JP6802735B2 - Fluid leak detector - Google Patents

Description

The present invention relates to a fluid leak detection device used in a fluid pressure device.

A fluid pressure device having a shaft that slides or rotates in the axial direction usually includes a sealing member that contacts the outer peripheral surface of the shaft in order to prevent fluid from leaking to the outside along the outer peripheral surface of the shaft. There is. Such a sealing member may deteriorate in sealing performance due to deterioration with time or the like, and may cause fluid leakage.

Patent Document 1 discloses a fluid leakage detection device that detects whether or not a fluid leakage has occurred in the fluid pressure device. In this fluid leakage detection device, it is determined that a fluid leakage has occurred when the amount of fluid accumulated in the measuring unit provided below the end of the cylinder exceeds the reference value.

Japanese Unexamined Patent Publication No. 06-207608

However, in the fluid leakage detection device described in Patent Document 1, the fluid leakage is determined after the fluid leaks to the outside of the fluid pressure device. After the fluid leaks to the outside of the fluid pressure device in this way, it becomes difficult to avoid malfunction of the fluid pressure device, and there is a risk that the mechanical device in which the fluid pressure device is used will be forced to stop operating suddenly. is there.

The present invention has been made in view of the above problems, and an object of the present invention is to detect a deterioration of the sealing function in the sealing region before the fluid leaks to the outside in the fluid pressure device.

The first invention includes a first load detecting unit that detects a first load acting on a first sealing portion that seals a sealed space to which a fluid pressure is applied, and a first load detecting portion that is outside the first sealing portion with respect to the sealed space. The second load detection unit that detects the second load acting on the second seal unit that seals the sealed space at the position, and the first load and the second load detection unit that are detected by the first load detection unit. It is characterized by including a determination unit for determining fluid leakage of the first seal unit based on two loads.

In the first invention, the first load acting on the first seal portion arranged at the position where the pressure of the fluid in the sealed space directly acts, and the first load located outside the first seal portion with respect to the sealed space. Based on the second load acting on the two seal portions, it is determined whether or not a fluid leak has occurred in the first seal portion. In this way, by monitoring whether or not the first seal portion arranged at the position where the pressure of the fluid directly acts in the sealed space can exert the sealing function, before the fluid leaks to the outside of the fluid pressure device. In addition, it is possible to detect a decrease in the sealing function in the sealing region.

In the second invention, when the determination unit has a difference between the first load detected by the first load detection unit and the second load detected by the second load detection unit, the difference is less than a predetermined reference value. It is characterized in that it is determined that the fluid leaks from the first seal portion.

In the second invention, when the difference between the first load detected by the first load detecting unit and the second load detected by the second load detecting unit is less than a predetermined reference value, the first seal is used. It is determined that a fluid leak has occurred in the portion. When a fluid leak occurs in the first seal portion, the pressure of the fluid acts on the second seal portion, and the magnitude of the second load rises to a value close to the first load. Therefore, it is possible to determine whether or not a fluid leak has occurred in the first seal portion by comparing the load difference, which is the difference between the first load and the second load, with a predetermined reference value.

In the third invention, the first seal portion and the second seal portion seal between the shaft and the housing that slides and supports the shaft, and the first load detection portion acts on the first seal portion of the shaft shaft. The feature is that the load in the directional or radial direction is detected, and the second load detecting unit detects the load in the same direction as the load detected by the first load detecting unit and the load acting on the second sealing unit. And.

In the third invention, the first load detecting unit and the second load detecting unit detect a load acting in the same direction. As described above, the first load and the second load used for determining whether or not a fluid leak has occurred in the first seal portion are loads acting in the same direction with respect to the first seal portion and the second seal portion. Is. Therefore, it is possible to accurately determine whether or not a fluid leak has occurred in the first seal portion based on the change in magnitude between the first load and the second load.

In the fourth invention, the housing has a first annular groove for accommodating the first seal portion and a second annular groove for accommodating the second seal portion, and the first load detecting portion is the first seal portion. The second load detection unit is housed in the second annular groove together with the second seal portion.

In the fourth invention, the first load detection unit and the second load detection unit are housed in the first annular groove and the second annular groove provided for accommodating the first seal portion and the second seal portion, respectively. To. Therefore, the fluid leakage detection device can be easily assembled to the fluid pressure device only by processing the housing for arranging the wiring connecting each load detection unit and the determination unit.

A fifth aspect of the present invention is characterized in that the first load detection unit is integrally formed with the first seal portion, and the second load detection unit is integrally formed with the second seal portion.

In the fifth invention, the first load detection unit is integrally formed with the first seal portion, and the second load detection unit is integrally formed with the second seal portion. Therefore, by assembling the first seal portion and the second seal portion to the fluid pressure device, the first load detection unit and the second load detection unit can also be assembled to the fluid pressure device, so that fluid leakage is detected for the fluid pressure device. The efficiency of the work of assembling the device can be improved.

In the sixth invention, the first load detection unit and the second load detection unit each have a pair of electrodes and a pressure-sensitive conductive rubber sandwiched between the pair of electrodes, and act on the first seal portion. The resistance value between the pair of electrodes of the first load detection unit changes according to the load applied, and the resistance value between the pair of electrodes of the second load detection unit changes according to the load acting on the second seal unit. It is characterized by.

In the sixth invention, the first load detecting unit and the second load detecting unit each have a pair of electrodes and a pressure-sensitive conductive rubber sandwiched between the pair of electrodes. As described above, since the first load detection unit and the second load detection unit have a simple structure, their molding can be easily performed. Therefore, even when the first load detection unit and the second load detection unit are provided in a wide range, it is possible to suppress an increase in the manufacturing cost of the fluid leakage detection device.

A seventh aspect of the present invention is characterized in that the first load detecting unit and the second load detecting unit are provided in an annular shape along the first sealing portion and the second sealing portion, respectively.

In the seventh invention, the first load detection unit and the second load detection unit are provided in an annular shape along the first seal portion and the second seal portion, respectively. Therefore, in the first load detection unit and the second load detection unit, even if the pressure of the fluid acting on each seal portion varies in the circumferential direction, the average load acting on each seal portion is detected. As a result, the fluid leakage detection device can accurately determine the deterioration of the sealing function in the sealing region.

