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Abstract

To provide a damper that is not only capable to expanding and retracting to exert a damping force, but also capable of maintaining a constant vehicle height in a locked state in which the damper is unable to expand and retract.SOLUTION: A damper D comprises: a cylinder 1; a piston 2 inserted in the cylinder 1 to divide the inside of the cylinder 1 into an extension-side chamber R1, in which a liquid is filled, and a pressure-side chamber R2; a piston rod 3 that is inserted into the extension-side chamber R1 of the cylinder 1 and connected to the piston 2; a damping passage 4 that provides communication between the extension-side chamber R1 and the pressure-side chamber R2 and applies resistance to a flow of the liquid passing therethrough; a reservoir 5 that stores the liquid, is connected to the inside of the cylinder 1, and compensates for a change of a displacement volume of the piston rod 3 in the cylinder 1; and an opening / closing valve 7 that is provided in a compensation passage 6 providing communication between the inside of the cylinder 1 and the reservoir 5 to open and close the compensation passage 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shock absorber. [Background technology]

[0002] A shock absorber is used, for example, by being interposed between the body and wheels of a vehicle, and expands and contracts while the vehicle is running to generate a damping force to attenuate vibrations in the body and improve the ride comfort of the vehicle.

[0003] A shock absorber used in a vehicle includes a cylinder, a piston inserted into the cylinder to divide the interior of the cylinder into an extension-side chamber and a compression-side chamber, a piston rod inserted into the cylinder and connected to the piston, and a damping passage provided in the piston to connect the extension-side chamber and the compression-side chamber. A damping valve provided in the damping passage provides resistance to the liquid passing through the damping passage during extension and contraction, thereby exerting a damping force that prevents extension and contraction (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-218817 Summary of the Invention [Problem to be solved by the invention]

[0005] Such shock absorbers are generally capable of expanding and contracting at all times, not only when the vehicle is moving but also when the vehicle is stopped. However, in vehicles such as camper vans and kitchen vans that are parked for long periods of time with passengers staying in the vehicle cabin, if the shock absorbers are in an expandable state, the vehicle body may shake when passengers move around in the vehicle cabin or when the vehicle body is blown by strong winds, which may cause discomfort to the passengers in the vehicle cabin.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a shock absorber that is not only expandable and retractable to exert a damping force, but also capable of maintaining a constant vehicle height in a locked state where it cannot expand and retract. [Means for solving the problem]

[0007] In order to achieve the above object, a shock absorber according to the problem-solving means of the present invention comprises a cylinder, a piston inserted into the cylinder to divide the interior of the cylinder into an extension-side chamber and a compression-side chamber filled with liquid, a piston rod inserted into the extension-side chamber of the cylinder and connected to the piston, a damping passage communicating between the extension-side chamber and the compression-side chamber and providing resistance to the flow of liquid passing through, a reservoir that stores liquid and is connected to the interior of the cylinder to compensate for changes in the displacement volume of the piston rod within the cylinder, and an on-off valve provided in a compensation passage communicating between the interior of the cylinder and the reservoir to open and close the compensation passage. The inside of the cylinder and the reservoir are communicated only through a compensation passage. are.

[0008] With a shock absorber configured in this manner, not only can it exert a damping force by opening the opening / closing valve and expanding / contracting, but it can also maintain a constant vehicle height by closing the opening / closing valve and entering a locked state where it cannot expand / contract.

[0009] The shock absorber may also include a tank that stores liquid, a supply passage and a discharge passage that communicate between the tank and the inside of the cylinder, a pump that is provided in the supply passage and is capable of sucking liquid from the tank and supplying it into the cylinder, and a discharge passage opening / closing valve that is capable of opening and closing the discharge passage. In a shock absorber configured in this manner, the pump is driven to supply liquid into the cylinder, thereby expanding the shock absorber to raise the vehicle height, and the discharge passage opening / closing valve is opened to discharge liquid from the cylinder to the tank, thereby contracting the shock absorber to lower the vehicle height.

[0010] The shock absorber also includes a relief passage that communicates between the tank and the inside of the cylinder, and a relief valve that can open and close the relief passage and that, with the cylinder side being the upstream side, opens when the pressure on the upstream side reaches a valve opening pressure to allow only the flow of liquid from inside the cylinder to the tank, and the on-off valve may be positioned so that it opens and closes the compensation passage but does not open or close the relief passage. With a shock absorber configured in this way, even if the on-off valve is closed to disable the exchange of liquid between the inside of the cylinder and the reservoir, if a large external force that expands or contracts the cylinder acts and the pressure in the cylinder 1 becomes excessive, the relief valve will open and release the pressure in the cylinder to the tank, thereby protecting the shock absorber.

