MXPA99010924A - Dual trailing arm vehicle suspension - Google Patents

Abstract

A suspension system for a vehicle includes a longitudinally extending frame, an axle (44) connected to the frame for relative movement with respect thereto, an air spring (38) mounted between the frame and the axle to yieldably support the axle with respect to the frame, and upper (22) and lower (24) trailing arms attached to each side of the frame. A first torsion bar (58) extends between and is rigidly attached to the upper trailing arms and a second torsion bar (60) extends between and is rigidly attached to the lower trailing arms. The torsion bar cooperates with the springs during deflection of the suspension system with respect to the frame to thereby yieldably resist relative movement between the trailing arms and the frame. In one embodiment, the upper and lower trailing arms are parallel to each other. This arrangement results in load equalization between the suspension assemblies. Any relative torque caused by deflection of the trailing arms is equally distributed between both torque bars. In another embodiment, the upper (63) and lower (64) trailing arms are non-parallel, and arranged such that when the trailing arms pivot due to road conditions or vehicle loading, fore and aft movement of the air spring and axle due to arcuate swing of the trailing arms is minimized.

Description

SUSPENSION FOR DOUBLE REAR VEHICLE VEHICLE Background of the Invention Field of the Invention This invention relates to suspension systems for vehicles. In one of its aspects, the invention relates to rear arm suspensions for mounting a traction axle in a vehicle frame, wherein each rear arm comprises a pair of arms pivotally mounted in a frame bracket at one end and pivotally mounted to a traction shaft plate at the other end. STATE OF THE ART Air spring suspensions are currently used to suspend the traction axles of trailers or other commercial vehicles. A typical air suspension assembly includes a rear arm pivotally mounted at one end to a vehicle frame by a frame bracket. An air spring is mounted between the frame and the other end of the rear arm. A traction shaft is usually mounted on the rear arm in proximity to the air spring. Two suspension assemblies are typically associated with each traction axis. A problem associated with the air spring suspensions of the state of the art occurs when the traction axle and the associated trailing arm are deflected due to load or irregularities in the road surface when the vehicle is traveling. "When deviating , one end of the rear arm rotates around a pivot point in the frame bracket, which causes the distal end of the rear arm to rotate in an arc, as the air spring and drive shaft are typically mounted at the end The arched movement of the lower part of the spring results in bow and stern movement and angular rotation of the lower portion of the air spring.As a result, the typical air springs are designed with a height to compensate both the deflection of the traction axis, as well as the bow and stern movement, and the rotational movement. The air needs an increase in material and bladder length, which results in a higher manufacturing expense. SUMMARY OF THE INVENTION According to the invention, a suspension system for a vehicle having a frame that extends longitudinally with a pair of opposite sides has a pair of frame clamps spaced laterally to each other, and each of which It is adapted to be mounted on one side of the frame. A first pair of rear, upper arms, extending longitudinally, has first ends pivotally connected to the frame clamps and second ends. The upper posterior arms are spaced vertically on the lower posterior arms. A traction shaft is mounted on and extends between the ends of each set of first and second rear arms, the traction shaft having opposite ends and a central axis. A pair of springs are mounted on the second ends of the first and second rear arms and are adapted to be mounted on the frame to dampen the movement of the first and second rear arms towards the frame. In one embodiment, a first torsion bar extends between and rigidly attaches to the upper rear arms. In a further embodiment, a second torsion bar extends between and rigidly attaches to the lower rear arms. The torsion bars resist in a deformable way the relative movement between the rear arms and the frame. In a further embodiment, the upper and lower rear arms are parallel to each other. This arrangement results in load equalization between the suspension sets. Any relative torsion caused by the deflection of the posterior arms is distributed equally between both torsion bars. Due to the arrangement of the arms in parallel, the drive shaft does not rotate or experience torsion about its central axis when at least one of the upper and lower rear arm assemblies rotates from a rest position to a deflection position.

