Arm member for vehicle and manufacturing method of arm member for vehicle

Abstract

According to the present invention, a vehicle arm member having a flanging processing section that ensures tensile load even when the raw material is made strong, and a method for manufacturing the vehicle arm member are provided. The vehicle arm member of the present invention has a cylindrical upright portion in the flanging processing section, which is fitted and held in place by fitting members for connecting with other components. On the inner periphery of the upright portion, there are a plurality of coaxial inner peripheral portions of the same diameter. The plurality of inner peripheral portions of the same diameter have annular steps at their boundaries and their inner diameters increase stepwise from the front end side to the root side, with the annular steps serving as fittings. In the manufacturing method of the vehicle arm component of the present invention, a flanging processing part is formed using a forming die and a forming punch. The inner diameter of the forming die corresponds to the outer periphery of the raised part of the processing part. The forming punch has an outer diameter at the foremost side with the same diameter inner periphery that has a gap (Ct) between it and the forming die that is 70% to 100% of the thickness of the raw material plate. The inner periphery at the adjacent root side has an outer diameter such that the gap (Cn) between it and the forming die is 60% to less than the gap (Ct) of the thickness of the raw material plate.

Description

Technical Field

[0001] This invention relates to a vehicle boom component and a method for manufacturing a vehicle boom component. More specifically, it relates to a vehicle boom component having a flanging section that ensures tensile load even when the raw material is made strong, and a method for manufacturing a vehicle boom component. Background Technology

[0002] As a representative vehicle arm component, the suspension arm is a key component of the suspension system, which supports the vehicle body and absorbs shocks between the wheels and the body. The suspension system, also known as a suspension, mainly consists of three parts: springs, shock absorbers, and suspension arms. On the front wheel side, depending on the wheel's suspension configuration, the suspension arm may consist of a combination of upper and lower arms, or only a lower arm. In the latter case, the suspension arm and lower arm are simply different names for the same component. On the rear wheel side, the suspension arm is sometimes constructed by adding a trailing arm to the upper and lower arms. The suspension arms illustrated here are sometimes also called automotive running gear components; since they share common requirements, they are collectively referred to here as vehicle arm components.

[0003] In recent years, from the perspective of reducing CO2 emissions from automobiles and ensuring safety, there has been a pursuit of thinner and stronger raw materials for vehicle boom components. Furthermore, lightweighting has been achieved by optimizing the structure and shape of each part of the vehicle boom component. For example, a known structure is as follows: for weight reduction, the boom body is composed of an upper half and a lower half formed into a U-shaped cross-section by stamping sheet metal, and the corresponding side walls are welded together with the openings of the upper and lower halves facing each other.

[0004] Patent Document 1 discloses the following invention: Further advancements in lightweighting based on the upper and lower half-body structure of a vehicle arm component, such as... Figure 1 and Figure 2As shown, the second vehicle body side connection 14 is formed by a simple structure in which only the extension of the lower half 10L of the arm body 10 is burringed. That is, in the vehicle arm member 1 described in this document, both the upper half 10U and the lower half 10L are stamped from sheet metal into a U-shaped cross-section, thereby reducing the number of parts in the arm body 10 and achieving weight reduction. Moreover, in the vehicle arm member 1 described in this document, except for the upper half 10U, an outer end extension is provided only in the lower half 10L, where a cylindrical burring part 20 is integrally formed to form the second vehicle body side connection 14, thereby also achieving weight reduction. Furthermore, in order to ensure the rigidity of the second vehicle body side connection 14, the upright portion of the burring part 20 formed in the outer end extension of the lower half 10L is connected to the outer end of the upper half 10U by a weld part w. The vehicle arm component 1 is connected to the vehicle body subframe 32 on the vehicle body side via a second bushing 30a2 that engages with the second vehicle body side connection portion 14. Furthermore, the vehicle arm component 1 described in Patent Document 1 is also referred to as an L-shaped suspension arm or an L-shaped lower arm.

[0005] In the vehicle boom component 1 described in Patent Document 1, such as Figures 1-4 As shown, the first body-side connecting portion 12 is also constructed by welding two components having the same flanged processing portion 20 to the arm body 10. Thus, the vehicle arm component 1 is connected to the body subframe 32 on the body side via a first bushing 30a1 that engages with the first body-side connecting portion 12 (see reference). Figure 1 , Figure 3 Furthermore, in the wheel support portion 16 of the vehicle boom member 1, the same flanged portion 20 is integrally formed by flanged processing, so that it is only provided on the outer end extension of the upper half 10U except for the lower half 10L. Thus, the vehicle boom member 1 is connected to the wheel support member 34 via the ball joint 30bj that fits into the wheel support portion 16 (see reference). Figure 1 , Figure 4 ).

[0006] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2010-111226 Summary of the Invention

[0007] The problem that the invention aims to solve From the perspective of reducing CO2 emissions from automobiles in recent years, the use of high-strength steel sheets for lightweighting has raised concerns about reducing the pull-out load of the fitting components in the flanging process. Figure 5 as well as Figure 6 This issue needs to be explained.

