JP2013091433A - Plastic-worked article, method for manufacturing the same, torsion beam, torsion beam assy, torsion beam suspension device, and method for manufacturing torsion beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic-worked article formed by deforming a material having a cylindrical part from the outside to the inside of the cylindrical part, configured to improve fatigue strength against an external force, such as a torsional force to be applied in a circumferential direction of the cylindrical part, and to provide a method for manufacturing the plastic-worked article, a torsion beam manufactured by applying the method for manufacturing the plastic-worked article, a torsion beam Assy, a torsion beam suspension device, and a method for manufacturing a torsion beam.SOLUTION: The method for manufacturing a torsion beam for connecting right and left arms in a suspension device includes: adding deformation from the outside to the inside in the longitudinal direction of a material tube to form a substantially V shape or a substantially U shape; applying circumferential tensile stress to the substantially V-shaped or substantially U-shaped closed cross section; uniformly adjusting the circumferential stress distributed in the thickness direction of the material constituting the substantially V-shape or U-shape; and reducing residual stress after spring-back.

Description

  The present invention relates to a plastic processed product capable of suppressing fatigue, a method of manufacturing a plastic processed product, a torsion beam, a torsion beam assembly, a torsion beam suspension device, and a method of manufacturing a torsion beam.

As is well known, it is widely used in various industrial fields to form a cylindrical part of a material having a cylindrical part, which is displaced from the outside to the inside, from components such as plants to automobile parts. It is used.
For example, a torsion beam type suspension device for an automobile includes a torsion beam, a pair of left and right arms that support left and right wheels, a spring receiving portion, a spring, and an absorber, and the left and right arms are connected by a torsion beam. 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 to the center.

  The torsion beam has a joint portion connected to the left and right trailing arms, and a closed section perpendicular to the longitudinal direction of the torsion beam has a substantially V-shaped or substantially U-shaped closed section, and the external force received by the vehicle body from the road surface is mainly twisted. And a torsion part that secures the roll rigidity of the vehicle body by rigidity, and is formed by, for example, plastic processing of a pipe along its axial direction (see, for example, Patent Document 1).

  However, even if the torsion beam of the torsion beam suspension device has sufficient roll rigidity, a complex stress distribution is generated via the wheels and arms due to the external force from the road surface, and the torsion beam fatigues depending on the use condition of the vehicle. A technique for suppressing fatigue cracks that occur in a torsion beam in some cases is disclosed (for example, see Patent Document 2).

JP 2011-635 A JP 2007-76410 A

  However, the fact that the torsion beam is easily fatigued by the external force received from the road surface as described above is common when the steel material having the cylindrical portion is molded. Therefore, the inventors formed a displacement from the outside to the inside of the tubular portion of the steel material having the tubular portion, and as a result of earnestly studying fatigue in the formed portion, for example, the compression stress is reduced. Even when tensile stress increases, fatigue progress is suppressed by reducing the average value of tensile stress by making the circumferential stress distribution (compressive stress, tensile stress) distributed in the thickness direction of the molded part closer to uniform. And gained the knowledge that fatigue strength is improved.

  The present invention has been made in consideration of such circumstances, and relates to a plastic work product in which a displacement from the outside of the tubular portion toward the inside is formed in the material having the tubular portion. Plastic processed product capable of improving fatigue strength against external force such as torsional force acting in the direction, manufacturing method of this plastic processed product, torsion beam manufactured by applying this manufacturing method of plastic processed product, torsion beam assembly, torsion beam suspension device And a method of manufacturing a torsion beam.

In order to solve the above problems, the present invention proposes the following means.
According to the first aspect of the present invention, a molded part is formed by applying a displacement inward from the outside of the cylindrical part to a material having a cylindrical part made of a metal material or a composite material composed of a metal and a resin. A method for manufacturing a plastic processed product, comprising: forming a molded part that displaces the cylindrical part from the outside to the inside; and forming the molded part in a circumferential direction on a closed cross section formed by the molded part. By applying a tensile stress, the stress in the circumferential direction distributed in the thickness direction of the molded part is made closer to uniform, and the residual stress after springback is reduced.

  The invention according to claim 5 is a plastic work product, and is manufactured using the method for producing a plastic work product according to any one of claims 1 to 4.