[0011] The shock absorber may further include a relief passage that connects the tank with the inside of the cylinder, and a relief valve that can open and close the relief passage and that, with the cylinder side as the upstream side, opens when the pressure on the upstream side reaches a valve opening pressure to allow only the flow of liquid from the inside of the cylinder to the tank, and the on-off valve may be capable of opening and closing the compensation passage, the supply passage, the discharge passage, and the relief passage. A shock absorber configured in this manner can maintain a locked state that cannot expand or contract even when a large external force is applied.

[0012] Furthermore, the shock absorber may be configured such that the tank, the supply passage, the discharge passage, the pump, and the discharge passage opening / closing valve are used as a pump unit, and the pump unit is connected to the inside of the cylinder via a compensation passage. With a shock absorber configured in this manner, the hydraulic circuit is simplified and the piping that connects the reservoir and the pump unit to the inside of the cylinder is easy to handle. .difference Furthermore, the shock absorber may be configured such that when the on-off valve is closed, the piston rod is unable to move relative to the cylinder. In the shock absorber, the damping passage may also be provided in the piston. [Effects of the Invention]

[0013] According to the shock absorber of the present invention, not only can it exert a damping force by being expandable and contractable, but it can also maintain a constant vehicle height in the vehicle by being in a locked state where it cannot be expanded and contracted. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a hydraulic circuit diagram showing a shock absorber according to an embodiment. [Figure 2] FIG. 4 is a hydraulic circuit diagram showing a shock absorber according to a first modified example of the embodiment. [Figure 3] FIG. 10 is a hydraulic circuit diagram showing a shock absorber according to a second modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described below based on the embodiments shown in the drawings. As shown in Fig. 1, a shock absorber D in one embodiment includes a cylinder 1, a piston 2 inserted into the cylinder 1 and dividing the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2 filled with liquid, a piston rod 3 inserted into the extension-side chamber R1 of the cylinder 1 and connected to the piston 2, a damping passage 4 communicating between the extension-side chamber R1 and the compression-side chamber R2 and providing resistance to the flow of liquid passing through it, a reservoir 5 that stores liquid and is connected to the cylinder 1 and compensates for changes in the displacement volume of the piston rod 3 within the cylinder 1, and an on-off valve 7 provided in a compensation passage 6 communicating between the cylinder 1 and the reservoir 5 and opening and closing the compensation passage 6. The shock absorber D is used by being interposed between the body and axle of a vehicle (not shown). The vehicle in which the shock absorber D is used is not limited to an automobile with four or more wheels, but may be a motorcycle or other vehicle.

[0016] Each part of the shock absorber D will be described in detail below. The cylinder 1 is cylindrical, and as described above, the piston 2 is inserted inside the cylinder 1 so as to be movable in the axial direction relative to the cylinder 1. The inside of the cylinder 1 is divided by the piston 2 into an expansion-side chamber R1 located at the top in FIG. 1 and a compression-side chamber R2 located at the bottom in FIG. 1. The shock absorber D may be mounted on a vehicle and used with the expansion-side chamber R1 at the bottom and the compression-side chamber R2 at the top.

[0017] The expansion-side chamber R1 and the compression-side chamber R2 are filled with a liquid, specifically, hydraulic oil, for example. Note that the liquid may be other liquids such as water or an aqueous solution, in addition to hydraulic oil.

[0018] Furthermore, a piston rod 3 connected to the piston 2 is inserted into the cylinder 1 so as to be movable in the axial direction. The piston rod 3 is inserted into the extension-side chamber R1. The piston rod 3 may protrude into the compression-side chamber R2, but does not penetrate the entire axial length of the compression-side chamber R2 even when the shock absorber D is displaced to the lowest position relative to the cylinder 1. Because the piston rod 3 is inserted into the cylinder 1 in this way, when it moves in the axial direction relative to the cylinder 1, the volume displaced within the cylinder 1 changes. Although not shown, a bracket is attached to the upper end of the piston rod 3, allowing the shock absorber D to be attached to the vehicle body, and the shock absorber D can be connected to the vehicle body.

