
[0009]
According to the present invention, an intermediate
product is produced by stamping a blank sheet of metal by
means of a drawing die assembly, and an L-shaped product
is produced by further stamping the intermediate product
by means of a bending die assembly. Thus, in the
stamping process by means of the bending die assembly,
10 the second leg is bent toward the inside curved portion.
The region of the top wall where material is usually
accumulated in excess is drawn by the bending process so
that material flows out and generation of wrinkles can be
suppressed. On the other hand, the inside flange
15 adjacent to the inside curved portion where, in an
ordinary drawing process, the wall thickness is reduced
and may result in cracks forming, and therefore is
compressed by the bending deformation so that reduction
of the wall thickness is suppressed and generation of
20 wrinkles or cracks can be avoided.
[ 0 0 10 ]
In this case, a relatively large margin which has
been required in ordinary drawing, does not need to be
provided in a blank, so that it is possible to reduce the
25 size of a blank. A product can be formed not only from a
steel sheet having high extensibility and relatively low
strength but also from high tensile strength steel
material which has been difficult to be shaped in prior
art, so that strength of an L-shaped product can be
30 increased and thickness of a blank can be reduced, which
contributes to weight reduction of the frame structure of
an automobile.
[ 0 0 11 ]
In the case where an outside curved portion
35 extending in the shape of circular arc is provided in the
outside wall opposite to the inside curved portion of an
L-shaped product, generation of wrinkles in the top wall
can be avoided by bulging the side edge between the
outside wall and the top wall in the shape of circular
arc upward from the top wall in the outside curved
portion.
[Brief Description of the Drawings]
[0012]
Figure 1 is a perspective view showing an L-shaped
product to be produced;
Figure 1A is a section of the L-shaped product along
line a-a in Figure 1;
Figure 2 is a perspective view showing an L-shaped
panel drawn;
Figure 3 is a section showing drawing process;
Figure 4 is a section showing bending process at the
time of start;
Figure 5 is a section showing bending process;
Figure 6 is a plan view showing an intermediate
product;
Figure 6A is a section showing the intermediate
product along line A-A in Figure 6;
Figure 6B is a section showing the intermediate
product along line B-B in Figure 6;
Figure 6C is a section showing the intermediate
product along line C-C in Figure 6;
25 Figure 6D is a section showing the intermediate
product along line D-D in Figure 6;
Figure 7 is a view useful for explaining movement of
blank material during bending process;
Figure 8 is a view useful for explaining movement of
30 blank material during bending process;
Figure 9A is a plan view showing a portion of the Lshaped
product after bending;
Figure 9B is a partial side view showing the Lshaped
product as seen in the direction of arrow E-E in
35 Figure 9A;
Figure 9C is a section showing the L-shaped product
along line F-F in Figure 9A;
Figure 10 is a perspective view showing an L-shaped
member after bending process;
Figure 11 is a perspective view showing an L-shaped
member after bending process;
Figure 12 is a perspective view of an L-shaped
product in one embodiment;
Figure 13 is a plan view showing the blank in the
embodiment of Figure 12;
Figure 14 is a schematic view showing the drawing
die assembly used in the drawing process in the
embodiment of Figure 12;
Figure 14A is a perspective view showing lower
surface of the drawing die assembly of Figure 14;
Figure 15 is a perspective view showing an
15 intermediate product after drawing in the embodiment of
Figure 12;
Figure 16 is a schematic view showing the bending
die assembly used in bending process in the embodiment of
Figure 12;
20 Figure 17A is a perspective view showing an L-shaped
product in another embodiment;
Figure 17B is a perspective view showing the Lshaped
product of Figure 17A as viewed from an opposite
side;
25 Figure 18 is a plan view showing the L-shaped
product of Figure 17A together with sections;
Figure 19 is a partial enlarged perspective view
showing the outside curved portion of the L-shaped
product of Figure 17A;
30 Figure 19A is a partial enlarged side view showing
the outside curved portion of the L-shaped product of
Figure 17A;
Figure 19B is a partial enlarged plan view showing
the outside curved portion of the L-shaped product of
35 Figure 17A;
Figure 20 is a schematic view showing the bending
die assembly used in drawing process in the embodiment of
Figure 17A;
Figure 21 is a schematic view showing the bending
die assembly used in bending process in the embodiment of
Figure 17A;
Figure 22 is a plan view showing the blank used in
the embodiment of Figure 17A;
Figure 23 is a perspective view showing an
intermediate product after drawing in the embodiment of
Figure 17A;
10 Figure 23A is a plan view showing the intermediate
product of Figure 23 together with sections.