  According to the plastic processed product and the method of manufacturing a plastic processed product according to the present invention, when a molded part is formed by giving a displacement from the outside of the cylindrical part to the inside, the molded part is molded into the cylindrical part. Or, after molding, a tensile stress in the circumferential direction (the direction in which the meat constituting the closed section extends) is applied to the closed section formed by the molded section, so that the circumferential direction distributed in the thickness direction of the tubular section Stress (compressive stress, tensile stress) can be made close to uniform. As a result, the maximum or average value of the tensile stress at the target site can be lowered after springback, and even if the compressive stress decreases and the tensile stress increases, the occurrence of fatigue cracks is suppressed and the fatigue strength is improved. can do.

  Here, the molded part that displaces the cylindrical part from the outside to the inside is a material (for example, a raw material pipe or the like) formed by forming a concave part recessed from the outside to the inside in the cylindrical part. This means that a displacement with compressive stress and tensile stress is formed in the thickness direction of the material. Press forming by pressing from outside to inside, hydroforming, forming by pressing member, buckling in the circumferential direction, etc. It may be formed by. Further, in addition to the displacement from the outside to the inside in the circumferential direction of the closed section, it may be displaced from the outside to the inside in the longitudinal direction.

In addition, the application of the circumferential tensile stress in the closed cross section formed by the molded part may only be to bring the circumferential stress distributed in the thickness direction of the molded part closer to uniform, and the displacement is formed by the tensile stress. It is more preferable that the formed displacement is restored after the spring back.
Moreover, in addition to applying tensile force in the circumferential direction of the closed cross-section, the application of external force (including pressure) to the side of the closed cross-section is applied to the circumferential stress in the closed cross-section formed by the molded part. Alternatively, a tensile stress may be formed by applying displacement by a router or the like in the vicinity of the target part. Furthermore, a tensile stress may be formed in the circumferential direction by applying a compressive stress in the axial direction.

Further, in this specification, a metal material or a material composed of a composite material composed of a metal and a resin is composed of metals (including pure metals and alloys) such as steel and aluminum, and these metals and resins. A composite material that is elastoplastically deformed.
As the form of the composite material, a clad structure in which resin and metal are arranged in layers along the spreading direction of the composite material, a structure in which resin and metal fiber are arranged, a resin plate (clad), and resin fiber are arranged on the metal A resin material and a metal plate arranged in a layered manner along a direction intersecting (for example, orthogonal) with the spreading direction of the composite material, a metal fiber arranged, a resin plate in the metal, It is intended to include those in which resin fibers are arranged, those in which metal particles are dispersed in a resin material, and those in which a resin is dispersed in a metal.

  Invention of Claim 2 is a manufacturing method of the plastic workpiece of Claim 1, Comprising: The said stress of the said circumferential direction with respect to the said shaping | molding part provides a clearance gap outside the object site | part of the said shaping | molding part. The inside of the closed cross section constituted by the molding part is pressurized.

  According to the method of manufacturing a plastic processed product according to the present invention, a gap is provided on the outer side of the molded part, and the inner side of the closed cross section formed by the molded part is pressurized by the hydraulic pressure of the hydroform. The stress in the circumferential direction distributed in the direction can be made close to uniformity efficiently. In addition, by providing a gap outside the target part, only the vicinity of the target part is selectively processed by pressurization, and only the part having a large circumferential stress distribution is subjected to the circumferential stress distributed in the thickness direction. It is possible to selectively approach uniform.

  The invention according to claim 3 is the method of manufacturing a plastic workpiece according to claim 1, wherein the stress in the circumferential direction with respect to the molded part is applied to the inside of the closed cross section constituted by the molded part. It is provided by pressing the material from the end of the cylindrical part while pressing.

  According to the method for manufacturing a plastic processed product according to the present invention, since tensile stress is formed in the circumferential direction by axial pressing of the material, the circumferential stress distributed in the thickness direction can be efficiently and uniformly approximated. . Also, by axially pushing the material, tensile stress can be applied without extending the material in the circumferential direction, and circumferential stress distributed in the thickness direction can be applied without reducing the thickness of the material. Can be approached uniformly.

  Invention of Claim 4 is a manufacturing method of the plastic workpiece of Claim 1, Comprising: The said stress of the said circumferential direction with respect to the said shaping | molding part provides a clearance gap outside the object site | part of the said shaping | molding part. The material is provided by axially pressing the material from the end of the cylindrical part while pressurizing the inside of the closed section constituted by the molding part.