[0008] Figure 5 This diagram schematically shows a cross-section of one side of the flanging section 20, which enlarges a bottom hole (not shown) in a metal sheet and forms a raised portion 26 around the bottom hole, extending from the peripheral plate-like portion 22 through the curved portion 24. Generally, the ratio of the formable inner diameter d of the flanged portion to the bottom hole diameter d0 (not shown), i.e., the enlargement ratio d / d0, has an inverse relationship with the strength of the raw material. Therefore, it should be noted that when high strength of the raw material is desired, the maximum enlargement ratio d / d0 decreases, and the achievable flanging height h decreases. This is because a reduction in the flanging height h directly leads to a decrease in the pull-out load of the mating member due to a narrowing of the contact area between the flanging section 20 and the mating member.

[0009] Furthermore, in the process of researching the problem of reduced pull-out load of the flanging section due to the increased strength of the vehicle arm component, the inventors of this application discovered that in addition to addressing the problem of reduced contact area due to the decrease in the aforementioned hole expansion ratio d / d0, there are other problems that need to be solved. For example, even when the flanging section is made stronger, the specifications of the mating components are rarely changed. In this case, it was considered that, relative to the strengthened flanging section, the collar of the mating component has relatively lower rigidity due to its lower strength or thinner plate thickness. Figure 6 The diagram schematically illustrates, in a cross-sectional view, the bushing 30a of the mating member (fitting member) 30 under such conditions is fitted to the flanged part 20, where the relatively low-rigidity mating member 30 flexes and the contact portion only becomes the periphery of the high-pressure bearing part P. In such contact only around the high-pressure bearing part P, it is impossible to ensure a large contact area at the fitting portion. Therefore, even if the vehicle arm member is made high-strength, it is difficult to ensure the pull-out load of the flanged part.

[0010] The present invention was made in view of the problems mentioned above, and its object is to provide a vehicle arm member having a flanging part that can ensure tensile load even when the raw material is made strong, and a method for manufacturing the vehicle arm member.

[0011] Methods for solving problems [1] A vehicle boom component having a flanged processing section. The flanging section has a cylindrical upright portion that engages with and holds together other components. The cylindrical upright portion has multiple coaxial inner circumferential portions of the same diameter on its inner periphery. These multiple inner circumferential portions of the same diameter are sandwiched by annular steps at their boundaries, and their inner diameter increases in a stepped manner from the front end side toward the root side. The annular step is used as the pull-out resistance step of the fitting member.

[0012] [2] According to the vehicle arm component described in [1], the step difference Δd in the direction perpendicular to the flange direction of the annular step is more than 1.8% of the plate thickness tL of the inner circumference of the same diameter on the root side of the annular step. When the height from the surface surrounding the flanging part to the front end of the annular step is set as hd, and the flanging height from the surface surrounding the flanging part is set as h, the height position of the annular step in the flanging direction satisfies hd≥0.49h.

[0013] [3] A method for manufacturing a vehicle boom member, the vehicle boom member having a flanged processing part having a cylindrical upright portion, and a plurality of coaxial inner circumferential portions of the same diameter being formed on the inner periphery of the upright portion, the plurality of inner circumferential portions of the same diameter having annular steps at their boundaries, and the inner diameter increasing in a stepped manner from the front end side toward the root side. In the manufacturing method of the vehicle arm component, the flanging part is formed in a single stamping process using a forming die and a forming punch. The forming mold has an inner diameter corresponding to the outer periphery of the upright portion of the flanging part. The forming punch has an outer peripheral shape corresponding to the inner periphery of the upright portion of the flanging section. A portion of the outer peripheral shape of the forming punch corresponding to the inner peripheral portion of the same diameter at the foremost end has an outer diameter such that the gap Ct between it and the forming die is 70% or more and 100% or less of the thickness of the metal raw material plate. A portion of the outer peripheral shape of the forming punch corresponding to the inner peripheral portion of the same diameter at the root side of the inner peripheral portion of the same diameter at the foremost end has an outer diameter such that the gap Cn between it and the forming die is 60% or more of the thickness of the metal raw material plate and less than the gap Ct.

[0014] [4] A method for manufacturing a vehicle boom member, the vehicle boom member having a flanged processing part having a cylindrical upright portion, and a plurality of coaxial inner peripheral portions of the same diameter being formed on the inner periphery of the upright portion, the plurality of inner peripheral portions of the same diameter having annular steps at their boundaries, and the inner diameter increasing in a stepped manner from the front end side toward the root side. The manufacturing method of the vehicle boom component includes: In the first stamping forming process, a forming die having an inner diameter corresponding to the outer periphery of the upright portion of the flanging part, and a forming punch having an outer diameter such that the gap Ct between the forming die and the flanging part is 70% to 100% of the thickness of the metal raw material sheet, are used to form the inner periphery of the same diameter at the foremost side of the inner periphery of the upright portion of the flanging part; and In the second stamping forming process, for the flanging part formed by the first stamping forming process, a forming die having an inner diameter corresponding to the outer periphery of the upright part of the flanging part, and a forming punch having an outer diameter such that the gap Cn between the die and the forming die is more than 60% of the thickness of the metal raw material plate and less than the gap Ct, forms the inner periphery of the upright part of the flanging part that is closer to the root than the foremost side.