[Embodiment for carrying out the Invention]
[0013]
Preferred embodiments of the present invention will
15 be described below.
Referring to Figures 1 and 1A, an L-shaped product
10, with a hat-shaped cross section is produced by a
stamping process according to the present invention. The
L-shaped production 10 comprises a top wall 12
20 substantially in the form of L having first and second
legs 12a and 12b connected to each other. The L-shaped
product 10 further comprises an inside wall 14 extending
along an inside edge 12c of the top wall 12 and forming a
first angle al relative to the top wall 12, and an outside
25 wall 16 extending along an outside edge 12d of the top
wall 12 and forming a second angle a2 relative to the top
wall 12. Each of the inside and outside walls 14 and 16
is terminated by inside and outside flanges 18 and 20
extending substantially parallel to the top wall 12. The
30 first and second angles al and a2 are in particular within
the range of 90 to 115O.
[0014]
Further, the L-shaped product 10 defines an inside
curved portion 22 and an outside curved portion 24
35 between the first and second legs 12a and 12b. The Lshaped
product can be used in a frame structure of an
automobile having a monocoque body as a lower portion of
a front pillar, extending from the lower edge of a wind
shield to a side sill. The first leg 12a is adapted to
be connected to an upper portion of the front pillar
which extends along a side edge of the wind shield. The
second leg 12b is adapted to be connected to the side
sill. The outside curved portion 24 extends
substantially along a circular arc so as to form a part
of a wheel house of a front wheel.
10 [0015]
Conventionally, in order to produce an L-shaped
product such as shown in Figure 1, a blank, made of sheet
metal and having a relatively large margin, is provided.
By drawing the blank, a drawn panel 100 as shown in
15 Figure 2 is formed, then excess portions are removed from
the drawn panel 100. In this method, wall thickness
becomes excessive in a portion I in the top wall 102
between first and second legs 102a and 102b of the drawn
panel, whereby wrinkles are generated, while in a curved
20 portion I1 of the inside flange 108 between the first and
second legs 102a and 102b, the amount of material becomes
insufficient, whereby cracks may occur in the flange 108.
In order to prevent generation of wrinkles and cracks, a
steel sheet having high extensibility and relatively low
25 strength is used. The steel sheet is extended by
providing a relatively large margin in a portion to be
formed into the second leg of the L-shaped product so
that the steel sheet is sufficiently clamped in order to
prevent material inflow during drawing process, and thus
30 generation of wrinkles in the top wall is prevented.
[0016]
Referring to Figure 2, in order to produce an Lshaped
product 10, according to the present invention,
firstly, a drawing die assembly 30 is provided. The
35 drawing die assembly 30 comprises a drawing die 32, a
holder 34 disposed to face the drawing die 32 and a punch
36. The drawing die 32 has a recess 32a having a shape
corresponding to the shapes of a top wall 52 and inside
and outside walls 54 and 56 of an intermediate product
50. The drawing die has further a flank 32b defining a
flat surface extending along the peripheral edge of the
5 recess 32a. The holder 34 has a flat clamping surface
34a facing the flank 32b of the,drawing die 32. In
particular, the clamping surface 34a of the holder 34 has
a substantially U-shaped form with one open end so as not
to clamp a portion of the blank 26 corresponding to the
10 edge 52e adjacent to the second leg 52b opposite to the
first leg 52a in the intermediate product 50. The punch
36 has an outer shape 36a corresponding to the shape of
the recess 32a of the drawing die 32. A blank 26 of a
flat sheet metal having a developed shape of completed
15 product is positioned between the drawing die 32 and the
holder 34. The blank 26 is clamped with the flank 32b of
the drawing die 32 and the clamping surface 34a of the
holder 34 along the peripheral edge of the recess 32a of
the drawing die 32. Then, the punch 36 is pressed into
20 the recess 32a of the drawing die 32 to produce an
intermediate product 50.
