Axle beam unit

Abstract

To improve the durability of the welded joint between the axle beam and the bracket. [Solution] The trailing arm bracket 6 is fixed to the outer circumferential surface of the axle beam 1 near its end via a first weld P1 extending in the longitudinal direction of the axle beam 1. The absorber bracket 8 is fixed to the outer circumferential surface of the axle beam 1 via a second weld P2(A) extending in the circumferential direction of the axle beam 1. The inner end P1a of the first weld P1 in the vehicle width direction is located further outward in the vehicle width direction than the second weld P2(A), and is provided within the circumferential region of the second weld P2(A).

Description

Technical Field

[0001] The present invention relates to an axle beam unit provided in an axle suspension type suspension.

Background Art

[0002] As a suspension that connects a vehicle body and wheels, an axle suspension type suspension having an axle beam extending in the vehicle width direction and left and right trailing arms for attaching both ends of the axle beam to the vehicle body is known (for example, see Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, in the axle suspension type suspension shown enlarged in FIG. 8, a trailing arm bracket 106 for attaching a trailing arm and an absorber bracket 108 for attaching a shock absorber are fixed by welding to the outer peripheral surface near the end of an axle beam 101.

[0005] A welded portion P1' that joins the axle beam 101 and the trailing arm bracket 106 is provided along the length direction (left - right direction in the figure) of the axle beam 101. For example, when a wheel rides over a convex portion during vehicle travel, bending stress is generated in the axle beam 101. In this case, since stress tends to concentrate on the end portion P1a' on the inner side in the vehicle width direction of the welded portion P1' extending in the length direction, it causes a decrease in durability.

[0006] On the other hand, the welded joint P2' that joins the axle beam 101 and the absorber bracket 108 is provided along the circumferential direction of the axle beam 101. When bending stress is applied to the axle beam 101, the stress is not concentrated at a single point in the welded joint P2' but is distributed in the circumferential direction, so the welded joint P2' that extends in the circumferential direction has high durability against bending stress.

[0007] For example, if a weld extending in the circumferential direction is added near the inner end in the vehicle width direction of a longitudinally extending weld P1' to join the trailing arm bracket 106 and the axle beam 101, the durability of the weld can be improved. However, since an absorber bracket 108 is provided near the trailing arm bracket 106, it is difficult to secure space to provide a circumferentially extending weld.

[0008] For example, as shown by the dotted line in Figure 8, if the absorber bracket 108 is shifted inward in the vehicle width direction, and the circumferentially extending weld P2' is positioned inward in the vehicle width direction than the longitudinally extending weld P1', then when bending stress occurs in the axle beam 101, the bending stress transmitted from the inside in the width direction is first applied to the weld P2', which has higher strength against bending stress, thus reducing the bending stress applied to the weld P1' which is positioned further outward in the vehicle width direction. However, since the position of the shock absorber is determined for each vehicle model, the fixing position of the absorber bracket 108 relative to the axle beam 101 cannot be arbitrarily moved. Even if the absorber bracket 108 could be moved to the position shown by the dotted line in Figure 8, since the welded parts P1' and P2' are located at different circumferential positions, stress may concentrate at the end P1a' of the welded part P1' that extends in the longitudinal direction depending on the direction of bending in the axle beam 101, thus limiting the improvement in durability.

[0009] Based on the above, the present invention aims to improve the durability of the welded joint between the axle beam and the bracket. [Means for solving the problem]

[0010] To solve the aforementioned problems, the present invention provides an axle beam unit comprising: an axle beam; a first bracket fixed to the outer circumferential surface of the axle beam near its end via a first weld extending in the longitudinal direction of the axle beam; and a second bracket fixed to the outer circumferential surface of the axle beam via a second weld extending in the circumferential direction of the axle beam. The present invention provides an axle beam unit in which the inner end of the first weld in the vehicle width direction is located further outward in the vehicle width direction than the second weld, and is provided in the circumferential region of the second weld.

[0011] Thus, in this invention, the inner end of the first weld, which extends in the longitudinal direction of the axle beam, is positioned further outward in the vehicle width direction than the second weld, which extends in the circumferential direction of the axle beam. As a result, when bending stress occurs in the axle beam, the bending stress transmitted from the inner side in the vehicle width direction is first applied to the second weld, which extends in the circumferential direction and has higher strength against bending stress. Therefore, bending stress is less likely to be applied to the inner end of the first weld, which is positioned further outward in the vehicle width direction than the second weld. Furthermore, because the inner end of the first weld, which extends in the vehicle width direction, is located within the circumferential region of the second weld, bending stress is less likely to be applied to the inner end of the first weld, regardless of the direction of bending in the axle beam. [Effects of the Invention]