According to the present invention, it is possible to detect a decrease in the sealing function in the sealing region before the fluid leaks to the outside in the fluid pressure device.

It is sectional drawing of the hydraulic cylinder which uses the fluid leakage detection apparatus which concerns on 1st Embodiment of this invention. It is an enlarged sectional view which shows the part where the fluid leakage detection apparatus which concerns on 1st Embodiment of this invention is provided. It is an enlarged sectional view which shows the seal member provided with the load detection part in an enlarged manner. It is sectional drawing of the load detection part. It is sectional drawing which follows the VV line of FIG. It is a graph which shows an example of the load detected by the load detection part. It is a graph for demonstrating the determination of the fluid leakage based on the load detected by the load detection part. It is sectional drawing which shows the 1st modification of the load detection part. It is sectional drawing which shows the 2nd modification of the load detection part. It is an enlarged sectional view which shows the part where the fluid leakage detection apparatus which concerns on 2nd Embodiment of this invention is provided. FIG. 5 is an enlarged cross-sectional view showing an enlarged seal member provided with a load detection unit of the fluid leakage detection device according to the second embodiment of the present invention.

Hereinafter, the fluid leakage detection device according to the embodiment of the present invention will be described with reference to the drawings.

<First Embodiment>
The fluid leakage detection device 100 according to the first embodiment of the present invention and the fluid pressure device including the fluid leakage detection device 100 will be described with reference to FIGS. 1 to 7.

Hereinafter, a case where the hydraulic pressure device is a hydraulic cylinder 1 driven by using hydraulic oil as a hydraulic fluid will be described. FIG. 1 is a cross-sectional view showing a hydraulic cylinder 1. FIG. 2 is an enlarged cross-sectional view showing the periphery of the portion where the fluid leakage detection device 100 is provided. In FIG. 1, the fluid leak detection device 100 is not shown.

As shown in FIGS. 1 and 2, the hydraulic cylinder 1 includes a tubular cylinder tube 2, a piston rod 3 as a shaft inserted into the cylinder tube 2, and a base end of the piston rod 3 (right end in FIG. 1). A piston 4 that is connected to and slides along the inner peripheral surface of the cylinder tube 2 is provided.

The inside of the cylinder tube 2 is partitioned by a piston 4 into two hydraulic chambers, a rod side chamber 5 and an anti-rod side chamber 6 as a sealing space. The hydraulic cylinder 1 expands and contracts by the hydraulic pressure guided from a hydraulic source (not shown) to the rod side chamber 5 or the opposite rod side chamber 6. The inner circumference of the cylinder tube 2 and the outer circumference of the piston 4 are sealed by a sealing member (not shown). As a result, the communication between the rod side chamber 5 and the anti-rod side chamber 6 through the inner circumference of the cylinder tube 2 and the outer circumference of the piston 4 is cut off.

The cylinder tube 2 is provided with a cylinder head 7 as a housing that closes the open end of the cylinder tube 2 and slidably supports the piston rod 3. The cylinder head 7 is fastened to the cylinder tube 2 via a plurality of fastening bolts (not shown) arranged in the circumferential direction.

As shown in FIG. 2, bush 11, a seal region 12, and a dust seal 15 are provided on the inner circumference of the cylinder head 7 in this order from the rod side chamber 5 side to the outside.

The bush 11 is arranged so as to be in sliding contact with the outer peripheral surface 3a of the piston rod 3. Therefore, the piston rod 3 is slidably supported by the cylinder head 7 via the bush 11, and can move along the axial direction of the cylinder tube 2.

The seal region 12 is an region for preventing the hydraulic oil in the rod side chamber 5 from leaking to the outside by the plurality of seal members. The seal region 12 has a main seal 13 as a first seal portion arranged on the bush 11 side and directly acted on by the pressure of hydraulic oil in the rod side chamber 5, and a predetermined distance from the main seal 13 in the axial direction of the piston rod 3. A sub-seal 14 as a second seal portion, which is arranged so as to be open, is provided.

The main seal 13 and the sub seal 14 are U-packings having a U-shaped cross section, and the first annular groove 8 and the first annular groove 8 formed in the cylinder head 7 in a state of being compressed between the piston rod 3 and the cylinder head 7. Each is arranged in the second annular groove 9. In addition to the main seal 13 and the sub seal 14, a plurality of seal members may be provided in the seal region 12.

The hydraulic oil in the rod side chamber 5 is usually prevented from leaking from the rod side chamber 5 by the main seal 13. However, if the sealing function of the main seal 13 deteriorates due to deterioration of the main seal 13 and hydraulic oil leaks from the rod side chamber 5 through the gap between the main seal 13 and the piston rod 3, the rod side chamber 5 is contacted. The sub-seal 14 arranged at a position outside the main seal 13 prevents the hydraulic oil in the rod side chamber 5 from leaking to the outside. That is, the sub-seal 14 functions as a backup seal member, and if the main seal 13 is functioning normally, the pressure of the hydraulic oil in the rod side chamber 5 does not act on the sub-seal 14.

The dust seal 15 prevents dust from entering the cylinder tube 2 from the outside, and like the main seal 13 and the sub seal 14, the cylinder is compressed between the piston rod 3 and the cylinder head 7. It is arranged in the groove formed in the head 7.

In the hydraulic cylinder 1 having the above configuration, when the rod side chamber 5 is communicated with the hydraulic source and the anti-rod side chamber 6 is communicated with a tank (not shown), hydraulic oil is supplied to the rod side chamber 5 and the hydraulic oil in the anti-rod side chamber 6 is supplied. Is discharged to the tank, and the hydraulic cylinder 1 contracts. On the other hand, when the anti-rod side chamber 6 is communicated with the hydraulic source and the rod side chamber 5 is communicated with the tank, hydraulic oil is supplied to the anti-rod side chamber 6 and the hydraulic oil in the rod side chamber 5 is discharged to the tank. , The hydraulic cylinder 1 is extended.

