Suspension arm

Abstract

To provide a suspension arm which can enhance bush holding force while restraining cost of manufacture and weight increase.SOLUTION: A suspension arm is a suspension arm which comprises an arm body and a bush press-fit part which is provided on an end part of the arm body in which a bush is press-fitted. The bush press-fit part includes an open hole formed on a plate-like part and a longitudinal wall part which is formed in cylindrical shape by standing up from circumference of the open hole. The suspension arm is provided with an annular member which is attached on outer peripheral surface of the longitudinal wall part.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a suspension arm. [Background technology]

[0002] In recent years, in order to reduce the weight of automobiles, the use of high-tensile steel has led to the thinning of automobile frame parts. However, when the suspension arm, which is an automobile undercarriage part, is thinned, the rigidity of the bush press-in part of the suspension arm decreases, and the bush retention force of the suspension arm decreases. Patent Document 1 discloses a technology in which a reinforcing plate is attached to the suspension arm to sufficiently ensure the cross-sectional shape of the transition part from the bush press-in part of the suspension arm to the arm body, thereby ensuring the necessary rigidity and strength of the transition part. The reinforcing plate is composed of an eye-shaped head and a tail part, and the eye-shaped head is located coaxially with the bush press-in part, and at least the tail part is welded to the arm body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-62675 A Summary of the Invention [Problem to be solved by the invention]

[0004] The technology disclosed in Patent Document 1 requires high manufacturing costs for the reinforcing plate attached to the suspension arm, and a significant increase in weight is unavoidable. Also, it is difficult in manufacturing to position the eye-shaped head of the reinforcing plate coaxially with the bush press-fitting portion and to attach the tail of the reinforcing plate to the arm body of the suspension arm by welding.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a suspension arm that can improve bush holding force while suppressing manufacturing costs and weight increases. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the objectives, (1) A suspension arm according to the present invention is a suspension arm comprising an arm body and a bush press-in portion provided at an end of the arm body and into which a bush is press-in, wherein the bush press-in portion has a through hole formed in a plate-shaped portion and a vertical wall portion rising from the periphery of the through hole and formed into a cylindrical shape, and comprises an annular member attached to the outer circumferential surface of the vertical wall portion.

[0007] (2) The suspension arm according to the present invention, in the above-mentioned (1) is characterized in that the annular member and the vertical wall portion are made of the same type of material.

[0008] (3) The suspension arm of the present invention, in the above (1) or (2), is characterized in that the position of the upper end of the annular member in the axial direction of the through hole is the same as the position of the upper end of the vertical wall portion, or is higher than the position of the upper end of the vertical wall portion.

[0009] (4) The suspension arm of the present invention, in any one of the above (1) to (3), is characterized in that the position of the lower end of the annular member in the axial direction of the through hole is at a first position that is further toward the lower end of the vertical wall portion by the thickness of the vertical wall portion than the position of the upper end of the vertical wall portion, or at a second position that is further toward the lower end of the vertical wall portion than the first position.

[0010] (5) The suspension arm of the present invention, in any one of the above (1) to (4), is characterized in that the position of the lower end of the annular member in the axial direction of the through hole is at a third position that is closer to the upper end of the vertical wall portion than the position of the lower end of the vertical wall portion by the thickness of the vertical wall portion, or at a fourth position that is closer to the upper end of the vertical wall portion than the third position.

[0011] (6) The suspension arm of the present invention, in any one of the above (1) to (5), is characterized in that the inner surface of the annular member is tapered such that the radius increases from the upper end to the lower end in the axial direction of the annular member.

[0012] (7) The suspension arm according to the present invention is any one of the above-mentioned (1) to (6), characterized in that the annular member is press-fitted into the vertical wall portion.

[0013] (8) The suspension arm according to the present invention, in any one of the above (1) to (7), is characterized in that the annular member is shrink-fitted into the vertical wall portion.

[0014] (9) The suspension arm of the present invention, in any one of the above (1) to (6), is characterized in that an outer peripheral surface of the vertical wall portion is formed with a male thread portion, and an inner peripheral surface of the annular member is formed with a female thread portion that screws into the male thread portion.

