Hydraulic damper

Abstract

To provide a hydraulic damper capable of obtaining stable attenuation characteristics.SOLUTION: To a channel 35 (second pressure chamber 9) on an outflow side of a first relief valve 23 and a channel 39 (first pressure chamber 7) on an outflow side of a second relief valve 17, a direction switching valve 31 is connected. The direction switching valve 31 opens a low-pressure side between the channel 35 (second pressure chamber 9) and the channel 39 (first pressure chamber 7), and can switch so as to connect the low pressure side of either one of the channel 35 (second pressure chamber 9) or the channel 39 (first pressure chamber 7) with an accumulator 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a hydraulic damper used for buildings and the like.

Background Art

[0002] Conventionally, hydraulic dampers have been used to reduce the sway of buildings caused by earthquakes, winds, etc. A hydraulic damper utilizes the fluid resistance of oil to generate a resistance force (damping force) against the sway of a building, absorbs the sway of the building, and improves earthquake resistance and habitability. That is, the hydraulic oil filled in the cylinder of the hydraulic damper generates a damping force due to the fluid resistance when passing through the hydraulic valve, and absorbs the sway of the building.

[0003] As such a hydraulic damper, for example, there is a hydraulic damper equipped with a pressure regulating valve that generates a damping force regardless of the direction in which the piston in the cylinder moves by using a plurality of check valves (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] FIG. 5 is a diagram showing the configuration of a conventional hydraulic damper 100. As shown in FIG. 5, the hydraulic damper 100 mainly includes a hydraulic circuit composed of a cylinder 103, a piston 105, a pressure regulating valve 113, an accumulator 111, and the like.

[0006] Inside the cylinder 103, it is partitioned by the piston 105 into a first pressure chamber 107 and a second pressure chamber 109. The first pressure chamber 107 and the second pressure chamber 109 are filled with hydraulic oil. The first pressure chamber 107 is connected via a flow path to the inflow side of the second check valve 117 and the outflow side of the fourth check valve 121, and the second pressure chamber 109 is connected via a flow path to the inflow side of the first check valve 115 and the outflow side of the third check valve 119.

[0007] Also, a pressure regulating valve 113 is connected between the outflow sides of the first check valve 115 and the second check valve 117 and the inflow sides of the third check valve 119 and the fourth check valve 121. The pressure regulating valve 113 generates a damping force due to the fluid resistance of the hydraulic oil from the outflow sides of the first check valve 115 and the second check valve 117 to the inflow sides of the third check valve 119 and the fourth check valve 121. Note that an accumulator 111 is connected to the outflow side of the pressure regulating valve 113 via a throttle valve 127.

[0008] Also, a first relief valve 123 and a second relief valve 125 are connected between the first pressure chamber 107 and the second pressure chamber 109. The first relief valve 123 allows the flow of hydraulic oil from the first pressure chamber 107 to the second pressure chamber 109 when the pressure on the first pressure chamber 107 side becomes a predetermined value or more, and the second relief valve 125 allows the flow of hydraulic oil from the second pressure chamber 109 to the first pressure chamber 107 when the pressure on the second pressure chamber 109 side becomes a predetermined value or more.

[0009] When the piston 105 moves to the left side in the figure and the first pressure chamber 107 becomes higher pressure than the second pressure chamber 109, the second check valve 117 opens, and the hydraulic oil from the first pressure chamber 107 flows out to the second pressure chamber 109 side through the pressure regulating valve 113 and via the third check valve 119. Also, when the piston 105 moves to the right side in the figure and the second pressure chamber 109 becomes higher pressure than the first pressure chamber 107, the first check valve 115 opens, and the hydraulic oil from the second pressure chamber 109 flows out to the first pressure chamber 107 side through the pressure regulating valve 113 and via the fourth check valve 21.

[0010] In this way, with a single pressure regulating valve 113, damping force can be generated regardless of the direction in which the piston 105 moves. Therefore, by adjusting a single pressure regulating valve 113, equal damping characteristics can be obtained in any direction.

