Spring devices – Vehicle – Torsion
Reexamination Certificate
2000-06-02
2002-04-02
Graham, Matthew C. (Department: 3613)
Spring devices
Vehicle
Torsion
C280S124137
Reexamination Certificate
active
06364297
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates in general to motor vehicles. More particularly, the present invention relates to an improved torsion bar and socket systems for motor vehicles. More specifically, but without restriction to the particular embodiment and/or use which is shown and described for purposes of illustration, the present invention relates to an improved torsion bar and socket system for motor vehicles that improves durability, manufacturability, and assembly of the torsion bar and socket.
2. Discussion
Every motor vehicle has a plurality of wheels that are adapted to contact a road surface. Practically every vehicle has some type of suspension system to compensate for variations in the road surface. Core to the essence of every vehicle suspension system is the spring associated with each vehicle wheel. The spring is the component that absorbs bumps and shocks while maintaining proper ride height. If the spring component is damaged or excessively worn, it affects not only ride height and shock absorption but it also detrimentally affects all of the other suspension components.
Automotive springs are generally classified in one of the following types: coil springs, air springs, leaf springs, and torsion bar springs. The spring urges a component, such as a control arm, which attaches the wheel to the frame downward. The springs are selected and set such that the weight of the vehicle determines its ride height position, a position where the spring is partially compressed by the weight of the vehicle. If the same spring is used on two separate vehicles, the lighter vehicle will have a higher ride height and the heavier vehicle would have a lower ride height. To maintain an equivalent ride height between two vehicles of varying weights, the heavier vehicle would require a stiffer (higher spring rate constant) spring that requires more force to compress. All automotive springs accommodate two types of vertical actions: jounce and rebound. Rebound occurs when the wheel of the vehicle hits a dip in the road and the wheel moves downward from its ride height position relative to the vehicle frame. This downward motion is encouraged by the spring, which wants to achieve its uncompressed state. The spring's uncompressed state is typically set beyond the full rebound position of the associated control arm. The weight of the vehicle acting against the extended spring is what returns the wheel to its ride height position. Jounce occurs when a wheel of the vehicle hits a bump and moves upward in relation to the vehicle frame. When this happens, the spring acts to push the wheel back downward towards its ride height position. The jounce condition compresses the spring from its previously described compressed ride height position. Therefore, the spring acts to move the wheel downward away from the vehicle frame.
The present invention concerns an improved torsion bar type spring and end socket for connecting the spring to the vehicle body. A torsion bar absorbs energy when rotated about its axis whereas a coil spring absorbs energy when moved in an axial direction. A conventional torsion bar is connected at a first end to the vehicle frame or other suitably fortified portion of a vehicle body. The second end of the torsion bar is typically attached to the lower control arm of the wheel support. The torsion bar is set-up to be prestressed so as the wheel moves towards its full rebound position, the torsion bar tends to unwind and become less stressed. At the vehicle ride height position, the torsion bar is partially compressed by rotation. As the lower control arm moves up such as during jounce movement, the torsion bar is twisted in a first direction tending to stress the spring because of its connection to the vehicle frame. This twisting of the spring creates a return force in a second direction, towards the full rebound position. As the lower control arm continues to an increased jounce condition, the torsion bar is twisted further in the first direction, thus producing an increasing return force in the second direction. After the jounce movement the lower control arm moves towards the rebound position, and the weight and downward inertia of the vehicle acts to partially stress the torsion bar and return the vehicle to its desireable ride height position.
A cross section of a conventional torsion bar type spring and end socket design is shown in
FIG. 2
of the present application. The torsion bar includes an elongated and generally cylindrical main shaft with hexagon shaped opposing end portions (only one is shown in FIG.
2
). Each end is inserted into a socket configured with a hexagonally shaped opening that is slightly larger than the end portion of the torsion bar. As is generally seen from
FIG. 1
, the first end portion is inserted into a first socket that is formed with the lower control arm. The second end portion is inserted into a similar second socket that is attached to the vehicle frame. Although a longitudinally extending torsion bar is shown in
FIG. 1
, it is also common to employ a laterally extending torsion bar. As the wheel and lower control arm move upward from a rebound position, the first socket imparts a twisting force on the torsion bar in a first direction. At the same time, the opposite end portion of the torsion bar is restrained from rotating by the second socket which exerts force on the frame. Because of the twisting of the torsion bar rotational energy is absorbed. As can be seen from
FIG. 2
, the end socket is required to either initiate or counteract the rotational tendencies of the torsion bar. Durability of sockets as well as the torsion bars is a concern.
The opening in the socket needs to be slightly larger than the end portion of the torsion bar, because of build variations and the fact the torsion bar must be inserted into the socket. The socket is subjected to line contact at six different locations around the opening. This line contact has a detrimental effect on the socket which might lead to deformation of the socket, and resultant loss of ride height.
Another inherent difficulty in construction of the conventional torsion bar system shown in
FIG. 2
is that the opening in the socket is constructed with very small radii in the six corners of the hexagon opening, which is very difficult and expensive to accomplish repeatedly and effectively.
Yet another difficulty with the construction of conventional torsion bar systems is an incapatibility between durability factors and installation considerations. For durability, the opening needs to be only slightly larger that the end portion of the torsion bar. For ease of installation, a larger opening is desired. This requires designers to balance these competing considerations, therefore, making it difficult to improve both the durability and installation of a torsion bar and socket system.
SUMMARY OF THE INVENTION
Accordingly, it is the principal objective of the present invention to provide a torsion bar and socket system with improved durability.
It is another objective of the present invention to provide a torsion bar and socket system that eases the installation of the torsion bar into the socket.
It is yet another objective of the present invention to provide a torsion bar and socket system that is easy to manufacture.
In one form, the present invention concerns an improved torsion bar and end socket system. The present invention works with a standard torsion bar having a hexagon shaped end portion that is adapted to be received in a socket. The socket of the present invention includes a main opening that is substantially equal in size to the hexagonal shaped end portion of the torsion bar. The socket includes six scalloped fillets or openings.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from a reading of the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.
REFEREN
DaimlerChrysler Corporation
Graham Matthew C.
Smith Robert E.
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