[0015] (10) The suspension arm of the present invention is characterized in that, in the invention of (1) or (2) above and any one of the inventions of (4) to (8) above, a portion of the annular member has a shape that covers an upper end of the vertical wall portion. Effect of the Invention

[0016] The suspension arm according to the present invention has an advantage in that it is possible to improve the bush retaining force while suppressing increases in manufacturing costs and weight. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a suspension arm according to the first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of a bush press-fitting portion according to the first embodiment. [Diagram 3]FIG. 3 is a cross-sectional view showing another example of the bush press-fitting portion according to the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a bush press-fitting portion according to a reference example. [Diagram 5] FIG. 5 is a plan view of a ring-shaped member in the suspension arm according to the second embodiment. [Figure 6] FIG. 6 is a cross-sectional view of a ring-shaped member according to the second embodiment. [Figure 7] FIG. 7 is an enlarged view showing a screwed portion between a vertical wall portion and a ring-shaped member in a suspension arm according to the third embodiment. [Figure 8] FIG. 8 is a cross-sectional view of a bush press-fit portion 2 in a suspension arm according to the fourth embodiment. [Figure 9] 9(a) is a plan view showing a CAE analysis model of a bushing press-fit portion according to an embodiment of the present invention, and FIG.9(b) is a cross-sectional view showing a CAE analysis model of a bushing press-fit portion according to an embodiment of the present invention. [Figure 10] Fig. 10(a) is a plan view showing a CAE analysis model of a bushing press-fit portion according to a comparative example, and Fig. 10(b) is a cross-sectional view showing a CAE analysis model of a bushing press-fit portion according to a comparative example. [Figure 11] Fig. 11(a) is a plan view showing the CAE analysis model of the bush, and Fig. 11(b) is a side view showing the CAE analysis model of the bush. [Figure 12] FIG. 12 is a diagram showing a CAE analysis model of a state in which a bush is press-fitted into a bush press-fitting portion. [Figure 13] FIG. 13 is a graph showing the change in bushing extraction force during bushing extraction. [Figure 14] Fig. 14(a) is a diagram showing the range of positions in the vertical wall portion for which surface pressure calculations were performed in the bush press-fit portion of the present invention, and Fig. 14(b) is a diagram showing the range of positions in the vertical wall portion for which surface pressure calculations were performed in the bush press-fit portion of the comparative example. [Figure 15] FIG. 15 is a graph showing the distribution of surface pressure within the vertical wall portion. [Figure 16]FIG. 16 is a diagram showing an example of the positional relationship between the vertical wall portion of the bushing press-fitting portion and the ring-shaped member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (Embodiment 1) A first embodiment of a suspension arm according to the present invention will be described below. Note that the present invention is not limited to this embodiment.

[0019] FIG. 1 is a diagram showing a schematic configuration of a suspension arm 1 according to the first embodiment.

[0020] As shown in FIG. 1, the suspension arm 1 of the first embodiment comprises an arm body 10, a bush press-fitting portion 2 provided at the end of the arm body 10 and into which a bush is press-fitted, and a ring-shaped member 3 which is an annular member.

[0021] 2 is a cross-sectional view of the bushing press-fitting portion 2 according to embodiment 1. The cross section of the bushing press-fitting portion 2 shown in FIG. 2 corresponds to the AA cross section in FIG.

[0022] The bush press-fitting portion 2 according to the first embodiment has a through hole 20 formed in a top plate portion 21, which is a plate-shaped portion, and a vertical wall portion 23 formed by rising from the periphery of the through hole 20 in the axial direction of the through hole 20. In the following description, the axial direction of the through hole 20 will also be simply referred to as the axial direction. The vertical wall portion 23 is formed into a cylindrical shape by burring. The top plate portion 21 and the vertical wall portion 23 are connected by a curved portion 22 formed by curving 90 degrees in an arc shape from the inner periphery of the top plate portion 21.