[0012] As described above, according to the present invention, the stress applied to the inner end in the vehicle width direction of the first welded portion extending in the longitudinal direction of the axle beam is relieved, thereby increasing durability. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view of an axle suspension system, seen from diagonally above. [Figure 2] Figure 1 is a perspective view of an axle beam unit according to one embodiment of the present invention, provided on the suspension. [Figure 3] Figure 2 is a perspective view of the axle beam unit, seen from diagonally below. [Figure 4] Figure 2 is a plan view of the axle beam unit. [Figure 5] Figure 2 is a bottom view of the axle beam unit. [Figure 6] This is an enlarged view of Figure 5. [Figure 7] Figure 2 is an enlarged perspective view of the bottom surface of the axle beam unit. [Figure 8] This is a bottom view of the end portion of the axle beam unit according to the comparative example. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0015] Figure 1 shows an axle-mounted suspension equipped with an axle beam unit according to one embodiment of the present invention. This suspension is a three-link suspension and comprises an axle beam 1, a pair of left and right trailing arms 2, a pair of left and right springs 3, a pair of left and right shock absorbers 4, and a lateral rod 5. In Figures 2 to 7 used in the following description, only the axle beam unit is shown, and the trailing arms 2, springs 3, shock absorbers 4, and lateral rod 5 are not shown.

[0016] The axle beam 1 is in the shape of a hollow pipe. The axle beam 1 is formed, for example, by rolling a single metal plate, butting the ends together, and welding the butt joint. In this embodiment, as shown in Figures 4 and 5, the axle beam 1 is provided with multiple bends in the longitudinal direction. Specifically, the axle beam 1 is provided with a linear end region 1a at both ends in the vehicle width direction, a linear central region 1b located in the center in the vehicle width direction and positioned further rearward than the end region 1a, a linear inclined portion 1c between the end region 1a and the central region 1b, an outer bend 1d connecting the end region 1a and the inclined portion 1c, and an inner bend 1e connecting the inclined portion 1c and the central region 1b.

[0017] As shown in FIG. 1, the trailing arm 2, the spring 3, the shock absorber 4, and the lateral rod 5 are respectively attached to the axle beam 1 via the trailing arm bracket 6, the spring seat bracket 7, the absorber bracket 8, and the lateral rod bracket 9. As shown in FIGS. 2 and 3, on the outer peripheral surfaces near both ends of the axle beam 1, in the illustrated example, on the outer peripheral surfaces of both end regions 1a, the trailing arm bracket 6, the spring seat bracket 7, and the absorber bracket 8 are respectively fixed. On the outer peripheral surface near one end of the axle beam 1, in the illustrated example, on the outer peripheral surface near one outer bending portion 1d, the lateral rod bracket 9 is fixed.

[0018] As shown in FIG. 3, the trailing arm bracket 6 has a beam fixing portion 6a fixed to the axle beam 1 and an arm fixing portion 6b to which the trailing arm 2 is fixed. The beam fixing portion 6a is fixed to the outer peripheral surface of the end region 1a of the axle beam 1 via the first welding portion P1 (see FIGS. 5 and 6). The first welding portion P1 extends in the length direction of the axle beam 1 (hereinafter, simply referred to as the "length direction"). That is, the dimension of the first welding portion P1 in the length direction is larger than the dimension in the circumferential direction (hereinafter, simply referred to as the "circumferential direction") of the axle beam 1. The trailing arm 2 is fixed to the arm fixing portion 6b by bolts or the like (see FIG. 1).

[0019] As shown in FIGS. 6 and 7, the absorber bracket 8 has a substantially U-shaped configuration integrally having a pair of flat plate-like side portions 8a facing each other in the length direction and a connecting portion 8b connecting the lower ends of the pair of side portions 8a. The pair of side portions 8a are respectively fixed to the outer peripheral surface of the end region 1a of the axle beam 1 via the second welding portion P2. The second welding portion P2 extends in the circumferential direction. That is, the dimension of the second welding portion P2 in the circumferential direction is larger than the dimension in the length direction. In the illustrated example, the second welding portion P2 is parallel to the circumferential direction.

[0020] As shown in Figure 2, the spring seat bracket 7 integrally comprises a beam fixing portion 7a fixed to the axle beam 1 and a spring seat 7b to which the spring 3 is attached. The lower end of the beam fixing portion 7a is fixed to the outer circumferential surface of the end region 1a of the axle beam 1 via a third weld portion P3 that extends in the longitudinal direction. In the illustrated example, the third weld portion P3 is parallel to the longitudinal direction. The spring seat 7b extends from the upper end of the beam fixing portion 7a toward the front of the vehicle body.

