Trailing arm and manufacturing method of the same

Abstract

To provide a trailing arm which can omit welding of a pair of steel plates having curved parts to enable easy manufacturing.SOLUTION: A trailing arm according to one embodiment of the disclosure includes: a main part having a curved part curved in an arm form along a longitudinal direction; and a pipe for press-fitting a bush welded to one end of the main part. The main part is formed by a single steel plate molded so as to have a U shaped cross section and has a pair of side walls facing each other. At the one end of the main part, a height of the pair of side walls is larger than an outer diameter of the pipe and arch shaped cutout parts are respectively formed along a height direction at the pair of side walls. A side surface of the pipe is fitted into the cutout parts and the pipe is welded to each of the pair of side walls so that a center axis direction of the pipe is orthogonal to the pair of side walls.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a trailing arm and a method for manufacturing the same. [Background technology]

[0002] Patent Document 1 discloses a torsion beam suspension that uses a trailing arm. The trailing arm disclosed in Patent Document 1 has a pair of opposing mounting holes formed at the end of a cylindrical trailing arm body, and bushings are press-fitted into the pair of mounting holes. In this method, annular walls are formed in the pair of mounting holes by burring. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-224016 Summary of the Invention [Problem to be solved by the invention]

[0004] In response to this, the inventors have developed a trailing arm in which a pipe for press-fitting a bushing is welded to one end of a cylindrical trailing arm body. Here, the trailing arm body is formed by bending a pair of steel plates to form each into a U-shaped cross section (hereinafter referred to as U-bending), and then welding the concave surfaces of the pair of steel plates together so that they face each other.

[0005] However, since the pair of steel plates have curved portions that are curved in an arc shape along the longitudinal direction, there have been problems in that it is difficult to align the steel plates with each other during welding, and the weld length is also long.

[0006] The present disclosure has been made in consideration of the above circumstances, and provides a trailing arm that is easy to manufacture and that can omit welding together a pair of steel plates having curved portions, and a method for manufacturing the same. [Means for solving the problem]

[0007] A trailing arm according to one aspect of the present disclosure includes: a main body portion having a curved portion curved in an arc shape along a longitudinal direction; a pipe for press-fitting a bushing, the pipe being welded to one end of the main body, The main body is made of a single steel plate formed into a U-shaped cross section and has a pair of side walls facing each other, At one end of the main body, the height of the pair of side walls is greater than the outer diameter of the pipe, and an arc-shaped notch is formed in each of the pair of side walls along the height direction, The side surfaces of the pipe are fitted into the notches, and the pipe is welded to each of the pair of side walls so that the central axis of the pipe is perpendicular to the pair of side walls.

[0008] In one aspect of the present invention, the trailing arm has a main body having a curved portion that is curved in an arc shape along the longitudinal direction and is made of a single steel plate formed into a U-shaped cross section, which eliminates the need to weld the pair of steel plates having the curved portion together, making the trailing arm easier to manufacture.

[0009] The main body may further include a rod-shaped reinforcing member provided on the opening side in the cross section of the main body so as to straddle the pair of side walls, thereby enabling reinforcement of the main body with a simple configuration. The steel plate may have a tensile strength of 440 MPa or more.

[0010] A method for manufacturing a trailing arm according to one aspect of the present disclosure includes: a step of locally heating a curved portion of a steel plate having a curved portion curved in an arc shape along a longitudinal direction; a step of U-bending the steel plate to form a main body portion having a U-shaped cross section made of a single steel plate; and welding a pipe to one end of the body portion. The main body portion having a U-shaped cross section has a pair of side walls facing each other, In the step of welding the pipe, At one end of the main body, the height of the pair of side walls is greater than the outer diameter of the pipe, and an arc-shaped notch is formed in each of the pair of side walls along the height direction, The side surfaces of the pipe are fitted into the notches, and the pipe is welded to each of the pair of side walls so that the central axis of the pipe is perpendicular to the pair of side walls.

