Rolling damping damper for a railroad vehicle and method for damping

Abstract

 To provide a damper for damping rolling of a railroad vehicle and a damping method, in which controlling of an attenuation force in an attenuation force control circuit is carried out merely by a vehicle body speed signal of a vehicle body without using a damper speed signal, and even when a power is off, controlling can be made in common by the same attenuation force control circuit as that is used at the time of control without the provision of a separate exclusive-use circuit, whereby the control system is simplified, the number of parts is reduced, and miniaturization can be accomplished.
A damper C for damping rolling of a railroad vehicle, comprising: a cylinder 106 interposed between a bogie A and a vehicle body B, a flow passage 121 merely allowing a flow of working fluid from a head-side chamber 111 to a rod-side chamber 112 of the cylinder, a reservoir 107 leading to the head-side chamber of the cylinder through a suction valve 122, a flow passage 120 for communicating the head-side chamber with the reservoir, an unload valve 118 for pressure side disposed in the flow passage, and an attenuation force control circuit 8 interposed between the rod-side chamber and the reservoir, said attenuation force control circuit having a fixed restrictor 126, and a proportional electromagnetic relief valve V provided in parallel with the fixed restrictor to continuously control a relief set pressure from the maximum pressure to the minimum pressure as an input from a proportional solenoid 45 increases, said proportional electromagnetic relief valve comprising a valve casing 7, an input port 32 and a return port 34 provided in the valve casing, a valve seat body 20 provided with a valve body 27 for intermittently communicating the input port with the return port, a spring 30 for setting a relief pressure for biasing the valve body in a closing direction, an adjusting screw body 9 having a pressing body 17 for supporting a base end of the spring slidably disposed, a stop member 19 provided on the adjusting screw body to control a stroke of the pressing body, an adjusting threaded rod 14 threadedly inserted into the adjusting screw body to support the base end of the pressing body, a pressure receiving chamber 18 formed between the pressing body and the adjusting screw body, a solenoid for applying a force in an opening direction to the valve body, and a switching valve 48 positioned between the valve body and a movable core 46 in the solenoid to switch the mode from communication with the return port of the pressure receiving chamber to communication with the input port thereof while pressing the valve body through the excitation of the solenoid.

Description

[0001] The present invention relates to a semi-active controlling damper for damping the rolling generated in a vehicle body of a railroad vehicle, and a damping method making use of the damper.

[0002] A semi-active controlling damper for damping the rolling which can, even if a bogie on the vibration generating side and a vehicle mass on the damping side as in a railroad vehicle are extremely large, effectively damp them and a control system making use of the damper are disclosed, for example, in Japanese Patent Application Laid-Open Nos. 8-99634 and 8-239040 Publications.

[0003] The control damper disclosed in these Publications comprises a stroke sensing cylinder interposed between a bogie and a vehicle body, a flow passage merely allowing a flow of working fluid from a head-side chamber to a rod-side chamber of the stroke sensing cylinder, a reservoir leading to the head-side chamber of the stroke sensing cylinder through a suction valve, an unload valve for pressure side having the head-side chamber disposed in the flow passage communicated with the reservoir, an unload valve for extension side likewise having the rod-side chamber disposed in the flow passage communicated with the head-side chamber, and an attenuation force control circuit interposed between the rod-side chamber and the reservoir.

[0004] In the former attenuation force control circuit, a plurality of fixed orifices for generating an attenuation force are arranged in series, and opening and closing valves for controlling the respective fixed orifices are provided in parallel. On the other hand, in the latter attenuation force control circuit, a fixed orifice, a normally open proportional valve for continuously proportionally controlling a restrictor opening or a proportional pressure control valve are provided in parallel.

[0005] Each control system making use of a damper as described above uses a vehicle body speed signal from a detector installed on the vehicle body, a damper displacement signal from a stroke sensing cylinder, and a damper speed signal calculated therefrom to control a generated attenuation force of an attenuation force generator circuit by a computer and control an unload valve for extension side and an unload valve for pressure side to suppress the rolling of a railroad vehicle.

[0006] In the case of the former, the opening and closing valves are switched by the computer in response to the vehicle speed signal and the damper speed signal, and in the case of the latter, the proportional valve or the proportional control valve is continuously controlled by the computer under the same signal.

[0007] While the above-described control systems particularly have no defect in function, improvement in the following inconveniences has been desired.

[0008] First, since the resistance of the fixed restriction is changed by the switching control of the selective opening and closing valves or the proportional control of the proportional valve to generate an attenuation force, the restriction resistance of the fixed orifice is determined by the passage flow rate of working oil passing therethrough.

[0009] As a result, the passage flow rate of working oil is in proportion to a damper speed, so that it has to be controlled by removing a damper displacement signal using a stroke sensing cylinder, calculating a damper speed signal by a computer, and operating an attenuation force using the calculated value. In other words, the stroke sensing cylinder and its signal are necessary without fail, so that the control system becomes large in size and the cost increases.

[0010] Secondly, in order that when a power is off, an appropriate attenuation force is generated to function the stroke sensing cylinder as a normal damper, a separate exclusive-use attenuation force control circuit is provided. This exclusive-use attenuation force control circuit is provided with a restrictor, a relief valve, and a switching valve. Therefore, the number of parts increases, the entire control system becomes large in size, and the cost increases. In addition, it is necessary for switching and controlling the switching valve to have an exclusive-use control signal system, whereby the control system becomes complicated, resulting in a larger control system and an increase in cost.

[0011] It is therefore an object of the present invention to provide a damper for damping rolling of a railroad vehicle and a damping method, in which controlling of an attenuation force in an attenuation force control circuit is carried out merely by a vehicle body speed signal of a vehicle body without using a damper speed signal, and even when a power is off, controlling can be made in common by the same attenuation force control circuit as that is used at the time of control without the provision of a separate exclusive-use circuit, whereby the control system is simplified, the number of parts is reduced, and miniaturization can be accomplished.

