Damper

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 when the vehicle is traveling to generate a damping force to damp vibrations of the vehicle 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 inside 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 communicate between 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 / contraction, thereby exerting a damping force that hinders extension / contraction (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-218817 A 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 cars that are used in such a way that passengers stay in the vehicle cabin while the vehicle is stopped for long periods of time, if the shock absorbers are in an expandable state, the vehicle body may shake when the passengers move around in the vehicle cabin or when the vehicle body is blown by a strong wind, causing discomfort to the passengers in the vehicle cabin.

[0006] SUMMARY OF THE PRESENT DISCLOSURE 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 in which it is unable to expand and retract. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the shock absorber in the problem-solving means of the present invention comprises a cylinder, a piston inserted into the cylinder to divide the inside 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 between the extension-side chamber and the compression-side chamber and provides resistance to the flow of liquid passing through, a reservoir that stores liquid and is connected to the inside of the cylinder to compensate for changes in the displacement volume of the piston rod inside the cylinder, and an opening / closing valve provided in a compensation passage that communicates between the inside of the cylinder and the reservoir to open and close the compensation passage.

[0008] With a shock absorber configured in this manner, not only can the shock absorber exert a damping force by opening the opening / closing valve and thereby expand / contract, but the shock absorber can also maintain a constant vehicle height by closing the opening / closing valve and entering a locked state that prevents expansion / contraction.

[0009] The shock absorber may also include a tank for storing 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 capable of sucking liquid from the tank and supplying the liquid into the cylinder, and a discharge passage opening / closing valve 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 to expand and raise the vehicle height, and the discharge passage opening / closing valve is opened to discharge liquid from the cylinder to the tank and contract to lower the vehicle height.

[0010] The shock absorber may also include 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 opens when the pressure on the upstream side reaches the valve opening pressure, with the cylinder side being the upstream side, to allow only the flow of liquid from inside the cylinder to the tank, and the on-off valve may be located in a position that opens and closes the compensation passage but does not open and 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 is applied and the pressure in the cylinder 1 becomes excessive, the relief valve opens to release the pressure in the cylinder to the tank, thereby protecting the shock absorber.

[0011] The shock absorber may further comprise a relief passage that communicates between the tank and the inside of the cylinder, and a relief valve that is capable of opening and closing the relief passage and that opens when the pressure on the upstream side reaches a valve opening pressure, with the cylinder side being the upstream side, to allow only the flow of liquid from the inside of the cylinder to the tank, and the opening and closing valve may be capable of opening and closing the compensation passage, the supply passage, the discharge passage, and the relief passage. With a shock absorber configured in this manner, it is possible to maintain a locked state in which it cannot expand or contract even when a large external force is applied.

[0012] In addition, 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 configured 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 manage. Effect 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 or contracted. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a hydraulic circuit diagram showing a shock absorber according to an embodiment. [Diagram 2] FIG. 4 is a hydraulic circuit diagram showing a shock absorber according to a first modified example of the embodiment. [Diagram 3] FIG. 11 is a hydraulic circuit diagram showing a shock absorber according to a second modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described below based on the embodiments shown in the drawings. As shown in FIG. 1, the shock absorber D in one embodiment includes a cylinder 1, a piston 2 inserted into the cylinder 1 to divide 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 the extension side chamber R1 and the compression side chamber R2 and providing resistance to the flow of liquid passing through, a reservoir 5 that stores liquid and communicates with the cylinder 1 and compensates for changes in the displacement volume of the piston rod 3 in the cylinder 1, and an opening / closing valve 7 provided in a compensation passage 6 communicating the cylinder 1 with the reservoir 5 to open and close the compensation passage 6, and is used by being interposed between the body and the axle of a vehicle (not shown). The vehicle in which the shock absorber D is used is not limited to an automobile having 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 the piston 2 is inserted inside the cylinder 1 so as to be axially movable relative to the cylinder 1 as described above. The inside of the cylinder 1 is partitioned 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 facing downward and the compression-side chamber R2 facing upward.

