Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MANUFACTURING METHOD OF THICKNESS-VARIED METAL PLATE,
MANUFACTURING METHOD OF PRESSED PART, AND PROCESSING MACHINE
BACKGROUND OF THE INVENTION
1. Field of the Invention
100011 The
present invention relates to a manufacturing method of a thickness-
varied metal plate, a manufacturing method of a pressed part from a thickness-
varied metal
plate, and a processing machine used to manufacture a thickness-varied metal
plate.
2. Description of Related Art
100021 In
the manufacturing method of a thickness-varied steel plate described in
Japanese Patent Application Publication No. 2015-033719, at least one of a
pair of work
rolls of a two-stage rolling machine is formed so that the radius is varied in
a circumferential
direction. A steel plate (metal plate) is inserted between the pair of work
rolls and rolled,
and thus a thickness-varied steel plate (thickness-varied metal plate) of
which the plate
thickness is partially varied is manufactured.
SUMMARY OF THE INVENTION
[0003] However, the
above manufacturing method of a thickness-varied steel plate
can vary the plate thickness of a steel plate in only one direction orthogonal
to a plate
thickness direction (only a feed direction of the steel plate). Thus, there is
room for
improvement from the viewpoint of allowing greater flexibility in setting a
variation in plate
thickness.
[0004] The present
invention provides a manufacturing method of a thickness-
varied metal plate, a manufacturing method of a pressed part, and a processing
machine that
allow greater flexibility in setting a variation in plate thickness of a
thickness-varied metal
plate.
[0005] A
first aspect of the present invention relates to a manufacturing method of
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a thickness-varied metal plate, the manufacturing method including:
manufacturing a cut
plate by cutting a metal plate into a predetermined shape; and manufacturing
the thickness-
varied metal plate of which the plate thickness is varied in two different
directions orthogonal
to a plate thickness direction by processing the cut plate by at least one of
rolling and forging,
using a processing machine including a first work roll and a second work roll
of which the
radius is varied in a circumferential direction and an axial direction of a
rotational axis.
[0006]
According to the first aspect of the present invention, first, the cut plate
is
manufactured by cutting a metal plate (e.g., steel plate) into the
predetermined shape. Next,
the thickness-varied metal plate is manufactured by processing the cut plate
by at least one
of rolling and forging using the (single) processing machine including the
pair of work
rolls (the first work roll and the second work roll). Here, the radius of the
second work roll
of the processing machine is varied in the circumferential direction and the
axial direction
of the rotational axis. Accordingly, the thickness-varied metal plate
manufactured by
processing the cut plate using the processing machine has the plate thickness
varied in two
different directions orthogonal to the plate thickness direction. Thus,
according to the first
aspect, greater flexibility is allowed in setting a variation in plate
thickness of the thickness-
varied metal plate.
[0007] In
the first aspect of the present invention, the processing machine may be
provided with a first backup roll that is disposed on the opposite side of the
first work roll
from the second work roll and comes in contact with the first work roll, and a
second backup
roll that is disposed on the opposite side of the second work roll from the
first work roll and
comes in contact with the second work roll. When the thickness-varied metal
plate
manufactures, the cut plate may be processed by rotating the first work roll
in forward and
reverse directions within a range in which a region with a constant radius of
the first work
roll comes in contact with the first backup roll, and rotating the second work
roll in forward
and reverse directions within a range in which a region with a constant radius
of the second
work roll comes in contact with the second backup roll.
[0008]
According to this first aspect, the processing machine includes the pair of
backup rolls (the first backup roll and the second backup roll), so that so-
called crowning is
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possible be prevented or suppressed. Moreover, to process the cut plate using
the
processing machine, the first work roll is rotated in the forward and reverse
directions within
the range in which the region with a constant radius of the first work roll
comes in contact
with the first backup roll, and the second work roll is rotated in the forward
and reverse
directions within the range in which the region with a constant radius of the
second work
roll comes in contact with the second backup roll. It is possible to prevent
an unstable
behavior that occurs when region with a varied radius of the first work roll
or the second
work roll comes in contact with the corresponding backup roll, so that the
pair of work rolls
is possible to be rotated stably (smoothly). As a result, the pair of work
rolls is possible to
give a variation in plate thickness to the plate to be processed with high
accuracy.
[0009] A second aspect of the present invention relates to a
manufacturing method
of a thickness-varied metal plate, the manufacturing method including:
manufacturing a cut
plate by cutting a metal plate into a predetermined shape; and manufacturing
the thickness-
varied metal plate of which a plate thickness is varied in two different
directions orthogonal
to a plate thickness direction by sequentially processing the cut plate by at
least one of rolling
and forging, using a first processing machine including a first work roll and
a second work
roll of which a radius is varied in a circumferential direction or an axial
direction of a
rotational axis, and a second processing machine including a pair of work
rolls that are
different in shape from the work rolls (the first work roll and the second
work roll) of the
first processing machine.
[0010] According to the second aspect of the present invention,
first, the cut plate
is manufactured by cutting a metal plate (e.g., steel plate) into the
predetermined shape.