[0019] 1, the lower end of the cylinder 1 is closed by a bottom. Although not shown, the bottom of the cylinder 1 is provided with a bracket that can be attached to a knuckle bracket or a suspension arm that holds the wheel, and the shock absorber D can be connected to the wheel.

[0020] The piston 2 is provided with a damping passage 4 including a passage 4a communicating between the extension-side chamber R1 and the compression-side chamber R2 and a damping valve 4b provided in the passage 4a and providing resistance to the flow of fluid passing through. Although not shown, the damping passage 4 may be configured to include at least two or more passages communicating between the extension-side chamber R1 and the compression-side chamber R2, an extension-side damping valve that opens and closes part of the passage to allow only the flow of fluid from the extension-side chamber R1 to the compression-side chamber R2 and provides resistance to the flow of fluid, and a compression-side damping valve that opens and closes the remaining passage to allow only the flow of fluid from the compression-side chamber R2 to the extension-side chamber R1 and provides resistance to the flow of fluid.

[0021] The reservoir 5 includes a cylindrical container 5a and a free piston 5b that is movably inserted into the container 5a and divides the container 5a into a liquid chamber L filled with hydraulic oil and an air chamber G in which gas is sealed. Gas is sealed in a compressed state in the air chamber G, and the pressure in the air chamber G pressurizes the liquid chamber L in the reservoir 5. The liquid chamber L of the reservoir 5 and the pressure-side chamber R2 in the cylinder 1 are connected to each other through a compensation passage 6, allowing hydraulic oil to move back and forth between the liquid chamber L and the pressure-side chamber R2. The liquid chamber L and the air chamber G in the reservoir 5 are separated by the free piston 5b, but they may be separated by a separating member such as a bladder, diaphragm, or bellows that can separate the liquid chamber L and the air chamber G and change the volume ratio between the liquid chamber L and the air chamber G in the container 5a. Furthermore, the separating member separating the liquid chamber L and the air chamber G may be eliminated if the connection portion of the compensation passage 6 in the container 5a can be positioned downward, for example, to prevent the movement of gas from the container 5a to the pressure-side chamber R2 in the reservoir 5. Furthermore, a structure may be adopted in which one end of the container 5a is open to the atmosphere and a spring is housed in the container 5a that biases the free piston 5b in a direction that pressurizes the liquid chamber L. In this case, the air chamber G filled with gas need not be provided in the container 5a.

[0022] The compensation passage 6 is provided with an on-off valve 7 that can open and close the compensation passage 6. The on-off valve 7 is a normally open electromagnetic on-off valve that includes a valve element 7a that has a communication position that opens the compensation passage 6 and a blocking position that blocks the compensation passage 6, a spring 7b that urges the valve element 7a to take the communication position, and a solenoid 7c that switches the valve element 7a to the blocking position against the urging force of the spring 7b when energized.

[0023] In addition to the above-mentioned configuration, the shock absorber D also includes a tank 10 for storing hydraulic oil, a supply passage 11 and a discharge passage 12 that communicate between the tank 10 and the compression-side chamber R2 in the cylinder 1, a pump unit P having a pump 13 provided in the supply passage 11 that can suck liquid from the tank 10 and supply hydraulic oil into the cylinder 1, and a discharge passage opening / closing valve 14 that can open and close the discharge passage 12, a relief passage 15 that communicates between the tank 10 and the compression-side chamber R2 in the cylinder 1, and a relief valve 16 that can open and close the relief passage 15, with the cylinder side as the upstream side, and that opens when the pressure on the upstream side reaches a valve opening pressure to allow only the flow of hydraulic oil from the inside of the cylinder 1 toward the tank 10. To It is prepared.

[0024] When pump 13 is driven by motor 17, it draws hydraulic oil from tank 10 and supplies it into cylinder 1. A check valve 18 is provided in supply passage 11 on the cylinder side of pump 13 to prevent hydraulic oil from flowing back from inside cylinder 1 to pump 13. When hydraulic oil is supplied from pump 13 into cylinder 1, shock absorber D expands, allowing the body of the vehicle to be raised.

[0025] The discharge passage on-off valve 14 that opens and closes the discharge passage 12 is a normally closed electromagnetic on-off valve that includes a valve element 14a that has a communication position that opens the discharge passage 12 and a blocking position that blocks the discharge passage 12, a spring 14b that urges the valve element 14a to the blocking position, and a solenoid 14c that switches the valve element 14a to the communication position against the urging force of the spring 14b when energized. Also, an orifice 19 is provided in the discharge passage 12.

