Spring devices – Vehicle – Comprising compressible fluid
Reexamination Certificate
1999-06-30
2001-08-07
Oberleitner, Robert J. (Department: 3613)
Spring devices
Vehicle
Comprising compressible fluid
C267S064230, C188S322190
Reexamination Certificate
active
06270064
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic shock absorber to be mounted on a suspension apparatus for a vehicle, such as an automobile.
Generally, in a suspension apparatus for a vehicle such as an automobile, a hydraulic shock absorber is provided between a sprung mass and an unsprung mass, to thereby damp vibrations of the suspension apparatus to provide good ride quality and steering stability.
In a vehicle having a relatively large loading capacity, such as a van and a station wagon, a change in vehicle height occurs due to a change in the load on the vehicle, for example, a change in the number of passengers or the number of articles carried. Such a change in vehicle height leads to a lowering of ride quality and steering stability. Therefore, it has been desired to develop a suspension apparatus having an ability to automatically maintain a predetermined vehicle height regardless of the load carried by the vehicle.
For obtaining a suspension apparatus which automatically maintains a predetermined vehicle height, for example, it has been proposed to use a so-called self-pumping type hydraulic shock absorber. Such a self-pumping type hydraulic shock absorber is disclosed in Unexamined Japanese Patent Application Public Disclosure Kokai No. 60-261713. This hydraulic shock absorber comprises: an oil tank and a reservoir each having a gas and a hydraulic fluid sealably contained therein under appropriate pressure; pumping means for supplying the hydraulic fluid in the oil tank into a cylinder in accordance with extension strokes and compression strokes of a piston rod; and return means for returning the hydraulic fluid in the pumping means and the cylinder to the oil tank depending on the position of the piston rod during the strokes. In this hydraulic shock absorber, the pumping means and the return means are operated by utilizing vibrations of the suspension apparatus during the running of the vehicle, thereby controlling the pressure in the cylinder appropriately and adjusting the degree of extension of the piston rod to a predetermined level, thus automatically maintaining a predetermined vehicle height.
In the self-pumping type hydraulic shock absorber of Kokai No. 60-261713, a double-cylinder structure is employed by providing an outer cylinder to cover an outer circumferential surface of the above-mentioned cylinder, and the oil tank and the reservoir are provided between these two cylinders. In this case, the volume of each of the oil tank and the reservoir is inevitably small and, therefore, when the load carried by the vehicle is large, the rate of increase in repulsive force of the gas during the strokes of the piston rod is large, leading to a lowering of ride quality.
For suppressing a change in repulsive force of the gas during the strokes of the piston rod to provide good ride quality, it has been desired to employ an oil tank and a reservoir each having a sufficiently large volume. An oil tank and a reservoir each having a large volume can be employed by providing the oil tank separately from the main body of the hydraulic shock absorber. However, for example, in a suspension apparatus for an automobile, the space for mounting of the hydraulic shock absorber is very limited, making it difficult to secure the space that is necessary for accomodating the separate oil tank.
The present assignee proposed, in Japanese Patent Application No. 7-331050 [corresponding to Unexamined Japanese Patent Application Public Disclosure (Kokai) No. 9-144801], a self-pumping type hydraulic shock absorber in which an annular oil tank is provided around an outer cylinder below a spring sheet which is attached to the outer cylinder to receive a suspension spring.
However, in the hydraulic shock absorber in which the oil tank is provided below the spring sheet, the length of the suspension spring is limited for securing the space for mounting of the oil tank. Further, the outer diameter of the hydraulic shock absorber around its portion to be connected to the suspension apparatus is large, so that the shape of the suspension apparatus at its portion to be connected to the hydraulic shock absorber is limited.
SUMMARY OF THE INVENTION
In view of the above situation, the present invention has been developed. It is an object of the present invention to provide a hydraulic shock absorber which enables the chambers communicated with cylinder chambers, such as a reservoir and an oil tank, to have sufficiently large volumes and which requires less space for mounting.
In the present invention, there is provided a hydraulic shock absorber comprising: a cylinder having a hydraulic fluid sealably contained therein; an outer cylinder provided so as to cover an outer circumferential surface of the cylinder; a piston slidably provided within the cylinder to divide the inside of the cylinder into two cylinder chambers; a piston rod having one end connected to the piston and the other end extending to the outside of the cylinder; and a damping force generating mechanism for generating a damping force by controlling flow of the hydraulic fluid which is generated due to a sliding motion of the piston within the cylinder. The hydraulic shock absorber is adapted to be provided so as to extend through a coil spring when used. The outer cylinder has an expanded portion formed at a portion thereof covered by the coil spring, and the expanded portion expands outwardly toward the coil spring. A first chamber is provided within the expanded portion of the outer cylinder so as to communicate with the cylinder chambers.
By this arrangement, the first cylinder chamber communicated with the cylinder chambers can be provided between the cylinder and the coil spring.
In the above-mentioned hydraulic shock absorber, a cylinder member in a generally cylindrical form may be attached to an outer circumferential surface of the outer cylinder extending through the coil spring so that the cylinder member extends from the expanded portion to a portion of the outer cylinder other than the expanded portion and a second chamber may be provided between the cylinder member and the outer cylinder so as to communicate with the cylinder chambers.
By this arrangement, the second chamber which is communicated with the cylinder chambers can be provided between the cylinder and the coil spring.
The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description and appended claims taken in connection with the accompanying drawings.
REFERENCES:
patent: 3790146 (1974-02-01), Hoffmann et al.
patent: 4226408 (1980-10-01), Tomita et al.
patent: 5107970 (1992-04-01), Driessen et al.
patent: 5115892 (1992-05-01), Yamaoka et al.
patent: 5878852 (1999-03-01), Masamura et al.
patent: 6105945 (2000-08-01), Takeuchi et al.
patent: 9-144801 (1997-06-01), None
Oberleitner Robert J.
Tokico Ltd
Torres Melanie
Wenderoth , Lind & Ponack, L.L.P.
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