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

[0018] In addition, 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 if the shock absorber D is displaced downward to the lowest position relative to the cylinder 1. Since the piston rod 3 is inserted into the cylinder 1 in this manner, when the piston rod 3 moves in the axial direction relative to the cylinder 1, the volume displaced within the cylinder 1 is changed. Although not shown, a bracket is attached to the upper end of the piston rod 3, which allows 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 knuckle bracket that holds the wheel or a bracket that can be attached to a suspension arm, and a 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 middle of the passage 4a and providing resistance to the flow of liquid 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 a part of the passage to allow only the flow of liquid from the extension-side chamber R1 to the compression-side chamber R2 and provides resistance to the flow of liquid, and a compression-side damping valve that opens and closes the remaining passage to allow only the flow of liquid from the compression-side chamber R2 to the extension-side chamber R1 and provides resistance to the flow of liquid.

[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 liquid chamber L in the reservoir 5 is pressurized by the pressure of the air chamber G. In addition, the liquid chamber L of the reservoir 5 and the pressure side chamber R2 in the cylinder 1 are mutually communicated through a compensation passage 6, allowing hydraulic oil to move 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 partitioned by the free piston 5b, but may be partitioned by a partitioning member such as a bladder, a diaphragm, or a bellows that can partition the liquid chamber L and the air chamber G and can change the ratio of the volume of the liquid chamber L to the volume of the air chamber G in the container 5a. Also, if the connection part of the compensation passage 6 in the container 5a in the reservoir 5 can be arranged downward, for example, the partitioning member that partitions the liquid chamber L and the air chamber G may be eliminated if the movement of gas from the container 5a to the pressure side chamber R2 in the reservoir 5 can be prevented. Furthermore, a structure in which one end of the container 5a is opened to the atmosphere and a spring that biases the free piston 5b in the direction of pressurizing the liquid chamber L is accommodated in the container 5a may be adopted. In this case, the air chamber G in which gas is sealed may not be provided in the container 5a.

[0022] The compensation passage 6 is provided with an on-off valve 7 capable of opening and closing the compensation passage 6. The on-off valve 7 is a normally open type electromagnetic on-off valve including a valve element 7a having a communication position for opening the compensation passage 6 and a blocking position for blocking the compensation passage 6, a spring 7b for biasing the valve element 7a to the communication position, and a solenoid 7c for switching the valve element 7a to the blocking position against the biasing force of the spring 7b when energized.

[0023] In addition to the above-mentioned configuration, the shock absorber D is equipped with a tank 10 for storing hydraulic oil, a supply passage 11 and a discharge passage 12 connecting 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 and capable of sucking liquid from the tank 10 and supplying hydraulic oil into the cylinder 1, and a discharge passage opening / closing valve 14 capable of opening and closing the discharge passage 12, a relief passage 15 connecting the tank 10 and the compression side chamber R2 in the cylinder 1, and a relief valve 16 capable of opening and closing the relief passage 15, with the cylinder side as the upstream side, and opening when the pressure on the upstream side reaches a valve opening pressure to allow only the flow of hydraulic oil from inside the cylinder 1 toward the tank 10.