Further, the above-mentioned hydraulic cylinder 1 incorporates a fluid leakage detection device 100 that detects a leakage of hydraulic oil that occurs when the sealing function deteriorates in the sealing region 12.

The fluid leakage detection device 100 will be described below with reference to FIGS. 2 to 5. FIG. 3 is an enlarged cross-sectional view showing a portion where the load detection units 21 and 22 described later are provided in an enlarged manner, FIG. 4 is a cross-sectional view showing a cross section of the load detection units 21 and 22 and FIG. , FIG. 2 is a cross-sectional view taken along the line VV of FIG. 2, showing a cross-sectional view of the hydraulic cylinder 1 at a portion where the first load detection unit 21 is provided.

As shown in FIG. 2, the fluid leakage detection device 100 includes a first load detection unit 21 provided between the main seal 13 and the cylinder head 7 for detecting a first load acting on the main seal 13, and a sub seal 14. A second load detection unit 22 that is provided between the cylinder head 7 and detects a second load acting on the sub-seal 14, and a first load detection unit 21 and a second load detection via the wiring shown by the broken line in FIG. It has a control unit 30 to which the unit 22 is connected.

Here, as shown in an enlarged manner in FIG. 3, the above-mentioned main seal 13 and sub-seal 14 are arranged in the first annular groove 8 and the second annular groove 9 formed in the cylinder head 7, respectively, and are annular. The base portions 13a, 14a formed in the base portion 13a, 14a, the first lip portions 13b, 14b extending axially from the base portions 13a, 14a and in contact with the bottom surfaces 8a, 9a of the annular grooves 8, 9 and the axial direction from the base portions 13a, 14a. It has second lip portions 13c and 14c that extend to and are in contact with the outer peripheral surface 3a of the piston rod 3.

As shown in FIG. 3, the first load detecting unit 21 is arranged between the base portion 13a of the main seal 13 and the side surface of the first annular groove 8. In this way, the first load detection unit 21 is arranged so as to be sandwiched between the main seal 13 and the cylinder head 7 in the axial direction of the piston rod 3, so that the first load detection unit 21 is placed on the main seal 13. The acting axial load will act.

Similarly, as shown in FIG. 3, the second load detection unit 22 is arranged between the base portion 14a of the sub-seal 14 and the side surface of the second annular groove 9. As described above, since the second load detection unit 22 is arranged so as to be sandwiched between the sub-seal 14 and the cylinder head 7 in the axial direction of the piston rod 3, the second load detection unit 22 acts on the sub-seal 14. Axial load will act.

As shown in FIG. 4, the first load detection unit 21 and the second load detection unit 22 include a pair of electrodes 25 arranged to face each other and a pressure-sensitive conductive rubber 24 provided between the pair of electrodes 25. It has an insulating material 26 that surrounds a pair of electrodes 25 and a pressure-sensitive conductive rubber 24.

The pressure-sensitive conductive rubber 24 is a rubber material such as silicon rubber having an insulating property mixed with conductive particles such as carbon and metal powder in a predetermined ratio. Therefore, when a force (pressure) as shown by an arrow A in FIG. 5 acts, the resistance value between the pair of electrodes 25 changes according to the magnitude of the force.

Therefore, the magnitude of the axial load acting on the main seal 13 by detecting the resistance value between the pair of electrodes 25 of the first load detecting unit 21 arranged between the main seal 13 and the cylinder head 7. It becomes possible to grasp. Similarly, by detecting the resistance value between the pair of electrodes 25 of the second load detecting unit 22 arranged between the sub-seal 14 and the cylinder head 7, the magnitude of the axial load acting on the sub-seal 14 can be determined. It becomes possible to grasp.

Further, as shown in FIG. 5, the first load detecting unit 21 is formed in an annular shape along the main seal 13, and is housed in the first annular groove 8 together with the main seal 13. Like the first load detection unit 21, the second load detection unit 22 is also formed in an annular shape along the sub-seal 14, and is housed in the second annular groove 9 together with the sub-seal 14.

As described above, the first load detection unit 21 and the second load detection unit 22 are housed in the annular grooves 8 and 9 conventionally provided for accommodating the main seal 13 and the sub seal 14. Therefore, only by forming a slit or the like for arranging the wiring connecting the first load detection unit 21, the second load detection unit 22, and the control unit 30 in the cylinder head 7, the hydraulic cylinder 1 is provided. The fluid leak detection device 100 can be easily assembled.

Further, since the first load detection unit 21 and the second load detection unit 22 have an extremely simple structure of a pair of electrodes 25 and a pressure-sensitive conductive rubber 24 as described above, their molding is easy. Therefore, as shown in FIG. 5, the fluid leakage detection device 100 is manufactured even when the first load detection unit 21 and the second load detection unit 22 are provided in a wide range along the seals 13 and 14. It is possible to suppress the increase in cost.

Further, since the first load detection unit 21 and the second load detection unit 22 are provided in an annular shape along the seals 13 and 14, the first load detection unit 21 and the second load detection unit 22 have each seal 13, Even if the pressure of the hydraulic oil acting in the axial direction with respect to 14 varies in the circumferential direction, the average load acting on the seals 13 and 14 is detected. For example, if the direction in which the weight of the piston rod 3 acts changes due to a change in the posture of the hydraulic cylinder 1, the pressure acting on the seals 13 and 14 may also partially increase or decrease. However, since the first load detection unit 21 and the second load detection unit 22 detect the average load acting on the seals 13 and 14, the influence of external factors such as the change in the posture of the hydraulic cylinder 1 is eliminated. The applied load can be detected.

Next, the control unit 30 will be described.

The control unit 30 is based on the resistance detection circuit 31 that detects the resistance value between the pair of electrodes 25 of the first load detection unit 21 and the second load detection unit 22, and the resistance value detected by the resistance detection circuit 31. It has a determination unit 32 for determining fluid leakage in the seal region 12.

