Torsion bar suspension

Abstract

Torsion bar suspension (2), comprising: a torsion bar (5) with a sheet metal part which is open in its longitudinal direction on a side designated as the open side, or in a tubular form which is open along its longitudinal direction on a side designated as the open side; and a pair of longitudinal control arms (6) mounted on the two longitudinal ends of the torsion bar (5), wherein each longitudinal control arm (6) has a hollow rod connecting section (13) which is connected as a support connection to the respective end of the torsion bar (5), characterized in that a connecting portion (27) between the longitudinal control arm (6) and the torsion bar (5) is inclined with respect to a reference line (B) extending in a longitudinal direction of the torsion bar (5), an end region of the torsion bar (5) becomes smaller from the non-open side to the open side in the torsion bar (5), an end portion of the rod connecting portion (13) has an inclined surface (28) which is inclined in accordance with a shape of the end portion of the torsion bar (5), and the rod connecting portion (13) has a concave portion (31) which is recessed into the inclined surface.

Description

Background of the inventionField of the invention

[0001] The present invention relates to a torsion bar suspension according to the preamble of claim 1. Description of the state of the art

[0002] To improve the fuel consumption of vehicles, such as automobiles, it is necessary to reduce the weight of the vehicle and thus also the weight of the suspension components through greater use of aluminum alloy. A torsion bar suspension system includes a torsion bar and a pair of trailing arms welded to either end of the torsion bar. While the trailing arms must exhibit high rigidity against lateral, longitudinal, and vertical forces acting on the vehicle, the torsion bar must exhibit moderate rigidity to absorb torsional forces when the right and left wheels are displaced in vertically opposite phases.

[0003] A torsion bar suspension is known that reduces the stress induced in the edge region of a torsion bar while simultaneously avoiding weight gain. The conventional torsion bar suspension includes a torsion bar inserted into a trailing arm (see, for example, patent JP 2012-140 031 A).

[0004] In conventional torsion bar suspension, due to the structure in which the torsion bar is inserted into the trailing arm, an overlap area is formed between the trailing arm and the torsion bar. This overlap area causes an additional increase in weight for the trailing arm or the torsion bar.

[0005] The trailing arm and torsion bar inevitably have different diameters. As a result, a step occurs in the overlap area. This step has the disadvantage of insufficient strength due to stress concentration.

[0006] Additionally, there is an unwelded area between the trailing arm and the edge of the torsion bar, forming a boundary between the welded and unwelded areas, leading to stress concentration and a consequent lack of strength. The unwelded area is also subject to fretting fatigue due to the small reciprocating sliding movement.

[0007] Furthermore, it is difficult to improve the longitudinal positional accuracy of the torsion bar when the trailing arm and the torsion bar are welded together.

[0008] DE 44 16 725 B4 shows a torsion bar suspension according to the preamble of claim 1. In this torsion bar suspension, each trailing arm has a hollow rod connecting section in the form of a trailing arm core with a round cross-section, which is welded to the round cross-section of the respective ends of the torsion bar.

[0009] DE 100 54 692 A1 also shows a torsion bar suspension according to the preamble of claim 1.

[0010] DE 196 43 001 A1 discloses a torsion bar suspension in which a connecting section between the trailing arm and the torsion bar is inclined relative to a reference line running parallel to the longitudinal direction of the torsion bar. The connecting section is inclined such that a non-open side in the open torsion bar is located on a side that is closer to a center in the longitudinal direction of the torsion bar than the open side of the torsion bar. End regions of the torsion bar become smaller from the non-open side toward the open side.

[0011] JP 2006-281 885 A shows a torsion bar suspension in which a bar connecting section between the torsion bar and the trailing arm has a rectangular and closed cross-section. DISCLOSURE OF THE INVENTION

[0012] The present invention has been made in view of the above-mentioned circumstances, and its object is to provide a torsion bar suspension which is characterized by high productivity, whose positional accuracy can be easily determined by reducing stress concentration at a connecting portion of a trailing arm and a torsion bar, and which brings about a significant reduction in weight.