  According to the method for manufacturing a plastic processed product according to the present invention, a gap is provided on the outer side of the molded part, and the inner side of the closed cross section constituted by the molded part is pressurized by hydraulic pressure or the like. It is possible to efficiently bring the circumferential stress to be close uniformly. In addition, by providing a gap outside the target part, only the vicinity of the target part is selectively processed by pressurization, and only the part having a large circumferential stress distribution is subjected to the circumferential stress distributed in the thickness direction. It is possible to selectively approach uniform. In addition, the material is plastically processed outward from the target part, and the material extends in the circumferential direction. By axially pushing the material, the circumferential direction is distributed in the thickness direction without reducing the thickness of the material. The stress can be made close to uniform.

  According to a sixth aspect of the present invention, the left and right arms are connected to each other in the suspension device, and in a cross section orthogonal to the width direction of the vehicle body, the front end and the rear end in the front-rear direction of the vehicle body protrude in either the vertical direction. A method for manufacturing a torsion beam having a V-shaped or substantially U-shaped closed cross section, wherein at least a part of the material tube in the longitudinal direction is displaced from the outside of the material tube toward the inside to form the substantially V A substantially U-shaped or substantially U-shaped closed section is formed, and a tensile stress in the circumferential direction is applied to the substantially V-shaped or substantially U-shaped closed section to constitute the substantially V-shaped or substantially U-shaped It is characterized in that the stress in the circumferential direction distributed in the thickness direction of the material to be made is made close to uniform.

  A tenth aspect of the present invention is a torsion beam, which is manufactured using the torsion beam manufacturing method according to the sixth to ninth aspects.

  The invention described in claim 11 is a torsion beam Assy, comprising the torsion beam described in claim 10.

  A twelfth aspect of the present invention is a torsion beam suspension device, comprising the torsion beam according to the eleventh aspect.

According to the torsion beam manufacturing method, torsion beam, torsion beam assembly, and torsion beam suspension device according to the present invention, after forming a substantially V-shaped or U-shaped closed section on the torsion beam, a circumferential tensile stress is applied to the closed section. Therefore, the stress in the circumferential direction distributed in the thickness direction of the material can be made close to uniform.
As a result, even if the compressive stress decreases after springback and the tensile stress increases, the average value of the tensile stress at the target site is lowered, the occurrence of fatigue cracks is suppressed, and as a result, the torsion beam is secured while ensuring the desired suspension performance. The fatigue strength of can be improved.

  The invention according to claim 7 is the method of manufacturing the torsion beam according to claim 6, wherein the fatigue strength is applied to impart a circumferential tensile stress in the substantially V-shaped or substantially U-shaped closed section. A gap is provided outside the substantially V-shaped or substantially U-shaped closed cross-section to be improved, and the inside of the closed cross-section is pressurized.

  According to the method of manufacturing a torsion beam according to the present invention, a gap is provided outside the closed cross-section to be improved in fatigue strength, and the inside of the closed cross-section is pressurized by the hydraulic pressure of the hydroform or the like. A tensile force is applied in the circumferential direction of the substantially V-shaped or U-shaped closed cross section by a uniform force from the outer side to the outer side, so that the circumferential stress distributed in the thickness direction can be efficiently and uniformly approached. be able to. In addition, by providing a gap outside the target part, only the vicinity of the target part is selectively processed by pressurization, and only the part having a large circumferential stress distribution is subjected to the circumferential stress distributed in the thickness direction. It is possible to selectively approach uniform.

  The invention according to claim 8 is the torsion beam manufacturing method according to claim 6, wherein the tensile strength in the circumferential direction in the substantially V-shaped or substantially U-shaped closed cross section is imparted. A material is axially pressed from an end portion of the material tube while pressurizing the inside of the substantially V-shaped or substantially U-shaped closed cross section to be improved.

  According to the torsion beam manufacturing method according to the present invention, since the tensile stress is formed in the circumferential direction by axial pressing of the material, the circumferential stress distributed in the thickness direction can be made to approach efficiently and uniformly. Also, by axially pushing the material, tensile stress can be applied without stretching the material in the circumferential direction, and the circumferential stress distributed in the thickness direction can be reduced without reducing the thickness of the material. Can be approached uniformly.

