damping force switching damper

Abstract

To effectively attenuate a pulse seismic motion.SOLUTION: An attenuation force switching damper 1 comprises elongation-side attenuation force switching means 110 for switching an attenuation force during an elongation operation, and pressure-side attenuation force switching means 120 for switching an attenuation force during a compression operation. When the elongation-side attenuation force switching means 110 operates to elongate by a magnitude equal to or longer than a first reference value S1, the pressure-side attenuation force switching means 120 switches the attenuation force during the compression operation so as to increase while the elongation-side attenuation force switching means maintains the attenuation force during the elongation operation. When the pressure-side attenuation force switching means 120 operates to compress by a magnitude is equal to or longer than the first reference value S1, the elongation-side attenuation force switching means 110 switches the attenuation force during the elongation operation so as to increase while the compression-side attenuation force switching means maintains the attenuation force during the compression operation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a damping force switching damper for a structure that switches the damping force depending on the magnitude of vibration of the structure. [Background technology]

[0002] When planning a building structure, it is advisable to prepare for pulse-type earthquakes, such as those occurring in the Uemachi fault zone. Pulse-type earthquakes generate large-amplitude pulse-like waves. Specifically, in pulse-type earthquakes, a first wave with a larger amplitude than that of a normal earthquake arrives in one direction, followed by a second wave with an even larger amplitude in the opposite direction. A typical seismic isolation oil damper is configured to exert a predetermined damping force when the amplitude exceeds a preset value. Therefore, for example, if the damping force of the seismic isolation oil damper is set large in anticipation of the amplitude of the second wave of the pulse-like seismic motion, the first wave will have a smaller amplitude than the second wave, and the piston of the seismic isolation oil damper will not displace significantly when damping the first wave. As a result, when damping the second wave following the first wave, the piston will not displace significantly in the opposite direction. As such, it may be impossible to ensure a sufficient braking distance for the piston when damping the second wave, and therefore the second wave may not be damped efficiently.

[0003] In response to this, it is conceivable to use a damping force switching damper as disclosed in Patent Documents 1 to 3 to switch the damping force according to the magnitude of the amplitude. For example, Patent Document 1 discloses the configuration of a variable damping device that changes the damping force of an oil damper that reduces vibrations occurring in a target to be damped in response to the vibrations occurring in the target. In this configuration, the relief load (damping amount) of the oil damper is calculated based on a response value due to the vibrations occurring in the target to be damped. The oil damper generates a damping force corresponding to the calculated relief load of the oil damper. The parameters required to calculate the relief load of the oil damper are changed according to the ratio or difference between the response value corresponding to the vibrations occurring in the target to be damped and a predetermined reference value of that response value. The relief load of the oil damper is a function of a variable α, and when the ratio of the response value to the predetermined reference value is below "1," the value of the variable α is increased, and when the ratio of the response value to the predetermined reference value is above "1," the value of the variable α is decreased. Furthermore, Patent Document 2 discloses a configuration in which, during an earthquake, the response amount of a column or a column-beam frame in a vibration-controlled structure in which a variable damper is installed is detected, and the damping coefficient of the variable damper is switched based on the detected value. In this configuration, the axial force acting on the column is evaluated from the detected value of the response amount of the column or the column-beam frame in the vibration-controlled structure, and the axial force acting on the column is compared with a preset axial force value, and if the axial force is greater than the set value, the damping coefficient of the variable damper is switched to a lower value. Furthermore, Patent Document 3 discloses a hydraulic damper in which, when an extension or compression operation occurs by a magnitude equal to or greater than a predetermined value, a control valve simultaneously closes both the extension-side logic valve and the compression-side logic valve, thereby closing the extension-side bypass path and the compression-side bypass path, thereby increasing the resistance to the flow of liquid between the rod-side chamber and the piston-side chamber and increasing the damping force. With this configuration, when the first wave of pulse-like seismic motion arrives, the hydraulic damper first extends (compresses) by a magnitude equal to or greater than a predetermined value, and at this time, the extension-side bypass path and the compression-side bypass path are closed, and the damping force is switched to a large value during subsequent extension and compression. During the subsequent compression (extension) operation due to the second wave, the seismic motion is attenuated by the switched-to large damping force.

[0004] However, even with the damping force switching dampers disclosed in Patent Documents 1 to 3, there are cases where pulse-like seismic motion cannot be efficiently damped. For example, in the above-mentioned Patent Document 3, even if a pulse-like seismic motion occurs, if the amplitude of the first wave is smaller than a predetermined value, the extension side logic valve and the compression side logic valve are not closed, so the damping force is not switched to a large value and remains small. Therefore, when a second wave with an amplitude larger than the first wave arrives, the second wave must be damped with a small damping force at least until the amplitude of the second wave reaches a predetermined value and the damping force is switched to a large value. Therefore, the second wave may not be damped efficiently.

[0005] To address this issue, it is conceivable to reduce the predetermined value, which is the threshold for switching the damping force. In this case, according to the configuration of Patent Document 3, the extension-side bypass path and the compression-side bypass path are closed the instant the first wave arrives and the damper is displaced by a magnitude equal to or greater than the predetermined value. This allows the damping force to be switched to a higher value before the first wave reaches its maximum amplitude. In other words, with the configuration of Patent Document 3, after the first wave arrives and the damper is displaced by a predetermined value, the damping force remains high until the first wave reaches its maximum amplitude. Therefore, the piston may not displace significantly when damping the first wave. In such a case, the piston does not displace significantly in the reverse direction (braking distance) when damping the second wave following the first wave. Therefore, the second wave cannot be damped as efficiently as with a conventional seismic isolation oil damper. Even if the predetermined value at which the damper displaces and closes the extension-side bypass path and the compression-side bypass path is set relatively high, a similar problem occurs if the amplitude of the first wave is larger than expected. In view of these circumstances, it is desirable to more efficiently attenuate pulse-like earthquake motion. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4144848 [Patent Document 2] Patent No. 5431185 [Patent Document 3] Patent No. 6006657 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide a damping force switching damper that can efficiently damp pulse-like seismic motion. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs the following means. That is, the damping force switching damper of the present invention is a damping force switching damper that is provided to a structure and that reduces vibration of the structure by extending and compressing while exerting a damping force, and that can switch the damping force in accordance with the magnitude of the vibration, and that includes: an extension side damping force switching means that switches the damping force during an extension operation; a compression side damping force switching means that switches the damping force during a compression operation; a cylinder; and a piston rod that moves relative to the cylinder, wherein when the amount of movement of the piston rod with respect to the cylinder extends by an amount equal to or greater than a first reference value, the extension side damping force switching means maintains the damping force during the extension operation, while the compression side damping force switching means switches to increase the damping force during the compression operation, and when the amount of movement of the piston rod compresses by an amount equal to or greater than the first reference value, the compression side damping force switching means maintains the damping force during the compression operation, while the extension side damping force switching means switches to increase the damping force during the extension operation. According to this configuration, a pulse-like seismic motion occurs in which a first wave with an amplitude larger than that of a normal earthquake arrives in one direction, followed by a second wave with an even larger amplitude than the first wave in the opposite direction. When the arrival of the first wave causes the damping-force-switching damper to extend to the extent that the movement amount of the piston rod relative to the cylinder is equal to or greater than a first reference value, once the movement amount reaches the first reference value, the damping force during the extension movement is maintained (small) and only the damping force during the compression movement is switched to be increased. Therefore, even after the movement amount of the extension movement of the damping-force-switching damper exceeds the first reference value during the extension movement of the damping-force-switching damper due to the first wave, the damping force during the extension movement remains small and the damping force switching damper damps the first wave. Because the damping force generated by the damping-force-switching damper remains small, the movement amount of the damping-force-switching damper until the movement amount of the extension movement due to the first wave reaches its maximum is larger than when the damping force is switched to a large value. Subsequently, after the amount of extension caused by the first wave exceeds the first reference value and reaches its maximum amount of extension, the second wave causes the damping-force switching damper to transition to a compression operation. At this time, the damping force during the compression operation of the damping-force switching damper is switched to a large state because the amount of extension caused by the extension operation exceeds the first reference value. Also, as described above, because the amount of extension of the damping-force switching damper during the first wave is large, a large braking distance, i.e., a large amount of compression of the damping-force switching damper, can be ensured when the damping-force switching damper transitions from an extension operation to a compression operation. In this way, the damping force switched to a large state and the large braking distance ensured allow the damping-force switching damper to more efficiently damp the second wave. On the other hand, if a pulse-like earthquake motion occurs and the arrival of a first wave causes the damping force switching damper to compress to the extent that the movement amount of the piston rod relative to the cylinder is equal to or greater than the first reference value, when the movement amount reaches the first reference value, the damping force during the compression movement is maintained (remains small), and only the damping force during the extension movement is switched to be increased. Therefore, even after the movement amount of the compression movement of the damping force switching damper due to the first wave exceeds the first reference value, the damping force during the compression movement remains small and the damping force switching damper damps the first wave. At this time, because the damping force of the damping force switching damper remains small, the movement amount of the compression movement of the damping force switching damper until the movement amount of the compression movement due to the first wave reaches its maximum is larger than when the damping force has switched to a large state. Subsequently, after the amount of compression caused by the first wave exceeds the first reference value and reaches its maximum amount of compression, the damping-force switching damper transitions to an extension operation due to the second wave. At this time, the damping force during the extension operation of the damping-force switching damper is switched to a large state because the amount of compression caused by the compression operation exceeds the first reference value. Also, as described above, because the amount of compression caused by the damping-force switching damper during the first wave is large, it is possible to ensure a large braking distance, i.e., a large amount of extension operation of the damping-force switching damper, when the damping-force switching damper transitions from a compression operation to an extension operation. In this way, the damping force switched to a large state and the large braking distance ensured allow the damping-force switching damper to more efficiently damp the second wave. Furthermore, even if the damping force switching damper performs an extension or compression operation when the first wave arrives and the movement amount of the piston rod relative to the cylinder is equal to or greater than the first reference value, the damping force at this time is maintained at a small state, so that even if the first reference value is set to a small value, the first wave can be damped with the small damping force. In other words, because the first reference value can be set to a certain degree independently of the damping performance for attenuating the first wave, it is possible to configure the damping force switching damper so as to prevent a situation in which, even when the first wave arrives, the damping force during compression or extension operation to accommodate the subsequently arriving, larger second wave cannot be switched to a large state because the amplitude is smaller than expected. The above effects are combined to provide a damping force switching damper that can more efficiently damp pulse-like seismic motion.

[0009] In one aspect of the present invention, when the damping force switching damper of the present invention performs an extension operation such that the operating amount is equal to or greater than a second reference value that is greater than the first reference value, the compression side damping force switching means switches the damping force during compression operation to increase, and the extension side damping force switching means also switches the damping force during extension operation to increase; and when the operating amount performs a compression operation such that the operating amount is equal to or greater than the second reference value, the extension side damping force switching means also switches the damping force during extension operation to increase. With this configuration, when a first wave causes the piston rod to move relative to the cylinder and the damping force switching damper is performing an extension operation, if the amount of operation reaches a second reference value greater than the first reference value, the damping force during the compression operation is switched to be increased, and the damping force during the extension operation is also switched to be increased. Therefore, during the extension operation caused by the first wave, after the amount of extension operation exceeds the second reference value until it reaches the maximum amount of extension operation, the damping force switching damper maintains a large damping force during the extension operation, thereby damping the first wave. This makes it possible to more efficiently damp the first wave even if the first wave has a larger amplitude than expected. Subsequently, when the amount of extension caused by the first wave exceeds the second reference value and reaches the maximum amount of extension, the damping force switching damper transitions to compression caused by the second wave. At this time, the damping force of the damping force switching damper during compression has been switched to a large state. This allows the damping force switching damper to efficiently damp the second wave. On the other hand, when the first wave causes the piston rod to move relative to the cylinder and the damping-force switching damper is performing a compression operation, if the amount of operation reaches a second reference value greater than the first reference value, the damping force during the extension operation is switched to be increased, and the damping force during the compression operation is also switched to be increased. Therefore, during the compression operation caused by the first wave, after the amount of compression operation exceeds the second reference value, until it reaches the maximum amount of compression operation, the damping-force switching damper maintains a large damping force during the compression operation, thereby damping the first wave. This makes it possible to more efficiently damp the first wave even if the first wave has a larger amplitude than expected. Subsequently, when the amount of compression caused by the first wave exceeds the second reference value and reaches the maximum amount of compression, the damping force switching damper transitions to an extension operation due to the second wave. At this time, the damping force of the damping force switching damper during extension has been switched to a large state. This allows the damping force switching damper to efficiently damp the second wave.

[0010] In one aspect of the present invention, the damping force switching damper of the present invention is configured such that the cylinder is filled with liquid, one end of the piston rod is provided within the cylinder and the other end protrudes outward from the cylinder and is connected to the one end of the piston rod, and the damping force switching damper includes a piston that divides the interior of the cylinder into a rod-side chamber located on the piston rod side and a piston-side chamber opposite the rod-side chamber, a main extension-side passage and an auxiliary extension-side passage that are provided in parallel to allow the liquid to flow from the rod-side chamber to the piston-side chamber, a main pressure-side passage and an auxiliary pressure-side passage that are provided in parallel to allow the liquid to flow from the piston-side chamber to the rod-side chamber, and a damping force switching damper that switches between the main extension-side passage, the auxiliary extension-side passage, the main pressure-side passage, and the auxiliary pressure-side passage. the damping force switching device is provided with a main extension side damping means, an auxiliary extension side damping means, a main compression side damping means, and an auxiliary compression side damping means that provide resistance to the flow of each of the fluids, an extension side logic valve that opens and closes the auxiliary extension side passage, and a compression side logic valve that opens and closes the auxiliary pressure side passage, wherein when the piston is displaced from the neutral position toward the rod side chamber by the first reference value or more, the extension side damping force switching device switches the compression side logic valve from an open state to a closed state while maintaining the open / closed state of the extension side logic valve, and when the piston is displaced from the neutral position toward the piston side chamber by the first reference value or more, the extension side damping force switching device switches the extension side logic valve from an open state to a closed state while maintaining the open / closed state of the compression side logic valve. According to this configuration, in the damping-force switching damper, seismic motion causes relative movement between the cylinder and the piston rod. When the damping-force switching damper performs an extension operation, the piston, together with the piston rod, is displaced within the cylinder in a direction that increases the volume of the piston-side chamber, i.e., toward the rod-side chamber. The displacement of the piston toward the rod-side chamber allows liquid in the rod-side chamber to flow from the rod-side chamber to the piston-side chamber through the main-extension-side passage and the auxiliary-extension-side passage. When the damping-force switching damper performs a compression operation, the piston, together with the piston rod, is displaced within the cylinder in a direction that increases the volume of the rod-side chamber, i.e., toward the piston-side chamber. The displacement of the piston toward the piston-side chamber allows liquid in the piston-side chamber to flow from the piston-side chamber to the rod-side chamber through the main-pressure-side passage and the auxiliary-pressure-side passage. During the extension operation of the damping force switching damper, when the extension side logic valve is open, the auxiliary extension side passage is open, and liquid flows from the rod side chamber to the piston side chamber through both the main extension side passage and the auxiliary extension side passage. When the extension side logic valve is closed, the auxiliary extension side passage is closed, and liquid flows from the rod side chamber to the piston side chamber through only the main extension side passage. In this way, when the extension side logic valve is closed, the cross-sectional area of ​​the passage through which liquid flows during the extension operation is smaller than when the extension side logic valve is open, so the resistance to the liquid flow is greater, and the damping force of the damping force switching damper is switched to a large state. In this way, the damping force during the extension operation of the damping force switching damper can be switched by opening and closing the extension side logic valve. Furthermore, when the compression-side logic valve is open during compression of the damping-force switching damper, the auxiliary pressure-side passage is open, and liquid flows from the piston-side chamber to the rod-side chamber through both the main pressure-side passage and the auxiliary pressure-side passage. When the compression-side logic valve is closed, the auxiliary pressure-side passage is closed, and liquid flows from the piston-side chamber to the rod-side chamber through only the main pressure-side passage. In this way, when the compression-side logic valve is closed, the cross-sectional area of ​​the passage through which liquid flows during compression is smaller than when the compression-side logic valve is open, so resistance to the flow of liquid increases, and the damping force of the damping-force switching damper switches to a high damping force state. In this way, the damping force during compression of the damping-force switching damper can be switched by opening and closing the compression-side logic valve. When the piston of this damping force switching damper is displaced from the neutral position toward the rod-side chamber by more than the first reference value from the neutral position, the compression-side logic valve is switched from the open state to the closed state while the extension-side logic valve is maintained in the open / closed state. As a result, the damping force of the damping force switching damper is maintained during the extension operation, and the damping force during the compression operation is switched to a large state. Furthermore, during compression of the damping force switching damper, when the piston is displaced from the neutral position toward the piston-side chamber by more than the first reference value, the expansion-side logic valve is switched from the open state to the closed state while maintaining the open / closed state of the compression-side logic valve. As a result, the damping force during compression of the damping force switching damper is maintained, and the damping force during expansion / contraction is switched to a large state. In this way, the damping force switching damper can be properly realized.