[0026] When the discharge passage opening / closing valve 14 is set to the shutoff position, communication between the tank 10 and the inside of the cylinder 1 is cut off, and hydraulic oil cannot move from inside the cylinder 1 to the tank 10. When the discharge passage opening / closing valve 14 is set to the communicating position, communication between the tank 10 and the inside of the cylinder 1 is established, and hydraulic oil can move from inside the cylinder 1 to the tank 10. As hydraulic oil moves from inside the cylinder 1 to the tank 10, the shock absorber D contracts and the body of the vehicle can be lowered.

[0027] A relief passage 15 connects the inside of the cylinder 1 with the tank 10. A relief valve 16 provided in the relief passage 15 opens when the pressure on the upstream cylinder side reaches a valve opening pressure, allowing hydraulic oil to flow from inside the cylinder 1 to the tank 10. Therefore, if hydraulic oil is supplied into the cylinder 1 by driving the pump 13 and the pressure inside the cylinder 1 becomes excessive, or if the pressure inside the cylinder 1 becomes excessive during the contraction operation of the shock absorber D, the relief valve 16 opens to prevent the pressure inside the cylinder 1 from exceeding the valve opening pressure of the relief valve 16, thereby protecting the shock absorber D.

[0028] The shock absorber D is configured as described above, and the operation of the shock absorber D will be described below. First, the operation of the shock absorber D will be described when damping force is generated in the shock absorber D, which expands and contracts as the vehicle travels, to suppress vibration of the vehicle body. In this case, the on-off valve 7 is set to the communication position to connect the inside of the cylinder 1 to the reservoir 5, and the discharge passage on-off valve 14 is set to the block position to stop the pump 13.

[0029] In this state, hydraulic oil can be exchanged between the inside of the cylinder 1 and the reservoir 5. When the piston rod 3 moves upward in FIG. 1 relative to the cylinder 1 and the shock absorber D extends, hydraulic oil moves from the extension-side chamber R1, which is compressed by the piston 2, to the compression-side chamber R2 through the damping passage 4. When the hydraulic oil passes through the damping passage 4, the damping valve 4b in the damping passage 4 applies resistance to the flow of hydraulic oil, so that the pressure in the extension-side chamber R1 rises and becomes higher than the pressure in the compression-side chamber R2, and the shock absorber D generates a damping force that prevents the piston 2 from moving upward.

[0030] Furthermore, when shock absorber D extends, the piston rod 3 retreats from within cylinder 1, reducing the volume displaced by the piston rod 3 within cylinder 1, resulting in a shortage of hydraulic oil within cylinder 1, but the shortage of hydraulic oil is supplied from fluid chamber L of reservoir 5 into cylinder 1. As reservoir 5 supplies hydraulic oil from fluid chamber L into cylinder 1, free piston 5b descends within container 5a, expanding air chamber G by that amount. In this way, the reservoir 5 compensates for changes in the displacement volume of piston rod 3 within cylinder 1, allowing shock absorber D to extend smoothly and generate the desired damping force.

[0031] Conversely, when the piston rod 3 moves downward in FIG. 1 relative to the cylinder 1 and the shock absorber D contracts, hydraulic oil moves from the compression-side chamber R2, which is compressed by the piston 2, to the extension-side chamber R1 through the damping passage 4. When the hydraulic oil passes through the damping passage 4, the damping valve 4b in the damping passage 4 applies resistance to the flow of hydraulic oil, so the pressure in the extension-side chamber R1 drops and becomes lower than the pressure in the compression-side chamber R2, and the shock absorber D generates a damping force that prevents the piston 2 from moving downward.

[0032] Furthermore, when shock absorber D contracts, piston rod 3 enters cylinder 1, increasing the volume displaced by piston rod 3 within cylinder 1, causing an excess of hydraulic oil within cylinder 1, but the excess hydraulic oil is pushed out from within cylinder 1 into liquid chamber L of reservoir 5. As hydraulic oil flows into liquid chamber L, free piston 5b rises within container 5a of reservoir 5, causing air chamber G to shrink by that amount, and liquid chamber L to absorb the hydraulic oil pushed out from within cylinder 1. In this way, reservoir 5 compensates for changes in the displacement volume within cylinder 1 by piston rod 3, and shock absorber D contracts smoothly while generating the desired damping force.

