JP7081282B2 - Torsion beam manufacturing method and torsion beam manufacturing equipment - Google Patents

Description

The present invention relates to a torsion beam manufacturing method and a torsion beam manufacturing apparatus for manufacturing a torsion beam provided in a torsion beam type suspension device of an automobile.

As is well known, a torsion beam type suspension device is widely used as a form of an automobile suspension system.
The torsion beam type suspension device includes a torsion beam assembly, a spring, and an absorber. The torsion beam assembly has a structure in which a pair of left and right trailing arms that rotatably support the left and right wheels are connected by a torsion beam, and a pair of left and right spring receiving portions are joined in the vicinity of the left and right ends of the torsion beam. The spring and absorber connect the torsion beam to the vehicle body. The torsion beam is swingably connected to the vehicle body via a pivot shaft extending from the left and right sides of the vehicle body toward the center side.

The torsion beam is formed by, for example, plastically deforming a metal tube by press forming or hydrofoam forming, and the cross section orthogonal to the longitudinal direction of the torsion beam is changed from the attachment portion with the trailing arm to a fixed cross section. It is formed in a substantially V-shaped or substantially U-shaped closed cross section (see, for example, Patent Document 1).
The torsion beam is located between a fixed-shaped closed cross-section having a substantially V-shaped or substantially U-shaped closed cross-section, a mounting portion connected to the left and right trailing arms, and a fixed-shaped closed cross-section and the mounting portion. It has a shape changing portion (gradual changing portion), and when the vehicle body receives an external force from the road surface, the roll rigidity of the vehicle body is secured mainly by the torsional rigidity of the torsion beam.

On the other hand, even if the torsion beam has sufficient roll rigidity, it receives various external forces from the road surface via the wheels and the trailing arm, so that a complicated stress distribution due to such external forces is generated. Metal fatigue tends to progress. This metal fatigue is remarkably likely to occur, for example, in the vicinity of the connection portion between the shape change portion and the constant shape closed cross-section portion.
Therefore, it is necessary to suppress the progress of metal fatigue even when various external forces are received from the road surface, and various techniques have been developed to suppress such metal fatigue (for example, Patent Documents 2 to 5). reference).

The technique described in Patent Document 2 improves the fatigue characteristics of a torsion beam by press-molding the torsion beam and then performing quenching, tempering, and shot peening to harden the outer surface of the torsion beam.
The technique described in Patent Document 3 improves the surface hardness of the torsion beam and improves the fatigue characteristics of the torsion beam by using a steel pipe whose surface hardness becomes high after the heat treatment.
The technique described in Patent Document 4 applies tensile stress by applying a pressure from the inside to the outside of the steel pipe by hydrofoam, and as a result, reduces the residual stress of the torsion beam and improves the fatigue characteristics.
In the technique described in Patent Document 5, when the tube body is formed into a torsion beam, a part of the tube body is crushed in the radial direction to form a substantially U-shaped cross section, and then the bottom line is set to the ventral side. Bending to apply a bending strain on the tension side of 2 to 6% to the ear. As a result, the fatigue intensity of the selvage portion, which is a fatigue risk portion of the torsion beam, is improved.

Japanese Unexamined Patent Publication No. 2011-635 Japanese Unexamined Patent Publication No. 2001-123227 Japanese Unexamined Patent Publication No. 2008-03656 Japanese Unexamined Patent Publication No. 2013-091433 International Publication No. 2010/114173

However, it is not always easy to improve the fatigue characteristics of the torsion beam by applying the techniques described in Patent Documents 2 to 4, and there is a problem that the initial cost such as capital investment and the manufacturing running cost increase. ..
Further, in the technique described in Patent Document 5, since bending strain on the selvage side is applied to the selvage portion, thinning of the selvage portion is unavoidable. Increasing the overall plate thickness in anticipation of this amount of wall reduction will lead to the problem of weight increase.
As described above, a manufacturing technique capable of efficiently manufacturing a torsion beam that is lightweight and has excellent fatigue characteristics is desired.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a torsion beam manufacturing method and a torsion beam manufacturing apparatus capable of efficiently manufacturing a torsion beam that is lightweight and has excellent fatigue characteristics.

In order to solve the above problems and achieve the above object, the present invention employs the following means. (1) In the torsion beam manufacturing method according to one aspect of the present invention, a central portion having a substantially V-shaped or substantially U-shaped closed cross section having an ear portion at an arbitrary position in the longitudinal direction having a cross section orthogonal to the longitudinal direction. A method of manufacturing a torsion beam including a shape changing portion which is connected to the central portion, has an ear portion, and whose closed cross section gradually changes along the longitudinal direction. A preparatory step for preparing a torsion beam material having the shape changing portion; the selvage portion of the torsion beam material is bent so as to be inside the bending of the bending deformation process, and the selvage portion is subjected to compressive plastic deformation to the selvage portion. It has a selvage compression bending step to increase the thickness.

(2) In the embodiment described in (1) above, a compression strain of 0.5% or more and 10% or less may be applied in the longitudinal direction in the selvage compression bending step.

(3) In the embodiment described in (1) or (2) above, the following may be performed: In the preparation step, the torsion beam material having a concave bottom line is prepared; the selvage compression bending step. The bottom line is made linear by adding a bend to the torsion beam material to reduce the concave bending of the bottom line.

(4) In the embodiment described in (1) or (2) above, the following may be performed: After the selvage compression bending step, there is further a bending back step of adding a bending to straighten the bottom line. The tensile strain applied in the bending back step is made smaller than the compression strain applied in the selvage compression bending step.

(5) The torsion beam manufacturing apparatus according to one aspect of the present invention is an apparatus for carrying out the torsion beam manufacturing method according to the above (1), and is the torsion beam material in which the central portion and the shape changing portion are formed. A first mold that abuts on the selvage side at the position of the central portion; and a second mold that abuts on the bottom line side at a position farther from the central portion than the shape change portion; A drive mechanism for relatively approaching the mold and the second mold;

(6) In the embodiment described in (5) above, the relative approach amount between the first mold and the second mold by the drive mechanism is controlled to obtain compression strain along the longitudinal direction. Further, a control mechanism for 0.5% or more and 10% or less may be provided.

According to the torsion beam manufacturing method and the torsion beam manufacturing apparatus according to each of the above aspects, the residual stress in the selvage can be reduced or removed by simply bending the torsion beam material, and the thickening of the selvage can also be obtained. , It is not necessary to increase the wall thickness of the torsion beam material in advance. Therefore, it is possible to efficiently manufacture a torsion beam that is lightweight and has excellent fatigue characteristics.