[0013] The above object and further objects can be achieved according to the invention by a torsion bar suspension having the features of claim 1

[0014] It may be desirable for the connecting portion to be inclined such that a non-open side in the open torsion bar is located on a side closer to the center in the longitudinal direction of the torsion bar than the open side of the torsion bar.

[0015] In addition, it may be preferable if the thickness of the rod connecting portion is increased gradually or stepwise with increasing distance from the torsion bar.

[0016] It may be preferable if a thickness of the rod connecting portion varies between a first zone corresponding to the connecting portion between the trailing arm and the torsion bar, a second zone corresponding to the concave portion different from the first zone, and a third zone different from the first zone and the second zone in the longitudinal direction of the torsion bar, wherein the first zone is the thinnest, the third zone is the thickest, and a thickness of the second zone changes gradually or stepwise within a difference between a thickness of the first zone and a thickness of the third zone.

[0017] In addition, it may be preferable that the concave portion has a rectangular cross-sectional shape or a V-shaped cross-sectional shape.

[0018] The rod connection section may have a closed cross-sectional shape.

[0019] The trailing arm may be forked, starting from the rod connecting section, so that the two fork sections form a circular arc shape continuously starting from the rod connecting section.

[0020] Furthermore, it may be preferred if the trailing arm is a cast part made of a non-ferrous alloy, while the torsion bar is an extrusion or a molded product made of a sheet material consisting of an aluminum alloy or an iron alloy.

[0021] According to the torsion bar suspension according to the present invention having the above-mentioned structures, high productivity for the torsion bar suspension can be achieved with high positioning performance and reduced stress concentration in a connecting portion between a trailing arm and a torsion bar, while preventing an increase in weight to a greater extent.

[0022] Further advantageous effects and functions of the present invention will become more apparent from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing a vehicle to which a torsion bar suspension according to an embodiment of the invention is applied; Fig. 2 is a perspective view illustrating the torsion bar suspension according to the embodiment of the invention; Fig. 3 is an exploded perspective view illustrating the torsion bar suspension according to the embodiment of the invention; Fig. 4 is a view illustrating a load acting on the torsion bar suspension according to the embodiment of the invention; Fig. 5 to 8 are cross-sectional views of different examples of a long torsion bar according to the embodiment of the invention; Fig. 9 is a sectional view illustrating the torsion bar suspension according to the embodiment of the invention taken along a reference line; Fig. 10 to 13 are sectional views of different examples of the torsion bar suspension according to the Fig. 9 illustrated embodiment; Fig. 14 is a perspective view illustrating a trailing arm of the torsion bar suspension according to the embodiment of the invention; Fig. 15 is a sectional view of another example of the torsion bar suspension according to the embodiment of the present invention taken along the reference line; Fig. 16 to 20 are sectional views showing different examples of the torsion bar suspension according to the embodiment of Fig. 15 illustrate; Fig. 21 is a perspective view illustrating the trailing arm of the torsion bar suspension according to the embodiment of the invention; Fig. 22 and Fig. 23 are cross-sectional views of one and other examples of the trailing arm according to the embodiment of the invention; Fig. 24 is a sectional view of another example of the torsion bar suspension according to the embodiment of the present invention taken along the reference line; and Fig. 25 is a sectional view illustrating another example of the torsion bar suspension according to the embodiment of the invention taken along the reference line. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] An embodiment of a torsion bar suspension according to the present invention will be described below with reference to the Fig. 1 to 25. It should also be noted that terms such as "top," "bottom," "right," "left," and the like, which indicate a direction, correspond here to the representations in the figures or to a typical installation position in a vehicle.

[0024] Fig. 1 is a perspective view illustrating a vehicle to which a torsion bar suspension according to the embodiment of the present invention is applied.

[0025] After Fig. 1, a motor vehicle 1 as a vehicle according to the present embodiment has a torsion bar suspension 2 (hereinafter referred to simply as "suspension 2") as a rear suspension. The suspension 2 supports a pair of right and left wheels 3 of the motor vehicle.