[0011] In one aspect of the present invention, a method for manufacturing a trailing arm includes a step of locally heating a curved portion of a steel plate having a curved portion that is curved in an arc shape along the longitudinal direction before a step of U-bending the curved portion. This improves the workability of the curved portion of the steel plate, allows the U-bending height of the curved portion to be increased, and allows the main body of the trailing arm to be constructed from a single steel plate. As a result, welding of a pair of steel plates having the curved portion together can be omitted, making it easier to manufacture the trailing arm. [Effects of the Invention]

[0012] The present disclosure makes it possible to provide a trailing arm that is easy to manufacture and a method for manufacturing the same, by eliminating the need to weld a pair of steel plates having curved portions together. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a partial plan view of the trailing arm according to the first embodiment. [Figure 2] FIG. 2 is a partial side view of the trailing arm according to the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view taken along the line III-III in FIG. [Figure 4] FIG. 10 is a partial side view of a trailing arm according to a comparative example. [Figure 5] 4 is a flowchart showing a method for manufacturing a trailing arm according to the first embodiment. [Figure 6] 2A to 2C are partial plan views schematically showing the main body 10 before and after U-bending. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, specific embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. In addition, the following description and drawings have been simplified appropriately for clarity of explanation.

[0015] (First embodiment) <Trailing arm configuration> First, the configuration of a trailing arm according to a first embodiment will be described with reference to Figures 1 to 3. Figure 1 is a partial plan view of the trailing arm according to the first embodiment. Figure 2 is a partial side view of the trailing arm according to the first embodiment. Figure 3 is a cross-sectional view taken along line III-III in Figure 1.

[0016] The trailing arm shown in FIGS. 1 to 3 includes a main body 10, a reinforcing member 20, and a pipe 30, as shown in FIG. Naturally, the right-handed XYZ Cartesian coordinate system shown in Figures 1 to 3 is for the sake of convenience in explaining the positional relationships of the components. In Figure 1 and other figures, the positive direction of the Z axis is vertically upward, and the XY plane is the horizontal plane, which is common to all the figures.

[0017] As shown in FIG. 1, the main body 10 is a steel plate member having a curved portion that is curved in an arc shape along the longitudinal direction. The main body 10 is not particularly limited, but may be made of, for example, a high-strength steel plate having a thickness of about 0.5 to 10 mm and a tensile strength of 440 MPa or more.

[0018] 2 and 3, the main body 10 is formed into a U-shaped cross section by U-bending, which is a type of press forming, and is made of a single steel plate. More specifically, as shown in FIGS. 2 and 3, the main body 10 having a U-shaped cross section has a pair of side walls 11 and 12 facing each other and a top plate 13.

[0019] When U-bending is performed on a steel plate having a curved portion, the radius of curvature Ri of the radially inner side wall (referred to as the "inner wall") 11 of the curved portion shown in Fig. 1 is smaller than the radius of curvature Ro of the radially outer side wall (referred to as the "outer wall") 12. Therefore, the inner wall 11 of the curved portion is difficult to form, and wrinkles, for example, are likely to occur.

[0020] 3, as the U-bending height H1 (i.e., the height of the inner wall 11) of the main body 10 at the curved portion increases, forming the inner wall 11 by U-bending becomes more difficult. That is, in U-bending of the main body 10 having a curved portion, the larger H1 / Ri becomes, the more difficult it becomes to form the inner wall at the curved portion. For example, if H1 / Ri > 0.6 at the curved portion of the main body 10, forming the inner wall at the curved portion becomes more difficult.

[0021] In the trailing arm according to this embodiment, the curved portion of the steel plate that constitutes the main body 10 is locally heated before the steel plate is U-bent. This improves the workability of the curved portion of the steel plate that constitutes the main body 10, and makes it possible to increase the U-bend height H1 at the curved portion shown in Figure 3. As a result, in the trailing arm according to this embodiment, the main body 10 can be constructed from a single steel plate.

[0022] 2, the reinforcing member 20 is a rod-shaped member provided on the opening side of the main body 10 in a cross section so as to straddle the pair of side walls 11, 12. The reinforcing member 20 is, for example, welded to the pair of side walls 11, 12. Furthermore, a plurality of reinforcing members 20 may be arranged side by side in the longitudinal direction of the main body 10. With a simple configuration such as the reinforcing member 20, the main body 10 can be reinforced. The reinforcing member 20 may be provided as needed and is not essential.

[0023] The pipe 30 is a pipe for press-fitting a bushing. That is, a bushing (not shown) is press-fitted into the pipe 30. As shown in Figures 1 and 2, the pipe 30 is welded to one end of the main body 10.