It is a perspective view which shows the schematic structure of the torsion beam type rear suspension apparatus which concerns on one Embodiment of this invention. It is a figure which shows the schematic structure of the torsion beam assembly provided in the torsion beam type rear suspension apparatus, and is the perspective view seen from the bottom. It is a perspective view which shows the schematic structure of the torsion beam which comprises the torsion beam assembly. It is a perspective view which shows the schematic structure of the shape change part of the torsion beam. It is a figure which shows the torsion beam, and is the closed sectional view when it looks at the arrow view VA-VA of FIG. It is a figure which shows the torsion beam, and is the closed sectional view when it looks at the arrow view VB-VB of FIG. It is a figure which shows the torsion beam, and is the closed sectional view when it looks at the arrow VC-VC of FIG. It is a flowchart which shows the manufacturing process of the torsion beam. It is a vertical sectional view of the torsion beam manufacturing apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the closed state of the movable type and the fixed type provided in the torsion beam manufacturing apparatus, and is the vertical sectional view at the position AA of FIG. It is a vertical sectional view which shows the selvage compression bending processing which is one step of the torsion beam manufacturing method which concerns on the same embodiment, (A) shows before selvage compression bending processing, (B) after selvage compression bending processing. Is shown. It is a vertical sectional view which shows the selvage compression bending processing which is one step of the torsion beam manufacturing method which concerns on 2nd Embodiment of this invention, (A) shows before selvage compression bending processing, (B) is an ear part. Shown after compression bending. It is a figure which shows the modification of selvage compression bending processing in the same embodiment, (A) shows before selvage compression bending processing, (B) shows after selvage compression bending processing. It is a vertical sectional view which shows the selvage compression bending processing which is one step of the torsion beam manufacturing method which concerns on 3rd Embodiment of this invention, (A) shows before selvage compression bending processing, (B) is an ear part. Shown after compression bending. It is a vertical sectional view which shows an example of the manufacturing apparatus which performs selvage compression bending processing in the same embodiment, (A) shows before selvage compression bending processing, (B) shows after selvage compression bending processing. It is a vertical sectional view which shows the other example of the manufacturing apparatus which performs selvage compression bending processing in the same embodiment, (A) shows before selvage compression bending processing, (B) after selvage compression bending processing. show. It is a vertical sectional view which shows the selvage compression bending processing which is one step of the torsion beam manufacturing method which concerns on 4th Embodiment of this invention, (A) shows before selvage compression bending processing, (B) is an ear part. Shown after compression bending. It is a vertical sectional view which shows the modification of selvage compression bending processing which concerns on the same embodiment, (A) shows before selvage compression bending processing, (B) shows after selvage compression bending processing. It is a vertical sectional view which shows the selvage compression bending processing which is one step of the torsion beam manufacturing method which concerns on 5th Embodiment of this invention, (A) shows before selvage compression bending processing, (B) is an ear part. Shown after compression bending. It is a vertical sectional view which shows the selvage compression bending processing which is one step of the torsion beam manufacturing method which concerns on 6th Embodiment of this invention, (A) shows before selvage compression bending processing, (B) is an ear part. Shown after compression bending. It is a figure which shows the modification of the torsion beam manufacturing method which concerns on the 3rd Embodiment to 6th Embodiment, and is the flowchart in the case of bending back. It is a figure explaining an example of how to obtain the compression strain by selvage compression bending processing of each above embodiment, (A) shows before selvage compression bending processing, (B) after selvage compression bending processing. show. It is a figure explaining another example of the method of obtaining the compression strain by the selvage compression bending processing of each above embodiment, (A) shows before selvage compression bending processing, (B) is the selvage part compression bending processing. Shown later. It is a figure explaining still another example of the method of obtaining the compression strain by selvage compression bending of each said embodiment, (A) shows before selvage compression bending processing, (B) is the selvage compression bending. Shown after processing. It is a figure which shows the Example which explains the effect of the selvage compression bending process, and is the graph which shows the relationship between the compression strain applied to the torsion beam material, and the residual stress in the cracking risk part inside the selvage part.

Each embodiment and modification of the torsion beam manufacturing method and the torsion beam manufacturing apparatus of the present invention will be described, but before that, an example of the torsion beam will be described below with reference to FIGS. 1 to 5C.

FIG. 1 is a perspective view showing an example of a schematic configuration of a torsion beam type rear suspension device (torsion beam type suspension device). In FIG. 1, reference numeral 1 indicates a torsion beam type rear suspension device, reference numeral 2 indicates a torsion beam assembly, and reference numeral 10 indicates a torsion beam. The reference numeral F shown in FIG. 1 indicates the front of the vehicle (not shown) on which the torsion beam type rear suspension device 1 is mounted, and the reference numeral R indicates the rear.
As shown in FIG. 1, the torsion beam type rear suspension device 1 includes a torsion beam assembly 2, a spring 3 connecting the torsion beam assembly 2 and a vehicle body (not shown), and an absorber and 4.

The torsion beam assembly 2 supports the left and right wheels WL and WR by a pair of left and right trailing arms 5, and is connected to the vehicle body via pivot shafts JL and JR extending slightly from the left and right sides of the vehicle body toward the front center side. ing. The torsion beam assembly 2 is configured to be swingable with respect to the vehicle body.
As shown in FIG. 2, the torsion beam assembly 2 includes, for example, a pair of left and right trailing arms (arms) 5, a torsion beam 10 connecting the trailing arms 5, and a pair of left and right spring receiving portions that support the spring 3. It is equipped with 3A. Further, one end side of the absorber 4 which is a shock absorber 4 is connected to a shock absorber receiving portion (not shown).
In the present embodiment, as shown in FIGS. 1 and 2, the torsion beam 10 has a substantially V-shaped closed cross-sectional shape that is convex upward.

As shown in FIG. 2, the trailing arm 5 is connected to, for example, the trailing arm main body 5A and the front end of the trailing arm main body 5A, and is supported by the vehicle body via the pivot shaft J. It includes a 5F and a wheel mounting member 5R connected to the rear end of the trailing arm main body 5A to support the wheels WL and WR.
The spring receiving portion 3A is arranged on the opposite side of the pivot mounting member 5F with the torsion beam 10 interposed therebetween, and one end side of the spring 3 is mounted. The load received from the road surface is transmitted to the vehicle via the wheels WL, WR, the trailing arm 5, and the spring 3.

Hereinafter, the torsion beam 10 according to the present embodiment will be described with reference to FIGS. 3 to 5C.
FIG. 3 is a perspective view illustrating a schematic configuration of the torsion beam 10 according to the present embodiment. FIG. 4 is a perspective view illustrating a schematic configuration in the vicinity of the shape changing portion of the torsion beam 10. 5A, 5B, and 5C are cross-sectional views showing a torsion beam 10, FIG. 5A shows a cross-sectional view taken along the line VA-VA in FIG. 4, and FIG. 5B shows a cross-sectional view taken along the line VB-VB in FIG. A cross-sectional view is shown, and FIG. 5C shows a cross-sectional view of the arrow VC-VC in FIG.

As shown in FIGS. 3 and 4, the torsion beam 10 is formed on the central side in the longitudinal direction and has a fixed cross-section portion 11 having a substantially V-shaped fixed cross-section, a shape change portion 12, and a mounting closed portion. It includes a cross-sectional portion 13 and a mounting portion 14 formed at the outer end of the mounting closed cross-sectional portion 13 and having a substantially elliptical closed cross-sectional shape to which the trailing arm 5 is mounted.

The constant shape closed cross-section portion 11 has a substantially V-shaped or substantially U-shaped substantially constant closed cross-sectional shape continuously formed along the longitudinal direction when the torsion beam 10 is viewed in a cross section perpendicular to the longitudinal direction thereof. This is the part that has been done. In the fixed cross-section portion 11, a partially uneven shape may be formed in a valley portion (bottom portion) of a wall portion forming a concave side having a substantially V-shape or a substantially U-shape.
In the shape changing portion 12, the depth of the valley portion (bottom portion) of the wall portion forming the concave side of the substantially V-shape or the substantially U-shape gradually becomes shallower toward the outside in the longitudinal direction (outside in the vehicle width direction). Is the part that becomes. It should be noted that a portion where the valley portion (bottom portion) becomes shallower may be partially formed in the middle of the shape changing portion 12.
The mounting closed cross-sectional portion 13 is arranged outside the longitudinal direction (outside in the vehicle width direction) of the shape changing portion 12, and refers to a portion in which a recess having a substantially V-shape or a substantially U-shape is not formed.

The constant shape closed cross-section portion 11, the shape changing portion 12, the mounting closed cross-section portion 13, and the mounting portion 14 are arranged in this order from the center in the longitudinal direction of the torsion beam 10 toward both ends. The constant shape closed cross-section portion 11 and the shape change portion 12 are connected by the connection portion 12A shown in FIG.

As shown in FIGS. 3 and 4, the constant shape closed cross-section portion 11 is located at the center of the torsion beam 10 in the longitudinal direction, and is connected to each shape changing portion 12 at both ends in the longitudinal direction thereof.
The constant shape closed cross section 11 has a cross section orthogonal to the longitudinal direction of the torsion beam 10 formed into a substantially V-shaped constant shape, and in this embodiment, for example, has a shape symmetrical in the vehicle body front-rear direction. There is.

The cross section of the constant shape closed cross section 11 is, for example, in the substantially V-shaped closed cross section shown in FIG. 5A, the first wall portion S110A forming the concave inner surface, the second wall portion S120A forming the convex outer surface, and the like. It is provided with two folded wall portions S130A that connect both ends of each of the first wall portion S110A and the second wall portion S120A and bulge outward in the closed cross section. The central portion in the circumferential direction of the first wall portion S110A is a valley portion (bottom portion) S111A on the concave side having a substantially V shape in the fixed cross-sectional portion 11.
The first wall portion S110A and the second wall portion S120A are in contact with each other via the close contact portion S150A.
Each folded wall portion S130A forms an ear portion e, and the lowermost lower end edge, which is a folded point of the second wall portion S120A, forms a bottom line bt. The pair of ears e extend along the longitudinal direction of the torsion beam 10. Similarly, the bottom line bt also extends along the longitudinal direction of the torsion beam 10.