[0026] The suspension 2 oscillates in the vertical direction of the vehicle 1. The suspension 2 comprises a long torsion bar 5 and a pair of trailing arms 6 which are attached to opposite ends of the torsion bar 5.

[0027] The long torsion bar 5 (hereinafter referred to simply as torsion bar 5) has a length in the longitudinal direction (in the vehicle width direction) of the motor vehicle 1. Each of the trailing arms 6 is coupled to the torsion bar 5 and extends in the vehicle width direction. The trailing arm 6 is also forked such that the two respective fork parts extend toward the front and rear of the vehicle, respectively (i.e., in the longitudinal direction of the vehicle).

[0028] A suspension spring 7 and a shock absorber 8 absorb a vertical force of the motor vehicle 1 acting on the suspension 2.

[0029] Referring to Fig. 2, which illustrates the torsion bar suspension according to the embodiment, and Fig. 3, which illustrates an exploded perspective view of the torsion bar suspension according to the embodiment, the suspension 2 is swingably mounted on an angle bracket 9 provided on the vehicle body. The suspension 2 supports the wheel 3 via a hub 11. A brake drum 12 is provided between the hub 11 and the wheel 3.

[0030] The trailing arm 6 is a cast part made of a non-ferrous alloy, for example, an aluminum alloy. The torsion bar 5 is an extruded part or a molded part made of a sheet metal workpiece made of an aluminum alloy or a ferrous alloy.

[0031] The trailing arm 6 includes a rod connecting portion 13 connected to the torsion bar 5 in the form of a support. The trailing arm 6 is forked in two parts, starting from the rod connecting piece 3. Each of the two fork portions has an arcuate shape R that extends continuously from the rod connecting piece 13. It is preferable that the arcuate shape has a smaller curvature (a larger radius of curvature). One of the two fork portions that extends toward the front of the vehicle is referred to as the front arm 15, and the other of the two fork portions that extends toward the rear of the vehicle is referred to as the rear arm 16. The front arm 15 includes a portion 17 for receiving a sleeve in a press fit (hereinafter referred to as the "sleeve press fit portion"). An elastic tubular sleeve 18 is press-fitted into the sleeve press fit portion 17. The sleeve 18 is pivotally mounted on the angle piece 9 via a bolt 21.The angle piece 9, the sleeve 18 and the sleeve press fit part 17 form a swing axis of the suspension 2.

[0032] The rear arm 16 includes a shock absorber holder 22, a spring seat 23 and a carrier 25.

[0033] The shock absorber bracket 22 is located on a surface of the rear arm 16 facing the torsion bar 5, that is, on an inner side when viewed in the vehicle width direction of the motor vehicle 1. The shock absorber bracket 22 swingably supports a lower end portion of the shock absorber 8. The shock absorber 8 is pivotally mounted on the shock absorber bracket 22 by means of a bolt 26.

[0034] The spring seat 23 extends from the connecting piece 13 to the rear arm 16. The spring seat 23 is also provided on the inner side as viewed in the vehicle width direction of the vehicle 1. The spring seat 23 is in contact with a lower end portion of the suspension spring 7. An upper end portion of the suspension spring 7 is in contact with a vehicle body frame of the vehicle 1 to support the vehicle body frame.

[0035] The carrier 25 is provided on a surface facing away from the torsion bar 5, i.e., on a surface facing outward when viewed in the width direction of the motor vehicle 1. The carrier 25 supports the wheel 3 via the hub 11.

[0036] A connecting portion 27 between the trailing arm 6 and the torsion bar 5 is inclined with respect to a reference line B extending in a longitudinal direction (an axial direction) of the torsion bar 5.

[0037] Fig. 4 is a view showing a torsion bar suspension according to the embodiment of Fig. 2 applied load is illustrated as an example.