Next, the thickness-varied metal plate is manufactured by sequentially
processing the cut
plate by at least one of rolling and forging, using the first processing
machine including the
first work roll and the second work roll of which the radius is varied in the
circumferential
direction or the axial direction of the rotational axis, and the second
processing machine
including the pair of work rolls that are different in shape from the work
rolls of the first
processing machine. Here, the pair of work rolls of the first processing
machine and the
pair of work rolls of the second processing machine are different from each
other. As the
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cut plate is sequentially processed by the first processing machine and the
second processing
machine, the thickness-varied metal plate of which the plate thickness is
varied in two
different directions orthogonal to the plate thickness direction is possible
to be manufactured.
Thus, according to the second aspect, greater flexibility is allowed in
setting a variation in
plate thickness of the thickness-varied metal plate.
[0011] In
the second aspect, when the thickness-varied metal plate manufactures,
a direction in which the cut plate is fed into the first processing machine
may be changed to
a direction that is different from a direction in which the cut plate is fed
into the second
processing machine.
[0012] According to
this second aspect, to manufacture the thickness-varied metal
plate, the direction in which the cut plate is fed into the first processing
machine is changed
to a direction that is different from the direction in which the cut plate is
fed into the second
processing machine. Thus changing a feed direction is possible to change the
direction in
which the plate thickness of the cut plate is varied, so that even greater
flexibility is allowed
in setting a variation in plate thickness of the thickness-varied metal plate.
[0013] In
the second aspect, the first processing machine may include a first backup
roll that is disposed on the opposite side of the first work roll from the
second work roll and
comes in contact with the first work roll, and a second backup roll that is
disposed on the
opposite side of the second work roll from the first work roll and comes in
contact with the
second work roll. When the thickness-varied metal plate manufactures, the cut
plate may be
processed by rotating the first work roll in forward and reverse directions
within a range in
which a region with a constant radius of the first work roll comes in contact
with the first
backup roll, and rotating the second work roll in forward and reverse
directions within a
range in which a region with a constant radius of the second work roll comes
in contact with
the second backup roll.
[0014]
According to this second aspect, the first processing machine is provided
with the pair of backup rolls (the first backup roll and the second backup
roll), so that so-
called crowning is possible to be prevented or suppressed. Moreover, to
process the cut
plate using the first processing machine, the first work roll is rotated in
the forward and
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reverse directions within the range in which the region with a constant radius
of the first
work roll comes in contact with the first backup roll, and the second work
roll is rotated in
the forward and reverse directions within the range in which the region with a
constant radius
of the second work roll comes in contact with the second backup roll. It is
possible to
prevent an unstable behavior that occurs when region with a varied radius of
the first work
roll and the second work roll comes in contact with the corresponding backup
roll, so that
the pair of work rolls can be rotated stably (smoothly). As a result, the pair
of work rolls
is possible to give a variation in plate thickness to the cut plate high
accuracy.
[0015] A
third aspect of the present invention relates to a manufacturing method of
a pressed part, the manufacturing method including: manufacturing a partially
processed
thickness-varied metal plate by the manufacturing method of a thickness-varied
metal plate
of the first or second aspect; and manufacturing a pressed part by performing
cold-press
bending on an unprocessed portion of the thickness-varied metal plate.
[0016]
According to the third aspect, the thickness-varied metal plate is
manufactured by the manufacturing method of the thickness-varied metal plate
of the first
aspect or the second aspect. Accordingly, the third aspect can offer the same
operational
advantages as the first aspect and the second aspect. Next, a pressed part is
manufactured
by performing cold-press bending on the unprocessed portion of the thickness-
varied metal
plate. The yield strength of the processed portion of this pressed part has
been enhanced
by work hardening while the plate thickness thereof has been reduced. Thus,
according to
the third aspect, a lightweight pressed part that is partially enhanced in
strength is possible
to be manufactured.
[0017] A
fourth aspect of the present invention relates to a processing machine
including a first work roll and a second work roll of which the radius is
varied in a
circumferential direction and an axial direction of a rotational axis.
[0018]
Including the same configuration as the processing machine described in
the first aspect, the processing machine of the fourth aspect is possible to
be applied to the
manufacturing method of a thickness-varied metal plate of the first aspect.
Accordingly,
the fourth aspect is possible to offer the same operational advantages as the
first aspect.
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[0019] In
the fourth aspect, the second work roll may include a second roll main
body of which the radius is constant in the circumferential direction and the
axial direction
of the rotational axis, and a second cam that is detachably mounted at a part
of an outer
circumferential surface of the second roll main body.
[0020] According to
this fourth aspect, the second work roll of which the radius is
varied in the circumferential direction and the axial direction of the
rotational axis is formed
by mounting the second cam at the part of the outer circumferential surface of
the second
roll main body of which the radius is constant in the circumferential
direction and the axial
direction of the rotational axis. As the second cam is detachably mounted on
the second
roll main body, an arbitrary variation in plate thickness is possible to be
given to the cut plate
by replacing the second cam. Moreover, the second cam is possible to be
separately
replaced during maintenance, which contributes to improving the
maintainability.
[0021] In
the fourth aspect, the radius of the first work roll may be varied in a
circumferential direction and an axial direction of a rotational axis.