Each folded wall portion S130A is a range indicated by an arrow in FIG. 5A, and each is formed between the first wall portion side folding point a and the second wall portion side folding point b.
The first wall portion side folding point a is a connection point between the end edge of the first wall portion S110A and the end edge of the folding wall portion S130A. Further, the second wall portion side folding point b is a connection point between the end edge of the second wall portion S120A and the end edge of the folding wall portion S130A.

The connection portion 12A (connection region) shown in FIG. 4 is a portion that connects between the constant shape closed cross section portion 11 and the shape change portion 12 and includes a boundary between the constant shape closed cross section portion 11 and the shape change portion 12. That is, as shown in FIG. 4, the connecting portion 12A is located at an intermediate position in the longitudinal direction of the shape changing portion 12 (for example, the shape changing portion 12) from the cross section S12A which is a boundary between the constant shape closed cross section 11 and the shape changing portion 12. The valley portion (bottom portion) of the wall portion constituting the concave side of the substantially V-shaped or substantially U-shaped shape gradually becomes shallower, and is a portion extending to the position of the cross section S12C which shifts to a form inclined with respect to the longitudinal direction). .. The range of the connecting portion 12A can be arbitrarily set based on the distribution of tensile residual stress and the like.

As shown in FIG. 5B, for example, the cross section S12B included in the connecting portion 12A includes a first wall portion S110B having a concave inner surface in a substantially V-shaped closed cross section and a second wall portion having a convex outer surface in the closed cross section. It is provided with S120B and two folded wall portions S130B that connect both ends of the first wall portion S110B and the second wall portion S120B and bulge outward in the closed cross section. Further, the central portion in the circumferential direction of the first wall portion S110B is a valley portion (bottom portion) S111B on the concave side having a substantially V shape in the connecting portion 12A.
A hollow portion S150B is formed between the first wall portion S110B and the second wall portion S120B.
Each folded wall portion S130B forms an ear portion e, and the lowermost lower end edge, which is a folded point of the second wall portion S120B, forms a bottom line bt. The pair of ears e extend along the longitudinal direction of the torsion beam 10 and are connected to the pair of ears e of the fixed-shaped closed cross-section portion 11. Similarly, the bottom line bt also extends along the longitudinal direction of the torsion beam 10 and is continuous with the bottom line bt of the constant-shaped closed cross-section portion 11.

Each folded wall portion S130B is a range indicated by an arrow in FIG. 5B, and each is formed between the first wall portion side folding point a1 and the second wall portion side folding point b1.
The first wall portion side folding point a1 is a connection point between the end edge of the first wall portion S110B and the end edge of the folding wall portion S130B. Further, the second wall portion side folding point b1 is a connection point between the end edge of the second wall portion S120B and the end edge of the folding wall portion S130B.

As shown in FIG. 4, in the shape changing portion 12, the torsion beam 10 near the center in the longitudinal direction is connected to the fixed shape closed cross-section portion 11, and the outside in the longitudinal direction is connected to the mounting closed cross-section portion 13.
Further, in the shape changing portion 12, the shape of the closed cross section orthogonal to the longitudinal direction of the torsion beam 10 gradually shifts from the constant shape closed cross section portion 11 toward the mounting closed cross section portion 13.

As shown in FIG. 5C, the shape changing portion 12 includes, for example, a first wall portion S110C having a concave inner surface in a substantially V-shaped closed cross section and a second wall portion S120C having a convex outer surface in the closed cross section. , Both ends of the first wall portion S110C and the second wall portion S120C are connected to each other, and two folded wall portions S130C that bulge outward in the closed cross section are provided. Further, the central portion in the circumferential direction of the first wall portion S110C is a valley portion (bottom portion) S111C on the concave side having a substantially V shape.
A hollow portion S150C is formed between the first wall portion S110C and the second wall portion S120C.
Each folded wall portion S130C forms an ear portion e, and the lowermost lower end edge, which is a folded point of the second wall portion S120C, forms a bottom line bt. The pair of ears e extend along the longitudinal direction of the torsion beam 10 and are connected to the pair of ears e of the shape changing portion 12. Similarly, the bottom line bt also extends along the longitudinal direction of the torsion beam 10 and is continuous with the bottom line bt of the shape changing portion 12.

The folded wall portion S130C is a range indicated by an arrow in FIG. 5C, and each is formed between the first wall portion side turning point a2 and the second wall portion side turning point b2.
The first wall portion side folding point a2 is a connection point between the end edge of the first wall portion S110C and the end edge of the folding wall portion S130C. Further, the second wall portion side folding point b2 is a connection point between the end edge of the second wall portion S120C and the end edge of the folding wall portion S130C.

As shown in FIG. 4, the mounting closed cross-section portion 13 is located, for example, outward in the longitudinal direction (outside in the vehicle width direction) of the shape changing portion 12, and has a substantially V-shaped or substantially U-shaped recess. It has a substantially elliptical closed cross section that does not have.

Hereinafter, embodiments of the torsion beam manufacturing method and the torsion beam manufacturing apparatus of the present invention will be described.
First, with reference to FIG. 6, the general flow of the manufacturing process of the torsion beam 10 will be described. FIG. 6 is a flowchart showing an example of the manufacturing process of the torsion beam 10, and is manufactured through each step of steps S101 to S105 as shown below.

(1) First, a metal material tube is prepared (step S101). As the metal material pipe to be prepared, for example, a circular steel pipe having a uniform wall thickness can be used.
(2) Next, a press working step of the metal material pipe is performed (step S102). That is, the torsion beam material M10 is formed by pressing the metal material tube. For press working, it is possible to use a well-known press working machine.
(3) The torsion beam material M10 is formed by the press working in step S102 (step S103). The torsion beam material M10 has a constant shape closed cross-section portion 11, a shape change portion 12, and a mounting closed cross-section portion 13, and a connection portion 12A (connection) that connects the constant shape closed cross-section portion 11 and the shape change portion 12. Region) is formed.

By the above steps S101 to S103, the preparation step for preparing the torsion beam material M10 having the constant shape closed cross-section portion 11 (central portion), the shape changing portion 12, the mounting closed cross-section portion 13, and the mounting portion 14 is completed. .. The shape of the torsion beam material M10 obtained through this preparation step is any of the following (a) to (c) when the bottom line bt is on the lower side and the selvage portion e is on the upper side. You may.
(A) A torsion beam material M10 that is straight along the longitudinal direction.
(B) A torsion beam material M10 that is curved in a bow shape so that the bottom line bt side is concave over the entire length in the longitudinal direction.
(C) The torsion beam material M10 is partially warped so that the bottom line bt side is concave only at the position of the shape changing portion 12 in the longitudinal direction, and the other portions are straight.

(4) In the selvage compression bending step (hereinafter, also referred to as selvage compression bending process) performed after the preparatory step, the torsion beam material M10 is subjected to a bending process for applying compression strain at least at the position of the selvage e. (Step S104). The compression strain to be applied at that time is preferably 0.5% or more and 10% or less. Further, it is more preferable that the lower limit value of the compression strain is set to 1% or more. Further, it is more preferable that the upper limit value of the compression strain is set to less than 2%.
That is, since the compression strain at which the plastic deformation at the selvage e begins is 0.5%, 0.5% or more can be used as the lower limit of the compression strain applied to the selvage e. Further, from the examination results shown in Examples described later, it is possible to impart sufficient compression strain to the selvage e by setting the compression strain to 1% or more.
On the other hand, if the compression strain exceeds 10%, buckling may occur in the torsion beam material M10. Therefore, less than 10% can be used as the upper limit setting of the compression strain. Further, from the viewpoint of preventing the V-shape or U-shape of the constant shape closed cross-section portion 11 and the shape change portion 12 from opening and deteriorating the dimensional accuracy, it is preferable to suppress the compression strain to less than 2%.
The compressive force on the selvage e may be applied only in the longitudinal direction of the torsion beam material M10 to a range in which the residual stress is particularly desired to be reduced, but when the compressive force is applied over the entire length of the selvage e, the residual stress is applied. It is more preferable in that it can be reduced without omission as a whole.