[0012] For achieving the aforesaid object, according to the present invention, there is provided a damper for damping rolling of a railroad vehicle, comprising: a cylinder interposed between a bogie and a vehicle body, a flow passage merely allowing a flow of working fluid from a head-side chamber to a rod-side chamber of the cylinder, a reservoir leading to the head-side chamber of the cylinder through a suction valve, a flow passage for communicating the head-side chamber with the reservoir, an unload valve for pressure side disposed in the flow passage, and an attenuation force control circuit interposed between the rod-side chamber and the reservoir, said attenuation force control circuit having a fixed restrictor, and a proportional electromagnetic relief valve provided in parallel with the fixed restrictor to continuously control a relief set pressure from the maximum pressure to the minimum pressure as an input from a proportional solenoid increases, said proportional electromagnetic relief valve comprising a valve casing, an input port and a return port provided in the valve casing, a valve seat body provided with a valve body for intermittently communicating the input port with the return port, a spring for setting a relief pressure for biasing the valve body in a closing direction, an adjusting screw body having a pressing body for supporting a base end of the spring slidably disposed, a stop member provided on the adjusting screw body to control a stroke of the pressing body, an adjusting threaded rod threadedly inserted into the adjusting screw body to support the base end of the pressing body, a pressure receiving chamber formed between the pressing body and the adjusting screw body, a solenoid for applying a force in an opening direction to the valve body, and a switching valve positioned between the valve body and a movable core in the solenoid to switch the mode from communication with the return port of the pressure receiving chamber to communication with the input port thereof while pressing the valve body through the excitation of the solenoid.

[0013] According to the present invention, there is further provided a damper for damping rolling of a railroad vehicle, comprising: a cylinder interposed between a bogie and a vehicle body, a flow passage merely allowing a flow of working fluid from a head-side chamber to a rod-side chamber of the cylinder, a reservoir leading to the head-side chamber of the cylinder through a suction valve, a flow passage for communicating the head-side chamber with the reservoir, an unload valve for pressure side disposed in the flow passage, and an attenuation force control circuit interposed between the rod-side chamber and the reservoir, said attenuation force control circuit having a fixed restrictor, and a proportional electromagnetic relief valve provided in parallel with the fixed restrictor to continuously control a relief set pressure from the maximum pressure to the minimum pressure as an input from a proportional solenoid increases, said proportional electromagnetic relief valve comprising a valve casing, an input port and a return port provided in the valve casing, a slidable valve seat body provided with a valve body for intermittently communicating the input port with the return port, a spring for setting a relief pressure for biasing the valve body in a closing direction, an adjusting screw body provided with an adjusting threaded rod for supporting a base end of the spring, a solenoid for applying a force in an opening direction to the valve body, a pressure receiving chamber formed between the valve seat body and the solenoid, and a switching valve positioned between the valve body and a movable core in the solenoid to switch the mode from communication with the return port of the pressure receiving chamber to communication with the input port thereof while pressing the valve body through the excitation of the solenoid.

[0014] In each of the above-described damping damper, the flow passage merely allowing a flow of working fluid from the head-side chamber to the rod-side chamber of the cylinder is preferably constituted by an unload flow passage for extension side and a check valve provided at an off position of the unload valve for extension side provided in the unload flow passage.

[0015] Likewise, the flow passage merely allowing a flow of working fluid from the head-side chamber to the rod-side chamber of the cylinder can be constituted by a flow passage provided in the piston and a check valve provided in said flow passage.

[0016] There is provided a method for damping rolling of a railroad vehicle using the above-described damper, the method comprising: using a damping damper comprising a cylinder interposed between a bogie and a vehicle body, a flow passage merely allowing a flow of working fluid from a head-side chamber to a rod-side chamber of the cylinder, a reservoir leading to the head-side chamber of the cylinder through a suction valve, a flow passage for communicating the head-side chamber with the reservoir, an unload valve for pressure side disposed in the flow passage, an unload valve for extension side having the rod-side chamber disposed in the flow passage communicated with the head-side chamber, and an attenuation force control circuit interposed between the rod-side chamber and the reservoir, said attenuation force control circuit having a fixed restrictor, and a proportional electromagnetic relief valve provided in parallel with the fixed restrictor to continuously control a relief set pressure from the maximum pressure to the minimum pressure as an input from a proportional solenoid increases, said proportional electromagnetic relief valve comprising a valve casing, an input port and a return port provided in the valve casing, a valve seat body provided with a valve body for intermittently communicating the input port with the return port, a spring for setting a relief pressure for biasing the valve body in a closing direction, an adjusting screw body having a pressing body for supporting a base end of the spring slidably disposed, a stop member provided on the adjusting screw body to control a stroke of the pressing body, an adjusting threaded rod threadedly inserted into the adjusting screw body to support the base end of the pressing body, a pressure receiving chamber formed between the pressing body and the adjusting screw body, a solenoid for applying a force in an opening direction to the valve body, and a switching valve positioned between the valve body and a movable core in the solenoid to switch the mode from communication with the return port of the pressure receiving chamber to communication with the input port thereof while pressing the valve body through the excitation of the solenoid; operating by a computer an attenuation force value closest to the optimum valve generated in the attenuation force control circuit on the basis of only a signal on the vehicle body side such as a vehicle body speed signal from detection means provided on the vehicle body; proportionally controlling the proportional electromagnetic relief valve on the basis of the result of operation; and judging by a computer the deflecting direction of the vehicle body by the vehicle body speed from the detection means to selectively switch and control the unload valve for pressure side and the unload valve for extension side.

[0017] There is further provided a method for damping rolling of a railroad vehicle using the damper, the method comprising: using a damping damper comprising a cylinder interposed between a bogie and a vehicle body, a flow passage merely allowing a flow of working fluid from a head-side chamber to a rod-side chamber of the cylinder, a reservoir leading to the head-side chamber of the cylinder through a suction valve, a flow passage for communicating the head-side chamber with the reservoir, an unload valve for pressure side disposed in the flow passage, an unload valve for extension side having the rod-side chamber disposed in the flow passage communicated with the head-side chamber, and an attenuation force control circuit interposed between the rod-side chamber and the reservoir, said attenuation force control circuit having a fixed restrictor, and a proportional electromagnetic relief valve provided in parallel with the fixed restrictor to continuously control a relief set pressure from the maximum pressure to the minimum pressure as an input from a proportional solenoid increases, said proportional electromagnetic relief valve comprising a valve casing, an input port and a return port provided in the valve casing, a slidable valve seat body provided with a valve body for intermittently communicating the input port with the return port, a spring for setting a relief pressure for biasing the valve body in a closing direction, an adjusting screw body provided with an adjusting threaded rod for supporting a base end of the spring, a solenoid for applying a force in an opening direction to the valve body, and a switching valve positioned between the valve body and a movable core in the solenoid to switch the mode from communication with the return port of the pressure receiving chamber to communication with the input port thereof while pressing the valve body through the excitation of the solenoid; operating by a computer an attenuation force value closest to the optimum value generated in the attenuation force control circuit on the basis of only a signal on the vehicle body side such as a vehicle body speed signal from detection means provided on the vehicle body; proportionally controlling the proportional electromagnetic relief valve on the basis of the result of operation; and judging by a computer the deflecting direction of the vehicle body by the vehicle body speed from the detection means to selectively switch and control the unload valve for pressure side and the unload valve for extension side.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 

FIG. 1 is a block diagram of a rolling damping system of a railroad vehicle according to the present invention;

FIG. 2 is a circuit view of one embodiment of a damping damper used in the damping system;

FIG. 3 is a circuit view of a damping damper according to a further embodiment;

FIG. 4 is a longitudinal front view of a proportional electromagnetic relief valve according to one embodiment of the present invention; and

FIG. 5 is a longitudinal front view of a proportional electromagnetic relief valve according to a further embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The embodiments of the present invention will be described hereinafter with reference to the accompanying drawings.