[0022] In the fourth
aspect, the first work roll may include a first roll main body of
which the radius is constant in the circumferential direction and the axial
direction of the
rotational axis, and a first cam that is detachably mounted at a part of an
outer circumferential
surface of the first roll main body.
[0023] As
has been described above, the manufacturing method of a thickness-
varied metal plate, the manufacturing method of a pressed part, and the
processing machine
of the present invention allow greater flexibility in setting a variation in
plate thickness of a
thickness-varied metal plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Features,
advantages, and technical and industrial significance of exemplary
embodiments of the invention will be described below with reference to the
accompanying
drawings, in which like numerals denote like elements, and wherein:
FIG. 1 is a perspective view illustrating a single-step rolling process in a
manufacturing
method of a thickness-varied metal plate (thickness-varied steel plate)
according to an
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embodiment of the present invention;
FIG. 2 is a side view illustrating the single-step rolling process;
FIG. 3 is a perspective view illustrating a first step of a multi-step rolling
process in
the manufacturing method of a thickness-varied steel plate according to the
embodiment of
the present invention;
FIG. 4 is a perspective view illustrating a second step of the multi-step
rolling process
in the manufacturing method of a thickness-varied steel plate according to the
embodiment
of the present invention;
FIG. 5 is a perspective view illustrating a third step of the multi-step
rolling process in
the manufacturing method of a thickness-varied steel plate according to the
embodiment of
the present invention;
FIG. 6 is a perspective view of a material to be rolled (thickness-varied
steel plate) that
has been rolled by a manufacturing method of a thickness-varied steel plate of
the related
art;
FIG. 7 is a plan view illustrating an example of blanking performed on the
thickness-
varied steel plate that has been rolled by the manufacturing method of a
thickness-varied
steel plate of the related art;
FIG. 8 is a perspective view illustrating an example of blanking in a cutting
process
according to the embodiment of the present invention;
FIG. 9 is a perspective view of blank materials that are combination-cut by
blanking
according to the embodiment of the present invention;
FIG. 10 is a perspective view showing an image of the blank material being
rolled
according to the embodiment;
FIG. 11 is a side view showing a modified example of a processing machine
according
to the embodiment of the present invention;
FIG. 12 is a front view of a center pillar reinforcement that is manufactured
using, as
material, a thickness-varied steel plate manufactured by the manufacturing
method of a
thickness-varied steel plate according to the embodiment of the present
invention;
FIG. 13 is a sectional view taken along the line XIII-XIII of FIG. 12;
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FIG. 14 is a perspective view of the center pillar reinforcement;
FIG. 15 is a front view of a front pillar lower part that is manufactured
using, as material,
a thickness-varied steel plate manufactured by the manufacturing method of a
thickness-
varied steel plate according to the embodiment of the present invention; and
FIG. 16 is a perspective view of a front floor that is manufactured using, as
material, a
thickness-varied steel plate manufactured by the manufacturing method of a
thickness-varied
steel plate according to the embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
100251 In the
following, a manufacturing method of a thickness-varied metal plate,
a manufacturing method of a pressed part, and a processing machine according
to an
embodiment of the present invention will be described using FIG. 1 to FIG. 16.
The
manufacturing method of a thickness-varied metal plate according to this
embodiment is a
method for manufacturing a thickness-varied steel plate (thickness-varied
metal plate) that
is used as material for a vehicle body component (pressed part) composing a
part of a vehicle
body of a vehicle, for example, and the method has a cutting process and a
rolling process
(working process). Hereinafter, the manufacturing method of a thickness-varied
metal
plate according to this embodiment will be referred to as a manufacturing
method of a
thickness-varied steel plate.
100261 In the cutting
process, a steel plate (metal plate) having a constant plate
thickness is cut into a predetermined shape (in this example, a rectangular
shape) by press
working etc., and thus a blank material (a cut plate, a plate to be processed,
or a plate to be
rolled) B shown in FIG. 1 and FIG. 3 is manufactured. The shape of the blank
material B
is not limited to a rectangular shape but may be an arbitrary shape. In
addition, the
manufacturing method of a thickness-varied steel plate according to this
embodiment is
applicable not only to steel plates but also to other metal plates having
plasticity.
100271 Next,
in the rolling process, the blank material B is rolled using a rolling
machine (processing machine) (the blank material B can be processed by at
least one of
rolling and forging), and thus a thickness-varied steel plate TB! (see FIG. 1
and FIG. 2) or
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a thickness-varied steel plate TB2 (see FIG. 5) is manufactured. There are two
types of this
rolling process: a single-step rolling process (single-step working process)
shown in FIG. 1
and FIG. 2, and a multi-step rolling process (multi-step working process)
shown in FIG. 3
to FIG. 5, and either one of these processes is adopted. These two types of
rolling process
will be described below.
[0028] Single-step Rolling Process
In the single-step rolling process shown in FIG. 1 and FIG. 2, the blank
material B is
rolled by a (single) rolling machine 10 to manufacture the thickness-varied
steel plate TB1.
The rolling machine 10 is a two-stage rolling machine, and includes a pair of
substantially
columnar work rolls 12 that are arranged one on top of the other in a position
parallel to each
other. The work rolls 12 are rotatably supported by a housing (not shown), and
are
configured to be driven to rotate in synchronization with each other by a
driving unit (not
shown). A specified clearance (a clearance smaller than the plate thickness of
the blank
material B) is provided between the work rolls 12. For the convenience of
description, FIG.