[0011] Note that the first relief valve 123 opens when the pressure of the hydraulic oil in the first pressure chamber 107 exceeds a certain value, allowing the hydraulic oil to flow from the first pressure chamber 107 side to the second pressure chamber 109 side. Also, the second relief valve 125 opens when the pressure of the hydraulic oil in the second pressure chamber 109 exceeds a certain value, allowing the hydraulic oil to flow from the second pressure chamber 109 side to the first pressure chamber 107 side. By doing so, two-stage damping characteristics can be exhibited.

[0012] On the other hand, when passing through the pressure regulating valve 113 and each relief valve, the temperature of the hydraulic oil rises. For example, the temperature of the outflow side (part Z in the figure) tends to rise compared to the inflow side (part Y in the figure) of the pressure regulating valve 113. When the temperature of the hydraulic oil rises, its volume expands. For this reason, the pressure in the pressure chamber that is originally on the low-pressure side may become higher than expected, and the pressure difference between the two pressure chambers becomes smaller, so the designed damping characteristics may not be obtained.

[0013] Normally, such volume fluctuations can be absorbed by the accumulator 111. Also in the hydraulic damper 100, since the accumulator 111 is connected to the outflow side of the pressure regulating valve 113, even if a volume increase occurs due to a temperature rise, excessive hydraulic oil can flow into the accumulator 111.

[0014] However, if the pressure regulating valve 113 that exhibits damping force and the accumulator 111 are directly connected, when the hydraulic damper 100 operates, there is a risk of excessive inflow of hydraulic oil from the circuit into the accumulator 111. For this reason, the working oil that originally flows from one pressure chamber to the other pressure chamber flows into the accumulator 111, which becomes a factor in the shortage of oil in the other pressure chamber. Therefore, a throttle valve 127 is provided between the pressure regulating valve 113 and the accumulator 111 to suppress the sudden inflow of hydraulic oil into the accumulator 111.

[0015] However, depending on the moving speed of the piston 105 or the like, the pressure fluctuation in the Z portion is not constant. For this reason, depending on the situation, if the throttle of the throttle valve 127 is weak, the effect of the throttle valve 127 becomes small, and if the throttle is too strong, there is a risk that the damping characteristic deteriorates without being able to follow the volume fluctuation. Thus, the design of the throttle valve 127 is not simple.

[0016] Also, as described above, when the moving speed of the piston 5 exceeds a certain value and the pressure in the first pressure chamber 107 or the second pressure chamber 109 becomes equal to or higher than a predetermined pressure, the first relief valve 123 or the second relief valve 125 opens and the hydraulic oil flows. However, even in this case, volume expansion due to a temperature rise on the outflow side occurs. For example, when the first pressure chamber 107 is on the high-pressure side, when passing through the first relief valve 123, volume expansion due to a temperature rise occurs on the outflow side (portion X in the figure).

[0017] In this case, compared with the inflow side (portion W in the figure) of the first relief valve 123, the X portion on the outflow side becomes the low-pressure side, so the second relief valve 125 is closed. Also, compared with the X portion, the Y portion becomes the high-pressure side, so the first check valve 115 does not open. Further, the third check valve 119 allows only the flow of the hydraulic oil from the Z portion side to the X portion side. For this reason, the flow path through which the hydraulic oil in the X portion flows to the accumulator 111 is closed, and the volume expansion in the X portion side cannot be absorbed by the accumulator 111.

[0018] Similarly, when the second pressure chamber 109 is on the high-pressure side, when passing through the second relief valve 125, volume expansion due to a temperature rise occurs on the outflow side (portion W in the figure). Also in this case, compared with the X portion on the inflow side of the second relief valve 125, the W portion on the outflow side becomes the low-pressure side, so the first relief valve 123 is closed. Also, compared with the W portion, the Y portion becomes the high-pressure side, so the second check valve 117 does not open. Further, the fourth check valve 121 allows only the flow of the hydraulic oil from the Z portion side to the W portion side. For this reason, the flow path through which the hydraulic oil in the W portion flows to the accumulator 111 is closed, and the volume expansion in the W portion side cannot be absorbed by the accumulator 111.

