JP7695871B2 - Hydraulic Damper - Google Patents

Description

The present invention relates to a hydraulic damper for use in buildings, etc.

Hydraulic dampers have traditionally been used to reduce the shaking of buildings caused by earthquakes, wind, etc. Hydraulic dampers use the fluid resistance of oil to generate resistance (damping force) against the shaking of buildings, absorbing the shaking of the building and improving earthquake resistance and livability. That is, hydraulic oil filled in the cylinder of the hydraulic damper generates a damping force due to the fluid resistance when passing through a hydraulic valve, absorbing the shaking of the building.

One example of such a hydraulic damper is one equipped with a pressure regulating valve that uses multiple check valves to generate a damping force regardless of the direction in which the piston in the cylinder moves (for example, Patent Document 1).

JP 2004-36677 A

Figure 5 is a diagram showing the configuration of a conventional hydraulic damper 100. As shown in Figure 5, the hydraulic damper 100 is mainly composed of a hydraulic circuit including a cylinder 103, a piston 105, a pressure regulating valve 113, an accumulator 111, etc.

The inside of the cylinder 103 is divided 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 to the inlet side of the second check valve 117 and the outlet side of the fourth check valve 121 via a flow path, and the second pressure chamber 109 is connected to the inlet side of the first check valve 115 and the outlet side of the third check valve 119 via a flow path.

The pressure regulating valve 113 is connected between the outflow side of the first check valve 115 and the second check valve 117 and the inflow side of the third check valve 119 and the fourth check valve 121. The pressure regulating valve 113 generates a damping force by the flow resistance of the hydraulic oil from the outflow side of the first check valve 115 and the second check valve 117 to the inflow side of the third check valve 119 and the fourth check valve 121. The accumulator 111 is connected to the outflow side of the pressure regulating valve 113 via a throttle valve 127.

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 hydraulic oil to flow from the first pressure chamber 107 to the second pressure chamber 109 when the pressure on the first pressure chamber 107 side reaches or exceeds a predetermined level, and the second relief valve 125 allows hydraulic oil to flow from the second pressure chamber 109 to the first pressure chamber 107 when the pressure on the second pressure chamber 109 side reaches or exceeds a predetermined level.

When the piston 105 moves to the left 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 hydraulic oil from the first pressure chamber 107 flows through the pressure regulating valve 113 and into the second pressure chamber 109 via the third check valve 119. Also, when the piston 105 moves to the right 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 hydraulic oil from the second pressure chamber 109 flows through the pressure regulating valve 113 and into the first pressure chamber 107 via the fourth check valve 21.

In this way, a single pressure regulating valve 113 can generate a damping force regardless of the direction in which the piston 105 moves. Therefore, by adjusting a single pressure regulating valve 113, it is possible to obtain equal damping characteristics in either direction.

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. 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. In this way, a two-stage damping characteristic can be achieved.

On the other hand, the temperature of the hydraulic oil rises as it passes through the pressure regulating valve 113 and each relief valve. For example, there is a tendency for the temperature to rise on the outlet side (part Z in the figure) of the pressure regulating valve 113 compared to the inlet side (part Y in the figure). When the temperature of the hydraulic oil rises, the volume expands. For this reason, the pressure in the pressure chamber that is originally the low pressure side becomes higher than expected, and the pressure difference between the two pressure chambers becomes small, so the designed damping characteristics may not be obtained.

Normally, such volume fluctuations can be absorbed by the accumulator 111. In the hydraulic damper 100, the accumulator 111 is also connected to the outlet side of the pressure regulating valve 113, so even if a volume increase occurs due to a temperature rise, excess hydraulic oil can be made to flow into the accumulator 111.

However, if the pressure regulating valve 113, which exerts the damping force, is directly connected to the accumulator 111, there is a risk that excessive hydraulic oil will flow from the circuit into the accumulator 111 when the hydraulic damper 100 operates. As a result, the hydraulic oil that would normally flow from one pressure chamber to the other pressure chamber will flow into the accumulator 111, causing a shortage of oil in the other pressure chamber. For this reason, a throttle valve 127 is provided between the pressure regulating valve 113 and the accumulator 111 to prevent a sudden inflow of hydraulic oil into the accumulator 111.