1 and FIG. 2 show the work rolls 12 at a greater distance from each other than
in reality.
The same applies to FIG. 3 to FIG. 5.
[0029] As shown in FIG. 1 and FIG. 2, a recess (shaping surface) 12A
that gives a
variation in plate thickness (thickness-varied shape) to the blank material B
is formed in an
outer circumferential surface (processing surface) of each work roll 12. The
recess 12A
may instead be formed only in one of work rolls 12. In addition, the shaping
surface may
be a protrusion instead of the recess 12A. The recess 12A is formed in a shape
corresponding to a target shape of the thickness-varied steel plate TB1 to be
manufactured
by the single-step rolling process. The target shape is a shape corresponding
to a variation
in plate thickness (thickness-varied shape) required of a pressed part (a
vehicle body
component of a vehicle) to be manufactured using the thickness-varied steel
plate TB!.
[0030] The recess 12A is formed only at a part of the outer
circumferential surface
of each work roll 12 in a circumferential direction. Accordingly, the radius
of each work
roll 12 is smaller at the circumferential region in which the recess 12A is
provided than at
the other circumferential region in which the recess 12A is not provided. The
depth of the
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recess 12A is larger at a central part of each work roll 12 in an axial
direction, and the radius
of each work roll 12 is even smaller at this deeper region. Thus, each work
roll 12 has the
radius varied in both the circumferential direction and the axial direction.
The work rolls
12 are configured to be driven to rotate in synchronization while always
maintaining a
vertically symmetrical position of rotation (see the arrows R in FIG. 1 and
FIG. 2). The
above-described shape of the recess 12A is a mere example and can be changed
as
appropriate.
[0031] In
the single-step rolling process using the rolling machine 10 of the above
configuration, the blank material B is inserted between the work rolls 12 of
the rolling
machine 10 and rolled (see the arrow RM in FIG. 1 and FIG. 2), and thereby the
shapes of
the processing surfaces of the work rolls 12 are impressed on the blank
material B. Thus,
the thickness-varied steel plate TB1 (see FIG. 1 and FIG. 2) of which the
plate thickness is
varied in two different directions (the directions of the arrow X and the
arrow Y in FIG. 1)
orthogonal to a plate thickness direction (the direction of the arrow Z in
FIG. 1) is
manufactured.
[0032] Multi-step Rolling Process
On the other hand, the multi-step rolling process includes a plurality of
steps (in this
example, a first step to a third step) shown in FIG. 3 to FIG. 5, and the
thickness-varied steel
plate TB2 is manufactured by sequentially rolling the blank material B using a
plurality of
(in this example, three) rolling machines 20, 30, 40. The rolling machine 20
includes
basically the same configuration as the rolling machine 10, and includes a
pair of work rolls
22 including recesses 22A formed in outer circumferential surfaces thereof.
The rolling
machine 30 includes basically the same configuration as the rolling machine
10, and includes
a pair of work rolls 32 including recesses 32A formed in outer circumferential
surfaces
thereof. The rolling machine 40 includes basically the same configuration as
the rolling
machine 10, and includes a pair of work rolls 42 including recess 42A formed
in outer
circumferential surfaces thereof. Only one of work rolls 22 may instead have
the recess
22A formed therein. Only one of work rolls 32 may instead have the recess 32A
formed
therein. Only one of work rolls 42 may instead have the recess 42A formed
therein. In
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addition, protrusions instead of the recesses 22A, 32A, 42A may be provided on
the outer
circumferential surfaces. The work rolls 22, 32, 42 are different in shape
from the work
rolls 12. Moreover, the pairs of work rolls 22, 32, 42 are different in shape
from one another.
[0033]
Specifically, the rolling machine 20 (see FIG. 3) used in the first step
includes the work rolls 22 of which the radii are respectively varied in a
circumferential
direction. The recess 22A is formed in the outer circumferential surface
(processing
surface) of each work roll 22. The recess 22A is formed only at a part of the
outer
circumferential surface of the work roll 22 in the circumferential direction,
and is formed in
a constant shape along an axial direction of the work roll 22.
[0034] The rolling
machine 30 (see FIG. 4) used in the second step includes the
work rolls 32 of which the radii are respectively varied in an axial
direction. The recess
32A is formed in the outer circumferential surface (processing surface) of
each work roll 32.
The recess 32A is formed at a central part of the outer circumferential
surface of the work
roll 32 in the axial direction, and is formed in a constant shape along a
circumferential
direction of the work roll 32.
[0035] The
rolling machine 40 (see FIG. 5) used in the third step includes the work
rolls 42 of which the radii are respectively varied in a circumferential
direction. The recess
42A is formed in the outer circumferential surface (processing surface) of the
work roll 42.
The recess 42A is formed only at a part of the outer circumferential surface
of the work roll
42 in the circumferential direction, and is formed in a constant shape along
an axial direction
of the work roll 42.
