Patent Application
20120098173
The present disclosure relates to an air spring with enhanced rebound control.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The function of a vehicle suspension is to control input forces and resulting displacements to achieve desired vibration isolation, natural frequency, impact feel, or transition to suspension hard stops. Tuning of springs, dampers, jounce bumpers and rebound bumpers together are typically necessary to obtain a compromise of all performance requirements. One area of particular difficulty is the transition to suspension hard stops in extremes of jounce or rebound travel. This is referred to as “bottoming” (jounce) or “topping” (rebound). When optimizing a suspension performance, trying to maintain good vibration isolation and good entry feel to topping or bottoming bumpers normally results in a compromise for all three characteristics—overall spring rate must be increased in order to improve entry feel—but this hurts vibration isolation. The competing effects are that the low spring rate required for good vibration isolation results in high end loads in rebound or high displacements in jounce. The transition to these end conditions must be well controlled or a harsh stop at the end of wheel travel (for a passenger car suspension) will be the result. This is why suspension systems utilize highly tuned jounce bumpers and rebound bumpers.
In
Air springs are commonly used for motor vehicles, various machines, and other equipment. The air springs are designed to support a suspension load. The air springs are often combined with a separate shock absorber device in the suspension that functions to dampen oscillations. As shown in
During operation of the air spring, the flexible sleeve 100 will compress to adjust a volume of the pressurized chamber 106. To accommodate this flexing, the sleeve 100 will form lobes 112, as the sleeve is compressed, that roll along surfaces of the end members 102, 104.
It has long been a goal of air spring designers to achieve a blend of the two curves so that much less compromise was needed. In essence, the ideal air spring force deflection curve would have a low spring rate in the middle portion of the curve that transitioned to a high spring rate at the ends. Both air spring piston shaping and air sleeve shaping have been used to achieve this, but success has been very marginal and too expensive. The jounce portion of the force curve has actually been very well handled. It is the rebound portion of the force curve that presents additional challenge which needs to be addressed.
The force-deflection curve of
With the above need in mind, the present teachings provide an air spring including a piston, and a flexible sleeve connected to the spring seat. The flexible sleeve forms a compression chamber and includes a lobe that rolls along a surface of the piston during compression of the flexible sleeve. The flexible sleeve is connected to the piston by an inverted crimp connection. The inverted crimp connection between the piston and the flexible sleeve includes an end of the sleeve being folded inward so that an exterior surface of the flexible sleeve is disposed against an outer surface of the piston and a crimp ring engages an outwardly facing interior surface of the flexible sleeve to secure the flexible sleeve to the piston.
The lower crimp ring can be provided with an outwardly curved portion that serves as a rebound travel limiter that can be specifically designed to tune the rebound response of the air spring.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
Referring to
Although in the embodiments shown, the piston 14 is shown connected to the lower end of the sleeve 16, it should be understood that the piston 14 could be disposed at the upper end and the end cap 12 could be disposed at the lower end of the flexible sleeve 16.
The end cap 12 is provided with an annular outer surface 12A to which an upper end of the sleeve 16 is clamped by a clamp ring 32. The piston 14 can include a radially outer surface 14A that can have a stepped portion 34 and a radially outwardly flared portion 36 against which the lobe on the flexible sleeve rolls along during compression and extension of the air spring 10. The piston 14 also includes a cylindrical upper portion 38 which is attached to the flexible sleeve 16. In particular, the flexible sleeve 16 is connected to the piston 14 by an inverted crimp connection as best illustrated in
The crimp ring 18 can optionally be provided with a radially outwardly curved and upwardly extending portion 18A that extends from the crimp ring 18 and serves as a rebound travel limiter around which a lower lobe of the sleeve 16 is formed. The rebound travel limiter has a radius of curvature that extends axially downward from the crimp ring 18 in a direction away from the end cap 12. The rebound travel limiter 18A then curves outward and upward back toward the end cap 12. With reference to
The inverted crimp connection of the present disclosure differs from prior art designs which use a reverse fold crimp connection as illustrated in
With reference to
The air spring with a prior art reverse fold crimp will require much greater rebound travel before converting from a compressive load device to a tensile load device. The volume of the spring will also increase, resulting in the pressure decreasing and thereby no added effect. The additional travel to “unroll” the lobe can be as much as 30 millimeters. Upon rebound deflections, the spring with the inverted crimp connection, according to the principles of the present disclosure, will begin to develop a tensile load with very little, but specified, travel into rebound. The volume of the spring will also decrease with more extension keeping internal pressure constant or increasing, adding to the tensile load. Because the load does not “unroll,” tensile load can be developed as much as 30 millimeters sooner into rebound travel.
The air spring of the present disclosure provides a new way to use an air spring to achieve greater control of rebound deflection and forces in an air spring suspension. This approach can be applied to any air suspension that uses a rolling lobe air spring. Additionally, the added feature of maintaining or increasing air spring internal pressure as the spring extends will have a direct benefit to increasing air damping.
The description of the present teachings is merely exemplary in nature and, thus, variations that do not depart from the gist of the present teachings are intended to be within the scope of the present teachings. Such variations are not to be regarded as a departure from the spirit and scope of the present teachings.