[0019] Thus, in particular, in the hydraulic damper 100 having two-stage damping characteristics, it is difficult to efficiently absorb the volume expansion associated with the temperature rise of the hydraulic oil after passing through the pressure regulating valve and the relief valve, and to ensure accurate damping characteristics.

[0020] The present invention has been made in view of such problems, and an object thereof is to provide a hydraulic damper capable of obtaining stable damping characteristics.

Means for Solving the Problems

[0021] The present invention for achieving the above-described object includes a cylinder, a piston that divides the cylinder into a first pressure chamber and a second pressure chamber and is movably provided in the cylinder, a first check valve having an inflow side connected to the second pressure chamber and an outflow side connected to a first flow path, a second check valve having an inflow side connected to the first pressure chamber and an outflow side connected to the first flow path, a pressure regulating valve having an inflow side connected to the first flow path, an outflow side connected to a second flow path, and generating fluid resistance in the hydraulic oil passing from the first flow path to the second flow path, a third check valve having an inflow side connected to the second flow path and an outflow side connected to the second pressure chamber, a fourth check valve having an inflow side connected to the second flow path and an outflow side connected to the first pressure chamber, a first relief valve having an inflow side connected to the first pressure chamber and an outflow side connected to the second pressure chamber and allowing only the flow of hydraulic oil from the first pressure chamber to the second pressure chamber, a second relief valve having an inflow side connected to the second pressure chamber and an outflow side connected to the first pressure chamber and allowing only the flow of hydraulic oil from the second pressure chamber to the first pressure chamber, a direction switching valve connected to the first pressure chamber and the second pressure chamber and opening on the low-pressure side, and an accumulator connected to the direction switching valve.

[0022] Throttle valves may be provided between the first pressure chamber and the second pressure chamber and the direction switching valve, respectively.

[0023] The direction switching valve may be held in a neutral state by an elastic member when the pressure difference between the first pressure chamber and the second pressure chamber is below a predetermined value.

[0024] According to the present invention, since the first pressure chamber and the second pressure chamber (i.e., the outflow sides of the pressure regulating valve, the first relief valve, and the second relief valve) are connected to the accumulator via a direction switching valve that opens on the low-pressure side, even if the volume of the hydraulic oil changes due to the temperature rise when passing through each valve, the accumulator can surely absorb the volume change. Therefore, fluctuations in the damping characteristics due to the volume change can be suppressed, and stable damping characteristics can be obtained.

[0025] Further, by providing throttle valves between the first pressure chamber and the second pressure chamber and the direction switching valve respectively, it is possible to suppress the impact of a sudden pressure change from being directly applied to the accumulator when the hydraulic damper starts operating or immediately after the direction is switched.

[0026] Also, if the direction switching valve is held in a neutral state by an elastic member when the pressure difference between the first pressure chamber and the second pressure chamber is below a predetermined value, the accumulator can absorb any volume change in either the first pressure chamber or the second pressure chamber with respect to temperature changes and the like in the stopped state of the hydraulic damper.

Advantages of the Invention

[0027] According to the present invention, it is possible to provide a hydraulic damper capable of obtaining stable damping characteristics.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0029] Hereinafter, a hydraulic damper according to an embodiment of the present invention will be described. As shown in FIG. 1, the hydraulic damper 1 mainly includes a cylinder 3, a piston 5, etc., and a hydraulic circuit including a pressure regulating valve 13, an accumulator 11, etc.

[0030] A piston 5 is movably provided in a cylindrical cylinder 3. Cylindrical piston rods are provided on both sides of the piston 5. Joints (not shown) are connected to the ends of the cylinder 3 and the piston rod, and are fixed to braces or bases of a building.

[0031] The inside of the cylinder 3 is divided into a first pressure chamber 7 and a second pressure chamber 9 by the piston 5. The first pressure chamber 7 and the second pressure chamber 9 are filled with hydraulic oil. Note that the cylinder 3, the piston 5, etc. are made of metal.

