WO2001060646A1

WO2001060646A1 - Front suspension system for a wheeled vehicle

Info

Publication number: WO2001060646A1
Application number: PCT/US2001/004585
Authority: WO
Inventors: Tjong T. Lie
Original assignee: Kumra, Mohinder
Priority date: 2000-02-15
Filing date: 2001-02-12
Publication date: 2001-08-23

Abstract

A front suspension system (16) for a vehicle (10) having a longitudinally extending chassis frame (12) having laterally spaced beams (146, 180), a front axle assembly (22) extending transversely with respect to the beams (146, 180), a pair of suspension radius arms (18), one suspension radius arm (18) being joined pivotally to each frame beam (146, 180), a front vehicule axle assembly (22) fixed to and carried by the arms (18), a compression spring (20) situated between each beam (146, 180) and its associated suspension arm (18), a steering spindle assembly (44, 46) located at each lateral side of the front axle (22), a steering gear mechanism comprising a steering torque input element (96) and a steering torque output element (86) secured to the axle assembly (22), a pitman arm (84) connected to the steering torque output element (86), a steering arm (80) forming part of one steering spindle assembly (44, 46), a drag link (82) connecting the pitman arm (84) to the steering arm (80), a tie rod (52) connecting together each steering spindle assembly (44, 46) for joint rotary movement.

Description

FRONT SUSPENSION SYSTEM FOR A WHEELED VEHICLE

TECHNICAL FIELD

The invention relates to suspension systems for wheeled vehicles, particularly buses and trucks having laterally situated frame beams and suspension springs between an axle and the frame beams.

BACKGROUND ART

Suspension systems for heavy vehicles, such as buses and trucks, typically use a forward frame that may be part of a so-called unibody frame construction or which may be a full structural frame. A front axle assembly for the suspension system is provided with steering spindles for each steerable wheel. A spring assembly is disposed between front frame beams and the front vehicle axle assembly whereby the weight of the vehicle body and chassis is supported.

A known suspension system for use with buses and trucks is disclosed in U.S. Patent 5, 118, 131. It includes a pair of radius arms pivoted on the vehicle chassis frame at forward ends of the radius arms, and a spring situated between the vehicle frame and the rearward end of each radius arm. The front vehicle axle assembly is secured to each radius arm at an intermediate location.

A steering spindle assembly at each end of the axle assembly has a steering arm. Steering torque is applied to each steering arm by means of a pitman arm that is a part of a steering gear assembly secured to the forward portion of the vehicle frame. A driver-controlled steering linkage mechanism used with the suspension system of the ' 131 patent distributes steering torque to the steering gear assembly as the pitman arm transmits output steering torque to the steering arms at each steering spindle assembly.

When the suspension system is subject to vertical displacement relative to the frame, such as during vehicle jounce or when one or both of the front wheels encounter a chuck hole in the roadway, either or both radius arms will pivot about a fixed pivot point with respect to the vehicle frame. This will induce a so-called bump-steer torque at the steering spindles because the steering gear assembly is fixed relative to the frame.

The bump-steer phenomenon is an undesirable steering characteristic for which the driver must compensate during road handling maneuvers. Further, such prior art suspension systems do not include provision for adjusting the position of the steering axle relative to the frame to effect a proper alignment of the steerable wheels. Such adjustments are desirable in those instances when the frame beams become over-stressed and are displaced, one with respect to the other, in a longitudinal direction.

DISCLOSURE OF INVENTION

It is an objective of the invention to provide an improved suspension system for a heavy vehicle having radius arms and a pair of vehicle frame beams. The radius arms of the suspension system are pivoted on the frame or the frame beams and are joined integrally to the vehicle front axle assembly. The steering gear associated with vehicles of this type is secured directly to the front axle assembly so that vertical movement of the front axle relative to the frame is accompanied by a corresponding vertical movement of the steering gear. The distance between the pitman arm of the steering gear assembly and the steering arm of the steering spindle assembly remains constant regardless of the degree of relative displacement of the radius arms relative to the frame. A bump-steering torque is not developed by the improved suspension system of the invention.

