Spring devices – Vehicle – Comprising compressible fluid
Reexamination Certificate
1999-12-21
2001-11-27
Graham, Matthew C. (Department: 3613)
Spring devices
Vehicle
Comprising compressible fluid
C267S064260, C188S269000
Reexamination Certificate
active
06322058
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an air suspension apparatus which is advantageously used for, for example, a suspension apparatus for a vehicle.
Generally, an air suspension apparatus mainly comprises a hydraulic shock absorber for generating a damping force for damping vibration, following extension and compression strokes of a piston rod and an air spring provided on an outer circumferential side of the hydraulic shock absorber so as to define an air chamber in which compressed air is sealably contained. The air spring biases the piston rod of the hydraulic shock absorber in a direction of extension.
Further, a suspension apparatus capable of controlling a damping force in accordance with variations in vehicle weight has been known [reference is made to, for example, Unexamined Japanese Patent Application Public Disclosure (Kokai) No. 57-205208].
The air suspension apparatus of Kokai No. 57-205208 mainly comprises: a cylinder; a piston slidably provided in the cylinder so as to divide an interior of the cylinder into two oil chambers; a piston rod having a proximal end portion thereof fixed to the piston and a distal end portion thereof protruding to the outside of the cylinder, the piston rod including an axial rod insertion hole; a hydraulic fluid passage formed in the piston rod so as to enable communication between the two oil chambers in the cylinder; a shutter slidably provided at a position in the hydraulic fluid passage for varying a flow path area of the hydraulic fluid passage to adjust a damping force; an actuator provided at the protruding end portion of the piston rod so as to operate the shutter; a transmission rod axially extending in the rod insertion hole in the piston rod so as to transmit an operating force of the actuator to the shutter; and an air spring provided between the cylinder and the protruding end portion of the piston rod so as to bias the piston rod in a direction of extension, the air spring including an air chamber in which compressed air is sealably contained.
The actuator includes a movable inner wall provided therein so as to define a pressure-receiving chamber for receiving air pressure. Movement of the movable inner wall is transmitted to the transmission rod through a cam member or the like. Further, an external pipe is provided between the pressure-receiving chamber in the actuator and the air chamber in the air spring so that the pressure of air in the air chamber is introduced into the pressure-receiving chamber through the external pipe.
The pressure in the air chamber varies, depending on the load (luggage or the like) carried by a vehicle. This pressure existing in the air chamber is introduced through the external pipe into the pressure-receiving chamber in the actuator, thus displacing the movable inner wall according to a change in pressure in the pressure-receiving chamber. Movement of the movable inner wall is transmitted from the transmission rod through the cam member or the like to the shutter. Consequently, the shutter slidably moves, to thereby change the flow path area of the hydraulic fluid passage, so that a damping force is varied automatically in accordance with the weight of the vehicle.
However, in the above-mentioned air suspension apparatus, the air chamber in the air spring and the pressure-receiving chamber in the actuator communicate with each other through the external pipe. Thus, there is a possibility of the occurrence of air leakage due to connection failure or breakage of the external pipe. This leads to a lowering of durability and reliability of the air suspension apparatus.
Further, when the external pipe is used, it is necessary to provide connecting holes for use in connecting the external pipe to the air spring and the actuator. Therefore, the number of necessary parts becomes large and a cumbersome operation for piping is necessary, leading to low productivity and high cost.
SUMMARY OF THE INVENTION
In view of the above situation regarding conventional air suspension apparatuses, the present invention has been made. It is an object of the present invention to provide an air suspension apparatus which is capable of introducing air pressure in the air chamber into the actuator without the need to use an external pipe. As a result, the air suspension apparatus of the present invention has high durability and reliability, and enables a reduction in the number of necessary parts thus facilitating easy assembly.
The present invention provides an air suspension apparatus comprising a cylinder, a piston, a piston rod, a fluid passage, a damping force adjusting mechanism, an actuator, a transmission rod, and an air spring.
The piston is slidably provided in the cylinder so as to divide an interior of the cylinder into two oil chambers. The piston rod has a proximal end portion thereof fixed to the piston and a distal end portion thereof extending to an outside of the cylinder, and the piston rod includes a hollow portion. The fluid passage is provided in the piston rod so as to enable communication between the two oil chambers in the cylinder. The damping force adjusting mechanism is provided in the fluid passage so as to vary a flow path area of the fluid passage. The actuator is connected to the distal end portion of the piston rod so as to operate the damping force adjusting mechanism by application of an operating force. The transmission rod extends axially in the hollow portion of the piston rod so as to transmit the operating force of the actuator to the damping force adjusting mechanism. The air spring is provided between the cylinder and the distal end portion of the piston rod, and the air spring forms an air chamber for containing air.
A characteristic feature of the air suspension apparatus of the present invention resides in that the actuator includes a movable inner wall defining a pressure-receiving chamber for receiving an air pressure on a side of the distal end portion of the piston rod. The movable inner wall is adapted to be displaced according to the air pressure in the pressure-receiving chamber, to thereby operate the damping force adjusting mechanism through the transmission rod, and the piston rod includes an air passage for introducing the pressure of air in the air chamber to the pressure-receiving chamber in the actuator so as to displace the movable inner wall.
By this arrangement, when the pressure in the air chamber of the air spring changes in accordance with the load carried by the vehicle, this change in pressure is introduced into the pressure-receiving chamber in the actuator through the air passage in the piston rod. Consequently, the movable inner wall in the actuator is displaced in accordance with the pressure in the air chamber and the pressure-receiving chamber. An operating force from the actuator is transmitted through the transmission rod to the damping force adjusting mechanism, according to displacement of the movable inner wall. Therefore, the damping force adjusting mechanism is operated, to thereby change the flow path area of the fluid passage. Thus, the damping force is varied automatically in accordance with the weight of the vehicle.
Further, because the air passage enabling communication between the air chamber of the air spring and the pressure-receiving chamber in the actuator is formed in the piston rod, the air pressure in the air chamber can be introduced into the pressure-receiving chamber through the air passage in the piston rod. This eliminates the need to use an external pipe.
The present invention also provides an air suspension apparatus comprising an air spring including an air chamber, and which is provided between a body and an axle of a vehicle; and a hydraulic shock absorber provided adjacent to the air spring so as to damp vibration of the air spring.
The hydraulic shock absorber includes a cylinder, a piston, a piston rod, a main fluid passage, a main damping force generating device, a sub fluid passage, a sub damping force generating device, a shutter device, and an actuator device.
The piston
Amemiya Akimasa
Tanigawa Fujio
Graham Matthew C.
Nguyen Xuan Lan
Tokico Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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