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

[0025] The discharge passage opening / closing valve 14 that opens and closes the discharge passage 12 is a normally closed type electromagnetic opening / closing valve that includes a valve element 14a with a communication position that opens the discharge passage 12 and a blocking position that blocks the discharge passage 12, a spring 14b that biases the valve element 14a to the blocking position, and a solenoid 14c that switches the valve element 14a to the communication position against the biasing 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 in the blocking 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 in 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. Since 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] The relief passage 15 communicates between the inside of the cylinder 1 and 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, when hydraulic oil is supplied into the cylinder 1 by driving the pump 13 and the pressure in the cylinder 1 becomes excessive, 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 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 a 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 communicate the inside of the cylinder 1 with the reservoir 5, and the discharge passage on-off valve 14 is set to the blocking 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 expansion-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 provides resistance to the flow of the hydraulic oil, so that the pressure in the expansion-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 the 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, and air chamber G expands by that amount. In this way, the reservoir 5 compensates for the change in the displacement volume of piston rod 3 within cylinder 1, and shock absorber D extends smoothly while generating 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 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 the hydraulic oil, so that 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 in 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 the hydraulic oil pushed out from within cylinder 1 is absorbed by liquid chamber L. In this way, the reservoir 5 compensates for the change 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 and push up the vehicle body to raise the vehicle height will be described. When the vehicle height is raised, 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 to the inside of the cylinder 1, the piston rod 3 is pushed out of the inside of the cylinder 1 by the hydraulic oil supplied into the cylinder 1, and the shock absorber D is extended to push up the vehicle body. The hydraulic oil in the expansion-side chamber R1 that is compressed moves to the expansion-side chamber R2 through the damping passage 4. Therefore, the vehicle height of the vehicle to which the shock absorber D is applied is raised by driving the pump 13 to supply hydraulic oil into the cylinder 1.

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

[0035] Incidentally, whether the on-off valve 7 in the compensation passage 6 is in the communicating position or the blocking position, the shock absorber D can be extended to raise the vehicle height; however, if the on-off valve 7 is set to the blocking position and the pump 13 is driven to raise the vehicle height, 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, when raising the vehicle height, it is preferable to set the on-off valve 7 to the communicating position.

[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 liquid 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, and the pressure in the air chamber G rises. Since the reservoir 5 and the cylinder 1 are connected to each other, the pressure in the air chamber G and the pressure in the cylinder 1 rise equally due to the supply of hydraulic oil from the pump 13. As the pressure in the cylinder 1 rises, the force pushing the piston rod 3 upward in FIG. 1 against the cylinder 1 increases, so the shock absorber D raises the vehicle height. However, in this case, since 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 the shock absorber D when the vehicle height is lowered by lowering the vehicle body will be described. When the vehicle height is lowered, the pump 13 is stopped and the discharge passage opening / closing valve 14 is set to the communication position to communicate the inside of the cylinder 1 with the tank 10. The shock absorber D is always biased to contract by the weight of the vehicle body, so when the inside of the cylinder 1 and the tank 10 are in a communication state, the piston rod 3 moves downward in FIG. 1 in the cylinder 1 by the biasing force from the vehicle body, and the shock absorber D contracts. When the piston rod 3 enters the cylinder 1, the hydraulic oil in the cylinder 1 becomes excessive by the volume of the piston rod 3 entering the cylinder 1, so that the hydraulic oil is pushed out of the cylinder 1 and moves to the tank 10 through the discharge passage 12. The hydraulic oil is supplied to the expansion side chamber R1, which expands as the shock absorber D contracts, from the compression side chamber R2, which is compressed, through the 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, so that the orifice 19 applies resistance to the flow of the hydraulic oil, slowing down the contraction speed of the shock absorber D and preventing the vehicle height from dropping too quickly. By providing the orifice 19 in this way, the lowering speed when lowering the vehicle height can be slowed down, so that discomfort is not caused to the 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 the hydraulic oil, and the discharge passage opening / closing valve 14 may be used instead of the orifice 19 to slow down the lowering speed of the vehicle body.

[0039] Next, the operation of the shock absorber D when the shock absorber D is in a locked state that cannot expand or contract and the vehicle height is maintained constant when the vehicle is stopped will be described. When the shock absorber D is in a locked state that cannot expand or contract, the on-off valve 7 is set to the blocking position to cut off communication between the inside of the cylinder 1 and the reservoir 5. In this way, even if the piston rod 3 tries to retract from the cylinder 1 to expand the shock absorber D, hydraulic oil cannot pass between the inside of the cylinder 1 and the reservoir 5, and hydraulic oil cannot be supplied to the inside of the cylinder 1, so the shock absorber D cannot expand. Also, even if the piston rod 3 tries to enter the cylinder 1 to contract the shock absorber D, hydraulic oil cannot pass between the inside of the cylinder 1 and the reservoir 5, and hydraulic oil cannot be discharged from the inside of the cylinder 1, so the shock absorber D cannot contract. In this way, the on-off valve 7 is closed to block the compensation passage 6 that communicates between the inside of the cylinder 1 and the reservoir 5, so the shock absorber D is in a locked state that cannot expand or contract. 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 described above, when the pressure in cylinder 1 becomes excessive due to hydraulic oil being supplied into cylinder 1 by the operation of pump 13, or when the pressure in cylinder 1 becomes excessive during the contraction operation of shock absorber D, relief valve 16 opens to prevent the pressure in cylinder 1 from exceeding the opening pressure of relief valve 16, thereby protecting shock absorber D.