The determination unit 32 is a microcomputer, and is a first load which is an axial load of the main seal 13 and an axial load of the sub seal 14 based on the resistance value between the pair of electrodes 25 detected by the resistance detection circuit 31. The calculation unit 33 that calculates the second load and the load calculated by the calculation unit 33 can be stored, and a calculation map showing the correlation between the resistance value and the load between the pair of electrodes 25 and the determination of fluid leakage. A storage unit 34 that stores reference values used in the above, auxiliary storage units such as ROM and RAM (not shown) that store programs and the like used in the calculation unit 33, and an input / output interface (I / O interface) (not shown). Has.

The calculation unit 33 further compares the difference between the calculated first load and the second load and the reference value stored in the storage unit 34, and based on the comparison result, the fluid leakage in the seal region 12 The presence or absence is determined.

The arithmetic unit 33 is a so-called central processing unit (CPU), and the storage unit 34 is a rewritable non-volatile memory such as EEPROM. The control unit 30 may be provided outside the hydraulic cylinder 1, or may be arranged inside the cylinder head 7 together with the first load detection unit 21 and the second load detection unit 22. Further, the control unit 30 may be incorporated in a control unit that controls the drive of the mechanical device provided with the hydraulic cylinder 1.

Subsequently, with reference to FIGS. 6 and 7, the fluid leakage determination in the seal region 12 by the fluid leakage detection device 100 having the above configuration will be described. FIG. 6 is a graph showing the time change of the first load and the second load from the state in which the main seal 13 is functioning normally to the occurrence of hydraulic oil leakage in the main seal 13, and FIG. 7 is a graph showing FIG. It is a graph which showed the time change of the difference between the 1st load and the 2nd load shown in.

Since the main seal 13 and the sub-seal 14 provided in the seal region 12 are formed of a rubber material, they gradually harden due to deterioration over time. When the elastic restoring force, which is the force for pressing the lip portions 13b and 14b against the outer peripheral surface 3a of the piston rod 3, gradually decreases due to such deterioration with time, the sealing functions of the seals 13 and 14 deteriorate. Further, the sealing function of the seals 13 and 14 is partially deteriorated by the contamination or the like contained in the hydraulic oil entering between the lip portions 13b and 14b and the outer peripheral surface 3a of the piston rod 3. In the fluid leak detection device 100, it is determined whether or not hydraulic oil is leaking in the main seal 13 due to such a decrease in the sealing function.

In the fluid leakage detection device 100, the first load acting on the main seal 13 and the second load acting on the sub-seal 14 are continuously detected while the mechanical device provided with the hydraulic cylinder 1 is operating. Specifically, the resistance value between the pair of electrodes 25 of the first load detection unit 21 is detected in the resistance detection circuit 31, and the first in the axial direction of the main seal 13 is detected in the calculation unit 33 based on the detected resistance value. The load is calculated. At the same time, the resistance value between the pair of electrodes 25 of the second load detection unit 22 is detected in the resistance detection circuit 31, and the second load in the axial direction of the subseal 14 is calculated in the calculation unit 33 based on the detected resistance value. To.

If the inclination of the hydraulic cylinder 1 changes depending on the operating state of the mechanical device, the influence of the weight of the piston rod 3 on the load detected by the first load detecting unit 21 and the second load detecting unit 22 may change. The detection of the first load and the second load is preferably performed when the posture of the hydraulic cylinder 1 is in the same state each time.

Further, the calculation unit 33 compares the difference between the calculated first load and the second load with a predetermined reference value. Then, when the difference between the first load and the second load is less than the reference value, it is determined that the hydraulic oil has leaked in the main seal 13.

Here, the axial load acting on the main seal 13 is mainly between the pressure of the hydraulic oil acting on the main seal 13 and the main seal 13 and the piston rod 3 transmitted through the second lip portion 13c. Due to frictional force. The pressure of the hydraulic oil acting on the main seal 13 is the pressure of the hydraulic oil in the rod side chamber 5, and when the rod side chamber 5 is communicated with the hydraulic source, the pressure is almost equal to the pressure of the hydraulic oil supplied from the hydraulic source. It becomes. Since the load caused by the pressure of the hydraulic oil supplied from the hydraulic source is very large compared to the frictional force between the main seal 13 and the piston rod 3, the load detected by the first load detection unit 21 is , The load is caused by the pressure of the hydraulic oil acting on the main seal 13.

Further, the axial load acting on the sub-seal 14 is also transmitted mainly through the pressure of the hydraulic oil acting on the sub-seal 14 and the second lip portion 14c, similarly to the axial load acting on the main seal 13. This is due to the frictional force between the sub-seal 14 and the piston rod 3. However, if the sealing function of the main seal 13 is in a normal state, the hydraulic oil in the rod side chamber 5 does not reach the sub-seal 14, so that the pressure of the hydraulic oil acting on the sub-seal 14 affects the operation of the hydraulic cylinder 1. Nevertheless, it is almost zero. Therefore, when the main seal 13 is normal, the load detected by the second load detecting unit 22 is substantially the frictional force between the sub seal 14 and the piston rod 3. That is, if the sealing function of the main seal 13 is in a normal state, the load detected by the second load detecting unit 22 becomes a very small value as compared with the load detected by the first load detecting unit 21.

Therefore, in FIG. 6, for a while after the detection of each load is started, that is, after the main seal 13 and the sub seal 14 are first assembled, or after the main seal 13 and the sub seal 14 are replaced. Since the sealing function of the main seal 13 is in a normal state, the second load becomes a relatively small value as compared with the first load. In other words, the load difference, which is the difference between the first load and the second load, is larger than the reference value as shown in FIG. 7.

When the rod side chamber 5 communicates with the hydraulic source, the pressure of the hydraulic oil acting on the main seal 13 becomes substantially equal to the pressure of the hydraulic oil supplied from the hydraulic source, while the rod side chamber 5 enters the tank. When communicated, the pressure becomes close to the atmospheric pressure, which is the pressure of the tank. Therefore, the load detected by the first load detecting unit 21 greatly fluctuates according to the operation of the hydraulic cylinder 1. Therefore, when comparing the first load and the second load, it is preferable to use the average value, the maximum value, and the effective value of each load in consideration of the fluctuation of the pressure due to the switching of the operating direction of the hydraulic cylinder 1.