[0036] In
the multi-step rolling process using the rolling machines 20, 30, 40 of the
above configurations, first, in the first step shown in FIG. 3, the blank
material B is inserted
between the work rolls 22 of the rolling machine 20 and rolled (see the arrow
RM in FIG.
3), and thereby the shapes of the processing surfaces of the work rolls 22 are
impressed on
the blank material B. Next, in the second step shown in FIG. 4, a blank
material B1 having
undergone the first step is inserted between the work rolls 32 of the
processing machine 30
and rolled (see the arrow RM in FIG. 4), and thereby the shapes of the
processing surfaces
of the work rolls 32 are impressed on the blank material BI.
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[0037] Next,
in the third step shown in FIG. 5, first, a blank material B2 having
undergone the second step is turned 90 degrees as seen in a plan view (see the
arrow T in
FIG. 5). Then, the blank material B2 is inserted between the work rolls 42 of
the rolling
machine 40 and rolled (see the arrow C and the arrow RM in FIG. 5). Thus, the
thickness-
varied steel plate TB2 (see FIG. 5) of which the plate thickness is varied in
the two different
directions (the directions of the arrow X and the arrow Y in FIG. 5)
orthogonal to a plate
thickness direction (the direction of the arrow Z in FIG. 5) is manufactured.
In this
embodiment, as the blank material B1 undergoes the second step before the
third step, the
blank material B2 (thickness-varied steel plate) of which the plate thickness
is varied in the
two different directions orthogonal to the plate thickness direction is
manufactured.
Therefore, the third step may be omitted.
[0038] In
the above multi-step rolling process, the blank material B2 is turned 90
degrees as seen in a plan view in the third step, and thereby a direction in
which the blank
material B2 is fed into the rolling machine 40 is changed to a direction that
is different from
a direction in which the blank materials B, B1 are fed into the rolling
machines 20, 30. The
feed direction of the blank material B2 refers to the orientation of the blank
material B2 in a
plan view relative to the rolling machine 40 during rolling of the blank
material B2 by the
rolling machine 40. The feed direction of the blank materials B, B1 refers to
the orientation
of the blank materials B, B1 in a plan view relative to the rolling machines
20, 30 during
rolling of the blank materials B, B1 by the rolling machines 20, 30. The
distribution and
combination of the rolling work in the multi-step rolling process can be
changed arbitrarily.
100391 Heat Treatment
Next, a heat treatment for the thickness-varied steel plates TB1, TB2 will be
described.
In this embodiment, the thickness-varied steel plates TB1, TB2 manufactured by
the above
rolling process (the single-step rolling process or the multi-step rolling
process) is shaped
into a predetermined shape by being bent in a subsequent pressing process.
However, work
hardening has occurred at rolled portions of the thickness-varied steel plates
TB1, TB2,
which represents difficult conditions for plastic forming to be performed
later. Therefore,
this embodiment is based on a premise that a heat treatment is performed on
the thickness-
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varied steel plates TB1, TB2 having undergone the rolling process.
[0040]
Specifically, for example, the pressing process after the rolling process is a
hot pressing process. In the hot pressing process, the thickness-varied steel
plates TB1,
TB2 are heated to a predetermined temperature by high-frequency induction
heating etc.
before press working. During this heating, work hardening resulting from
rolling
(thickness varying processing) is removed.
[0041] For
example, in the case where the pressing process after the rolling process
is a cold pressing process, an annealing process of annealing the thickness-
varied steel plates
TB1, TB2 is additionally performed before the cold pressing process. The work
hardening
is removed in this annealing process. Thus, although the number of processes
is increased
by the addition of the annealing process, the annealing process makes the
thickness-varied
steel plates TB1, TB2 usable as ordinary cold-pressed parts.
[0042] The
thickness-varied steel plates TB1, TB2 according to this embodiment
are not limited to those that undergo the above-described heat treatment. That
is, it is
possible to partially enhance the strength of the thickness-varied steel
plates TB1, TB2
according to this embodiment by maintaining the work-hardened conditions and
taking
advantage of the enhanced yield strength. As a result, compared with if the
plate thickness
of the entire thickness-varied steel plate is increased to enhance the
strength, for example, a
reduction in thickness and weight of the thickness-varied steel plate can be
achieved.
[0043] Operations and Advantages
Next, operations and advantages of this embodiment will be described.
[0044]
According to the manufacturing method of a thickness-varied steel plate of
this embodiment, in the cutting process, the blank material B is manufactured
by cutting a
steel plate having a constant plate thickness into a predetermined shape.
Next, the rolling
process is performed. The rolling process is either the single-step rolling
process or the
multi-step rolling process. When the rolling process is the single-step
rolling process, the
thickness-varied steel plate TB1 is manufactured by rolling the blank material
B using the
single rolling machine 10 including the pair of work rolls 12. Here, each work
roll 12 of
the rolling machine 10 has the radius varied in the circumferential direction
and the axial
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direction. Accordingly, the thickness-varied steel plate TB1 manufactured by
rolling the
blank material B using the rolling machine 10 has the plate thickness varied
in two different
directions orthogonal to the plate thickness direction. Thus, this
manufacturing method
allows greater flexibility in setting a variation in plate thickness than the
manufacturing
method of a thickness-varied steel plate described in the section of
Description of Related
Art (hereinafter referred to simply as a manufacturing method of a thickness-
varied steel
plate of the related art).