[0015] [5] According to the manufacturing method of the vehicle arm component described in [3] or [4], the step difference Δd in the direction perpendicular to the flange direction of the annular step is more than 1.8% of the plate thickness tL of the inner circumference of the same diameter on the root side of the annular step. When the height from the surface surrounding the flanging part to the front end of the annular step is set as hd, and the flanging height from the surface surrounding the flanging part is set as h, the height position of the annular step in the flanging direction satisfies hd≥0.49h.

[0016] According to the present invention, the inner circumference of the cylindrical upright portion of the flanging section has a plurality of coaxial inner circumferential portions of the same diameter. These portions have annular steps at their boundaries, and their inner diameters increase in a stepped manner from the front end side towards the root side. This allows the annular steps to serve as pull-out resistance steps for the fitting member. Such a flanging section can be formed using a forming punch with an outer diameter having a clearance different from that of the forming die. As described above, according to the present invention, it is possible to provide a vehicle arm member having a flanging section that ensures pull-out load even when the raw material is made high-strength, and a method for manufacturing the vehicle arm member. Attached Figure Description

[0017] Figure 1 This is a simplified 3D diagram illustrating the vehicle mounting method of a vehicle arm component in the prior art.

[0018] Figure 2 It is represented by a cross-sectional view that includes the flanging shaft. Figure 1 A diagram showing the main part of the second body side connection of the flanged part of the vehicle arm component.

[0019] Figure 3 It is represented by a cross-sectional view that includes the flanging shaft. Figure 1 A diagram showing the main part of the first body-side connection of the flanged part of the vehicle arm component.

[0020] Figure 4 It is represented by a cross-sectional view that includes the flanging shaft. Figure 1A diagram of the main part of the wheel support section of the flanged part of the vehicle arm component.

[0021] Figure 5 The diagram schematically illustrates the flanging section of a conventional vehicle arm member as a comparative example, using a partial cross-sectional view of one side of the flanging section, including the flanging shaft.

[0022] Figure 6 The diagram schematically illustrates the appearance of a mating member in the flanging section of a conventional vehicle arm member used as a comparative example, by showing a partial cross-sectional view of one side of the flanging section, including the flanging shaft.

[0023] Figure 7 This is a plan view schematically illustrating a vehicle boom member according to an embodiment of the present invention.

[0024] Figure 8 This diagram schematically illustrates the flanging portion of a vehicle arm member according to an embodiment of the present invention by showing a partial cross-sectional view of one side of the flanging portion, including the flanging shaft.

[0025] Figure 9 This diagram schematically illustrates the case where the flanging portion of the vehicle arm member in an embodiment of the present invention is fitted with a mating member, using a partial cross-sectional view of one side of the flanging portion including the flanging shaft.

[0026] Figure 10 This is a diagram illustrating the effect of the step difference and the position in the flange height direction of the annular step provided in the flange processing section of the vehicle arm member according to an embodiment of the present invention on the effect of improving the pull-out load.

[0027] Figure 11A This diagram schematically illustrates, using a partial cross-sectional view including the flanging axis, the stage in the flanging process of the manufacturing method of the vehicle arm member according to an embodiment of the present invention, in which the inner circumference of the same diameter on the front end side is formed in the entire area of ​​the erected portion.

[0028] Figure 11B This diagram schematically illustrates the stage in the flanging process of the manufacturing method of the vehicle arm member according to an embodiment of the present invention, which involves completing the root-side inner circumference of the same diameter at the root of the erected part, using a partial cross-sectional view including the flanging processing shaft.

[0029] Figure 11C This is a cross-sectional view schematically showing the composite forming punch used in the flanging process of the manufacturing method of the vehicle arm member according to an embodiment of the present invention, including the cross-section of the flanging processing shaft.

[0030] Figure 12A This diagram schematically illustrates, through a partial cross-sectional view including the flanging shaft, a variation of the method for manufacturing a vehicle arm member according to an embodiment of the present invention, the stage in which the front end side inner circumference of the same diameter is set onto the erected portion by a first forming punch during the flanging process.

[0031] Figure 12B This diagram schematically illustrates, through a partial cross-sectional view including the flanging shaft, a variation of the manufacturing method for a vehicle arm member according to an embodiment of the present invention, the stage in the flanging process where the inner circumference of the root side with the same diameter is set at the root of the erected portion by a second forming punch. Detailed Implementation

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the embodiments shown below, a suspension arm or lower arm is taken as an example as a vehicle arm component, and the description will focus on the flanged part. Figure 7 The diagram is a schematic plan view of an L-shaped lower arm 1a, which is an example of a vehicle arm member 1 according to an embodiment of the present invention. Figure 8 This diagram schematically illustrates the flanging portion of a vehicle arm member according to an embodiment of the present invention by showing a partial cross-sectional view of one side of the flanging portion, including the flanging shaft. Figure 9 This diagram schematically illustrates the case where the flanging portion of the vehicle arm member in an embodiment of the present invention is fitted with a mating member, using a partial cross-sectional view of one side of the flanging portion including the flanging shaft. Figure 10 This diagram illustrates the effect of the step difference and the position of the annular step in the flanging section of the vehicle arm member according to an embodiment of the present invention on the improvement of the pull-out load. In the embodiments shown below, the same or common parts are labeled with the same reference numerals in the figures, and their descriptions are not repeated. Furthermore, the present invention is not limited to the following embodiments.