[0033] Next, the operation of the shock absorber D when the pump 13 is driven to extend the shock absorber D, thereby pushing up the vehicle body and increasing the vehicle height will be described. When raising the vehicle height, the discharge passage opening / closing valve 14 is set to the shutoff position to cut off communication between the inside of the cylinder 1 and the tank 10. Then, when the pump 13 is driven to supply hydraulic oil from the pump 13 into the cylinder 1, the hydraulic oil supplied into the cylinder 1 pushes the piston rod 3 out of the cylinder 1, causing the shock absorber D to extend and push up the vehicle body. Note that the hydraulic oil in the expansion-side chamber R1, which is compressed, moves through the damping passage 4 to the expanding compression-side chamber R2. Therefore, by driving the pump 13 to supply hydraulic oil into the cylinder 1, the vehicle height of a vehicle to which the shock absorber D is applied is increased.

[0034] Since shock absorber D is a single-rod shock absorber in which the piston rod 3 is inserted into the extension-side chamber R1 but does not penetrate the compression-side chamber R2, the pressure-receiving area of ​​the piston 2 on the compression-side chamber R2 side is larger than the pressure-receiving area on the extension-side chamber R1 side, and increasing the pressure in cylinder 1 increases the force pushing the piston rod 3 upward in Fig. 1 relative to the cylinder 1. Suspension springs are provided in parallel to shock absorber D between the vehicle body and the wheels, and as the vehicle height increases, the suspension springs expand and the vehicle weight borne by the suspension springs decreases, but the reduced load on the suspension springs is borne by shock absorber D due to the increase in pressure in cylinder 1, causing the vehicle height to increase.

[0035] Whether the on-off valve 7 in the compensation passage 6 is in the communicating position or the blocking position, the shock absorber D will extend and the vehicle height can be raised. However, if the on-off valve 7 is set to the blocking position and the pump 13 is driven to raise the vehicle height, and then the on-off valve 7 is set to the communicating position, the hydraulic oil in the cylinder 1 will flow into the reservoir 5, and the volume of the air chamber G will be compressed until the pressure in the air chamber G and the pressure in the cylinder 1 are balanced, which may cause the vehicle height to drop all at once. Therefore, it is preferable to set the on-off valve 7 to the communicating position when raising the vehicle height.

[0036] When hydraulic oil is supplied from the pump 13 into the cylinder 1 with the on-off valve 7 in the communicating position, hydraulic oil is supplied to the cylinder 1 and the fluid chamber L of the reservoir 5. Then, the air chamber G in the reservoir 5 contracts in proportion to the amount of hydraulic oil flowing into the reservoir 5, causing the pressure in the air chamber G to rise. Because the reservoir 5 and the cylinder 1 are connected to each other, the supply of hydraulic oil from the pump 13 causes the pressure in the air chamber G and the pressure in the cylinder 1 to rise equally. As the pressure in the cylinder 1 rises, the force pushing the piston rod 3 upward in FIG. 1 relative to the cylinder 1 increases, so the shock absorber D raises the vehicle height. However, in this case, because the pressure in the cylinder 1 and the pressure in the reservoir 5 are equal, the vehicle height does not drop all at once.

[0037] Conversely, the operation of shock absorber D when the vehicle body is lowered to lower the vehicle height will be described below. When lowering the vehicle height, pump 13 is stopped and discharge passage opening / closing valve 14 is set to the communicating position to communicate between the inside of cylinder 1 and tank 10. Shock absorber D is always urged to contract by the weight of the vehicle body, so when the inside of cylinder 1 and tank 10 are in a communicating state, the urging force from the vehicle body causes piston rod 3 to move downward in cylinder 1 in FIG. 1, causing shock absorber D to contract. When piston rod 3 enters cylinder 1, the hydraulic oil in cylinder 1 becomes excessive by the volume of the piston rod 3 entering cylinder 1, so it is pushed out of cylinder 1 and moves to tank 10 via discharge passage 12. Hydraulic oil is supplied to extension-side chamber R1, which expands as shock absorber D contracts, from compression-side chamber R2, which is compressed, via damping passage 4.