[0020] In FIG. 1, semi-active controlling dampers C and D according to the present invention are arranged horizontally opposite to each other between a bogie A on the vibration generating side and a vehicle body B on the damping side.

[0021] While any one of these semi-active controlling dampers C and D will suffice to be provided, it is noted that two of them are used as in this embodiment to thereby obtain a fail-safe effect when one of them is in trouble.

[0022] The vehicle body B on the damping side is provided with a detector E formed from an accelerometer or speedometer for detecting a vibration state of the vehicle body B.

[0023] The semi-active controlling damper C, D comprise a cylinder 106, a reservoir 107, and an attenuation force control circuit 108, as shown in FIG. 2.

[0024] The cylinder 106 divides the interior of the cylinder 106 into a head-side chamber 111 and a rod-side chamber 112 by a slidable piston 110, and a piston rod 113 extends from the piston 110 to the outside.

[0025] The semi-active controlling damper C, D are provided with two unload valves 118 and 119 for pressure side and for extension side, which respectively maintain a position of check valves 116 and 117 at their off position and a conductive position at its on position.

[0026] The unload valve 118 for pressure side is interposed in the middle of a flow passage 120 for communication between the head-side chamber 111 and the reservoir 107, and is arranged so that at an off position, a flow of working fluid from the head-side chamber 111 toward the reservoir 107 is checked by the check valve 116, and at an on position, the head-side chamber 111 is communicated with the reservoir 107 through the flow passage 120.

[0027] On the other hand, the unload valve 119 for extension side is interposed in the middle of a flow passage 121 which extends from an inlet side of the unload valve 118 for pressure side toward the rod-side chamber 112, and is arranged so that at an off position, a flow of working fluid from the rod-side chamber 112 toward the head-side chamber 111 of the cylinder 106 is checked by the check valve 117, and at an on position, the rod-side chamber 112 is communicated with the head-side chamber 111.

[0028] The head-side chamber 111 is communicated with the reservoir 107 also by a suction flow passage 123 having a suction valve 122, and the rod-side chamber 112 is communicated with the reservoir 107 through an attenuation force control circuit 108 from a filter 124.

[0029] In the attenuation force control circuit 108, a fixed restrictor 126 for controlling the maximum generated attenuation force and a proportional electromagnetic relief valve V for continuously proportioning a relief pressure are arranged in parallel, from the rod-side chamber 112 on the upstream side to the reservoir 107 on the downstream side.

[0030] With this, first, in a low-speed area where the piston 110 of the cylinder 106 begins to move, the working fluid extruded from the rod-side chamber 112 to the attenuation force circuit 108 flows into the reservoir 107 through the fixed restrictor 126 to generate the attenuation force due to the pressure loss thereof.

[0031] When the piston speed enters a middle and high speed area and the pressure loss reaches a relief setting pressure of the proportional electromagnetic relief valve V arranged in parallel with the fixed restrictor 126, the valve body 27 is opened and closed to cause the working fluid to flow to the reservoir 107 so that a circuit pressure is maintained constant and the maximum attenuation force is controlled.

[0032] Thereby, the relief setting pressure of the proportional electromagnetic relief valve V can be continuously operated to thereby continuously change the maximum attenuation force irrespective of the speed of the piston.

[0033] The proportional electromagnetic relief valve V comprises a valve casing 1, a valve body 27 provided openably and closably between an inlet port 32 and a return port 34, a spring 30 for biasing the valve body 27 in a closing direction, a pressure receiving chamber 17 provided at the rear of the spring 30, a switching valve 48 for selectively communicating the pressure receiving chamber 17 with the inlet port 32 and the return port 34, and a solenoid 45 for switching and controlling the switching valve 48.

[0034] Supposing that a lateral deflection occurs in the vehicle body B due to the rolling of the bogie A to generate a relative displacement between the bogie A and the vehicle body B, the cylinder 106 interposed between the bogie A and the vehicle body B expands and contracts in response to the deflecting direction of the bogie A and the vehicle body B.

[0035] When the cylinder 106 expands, the working fluid in the reservoir 107 is caused to take into the head-side chamber 111 through the suction flow passage 123 from the suction valve 122, during which the working fluid within the rod-side chamber 112 is extruded through the filter 124 toward the attenuation force control circuit 108.

[0036] Conversely, when the cylinder 106 contracts, the suction valve 122 is closed so that the check valve 117 of the unload valve 114 for extension side is open to cause the working fluid in the rod-side chamber 111 to flow into the rod-side chamber 112 and to extrude the working fluid in the amount corresponding to the entry volume portion of the piston rod 113 from the rod-side chamber 112 to the attenuation force control circuit 108 through the filter 124. The working fluid extruded toward the attenuation force control circuit 108 flows into the reservoir 107 under the control of the fixed restrictor 126 and the proportional electromagnetic relief valve V.

[0037] The proportional electromagnetic relief valve V is appropriately operated in response to the relative rolling speed between the bogie A and the vehicle body B to thereby effectively suppress the rolling of the vehicle body B for the reason that the attenuation force control circuit 108 generates an appropriate attenuation force.

[0038] In FIG. 1, the detector E provided on the vehicle body B detects a deflection of the vehicle body B as a vehicle body signal T, which is processed by a processing circuit F for converting a computer signal into a plus vehicle body speed signal U1 and a minus vehicle body speed signal U2, after which they are input into a computer G.

[0039] In the case where the detector E is a speedometer, the signal is processed by the processing circuit F into the plus vehicle body speed signal U1 and the minus vehicle body speed signal U2 as described above, but in the case of an accelerometer, an acceleration is once converted by the processing circuit F into a speed, after which it is processed into the plus vehicle body speed signal U1 and the minus vehicle body speed signal U2.