On the other hand, when the sealing function of the main seal 13 deteriorates due to deterioration or the like and the hydraulic oil leaks from the gap between the main seal 13 and the piston rod 3, the pressure of the hydraulic oil in the rod side chamber 5 acts on the sub seal 14. It becomes a state. That is, when the sealing function of the main seal 13 deteriorates, a pressure similar to the pressure of the hydraulic oil acting on the main seal 13 acts on the sub seal 14, and the pressure is detected by the second load detecting unit 22. The load is about the same as the load detected by the first load detection unit 21.

Therefore, when a considerable amount of time elapses from the start of detection of each load in FIG. 6 and the sealing function of the main seal 13 gradually deteriorates due to deterioration or the like, hydraulic oil leaks from the main seal 13. The magnitude of the second load rises to a value close to the first load, and the load difference, which is the difference between the first load and the second load, becomes a value smaller than the reference value as shown in FIG.

The reference value to be compared with the load difference may be set to such a size that it is clear that the pressure of the hydraulic oil in the rod side chamber 5 acts on the sub-seal 14. For example, it is set based on the initial value of the first load and the initial value of the second load detected when the detection of each load is started. Specifically, it is set to a value that is half of the initial load difference, which is the difference between the initial value of the first load and the initial value of the second load.

When the difference between the first load and the second load falls below the reference value and the calculation unit 33 determines that the hydraulic oil has leaked from the main seal 13, the operator displays a warning lamp or the like (not shown). Is notified that the sealing function is deteriorated in the sealing region 12.

Further, the resistance value between the pair of electrodes 25 of the first load detection unit 21 and the second load detection unit 22 detected by the resistance detection circuit 31 and the first load and the second load calculated by the calculation unit 33 are shown in the figure. It may be wirelessly transmitted to a server for maintenance of mechanical devices or the like located at a remote location via a communication unit. In this case, it is possible to grasp the presence or absence of hydraulic oil leakage in the seal region 12 at a remote location, and instruct the replacement of the main seal 13 and the sub seal 14 before the hydraulic oil leaks to the outside of the hydraulic cylinder 1. Can be done.

According to the above first embodiment, the following effects are obtained.

In the fluid leakage detection device 100, the first load acting on the main seal 13 arranged at the position where the pressure of the hydraulic oil directly acts, and the sub-seal 14 arranged apart from the main seal 13 in the axial direction of the piston rod 3 Based on the acting second load, it is determined whether or not the hydraulic oil has leaked in the main seal 13. In this way, by monitoring whether or not the main seal 13 arranged at the position where the pressure of the hydraulic oil directly acts can exert the sealing function, the hydraulic oil deteriorates before leaking to the outside of the hydraulic cylinder 1. It is possible to detect that the sealing function of the sealing region 12 is deteriorated due to the above.

Further, by preventing the hydraulic oil from leaking from the hydraulic cylinder 1, it is possible to avoid an unexpected situation such as a sudden stop of operation of the mechanical device in which the hydraulic cylinder 1 is used. Further, since the hydraulic oil leak in the seal region 12 is automatically detected by the fluid leak detection device 100 incorporated in the hydraulic cylinder 1, the hydraulic cylinder 1 is disassembled and the hydraulic oil leak in the seal region 12 is visually observed. By eliminating the need to confirm the presence or absence, the efficiency of inspection work can be improved.

Next, a modified example of the first embodiment will be described.

In the first embodiment, the case where the fluid pressure device is the hydraulic cylinder 1 has been described. Not limited to this, the fluid leakage detection device 100 is used as a fluid pressure device having a shaft that slides or rotates in the axial direction to supply and discharge a working fluid, such as a shock absorber, a hydraulic motor, or a hydraulic pump. It may be used. The hydraulic fluid is not limited to hydraulic oil, and for example, water, other liquids, gases, or the like may be used.

Further, in the first embodiment, the case where the main seal 13 and the sub seal 14 are U packings has been described. Not limited to this, the main seal 13 and the sub seal 14 may be of any type as long as the load in the axial direction changes due to the pressure of the hydraulic oil in the rod side chamber 5, and the O-ring may be used. Or an oil seal.

Further, in the first embodiment, the calculation unit 33 calculates each load from the resistance value between the pair of electrodes 25, and compares the difference between the calculated loads with the reference value. Instead of this, the difference between the resistance value between the pair of electrodes 25 of the first load detection unit 21 and the resistance value between the pair of electrodes 25 of the second load detection unit 22 is used as a reference value without calculating each load. May be compared with.

Further, in the first embodiment, the calculation unit 33 notifies the operator and the like only when it is determined that the hydraulic oil leak has occurred in the main seal 13. Instead, the initial value of the load difference is set to 0%, the reference value is set to 100%, and the detected load difference between the first load and the second load is always displayed as the degree of deterioration of the sealing function of the sealing area 12 by the percentage. You may. In this case, it is preferable to encourage the operator or the like to replace the main seal 13 and the sub seal 14 by changing the display color and the display method as the value approaches 100%.

Further, in the first embodiment, by comparing the load difference between the first load and the second load with the reference value, whether or not hydraulic oil leakage has occurred in the main seal 13, that is, the rod side chamber in the sub seal 14. It is determined whether or not the pressure of the hydraulic oil in 5 acts. As described above, when a hydraulic oil leak occurs in the main seal 13, the second load acting on the sub-seal 14 fluctuates greatly according to the operation of the hydraulic cylinder 1 like the first load acting on the main seal 13. On the other hand, when the hydraulic oil leak does not occur in the main seal 13, the second load acting on the sub seal 14 hardly fluctuates. From this, when the magnitude of the peak peak value of the second load approaches the peak peak value of the first load, that is, the difference between the peak peak value of the first load and the peak peak value of the second load is predetermined. If it falls below the reference value, it may be determined that the hydraulic oil leak has occurred in the main seal 13.

Further, in the first embodiment, the first load detection unit 21 and the second load detection unit 22 have a pair of electrodes 25 and a pressure-sensitive conductive rubber 24. The first load detection unit 21 and the second load detection unit 22 are not limited to this, as long as they can detect the axial force acting between the cylinder head 7 and the seals 13 and 14. , Any type of load sensor may be used. For example, it may be a load sensor using a strain gauge or a piezoelectric element.