In even a further embodiment, the upper and lower rear arms are non-parallel, and are arranged such that when the rear arms pivot due to the conditions of the road or the load of the vehicle, the bow and stern movement of the springs of Air due to the arched oscillation of the posterior arms is minimized. In this arrangement, the drive shaft functions as a torsion rod and cooperates with the torsion bars, when provided, to equalize the forces generated in the suspension system on both sides of the frame. Alternatively, or in addition to the torsion bars, the non-parallel suspension assembly may include a rail bar or other stabilization components. In addition, the rotation of the air spring piston is also greatly reduced. With the bow and stern movement and greatly reduced rotation, the air springs can be of lower height and have a reduced weight and cost while retaining the load carrying performance of larger springs. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a side elevational view of a portion of a vehicle frame and a suspension assembly according to the invention; Figure 2 is a front elevational view of the vehicle frame and suspension assembly, taken along line 2-2 of Figure 1; Figure 3 is a schematic perspective view of a sub-assembly of the suspension assembly illustrated in Figures 1 and 2; and Figure 4 is a side elevational view, like Figure 1, of a portion of a vehicle frame and suspension system according to a second embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and to Figures 1 and 3 in particular, there is shown a vehicle frame comprising side frame beams 12 and 14 and a cross clamp 16 joined together. The front of the vehicle is on the right, as seen in figure 1. For simplicity, only one side of the suspension assembly will be described in detail, although it is understood that each side of the vehicle has an identical portion of the assembly. Each side of the suspension assembly comprises a hanging bracket 18 secured to the frame beam 12 by bolts 20 or welding. The upper and lower rear arms 22 and 24 are pivotally mounted to the hanging bracket 18 by sleeve seals 26 and 28, respectively. The other ends of the rear arms 22 and 24 are secured by sleeve seals 32 and 34, respectively, to the shaft bracket 30. Sleeve seals of the type used in the sleeve seals 26, 28, 32 and 34 are disclosed in U.S. Patent No. 3,140,880, for example. An air spring 38 is mounted at an upper end on the beam 12 by the frame clamp 40 and bolts 42, or welded. The air spring 38 is mounted on the shaft clamp 30 at a lower end thereof, by means of a suitable clamp and bolts (not shown). A traction shaft 44 is secured to a central portion of the shaft bracket 30. An upper end of a shock absorber 46 is pivotally mounted in a bracket 48 by a bolt 50. The bracket 48 in turn is mounted to the beam 12 by bolts 52. The lower end of the shock absorber 46 is pivotally mounted to the shaft bracket 30 by an extension 54 and the bolt 56. As shown in figures 2 and 3, an upper torsion bar 58 extends between the upper rear arms 22 located on opposite sides of the vehicle frame. The upper torsion bar 58 is rigidly attached to the upper rear arms 22 for rotational movement therewith. Similarly, a lower torsion bar 60 extends between the lower rear arms 24 and is rigidly joined thereto for rotation movement therewith. Due to the parallelogram arrangement of the upper and lower rear arms 22, 24, the shaft clamp 30 and the hanging clamp 18, any deflection of the shaft clamp 30 will cause vertical deflection of the air spring 38, as well as deflection of the front back or longitudinal. The amount of longitudinal deflection can be controlled by the length of the upper and lower rear arms 22, 24 and their angular position relative to the ground. The higher level they are in, the less longitudinal movement will be made. In this way, with a longer back arm, the longitudinal deflection of the air spring 38 can be reduced to a minimum. The rotation of the piston of the air spring is therefore very close to zero. With the double torsion bar arrangement according to the invention, the inclination of the vehicle is resisted. When one end of the traction axis is tilted upward and the other end is tilted downwards, as shown in the dotted line in figure 3, such as during a turn to the right, the first back arms 22 and 24 attempt to twist the torsion bars 58 and 60 in a counter-clockwise direction, as seen in Figure 3, and the second rear arms 22 and 24 resist by twisting the bars in a clockwise direction. These movements are resisted by the torsion bars 58, 60. Thus, the torsion bars will exert a stabilizing influence on the vehicle in the sense that the vehicle frame