[0040] The computer G, on the other hand, judges a deflecting direction of the vehicle body B by the vehicle body speed signals U1 and U2 being fed from the detector E on the vehicle body B side to output a switching signal P or Q to the unload valves 118 and 119 for pressure side or for extension side of the control valves C and C through valve driver circuits H and H to selectively turn them on and off.

[0041] Likewise, an attenuation force closest to the optimum value generated in the attenuation force control circuit 108 is operated by the computer G on the basis of a signal on the vehicle body side, and a result of operation is output as a control signal X, which is then applied to a solenoid 45 to proportionally control the electromagnetic relief valve V.

[0042] The semi-active controlling dampers C and C perform the damping operation while operating with respect to the lateral deflection generated between the bogie A and the vehicle body B under the control described below.

[0043] However, in performing the above-described control, the semi-active controlling dampers C and C perform the similar function as the operation with the operating directions merely reversed.

[0044] Accordingly, if one operation is explained, the other operation can be easily understood. For the sake of avoiding the complicateness of the explanation, the damper system using one semi-active controlling damper will be mentioned here.

[0045] (1) When the vehicle body B is deflected to the left hand:

[0046] Supposing that the vehicle body B is deflected to the left hand during traveling, the plus vehicle body speed signal U1 is input into the computer G through the processing circuit F from the detector E.

[0047] The computer G judges that the vehicle body B is deflected to the left hand on the basis of the plus vehicle body speed signal U1 to output a switching signal P to the unload valve 118 for pressure side to switch it to a on-position.

[0048] When the bogie A is deflected to the left hand at a lower speed than the vehicle body B, or when it is deflected to the right hand reversely to the vehicle body B, the cylinder 106 operates on the extension side to extrude the internal working fluid to the attenuation force control circuit 108.

[0049] When the rolling speed of the vehicle body B is within a normal ranged, a control signal X corresponding to the rolling speed is fed to the electromagnetic relief valve V from the computer G to control the relief pressure thereof, while the working fluid extruded to the attenuation force control circuit 108 through the cylinder 106 is controlled by the fixed restrictor 126 and the proportional electromagnetic relief valve V, and the causally generated attenuation force is controlled to suppress the rolling of the vehicle body B.

[0050] On the other hand, supposing that when the vehicle body B is deflected to the left hand, the bogie A is deflected to the left hand at a higher speed than the rolling speed leftward of the vehicle body B, for example, due to the dislocation of a rail. Then, the cylinder 106 contracts to generate the fluid pressure corresponding to the generated attenuation force of the attenuation force control circuit 108 also in the head-side chamber 111 of the cylinder 106.

[0051] The fluid pressure generated in the head-side chamber 111 operates as a pressing force in a direction of extension of the cylinder 106 due to a difference in pressure receiving area between the head-side chamber 111 and the rod-side chamber 112 caused by the presence of the piston rod 113 to deflect the vehicle body B further to the left hand. It is therefore necessary not to generate the fluid pressure.

[0052] However, even in this case, the vehicle body B itself is deflecting to the left hand. Therefore, the computer G keeps outputting the switching signal P to the unload valve 118 for pressure side on the basis of the plus vehicle body speed signal U1 from the detector E to keep maintaining the unload valve 118 for pressure side in an on-position.

[0053] Thereby, the working fluid of the head-side chamber 111 escapes to the reservoir 107 through the unload valve 118 for pressure side from the flow passage 120.

[0054] As a result, the fluid pressure is not generated in the head-side chamber 111 of the cylinder 106 to prevent the vehicle body B from being deflected further to the left hand by the cylinder 106.

[0055] (2) When the vehicle body B is deflected to the right hand:

[0056] When the vehicle body B is deflected to the right hand reversely to the former, the minus vehicle body speed signal U2 is input into the computer G from the detector E.

[0057] This time, the computer G outputs the switching signal Q to the unload valve 119 for extension side on the basis of the minus vehicle body speed signal U2 to switch it to an on-position.

[0058] Suppose that the bogie A is deflected to the right hand at a lower speed than the vehicle body B, or it is deflected to the left hand reversely to the vehicle body B. Then, the cylinder 106 operates on the contract side to extrude the internal working fluid toward the attenuation force control circuit 108.

[0059] Similarly to the previous case where the vehicle body B is deflected to the left hand, the computer G outputs the control signal X on the basis of the minus vehicle body speed signal U2 to proportionally control the relief pressure of the proportional electromagnetic relief valve V and appropriately control the generated attenuation force of the attenuation force control circuit 108 to effectively suppress the rolling of the vehicle body B to the right hand.

[0060] (3) Impossible control due to the occurrence of power-off and abnormal situation:

[0061] Even in this case, the cylinder 106 repeats the extension and contract operations as the vehicle body B deflects to the left and right hands, and the internal working fluid is extruded toward the attenuation force control circuit 108.

[0062] However, when the power is off, or when a stand-by signal disappears, the switching signals P, Q from the computer G as well as the control signal X are shut off, and the unload valves 118, 119 for pressure side and extension side and the proportional electromagnetic relief valve V maintain their off position in FIG. 2.

[0063] Thereby, the working fluid being extruded from the cylinder 106 to the attenuation force control circuit 108 flows into the reservoir 107 through the fixed restrictor 126, and the pressure loss of the restrictor 126 functions as a normal damper while generating an appropriate attenuation force at a relief set pressure at an off position of the proportional electromagnetic relief valve V to damp rolling in a lateral direction of the vehicle body B, thus realizing a fail-safe effect.

[0064] FIG. 3 shows a further embodiment of the present invention.

[0065] In the constitution shown in FIG. 2 so far described, the flow passage for causing working fluid to flow from the head-side chamber 111 toward the rod-side chamber 112 when the cylinder 106 contracts is constituted by the flow passages 120, 120 and the check valve 117 provided at an off position of the unload valve 119 for extension side.

[0066] On the other hand, in the embodiment shown in FIG. 3, the check valves 116 and 117 provided at an off position of the unload valves 118 and 119 for pressure side and extension side, respectively, are eliminated, and said off position are made to serve as a block position.

[0067] Instead, a flow passage 130 for communicating the head-side chamber 111 with the rod-side chamber 112 is formed in the piston 110 of the cylinder 106, and a check valve 131 for merely allowing a flow of working fluid from the head-side chamber 111 toward the rod-side chamber 112 is housed in the flow passage 130.