  The invention according to claim 9 is the method of manufacturing a torsion beam according to claim 6, wherein the fatigue strength is applied in order to apply a tensile stress in the circumferential direction in the substantially V-shaped or substantially U-shaped closed section. An end of the material tube is formed by providing a gap outside the substantially V-shaped or substantially U-shaped closed cross section to be improved and pressurizing the inside of the closed cross section constituted by the molding portion. The material is axially pressed from the part.

  According to the method of manufacturing a torsion beam according to the present invention, a gap is provided outside the closed cross-section to be improved in fatigue strength, and the inside of the closed cross-section is pressurized by the hydraulic pressure of the hydroform or the like. A tensile force is applied in the circumferential direction of the substantially V-shaped or U-shaped closed cross section by a uniform force from the outer side to the outer side, so that the circumferential stress distributed in the thickness direction can be efficiently and uniformly approached. be able to. In addition, by providing a gap outside the target part, only the vicinity of the target part is selectively processed by pressurization, and only the part having a large circumferential stress distribution is subjected to the circumferential stress distributed in the thickness direction. It is possible to selectively approach uniform. Furthermore, the material is plastically processed outward from the target part, and the material expands in the circumferential direction. By axially pushing the material, the circumferential direction is distributed in the thickness direction without reducing the thickness of the material. The stress can be made close to uniform.

According to the plastic processed product and the method of manufacturing a plastic processed product according to the present invention, the circumferential stress (compressive stress, tensile stress) distributed in the thickness direction of the molded part can be made close to uniform. As a result, the maximum or average value of the tensile stress at the target site can be lowered after springback, and even if the compressive stress decreases and the tensile stress increases, the occurrence of fatigue cracks is suppressed and the fatigue strength is improved. can do.
In addition, according to the torsion beam, torsion beam assembly, torsion beam suspension device, and torsion beam manufacturing method according to the present invention, it is possible to improve the fatigue strength of the torsion beam, thereby improving the durability of the torsion beam assembly and torsion beam suspension device. Can do.

1 is a perspective view showing an outline of a torsion beam type rear suspension device according to a first embodiment of the present invention. It is a perspective view which shows the outline of the torsion beam Assy which concerns on 1st Embodiment. It is a top view which shows the outline of the torsion beam Assy which concerns on 1st Embodiment. It is a bottom view which shows the outline of the torsion beam Assy which concerns on 1st Embodiment. It is a figure which shows the schematic cross section of the torsion beam which concerns on 1st Embodiment, (A), (B), (C), (D) is the arrows AA, BB, CC of FIG. , DD corresponding to a closed cross section. It is a figure which shows the detail of the closed cross section of the torsion beam which concerns on 1st Embodiment. It is a block diagram explaining the outline of the manufacturing process of the torsion beam which concerns on 1st Embodiment. It is a figure explaining the outline of the manufacturing process of the torsion beam concerning a 1st embodiment. It is a figure explaining the effect | action of the torsion beam which concerns on 1st Embodiment. It is a figure explaining the modification of the effect | action of the torsion beam which concerns on 1st Embodiment. It is a figure explaining the plastic work goods which concern on 2nd Embodiment.

The first embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 is a diagram showing an outline of a torsion beam type rear suspension device (torsion beam type suspension device) according to a first embodiment of the present invention. Reference numeral 1 denotes a torsion beam type rear suspension device, reference numeral 10 denotes a torsion beam Assy, Reference numeral 12 denotes a torsion beam. In addition, the code | symbol F shown in the figure has shown the front of the vehicle, and the code | symbol R has shown back.

  As shown in FIG. 1, the torsion beam type rear suspension device 1 includes a torsion beam Assy 10, a spring 20 that connects the torsion beam Assy 10 and the vehicle body, and an absorber 30, and the torsion beam Assy 10 is located slightly in front of the left and right sides of the vehicle body. The vehicle is connected to the vehicle body via extending pivot shafts JL and JR, and the left and right wheels WL and WR can swing with respect to the vehicle body. The orientation of the pivot shafts JL and JR may be configured to be orthogonal to the longitudinal direction of the vehicle body.

