US 7766349 B2
A self-steering axle suspension system utilizing a rotary damper coaxially aligned with and acting directly about the king pin centerline on one side of the vehicle is disclosed. Alternatively, the rotary damper may be mounted at, and axially aligned with, a pivot joint joining a steering knuckle with the tie rod. When used as such, the rotary damper constitutes a rotary stabilizer. The rotary stabilizer is used to control the steerability of the self-steering axle suspension system and has a self-centering axle mechanism incorporated therein.
1. A steerable vehicle axle assembly, comprising:
a vehicle axle having a first end and a second end;
a first steering knuckle mounted to said vehicle axle at said first end;
a second steering knuckle mounted to said vehicle axle at said second end;
a tie rod connected between said first steering knuckle and said second steering knuckle; and
a rotary stabilizer mounted at a pivot joint associated with said tie rod, said rotary stabilizer designed to control steerability in both steering directions.
2. The steerable vehicle axle assembly as defined by
3. The steerable vehicle axle assembly as defined by
4. The steerable vehicle axle assembly as defined by
5. The steerable vehicle axle assembly as defined by
6. The steerable vehicle axle assembly as defined by
7. The steerable vehicle axle assembly as defined by
8. The steerable vehicle axle assembly as defined by
9. The steerable vehicle axle assembly defined by
10. The steerable vehicle axle assembly as defined by
11. The steerable vehicle axle assembly as defined by
This patent application is a continuation-in-part patent application of U.S. patent application Ser. No. 12/107,493, filed Apr. 22, 2008, now abandoned which is a continuation patent application of U.S. patent application Ser. No. 11/459,212, filed Jul. 21, 2006 (now U.S. Pat. No. 7,360,773).
The present invention relates generally to stabilizers used in self-steering axle suspension systems for wheeled vehicles. More particularly, the present invention relates to a rotary damper used as a stabilizer in self-steering axle suspension systems for wheeled vehicles to suppress oscillations during travel of the vehicle and to control the steerability of the self-steering axle suspension system.
Self-steering axle suspension systems in the medium and heavy duty truck and semitrailer industry are known. Typically, such suspensions are made self-steering by adjusting the pitch or caster angle of the wheels so that the drag of the wheels as the vehicle proceeds in the forward direction causes the suspension (including the wheels of the system) to steer automatically in response to steering of the (typically front) steering axle of the vehicle and in response to steering created by other vehicle motion such as vehicle cornering (i.e., as the vehicle goes into a turn). Typical of self-steering axle suspension systems are those referred to as pusher, tag or trailing axles found on trucks and semi-trailers. They may be of the liftable or non-liftable type.
In most self-steering axle suspensions in common use, a pair of dampers is used to suppress (dampen) oscillations during automatic steering at the self-steering axle resulting from travel of the vehicle. Typically, such dampers are in the form of conventional shock absorbers either with, or without, an external auxiliary coil spring. Such devices are often referred to as stabilizers for the self-steering axle suspension systems and they control the steerability of the suspension. In such a damper, a cylinder is provided which houses a fluid reservoir that is almost completely filled with an incompressible hydraulic fluid. This cylinder is separated into two chambers by a piston having an orifice, or orifices, in its head, thus to form a flow path between the two chambers, but which otherwise seals the two chambers against fluid flow therebetween. Dampening is accomplished by attaching one end of the stabilizer (usually by a piston rod connected to the piston head) to one of the components of the steering assembly of the suspension and the other end of the stabilizer to the axle beam structure of the suspension or vehicle. Since the orifice(s) in the piston head restricts flow between the two chambers as the piston slides in the cylinder due to oscillations experienced during vehicle operation (e.g. road shocks and wheel shimmy), such oscillations are appropriately dampened and tracking is stabilized.
Linear stabilizers, such as those illustrated in
In view of the foregoing, there is a need for a relatively lightweight self-steering axle suspension system stabilizer. There is also a need for a relatively inexpensive self-steering axle suspension system stabilizer. Further, there is a need for a relatively compact self-steering axle suspension system stabilizer. Moreover, there is a need for a self-steering axle suspension system stabilizer that requires little maintenance and is relatively easy to maintain.
The present invention is directed to a self-steering axle suspension system utilizing a rotary damper acting directly about the king pin centerline on one side of the vehicle in a manner such that the rotary damper constitutes a rotary stabilizer. The rotary stabilizer is coaxially aligned with the king pin centerline. Alternatively, the rotary stabilizer may be mounted at, and coaxially aligned with, a pivot joint associated with a tie rod. The rotary stabilizer is used to control the steerability of the self-steering axle suspension system. The rotary stabilizer may also have a self-centering axle mechanism incorporated therein. The present invention is also directed to a rotary stabilizer component used in a self-steering axle suspension system.