An improved pin-type eye assembly, together with a yieldable grommet and bushing, is used to establish a pivotal connection between each radius arm and the vehicle frame. The distance between the eye of the radius arm bushing and the frame can be controlled by using shims of selected thickness as proper alignment of the front axle relative to the frame is established.

The radius arm may be made of high-strength alloy steel (e.g. , a forging). The arm need not be made using a fabricated beam design. This makes it possible to lower the floor height of the vehicle, which is an important advantage if the vehicle is a passenger bus.

In practicing the invention, the front wheel axle assembly is connected to radius arms, which are pivotally connected to the frame at a forward end of the radius arms. A spring is located between the frame and each radius arm to accommodate vertical loads. A steering gear assembly, having a steering torque output member connected to steering wheel spindles, is connected to and is supported by the front wheel axle assembly whereby vertical displacement of the front wheels of the vehicle effects vertical displacement of the steering gear assembly relative to the frame. This eliminates unwanted steering torque as the axle assembly moves relative to the frame.

BRIEF DESCRIPTION OF DRAWINGS

FIGURE 1 is a schematic side elevation view of a passenger bus capable of using the improved suspension system of the invention;

FIGURE 2 is a partial plan view of the front portion of the vehicle frame and front axle assembly for a bus equipped with the improved suspension system of the invention;

FIGURE 2a is an isometric, schematic view of a front axle assembly for a vehicle of the type shown in Figure 1 ;

FIGURE 3 is a side view of the radius arm and the adjacent frame beam, which form a part of the suspension system of the invention;

FIGURE 4 is an isometric, exploded view of the steering spindle assembly located at each end of the front axle assembly;

FIGURE 5 is a view seen from the plane of a transverse cross-section showing a torque rod for transferring transverse forces from the suspension system to the vehicle frame; FIGURE 6 is a partial plan view of the axle assembly and steering gear arrangement for the improved suspension system of the invention;

FIGURE 7 is a partial assembly view showing a radius arm and an air spring between the frame beam and the radius arm;

FIGURE 8 is an overall assembly view of the front axle as seen from a plane perpendicular to the centerline of the vehicle;

FIGURES 9 and 9a are detailed views of the radius arms, Figure 9a being a plan view and Figure 9 being a side view;

FIGURE 10 is an overall assembly view of a suspension system of the assembly including a schematic representation of a steering linkage mechanism for transferring steering torque to the torque input element of the steering gear assembly;

FIGURES 11a and l ib show universal joint coupling yokes used in the steering gear linkage associated with the suspension system of the invention;

FIGURE l ie shows a universal joint coupling spider member or journal; and

FIGURE l id shows a universal joint coupling support bearing assembly, which secures the universal joint coupling to the vehicle frame.

BEST MODE FOR CARRYING OUT THE INVENTION

In Figure 1. a bus body and chassis 10 is supported on a frame shown partly at 12 at the front of the bus. Rearward road wheels 14 are supported on a suspension system that is independent of the suspension system for the front steerable road wheels 17. The suspension system for the forward frame 12, generally identified by reference numeral 16, includes a radius arm 18, which is pivoted at the forward end to the vehicle frame 12. An air spring assembly 20 is situated between the rearward end of the radius arm 18 and the vehicle frame 12. A preferred embodiment of the invention has a radius arm made of a forged, high-strength alloy steel.

Figures 2 and 2a show a front axle assembly 22, which is joined to radius arm 18 at an intermediate location by means of U-bolts 24 and 26, as will be described subsequently. A radius arm also is located on the opposite side of the axle assembly, as seen at 28. It is secured to the opposite end of the axle assembly by U- bolts 30 and 32.