[0024] 2, at one end of the main body 10, the height H2 of the pair of side walls 11, 12 is greater than the outer diameter D of the pipe, and each of the pair of side walls 11, 12 has an arc-shaped notch (not shown) formed along the height direction. The side of the pipe 30 is fitted into the notch. The pipe 30 is welded to each of the pair of side walls 11, 12 so that the direction of the central axis C2 of the pipe 30, indicated by the dashed dotted line, is perpendicular to the pair of side walls 11, 12, as shown in FIG.

[0025] <Configuration of a Trailing Arm According to a Comparative Example> The configuration of a trailing arm according to a comparative example will now be described with reference to Fig. 4. Fig. 4 is a partial side view of the trailing arm according to the comparative example. Fig. 4 corresponds to Fig. 2. The planar configuration of the trailing arm according to the comparative example is the same as that shown in Fig. 1.

[0026] As shown in Fig. 4, the trailing arm according to the comparative example includes a first steel plate 100, a second steel plate 200, and a pipe 30. Similar to the main body 10 shown in Fig. 1, both the first steel plate 100 and the second steel plate 200 have curved portions that are curved in an arc shape along the longitudinal direction.

[0027] As shown in Fig. 4, the first steel plate 100 and the second steel plate 200 are both formed with a U-shaped cross section and are welded together so that the concave surfaces of the first steel plate 100 and the second steel plate 200 face each other to form a rectangular tubular main body. More specifically, the first steel plate 100 and the second steel plate 200 are U-bent in the same manner as the main body 10 shown in Figs. 2 and 3, and then welded together. Fig. 4 schematically shows the welded portion WP.

[0028] In this way, the trailing arm according to the comparative example welds together the first steel plate 100 and the second steel plate 200, each having a curved portion that is curved in an arc shape along the longitudinal direction. This makes it difficult to align the first steel plate 100 and the second steel plate 200 during welding, and also poses the problem of a long weld length.

[0029] 1 to 3, the curved portion of the steel plate constituting the main body 10 is locally heated before U-bending the steel plate. This improves the workability of the curved portion of the steel plate constituting the main body 10, and makes it possible to increase the U-bend height H1 of the curved portion shown in FIG.

[0030] As a result, in the trailing arm according to this embodiment, the main body 10 can be constructed from a single steel plate, eliminating the need to weld the first steel plate 100 and the second steel plate 200 as in the comparative example. This means that the trailing arm according to this embodiment is easier to manufacture than the trailing arm according to the comparative example. Furthermore, the trailing arm according to this embodiment can be made lighter and less expensive to manufacture than the trailing arm according to the comparative example.

[0031] Furthermore, welding of the reinforcing member 20 to the main body 10 in the trailing arm according to this embodiment is easier to align and the weld length is shorter than welding of the first steel plate 100 and the second steel plate 200 in the comparative example.

[0032] <Trailing arm manufacturing method> Next, a method for manufacturing a trailing arm according to the first embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the method for manufacturing a trailing arm according to the first embodiment.

[0033] First, as shown in Fig. 5, a steel plate having a curved portion curved in an arc shape along the longitudinal direction is locally heated at the curved portion (step ST1). The steel plate in question is the steel plate that constitutes the main body 10. For example, if the curved portion is locally heated by induction heating, the curved portion can be locally heated with a simple configuration. Heating conditions are, for example, a heating temperature of about 500 to 830°C and a heating time of 10 seconds or less. However, the heating time may exceed 10 seconds.

[0034] Next, as shown in Fig. 5, the steel plate with the curved portion heated is subjected to U-bending (step ST2). Fig. 6 is a partial plan view schematically showing the main body 10 before and after U-bending. In Fig. 6, the solid line indicates the main body 10 before U-bending, i.e., the flat steel plate, and the two-dot chain line indicates the main body 10 after U-bending.

[0035] In step ST2, a flat steel plate having a curved portion is subjected to U-bending, which is a type of press forming, as shown in Fig. 6. As a result, the main body 10 is formed into a U-shaped cross section as shown in Fig. 3.

[0036] 1, the radius of curvature Ri of the inner wall 11 at the curved portion is smaller than the radius of curvature Ro of the outer wall 12. Therefore, it is difficult to form the inner wall 11 at the curved portion in step ST2, and wrinkles, for example, are likely to occur.

