Oil leak detection device

Abstract

To provide an oil leak detection device that can detect oil leaks even while the cylinder device is in use, without increasing costs. [Solution] The oil leak detection device 1 is a cylinder device 10 having a cylinder 11, a piston 12 inserted into the cylinder 11 so as to be movable in the axial direction and dividing the inside of the cylinder 11 into a rod side chamber 14 and a piston side chamber 15, and a rod 13 inserted into the cylinder 11 so as to be movable in the axial direction and connected to the piston 12, wherein the rod side chamber 14 and the piston side chamber 15 are pressurized during either extension or contraction, and only the rod side chamber 14 is pressurized during the other extension or contraction, and the oil leak detection device 1 is a cylinder device 10 having a cylinder 11, a piston 12 inserted so as to be movable in the axial direction and dividing the inside of the cylinder 11 into a rod side chamber 14 and a piston side chamber 15, and a rod 13 inserted into the cylinder 11 so as to be movable in the axial direction and connected to the piston 12, and the rod side chamber 14 and the piston side chamber 15 are pressurized during either extension or contraction, and only the rod side chamber 14 is pressurized during the other extension or contraction, and the device 1 is a cylinder device 10 having a thrust detection unit 2 that detects the thrust output by the cylinder device 10, and an oil leak detection unit 3 that detects the presence or absence of oil leakage based on the difference between the thrust command Fref to the cylinder device 10 and the thrust Freal detected by the thrust detection unit 2.

Description

Technical Field

[0001] The present invention relates to an improvement of an oil leakage detection device.

Background Art

[0002] Conventionally, as an oil leakage detection device for detecting oil leakage of a cylinder device, for example, there is an inspection cylinder that detects the pressure in the cylinder device. The inspection cylinder includes a cylinder, a piston that is movably inserted into the cylinder and partitions a room in the cylinder, and a rod-shaped gauge that is connected to the piston and protrudes outside the cylinder. When the inspection cylinder is attached to the cylinder device, the room is communicated with the inside of the cylinder device, and the amount of protrusion of the gauge outside the cylinder changes according to the pressure in the cylinder device propagated into the room. Therefore, when inspecting the cylinder device, an operator connects the inspection cylinder to the cylinder device and reads the memory of the gauge, and when the pressure in the cylinder device is not appropriate, it can be grasped that the amount of oil in the pressure cylinder device is insufficient and oil leakage has occurred (see Patent Document 1).

[0003] In such an oil leakage detection device, since it is necessary to attach an inspection cylinder to the cylinder device for detecting oil leakage, oil leakage cannot be detected in real time during the use of the cylinder device.

[0004] As an oil leakage detection device capable of detecting oil leakage in real time, for example, there is one provided on an annular rod guide that is attached to an end of a cylinder in a cylinder device and through which a piston rod is inserted on the inner circumference. Specifically, the oil leakage detection device includes a pair of flat plates installed facing each other in a recess provided between a main seal and a sub-seal that are in sliding contact with the outer circumference of the piston rod on the inner circumference of the rod guide, and a detection unit that detects the capacitance between the flat plates. In the oil leakage detection device configured in this way, when oil leakage occurs and oil that functions as a dielectric enters between the flat plates, the capacitance between the flat plates changes. Therefore, by monitoring the change in capacitance with the detection unit, the presence or absence of oil between the flat plates can be detected (for example, see Patent Document 2). [Patent Document 1] Japanese Patent Publication No. 2005-120777 [Patent Document 2] Japanese Patent Publication No. 2018-112464 [Overview of the project] [Problems that the invention aims to solve]

[0005] As mentioned above, the oil leak detection device disclosed in Patent Document 1 cannot detect oil leaks while the cylinder device is in use. Furthermore, while the oil leak detection device disclosed in Patent Document 2 can detect oil leaks even while the cylinder device is in use, it has the problem of increasing the cost of the cylinder device because it needs to be installed on the cylinder device solely for the purpose of detecting oil leaks.

[0006] Therefore, the objective of the present invention is to provide an oil leak detection device that can detect oil leaks even while a cylinder device is in use, without increasing costs. [Means for solving the problem]

[0007] To solve the aforementioned problems, the present invention provides an oil leak detection device for a cylinder device having a cylinder, a piston inserted into the cylinder so as to be movable in the axial direction and dividing the inside of the cylinder into a rod side chamber and a piston side chamber, and a rod inserted into the cylinder so as to be movable in the axial direction and connected to the piston, wherein the rod side chamber and the piston side chamber are pressurized during either extension or contraction, and only the rod side chamber is pressurized during the other extension or contraction, and the device provides an oil leak detection device that includes a thrust detection unit that detects the thrust output by the cylinder device, and an oil leak detection unit that detects the presence or absence of oil leakage based on the difference between the thrust command to the cylinder device and the thrust detected by the thrust detection unit.

[0008] In this configured oil leak detection device, the information used for detecting oil leaks is only the thrust command and the thrust of the cylinder device, which are the information used to control the cylinder device. Therefore, no special device is required to detect only oil leaks from the cylinder device, and oil leaks can be detected accurately in real time using the information obtained during the operation of the cylinder device.

[0009] Furthermore, if the cylinder device is an actuator in which the rod side chamber and piston side chamber are pressurized during extension and only the rod side chamber is pressurized during contraction, the oil leak detection unit may determine that an oil leak has occurred if the number of times the difference between the thrust command to extend the cylinder device and the thrust detected by the thrust detection unit exceeds a predetermined threshold is greater than or equal to a predetermined number of times, and the operation of the cylinder device during contraction is normal.