The radius arm 18 has a pivotal attachment in the form of a bar pin 36, which forms a part of an eye bracket structure that is secured to frame member 38 by clamping bolts 40. A similar bar pin type eye bracket structure 42 secures the forward end of the radius arm 28 to the frame 38.

A steering spindle assembly 44 is secured to the left end of the axle assembly 22, and a corresponding steering spindle assembly 46 is secured to the right end of the axle assembly 22. A tie rod arm 48 forms a pan of the steering spindle assembly 44, and a corresponding tie rod arm 50 forms a part of the steering spindle assembly 46. The ends of the tie rod arms 48 and 50 are joined together by a transversely extending tie rod 52.

The outboard end of each spindle assembly is adapted to be received in a wheel hub that can be bolted by wheel bolts to a steering knuckle flange 54. A steering knuckle flange 56 forms a part of the spindle shaft assembly 46.

Air or gas spring assembly 20 is situated at the rearward end of radius arm 18, and a corresponding assembly 60 is located at the rearward end of the radius arm 28. The spring assemblies 20 and 60 are secured to their respective radius arms by a threaded connection that can be seen best in Figure 7, as will be described subsequently.

A torque rod, shown at 62 in Figure 2. is secured at one end thereof to frame member 64. A reinforcing plate 66 is joined to the rearward end of radius arm 28 by bolts or other suitable fasteners shown at 68. The opposite end of the reinforcing plate 66 is connected to the rearward end of the other radius arm 18. The torque rod 62 is connected to the plate 66, thereby joining the ends of each radius arm to the frame 64. Transverse loads on the radius arms then are transferred directly to the frame through the rod 62.

The center region of the axle assembly 22 has secured thereto a bracket plate 70, which supports a steering gear mechanism as will be described subsequently with respect to Figure 10. The steering gear mechanism is not included in the assembly view of Figure 2. Such steering gear mechanisms for heavy vehicles are well know. An example of a mechanism of this type is the steering gear manufactured by the R.H. Sheppard Company (M-Series).

Figure 2a is an isometric view of the axle assembly 22. A friction brake and wheel hub assembly 68 is located at the right end of the axle assembly 22, and a corresponding brake and wheel hub assembly 68' is located at the left end of the axle assembly 22. A drum brake is shown, but a disc brake may also be used.

The steering spindle assembly 44 comprises a spindle shaft 72, as seen in Figure 4. It includes a steering knuckle 74, which has spaced openings that receive king pin 76. King pin bushing 78 and corresponding king pin bushing 78' provide end supports for the king pin 76.

Tie rod arm 48 connects steering knuckle 74 to one end of the tie rod, which transfers steering motion to the opposite steering spindle assembly.

Steering arm 80 also is connected to the steering knuckle 74. It provides a connection between the steering knuckle and one end of a drag link 82, seen in Figure 6. The opposite end of the drag link 82 is connected to one end of the pitman arm 84. The other end of the pitman arm is connected to the steering torque output element of a power steering gear, generally indicated at 86.

As previously mentioned, the steering gear 86 is supported on a bracket 70 and connected directly to the center of the front axle assembly 22, as seen in Figure 6. The front axle assembly has a platform portion located in a generally horizontal plane, which is welded or otherwise secured to a plate 92 secured to the top of the front axle assembly 22 by bolts 94 or by other suitable fastener means.

The torque input element of the steering gear 86 is shown in Figure 6 at 96. It is connected to the torque output end of a miter gear box 98, which includes a right angle bevel gear drive indicated schematically at 100 in Figure 6. The torque input side of the miter gear box 98 comprises a shaft schematically indicated in Figure 6 at 102. The shaft 102 will be described with reference to Figures 11a, l ib, lie and l id.

One end of the shaft schematically shown at 102 is connected to a torque transmitting shaft, schematically indicated in Figure 10 at 104, by means of a universal joint connection indicated schematically in Figure 10 at 106. The opposite end of the shaft 104 is connected to a miter gear box schematically shown in Figure 10 at 108. The torque input end of the miter gear box 108 is connected by shaft 110 to the torque output end of a third miter gear box 112. The torque input side of the miter gear box 112 is connected directly through a spline joint or by other positive drive elements to a steering shaft 114, which is under the steering control of a vehicle operator by means of a steering wheel 116.