[0033] like Figures 7-10 As shown, the vehicle arm member 1 (L-shaped lower arm 1a) of the embodiment of the present invention has a flanged portion 20 at the second vehicle body side connection 14. This flanged portion 20 can ensure tensile load even when the raw material is made high-strength. Furthermore, Figure 8 Is Figure 7 The partial cross-sectional view shown in view AA, which only extracts the flanged processing portion 20 of the second vehicle body side connection portion 14. Furthermore, the L-shaped lower arm 1a of this embodiment serves as a vehicle arm component and... Figures 1-4 The L-shaped lower arm 1a shown in the prior art is equivalent to it; therefore, when mentioning... Figure 7In cases where the prior art is not explicitly stated, the accompanying drawings and reference numerals are sometimes used for illustration.

[0034] The vehicle boom member or manufacturing method of the present embodiment is particularly preferred for steel members with a tensile strength of 590 MPa or more. Furthermore, the vehicle boom member or manufacturing method of the present embodiment is preferably used for steel members with a tensile strength of 780 MPa or more to 980 MPa or more. Moreover, the vehicle boom member or manufacturing method of the present embodiment is more preferably used for steel members with a tensile strength of 1180 MPa or more.

[0035] When tensile test pieces can be collected from a location on the vehicle arm component that corresponds to the head of the forming punch of the stamping machine and is almost unaffected by the work hardening of the stamping process, the tensile strength of the steel component can be evaluated by tensile testing of the test pieces.

[0036] On the other hand, even if it is impossible to ensure a component area equivalent to that of a tensile test piece at the location corresponding to the head of the forming punch in the vehicle arm component, the tensile strength of the steel component can still be evaluated by cutting a cross-sectional specimen from that location and measuring the Vickers hardness at a 1 / 4 thickness position. For the Vickers hardness test load in this case, within the range of 590 MPa to 1480 MPa of the tensile strength of the steel preferably used in this embodiment, a load of 9.807 N is preferred, considering the size of the indentation that appears proportional to the strength of the test specimen. The Vickers hardness of steels with tensile strengths of 590 MPa, 780 MPa, 980 MPa, and 1180 MPa, exemplified as preferred steels in this embodiment, is estimated to be 184 Hv, 245 Hv, 310 Hv, and 372 Hv or higher, respectively.

[0037] In the vehicle boom member or the manufacturing method of the vehicle boom member in this embodiment, the thickness of the steel used is not particularly limited, for example, it is 3 mm or more and 6 mm or less.

[0038] like Figure 7As shown, the L-shaped lower arm 1a of this embodiment is roughly L-shaped when viewed from above. A wheel support portion 16 is provided at one end, which is connected to a wheel support member 34 (not shown) in a swingable manner via a ball joint 30bj (not shown). Furthermore, a first vehicle body side connection portion 12 is provided at the curved middle portion of the arm body 10. This first vehicle body side connection portion 12 is connected to the vehicle body in a swingable manner via a first bushing 30a1 (not shown), the axis of which is arranged along the longitudinal direction of the vehicle body. Moreover, at the rear end of the arm body 10 in the longitudinal direction of the vehicle body, a second vehicle body side connection portion 14 is provided. This second vehicle body side connection portion 14 is connected to the vehicle body in a swingable manner via a second bushing 30a2 (not shown), the axis of which is arranged along the vertical direction.

[0039] The arm body 10 of the L-shaped lower arm 1a in this embodiment is preferably lightweight through an upper and lower half-body structure, similar to the prior art. That is, the arm body 10 of this embodiment is a hollow, closed-section structure obtained by integrally combining an upper half-body 10U and a lower half-body 10L, which are formed separately by stamping steel plates. The upper half-body 10U has an upper wall portion and a pair of side wall portions (not shown) extending downwards from both sides of the upper wall portion in the width direction, forming an inverted U-shaped cross-section. Furthermore, the lower half-body 10L is essentially formed as a flat plate, forming a roughly L-shaped shape when viewed from above, thus blocking the open lower end of the upper half-body 10U. The two end faces (not shown) of the lower half-body 10L in the width direction are welded to the inner surfaces of the pair of side wall portions (not shown) of the upper half-body 10U.