[0032] A first check valve 15, a second check valve 17, a third check valve 19, and a fourth check valve 21 are connected between the first pressure chamber 7 and the second pressure chamber 9 via flow paths. The first check valve 15 has its inflow side (flow path 16) connected to the second pressure chamber 9 and its outflow side connected to a flow path 27 which is a first flow path. The second check valve 17 has its inflow side (flow path 18) connected to the first pressure chamber 7 and its outflow side connected to the flow path 27.

[0033] The flow path 27 is connected to a flow path 29 which is a second flow path via the pressure regulating valve 13. That is, the pressure regulating valve 13 has its inflow side as the flow path 27 and its outflow side as the flow path 29. The pressure regulating valve 13 generates fluid resistance to the hydraulic oil passing from the flow path 27 to the flow path 29.

[0034] The third check valve 19 has its inflow side as the flow path 29 and its outflow side connected to the second pressure chamber 9 via the flow path 20. Also, the fourth check valve 21 has its inflow side as the flow path 29 and its outflow side connected to the first pressure chamber 7 via the flow path 22.

[0035] Also, a first relief valve 23 and a second relief valve 25 are connected between the first pressure chamber 7 and the second pressure chamber 9 via a flow path. The first relief valve 23 has an inflow side (flow path 33) connected to the first pressure chamber 7 and an outflow side (flow path 35) connected to the second pressure chamber 9. The first relief valve 23 allows the flow of hydraulic oil only from the first pressure chamber 7 to the second pressure chamber 9. Further, the second relief valve 25 has an inflow side (flow path 37) connected to the second pressure chamber 9 and an outflow side (flow path 39) connected to the first pressure chamber 7. The second relief valve 25 allows the flow of hydraulic oil only from the second pressure chamber 9 to the first pressure chamber 7.

[0036] A direction switching valve 31 is connected to the outflow side flow path 35 (second pressure chamber 9) of the first relief valve 23 and the outflow side flow path 39 (first pressure chamber 7) of the second relief valve 25. The direction switching valve 31 can be switched such that the low-pressure side opens between the flow path 35 (second pressure chamber 9) and the flow path 39 (first pressure chamber 7), and the low-pressure side of either the flow path 35 (second pressure chamber 9) or the flow path 39 (first pressure chamber 7) is connected to the accumulator 11.

[0037] Next, with reference to FIGS. 1 and 2, the operation of the hydraulic damper 1 will be described in detail. FIG. 1 shows a case where a force such as an earthquake or wind acts on a building and an external force in the A direction acts on the piston 5. When the piston 5 moves in the A direction, the hydraulic oil filled in the second pressure chamber 9 is compressed. The hydraulic oil compressed in the second pressure chamber 9 flows from the first check valve 15 into the flow path 27 via the flow path 16 (in the direction of arrow B in the figure). At this time, the second check valve 17 and the third check valve 19 are closed.

[0038] The hydraulic oil flowing from the first check valve 15 into the flow path 27 flows into the pressure regulating valve 13. When hydraulic oil above a predetermined pressure flows into the pressure regulating valve 13, the hydraulic oil flows out of the pressure regulating valve 13 into the flow path 29. The hydraulic oil flowing out of the pressure regulating valve 13 flows into the first pressure chamber 7 from the fourth check valve 21 via the flow path 22 (in the direction of arrow C in the figure). Since the second pressure chamber 9 is at a higher pressure than the pressure of the hydraulic oil after passing through the pressure regulating valve 13, the third check valve 19 does not open.

[0039] In this way, by adjusting the spring or the like housed in the pressure regulating valve 13 with respect to the speed at which the piston 5 moves in the A direction, a damping force is generated in the piston 5 in a direction that cancels out the force in the A direction. That is, by adjusting the pressure regulating valve 13, the damping force of the hydraulic damper 1 can be adjusted.

[0040] Here, since the second pressure chamber 9 is at a higher pressure than the first pressure chamber 7, the direction switching valve 31 connects the low-pressure first pressure chamber 7 and the accumulator 11 (E in the figure). As described above, when passing through the pressure regulating valve 13, the temperature of the hydraulic oil rises. For this reason, the volume of the hydraulic oil expands. The hydraulic oil that has flowed out to the flow path 22 (first pressure chamber 7) through the flow path 29 and the fourth check valve 21 after passing through the pressure regulating valve 13 is connected to the accumulator 11 via the direction switching valve 31, so the change in volume of the hydraulic oil can be absorbed by the accumulator 11.