[0011] In one aspect of the present invention, the damping force switching damper of the present invention further includes a tank in which the liquid is stored, and the extension-side logic valve includes an extension-side valve element that opens and closes the auxiliary extension-side passage, an extension-side biasing member that biases the extension-side valve element in a direction to close the auxiliary extension-side passage, and an extension-side pilot passage that connects an extension-side back-pressure chamber located on the opposite side of the extension-side valve element from the auxiliary extension-side passage to the tank, and the compression-side logic valve includes a compression-side valve element that opens and closes the auxiliary pressure side passage, a compression-side biasing member that biases the compression-side valve element in a direction to close the auxiliary pressure side passage, and an extension-side pilot passage that connects a compression-side back-pressure chamber located on the opposite side of the compression-side valve element from the auxiliary pressure side passage to the tank. and a compression side pilot passage through which pressure is passed, wherein the extension side damping force switching means closes the extension side pilot passage when the piston is displaced from the neutral position toward the piston side chamber by the first reference value or more, and the compression side damping force switching means closes the compression side pilot passage when the piston is displaced from the neutral position toward the rod side chamber by the first reference value or more, and when pressure acts on the auxiliary extension side passage with the extension side pilot passage open, the extension side logic valve is opened, and when pressure acts on the auxiliary compression side passage with the compression side pilot passage open, the compression side logic valve is opened. According to this configuration, the expansion-side valve element of the expansion-side logic valve receives the pressure of the auxiliary expansion-side passage on the auxiliary expansion-side passage side. The pressure in the expansion-side back pressure chamber acts on the side of the expansion-side valve element opposite to the auxiliary expansion-side passage. When the expansion-side pilot passage is open and connected to the tank, the expansion-side back pressure chamber becomes tank pressure. In this state, when the pressure in the rod-side chamber increases due to the expansion action of the damping force switching damper, pressure acts on the auxiliary expansion-side passage in response to the pressure in the rod-side chamber, causing the expansion-side valve element to move in a direction compressing the expansion-side back pressure chamber, and the expansion-side logic valve opens. Furthermore, when the compression action of the damping force switching damper displaces the piston from the neutral position toward the piston-side chamber by more than the first reference value, the expansion-side pilot passage is closed. With the extension-side pilot passage closed and communication with the tank blocked, even if the pressure in the rod-side chamber rises due to the extension operation of the damping force switching damper, the liquid in the extension-side back pressure chamber has no escape route, and the extension-side valve body cannot move toward the extension-side back pressure chamber. As a result, the extension-side valve body keeps the auxiliary extension-side passage closed, and the extension-side logic valve is in a closed state. With the extension-side logic valve in a closed state and the extension-side valve body closing the auxiliary extension-side passage, the damping force during the extension operation of the damping force switching damper is switched to a large state. Furthermore, the compression-side valve element of the compression-side logic valve receives pressure from the sub-pressure side passage on the sub-pressure side passage side. The pressure in the compression-side back pressure chamber acts on the side of the compression-side valve element opposite the sub-pressure side passage. When the compression-side pilot passage is open and connected to the tank, the pressure in the compression-side back pressure chamber becomes tank pressure. In this state, when the pressure in the piston-side chamber increases due to the compression action of the damping force switching damper, pressure acts on the sub-pressure side passage in response to the pressure in the piston-side chamber, causing the compression-side valve element to move in the direction compressing the compression-side back pressure chamber, and opening the compression-side logic valve. Furthermore, when the piston is displaced from the neutral position toward the rod-side chamber by more than the first reference value due to the extension action of the damping force switching damper, the compression-side pilot passage is closed. With the compression-side pilot passage closed and communication with the tank blocked, even if the pressure in the piston-side chamber rises due to the compression operation of the damping force switching damper, the liquid in the compression-side back-pressure chamber has nowhere to escape, and the compression-side valve element cannot move toward the compression-side back-pressure chamber. As a result, the compression-side valve element keeps the auxiliary pressure-side passage closed, and the compression-side logic valve is in a closed state. With the compression-side logic valve in a closed state and the compression-side valve element closing the auxiliary pressure-side passage, the damping force during the compression operation of the damping force switching damper is switched to a high state. In this way, the damping force switching damper can be properly realized.

[0012] In one aspect of the present invention, the damping force switching damper of the present invention includes a detection rod provided outside the cylinder, connected to the piston rod and moving in conjunction with the piston rod, the detection rod having a recess extending along the axial direction of the piston rod, the extension side damping force switching means and the compression side damping force switching means each provided opposite to the detection rod, and each including a control valve element that opens and closes a corresponding pilot passage between the extension side pilot passage and the compression side pilot passage, and a switching lever that protrudes toward the detection rod and is provided so as to be able to move back and forth in a direction toward the detection rod, and operates in conjunction with the control valve element to switch between opening and closing of the control valve element, Each of the damping force switching means is positioned corresponding to the recess and opens the control valve body when the switching lever is in contact with the recess, and closes the control valve body when the switching lever is positioned corresponding to the outside of the recess and in contact with the outside of the recess, and when the piston is in the neutral position, the switching lever of each of the extension side damping force switching means and the compression side damping force switching means abuts against the recess, the axial distance between the switching lever of the extension side damping force switching means and the end of the recess located on the piston rod side is the first reference value, and the axial distance between the switching lever of the compression side damping force switching means and the end of the recess located on the piston side is also the first reference value. According to this configuration, the switching levers of the extension side damping force switching means and the compression side damping force switching means are each provided to be able to move forward and backward in a direction toward the detection rod and abut against the recessed portion of the detection rod when the piston is in the neutral position. The control valve bodies of the extension side damping force switching means and the compression side damping force switching means are each in an open state when the switching lever advances toward the detection rod and abuts against the recessed portion of the detection rod. The control valve bodies of the extension side damping force switching means and the compression side damping force switching means are each in a closed state when the switching lever retreats from the direction toward the detection rod and abuts against the outside of the recessed portion of the detection rod. In this way, the control valve bodies are switched between being open and closed depending on whether the switching lever abuts against the recessed portion of the detection rod or the outside of the recessed portion. Because the detection rod moves in conjunction with the piston rod, the detection rod moves together with the piston rod when the piston rod moves relative to the cylinder. This changes the position of the recessed portion relative to each switching lever, allowing the control valve bodies to be opened and closed by the switching lever. In this configuration, when the piston is in the neutral position, the switching levers of the extension side damping force switching means and the compression side damping force switching means advance toward the detection rod and abut against the recesses, thereby opening the control valve bodies and opening the extension side pilot passage and the compression side pilot passage, thereby achieving a state in which the damping force is large during extension and compression operations. Furthermore, when the piston moves from the neutral position toward the rod-side chamber during the extension operation of the damping-force switching damper, the detection rod moves toward the rod-side chamber in conjunction with the piston rod. When the detection rod moves toward the rod-side chamber by a distance equal to or greater than the first reference value, the switching lever of the compression-side damping-force switching means climbs over the end of the recess located on the piston side, moves back from the direction toward the detection rod, and comes into contact with the outside of the recess. This causes the control valve element of the compression-side damping-force switching means to close, and the compression-side pilot passage is closed. Therefore, when the piston moves from the neutral position toward the rod-side chamber by a distance equal to or greater than the first reference value, the damping force switches to a large state during the compression operation following the extension operation. Furthermore, when the piston moves from the neutral position toward the piston-side chamber during compression of the damping-force switching damper, the detection rod moves toward the piston-side chamber in conjunction with the piston rod. When the detection rod moves toward the piston-side chamber by a distance equal to or greater than the first reference value, the switching lever of the extension-side damping force switching means climbs over the end of the recess located on the piston rod side, moves back from the direction toward the detection rod, and comes into contact with the outside of the recess. This causes the control valve element of the extension-side damping force switching means to close, and the extension-side pilot passage is closed. Therefore, when the piston moves from the neutral position toward the piston-side chamber by a distance equal to or greater than the first reference value, the damping force switches to a large state during extension following compression. In this way, the damping force switching damper can be properly realized. [Effects of the Invention]

[0013] According to the present invention, it is possible to efficiently attenuate pulse-like earthquake motion. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating a configuration of a damping force switching damper according to an embodiment of the present invention. [Figure 2] 10 is a diagram showing a state in which the damping-force switching damper performs a compressive operation due to the arrival of waves caused by seismic motion, and the amount of the compressive operation is less than a first reference value. FIG. [Figure 3] 10 is a diagram showing a state in which the damping force switching damper is expanded due to the arrival of waves caused by seismic motion, and the amount of expansion is less than a first reference value. FIG. [Figure 4] 10 is a diagram showing a state in which pulse-like earthquake motion occurs, the arrival of a first wave due to the earthquake motion causes the damping-force switching damper to perform a compressive operation, and the amount of this compressive operation is equal to or greater than a first reference value. FIG. [Figure 5] 5 is a diagram showing a state in which the damping force switching damper has expanded due to the arrival of a second wave caused by seismic motion from the state shown in FIG. 4. FIG. [Figure 6]10 is a diagram showing a state in which pulse-like earthquake motion occurs, the arrival of a first wave due to the earthquake motion causes the damping force switching damper to perform an extension operation, and the amount of this extension operation is equal to or greater than a first reference value. FIG. [Figure 7] 6 is a diagram showing a state in which the damping force switching damper performs a compressing operation due to the arrival of a second wave caused by seismic motion from the state shown in FIG. 5. FIG. [Figure 8] 5 is a diagram showing a state in which the amount of compression operation of the damping-force switching damper is further increased from the state shown in FIG. 4. FIG. [Figure 9] 7 is a diagram showing a state in which the amount of extension of the damping-force switching damper is further increased from the state shown in FIG. 6. FIG. [Figure 10A] FIG. 10 is a diagram showing simulation results for an example of a damping force switching damper according to an embodiment of the present invention, and is a diagram showing changes over time in seismic isolation displacement in response to pulse-like seismic motion. [Figure 10B] FIG. 10 is a diagram showing simulation results for an example of a damping force switching damper according to an embodiment of the present invention, illustrating the correlation between seismic isolation displacement and damping amount for pulse-like seismic motion. [Figure 11A] FIG. 10 is a diagram showing other simulation results for an example of a damping force switching damper according to an embodiment of the present invention, and is a diagram showing the change over time in seismic isolation displacement in response to pulse-like seismic motion. [Figure 11B] FIG. 10 is a diagram showing other simulation results for an example of the damping force switching damper according to an embodiment of the present invention, illustrating the correlation between seismic isolation displacement and damping amount for pulse-like seismic motion. [Figure 12A] FIG. 10 is a diagram showing other simulation results for an example of a damping force switching damper according to an embodiment of the present invention, and is a diagram showing the change over time in seismic isolation displacement in response to pulse-like seismic motion. [Figure 12B] FIG. 10 is a diagram showing other simulation results for an example of the damping force switching damper according to an embodiment of the present invention, illustrating the correlation between seismic isolation displacement and damping amount for pulse-like seismic motion. [Figure 13] FIG. 10 is a diagram showing other simulation results for an example of the damping force switching damper according to an embodiment of the present invention, and is a diagram showing the maximum value of seismic isolation displacement for pulse-like seismic motion. [Figure 14] FIG. 10 is a diagram showing another simulation result of an example of the damping force switching damper according to an embodiment of the present invention, showing the inter-story deformation angle in response to pulse-like seismic motion. [Figure 15] FIG. 15 is a diagram showing other simulation results for an example of the damping-force switching damper according to an embodiment of the present invention, and is a diagram showing the maximum and average values ​​of the response reduction rate for each of the study examples shown in FIGS. 13 and 14. [Figure 16A] FIG. 16 shows other simulation results for an example of a damping force switching damper according to an embodiment of the present invention, and is a diagram showing the time-dependent change in seismic isolation displacement in response to pulse-like seismic motion for cases in which the maximum value of seismic isolation displacement was greater than that of the comparative example among the examples studied in FIGS. 13 and 14. [Figure 16B] FIG. 16 shows other simulation results for an example of a damping-force switching damper according to an embodiment of the present invention, and is a diagram showing the correlation between seismic isolation displacement and damping amount in response to pulse-like seismic motion for cases in which the maximum seismic isolation displacement was greater than that of the comparative example among the examples studied in FIGS. 13 and 14. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention provides a damping force switching damper for a structure that switches the damping force according to the magnitude of vibration of the structure. The damping force switching damper 1 is characterized in that it is equipped with two types of damping force switching means (main extension side damping means 5 and main compression side damping means 6) that switch the damping force based on the amount of movement of the piston rod 23. Specifically, the first switching rule, which combines two types of damping force switching means, has a displacement detection mechanism similar to conventional displacement switching oil dampers, and after detecting a predetermined amount of displacement (first reference value), maintains low damping mode until the direction of displacement reverses (the speed becomes 0), and then switches to high damping mode near the maximum point of displacement at that time. In addition, the second switching rule is that if the preset first detected displacement is exceeded but the preset second detected displacement (second reference value) is not exceeded, low damping mode is maintained until the direction of displacement reverses (speed becomes 0), and then the mode is switched to high damping mode near the maximum displacement point at that time.If the second detected displacement (second reference value) is exceeded before the maximum displacement is reached, the mode is immediately switched to high damping mode and maintained thereafter. The low damping mode referred to above is a state in which the pressure regulating valve 62 and the relief valve 63, as well as the extension side logic valve 13 and the compression side logic valve 16, are open, and a basic initial stage damping force is exerted according to the flow rate of fluid between the rod side chamber R1 and the piston side chamber R2. In contrast, the high damping mode is a state in which the pressure regulating valve 62 and the relief valve 63 are open, and at least one of the extension side logic valve 13 and the compression side logic valve 16 is closed, and a higher damping force is exerted compared to the damping force in the low damping mode.