However, the pressure fluctuations at section Z are not constant, depending on factors such as the moving speed of piston 105. For this reason, if the throttle valve 127 is not tight enough in some circumstances, the effect of the throttle valve 127 will be small, and if it is too tight, it may not be able to keep up with the volume fluctuations and the damping characteristics may deteriorate. As such, designing the throttle valve 127 is not simple.

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 exceeds a predetermined pressure, the first relief valve 123 or the second relief valve 125 opens and hydraulic oil flows, but even in this case, volume expansion occurs due to a rise in temperature on the outflow side. For example, when the first pressure chamber 107 is on the high pressure side, volume expansion occurs on the outflow side (part X in the figure) due to a rise in temperature when passing through the first relief valve 123.

In this case, the outflow side, X, is at a lower pressure compared to the inflow side (W in the figure) of the first relief valve 123, so the second relief valve 125 is closed, and the first check valve 115 does not open because Y is at a higher pressure compared to X. The third check valve 119 only allows hydraulic oil to flow from Z to X. Therefore, the flow path through which hydraulic oil from X flows to the accumulator 111 is closed, and the accumulator 111 cannot absorb the volume expansion on the X side.

Similarly, when the second pressure chamber 109 is at high pressure, volume expansion occurs in the outlet W section due to temperature rise when passing through the second relief valve 125. In this case, the outlet W section is at low pressure compared to the inlet X section of the second relief valve 125, so the first relief valve 123 is closed, and the second check valve 117 does not open because the Y section is at high pressure compared to the W section. The fourth check valve 121 only allows hydraulic oil to flow from the Z section to the W section. Therefore, the flow path through which the hydraulic oil in the W section flows to the accumulator 111 is closed, and the accumulator 111 cannot absorb the volume expansion on the W section side.

As such, it is difficult for the hydraulic damper 100, which has a two-stage damping characteristic in particular, to efficiently absorb the volume expansion that accompanies the temperature rise of the hydraulic oil after passing through the pressure regulating valve and the relief valve and ensure accurate damping characteristics.

The present invention was made in consideration of these problems, and aims to provide a hydraulic damper that can achieve stable damping characteristics.

In order to achieve the above-mentioned object, the present invention comprises a cylinder, a piston which divides the cylinder into a first pressure chamber and a second pressure chamber and is movably provided within the cylinder, a first check valve having an inlet side connected to the second pressure chamber and an outlet side connected to the first flow path, a second check valve having an inlet side connected to the first pressure chamber and an outlet side connected to the first flow path, a pressure regulating valve having an inlet side connected to the first flow path and an outlet side connected to the second flow path, and which generates fluid resistance in hydraulic oil passing from the first flow path to the second flow path, a third check valve having an inlet side connected to the second flow path and an outlet side connected to the second pressure chamber, and a pressure regulating valve having an inlet side connected to the second flow path and an outlet side connected to the first pressure chamber, The hydraulic damper is characterized by comprising the second flow path, a fourth check valve whose outlet side is connected to the first pressure chamber, a first relief valve whose inlet side is connected to the first pressure chamber and whose outlet side is connected to the second pressure chamber, and which allows hydraulic oil to flow only from the first pressure chamber to the second pressure chamber, a second relief valve whose inlet side is connected to the second pressure chamber and whose outlet side is connected to the first pressure chamber, and which allows hydraulic oil to flow only from the second pressure chamber to the first pressure chamber, a directional control valve connected to the first pressure chamber and the second pressure chamber, and whose low pressure side is open, and an accumulator connected to the directional control valve.

A throttle valve may be provided between the first pressure chamber and the second pressure chamber and between the direction change valve.

The directional control valve may be maintained 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.

According to the present invention, 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 directional control valve that opens on the low pressure side. Therefore, even if the volume of the hydraulic oil changes due to the temperature rise when passing through each valve, the volume change can be reliably absorbed by the accumulator. This makes it possible to suppress fluctuations in the damping characteristics due to volume changes, and to obtain stable damping characteristics.

In addition, by providing a throttle valve between the first and second pressure chambers and the direction change valve, it is possible to prevent the impact of a sudden pressure change from being directly applied to the accumulator when the hydraulic damper starts to operate or immediately after the direction is changed.