[0010] With this configured oil leak detection device, the difference between the thrust command and the thrust when the cylinder device acting as an actuator is in extension operation, which makes it easier to detect a shortage of hydraulic fluid, is used to detect oil leaks with high accuracy.

[0011] Furthermore, if the cylinder device is a semi-active damper in which the rod side chamber and piston side chamber are pressurized during contraction and only the rod side chamber is pressurized during extension, the oil leak detection unit may determine that an oil leak has occurred if the number of times the difference between the thrust command to contract the cylinder device and the thrust detected by the thrust detection unit exceeds a predetermined threshold is greater than or equal to a predetermined number of times, and the extension side operation of the cylinder device is normal.

[0012] With this configured oil leak detection device, the difference between the thrust command and the thrust when the cylinder device is contracting, which makes it easier to detect a shortage of hydraulic fluid, is used to detect oil leaks, thus enabling high-precision detection of oil leaks. [Effects of the Invention]

[0013] According to the oil leak detection device of the present invention, oil leaks can be detected even while the cylinder device is in use, without increasing costs. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows the configuration of an oil leak detection device in one embodiment. [Figure 2] This is a cross-sectional view of a railway vehicle equipped with an oil leak detection device and a cylinder device according to one embodiment. [Figure 3] This is a hydraulic circuit diagram of a cylinder device. [Figure 4] This figure shows the configuration of the drive control unit in a controller incorporating an oil leak detection device according to one embodiment. [Figure 5] This figure shows the configuration of the thrust detection unit of an oil leak detection device in one embodiment. [Figure 6] This figure shows an example of a flowchart illustrating the processing procedure of an oil leak detection device according to one embodiment. [Modes for carrying out the invention]

[0015] The present invention will be described below based on the embodiments shown in the figures. In one embodiment, the oil leak detection device 1, as shown in Figure 1, is configured to include a thrust detection unit 2 that detects the thrust Freal output by the cylinder device 10, and an oil leak detection unit 3 that detects oil leakage from the cylinder device 10 based on the thrust command Fref to the cylinder device 10 and the thrust Freal. More specifically, the oil leak detection device 1 is incorporated into a controller C that controls the cylinder device 10.

[0016] The following describes the various parts of the oil leak detection device 1, the cylinder device 10 in which the oil leak detection device 1 is used, and the controller C that encloses the oil leak detection device 1.

[0017] First, as shown in FIGS. 2 and 3, the cylinder device 10 is interposed between the car body B and the bogie T in the railway vehicle V and generates a thrust force to suppress the lateral vibration of the car body B. The railway vehicle V to which the cylinder device 10 is applied includes, as shown in FIG. 2, a bogie T that holds wheels W running on a track, and a car body B that is elastically supported with respect to the bogie T via springs S, respectively. Since the car body B is elastically supported via the springs S, relative movement in the up, down, left, and right directions in FIG. 2 with respect to the bogie T is allowed.

[0018] As shown in FIG. 3, the cylinder device 10 includes a cylinder 11, a piston 12 slidably inserted into the cylinder 11, a rod 13 inserted into the cylinder 11 and connected to the piston 12, a rod-side chamber 14 and a piston-side chamber 15 partitioned by the piston 12 in the cylinder 11, a tank 16, a first on-off valve 18 provided in the middle of a first passage 17 that communicates the rod-side chamber 14 and the piston-side chamber 15, a second on-off valve 20 provided in the middle of a second passage 19 that communicates the piston-side chamber 15 and the tank 16, a pump 21 that supplies hydraulic oil to the rod-side chamber 14 in the cylinder 11, a motor 22 that drives the pump 21, a discharge passage 23 that communicates the rod-side chamber 14 and the tank 16, and a pressure control valve 24 provided in the discharge passage 23 to adjust the pressure in the cylinder 11, and is configured as a single-rod type cylinder device. Further, the rod-side chamber 14 and the piston-side chamber 15 are filled with hydraulic oil, and the tank 16 is filled with gas in addition to the hydraulic oil.

[0019] The cylinder 11 is cylindrical, the right end in FIG. 3 is closed by a lid 25, and an annular rod guide 26 is attached to the left end in FIG. 3. Further, a rod 13 that is movably inserted into the cylinder 11 is slidably inserted into the rod guide 26. One end of this rod 13 protrudes outside the cylinder 11 through the rod guide 26, and the other end of the rod 13 inside the cylinder 11 is connected to a piston 12 that is slidably inserted into the cylinder 11.

[0020] A bracket (not shown) is provided between the left end of the rod 13 in FIG. 3 and the lid 25 that closes the right end of the cylinder 11, and the cylinder device 10 can be interposed between the vehicle body B and the bogie T in the railway vehicle V through the bracket outside the figure.

[0021] The rod side chamber 14 and the piston side chamber 15 are communicated with each other by the first passage 17, and a first on-off valve 18 is provided in the middle of the first passage 17. In this embodiment, the first on-off valve 18 is an electromagnetic on-off valve. When energized, the first passage 17 is opened to communicate the rod side chamber 14 and the piston side chamber 15, and when de-energized, the communication between the rod side chamber 14 and the piston side chamber 15 is blocked.

[0022] The piston side chamber 15 and the tank 16 are communicated with each other by the second passage 19, and a second on-off valve 20 is provided in the middle of the second passage 19. In this embodiment, the second on-off valve 20 is an electromagnetic on-off valve. When energized, the second passage 19 is opened to communicate the piston side chamber 15 and the tank 16, and when de-energized, the communication between the piston side chamber 15 and the tank 16 is blocked.