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a damping force switching damper according to an embodiment of the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1 , the damping force switching damper 1 mainly comprises a damper main body 2, a circuit unit 3, and a damping force switching unit 100. The damping force switching damper 1 is suitable for use in a seismic isolation device. The damping force switching damper 1 is provided in a structure and reduces vibration of the structure by expanding and compressing while exerting a damping force. The damping force switching damper 1 can switch the damping force depending on the magnitude of the vibration. Although not shown, the damping force switching damper 1 is incorporated into a seismic isolation device, for example, by being interposed between the ground and the structure together with an elastic body such as a ball isolator or laminated rubber. There are no limitations on the use, installation location, etc. of the damping force switching damper 1. The damper body 2 includes a cylinder 21, a piston 22, and a piston rod 23. The cylinder 21 is formed in a cylindrical shape extending in the axial direction Dc. One end of the cylinder 21 is closed by a lid 24. A rod guide 25 is attached to the other end of the cylinder 21. The rod guide 25 is formed in an annular shape with a rod insertion hole 25h in its center. The piston 22 is disposed within the cylinder 21. The piston 22 is provided within the cylinder 21 so as to be movable in the axial direction Dc. The piston 22 is connected to one end of a piston rod 23. The piston rod 23 is provided on one side Dc1 of the piston 22 in the axial direction Dc. The piston 22 is divided into a rod side chamber R1 and a piston side chamber R2. The rod side chamber R1 is located on the side of the piston rod 23 provided on one side Dc1 of the piston 22 in the axial direction Dc. The piston side chamber R2 is located on the opposite side of the rod side chamber R1 with respect to the piston 22, i.e., on the other side Dc2 of the axial direction Dc. The rod side chamber R1 and the piston side chamber R2 within the cylinder 21 are filled with a liquid such as hydraulic oil. In addition to hydraulic oil, water or an aqueous solution can also be used as the liquid. The piston rod 23 extends in the axial direction Dc of the cylinder 21. The piston rod 23 is inserted into a rod insertion hole 25h of the rod guide 25. The other end of the piston rod 23 protrudes outward from the cylinder 21 through the rod insertion hole 25h. The piston rod 23 moves together with the piston 22 relative to the cylinder 21 in the axial direction Dc. In this damper body 2, the cylinder 21 is fixed to the ground side or the structure side via a bracket (not shown). The other end of the piston rod 23 is fixed to the structure side or the ground side, opposite the cylinder 21, via a bracket (not shown). As a result, when seismic motion causes relative displacement of the cylinder 21 in the axial direction Dc between the ground and the structure, the piston rod 23 and the piston 22 move in the axial direction Dc relative to the cylinder 21. Here, the movement of the piston rod 23 and the piston 22 in the axial direction Dc to one side Dc1 in the axial direction Dc where the rod-side chamber R1 is located relative to the cylinder 21, causing the damper body 2 to expand in the axial direction Dc, is referred to as an extension operation of the damping-force switching damper 1. Similarly, the movement of the piston rod 23 and the piston 22 in the axial direction Dc to the other side Dc2 in the axial direction Dc where the piston-side chamber R2 is located relative to the cylinder 21, causing the damper body 2 to compress in the axial direction Dc, is referred to as a compression operation of the damping-force switching damper 1.

[0017] The piston 22 is provided with a main expansion side passage 51, a main pressure side passage 61, a main expansion side damping means 5, and a main pressure side damping means 6. The main expansion-side passage 51 is provided in the piston 22 and connects the rod-side chamber R1 to the piston-side chamber R2. The main pressure-side passage 61 is provided in the piston 22 and connects the piston-side chamber R2 to the rod-side chamber R1. The main expansion side damping means 5 includes a pressure regulating valve 52 and a relief valve 53 provided in parallel to the main expansion side passage 51. Both the pressure regulating valve 52 and the relief valve 53 allow liquid to flow only from the rod side chamber R1 to the piston side chamber R2 and provide resistance to the liquid flow. As a result, the main expansion side damping means 5 allows liquid to flow from the rod side chamber R1 to the piston side chamber R2 and provides resistance to the liquid flow. The pressure regulating valve 52 has a characteristic such that pressure loss is approximately proportional to the flow rate of liquid passing through it. Until the differential pressure between the rod side chamber R1 and the piston side chamber R2 reaches a predetermined valve opening pressure and the relief valve 53 opens, the pressure loss of the pressure regulating valve 52 is approximately proportional to the flow rate of liquid passing through the main expansion side passage 51. On the other hand, when the relief valve 53 is opened, the effective cross-sectional area of ​​the main expansion-side passage 51 increases, and therefore the slope of the flow-pressure characteristics in the main expansion-side damping means 5 when the relief valve is open becomes smaller than the slope of the characteristics when the relief valve 53 is in the closed state. The main pressure side damping means 6 includes a pressure regulating valve 62 and a relief valve 63 that are provided in parallel to the main pressure side passage 61. Both the pressure regulating valve 62 and the relief valve 63 only allow liquid to flow from the piston side chamber R2 to the rod side chamber R1 and provide resistance to the liquid flow. As a result, the main pressure side damping means 6 allows liquid to flow from the piston side chamber R2 to the rod side chamber R1 and provides resistance to the liquid flow. Like the pressure regulating valve 52, the pressure regulating valve 62 has a characteristic such that the pressure loss is approximately proportional to the flow rate through it. As a result, the flow-pressure characteristic of the main pressure side damping means 6 exhibits a characteristic in which the slope after the relief valve 63 opens is smaller than before the relief valve 63 opens.

[0018] The circuit section 3 is connected to the rod-side chamber R1 and the piston-side chamber R2 of the damper body 2. The circuit section 3 includes a tank 4, a tank-side passage 7, a suction passage 8, a secondary extension-side passage 9, a secondary pressure-side passage 10, a discharge passage 11, a tank-side secondary pressure damping means 15, and a tank-side damping means 70. The tank 4 stores the liquid that fills the cylinder 21 and the circuit section 3. In addition to the liquid, the tank 4 is filled with gas. Note that the inside of the tank 4 does not need to be pressurized by compressing and filling the gas, but may be pressurized.

[0019] The auxiliary extension-side passage 9 communicates between the rod-side chamber R1 and the piston-side chamber R2, bypassing the main extension-side damping means 5. The auxiliary extension-side passage 9 is provided outside the cylinder 21 and in parallel with the main extension-side passage 51. The auxiliary extension-side passage 9 allows fluid to flow from the rod-side chamber R1 to the piston-side chamber R2. The auxiliary pressure side passage 10 communicates between the rod side chamber R1 and the piston side chamber R2, bypassing the main pressure side damping means 6. The auxiliary pressure side passage 10 is provided outside the cylinder 21 and in parallel with the main pressure side passage 61. The auxiliary pressure side passage 10 allows liquid to flow from the piston side chamber R2 to the rod side chamber R1. The discharge passage 11 branches off from the auxiliary pressure side passage 10 and is provided to connect the piston side chamber R2 to the tank 4.

[0020] The tank-side passage 7 connects the piston-side chamber R2 to the tank 4. The tank-side damping means 70 includes a pressure regulating valve 72 and a relief valve 73 that are provided in parallel to the tank-side passage 7. Both the pressure regulating valve 72 and the relief valve 73 only allow liquid to flow from the piston-side chamber R2 toward the tank 4, and provide resistance to the liquid flow. As a result, the tank-side damping means 70 allows liquid to flow from the piston-side chamber R2 to the tank 4, and provides resistance to the liquid flow. Like the pressure regulating valve 52, the pressure regulating valve 72 has a characteristic in which the pressure loss is approximately proportional to the flow rate through it, and the flow-pressure characteristic of the tank-side damping means 70 exhibits a characteristic in which the slope after the relief valve 73 opens is smaller than before the relief valve 73 opens. The tank-side secondary pressure damping means 15 is provided in the discharge passage 11. The tank-side secondary pressure damping means 15 allows liquid to flow from the piston-side chamber R2 to the tank 4 and provides resistance to the liquid flow. The tank-side secondary pressure damping means 15 is a pressure regulating valve that only allows liquid to flow from the piston-side chamber R2 toward the tank 4. Like the pressure regulating valve 72, the tank-side secondary pressure damping means 15 has a characteristic in which the pressure loss is approximately proportional to the flow rate through it. When the damping force switching damper 1 performs a compression operation, an amount of liquid corresponding to the volume of the piston rod 23 entering the cylinder 21 is discharged from the piston-side chamber R2 to the tank 4 via the tank-side passage 7 and the tank-side secondary pressure damping means 15. The suction passage 8 allows liquid to flow from the tank 4 to the piston-side chamber R2. The suction passage 8 is equipped with a communication passage 81 that connects the tank 4 with the piston-side chamber R2, and a check valve 82 that is provided midway through the communication passage 81 and that allows liquid to flow only from the tank 4 to the piston-side chamber R2. When the damping force switching damper 1 extends, an amount of liquid corresponding to the volume of the piston rod 23 displaced from inside the cylinder 21 is supplied from the tank 4 into the piston-side chamber R2 via this suction passage 8.

[0021] The circuit unit 3 further includes an auxiliary extension-side damping means 12 , an extension-side logic valve 13 , an auxiliary compression-side damping means 14 , and a compression-side logic valve 16 . The extension side logic valve 13 and the auxiliary extension side damping means 12 are provided in the auxiliary extension side passage 9. The extension side logic valve 13 and the auxiliary extension side damping means 12 are provided in this order with the rod side chamber R1 located upstream. The auxiliary extension side damping means 12 is a pressure regulating valve and allows only the flow of liquid from the rod side chamber R1 to the piston side chamber R2. The auxiliary extension side damping means 12 allows the flow of liquid from the rod side chamber R1 to the piston side chamber R2 and provides resistance to the liquid flow. Similar to the pressure regulating valve 52, the auxiliary extension side damping means 12 has a characteristic in which the pressure loss is approximately proportional to the flow rate of the liquid passing through it. The expansion-side logic valve 13 opens and closes the auxiliary expansion-side passage 9. The expansion-side logic valve 13 includes an expansion-side valve element 131, an expansion-side biasing member 132, and an expansion-side pilot passage 134. The expansion-side valve element 131 opens and closes the auxiliary expansion-side passage 9. The expansion-side biasing member 132 is a spring that biases the expansion-side valve element 131 in a direction to close the auxiliary expansion-side passage 9. The expansion-side biasing member 132 may be a member other than a spring as long as it is a member that can bias the expansion-side valve element 131 to close the auxiliary expansion-side passage 9. The expansion-side pilot passage 134 connects an expansion-side back pressure chamber 133 located on the back side of the expansion-side valve element 131, i.e., on the opposite side to the auxiliary expansion-side passage 9, to the tank 4.

[0022] In such an expansion-side logic valve 13, the expansion-side valve element 131 receives the pressure upstream of the auxiliary expansion-side passage 9, i.e., the pressure in the rod-side chamber R1, on a front side 135 of the expansion-side valve element 131. The pressure in the expansion-side back-pressure chamber 133 acts on the back side of the expansion-side valve element 131. Therefore, when the expansion-side pilot passage 134 is in communication with the tank 4, the inside of the expansion-side back-pressure chamber 133 becomes tank pressure. In this state, when the rod-side chamber R1 is compressed and the pressure in the rod-side chamber R1 increases, the expansion-side valve element 131 receives the pressure of the rod-side chamber R1 and moves in a direction that compresses the expansion-side back-pressure chamber 133, and the expansion-side logic valve 13 is brought into an open state. Conversely, when the expansion-side pilot passage 134 is closed by the expansion-side damping force switching means 110 (described later) and communication with the tank 4 is blocked, even if the rod-side chamber R1 is compressed and the pressure in the rod-side chamber R1 increases, the liquid in the expansion-side back-pressure chamber 133 has no escape route. Therefore, the expansion-side valve element 131 cannot compress the expansion-side back-pressure chamber 133, and the expansion-side valve element 131 keeps the sub-expansion-side passage 9 closed, and the expansion-side logic valve 13 is in a closed state. The expansion-side valve element 131 is provided with a throttle passage 131a that introduces the pressure upstream of the expansion-side valve element 131 to the expansion-side back-pressure chamber 133. In the expansion-side logic valve 13, when the expansion-side valve element 131 retreats toward the expansion-side back pressure chamber 133 and is in an open state where the auxiliary expansion-side passage 9 is opened, and the expansion-side pilot passage 134 is closed, the communication between the expansion-side back pressure chamber 133 and the tank 4 is closed. Then, the pressure in the expansion-side back pressure chamber 133 increases, causing the expansion-side valve element 131 to move in a direction to close the auxiliary expansion-side passage 9, and the expansion-side logic valve 13 is brought into a closed state. In this way, the expansion-side logic valve 13 is in an openable state when the expansion-side pilot passage 134 is open and the expansion-side back-pressure chamber 133 is in communication with the tank 4, and is in an open state when the rod-side chamber R1 is compressed and pressure acts on the auxiliary expansion-side passage 9. Conversely, the expansion-side logic valve 13 is in a closed state when the expansion-side pilot passage 134 is closed and communication between the expansion-side back-pressure chamber 133 and the tank 4 is cut off. In this way, the extension-side logic valve 13 is put into an openable state when the extension-side pilot passage 134 communicates with the tank 4, and is closed when the extension-side pilot passage 134 is closed.

[0023] The secondary pressure side damping means 14 is provided in the secondary pressure side passage 10, downstream of the branch point of the discharge passage 11. The secondary pressure side damping means 14 allows the flow of liquid from the piston side chamber R2 to the rod side chamber R1 and provides resistance to the flow of liquid. The secondary pressure side damping means 14 is a pressure regulating valve and only allows the flow of liquid from the piston side chamber R2 to the rod side chamber R1. Similar to the pressure regulating valve 62, the secondary pressure side damping means 14 has a characteristic in which the pressure loss is approximately proportional to the flow rate through it. The compression side logic valve 16 is provided in the sub-pressure side passage 10, upstream of the branch point of the discharge passage 11. The compression side logic valve 16 opens and closes the sub-pressure side passage 10. The compression side logic valve 16 includes a compression side valve element 161, a compression side biasing member 162, and a compression side pilot passage 164. The compression side valve element 161 opens and closes the sub-pressure side passage 10. The compression side biasing member 162 is a spring that biases the compression side valve element 161 in a direction to close the sub-pressure side passage 10. The compression side biasing member 162 may be a member other than a spring, as long as it is a member that can bias the compression side valve element 161 to close the sub-pressure side passage 10. The compression side pilot passage 164 connects a compression side back pressure chamber 163 located on the back side of the compression side valve element 161, i.e., on the opposite side from the sub-pressure side passage 10, to the tank 4.