[0038] As in Fig. 4, the suspension 2 according to the present embodiment is supported by the angle piece 9 such that it can swing in the vertical direction of the motor vehicle 1, wherein the position of the suspension 2 in the vertical direction of the motor vehicle 1 is determined by the suspension spring 7 and the shock absorber 8.

[0039] A lateral force, a longitudinal force, and a vertical force acting from a mounting point of the wheel 3, and a twisting load acting when the pair of right and left wheels 3 are displaced in the vertical direction in opposite phases, act on the torsion bar 5.

[0040] Fig. 5 to 7 are cross-sectional views of various examples of the torsion bar according to the embodiment of the invention.

[0041] As in the Fig. 5 to 7, the torsion bar 5 of the suspension 2 according to the present embodiment is a plate-shaped bar having an opening in a direction of its cross-sectional shape, that is, in a cross-sectional shape in a direction perpendicular to the reference line B.

[0042] In particular, the torsion bar 5 has a length measured in its longitudinal direction and offers a U-shaped cross-section ( Fig. 5), a V-shaped cross-section ( Fig. 6) or a C-shaped cross-section ( Fig. 7), which is formed with an open side along the longitudinal direction (i.e., in the axial direction corresponding to the reference line B) of the torsion bar 5. It should be noted that in the embodiments described here, the torsion bar 5 has, in its longitudinal direction, an upper side that is closed as a non-open side and a lower side that is open as an open side, referring to the accompanying drawings.

[0043] Fig. 8 also shows a cross-sectional view of another example of the torsion bar according to the embodiment.

[0044] As in Fig. 8, the torsion bar 5 may be a tubular bar having an opening in a direction of the cross-sectional shape, that is, a cross-sectional shape in the direction perpendicular to the reference line B. Specifically, the torsion bar 5 has a U-shaped cross section obtained, for example, by compressing a tube having a circular cross section by plastic working so as to open the cross section in the longitudinal (i.e., axial) direction of the torsion bar 5.

[0045] The following description refers to the torsion bar 5 with a U-shaped cross-section.

[0046] Fig. 9 is a sectional view illustrating the torsion bar suspension according to the embodiment of the invention taken along the reference line B.

[0047] Fig. 10 to 13 are sectional views showing the torsion bar suspension as viewed along a line XX in Fig. 9, when viewed along a line XI-XI in Fig. 9, when viewed along a line XII-XII in Fig. 9 and when viewed along a line XIII-XIII in Fig. 9 illustrates.

[0048] Fig. Fig. 14 is a perspective view showing the trailing arm of the torsion bar suspension according to the embodiment of the invention on an enlarged scale. As shown in Figs. Fig. 9 to 13, the torsion bar link 13 of the suspension 2 of this embodiment has a hollow structure with a substantially uniform thickness and a closed cross-sectional shape.

[0049] The torsion bar 5 of the suspension 2 is a sheet-metal or plate-like bar that has an open shape or opening in one direction. The torsion bar 5 is open on an underside of the motor vehicle 1, i.e., toward a road surface, in the longitudinal (i.e., axial) direction of the torsion bar.

[0050] An end face of the torsion bar 5 is inclined toward a vehicle center side with respect to a plane perpendicular to the reference line B.

[0051] The connecting portion 27 is inclined such that a non-open side C (the top side in the illustration) of the torsion bar 5 with the opened shape is closer to the center (left side in Fig. 4) in the longitudinal direction of the torsion bar 5 is located as an open side O (the lower side in the illustration). In other words, an end portion of the torsion bar 5 becomes smaller toward the end portion from the non-open side C toward the open side O in the open-designed torsion bar 5. On the other hand, an end portion of the connecting piece 13 becomes larger from a position corresponding to the non-open side C of the torsion bar 5 toward a position corresponding to the open side O of the torsion bar 5. The end portion of the connecting piece 13 includes an inclined surface 28 inclined according to the shape of the end portion of the torsion bar 5.