[0045] On
the other hand, when the rolling process is the multi-step rolling process,
the thickness-varied steel plate TB2 is manufactured by sequentially rolling
the blank
material B by the plurality of rolling machines 20, 30, 40 respectively
including the work
rolls 22, 32, 42 of which the radii are varied in the circumferential
directions or the axial
directions. Here, the pairs of work rolls 22, 32, 42 of the plurality of
rolling machines 20,
30, 40 are different in shape from one another. As the blank material B is
sequentially
rolled by the plurality of rolling machines 20, 30, 40, the thickness-varied
steel plate TB2 of
which the plate thickness is varied in two different directions orthogonal to
the plate
thickness direction can be manufactured. Thus, this manufacturing method
allows greater
flexibility in setting a variation in plate thickness than the manufacturing
method of a
thickness-varied steel plate of the related art.
[0046] As
has been described above, according to this embodiment, whether the
rolling process is the single-step rolling process or the multi-step rolling
process, the
thickness-varied steel plate TB1 or TB2 of which the plate thickness is varied
in two different
directions orthogonal to the plate thickness direction (arbitrary directions
within a plane
orthogonal to the plate thickness direction) can be manufactured. Thus, the
plate thickness
of a vehicle body component manufactured using the thickness-varied steel
plate TB1 or
TB2 can be varied in an arbitrary direction, such as a vehicle up-down
direction or a vehicle
front-rear direction. As a result, it is possible to secure the strength and
rigidity required of
the vehicle body and yet to reduce the weight of the vehicle body, and thereby
to improve
the fuel efficiency and kinematic performance of the vehicle.
[0047] In
the single-step rolling process, the thickness-varied steel plate T131 is
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manufactured simply by rolling the blank material B using the single rolling
machine 10.
Thus, this process simplifies the manufacturing process and contributes to
cost reduction.
On the other hand, in the multi-step rolling process, the thickness-varied
steel plate TB2 is
manufactured by sequentially rolling the blank material B using the plurality
of rolling
machines 20, 30, 40. Thus, a processing force required to roll the blank
material B can be
distributed among the rolling machines 20, 30, 40. Accordingly, the durability
of the
rolling machines 20, 30, 40 can be more easily secured.
[0048]
Moreover, in the multi-step rolling process, the direction in which the blank
material B is fed into the rolling machine 40 that is one of the plurality of
rolling machines
20, 30, 40 is changed to a direction different from the direction in which the
blank material
B is fed into the other rolling machines 20, 30. Thus changing the feed
direction can change
the direction in which the plate thickness of the blank material B is varied,
so that even
greater flexibility is allowed in setting a variation in plate thickness, and
a complicated shape
can be given to the thickness-varied steel plate TB2.
[00491 lii this
embodiment, rolling (thickness varying processing) is performed on
the blank material B (cut plate) that can be cut into an arbitrary shape.
Thus, the direction
in which the blank material B is fed into each rolling machine (i.e., the
direction in which a
variation in plate thickness is given to the blank material B) can be set
arbitrarily, without
being limited to the example in the above-described multi-step rolling
process.
Accordingly, a complicated thickness-varied shape required of a vehicle body
component
etc. can be easily processed.
[0050]
Moreover, in this embodiment, rolling is performed on the blank material B
as described above, which can improve the material yield compared with the
manufacturing
method of a thickness-varied steel plate of the related art.
Specifically, in the
manufacturing method of a thickness-varied steel plate of the related art, as
shown in FIG.
6, rolling (thickness varying processing) is performed on a steel plate (metal
strip) S that is
a material to be rolled, in a state where the steel plate S is wound around a
payoff reel R1
and a take-up reel R2, and then the steel plate S is cut along blank lines Li,
L2 shown in
FIG. 6. Thereafter, a cut steel plate SB (see FIG. 7) is cut into a shape P of
a part to be
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manufactured (see FIG. 6 and FIG. 7). Thus, combination processing cannot be
performed
unless the distribution of the plate thickness is symmetrical relative to the
part shape P.
[0051] More
specifically, in the case where rolling is performed on the steel plate
S wound around the payoff reel RI and the take-up reel R2, for example, the
dotted area in
FIG. 6 and FIG. 7 constitutes a thick plate part Si having a large plate
thickness, while the
other areas constitute thin plate parts S2 having a small plate thickness.
Pluralities of thick
plate parts S1 and thin plate parts S2 are formed at a regular pitch. Thus, if
the arrangement
of the thick plate part S I relative to the part shape P is asymmetrical as
shown in FIG. 6 and
FIG. 7, only one part can be cut out of one steel plate SB, so that a large
amount of scrap SC
(a part of the steel plate SB outside the part shape P) is generated.
Depending on the shape
of the part, therefore, the material yield is very low and the manufacturing
cost is high.
[0052] In
this embodiment, by contrast, the blank material B is manufactured by
cutting the steel plate before rolling, and rolling is performed on the blank
material B.
Therefore, as shown in FIG. 8 and FIG. 9, to manufacture the blank material B,
a plurality
of blank materials B can be cut out (so-called combination-cut) from the steel
plate SB before
being rolled. Thereafter, the blank material B having been cut out is rolled
(see FIG. 10).
