JPH0598845A - Damping device - Google Patents

Abstract

PURPOSE:To provide a damping device that is equipped with a damper unit capable of easily setting an almost constant specified damping force. CONSTITUTION:A controller controls the opening or closing of solenoid valves 12, 13 and thereby two relief valves 10, 11 installed in oil passages 8, 9 of an oil damper 55 of a damper unit are loaded or unloaded, selecting the extent of damping force in the damper unit. These relief valves 10, 11 operates its opening when each pressure of oil in the oil passages 8, 9 is reached to an open working pressure, and opening is automatically regulated so as to keep the oil pressure almost in the open working pressure. Therefore, even if a relative speed between a cylinder 1 and a piston 2 is varied to some extent, hydraulic pressure in this cylinder 1 comes almost to a constant. Accordingly, an almost constant specified damping force that is almost independent of the relative speed between the piston 2 and the cylinder 1 is easily maintainable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping device having a damper device for reducing the shaking of a building during an earthquake.

[0002]

2. Description of the Related Art Conventionally, as this type of vibration damping device, there is one that includes a damper device connected to a foundation and a building, and a control device for controlling the braking force of the damper device.

The damper device has an oil damper 60 shown in FIG. In FIG. 9, 61 is a cylinder chamber, 62 is an oil sump chamber, 63 is a housing, 65 is a piston rod, 66 is a piston, and 68 and 70 are check valves which allow only the flow of fluid in the arrow Z direction. The control device controls the solenoid valve 7 provided in the throttle 71 of the oil damper 60 according to the degree of the earthquake and the state of the building.
2, the braking force of the oil damper 60 is adjusted by adjusting the opening degree of the throttle 71 as shown in FIG.

[0004]

However, in the above conventional vibration damping device, as shown in FIG. 11, although the braking force of the oil damper 60 can be adjusted by adjusting the opening of the throttle 71 by the solenoid valve 72, Damper 6
The braking force of 0 depends on the relative speed between the piston 65 and the cylinder 63. Therefore, there is a problem that it is difficult to control the damper device to a predetermined constant braking force, and it is difficult to set the braking force according to the degree of the earthquake.

Therefore, an object of the present invention is to provide a damper device that can easily maintain a substantially constant predetermined braking force regardless of the value of the relative speed between the piston and the cylinder, depending on the extent of the earthquake. An object of the present invention is to provide a vibration damping device that can easily set a braking force.

[0006]

In order to achieve the above object, the invention according to claim 1 is a damper device which is connected to a foundation and a building and applies a multi-step braking force to the building, and the degree of earthquake. A damping device having a control device for selecting the braking force of the damper device according to the state of the building and the building, wherein the damper device, an oil damper, and a relief valve provided in the oil passage of the oil damper, A solenoid valve for unloading or on-loading the relief valve by opening and closing, and the control device selects the braking force of the damper device by controlling the opening and closing of the solenoid valve. ..

Further, it is desirable that the damper device has a plurality of oil dampers, and each oil damper is provided with one relief valve.

A plurality of relief valves are provided,
It is desirable that the opening operating pressures of the plurality of relief valves be different.

According to a fourth aspect of the present invention, there is provided a damper device which is connected to a foundation and a building and applies a multi-step braking force to the building, and the damper device according to the degree of an earthquake and the state of the building. A vibration damping device having a control device for selecting a braking force, wherein the damper device includes an oil damper,
And a relief valve provided in an oil passage of the oil damper, the opening operating pressure of which is variable, and the control device selects the braking force of the damper device by controlling the opening operating pressure of the relief valve. It is characterized by

[0010]

According to the first aspect of the present invention, the control device controls the opening / closing of the solenoid valve to unload or on-load the relief valve provided in the oil passage of the oil damper of the damper device. Select the braking force of the damper device.

The relief valve closes when the pressure of the oil in the oil passage does not reach the opening operating pressure, while it opens when the pressure of the oil reaches the opening operating pressure. The opening is automatically adjusted so that the pressure of 1 is maintained at the above-mentioned opening operating pressure. Therefore, while the relief valve is open and operating, the hydraulic pressure in the cylinder remains substantially constant even if the relative speed between the cylinder and the piston changes. Therefore, the damper device can easily maintain a substantially constant predetermined braking force that hardly depends on the relative speed between the piston and the cylinder, and the braking force can be easily set according to the degree of the earthquake.