(5) The torsion beam 10 is formed by performing the selvage compression bending process of the torsion beam material M10 in step S104 as described above (step S105).
The shape of the torsion beam 10 obtained in step S105 may be any of the following (d) to (f) depending on the intended use and the content of the selvage compression bending process when viewed from the side. ..
(D) A torsion beam 10 that is straight along the longitudinal direction.
(E) A torsion beam 10 that is curved in a bow shape so that the bottom line bt side is convex over the entire length in the longitudinal direction.
(F) A torsion beam 10 in which only the position of the shape changing portion 12 is locally warped so that the bottom line bt side is convex in the longitudinal direction, and the other portions are straight.

Of the steps described above, since the selvage compression bending process is common to each embodiment except for the selvage compression bending process shown in step S104, the selvage compression bending process will be mainly described in the following description of each embodiment.

[First Embodiment]
A first embodiment of the present invention and a modification thereof will be described below with reference to the drawings.
FIG. 7 is a vertical sectional view of the torsion beam manufacturing apparatus 50 according to the present embodiment. Further, FIG. 8 is a view showing a closed state of the fixed mold 51 and the movable mold 52 provided in the torsion beam manufacturing apparatus 50, and is a vertical sectional view at the position AA of FIG. 7.
The torsion beam manufacturing apparatus 50 mainly performs the selvage compression bending process, but may be configured so that the press process shown in step S102 can also be performed as a pre-process. However, since the residual stress generated in the selvage e of the torsion beam material M10 is generated after the metal material tube is formed into a V shape or a U shape by press working, the press working (step S102) and the selvage compression bending work (step S102) Excludes the configuration in which step S104) is performed at the same time.

The torsion beam manufacturing apparatus 50 is an apparatus that mainly performs compression bending of the selvage portion in step S104, and is a fixed mold (second mold) 51, a movable mold (first mold) 52, and a drive unit (drive mechanism). ) 53 and.
As shown in FIG. 8, the fixed mold 51 is a mold having a concave groove 51a that supports the bottom line bt side of the torsion beam material M10, that is, the lower surface side having a convex closed cross section, and is fixed at a fixed position. ing. The concave groove 51a is a concave groove having a linearly long vertical cross section along one direction in which the torsion beam material M10 is arranged. On the other hand, when the concave groove 51a is viewed in a cross section perpendicular to the longitudinal direction, the cross-sectional shape is the outer shape on the bottom line bt side in each of the constant shape closed cross-sectional portion 11, the shape changing portion 12, and the mounting closed cross-sectional portion 13. It has a shape that matches.

However, in the present embodiment, as shown in FIG. 9, the torsion beam material M10 before the selvage compression bending process is curved in a bow shape so that the bottom line bt side is concave over the entire length in the longitudinal direction. Therefore, when the torsion beam material M10 is placed in the concave groove 51a, it is supported at two points at both ends thereof, and the constant shape closed cross-section portion 11 and the shape changing portion 12 are slightly raised from the concave groove 51a. .. Then, after the selvage compression bending process, as shown in FIG. 8, the entire surface on the bottom line bt side, including the constant shape closed cross-section portion 11 and the shape change portion 12, comes into surface contact with the concave groove 51a. Be supported.
Therefore, the dimension of the raised portion of the fixed shape closed cross-section portion 11 with respect to the concave groove 51a before the selvage compression bending process becomes the processing allowance when the selvage compression bending process is performed. In the case of the present embodiment, this processing allowance is determined by the degree of warpage of the torsion beam material M10. Therefore, by adjusting the degree of warpage (curvature) of the torsion beam material M10 after step S102, the compression strain applied to the selvage e is controlled. It is possible.

The movable type 52 is attached to the drive unit 53, and is relatively close to and separated from the fixed type 51 by receiving the driving force of the drive unit 53.
The lower surface shape of the movable type 52 has a linear shape at the central portion 52a along the longitudinal direction when viewed from the side shown in FIG. 7, and is fixed at a pair of both side portions 52b connected to both sides of the central portion 52a. It has an inclined shape that warps in the direction away from the mold 51. The central portion 52a has a length dimension corresponding to the length of the concave groove when the fixed-shaped closed cross-section portion 11 is linearized. Further, both side portions 52b have shape dimensions corresponding to the length and inclination angle of the concave groove when the shape changing portion 12 is made linear.

On the other hand, when the lower surface shape of the movable type 52 is viewed in a cross section perpendicular to the longitudinal direction thereof, for example, in the central portion 52a shown in FIG. 8, a V-shaped or U-shaped convex corresponding to the concave groove of the fixed shape closed cross-sectional portion 11 It has a shape. Similarly, both side portions 52b have a V-shaped or U-shaped convex shape corresponding to the concave groove of the shape changing portion 12. The height of the central portion 52a of the movable type 52 is substantially constant in the longitudinal direction thereof, but the height of both side portions 52b gradually decreases as the distance from the central portion 52a increases.
Further, as shown in FIG. 8, on the lower surface of the movable mold 52, a pair of concave grooves 52c which are connected to both sides of the central portion 52a and have a cross-sectional shape corresponding to the selvage portion of the torsion beam material M10 are formed. These concave grooves 52c have a cross-sectional shape capable of pressing the selvage portion e side of the torsion beam material M10 together with the central portion 52a.

According to the torsion beam manufacturing apparatus 50 having the above-described configuration, the residual stress in the selvage can be reduced or removed by performing the selvage compression bending process on the torsion beam material M10. The details will be described with reference to FIGS. 7 and 9. Reference numerals S1 and S2 shown in FIG. 9 indicate support points by the fixed type 51.
In the selvage compression bending process, first, as shown in FIGS. 7 and 9A, the movable die 52 is brought closer to the torsion beam material M10 arranged in the fixed die 51 by the driving force of the drive section 53. .. Then, the central portion 52a of the movable mold 52 abuts at one point (the position of the white arrow) in the longitudinal direction of the fixed-shaped closed cross-sectional portion 11. When the movable type 52 is further pressed from this state, the torsion beam material M10 is straightened with less warpage. At this time, the range of the contact portion between the central portion 52a of the movable mold 52 and the constant-shaped closed cross-sectional portion 11 of the torsion beam material M10 gradually expands, and finally both side portions 52b are concave grooves of the shape changing portion 12. Matches within. This point becomes the bottom dead center of the movable mold 52, and as shown in FIG. 9B, the torsion beam material M10 is straightened, and the bottom line bt matches the concave groove 51a of the fixed mold 51 over its entire length. ..

When the torsion beam material M10 is straightened in this way, a tensile force along the longitudinal direction is applied below the central axis CL, and a compressive force along the longitudinal direction is applied above the central axis. The compressive force generated at this time is applied to the selvage portion e of the torsion beam material M10, so that the residual stress of the selvage portion e is reduced or removed. Moreover, due to the compressive force applied to the selvage portion e, the selvage portion e is thickened and the plate thickness is increased. Therefore, it is possible to increase the mechanical strength of the selvage e by increasing the plate thickness in addition to reducing or removing the residual stress.
As described above, according to the torsion beam manufacturing method using the torsion beam manufacturing apparatus of the present embodiment, the strength of the ear portion can be increased by simple processing without increasing the wall thickness of the metal material tube itself, so that the weight is lightweight. It is possible to efficiently manufacture a torsion beam having excellent fatigue characteristics.

The outline of this embodiment described above is summarized below.
In the torsion beam manufacturing method of the present embodiment, the fixed cross-section portion 11 (center), which is a substantially V-shaped or substantially U-shaped closed cross section having the selvage portion e at an arbitrary position in the longitudinal direction in which the cross section orthogonal to the longitudinal direction is an arbitrary position in the longitudinal direction. This is a method for manufacturing a torsion beam 10 including a portion), a shape changing portion 12 connected to a fixed shape closed cross section portion 11, having an ear portion e, and a shape changing portion 12 in which the closed cross section gradually changes along the longitudinal direction. .. Then, this torsion beam manufacturing method includes a preparatory step of preparing a torsion beam material M10 having a constant shape closed cross-section portion 11 and a shape changing portion 12; the selvage portion e of the shape changing portion 12 is bent with respect to the total length of the torsion beam material M10. It has a selvage compression bending step that applies bending to the inside of the;
According to the above-mentioned torsion beam manufacturing method, the torsion beam material M10 is bent so that the selvage portion e of the shape changing portion 12 is inside the bend, so that the selvage portion e of the torsion beam material M10 is formed along the longitudinal direction. Compressive force is applied. With this compressive force, the residual stress of the selvage e can be reduced or removed. Further, the selvage e can be thickened by the compressive force. Therefore, the torsion beam 10 which is lightweight and has excellent fatigue characteristics can be efficiently manufactured.