[0068] Also with this constitution, the cylinder 106 closes, at the time of contraction, the suction valve 122 and opens the check valve 131 to flow the working fluid in the head-side chamber 111 from the flow passage 130 to the rod-side chamber 112, and extrudes the working fluid in the amount corresponding to the entry volume portion of the piston rod 113 from the rod-side chamber 112 to the attenuation force control circuit 108 through the filter 124.

[0069] Thus, also in the embodiment shown in FIG. 3, the cylinder 106 operates as a unidirectional damper similar to the previous embodiment.

[0070] Next, an embodiment of the proportional electromagnetic relief valve V will be described.

[0071] FIG. 4 shows one embodiment of the proportional electromagnetic relief valve V. In the proportional electromagnetic relief valve V, the contour portion is shaped by a valve casing 7 having three annular grooves 2, 3 and 4 axially arranged, and a through-bore 6 formed with an annular projection between the annular grooves 3 and 4. The proportional electromagnetic relief valve V is connected to the attenuation force control circuit 108 shown in FIG. 2 or 3, and is provided with an inlet port 32 in communication with the head-side chamber 112 of the cylinder 106 and a return port 34 in communication with the reservoir 107.

[0072] One opening of the bore 6 is closed by an adjusting screw body 9 provided for advance and (or) retreat through a feed screw 8, and held in an oil-tight state by seals 10 and 11 disposed on the adjusting screw body 9 through the annular groove 2.

[0073] The adjusting screw body 9 is internally formed with a large diameter hole 12 from the inward end to the halfway portion, and an adjusting screw rod 14 is inserted through the adjusting screw body 9 from the outside into the hole 12 in an oil-tight state through a seal 13.

[0074] The adjusting screw body 9 and the adjusting screw rod 14 are provided with independent stop nuts 15 and 16, respectively. These stop nuts 15 and 16 can freely lock between the valve casing 7 and the adjusting screw body 9 and between the adjusting screw body 9 and the adjusting screw rod 14 in a suitable relative positional relation.

[0075] A pressing body 17 is slidably fitted into the hole 12 of the adjusting screw body 9 to define a pressure receiving chamber 18 in a base end portion thereof, and to threadedly mount an annular stop member 19 in an outlet portion thereof so as to limit the sliding range of the pressing body 17 while cooperating with the extreme end of the adjusting screw rod 14.

[0076] On the other hand, a valve seat body 20 and an end lid 21 are sequentially inserted in an axial direction, from the other opening of the bore 6 with a seal 56 interposed therebetween, and the end lid 21 is screwed in and mounted while maintaining an oil-tight state by a seal 22 whereby the valve seat body 20 is held between an annular projection 5 provided in the bore 6 and the end lid 21 and fixedly arranged.

[0077] In the case of this embodiment, the valve seat body 20 is provided with limiting tubes 23 arranged on the extreme end side in an axial direction, and the base end portions of the limiting tubes 23 are pressed against the annular projection 5 of the bore 6 by the end lid 21 and fixed.

[0078] Thereby, a seal 24 interposed between the valve seat body 20 and the limiting tube 23 is pressed against the inner wall surface of the bore 6, and the extreme end of the limiting tube 23 is opposed to the adjusting screw body 9 so as to limit the maximum insert position of the adjusting screw body 9 while maintaining a portion between the valve seat body 20 and the inner wall surface of the bore 6 in an oil-tight state by the seal 24.

[0079] The valve seat body 20 is provided with an axial through-hole 25 positioned at a center portion and a through-oil path 26 parallel thereto, and a guide 28 of the valve body 27 is slidably inserted from the inward end of the through-hole 25 to thereby support the valve body 27.

[0080] A labyrinth groove 29 is provided in an outer peripheral surface of the guide portion 28 in the valve body 27 to seal the through-hole 25, and a relief pressure setting spring 30 is interposed between the valve body 27 and the pressing body 17. The valve body 27 is pressed against the valve seat body 20 by the relief pressure setting spring 30 to thereby close the inward end of the through-hole 25 opposite to the guide portion 28.

[0081] The through-hole 25 is communicated with an inlet port 32 for introducing a circuit pressure provided in the valve casing 7 from the annular groove 4 through an oil port 31 provided in the valve seat body 20, and is further communicated with a return port 34 through the annular groove 3 on the valve casing 7 side from an oil port 33 provided in the limiting tube 23 by press-opening the valve body 27 against the relief pressure setting spring 30.

[0082] Further, in parallel with the foregoing, the annular groove 4 communicated with the inlet port 32 is also communicated with an annular oil path 36 formed between the valve casing 7 and the end lid 21 through an oil path 35 provided in the valve casing 7, and is communicated with an annular groove 37 provided in the outer peripheral surface of the end lid 21 from the annular oil path 36 and a through-hole 39 provided in an axial direction in the center portion of the end lid 21 through an oil path 38 which extends in a diametral direction.

[0083] The through-holes 39 is communicated with a return port 34 through the through-oil path 26 of the valve seat body 20, the oil hole 33 of the limiting tube 23, and the annular groove 3 of the valve casing 7, and is also communicated with the pressure receiving chamber 18 located at the rear of the pressing body 17 from the annular groove 2 through an oil path 41 provided in the end lid 21 isolated from an oil path 38 by a seal 40 and a junction oil path 43 provided in the valve casing 7 from the annular groove 42.

[0084] On the other hand, a solenoid 45 is threadedly mounted on the outer end of the end lid 21 while maintaining an oil-tight state by a seal 44, and the end lid 21 and the solenoid 45 constitutes a proportional type solenoid. A switching valve 48 is housed in the through-hole 39 of the end lid 21 with an appropriate switching clearance 47 left between a movable core 46 of the proportional type solenoid 45 and the guide portion 28 of the valve body 27.

[0085] In the switching valve 48, when the solenoid 45 is off, the oil path 41 of the end lid 21 is offset at a retreat position communicated with the return port 34 through the oil hole 33 of the limiting tube 23 and the annular groove 3 of the valve casing 7 from the through-oil path 26 of the valve seat body 20 by means of a spring 49 provided between it and the end lid 21.

[0086] The switching valve 48 is pressed against the spring 49 by the movable core 46 as the solenoid 45 is excited, so that the oil path 41 so far communicated with the return port 34 is brought into communication with the oil path 38, and the pressure receiving chamber 18 at the rear of the pressing body 17 is switched to the communication with the inlet port 32.