[0024] In this compression-side logic valve 16, the compression-side valve element 161 receives the pressure upstream of the auxiliary pressure-side passage 10, i.e., the pressure in the piston-side chamber R2, on a front side 165 of the compression-side valve element 161. The pressure in the compression-side back-pressure chamber 163 acts on the back side of the compression-side valve element 161. Therefore, when the compression-side pilot passage 164 is in communication with the tank 4, the pressure in the compression-side back-pressure chamber 163 becomes tank pressure. In this state, when the piston-side chamber R2 is compressed and the pressure in the piston-side chamber R2 increases, the pressure in the piston-side chamber R2 causes the compression-side valve element 161 to move in a direction that compresses the compression-side back-pressure chamber 163, and the compression-side logic valve 16 is brought into an open state. Conversely, when the compression-side pilot passage 164 is closed by the compression-side damping force switching means 120 (described later) and communication with the tank 4 is blocked, even if the piston-side chamber R2 is compressed and the pressure in the piston-side chamber R2 increases, there is no escape route for the liquid in the compression-side back-pressure chamber 163. For this reason, the compression-side valve element 161 cannot compress the compression-side back-pressure chamber 163, so the compression-side valve element 161 remains closed to the auxiliary pressure-side passage 10, and the compression-side logic valve 16 is in a closed state. The compression-side valve element 161 is provided with a throttle passage 161a that introduces pressure upstream of the compression-side valve element 161 to the compression-side back-pressure chamber 163. In the compression side logic valve 16, when the compression side valve element 161 retreats toward the compression side back pressure chamber 163 and is in an open state opening the auxiliary pressure side passage 10, and the compression side pilot passage 164 is closed, communication between the compression side back pressure chamber 163 and the tank 4 is closed. Then, the pressure in the compression side back pressure chamber 163 rises, moving the compression side valve element 161 in a direction closing the auxiliary pressure side passage 10, and the compression side logic valve 16 is in a closed state. In this way, the compression side logic valve 16 also operates in the same manner as the expansion side logic valve 13. Specifically, when the compression side pilot passage 164 is open and the compression side back pressure chamber 163 is in communication with the tank 4, the compression side logic valve 16 is in an open state, and when the piston side chamber R2 is compressed and pressure acts on the auxiliary pressure side passage 10, the compression side logic valve 16 is in an open state. Conversely, when the compression side pilot passage 164 is closed and communication between the compression side back pressure chamber 163 and the tank 4 is cut off, the compression side logic valve 16 is in a closed state. In this way, the compression side logic valve 16 is placed in an openable state when the compression side pilot passage 164 communicates with the tank 4, and is closed when the compression side pilot passage 164 is closed.

[0025] The damping force switching unit 100 switches the damping force of the damping force switching damper 1 in accordance with the magnitude of vibration. The damping force switching unit 100 includes a detection rod 200, an extension side damping force switching means 110, and a compression side damping force switching means 120. The detection rod 200 is provided outside the cylinder 21. The detection rod 200 is connected to the piston rod 23 via a connecting rod 28. When the piston rod 23 moves in the axial direction Dc relative to the cylinder 21, the detection rod 200 moves in conjunction with the piston rod 23. The detection rod 200 extends in parallel with the piston rod 23 in the axial direction Dc. The detection rod 200 has a recess 201 at the center in the extension direction thereof. The recess 201 is recessed in a direction perpendicular to the axial direction Dc relative to a surface 202 of the detection rod 200. The recess 201 extends a predetermined length along the axial direction Dc.

[0026] The extension side damping force switching means 110 switches the damping force during extension operation of the damping force switching damper 1. The compression side damping force switching means 120 switches the damping force during compression operation of the damping force switching damper 1. The extension side damping force switching means 110 and the compression side damping force switching means 120 are each provided opposite to the detection rod 200. When the piston 22 is in the neutral position in the initial state where no seismic motion is occurring, the extension side damping force switching means 110 and the compression side damping force switching means 120 are arranged symmetrically across the center portion 201c of the recess 201 in the axial direction Dc.

[0027] The extension side damping force switching means 110 is provided in the middle of the extension side pilot passage 134. The extension side damping force switching means 110 controls the opening and closing of the extension side logic valve 13 by opening and closing the extension side pilot passage 134. The extension side damping force switching means 110 includes a control valve element 111, a switching lever 114, and a control valve biasing means 115. The control valve element 111 opens and closes the extension side pilot passage 134. More specifically, the control valve element 111 is switchable between a closed position 113 where the extension side pilot passage 134 is closed and an open position 112 where the extension side pilot passage 134 is opened. The switching lever 114 is provided so as to be able to move forward and backward in a direction perpendicular to the surface 202 of the detection rod 200 and toward the detection rod 200. The switching lever 114 operates in conjunction with the control valve element 111. The switching lever 114 moves forward and backward in a direction perpendicular to the surface 202, thereby switching the control valve element 111 between a closed position 113 and an open position 112. A roller 114a is provided at the tip of the switching lever 114. When the switching lever 114 advances in the direction toward the detection rod 200, the control valve element 111 is located at the open position 112 and in an open state. When the switching lever 114 retreats from the direction toward the detection rod 200, the control valve element 111 is located at the closed position 113 and in a closed state. The control valve biasing means 115 biases the control valve element 111 to bring the roller 114a of the switching lever 114 into contact with the detection rod 200. A spring is used as the control valve biasing means 115. However, the control valve biasing means 115 may be a member other than a spring.

[0028] When the piston 22 is in the neutral position, the switching lever 114 of the extension-side damping force switching means 110 abuts against the recess 201 . The distance in the axial direction Dc between the switching lever 114 of the extension-side damping force switching means 110 and the end of the recessed portion 201 located on one side Dc1 in the axial direction Dc, closer to the piston rod 23, is a first reference value S1. Further, the distance in the axial direction Dc between the switching lever 114 of the extension side damping force switching means 110 and the end of the recessed portion 201 located on the piston 22 side on the other side Dc2 in the axial direction Dc is a second reference value S2.

[0029] In such an extension-side damping force switching means 110, when the detection rod 200 is displaced in the axial direction Dc as the piston rod 23 moves relative to the cylinder 21 in the axial direction Dc, the roller 114a rolls along the detection rod 200. When the roller 114a of the extension-side damping force switching means 110 is in contact with the recess 201, the control valve element 111 is positioned at the open position 112 and is in an open state, thereby opening the extension-side pilot passage 134 and connecting the extension-side back pressure chamber 133 to the tank 4. When the piston 22 is displaced from the neutral position toward the piston-side chamber R2 on the other side Dc2 in the axial direction Dc by more than the first reference value S1 due to the compression operation of the damping-force switching damper 1, the extension-side damping-force switching means 110 causes the roller 114a to ride up from the recess 201 to the surface 202 on one side Dc1 in the axial direction Dc of the recess 201. Furthermore, when the piston 22 is displaced from the neutral position toward the rod-side chamber R1 on one side Dc1 in the axial direction Dc by more than the second reference value S2, which is larger than the first reference value S1, due to the extension operation of the damping-force switching damper 1, the extension-side damping-force switching means 110 causes the roller 114a to ride up from the recess 201 to the surface 202 on the other side Dc2 in the axial direction Dc of the recess 201. In this way, when the amount of movement of the piston rod 23 relative to the cylinder 21 becomes greater than or equal to the first reference value S1 and the roller 114a rides up onto the surface 202 on one side Dc1 or the other side Dc2 of the axial direction Dc of the recess 201, the switching lever 114 retracts, the control valve body 111 moves from the open position 112 to the closed position 113 and enters a closed state, and the extension side pilot passage 134 is closed. The extension side damping force switching means 110 is provided with a detent mechanism (not shown) on the switching lever 114. Once the extension side logic valve 13 is closed, the detent mechanism of the extension side damping force switching means 110 maintains the closed state of the extension side logic valve 13 thereafter. More specifically, as described above, when the extension side damping force switching means 110 switches from the open position 112 to the closed position 113, the detent mechanism causes the extension side damping force switching means 110 to maintain the closed position 113 as is, thereby maintaining the extension side pilot passage 134 in a closed state. After the extension side damping force switching means 110 reaches the closed position 113, the detent mechanism can be manually operated to return it to the open position 112. Furthermore, since a roller 114a is provided at the tip of the switching lever 114, the switching lever 114 can move smoothly on the detection rod 200, and the relative movement of the piston rod 23 with respect to the cylinder 21 is not easily impeded.

[0030] The compression side damping force switching means 120 is provided in the middle of the compression side pilot passage 164. The compression side damping force switching means 120 controls the opening and closing of the compression side logic valve 16 by opening and closing the compression side pilot passage 164. The compression side damping force switching means 120 includes a control valve element 121, a switching lever 124, and a control valve biasing means 125, similar to the extension side damping force switching means 110. The control valve element 121 opens and closes the compression side pilot passage 164. More specifically, the control valve element 121 is switchable between a closed position 123 at which the compression side pilot passage 164 is closed and an open position 122 at which the compression side pilot passage 164 is opened. The switching lever 124 is provided so as to be able to move forward and backward in a direction perpendicular to the surface 202 of the detection rod 200 and toward the detection rod 200. The switching lever 124 operates in conjunction with the control valve element 121. The switching lever 124 moves forward and backward in a direction perpendicular to the surface 202, thereby switching the control valve element 121 between a closed position 123 and an open position 122. A roller 124a is provided at the tip of the switching lever 124. When the switching lever 124 advances in the direction toward the detection rod 200, the control valve element 121 is located at the open position 122 and in an open state. When the switching lever 124 retreats from the direction toward the detection rod 200, the control valve element 121 is located at the closed position 123 and in a closed state. The control valve biasing means 125 biases the control valve element 121 to bring the roller 124a of the switching lever 124 into contact with the detection rod 200. A spring is used as the control valve biasing means 125. However, the control valve biasing means 125 may be a member other than a spring.

[0031] When the piston 22 is in the neutral position, the switching lever 124 of the compression side damping force switching means 120 abuts against the recessed portion 201 . The distance in the axial direction Dc between the switching lever 124 of the compression side damping force switching means 120 and the end of the recessed portion 201 located on the piston 22 side on the other side Dc2 in the axial direction Dc is a first reference value S1. Further, the distance in the axial direction Dc between the switching lever 124 of the compression side damping force switching means 120 and the end of the recessed portion 201 located on one side Dc1 in the axial direction Dc on the piston rod 23 side is a second reference value S2.

[0032] In such a compression side damping force switching means 120, when the detection rod 200 is displaced in the axial direction Dc as the piston rod 23 moves relative to the cylinder 21 in the axial direction Dc, the roller 124a rolls along the detection rod 200. When the roller 124a is in contact with the recess 201, the control valve body 121 of the compression damping force switching means 120 is positioned in the open position 122 and is in an open state, thereby opening the compression pilot passage 164 and connecting the compression back pressure chamber 163 to the tank 4. When the piston 22 is displaced from the neutral position toward the rod-side chamber R1 on one side Dc1 in the axial direction Dc by more than a first reference value S1 due to the extension operation of the damping-force switching damper 1, the roller 124a climbs up from the recessed portion 201 to the surface 202 on the other side Dc2 in the axial direction Dc of the recessed portion 201. Furthermore, when the piston 22 is displaced from the neutral position toward the piston-side chamber R2 on the other side Dc2 in the axial direction Dc by more than a second reference value S2 that is larger than the first reference value S1 due to the compression operation of the damping-force switching damper 1, the roller 124a climbs up from the recessed portion 201 to the surface 202 on the one side Dc1 in the axial direction Dc of the recessed portion 201. In this way, when the amount of movement of the piston rod 23 relative to the cylinder 21 becomes greater than or equal to the first reference value S1 and the roller 124a rides up onto the surface 202 on one side Dc1 or the other side Dc2 of the axial direction Dc of the recess 201, the switching lever 124 retracts, the control valve body 121 moves from the open position 122 to the closed position 123 and enters the closed state, and the compression side pilot passage 164 is closed. The compression side damping force switching means 120 is provided with a detent mechanism (not shown) on the switching lever 124. Once the compression side logic valve 16 is closed, the detent mechanism of the compression side damping force switching means 120 maintains the closed state of the compression side logic valve 16 thereafter. More specifically, as described above, when the compression side damping force switching means 120 switches from the open position 122 to the closed position 123, the compression side damping force switching means 120 maintains the closed position 123 as is by the detent mechanism, and maintains the closed state of the compression side pilot passage 164. After the compression side damping force switching means 120 reaches the closed position 123, the detent mechanism can be manually operated to return it to the open position 122.

[0033] The following describes the operation of the damping-force switching damper 1 configured as above. Hereinafter, the operation will be explained focusing on the main extension-side passage 51, the main pressure-side passage 61, the auxiliary extension-side passage 9, and the auxiliary pressure-side passage 10, which are related to the flow of liquid between the rod-side chamber R1 and the piston-side chamber R2 when the damping-force switching damper 1 expands or contracts. First, a case where the movement amount of the piston rod 23 from the neutral position is less than the first reference value S1 will be described. FIG. 2 is a diagram showing a state in which the damping force switching damper performs a compressive operation due to the arrival of waves caused by seismic motion, and the amount of the compressive operation is less than a first reference value. 2, when the damping force switching damper 1 compresses due to the arrival of waves caused by seismic motion, unless the amount of compression reaches the first reference value S1, both the roller 114a of the extension side damping force switching means 110 and the roller 124a of the compression side damping force switching means 120 abut against the recess 201, and the switching levers 114, 124 of both the extension side damping force switching means 110 and the compression side damping force switching means 120 advance in directions toward the detection rod 200. In this state, the extension side damping force switching means 110 and the compression side damping force switching means 120 are in an open state with the control valve elements 111, 112 respectively taking the open positions 112, 122, and both the extension side pilot passage 134 and the compression side pilot passage 164 are open. Then, as the compression operation progresses, the pressure in the piston side chamber R2 increases, and when pressure acts on the auxiliary pressure side passage 10, the pressure side logic valve 16 opens, and the liquid flows from the piston side chamber R2 to the rod side chamber R1 through both the main pressure side passage 61 and the auxiliary pressure side passage 10. Here, compared to a case where the compression side logic valve 16 is in a closed state, the secondary pressure side passage 10 is closed, and the liquid can only pass through the main pressure side passage 61, as will be described later, when the compression operating amount as described above is compressed to an extent that does not reach the first reference value S1, the cross-sectional area of ​​the passage through which the liquid flows becomes larger and the resistance to the liquid flow becomes smaller, resulting in a small damping force of the damping force switching damper 1. In this way, if the amount of compression caused by the seismic wave is less than or equal to the first reference value S1, the damping force of the damping force switching damper 1 during compression is small, and the damping force switching damper 1 damps the seismic wave while maintaining the damping force during compression at a small level.