In the selvage compression bending step, at least the selvage e of the shape changing portion 12 is subjected to a compression strain of 0.5% or more and 10% or less in the longitudinal direction.
As a result, the residual stress of the selvage e can be more reliably reduced or removed.

In the preparatory step, a torsion beam material in which the bottom line bt is curved in a concave shape over the entire length in the longitudinal direction is prepared; in the selvage compression bending step, a bending that reduces the concave bending of the bottom line bt is added to the torsion beam material M10. As a result, the bottom line bt is made linear.
As a result, a linear torsion beam 10 can be obtained.

The torsion beam manufacturing apparatus 50 of the present embodiment includes a movable type 52 that abuts on the selvage side at the position of the fixed shape closed cross section portion 11 among the torsion beam material M10 in which the constant shape closed cross section portion 11 and the shape changing portion 12 are formed. A fixed mold 51 that abuts on the bottom line bt side at a position farther from the fixed shape closed cross-section portion 11 than the shape changing portion 12; and a drive portion 53 that brings the movable mold 52 relatively close to the fixed mold 51; Be prepared.
According to the torsion beam manufacturing apparatus 50, a compressive force along the longitudinal direction is applied to the selvage portion e of the torsion beam material M10 by bringing the movable mold 52 closer to the fixed mold 51 by the drive portion 53. With this compressive force, the residual stress of the selvage e can be reduced or removed. Further, the selvage e can be thickened by the compressive force. Therefore, the torsion beam 10 which is lightweight and has excellent fatigue characteristics can be efficiently manufactured.

In the above embodiment, the compression strain applied to the selvage e is adjusted within a predetermined range by the warp amount of the torsion beam material M10, but the compression of the selvage e is performed by controlling the movement amount of the movable type 52. The distortion may be controlled. That is, the amount of relative approach of the movable mold 52 to the fixed mold 51 by the drive unit 53 is controlled so that the compression strain along the longitudinal direction of the selvage portion e of the shape changing portion 12 is 0.5% or more and 10% or less. A control mechanism (not shown) may be further provided.
In this case as well, the residual stress of the selvage e can be reliably reduced or removed.

[Second Embodiment]
A second embodiment of the present invention and a modification thereof will be described below with reference to FIGS. 10 and 11. 10A and 10B are vertical cross-sectional views showing selvage compression bending, which is one step of the torsion beam manufacturing method according to the present embodiment. FIG. 10A shows before selvage compression bending, and FIG. 10B shows the selvage compression bending process. The figure after the selvage compression bending process is shown. Note that FIGS. 10A and 10B are drawings corresponding to FIGS. 9A and 9B, and the torsion beam manufacturing apparatus 50 is not shown.

In the selvage compression bending step of the first embodiment, the torsion beam material M10 warped in a bow shape was bent so that the bottom line bt side was concave over the entire length in the longitudinal direction. On the other hand, in the present embodiment, the torsion beam material M10 is partially warped so that the bottom line bt side is concave only at the position of the shape changing portion 12 in the longitudinal direction, and the other portions are straight. It is bent into a straight torsion beam 10 along the above.

That is, in the preparation step of the present embodiment, the torsion beam material M10 having the shape shown in FIG. 10A is prepared and arranged in the fixed mold 51 of the torsion beam manufacturing apparatus 50.
As shown in FIG. 10A, the central axis CL when the torsion beam material M10 before the compression bending process of the ear portion is viewed from the side is a straight line in the constant shape closed cross-section portion 11 and the bottom in the shape change portion 12. The line bt side forms a curved curve so as to form a concave shape, and the mounting closed cross-section portion 13 forms a straight line.
The positions for supporting the torsion beam material M10 are two support points within the range where the mounting closed cross-sectional portion 13 exists and at a position close to the shape changing portion 12 when viewed along the longitudinal direction of the torsion beam material M10. It is preferably S1 and S2. In order to perform this two-point support with the fixed mold 51, a form is provided in which a protrusion is provided at a position corresponding to the support points S1 and S2 in the concave groove 51a shown in FIG. 7 to support the torsion beam material M10 from below. Conceivable.

In the subsequent selvage compression bending step, as shown by the white arrow in FIG. 10A, the range of the fixed shape closed cross-section portion 11 in the longitudinal range of the torsion beam material M10 is pressed with an equal force. That is, the movable mold 52 shown in FIG. 7 is pressed against the fixed cross-sectional portion 11 having a constant shape. Then, the bending of the shape changing portion 12 is straightened while maintaining the linear shape of the constant shape closed cross section portion 11, and the torsion beam 10 shown in FIG. 10B is obtained. At that time, a compressive force in the direction along the axis CL is applied to the selvage portion e of the shape changing portion 12. This compressive force reduces or eliminates the residual stress in the selvage e.

The bending to the shape changing portion 12 can be similarly added by the modification shown in FIG. 11, for example. In FIG. 11, (A) shows before the selvage compression bending process, and (B) shows after the selvage compression bending process.
In this modification, the split type 51A is adopted instead of the fixed type 51. The split type 51A is a central type 51A1 that supports the bottom line bt side of the constant shape closed cross-section portion 11 in the torsion beam material M10, and an end type 51A2 that is arranged adjacent to both sides of the central type 51A1 and rotates around the support pin 51A3. And have.

In the selvage compression bending step according to this modification, first, the torsion beam material M10 is placed on the central mold 51A1. At this time, both end molds 51A2 are lowered toward the lower side around the support pin 51A3. In this state, the movable mold 52 is lowered this time to sandwich the constant-shaped closed cross-sectional portion 11 with the central mold 51A1, so that the state shown in FIG. 11A is obtained.
Subsequently, as shown in FIG. 11B, both end molds 51A2 are rotated upward around the support pin 51A3. Then, since each end type 51A2 pushes up the bottom line bt side of the mounting closed cross-section portion 13 upward, a compressive force in the direction along the axis CL is applied to the selvage portion e of each shape change portion 12. .. This compressive force reduces or eliminates the residual stress in the selvage e.

[Third Embodiment]
A third embodiment of the present invention and a modification thereof will be described below with reference to FIGS. 12 and 13. 12A and 12B are vertical cross-sectional views showing selvage compression bending, which is one step of the torsion beam manufacturing method according to the present embodiment, in which FIG. 12A shows before selvage compression bending, and FIG. 12B shows the selvage compression bending process. The figure after the selvage compression bending process is shown. Note that FIGS. 12A and 12B are drawings corresponding to FIGS. 9A and 9B, and the torsion beam manufacturing apparatus 50 is not shown.

In the selvage compression bending step of the first embodiment, the torsion beam material M10 warped in a bow shape was bent so that the bottom line bt side was concave over the entire length in the longitudinal direction. On the other hand, in the present embodiment, the torsion beam material M10 that is straight over the entire length in the longitudinal direction is bent into a torsion beam 10 that is curved in a bow shape so that the bottom line bt side is convex over the entire length in the longitudinal direction.

That is, in the preparation step of the present embodiment, as shown in FIG. 12A, the torsion beam material M10 is prepared and arranged in the fixed mold 51 of the torsion beam manufacturing apparatus 50.
As shown in FIG. 12A, the central axis CL when the torsion beam material M10 before the selvage compression bending process is viewed from the side is the fixed shape closed cross-section portion 11, the shape change portion 12, and the mounting closed cross-section portion 13. Everything is straight.
As the positions for supporting the torsion beam material M10, when viewed along the longitudinal direction of the torsion beam material M10, two supports within the range where the mounting closed cross-sectional portion 13 exists and at a position close to the shape changing portion 12. The points S1 and S2 are preferable. In order to perform this two-point support with the fixed mold 51, a form is provided in which a protrusion is provided at a position corresponding to the support points S1 and S2 in the concave groove 51a shown in FIG. 7 to support the torsion beam material M10 from below. Conceivable.