[0017]
Referring to Figure 6, the intermediate product 50
comprises a substantially L-shaped flat top wall 52
25 having first and second legs 52a and 52b, respectively
corresponding to the first and second legs 12a and 12b of
the top wall 12 of the completed L-shaped product 10.
The intermediate product 50 further comprises inside and
outside walls 54 and 56 extending along inside and
30 outside edges 52c and 52d of the top wall 52, and
respectively corresponding to the inside and outside
walls 14 and of the L-shaped product 10. The
intermediate product further includes inside and outside
flanges 58 and 60, respectively corresponding to the
35 inside and outside flanges 18 and 20 of the L-shaped
product 10.
[ 0 0 18 ]
The intermediate product 50 includes a first region
adjacent to the free end of the first leg 52a and a
second region adjacent to the second leg 52b. In the
first region, as shown in Figures 6A and 6B, which show
the sections of the intermediate product 50 along lines
A-A and B-B of Figure 6, first angles PIA and P1B and
second angles P2A and P2Bf formed by each of the inside and
outside walls 54 and 56 relative to the top wall 52, are
substantially equal to the first and second angles al and
a2 formed by the inside and outside walls 14 and 16
relative to the top wall 12 of the completed L-shaped
product 10, and are in the range of 90-115'. Thus, in the
first region, the shape of the intermediate product 50
substantially coincides with the corresponding shape of
the completed L-shaped product 10.
[0019]
In the second region, as shown in Figure 6, which is
a section of the intermediate product 50 along line C-C
of Figure 6, first and second angles Pic and P2C, formed by
each of the inside and outside walls 54 and 56 relative
to the top wall 52, are larger than the first and second
angles al and a2 of the completed L-shaped product 10.
The first and second angles gradually increase toward the
second leg 52b. In particular, the first and second
angles PIC and P2C of the intermediate product 50 in C-C
section are in the range of 120-180'. Further, in the
section along line D-D in Figure 6, the first angle of
the intermediate product 50 disappears, and thus, in this
portion, that is, in the vicinity of the edge 52e
adjacent to the second leg 52b of the intermediate
product 50, the inside wall 54 extends substantially in
the same plane as the top wall 52.
[0020]
In order to obtain the final completed L-shaped
product 10 from the intermediate product 50 thus formed,
a bending die assembly 40 is provided. Referring to
Figures 3 and 4, the bending die assembly 40 comprises an
anvil 42 having an exterior shape 42a corresponding to
the shape of the completed L-shaped product 10, a pad 44
having an abutting surface 44a for clamping the top wall
52 of the intermediate product 50 in cooperation with the
anvil 42 and a bending die 46 for pressing the
intermediate product 50 to the anvil 42. The anvil 42
includes a flat top surface 42b facing the abutting
surface 44a of the pad 44. The L-shaped top wall 52 of
intermediate product 50 is disposed between the top
surface 42b of the anvil 42 and the abutting surface 44a
of the pad 44.
[0021]
As described above, in the first region adjacent to
the free end of the first leg 12a of the L-shaped product
10, the changes in its shape are relatively small, and
thus, it can be formed into substantially same shape as
the final shape by drawing. In contrast, in the second
region, including the inside and outside curved portions
22 and 24, adjacent to the second leg 12b, the changes in
the shape of the L-shaped product 10 is relatively large,
and thus, wrinkles and cracks may occur. In the present
embodiment described above, the intermediate product 50
is produced from a blank by a first drawing process.
Then, the intermediate product 50, especially the second
region, undergoes a second bending process, whereby the
shape coincided with the final shape of the L-shaped
product 10 is obtained.