The above-mentioned damper device has a plurality of oil dampers. When each oil damper is provided with one relief valve, an oil damper for performing a braking action can be selected, and the degree of freedom in setting the braking force of the damper device can be selected. Is improved.

When the opening operating pressures of the plurality of relief valves are different, the degree of freedom in setting the braking force of the damper device is improved.

According to the fourth aspect of the present invention, the controller selects the braking force of the damper device by controlling the opening operating pressure of the relief valve whose opening operating pressure is variable.

The relief valve closes when the pressure of the oil in the oil passage has not reached the operating pressure for opening, and when the pressure of the oil has reached the operating pressure for opening, the relief valve operates to open the oil. The opening is automatically adjusted so that the pressure of 1 is maintained at the above-mentioned opening operating pressure. Therefore, while the relief valve is open and operating, the hydraulic pressure in the cylinder remains substantially constant even if the relative speed between the cylinder and the piston changes. Therefore, the damper device can easily maintain a substantially constant predetermined braking force that hardly depends on the relative speed between the piston and the cylinder, and the braking force can be easily set according to the degree of the earthquake.

[0016]

The present invention will be described in detail with reference to the embodiments shown in the drawings.

FIG. 7 shows a first embodiment of the vibration damping device of the present invention.

In FIG. 7, 57 is a foundation, 50 is a building,
Reference numeral 56 is a laminated rubber as an isolator that supports the building 50 on the foundation 57, and 55 is an oil damper that connects the foundation 57 and the building 50 to form a damper device.

As shown in FIG. 1, the oil damper 55 includes a cylinder 1, a piston 2 connected to the piston rod 3 and slidably fitted in the cylinder 1, and an oil tank 6. The piston 2 includes a chamber R1 on the piston rod 3 side and a chamber R on the cylinder head side in the chamber in the cylinder 1.
Divide into two. At this time, the sectional area of the piston rod 3 is set to half the sectional area of the chamber R2, and the sectional area of the chamber R1 is set to the chamber R2.
It is desirable to reduce the cross-sectional area to half. The piston 2
Has a through passage 2A communicating with the chamber R1 and the chamber R2. In the through passage 2A, the flow of oil in the through passage 2A
There is provided a first check valve 4 which limits the flow from the second side to the chamber R1 side in one direction. The oil tank 6 communicates with the chamber R1 of the cylinder 1 via passages 8 and 9 on the piston rod 3 side, and also communicates with the chamber R2 of the cylinder 1 via a passage 7 on the cylinder head side. The flow of the oil in the passage 7 is passed from the oil tank 6 side to the chamber R in the passage 7 on the cylinder head side.
The 2nd check valve 5 which limits to one side to the 2 side is provided.

In the passage 8 on the piston rod side, a relief valve 10 having a predetermined opening working pressure and a solenoid valve 1 are provided.
2 are provided in parallel. Further, in the other passage 9 on the piston rod side, a relief valve 11 having a smaller opening operating pressure than the relief valve 10 and a solenoid valve 13 are provided in series. Solenoid valves 12 and 13
Is opened and closed by sliding the spools 12a and 13a in the axial direction, so that the relief valve 10 and the relief valve 11 can be loaded or unloaded.

In the oil damper 55, when the piston 2 moves in the X direction, the check valve 4 is closed and the check valve 5 is opened. On the other hand, piston 2 shows arrow X
When moving in the opposite direction, the check valve 4 is opened and the check valve 5 is closed. Therefore, the oil in the cylinder 1 flows from the inside of the cylinder 1 to the inlets of the passages 8 and 9 on the piston rod side both when the piston 2 moves in the arrow X direction and when the piston 2 moves in the direction opposite to the arrow X direction. Try to flow to 8a, 9a. At this time, if the cross-sectional area of the chamber R1 is half the cross-sectional area of the chamber R2, the amount of oil flowing through the passage 8 or 9 is the same regardless of which direction the piston 2 moves.

When both the solenoid valves 12 and 13 are opened, the relief valve 10 is unloaded while the relief valve 11 is on-loaded. At this time, since the solenoid valve 12 is opened, the movement of the piston 2 causes the oil in the cylinder 1 to pass from the chamber R1 through the inlet 8a of the passage 8, the solenoid valve 12, and the outlet 8b of the passage 8 in this order to the oil tank 6 Flow into.