[0038] When the hydraulic oil pushed out from inside the cylinder 1 passes through the discharge passage 12, it passes through an orifice 19 provided in the discharge passage 12, and the orifice 19 applies resistance to the flow of the hydraulic oil, slowing the contraction speed of the shock absorber D and preventing the vehicle height from lowering too quickly. By providing the orifice 19 in this way, the lowering speed when the vehicle height is lowered can be slowed down to avoid causing discomfort to vehicle occupants, but the orifice 19 can also be omitted. Also, when the discharge passage opening / closing valve 14 is in the communicating position, resistance may be applied to the flow of hydraulic oil, and the discharge passage opening / closing valve 14 may be used instead of the orifice 19 to slow down the speed at which the vehicle body is lowered.

[0039] Next, we will explain the operation of shock absorber D when the shock absorber D is locked so as to maintain a constant vehicle height while the vehicle is stopped and unable to extend or retract. When shock absorber D is locked so as to be unable to extend or retract, the on-off valve 7 is set to the shutoff position, cutting off communication between the inside of cylinder 1 and the reservoir 5. In this way, even if the piston rod 3 attempts to retract from the cylinder 1 to extend the shock absorber D, hydraulic oil cannot pass between the inside of cylinder 1 and the reservoir 5, making it impossible to supply hydraulic oil to the inside of cylinder 1, and shock absorber D cannot extend. Also, even if the piston rod 3 attempts to retract from the cylinder 1 to retract the shock absorber D, hydraulic oil cannot pass between the inside of cylinder 1 and the reservoir 5, making it impossible to discharge hydraulic oil from the inside of cylinder 1, and shock absorber D cannot retract. In this way, by closing the on-off valve 7 and cutting off the compensation passage 6 that connects the inside of cylinder 1 and the reservoir 5, shock absorber D is locked so as to be unable to extend or retract. On the other hand, when the on-off valve 7 is set to the communicating position to open the compensation passage 6, the shock absorber D returns to a state in which it can expand and contract.

[0040] As mentioned above, when the pressure in the cylinder 1 becomes excessive due to the supply of hydraulic oil into the cylinder 1 by the operation of the pump 13, or when the pressure in the cylinder 1 becomes excessive during the contraction operation of the shock absorber D, the relief valve 16 opens to prevent the pressure in the cylinder 1 from exceeding the opening pressure of the relief valve 16, thereby protecting the shock absorber D.

[0041] As described above, the shock absorber D of this embodiment includes the cylinder 1, the piston 2 inserted into the cylinder 1 to divide the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2 filled with hydraulic oil (liquid), the piston rod 3 inserted into the extension-side chamber R1 of the cylinder 1 and connected to the piston 2, the damping passage 4 communicating between the extension-side chamber R1 and the compression-side chamber R2 and providing resistance to the flow of hydraulic oil (liquid) passing through, the reservoir 5 that stores the hydraulic oil (liquid) and is connected to the interior of the cylinder 1 to compensate for changes in the displacement volume of the piston rod 3 within the cylinder 1, and the on-off valve 7 provided in the compensation passage 6 communicating between the interior of the cylinder 1 and the reservoir 5 and that opens and closes the compensation passage 6.

[0042] The shock absorber D configured in this manner can not only exert a damping force by expanding and contracting by opening the on-off valve 7, but also maintain a constant vehicle height in the vehicle by closing the on-off valve 7 to enter a locked state where expansion and contraction are not possible. Because the shock absorber D can maintain a constant vehicle height, it does not cause discomfort to passengers in the vehicle cabin when the vehicle is stopped.

[0043] Furthermore, in the shock absorber D of this embodiment, the on-off valve 7 is a normally open on-off valve, so in the event of a malfunction that makes it difficult to energize the on-off valve 7, the valve opens to communicate between the inside of the cylinder 1 and the reservoir 5, allowing it to expand and contract and exert a damping force, so that it is possible to exert a damping force and suppress vibration of the vehicle body even in the event of a malfunction. If the on-off valve 7 is a normally closed on-off valve that opens when energized and closes when not energized, no power is consumed when the vehicle is parked and the vehicle height is maintained constant, so energy consumption can be reduced. Note that although the on-off valve 7 is an electromagnetic on-off valve, it may also be an on-off valve that is manually switched.