[0087] At the same time, the switching clearance 47 is removed, and an input from the solenoid 45 is applied as a force in an opening direction to the valve body 27 while pressing the guide portion 28 of the valve body 27. An apparent spring force of the relief pressure setting spring 30 is lowered by the force in an opening direction so as to control the relief setting pressure of the valve body 27 to be high or low.

[0088] Next, the operation of the proportional electromagnetic relief valve V according to the embodiment shown in FIG. 3 constituted as described above will be explained.

[0089] In the operation of adjusting the relief setting pressure in the proportional electromagnetic relief valve V to the maximum pressure, first, the adjusting screw rod 14 is screwed in to press the pressing body 17 along the adjusting screw body 9, and the extreme end of the pressing body 17 is urged against the stop member 19 provided on the adjusting screw body 9.

[0090] Then, the adjusting screw body 9 is turned and moved forward and backward while being accompanied by the adjusting screw rod 14 and the pressing body 17 by means of the feed screw 8 to change the length of the relief pressure setting spring 30 interposed between the pressing body 17 and the valve body 27 whereby the spring force is set to the desired value.

[0091] On the other hand, the intermediate pressure of the relief setting pressure when the solenoid 45 is off is set to a suitable relief setting pressure which is lower than the previous maximum pressure and higher than the minimum pressure determined by the maximum input from the solenoid 45 by retreating the adjusting screw rod 14 from the aforementioned state, extending the length of the relief pressure setting spring 30, and lowering the spring force to the desired value.

[0092] On the other hand, in use from this state, when the solenoid 45 is turned on to flow a fine current, the solenoid 45 starts to operate, and the switching valve 48 is switched by the movable core 46. The input from the solenoid 45 is applied to the guide portion 28 of the valve body 27 through the switching valve 48, and the oil paths 38 and 41 are communicated to switch the pressure receiving chamber 18 from the communication with the return port 34 to the communication with the inlet port 32.

[0093] However, the input from the solenoid 45 applied to the guide portion 28 of the valve body 27 through the switching valve 48 is so small that the fine current becomes consumed merely for switching the switching valve 48 against the spring 49. Therefore, the force cannot be applied to the guide portion 28 of the valve body 27 merely by removing the switching clearance 47 and switching the switching valve 48.

[0094] Even so, since the circuit pressure from the inlet port 32 is guided into the pressure receiving chamber 18 through the switching valve 48 by switching the switching valve 48, the relief pressure setting spring 30 is forced to be contracted and the pressing body 17 is pressed leaving the adjusting screw rod 14, and the pressing body 17 is pressed against the stop member 19 provided on the adjusting screw body 9.

[0095] Thereby, the positional relation between the pressing body 17 and the valve seat body 20 is exactly the same as that when the relief setting pressure is set to the maximum pressure as previously mentioned, and the length of the relief pressure setting spring 30 becomes also the same accordingly, as a consequence of which the relief setting pressure at that time holds the maximum pressure.

[0096] Moreover, when a current value applied to the solenoid 45 is increased from the above-described state, the input from the solenoid 45 with respect to the guide portion 28 of the valve body 27 increases substantially proportionally thereto, and the relief setting pressure continuously lowers towards the minimum pressure.

[0097] Further, when during the operation, the solenoid 45 is turned off due to the trouble or for some other reasons, the input from the solenoid 45 is zero so that the switching valve 48 returns to its original state due to the restoring force of the spring 49, and the pressure receiving chamber 18 is switched to the communication with the return port 34.

[0098] Thereby, the circuit pressure from the inlet port 32 being applied to the pressure receiving chamber 18 is cutoff and is communicated with the low pressure side, and the pressing body 17 is pressed by the relief pressure setting spring 30 and retreats at a position in contact with the adjusting screw rod 14.

[0099] Also in this state, the positional relation between the pressing body 17 and the valve seat body 20 is exactly the same as that when the relief setting pressure is set to the intermediate pressure as previously mentioned, and the length of the relief pressure setting spring 30 also becomes the same, and therefore, the relief setting pressure at this time is an intermediate pressure which is lower than the maximum pressure and higher than the minimum pressure determined by the maximum input from the solenoid 45.

[0100] In this manner, it is possible to remove inconveniences that fail to satisfactorily exhibit the performance as apparatus, while in the normal operation, carrying out the appropriate control as the proportional electromagnetic relief valve V, and while when the solenoid 45 is turned off for some reasons, maintaining the relief setting pressure at a suitable intermediate pressure to secure the minimum control force required by an apparatus.

[0101] FIG. 5 shows a proportional electromagnetic relief valve V according to another embodiment of the present invention, basic constitution of which is the same as a proportional electromagnetic relief valve V according to another embodiment as shown in FIG. 4. Therefore, here, only those different from the former will be explained for avoiding duplication of explanation.

[0102] In the proportional electromagnetic relief valve V shown in FIG. 5, the base end of the relief pressure setting spring 30 is directly supported through a spring tray 30a by the adjusting screw rod 14 without interposing the pressing body 17 between the adjusting screw rod 14 and the relief pressure setting spring 30 to constitute the pressure receiving chamber 18 as the embodiment shown in the FIG. 4.

[0103] Instead, a projection 50 is formed on the extreme end of an end lid 21a and a base end of a valve seat body 20a is fitted, only the valve seat body 20a being slidable with respect to the bore 6 of the valve casing 7 between the adjusting screw body 9a and the end lid 21a, and a pressure receiving chamber 18a is formed between the solenoid 45 and the end lid 21a.

[0104] The pressure receiving chamber 18a is communicated with a return port 34 by an oil hole 33a of the adjusting screw body 9a and an annular groove 3 of the valve casing 7 by an oil path 26a provided in the valve seat body 20a through the interior of a switching valve 48a from an oil path 41a, and oil paths 38 and 41a are brought into communication as the switching valve 48a performs switching operation to switch the pressure receiving chamber 18a from communication with the return port 34 to the communication with the inlet port 32.

[0105] Even the proportional electromagnetic relief valve V shown in FIG. 5 constituted as described above, the adjusting operation of the relief setting pressure to the maximum pressure is accomplished by screwing the adjusting screw body 9a to press the valve seat body 20a along the bore 6 and the projection 50 of the end lid 21a, and pressing the base end of the valve seat body 20a against the end lid 21a of the solenoid 45.

[0106] Then, the adjusting screw rod 14 is turned to change the length of the relief setting spring 30, and the force of the relief pressure setting spring 30 is set to the desired value.