[0034] FIG. 3 is a diagram showing a state in which the damping force switching damper expands due to the arrival of waves caused by seismic motion, and the amount of expansion is less than a first reference value. 3, when the damping force switching damper 1 extends due to the arrival of waves caused by seismic motion, unless the amount of extension reaches the first reference value S1, both the roller 114a of the extension side damping force switching means 110 and the roller 124a of the compression side damping force switching means 120 abut against the recess 201, and the switching levers 114, 124 of both the extension side damping force switching means 110 and the compression side damping force switching means 120 advance in directions toward the detection rod 200. In this state, the extension side damping force switching means 110 and the compression side damping force switching means 120 are in an open state with the control valve elements 111, 112 respectively taking the open positions 112, 122, and both the extension side pilot passage 134 and the compression side pilot passage 164 are open. Then, as the extension operation progresses, the pressure in the rod-side chamber R1 increases, and when pressure acts on the auxiliary extension-side passage 9, the extension-side logic valve 13 opens, and the liquid flows from the rod-side chamber R1 to the piston-side chamber R2 through both the main extension-side passage 51 and the auxiliary extension-side passage 9. Here, compared to a case where the extension-side logic valve 13 is in a closed state, the auxiliary extension-side passage 9 is closed, and the liquid can pass only through the main extension-side passage 51, as will be described later, when the extension amount as described above does not reach the first reference value S1, the cross-sectional area of ​​the passage through which the liquid flows becomes larger and the resistance to the liquid flow becomes smaller, so the damping force of the damping-force switching damper 1 becomes small. In this way, if the amount of extension caused by the seismic wave is less than or equal to the first reference value S1, the damping force of the damping force switching damper 1 during extension is small, and the damping force switching damper 1 damps the seismic wave while maintaining the damping force during extension at a small level.

[0035] Figure 4 shows a state in which a pulse-like seismic motion occurs, the arrival of the first wave due to the seismic motion causes the damping force switching damper 1 to compress, and the amount of compression is greater than or equal to the first reference value and less than or equal to the second reference value. In pulse-type earthquake motion, a first wave with an amplitude larger than that of a normal earthquake first arrives in one direction, followed by a second wave with an even larger amplitude in the opposite direction. The damping force switching damper 1 of this embodiment efficiently attenuates such pulse-type earthquake motion. First, as shown in Fig. 4, consider a case where a pulse-like earthquake motion occurs, and the arrival of a first wave due to the earthquake motion causes the damping-force switching damper 1 to compress, with the amount of compression being equal to or greater than the first reference value S1 and equal to or less than the second reference value S2. In this case, the piston rod 23 moves relative to the cylinder 21, the amount of movement of the piston rod 23 being equal to or greater than the first reference value S1, and the piston 22 is displaced from the neutral position toward the piston-side chamber R2 by an amount equal to or greater than the first reference value S1. Then, the roller 114a of the extension-side damping-force switching means 110 rides on the surface 202 of the detection rod 200 on one side Dc1 in the axial direction Dc of the recess 201, and the switching lever 114 of the extension-side damping-force switching means 110 retracts from the direction toward the detection rod 200. As a result, the control valve element 111 of the extension side damping force switching means 110 moves from the open state to the closed position 113, the extension side pilot passage 134 is closed, and the extension side logic valve 13 is closed. Here, since the compression side logic valve 16 is still in the open state, when the piston 22 displaces together with the piston rod 23 toward the piston side chamber R2 within the cylinder 21, the liquid in the piston side chamber R2 passes through both the main pressure side passage 61 and the auxiliary pressure side passage 10 and flows from the piston side chamber R2 to the rod side chamber R1, as in the case described with reference to FIG. 2 . In this way, the compression side damping force switching means 120 maintains the open state of the compression side logic valve 16, while the extension side damping force switching means 110 switches the extension side logic valve 13 from the open state to the closed state. Therefore, during the compression operation of the damping force switching damper 1 caused by the first wave, even after the amount of compression operation exceeds the first reference value S1, the damping force switching damper 1 damps the first wave while maintaining the damping force during the compression operation at a small state. In this way, because the damping force of the damping force switching damper 1 remains at a small state, the amount of compression operation of the damping force switching damper 1 is larger than in a state where the damping force of the damping force switching damper 1 has switched to a large state. In this way, even if the first wave arrives and compresses by a magnitude equal to or greater than the first reference value S1, the damping force during compression remains small. Therefore, even if the first reference value S1 is set small, the first wave can be efficiently damped.

[0036] FIG. 5 is a diagram showing a state in which the damping force switching damper has expanded from the state shown in FIG. 4 due to the arrival of a second wave caused by seismic motion. After the compression amount of the damping-force switching damper 1 caused by the first wave exceeds the first reference value S1 and reaches the maximum compression amount (equal to or less than the second reference value S2), the damping-force switching damper 1 transitions to an extension operation due to the second wave caused by the seismic motion, as shown in FIG. 5. At this time, the detent mechanism of the switching lever 114 of the extension-side damping force switching means 110 keeps the control valve element 111 in the closed position 113, and the extension-side logic valve 13 is maintained in a closed state. Therefore, even if the piston 22 together with the piston rod 23 is displaced toward the rod-side chamber R1 within the cylinder 21 and the pressure in the rod-side chamber R1 increases, causing pressure to act on the auxiliary extension-side passage 9, the liquid in the rod-side chamber R1 cannot flow through the auxiliary extension-side passage 9. Therefore, the liquid flows from the rod-side chamber R1 to the piston-side chamber R2 only through the main extension-side passage 51. That is, compared to when the extension-side logic valve 13 is in the open state and the liquid flows through both the main extension-side passage 51 and the sub-extension-side passage 9, the cross-sectional area of ​​the passage through which the liquid flows is smaller and the resistance to the liquid flow is greater, so the damping force during the extension operation of the damping-force switching damper 1 is greater. In this way, from the moment the damping force switching damper 1 shifts to the extending operation, it is possible to exert a large damping force in response to the extending operation. 4, during compression, the damping force during compression is maintained at a small value even after the amount of compression exceeds the first reference value S1, so the amount of compression of the damping-force switching damper 1 increases. Therefore, when the damping-force switching damper 1 transitions from compression to extension, a large amount of extension (braking distance) of the damping-force switching damper 1 can be ensured. In this way, the damping force switching damper 1 efficiently damps the second wave.

[0037] As described above, when the piston 22 is displaced from the neutral position toward the piston-side chamber R2 by the first reference value S1 or more, the compression-side damping force switching means 120 maintains the compression-side logic valve 16 in the open state. 4, a case is considered in which a pulse-like earthquake motion occurs, and the arrival of a first wave due to the earthquake motion causes the damping force switching damper 1 to compress, with the amount of compression being equal to or greater than the first reference value S1 and equal to or less than the second reference value S2. For this reason, in FIG. 4, the compression side logic valve 16 in the compression side damping force switching means 120 is in the open state. Here, in a case in which an expansion motion equal to or greater than the first reference value S1 occurs first, and then a compression motion equal to or greater than the first reference value S1 occurs, as will be explained next using FIGS. 6 and 7, the expansion motion equal to or greater than the first reference value S1 causes the compression side logic valve 16 in the compression side damping force switching means 120 to be in the closed state. In this case, in the subsequent compression operation equal to or greater than the first reference value S1, as shown in FIG. 7, the compression side logic valve 16 is closed, and the detent mechanism of the switching lever 124 of the compression side damping force switching means 120 maintains the closed position 123 of the control valve body 121, thereby maintaining the closed state of the compression side logic valve 16. In this way, when the piston 22 is displaced toward the piston-side chamber R2, the compression-side damping force switching means 120 maintains the open / closed state of the compression-side logic valve 16.

[0038] Figure 6 shows a state in which a pulse-like seismic motion occurs, the arrival of the first wave due to the seismic motion causes the damping force switching damper 1 to extend, and the amount of extension is greater than or equal to the first reference value and less than or equal to the second reference value. Next, as shown in Figure 6, consider a case where a pulse-like earthquake motion occurs, and the arrival of a first wave due to the earthquake motion causes the damping-force switching damper 1 to extend, with the amount of extension being equal to or greater than the first reference value S1 and equal to or less than the second reference value S2. In this case, the piston rod 23 moves relative to the cylinder 21, and the amount of movement of the piston rod 23 is equal to or greater than the first reference value S1, displacing the piston 22 from the neutral position toward the rod-side chamber R1 by an amount equal to or greater than the first reference value S1. Then, the roller 124a of the compression-side damping-force switching means 120 rides on the surface 202 of the detection rod 200 on the other side Dc2 in the axial direction Dc of the recess 201, and the switching lever 124 of the compression-side damping-force switching means 120 retracts from the direction toward the detection rod 200. As a result, the control valve element 121 of the compression side damping force switching means 120 moves from the open state to the closed state as it shifts to the closed position 123, the compression side pilot passage 164 is closed, and the compression side logic valve 16 is closed. Here, since the extension side logic valve 13 is still in the open state, when the piston 22 displaces together with the piston rod 23 toward the rod side chamber R1 in the cylinder 21, the liquid in the rod side chamber R1 passes through both the main extension side passage 51 and the auxiliary extension side passage 9 and flows from the rod side chamber R1 to the piston side chamber R2, as in the case described with reference to FIG. 3 . In this way, the extension side damping force switching means 110 maintains the open state of the extension side logic valve 13, while the compression side damping force switching means 120 switches the compression side logic valve 16 from the open state to the closed state. Therefore, during the extension operation of the damping force switching damper 1 caused by the first wave, even after the amount of extension operation exceeds the first reference value S1, the damping force switching damper 1 damps the first wave while keeping the damping force during the extension operation small. In this way, because the damping force of the damping force switching damper 1 remains small, the amount of extension operation of the damping force switching damper 1 is larger than in a state where the damping force of the damping force switching damper 1 has switched to a large state. In this way, even if the first wave arrives and the extension operation is performed by a magnitude equal to or greater than the first reference value S1, the damping force during the extension operation remains small. Therefore, even if the first reference value S1 is set to a small value, the first wave can be efficiently damped.

[0039] FIG. 7 is a diagram showing a state in which the damping force switching damper has undergone a compressive operation due to the arrival of a second wave caused by seismic motion from the state shown in FIG. After the extension amount of the damping-force switching damper 1 caused by the first wave exceeds the first reference value S1 and reaches the maximum extension amount (equal to or less than the second reference value S2), the damping-force switching damper 1 transitions to a compression operation due to the second wave caused by seismic motion, as shown in FIG. 7. At this time, the detent mechanism of the switching lever 124 of the compression-side damping-force switching means 120 maintains the control valve element 121 in the closed position 123, and the compression-side logic valve 16 is maintained in a closed state. Therefore, even if the piston 22 and the piston rod 23 are displaced toward the piston-side chamber R2 within the cylinder 21 and the pressure in the piston-side chamber R2 increases, causing pressure to act on the sub-pressure-side passage 10, the liquid in the piston-side chamber R2 cannot flow through the sub-pressure-side passage 10. Therefore, the liquid flows only through the main-pressure-side passage 61, from the piston-side chamber R2 to the rod-side chamber R1. In other words, compared to when the compression side logic valve 16 is in the open state and the liquid passes through both the main pressure side passage 61 and the sub-pressure side passage 10, the cross-sectional area of ​​the passage through which the liquid flows is smaller and the resistance to the liquid flow is greater, resulting in a greater damping force during the compression operation of the damping force switching damper 1. In this way, from the moment the damping-force switching damper 1 shifts to the compression operation, it is possible to exert a large damping force in response to the compression operation. 6, during extension, the damping force during extension is maintained at a small value even after the amount of extension exceeds the first reference value S1, so the amount of extension of the damping force switching damper 1 increases. Therefore, when the damping force switching damper 1 transitions from an extension operation to a compression operation, a large amount of compression (braking distance) can be ensured in the damping force switching damper 1. In this way, the damping force switching damper 1 efficiently damps the second wave.

[0040] As described above, when the piston 22 is displaced from the neutral position toward the rod-side chamber R1 by the first reference value S1 or more, the extension-side damping force switching means 110 maintains the extension-side logic valve 13 in the open state. 6 considers a case in which a pulse-like earthquake motion occurs, and the arrival of a first wave due to the earthquake motion causes the damping force switching damper 1 to perform an extension operation, with the amount of extension operation being equal to or greater than the first reference value S1 and equal to or less than the second reference value S2. Therefore, in FIG. 6, the extension side logic valve 13 in the extension side damping force switching means 110 is in the open state. Here, in a case in which a compression operation equal to or greater than the first reference value S1 occurs first, and then an extension operation equal to or greater than the first reference value S1 occurs, as explained using FIGS. 4 and 5, the compression operation equal to or greater than the first reference value S1 causes the extension side logic valve 13 in the extension side damping force switching means 110 to be in the closed state. In this case, during the subsequent extension operation equal to or greater than the first reference value S1, as shown in FIG. 5, the extension-side logic valve 13 is closed, and the detent mechanism of the switching lever 114 of the extension-side damping force switching means 110 maintains the closed position 113 of the control valve element 111, thereby maintaining the extension-side logic valve 13 in the closed state. In this way, when the piston 22 is displaced toward the rod-side chamber R1, the extension-side damping force switching means 110 maintains the open / closed state of the extension-side logic valve 13.

[0041] Next, consider a case where pulse-like earthquake motion occurs, the arrival of a first wave due to the earthquake motion causes the damping force switching damper 1 to perform a compressive operation, and the amount of this compressive operation becomes equal to or greater than the second reference value S2. First, during the process of compressing the damping-force switching damper 1 by an amount equal to or greater than the second reference value S2, when the piston 22 is displaced from the neutral position by an amount equal to or greater than the first reference value S1 toward the piston-side chamber R2, as described with reference to FIG. 4 , the roller 114a of the extension-side damping-force switching means 110 rides on the surface 202 of the detection rod 200 at one side Dc1 in the axial direction Dc of the recess 201. As a result, the extension-side damping-force switching means 110 moves to the closed position 113, closing the extension-side logic valve 13. As the compression operation progresses in this state, when the piston 22 displaces toward the piston-side chamber R2 together with the piston rod 23 within the cylinder 21, the fluid in the piston-side chamber R2 flows from the piston-side chamber R2 to the rod-side chamber R1 through the main pressure-side passage 61 and the sub-pressure-side passage 10. In this way, the compression side damping force switching means 120 maintains the damping force during compression, while the extension side damping force switching means 110 switches the damping force to be larger during extension.

[0042] FIG. 8 is a diagram showing a state in which the amount of compressive operation of the damping-force switching damper has increased from the state shown in FIG. 4 to a value equal to or greater than the second reference value. 8, when the first wave causes the damping force switching damper 1 to further compress and the piston 22 to be displaced from the neutral position by more than the second reference value S2 toward the piston-side chamber R2, the roller 114a of the extension side damping force switching means 110 and the roller 124a of the compression side damping force switching means 120 both run onto the surface 202 of the detection rod 200 on one side Dc1 in the axial direction Dc with respect to the recess 201, and the switching lever 124 of the compression side damping force switching means 120 moves backward from the direction toward the detection rod 200. As a result, not only in the extension side damping force switching means 110 but also in the compression side damping force switching means 120, the control valve element 121 moves to the closed position 123 and enters the closed state, the compression side pilot passage 164 is closed, the compression side logic valve 16 is entered the closed state, and fluid no longer passes through the sub-pressure side passage 10. In this state, when the piston 22, together with the piston rod 23, attempts to further displace toward the piston side chamber R2 within the cylinder 21, the liquid in the piston side chamber R2 passes only through the main pressure side passage 61 and flows from the piston side chamber R2 to the rod side chamber R1. In this way, when the compression operation amount becomes equal to or greater than the second reference value S2, the compression side damping force switching means 120 switches the compression side logic valve 16 to a closed state during the compression operation. Therefore, the compression side damping force switching means 120 increases the damping force during the compression operation, and can efficiently damp the first wave even if it is larger than expected. After that, the amount of compression caused by the first wave reaches its maximum, and the second wave causes the damping-force switching damper 1 to transition to an extension operation. At this time, as explained with reference to FIG. 5 , the detent mechanism of the switching lever 114 of the extension-side damping-force switching means 110 keeps the control valve element 111 in the closed position 113, maintaining a state in which the damping force during the extension operation is large. Therefore, when the piston 22, together with the piston rod 23, is displaced toward the rod-side chamber R1 within the cylinder 21, the fluid in the rod-side chamber R1 flows only through the main extension-side passage 51 and into the piston-side chamber R2. As a result, a large damping force can be exerted during the extension operation from the moment the damping-force switching damper 1 transitions to the extension operation.