will be maintained deformably in parallel relation with the traction axis. This same action and reaction also occurs when irregularities are found on the road surface or uneven loading of the vehicle. When the parallel rear arms pivot up and down, the rear arms pivot around an arc and in this way the lower ends of the air spring move slightly forward and aft, without turning, with respect to the vehicle frame. However, the ends of the traction shaft retain their rotational orientation due to any movement to the bow or stern. Turning now to Figure 4, and in accordance with a preferred embodiment of the invention, a suspension assembly having a non-parallel rear arm arrangement is shown. Equal parts in this figure are represented by equal numbers of parts shown in Figures 1-3. As in figure 1, the front of the vehicle is on the right. The rear arm arrangement comprises an elongated hanging bracket 68 secured to opposite sides of the frame beam 12 by bolts 20 or by means of welding (only one side of the frame is shown, for simplicity). The upper and lower rear arms 63 and 64 are pivotally mounted to the hanging bracket 68 by sleeve gaskets 26 and 28, respectively. The other ends of the rear arms 63 and 64 are secured by sleeve seals 32 and 34, respectively, to the shaft clamp 30. As in the previous embodiment, an air spring 38 is mounted to the beam 12 by a clamp 40 or by means of welding. A lower end of the air spring is mounted on the shaft clamp 30. A traction shaft 44 is secured to a middle portion of the shaft clamp 30. A damper 46 is pivotally mounted at an upper end in a clamp 48 by a bolt 50. The clamp 48 in turn is mounted to beam 12 by bolts 52. The lower end of shock absorber 46 is pivotally mounted to shaft bracket 30 by extension 54 and bolt 56. Upper and lower rear arms 63 and 64 converge to each other, between the frame bracket 68 and the shaft bracket 30. The rear arms 63, 64 have a length ^ and are positioned at a converging angle such that when the drive shaft 44 undergoes deflection at one end in relation to the other end, due to irregularities in the road or different load conditions found by the vehicle, the drive shaft ~~ 44¡ moves in a direction essentially vertical with respect to the side frame 12. At the same time, however, one end of the drive shaft will tend to twist with respect to the other end, thereby introducing an effort of torque on the traction shaft 44. The sleeve joint 28 can be placed horizontally at the same level or below a joint with sleeve 34. When the traction axis undergoes upward deflection, the lower rear arm 64 will tend to rotate the clamp 30. counterclockwise, as seen in Figure 4. Similarly, a gasket with sleeve 26 is placed higher than the gasket with sleeve 32 such that when the traction shaft undergoes deflection upwards, the upper rear arm 63 will tend to rotate the clamp 30 counterclockwise. When the traction axis is subjected to downward deflection, the rear arms tend to rotate the shaft clamp 30 in the clockwise direction. Due to the convergent movement of the rear arms 63, 64, "the shaft clamp 30 will tend to move in a linear, vertical direction to move the air spring in a vertical direction.This linear movement will tend to rotate one end of the traction shaft. 44 about its longitudinal axis with respect to the other end as the axis plate 30 moves linearly as long as the other end of the traction axis is not subjected to the same deflection forces. It will twist slightly with respect to the other end during deflection of the air spring.The traction axle, therefore, is operated as a torsion arm between the suspension assemblies located on each side of the vehicle.Air springs with shorter dimensions can to be used as the air springs are not subject to rotational movement or considerable bow and stern.As in the previous embodiment, a bar d The torque is preferably rigidly attached to each pair of rear arms on each side of the suspension. Alternatively, the non-parallel suspension assembly may include a rail bar or other stabilizing components, such as those disclosed in U.S. Patent No. 4,262,929. Although the sleeve gasket 26 has been described as being higher than the sleeve gasket 32, and the sleeve gasket 28 has been described as being at or about the level of the sleeve gasket 34, the gaskets with sleeve can be arranged such that the upper and lower rear arms rotate the traction axis clockwise when the traction axis is subjected to upward deflection. In any case, the upper and lower rear arms must be non-parallel. Reasonable variations and modifications are possible within the spirit of the foregoing description and the drawings, without departing from the scope of the invention.