In this state, the minimum cross-sectional area of passage of the oil in the passage 8 is equal to the cross-sectional area of the passage 8 and is constant, so the braking force of the oil damper 55 is as shown by the curve L1 in FIG. It is approximately directly proportional to the relative speed between the piston 2 and the cylinder 1.

Next, with the solenoid valve 12 closed and the solenoid valve 13 open, both the relief valve 10 and the relief valve 11 are on-loaded. Then, since the relief valve 11 is opened and the operating pressure is smaller than that of the relief valve 10, the movement of the piston 2 causes the oil in the cylinder 1 to first pass through the passage 9 side. That is, the oil tries to flow into the oil tank 6 from the chamber R1 through the inlet 9a of the passage 9, the solenoid valve 13, the relief valve 11, and the outlet 9b of the passage 9 in order.

In this state, when the relative displacement between the piston 2 and the cylinder 1 is small, the oil pressure in the passage 9 has not reached the opening operating pressure of the relief valve 11 in the process of compressing the oil. In addition, the relief valve 11 is closed. Therefore, as indicated by the curve L2 in FIG. 3, while the apparent relative speed is small, the oil is compressed and the braking force with respect to the relative movement between the piston 2 and the cylinder 1 rises sharply. Then, the pressure of the oil in the passage 9 causes the relief valve 11
When the pressure exceeds the opening operating pressure of, the relief valve 11 opens to maintain the pressure of the oil substantially at the opening operating pressure.
Adjust the opening automatically. Therefore, while the relief valve 11 is open and operating, the hydraulic pressure in the cylinder 1 can be made substantially constant even if the relative speed between the piston 2 and the cylinder 1 changes. Therefore, as shown by the curve L2 in FIG. 3, it is possible to suppress the change in the braking force with respect to the change in the relative speed between the piston 2 and the cylinder 1.

When both the solenoid valves 12 and 13 are closed, the relief valve 10 whose opening and operating pressure is larger than the relief valve 11 is on-loaded, while the relief valve 11 is unloaded. The movement of the piston 2 causes the oil in the cylinder 1 to move from the chamber R1 to the inlet 8a of the passage 8,
The relief valve 10 and the outlet 8b of the passage 8 are sequentially passed to try to flow into the oil tank 6.

In this state, when the relative displacement between the piston 2 and the cylinder 1 is small, the pressure of the oil in the passage 8 has not reached the opening operating pressure of the relief valve 10 in the process of compressing the oil. In addition, the relief valve 10 is closed. Therefore, as shown by the curve L3 in FIG. 3, while the apparent relative speed is small, the oil is compressed and the braking force with respect to the relative movement between the piston 2 and the cylinder 1 rises sharply. Then, the pressure of the oil in the passage 8 is changed to the relief valve 10
When the pressure becomes equal to or higher than the opening operating pressure of, the relief valve 10 operates to open and keeps the pressure of the oil substantially at the opening operating pressure.
Adjust the opening automatically. Therefore, while the relief valve 10 is open and operating, the hydraulic pressure in the cylinder 1 can be made substantially constant even if the relative speed between the piston 2 and the cylinder 1 changes. Therefore, as shown by the curve L3 in FIG. 3, it is possible to suppress the change in the braking force with respect to the change in the relative speed between the piston 2 and the cylinder 1.

Further, in FIG. 7, 53 is a seismograph for detecting shaking on the ground side, 52 is a seismograph for detecting shaking of the building 50, 51 is output from the seismographs 53, 52 and is as shown in FIG. The control device includes a microcomputer that controls the solenoid valves 12 and 13.

The operation of the vibration damping device having the above structure will be described with reference to FIGS.

In step S1, the control device 51 receives the output of the seismograph 53 on the ground side and determines whether or not an earthquake has occurred. If no earthquake has occurred, the process proceeds to step S7 and the solenoid valve 12 Both 13 are closed to maximize the braking force of the oil damper 55 as shown by the curve L3 in FIG. Therefore, when no earthquake occurs, the building 50 is firmly connected to the foundation 57 by the large braking force of the oil damper 55. Therefore, the building 50 can be prevented from shaking even if it receives a strong wind or the like.

On the other hand, when it is determined in step S1 that an earthquake has occurred, the process proceeds to step S2, in which the control device 51 opens both solenoid valves 12 and 13 to apply the braking force of the oil damper 55 to the curve L1 in FIG. Minimize as shown in. Therefore, when an earthquake occurs, the braking force, that is, the damping force of the oil damper 55 is small as shown by the curve L1 of FIG.
Through the building 50. Therefore, the transmission of seismic energy to the building 50 is extremely small, and the shaking of the building 50 can be reduced.

