Spring devices – Vehicle – Mechanical spring and nonresilient retarder
Reexamination Certificate
1999-11-15
2001-10-02
Butler, Douglas C. (Department: 3613)
Spring devices
Vehicle
Mechanical spring and nonresilient retarder
C267S140300, C267S292000, C267S153000, C267S140000
Reexamination Certificate
active
06296237
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bump stopper which is employed in a suspension system of a vehicle, for elastically limiting the amount of operation of the suspension system.
2. Related Art Statement
There is known a bump stopper which is formed of an elastic material and which is employed in, e.g., a suspension system of an automotive vehicle, for limiting elastically a stroke amount of a wheel which is elastically supported such that the wheel is movable relative to the vehicle's body, or assisting the suspension system in supporting elastically the wheel. The bump stopper is provided solely between two suspension arms, or between a suspension arm and the body, or is externally fitted on a piston rod of a shock absorber. The bump stopper is required, for the purpose of simultaneously meeting high ride quality and high stability and controllability, to have a non-linear spring characteristic wherein the stopper is soft while the amount of operation of the suspension system is small but it changes to be hard, once the operation amount exceeds a reference amount, so as to limit reliably the operation amount around the reference amount.
To this end, there has been proposed a bump stopper which includes a generally cylindrical spring member having a low spring constant and a rigid restraint ring externally fitted on, and fixed to, an outer circumferential surface of an axially intermediate portion of the spring member. The restraint ring may be formed of resin. In this bump stopper, the restraint ring prevents the spring member from elastically swelling radially outwardly. In addition, when the amount of compression of the spring member exceeds a reference mount, the restraint ring butts against another rigid member and accordingly the movement of the ring is limited by that rigid member. Consequently, the spring characteristic of the bump stopper changes to be much harder to limit effectively the amount of elastic deformation of the spring member and accordingly the amount of operation of the suspension system.
However, in the above-identified bump stopper, the elastic deformation of the spring member is locally or non-uniformly limited by the restraint ring. Therefore, when the spring member is elastically deformed and the amount of elastic deformation increases, stresses are likely to be concentrated at the position where the restraint ring is provided. Thus, the durability of the spring member is lowered.
In the case where the restraint ring frequently butts against the rigid member upon inputting of a large load to the suspension system, or in the case where the ring butts with a great force or energy against the rigid member, the durability of the ring or the rigid member is also lowered. If the restraint ring breaks, the bump stopper cannot effectively limit the amount of elastic deformation of the spring member, so that the stability and controllability of the vehicle may be significantly lowered.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a bump stopper which enjoys a high durability, exhibits a non-linear spring characteristic, and effectively and stably limits the amount of operation of a suspension system.
The present invention provides a bump stopper which has one or more of the technical features that are described below in respective paragraphs (1) to (9). Any feature which includes another feature shall do so by referring to the paragraph number given to that feature. Thus, two or more of the following features may be combined, if appropriate. Although each feature may be accompanied by a supplemental explanation where appropriate the following features and the appropriate combinations thereof are just examples to which the present invention is by no means limited.
(1) According to a first feature of the present invention, there is provided a bump stopper for elastically limiting the amount of operation of a suspension system of a vehicle. The bump stopper is provided between two suspension members of the suspension system which are moved toward, and away from, each other upon operation of the suspension system. The bump stopper comprises a rigid holding member which is attached to one of the two suspension members and which includes a hollow holding portion opening toward the other suspension member; a spring member which is formed of a foamed elastic material and which includes a base end portion held by the hollow holding portion of the holding member and also includes a free end portion projecting away from the holding portion toward the other suspension member; and a stopper rubber which projects from an end surface of the hollow holding portion of the holding member toward the other suspension member such that a free end surface of the stopper rubber is more distant from the other suspension member than a free end surface of the spring member, wherein when the other suspension member bumps against the free end surface of the spring member, the spring member is elastically deformed and compressed into an inside space of the stopper rubber, so that the other suspension member bumps against the free end surface of the stopper rubber.
The present bump stopper advantageously exhibits a non-linear spring characteristic wherein the spring characteristic remains soft while the operation amount of the suspension system is small and changes to be hard, once the operation amount exceeds a reference amount, so as to limit reliably the operation amount around the reference amount. Thus, the bump stopper functions as not only a stopper but also a shock absorber. While the load input to the suspension system remains small, the stopper rubber is not deformed by the other suspension member and only the spring member is deformed, i.e., compressed by the same. Thus, the bump stopper exhibits only the spring characteristic of the spring member. Meanwhile, once the input load exceeds a reference load, the amount of compression of the spring member exceeds a reference amount and accordingly the other suspension member bumps against the stopper rubber. Thus, both the spring member and the stopper rubber are compressed. Consequently the spring characteristic of the bump stopper changes non-linearly, i.e., changes to be much harder. Since the stopper rubber is provided on the end surface of the hollow holding portion of the rigid holding member, the bump stopper can elastically and reliably limit the amount of relative movement of the two suspension members. Since the amount of elastic deformation of the spring member is effectively limited, the spring member enjoys a high durability. In addition, since the spring member is formed of a foamed elastic material, the volume of the spring member is easily decreased when being compressed. Therefore, the spring member being compressed does not obstruct the other suspension member which is bumping against the free end surface of the stopper rubber. Since the spring member is compressed into the inside space of the stopper rubber, it does not interfere with other members.
(2) According to a second feature of the present invention that includes the first feature (1), the bump stopper further comprises a holding rubber layer which is formed on an inner surface of the hollow holding portion of the holding member and which has, on an inner surface thereof, either one of an engageable projection or an engageable recess, wherein the spring member has, on an outer surface thereof, the corresponding engageable projection or recess to engage with the projection and the recess so as to prevent the spring member from coming off the holding rubber layer.
In the present bump stopper, the spring member is fitted in the hollow holding portion of the holding member, so that the spring member is strongly held by the holding member. Since the holding rubber layer is provided on the inner surface of the hollow holding portion, the holding member may have a simple shape which can be easily produced. In addition, the holding rubber layer is easily provided
Burr & Brown
Butler Douglas C.
Tokai Rubber Industries Ltd.
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