Accordingly, the amount of scrap SC generated can be significantly reduced and
the material
yield is significantly improved, so that the manufacturing cost can be
reduced. FIG. 10
shows the first step of the multi-step rolling process.
[0053] Moreover, in
this embodiment, the thickness-varied steel plates TB1, TB2
are manufactured by rolling using the rolling machines (rolls), which can
significantly
reduce the required processing force compared with if a thickness-varied steel
plate is
manufactured by forging using an ordinary pressing machine. Specifically, for
example,
several tens of thousands of tons of processing force is required when an
ordinary pressing
machine is used. By contrast, when a rolling machine is used, thickness
varying processing
can be performed, for example, with a processing force not larger than a tenth
of the
processing force required for the pressing machine. Alternatively, the blank
material B
may be heated before being rolled by the rolling machine. Thus, the processing
force can
be further reduced, and a more complicated thickness-varied shape can be given
to the blank
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material B.
[0054] Modified Example of Rolling
Machine 10
Next, a modified example of the rolling machines 10, 20, 30, 40 according to
this
embodiment will be descried using FIG. 11. Like the rolling machine 10, a
rolling machine
50 of this modified example includes a pair of work rolls 52. However, each
work roll 52
include a columnar roll main body 54 of which the radius is constant in a
circumferential
direction and an axial direction, and a cam 56 that is detachably mounted at a
part of an outer
circumferential surface of the roll main body 54. Each cam 56 has a
substantially
semicircular arc shape as seen from the axial direction of the roll main body
54. The cam
56 has a shape that gives a variation in plate thickness (thickness-varied
shape) to the blank
material B.
[0055] The
rolling machine 50 further includes a pair of backup rolls 58 that
support the pair of work rolls 52 from upper and lower sides. The backup rolls
58 are
disposed with the work rolls 52 therebetween, and are opposed to each other.
The backup
rolls 58 are disposed parallel to the pair of work rolls 52. Each backup roll
58 is in contact
with a side of the roll main body 54 of the corresponding one of the work
rolls 52 at which
the cam 56 is not mounted. During rolling of the blank material B by the pair
of work rolls
52, the backup rolls 58 prevent or suppress elastic deformation (deflection)
of the pair of
work rolls 52 caused by an excessive reaction force from the blank material B
(workpiece).
Thus, so-called crowning can be prevented or suppressed.
[0056] To
roll the blank material B using the rolling machine 50, eachwork roll 52
is rotated in forward and reverse directions like a pendulum within a range in
which a region
with a constant radius (in this example, a region of the outer circumferential
surface of the
roll main body 54 in which the cam 56 is not mounted) of the work roll 52
comes in contact
with the corresponding one of the backup rolls 58 (see the arrows SW1 and SW2
in FIG. 11).
[0057] Thus,
as the rolling machine 50 performs rolling on the blank material B, it
is not absolutely necessary that the work rolls 52 are continuously rotated
during rolling. It
is therefore possible, as with the rolling machine 50, to adopt a half-split
structure of the
cams 56 (processing parts) of the pair of work rolls 52, and to perform
rolling by rotating
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the pair of work rolls 52 like a pendulum in the forward and reverse
directions. This can
prevent an unstable behavior that occurs when region with a varied radius of
the work roll
52 and the pair of backup roll 58 comes in contact with each other, so that
the pair of work
rolls 52 can be rotated stably (smoothly). As a result, the pair of work rolls
52 can give a
variation in plate thickness to the blank material B with high accuracy.
[0058]
Specifically, in FIG. 5 of JP 2015-033719 A that discloses the
manufacturing method of a thickness-varied steel plate, a configuration is
shown in which
backup rolls 33, 34 that are different in cross-sectional shape from columnar
work rolls 31,
32 are provided for the work rolls 31, 32, and a thickness-varied shape is
given to a material
to be rolled as the work rolls 31, 32 are moved up and down along the shapes
of the backup
rolls 33, 34. However, according to this configuration, rotation of the work
rolls 31, 32 and
the backup rolls 33, 34 becomes momentarily very unstable when these rolls
come in contact
with each other at corners (ends) of regions with a radius r4 of the backup
rolls 33, 34. For
this reason, it would be difficult to stably give a thickness-varied shape to
a material to be
rolled. In this respect, according to this modified example, a thickness-
varied shape can be
stably given to the blank material B through the stable rotation of the pair
of work rolls 52.
[0059] In
the rolling machine 50, the work roll 52 of which the radius is varied in
the circumferential direction and the axial direction is formed by mounting
the cam 56 at a
part of the outer circumferential surface of the roll main body 54 of which
the radius is
constant in the circumferential direction and the axial direction. As the cam
56 is
detachably mounted on the roll main body 54, an arbitrary variation in plate
thickness can
be given to the blank material B by replacing the cam 56. Moreover, the cam 56
can be
separately replaced during maintenance, which contributes to improving the
maintainability.
[0060] Examples
Next, examples of a vehicle body component (vehicle frame member) manufactured
using a thickness-varied steel plate according to this embodiment will be
described using
FIG. 12 to FIG. 16. The arrows FR, UP, and OUT indicated as necessary in FIG.