[0107] The intermediate pressure of the relief setting pressure when the proportional solenoid is turned off is set to a suitable relief setting pressure which is lower than the previous maximum pressure and higher than the minimum pressure determined by the maximum input from the solenoid by moving the adjusting screw body 9a while being accompanied by the adjusting screw rod 14 from the aforesaid state to extend the length of the relief pressure setting spring 30, and lowering the spring force to the desired value.

[0108] When in use, the solenoid 45 is turned on to flow a fine current, the solenoid 45 starts its operation to switch the switching valve 48a and the pressure receiving chamber 18a is switched form communication with the return port 34 to communication with the inlet port 32 while applying the input from the solenoid 45 to the guide portion 28 of the valve body 27 through the switching valve 48a.

[0109] Thereby, the circuit pressure from the inlet port 32 is guided into the pressure receiving chamber 18a through the switching valve 48a. Therefore, the valve seat body 20a is pressed while contracting the relief pressure setting spring 30, and the valve seat body 20a is pressed against the extreme end of the adjusting screw body 9a.

[0110] In this state, the positional relation between the adjusting screw body 9a and the valve seat body 20a is exactly the same as that when the relief setting pressure is set to the maximum pressure as previously mentioned, and the length of the relief pressure sitting spring 30 also becomes the same. Thus, the relief setting pressure is the maximum pressure.

[0111] Moreover, when a current value applied to the solenoid is increased from that state, the input from the solenoid 45 with respect to the guide portion 28 of the valve body 27 increases substantially proportional thereto, similar to the case of the embodiment shown in FIG. 1, and the relief setting pressure continuously lowers toward the minimum pressure.

[0112] On the other hand, when the solenoid 45 is turned off due to the trouble or for some other reasons during the operation, the switching valve 48a is switched to its original state and the pressure receiving chamber 18a is communicated with the return port 34.

[0113] Accordingly, since the circuit pressure from the inlet port 32 being applied to the pressure receiving chamber 18a is cutoff and the pressure lowers, the valve seat body 20a is pressed by the relief pressure setting spring 30 while being accompanied by the valve body 37 and moved away from the adjusting screw body 9a, and moves to a final retreating position on which the end lid 21a of the solenoid 45 impinges.

[0114] In this case, however, if the proportional electromagnetic relieve valve V is in a relief operating state, the valve body 27 is moved away from the valve seat body 20a so that the through-hole 25 is opened. Therefore, the valve seat body 20a cannot be pushed back through the valve body 27 by the relief pressure setting spring 30.

[0115] So, in the using state in which such a state as described possibly occurs, as shown in FIG. 2, a return spring 55 is interposed between the adjusting screw body 9a and the valve seat body 20a so as to move the valve seat body 20a to a final retreating position on which the end lid 21a of the solenoid 45 impinges by means of the force of the return spring 55.

[0116] Also in this state the positional relation between the adjusting screw body 9a and the valve seat body 20a is exactly the same as that when the relief setting pressure is set to the intermediate pressure as previously mentioned, and the length of the relief pressure setting spring 30 also becomes the same. Thus, the relief setting pressure is an intermediate pressure which is lower than the maximum pressure and higher than the minimum pressure determined by the maximum input from the solenoid 35.

[0117] In this manner, it is possible to remove inconveniences that fail to satisfactorily exhibit the performance as apparatus, while in the normal operation, carrying out the appropriate control as the proportional electromagnetic relief valve V, and while when the solenoid 45 is turned off for some reasons, maintaining the relief setting pressure at a suitable intermediate pressure to secure the minimum control force required by an apparatus.

[0118] While in the embodiments shown in FIGS. 1 and 2 described above, the damping orifices 52 and 53 are disposed in the oil paths 26, 26a of the valve seat bodies 20, 20a and the oil path 51 joining space portions on both sides of the movable core 46 in the solenoid 45, these damping orifices 52, 53 are provided to stabilize the operation as the proportional electromagnetic relief valve V.

[0119] Further, while the check valve 54 for impeding a back flow of working medium from the annular oil path 36 toward the inlet port 32 is disposed in the midway of the oil path 35, the check valve 54 is provided to prevent that the pressure on the inlet port 32 side lowers down to the pressure on the return port 34 side during the operation of the proportional electromagnetic relief valve V, and accordingly, the pressure of the pressure receiving chambers 18, 18a lowers and the relief setting pressure is the intermediate pressure.

[0120] Accordingly, it is of course that these damping orifices 52, 53 and the check valve 54 including the return spring 55 in FIG. 2 described previously are not always provided in the case where such a provision as described is not necessary in terms of the use of the proportional electromagnetic relief valve V.

[0121] The present invention has the following effects:

(1) According to the damping damper and the damping method making use of the damper relating to the present invention, the attenuation force control circuit has a fixed restrictor, and a proportional electromagnetic relief valve provided in parallel with the fixed restrictor to continuously control the relief setting pressure to the maximum pressure as the input from the proportional solenoid increases. Therefore, it is not necessary to use damper displacement detection means such as a stroke sensing cylinder, and a damper speed signal is not necessary for the control of an attenuation force. Accordingly, the number of parts is small, and the entire control system is small in size, thus reducing the cost.

(2) A power damper for a damping damper generates an appropriate attenuation force when the power is off to function as a normal damper. Therefore, it is not necessary to specially provide a separate exclusive-use attenuation force control circuit, and accordingly, miniaturization is realized and the cost can be reduced. That is, the proportional electromagnetic relief valve is designed so that, when power is off, the characteristics when power is off can be set freely in a range of characteristics. Therefore, a separate attenuation force control circuit for use when power is off and a special control are not necessary so that the control system is simplified, the control system is miniaturized, and the cost is reduced.

Claims

1. A damper for damping rolling of a railroad vehicle, comprising: a cylinder interposable between a bogie and a vehicle body, a flow passage merely allowing a flow of working fluid from a head-side chamber to a rod-side chamber of the cylinder, a reservoir leading to the head-side chamber of the cylinder through a suction valve, a flow passage for communicating the head-side chamber with the reservoir, an unload valve for pressure side disposed in the flow passage, and an attenuation force control circuit interposed between the rod-side chamber and the reservoir, said attenuation force control circuit having a fixed restrictor, and a proportional electromagnetic relief valve provided in parallel with the fixed restrictor to continuously control a relief set pressure from the maximum pressure to the minimum pressure as an input from a proportional solenoid increases, said proportional electromagnetic relief valve comprising a valve casing, an input port and a return port provided in the valve casing, a valve seat body provided with a valve body for intermittently communicating the input port with the return port, a spring for setting a relief pressure for biasing the valve body in a closing direction, an adjusting screw body having a pressing body for supporting a base end of the spring slidably disposed, a stop member provided on the adjusting screw body to control a stroke of the pressing body, an adjusting threaded rod threadedly inserted into the adjusting screw body to support the base end of the pressing body, a pressure receiving chamber formed between the pressing body and the adjusting screw body, a solenoid for applying a force in an opening direction to the valve body, and a switching valve positioned between the valve body and a movable core in the solenoid to switch the mode from communication with the return port of the pressure receiving chamber to communication with the input port thereof while pressing the valve body through the excitation of the solenoid.