A rotary stabilizer designed in accordance with the principles of the present invention and used in a self-steering axle suspension system is preferably relatively lightweight, translating into increased payload capacity and more readily permitting compliance with relevant bridge weight and stress laws and regulations. The stabilizer is preferably relatively inexpensive, having fewer components than conventional stabilizers used in self-steering axle suspension systems. In addition, only a single stabilizer is required for control of the steerability of the suspension system in both steering directions. The stabilizer is preferably compact, fitting tight in relation to the axle or axle beam and acting directly about the king pin centerline. The stabilizer is preferably relatively low maintenance insofar as it includes a fully-enclosed housing and it is mounted above the axle in a position where it is less likely to be subjected to road debris and the like. Maintenance of the stabilizer is also relatively easy, as it is positioned above the king pin centerline in coaxial relationship therewith and is positioned above the axle or axle beam, permitting its relatively simple installation, removal and replacement. The stabilizer preferably includes material that resists velocity motion and the accompanying oscillations that would otherwise occur during road travel of the vehicle. The stabilizer also preferably includes material that provides for self-centering of the self-steering axle suspension system.
Reference has been and will frequently be made to the following figures, in which like reference numerals refer to like components, and in which:
While suspension system 30 is described as having these additional features, it will be appreciated that the present invention applies to all self-steering axle suspension systems for wheeled vehicles.
The suspension 30 illustrated in the figures is representative of an embodiment of the steerable, wheel-bearing lift axle suspension systems disclosed in U.S. Pat. No. 5,403,031 and 5,620,194. The entire disclosure of U.S. Pat. No. 5,403,031 and the entire disclosure of U.S. Pat. No. 5,620,194 are hereby incorporated herein by reference.
With respect to suspension system 30, the majority of the components positioned on one side of the vehicle will have correspondingly similar components positioned on the other side. Accordingly, in this description, when reference is made to a particular suspension component, it will be understood that a similar component is present on the opposite side of the vehicle, unless otherwise apparent. It will be appreciated that like elements are duplicated on opposite sides of the vehicle centerline.
As shown, suspension system 30 includes a pair of longitudinally extending parallel beams 34, 36 on each side of the vehicle, preferably constructed as cast aluminum beams. Beams 34, 36 are pivotally connected at their forward ends in known manner by pivots 38, 40 to a side rail frame hanger bracket 42 which, in turn, is fastened to a longitudinal frame member 44 for the vehicle. Frame member 44 extends longitudinally and preferably has a C-shaped cross-section in conventional manner.
Parallel beams 34, 36 are also pivotally connected at their rearward ends to an axle seat 46 by pivots 48, 50. Pivot 48 preferably includes an eccentric cam 52 designed to permit adjustment of the caster angle, permitting self-steering operation of the suspension system. Adjustment of the caster angle is made by turning eccentric cam 52 the requisite amount. The adjustable caster angle is typically oriented within the range of about positive three degrees to positive six degrees from the king pin centerline.
Axle seat 46 is mounted onto a laterally extending fabricated axle 54 having a hollow axle body 56 and gooseneck portions 58 on each end of the axle body (see
Steering knuckles 70 are rotatably mounted on opposite ends of the axle 54 by king pin assemblies (not shown) in known manner. King pins are used to mount the steering knuckles to the axle at 71, as shown in
When one rotary stabilizer 78 is used (as shown), total weight and cost are minimized. When a rotary stabilizer is mounted on each side of the axle beam, size per stabilizer is minimized, translating into better packaging.
The rotary stabilizer 78 includes a housing 90. Shaft 80 is positioned within housing 90 and extends axially in relation thereto. A portion of shaft 80 extends axially out of housing 90 and is exposed from the housing, as shown. The housing is generally cylindrical and preferably forms a unitary construction with mounting base 84 of stabilizer 78. The mounting base 84 and the housing 90 are together rotatably maneuverable about the shaft 80, as further described.
As further shown, panes 96A, 96B are preferably associated with chambers 92A, 92B, respectively, and partition each such chamber into two variable volume sub-chambers. The sum of the variable volume sub-chambers for a particular chamber 92A, 92B is equal to the total volume of the chamber.
Each pane 96A, 96B preferably projects radially from the shaft 80 and preferably bisects the arc angle for its associated chamber 92A, 92B when the suspension system is in its resting (centered) position. The panes 96A, 96B may be formed with the shaft 80 as a unitary component, or alternatively may be secured to the shaft 80 by appropriate means. Pane 96A includes orifices 100 to provide for a fluid flow path during steering of the suspension system 30, which controls the steerability of the suspension system. Pane 96B may or may not include orifices, as desired.