[0037] 3, as the U-bending height H1 of the main body 10 at the curved portion increases, it becomes more difficult to form the inner wall 11. That is, in the U-bending process of the main body 10 having a curved portion, the larger H1 / Ri becomes, the more difficult it becomes to form the inner wall at the curved portion.

[0038] In the method for manufacturing a trailing arm according to this embodiment, the curved portion of the main body 10 is locally heated in step ST1 before step ST2. This improves the workability of the curved portion in the steel plate that constitutes the main body 10, and makes it possible to increase the U-bend height H1 in the curved portion shown in Figure 3. As a result, the main body 10 can be constructed from a single steel plate.

[0039] Finally, as shown in Fig. 5, a pipe is welded to one end of the main body 10 (step ST3). More specifically, as shown in Fig. 2, at one end of the main body 10, the height H2 of the pair of side walls 11, 12 is greater than the outer diameter D of the pipe, and each of the pair of side walls 11, 12 has an arc-shaped cutout (not shown) formed along the height direction. Then, the side of the pipe 30 is fitted into the cutout, and the pipe 30 is welded to each of the pair of side walls 11, 12 so that the direction of the central axis C2 of the pipe 30, indicated by the dashed dotted line, is perpendicular to the pair of side walls 11, 12, as shown in Fig. 1.

[0040] The notch for fitting the pipe 30 is formed, for example, after U-bending (step ST2) and before welding (step ST3) the main body 10 and the pipe 30. The method for forming the notch in the pair of side walls 11, 12 is not particularly limited, and they may be formed, for example, by punching or the like.

[0041] As described above, in the method for manufacturing a trailing arm according to this embodiment, step ST1 of locally heating the curved portion is performed before step ST2 of U-bending main body 10, which has a curved portion that is curved in an arc shape along the longitudinal direction. This improves the workability of the curved portion in the steel plate that constitutes main body 10, and makes it possible to increase the U-bend height H1 of the curved portion shown in FIG. 3.

[0042] As a result, with the trailing arm manufacturing method according to this embodiment, the main body 10 can be constructed from a single steel plate, and the welding of the first steel plate 100 and the second steel plate 200 required in the comparative example can be omitted. In other words, the trailing arm manufacturing method according to this embodiment is easier to manufacture than the trailing arm according to the comparative example. Furthermore, the trailing arm manufactured by the trailing arm manufacturing method according to this embodiment can be made lighter and at lower manufacturing costs than the trailing arm according to the comparative example.

[0043] The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0044] 10 Main body 11 Side wall (inner wall) 12 Side wall (exterior wall) 13 Top plate 20 Reinforcement member 30 pipes

Claims

1. a main body portion having a curved portion curved in an arc shape along a longitudinal direction; a pipe for press-fitting a bushing, the pipe being welded to one end of the main body, the main body is made of a single steel plate formed into a U-shaped cross section and has a pair of side walls facing each other; At one end of the main body, the height of the pair of side walls is greater than the outer diameter of the pipe, and an arc-shaped notch is formed in each of the pair of side walls along the height direction, The side surfaces of the pipe are fitted into the notches, and the pipe is welded to each of the pair of side walls so that the central axis of the pipe is perpendicular to the pair of side walls. Trailing arm.

2. The main body further includes a rod-shaped reinforcing member provided on an opening side in a cross section thereof so as to straddle the pair of side walls. The trailing arm of claim 1 .

3. The tensile strength of the steel plate is 440 MPa or more. The trailing arm of claim 1 .

4. a step of locally heating a curved portion of a steel plate having a curved portion curved in an arc shape along a longitudinal direction; a step of U-bending the steel plate to form a main body portion having a U-shaped cross section made of a single steel plate; and welding a pipe to one end of the body portion. The main body portion having a U-shaped cross section has a pair of side walls facing each other, In the step of welding the pipe, At one end of the main body, the height of the pair of side walls is greater than the outer diameter of the pipe, and an arc-shaped notch is formed in each of the pair of side walls along the height direction, The side surfaces of the pipe are fitted into the notches, and the pipe is welded to each of the pair of side walls so that the central axis of the pipe is perpendicular to the pair of side walls. A manufacturing method for a trailing arm.

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