As shown in FIGS. 1 and 2, the torsion beam assembly 10 includes a pair of left and right trailing arms (arms) 11L and 11R that rotatably support the left and right wheels WL and WR, a trailing arm 11L, and a trailing arm 11R. And a pair of left and right spring receiving portions 16L and 16R for supporting the spring 20 are provided.
Further, spring receiving portions 16L and 16R that support one end side of the spring 20 are formed on the opposite side of the pivot shafts JL and JR with the torsion beam 12 interposed therebetween. Moreover, one end side of the absorber which is a buffer device is connected to a buffer receiving portion (not shown).

  In the first embodiment, the torsion beam 12 is substantially V-shaped (partially U-shaped) with the top at the top as shown in FIGS. 3, 4, and 5. Along the axial direction, for example, it is formed by plastic working by press molding.

  The torsion beam 12 includes torsion parts 12A, 12B, and 12C that are substantially V-shaped, and a connection part 12D that is connected to the trailing arms 11L and 11R. The torsion parts 12A, 12B, and 12C The cross section orthogonal to the longitudinal direction is gradually displaced from the torsion part 12A symmetrical in the vehicle longitudinal direction toward the joint part 12D. 5A, 5B, 5C, and 5D show closed cross sections corresponding to the arrows AA, BB, CC, and DD in FIG. .

FIG. 6 is a diagram for explaining the details of a closed cross section 12B (hereinafter referred to as torsion section 12B) as an example of the closed cross section included in the torsion section.
As shown in FIG. 6, the torsion part 12B is surrounded by a first wall part 14 forming a substantially V-shaped protruding (upper) outer surface 13A and a second wall part 15 forming a hollow (lower) outer surface 13B. It has a substantially V-shaped (or substantially U-shaped) closed cross section, a top portion 14T is formed on the first wall portion 14, and a top portion 15T is formed on the second wall portion 15. Here, the top portion is constituted by a bent portion of the first wall portion 14 and the second wall portion 15. The outer wall portion 14 and the inner wall portion 15 of the torsion beam 12 are connected by a U-shaped folded shape portion 12K.

  The connecting portion 12D is a portion that connects the torsion beam 12 to the trailing arms 11L and 11R, and has a closed cross section that can be connected to the shape of the trailing arms 11L and 11R as shown in FIG.

Next, a method for manufacturing the torsion beam 12 according to the first embodiment will be described with reference to FIGS.
FIG. 7 is a block diagram showing an outline of a method for manufacturing the torsion beam 12.
(1) First, the steel pipe W0 is pressed to form substantially V-shaped (or substantially U-shaped) torsion parts 12A and 12B constituting an intermediate molded product of the torsion beam 12 (hereinafter referred to as an intermediate molded product 12L of the torsion beam). 12C and the connecting portion 12D are formed (S1).
The number of press working steps when forming the torsion beam 12 can be arbitrarily set.
(2) Next, a clearance is provided outside the portion of the substantially V-shaped (or substantially U-shaped) fatigue strength improvement target formed by pressing (S2).
The steps of S1 and S2 may be made the same by previously providing a gap outward in the mold used for the press working of S1.
(3) Next, both end openings of the intermediate molded product 12L of the torsion beam are sealed in a liquid-tight manner, and the inside is pressurized by the hydraulic pressure of the hydroform. (S3) As a result, the circumferential tensile stress in the closed cross section of the target site is applied, the circumferential stress distributed in the thickness direction of the target site approaches uniformly, and the average value or maximum of the circumferential stress after springback The value is reduced.

FIG. 8 is a diagram showing an outline of a method for manufacturing the torsion beam 12. FIGS. 8A and 8B correspond to S1 in FIG. 7, and FIG. 8C corresponds to S2 and S3 in FIG. Yes.
(1) As shown in FIG. 8 (A), the steel pipe W0 is disposed between the lower mold P1 and the upper mold P2 of the press mold PA, the lower mold P1 and the upper mold P2 are relatively moved, and the mold is clamped. The core P3 of the upper mold P2 is advanced to press-mold the steel pipe W0.
(2) FIG. 8B shows a state in which the intermediate molded product 12L of the torsion beam is molded in the press die PB in the final step of press molding. The number of press moldings may be one or more.
(3) Next, as shown in FIG. 8C, a torsion beam intermediate molded product 12L is formed by a mold P4 in which a gap T is provided between the molds outside the U-shaped folded shape portion 12K. It arrange | positions in P5 and the tension | pulling stress of the circumferential direction is provided to an object site | part by pressurizing the inner side of the intermediate molded product 10A of a torsion beam with hydroform.