[0023] The pump 21 is driven by the motor 22. The pump 21 is a pump that discharges hydraulic oil only in one direction. Its discharge port is communicated with the rod side chamber 14 through the supply passage 27, and its suction port leads to the tank 16. When driven by the motor 22, it sucks hydraulic oil from the tank 16 and supplies hydraulic oil to the rod side chamber 14. A check valve 28 for preventing the reverse flow of hydraulic oil from the rod side chamber 14 to the pump 21 is provided in the middle of the supply passage 27.

[0024] In addition, in this embodiment, the rod side chamber 14 and the tank 16 are connected through the discharge passage 23, and a pressure control valve 24 with a variable opening pressure is provided in the middle of the discharge passage 23.

[0025] The pressure control valve 24 is a variable relief valve capable of adjusting the opening pressure according to the amount of current supplied. When the pressure in the rod-side chamber 14 within the cylinder 11, which is upstream of the discharge passage 23, exceeds the relief pressure (opening pressure), the valve opens the discharge passage 23, connecting the rod-side chamber 14 to the tank 16. The pressure control valve 24 minimizes the opening pressure when the amount of current supplied is maximized, and conversely, maximizes the opening pressure when no current is supplied at all. In this way, the pressure control valve 24 decreases the opening pressure as the amount of current supplied increases. Note that the pressure control valve 24 may be a valve other than a variable relief valve, as long as it is possible to adjust the pressure on the upstream side.

[0026] Furthermore, regardless of the open / closed state of the first on-off valve 18 and the second on-off valve 20, if there is an excessive input in the expansion / contraction direction to the cylinder device 10 and the pressure in the rod side chamber 14 exceeds the valve opening pressure, the pressure control valve 24 will open and connect the rod side chamber 14 and the tank 16 through the discharge passage 23. Thus, the pressure control valve 24 plays a role in protecting the entire system of the cylinder device 10 by preventing the pressure in the rod side chamber 14 from becoming excessive.

[0027] Furthermore, the cylinder device 10 includes a flow straightening passage 29 connecting the piston side chamber 15 and the rod side chamber 14, and a suction passage 30 connecting the tank 16 and the piston side chamber 15. The flow straightening passage 29 is equipped with a check valve 29a in the middle and is set as a one-way passage that only allows the flow of liquid from the piston side chamber 15 to the rod side chamber 14. Furthermore, the suction passage 30 is equipped with a check valve 30a in the middle and is set as a one-way passage that only allows the flow of liquid from the tank 16 to the piston side chamber 15.

[0028] In the cylinder device 10 configured in this way, when the first passage 17 is opened by the first on-off valve 18 and the second on-off valve 20 is closed, the pump 21 is driven, and the hydraulic fluid supplied from the pump 21 is supplied to both the rod side chamber 14 and the piston side chamber 15, pressurizing the rod side chamber 14 and the piston side chamber 15, causing an extension operation that pushes the piston 12 and rod 13 out of the cylinder 11 and generates thrust in the extension direction.

[0029] On the other hand, when the cylinder device 10 opens the second passage 19 with the second on-off valve 20 and drives the pump 21 with the first on-off valve 18 closed, the hydraulic fluid supplied from the pump 21 is supplied only to the rod side chamber 14, pressurizing only the rod side chamber 14, which causes an extension operation that pushes the piston 12 and rod 13 out of the cylinder 11, generating thrust in the contraction direction.

[0030] Furthermore, since the cylinder device 10 of this embodiment is equipped with a rectifying passage 29 and a suction passage 30, it functions as a uniflow type damper even when both the first on-off valve 18 and the second on-off valve 20 are closed. When it is forcibly extended or retracted by an external force, hydraulic fluid is discharged from inside the cylinder 11 to the tank 16 through the discharge passage 23 and the pressure control valve 24. The pressure control valve 24 resists the flow of hydraulic fluid, generating a damping force that hinders the extension and retraction operation. Therefore, in the event of a failure that prevents power from being supplied to the cylinder device 10, the first on-off valve 18 and the second on-off valve 20 close, and the pressure control valve 24 opens to its maximum pressure, causing the cylinder device 10 to automatically function as a passive damper.

[0031] Furthermore, if the motor 22 is stopped and the pump 21 is not driven, the cylinder device 10 can generate damping force only during extension or contraction by opening only one of the first on-off valve 18 or the second on-off valve 20. In this way, the cylinder device 10 can exert damping force only in the desired direction, and thus function as a semi-active damper.

[0032] Next, the controller C, in order to control the cylinder device 10, is configured as shown in Figure 1, to include an acceleration sensor 4 that detects the horizontal lateral acceleration α of the vehicle body B, a thrust command generation unit 5 that determines a thrust command Fref that instructs the cylinder device 10 to generate a target thrust based on the acceleration α detected by the acceleration sensor 4, a thrust detection unit 2 that detects the thrust output by the cylinder device 10, an oil leak detection unit 3 that detects oil leakage from the cylinder device 10 based on the thrust command Fref and thrust Freal to the cylinder device 10, and a drive control unit 6 that supplies current to the motor 22, the first on-off valve 18, the second on-off valve 20, and the pressure control valve 24 according to the thrust command Fref generated by the thrust command generation unit 5.

[0033] The acceleration sensor 4 is installed on the vehicle body B and detects the horizontal lateral acceleration α of the vehicle body B at a predetermined sampling period. The thrust command generation unit 5 determines the thrust command Fref to be generated by the cylinder device 10 based on the acceleration α detected by the acceleration sensor 4.