In the subsequent selvage compression bending step, as shown by the white arrow in FIG. 12 (A), when viewed along the longitudinal direction of the torsion beam material M10, the central position in the longitudinal direction of the fixed shape closed cross-section portion 11 is downward. Pressurize toward. As the lower shape of the movable type 52 for such pressurization, a shape in which the central position in the longitudinal direction is convex in a bow shape so as to be closest to the torsion beam material M10 can be adopted.
The torsion beam material M10 pressurized by the movable type 52 is curved in a bow shape so that its bottom line bt side is convex, and the torsion beam 10 shown in FIG. 12 (B) is obtained. At that time, a compressive force in the direction along the axis CL is applied to the selvage portion e of the shape changing portion 12. This compressive force reduces or eliminates the residual stress in the selvage e.

It should be noted that the same bending as in the form of FIG. 12 can be added by, for example, the modification shown in FIG. In FIG. 13, (A) shows before the selvage compression bending process, and (B) shows after the selvage compression bending process.
In this modification, the split type 51B is adopted instead of the fixed type 51. The split type 51B includes a central type 51B1 that supports the bottom line bt side of the constant-shaped closed cross-section portion 11 in the torsion beam material M10, and an end type 51B2 that is adjacent to both sides of the central type 51B1 and moves up and down. .. Although the movable type 52 is not shown in FIG. 13, a shape is adopted in which the central position in the longitudinal direction is convex in a bow shape so as to be closest to the torsion beam material M10, as in the third embodiment. It is preferable to do so.

In the selvage compression bending step according to this modification, first, as shown in FIG. 13A, the upper surface of the central mold 51B1 and the upper surfaces of the end molds 51B2 arranged adjacent to each other are set to the same height. In this state, the torsion beam material M10 is placed.
Subsequently, the central position of the torsion beam material M10 on the split die 51 in the longitudinal direction is pressed by the movable die 52 from above. That is, the central position of the torsion beam material M10 is sandwiched between the central type 51B1 and the movable type 52. As a result, the state shown in FIG. 13 (A) is obtained.
Subsequently, as shown in FIG. 13B, both end molds 51B2 are raised relative to the central mold 51B1. Then, since each end type 51B2 pushes up the bottom line bt of the mounting closed cross-section portion 13 upward, a compressive force in the direction along the axis CL is applied to the selvage portion e of each shape changing portion 12. This compressive force reduces or eliminates the residual stress in the selvage e.

FIG. 14 shows another modification of the present embodiment. In FIG. 14, (A) shows before the selvage compression bending process, and (B) shows after the selvage compression bending process.
In this modification, the split type 51C is adopted instead of the fixed type 51. The split type 51C is a central type 51C1 that supports the bottom line bt side of the constant shape closed cross-section portion 11 in the torsion beam material M10, and an end type 51C2 that is arranged adjacent to both sides of the central type 51C1 and rotates around the support pin 51C3. And have. Although the movable type 52 is not shown in FIG. 14, a shape is adopted in which the central position in the longitudinal direction is convex in a bow shape so as to be closest to the torsion beam material M10, as in the third embodiment. It is preferable to do so.

In the selvage compression bending step according to this modification, first, as shown in FIG. 14A, the upper surface of the central mold 51C1 and the upper surfaces of the end molds 51C2 arranged adjacent to each other are set to the same height. In this state, the torsion beam material M10 is placed.
Subsequently, the central position of the torsion beam material M10 on the split die 51C in the longitudinal direction is pressed by the movable die 52 from above. That is, the central position of the torsion beam material M10 is sandwiched between the central type 51C1 and the movable type 52. As a result, the state shown in FIG. 14 (A) is obtained.
Subsequently, as shown in FIG. 14 (B), both end molds 51C2 are rotated upward around the support pin 51C3. Then, since each end type 51C2 pushes up the bottom line bt side of the mounting closed cross-section portion 13 upward, a compressive force in the direction along the axis CL is applied to the selvage portion of each shape changing portion 12. This compressive force reduces or eliminates the residual stress in the selvage e.

[Fourth Embodiment]
A fourth embodiment of the present invention and a modification thereof will be described below with reference to FIGS. 15 and 16. 15A and 15B are vertical cross-sectional views showing selvage compression bending, which is one step of the torsion beam manufacturing method according to the present embodiment, in which FIG. 15A shows before selvage compression bending, and FIG. 15B shows the selvage compression bending process. The figure after the selvage compression bending process is shown. Note that FIGS. 15A and 15B are drawings corresponding to FIGS. 9A and 9B, and the torsion beam manufacturing apparatus 50 is not shown.

In the selvage compression bending step of the first embodiment, the torsion beam material M10 warped in a bow shape was bent so that the bottom line bt side was concave over the entire length in the longitudinal direction. On the other hand, in the present embodiment, the bottom line bt side of the shape changing portion 12 is convex while maintaining the linear shape of the torsion beam material M10 which is straight over the entire length in the longitudinal direction and the constant shape closed cross section portion 11. Add a bending process that bends like a bow.

That is, in the preparation step of the present embodiment, the torsion beam material M10 having a linear shape shown in FIG. 15A is prepared and arranged in the fixed mold 51 of the torsion beam manufacturing apparatus 50.
As shown in FIG. 15A, in the torsion beam material M10 before the selvage compression bending process, the central axis CL when viewed from the side is a constant shape closed cross-section portion 11, a shape change portion 12, and a mounting closed cross-section portion 13. It is a straight line in all of.
As the positions for supporting the torsion beam material M10, when viewed along the longitudinal direction of the torsion beam material M10, two support points S1 at positions within the range where the mounting closed cross-sectional portion 13 exists and close to the shape changing portion 12. It is preferably S2. In order to perform this two-point support with the fixed mold 51, a form is provided in which a protrusion is provided at a position corresponding to the support points S1 and S2 in the concave groove 51a shown in FIG. 7 to support the torsion beam material M10 from below. Conceivable.

In the subsequent selvage compression bending step, as shown by the white arrow in FIG. 15 (A), when viewed along the longitudinal direction of the torsion beam material M10, the range of the fixed shape closed cross-section portion 11 is applied with an equal force. Press. That is, the movable mold 52 shown in FIG. 7 is pressed against the fixed cross-sectional portion 11 having a constant shape.
The torsion beam material M10 pressurized by the movable mold 52 is curved in a bow shape so that the bottom line bt side is convex in each of the shape changing portions 12, but the constant shape closed cross-sectional portion 11 is maintained in a linear shape. In this way, the torsion beam 10 shown in FIG. 15B is obtained, and at that time, a compressive force in the direction along the axis CL is applied to the selvage portion e of the shape changing portion 12. This compressive force reduces or eliminates the residual stress in the selvage e.

It should be noted that the same bending as in the form of FIG. 15 can be added by, for example, the modification shown in FIG. In FIG. 16, (A) shows before the selvage compression bending process, and (B) shows after the selvage compression bending process.
In the selvage compression bending step according to this modification, first, as shown in FIG. 16 (A), only the portion of the constant-shaped closed cross-section portion 11 of the torsion beam material M10 is covered with a mold (not shown) from above and below over the entire length. Hold it.
Subsequently, as shown in FIG. 16B, by pushing up the bottom line bt side of each mounting closed cross-section portion 13 upward, each shape changing portion 12 becomes a bow so that the bottom line bt side becomes convex. Add bending to warp. As a result, a compressive force in the direction along the axis CL is applied to the selvage portion e of each shape changing portion 12. This compressive force reduces or eliminates the residual stress in the selvage e.

[Fifth Embodiment]
A fifth embodiment of the present invention will be described below with reference to FIG. 17A and 17B are vertical cross-sectional views showing selvage compression bending, which is one step of the torsion beam manufacturing method according to the present embodiment, in which FIG. 17A shows before selvage compression bending, and FIG. 17B shows the selvage compression bending process. The figure after the selvage compression bending process is shown. Note that FIGS. 17A and 17B are drawings corresponding to FIGS. 9A and 9B, and the torsion beam manufacturing apparatus 50 is not shown.
In the selvage compression bending process of the present embodiment, a torsion beam material M10 that is curved in a bow shape so that the bottom line bt side is concave over the entire length in the longitudinal direction is prepared, and the torsion beam material M10 is applied to the overall length in the longitudinal direction. Bending is performed in the direction opposite to that before the selvage compression bending so that the bottom line bt side is convex over the bow.