[0043] Next, consider a case where pulse-like earthquake motion occurs, the arrival of a first wave due to the earthquake motion causes the damping force switching damper 1 to expand, and the amount of this expansion becomes equal to or greater than the second reference value S2. First, in the process of the damping-force switching damper 1 extending by an amount equal to or greater than the second reference value S2, at the stage where the piston 22 is displaced from the neutral position by an amount equal to or greater than the first reference value S1 toward the rod-side chamber R1, as described with reference to FIG. 6 , the roller 124a of the compression-side damping-force switching means 120 rides on the surface 202 of the detection rod 200 on the other side Dc2 in the axial direction Dc of the recess 201. As a result, the compression-side damping-force switching means 120 moves to the closed position 123, closing the compression-side logic valve 16. When the extension operation progresses in this state and the piston 22 is displaced toward the rod-side chamber R1 together with the piston rod 23 within the cylinder 21, the fluid in the rod-side chamber R1 flows from the rod-side chamber R1 to the piston-side chamber R2 through the main-extension-side passage 51 and the sub-extension-side passage 9. In this way, the expansion-side damping force switching means 110 maintains the damping force during expansion, while the compression-side damping force switching means 120 switches the damping force to be larger during compression.

[0044] FIG. 9 is a diagram showing a state in which the amount of extension of the damping-force switching damper has increased from the state shown in FIG. 6 to a value equal to or greater than the second reference value. 9, when the first wave causes the damping force switching damper 1 to further extend and the piston 22 to be displaced from the neutral position toward the rod-side chamber R1 by more than the second reference value S2, the roller 124a of the compression side damping force switching means 120 and the roller 114a of the extension side damping force switching means 110 both run onto the surface 202 of the detection rod 200 on the other side Dc2 in the axial direction Dc with respect to the recess 201, and the switching lever 114 of the extension side damping force switching means 110 moves backward from the direction toward the detection rod 200. As a result, not only in the compression side damping force switching means 120 but also in the extension side damping force switching means 110, the control valve element 111 moves to the closed position 113 and enters the closed state, the extension-side pilot passage 134 is closed, the extension-side logic valve 13 is entered the closed state, and the fluid does not pass through the sub-extension-side passage 9. In this state, when the piston 22, together with the piston rod 23, attempts to further displace toward the rod-side chamber R1 within the cylinder 21, the liquid in the rod-side chamber R1 passes only through the main extension-side passage 51 and flows from the rod-side chamber R1 to the piston-side chamber R2. In this way, when the extension operation amount becomes equal to or greater than the second reference value S2, the extension side damping force switching means 110 switches the extension side logic valve 13 to the closed state during the extension operation. Therefore, the extension side damping force switching means 110 increases the damping force during the extension operation, and can efficiently damp the first wave even if it is larger than expected. After that, the amount of expansion caused by the first wave reaches its maximum, and the second wave causes the damping-force switching damper 1 to transition to compression. At this time, as explained with reference to FIG. 7 , the detent mechanism of the switching lever 124 of the compression-side damping-force switching means 120 keeps the control valve element 121 in the closed position 123, maintaining a state in which the damping force during compression is large. Therefore, when the piston 22, together with the piston rod 23, is displaced toward the piston-side chamber R2 within the cylinder 21, the fluid in the piston-side chamber R2 flows only through the main pressure-side passage 61 and into the rod-side chamber R1. As a result, from the moment the damping-force switching damper 1 transitions to compression, it is possible to exert a large damping force during compression.

[0045] The damping force switching damper 1 as described above is provided to a structure, and by extending and compressing while exerting a damping force, it alleviates vibration of the structure and is capable of switching the damping force according to the magnitude of the vibration. The damping force switching damper 1 includes an extension side damping force switching means 110 that switches the damping force during an extension operation, a compression side damping force switching means 120 that switches the damping force during a compression operation, a cylinder 21, and a piston rod 23 that moves relative to the cylinder 21. When the amount of movement of the piston rod 23 relative to the cylinder 21 extends the damping force by an amount equal to or greater than a first reference value S1, the extension side damping force switching means 110 maintains the damping force during the extension operation, while the compression side damping force switching means 120 switches the damping force to an increased damping force during the compression operation. When the amount of movement of the piston rod 23 relative to the cylinder 21 extends the damping force by an amount equal to or greater than a first reference value S1, the extension side damping force switching means 110 maintains the damping force during the extension operation, while the compression side damping force switching means 120 switches the damping force to an increased damping force during the compression operation. With this configuration, a pulse-like seismic motion occurs in which a first wave with an amplitude larger than that of a normal earthquake arrives in one direction, followed by a second wave with an even larger amplitude than the first wave in the opposite direction, and if the arrival of the first wave causes the damping force switching damper 1 to extend to the extent that the amount of movement of the piston rod 23 relative to the cylinder 21 becomes equal to or greater than the first reference value S1, then when the amount of extension movement reaches the first reference value S1, the damping force during extension movement is maintained (remains small) and only the damping force during compression movement is switched to be increased. Therefore, even after the amount of extension movement exceeds the first reference value S1 during the extension movement of the damping force switching damper 1 caused by the first wave, the damping force during extension movement remains small and the damping force switching damper 1 continues to damp the first wave. At this time, the damping force of the damping force switching damper 1 remains small, so compared to the state when the damping force has switched to a large state, the amount of extension movement of the damping force switching damper 1 until the amount of extension movement caused by the first wave reaches its maximum amount is larger. Subsequently, after the amount of extension caused by the first wave exceeds the first reference value S1, when the amount of extension reaches its maximum amount, the damping force switching damper 1 transitions to a compression operation due to the second wave. At this time, the damping force during the compression operation of the damping force switching damper 1 is switched to a large state because the amount of extension during the extension operation exceeds the first reference value S1. Furthermore, because the amount of extension of the damping force switching damper 1 during the first wave is large, a large braking distance, i.e., a large amount of compression of the damping force switching damper 1, can be ensured when the damping force switching damper 1 transitions from an extension operation to a compression operation. In this way, the damping force switched to a large state and the large braking distance ensured allow the damping force switching damper 1 to more efficiently damp the second wave. On the other hand, if a pulse-like earthquake motion occurs and the arrival of a first wave causes the damping-force-switching damper 1 to perform a compression operation such that the amount of movement of the piston rod 23 relative to the cylinder 21 is equal to or greater than the first reference value S1, then when the amount of compression reaches the first reference value S1, the damping force during the compression operation is maintained (remains small), and only the damping force during the extension operation is switched to be increased. Therefore, even after the amount of compression operation exceeds the first reference value S1 during the compression operation of the damping-force-switching damper 1 caused by the first wave, the damping-force-switching damper 1 damps the first wave while maintaining the damping force during the compression operation at a small value. At this time, because the damping force of the damping-force-switching damper 1 remains small, the amount of compression operation of the damping-force-switching damper 1 until the amount of compression operation caused by the first wave reaches its maximum is larger than when the damping force has been switched to a large value. Subsequently, after the amount of compression caused by the first wave exceeds the first reference value S1, when the amount of compression reaches its maximum, the damping-force switching damper 1 transitions to an extension operation due to the second wave. At this time, the damping force during the extension operation of the damping-force switching damper 1 is switched to a large state because the amount of compression during the compression operation exceeds the first reference value S1. Furthermore, because the amount of compression of the damping-force switching damper 1 during the first wave is large, a large braking distance, i.e., a large amount of extension operation of the damping-force switching damper 1, can be ensured when the damping-force switching damper 1 transitions from a compression operation to an extension operation. In this way, the damping force switched to a large state and the large braking distance ensured allow the damping-force switching damper 1 to more efficiently damp the second wave. Furthermore, even if the damping force switching damper 1 performs an extension or compression operation when the first wave arrives and the amount of movement of the piston rod 23 relative to the cylinder 21 becomes equal to or greater than the first reference value S1, the damping force at this time is maintained at a small state, so that even if the first reference value S1 is set to a small value, the first wave can be damped with the small damping force. In other words, because the first reference value S1 can be set to a certain degree independently of the damping performance for attenuating the first wave, it is possible to set the damping force switching damper 1 so as to prevent a situation in which, even when the first wave arrives, the damping force during compression or extension operation to accommodate the subsequently arriving, larger second wave cannot be switched to a large state because the amplitude is smaller than expected. The above effects are combined to provide a damping force switching damper 1 that can more efficiently damp pulse-like seismic motion.

[0046] Furthermore, when the damping force switching damper 1 performs an extension operation such that the operating amount is equal to or greater than a second reference value S2 that is greater than the first reference value S1, the compression side damping force switching means 120 switches the damping force to be increased during compression operation, and the extension side damping force switching means 110 also switches the damping force to be increased during extension operation, and when the damping force switching damper 1 performs a compression operation such that the operating amount is equal to or greater than the second reference value S2, the extension side damping force switching means 110 switches the damping force to be increased during extension operation, and the compression side damping force switching means 120 also switches the damping force to be increased during compression operation. With this configuration, when the first wave causes piston rod 23 to move relative to cylinder 21 and damping-force switching damper 1 to perform an extension operation, if the amount of operation reaches second reference value S2, which is greater than first reference value S1, not only is the damping force switched to be greater during compression, but also the damping force switched to be greater during extension. Therefore, during the extension operation caused by the first wave, after the amount of extension operation exceeds second reference value S2, until the maximum amount of extension operation is reached, damping-force switching damper 1 damps the first wave by maintaining a large damping force during extension. This makes it possible to more efficiently damp the first wave even when the first wave has a larger amplitude than expected. Subsequently, when the amount of extension caused by the first wave exceeds the second reference value S2 and reaches the maximum amount of extension, the damping force switching damper 1 transitions to compression caused by the second wave. At this time, the damping force of the damping force switching damper 1 during compression has been switched to a large state. This allows the damping force switching damper 1 to efficiently damp the second wave. On the other hand, when the first wave causes piston rod 23 to move relative to cylinder 21 and damping-force switching damper 1 to perform a compression operation, if the amount of operation reaches second reference value S2, which is greater than first reference value S1, the damping force during extension is increased, and the damping force during compression is also increased. Therefore, during the compression operation caused by the first wave, after the amount of compression operation exceeds second reference value S2, until the maximum amount of compression operation is reached, damping-force switching damper 1 damps the first wave by increasing the damping force during compression. This makes it possible to more efficiently damp the first wave, even if the first wave has a larger amplitude than expected. Subsequently, when the amount of compression caused by the first wave exceeds the second reference value S2 and reaches the maximum amount of compression, the damping force switching damper 1 transitions to an extension operation due to the second wave. At this time, the damping force of the damping force switching damper 1 during the extension operation has been switched to a large state. This allows the damping force switching damper 1 to efficiently damp the second wave.

[0047] The damping force switching damper 1 further comprises: a cylinder 21 filled with liquid; a piston rod 23 having one end disposed within the cylinder 21 and the other end protruding outward from the cylinder 21 and connected to one end of the piston rod 23; a piston 22 dividing the interior of the cylinder 21 into a rod-side chamber R1 located on the piston rod 23 side and a piston-side chamber R2 opposite the rod-side chamber R1; a main-extension-side passage 51 and an auxiliary-extension-side passage 9 provided in parallel to allow liquid to flow from the rod-side chamber R1 to the piston-side chamber R2; a main-pressure-side passage 61 and an auxiliary-pressure-side passage 10 provided in parallel to allow liquid to flow from the piston-side chamber R2 to the rod-side chamber R1; and a pressure-transmitting valve 61 for controlling the flow of liquid in each of the main-extension-side passage 51, the auxiliary-extension-side passage 9, the main-pressure-side passage 61, and the auxiliary-pressure-side passage 10. The damping force switching device includes a main extension side damping means 5, an auxiliary extension side damping means 12, a main compression side damping means 6, and an auxiliary compression side damping means 14 that apply resistance, an extension side logic valve 13 that opens and closes the auxiliary extension side passage 9, and a compression side logic valve 16 that opens and closes the auxiliary pressure side passage 10. When the piston 22 is displaced from the neutral position toward the rod side chamber R1 by a distance equal to or greater than a first reference value S1, the extension side damping force switching means 110 maintains the open / closed state of the extension side logic valve 13, while the compression side damping force switching means 120 switches the compression side logic valve 16 from the open state to the closed state. When the piston 22 is displaced from the neutral position toward the piston side chamber R2 by a distance equal to or greater than the first reference value S1, the extension side damping force switching means 110 switches the extension side logic valve 13 from the open state to the closed state, while the compression side damping force switching means 120 maintains the open / closed state of the compression side logic valve 16. With this configuration, in the damping-force switching damper 1, seismic motion causes relative movement between the cylinder 21 and the piston rod 23. When the damping-force switching damper 1 performs an extension operation, the piston 22, together with the piston rod 23, is displaced within the cylinder 21 in a direction that increases the volume of the piston-side chamber R2, i.e., toward the rod-side chamber R1. The displacement of the piston 22 toward the rod-side chamber R1 allows liquid within the rod-side chamber R1 to flow from the rod-side chamber R1 to the piston-side chamber R2 through the main-extension-side passage 51 and the sub-extension-side passage 9. When the damping-force switching damper 1 performs a compression operation, the piston 22, together with the piston rod 23, is displaced within the cylinder 21 in a direction that increases the volume of the rod-side chamber R1, i.e., toward the piston-side chamber R2. The displacement of the piston 22 toward the piston-side chamber R2 allows liquid within the piston-side chamber R2 to flow from the piston-side chamber R2 to the rod-side chamber R1 through the main-pressure-side passage 61 and the sub-pressure-side passage 10. When the extension side logic valve 13 is open during the extension operation of the damping force switching damper 1, the auxiliary extension side passage 9 is open, and the liquid flows from the rod side chamber R1 to the piston side chamber R2 through both the main extension side passage 51 and the auxiliary extension side passage 9. When the extension side logic valve 13 is closed, the auxiliary extension side passage 9 is closed, and the liquid flows from the rod side chamber R1 to the piston side chamber R2 through only the main extension side passage 51. In this way, when the extension side logic valve 13 is closed, the cross-sectional area of ​​the passage through which the liquid flows during the extension operation is smaller than when the extension side logic valve 13 is open, so the resistance to the liquid flow is larger and the damping force of the damping force switching damper 1 is switched to a large state. In this way, the damping force during the extension operation of the damping force switching damper 1 can be switched by opening and closing the extension side logic valve. Furthermore, when the compression side logic valve 16 is open during compression of the damping force switching damper 1, the auxiliary pressure side passage 10 is open, and fluid flows from the piston side chamber R2 to the rod side chamber R1 through both the main pressure side passage 61 and the auxiliary pressure side passage 10. When the compression side logic valve 16 is closed, the auxiliary pressure side passage 10 is closed, and fluid flows from the piston side chamber R2 to the rod side chamber R1 through only the main pressure side passage 61. In this way, when the compression side logic valve 16 is closed, the cross-sectional area of ​​the passage through which fluid flows during compression is smaller than when the compression side logic valve 16 is open. Therefore, resistance to the fluid flow increases, and the damping force of the damping force switching damper 1 switches to a high damping force state. In this way, by opening and closing the compression side logic valve 16, the damping force during compression of the damping force switching damper 1 can be switched. During an extension operation of the damping force switching damper 1, when the piston 22 is displaced from the neutral position by more than the first reference value S1 toward the rod-side chamber R1, the compression-side logic valve 16 is switched from the open state to the closed state while maintaining the open / closed state of the extension-side logic valve 13. As a result, the damping force during the extension operation of the damping force switching damper 1 is maintained, and the damping force during the compression operation is switched to a large state. Furthermore, during compression operation of the damping force switching damper 1, when the piston 22 is displaced from the neutral position by more than the first reference value S1 toward the piston-side chamber R2, the expansion-side logic valve 13 is switched from the open state to the closed state while maintaining the open / closed state of the compression-side logic valve 16. As a result, the damping force during compression operation of the damping force switching damper 1 is maintained, and the damping force during expansion / contraction operation is switched to a large state. In this way, the damping force switching damper 1 can be properly realized.