[0052] A convex (protruding) portion 29 is located at the end portion of the connecting piece 13, and it mates with the end portion of the torsion bar 5. The convex portion 29 may have a minimal protrusion as required for positioning and connecting the connecting piece 13 to the torsion bar 5. When the convex portion 29 is attached to the torsion bar 5, the end surface of the torsion bar 5 abuts the end portion of the connecting piece 13, and the outer surfaces of the torsion bar 5 and the connecting piece 13 are almost flush with each other. The connecting portion 27 is attached over its entire circumference by welding or friction stir welding to unite the torsion bar 5 with the trailing arm 6.

[0053] In the suspension 2 having the above-described structure, a cross-sectional area of ​​the trailing arm 6 gradually increases from the torsion bar 5, which has an open cross-sectional shape and relatively low rigidity, toward the trailing arm 6 (more specifically, toward the connecting piece 13) with a closed cross-sectional shape and relatively high rigidity. Accordingly, a sudden change in the rigidity of the connecting portion 27 between the torsion bar 5 and the trailing arm 6 can be suppressed.

[0054] Further examples of the suspension 2 according to the embodiment will be described below. Note that elements or parts having the same or substantially the same configuration as those in the suspension 2 are denoted by the same reference numerals in the examples of suspensions 2A, 2B, and 2C described below, and repeated descriptions are omitted.

[0055] Fig. 15 is a sectional view showing another example of the torsion bar suspension according to the embodiment of the present invention along the reference line B shown in Fig. 15 itself is not shown.

[0056] Fig. 16 to 20 are sectional views illustrating the torsion bar suspension according to this embodiment of the invention, as viewed along a line XVI-XVI in Fig. 15, when viewed along a line XVII-XVII in Fig. 15, when viewed along a line XVIII-XVIII in Fig. 15, when viewed along a line XIX-XIX in Fig. 15 and when viewed along a line XX-XX in Fig. 15.

[0057] Fig. 21 is a perspective view illustrating the trailing arm of the torsion bar suspension according to the embodiment of the invention.

[0058] As in the Fig. 14 to 21, a suspension 2A of this embodiment includes a concave (recessed) portion 31 recessed into the inclined surface 28 of the connecting piece 13.

[0059] When viewed in the longitudinal direction of the torsion bar according to Fig. 15, the concave portion 31 presents a shape in which a depth h1 of the depression gradually increases from an edge portion P located furthest from the torsion bar 5 to a distal end Q of the torsion bar 5, while a depth h2 of the depression gradually decreases from the distal end Q of the torsion bar 5 to the distal end R of the connecting piece 13.

[0060] The concave section 31 corresponds to an arc shape in a cross-section perpendicular to the reference line B.

[0061] Fig. 22 and Fig. 23 are cross-sectional views illustrating other examples of the trailing arm according to the embodiment of the invention.

[0062] As in the Fig. 22 and Fig. 23, the concave portion 31 of the suspension 2A of this embodiment forms a rectangular ( Fig. 22) or a V-shaped ( Fig. 23) Cross-section other than the arcuate cross-sectional shape in the direction perpendicular to the reference line B.

[0063] Since the suspension 2A of the above-mentioned structure has the concave portion 31 in the inclined surface 28 of the trailing arm 6, it can be configured to have an increasing and changing amount of the cross-sectional area of ​​the trailing arm 6 from the torsion bar 5 toward the trailing arm 6 (more specifically, toward the link 13), this increase being slower and smoother than in the suspension 2. Accordingly, a rapid change in the rigidity of the use portion 27 between the torsion bar 5 and the trailing arm 6 can be further suppressed.

[0064] Fig. 24 is a cross-sectional view of another example of the torsion bar suspension according to the embodiment of the present invention taken along reference line B.

[0065] As in Fig. As shown in Fig. 24, the thickness of the connecting portion 13 of the suspension 2B of this embodiment increases either gradually or stepwise as the distance from the torsion bar 5 increases. The connecting portion 13 has the smallest thickness at the distal end R, and from there, the thickness gradually or stepwise increases toward the edge portion P of the concave portion 31 farthest from the torsion bar 5, and then reaches the same thickness as the trailing arm 6 at the other end.