Further, in the first embodiment, the first load detection unit 21 and the second load detection unit 22 are provided separately from the seals 13 and 14. Instead of this, as shown in the first modification of FIG. 8, the first load detection unit 21 and the second load detection unit 22 may be integrally formed with the seals 13 and 14, respectively. In this case, since the first load detection unit 21 and the second load detection unit 22 are also assembled to the hydraulic cylinder 1 simply by assembling the seals 13 and 14 to the hydraulic cylinder 1, the efficiency of the assembly work can be improved.

Further, in the first embodiment, the first load detecting unit 21 is provided in an annular shape along the main seal 13. Instead of this, as shown in the second modification of FIG. 9, a plurality of first load detecting units 21a to 21d may be provided along the main seal 13. In this case, in order to prevent the sealing force of the main seal 13 from becoming non-uniform in the circumferential direction, the first load detecting portions 21a to 21d are arranged at equal angular intervals with respect to the center of the piston rod 3. Is preferable. The same applies to the second load detection unit 22.

Further, in the first embodiment, the first load detecting unit 21 is provided in an annular shape along the main seal 13. Instead of this, a first load detection unit may be provided in a part along the main seal 13. In this case, in order to prevent the sealing force of the main seal 13 from becoming non-uniform in the circumferential direction, the main seal is located symmetrically with respect to the position where the first load detection unit is provided with the center of the piston rod 3 interposed therebetween. It is preferable to provide a support surface that supports 13 in the axial direction. The same applies to the second load detection unit 22.

Further, in the first embodiment, the first load acting on the main seal 13 and the second load acting on the sub-seal 14 are continuously detected while the mechanical device provided with the hydraulic cylinder 1 is operating. Cylinder. Since the deterioration of the main seal 13 and the sub seal 14 progresses over a relatively long time, when the deterioration of the seal function due to the deterioration is detected, the first load and the second load may be detected for several weeks. It may be done every few months.

While the mechanical device provided with the hydraulic cylinder 1 is operating, the first load and the second load are constantly detected, and the presence or absence of hydraulic oil leakage in the main seal 13 is determined to form the lip portion 13b. It is also possible to detect a hydraulic oil leak that suddenly occurs due to contamination or the like entering between the piston rod 3 and the outer peripheral surface 3a.

<Second Embodiment>
Next, the fluid leakage detection device 200 according to the second embodiment of the present invention will be described with reference to FIGS. 10 and 11. Hereinafter, the points different from those of the first embodiment will be mainly described, and the same reference numerals will be given to the same configurations as those of the first embodiment, and the description thereof will be omitted.

The basic configuration of the fluid leak detection device 200 is the same as that of the fluid leak detection device 100 according to the first embodiment. The fluid leak detection device 200 differs from the fluid leak detection device 100 in that the first load detection unit 121 and the second load detection unit 122 are arranged on the radial outer sides of the seals 13 and 14.

As shown in FIG. 10, the fluid leak detection device 200 includes a first load detection unit 121, which is provided between the main seal 13 and the cylinder head 7 and detects a first load acting on the main seal 13, and a sub seal 14. A second load detection unit 122 that is provided between the cylinder head 7 and detects a second load acting on the sub-seal 14, and a first load detection unit 121 and a second load detection unit via the wiring shown by the broken line in FIG. It has a control unit 30 to which the unit 122 is connected.

Here, the main seal 13 and the sub-seal 14 described above are the first annular groove 8 and the second annular groove 9 formed in the cylinder head 7, as shown in an enlarged manner in FIG. 11, as in the first embodiment. Base portions 13a and 14a, which are arranged in an annular shape, and first lip portions 13b and 14b which extend axially from the base portions 13a and 14a and are in contact with the bottom surfaces 8a and 9a of the annular grooves 8 and 9, respectively. The second lip portions 13c and 14c extend axially from the base portions 13a and 14a and are in contact with the outer peripheral surface 3a of the piston rod 3.

Further, the first annular groove 8 and the second annular groove 9 are deeper than the bottom surfaces 8a and 9a and are formed on the base portions 13a and 14a of the seals 13 and 14 continuously on the bottom surfaces 8a and 9a. It has second bottom surfaces 8b and 9b. The first load detection unit 121 and the second load detection unit 122 are both formed in an annular shape and are arranged between the second bottom surfaces 8b and 9b and the portions of the seals 13 and 14 near the base portions 13a and 14a. To.

In this way, the first load detection unit 121 and the second load detection unit 122 are contact portions between the first lip portions 13b and 14b and the cylinder head 7 so as not to interfere with the sealing function of the first lip portions 13b and 14b. The seals 13 and 14 are arranged closer to the base portions 13a and 14a. Therefore, even if the first load detection unit 121 and the second load detection unit 122 are provided, the first lip portions 13b and 14b of the seals 13 and 14 are in contact with the bottom surfaces 8a and 9a, and the second lip portions 13c are provided. , 14c are in contact with the outer peripheral surface 3a of the piston rod 3, so that the hydraulic oil flowing into the annular grooves 8 and 9 can be reliably prevented from leaking to the outside.

Further, since the first load detection unit 121 is arranged so as to be sandwiched between the main seal 13 and the cylinder head 7 in the radial direction of the piston rod 3, the first load detection unit 121 acts on the main seal 13. A tense force, which is a radial load, acts. The tense force of the main seal 13 detected by the first load detection unit 121 is elastically restored when the second lip portion 13c of the main seal 13 is pressed against the outer peripheral surface 3a of the piston rod 3 and elastically deforms. It corresponds to the resultant force of the force and the pressing force that the second lip portion 13c is pressed against the outer peripheral surface 3a of the piston rod 3 by the hydraulic pressure of the hydraulic oil that has flowed into the first annular groove 8.

