Suspension device

1. A suspension device comprising:

a damper that has a cylinder and a piston, the piston being inserted into the cylinder to be free to move and defines an extension-side chamber and a contraction-side chamber within the cylinder;

a pump;

a reservoir connected to an intake side of the pump;

a supply passage connected to a discharge side of the pump;

a discharge passage connected to the reservoir;

an extension-side passage connected to the extension-side chamber;

a contraction-side passage connected to the contraction-side chamber;

a switching device that connects one of the extension-side passage and the contraction-side passage to the supply passage and connecting the other of the extension-side passage and the contraction-side passage to the discharge passage selectively;

an extension-side damping element provided in the extension-side passage to apply resistance to a flow traveling from the extension-side chamber toward the switching device and permit a flow traveling in an opposite direction;

a contraction-side damping element provided in the contraction-side passage to apply resistance to a flow traveling from the contraction-side chamber toward the switching device and permit a flow traveling in an opposite direction;

a control valve capable of adjusting a pressure in the supply passage in accordance with a supplied current;

an intake passage that connects the supply passage to the discharge passage;

an intake check valve provided midway in the intake passage in order to permit only a flow of fluid traveling from the discharge passage toward the supply passage; and

a supply-side check valve provided in the supply passage between the control valve and the pump in order to permit only a flow traveling from the pump side toward the control valve side.

2. A suspension device comprising:

a plurality of dampers, each having a cylinder and a piston, the piston being inserted into the cylinder to be free to move and defines an extension-side chamber and a contraction-side chamber within the cylinder;

a pump;

a reservoir connected to an intake side of the pump;

a plurality of fluid pressure circuits provided respectively for the dampers; and

a flow dividing valve that distributes fluid discharged from the pump to the respective fluid pressure circuits,

each fluid pressure circuit comprising:

a supply passage connected to a discharge side of the pump via the flow dividing valve;

a discharge passage connected to the reservoir;

an extension-side passage connected to the extension-side chamber;

a contraction-side passage connected to the contraction-side chamber;

a switching device that connects one of the extension-side passage and the contraction-side passage to the supply passage and connecting the other of the extension-side passage and the contraction-side passage to the discharge passage selectively;

an extension-side damping element provided in the extension-side passage to apply resistance to a flow traveling from the extension-side chamber toward the switching device and permit a flow traveling in an opposite direction;

a contraction-side damping element provided in the contraction-side passage to apply resistance to a flow traveling from the contraction-side chamber toward the switching device and permit a flow traveling in an opposite direction;

a control valve capable of adjusting a pressure in the supply passage in accordance with a supplied current;

an intake passage that connects the supply passage to the discharge passage;

an intake check valve provided midway in the intake passage in order to permit only a flow of fluid traveling from the discharge passage toward the supply passage; and

a supply-side check valve provided in the supply passage between the control valve and the pump in order to permit only a flow traveling from the pump side toward the control valve side.

3. The suspension device as defined in claim 1 , wherein

the control valve has a pressure non override property for a flow amount.

4. The suspension device as defined in claim 1 , wherein

the extension-side damping element comprises:

an extension-side damping valve that applies resistance to a flow traveling from the extension-side chamber toward the switching device; and

an extension-side check valve provided parallel to the extension-side damping valve in order to permit only a flow traveling from the switching device toward the extension-side chamber, and

the contraction-side damping element comprises:

a contraction-side damping valve that applies resistance to a flow traveling from the contraction-side chamber toward the switching device; and

a contraction-side check valve provided parallel to the contraction-side damping valve in order to permit only a flow traveling from the switching device toward the contraction-side chamber.

5. The suspension device as defined in claim 4 , wherein the extension-side damping element comprises:

an extension-side bypass passage provided parallel to the extension-side damping valve; and

a second extension-side damping valve and an extension-side open/close valve provided in the extension-side bypass passage, and

the extension-side open/close valve closes the extension-side bypass passage when a pressure in the supply passage is lower than a predetermined value, and opens the extension-side bypass passage when the pressure in the supply passage equals or exceeds the predetermined value.

6. The suspension device as defined in claim 4 , wherein the contraction-side damping element comprises:

a contraction-side bypass passage provided parallel to the contraction-side damping valve; and

a second contraction-side damping valve and a contraction-side open/close valve provided in the contraction-side bypass passage, and

the contraction-side open/close valve closes the contraction-side bypass passage when a pressure in the supply passage is lower than a predetermined value, and opens the contraction-side bypass passage when the pressure in the supply passage equals or exceeds the predetermined value.

7. The suspension device defined in claim 1 , wherein the switching device is a direction switching valve,

the direction switching valve includes:

an extension-side supply position in which the supply passage is connected to the extension-side passage and the discharge passage is connected to the contraction-side passage;

a contraction-side supply position in which the supply passage is connected to the contraction-side passage and the discharge passage is connected to the extension-side passage; and

a communication position in which the supply passage, the discharge passage, the extension-side passage, and the contraction-side passage all communicate with each other.

8. The suspension device defined in claim 1 , wherein

the control valve is a solenoid throttle valve controlled on the basis of a pressure in the supply passage, which is detected by a pressure sensor.

9. The suspension device defined in claim 1 , wherein

the damper includes a rod that is inserted into the cylinder to be free to move and coupled to the piston.

10. The suspension device as defined in claim 2 , wherein

the control valve has a pressure non override property for a flow amount.

11. The suspension device as defined in claim 2 , wherein

the extension-side damping element comprises:

an extension-side damping valve that applies resistance to a flow traveling from the extension-side chamber toward the switching device; and

an extension-side check valve provided parallel to the extension-side damping valve in order to permit only a flow traveling from the switching device toward the extension-side chamber, and

the contraction-side damping element comprises:

a contraction-side damping valve that applies resistance to a flow traveling from the contraction-side chamber toward the switching device; and

a contraction-side check valve provided parallel to the contraction-side damping valve in order to permit only a flow traveling from the switching device toward the contraction-side chamber.

12. The suspension device as defined in claim 11 , wherein the extension-side damping element comprises:

an extension-side bypass passage provided parallel to the extension-side damping valve; and

a second extension-side damping valve and an extension-side open/close valve provided in the extension-side bypass passage, and

the extension-side open/close valve closes the extension-side bypass passage when a pressure in the supply passage is lower than a predetermined value, and opens the extension-side bypass passage when the pressure in the supply passage equals or exceeds the predetermined value.

13. The suspension device as defined in claim 11 , wherein the contraction-side damping element comprises:

a contraction-side bypass passage provided parallel to the contraction-side damping valve; and

a second contraction-side damping valve and a contraction-side open/close valve provided in the contraction-side bypass passage, and

the contraction-side open/close valve closes the contraction-side bypass passage when a pressure in the supply passage is lower than a predetermined value, and opens the contraction-side bypass passage when the pressure in the supply passage equals or exceeds the predetermined value.

14. The suspension device defined in claim 2 , wherein the switching device is a direction switching valve,

the direction switching valve includes:

an extension-side supply position in which the supply passage is connected to the extension-side passage and the discharge passage is connected to the contraction-side passage;

a contraction-side supply position in which the supply passage is connected to the contraction-side passage and the discharge passage is connected to the extension-side passage; and

a communication position in which the supply passage, the discharge passage, the extension-side passage, and the contraction-side passage all communicate with each other.

15. The suspension device defined in claim 2 , wherein

the control valve is a solenoid throttle valve controlled on the basis of a pressure in the supply passage, which is detected by a pressure sensor.

16. The suspension device defined in claim 2 , wherein

the damper includes a rod that is inserted into the cylinder to be free to move and coupled to the piston.