[0022]
During the bending process, the intermediate product
50 is pressed to the anvil 42 by the bending die 46. In
the inside curved portion 62 of the inside wall 54 of the
intermediate product 50, material flows along the surface
of the anvil, which surface corresponds to the inside
curved portion 22 of the L-shaped product 10.
Accordingly, in the inside flange 58, corresponding to
the portion I1 of the inside flange 108 of the panel 100,
the material flows into a portion IV (Figures 7 and 8)
which extends from the inside curved portion 62 of the
inside wall 54, whereby generation of crack in the
portion IV is prevented. On the other hand, the material
flows out of the portion I11 of the intermediate product
50 (portion I of the top wall 102 of the panel loo),
where wrinkles may occur due to an excess amount of
material in prior art, whereby the generation of wrinkles
is prevented.
[0023]
In this way, the material flows into the inside part
from the free end of the lower part of the L-shaped
member, while a portion K of the end of the lower part of
L-shaped member is stretched, and is prevented from being
thickened. For this purpose, the portion in the blank to
be formed into the second leg 12b of the completed Lshaped
product 10 is shaped into a curved protrusion, as
shown in Figure 13, so that the end of the lower part of
the L-shaped member is tightly formed into the designed
shape, whereby excessive material to be removed can be
minimized or eliminated, and thus substantially
contributing to improvement of yield rate. Regarding the
curved protrusion in the end of the lower part of the Lshaped
member before the stamping process, the curved
protrusion may be defined by a constant curvature line or
a combination of plural lines of various curvatures, an
ellipsoidal line, a straight line, a combination of
straight and curved lines or a wavy line, depending on
the shape of the completed L-shaped member or the
necessary margin for jointing with other parts. The
amount of protrusion may also be suitably adjusted
according to the shape of parts and extent of processing.
In order to adjust the curvature or the amount of
protrusion, a computer simulation may be advantageously
used.
[0024]
Due to the mode of deformation of the second leg of
the intermediate product, described above, a large
margin, as is usual in conventional shaping method, does
not necessary have to be provided, and thus, the size of
the blank can be reduced compared with the conventional
shaping methods. Reduction in the wall thickness during
the stamping process is reduced so that high tensile
strength material, as well as a steel sheet having high
extensibility and relatively low strength, can be used so
as to achieve good stamping.
[0025]
Regarding the outside curved portion 24 extending
along a circular arc, if the outside edge 12d of the top
wall 12 is simply bent to fit the outside curved portion
24, then the outside wall 16 is likely to be thickened,
resulting in generation of wrinkles. Therefore,
according to the present invention, in the outside curved
portion 24, a protrusion 16a in the form of a circular
arc extending upwardly from the top wall 12 as shown in
Figure 9B is provided in the outside edge 12d between the
top wall 12 and the outside wall 16. In particular,
difference between the arcuate profile of the outside
curved portion 24, seeing in a plan view of the top wall
12 shown in the left side of Figure 9A, and the arcuate
profile of the upper end portion 9, seeing in side view
as shown in Figure 9, is set to within 10 mm. By
providing the protrusion 16a in this way, excess material
of the outside wall 16 can be absorbed, preventing the
generation of wrinkles.
COO261
Further, for reasons described below, the width h of
the inside flange 18 of the L-shaped product 10 are
preferably in the range of 25-100 mm, in a predetermined
area Fi,, in the present embodiment in the area Fip of 100
mm, from the center portion C22 of the inside curved
portion 22 of the bent L-shaped product toward the first
leg 12a, as shown in Figure 10. First, in bending
process, when the intermediate product 50 is pressed to
the anvil 42 by the bending die 46, the second leg 52b of
the intermediate product 50 is pulled and bent toward the
first leg 52a, as shown by arrow A in Figure 8. At this
point, the force that pulls the second leg 52b toward the
first leg 52a is exerted to the portion in the
predetermined area Fip of the inside flange 18 of the Lshaped
product 10. In the case where the width h is
equal to or less than 25 mm, the stress in the portion
indicated by V in Figure 11 becomes excessive, so that
there is a problem that, in the end portion I11 adjacent
to the second leg 52b of the top wall 52 of the
intermediate product 50 (Figures 7 and 8), the material
outflow becomes excessive and wall thickness decreases
significantly and cracks may occur. In the case where
the width h is equal to or more than 100 mm, compression
in the portion IV adjacent to the inside curved portion
62 in the inside flange of the intermediate product 50
(Figure 11) becomes excessive. Therefore, in the inside
flange 18 of the completed L-shaped product 10, wrinkles
may occur in the portion IV adjacent to the inside curved
portion 22. By setting the width h to 25-100 mm,
generation of wrinkles and excessive reduction in wall
thickness can be avoided in the entire inside flange 18
including the portions IV and V of Figure 11.