[0044] The shock absorber D of this embodiment also includes a tank 10 that stores hydraulic oil (liquid), a supply passage 11 and a discharge passage 12 that communicate between the tank 10 and the inside of the cylinder 1, a pump 13 that is provided in the supply passage 11 and is capable of drawing in hydraulic oil (liquid) from the tank 10 and supplying the hydraulic oil (liquid) into the cylinder 1, and a discharge passage on-off valve 14 that can open and close the discharge passage 12. The shock absorber D configured in this manner can be extended to raise the vehicle height by driving the pump 13 to supply hydraulic oil (liquid) into the cylinder 1, and can be contracted to lower the vehicle height by opening the discharge passage on-off valve 14 to discharge hydraulic oil (liquid) from the cylinder 1 to the tank 10. Thus, the shock absorber D of this embodiment is height adjustable, and can maintain a constant vehicle height of the vehicle by closing the on-off valve 7 after adjusting the vehicle height and locking the shock absorber D so that it cannot be extended or retracted. When the shock absorber D is height adjustable, a detection means for detecting the vehicle height may be provided, and a control device may be provided that automatically adjusts the vehicle height to a predetermined height when the vehicle height changes due to a change in the load weight on the vehicle. The control device may be any device that is equipped with the detection means and can control the motor 17 that drives the pump 13 and the discharge passage opening / closing valve 14. The detection means may be, for example, a stroke sensor that detects the stroke displacement of the shock absorber D, a distance sensor that detects the distance of the vehicle body from the road surface, a pressure sensor that detects the pressure inside the cylinder 1, etc. Note that if the shock absorber D does not need to be equipped with a vehicle height adjustment function, it does not need to be equipped with the pump unit P that is made up of the tank 10, supply passage 11, discharge passage 12, pump 13, and discharge passage opening / closing valve 14.

[0045] Furthermore, shock absorber D of this embodiment includes relief passage 15 that communicates tank 10 with the inside of cylinder 1, and relief valve 16 that can open and close relief passage 15 and that, with the cylinder side being the upstream side, opens when the pressure on the upstream side reaches a valve opening pressure to allow only the flow of hydraulic oil (liquid) from inside cylinder 1 toward tank 10, and on-off valve 7 is disposed in a position that opens and closes compensation passage 6 but does not open or close relief passage 15. With shock absorber D configured in this manner, even if on-off valve 7 is closed to disable the exchange of hydraulic oil (liquid) between inside cylinder 1 and reservoir 5, relief valve 16 opens to release the pressure in cylinder 1 to tank 10 when a large external force that expands or contracts the cylinder acts and the pressure in cylinder 1 becomes excessive, thereby protecting shock absorber D. Furthermore, even if the vehicle is accidentally driven with on-off valve 7 closed, relief passage 15 and relief valve 16 can prevent the pressure in cylinder 1 from becoming excessive.

[0046] In the shock absorber D of this embodiment, the on-off valve 7 is arranged to open and close only the compensation passage 6, and not to open and close the supply passage 11, the discharge passage 12, and the relief passage 15. However, like the shock absorber D1 shown in FIG. 2, the shock absorber D may be provided with a relief passage 15 that connects the tank 10 with the inside of the cylinder 1, and a relief valve 16 that can open and close the relief passage 15, with the cylinder side being the upstream side, and that opens when the pressure on the upstream side reaches a valve opening pressure to allow only the flow of hydraulic oil (liquid) from the inside of the cylinder 1 toward the tank 10, and the supply passage 11, the discharge passage 12, and the relief passage 15 may be connected midway through the compensation passage 6 on the side opposite the cylinder from the on-off valve 7, so that the compensation passage 6, the supply passage 11, the discharge passage 12, and the relief passage 15 can be opened and closed by opening and closing the on-off valve 7. 1 According to this, even if a large external force acts, the locked state in which expansion and contraction is impossible can be maintained.

[0047] 3, the shock absorber D2 may be provided with a compression side damping valve 20 that provides resistance to the flow of hydraulic oil from the compression side chamber R2 toward the reservoir 5, and a check valve 21 that only allows the flow of hydraulic oil from the reservoir 5 toward the compression side chamber R2, in parallel between the reservoir 5 and the compression side chamber R2. In the shock absorber D2 configured in this manner, too, a locked state in which expansion and contraction are disabled can be achieved by cutting off communication between the interior of the cylinder 1 and the reservoir 5 by closing the on-off valve 7, and expansion and contraction can be enabled by opening the on-off valve 7, thereby generating a damping force during expansion and contraction.