Next, the operation of the torsion beam 12 will be described with reference to FIG.
FIGS. 9A, 9B, and 9C show the circumferential stress distributed in the thickness direction of the folded portion 12K when the torsion beam intermediate formed product 12L is formed by pressing the steel pipe W0. FIG. In addition, as for the arrow shown in a figure, the right direction represents tensile stress and the left direction represents compressive stress.

  FIG. 9A shows the stress in the circumferential direction distributed in the thickness direction of the folded portion 12K after the steel pipe W0 is pressed, and on the outside of the protrusion 12A of the intermediate product 12A of the torsion beam across the neutral line Z. The tensile stress S1 and the compressive stress S2 are formed inside.

  FIG. 9B shows a state in which a circumferential tensile force R is applied to the folded shape portion 12K and a circumferential tensile stress S3 is generated by pressurizing the inside of the torsion beam 12A with hydroform. .

  FIG. 9C shows a state in which the tensile stress S2 of the folded shape portion 12K becomes the tensile stress S11 by applying the circumferential tensile stress S3 to the folded shape portion 12K, and the folded shape portion 12K is extended in the circumferential direction. Is shown.

  FIG. 9D is a schematic diagram showing that the tensile stress S11 formed in the folded shape portion 12K by the hydroform and the extension in the circumferential direction spring back in the arrow SP direction by releasing the pressurization by the hydroform. It is.

  FIG. 9E is a schematic diagram showing an example after the tensile stress S11 and the circumferential extension are spring-backed. For example, the tensile stress S12 distributed in the thickness direction after the spring-back is a tensile force during press molding. It becomes smaller than the stress S1. Further, it is more preferable that the compressive stresses S21 and 22 are smaller than the compressive stress S2 at the time of press forming. Here, it is preferable that the neutral line Z is displaced to the outside (concave side) of the folded shape portion 12K, and this displacement is realized by applying a tensile stress S3 (FIG. 9C to FIG. 9C). (See (E)).

  Thus, the progress of metal fatigue is suppressed by reducing the average value of the tensile stress after springback, preferably the maximum value of the local tensile stress. The stress distribution in the thickness direction after the spring back shown in FIG. 9 (E) is an example. For example, if the tensile stress S21 is smaller than the tensile stress S1 during press molding, FIG. 9 (E) It is not limited to the stress distribution shown.

FIG. 10 is a view showing a modified example of the action of the torsion beam 12, and corresponds to FIG. 9 (E). FIG. 10 differs from FIG. 9 (E) in that after releasing the pressure by the hydroform, the tensile stress S31 and the compressive stress S32 are partially distributed in the thickness direction of the folded shape portion 12K, and the neutral line Z Is located inside the folded shape portion 12K in the thickness direction.
Thus, even when the compressive stress S32 remains in part, the average value of the tensile stress after the springback, preferably the maximum value of the local tensile stress, should be below the yield point of the material. This suppresses metal fatigue. Even if the average value of the residual tensile stress or the maximum value of the local tensile stress is larger than the yield point, it is effective in that metal fatigue can be suppressed.

  As described above, the folded shape portion 12K is expanded, and a tensile stress is generated in the circumferential direction of the torsion beam intermediate product 12A in the folded shape portion 12K, so that the stress distributed uniformly in the thickness direction of the folded shape portion 12K is uniform. The average value of the tensile stress, preferably the maximum value of the local tensile stress, can be reduced after the springback.

  According to the torsion beam 12 according to the first embodiment, the stress in the circumferential direction distributed in the thickness direction of the folded shape portion 12K is made to remain uniformly close and the tensile stress after springback is reduced, thereby reducing the metal fatigue. Can be suppressed and the fatigue strength can be improved. As a result, the metal fatigue of the torsion beam can be effectively reduced while ensuring the desired suspension performance.

  Further, since the change with respect to the outer shape is small, even after the shape of the torsion beam is set, the fatigue strength can be improved without worrying about the spatial relationship of the vehicle parts.