[0023] Here, the inventors of the present application have studied the surface pressure that the bush receives from the bushing press-fitting portion 2, and have found that the surface pressure is high near the upper end 230 (the end opposite the top plate portion 21 in the axial direction) of the vertical wall portion 23 of the bushing press-fitting portion 2, and that reinforcing this portion with an annular member has a significant effect of improving the bushing retention force. Therefore, in the suspension arm 1 according to the first embodiment, the inner peripheral surface of the ring-shaped member 3 is brought into contact with the outer peripheral surface of the vertical wall portion 23, and the ring-shaped member 3 is press-fitted into the outer peripheral surface of the vertical wall portion 23 for attachment.

[0024] As a method for joining the vertical wall portion 23 of the bushing press-fit portion 2 and the ring-shaped member 3, for example, welding or brazing can be applied. Also, the ring-shaped member 3 may be fixed to the vertical wall portion 23 of the bushing press-fit portion 2 by, for example, shrink fitting. That is, the ring-shaped member 3 that has been heated and expanded is fitted into the vertical wall portion 23 of the bushing press-fit portion 2, and then the ring-shaped member 3 is cooled to room temperature, thereby fitting the ring-shaped member 3 into the vertical wall portion 23 of the bushing press-fit portion 2.

[0025] In addition, it is desirable that the positional relationship between the vertical wall portion 23 of the bush press-fitting portion 2 and the ring-shaped member 3 satisfy the following three conditions. That is, as a first condition, as shown in FIG. 2, the position of the upper end 31 of the ring-shaped member 3 is the same as the position of the upper end 230 of the vertical wall portion 23 of the bush press-fitting portion 2, or as shown in FIG. 3, it is in a position higher than the upper end 230 of the vertical wall portion 23 of the bush press-fitting portion 2. Note that a position higher than the upper end 230 of the vertical wall portion 23 means a position higher than the upper end 230 when the bush press-fitting portion 2 (suspension arm 1) is placed on a stand or the like so that the vertical wall portion 23 rises upward in the axial direction. As a second condition, the position of the lower end 32 of the ring-shaped member 3 in the axial direction of the through hole 20 is at a first position that is located on the lower end side of the vertical wall portion 23 by the plate thickness of the vertical wall portion 23 from the position of the upper end 230 of the vertical wall portion 23, or at a second position that is located on the lower end side of the vertical wall portion 23 from the first position. The third condition is that the position of the lower end 32 of the ring-shaped member 3 in the axial direction of the through hole 20 is at a third position that is closer to the upper end 230 of the vertical wall portion 23 than the position of the lower end of the vertical wall portion 23 by the thickness of the vertical wall portion 23, or at a fourth position that is closer to the upper end 230 of the vertical wall portion 23 than the third position.

[0026] Furthermore, it is desirable that the ring-shaped member 3 and the bush press-in portion 2 (vertical wall portion 23) are made of the same type of material. For example, if the bush press-in portion 2 (vertical wall portion 23) is made of a steel material, it is desirable that the ring-shaped member 3 is also made of a steel material. This is because, although a coating is formed on the surface of the suspension arm 1 by cathodic painting or the like, if the coating is damaged while the automobile is traveling, and the vertical wall portion 23 and the ring-shaped member 3 come into contact with each other as metals, galvanic corrosion may occur if they are made of dissimilar materials.

[0027] In the bushing press-fitting portion 2 according to the first embodiment, the bushing is press-fitted into the through-hole 20 from the side opposite to the side where the vertical wall portion 23 stands in the axial direction, and the bushing is held in place by the inner peripheral surface of the vertical wall portion 23 abutting against the side surface of the bushing. When the bushing is press-fitted into the bushing press-fitting portion 2, the surface pressure acting on the side surface of the bushing is increased by the ring-shaped member 3, and the force with which the vertical wall portion 23 holds the bushing can be increased.

[0028] FIG. 4 is a cross-sectional view of a bushing press-fitting portion 2 according to a reference example.

[0029] 4, the bushing press-fitting portion 2 according to the reference example has a through hole 20 formed in a top plate portion 21, and a vertical wall portion 23 formed rising from the periphery of the through hole 20. The top plate portion 21 and the vertical wall portion 23 are connected by a curved portion 22 formed by curving at 90 degrees in an arc shape from the periphery of the top plate portion 21. A bushing press-fitted into the bushing press-fitting portion 2 according to the reference example is held by the vertical wall portion 23.