That is, in the preparation step of the present embodiment, the torsion beam material M10 having the shape shown in FIG. 17A is prepared and arranged in the fixed mold 51 of the torsion beam manufacturing apparatus 50.
As shown in FIG. 17 (A), the central axis CL when the torsion beam material M10 before the selvage compression bending process is viewed from the side forms a curved curve so that the bottom line bt side forms a concave shape over the entire length. There is.
As the positions for supporting the torsion beam material M10, when viewed along the longitudinal direction of the torsion beam material M10, two supports are provided within the range where the mounting closed cross-sectional portion 13 exists and at a position close to the shape changing portion 12. The points S1 and S2 are preferable. Further, as shown in FIG. 17B, the range between the support points S1 and S2 is fixed in order to perform a bending process for pushing down the fixed-shaped closed cross-sectional portion 11 below the support heights of the support points S1 and S2. It is conceivable to adopt a shape in which the range corresponding to the support points S1 and S2 in the concave groove 51a of the mold 51 is deeper than the other ranges.

In the subsequent selvage compression bending step, as shown by the white arrow in FIG. 17 (A), the central position of the fixed shape closed cross-section portion 11 is directed downward when viewed along the longitudinal direction of the torsion beam material M10. Pressurize. Then, the overall shape of the central axis CL of the torsion beam material M10 changes from a shape that is convex upward, to a linear shape, and further to a shape that is convex downward as shown in FIG. 17 (B). It is bent into a shape. At that time, a compressive force in the direction along the axis CL is applied to the selvage portion e of the shape changing portion 12. This compressive force reduces or eliminates the residual stress in the selvage e.
In the present embodiment, the case where the torsion beam material M10 is supported from below and pushed down from above has been described, but the present invention is not limited to this embodiment. For example, the mounting closed cross-section portion 13 may be pushed upward at the support points S1 and S2 while the central position of the fixed-shaped closed cross-section portion 11 of the torsion beam material M10 is pressed from above, or the central position may be pushed down from above at the same time. Bending processing such as pushing up the mounting closed cross-section portion 13 at the positions of the support points S1 and S2 can also be adopted.

[Sixth Embodiment]
A sixth embodiment of the present invention will be described below with reference to FIG. 18 is a vertical sectional view showing selvage compression bending, which is one step of the torsion beam manufacturing method according to the present embodiment, in which FIG. 18A shows before selvage compression bending, and FIG. 18B shows the selvage compression bending process. The figure after the selvage compression bending process is shown. Note that FIGS. 18A and 18B are drawings corresponding to FIGS. 9A and 9B, and the torsion beam manufacturing apparatus 50 is not shown.
In the selvage compression bending step of the present embodiment, the torsion beam material M10 is partially warped so that the bottom line bt side is concave only at the position of the shape changing portion 12 in the longitudinal direction, and the other portions are straight. Only the position of the shape changing portion 12 is bent into a partially warped torsion beam 10 so that the bottom line bt side is convex.

That is, in the preparation step of the present embodiment, the torsion beam material M10 having the shape shown in FIG. 18A is prepared and arranged in the fixed mold 51 of the torsion beam manufacturing apparatus 50.
As shown in FIG. 18A, the central axis CL when the torsion beam material M10 before the compression bending process of the ear portion is viewed from the side is a straight line in the constant shape closed cross-section portion 11 and the bottom in the shape change portion 12. The line bt side forms a curved curve so as to form a concave shape, and the mounting closed cross-section portion 13 forms a straight line.
The positions that support the torsion beam material M10 are two points S1 that are within the range where the mounting closed cross-sectional portion 13 exists and are close to the shape changing portion 12 when viewed along the longitudinal direction of the torsion beam material M10. , S2 is preferable. Further, as shown in FIG. 18B, in order to perform a bending process of pushing down the portion between the two points S1 and S2 below the support height of the two points S1 and S2, the concave groove 51a of the fixed mold 51 is formed. Of these, it is conceivable to adopt a form in which the range corresponding to the two points S1 and S2 is dug deeper than the other ranges.

In the subsequent selvage compression bending step, as shown by the white arrow in FIG. 18A, the range of the fixed shape closed cross-section portion 11 is added downward when viewed along the longitudinal direction of the torsion beam material M10. Press. Then, the torsion beam material M10 has a shape in which the central axis CL is concave on the bottom line bt side at the two points of the shape changing portion 12, passes through a linear shape, and further, as shown in FIG. 18B, the bottom line bt. It is bent into a shape with a convex side. At that time, a compressive force in the direction along the axis CL is applied to the selvage portion e of the shape changing portion 12. This compressive force reduces or eliminates the residual stress in the selvage e.
In the present embodiment, the case where the torsion beam material M10 is supported from below and the portion of the constant shape closed cross-section portion 11 is pressed from above is described, but the present invention is not limited to this embodiment. For example, at the same time as bending to push up the mounting closed cross-section portion 13 at the support points S1 and S2 while pressing the constant-shaped closed cross-section portion 11 of the torsion beam material M10 from above, or pushing down the fixed-shaped closed cross-section portion 11 from above. Bending processing that pushes up the mounting closed cross-section portion 13 at the positions of the support points S1 and S2 can also be adopted.

Of the above-described embodiments, when the torsion beam 10 having a bend is finally obtained as in the third embodiment, the reverse bending is performed in order to reduce the bending or correct the bending to a linear shape. Further, bending back processing may be performed.
That is, instead of the process shown in the follow chart of FIG. 6, the process shown in the flowchart of FIG. 19 may be adopted. The difference between the flowchart of FIG. 19 and the flowchart of FIG. 6 is that S104a, which performs bending back processing, is performed after step S104, which performs compression bending processing of the selvage portion. Since the other steps are the same, duplicate explanations will be omitted using the same reference numerals.

In the bending back processing of step S104a, after the selvage compression bending step of step S104, bending is added to at least the shape changing portion 12 of the torsion beam material M10 to make the bottom line bt linear or close to a linear shape.
When this bending is applied, the amount of pull applied to the selvage portion e of the shape changing portion 12 may be smaller than the amount of compression applied to the selvage portion e of the selvage portion 12 in the selvage compression bending step. In this case, since the amount of thickening in the selvage e obtained in the selvage compression bending step is not significantly impaired by the bending back processing, it is possible to maintain the mechanical strength of the selvage changing portion 12 at a high level. ..

Further, as the compression strain applied to the selvage e in the selvage compression bending process of each of the above-described embodiments, 0.5% or more and 10% or less are exemplified. Regarding the definition of this compression strain, each case of FIGS. 20 to 22 will be described. In each figure, (A) shows a side view of the torsion beam material M10 before the selvage compression bending process, and (B) shows a side view of the torsion beam 10 after the selvage compression bending process. Further, in each figure, the reference numeral e indicates the selvage portion, and the reference numeral bt indicates the bottom line.
First, as a basic idea about the compression strain, first, a difference indicating how much the selvage e is shrunk compared to before the processing by the selvage compression bending process is obtained. Then, this difference is divided by the total length at the position of the central axis CL of the torsion beam material M10. Since the total length at the position of the central axis CL does not change before and after the selvage compression bending process, this is used as a reference.

For example, in the case of FIG. 20, a torsion beam material M10 curved over the entire length is prepared so that the bottom line bt side has a concave shape as shown in FIG. 20 (A), and this is a straight line as shown in FIG. 20 (B). This is a case where the selvage compression bending process is performed by bending and deforming the shape. In order to obtain the compression strain (%) in this case, first, the length L1 (mm) before the selvage compression bending process at the selvage e is subtracted from the length L2 (mm) after the selvage compression bending process. Find the difference D (mm). Then, the difference D (mm) is divided by the length L1 (mm) before the selvage compression bending process, and the result is multiplied by 100 to obtain the compression strain (%).
Here, in the selvage portion e, compression along the longitudinal direction is applied and the difference D (mm) is shortened, so that L2 <L1. Further, at the position of the central axis CL, neither compression nor pulling acts along the longitudinal direction, so that the length dimension L3 does not change before and after the selvage compression bending process. Further, since the bottom line bt is pulled along the longitudinal direction, it becomes longer after the selvage compression bending process than before the selvage compression bending process.
When the bending curvature shown in FIG. 20A is uniform at each position in the longitudinal direction of the torsion beam material M10 and L3 = L2, the radius of curvature Re, is replaced with the lengths L1 and L2. It is also possible to obtain the compression strain (%) using Rc. Here, the radius of curvature Rc is the curve at the central axis CL before the ear compression bending process, and the radius of curvature Re is the curve at the ear portion e before the ear compression bending process. Based on the above premise, the compression strain (%) in the selvage e is obtained by 100 × (Rc—Re) / Rc.