2. A damper for damping rolling of a railroad vehicle, comprising: a cylinder interposable between a bogie and a vehicle body, a flow passage merely allowing a flow of working fluid from a head-side chamber to a rod-side chamber of the cylinder, a reservoir leading to the head-side chamber of the cylinder through a suction valve, a flow passage for communicating the head-side chamber with the reservoir, an unload valve for pressure side disposed in the flow passage, and an attenuation force control circuit interposed between the rod-side chamber and the reservoir, said attenuation force control circuit having a fixed restrictor, and a proportional electromagnetic relief valve provided in parallel with the fixed restrictor to continuously control a relief set pressure from the maximum pressure to the minimum pressure as an input from a proportional solenoid increases, said proportional electromagnetic relief valve comprising a valve casing, an input port and a return port provided in the valve casing, a slidable valve seat body provided with a valve body for intermittently communicating the input port with the return port, a spring for setting a relief pressure for biasing the valve body in a closing direction, an adjusting screw body provided with an adjusting threaded rod for supporting a base end of the spring, a solenoid for applying a force in an opening direction to the valve body, a pressure receiving chamber formed between the valve seat body and the solenoid, and a switching valve positioned between the valve body and a movable core in the solenoid to switch the mode from communication with the return port of the pressure receiving chamber to communication with the input port thereof while pressing the valve body through the excitation of the solenoid.

3. The damper for damping rolling of a railroad vehicle according to claim 1 or 2, wherein the flow passage merely allowing a flow of working fluid from the head-side chamber to the rod-side chamber of the cylinder is constituted by an unload flow passage for extension side and a check valve provided at an off position of the unload valve for extension side provided in the unload flow passage.

4. The damper for damping rolling of a railroad vehicle according to claim 1 or 2, wherein the flow passage merely allowing a flow of working fluid from the head-side chamber to the rod-side chamber of the cylinder can be constituted by a flow passage provided in the piston and a check valve provided in said unload flow passage.

5. A method for damping rolling of a railroad vehicle using a damper, the method comprising: using a damping damper comprising a cylinder interposed between a bogie and a vehicle body, a flow passage merely allowing a flow of working fluid from a head-side chamber to a rod-side chamber of the cylinder, a reservoir leading to the head-side chamber of the cylinder through a suction valve, a flow passage for communicating the head-side chamber with the reservoir, an unload valve for pressure side disposed in the flow passage, an unload valve for extension side having the rod-side chamber disposed in the flow passage communicated with the head-side chamber, and an attenuation force control circuit interposed between the rod-side chamber and the reservoir, said attenuation force control circuit having a fixed restrictor, and a proportional electromagnetic relief valve provided in parallel with the fixed restrictor to continuously control a relief set pressure from the maximum pressure to the minimum pressure as an input from a proportional solenoid increases, said proportional electromagnetic relief valve comprising a valve casing, an input port and a return port provided in the valve casing, a valve seat body provided with a valve body for intermittently communicating the input port with the return port, a spring for setting a relief pressure for biasing the valve body in a closing direction, an adjusting screw body having a pressing body for supporting a base end of the spring slidably disposed, a stop member provided on the adjusting screw body to control a stroke of the pressing body, an adjusting threaded rod threadedly inserted into the adjusting screw body to support the base end of the pressing body, a pressure receiving chamber formed between the pressing body and the adjusting screw body, a solenoid for applying a force in an opening direction to the valve body, and a switching valve positioned between the valve body and a movable core in the solenoid to switch the mode from communication with the return port of the pressure receiving chamber to communication with the input port thereof while pressing the valve body through the excitation of the solenoid; operating by a computer an attenuation force value closest to the optimum value generated in the attenuation force control circuit on the basis of only a signal on the vehicle body side such as a vehicle body speed signal from detection means provided on the vehicle body; proportionally controlling the proportional electromagnetic relief valve on the basis of the result of operation; and judging by a computer the deflecting direction of the vehicle body by the vehicle body speed from the detection means to selectively switch and control the unload valve for pressure side and the unload valve for extension side.

6. A method for damping rolling of a railroad vehicle using a damper, the method comprising: using a damping damper comprising a cylinder interposed between a bogie and a vehicle body, a flow passage merely allowing a flow of working fluid from a head-side chamber to a rod-side chamber of the cylinder, a reservoir leading to the head- side chamber of the cylinder through a suction valve, a flow passage for communicating the head-side chamber with the reservoir, an unload valve for pressure side disposed in the flow passage, an unload valve for extension side having the rod-side chamber disposed in the flow passage communicated with the head-side chamber, and an attenuation force control circuit interposed between the rod-side chamber and the reservoir, said attenuation force control circuit having a fixed restrictor, and a proportional electromagnetic relief valve provided in parallel with the fixed restrictor to continuously control a relief set pressure from the maximum pressure to the minimum pressure as an input from a proportional solenoid increases, said proportional electromagnetic relief valve comprising a valve casing, an input port and a return port provided in the valve casing, a slidable valve seat body provided with a valve body for intermittently communicating the input port with the return port, a spring for setting a relief pressure for biasing the valve body in a closing direction, an adjusting screw body provided with an adjusting threaded rod for supporting a base end of the spring, a solenoid for applying a force in an opening direction to the valve body, and a switching valve positioned between the valve body and a movable core in the solenoid to switch the mode from communication with the return port of the pressure receiving chamber to communication with the input port thereof while pressing the valve body through the excitation of the solenoid; operating by a computer an attenuation force value closest to the optimum value generated in the attenuation force control circuit on the basis of only a signal on the vehicle body side such as a vehicle body speed signal from detection means provided on the vehicle body; proportionally controlling the proportional electromagnetic relief valve on the basis of the result of operation; and judging by a computer the deflecting direction of the vehicle body by the vehicle body speed from the detection means to selectively switch and control the unload valve for pressure side and the unload valve for extension side.

Drawing