[0030] The bush press-fit portion 2 according to the first embodiment can improve the bush holding force while suppressing increases in manufacturing cost and weight, with only slight increases in manufacturing cost and weight compared to the bush press-fit portion 2 according to the reference example, by attaching the ring-shaped member 3 to the outer peripheral surface of the vertical wall portion 23. Furthermore, in the suspension arm 1 according to the first embodiment, the bush press-fit portion 2 and the ring-shaped member 3 can be easily positioned coaxially by fitting the ring-shaped member 3 onto the outer peripheral surface of the vertical wall portion 23.

[0031] (Embodiment 2) Hereinafter, a suspension arm structure according to a second embodiment of the present invention will be described. Note that in this embodiment, the same descriptions as those in the first embodiment will be omitted as appropriate.

[0032] Fig. 5 is a plan view of the ring-shaped member 3 in the suspension arm 1 according to embodiment 2. Fig. 6 is a cross-sectional view of the ring-shaped member 3 according to embodiment 2. The cross section of the ring-shaped member 3 shown in Fig. 6 corresponds to the cross section BB in Fig. 5.

[0033] In the ring-shaped member 3 according to the second embodiment, the inner radius, which is the radial distance between the inner peripheral surface 33 and the axis AX at the upper end 31 of the ring-shaped member 3, is denoted as R11, and the inner radius, which is the radial distance between the inner peripheral surface 33 and the axis AX at the lower end 32 of the ring-shaped member 3, is denoted as R12. In the ring-shaped member 3 according to the second embodiment, R11 < R12, and the inner peripheral surface 33 of the ring-shaped member 3 has a tapered shape such that the inner radius linearly increases from the upper end 31 side to the lower end 32 side in the axial direction. Thereby, in the suspension arm 1 according to the second embodiment, it is possible to easily press-fit the ring-shaped member 3 into the vertical wall portion 23 of the bush press-fitting portion 2 from the lower end 32 side.

[0034] Further, the ring-shaped member 3 according to the second embodiment may be fixed to the vertical wall portion 23 of the bush press-fitting portion 2 by shrink fitting, for example.

[0035] (Embodiment 3) Hereinafter, Embodiment 3 of the structure of the suspension arm according to the present invention will be described. In this embodiment, descriptions similar to those in Embodiment 1 will be omitted as appropriate.

[0036] FIG. 7 is an enlarged view showing a screwed portion between the vertical wall portion 23 and the ring-shaped member 3 in the suspension arm 1 according to the third embodiment.

[0037] In the suspension arm 1 according to the third embodiment, as shown in FIG. 7, a male screw portion 231 is provided on the outer peripheral surface of the vertical wall portion 23 of the bush press-fitting portion 2, and a female screw portion 331 that engages with the male screw portion 231 is provided on the inner peripheral surface of the ring-shaped member 3. The male screw portion 231 provided on the outer peripheral surface of the vertical wall portion 23 is provided, for example, in the axial direction from the upper end 230 of the vertical wall portion 23 to the range corresponding to the female screw portion 331. In the suspension arm 1 according to the third embodiment, the female screw portion 331 of the ring-shaped member 3 is screwed into the male screw portion 231 of the vertical wall portion 23, and the vertical wall portion 23 and the ring-shaped member 3 are screwed together, whereby the ring-shaped member 3 can be easily attached to the vertical wall portion 23.

[0038] (Embodiment 4) Hereinafter, a fourth embodiment of the suspension arm structure according to the present invention will be described. Note that in this embodiment, the same descriptions as those in the first embodiment will be omitted as appropriate.

[0039] FIG. 8 is a cross-sectional view of the bush press-fit portion 2 in the suspension arm 1 according to the fourth embodiment.