Subsequently, the case of FIG. 21 will be described. In this case, a torsion beam material M10 having a linear shape over the entire length is prepared as shown in FIG. 21 (A), and this is curved over the entire length so that the bottom line bt side forms a convex shape as shown in FIG. 21 (B). This is a case where the selvage compression bending process is performed by bending and deforming the shape. In this case, in order to obtain the compression strain (%), first, the difference between the length L1a (mm) before the selvage compression bending process and the length L1b (mm) after the selvage compression bending process in the selvage e. Find D (mm). Then, the difference D (mm) is divided by the total length L1a (mm) at the position of the central axis CL, and the result is multiplied by 100 to obtain the compression strain (%). Here, since the torsion beam material M10 shown in FIG. 21A is a straight tube, the length at the position of the selvage e and the length at the position of the central axis CL are both equal and become L1a.
When the compression strain (%) is obtained from the radii of curvature Rc and Re shown in FIG. 21B, the bending curvature shown in FIG. 21B is uniform at each position in the longitudinal direction of the torsion beam 10 and is mounted. When the portion 14 is orthogonal to the central axis CL, the compression strain (%) can be obtained by using the radii of curvature Re and Rc instead of the lengths L1a and L1b. Here, the radius of curvature Rc is the curve at the central axis CL before the ear compression bending process, and the radius of curvature Re is the curve at the ear portion e before the ear compression bending process. Under the above settings, the compression strain (%) in the selvage e is obtained by 100 × (Re—Rc) / Re.

Subsequently, the case of FIG. 22 will be described. In this case, as shown in FIG. 22 (A), a torsion beam material M10 having a linear shape over the entire length is prepared, and as shown in FIG. 22 (B), only the portion of the shape changing portion 12 has the bottom line bt side. This is a case where the selvage compression bending process is performed by bending and deforming the curved shape so as to form a convex shape. In this case, in order to obtain the compression strain (%) in the selvage of the shape changing portion 12, first, from the length L2a (mm) in the selvage e before the selvage compression bending process, after the selvage compression bending process. The difference D (mm) of the length L2b (mm) of is obtained. Then, the difference D (mm) is divided by the length dimension L2a (mm) at the position of the central axis CL, and the result is multiplied by 100 to obtain the compression strain (%). Here, since the torsion beam material M10 shown in FIG. 22A is a straight tube, the length at the position of the selvage portion e and the length at the position of the central axis CL are both equal in the range of the shape changing portion 12. It becomes L2a.
When the compression strain (%) of the selvage portion e in the shape changing portion 12 is obtained using the radii of curvature Rc and Re shown in FIG. 22B, the radii of curvature Re and Rc are used instead of the lengths L2a and L2b. It is also possible to obtain the compression strain (%). Here, the radius of curvature Rc is the curve at the central axis CL before the ear compression bending process, and the radius of curvature Re is the curve at the ear portion e before the ear compression bending process. The compression strain (%) in the selvage portion e of the shape changing portion 12 is determined by 100 × (Re—Rc) / Re.

The method of obtaining the compression strain in each case has been described above. In addition to these, for example, in the case of the fifth embodiment shown in FIG. 17, the compression strain obtained in the case shown in FIG. 20 and the compression strain in FIG. 21 are shown. It is obtained by adding up the compression distortions obtained in the case shown.
Further, in the case of performing the bending back described with reference to FIG. 19, it is preferable that the compression strain can be satisfied at the time when the selvage compression bending process is completed before the bending back.

When a linear torsion beam material is prepared and this torsion beam material is compression-bent to obtain a torsion beam by applying compression strain, which is the crack risk portion (point shown by the symbol CP in FIG. 5C) in the ear. It was determined by numerical analysis whether the residual stress could be reduced by the amount. The result is shown in FIG. In FIG. 23, the horizontal axis indicates the compression strain (%). Further, the vertical axis shows the residual stress in the selvage risk portion in the selvage portion at a ratio of 100% when the selvage compression bending process is not performed. Further, in the figure, the solid line shows the result at the position 250 mm from the longitudinal center position of the torsion beam toward the mounting portion 14, and the broken line is 400 mm from the longitudinal center position of the torsion beam toward the mounting portion 14. It shows the result at the position.

As calculation conditions, a torsion beam material having a constant shape closed cross section, a shape change part, and a mounting part using a pipe having an outer diameter of 90 mmφ, a length of 1200 mm, a plate thickness of 2.8 mm, and a tensile strength of 690 MPa. It was set. Then, when the selvage compression bending process is not performed on the torsion beam material (compression strain 0%), the selvage compression bending process is performed to reduce the compression strain to 1.0%, 1.3%, and 2.6. %, 3.8% and a total of 5 cases were calculated.
As is clear from FIG. 23, it was confirmed that the residual stress can be reduced by adding the selvage compression bending process as compared with the case where the selvage compression bending process is not performed (compression strain 0%). In particular, it was confirmed that the residual stress can be significantly reduced when the compressive strain is set to 1% or more. On the other hand, it was also confirmed that when the compressive strain was 1.3% or more, the residual stress was suppressed to a low level, but no further reduction effect was observed.
From the examples described above, it was possible to confirm the compression strain reduction effect of the selvage compression bending process of the present invention.

10 Torsion beam 11 Constant shape closed cross section (central part)
12 Shape change part 14 Mounting part (end)
50 Torsion beam manufacturing equipment 51 Fixed mold (second mold)
52 Movable mold (first mold)
53 Drive unit (drive mechanism)
54 Elongation regulation mechanism (first regulation means, second regulation means)
bt Bottom line e Ear M10 torsion beam material

Claims (6)

A central portion having a substantially V-shaped or substantially U-shaped closed cross section having an ear portion and having an ear portion connected to the central portion and having a cross section orthogonal to the longitudinal direction at an arbitrary position in the longitudinal direction. , A method of manufacturing a torsion beam comprising a shape changing portion in which the closed cross section gradually changes along the longitudinal direction.
A preparatory step for preparing a torsion beam material having the central portion and the shape changing portion;
A selvage compression bending step in which the selvage portion of the torsion beam material is bent so as to be inside the bending of the bending deformation process, and the selvage portion is subjected to compressive plastic deformation to thicken the selvage portion.
A torsion beam manufacturing method characterized by having. The torsion beam manufacturing method according to claim 1, wherein in the selvage compression bending step, a compression strain of 0.5% or more and 10% or less is applied in the longitudinal direction. In the preparation step, the torsion beam material having a concave bottom line is prepared;
In the selvage compression bending step, the bottom line is made linear by applying a bending to the torsion beam material to reduce the concave bending of the bottom line;
The torsion beam manufacturing method according to claim 1 or 2, wherein the torsion beam is manufactured. After the selvage compression bending step, there is further a bending back step of adding a bending to straighten the bottom line;
The tensile strain applied in the bending back step is made smaller than the compression strain applied in the selvage compression bending step;
The torsion beam manufacturing method according to claim 1 or 2, wherein the torsion beam is manufactured. An apparatus for carrying out the torsion beam manufacturing method according to claim 1 .
With the first mold of the torsion beam material on which the central portion and the shape changing portion are formed, which abuts on the selvage side at the position of the central portion;
With the second mold that abuts on the bottom line side at a position farther from the central portion than the shape change portion;
With a drive mechanism that makes the first mold and the second mold relatively close to each other;
A torsion beam manufacturing apparatus characterized by being provided with. Further, a control mechanism for controlling the relative approach amount between the first mold and the second mold by the drive mechanism to reduce the compression strain along the longitudinal direction to 0.5% or more and 10% or less. The torsion beam manufacturing apparatus according to claim 5, further comprising.

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