[0048] The damping force switching damper 1 further includes a tank 4 in which a liquid is stored, and the expansion-side logic valve 13 includes an expansion-side valve element 131 that opens and closes the auxiliary expansion-side passage 9, an expansion-side biasing member 132 that biases the expansion-side valve element 131 in a direction to close the auxiliary expansion-side passage 9, and an expansion-side pilot passage 134 that connects an expansion-side back pressure chamber 133 located on the opposite side of the expansion-side valve element 131 from the auxiliary expansion-side passage 9 to the tank 4. The compression-side logic valve 16 includes a compression-side valve element 161 that opens and closes the auxiliary pressure-side passage 10, a compression-side biasing member 162 that biases the compression-side valve element 161 in a direction to close the auxiliary pressure-side passage 10, and an expansion-side pilot passage 134 that connects a compression-side back pressure chamber 163 located on the opposite side of the compression-side valve element 161 from the auxiliary pressure-side passage 10 to the tank 4. The extension side damping force switching means 110 closes the extension side pilot passage 134 when the piston 22 is displaced from the neutral position toward the piston side chamber R2 by the first reference value S1 or more, and the compression side damping force switching means 120 closes the compression side pilot passage 164 when the piston 22 is displaced from the neutral position toward the rod side chamber R1 by the first reference value S1 or more. When pressure acts on the auxiliary extension side passage 9 with the extension side pilot passage 134 open, the extension side logic valve 13 is opened, and when pressure acts on the auxiliary compression side passage 10 with the compression side pilot passage 164 open, the compression side logic valve 16 is opened. According to this configuration, the expansion-side valve element 131 of the expansion-side logic valve 13 receives the pressure of the auxiliary expansion-side passage 9 on the auxiliary expansion-side passage 9 side. The pressure in the expansion-side back pressure chamber 133 acts on the side opposite to the expansion-side valve element 131 and the auxiliary expansion-side passage 9. When the expansion-side pilot passage 134 is opened and communicates with the tank 4, the expansion-side back pressure chamber 133 becomes the tank 4 pressure. In this state, when the pressure in the rod-side chamber R1 increases due to the expansion action of the damping force switching damper 1, pressure acts on the auxiliary expansion-side passage 9 due to the pressure in the rod-side chamber R1, and the expansion-side valve element 131 moves in a direction compressing the expansion-side back pressure chamber 133, and the expansion-side logic valve 13 is opened. Furthermore, when the piston 22 is displaced from the neutral position by more than the first reference value S1 toward the piston side chamber R2 due to the compression action of the damping force switching damper 1, the expansion-side pilot passage 134 is closed. With the extension-side pilot passage 134 closed and communication with the tank 4 blocked, even if the pressure in the rod-side chamber R1 increases due to the extension action of the damping force switching damper 1, there is no escape route for the liquid in the extension-side back-pressure chamber 133, and therefore the extension-side valve element 131 cannot move toward the extension-side back-pressure chamber 133. As a result, the extension-side valve element 131 keeps the auxiliary extension-side passage 9 closed, and the extension-side logic valve 13 is in a closed state. With the extension-side logic valve 13 in a closed state and the extension-side valve element 131 closing the auxiliary extension-side passage 9, the damping force during the extension action of the damping force switching damper 1 is switched to a large state. Furthermore, the compression-side valve element 161 of the compression-side logic valve 16 is subjected to the pressure of the sub-pressure side passage 10 on the sub-pressure side passage 10 side. The pressure in the compression-side back pressure chamber 163 acts on the side of the compression-side valve element 161 opposite to the sub-pressure side passage 10. When the compression-side pilot passage 164 is open and in communication with the tank 4, the pressure in the compression-side back pressure chamber 163 becomes the tank 4 pressure. In this state, when the pressure in the piston-side chamber R2 increases due to the compression action of the damping-force switching damper 1, pressure acts on the sub-pressure side passage 10 in response to the pressure in the piston-side chamber R2, and the compression-side valve element 161 moves in a direction that compresses the compression-side back pressure chamber 163, thereby opening the compression-side logic valve 16. Furthermore, when the piston 22 is displaced from the neutral position by more than the first reference value S1 toward the rod-side chamber R1 due to the extension action of the damping-force switching damper 1, the compression-side pilot passage 164 is closed. With the compression-side pilot passage 164 closed and communication with the tank 4 blocked, even if the pressure in the piston-side chamber R2 increases due to the compression operation of the damping force switching damper 1, there is no escape route for the liquid in the compression-side back-pressure chamber 163, and the compression-side valve element 161 cannot move toward the compression-side back-pressure chamber 163. As a result, the compression-side valve element 161 remains closed to the auxiliary pressure-side passage 10, and the compression-side logic valve 16 is in a closed state. With the compression-side logic valve 16 in a closed state and the compression-side valve element 161 closing the auxiliary pressure-side passage 10, the damping force during the compression operation of the damping force switching damper 1 is switched to a state where it is large. In this way, the damping force switching damper 1 can be properly realized.

[0049] The damping force switching damper 1 also includes a detection rod 200 that is provided outside the cylinder 21 and is connected to the piston rod 23 to move in conjunction with the piston rod 23. The detection rod 200 has a recess 201 that extends along the axial direction Dc of the piston rod 23. The extension side damping force switching means 110 and the compression side damping force switching means 120 are each provided opposite to the detection rod 200 and include control valve elements 111, 121 that open and close the corresponding pilot passages of the extension side pilot passage 134 and the compression side pilot passage 164, and switching levers 114, 124 that protrude toward the detection rod 200 and are provided so as to be able to move back and forth in the direction toward the detection rod 200, and operate in conjunction with the control valve elements 111, 121 to switch between opening and closing the control valve elements 111, 121. When the switching levers 114, 124 are positioned corresponding to the recess 201 and abut against the recess 201, the control valve bodies 111, 121 are in the open state, and when the switching levers 114, 124 are positioned corresponding to the outside of the recess 201 and abut against the outside of the recess 201, the control valve bodies 111, 121 are in the closed state. When the piston 22 is in the neutral position, the switching levers 114, 124 of the extension side damping force switching means 110 and the compression side damping force switching means 120 abut against the recess 201, and the distance in the axial direction Dc between the switching lever 114 of the extension side damping force switching means 110 and the end of the recess 201 located on the piston rod 23 side Dc1 is a first reference value S1, and the distance in the axial direction Dc between the switching lever 124 of the compression side damping force switching means 120 and the end of the recess 201 located on the piston 22 side Dc2 is also the first reference value S1. According to this configuration, the switching levers 114, 124 of the extension side damping force switching means 110 and the compression side damping force switching means 120 are provided so as to be movable forward and backward in a direction toward the detection rod 200, and are in contact with the recessed portion 201 of the detection rod 200 when the piston 22 is in the neutral position. When the switching levers 114, 124 of the extension side damping force switching means 110 and the compression side damping force switching means 120 advance in a direction toward the detection rod 200 and are in contact with the recessed portion 201 of the detection rod 200, the control valve elements 111, 121 are in the open state. When the switching levers 114, 124 of the extension side damping force switching means 110 and the compression side damping force switching means 120 retreat from the direction toward the detection rod 200 and are in contact with the outside of the recessed portion 201 of the detection rod 200, the control valve elements 111, 121 are in the closed state. In this way, the open / close state of the control valve bodies 111, 121 is switched between when the switching levers 114, 124 are in contact with the recessed portion 201 of the detection rod 200 and when they are in contact with the outside of the recessed portion 201. Because the detection rod 200 moves in conjunction with the piston rod 23, when the piston rod 23 moves relative to the cylinder 21, the detection rod 200 moves together with the piston rod 23 in response to the extension and compression of the damping-force switching damper 1. This changes the position of the recessed portion 201 relative to the switching levers 114, 124, so the control valve bodies 111, 121 can be opened or closed by the switching levers 114, 124. In this configuration, when the piston 22 is in the neutral position, the switching levers 114, 124 of the extension side damping force switching means 110 and the compression side damping force switching means 120 advance in a direction toward the detection rod 200 and come into contact with the recess 201, thereby opening the control valve bodies 111, 121 and opening the extension side pilot passage 134 and the compression side pilot passage 164, thereby achieving a state in which the damping forces are large during the extension operation and the compression operation. Furthermore, when the piston 22 moves from the neutral position toward the rod-side chamber R1 during the extension operation of the damping-force switching damper 1, the detection rod 200 moves toward the rod-side chamber R1 in conjunction with the piston rod 23. When the detection rod 200 moves toward the rod-side chamber R1 by more than the first reference value S1, the switching lever 124 of the compression-side damping-force switching means 120 climbs over the end of the recess 201 located on the piston 22 side Dc2, moves back from the direction toward the detection rod 200, and comes into contact with the outside of the recess 201. This causes the control valve element 121 of the compression-side damping-force switching means 120 to be in the closed state, and the compression-side pilot passage 164 is closed. Therefore, when the piston 22 moves from the neutral position toward the rod-side chamber R1 by more than the first reference value S1, the damping force is switched to a large state during the compression operation following the extension operation. Furthermore, when the piston 22 moves from the neutral position toward the piston-side chamber R2 during the compression operation of the damping-force switching damper 1, the detection rod 200 moves toward the piston-side chamber R2 in conjunction with the piston rod 23. When the detection rod 200 moves toward the piston-side chamber R2 by more than the first reference value S1, the switching lever 114 of the extension-side damping-force switching means 110 climbs over the end of the recess 201 located on the piston rod 23 side Dc1, moves back from the direction toward the detection rod 200, and comes into contact with the outside of the recess 201. This causes the control valve element 111 of the extension-side damping-force switching means 110 to be in the closed state, and the extension-side pilot passage 134 is closed. Therefore, when the piston 22 moves from the neutral position toward the piston-side chamber R2 by more than the first reference value S1, the damping force is switched to a large state during the extension operation following the compression operation. In this way, the damping force switching damper 1 can be properly realized.

[0050] Furthermore, in the damping force switching damper 1, when the piston 22 is displaced from the neutral position toward the rod side chamber R1 by an amount equal to or greater than a second reference value S2 that is larger than the first reference value S1, the compression side damping force switching means 120 switches the compression side logic valve 16 to a closed state, and the extension side damping force switching means 110 also switches the extension side logic valve 13 to a closed state; when the piston 22 is displaced from the neutral position toward the piston side chamber R2 by an amount equal to or greater than the second reference value S2, the extension side damping force switching means 110 switches the extension side logic valve 13 to a closed state, and the compression side damping force switching means 120 also switches the compression side logic valve 16 to a closed state. According to this configuration, when the damping force switching damper 1 is extending due to a first wave and the piston 22 is displaced from the neutral position toward the rod-side chamber R1 by an amount equal to or greater than the second reference value S2, which is greater than the first reference value S1, the compression side damping force switching means 120 closes the compression side logic valve 16 to increase the damping force during compression, and the extension side damping force switching means 110 also closes the extension side logic valve 13 to increase the damping force during extension. Therefore, during the extension of the damping force switching damper 1 due to the first wave, after the extension amount exceeds the second reference value S2, until the maximum extension amount is reached, the damping force switching damper 1 increases the damping force during extension, thereby damping the first wave. This allows the first wave to be more efficiently damped even when the first wave has a larger amplitude than expected. Subsequently, the second wave causes the damping force switching damper 1 to transition to compression operation. At this time, the damping force of the damping force switching damper 1 during compression operation has been switched to a large state. This allows the damping force switching damper 1 to efficiently damp the second wave. On the other hand, when the damping force switching damper 1 is compressing due to the first wave, if the piston 22 is displaced from the neutral position toward the piston-side chamber R2 by an amount equal to or greater than the second reference value S2, which is greater than the first reference value S1, the extension-side damping force switching means 110 closes the extension-side logic valve 13 to increase the damping force during the extension operation, and the compression-side damping force switching means 120 also closes the compression-side logic valve 16 to increase the damping force during the compression operation. Therefore, during the compression operation of the damping force switching damper 1 due to the first wave, after the compression operation amount exceeds the second reference value S2, until the compression operation amount reaches the maximum compression operation amount, the damping force switching damper 1 increases the damping force during the compression operation, thereby damping the first wave. This allows the first wave to be damped more efficiently, even if the first wave has a larger amplitude than expected. Subsequently, the second wave causes the damping force switching damper 1 to transition to an extension operation. At this time, the damping force of the damping force switching damper 1 during the extension operation has been switched to a large state. This allows the damping force switching damper 1 to efficiently damp the second wave.