[0066] Although the suspension 2B includes the concave portion 31 as in the suspension 2A, the suspension 2B may include the flat inclined surface 28 as in the suspension 2.

[0067] In the suspension 2B of the above-described structure, the thickness of the link 13 increases gradually or stepwise from the torsion bar 5. Thus, the cross-sectional area increase and the cross-sectional change of the trailing arm 6 toward the torsion bar 5 (more precisely, the link 13) change even more slowly and smoothly than in the suspensions 2 and 2A. Consequently, a rapid change in the rigidity of the connecting portion 27 between the torsion bar 5 and the trailing arm 6 can be further suppressed.

[0068] Fig. 25 is a sectional view illustrating another example of the torsion bar suspension according to the embodiment of the invention taken along the reference line B.

[0069] As in Fig. 25, there are differences in the thickness of the connecting portion 13 of the suspension 2C of this embodiment in the longitudinal direction of the torsion bar 5 in a first zone A1 corresponding to the connecting portion 27, the trailing arm 6 and the torsion bar 5, a second zone A2 corresponding to the concave portion 31 different from the first zone A1, and a third zone A3 different from the first zone A1 and the second zone A2.

[0070] The first zone A1 is a zone extending from the distal end R of the connecting piece 13 to the distal end Q of the torsion bar 5.

[0071] The second zone A2 is a zone from the distal end Q of the torsion bar 5 to the edge region P located farthest from the torsion bar 5 within the concave portion 31.

[0072] The third zone A3 is a zone in the vehicle width direction starting from the edge region P, and is a base portion of the connecting piece 13.

[0073] The first zone A1 is the thinnest, and the third zone A3 is the thickest. The first zone A1 and the third zone A3 have a substantially uniform thickness within each zone.

[0074] The thickness of the second zone A2 changes gradually or stepwise within a difference range between the thickness of the first zone A1 and the thickness of the third zone A3.

[0075] The suspension 2C of the structure described above includes the second zone A2, the thickness and hence the rigidity of which changes, so that stress generated in the connecting portion 27 between the trailing arm 6 and the torsion bar 5 (i.e., the first zone A1) is distributed between the first zone A1 and the second zone A2, whereby the stress concentration portion S shifts toward the second zone A2 to reduce the load applied to the connecting portion 27 between the trailing arm 6 and the torsion bar 5 (the stress concentration region S moves from the two-dot chain line S1 to the two-dot chain line S2 in Fig. 25). When the thickness of the second zone A2 suddenly changes in the area near the third zone A3, the effect described above becomes apparent.

[0076] In the suspensions 2, 2A, 2B and 2C according to the present embodiment, since the torsion bar 5 is combined with the trailing arm 6 in a support connection, the suspension can be reduced in weight more reliably, and its position can also be determined more easily than a conventional suspension.

[0077] In addition, since the connecting portion 27 is inclined in the suspensions 2, 2A, 2B and 2C of this embodiment, a rapid change in the rigidity of the connecting portion 27 can be suppressed, and thus the stress concentration can be reduced.

[0078] Furthermore, in the suspensions 2, 2A, 2B, and 2C of the present embodiment, the connecting portion 27 is welded over the entire circumference. Consequently, there is no boundary between a welded and a non-welded area, so stress concentration can be suppressed and fretting fatigue can be avoided.

[0079] In the suspensions 2, 2A, 2B, and 2C of this embodiment, stress concentration around the outer surface can be avoided because the outer surfaces are almost flush in the connecting portion 27. Although there may be a step between the inner surface of the torsion bar 5 and the inclined surface 28 of the trailing arm 6, this does not cause any problems because the stress is lower than on the outer surface.

[0080] In the suspensions 2, 2A, 2B and 2C of the present embodiment, since the area between the connecting portion 13 and the front arm 15 and the portion between the link 13 and the rear arm 16 form an arc shape, a load is gradually transmitted from the sleeve press-fit portion 17, the shock absorber holder 22, the spring seat 23 and the bracket 25 to the torsion bar 5, thereby reducing stress concentration.