<Example>
Next, the present invention will be further described with reference to examples. Conditions in the examples are one example of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is examples of these one condition. It is not limited to. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

  As an example, the torsion beam 12 is manufactured under a plurality of processing conditions as shown in Table 2 using the material pipe shown in Table 1 in the outline of the first embodiment, and the meat in the folded shape portion 12K of the torsion beam is obtained. The thickness reduction rate, the maximum value of residual stress, and the maximum value in the surface layer portion were examined. The results are shown in Table 2. It can be seen that any of the inventive examples can reduce the maximum residual stress and improve the fatigue strength as compared with the comparative example. Moreover, it turns out that the maximum residual stress of a surface layer part also reduces and generation | occurrence | production of a fatigue crack can be suppressed.

Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 11 is a diagram showing a hollow rotating shaft (plastic work product) 50 used in a plant, for example, and repeatedly rotating in the circumferential direction, according to the second embodiment of the present invention. ) Is a perspective view of the rotating shaft 50, FIG. 11B is an XX section in FIG. 11A, and FIG. 11C is a YY section in FIG. 11A. .

  The next rotation shaft 50 is a spherical surface that bulges inward of the rotation shaft 50 in order to dispose the head of a sensor (not shown) disposed on the outer periphery of the rotation shaft closer to the inner peripheral side than the outer peripheral surface of the rotation shaft 50. A mounting concave portion (molded portion) 55 is formed, and a sensor mounting hole 56 is formed in the center of the mounting concave portion 55 when viewed from the side of the rotation shaft 50. .

The mounting concave portion 55 is formed by, for example, pressing a pressing member against the steel pipe from the outside and pressing the steel pipe from the outside to the inside.
After forming the mounting concave portion 55, the openings at both ends of the rotation shaft 50 are sealed in a liquid-tight manner, and a gap is provided outside the target portion (target portion where fatigue strength should be improved) in the mounting concave portion 55. The outer mold is placed, the inner part is pressurized with hydroform, the target part is expanded outward and displaced.
Release the pressure by the hydroform and the part displaced outwardly will spring back.
The attachment hole 56 is processed by machining or the like after completion of pressurization by hydroforming.

  According to the rotating shaft 50 according to the second embodiment, a circumferential tensile stress is applied to the closed cross section formed by the mounting concave portion 55, so that the circumferential direction distributed in the thickness direction of the target portion. The stress can be made close to uniform, the residual stress after springback can be reduced, and the fatigue strength can be improved. Further, according to the second embodiment, in addition to the circumferential stress distributed in the thickness direction of the target portion, the stress in the longitudinal direction of the steel pipe can be made uniform.

  In addition, in 2nd Embodiment, although the case where the attachment concave shape part 55 was shape | molded with a press member was demonstrated, you may make it shape | mold by press molding etc., and it consists of a part of spherical surface which bulges inward. Instead of the concave mounting portion 55, it may be formed into another shape.

  Moreover, although the case where the attachment concave shape part 55 is applied by expanding the tube by hydroforming has been described, for example, a tensile force may be applied directly in the circumferential direction of the closed section, or a tensile stress may be applied by applying a displacement by a router or the like. It may be given.

Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention.
For example, in the above-described embodiment, the case where the top portion 14T of the torsion beam 12 is formed upward and the closed section is symmetric in the vehicle front-rear direction has been described. However, the top portion 14T may be formed downward. . Further, whether the closed section is substantially V-shaped or U-shaped can be arbitrarily set, and the closed section may be formed asymmetrically in the vehicle front-rear direction. Moreover, although the case where the tensile stress S3 is applied to the folded shape portion 12K has been described, it goes without saying that the tensile stress S3 may be applied to portions other than the folded shape portion 12K.

  In the above embodiment, the case where the tensile stress in the circumferential direction is applied by the hydroform has been described. However, an external force (pressure) is applied to the side of the closed cross section other than the hydroform, such as mechanical means for expanding the pipe from the inside of the closed cross section. A tensile stress may be formed by applying a displacement by a router or the like in the vicinity of the target part.

  Further, in the above embodiment, the case where the torsion beam type suspension device is the torsion beam type rear suspension device 1 has been described, but it may be applied to, for example, a leading arm type suspension device.

  Moreover, in the said 2nd Embodiment, although the case where the plastic workpiece was the rotation axis | shaft 50 made into the cylinder shape over the full length was demonstrated, it cannot be overemphasized that it is not limited to a rotation axis | shaft. For example, when the shape part has a taper, when the cylindrical part is formed in a part of the length direction of the steel material, when the forming part is formed in a part of the length direction, or Needless to say, the present invention can be applied when a plurality of molded portions are formed. Further, the position and size of the molding part can be arbitrarily set.