[0040] In the suspension arm 1 according to the fourth embodiment, as shown in FIG. 8, a part of the ring-shaped member 3 has a shape that covers the upper end 230 of the vertical wall portion 23 of the bush press-fitting portion 2. That is, the ring-shaped member 3 according to the fourth embodiment has a main body portion 301 extending in the axial direction and an inner edge portion 302 provided along the inner edge of the main body portion 301 on the upper end 230 side in the axial direction. In the suspension arm 1 according to the fourth embodiment, the ring-shaped member 3 is fitted into the vertical wall portion 23 so that the inner edge portion 302 of the ring-shaped member 3 covers the upper end 230 of the vertical wall portion 23 of the bush press-fitting portion 2. As a result, when the ring-shaped member 3 is fitted into the vertical wall portion 23 of the bush press-fitting portion 2, the inner edge portion 302 of the ring-shaped member 3 comes into contact with the upper end 230 of the vertical wall portion 23, so that it is possible to prevent the ring-shaped member 3 from being inserted too deeply into the vertical wall portion 23. Therefore, in the suspension arm 1 of embodiment 4, it is possible to prevent the upper part of the vertical wall portion 23 from being unable to be reinforced by the ring-shaped member 3, and to prevent stress concentration from occurring in the lower part of the vertical wall portion 23 or in the curved portion 22 when the vehicle is traveling, etc. EXAMPLES

[0041] In order to confirm the superiority of the structure of the bushing press-fit portion 2 according to the present invention, a CAE analysis was carried out on the press-fitting and drawing of the bushing 4 into the bushing press-fit portion 2. Note that the material of the bushing press-fit portion 2 was assumed to be a 590 MPa class hot-rolled steel plate.

[0042] Example 1 In Example 1, a bushing press-fit portion 2 according to an example of the present invention and a bushing press-fit portion 2 according to a comparative example were used to carry out a CAE analysis of pressing a bushing 4 into the bushing press-fit portion 2 and a CAE analysis of pulling the bushing 4 out of the bushing press-fit portion 2. When there is no particular need to distinguish between the bushing press-fit portion 2 according to the example of the present invention and the bushing press-fit portion 2 according to the comparative example, they will simply be referred to as the bushing press-fit portion 2.

[0043] Fig. 9(a) is a plan view showing a CAE analysis model of the bushing press-fit portion 2 according to the present invention. Fig. 9(b) is a cross-sectional view showing the CAE analysis model of the bushing press-fit portion 2 according to the present invention. The cross section of the bushing press-fit portion 2 shown in Fig. 9(b) corresponds to the CC cross section of Fig. 9(a).

[0044] In the CAE analysis model of the bushing press-fitting portion 2 according to the present invention, the top plate portion 21 is disk-shaped with a radius of 58 mm, and the radius of the through hole 20 provided concentrically with the top plate portion 21 is 25 mm. In the CAE analysis model of the bushing press-fitting portion 2 according to the present invention, the plate thickness t1 is 2 mm, the radial length L1 of the top plate portion 21 is 30 mm, the inner radius R1 of the curved portion 22 is 1 mm, and the outer radius R2 of the curved portion 22 is 3 mm. In the CAE analysis model of the bushing press-fitting portion 2 according to the present invention, the axial length L2 of the vertical wall portion 23 is 8 mm. In the CAE analysis model of the bushing press-in portion 2 according to the present invention, a ring-shaped member 3 having an inner radius of 27 mm, an outer radius of 29 mm, a plate thickness t2 of 2 mm, and an axial height L3 of 5 mm was attached in a range from the upper end of the vertical wall portion 23 of the bushing press-in portion 2 to the lower end side of 5 mm in the axial direction. In the CAE analysis model of the bushing press-in portion 2 according to the present invention, the bushing press-in portion 2 according to the present invention was modeled with solid elements of 0.4 mm in size obtained by dividing the bushing press-in portion 2 according to the present invention into 5 in the plate thickness direction. Note that, although a contact interface is originally present between the vertical wall portion 23 of the bushing press-in portion 2 and the ring-shaped member 3, in this embodiment, the CAE analysis was performed assuming that the vertical wall portion 23 of the bushing press-in portion 2 and the ring-shaped member 3 are integrated. In addition, the plate thickness t3 of the portion where the vertical wall portion 23 and the ring-shaped member 3 are integrated is 4 mm.