[0027]
Further, in the inside curved portion 22 of the Lshaped
product 10, the inside wall 14 has a radius of
curvature of at least 5 mm. If, in the inside curved
portion 22, the radius of curvature of the inside wall 14
is equal to or less than 5 mm, the curvature is too
large. This results in a locally bulging deformation in
the portion around the joint between the inside wall 14
and the inside flange 18, at a portion of the maximum
curvature. Thus, cracks may occur. On the other hand,
if the radius of curvature of the inside curved portion
22 of the inside wall 14 exceeds 300 mm, the second leg
12b of the L-shaped product 10 becomes too long, so that
N the distance for the second leg 12b of the L-shaped
product 10 to be drawn into the inside curved portion 22
in bending process becomes large. Therefore, the bending
die assembly 40 and the intermediate product 50
5 relatively slide to each other along a long distance,
resulting in earlier wear of the bending die assembly 40.
Thus, the radius of curvature of the inside curved
portion 22 of the inside wall 14 is preferably in the
range of 5-300 mm. Further, since, in the stamping
10 process of the present invention, reduction of plate
thickness of the blank 26 can be made small, a high
tensile strength and low extensibility steel sheet, such
as a steel sheet having tensile strength of 400 MPa or
more to 1600 MPa or less can be used as the sheet metal
15 forming the blank 26.
[0028]
According to the method of the present invention, an
L-shaped product 10 having an inside curved portion 22
and an outside curved portion 24 can be processed by
20 stamping the blank 26 of sheet metal, which has a
relatively small margin compared with sheet metal used
for conventional drawing processes, without generating
wrinkles or cracks.
[Example 11
25 [0029]
Figure 12 shows an example of L-shaped product
produced by the method of producing an L-shaped product
according to a preferred embodiment of the present
invention described above.
30 In Figure 12, the L-shaped product 200 provides a
lower part of a front pillar extending from a lower edge
of a wind shield to a side sill (not shown) in a frame
structure of an automobile having a monocoque body. The
L-shaped product 200 includes a portion of the front
35 pillar upper portion 206 extending along the wind shield
side edge 208, a first leg 202 adapted to be connected to
the front pillar upper part 206, and a second leg 204
adapted to be connected to the side sill. The outside
curved portion 200a extends substantially along a
circular arc and forms a part of a wheel house (not
shown) of a front wheel.
5 [0030]
A blank 210 shown in Figure 13 is made of a high
tensile strength steel sheet having thickness of 1.8 mm,
tensile strength of 980 MPa, and fracture elongation
limit of 17.2%. The blank has a developed shape of the
10 L-shaped product 200 of Figure 12 with a margin of 5 mm.
The blank 210 also has an outwardly curved protrusion
212. Referring to Figure 14, a drawing die assembly 220
comprises a punch 222, a blank holder 224 and a drawing
die 226. By drawing the blank 210 using the drawing die
15 assembly 220, an intermediate product 230 shown in Figure
15 is formed.
[0031]
Referring to Figure 16, a bending die assembly 240
comprises a bending die 242, a pad 246 and a punch 248.
20 By bending the intermediate product 230 using the bending
die assembly, the L-shaped product 200 is formed. The
margin was trimmed after bending. The L-shaped product
200 subjected to bending process after drawing process
has a good top wall 202a that was formed smooth without
25 including wrinkles or cracks.