[0041] As described above, the shock absorber D of this embodiment includes a cylinder 1, a piston 2 inserted into the cylinder 1 to divide the inside of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2 filled with hydraulic oil (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 that communicates between the extension-side chamber R1 and the compression-side chamber R2 and provides resistance to the flow of hydraulic oil (liquid) passing through, a reservoir 5 that stores the hydraulic oil (liquid) and communicates with the inside of the cylinder 1 to compensate for changes in the displacement volume of the piston rod 3 in the cylinder 1, and an on-off valve 7 provided in a compensation passage 6 that communicates between the inside 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 exhibit 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 in which the shock absorber cannot expand and contract. Since 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] In addition, in the shock absorber D of this embodiment, the on-off valve 7 is a normally open type on-off valve, so that 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 the valve to expand and contract to exert a damping force, so that the damping force can be exerted to suppress vibration of the vehicle body even in the event of a malfunction. If the on-off valve 7 is a normally closed type 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. Although the on-off valve 7 is an electromagnetic on-off valve, it may be an on-off valve that is manually switched.

[0044] The shock absorber D of this embodiment includes a tank 10 for storing hydraulic oil (liquid), a supply passage 11 and a discharge passage 12 communicating between the tank 10 and the inside of the cylinder 1, a pump 13 provided in the supply passage 11 and capable of sucking in liquid from the tank 10 and supplying the hydraulic oil (liquid) into the cylinder 1, and a discharge passage opening / closing valve 14 capable of opening and closing the discharge passage 12. In the shock absorber D configured in this manner, the shock absorber D can be expanded to raise the vehicle height by driving the pump 13 to supply the hydraulic oil (liquid) into the cylinder 1, and can be contracted to lower the vehicle height by discharging the hydraulic oil (liquid) from the inside of the cylinder 1 to the tank 10 by opening the discharge passage opening / closing valve 14. Thus, according to the shock absorber D of this embodiment, the vehicle height can be adjusted, and the vehicle height of the vehicle can be kept constant by closing the opening / closing valve 7 after the vehicle height adjustment in a locked state that cannot be expanded or contracted. 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 to automatically set 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, in the case where 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 consisting of the tank 10, the supply passage 11, the discharge passage 12, the pump 13, and the discharge passage opening / closing valve 14.

[0045] The shock absorber D of this embodiment is provided with a relief passage 15 that communicates the tank 10 with the inside of the cylinder 1, and a relief valve 16 that can open and close the relief passage 15 and opens when the pressure on the upstream side reaches the valve opening pressure with the cylinder side as the upstream side to allow only the flow of hydraulic oil (liquid) from the inside of the cylinder 1 toward the tank 10, and the on-off valve 7 is disposed in a position that opens and closes the compensation passage 6 but does not open and close the relief passage 15. According to the shock absorber D configured in this manner, even if the on-off valve 7 is closed to disable the exchange of hydraulic oil (liquid) between the inside of the cylinder 1 and the reservoir 5, the relief valve 16 opens to release the pressure in the cylinder 1 to the tank 10 when a large external force acts to expand and contract and the pressure in the cylinder 1 becomes excessive, so that the shock absorber D can be protected. Also, even if the vehicle is mistakenly driven with the on-off valve 7 closed, the relief passage 15 and the relief valve 16 can prevent the pressure in the 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, but the shock absorber D may be provided with a relief passage 15 that communicates between the tank 10 and 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 opens when the pressure on the upstream side reaches the valve opening pressure to allow only the flow of hydraulic oil (liquid) from the inside of the cylinder 1 toward the tank 10, as in the shock absorber D1 shown in Fig. 2, and the supply passage 11, the discharge passage 12, and the relief passage 15 may be connected to the middle of the compensation passage 6 on the opposite side to 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. According to the shock absorber D configured in this way, a locked state in which it cannot expand or contract can be maintained even if a large external force is applied.