The miter gear boxes 108 and 112 may be similar in design to the miter gear box 98 of Figure 6. That is, each comprises meshing right angle bevel gears as shown at 100 in Figure 6. The miter gear boxes 108 and 112 are secured in a fixed manner to the vehicle frame, but miter box 98 is connected to steering gear

86.

The connection between shaft 104 and shaft 102 includes a universal joint having elements indicated in Figures 11a, lib, l ie and lid. These include a first yoke 118 and a companion yoke 120, as seen respectively in Figures 11a and 1 lb. The arms of the yoke 118 are journalled on spider member 122, seen in Figure l ie. Bearing members 124 and 126 are provided for this purpose. The arms of yoke 120 similarly are journalled on the spider member 122 by bearing members 128 and 130. A support bearing assembly 134, as seen in Figure l id, includes a bearing opening that receives the shaft 104. Assembly 134 provides rotary support for shaft 104. The support bearing assembly 134 is secured to a portion of the vehicle frame indicated schematically at 136. The end of shaft 102 may have an internal spline that slidably registers with the external spline of the yoke 120.

Seen in Figures 5 and 10 is a frame member 136, which extends longitudinally with respect to the centerline of the vehicle in parallel relationship with respect to the frame member 12. The reinforcing plate 66, seen in Figure 5, carries eyelet bracket 138 to which the arm 62 is pinned, as shown at 140.

Shown in Figure 9 is an eyelet 140 at one end of radius arm 18.

Figures 9a and 3 show a bar pin received in spaced arms of a support eye bracket 144 secured to frame cross-member 146 which forms a part of frame or frame beam 12. The bracket 144 is threadably connected to the frame cross-member 146 by clamping bolts 148.

According to a feature of the invention, one or more spacer shims

145, seen in Figure 3, can be placed between the frame cross-member 146 and the bracket 144 to provide alignment of the front axle assembly with respect to the frame. This feature is of importance for adjustment of the front axle assembly if the frame members at the lateral sides of the vehicle should become misaligned or displaced, one with respect to the other.

Figure 3 shows a bumper assembly 150. This comprises a rubber bumper 152 carried by a metal clamp member 154. The clamp member 154 is secured to a companion clamp member 156 on the underside of the radius arm 18. A threaded U-bolt 158 surrounds the clamp member 154 and clamps the member 156 securely in place. A second threaded U-bolt 160 clamps the opposite side of the clamping member 156 to the clamping member 154.

A shock absorber mounting bracket 162 is secured to the intermediate poπion of each of the radius arms 18 and 28 by means of U-bolts 160. One end of a shock absorber 164 is pinned or otherwise secured to eyelet openings at one end of the bracket 162, as seen at 166. The opposite end of the shock absorber 164 is pinned or otherwise connected to bracket 168, as shown at 170. As the radius arm 18 oscillates about the pivotal connection 142, the shock absorber 164 will accommodate controlled, damped, pivotal motion of the radius arm 18. The bumper 152 may be formed of a rubber-like, elastomeric material, for example, so that it may engage the lower surface of the frame 12 to limit the pivotal motion of the radius arm.

Figure 7 shows in schematic form a gas or air spring assembly 20, which is seen also in Figure 1. The spring assembly 20 comprises pneumatic chambers defined by flexible, rubber-like material, as shown at 172. Preferably, each spring assembly has two pneumatic chambers consisting of collapsible rubber that are separated by a steel separator plate 174. The bottom of the spring assembly 20 is connected by a threaded fastener 176 to the free end of the radius arm 18. The upper end of the spring assembly 20 of Figure 7 is secured in a suitable fashion, such as by bolts 178, to the lower surface of the frame beam 12.

