Spring devices – Vehicle – Comprising compressible fluid
Reexamination Certificate
1998-10-09
2001-01-16
Schwartz, Christopher P. (Department: 3613)
Spring devices
Vehicle
Comprising compressible fluid
C280S124162
Reexamination Certificate
active
06173946
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a system which includes an air spring flexible member clamped between a cover plate and a rolloff piston. The rolloff piston is mounted so as to be movable relative to the cover plate of the flexible member of the air spring. The movement of the rolloff piston is predetermined through a curved path. The air spring rolls off on the rolloff piston while forming a rolling lobe during movement of the rolloff piston. The invention also relates to a rolloff piston for use in such a system.
BACKGROUND OF THE INVENTION
Modern motor vehicles already often have an air spring system which preferably is used on the rear axle because a level control is possible in a simple manner with the aid of the air spring system. The rear axle of a motor vehicle includes connecting rods having first and second ends. The connecting rods are pivotally suspended on the motor vehicle at the respective first ends thereof. The rear wheels and the rolloff pistons with the flexible members of the air springs associated therewith are arranged in the region of the respective second ends of the connecting rods. The end of the flexible member lying opposite the rolloff piston is attached to the vehicle chassis with the aid of a cover plate. During spring action, the connecting rods are pivoted about their respective suspension points on the motor vehicle so that there is a relative movement between the rear axle and the chassis of the motor vehicle. The rear axle, and therefore the rolloff pistons, move during an action of the spring along a curved path having a radius of curvature substantially pregiven by the length of the connecting rod. During the movement, the rolloff piston plunges into the flexible member assigned thereto and is then pulled out of the flexible member.
The flexible member of the air spring attempts to follow the curved path of the rolloff piston during a relative movement between the rolloff piston and the flexible member of the air spring. For this reason, a lateral offset of the flexible member of the air spring can occur relative to the cover plate with which the flexible member is attached to the chassis of the motor vehicle or a rolling lobe can form which has a non-constant width about its periphery. Stresses form within the flexible member of the air spring because of the lateral offset between the flexible member and the deck plate as well as because of the formation of a rolling lobe which has a non-constant width about its periphery. These stresses of the flexible member of the air spring shorten the service life thereof and therefore also of the air spring per se.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a system wherein the rolloff piston is moved on a curved path and wherein the service life of the flexible member of the air spring is increased. It is also an object of the invention to provide a rolloff piston which can be used in a system of this kind.
The air spring system of the invention includes: a flexible member; a cover plate; a rolloff piston; clamping means for clamping the flexible member between the cover plate and the rolloff piston; means for moving the rolloff piston relative to the plate through a pregiven curved path so as to cause the flexible member to form a rolling lobe as the flexible member rolls up and down on the rolloff piston; and, the rolloff piston being curved so as to have a curvature which has the same orientation as the curvature of the path at least over a segment thereof.
The basic idea of the invention is that the curvature of the rolloff piston is adapted to the curvature of the curved path on which the rolloff piston moves. With a suitable curvature of the rolloff piston, it can be ensured that no transverse forces act on the flexible member which could lead to an offset of the flexible member relative to the cover plate or to the formation of a rolling lobe having a non-constant width over its periphery.
The advantages achieved with the invention are especially seen in that the shearing forces which operate in the flexible member are significantly reduced. For this reason, the service life of the flexible member of the air spring is considerably increased. It is further possible to manufacture the flexible member of the air spring from materials which, because of their material properties, were up to now deemed to be unsuitable for the manufacture of a greatly loaded flexible member. These materials include, for example, tensile stiff aramide yarns (Kevlar, et cetera) which bring comfort advantages. It is also possible to utilize a flexible member of an air spring with a simple configuration which, nonetheless, has the same service life as do the flexible members in conventional systems used up to now. For example, a flexible member having a reduced number of reinforcement cords can be utilized. This flexible member is correspondingly simple and can therefore be manufactured cost effectively.
A further advantage of the invention is seen in that, with the curvature of the piston, a targeted inclined position of the pressure effective surface (that is, the rolling lobe of the flexible member) can be obtained. With the aid of the targeted inclined position, other forces within the air spring module can be countered, for example, a compensation of transverse forces can be achieved.
According to a first embodiment of the invention, the center curvature line of the curvature of the rolloff piston has, at least segmentwise, the same radius of curvature as the curved path. Preferably, the center curvature line of the curvature of the rolloff piston corresponds to the curvature radius of the curved path of the rolloff piston in the region of the entire rolloff piston.
According to another feature of the invention, the curved path has a specific curvature in the start region. The end of the rolloff piston facing toward the cover plate has a curvature which is significantly less than the curvature at the start of the curved path, that is, a curvature which is opposite to the curvature at the start of the curved path. The end of the rolloff piston, which faces toward the cover plate, plunges the deepest into the flexible member of the air spring. For a curved path on which the rolloff piston is moved, this end of the rolloff piston therefore moves toward the wall of the flexible member and can possibly destroy the flexible member when coming into contact therewith. With the further embodiment, it is achieved that the end of the rolloff piston, which is assigned to the cover plate, touches the flexible member significantly later so that the rolloff piston can plunge deeper into the flexible member and therefore achieves the advantage of a free movement.
REFERENCES:
patent: 4386791 (1983-06-01), Watanabe
patent: 4817922 (1989-04-01), Hovance
patent: 4854557 (1989-08-01), Goshima et al.
patent: 1048165 (1958-12-01), None
Jeischik Joachim
Kirsten Bernhard
Thurow Gerhard
Wode Stefan
Continental Aktiengesellschaft
Nguyen Xuan Lan
Ottesen Walter
Schwartz Christopher P.
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