[0034] In this embodiment, the thrust command generation unit 5 is an H∞ controller. It extracts the resonant frequency band component of the vehicle body B of the railway vehicle V extracted from the acceleration α, and weights the extracted resonant frequency band component of the acceleration α by frequency to obtain a thrust command Fref that suppresses vibration of the vehicle body B. The sign of the value of the thrust command Fref indicates the direction of the thrust that the cylinder device 10 should output, and the numerical value of the thrust command Fref indicates the magnitude of the thrust that the cylinder device 10 should output. In this embodiment, the thrust command generation unit 5 obtains the thrust command Fref from only the lateral acceleration α of the vehicle body B. However, based on the sway acceleration and yaw acceleration of the vehicle body B, a control force to suppress vibration in the sway direction and a control force to suppress vibration in the yaw direction of the vehicle body B may be obtained separately, and these may be added together to obtain the thrust command Fref. Alternatively, the thrust command generation unit 5 may be a controller that performs skyhook control, which obtains the velocity of the vehicle body B from the acceleration α and multiplies it by the skyhook gain to obtain the thrust command Fref. Furthermore, the thrust command generation unit 5 may have multiple control laws for determining the thrust command Fref and may select and use the optimal control law according to the running conditions of the railway vehicle to determine the thrust command Fref.

[0035] As shown in Figure 4, the drive control unit 6 includes a pressure control valve control unit 61 that controls the pressure control valve 24 based on the thrust command Fref, an on-off valve control unit 62 that generates commands to instruct the supply of power to the first on-off valve 18 and the second on-off valve 20 based on the thrust command Fref, and a motor control unit 63 that monitors the rotational speed of the motor 22 and generates a control command to rotate the motor 22 at a predetermined rotational speed Rref.

[0036] The pressure control valve control unit 61, although not shown in the figure, includes a current sensor that detects the current flowing through the pressure control valve 24, and a solenoid driver that determines the amount of current to be supplied to the pressure control valve 24 from the thrust command Fref, determines a current command from the difference between the amount of current and the amount of current detected by the current sensor, and supplies current to the pressure control valve 24 as instructed by the generated current command.

[0037] The valve control unit 62, although not shown in the figures, includes a determination unit that determines whether or not to supply current to the first valve 18 and the second valve 20 from the thrust command Fref, and a solenoid driver that supplies current to the first valve 18 and the second valve 20 based on the determination result of the determination unit.

[0038] Furthermore, the motor control unit 63 includes a current sensor 63a that detects the current flowing through the motor 22, and a motor driver 63b that, when the thrust command Fref instructs the cylinder device 10 to actively generate thrust, monitors the rotational speed of the motor 22 and the current flowing through the motor 22, and in order to rotate the motor 22 at a predetermined rotational speed Rref, feeds back the actual rotational speed of the motor 22 and the current detected by the current sensor 63a to obtain a current command that instructs the current to be supplied to the motor 22, and supplies current to the motor 22 as instructed by the generated current command. The rotational speed of the motor 22 can be obtained from the rotational position information of the rotor obtained from a rotational position sensor provided by the motor 22 for energizing the windings of the motor 22, although this is not shown in the figures. If the motor 22 does not have a rotational position sensor, the motor control unit 63 may include a rotational speed sensor that detects the rotational speed of the motor 22.

[0039] In this way, the controller C generates thrust in the cylinder device 10 to suppress vibrations of the vehicle body B by having the thrust command generation unit 5 determine the thrust command Fref based on the acceleration α detected by the acceleration sensor 4, and then having the drive control unit 6 control the pressure control valve 24, the first on-off valve 18, the second on-off valve 20, and the motor 22 based on the thrust command Fref.

[0040] Next, the thrust detection unit 2 and the oil leak detection unit 3, which constitute the oil leak detection device 1, will be described. In this embodiment, as shown in Figure 5, the thrust detection unit 2 includes a torque detection unit 2a that determines the torque of the motor 22 from the current flowing through the motor 22, a low-pass filter 2b that removes the high-frequency components of the torque detected by the torque detection unit 2a, and a thrust calculation unit 2c that determines the thrust of the cylinder device 10 based on the torque processed by the low-pass filter 2b.

[0041] Since the motor 22 is driven at a predetermined rotational speed Rref when the cylinder device 10 exerts thrust, the torque exerted by the motor 22 can be obtained by monitoring the current flowing through the motor 22, the rotational speed, and the characteristics of the motor 22. Therefore, the torque detection unit 2a monitors the current flowing through the motor 22 detected by the current sensor 63a and the rotational speed of the motor 22 to determine the torque output by the motor 22. In the case of the cylinder device 10 of this embodiment, the pump 21 is driven to rotate at a constant speed by the motor 22 against the pressure in the rod side chamber 14, so the torque of the motor 22 is the resultant force of the torque against the pressure in the rod side chamber 14 and the frictional torque of the pump 21 and motor 22. In other words, since the motor 22 and pump 21 experience frictional resistance when rotating, the torque obtained from the rotational speed and current of the motor 22 as described above has the torque due to frictional resistance (frictional torque) superimposed on it.

[0042] When the first on-off valve 18 and the second on-off valve 20 are opened and the motor 22 is driven to rotate at a predetermined rotational speed Rref, the hydraulic fluid passes from the tank 16 through the cylinder 11 without resistance and returns to the tank 16, so the pump 21 rotates without resistance from the pressure inside the cylinder 11. The torque exerted by the motor 22 when rotating the pump 21 at a constant speed is approximately equal to the friction torque due to the resistance caused by dynamic friction accompanying the rotation of the pump 21, so the torque detected by the torque detection unit 2a under these conditions is the friction torque.