As further shown, rotary stabilizer 78 also preferably includes resilient members 102 used for self-centering. Resilient members 102 may be formed with an elastomer-type material. For illustrative purposes, resilient members 102 are shown as being rubber cushion inserts having orifices or holes to permit their expansion and compression. However, it will be appreciated that the resilient members may take a variety of forms, such as, for example, air bladders, coil springs, etc. In the illustrative embodiment, the rubber cushion inserts 102 are positioned under compression within chamber 92B on opposite sides of pane 96B.
Referring now to
In operation, when the vehicle corners, a force is imparted upon the self-steering axle suspension system 30, causing the suspension system to steer in the appropriate direction. At this time, the steering knuckles 70 rotate about their respective king pins. At least one of the linked steering knuckles 70 carries the mounting base 84 and the housing 90 of the rotary stabilizer 78. As the housing 90 of the stabilizer 78 rotates about its shaft 80, the volumes of the variable volume sub-chambers within fluid reservoir chamber 96A vary in accordance with the steering direction and cause the viscous fluid to flow through the orifices 100 of the radially extending pane 96A, which, with shaft 80 and pane 96B, remains stationary relative to the axle. In addition, during such steering action, one of the rubber cushion inserts 102 is also further compressed when its associated radially extending wall defining one of the boundaries of chamber 92B rotates with the housing towards the pane such that the wall presses against the insert. When this happens, the insert 102 is further compressed between that wall and pane 96B and its resilient nature tends to prevent further compression. As a result, there is additional control of the steerability of the system 30 by limiting free movement of the steering knuckles.
Upon straightening of the vehicle, however, the steering force imparted on the self-steering axle suspension system 30 is reduced to such an extent that the spring back force imparted on pane 96B by the force differential between the overly compressed rubber cushion insert 102 and the expanded (less compressed) rubber cushion insert 102 on the opposite side of pane 96B will overcome such steering force and cause the rotary stabilizer 78 to return to its resting (centered) position in a controlled manner due to the viscous fluid return flow through the orifices 100 of pane 96A.
It will be appreciated by those skilled in the art that the self-steering and self-centering of the rotary stabilizer used in the above illustrated embodiment of the present invention may be tuned by varying, for example, the size of the stabilizer, the size of the chambers, the number of pane orifices, the size of the pane orifices, the material and configuration of the resilient members, and the composition of the viscous material.
In operation, when the vehicle corners, a force is imparted upon the self-steering axle suspension system, causing the suspension system to steer in the appropriate direction. At this time, the steering knuckles mounted on opposite ends of the axle rotate about their respective king pins, which in this preferred illustrated case at least one of which may be the central shaft 116, as shown. At least one of the linked steering knuckles carries the outer housing element 112 of the rotary stabilizer 110. As the outer housing element 112 rotates in relation to the inner housing element 114 and the keyed shaft 114, the viscous material 115 acts in shear to provide resistance to the rotary motion of the steering knuckle resulting in smooth motion and controlled steering of the self-steering axle suspension system.
Alternatively, any of several self-steering mechanisms may be used to cause the rotary stabilizer 110 to return to its resting (centered) position in a controlled manner, as desired. As one example, when the steering knuckle rotates about the king pin/central shaft, it may bear against a leaf spring having sufficient force to cause the steering knuckle to return to the resting position upon straightening of the vehicle.
In the illustrated preferred embodiment, a self-steering liftable vehicle axle assembly is shown as including an axle 54 that extends laterally across the vehicle. Axle 54 includes a gooseneck portion 58 at each end thereof. Steering knuckle 70 is mounted in conventional manner as described above and includes a steering arm 72, which may also be described as a tie rod arm. Tie rod 74 links steering arms/tie rod arms 72 on opposite sides of the vehicle. Each tie rod arm 72 and tie rod 74 forms a tie rod arm-tie rod pivot joint designated 275 joining steering knuckle 70 at the steering knuckle tie rod arm 72 with tie rod 74, and which joint pivots during steering of the vehicle in known manner.
Rotary stabilizer 278 is mounted at pivot joint 275 and is preferably positioned so that it is axially aligned with the pivot joint. Rotary stabilizer 278 is also attached to tie rod 74 by a bracket 279 and coupling 281 fastened to the rotary stabilizer, the tie rod and to each other in the manner shown in
It will be appreciated by those skilled in the art that while this invention has been described with reference to certain illustrative embodiments, it will be understood that this description shall not be construed in a limiting sense. Rather, various changes and modifications can be made to the described embodiments without departing from the true spirit and scope of the invention, as defined by the following claims. Furthermore, it will be appreciated that any such changes and modifications will be recognized by those skilled in the art as an equivalent to one or more elements of the following claims, and shall be covered by such claims to the fullest extent permitted by law.