Torsion beam

Abstract

Proposed is a torsion beam capable of increasing the degree of freedom of a shape such as a cross-sectional area of a connection part while ensuring a cross-sectional area of a central part in an axial direction. A cylindrical member is deformed to form a recessed part 2 extending in the axial direction at least at the central part in the axial direction, connection parts 5, 5 having substantially rectangular longitudinal sectional shapes are provided at both ends in the axial direction, and cross-section transition parts 10 having a cross-sectional shape that changes gradually and a circumferential length that changes are formed between the central part in the axial direction and the respective connection parts 5, 5. In each cross-section transition part 10, at least one circumferential length decreasing part 7 having a circumferential length that gradually decreases from the central part side toward the connection part 5 side is formed. Circumferential length increasing parts 6, 8 having a circumferential length that gradually increases from the central part side toward the connection part 5 side are respectively provided on both side parts in the axial direction of the circumferential length decreasing part 7.

Description

torsion beam

[0001] The present invention relates to a torsion beam used in a suspension device.

[0002] A known torsion beam suspension for use in vehicles is one in which a torsion beam, which is a hollow cylindrical member, is crushed over a certain area of ​​its axial center until the walls of the torsion beam nearly touch each other to form a U-shaped or V-shaped cross section. From the axial center toward each end, the cross section gradually becomes more rectangular, and the rectangular cross sections at both ends are connected to trailing arms.

[0003] In order to optimize the torsional characteristics of the torsion beam, which has a significant impact on suspension characteristics, the cross-sectional shape of the torsion beam is required to be gradually deformed from the center toward the connection points at both ends, and stress concentration at the connections at both ends is required to be alleviated.

[0004] To satisfy this requirement, a torsion beam has been proposed that has an increasing circumferential section in which the circumferential length in a vertical cross section perpendicular to the axis gradually increases from the axial center toward each end, and in which the longitudinal width of the torsion beam also gradually increases from the axial center toward each end, and at the same time, the rate of gradual increase (see Patent Document 1). This configuration achieves both optimal torsional rigidity and secure connection strength without inducing stress concentration.

[0005] Patent Document 1: Patent No. 6893637

[0006] However, in the torsion beam described in Patent Document 1, the circumference gradually increases from the axial center toward each end, and the front-to-rear width also gradually increases, and the rate of increase also increases, which makes it easy for the connection part to become large, and there is a risk that design constraints such as the connection shape with the trailing arm side will no longer be met.

[0007] On the other hand, if the connection shape and cross-sectional area of ​​both ends are satisfied, there is a risk that the cross-sectional area will become too small in the axial center, which will narrow the range of applicability.

[0008] Therefore, an object of the present invention is to provide a torsion beam that can increase the degree of freedom in the shape of the cross-sectional area of ​​the connection portion while ensuring the cross-sectional area of ​​the central portion in the axial direction.

[0009] In order to solve the above problems, the present invention provides a torsion beam for use in a suspension device, characterized in that a cylindrical member is deformed to form an axially extending recessed portion at least in the axial center portion, connection portions having a substantially rectangular cross-sectional shape at each of both axial ends, cross-sectional transition portions whose cross-sectional shape gradually changes and whose perimeter changes are formed between the axial center portion and each connection portion, at least one perimeter decreasing portion is formed in each cross-sectional transition portion, whose perimeter gradually decreases from the center portion toward the connection portion, one perimeter increasing portion is provided between the axial center portion and the axial center, whose perimeter gradually increases from the center portion toward the connection portion, and another perimeter increasing portion is provided between the perimeter decreasing portion and the connection portion, whose perimeter gradually increases from the center portion toward the connection portion.

[0010] The depth of the recessed portion may be changed to change the perimeter of the reduced perimeter portion.