[0043] Therefore, the torque detection unit 2a determines the actual torque of the motor 22 by subtracting the friction torque, which has been determined in advance, from the torque obtained from the current flowing through the motor 22 and the rotational speed of the motor 22.

[0044] The low-pass filter 2b removes noise from the actual torque detected by the torque detection unit 2a and inputs the noise-removed actual torque to the thrust calculation unit 2c. Since the pump 21 is subjected to the pressure of the rod side chamber 14 and the motor 22 rotates the pump 21 against the pressure of the rod side chamber 14, the actual torque is proportional to the pressure of the rod side chamber 14. When the cylinder device 10 is extended, the pressure of the rod side chamber 14 and the pressure of the piston side chamber 15 are equal, and when the cylinder device 10 is retracted, the pressure of the piston side chamber 15 becomes the tank pressure, the piston 12 is subjected to the pressure of the rod side chamber 14, and the pressure-receiving area on which the piston 12 is subjected to the pressure of the rod side chamber 14 and the piston side chamber 15 is also known. Furthermore, the relationship between the actual torque and the pressure of the rod side chamber 14 can also be known in advance. From the above, the thrust calculation unit 2c can determine the thrust Freal during the extension and retraction of the cylinder device 10 from the actual torque.

[0045] The oil leak detection unit 3 detects the presence or absence of oil leakage based on the thrust command Fref and thrust Freal generated by the thrust command generation unit 5. Specifically, the oil leak detection unit 3 determines that oil leakage has occurred if the number of times the difference between the extension-side thrust command Fref, which instructs the cylinder device 10 to exert thrust in the direction of extension, and the thrust Freal obtained by the thrust detection unit 2 detecting the thrust output by the cylinder device 10 in response to the input of this extension-side thrust command Fref exceeds a predetermined threshold X is a predetermined number of times Z or more, and the contraction side operation of the cylinder device 10 is normal. In all other situations, the oil leak detection unit 3 determines that oil leakage has not occurred.

[0046] In this embodiment, in order to extend the cylinder device 10, the first on-off valve 18 is opened to connect the rod side chamber 14 and the piston side chamber 15, and the second on-off valve 20 is closed to disconnect the piston side chamber 15 from the tank 16, and then hydraulic fluid is supplied from the pump 21 to both the rod side chamber 14 and the piston side chamber 15. Thus, in order to extend the cylinder device 10, it is necessary to supply hydraulic fluid to both the rod side chamber 14 and the piston side chamber 15 and pressurize both the rod side chamber 14 and the piston side chamber 15. If oil leakage occurs during the extension operation of the cylinder device 10, the thrust Freal will not follow the thrust command Fref on the extension side and will tend to be extremely small compared to the thrust command Fref, and the discrepancy between the thrust command Fref and the thrust Freal tends to become large. On the other hand, in order to retract the cylinder device 10, the first on-off valve 18 is closed to cut off communication between the rod side chamber 14 and the piston side chamber 15, and the second on-off valve 20 is opened to connect the piston side chamber 15 and the tank 16, with the pump 21 supplying hydraulic fluid only to the rod side chamber 14. In this way, in order to retract the cylinder device 10, hydraulic fluid is supplied only to the rod side chamber 14 and pressurized only the rod side chamber 14. Therefore, since the amount of hydraulic fluid supplied into the cylinder 11 is less during retraction than during extension, even if oil leakage occurs, the discrepancy between the thrust command Fref and the thrust Freal on the retraction side tends to be smaller. Thus, in a cylinder device 10 in which the rod side chamber 14 and the piston side chamber 15 are pressurized during extension and only the rod side chamber 14 is pressurized during retraction, oil leakage can be detected early by monitoring the difference between the thrust command Fref and the thrust Freal during extension.

[0047] When the oil leak detection unit 3 determines that an oil leak has occurred in the cylinder device 10, it outputs a signal to the vehicle monitor of the railway vehicle V (not shown) notifying it that an oil leak has occurred in the cylinder device 10. Also, when the oil leak detection unit 3 detects an oil leak, the thrust command generation unit 5 generates a command to stop the power supply to the motor 22, the first on-off valve 18, the second on-off valve 20, and the pressure control valve 24 in order to make the cylinder device 10 function as a passive damper, and inputs it to the drive control unit 6. When the drive control unit 6 receives the command to stop the power supply, it stops the power supply to the motor 22, the first on-off valve 18, the second on-off valve 20, and the pressure control valve 24, making the cylinder device 10 function as a passive damper.

[0048] Excluding the sensors for the motor 22, including the acceleration sensor 4 and the current sensor 63a, and the circuit in the drive control unit 6 that supplies current to the motor 22, the first on-off valve 18, the second on-off valve 20, and the pressure control valve 24, the hardware resources, although not shown in the diagram, should consist of a computer system comprising, for example, an operating system and a CPU (Central Processing Unit) that executes other programs for controlling the motor 22, the first on-off valve 18, the second on-off valve 20, and the pressure control valve 24; a storage device such as a ROM (Read Only Memory) that stores the programs necessary for the control; a storage device such as a RAM (Random Access Memory) that provides a memory area to the CPU; an interface for exchanging signals between the CPU, the sensors for the acceleration sensor 4 and the motor 22, and the circuit in the drive control unit 6; a crystal oscillator; and bus lines connecting these. The CPU then executes the program, thereby realizing all circuits in the controller C except for the thrust detection unit 2, the oil leak detection unit 3, the thrust command generation unit 5, and the drive control unit 6.

