Brakes – Internal-resistance motion retarder – Resistance alters relative to direction of thrust member
Reexamination Certificate
1999-12-13
2001-09-25
Butler, Douglas C. (Department: 3613)
Brakes
Internal-resistance motion retarder
Resistance alters relative to direction of thrust member
C188S266500, C188S299100, C188S319100
Reexamination Certificate
active
06293377
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. HEI 10-358254 filed on Dec. 16, 1998, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shock absorber that creates a damping force for restraining vibratory motions of an object that is elastically supported by a supporting member, for example, a vehicle body. More particularly, the invention relates to a variable-damping force shock absorber in which the damping force can be changed.
2. Description of the Related Art
A conventional shock absorber apparatus is formed by various components as follows. A cylinder containing operating fluid is divided into first and second chambers by a piston disposed in the cylinder slidably in directions of an axis thereof. A hollow piston rod is connected at an end portion thereof to the piston. Another end portion of the hollow piston rod protrudes from an end face of the cylinder. A spool of a valve mechanism is provided at a piston-side end portion of the piston rod in such a manner that the spool is displaceable in directions of an piston rod axis. In accordance with the displacement of the spool in a direction of the piston rod axis, the valve mechanism changes the opening of a communication passage interconnecting the first and second chambers. An actuator is substantially made up of a stator mounted to an inner peripheral surface of the piston rod, a rotor disposed facing the stator so as to rotate about the piston rod axis relative to the stator, and a rotating body supported on an inner peripheral surface of the piston rod for rotation about the piston rod axis. The rotating body is fixed to the rotor so that the rotating body rotates together with the rotor. The actuator outputs rotating drive force created by rotation of the rotor via the rotating body. The shock absorber apparatus further includes a drive force converting mechanism that converts rotating drive force from the actuator into drive force in a direction of the piston rod axis. Furthermore, the drive force converting mechanism transfers the converted drive force to the spool of the valve mechanism so as to displace the spool in a direction of the piston rod axis. In the conventional shock absorber apparatus, the rotor of the actuator and the drive force converting mechanism are disposed overlapping each other in a direction of a radius of the piston rod, as disclosed in, for example, Japanese Patent Application Laid-Open No. HEI 5-60165.
However, since the rotor of the actuator and the drive force converting mechanism are disposed overlapping each other in a radial direction with respect to the piston rod, this conventional shock absorber apparatus has a problem of an increased diameter of the piston rod.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a variabledamping force shock absorber in which a piston rod has a reduced diameter.
In accordance with the invention, a rotor of an actuator and a drive force converting mechanism are arranged at different positions in a direction of an axis of a piston rod. Therefore, it becomes possible to arrange the rotor of the actuator and the drive force converting mechanism so that they do not overlap each other in a direction of a radius of the piston rod. As a result, the piston rod is allowed to have a reduced diameter.
In the above-described variable-damping force shock absorber, the drive force converting mechanism may include a shaft disposed in the piston rod in such a manner that the shaft is allowed to move in the direction of the piston rod axis and is prevented from turning about the axis, the shaft being connected at an end of the shaft to the spool, and a screw mechanism having a screw portion formed in another end portion of the shaft and another screw portion formed in the rotating body of the actuator which screw portions are engaged with each other, the screw mechanism displacing the shaft in the direction of the piston rod axis as the rotating body rotates. Therefore, the drive force converting mechanism does not require a complicated construction in order to convert the rotating drive force from the actuator into a drive force in a direction of the piston rod axis and to transfer the drive force to the spool of the valve mechanism and thereby displace the spool in the direction of the piston rod axis.
The variable-damping force shock absorber may further have a construction as follows. That is, the rotating body of the actuator may be cylindrically shaped and disposed coaxially with the piston rod with the rotor embedded in a side face of the rotating body, and with an insert hole into which an end portion of the shaft is inserted formed in an end face of the rotating body. Furthermore, the screw mechanism may include a female thread formed in the insert hole of the rotating body and a male thread formed on an outer peripheral face of the end portion of the shaft. This construction makes it possible to form the rotor and the rotating body of the actuator and the female thread of the drive force converting, mechanism into an integral cylindrical shape, thereby facilitating accommodation or containment of these members into the piston rod.
The variable-damping force shock absorber may further have a construction as follows. The rotating body of the actuator may have a bypass passage connected between an outside of the rotating body and a bottom portion of the insert hole. At least one of the first and second chambers of the cylinder may be connected to the insert hole of the rotating body in communication via an outer peripheral face of the shaft, an outer peripheral face of the rotating body and the bypass passage. Therefore, volume changes of the operating fluid in the insert hole are allowed by the operating fluid flowing into or out of the insert hole through the bypass passage. Consequently, the shaft can be displaced within the insert hole in the directions of the piston rod axis without a need to form a special bleed channel or hole in the shaft. Since the rotating body of the actuator, in comparison with the shaft, is not required to have a considerable strength, the rotating body can easily be forraed. Therefore, it becomes possible to produce the variable-damping force shock absorber at a low cost.
Furthermore, the rotating body may have, in a side face of the rotating body, a groove extending in a direction of an axis of the rotating body. The groove guides the operating fluid from the vicinity of the outer peripheral surface of the shaft to the bypass passage. Therefore, it becomes unnecessary to arrange a special space around the outer peripheral surface of the rotating body for passing the operating oil. As a result, the piston rod can have a reduced diameter.
The variable-damping force shock absorber may further include a bottomed hollow-cylindrical support member fixed to the inner peripheral face of the piston rod coaxially with the piston rod, the support member accommodating therein the rotating body of the actuator, and an annular fixed bearing fixed, on an inner peripheral face of the fixed bearing, to the rotating body at a side of an open end of the support member. The outer peripheral face of the fixed bearing is positioned and fixed to an open end portion of the support member in the direction of the axis. In this construction, the rotating body is inserted into the support member from the open end of the support member. The fixed bearing is fixed in position relative to the support member in directions of an axis of the support member. As a result, the rotating body is positioned relative to the piston rod in the directions of the axis, and the rotating body is supported within the piston rod in such a manner that the rotating body is rotatable about the piston rod axis. Therefore, the rotating body can easily be mounted. Furthermore, in this construction, the fixed bearing is positioned and fixed to the support member in the d
Kamimura Ichisei
Kono Kiyoshi
Okada Yoshimasa
Butler Douglas C.
Kenyon & Kenyon
King Bradley
Toyota Jidosha & Kabushiki Kaisha
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