Next, in step S3, it is determined whether the dominant frequency of the earthquake is different from the natural frequency of the building 50. If the predominant frequency of the earthquake matches the natural frequency of the building 50, the shaking of the building 50 may be large even if a small amount of seismic energy is input.
Then, the control device 51 closes the solenoid valve 12 and opens the solenoid valve 13 to set the braking force of the oil damper 55 to an intermediate value as shown by the curve L2 in FIG. Brake on. When it is determined in step S3 that the predominant frequency of the earthquake does not match the natural frequency of the building 50, the process proceeds to step S4, where the input from the ground-side seismometer 53 and the seismometer 52 provided in the building 50 Based on the input, the control device 51 determines whether the vibration of the building 50 is smaller than the vibration of the foundation 57. When the vibration of the building 50 is larger than the vibration of the foundation 57, the process proceeds to step S6, the solenoid valve 12 is closed and the solenoid valve 13 is opened, and the curve L of FIG.
With the braking force shown in 2, the shaking of the building 2 is reduced. When it is determined in step S4 that the vibration of the building 50 is smaller than the vibration of the foundation 57, the process proceeds to step S5, in which it is determined whether or not the earthquake ends based on the input from the seismometer 53 on the ground side, and the earthquake If so, proceed to step S7, close both solenoid valves 12 and 13, and maximize the braking force of the oil damper 55 as shown by the curve L3, while if the earthquake has not ended, proceed to step S7. S
Return to 3.

Thus, when no earthquake occurs, the solenoid valves 12 and 13 of the oil damper 55 are
Closed to close the building 50 strongly to the foundation 57, and when the vibration of the building 50 is larger than the vibration of the foundation 57 during the occurrence of an earthquake, or when the predominant frequency of the earthquake matches the natural frequency of the building 50, the oil damper It is possible to output a moderate braking force to 55, absorb the energy of the shaking of the building 50, and reduce the shaking of the building 50. On the other hand, when an earthquake occurs, both the solenoid valves 12 and 13 of the oil damper 55 should be opened so that the oil damper 55
It is possible to suppress the shaking of the building 50 by minimizing the braking force of the building 50 to reduce the input of seismic energy to the building 50.

Further, since the oil damper 55 can maintain a substantially constant predetermined braking force even if the relative speed between the piston 2 and the cylinder 1 changes, any value of the relative speed can be obtained. , You can easily set the braking force according to the degree of the earthquake.

Next, a second embodiment will be described. This embodiment is different from the first embodiment only in that a control device having a different oil damper control method is provided in place of the control device 51 of the first embodiment described above. The operation contents of the control device will be mainly described based on the flowchart of FIG.

Each parameter value for calculating the feedback coefficient used for calculating the optimum braking force of the damper device is input to the control device in step S11. That is, the mass m of the building 50, which is a structure, the viscous damping coefficient c, and the spring constant k are input. In addition, the weighting factors α, β, γ and the seismographs 53, 52 used for calculating the feedback factor
The sampling time Δt, which is the time interval for reading the measurement data of 1, is input.

Next, in step S12, the feedback coefficients k1 and k2 used to calculate the optimum braking force of the damper device are obtained by the following calculation based on the parameters m, c, k and α, β, γ. That is, first, a motion equation of the building represented by the following equation 1 and a state equation represented by the equations 2, 3, and 4 are created.

[Equation 1]

[Formula 2] x1 = x

[Equation 3]

[Equation 4]

In Equations 1 to 4, x is the relative displacement of the building 50 with respect to the foundation 57, and x dot is the foundation 57 of the building 50.
Is a relative response speed to x, the x is a relative acceleration of the building 50 to the foundation 57, f is a braking force of the oil damper 55 of the damper device, and mz is a seismic force acting on the building 50. The following equation 5 is obtained from the above equation 3.

[Equation 5]

In the above equation 1, z two dots =
The following equation 6 is obtained by setting 0.

[Equation 6]

From Equations 5 and 6, the following Equation 7 and Equation 8 equivalent to Equation 7 are obtained.

[Equation 7]

[Equation 8]

On the other hand, the evaluation function J is expressed by the following expression 9, and expression 10 equivalent to expression 9 is obtained.