[0045] Fig. 10(a) is a plan view showing a CAE analysis model of the bushing press-fit portion 2 according to a comparative example. Fig. 10(b) is a cross-sectional view showing the CAE analysis model of the bushing press-fit portion 2 according to a comparative example. The cross section of the bushing press-fit portion 2 shown in Fig. 10(b) corresponds to the DD cross section of Fig. 10(a).

[0046] In the CAE analysis model of the bush press-fitting portion 2 according to the comparative example, the top plate portion 21 is disk-shaped with a radius of 58 [mm], and the radius of the through hole 20 provided concentrically with the top plate portion 21 is 25 [mm]. In the CAE analysis model of the bush press-fitting portion 2 according to the comparative example, the plate thickness t1 is 2 [mm], the radial length L1 of the top plate portion 21 is 30 [mm], the inner radius R1 of the curved portion 22 is 1 [mm], and the outer radius R2 of the curved portion 22 is 3 [mm]. In the CAE analysis model of the bush press-fitting portion 2 according to the comparative example, the axial length L2 of the vertical wall portion 23 is 8 [mm]. In the CAE analysis model of the bush press-fitting portion 2 according to the comparative example, the bush press-fitting portion 2 according to the comparative example is modeled with solid elements with a size of 0.4 [mm] divided into 5 in the plate thickness direction.

[0047] Fig. 11(a) is a plan view showing the CAE analysis model of the bush 4. Fig. 11(b) is a side view showing the CAE analysis model of the bush 4.

[0048] In the CAE analysis model of the bush 4, the outer circumferential surface of the bush 4 is tapered such that the diameter increases linearly from the tip 41 side toward the base end 42 side in the height direction of the bush 4. That is, within a distance of 50 [mm] from the base end 42 to the tip 41 in the height direction of the bush 4, the radius of the bush 4 increases linearly from the tip 41 side of radius 25.0 [mm] toward the base end 42 side of radius 25.5 [mm]. The corners on the tip 41 side of the bush 4 are rounded with a radius R3 = 5 [mm]. In addition, the CAE analysis model of the bush 4 was modeled using shell elements with the bush 4 as a rigid body.

[0049] Fig. 12 is a diagram showing a CAE analysis model of a state in which a bushing 4 is press-fitted into a bushing press-fit portion 2. Note that Fig. 12 shows a case in which a bushing press-fit portion 2 according to a comparative example is used as a representative example, but a case in which a bushing press-fit portion 2 according to an example of the present invention is used is similar except for the provision of a ring-shaped member 3, so is not shown in the figure.

[0050] First, in the CAE analysis of pressing the bushing 4 into the bushing press-fitting portion 2, the bushing 4 was pressed into the bushing press-fitting portion 2 while the top plate portion 21 of the bushing press-fitting portion 2 was restrained by a holder (not shown) so as not to move. At this time, as shown in Fig. 12, the bushing 4 was pressed into the bushing press-fitting portion 2 until the distance from the tip 41 of the bushing 4 to the top plate portion 21 of the bushing press-fitting portion 2 in the axial direction of the bushing press-fitting portion 2 became 35 [mm].

[0051] Next, in the CAE analysis of pulling out the bush 4 from the bush press-fit portion 2, the top plate portion 21 of the bush press-fit portion 2 was restrained by a holder not shown in the figure to prevent the top plate portion 21 from moving, and the bush 4 was pulled out from the bush press-fit portion 2 toward the base end 42 (downward in Figure 12).

[0052] Figure 13 is a graph showing the change in bushing extraction force when the bushing is extracted. The horizontal axis in Figure 13 represents the bushing displacement, which is the amount of change in the position of the bushing 4 when it is extracted in the axial direction from the bushing press-fit portion 2, starting from the position of the bushing 4 pressed into the bushing press-fit portion 2. The vertical axis in Figure 13 represents the bushing extraction force, which is the force used to extract the bushing 4 from the bushing press-fit portion 2.