Similarly, since the second load detection unit 122 is arranged so as to be sandwiched between the sub-seal 14 and the cylinder head 7 in the radial direction of the piston rod 3, the second load detection unit 122 has a diameter acting on the sub-seal 14. A tense force, which is a load in the direction, acts. The tense force of the sub-seal 14 detected by the second load detection unit 122 is the elastic restoring force generated when the second lip portion 14c of the sub-seal 14 is pressed against the outer peripheral surface 3a of the piston rod 3 and elastically deforms. , Corresponds to the resultant force with the pressing force that the second lip portion 14c is pressed against the outer peripheral surface 3a of the piston rod 3 by the hydraulic pressure of the hydraulic oil that has flowed into the second annular groove 9.

Similar to the first embodiment, the first load detection unit 121 and the second load detection unit 122 are pressure-sensitive conductive rubbers provided between a pair of electrodes 25 arranged to face each other and a pair of electrodes 25. It has 24, and an insulating material 26 that surrounds the pair of electrodes 25 and the pressure-sensitive conductive rubber 24.

Therefore, the magnitude of the radial load acting on the main seal 13 by detecting the resistance value between the pair of electrodes 25 of the first load detecting unit 21 arranged between the main seal 13 and the cylinder head 7. It becomes possible to grasp. Similarly, by detecting the resistance value between the pair of electrodes 25 of the second load detecting unit 22 arranged between the sub-seal 14 and the cylinder head 7, the magnitude of the radial load acting on the sub-seal 14 can be determined. It becomes possible to grasp.

Since the configuration of the control unit 30 is the same as that of the first embodiment, the description thereof will be omitted.

Subsequently, with reference to FIGS. 6 and 7, the fluid leakage determination in the seal region 12 by the fluid leakage detection device 200 having the above configuration will be described.

In the fluid leak detection device 200, the first load acting on the main seal 13 and the second load acting on the sub-seal 14 are continuously detected while the mechanical device provided with the hydraulic cylinder 1 is operating. Specifically, the resistance value between the pair of electrodes 25 of the first load detection unit 121 is detected in the resistance detection circuit 31, and the first in the axial direction of the main seal 13 is detected in the calculation unit 33 based on the detected resistance value. The load is calculated. At the same time, the resistance value between the pair of electrodes 25 of the second load detection unit 122 is detected by the resistance detection circuit 31, and the second load in the axial direction of the subseal 14 is calculated by the calculation unit 33 based on the detected resistance value. To.

Further, the calculation unit 33 compares the difference between the calculated first load and the second load with a predetermined reference value. Then, when the difference between the first load and the second load is less than the reference value, it is determined that the hydraulic oil has leaked in the main seal 13.

Here, the radial load acting on the main seal 13 is elastically restored by being elastically deformed by pressing the second lip portion 13c of the main seal 13 against the outer peripheral surface 3a of the piston rod 3 as described above. It corresponds to the resultant force of the force and the pressing force that the second lip portion 13c is pressed against the outer peripheral surface 3a of the piston rod 3 by the hydraulic pressure of the hydraulic oil that has flowed into the first annular groove 8. The pressure of the hydraulic oil flowing into the first annular groove 8 is the pressure of the hydraulic oil in the rod side chamber 5, and when the rod side chamber 5 communicates with the hydraulic source, it becomes the pressure of the hydraulic oil supplied from the hydraulic source. It will be about the same size. The pressing force that the hydraulic oil supplied from the hydraulic source presses the second lip portion 13c against the outer peripheral surface 3a of the piston rod 3 is very large as compared with the elastic restoring force, and is therefore detected by the first load detecting portion 21. The load is a pressing force caused by the hydraulic oil flowing into the first annular groove 8.

Further, the radial load acting on the sub-seal 14 is also elastically deformed when the second lip portion 14c of the sub-seal 14 is pressed against the outer peripheral surface 3a of the piston rod 3 in the same manner as the radial load acting on the main seal 13. This corresponds to the resultant force of the elastic restoring force generated by the movement and the pressing force of the second lip portion 14c being pressed against the outer peripheral surface 3a of the piston rod 3 by the hydraulic pressure of the hydraulic oil flowing into the second annular groove 9. However, if the sealing function of the main seal 13 is in a normal state, the hydraulic oil in the rod side chamber 5 does not reach the inside of the second annular groove 9, so that the hydraulic oil passes through the second lip portion 14c to the piston rod 3. The pressing force pressed against the outer peripheral surface 3a is almost zero regardless of the operation of the hydraulic cylinder 1. Therefore, when the main seal 13 is normal, the load detected by the second load detecting unit 122 is substantially the elastic restoring force of the second lip portion 14c. That is, if the sealing function of the main seal 13 is in a normal state, the load detected by the second load detecting unit 122 becomes a very small value as compared with the load detected by the first load detecting unit 121.

Therefore, as in the first embodiment, in FIG. 6, after the detection of each load is started, that is, after the main seal 13 and the sub seal 14 are first assembled, or after the main seal 13 and the sub seal 14 are assembled. For a while after the replacement, the seal function of the main seal 13 is in a normal state, so that the second load becomes a relatively small value as compared with the first load. In other words, the load difference, which is the difference between the first load and the second load, is larger than the reference value as shown in FIG. 7. In comparing the first load and the second load, as in the first embodiment, the average value and the maximum value of each load are set in consideration of the pressure fluctuation due to the switching of the operating direction of the hydraulic cylinder 1. It is preferable to use the effective value.

On the other hand, when the sealing function of the main seal 13 deteriorates and the hydraulic oil leaks from the gap between the main seal 13 and the piston rod 3, the pressure of the hydraulic oil in the rod side chamber 5 acts on the sub seal 14. .. That is, when the sealing function of the main seal 13 is deteriorated, the hydraulic oil having the same pressure as the hydraulic oil flowing into the first annular groove 8 flows into the second annular groove 9. Therefore, the load detected by the second load detecting unit 122 is about the same as the load detected by the first load detecting unit 121.

Therefore, as in the first embodiment, when a considerable amount of time has passed since the detection of each load was started in FIG. 6 and the sealing function of the main seal 13 gradually deteriorates due to deterioration or the like, the main seal 13 is used. Due to the leakage of hydraulic oil, the magnitude of the second load rises to a value close to the first load, and the load difference, which is the difference between the first load and the second load, is as shown in FIG. The value is smaller than the reference value.