[0049] Next, the procedure for detecting oil leaks in the controller C will be explained based on the flowchart shown in Figure 6. First, the controller C reads the acceleration α detected by the acceleration sensor 4 (step S1). Next, the controller C generates a thrust command Fref from the acceleration α (step S2). Furthermore, the controller C controls the cylinder device 10 to generate the thrust indicated by the obtained thrust command Fref (step S3).

[0050] Next, the controller C determines whether the thrust command Fref is a command to generate extension thrust in the cylinder device 10 (step S4). If the thrust command Fref is a command to generate extension thrust in the cylinder device 10, the controller C determines the thrust Freal output by the cylinder device 10 from the value of the current detected by the current sensor 63a (step S5). On the other hand, if the determination in step S4 is that the thrust command Fref is a command to generate contraction thrust in the cylinder device 10, the controller C determines that there is no oil leakage in the cylinder device 10 and terminates the process.

[0051] In step S5, the controller C determines whether the difference between the thrust command Fref and the thrust Freal is greater than or equal to a threshold X (step S6). If the difference is greater than or equal to the threshold X, there is a possibility that there is a shortage of hydraulic fluid in the cylinder device 10. The threshold X is set, for example, so that the difference between the thrust command Fref and the thrust Freal is approximately 70% of the upper limit of the thrust command Fref, but it should be set to a value that can be taken when there is a shortage of hydraulic fluid in the cylinder 11 of the cylinder device 10. If, as a result of the determination in step S6, the difference between the thrust command Fref and the thrust Freal is less than the threshold X, the controller C determines that there is no oil leakage in the cylinder device 10 and terminates the process.

[0052] Incidentally, while the railway vehicle V is in motion, the vehicle body B is constantly subjected to vibrations of multiple frequency bands that cause it to reciprocate from side to side. As a result, the vehicle body B exhibits complex vibrations, and these vibrations are also input to the cylinder device 10, causing the cylinder device 10 to repeatedly expand and contract in response to the disturbance input. When no disturbance is input to the cylinder device 10, if the cylinder device 10 can function normally, the thrust Freal output by the cylinder device 10 follows the thrust command Fref on the extension side, and the difference between the thrust command Fref and the thrust Freal becomes small. However, when a disturbance is input to the cylinder device 10, the difference between the thrust command Fref and the thrust Freal becomes large enough that it cannot be ignored, meaning that the difference may exceed the threshold X. Therefore, if it is determined that there is a hydraulic fluid shortage in the cylinder device 10 immediately when the difference between the thrust command Fref and the thrust Freal exceeds the threshold X, then it will also be determined that there is a hydraulic fluid shortage even when the cylinder device 10 is functioning normally but the difference exceeds the threshold X due to the input of a disturbance.

[0053] Therefore, in the oil leak detection device 1 of this embodiment, if the difference between the thrust command Fref and the thrust Freal is greater than or equal to the threshold X, in the subsequent step S7, the controller C determines whether the number of times the difference between the thrust command Fref and the thrust Freal has been greater than or equal to the threshold X within the past Y seconds is greater than or equal to the number of times Z.

[0054] Thus, if the number of times the difference between the thrust command Fref and the thrust Freal has exceeded the threshold X within the past Y seconds exceeds Z, it means that an event suggesting a hydraulic fluid shortage may have occurred many times recently, making it highly likely that a hydraulic fluid shortage is occurring in the cylinder device 10. Therefore, the oil leak detection device 1 of this embodiment can detect a hydraulic fluid shortage in the cylinder device 10 with a high probability by making the determination in step S6. The values ​​of Y seconds and the number of times Z can be set arbitrarily by considering the control cycle, the natural frequency of the vehicle body B, etc., but if they are too long, the detection of the oil leak will be delayed, so it is best to set them as short as possible to avoid false detections.

[0055] If, as a result of the judgment in step S7, the number of times the difference between the thrust command Fref and the thrust Freal has exceeded the threshold X within the past Y seconds is Z or more, there is a possibility that there is a shortage of hydraulic fluid in the cylinder device 10. Therefore, the controller C proceeds to step S8 to determine whether an abnormality is also observed during the contraction operation of the cylinder device 10. In other words, it determines whether the cylinder device 10 is operating normally during the contraction operation.

[0056] On the other hand, if the result of the judgment in step S7 is that the number of times the difference between the thrust command Fref and the thrust Freal has been greater than or equal to the threshold X within the past Y seconds is less than Z, the controller C makes a normal determination that there is no oil leakage in the cylinder device 10 (step S11) and terminates the current process.

[0057] In step S8, as described above, the controller C determines whether the cylinder device 10 is operating normally during the contraction operation. Specifically, for example, within the Y seconds following the determination in step S7, the controller C determines whether the number of times the difference between the thrust command Fref that causes the cylinder device 10 to contract and the thrust Freal output by the cylinder device 10 as a result of the drive control unit 6 controlling the cylinder device 10 with the thrust command Fref has been greater than or equal to a predetermined threshold X is Z or greater.

