Damping force control type shock absorber
A damping force control type shock absorber capable of achieving both air bleeding performance and damping force responsiveness at reduced cost. When a pilot valve ( 47 ) is closed during the extension stroke of a piston rod ( 6 ), a cylinder upper chamber ( 2 A) is communicated with a back-pressure chamber ( 46 ) through a passage ( 73 ) including an orifice ( 76 ), a communicating passage ( 70 ), a pilot chamber ( 33 ), and a communicating passage ( 50 ). At this time, the cylinder upper chamber ( 2 A) is not communicated with a cylinder lower chamber ( 2 B); therefore, damping force responsiveness is ensured. Further, because there is no need to provide a check valve in the passage, it is possible to suppress an increase in manufacturing cost. Further, air entering the pilot chamber ( 33 ) moves upward through the communicating passage ( 70 ). Therefore, the air can be discharged into the cylinder upper chamber ( 2 A) through the passage ( 73 ).
1. A damping force control type shock absorber comprising:
a cylinder having a hydraulic fluid sealed therein;
a piston slidably fitted in the cylinder to divide an interior of the cylinder into two chambers;
a piston rod connected at one end thereof to the piston and extended at an other end thereof to an outside of the cylinder; and
a damping valve mechanism provided in the cylinder to generate damping force by controlling a flow of hydraulic fluid between the two chambers in the cylinder that is caused by movement of the piston rod;
the damping valve mechanism including
a damping force generating valve that is urged in a valve closing direction by pressure in a pilot chamber, and
a control valve that discharges pressure from the pilot chamber into a downstream one of the two chambers in the cylinder;
the control valve including
a shaft portion provided therein with a communicating passage extending in an axial direction,
a movable element provided around a periphery of the shaft portion,
a solenoid that drives the movable element in the axial direction,
a valving element provided at one end of the shaft portion, and
a valve seat on which the valving element seats;
the communicating passage in the shaft portion being communicated at one end thereof with the pilot chamber and at an other end thereof with an upstream one of the two chambers in the cylinder.
2. The damping force control type shock absorber of claim 1 , wherein the other end of the communicating passage is communicated directly with the upstream one of the two chambers in the cylinder.
3. The damping force control type shock absorber of claim 1 , wherein a valving element back-pressure chamber is provided at the other end of the communicating passage in the shaft portion,
the valving element back-pressure chamber being configured such that pressure in the valving element back-pressure chamber acts on the valving element in a direction in which the valving element is urged toward the valve seat, and
when the pilot chamber and the valving element back-pressure chamber are communicated with each other through the communicating passage in the shaft portion in a state where the valving element is seated on the valve seat, a pressure-receiving area of the valving element is an area obtained by subtracting an area of the valving element back-pressure chamber from an area of a surface of the valving element on a side thereof closer to the valve seat.
4. A damping force control type shock absorber comprising:
a cylinder having a hydraulic fluid sealed therein;
a piston slidably fitted in the cylinder to divide an interior of the cylinder into two chambers;
a piston rod connected at one end thereof to the piston and extended at an other end thereof to an outside of the cylinder; and
a damping valve mechanism provided in the cylinder to generate damping force by controlling a flow of hydraulic fluid between the two chambers in the cylinder that is caused by movement of the piston rod;
the damping valve mechanism including
a damping force generating valve that is urged in a valve closing direction by pressure in a pilot chamber, and
a control valve that discharges pressure from the pilot chamber into a downstream one of the two chambers in the cylinder;
the damping valve mechanism including a passage communicating between the two chambers in the cylinder;
the passage being provided with
an orifice communicating with an upstream one of the two chambers in the cylinder,
a back-pressure chamber communicating with the passage through the orifice, and
the control valve that controls a flow of hydraulic fluid flowing from the upstream chamber to the downstream chamber through the orifice.