[0041] Also, when the moving speed of the piston 5 in the A direction exceeds a certain value and the pressure in the second pressure chamber 9 becomes a predetermined pressure or more, the second relief valve 25 opens and the hydraulic oil flows from the second pressure chamber 9 to the first pressure chamber 7 (arrow D in the figure). That is, when the damping force generated in the piston 5 exceeds a certain value, the second relief valve 25 opens to suppress the increase in the damping force with respect to the increase in speed. That is, the hydraulic damper 1 has two-stage damping characteristics.

[0042] Even in this case, when passing through the second relief valve 25, the temperature of the hydraulic oil rises and the volume expands. However, since the flow path 39 (first pressure chamber) on the outflow side of the second relief valve 25 is connected to the accumulator 11 via the direction switching valve 31, the change in volume of the hydraulic oil can be absorbed by the accumulator 11.

[0043] Next, the case where the direction of the force such as earthquake or wind acting on the building is reversed will be described. FIG. 2 shows a case where a force such as earthquake or wind acts on the building and an external force in the F direction acts on the piston 5.

[0044] When the piston 5 moves in the F direction, the hydraulic oil filled in the first pressure chamber 7 is compressed. The hydraulic oil compressed in the first pressure chamber 7 flows into the flow path 27 from the second check valve 17 through the flow path 18 (in the direction of arrow G in the figure). At this time, the first check valve 15 and the fourth check valve 21 are closed.

[0045] The hydraulic oil flowing into the flow path 27 from the second check valve 17 flows into the pressure regulating valve 13. When the hydraulic oil above a predetermined pressure flows into the pressure regulating valve 13, the hydraulic oil flows out into the flow path 29 through the pressure regulating valve 13. The hydraulic oil flowing out from the pressure regulating valve 13 flows into the second pressure chamber 9 from the third check valve 19 through the flow path 20 (in the direction of arrow H in the figure). Since the first pressure chamber 7 is at a higher pressure than the pressure of the hydraulic oil after passing through the pressure regulating valve 13, the fourth check valve 21 does not open.

[0046] In this way, by adjusting the spring or the like installed in the pressure regulating valve 13 with respect to the speed at which the piston 5 moves in the F direction, a damping force is generated in the direction that cancels the force in the F direction on the piston 5. That is, by adjusting one pressure regulating valve 13, the damping force in any direction of the hydraulic damper 1 can be adjusted.

[0047] Here, since the first pressure chamber 7 is at a higher pressure than the second pressure chamber 9, the direction switching valve 31 connects the second pressure chamber 9 on the low pressure side and the accumulator 11 (J in the figure). As described above, when passing through the pressure regulating valve 13, the temperature of the hydraulic oil rises. Therefore, the volume of the hydraulic oil expands. The hydraulic oil flowing out through the pressure regulating valve 13 and through the flow path 29 and the third check valve 19 into the flow path 20 (second pressure chamber 9) is connected to the accumulator 11 through the direction switching valve 31, so the volume change of the hydraulic oil can be absorbed by the accumulator 11.

[0048] Also, when the moving speed of the piston 5 in the F direction exceeds a certain value and the pressure in the first pressure chamber 7 becomes equal to or higher than a predetermined pressure, the first relief valve 23 opens and the hydraulic oil flows from the first pressure chamber 7 to the second pressure chamber 9 (arrow I in the figure). That is, when the damping force generated on the piston 5 exceeds a certain value, the first relief valve 23 opens to suppress the increase in the damping force with respect to the increase in speed.

[0049] Even in this case, when passing through the first relief valve 23, the hydraulic oil rises in temperature and expands in volume. However, since the flow path 35 (second pressure chamber 9) on the outflow side of the first relief valve 23 is connected to the accumulator 11 via the direction switching valve 31, the volume change of the hydraulic oil can be absorbed by the accumulator 11.