[0040] Next, refer to Figure 7 as well as Figure 1 , Figure 2 The structure of the second vehicle body side connecting portion 14 with the flanged processing portion 20 in this embodiment will be described. On the second vehicle body side connecting portion 14 side of the arm body 10, the lower half 10L extends further outward (towards the rear of the vehicle body) than the upper half 10U, and a flanged processing portion 20, which becomes the second vehicle body side connecting portion 14, is formed in this extension. An upwardly cylindrical upright portion 26 is integrally formed in the flanged processing portion 20, which can press and fit the second bushing 30a2. The outer peripheral surface of the cylindrical upright portion 26 near the middle part of the arm body 10 is joined to the outer end of the upper half 10U, which has a topographical arc shape, through a welding portion w. This structure of the second body side connection 14 ensures strength and rigidity while reducing the amount of the upper half 10U extending rearward towards the body, thus achieving weight reduction. Furthermore, it eliminates the need for flanging the upper half 10U, simplifying manufacturing processes. Additionally, in Figure 7In the L-shaped lower arm 1a of the present embodiment shown, the flanging portion is only adopted at the second vehicle body side connecting portion 14, but it can also be adopted at the first vehicle body side connecting portion 12 or the wheel support portion 16 in the same manner as the L-shaped lower arm 1a of the prior art shown in Figures 1-4 shown.

[0041] In the flanging portion 20 of the present embodiment, the annular step 28 provided on the inner periphery of the erected portion 26 functions as a pulling resistance step for increasing the pulling load of the fitting member 30 fitted to the inner periphery of the erected portion 26. Use Figure 5 、 Figure 6 、 Figures 8-10 To explain this. In addition, Figure 5 is a view showing a flanging portion of a conventional vehicle arm member in a partial cross-section of one side in a cross-section including the flanging axis, and Figure 6 is a view showing the state where a fitting member is fitted in the flanging portion of a conventional vehicle arm member in a partial cross-section of one side in a cross-section including the flanging axis.

[0042] As described above, when the flanging portion 20 of the conventional vehicle arm member shown in Figure 5 is strengthened, as shown in Figure 6 shown, the relatively low-rigidity fitting member 30 flexes and the contact portion is only around the high-pressure portion P, and there is a problem that it is difficult to ensure the pulling load.

[0043] Compared with such prior art, as shown in Figure 8 shown, the flanging portion 20 of the present embodiment has a plurality of coaxial and same-diameter inner peripheral portions 26A (26A1, 26A2) on the inner periphery of the cylindrical erected portion 26, and the inner diameters of the same-diameter inner peripheral portions 26A (26A1, 26A2) increase stepwise from the front end side toward the root side (d1 < d2). An annular step 28 is formed at the boundary between the front-end side same-diameter inner peripheral portion 26A1 and the root-side same-diameter inner peripheral portion 26A2 with different inner diameters. According to the present embodiment, as shown in Figure 9 shown, the front-end side same-diameter inner peripheral portion 26A1隔着环状台阶28 can be used to Figure 6The gap generated in the prior art, namely the gap between the inner periphery of the raised portion 26 and the outer periphery of the mating member 30, is filled at the front end side of the high-pressure bearing portion P. Therefore, in the flanging section 20 of this embodiment, cylindrical contact portions between the inner periphery of the raised portion 26 and the mating member 30 can be formed around at least two high-pressure bearing portions P, namely around the front end high-pressure bearing portion P1 and around the root end high-pressure bearing portion P2. Therefore, for the flanging section 20 of this embodiment, even if the raw material is made high-strength, it can become a flanging section 20 that can advantageously ensure pull-out load. Furthermore, in the description up to this point, the case of two inner periphery portions 26A of the same diameter and one annular step 28 at the boundary has been described, but it is not limited to this; it is also possible to have a combination of three or more inner periphery portions 26A of the same diameter and two or more annular steps 28 at the boundary.

[0044] The size of the flanged portion in the vehicle boom member or the manufacturing method of the vehicle boom member in this embodiment is not particularly limited, for example, the inner diameter (refer to...). Figure 8 The d1 value is between 10mm and 100mm, and the flange height is (refer to...). Figure 8 The h) is between 3mm and 15mm.

[0045] As a preliminary experiment to achieve the present invention, the inventors of this application investigated... Figure 8 The study investigates the influence of the step difference Δd of the annular step 28 in the flanged section 20 and the flange height direction position (height hd) on the effect of improving the pull-out load. The raw material used in the investigation was a high-strength steel plate with a thickness of 3.2 mm and a tensile strength of 980 MPa. Regarding the flanged section, the following description will be used. Figures 11A-11C or Figure 12A , Figure 12B The experimental apparatus for the mold structure shown was formed in a manner that yielded the step difference Δd of multiple level annular steps and the flange height direction position (height hd). Furthermore, here, as... Figure 8 As shown, the position of the flange height direction is represented by the height hd from the surface around the flange processing part to the front end of the annular step.