The frame beam 12 is connected to a cross-member 180, seen in Figure 7, which corresponds to the frame cross-member 146 described previously.

One of the features of the invention, as mentioned previously, is the ability of the steering gear to rise and fall with the axle assembly 22 when the front road wheels 17, which are the steerable wheels, rise and fall relative to the vehicle frame.

During instances in which the front axle rises or falls relative to the frame, the distance between the end of the pivot arm 84 and the end of the steering arm 80 will remain constant. This is due to the fact that the steering gear itself travels with the front axle assembly. This eliminates the so-called bump-steer torque normally associated with axles of this kind.

When the front axle assembly rises and falls relative to the frame, the distance between miter gear box 98, seen in Figure 6, and the universal joint connection at 106 in Figure 10 will change. That change in distance is accommodated by slipping at the spline connection between shaft 102, seen in Figure 6, and the universal joint yoke 120, seen in Figure l ib.

Claims

WHAT IS CLAIMED IS:

1. A suspension system for a wheeled vehicle comprising a structural frame member, steerable front wheels, a front wheel axle assembly including a wheel spindle assembly rotatably supporting each front wheel; a vehicle frame at the forward end of the vehicle; radius arms pivotally connected to the frame at a forward ends of the radius arms; a spring located between the frame and each radius arm at a rearward end thereof whereby vertical loads are transmitted between the frame and each radius arm; said front wheel axle assembly being connected to the radius arms at a location between the spring and the forward ends of the radius arms; a steering gear assembly including a steering torque output member connected to one of the spindle assemblies and a steering torque input member connected to a driver-operated shaft; said steering gear assembly being connected to and supported by the front wheel axle assembly whereby vertical displacement of a front wheel of the vehicle effects a vertical displacement of the steering gear assembly thereby eliminating development of unwanted steering torque at the wheel spindle as a radius arm is displaced relative to the frame.

2. The suspension system set forth in claim 1 wherein said spring is a gas spring with at least one compressible, pneumatic gas chamber whereby pneumatic forces support the vertical load on the vehicle frame.

3. The suspension system set forth in clam 1 wherein the pivotal connections between the frame and the radius arms each comprises an eye member at the forward end of each radius arm; an eye bracket connected to the frame, said eye bracket having pin openings, a pivot pin extending through the eye member and the eye bracket openings thereby providing a pivot joint for a radius arm; and means for adjusting the distance between the eye bracket and the frame thereby providing an adjustment of the axle assembly relative to the frame.

4. The suspension system set forth in claim 3 wherein the adjusting means comprises at least one shim of selected thickness between the eye bracket and the frame.

5. The suspension system set forth in claim 1 including a shock absorber assembly between each radius arm and the frame whereby vertical displacement of each radius arm relative to the frame is dampened.

6. The suspension system set forth in claim 1 wherein the steering gear assembly comprises a pitman arm connected at one end to the steering torque output member for oscillatory movement thereof; the wheel spindle assembly including a steering arm extending from a spindle steering axis; a drag link connecting the other end of the pitman arm to the steering arm; each wheel spindle assembly having a tie rod arm extending from the spindle steering axis; and a steering tie rod connecting together the tie rod arms whereby steering torque output of the steering gear assembly is transmitted to each wheel spindle assembly.

7. The suspension system set forth in claim 1 including a torque rod extending generally transversely relative to the frame, said torque rod being connected at one end thereof to the frame and being connected at the other end thereof to one of the radius arms, whereby transverse forces acting on the radius arms and on the front axle assembly are transferred to the frame.

8. The suspension system set forth in claim 1 wherein a radius arm is located on each lateral side of the vehicle frame, at least one structural cross- member being connected to the radius arms to define a unitary radius arm assembly that carries the front wheel axle assembly.