12 to FIG.
16 indicate a vehicle front side, a vehicle upper side, and an outer side in a
vehicle width
direction, respectively.
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[0061] FIG.
12 to FIG. 14 show a center pillar reinforcement 60 that is
manufactured using a thickness-varied steel plate according to this
embodiment. The
center pillar reinforcement 60 has: a side wall 60A; a front wall 60B and a
rear wall 60C that
extend respectively from a front side and a rear side of the side wall 60A
toward an inner
side in the vehicle width direction; and a front flange 60D and a rear flange
60E that extend
respectively from ends of the front wall 6013 and the rear wall 60C on the
inner side in the
vehicle width direction toward the opposite sides.
[0062] In
the center pillar reinforcement 60, a thick plate part 62 (see the dotted
area in FIG. 12 to FIG. 14) is provided at an upper part of the side wall 60A,
the front wall
60B, and the rear wall 60C, while the other parts have a smaller plate
thickness. More
specifically, the center pillar reinforcement 60 is formed so that the plate
thickness decreases
gradually toward both sides of the thick plate part 62 in a vehicle up-down
direction, and
that the plate thickness of the front wall 60B and the rear wall 60C decreases
gradually
toward the front flange 60D and the rear flange 60E at a level at which the
thick plate part
62 is provided (see the arrows Al to A3 in FIG. 13 and FIG. 14). Thus, the
strength of an
upper part of the center pillar reinforcement 60 that protects a cabin is
enhanced, while a
lower part thereof that absorbs energy in the event of a lateral collision of
the vehicle etc.
and the front and rear flanges 60D, 60E that are not required to be strong are
reduced in
thickness and weight.
[0063] Similarly, FIG.
15 shows a front pillar lower part 70 that is manufactured
using a thickness-varied steel plate according to this embodiment. The front
pillar lower
part 70 has: a side wall 70A; a front wall 70B and a rear wall 70C that extend
respectively
from a front side and a rear side of the side wall 70A toward the inner side
in the vehicle
width direction; and a front flange 70D and a rear flange 70E that extend
respectively from
ends of the front wall 70B and the rear wall 70C on the inner side in the
vehicle width
direction toward the opposite sides. In the front pillar lower part 70, a
thick plate part 72
(see the dotted area in FIG. 15) is provided at a middle part of the side wall
70A, the front
wall 70B, and the rear wall 70C in an up-down direction, while the other parts
have a smaller
plate thickness. The front pillar lower part 70 is formed so that the plate
thickness
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decreases gradually from the thick plate part 72 toward both sides in the
vehicle up-down
direction, and that the plate thickness of the front wall 70B and the rear
wall 70C decreases
gradually toward the front flange 70D and the rear flange 70E at a level at
which the thick
plate part 72 is provided. The front pillar lower part 70 can offer the same
operational
advantages as the center pillar reinforcement 60.
[0064] On
the other hand, FIG. 16 shows a front floor 80 that is manufactured using
a thickness-varied steel plate according to this embodiment. In the front
floor 80, a floor
tunnel 80A provided at a central part in the vehicle width direction bulges
toward the upper
side of the vehicle, and a left floor part 8013 and a right floor part 80C
located one on each
side of the floor tunnel 80A in the vehicle width direction are formed in a
substantially flat
plate shape. In the front floor 80, middle parts (see the dotted areas in FIG.
16) of the left
floor part 80B and the right floor part 80C in a vehicle front-rear direction
constitute thin
plate parts 82 having a smaller plate thickness than the other parts.
[0065] The
front floor 80 corresponds to the pressed part in the present invention,
and is manufactured by performing cold press working on the thickness-varied
steel plate
TB1 or the thickness-varied steel plate TB2 without performing a heat
treatment such as
annealing thereon. Thus,
the thin plate parts 82, i.e., the portions rolled by the
manufacturing method of a thickness-varied steel plate according to this
embodiment,
maintain the work-hardened conditions after being reduced in thickness. The
yield strength
of the thin plate parts 82 has been enhanced due to work hardening. According
to the front
floor 80, the middle parts of the left floor part 80B and the right floor part
80C in the vehicle
front-rear direction that tend to lack strength is enhanced in strength by
work hardening, and
at the same time these middle parts are reduced in plate thickness. Thus, the
strength of
the front floor 80 is locally enhanced and the weight thereof is reduced.
[0066] The present
invention is highly versatile, as there are a wide variety of
vehicle body components in which locally causing work hardening as described
above is
expected to have advantageous effects. The plate thickness of a vehicle body
component
(vehicle frame part) is typically set according to a portion thereof that is
required to be strong,
so that the plate thicknesses of the other portions that are not required to
be strong often have
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an excessively large plate thickness.
However, using a thickness-varied steel plate
according to the present invention can eliminate such excess of plate
thickness. Thus, the
present invention is a technology that is widely applicable to vehicle frame
parts to reduce
the weight of the vehicle.
[0067] The present
invention has been described above by showing the
embodiment and some examples, but the invention can be implemented with
various
modifications made thereto within the scope of the gist of the invention. It
should be
understood that the scope of right of the present invention is not limited to
the above
embodiment.
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