[0046] Furthermore, as a mating component that mates with the flanging part, a bushing collar with a plate thickness of 2.3 mm and a tensile strength of 590 MPa was used to measure the pull-out load from the flanging part under the various conditions described above. The results are summarized and presented in... Figure 10In addition, the increase rate of the pull-out load on the longitudinal axis (Fd-F) / F is expressed as the maximum pull-out load Fd of the various prepared annular steps, based on the pull-out load F without the annular step. Furthermore, the step difference Δd / tL of the annular step on the transverse axis is obtained by dimensionlessly approximating the step difference Δd in the direction perpendicular to the flange direction using the plate thickness tL of the inner circumference of the same diameter on the root side of the annular step. Furthermore, Figure 10 The data is represented in layers by using the flanging height h from the flanging part to the height hd from the flanging part to the front end of the annular step, which is dimensionless, to obtain hd / h.

[0047] according to Figure 10 If the increase rate of the pull-out load (Fd-F) / F is preferably 10% or more, then when the height hd / h in the flange direction of the annular step is 32%, the step difference Δd / tL of the annular step does not have a preferred range. On the other hand, when the height hd / h in the flange direction of the annular step is 49-84%, the step difference Δd / tL of the annular step is 1.8% or more, and the increase rate of the pull-out load (Fd-F) / F is 10% or more, which is a preferred range. However, even in this case, if the step difference Δd / tL of the annular step becomes larger, the increase rate of the pull-out load (Fd-F) / F will be less than 10%. Thus, the upper limit of the step difference Δd / tL of the annular step where the increase rate of the pull-out load (Fd-F) / F is less than 10% varies for each height hd / h in the flange direction of the annular step. That is, when hd / h=84%, the upper limit of the step difference Δd / tL of the annular step is 23%; when hd / h=66%, the upper limit of the step difference Δd / tL of the annular step is 10%; and when hd / h=49%, the upper limit of the step difference Δd / tL of the annular step is 5%.

[0048] In particular, the maximum value of the pull-out load increase rate (Fd-F) / F exceeds 30% when the height hd / h in the flange direction of the annular step is in the range of 49-84% and the step difference Δd / tL of the annular step is in the range of 1.8-5%, indicating that the conditions for the annular step are particularly preferred.

[0049] Based on the preliminary experimental results described above, the inventors of this application determined that the step difference Δd in the direction perpendicular to the flange direction of the annular step is preferably 1.8% or more of the plate thickness tL of the inner circumference of the same diameter on the root side of the annular step. In this case, regarding the height position of the annular step in the flange direction, when the height from the periphery of the flanged processing portion to the front end of the annular step is defined as hd, and the flange height from the periphery of the flanged processing portion is defined as h, it is determined that it is preferable to simultaneously satisfy hd ≥ 0.49h.

[0050] When the step difference Δd / tL of the annular step is less than 1.8%, Figure 6 The gap on the front end side of the high-pressure bearing part P shown was not... Figure 8 The inner circumference 26A1 of the same diameter on the front side of the annular step 28, as shown in the diagram, was filled without producing any defects. Figure 9 The high-pressure bearing section P1 on the front side, as shown, cannot achieve an increase in pull-out load. Conversely, when the step difference Δd / tL of the annular step is large and the increase rate of pull-out load Fd / F is less than 10%, it is presumed that no increase will occur. Figure 9 The high-pressure bearing portion P2 on the root side of the same diameter inner circumference portion 26A2 on the root side, as shown by the annular step 28, reduces the effect of increasing the pull-out load.

[0051] Next, refer to Figures 11A-11C , Figure 12A , Figure 12B The manufacturing method of the vehicle boom member according to this embodiment will be described. Furthermore, the flanging section occupies, for example, a portion of the stamped part, such as the lower half. This flanging process and the overall stamping process of the component can be provided separately, but generally, for production efficiency, the flanging process is incorporated into the overall stamping process of the component. In addition, the manufacturing method of the vehicle boom member of this embodiment, apart from the flanging section, includes, for example, the stamping of each constituent component such as the lower half, and the assembly such as welding of the constituent components obtained by stamping, which are the same as conventional manufacturing methods. Therefore, the description of the manufacturing method of the vehicle boom member of this embodiment here omits detailed descriptions of manufacturing methods common to conventional manufacturing methods and focuses on the description of the manufacturing method of the flanging section.

[0052] Figure 11A , Figure 11B This is a diagram illustrating the final stage of the flanging process in a method for manufacturing a vehicle arm component according to an embodiment of the present invention, using a partial cross-sectional view including the flanging shaft.

[0053] In addition, Figure 11CThe cross-sectional shape, including the central axis of the compound forming punch 40A used herein, is shown. A narrow-diameter cylindrical portion 40Aa is provided at the front end of the compound forming punch 40A. By inserting a portion of this narrow-diameter cylindrical portion 40Aa into the prepared hole of the blank before flanging, the flanging position of the blank can be aligned with the center positions of the flanging section 20, the forming punch 40, and the forming die 44. The conical portion 40Ab of the punch is a portion in which the peripheral plate-like portion 22 around the flanging section is held by the retainer 42 and the forming die 44, and the peripheral plate-like portion 22 around the bottom hole is pushed outward while the bottom hole of the blank is gradually expanded to the inner diameter of the flanging section. The cylindrical front portion 40Ac of the punch is a portion where a raised portion 26 with an inner diameter d1 of the same diameter 26A is formed by a flanging portion extending through the conical portion 40Ab while maintaining a predetermined gap Ct with the inner diameter of the forming die 44. The cylindrical rear portion 40Ae of the punch is a portion where an inner diameter d2 of the same diameter 26A2 is formed at a predetermined height on the root side of the inner diameter d1 of the inner diameter 26A formed through the cylindrical front portion 40Ac while maintaining a predetermined gap Cn with the inner diameter of the forming die 44. The stepped portion 40Ad of the punch is the boundary between the cylindrical front portion 40Ac and the cylindrical rear portion 40Ae, and is a portion where an annular step 28 is formed on the inner circumference of the flanging portion 20.