[0050] Note that when the movement of the piston 5 stops, the pressure difference between the first pressure chamber 7 and the second pressure chamber 9 disappears, so the movement of the hydraulic oil stops. Here, when the movement of the hydraulic oil stops, it is desirable that the direction switching valve 31 opens to both the first pressure chamber 7 side and the second pressure chamber 9 side.

[0051] FIG. 3 is a conceptual diagram showing the structure of the direction switching valve 31. The direction switching valve 31 is, for example, a pair of valve bodies 41a and 41b connected together and arranged so as to be able to contact either one of the valve seats 43a and 43b from the outside of the pair of valve seats 43a and 43b. In the oil chambers in which the respective valve bodies 41a and 41b are accommodated, hydraulic oil inflow / outflow ports (K and L in the figure) are provided, and further, a hydraulic oil inflow / outflow port (M in the figure) is provided between the pair of valve seats 43a and 43b.

[0052] For example, when the K side becomes the high-pressure side with respect to the L side, the valve body 41a moves to the right side in the figure together with the valve body 41b and contacts the valve seat 43a on the left side in the figure. In this state, since the K side is closed, the L side and the M side communicate with each other. Conversely, when the L side becomes the high-pressure side with respect to the K side, the valve body 41b moves to the left side in the figure together with the valve body 41a and contacts the valve seat 43b on the right side in the figure. In this state, since the L side is closed, the K side and the M side communicate with each other.

[0053] Here, if necessary, elastic members 45 are arranged for the respective valve bodies 41a and 41b. In a state where the forces of the pair of elastic members 45 balance each other, neither of the valve bodies 41a and 41b contacts the valve seats 43a and 43b.

[0054] For example, if the outflow side of the first relief valve 23 (the second pressure chamber 9) is taken as port L and the outflow side of the second relief valve (the first pressure chamber 7) is taken as port K, when this pressure difference is below a predetermined value, the elastic member 45 maintains a neutral state (i.e., a state where both ports K and L are open). In this state, since all ports K, L, and M are connected, the first pressure chamber 7, the second pressure chamber 9, and the accumulator 11 are connected via the direction switching valve 31.

[0055] By doing so, the accumulator 11 can absorb the volume change of the hydraulic oil when the hydraulic damper 1 is stopped. For example, when the elastic member 45 is not used, when the operation of the hydraulic damper stops, the direction switching valve 31 is held in a state where the last opened port is connected to the accumulator 11. In this state, due to the influence of changes in environmental temperature and leakage of hydraulic oil, the accumulator 11 cannot absorb the volume change of the hydraulic oil in the pressure chamber on the side that was the high-pressure side last.

[0056] On the other hand, in the stopped state of the hydraulic damper 1, by connecting both the first pressure chamber 7 and the second pressure chamber 9 to the accumulator 11, even in the stopped state of the hydraulic damper 1, the accumulator 11 can surely absorb the volume fluctuation of the hydraulic oil in any hydraulic chamber. Therefore, when the hydraulic damper 1 starts operating again later, stable damping characteristics can be obtained from the beginning.

[0057] As described above, according to the present embodiment, it is possible to ensure the damping characteristics in two stages: the damping force by the pressure regulating valve 13 and the damping force obtained by adding the first relief valve 23 and the second relief valve 25. Also, the low-pressure outflow sides (i.e., the low-pressure hydraulic chambers) of the pressure regulating valve 13, the first relief valve 23, and the second relief valve 25 are connected to the accumulator 11 via the direction switching valve 31. Therefore, the volume fluctuation of the hydraulic oil after passing through each valve can be surely absorbed by the accumulator. Thus, stable damping characteristics can be obtained.

[0058] Further, when the hydraulic damper 1 stops, the switching valve 31 connects both the first pressure chamber 7 and the second pressure chamber 9 to the accumulator 11. Therefore, the accumulator 11 can also absorb the change in the volume of the hydraulic oil when the hydraulic damper 1 stops. For this reason, stable damping characteristics can be obtained from the initial stage of operation.