In addition, if the directional control valve is maintained in a neutral state by the elastic member when the pressure difference between the first and second pressure chambers is below a predetermined level, the accumulator can absorb volume changes in both the first and second pressure chambers due to temperature changes, etc., when the hydraulic damper is stopped.

The present invention provides a hydraulic damper that can achieve stable damping characteristics.

FIG. 2 is a hydraulic circuit diagram of the hydraulic damper 1. FIG. 2 is a hydraulic circuit diagram of the hydraulic damper 1. FIG. 4 is a diagram showing the structure of a directional control valve 31. FIG. 2 is a hydraulic circuit diagram of the hydraulic damper 1a. FIG. 2 is a hydraulic circuit diagram of the hydraulic damper 100.

The following describes a hydraulic damper according to an embodiment of the present invention. As shown in FIG. 1, the hydraulic damper 1 is mainly composed of a hydraulic circuit including a cylinder 3, a piston 5, a pressure regulating valve 13, an accumulator 11, etc.

A piston 5 is movably mounted inside the cylindrical cylinder 3. Cylindrical piston rods are mounted on both sides of the piston 5. Joints (not shown) are connected to the ends of the cylinder 3 and the piston rod, and the ends are fixed to the braces or base of the building.

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

The first check valve 15, the second check valve 17, the third check valve 19, and the 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 an inlet side (flow path 16) connected to the second pressure chamber 9, and an outlet side connected to the flow path 27, which is the first flow path. The second check valve 17 has an inlet side (flow path 18) connected to the first pressure chamber 7, and an outlet side connected to the flow path 27.

Flow path 27 is connected to flow path 29, which is the second flow path, via pressure regulating valve 13. That is, the inflow side of pressure regulating valve 13 is flow path 27, and the outflow side is flow path 29. Pressure regulating valve 13 generates fluid resistance in the hydraulic oil passing from flow path 27 to flow path 29.

The third check valve 19 has an inlet side connected to a flow path 29 and an outlet side connected to the second pressure chamber 9 via a flow path 20. The fourth check valve 21 has an inlet side connected to a flow path 29 and an outlet side connected to the first pressure chamber 7 via a flow path 22.

The first relief valve 23 and the 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 hydraulic oil to flow only from the first pressure chamber 7 to the second pressure chamber 9. 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 hydraulic oil to flow only from the second pressure chamber 9 to the first pressure chamber 7.

A directional control valve 31 is connected to the flow path 35 (second pressure chamber 9) on the outflow side of the first relief valve 23 and the flow path 39 (first pressure chamber 7) on the outflow side of the second relief valve 25. The directional control valve 31 is switchable so that the low pressure side between the flow path 35 (second pressure chamber 9) and the flow path 39 (first pressure chamber 7) is open 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.

Next, the operation of the hydraulic damper 1 will be described in detail using Figures 1 and 2. Figure 1 shows a case where an earthquake, wind, or other force acts on a building, causing an external force in direction A to act on the piston 5. When the piston 5 moves in direction A, 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 through the flow path 16 into the flow path 27 (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.

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

In this way, by adjusting the spring housed in the pressure regulating valve 13 in relation 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 counteracts the force in the A direction. In other words, by adjusting the pressure regulating valve 13, the damping force of the hydraulic damper 1 can be adjusted.

Here, because the second pressure chamber 9 is higher in pressure than the first pressure chamber 7, the directional control valve 31 connects the first pressure chamber 7, which is on the low pressure side, to the accumulator 11 (E in the figure). As described above, the temperature of the hydraulic oil rises when it passes through the pressure regulating valve 13. This causes the volume of the hydraulic oil to expand. The hydraulic oil that passes through the pressure regulating valve 13 and flows out to the flow path 22 (first pressure chamber 7) via the flow path 29 and the fourth check valve 21 is connected to the accumulator 11 via the directional control valve 31, so the change in volume of the hydraulic oil can be absorbed by the accumulator 11.

Furthermore, when the speed of movement of the piston 5 in direction A exceeds a certain value and the pressure in the second pressure chamber 9 exceeds a predetermined pressure, the second relief valve 25 opens and hydraulic oil flows from the second pressure chamber 9 to the first pressure chamber 7 (arrow D in the figure). In other words, when the damping force generated in the piston 5 exceeds a certain value, the second relief valve 25 opens and suppresses the increase in damping force in response to an increase in speed. In other words, the hydraulic damper 1 has a two-stage damping characteristic.