[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 to the reservoir 5, and a check valve 21 that allows only the flow of hydraulic oil from the reservoir 5 to the compression side chamber R2, in parallel between the reservoir 5 and the compression side chamber R2. The shock absorber D2 configured in this way can also achieve a locked state in which expansion and contraction are disabled by closing the on-off valve 7 to cut off communication between the inside of the cylinder 1 and the reservoir 5, and can generate a damping force during expansion and contraction by opening the on-off valve 7.

[0048] The compensation passage 6 and the pump unit P, or the height adjustment unit C further including the compensation passage 6 and the pump unit P and the relief passage 15 and the relief valve 16, 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 the vehicle height of the vehicle constant by closing the on-off valve 7 to a locked state in which expansion and contraction is not possible, and can also adjust the vehicle height by the pump unit P. Therefore, the shock absorber D configured in this manner can maintain the vehicle height constant, so that the 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 may be connected to the inside of the cylinder 1 independently without the compensation passage 6. However, when a structure in which the pump unit P is connected to the inside of the cylinder 1 via the compensation passage 6 is adopted, as in the shock absorbers D, D1, and D2 shown in Figures 1 to 3, the hydraulic circuit is simplified and the layout of the piping that connects the reservoir 5 and the pump unit P to the inside of the cylinder 1 is also facilitated.

[0050] In addition, when a partition member (not shown) that includes an on-off valve 7 and separates the pressure side chamber R2 from the reservoir 5 is provided inside the cylinder 1, the reservoir 5 can be installed below the pressure 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 above, modifications, variations and changes can be made without departing from the scope of the appended claims. [Explanation of symbols]

[0052] Reference Signs List 1 cylinder, 2 piston, 3 piston rod, 4 damping passage, 5 reservoir, 6 compensation passage, 7 on-off valve, 10 tank, 11 supply passage, 12 discharge passage, 13 pump, 14 discharge passage on-off valve, 15 relief passage, 16 relief valve, D, D1, D2 shock absorber, P pump unit, R1 expansion side chamber, R2 compression side chamber

Claims

1. A cylinder; a piston inserted into the cylinder to divide the inside of the cylinder into an expansion-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 liquid passing therethrough; a reservoir for storing a liquid, communicating with the cylinder and compensating for a change in displacement volume of the piston rod in the cylinder; a valve provided in a compensation passage that communicates between the inside of the cylinder and the reservoir and that opens and closes the compensation passage A shock absorber characterized by:

2. A tank for storing 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 capable of opening and closing the discharge passage; 2. The shock absorber according to claim 1 .

3. a relief passage communicating between the tank and the inside of the cylinder; a relief valve capable of opening and closing the relief passage, the relief valve opening when the pressure on the upstream side reaches a valve opening pressure, the cylinder side being an upstream side, to allow only the flow of liquid from inside the cylinder to 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.

4. a relief passage communicating between the tank and the inside of the cylinder; a relief valve capable of opening and closing the relief passage, the relief valve opening when the pressure on the upstream side reaches a valve opening pressure, the cylinder side being an upstream side, to allow only the flow of liquid from inside the cylinder to the tank, The on-off valve opens and closes the compensation passage, the supply passage, the discharge passage, and the relief passage.

3. The shock absorber according to claim 2.

5. 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.

6. The inside of the cylinder and the reservoir are communicated only through the compensation passage.

2. The shock absorber according to claim 1 .

7. 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 .

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