[0059] Next, a second embodiment will be described. FIG. 4 is a circuit diagram showing the configuration of the hydraulic damper 1a. In the following description, components having the same functions as those of the hydraulic damper 1 are denoted by the same reference numerals as those in FIG. 1 and the like, and redundant descriptions are omitted. The hydraulic damper 1a has substantially the same configuration as the hydraulic damper 1, but is different in that throttle valves 47 are provided between the first pressure chamber 7 and the second pressure chamber 9 and the switching valve 31, respectively.

[0060] As described above, among the hydraulic oil flowing out from the pressure regulating valve 13 through the flow path 29 in the flow path 22 or the flow path 20, the volume increase due to the temperature rise can flow into the accumulator 11. On the other hand, since each pressure chamber is connected to the switching valve 31, there is a possibility that the switching valve 31 may be subjected to an impact due to the pressure fluctuation of the hydraulic oil. Therefore, there is a risk of damage to the switching valve 31 or the like.

[0061] On the other hand, since the throttle valve 47 is provided at the inflow portion to the switching valve 31, resistance is applied to the inflow of the hydraulic oil from each pressure chamber to the switching valve 31. Therefore, the impact of the hydraulic oil on the switching valve 31 can be suppressed.

[0062] As described above, according to the second embodiment, the same effects as those of the first embodiment can be obtained. Further, the throttle valve 47 can suppress the impact of the hydraulic oil on the switching valve 31.

[0063] The embodiments of the present invention have been described above with reference to the attached drawings. However, the technical scope of the present invention is not limited by the above-described embodiments. It is obvious that those skilled in the art can conceive various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that those also belong to the technical scope of the present invention.

Explanation of Reference Numerals

[0064] 1, 1a... Hydraulic damper 3......... Cylinder 5......... Piston 7......... First pressure chamber 9......... Second pressure chamber 11......... Accumulator 13......... Pressure regulating valve 15......... First check valve 16, 18, 20, 22, 27, 29, 33, 35, 37, 39... Flow path 17......... Second check valve 19......... Third check valve 21......... Fourth check valve 23......... First relief valve 25......... Second relief valve 31......... Direction switching valve 41a, 41b... Valve body 43a, 43b... Valve seat 45......... Elastic member 47......... Throttle valve 100... Hydraulic damper 103......... Cylinder 105......... Piston 107......... First pressure chamber 109......... Second pressure chamber 101......... Accumulator 103......... Pressure regulating valve 105......... First check valve 117......... Second check valve 119......... Third check valve 121......... Fourth check valve 123......... First relief valve 125………Second relief valve 127………Throttle valve

Claims

1. A cylinder, which divides the cylinder into a first pressure chamber and a second pressure chamber, and a piston movably provided in the cylinder, a first check valve having an inflow side connected to the second pressure chamber and an outflow side connected to a first flow path, a second check valve having an inflow side connected to the first pressure chamber and an outflow side connected to the first flow path, a pressure regulating valve having an inflow side connected to the first flow path, an outflow side connected to a second flow path, and generating a fluid resistance in the hydraulic oil passing from the first flow path to the second flow path, a third check valve having an inflow side connected to the second flow path and an outflow side connected to the second pressure chamber, a fourth check valve having an inflow side connected to the second flow path and an outflow side connected to the first pressure chamber, a first relief valve having an inflow side connected to the first pressure chamber, an outflow side connected to the second pressure chamber, and allowing only the flow of hydraulic oil from the first pressure chamber to the second pressure chamber, a second relief valve having an inflow side connected to the second pressure chamber, an outflow side connected to the first pressure chamber, and allowing only the flow of hydraulic oil from the second pressure chamber to the first pressure chamber, a direction switching valve connected to the first pressure chamber and the second pressure chamber and opening in the low-pressure side direction, an accumulator connected to the direction switching valve, and a hydraulic damper characterized by comprising the above.

2. The hydraulic damper according to claim 1, wherein throttle valves are respectively provided between the first pressure chamber, the second pressure chamber, and the direction switching valve.

3. The hydraulic damper according to claim 1 or claim 2, wherein the direction switching valve is held in a neutral state by an elastic member when the pressure difference between the first pressure chamber and the second pressure chamber is equal to or less than a predetermined value.

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