[0032]
Similarly, a good L-shaped product could be formed
also in the case where an aluminum plate, having
thickness of 1.8 rnrn, tensile strength of 296 MPa and
30 fracture elongation limit of 24.0%, was used as the blank
210 and was subjected to stamping using the drawing die
assembly 220 and the bending die assembly 240.
[0033]
As shown by the Example 1 described above, according
35 to the stamping method of the present invention, a good
L-shaped product can be produced using a smaller blank
compared with a blank used for conventional drawing
C methods. Also, an L-shaped product can be easily
produced using a high tensile strength material that has
been conventionally difficult to use, making it possible
to reduce weight and increase strength of a monocoque
5 body. As has been described above, the sheet metal used
as the blank is not limited to a steel sheet and an
aluminum plate used in the Example 1, and the present
invention can be applied also to an alloy having steel
and aluminum as main components as long as the sheet
10 metal is suitable for stamping.
[Example 21
[ 0 0 3 4 1
Next, referring to Figures 17A-24A, an experimental
example is shown, in which the stamping process according
15 to the method of producing an L-shaped product of the
present invention was carried out with various parameters
varied. In the experiment, it was observed whether or
not wrinkles and/or cracks were generated.
[0035]
20 In this experimental example, an L-shaped product
300 with a hat-shaped cross section to be produced by the
stamping process comprises, as is the above-described
embodiment, a top wall 302 substantially in the shape of
L having first and second legs 302a and 302b. The L-
25 shaped product 300 further comprises an inside wall 304
extending along an inside edge 302c of the top wall 302
and forming a first angle al relative to the top wall 302,
and an outside wall 306 extending along an outside edge
302d of the top wall 302 and forming a second angle a2
30 relative to the top wall 302. Each of the inside and
outside walls 304 and 306 is terminated by an inside
flange 308 and an outside 310 extending substantially
parallel to the top wall 302. Further, the L-shaped
product 300 has an inside curved portion 312 and an
35 outside curved portion 314 between the first and second
legs 302a and 302b. The outside curved portion 314
extends substantially along a circular arc. In the
u outside curved portion 314, a protrusion 306a in the form
of a circular arc, extending upwardly from the top wall,
is provided on an outside edge 302d between the top wall
302 and the outside wall 308.
5 [0036]
As shown in Figure 20, a drawing die assembly 320,
which includes a drawing die 322, a holder 324 facing the
drawing die 322 and a punch 326, was provided. A blank
318 was stamped with the drawing die assembly 320 to
10 produce an intermediate product 350. The blank 318 has
an outwardly-curved protrusion 318a which is adapted to
be formed into the second leg 302b of the completed Lshaped
product 300.
[0037]
The intermediate product 350 comprises a
substantially L-shaped flat top wall 352 having first and
second legs 352a and 352bf respectively corresponding to
the first and second legs 302a and 302b of the top wall
302 of the L-shaped product 300. The intermediate
product 350 further comprises inside and outside walls
354 and 356, respectively corresponding to the inside and
outside walls 304 and 306 of the L-shaped product 300.
The inside and outside walls extends along inside and
outside edges 352c and 352d of the top wall 352. The
intermediate product further includes inside and outside
flanges 358 and 360, respectively corresponding to the
inside and outside flanges 308 and 310 of the L-shaped
product 300.
[ 0 0 3 8 1
The intermediate product 350 includes a first region
adjacent to the free end of the first leg 352a and an
opposite second region adjacent to the second leg 352b.
In the first region, the section of the intermediate
product 350, along line A-A in Figure 23A, has a shape
substantially coincided with that of the L-shaped product
300, and a first angle PIA and a second angle P2A formed by
the inside and outside walls 354 and 356 relative to the
top wall 352 are substantially equal to the first angle al
and a second angle a2 formed by the inside and outside
walls 354 and 356 relative to the top wall 352 in the
completed L-shaped product 10, and are in the range of
90-115'.
[0039]
In the second region, as shown in sections of the
intermediate product 350 along lines B-B and C-C of
Figure 23A, a first angle PIC and a second angle PzC formed
by each of the inside and outside walls 354 and 356
relative to the top wall 352 are larger than the first
angle al and a second angle a2 of the completed L-shaped
product 300, and gradually increase toward the second leg
52b. Arrow C-C passed through the center portion of the
L-shaped product 300.