[0054] In the manufacturing method of the vehicle arm component according to an embodiment of the present invention, a forming die 44 having an inner diameter corresponding to the outer periphery of the raised portion of the flanging section is used. Furthermore, the forming punch 40 uses, for example... Figure 11C The figure shown is a composite forming punch 40A having an outer peripheral shape corresponding to the inner periphery of the raised portion 26 of the flanging section 20. By employing such a die structure, the flanging section 20 of the vehicle arm member of this embodiment can be formed in a single stamping process.

[0055] The stamping process in this step Figure 11A The process up to this point is a stage in which a predetermined gap Ct is achieved between the cylindrical front portion 40Ac of the compound forming punch 40A and the inner diameter portion of the forming die 44, while forming the entire inner circumference of the raised portion 26 to complete the inner circumference portion 26A of the same diameter as the inner diameter d1. Furthermore, up to this... Figure 11A The descriptions of the various stages of the flanging process up to this point are redundant with those of the small-diameter cylindrical portion 40Aa and conical portion 40Ab of the composite forming punch, so their descriptions are omitted. Figure 11BThis indicates that during a single stamping process, a predetermined gap Cn is achieved between the cylindrical rear portion 40Ae of the composite forming punch 40A and the inner diameter portion of the forming die 44, while simultaneously forming the root-side inner circumferential portion 26A2 with an inner diameter d2 at the root of the inner circumference of the raised portion 26. Furthermore, at this stage, an annular step 28 is formed at a predetermined height position on the inner circumference of the raised portion 26 as the boundary between the front-side inner circumferential portion 26A1 and the root-side inner circumferential portion 26A2.

[0056] Here, the specified gap Ct will be explained. That is, the gap Ct between the cylindrical front portion 40Ac of the composite forming punch 40A corresponding to the inner circumference portion 26A1 of the same diameter at the front end and the inner diameter portion of the forming die 44 is 70% or more and 100% or less of the thickness of the metal raw material sheet. This is because if the gap Ct exceeds 100% of the thickness of the metal raw material sheet, the cylindrical shape of the upright portion of the flanging part 20 is prone to instability, which is not preferred. On the other hand, if the gap Ct is less than 70% of the thickness of the metal raw material sheet, the thinning, drawing, and flanging process, which becomes a strong processing condition from the front end to the root end, increases the risk of the flanging part breaking, which is also not preferred.

[0057] Furthermore, the gap Cn between the cylindrical rear portion 40Ae of the composite forming punch 40A corresponding to the inner diameter portion 26A2 of the same diameter as the front end and closer to the root end, and the inner diameter portion of the forming die 44, is at least 60% of the thickness of the metal raw material sheet and less than the gap Ct. This is because setting this gap Cn to be greater than or equal to the gap Ct is equivalent to making the inner diameter of the root end of the inner diameter portion 26A smaller than the inner diameter of the front end. Such a shape of the inner diameter portion 26A cannot be formed in a single stamping process and is therefore not preferred. On the other hand, if this gap Cn is less than 60% of the thickness of the metal raw material sheet, it becomes an extremely stringent processing condition that exceeds the thinning, drawing, and flanging processing conditions, making it impossible to avoid breakage of the flanging portion, and is therefore not preferred.

[0058] As mentioned above, using Figures 11A-11C A method for manufacturing a vehicle boom member with a flanging portion formed in a single stamping process according to this embodiment has been described. However, in this embodiment, the forming of the flanging portion is not limited to a single stamping process. For example, as... Figure 12A As shown, the process of forming an inner circumferential portion 26A with an inner diameter d1 in the entire inner circumferential area of ​​the upright portion 26 using the first forming punch 40B1, up to the middle stage of the flanging process, can also be divided into two parts: one to the end of the process. Figure 11A The same flanging process is performed until then. Afterwards, as... Figure 12B As shown, an additional inner circumferential portion 26A2 with an inner diameter d2 is formed at the root of the inner circumference of the raised portion 26 using a second forming punch 40B2, and is of the same diameter as the root side. Figure 11BThe same flanging process is used; once the flanging is completed, the flanging process is finished.

