Damping force variable shock absorber

Abstract

There is provided a compact damping force variable shock absorber capable of implementing different adjustments for a compression-side stroke and an extension-side stroke as initial settings. A damping force variable device in one embodiment includes: a main valve that opens and closes to control flow of oil caused by sliding of a piston in a cylinder, thereby generating damping force; a pilot chamber into which a portion of the flow of the oil is introduced so that internal pressure is applied to the main valve in a valve-closing direction; a pilot valve that opens and closes to adjust the internal pressure of the pilot chamber; and a communication passage that communicates the pilot chamber with a rod-side oil chamber or a piston-side fluid chamber.

What is claimed is: 
     
         1 . A damping force variable shock absorber comprising:
 a cylinder in which fluid is enclosed;   a piston slidably fitted into the cylinder;   a piston rod having one end connected to the piston and the other end extended outside the cylinder;   a rod-side fluid chamber partitioned by the piston and provided closer to the other end in an axial direction of the cylinder than the piston;   a piston-side fluid chamber provided closer to one end in the axial direction of the cylinder than the piston; and   a damping force variable device that controls flow of the fluid enclosed in the cylinder so that damping force can be varied, wherein   the damping force variable device includes:
 a main valve that opens and closes to control the flow of the fluid caused by sliding of the piston in the cylinder, thereby generating damping force; 
 a pilot chamber into which a portion of the flow of the fluid is introduced so that internal pressure is applied to the main valve in a valve-closing direction; 
 a pilot valve that opens and closes to adjust the internal pressure of the pilot chamber; and 
 a communication passage that allows the pilot chamber or a passage between the pilot chamber and the pilot valve to communicate with the rod-side fluid chamber or the piston-side fluid chamber. 
   
     
     
         2 . The damping force variable shock absorber according to  claim 1 , wherein
 the communication passage allows the pilot chamber or the passage between the pilot chamber and the pilot valve to communicate with the rod-side fluid chamber.   
     
     
         3 . The damping force variable shock absorber according to  claim 1 , wherein
 the communication passage allows the pilot chamber or the passage between the pilot chamber and the pilot valve to communicate with the piston-side fluid chamber.   
     
     
         4 . The damping force variable shock absorber according to  claim 1 , further comprising:
 an outer tube provided on a vehicle body side, the other end of the piston rod being attached to the outer tube;   an inner tube as the cylinder slidably inserted in an inner circumference of the outer tube, the piston being slidably provided in an inner circumference of the inner tube;   a first bush provided on an inner circumference on an axle side of the outer tube;   a second bush provided on an outer circumference on the vehicle body side of the inner tube;   an annular fluid chamber surrounded by the outer tube, the inner tube, the first bush, and the second bush, a cross-sectional area of the piston rod being smaller than a cross-sectional area of the annular fluid chamber;   a bottomed cylindrical partition wall member, a portion of which is provided in the inner tube, the piston rod being slidably inserted in the partition wall member;   a fluid storage chamber partitioned by the partition wall member in the inner tube and formed closer to the vehicle body side than the partition wall member;   a fluid chamber partitioned by the partition wall member in the inner tube and formed closer to the axle side than the partition wall member, the rod-side fluid chamber being partitioned by the piston in the fluid chamber and formed closer to the vehicle body side than the piston, the piston-side fluid chamber partitioned by the piston in the fluid chamber and formed closer to the axle side than the piston;   a communication hole formed in the inner tube so as to allow the annular fluid chamber and the rod-side fluid chamber to communicate with each other;   a check valve provided in the partition wall member so as to allow only flow of fluid from the fluid storage chamber to the rod-side fluid chamber; and   a throttle provided in the partition wall member so as to restrict the flow of the fluid between the fluid storage chamber and the rod-side fluid chamber.   
     
     
         5 . The damping force variable shock absorber according to  claim 1 , wherein
 the damping force variable device is provided inside the piston.   
     
     
         6 . The damping force variable shock absorber according to  claim 1 , wherein
 the damping force variable device is provided outside the piston.   
     
     
         7 . The damping force variable shock absorber according to  claim 1 , wherein
 the damping force variable device further includes an actuator that generates thrust to the pilot valve in a valve-closing direction.   
     
     
         8 . The damping force variable shock absorber according to  claim 2 , wherein
 the damping force variable device is provided inside the piston.   
     
     
         9 . The damping force variable shock absorber according to  claim 2 , wherein
 the damping force variable device is provided outside the piston.   
     
     
         10 . The damping force variable shock absorber according to  claim 2 , wherein
 the damping force variable device further includes an actuator that generates thrust to the pilot valve in a valve-closing direction.   
     
     
         11 . The damping force variable shock absorber according to  claim 3 , wherein
 the damping force variable device is provided inside the piston.   
     
     
         12 . The damping force variable shock absorber according to  claim 3 , wherein
 the damping force variable device is provided outside the piston.   
     
     
         13 . The damping force variable shock absorber according to  claim 3 , wherein
 the damping force variable device further includes an actuator that generates thrust to the pilot valve in a valve-closing direction.   
     
     
         14 . The damping force variable shock absorber according to  claim 4 , wherein
 the damping force variable device is provided inside the piston.   
     
     
         15 . The damping force variable shock absorber according to  claim 4 , wherein
 the damping force variable device is provided outside the piston.   
     
     
         16 . The damping force variable shock absorber according to  claim 4 , wherein
 the damping force variable device further includes an actuator that generates thrust to the pilot valve in a valve-closing direction.