Even in this case, the temperature of the hydraulic oil rises and the volume expands as it passes through the second relief valve 25. However, because the flow path 39 (first pressure chamber) on the outlet side of the second relief valve 25 is connected to the accumulator 11 via the directional control valve 31, the change in volume of the hydraulic oil can be absorbed by the accumulator 11.

Next, we will explain what happens when the direction of a force such as an earthquake or wind acting on a building is reversed. Figure 2 shows a case where a force such as an earthquake or wind acts on the building, and an external force in the direction F acts on the piston 5.

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

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

In this way, by adjusting the spring housed in the pressure regulating valve 13 in relation to the speed at which the piston 5 moves in the F direction, a damping force is generated in the piston 5 in a direction that counteracts the force in the F direction. In other words, by adjusting one pressure regulating valve 13, the damping force of the hydraulic damper 1 in any direction can be adjusted.

Here, because the first pressure chamber 7 is higher than the second pressure chamber 9, the directional control valve 31 connects the low-pressure second pressure chamber 9 to the accumulator 11 (J in the figure). As described above, the temperature of the hydraulic oil rises as it passes through the pressure regulating valve 13. This causes the volume of the hydraulic oil to expand. The hydraulic oil that passes through the pressure regulating valve 13 and flows out to the flow path 20 (second pressure chamber 9) via the flow path 29 and the third check valve 19 is connected to the accumulator 11 via the directional control valve 31, so the change in volume of the hydraulic oil can be absorbed by the accumulator 11.

Furthermore, when the speed of movement 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 greater than a predetermined pressure, the first relief valve 23 opens and hydraulic oil flows from the first pressure chamber 7 to the second pressure chamber 9 (arrow I in the figure). In other words, when the damping force generated in the piston 5 exceeds a certain value, the first relief valve 23 opens to suppress the increase in damping force in response to an increase in speed.

Even in this case, the temperature of the hydraulic oil rises and the volume expands as it passes through the first relief valve 23. However, because the flow path 35 (second pressure chamber 9) on the outlet side of the first relief valve 23 is connected to the accumulator 11 via the directional control valve 31, the change in volume of the hydraulic oil can be absorbed by the accumulator 11.

When the movement of the piston 5 stops, the pressure difference between the first pressure chamber 7 and the second pressure chamber 9 disappears, and the movement of the hydraulic oil stops. Here, when the movement of the hydraulic oil has stopped, it is desirable for the directional control valve 31 to open to both the first pressure chamber 7 side and the second pressure chamber 9 side.

Figure 3 is a conceptual diagram showing the structure of the directional control valve 31. The directional control valve 31 has, for example, a pair of valve bodies 41a, 41b connected together, and is arranged so that it can contact either of the pair of valve seats 43a, 43b from the outside of the pair of valve seats 43a, 43b. The oil chambers housing the valve bodies 41a, 41b are provided with inlet and outlet ports for hydraulic oil (K, L in the figure), and further, between the pair of valve seats 43a, 43b, a port for hydraulic oil inlet and outlet (M in the figure) is provided.

For example, when the K side becomes the high pressure side relative to the L side, the valve body 41a moves to the right in the figure together with the valve body 41b and comes into contact with the valve seat 43a on the left side in the figure. In this state, the K side is closed, so the L side and the M side are in communication. Conversely, when the L side becomes the high pressure side relative to the K side, the valve body 41b moves to the left in the figure together with the valve body 41a and comes into contact with the valve seat 43b on the right side in the figure. In this state, the L side is closed, so the K side and the M side are in communication.

Here, elastic members 45 are arranged for each of the valve bodies 41a, 41b as necessary. When the forces of the pair of elastic members 45 are in balance, neither of the valve bodies 41a, 41b comes into contact with the valve seats 43a, 43b.

For example, if the outflow side of the first relief valve 23 (second pressure chamber 9) is port L and the outflow side of the second relief valve (first pressure chamber 7) is port K, when this pressure difference is below a predetermined level, the neutral state (i.e., both ports K and L are open) is maintained by the elastic member 45. In this state, all ports K, L, and M are connected, so the first pressure chamber 7, second pressure chamber 9, and accumulator 11 are connected via the directional control valve 31.