[0040]
Next, a bending die assembly 330 comprising an anvil
332, a pad 334 having an abutting surface 334a for
clamping the top wall 352 of the intermediate product 350
together with the anvil 332, and a bending die 336 for
stamping the intermediate product 350 to the anvil 332
was provided, and the intermediate product 350 was
processed by stamping by the bending die assembly 330 to
form the L-shaped product 300.
[ 0 0 4 1 ]
Result of implementing the present invention by
varying various parameters is shown in Table 1.
[Table 11
crack: 0 no crack, X crack found
wrinkle: 0 no wrinkle, A fine wrinkle, X wrinkle found
27
Example
28
1180 1.2 400 75 5.3320 7 7 0 0 0 0 0
In Table 1:
L: Length of the portion in the second region where
angles Pl and P2 change
H: Height of the inside and outside walls 352 and 354
5 8: Exterior angle formed by the inside and outside
walls 354 and 352 of the intermediate product in the
section along line C-C, and 8 = 180-PIC
a: Height of the protrusion 306a as seen in the
direction parallel to the top wall 302 of the L-shaped
10 product 300
b: Width of the protrusion 306a as seen in the
direction perpendicular to the top wall 302 of the Lshaped
product 300
[0042]
15 Referring to Table 1, L/H is a parameter related to
generation of wrinkles in the inside flange 308 of the Lshaped
product 300. If L/H is small, in particular,
smaller than 3, wrinkles occur in the portion indicated
by 300D (Figure 17A) of the inside flange 308.
20 100431
8 is a parameter related to generation of wrinkles in
the top wall 352 of the intermediate product 350 after
drawing and to generation of cracks in the inside flange
312 adjacent to the inside curved portion 312 of the L-
25 shaped product 300 after bending process. In particular,
if 8 is larger than 40°, wrinkles may occur in the portion
adjacent to the second leg 352b in the top wall 352 of
the intermediate product 350 (the portion 300A adjacent
to the second leg 302b of the top wall 302in the L-shaped
30 product 300 shown in Figure 17A). Further, if 8 is larger
than 70°, cracks may occur in the portion 300B (Figure
17A) of the inside flange 312 adjacent to the inside
curved portion 312 of the L-shaped product 300 after
bending process.
35 [List of Reference Numerals]
100441
L-shaped product
top wall
first leg
second leg
inside edge
outside edge
inside wall
outside wall
protrusion
inside flange
outer flange
inside curved portion
outside curved portion
blank
drawing die assembly
drawing die
recess
flank
holder
clamping surface
punch
outer shape
bending die assembly
anvil
outer shape
top surface
pad
abutting surface
bending die
intermediate product
top wall
first leg
second leg
inside edge
outside edge
inside wall
outside wall
inside flange
outer flange
inside curved portion
drawn panel
top wall
first leg
second leg
inside flange
L-shaped product
outside curved portion
first leg
top wall
second leg
front pillar upper part
wind shield side edge
blank
drawing die assembly
punch
blank holder
drawing die
intermediate product
bending die assembly
bending die
pad
punch
L-shaped product
top wall
first leg
second leg
inside edge
outside edge
inside wall
outside wall
protrusion
inside flange
outer flange
inside curved portion
outside curved portion
blank
drawing die assembly
drawing die
holder
punch
bending die assembly
anvil
pad
bending die
intermediate product
top wall
inside wall
first leg
second leg
inside edge
outside edge
inside wall
outside wall
inside flange
outer flange

[Name of Document] Claims
[Claim 11
A method of producing an L-shaped product which
includes an L-shaped flat top wall having first and
second legs connected to each other so as to define
inside and outside edges, an inside wall extending along
and connected to the inside edge of the top wall and
forming a first angle relative to the top wall, and an
outside wall extending along and connected to the outside
edge of the top wall and forming a second angle relative
to the top wall, each of the inside and outside walls
being terminated by a flange substantially parallel to
the top wall, the method comprising the steps of:
providing sheet metal material;
providing a drawing die assembly; and
stamping the sheet metal material with the
drawing die assembly to produce an intermediate product
which includes an L-shaped flat top wall having first and
second legs corresponding to the first and second legs of
the L-shaped flat top wall of the L-shaped product, and
inside and outside walls corresponding to the inside and
outside walls of the completed L-shaped product, and
flanges corresponding to the flanges of the completed Lshaped
product;
wherein the intermediate product includes a
first region adjacent to a free end of the first leg and
an opposite second region adjacent to the second leg, and
wherein, in the first region, the angle between each of
the inside and outside walls relative to the top wall of
the intermediate product substantially coincide with the
first and second angles of the completed L-shaped
product, and wherein, in the second region, the angle
between each of the inside and outside walls relative to
the top wall gradually increases toward the second leg;
the method further comprising the steps of:
providing a bending die assembly;
stamping the intermediate product by the
bending die assembly to produce the completed L-shaped
product.