[0011] The present invention provides a cross-sectional transition section between the axial central section and each connection section, each section having a gradually changing cross-sectional shape and a gradually changing perimeter. Each cross-sectional transition section has at least one decreasing perimeter section whose perimeter gradually decreases from the central section toward the connection section. Furthermore, between the decreasing perimeter section and the connection section and between the decreasing perimeter section and the axial center, two increasing perimeter sections whose perimeter gradually increases from the central section toward the connection section are provided. This increases the stress in the decreasing perimeter section, thereby reducing the stress in the nearby increasing perimeter sections and dispersing stress throughout the cross-sectional transition section. This allows for optimization of the torsional rigidity of the torsion beam and ensures connection strength without excessively large connection sections, while ensuring the cross-sectional area of ​​the axial center. It also allows for greater flexibility in the shape of the connection section, such as the cross-sectional area.

[0012] Fig. 1 is a top view of a torsion beam according to a first embodiment of the present invention; Fig. 2 is a front view of Fig. 1; Fig. 2 is a cross-sectional view taken along line A-A in Fig. 2; Fig. 2 is a cross-sectional view taken along line B-B in Fig. 2; Fig. 2 is a cross-sectional view taken along line CC in Fig. 2; Fig. 3 is a graph showing the change in circumferential length relative to the distance from the center of

[0013] An embodiment of the torsion beam of the present invention will be described based on the examples shown in the drawings.

[0014] FIG. 1 is a top view of a torsion beam 1 according to an embodiment of the present invention.

[0015] The torsion beam 1 is formed by deforming a cylindrical member by press molding or the like. The torsion beam 1 has a recessed portion 2 formed by crushing or the like at least in its axial central portion 4 so as to extend in the axial direction, and a hollow portion 3 formed inside.

[0016] The longitudinal cross section of the recessed portion 2 in a direction perpendicular to the axis X-X is U-shaped as shown in Figures 2 and 3. The longitudinal cross section of the recessed portion 2 may be formed in any shape other than U-shape as long as a recess is formed. The opening direction of the recessed portion 2 is not limited to the direction shown in the figures and can be set arbitrarily. When the torsion beam suspension, which includes the torsion beam 1, is mounted on a vehicle, which is the operating position of the suspension, the opening direction of the recessed portion 2 can be in the up / down, front / rear, or diagonal direction of the vehicle. Furthermore, the shape of the torsion beam 1 is not limited to a straight pipe shape and may include a curved or bent shape.

[0017] At both axial ends of the torsion beam 1, connecting portions 5, 5 having a substantially rectangular cross section are formed.

[0018] The cross-sectional shape of the torsion beam 1 gradually changes from the central portion in the axis X-X direction to the A-A cross section in Figure 2, and as shown in Figure 6, a first increasing perimeter portion 6 is formed, which is a single increasing perimeter portion in which the perimeter, which is the length in the circumferential direction about the axis X-X, gradually increases from the central portion 4 side toward the connection portion 5 side. In this embodiment, the increasing rate of the perimeter of the first increasing perimeter portion 6 on the central portion 4 side and the connection portion 5 side in the axis X-X direction gradually increases toward the connection portion 5 side. Furthermore, the increasing rate of the perimeter of the first increasing perimeter portion 6 in the intermediate portion between the central portion 4 and the connection portion 5 in the axis X-X direction gradually decreases toward the connection portion 5 side.

[0019] In the axial direction of the torsion beam 1, the cross-sectional shape gradually changes between the cross-sectional portion A-A in Figure 2 and the cross-sectional portion B-B in Figure 2, and as shown in Figure 6, a circumference decreasing portion 7 is formed in which the circumference gradually decreases from the center portion 4 toward the connection portion 5.

[0020] In the axial direction of the torsion beam 1, the longitudinal cross-sectional shape gradually changes between the cross-sectional portion B-B in the figure and the cross-sectional portion C-C in the figure, and as shown in Figure 6, a second increasing perimeter portion 8 is formed, which is another increasing perimeter portion whose perimeter gradually increases from the center toward the connection portion 5. In this embodiment, the rate of increase in perimeter in the second increasing perimeter portion 8 gradually decreases toward the connection portion 5 side.