[0021] As shown in Figures 2 and 4, the lateral rod bracket 9 is fixed to the outer circumferential surface of the axle beam 1 near the outer bend 1d via a fourth weld P4 extending in the circumferential direction. In the illustrated example, the lateral rod bracket 9 has a pair of flat plate-shaped side portions spaced apart in the longitudinal direction and a connecting portion that connects these side portions, forming a roughly U-shape in plan view (see Figure 4). The pair of side portions of the lateral rod bracket 9 are each fixed to the axle beam 1 via a fourth weld P4 extending in the circumferential direction. In the illustrated example, the fourth weld P4 is roughly parallel to the circumferential direction.

[0022] The overall structure of the suspension in this embodiment is as described above. Below, the positional relationship between the first weld P1 between the trailing arm bracket 6 (first bracket) and the axle beam 1, and the second weld P2 between the absorber bracket 8 (second bracket) and the axle beam 1, which are characteristic features of the present invention, will be described in detail. In the following, the weld between the inner side portion 8a of the absorber bracket 8 in the vehicle width direction and the axle beam 1 will be referred to as the "inner second weld P2(A) in the width direction," and the weld between the outer side portion 8a of the absorber bracket 8 in the vehicle width direction and the axle beam 1 will be referred to as the "outer second weld P2(B) in the width direction."

[0023] As shown in Figure 6, the longitudinal region of the absorber bracket 8 partially overlaps with the longitudinal region of the trailing arm bracket 6. In the illustrated example, a protruding portion 6d is provided in the beam contact region 6c of the trailing arm bracket 6 that contacts the axle beam 1, projecting inward in the vehicle width direction toward the rear of the vehicle body. The longitudinal region of this protruding portion 6d partially overlaps with the longitudinal region of the absorber bracket 8.

[0024] The rear edge of the beam fixing portion 6a of the trailing arm bracket 6 is fixed to the outer surface of the axle beam 1 via a first weld P1. The inner end P1a of the first weld P1 in the vehicle width direction (left side in the figure) is positioned further outward in the vehicle width direction than the second weld P2(A) which is also on the inner side in the vehicle width direction. In the illustrated example, the inner end P1a of the first weld P1 in the vehicle width direction is positioned in the longitudinal region of the absorber bracket 8.

[0025] The inner end P1a of the first weld P1 in the vehicle width direction is located in the circumferential region of the second weld P2(A) on the inner side in the vehicle width direction. In the illustrated example, the vicinity of the inner end P1a of the first weld P1 in the vehicle width direction, specifically the rear edge of the protruding portion 6d of the trailing arm bracket 6, is inclined towards the rear of the vehicle (downward in Figure 6) toward the inward side in the vehicle width direction. As a result, most of the first weld P1 is located on the front side of the vehicle (upward in Figure 6) than the second weld P2(A) on the inner side in the vehicle width direction, while the inner end P1a of the first weld P1 in the vehicle width direction is located on the rear side of the vehicle than the front end P2a of the second weld P2(A) on the inner side in the vehicle width direction.

[0026] For example, when a wheel attached to the suspension rides over a protrusion while the vehicle is in motion, bending stress is generated in the part of the axle beam 1 with low rigidity against bending, such as the outer bent portion 1d. In this embodiment, as described above, the inner end P1a in the vehicle width direction of the first weld P1 extending in the longitudinal direction is provided further outward in the vehicle width direction than the second weld P2(A) extending in the circumferential direction and on the inner side in the vehicle width direction. In this case, the bending stress generated in the outer bent portion 1d is first applied to the second weld P2(A) on the inner side in the width direction. At this time, since the second weld P2(A) extends in the circumferential direction, the bending stress is not concentrated at one point but is distributed in the circumferential direction, resulting in high durability. In this way, by causing the bending stress to be applied first to the second weld P2(A), which has high durability against bending stress, it becomes less likely for stress to be applied to the inner end P1a in the vehicle width direction of the first weld P1, which is provided on the outer side in the vehicle width direction.

[0027] Furthermore, in this embodiment, as described above, the inner end P1a of the first weld P1 in the vehicle width direction is provided in the circumferential region of the second weld P2(A), which has high durability against bending stress. This reduces the stress applied to the inner end P1a of the first weld P1 in the vehicle width direction, regardless of the direction of bending that occurs in the axle beam 1. As described above, by providing the inner end P1a of the first weld P1 in the vehicle width direction further outward in the vehicle width direction than the inner second weld P2(A) in the vehicle width direction, and within the circumferential region of the second weld P2(A), the stress applied to the end P1a can be mitigated, thereby increasing the durability of the first weld P1.

