Patent Application
20070158925
A shock absorber assembly includes an adjustable two-piece spring seat that is used to set a spring pierce point at a desired location prior to installation in a vehicle.
Shock absorber assemblies react between a vehicle frame and vehicle wheel to reduce vibration and shock load inputs to improve ride comfort. A typical shock absorber assembly includes a cylinder that slidably receives a piston coupled to a rod. One end of the rod is mounted to the vehicle frame and the cylinder is mounted to a vehicle wheel structure. A coil spring reacts between a first spring seat on the cylinder and a second spring seat on the rod.
Side loads generated by the coil spring can cause wear and increased levels of friction between the rod and associated cylinder bearings and seals. This can lead to premature failure of the shock absorber assembly.
It is preferred to maintain a center of load, i.e. spring pierce point, to be generally concentric with the rod. However, the coil ends are typically provided with non-parallel coil end planes, which results in dynamically varying spring pierce points. The interface between the coil ends and associated spring supports can often result in non-uniform distribution of load into the spring supports. This can cause the spring pierce point to move out of a desired location, increasing stress on other shock components.
Dynamic adjustment systems have been used in an attempt to actively maintain the spring pierce point near a center of the rod during vehicle operation. These systems are often expensive and require additional components, which further increases cost. An example of one such system is found in co-pending application no. ______, which is assigned to the assignee of the present invention, and titled “Dynamic Pierce Point Centering spring Seat” and filed on even date herewith. While this system is an improvement over known dynamic systems, there is still a need for a simplified system that does not require dynamic adjustment.
Thus, there is a need for a shock absorber assembly with a simplified adjustment feature that can be used to set a spring pierce point at a desired location to reduce component wear. SUMMARY OF THE INVENTION
A shock absorber assembly includes a two-piece spring seat that allows pre-vehicle installation adjustment to achieve a desired spring pierce point location for a selected operational position. By adjusting the two-piece spring seat prior to installation, the effects of spring side load forces are significantly reduced during vehicle operation.
When the two-piece spring seat is properly positioned, the spring pierce point is maintained generally concentric with a shock absorber piston rod. The spring pierce point comprises a center of load at the spring seat, and maintaining the spring pierce point to be generally concentric with the shock absorber piston rod reduces the effects of side loads.
The subject invention provides a spring seat having a first seat portion and a second seat portion that are movable between a plurality of adjustment positions. Each adjustment position has a unique spring pierce point location. A desired spring pierce point location is selected that corresponds to one of a plurality of operational positions for the shock absorber assembly, e.g. rebound, compression, curb, etc. A shock absorber spring is coupled to one of the first and second seat portions and is moved into the selected operational position. The first and second seat portions are then adjusted to move the spring pierce point to be generally concentric with the shock absorber piston rod. The first and second seat portions are then permanently attached to each other.
In one example the first and second spring seat portions are hemispherical members with mating curved surfaces that are in sliding contact during adjustment. In another example, the first and second spring seat portions are cam surfaces are in sliding contact during adjustment. In either embodiment, once the first and second spring seat portions are in the desired adjustment position, the first and second spring seat portions are fixed to each other by welding, adhesives, fasteners, etc.
The subject invention provides a shock absorber assembly that utilizes a two-piece spring seat configuration to achieve a desired spring pierce point location for a selected shock absorber operational position. This reduces stress on other components of the shock absorber assembly over the operational life of the shock absorber assembly.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A second mount 20 is attached to the rod 18. The second mount 20 is attached to a vehicle structure 22, such as a frame or chassis member for example. The first mount 14 is attached to a wheel structure 24, such as control arm for example. A reverse orientation could also be used with the first mount 14 being attached to the vehicle structure 22 and the second mount 20 being attached to the wheel structure 24. Further, the first 14 and second 20 mounts can be pivoting mounts as shown in
A first spring seat 30 is fixed to the cylinder 12. A second spring seat 32 is fixed to the rod 18. The first spring seat 30 is preferably mounted directly to an exterior surface of the cylinder 12. The second spring seat 32 is preferably fixed to a portion of the rod 18 that extends outwardly of the cylinder 12, and which is positioned near the second mount 20.
A spring 34 reacts between the first 30 and second 32 spring seats. The spring 34 has a first coil end 36 that is associated with the first spring seat 30 and a second coil end 38 that is associated with the second spring seat 32.
At least one of the first 30 and second 32 spring seats comprises an adjustable spring seat that is formed in two (2) pieces. Optionally, both the first 30 and second 32 spring seats could be adjustable spring seats formed in two pieces. In the examples described below, the second spring seat 32 is described as being formed in two pieces. It should be understood that the first spring seat 30 could be similarly formed if needed.
The second spring seat 32 includes a first seat portion 40 and a second seat portion 42 that are initially movable relative to each other. The first 40 and second 42 seat portions are adjustable between a plurality of different positions to provide the spring 34 of the shock absorber 10 with a desired spring pierce point location 44 (see
The shock absorber 10 is moveable between a plurality of different operational positions, such as a compression position, rebound position, curb position, etc. Each of these positions has a unique spring pierce point location. Depending upon the type of vehicle and the vehicle application, a desired operational position and corresponding spring pierce point location is selected. Preferably, the operational position, which corresponds to a certain spring height, is selected that results in a side force that would potentially be most undesirable for that shock absorber application.
The first spring seat 30 is fixed to the cylinder 12, and the second spring seat 32 is fixed to the rod 18. Once the desired operational position is selected (compression, rebound, curb, etc.), the spring 34 and associated first 40 and second 42 seat portions of the first 30 and second 32 spring seats are moved into the selected operational position by positioning the rod 18 relative to the cylinder 12 in the selected position. The first 40 and second 42 seat portions then move, i.e. adjust, relative to each other such that the spring pierce point location 44 is centered near the center of the rod 18. Once this adjustment position is achieved, the first 40 and second 42 seat portions are permanently attached to each other. This allows the spring pierce point location 44 to be at an “ideal” position for the selected operational position during vehicle operation. The spring pierce point may move out of this “desired” or “ideal” position at other operational positions, however, if properly selected for the vehicle application, the spring pierce point location 44 will be maintained near the ideal location during a significant portion of vehicle operating time.
In the example shown in
Once this adjustment position is achieved the first 50 and second 54 body members are fixed together. In the example, shown in
In the example shown, the spring seat 70 is initially formed as a single piece component (see
As shown in
By reducing the effects of side loads, a smaller shock absorber can be utilized. For example, the size of the rod 18 could be reduced, the wall thickness of the cylinder could be decreased, and/or lower capacity bearings/seals could be realized. Any of these would provide reduced costs and weight of the assembly. Further, lower side loads also reduce friction between the rod and associated bearings/seals, resulting in an improved vehicle ride.
The two-piece spring seat configuration allows an operational position to be selected, which corresponds to a side force that is most undesirable for that shock absorber application. The spring is then positioned at the spring height that corresponds to this selected position. Once this height is reached, the two pieces of the spring seat are fixed to each other to prevent movement through the remainder of the stroke of the spring. This allows piston diameter to be reduced and shock body thickness to be decreased due to the reduction in side force loading at the worst-case assembly height.
The subject invention also provides a system that requires less maintenance than a dynamic, self-adjusting system. Further, less expensive materials can be used for the manufacture of the spring seat pieces because sealing joints and contact wear are not an issue. Also, this unique design improves the overall wear life of the shock absorber, reducing warranty and noise issues.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