[0081] Since the suspensions 2, 2A, 2B and 2C of this embodiment further include the torsion bar 5 having an open shape in one direction, that is, having an opening, the present invention can be applied to a vehicle requiring high torsional rigidity.

[0082] Furthermore, in the suspension 2C of this embodiment, when the connecting portion 27 has a welded structure made of an aluminum alloy, the stress concentration in the connecting portion 27 can be reduced by forming the connecting portion 27 with increasing pitch on an aluminum alloy which decreases in material strength from the stress concentration region.

[0083] As explained above, in the suspensions 2, 2A, 2B and 2C of this embodiment, an increase in weight can be more reliably prevented, the stress concentration in the connecting portion 27 between the trailing arm 6 and the torsion bar 5 can be reduced, and the suspension can be determined with positional accuracy.

[0084] Furthermore, it should be noted that the present invention is not limited to the embodiments described above, but various changes and modifications or variations are possible without departing from the scope of the appended claims.

Claims

[1] Torsion bar suspension (2), comprising: a torsion bar (5) with a sheet metal part which is open in its longitudinal direction on a side referred to as the open side, or in a tubular form which is open along its longitudinal direction on a side referred to as the open side; and a pair of longitudinal control arms (6) attached to the two longitudinal ends of the torsion bar (5), wherein each longitudinal link (6) has a hollow rod connection section (13) which is connected as a support connection to the respective end of the torsion bar (5), characterized by , that a connecting section (27) between the longitudinal control arm (6) and the torsion bar (5) is inclined with respect to a reference line (B) which extends in a longitudinal direction of the torsion bar (5), an end region of the torsion bar (5) starting from the non-open side to the open side in which the torsion bar (5) becomes smaller, an end region of the rod connection section (13) has an inclined surface (28) which is inclined according to a shape of the end region of the torsion bar (5), and the rod connection section (13) has a concave section (31) which is recessed into the inclined surface. [2] Torsion bar suspension (2) according to claim 1, wherein the connecting section (27) is inclined such that a non-open side in the open torsion bar (5) is located on a side which is closer to a center in the longitudinal direction of the torsion bar (5) than the open side of the torsion bar (5). [3] Torsion bar suspension (2) according to claim 1 or 2, wherein the thickness of the bar connection section (13) gradually or stepwise increases with increasing distance from the torsion bar (5). [4] Torsion bar suspension (2) according to any one of claims 1 to 3, wherein the thickness of the bar connection section (13) varies between a first zone (A1) corresponding to the connection section (27) between the longitudinal link (6) and the torsion bar (5), a second zone (A2) corresponding to the concave section (31) different from the first zone (A1), and a third zone (A3) different from the first zone (A1) and the second zone (A2) in the longitudinal direction of the torsion bar (5), wherein the first zone (A1) is the thinnest, the third zone (A3) is the thickest, and the thickness of the second zone (A2) changes gradually or stepwise within a difference between the thickness of the first zone and the thickness of the third zone. [5] Torsion bar suspension (2) according to one of claims 1 to 3, wherein the concave section (31) has a rectangular cross-sectional shape. [6] Torsion bar suspension (2) according to one of claims 1 to 3, wherein the concave section (31) has a V-shaped cross-sectional form. [7] Torsion bar suspension (2) according to one of claims 1 to 6, wherein the bar connection section (13) has a closed cross-sectional shape. [8] Torsion bar suspension according to one of claims 1 to 7, wherein the longitudinal link is forked starting from the rod connection section in such a way that the respective two fork sections form a continuous arc shape starting from the rod connection section. [9] Torsion bar suspension (2) according to any one of claims 1 to 8, wherein the longitudinal control arm (6) is a casting made of a non-ferrous alloy and the torsion bar (5) is an extruded element or a formed product made of a sheet material consisting of an aluminium alloy or an iron alloy.

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