[0028] Furthermore, in the illustrated example, the inner end P1a of the first weld P1 in the vehicle width direction is positioned further inward in the vehicle width direction than the second weld P2(B) on the outer side in the vehicle width direction. As a result, within the end region 1a of the axle beam 1, the region where the trailing arm bracket 6 is fixed and thus has increased rigidity and the region where the absorber bracket 8 is fixed and thus has increased rigidity are continuous in the longitudinal direction. Since the inner end P1a of the first weld P1 in the vehicle width direction is located in the middle of the longitudinal direction of the region with increased rigidity, the stress applied to the end P1a is further reduced.

[0029] Furthermore, in the illustrated example, the end of the first weld P1 on the inner side in the vehicle width direction is curved towards the rear of the vehicle body in the vehicle width direction. Therefore, compared to the case where the first weld P1 is parallel to the length direction, the actual length of the first weld P1 can be increased without changing the overall length dimension of the first weld P1. By ensuring the actual length of the first weld P1 in this way, the joint strength between the trailing arm bracket 6 and the axle beam 1 is ensured.

[0030] For example, as shown by the dotted line in Figure 6, if the front end of the connecting portion 8b of the absorber bracket 8 is extended parallel to the length direction from the front end of the side portion 8a on the inside in the vehicle width direction, the connecting portion 8b and the end of the protruding portion 6d of the trailing arm bracket 6 will overlap in the radial direction of the axle beam 1. Even in this case, a radial gap is formed between the front end of the connecting portion 8b and the axle beam 1, so the end of the protruding portion 6d of the trailing arm bracket 6 can be inserted into this gap. However, in this case, the inner end P1a in the width direction of the first weld P1 is covered from the outside by the connecting portion 8b of the absorber bracket 8, making it difficult to check the quality of the welding of the inner end P1a in the width direction of the first weld P1 during the inspection process after the welding process.

[0031] Therefore, in this embodiment, as shown in Figures 6 and 7, the front end of the connecting portion 8b is set back further to the rear of the vehicle than the front end P2a of the second welded portion P2(A) on the inside in the vehicle width direction. In the illustrated example, a recess 8c is provided at the front end of the connecting portion 8b of the absorber bracket 8 on the vehicle body side. As a result, the inner end P1a in the width direction of the first welded portion P1 is not covered by the connecting portion 8b of the absorber bracket 8 and is exposed to the outer circumference, making it easier to check the quality of the weld during the inspection process.

[0032] Furthermore, in the illustrated example, the front end of the second weld P2(B) on the outer side in the vehicle width direction (upper end in Figure 6) is set back further to the rear of the vehicle (lower end in Figure 6) than the front end P2a of the second weld P2(A) on the inner side in the vehicle width direction. This ensures a longitudinal gap between the second weld P2(B) on the outer side in the vehicle width direction and the first weld P1, making welding easier.

[0033] The present invention is not limited to the embodiments described above. For example, in the embodiments described above, the first bracket is a trailing arm bracket 6 and the second bracket is an absorber bracket 8, but these may be composed of other brackets. For example, the first bracket may be a spring seat bracket 7. In this case, the inner end in the vehicle width direction of the third weld P3 (see Figure 2) between the spring seat bracket 7 and the axle beam 1 is located outside in the vehicle width direction of the second weld P2(A) between the inner side portion 8a of the absorber bracket 8 and the axle beam 1, and is provided in the circumferential region of the second weld P2(A).

[0034] Furthermore, although the above embodiment shows the axle beam 1 as a pipe with a substantially circular cross-section, it is not limited to this, and may, for example, be a pipe with a rectangular cross-section. [Explanation of Symbols]

[0035] 1 Axle beam 2 trailing arms 3 Springs 4 Shock absorbers 5 Lateral Rod 6. Trailing arm bracket (first bracket) 7 Spring seat bracket 8. Absorber bracket (second bracket) 9. Lateral rod bracket P1 First Weld P2 Second Weld P3 Third Weld P4 4th welding section

Claims

1. An axle beam unit comprising an axle beam, a first bracket fixed to the outer circumferential surface of the axle beam near its end via a first weld extending in the longitudinal direction of the axle beam, and a second bracket fixed to the outer circumferential surface of the axle beam via a second weld extending in the circumferential direction of the axle beam, An axle beam unit provided in the circumferential region of the second weld, wherein the inner end of the first weld in the vehicle width direction is located further outward in the vehicle width direction than the second weld.

2. The axle beam unit according to claim 1, wherein the first bracket is a trailing arm bracket for attaching a trailing arm to the axle beam, and the second bracket is an absorber bracket for attaching a shock absorber to the axle beam.

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