[0058] If, as a result of the judgment in step S8, the number of times the difference between the thrust command Fref and thrust Freal on the contraction side exceeds a predetermined threshold X within Y seconds is Z or more, then the thrust Freal during the contraction operation of the cylinder device 10 is not following the thrust command Fref. In this case, as determined in step S7, the thrust Freal is not following the thrust command Fref even during the extension operation, and as determined in step S8, the thrust Freal is not following the thrust command Fref even during the contraction operation. Therefore, although the processing up to steps S6 and S8 has detected that a discrepancy between the thrust command Fref and thrust Freal on the extension side of the cylinder device 10 has continued, it is considered that this condition occurred due to the influence of an external disturbance. For this reason, the controller C makes a normal determination (step S11) that there is no oil leakage in the cylinder device 10 and terminates the current process.

[0059] Conversely, if the result of the judgment in step S8 is that the number of times the difference between the thrust command Fref and the thrust Freal on the contraction side exceeds a predetermined threshold X during Y seconds is less than Z, then no abnormality is observed in the contraction operation of the cylinder device 10. As mentioned above, when oil leakage occurs in the cylinder device 10, the thrust Freal does not follow the thrust command Fref on the extension side and tends to become extremely small compared to the thrust command Fref. On the other hand, due to its structure, the amount of hydraulic fluid supplied into the cylinder 11 is less during contraction operation than during extension operation, so even if oil leakage occurs, the discrepancy between the thrust command Fref and the thrust Freal on the contraction side becomes smaller. In the processing from step S6 to step S8, the state of discrepancy between the thrust command Fref and the thrust Freal on the extension side of the cylinder device 10 continues to occur, and it can be seen that the cylinder device 10 is operating normally during contraction operation. In other words, if the judgment in step S8 determines that the operation of the cylinder device 10 during retraction is normal, then a phenomenon has occurred in which the operation of the cylinder device 10 is abnormal during extension but normal during retraction, and this phenomenon matches the aforementioned phenomenon that occurs when oil leakage occurs in the cylinder device 10. Therefore, if the judgment in step S8 determines that the operation of the cylinder device 10 during retraction is normal, the controller C determines that there is insufficient hydraulic fluid in the cylinder device 10 and that oil leakage has occurred (step S9).

[0060] If it is determined in step S9 that an oil leak has occurred, the controller C stops the power supply to the motor 22, the first on-off valve 18, the second on-off valve 20, and the pressure control valve 24, causing the cylinder device 10 to function as a passive damper, and terminates the process.

[0061] While the controller C is controlling the cylinder device 10, it continues the process described above to detect oil leakage until it determines that oil leakage has occurred and stops controlling the cylinder device 10 by passively damping it. Note that the flowchart described above is just an example and can be arbitrarily modified as long as it functions as an oil leakage detection device 1.

[0062] As described above, the oil leak detection device 1 of this embodiment is an oil leak detection device for detecting oil leaks of a cylinder device 10 having a cylinder 11, a piston 12 inserted into the cylinder 11 so as to be movable in the axial direction and dividing the inside of the cylinder 11 into a rod side chamber 14 and a piston side chamber 15, and a rod 13 inserted into the cylinder 11 so as to be movable in the axial direction and connected to the piston 12, wherein the rod side chamber 14 and the piston side chamber 15 are pressurized when the cylinder is extended and only the rod side chamber 14 is pressurized when the cylinder is retracted, and the device includes a thrust detection unit 2 that detects the thrust output by the cylinder device 10, and an oil leak detection unit 3 that detects the presence or absence of oil leaks based on the difference between the thrust command Fref to the cylinder device 10 and the thrust Freal detected by the thrust detection unit 2.

[0063] In the oil leak detection device 1 configured in this way, the information used to detect oil leaks is only the thrust command Fref and the thrust Freal of the cylinder device 10, which are the only information used to control the cylinder device 10. Therefore, no special device is required to detect only oil leaks from the cylinder device 10, and oil leaks can be detected accurately in real time using the information obtained while the cylinder device 10 is in use. Thus, according to the oil leak detection device 1 of this embodiment, oil leaks can be detected even while the cylinder device 10 is in use, without increasing costs.

[0064] Furthermore, in this embodiment, the cylinder device 10 is an actuator in which the rod side chamber 14 and the piston side chamber 15 are pressurized when it extends, and only the rod side chamber 14 is pressurized when it retracts. The oil leak detection unit 3 determines that an oil leak has occurred when the number of times the difference between the thrust command Fref for extending the cylinder device 10 and the thrust Freal detected by the thrust detection unit 2 exceeds a predetermined threshold X is greater than or equal to a predetermined number of times Z or more, and when the operation of the cylinder device 10 during retraction is normal.

[0065] With the oil leak detection device 1 configured in this way, the difference between the thrust command Fref and the thrust Freal when the cylinder device 10, which is operating as an actuator, is in extension operation, which makes it easy to detect a shortage of hydraulic fluid, is used for detecting oil leaks, thus enabling high-precision detection of oil leaks.

[0066] Furthermore, when the motor 22 is stopped and no hydraulic fluid is supplied from the pump 21 to the cylinder 11, the cylinder device 10 can function as a semi-active damper that generates damping force only during extension or contraction by controlling the first on-off valve 18, the second on-off valve 20, and the pressure control valve 24.