[0053] As can be seen from Fig. 13, in both the example of the present invention and the comparative example, the bushing pull-out force increases rapidly immediately after the bushing 4 starts to be displaced. Then, in both the example of the present invention and the comparative example, after the bushing pull-out force reaches its peak value, the bushing pull-out force decreases when the bushing 4 and the bushing press-fit portion 2 start to slide relative to each other. The peak value of the bushing pull-out force was 18.8 kN in the comparative example and 24.9 kN in the example of the present invention. This shows that the peak value of the bushing pull-out force in the example of the present invention is increased by 32.4% compared to the comparative example. And, since the higher the peak value of the bushing pull-out force, the more difficult it is for the bushing 4 to come out of the bushing press-fit portion 2, it can be seen that the bushing retention force of the bushing press-fit portion 2 in the example of the present invention is improved compared to the bushing press-fit portion 2 in the comparative example.

[0054] In addition, the surface pressure that the vertical wall portion 23 of the bushing press-fitting portion 2 receives from the bushing 4 after the bushing is press-fitted into the bushing press-fitting portion 2 was calculated by simulation. Fig. 14(a) is a diagram showing the range of positions within the vertical wall portion 23 for which the surface pressure calculation was performed in the bushing press-fitting portion 2 according to the present invention. Fig. 14(b) is a diagram showing the range of positions within the vertical wall portion 23 for which the surface pressure calculation was performed in the bushing press-fitting portion 2 according to the comparative example.

[0055] The surface pressure calculations were performed on each mesh in Figures 14(a) and 14(b) that was located between 0 [mm] and 8 [mm] in the axial direction within vertical wall portion 23, starting from the lower end (the end on the curved portion 22 side) of vertical wall portion 23.

[0056] Fig. 15 is a graph showing the distribution of surface pressure within the vertical wall portion 23. The horizontal axis in Fig. 15 represents the position in the axial direction within the vertical wall portion 23. The vertical axis in Fig. 15 represents the surface pressure that the vertical wall portion 23 receives from the bush 4.

[0057] In both the present invention example and the comparative example, the surface pressure occurs only in the lower part (0 mm to 2 mm) and upper part (6 mm to 8 mm) of the vertical wall part 23. There is almost no difference in the surface pressure distribution in the lower part of the vertical wall part 23 between the present invention example and the comparative example, but the surface pressure in the upper part of the vertical wall part 23 is higher in the present invention example than in the comparative example due to the increased rigidity of the ring-shaped member 3. It is believed that the difference in surface pressure in this area contributes to the improvement of the bush pull-out force in the bush press-fitting part 2 of the present invention example.

[0058] 15, the effect of reinforcing the upper part of the vertical wall portion 23 is particularly large. The part of the upper part of the vertical wall portion 23 where the surface pressure is high is about 2 mm, that is, the range equivalent to the plate thickness t1 of the vertical wall portion 23 of the bushing press-fitting portion 2.

[0059] From this, it can be seen that it is desirable for the positional relationship between the vertical wall portion 23 of the bush press-fitting portion 2 and the ring-shaped member 3 to satisfy, for example, the relationship shown in Fig. 16. That is, it is desirable for the position P31 of the upper end 31 of the ring-shaped member 3 to coincide with the position P21 of the upper end 230 of the vertical wall portion 23, or to be at a position higher than the position P21 of the upper end 230 of the vertical wall portion 23. Also, it is desirable for the position P32 of the lower end 32 of the ring-shaped member 3 to be the same as the position P23 (first position) that is lower than the position P21 of the upper end 230 of the vertical wall portion 23 by the plate thickness t1 of the vertical wall portion 23, or to be at an even lower position (second position) than the lower position P23 (first position).

[0060] In addition, if the lower part of the vertical wall part 23 is reinforced by the ring-shaped member 3, when a lateral force as shown by the arrow in FIG. 12 acts on the bush 4 while the vehicle is running, the stress concentration occurring from the lower part of the vertical wall part 23 to the curved part 22 of the bush press-fitting part 2 becomes large. Therefore, although the surface pressure of the lower part of the vertical wall part 23 is also high, if the lower part of the vertical wall part 23 is reinforced by the ring-shaped member 3, the fatigue life of the bush press-fitting part 2 may be deteriorated. In addition, from the surface pressure distribution shown in FIG. 15, the part with high surface pressure in the lower part of the vertical wall part 23 is about 2 [mm], that is, the range corresponding to the plate thickness t1 of the vertical wall part 23. From these facts, it can be seen that it is desirable that the position P32 of the lower end 32 of the ring-shaped member 3 is the same as the position P24 (third position) that is higher by the plate thickness t1 of the vertical wall part 23 than the position P22 of the lower end of the vertical wall part 23, or a position (fourth position) higher than the higher position P24 (third position). [Explanation of symbols]