  According to the plastic processed product, the plastic processed product manufacturing method, the torsion beam, the torsion beam Assy, the torsion beam type suspension device, and the torsion beam manufacturing method according to the present invention, the fatigue strength is improved and can be used industrially.

W0 Steel pipe 1 Torsion beam type rear suspension device (torsion beam type suspension device)
10 Torsion Beam Assy
12 Torsion beam 12K Folding shape part (target part)
50 Rotating shaft (plastic processed product)
55 Mounting concave part (molded part)

Claims (12)

A method of manufacturing a plastic work product that is made of a metal material or a composite material composed of a metal and a resin and that has a cylindrical portion and gives a displacement from the outside to the inside of the cylindrical portion to form a molded portion. There,
Molding a molded part that displaces the cylindrical part from the outside to the inside,
By applying a tensile stress in the circumferential direction to a closed cross section formed by the molded part, the molded part is made to approach the circumferential stress distributed in the thickness direction of the molded part uniformly, and the residual stress after springback is reduced. A method for producing a plastically processed product, characterized in that it is reduced. A method for producing a plastic workpiece according to claim 1,
In order to give the circumferential tensile stress in the circumferential direction to the molded part, a gap is provided outside the target part of the molded part to pressurize the inner side of the closed cross section constituted by the molded part. A method for producing a plastic processed product. A method for producing a plastic workpiece according to claim 1,
In order to apply the circumferential tensile stress to the molded part, the material is axially pressed from the pipe end of the molded part while pressurizing the inside of the closed cross section constituted by the molded part. A method for manufacturing a plastic processed product. A method for producing a plastic workpiece according to claim 1,
In order to apply the circumferential tensile stress to the molded part, a gap is provided outside the target part of the molded part, and the inner side of the closed cross section constituted by the molded part is pressed while the molded part is pressed. A method of manufacturing a plastic processed product, characterized in that a material is axially pressed from a pipe end of the part.   A plastic processed product manufactured using the method for manufacturing a plastic processed product according to claim 1. In the suspension device, the left and right arms are connected, and in a cross section perpendicular to the width direction of the vehicle body, the front and rear ends of the vehicle body in the front-rear direction have a substantially V-shape or a substantially U-shape projecting in either the vertical direction. A method for producing a torsion beam having a closed cross-section,
Forming a substantially V-shaped or substantially U-shaped closed cross section by giving a displacement from the outside to the inside of the material tube in at least a part of the longitudinal direction of the material tube;
Applying a circumferential tensile stress to the substantially V-shaped or substantially U-shaped closed cross section, the circumferential stress distributed in the thickness direction of the material constituting the substantially V-shaped or substantially U-shaped A method for producing a torsion beam, characterized in that the residual stress after springback is reduced to be close to uniform. It is a manufacturing method of the torsion beam according to claim 6,
In order to give a tensile stress in the circumferential direction in the substantially V-shaped or substantially U-shaped closed cross section, the outer side of the substantially V-shaped or substantially U-shaped closed cross section, which is an object of fatigue strength improvement. A method for producing a torsion beam, wherein a gap is provided to pressurize the inside of the closed section. It is a manufacturing method of the torsion beam according to claim 6,
In order to apply the tensile stress in the circumferential direction in the substantially V-shaped or substantially U-shaped closed cross section, the material is axially pressed from the tube end of the molded portion while pressurizing the inside of the closed cross section. A method of manufacturing a torsion beam. It is a manufacturing method of the torsion beam according to claim 6,
In order to give a tensile stress in the circumferential direction in the substantially V-shaped or substantially U-shaped closed cross section, the outer side of the substantially V-shaped or substantially U-shaped closed cross section, which is an object of fatigue strength improvement. A method for producing a torsion beam, characterized in that a material is axially pressed from a tube end portion of the forming portion while providing a gap and pressurizing the inside of the closed section.   A torsion beam manufactured using the method for manufacturing a torsion beam according to claim 6.   A torsion beam Assy comprising the torsion beam according to claim 10.   A torsion beam type suspension apparatus comprising the torsion beam assembly according to claim 11.

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