9. The suspension system set forth in claim 1 wherein the connection of the driver-operated steering shaft to the steering torque input member of the steering gear assembly includes a slip-spline assembly having an internally splined steering torque shaft and an externally splined steering torque shaft, one of said splined steering torque shafts being fixed against movement in the direction of steering torque distribution to said steering gear assembly and the other splined steering torque shaft being movable with said steering gear assembly when said axle assembly rises and falls relative to the said vehicle frame.

10. The suspension system set forth in claim 9 wherein the slip- spline assembly comprises a universal joint connection between the steering torque input member of the steering gear assembly and the driver-operated steering shaft whereby the steering torque input member and the driver-operated steering shaft may be angularly disposed, one with respect to the other.

AMENDED CLAIMS

[received by the International Bureau on 31 July 2001 (31.07.01); original claims 1,3 and 6-10 amended ; remaining claims unchanged (3 pages)] 1. A trailing link suspension system for a wheeled vehicle comprising a vehicle frame, steerable front wheels, a front wheel axle assembly including a steering spindle assembly rotatably supporting each front wheel; a vehicle frame having a frame portion at the forward end of the vehicle; radius arms pivotally connected to the frame portion at forward ends of the radius arms; a spring located between the frame portion and each radius arm at a rearward end thereof whereby vertical loads are transmitted between the frame portion and each radius arm; said front wheel axle assembly being connected to the radius arms at a location between the springs and the forward ends of the radius arms; a steering gear mechanism including a steering torque output member connected to one of the spindle assemblies and a steering torque input member connected to a driver-operated shaft; said steering gear mechanism being connected to and supported by the front wheel axle assembly whereby vertical displacement of a front wheel of the vehicle effects a vertical displacement of the steering gear assembly thereby elirninating development of unwanted steering torque at the steering spindle assemblies as a radius arm is displaced relative to the frame.

3. The suspension system set forth in claim 1 wherein the pivotal connections between the frame and the radius arms each comprises an eye bracket at the forward end of each radius arm; each eye bracket having pin openings, a pivot pin extending through each eye bracket openings thereby providing a pivot point for each radius arm; and means for adjusting the distance between an eye bracket and the frame thereby providing an adjustment of the axle assembly relative to the frame.

6. The suspension system set forth in claim 1 wherein the steering gear assembly comprises a pitman arm connected at one end to the steering torque output member for oscillatory movement thereof; one steering spindle assembly including a steering arm extending from a spindle steering axis; a drag link connecting the other end of the pitman arm to the steering arm; each steering spindle assembly having a tie rod arm extending from a spindle steering axis; and a steering tie rod connecting together the tie rod arms whereby steering torque output of the steering gear assembly is transmitted to each steering spindle assembly.

7. The suspension system set forth in claim 1 including a torque rod extending generally transversely relative to the frame, said torque rod being connected at one end thereof to the frame and being connected at the other end thereof to one of the radius arms, and a reinforcing plate connecting together rearward ends of the radius arms whereby transverse forces acting on the radius arms and on the front axle assembly are transferred to the frame.

8. The suspension system set forth in claim 7 wherein a radius arm is located on each lateral side of the vehicle frame, at least one frame cross- member of the frame being connected to the radius arms to define a unitary radius arm assembly, the unitary radius arm assembly carrying the front wheel axle assembly.

9. The suspension system set forth in claim 1 wherein the connection of the driver-operated steering shaft to the steering torque input member of the steering gear mechanism includes a slip-spline assembly having an internally splined steering torque shaft and an externally splined steering torque shaft, one of said splined steering torque shafts being fixed against movement in the direction of steering torque distribution to said steering gear mechanism and the other splined steering torque shaft being movable with said steering gear mechanism when said axle assembly rises and falls relative to the said vehicle frame.

10. The suspension system set forth in claim 9 wherein the slip- spline assembly comprises in part a universal joint connection between the steering torque input member of the steering gear mechanism and the driver-operated steering shaft whereby the steering torque input member and the driver-operated steering shaft may be angularly disposed, one with respect to the other.