[0021] The first circumference increasing portion 6, the circumference decreasing portion 7, and the second circumference increasing portion 8 form a cross-sectional transition portion 10 in which the longitudinal cross-sectional shape gradually changes and the circumference also changes.

[0022] In Figure 1, a first circumference increasing portion 6, a circumference decreasing portion 7, and a second circumference increasing portion 8 are formed in the axial direction of the torsion beam 1 from the center to the right side, but similarly, a first circumference increasing portion 6, a circumference decreasing portion 7, a second circumference increasing portion 8, and a cross-sectional transition portion 10 are formed in the axial direction from the center to the left side, which is the carrier side, and the torsion beam 1 has cross-sectional transition portions 10 formed in two places.

[0023] In this embodiment, one circumferential decrease portion 7 is provided in each cross-sectional transition portion 10, but two or more may be provided. In this case, one circumferential increase portion is provided between each circumferential decrease portion and the connection portion 5, and another circumferential increase portion is provided between each circumferential decrease portion and the axial center portion. In other words, when two or more circumferential decrease portions are provided in each cross-sectional transition portion 10, an circumferential increase portion is formed between adjacent circumferential decrease portions 7.

[0024] As shown in FIG. 1, the width L1 of the vertical cross section of each cross section transition portion 10 is formed so as to gradually increase from the central portion side toward the connecting portion 5 side.

[0025] The perimeters of the first increasing perimeter portion 6, the decreasing perimeter portion 7, and the second increasing perimeter portion 8 are each formed to change by changing the depth L2 and width L1 of the recess of the recessed portion 2. In the decreasing perimeter portion 7, the depth L2 of the recess of the recessed portion 2 is gradually made shallower from the center toward the connecting portion 5, so that the perimeter gradually decreases. This makes it easy to set the perimeter of the decreasing perimeter portion 7.

[0026] In the torsion beam described in Patent Document 1, the circumference gradually increases from the axial center toward each end, and the front-to-rear width also gradually increases, and the rate of increase also increases, which can result in areas where stress is high.

[0027] In this embodiment, by providing a circumferential decrease section 7 at the cross-sectional transition section 10, the stress in the circumferential decrease section 7 can be intentionally increased, thereby reducing the stress in the circumferential increase sections 6 and 8 located near the circumferential decrease section 7. This distributes the stress throughout the cross-sectional transition section 10, and keeps the stress value within a set value.

[0028] This makes it possible to optimize the torsional rigidity of the torsion beam 1 and ensure connection strength without making the connection portion 5 excessively large, while ensuring the cross-sectional area of ​​the axial center portion, and makes it possible to apply the torsion beam 1 to a variety of vehicle models.In addition, it is possible to increase the degree of freedom in the shape of the cross-sectional area of ​​the vertical cross section of the connection portion 5, etc.

[0029] REFERENCE SIGNS LIST 1 Torsion beam 2 Recessed portion 5 Connection portion 6, 8 Circumferential length increasing portion 7 Circumferential length decreasing portion 10 Cross-sectional transition portion

Claims

1. A torsion beam for use in a suspension device, characterized in that a cylindrical member is deformed to form an axially extending recess in at least the axial center portion, and connection portions having a generally rectangular cross-sectional shape are provided at both axial ends, and cross-sectional transition portions are formed between the axial center portion and each connection portion, whose cross-sectional shape gradually changes and whose perimeter changes, and at least one decreasing perimeter portion is formed in each cross-sectional transition portion, whose perimeter gradually decreases as it moves from the center portion to the connection portion, and between the decreasing perimeter portion and the axial center, one increasing perimeter portion is provided, whose perimeter gradually increases as it moves from the center portion to the connection portion, and another increasing perimeter portion is provided between the decreasing perimeter portion and the connection portion, whose perimeter gradually increases as it moves from the center portion to the connection portion.

2. A torsion beam according to claim 1, characterized in that the depth of said recessed portion is changed to change the perimeter of said reduced perimeter portion.

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