[0061] 1 Suspension arm 2 Bush press-fit part 3 Ring-shaped member 4. Bush 20 Through hole 21 Top plate 22 Curved section 23 Vertical wall section 230 Upper end 301 Main body 302 Inner edge

Claims

1. An arm body; a bush press-fitting portion provided at an end of the arm body and into which a bush is press-fitted; A suspension arm comprising: the bushing press-fitting portion has a through hole formed in a plate-like portion and a vertical wall portion rising from a periphery of the through hole and formed into a cylindrical shape, A suspension arm comprising: an annular member attached to an outer circumferential surface of the vertical wall portion.

2. 2. The suspension arm according to claim 1, wherein the annular member and the vertical wall portion are made of the same material.

3. 3. The suspension arm according to claim 1, wherein the position of the upper end of the annular member in the axial direction of the through hole is the same as the position of the upper end of the vertical wall portion or is higher than the position of the upper end of the vertical wall portion.

4. 3. The suspension arm according to claim 1, wherein a position of a lower end of the annular member in the axial direction of the through hole is at a first position which is located toward the lower end of the vertical wall portion by a thickness of the vertical wall portion from a position of an upper end of the vertical wall portion, or at a second position which is located toward the lower end of the vertical wall portion from the first position.

5. 4. The suspension arm according to claim 3, wherein a position of a lower end of the annular member in the axial direction of the through hole is at a first position that is closer to the lower end of the vertical wall portion by an amount corresponding to a thickness of the vertical wall portion than a position of an upper end of the vertical wall portion, or at a second position that is closer to the lower end of the vertical wall portion than the first position.

6. 3. The suspension arm according to claim 1, wherein the position of the lower end of the annular member in the axial direction of the through hole is at a third position which is closer to the upper end of the vertical wall portion than the position of the lower end of the vertical wall portion by an amount corresponding to a thickness of the vertical wall portion, or at a fourth position which is closer to the upper end of the vertical wall portion than the third position.

7. 4. The suspension arm according to claim 3, characterized in that the position of the lower end of the annular member in the axial direction of the through hole is at a third position that is closer to the upper end of the vertical wall portion than the position of the lower end of the vertical wall portion by an amount equivalent to the thickness of the vertical wall portion, or at a fourth position that is closer to the upper end of the vertical wall portion than the third position.

8. 5. The suspension arm according to claim 4, characterized in that the position of the lower end of the annular member in the axial direction of the through hole is at a third position that is closer to the upper end of the vertical wall portion than the position of the lower end of the vertical wall portion by an amount corresponding to a thickness of the vertical wall portion, or at a fourth position that is closer to the upper end of the vertical wall portion than the third position.

9. 6. The suspension arm according to claim 5, characterized in that the position of the lower end of the annular member in the axial direction of the through hole is at a third position that is closer to the upper end of the vertical wall portion than the position of the lower end of the vertical wall portion by an amount equivalent to the thickness of the vertical wall portion, or at a fourth position that is closer to the upper end of the vertical wall portion than the third position.

10. 2. The suspension arm according to claim 1, wherein the inner peripheral surface of the annular member is tapered such that the radius of the inner peripheral surface increases from the upper end to the lower end in the axial direction of the annular member.

11. 2. The suspension arm according to claim 1, wherein the annular member is press-fitted into the vertical wall portion.

12. 2. The suspension arm according to claim 1, wherein the annular member is shrink-fitted to the vertical wall portion.

13. 2. The suspension arm according to claim 1, wherein an outer peripheral surface of the vertical wall portion is formed with a male thread portion, and an inner peripheral surface of the annular member is formed with a female thread portion that screws into the male thread portion.

14. The suspension arm according to claim 1, wherein a portion of the annular member is shaped to cover an upper end of the vertical wall portion.

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