[0059] Explanation of reference numerals in the attached figures 1. Vehicle boom component; 1a. L-shaped lower boom; 10. Boom body; 10L. Lower half; 10U. Upper half; 12. First body side connection; 14. Second body side connection; 16. Wheel support; 20. Flanging part; 22. Peripheral plate-like part; 24. Bending part; 26. Erecting part; 26A. Inner circumference of the same diameter; 26A1. Inner circumference of the same diameter on the front side; 26A2. Inner circumference of the same diameter on the root side; 28. Annular step; 30. Fitting component; 30a. Bushing collar; 30a1. First bushing; 30a2. Second bushing; 30bj. Ball joint; 32. Body subframe; 34. Wheel support component; 40. Forming punch; 40A. Composite forming punch; 40Aa. Small diameter cylindrical part; 40Ab. Conical part; 40Ac. Front cylindrical part; 40Ad. Stepped section; 40Ae Rear part of cylinder; 40B1 First forming punch; 40B2 Second forming punch; 42 Holder; 44 Forming die; d Inner diameter of flanged section; d1 Inner diameter of inner circumference of the same diameter on the front end side; d2 Inner diameter of inner circumference of the same diameter on the root side; Δd ​​Step difference of the annular step; F Pull-out load when there is no annular step; Fd Pull-out load when there is annular step; h Flanged height; hd Height of the position of the annular step; tL Thickness of the inner circumference of the same diameter on the root side; P High bearing section; P1 High bearing section on the front end side; P2 High bearing section on the root side; w Welded section.

Claims

1. A vehicle boom component, comprising a flanging processing section, The flanging section has a cylindrical upright portion that engages with and holds together other components. The cylindrical upright portion has multiple coaxial inner circumferential portions of the same diameter on its inner periphery. These multiple inner circumferential portions of the same diameter are sandwiched by annular steps at their boundaries, and their inner diameter increases in a stepped manner from the front end side toward the root side. The annular step is used as the pull-out resistance step of the fitting member.

2. The vehicle boom assembly as described in claim 1, The step difference Δd in the direction perpendicular to the flange direction of the annular step is more than 1.8% of the plate thickness tL of the inner circumference of the same diameter on the root side of the annular step. When the height from the surface surrounding the flanging part to the front end of the annular step is set as hd, and the flanging height from the surface surrounding the flanging part is set as h, the height position of the annular step in the flanging direction satisfies hd≥0.49h.

3. A method for manufacturing a vehicle boom component, The vehicle arm component has a flanged portion forming a cylindrical upright section. Multiple coaxial inner circumferential portions of the same diameter are formed on the inner periphery of the upright section. These multiple inner circumferential portions of the same diameter have annular steps at their boundaries, and their inner diameter increases in a stepped manner from the front end side towards the root side. In the manufacturing method of the vehicle arm component, the flanging part is formed in a single stamping process using a forming die and a forming punch. The forming mold has an inner diameter corresponding to the outer periphery of the upright portion of the flanging part. The forming punch has an outer peripheral shape corresponding to the inner periphery of the upright portion of the flanging section. A portion of the outer peripheral shape of the forming punch corresponding to the inner peripheral portion of the same diameter at the foremost end has an outer diameter such that the gap Ct between it and the forming die is 70% or more and 100% or less of the thickness of the metal raw material plate. A portion of the outer peripheral shape of the forming punch corresponding to the inner peripheral portion of the same diameter at the root side of the inner peripheral portion of the same diameter at the foremost end has an outer diameter such that the gap Cn between it and the forming die is 60% or more of the thickness of the metal raw material plate and less than the gap Ct.

4. A method for manufacturing a vehicle boom component, The vehicle arm component has a flanged portion forming a cylindrical upright section. Multiple coaxial inner circumferential portions of the same diameter are formed on the inner periphery of the upright section. These multiple inner circumferential portions of the same diameter have annular steps at their boundaries, and their inner diameter increases in a stepped manner from the front end side towards the root side. The manufacturing method of the vehicle boom component includes: In the first stamping forming process, a forming die having an inner diameter corresponding to the outer periphery of the upright portion of the flanging part and a forming punch having an outer diameter such that the gap Ct between the forming die and the flanging part is 70% or more and 100% or less of the thickness of the metal raw material plate are formed, the inner periphery portion of the same diameter at the foremost side of the inner periphery of the upright portion of the flanging part is formed. as well as In the second stamping forming process, for the flanging part formed by the first stamping forming process, a forming die having an inner diameter corresponding to the outer periphery of the upright part of the flanging part, and a forming punch having an outer diameter such that the gap Cn between the die and the forming die is more than 60% of the thickness of the metal raw material plate and less than the gap Ct, forms the inner periphery of the upright part of the flanging part that is closer to the root than the foremost side.

5. The method for manufacturing a vehicle boom component as described in claim 3 or 4, The step difference Δd in the direction perpendicular to the flange direction of the annular step is more than 1.8% of the plate thickness tL of the inner circumference of the same diameter on the root side of the annular step. When the height from the surface surrounding the flanging part to the front end of the annular step is set as hd, and the flanging height from the surface surrounding the flanging part is set as h, the height position of the annular step in the flanging direction satisfies hd≥0.49h.

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