[0067] When the cylinder device 10 functions as a semi-active damper, in order to generate a damping force in the cylinder device 10 during contraction, the first on-off valve 18 is opened to connect the rod side chamber 14 and the piston side chamber 15, and the second on-off valve 20 is closed to disconnect the piston side chamber 15 from the tank 16. In this way, in order to generate a damping force in the cylinder device 10 during contraction, both the rod side chamber 14 and the piston side chamber 15 are pressurized by the entry of the rod 13 into the cylinder 11. Therefore, if there is an oil leak in the cylinder device 10, the thrust Freal will not follow the thrust command Fref on the contraction side and will tend to be extremely small compared to the thrust command Fref, and the discrepancy between the thrust command Fref and the thrust Freal tends to become large. On the other hand, in order to generate a damping force in the cylinder device 10 during extension, the first on-off valve 18 is closed to disconnect the rod side chamber 14 and the piston side chamber 15, and the second on-off valve 20 is opened to connect the piston side chamber 15 and the tank 16. In this way, in order to generate a damping force in the cylinder device 10 during extension, only the rod side chamber 14 is pressurized by the movement of the piston 12 within the cylinder 11. Therefore, the amount of hydraulic fluid pressurized when the cylinder device 10 generates a damping force during extension is less than when it generates a damping force during contraction. As a result, even if oil leakage occurs, the discrepancy between the thrust command Fref and the thrust Freal on the extension side tends to be smaller. Therefore, when the cylinder device 10 functions as a semi-active damper in which both the rod side chamber 14 and the piston side chamber 15 are pressurized during contraction and only the rod side chamber 14 is pressurized during extension, oil leakage can be detected early by monitoring the difference between the thrust command Fref and the thrust Freal during contraction. Furthermore, even in a semi-active damper that eliminates the pump 21, motor 22, supply passage 27, and check valve 28 from the configuration of the cylinder device 10 described above, oil leakage can be detected early by monitoring the difference between the thrust command Fref and the thrust Freal during contraction.

[0068] Therefore, even in a cylinder device 10 where the rod side chamber 14 and the piston side chamber 15 are pressurized during retraction and only the rod side chamber 14 is pressurized during extension, the oil leak detection device 1 can detect oil leaks by comprising a thrust detection unit 2 that detects the thrust output by the cylinder device 10 and an oil leak detection unit 3 that detects the presence or absence of oil leaks based on the difference between the thrust command Fref to the cylinder device 10 and the thrust Freal detected by the thrust detection unit 2. In this case, in the process from steps S4 to S7 in the flowchart shown in Figure 6, the thrust command Fref during extension should be read as the thrust command Fref during retraction, and in the process in step S8, the judgment of whether the operation of the cylinder device 10 during retraction is normal should be replaced with the judgment of whether the operation of the cylinder device 10 during extension is normal.

[0069] Furthermore, in the oil leak detection device 1 configured in this way, the information used for detecting oil leaks is only the thrust command Fref and the thrust Freal of the cylinder device 10, which are the only information used to control the cylinder device 10. Therefore, no special device is required to detect only oil leaks from the cylinder device 10, and oil leaks can be detected accurately in real time using the information obtained while the cylinder device 10 is in use. Thus, according to the oil leak detection device 1 of this embodiment, oil leaks can be detected even while the cylinder device 10 is in use, without increasing costs.

[0070] Furthermore, the cylinder device 10 is a semi-active damper in which the rod side chamber 14 and the piston side chamber 15 are pressurized when it is retracting, and only the rod side chamber 14 is pressurized when it is extending, and the oil leak detection unit 3 may be configured to determine that oil leakage has occurred when the number of times the difference between the thrust command Fref that retracts the cylinder device 10 and the thrust detected by the thrust detection unit 2 exceeds a predetermined threshold X exceeds a predetermined number of times Z or more, and when the extension side operation of the cylinder device 10 is normal.

[0071] With the oil leak detection device 1 configured in this way, the difference between the thrust command Fref and the thrust Freal when the cylinder device 10 is in a contraction operation that makes it easy to detect a shortage of hydraulic fluid is used to detect oil leaks, thus enabling high-precision detection of oil leaks.

[0072] Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims. [Explanation of symbols]

[0073] 1... Oil leak detection device, 2... Thrust detection unit, 3... Oil leak detection unit, 10... Cylinder device, 11... Cylinder, 12... Piston, 13... Rod, 14... Rod side chamber, 15... Piston side chamber

Claims

1. An oil leak detection device for detecting oil leaks in a cylinder device having a cylinder, a piston inserted axially movably into the cylinder and dividing the inside of the cylinder into a rod side chamber and a piston side chamber, and a rod inserted axially movably into the cylinder and connected to the piston, wherein the rod side chamber and the piston side chamber are pressurized during either extension or retraction, and only the rod side chamber is pressurized during the other extension or retraction, A thrust detection unit that detects the thrust output by the cylinder device, The system includes an oil leak detection unit that detects the presence or absence of oil leakage based on the difference between the thrust command to the cylinder device and the thrust detected by the thrust detection unit. An oil leak detection device characterized by the following features.

2. The cylinder device is An actuator in which the rod side chamber and the piston side chamber are pressurized during the extension operation, and only the rod side chamber is pressurized during the contraction operation, The aforementioned oil leak detection unit is If the number of times the difference between the thrust command for extending the cylinder device and the thrust detected by the thrust detection unit exceeds a predetermined threshold exceeds a predetermined threshold, and the operation of the cylinder device during contraction is normal, then it is determined that oil leakage has occurred. The oil leak detection device according to feature 1.

3. The cylinder device is A semi-active damper in which the rod side chamber and the piston side chamber are pressurized during the contraction operation, and only the rod side chamber is pressurized during the extension operation, The aforementioned oil leak detection unit is If the number of times the difference between the thrust command for retracting the cylinder device and the thrust detected by the thrust detection unit exceeds a predetermined threshold exceeds a predetermined threshold, and the extension side of the cylinder device operates normally, then it is determined that oil leakage has occurred. The oil leak detection device according to feature 1.

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