[Equation 9]

[Equation 10]

An oil damper 5 that solves the optimum regulator problem consisting of equations (8) and (10) and minimizes the evaluation function J
When the u asterisk representing the optimum braking force of 5 is obtained, the u asterisk is expressed by the following equation 11.

[Equation 11]

The feedback coefficient k
1, k2 can be obtained. In Expression 11, P is a solution of the Riccati equation shown in Expression 12 below.

[Equation 12]

The following equation 13 is obtained from equations 8 and 11.

[Equation 13]

Next, in step S13, the seismograph 5
Relative displacement of building from 3,52 and oil damper 55
x, relative response acceleration x two dots, seismic acceleration z two dots,
Read the braking force f. Next, in step S14, the relative velocity x dot of the building 50, that is, dx / dt is calculated from the previously measured relative displacement xo and the sampling time Δt. (That is, dx / dt = (x−xo) / Δt)

Then, the process proceeds to step S15, and step S
Feedback coefficients k1 and k2 calculated in 12 and relative displacement x
Then, u asterisk representing the optimum braking force of the oil damper 55 is calculated from the relative velocity x dot.

Next, in step S16, it is determined whether the direction of the relative speed of the building and the direction of the optimum braking force are opposite,
When the direction of the relative speed and the direction of the braking force are opposite, the process proceeds to step S17, and when the direction of the relative speed and the direction of the braking force are not opposite, the process proceeds to step S18.

In step S17, the braking force which is closest to the optimum braking force represented by u asterisk and which can be set by the oil damper 55 is selected, and the process proceeds to step S19.

In step S18, the damper cannot output the braking force in the same direction as the relative speed, so the value u representing the braking force of the oil damper is set to zero.

Next, in step S19, the braking force of the oil damper 55 is set.

Next, in step S20, the solenoid valves 12, 1 of the oil damper 55 are arranged so that the oil damper 55 outputs the braking force set in step S19.
Switch 3 Then, the process returns to step S13.

As described above, in steps S11 and S12, the building 5 is calculated from the motion equation of the building 50 and the evaluation function J.
Feedback coefficients k1, k representing the relationship between the relative displacement and relative speed of 0 and the optimum braking force of the oil damper 55.
2 is calculated in advance. After that, based on the relative displacement and relative velocity of the building 50 obtained from the measurement data obtained from the seismographs 53, 52 at every sampling time Δt, whatever the relative velocity of the building 50 is, By opening and closing the solenoid valves 12 and 13, the braking force of the oil damper 55 can be easily set to an optimum value.

Therefore, according to this embodiment, the braking force can be optimally set to the oil damper 55 regardless of the value of the relative speed of the building, depending on the degree of the earthquake and the state of the building 50. The shaking of 50 can be suppressed.

In the first and second embodiments, the damper device including the oil damper 55 having the relief valves 10 and 11 having different opening operating pressures is used, but the damper device is shown in FIG. As described above, the oil damper 59 having the relief valve 40 whose opening operating pressure is variable may be provided. In this case, the control device can select the braking force of the damper device by controlling the opening operating pressure of the relief valve 40. Further, the braking force of the oil damper 59 can be set within the range surrounded by the curve L4 of FIG. 4 by controlling the opening actuation pressure of the relief valve 40 and almost without depending on the relative speed between the piston 32 and the cylinder 31.

Further, in the first and second embodiments, the oil damper 55 having the plurality of relief valves 10 and 11 having different opening operating pressures is used, but as shown in FIG. 8, the foundation 57 and the building 50 are used. Oil dampers 551, 5 connected to each other and provided with respective relief valves with different opening operating pressures.
52, 553 are arranged at a plurality of places between the foundation 57 and the building 50, and the control device controls the oil dampers 551 to 551.
By opening / closing the solenoid valve of 553, the relief valve of an arbitrary oil damper 551-553 may be on-loaded or unloaded, and the braking force of the damper device may be selected. Further, the opening operating pressures of the relief valves included in the oil dampers 551 to 553 may be the same. In this case, the braking force of the damper device can be selected by setting the number of relief valves to be on-loaded.