[Claim 21
The method of producing an L-shaped product
according to claim 1, wherein the drawing die assembly
comprises a recess having a shape corresponding to the
top, inside and outside walls of the intermediate
product, a drawing die having a flank extending along the
peripheral edge of the recess, a holder having a clamping
surface for clamping the sheet metal material in
cooperation with the flank of the drawing die, and a
punch provided so as to be able to press the sheet metal
material into the recess of the drawing die.
[Claim 31
The method of producing an L-shaped product
according to claim 2, wherein the clamping surface of the
holder has a shape which does not clamp a portion of the
blank opposite to the free end of the first leg and
corresponding to an edge adjacent the second leg of the
intermediate product.
[Claim 41
The method of producing an L-shaped product
according to claim 3, wherein in a region adjacent to the
second leg and in the vicinity of an edge opposite to the
free end of the first leg, the inside wall of the
intermediate product extends substantially in the same
plane as the top wall.
[Claim 51
The method of producing an L-shaped product
30 according to claim 1, wherein the bending die assembly
comprises an anvil having a shape corresponding to the
shape of the completed L-shaped product, a pad having an
abutting surface for clamping the top wall of the
intermediate product in cooperation with the anvil, and a
35 bending die for pressing the intermediate product to the
anvil.
[Claim 61
The method of producing an L-shaped product
according to claim 5, wherein the anvil includes a flat
top surface facing to the abutting surface of the pad,
the L-shaped top wall of the intermediate product being
positioned between the top surface of the anvil and the
abutting surface of the pad, and wherein, during the
stamping process by the bending die assembly, the inside
wall and the inside flange and the outside wall and the
outer flange of the L-shaped product are bent by the
bending die assembly under the condition where the top
wall of the intermediate product is clamped by the top
surface of the anvil and the abutting surface of the pad.
[Claim 71
The method of producing an L-shaped product
according to claim 6, wherein the completed L-shaped
product includes an outside curved portion recessed into
a circular arc shape along the outside edge between the
first and second legs, and
wherein the anvil has a ridge portion
protruding from the top surface, and the pad includes a
recess for receiving the ridge portion of the anvil, so
that a rib projecting outward is formed on the top
surface along the outside curved portion recessed in
circular arc shape of the completed L-shaped product.
[Claim 81
The method of producing an L-shaped product
according to any one of claims 1-7, wherein the L-shaped
product has an inside curved portion curved in circular
arc shape between the first and second legs along the
inside wall, and
wherein the flange of the inside wall has width
of 25-100 mrn in the range of 100 mrn from the center of
the inside curved portion toward the frontend of the
first leg.
[Claim 91
The method of producing an L-shaped product
according to any one of claims 1-7, wherein the inside
curved portion of the inside wall has a radius of
curvature of 10-300 mm.
[Claim 101
The method of producing an L-shaped product
according to any one of claims 1-7, wherein the outside
curved portion of the outside wall has a radius of
curvature of 200-1000 mm.
[Claim 111
The method of producing an L-shaped product
according to any one of claims 1-7, wherein the sheet
metal material has tensile strength of 400-1600 MPa.