Claims (19)

1. CLAIMS 1. In a suspension system for a vehicle having a frame with a pair of opposite sides, the suspension system includes a pair of frame clamps laterally separated from each other and each of which is adapted to be mounted on one side of the frame. frame; a first _par of upper rear arms, which extend longitudinally, having first ends pivotally connected to the frame clamps and second ends; a second pair of lower rear arms extending longitudinally, having first ends pivotally connected to the frame clamps and second ends, the upper rear arms being vertically spaced on the lower rear arms; a traction shaft pivotally mounted on and extending between the second ends of each first and second back set of arms, the traction shaft having opposite ends and a central axis, a pair of springs mounted on the second ends of the rear arms first and second and adapted to be mounted on the vehicle frame to dampen the movement of the first and second rear arms towards the vehicle frame, a first torsion bar extending between and being rigidly joined to the first ends of one of the pairs of upper and lower rear arms, the torsion bar being adapted to deformably resist the relative rotational movement between the pair of rear arms, and the improvement comprising: the second ends of the first rear arms are mounted on the traction shaft vertically on the traction axis and the second ends of the second arms the rear axles are mounted on the traction axle vertically below the traction axle, and the pivotal mounting of the second ends of the first and second trailing arms on the traction axle and the central axis of the traction axle are aligned. A suspension system according to claim 1, wherein the upper rear arms are in a common vertical plane with the lower rear arms. A suspension system according to claim 1, wherein the pivotal mounting of the second ends of the first and second rear arms to the traction axis and the central axis of the traction shaft are vertically aligned. 4. A suspension system according to any of claims 1-3, and further comprising a second torsion bar extending between and being rigidly joined to the other of the pairs of upper and lower rear arms, the second torsion bar being adapted to deformably resist the relative rotational movement between the other pair of rear arms. 5. A suspension system according to any of claims 1-3, and further comprising a pair of axle support plates rigidly attached to opposite ends of the traction axle, and wherein the second ends of the upper and lower rear arms are assembled pivotally on the drive shaft by means of the axle support plates. 6. A suspension system according to any of claims 1-3, wherein the upper rear arms are parallel to the lower rear arms. A suspension system according to claim 6, wherein the upper rear arms are substantially of the same length as the lower rear arms, whereby the traction axis maintains the same angular orientation about its central axis during the movement of the drive shaft from a rest position to a deflection position. 8. A suspension system according to any of claims 1-3, wherein the upper rear arms are divergent from the lower rear arms between the traction axle and the frame clamps. 9. A suspension system according to claim 8, where one of the upper and lower rear arms is sufficient longer than the other of the upper and lower rear arms so that the traction axis rotates about its central axis during the movement of a set of upper and lower rear arms with with respect to the other set of upper and lower posterior arms. 10. A suspension system according to any of claims 1-3, wherein the spring is an air spring. 11. In a suspension system for a vehicle having a frame with a pair of opposite sides, the suspension system includes a pair of frame brackets spaced laterally from each other and each of which is adapted to be mounted on one side of the frame; a first pair of upper rear arms, extending longitudinally, having first ends pivotally connected to the frame clamps and second ends, a second pair of lower rear arms extending longitudinally, having first ends pivotally connected to the frame clamps and second ends, the upper rear arms being vertically spaced on the lower rear arms, a traction shaft pivotally mounted on and extending between the second ends of each set of first and second rear arms, the traction shaft having opposite ends and a shaft central, a pair of springs mounted on the second ends of the first and second rear arms and adapted to be mounted on the vehicle frame to dampen the movement of the first and second rear arms towards the vehicle frame, a first torsion bar that it extends and being rigidly joined to the "first ends of one of the pairs of upper and lower rear arms, the torsion bar being adapted to deformably resist the relative rotational movement between the pair of rear arms, and the improvement comprising: Upper posterior arms are in a common vertical plane with the lower posterior arms. 12. A suspension system according to claim 11, wherein the second ends of the first rear arms are mounted on the traction axle vertically on the traction axle and the second ends of the second trailing arms are mounted on the axle. Traction axis vertically below the traction axis. A suspension system according to claim 11, and further comprising a second torsion bar extending between and being rigidly joined to the other of the pairs of upper and lower rear arms, the second torsion bar being adapted to withstand in a deformable way the relative rotational movement between the other pair of posterior arms. A suspension system according to any of claims 11-13, and further comprising a pair of axle support plates rigidly attached to the opposite ends of the traction axle, and wherein the second ends of the upper rear arms and The lower ones are mounted pivotally on the traction axle by means of the axle support plates. 15. A suspension system according to any of claims 11-13, wherein the upper rear arms are parallel to the lower rear arms. 16. A suspension system according to claim 15, wherein the upper rear arms are substantially of the same length as the lower rear arms, whereby the traction axis retains the same angular orientation about its central axis during movement of the traction axis from a resting position to a deflection position. 17. A suspension system according to any of claims 11-13, wherein the upper rear arms are divergent from the lower rear arms between the traction shaft and the frame clamps. A suspension system according to claim 17, wherein one of the upper and lower rear arms is sufficiently longer than the other of the upper and lower rear arms so that the traction axis rotates about its central axis during movement of a set of upper and lower rear arms with respect to the other set of upper and lower rear arms. 19. A suspension system according to any of claims 11-13, wherein the spring is an air spring. Resist A suspension system for a vehicle includes a longitudinally extending frame, a traction shaft (44) connected to the frame for relative movement therewith, an air spring (38) mounted between the frame and the shaft. of traction for deformably supporting the traction axis with respect to the frame, and upper (22) and lower (24) rear arms attached to each side of the frame. A first torsion bar (58) extends between and is rigidly attached to the upper rear arms and a second torsion bar (60) extends between and is rigidly attached to the lower rear arms. The torsion bar cooperates with the springs during deflection of the suspension system with respect to the frame to thereby resist in a deformable way the relative movement between the rear arms and the frame. In one embodiment, the upper and lower rear arms are parallel to each other. This arrangement results in load equalization between the suspension sets. Any relative torsion caused by the deflection of the posterior arms is distributed equally between both torsion bars. In another embodiment, the upper (63) and lower (64) rear arms are non-parallel, and are arranged such that when the rear arms pivot due to the conditions of the road or the load of the vehicle, the bow and stern movement of the air spring and the traction axis due to the arched oscillation of the rear arms is minimized.