[0055]

As is apparent from the above description, according to the invention described in claim 1, the control device controls the opening / closing of the solenoid valve, so that the relief valve provided in the oil passage of the oil damper of the damper device. Is unloaded or on-loaded, and the braking force of the damper device is selected. The relief valve closes when the pressure of the oil in the oil passage does not reach the opening working pressure, and when the pressure of the oil reaches the opening working pressure, the relief valve operates to open to reduce the pressure of the oil. The opening is automatically adjusted so as to keep the opening operating pressure substantially above.
Therefore, while the relief valve is open and operating, the hydraulic pressure in the cylinder remains substantially constant even if the relative speed between the cylinder and the piston changes. Therefore, the damper device can easily maintain a substantially constant predetermined braking force that hardly depends on the relative speed of the piston and the cylinder,
The braking force can be easily set according to the degree of the earthquake.

The above-mentioned damper device has a plurality of oil dampers, and when each oil damper is provided with one relief valve, the operating oil damper can be selected and the braking force of the damper device can be set easily. ..

When the opening operating pressures of the plurality of relief valves are different, the degree of freedom in setting the braking force of the damper device can be improved.

According to the fourth aspect of the present invention, the controller selects the braking force of the damper device by controlling the opening operating pressure of the relief valve whose opening operating pressure is variable. The relief valve closes when the pressure of the oil in the oil passage has not reached the operating pressure for opening, and when the pressure of the oil has reached the operating pressure for opening, the relief valve operates to open to reduce the pressure of the oil. The opening is automatically adjusted so as to keep the opening operating pressure substantially above. Therefore, while the relief valve is open and operating, even if the relative speed of the cylinder and piston changes,
The hydraulic pressure in the cylinder is substantially constant. Therefore, the damper device can easily maintain a substantially constant predetermined braking force that hardly depends on the relative speed between the piston and the cylinder, and can easily set the braking force according to the degree of the earthquake.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of oil dampers of first and second embodiments of a vibration damping device of the present invention.

FIG. 2 is a sectional view of the oil damper of the first and second embodiments of the vibration damping device of the present invention.

3 is a braking force characteristic diagram of the oil damper shown in FIG. 1. FIG.

FIG. 4 is a braking force characteristic diagram of the oil damper shown in FIG.

FIG. 5 is a flowchart of the control device of the first embodiment.

FIG. 6 is a flowchart of the control device of the second embodiment.

FIG. 7 is a structural diagram of first and second embodiments.

FIG. 8 is a plan view showing an arrangement example of oil dampers.

FIG. 9 is a sectional view of an oil damper of a conventional vibration damping device.

FIG. 10 is a view showing a main part of the oil damper.

FIG. 11 is a braking force characteristic diagram of the oil damper.

[Explanation of symbols]

1,31 Cylinder 2,32,66 Piston 3,33 Piston rod 4,5,34,35,68,70 Check valve 6,36 Oil tank 7,8,37,38 Passage 8a, 9a, 38a Inlet 8b, 9b , 38b Outlet 10,11,40 Relief valve 12,13 Solenoid valve R1, R2 Room 50 Building 51 Control device 52,53 Seismometer 55,551,552,553 Oil damper 56 Isolator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kenji Yasui 2-2-2 Matsuzaki-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Okumura Gumi Co., Ltd. (72) Hiroshi Sugimoto 2-chome, Matsuzaki-cho, Abeno-ku, Osaka-shi, Osaka No. 2 Okumura Gumi Co., Ltd.

Claims (4)

[Claims] 1. A damper device, which is connected to a foundation and a building and applies a multi-step braking force to the building, and a control device that selects the braking force of the damper device according to the degree of an earthquake or the state of the building. A vibration damping device, wherein the damper device includes an oil damper, a relief valve provided in an oil passage of the oil damper, and a solenoid valve that opens and closes the relief valve to unload or on-load the relief valve. The damping device is characterized in that the control device selects the braking force of the damper device by controlling opening / closing of the solenoid valve. 2. The vibration damping device according to claim 1, wherein the damper device includes a plurality of oil dampers, and each oil damper includes one relief valve. 3. The vibration damping device according to claim 1, wherein a plurality of the relief valves are provided, and the opening operating pressures of the plurality of relief valves are different. 4. A damper device, which is connected to a foundation and a building and applies a multi-step braking force to the building, and a control device that selects the braking force of the damper device according to the degree of an earthquake or the state of the building. A damping device, wherein the damper device includes an oil damper and a relief valve provided in an oil passage of the oil damper and having a variable opening operating pressure, and the control device opens the relief valve. A damping device, wherein the braking force of the damper device is selected by controlling the pressure.