[0051] In addition, the extension side damping force switching means 110 is provided with a detent mechanism for maintaining the extension side logic valve 13 in a closed state once the extension side logic valve 13 is closed, and the compression side damping force switching means 120 is provided with a detent mechanism for maintaining the compression side logic valve 16 in a closed state once the compression side damping force switching means 110 is closed. For example, when the damping force switching damper 1 compresses due to a first wave, the amount of operation exceeds the first reference value S1, reaches the maximum amount of compression, and then transitions to an extension operation due to a second wave caused by seismic motion. In this case, the switching lever 114 of the extension-side damping force switching means 110 temporarily rides up onto the surface 202 of the detection rod 200 on one side Dc1 of the axial direction Dc relative to the recess 201, moves back from the direction toward the detection rod 200, and then returns to a position corresponding to the recess 201. Here, if the extension-side damping force switching means 110 does not have a detent mechanism, the control valve biasing means 115 causes the switching lever 114 to abut against the recess 201, causing the control valve element 111 to be in the open position 112 and the extension-side logic valve 13 to be in the open state. Therefore, the extension operation due to the second wave is damped with a small damping force. On the other hand, in the above-described embodiment, once the extension side logic valve 13 is closed, the detent mechanism of the extension side damping force switching means 110 maintains the closed state of the extension side logic valve 13. Therefore, the extension side logic valve 13 is prevented from being opened again, and the damping force during the extension operation can be maintained at a large value. Similarly, when the damping force switching damper 1 expands due to a first wave, the amount of expansion exceeds the first reference value S1, reaches the maximum amount of expansion, and then transitions to a compression operation due to a second wave caused by seismic motion. The switching lever 124 of the compression damping force switching means 120 temporarily rides onto the surface 202 of the detection rod 200 on the other side Dc2 of the axial direction Dc relative to the recess 201, recedes from the direction toward the detection rod 200, and then returns to a position corresponding to the recess 201. If the compression damping force switching means 120 does not include a detent mechanism, the control valve biasing means 125 causes the switching lever 124 to abut against the recess 201, causing the control valve element 121 to be in the open position 122 and the compression side logic valve 16 to be in the open state. Therefore, the compression operation due to the second wave is damped with a small damping force. In contrast to this, in the above-described embodiment, once the compression side logic valve 16 is closed, the detent mechanism of the compression side damping force switching means 120 maintains the closed state of the compression side logic valve 16. This prevents the compression side logic valve 16 from being opened again, and makes it possible to maintain a large damping force during the compression operation.

[0052] (Other variations) In the above embodiment, the detection rod 200 is provided with the recess 201, and when the switching levers 114, 124 abut against this recess 201, the extension side damping force switching means 110 and the compression side damping force switching means 120 open, but this is not limited to this. For example, it is also possible to provide a protrusion on the detection rod 200 and adopt a structure in which the open positions 112, 122 and the closed positions 113, 123 of the control valve bodies 111, 121 in Fig. 1 are arranged upside down, so that when the switching levers 114, 124 abut against the protrusion, the extension side damping force switching means 110 and the compression side damping force switching means 120 open. The detection rod 20 may be a single rod, or may be provided as two separate rods corresponding to the extension side damping force switching means 110 and the compression side damping force switching means 120, respectively. In addition, the configurations given in the above embodiments can be selected or changed as appropriate without departing from the spirit of the present invention.

[0053] [Example of study] Using the above-described configuration, we conducted a simulation of the response of a base-isolated building to pulse-like earthquake motion, and the results are shown below. A seismically isolated building with a height of 80m, a building weight of approximately 30,000t, and a seismic isolation period of 6 seconds was equipped with oil dampers as shown below as seismic isolation devices, and a simulation was conducted to examine the response to pulse-type earthquake motion (anticipated seismic waves from the Uemachi fault zone), and the change in seismic isolation displacement over time and the correlation between seismic isolation displacement and damping amount were examined. (Comparative Example 1) The seismic isolation device used was a general relief-type oil damper (a normal seismic isolation oil damper) with a total maximum damping force of 3600tf. (Comparative Example 2) The seismic isolation device used was a general relief-type oil damper (a normal seismic isolation oil damper) with a total maximum damping force of 6,600 tf. (Comparative Example 3) A displacement-switching oil damper was used, which switches to a low damping mode with low damping force up to a displacement of 40 cm, and to a high damping mode with high damping force when the displacement exceeds 40 cm.

[0054] The results of the comparison are shown in FIGS. 10A and 10B. As shown in Figures 10A and 10B, in Comparative Examples 1 and 2 using a general relief-type oil damper, the seismic isolation displacement for the second wave (the negative wave at around 12 seconds in Figure 10A) is larger than the seismic isolation displacement for the first wave (the positive wave at around 10 seconds in Figure 10A) compared to Comparative Example 3. The relief-type oil dampers of Comparative Examples 1 and 2 have symmetrical characteristics when the oil damper expands and compresses due to seismic motion. Therefore, in the case of pulse-like seismic motion in which the displacement of the second wave is larger than that of the first wave, when the second wave is reduced, the first wave, which has a smaller displacement than the second wave, is simultaneously reduced. As a result, the displacement (braking distance) of the oil damper that can be ensured from the maximum amplitude of the first wave to the maximum amplitude of the second wave is reduced, and sufficient damping effect cannot be imparted to the second wave, which acts to increase the amplitude of the second wave. In contrast, in Comparative Example 3, which uses a displacement switching oil damper, the damping force is set to switch from low damping mode to high damping mode after the displacement exceeds 40 cm. As a result, the first wave is resisted in low damping mode, and the seismic isolation displacement is greater than in Comparative Examples 1 and 2. However, because the seismic isolation displacement of the first wave is large, the braking distance for the second wave increases, reducing the maximum displacement without increasing the maximum damping force. However, in a configuration such as that of Comparative Example 3, if the displacement (amplitude) of the first wave is smaller than expected and does not reach the set displacement at which the mode switches from low damping mode to high damping mode, the second wave will be in low damping mode until its displacement reaches the set displacement, and the damping effect on the second wave will not be sufficient, which may result in an increase in the displacement of the second wave. Furthermore, if the set displacement at which the mode switches from low to high damping mode is reduced to accommodate pulse-type seismic motion with a small displacement of the first wave, the mode may switch from low to high damping mode before the maximum displacement of the first wave is reached, exerting a large damping force on the first wave, resulting in a small displacement of the first wave and potentially preventing the effect of increasing the braking distance against the second wave from being fully realized.

[0055] Therefore, a simulation similar to that of Comparative Examples 1 to 3 was carried out using a displacement switching damper simulating the same configuration as the damping force switching damper according to this embodiment. Example 1 This example uses a displacement-switching oil damper that maintains low damping mode after the displacement reaches 15 cm until the direction of displacement reverses (the speed becomes 0), and then switches to high damping mode near the maximum point of displacement at that time. However, this example 1 does not have a configuration that increases the damping force to switch from low damping mode to high damping mode when the displacement exceeds the second reference value S2 in the first wave. Comparative Example 4 A displacement switching oil damper similar to that in Comparative Example 3 was used, and the set displacement at which the damping mode was switched from low to high was set to 25 cm. (Comparative Example 5) A displacement switching oil damper similar to that in Comparative Example 3 was used, and the set displacement at which the damping mode was switched from low to high was set to 40 cm. The results of the comparison are shown in Figures 11A, 11B, 12A, and 12B. The input seismic waves in Figures 11A and 11B are different from those in Figures 12A and 12B. As shown in FIGS. 11A and 11B, in Comparative Example 5 where the set displacement was 40 cm, the first wave did not reach the set displacement, and the second wave increased. Furthermore, as shown in Figures 12A and 12B, in Comparative Example 4, in which the set displacement was 25 cm, the first wave side transitioned to high damping mode early, reducing the displacement of the first wave and shortening the braking distance to reach the second wave, resulting in an increase in the second wave. In contrast to this, in Figures 11A, 11B, 12A, and 12B, in Example 1, by maintaining the low attenuation mode until the first wave reaches its maximum value, a damping effect is obtained for the first wave, while by ensuring a limited distance for the second wave, an effective damping effect is obtained for both the first wave and the second wave.

[0056] Responses were examined when various input seismic waves were input under the same analytical conditions as in Figures 10A, 10B to 12A, and 12B. The maximum seismic isolation displacement and the maximum story deformation angle of the superstructure were calculated for 14 cases of assumed seismic waves from the Uemachi fault zone, 5 cases of assumed seismic waves from the Ikoma fault zone, and 1 case of observed waves from the Kumamoto earthquake, which resulted in large seismic isolation displacement (cases in which the seismic isolation displacement exceeded 60 cm with relief-type oil dampers with a total maximum damping force of 3,600 tf were extracted). The results are shown in Figures 13 and 14. Furthermore, the maximum and average values ​​of the response reduction rates for each comparative example and Example 1 in the cases examined in Figures 13 and 14 are shown in Figure 15. As shown in Figs. 13 to 15, it is clear that the configuration of Example 1 can effectively reduce the response of the seismic isolation layer and the response of the superstructure to pulse-like earthquake motion. 13, there is a case (Ikoma A7B2EW1) in which the seismic isolation displacement in Example 1 is larger than the others. Figures 16A and 16B are diagrams showing the time-dependent change in seismic isolation displacement in this case. As shown in Figures 16A and 16B, in the case of an input seismic waveform in which the first wave is the largest, the configuration of Example 1 maintains the low damping mode until the maximum point of the first wave, so the seismic isolation displacement is larger than in Comparative Examples 4 and 5. In such a case, as shown in the above embodiment, when the displacement amount in the first wave exceeds the second reference value S2, the damping force is increased to transition from low damping mode to high damping mode, thereby effectively reducing the seismic isolation displacement in the first wave. [Explanation of symbols]

[0057] 1 damping force switching damper 121 control valve body 4 Tank 124 Switching Lever 5 Main extension side damping means 125 Control valve biasing means 6 Main pressure side damping means 131 Extension side valve body 9 Sub-extension side passage 132 Extension side biasing member 10 Sub-pressure side passage 133 Extension side back pressure chamber 12 auxiliary extension side damping means 134 extension side pilot passage 13 Retraction side logic valve 161 Compression side valve body 14 Secondary compression side damping means 162 Compression side biasing member 16 Pressure side logic valve 163 Pressure side back pressure chamber 20 Detection rod 164 Compression side pilot passage 21 Cylinder 200 Detection rod 22 piston 201 recess 23 Piston rod R1 Rod side chamber 51 Main extension side passage R2 Piston side chamber 61 Main pressure side passage S1 First reference value 110 Rebound side damping force switching means S2 Second reference value 111 Control valve body Dc Axial direction 114 Switching lever Dc1 One side of the axial direction (piston rod side) 115 Control valve biasing means Dc2 Other side in the axial direction (piston side) 120 Compression damping force switching means

Claims

1. A damping force switching damper that is provided to a structure, extends and compresses while exerting a damping force, thereby mitigating vibration of the structure, and is capable of switching the damping force depending on the magnitude of the vibration, an extension-side damping force switching means for switching the damping force during an extension operation; a compression side damping force switching means for switching the damping force during a compression operation; A cylinder; a piston rod that moves relative to the cylinder; Equipped with When the movement amount of the piston rod relative to the cylinder extends to an extent that is equal to or greater than a first reference value, the extension side damping force switching means maintains the damping force during the extension movement, while the compression side damping force switching means switches to increase the damping force during the compression movement, a damping force switching damper, characterized in that, when the operating amount is compressed to an amount equal to or greater than the first reference value, the compression side damping force switching means maintains the damping force during the compression operation, while the extension side damping force switching means switches to increase the damping force during the extension operation.

2. When the operation amount is extended to a magnitude equal to or greater than a second reference value that is greater than the first reference value, the compression side damping force switching means switches the damping force during the compression operation to be larger, and the extension side damping force switching means also switches the damping force during the extension operation to be larger, When the operation amount is compressed to a value equal to or greater than the second reference value, the extension side damping force switching means switches the damping force during the extension operation to be larger, and the compression side damping force switching means also switches the damping force during the compression operation to be larger.

2. The damping force switching damper according to claim 1.

3. The cylinder is filled with a liquid; The piston rod has one end provided within the cylinder and the other end protruding outward from the cylinder, a piston connected to the one end of the piston rod and dividing the interior of the cylinder into a rod-side chamber located on the piston rod side and a piston-side chamber opposite to the rod-side chamber; a main extension-side passage and a sub-extension-side passage provided in parallel to each other so as to allow the liquid to flow from the rod-side chamber to the piston-side chamber; a main pressure side passage and a sub-pressure side passage provided in parallel to each other so as to allow the liquid to flow from the piston side chamber to the rod side chamber; a main expansion side damping means, an auxiliary expansion side damping means, a main pressure side damping means, and an auxiliary pressure side damping means that apply resistance to the flow of the fluid in each of the main expansion side passage, the auxiliary expansion side passage, the main pressure side passage, and the auxiliary pressure side passage; an expansion-side logic valve that opens and closes the auxiliary expansion-side passage; a pressure-side logic valve that opens and closes the auxiliary pressure-side passage; Equipped with When the piston is displaced from the neutral position toward the rod-side chamber by the first reference value or more, the extension-side damping force switching means maintains the extension-side logic valve in an open / closed state, while the compression-side damping force switching means switches the compression-side logic valve from an open state to a closed state, When the piston is displaced from the neutral position toward the piston-side chamber by the first reference value or more, the compression-side damping force switching means maintains the compression-side logic valve in an open / closed state, while the extension-side damping force switching means switches the extension-side logic valve from an open state to a closed state.

2. The damping force switching damper according to claim 1.

4. Further, a tank for storing the liquid is provided, The expansion side logic valve is an expansion-side valve body that opens and closes the auxiliary expansion-side passage; an expansion-side biasing member that biases the expansion-side valve body in a direction that closes the auxiliary expansion-side passage; an expansion-side pilot passage that connects an expansion-side back pressure chamber located on an opposite side of the expansion-side valve body from the auxiliary expansion-side passage to the tank, The pressure side logic valve is a pressure-side valve body that opens and closes the auxiliary pressure-side passage; a compression-side biasing member that biases the compression-side valve body in a direction that closes the auxiliary pressure-side passage; a compression-side pilot passage that connects a compression-side back pressure chamber located on the opposite side of the compression-side valve body from the auxiliary pressure-side passage to the tank, the extension-side damping force switching means closes the extension-side pilot passage when the piston is displaced from the neutral position toward the piston-side chamber by the first reference value or more, the compression side damping force switching means closes the compression side pilot passage when the piston is displaced from the neutral position toward the rod side chamber by the first reference value or more, When pressure acts on the auxiliary extension-side passage while the extension-side pilot passage is open, the extension-side logic valve is opened, When pressure acts on the auxiliary pressure side passage while the pressure side pilot passage is open, the pressure side logic valve is opened.

4. The damping force switching damper according to claim 3.

5. a detection rod provided outside the cylinder, the detection rod being connected to the piston rod and moving in conjunction with the piston rod; The detection rod has a recess formed therein that extends along the axial direction of the piston rod, The extension side damping force switching means and the compression side damping force switching means are each provided opposite to the detection rod, and each of them is a control valve element that opens and closes a corresponding pilot passage between the extension side pilot passage and the compression side pilot passage; a switching lever that protrudes toward the detection rod, is provided so as to be able to move back and forth in a direction toward the detection rod, and operates in conjunction with the control valve body to switch the control valve body between open and closed states; Equipped with each of the extension side damping force switching means and the compression side damping force switching means is positioned corresponding to the recess and opens the control valve body when the switching lever is in contact with the recess, and closes the control valve body when the switching lever is positioned corresponding to the outside of the recess and in contact with the outside of the recess, When the piston is in a neutral position, the switching levers of the extension side damping force switching means and the compression side damping force switching means are in contact with the recessed portion, and the distance in the axial direction between the switching lever of the extension side damping force switching means and an end of the recessed portion located on the piston rod side is the first reference value, and the distance in the axial direction between the switching lever of the compression side damping force switching means and an end of the recessed portion located on the piston side is also the first reference value.

5. The damping force switching damper according to claim 4.

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