In this way, the accumulator 11 can absorb changes in the volume of the hydraulic oil when the hydraulic damper 1 is stopped. For example, if the elastic member 45 is not used, when the hydraulic damper stops operating, the directional control valve 31 is held in a state in which the last open port is connected to the accumulator 11. In this state, the accumulator 11 cannot absorb changes in the volume of the hydraulic oil in the pressure chamber on the side that was last on the high-pressure side due to factors such as changes in environmental temperature and hydraulic oil leakage.

In response to this, by connecting both the first pressure chamber 7 and the second pressure chamber 9 to the accumulator 11 when the hydraulic damper 1 is stopped, the accumulator 11 can reliably absorb any volumetric fluctuations in the hydraulic oil in either hydraulic chamber even when the hydraulic damper 1 is stopped. This makes it possible to obtain stable damping characteristics from the beginning when the hydraulic damper 1 starts operating again.

As described above, according to this embodiment, it is possible to ensure two-stage damping characteristics, namely, the damping force by the pressure regulating valve 13 and the damping force by the first relief valve 23 and the second relief valve 25. In addition, the low-pressure outlet side (i.e., the low-pressure hydraulic chamber) of the pressure regulating valve 13, the first relief valve 23, and the second relief valve 25 is connected to the accumulator 11 via the directional control valve 31. This allows the accumulator to reliably absorb the volumetric fluctuations of the hydraulic oil after it has passed through each valve. This makes it possible to obtain stable damping characteristics.

In addition, when the hydraulic damper 1 is stopped, the directional control valve 31 connects both the first pressure chamber 7 and the second pressure chamber 9 to the accumulator 11, so that the change in volume of the hydraulic oil when the hydraulic damper 1 is stopped can also be absorbed by the accumulator 11. This makes it possible to obtain stable damping characteristics from the initial stage of operation.

Next, a second embodiment will be described. Figure 4 is a circuit diagram showing the configuration of hydraulic damper 1a. In the following description, components that perform the same functions as hydraulic damper 1 are given the same reference numerals as in Figure 1 and the like, and duplicated descriptions will be omitted. Hydraulic damper 1a has a configuration substantially similar to hydraulic damper 1, but differs in that throttle valves 47 are provided between first pressure chamber 7 and second pressure chamber 9, and between directional control valve 31.

As mentioned above, the hydraulic oil in flow path 22 or flow path 20 that flows out from pressure regulating valve 13 via flow path 29 and that has increased in volume due to temperature rise can flow into accumulator 11. However, because each pressure chamber is connected to directional control valve 31, there is a risk that directional control valve 31 may be subjected to impact due to pressure fluctuations of the hydraulic oil. This raises the risk of damage to directional control valve 31, etc.

In response to this, a throttle valve 47 is provided at the inlet to the directional control valve 31, so that resistance is applied to the inflow of hydraulic oil from each pressure chamber to the directional control valve 31. This makes it possible to suppress the impact of hydraulic oil on the directional control valve 31.

As described above, the second embodiment can achieve the same effects as the first embodiment. In addition, the throttle valve 47 can suppress the impact of the hydraulic oil on the directional control valve 31.

Although the embodiment of the present invention has been described above with reference to the attached drawings, the technical scope of the present invention is not limited to the above-mentioned embodiment. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

REFERENCE SIGNS LIST 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... Directional 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 (3)

A cylinder;
a piston that divides the cylinder into a first pressure chamber and a second pressure chamber and is movably provided within the cylinder;
a first check valve having an inflow side connected to the second pressure chamber and an outflow side connected to the 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 and an outflow side connected to the second flow path, the pressure regulating valve 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 and an outflow side connected to the second pressure chamber, and allowing hydraulic oil to flow only 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 hydraulic oil to flow only from the second pressure chamber to the first pressure chamber;
a directional control valve connected to the first pressure chamber and the second pressure chamber and having a low pressure side open;
an accumulator connected to the directional control valve;
A hydraulic damper comprising: The hydraulic damper according to claim 1, characterized in that a throttle valve is provided between the first pressure chamber and the second pressure chamber and between the directional control valve. The hydraulic damper according to claim 1 or 2, characterized in that the directional control valve is maintained 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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