[0048] In addition, the vehicle height adjusting unit may be provided with a compensation passage 6 and a pump unit P, or a compensation passage 6 and a pump unit P, and further provided with a relief passage 15 and a relief valve 16. To , may be connected to the expansion-side chamber R1. The shock absorber D configured in this manner can also exert a damping force by opening the on-off valve 7 to enable expansion and contraction, and can maintain a constant vehicle height of the vehicle by closing the on-off valve 7 to enter a locked state where expansion and contraction are not possible, and the vehicle height can also be adjusted by the pump unit P. Therefore, the shock absorber D configured in this manner can maintain a constant vehicle height, so that passengers in the vehicle compartment do not feel uncomfortable when the vehicle is stopped.

[0049] Furthermore, the pump unit P is connected to the inside of the cylinder 1 via a compensation passage 6 that connects the reservoir 5 to the inside of the cylinder 1, but it may also be connected to the inside of the cylinder 1 independently without using the compensation passage 6. However, when a structure is adopted in which the pump unit P is connected to the inside of the cylinder 1 via the compensation passage 6, as in the shock absorbers D, D1, and D2 shown in Figures 1 to 3, the hydraulic circuit is simplified and the routing of piping that connects the reservoir 5 and the pump unit P to the inside of the cylinder 1 is also facilitated.

[0050] Furthermore, when a partition member (not shown) that includes an on-off valve 7 and separates the compression side chamber R2 from the reservoir 5 is provided inside the cylinder 1, the reservoir 5 can be installed below the compression side chamber R2 inside the cylinder 1 in the shock absorbers D, D1, and D2 shown in Figures 1 to 3. Furthermore, an outer cylinder (not shown) that covers the outer periphery of the cylinder 1 may be provided outside the cylinder 1, and the reservoir 5 may be formed between the cylinder 1 and the outer cylinder.

[0051] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims. [Explanation of symbols]

[0052] 1····Cylinder, 2···Piston, 3···Piston rod, 4···Damping passage, 5···Reservoir, 6···Compensation passage, 7···Shut-off valve, 10···Tank, 11···Supply passage, 12···Discharge passage, 13···Pump, 14···Discharge passage shut-off valve, 15···Relief passage, 16···Relief valve, D, D1, D2···Shock absorber, P···Pump unit, R1···Extension side chamber, R2···Compression side chamber

Claims

1. A cylinder; a piston inserted into the cylinder to divide the interior of the cylinder into an extension-side chamber and a compression-side chamber filled with liquid; a piston rod inserted into the extension-side chamber of the cylinder and connected to the piston; a damping passage that communicates the expansion-side chamber and the compression-side chamber and provides resistance to the flow of fluid passing through the damping passage; a reservoir that stores a liquid and is in communication with the cylinder, and that compensates for changes in the displacement volume of the piston rod in the cylinder; an on-off valve provided in a compensation passage that communicates the inside of the cylinder with the reservoir, and that opens and closes the compensation passage; The inside of the cylinder and the reservoir are in communication only through the compensation passage. A shock absorber characterized by:

2. a tank for storing a liquid; a supply passage and a discharge passage communicating between the tank and the inside of the cylinder; a pump provided in the supply passage and capable of sucking liquid from the tank and supplying the liquid into the cylinder; a discharge passage opening / closing valve that can open and close the discharge passage; 2. The shock absorber according to claim 1.

3. When the on-off valve is closed, the piston rod is unable to move relative to the cylinder.

2. The shock absorber according to claim 1.

4. The damping passage is provided in the piston.

2. The shock absorber according to claim 1.

5. a relief passage communicating the tank with the inside of the cylinder; a relief valve that can open and close the relief passage, with the cylinder side as the upstream side, and that opens when the pressure on the upstream side reaches a valve opening pressure to allow only the flow of liquid from inside the cylinder toward the tank, The on-off valve opens and closes the compensation passage but does not open and close the relief passage.

3. The shock absorber according to claim 2.

6. a relief passage communicating the tank with the inside of the cylinder; a relief valve that can open and close the relief passage, with the cylinder side as the upstream side, and that opens when the pressure on the upstream side reaches a valve opening pressure to allow only the flow of liquid from inside the cylinder toward the tank, The on-off valve opens and closes the supply passage, the discharge passage, and the relief passage, as well as the compensation passage.

3. The shock absorber according to claim 2.

7. the tank, the supply passage, the discharge passage, the pump, and the discharge passage opening / closing valve constitute a pump unit, The pump unit is connected to the inside of the cylinder via the compensation passage.

3. The shock absorber according to claim 2.

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