When the difference between the first load and the second load falls below the reference value and the calculation unit 33 determines that the hydraulic oil leaks from the main seal 13, it is not shown as in the first embodiment. The operator is notified via a display such as a warning lamp that the sealing function is deteriorated in the sealing area 12.

According to the above second embodiment, the following effects are obtained.

In the fluid leak detection device 200, the first load in the radial direction acting on the main seal 13 arranged at the position where the pressure of the hydraulic oil directly acts, and the first load in the radial direction are arranged apart from the main seal 13 in the axial direction of the piston rod 3. Based on the second load acting on the sub-seal 14 in the radial direction, it is determined whether or not the hydraulic oil has leaked in the main seal 13. In this way, by monitoring whether or not the main seal 13 arranged at the position where the pressure of the hydraulic oil directly acts can exert the sealing function, the hydraulic oil deteriorates before leaking to the outside of the hydraulic cylinder 1. It is possible to detect that the sealing function of the sealing region 12 is deteriorated due to the above.

Hereinafter, the configurations, actions, and effects of the embodiments of the present invention will be collectively described.

The fluid leakage detection devices 100 and 200 for detecting the fluid leakage in the main seal 13 that seals the rod side chamber 5 to which the pressure of the hydraulic oil is applied are the first load detection unit 21 for detecting the first load acting on the main seal 13. 121, second load detection units 22, 122 for detecting a second load acting on the sub-seal 14 that seals the rod side chamber 5 at a position outside the main seal 13 with respect to the rod side chamber 5, and a first load detection unit. A determination unit 32 for determining fluid leakage of the main seal 13 based on the first load detected by 21 and 121 and the second load detected by the second load detection units 22 and 122 is provided.

In this configuration, the first load acting on the main seal 13 arranged at the position where the pressure of the hydraulic oil in the rod side chamber 5 directly acts, and the sub seal arranged apart from the main seal 13 in the axial direction of the piston rod 3. Based on the second load acting on 14, it is determined whether or not the hydraulic oil has leaked in the main seal 13. In this way, by monitoring whether or not the main seal 13 arranged at the position where the pressure of the hydraulic oil directly acts can exert the sealing function, the hydraulic oil deteriorates before leaking to the outside of the hydraulic cylinder 1. It is possible to detect that the sealing function of the sealing region 12 is deteriorated due to the above. As a result, by preventing the hydraulic oil from leaking from the hydraulic cylinder 1, it is possible to avoid an unexpected situation such as a sudden stop of operation of the mechanical device in which the hydraulic cylinder 1 is used.

Further, in this configuration, the hydraulic oil leak in the seal region 12 is automatically detected by the fluid leak detection device 100 incorporated in the hydraulic cylinder 1, so that the hydraulic cylinder 1 is disassembled and visually in the seal region 12. By eliminating the need to check for hydraulic oil leaks, the efficiency of inspection work can be improved. Further, when the main seal 13 and the sub-seal 14 provided in the seal region 12 are regularly replaced, the seal members that have not yet deteriorated are also replaced, but the seals are sealed by the fluid leakage detection devices 100 and 200 having the above configuration. The maintenance cost can be reduced by replacing the main seal 13 and the sub seal 14 only when it is determined that the sealing function of the region 12 is deteriorated. By replacing the main seal 13 and the sub-seal 14 at an appropriate time in this way, it is possible to avoid an unexpected situation such as a sudden stop of operation of the mechanical device in which the hydraulic cylinder 1 is used.

Further, the determination unit 32 sets the difference between the first load detected by the first load detection units 21 and 121 and the second load detected by the second load detection units 22 and 122 as a predetermined reference value. If it falls below the limit, it is determined that the main seal 13 has leaked fluid.

In this configuration, when the difference between the first load detected by the first load detecting units 21 and 121 and the second load detected by the second load detecting units 22 and 122 is less than a predetermined reference value. It is determined that a fluid leak has occurred in the main seal 13. When the sealing function of the main seal 13 deteriorates due to deterioration or the like and hydraulic oil leaks from the main seal 13, the pressure of the hydraulic oil acts on the sub-seal 14, and the magnitude of the second load becomes the first load. It rises to a close value. Therefore, by comparing the load difference, which is the difference between the first load and the second load, with a predetermined reference value, whether or not hydraulic oil leaks in the main seal 13, that is, the seal in the seal region 12. It is possible to accurately determine whether or not the function is deteriorated.

Further, the main seal 13 and the sub seal 14 seal between the piston rod 3 and the cylinder head 7 that slidably supports the piston rod 3, and the first load detecting units 21 and 121 are the piston rods that act on the main seal 13. The load in the axial direction or the radial direction of 3 is detected, and the second load detection units 22 and 122 are loads in the same direction as the load detected by the first load detection units 21 and 121 and act on the sub-seal 14. Detect the load.

In this configuration, the first load detecting units 21 and 121 and the second load detecting units 22 and 122 detect loads acting in the same direction. As described above, the first load and the second load used for determining whether or not hydraulic oil is leaking in the main seal 13 are loads acting in the same direction on the main seal 13 and the sub seal 14. .. Therefore, it is possible to more accurately determine whether or not the hydraulic oil has leaked in the main seal 13 based on the change in magnitude between the first load and the second load.

Further, the cylinder head 7 has a first annular groove 8 for accommodating the main seal 13 and a second annular groove 9 for accommodating the sub seal 14, and the first load detecting units 21 and 121 together with the main seal 13. It is housed in the first annular groove 8, and the second load detecting units 22, 122 are housed in the second annular groove 9 together with the sub-seal 14.

In this configuration, the first load detection units 21, 121 and the second load detection units 22, 122 are conventionally provided for accommodating the main seal 13 and the sub seal 14, and the first annular groove 8 and the second annular groove 8 are provided. Each is housed in 9. Therefore, the cylinder head 7 is simply formed with a slit or the like for arranging the wiring connecting the first load detecting units 21, 121, the second load detecting units 22, 122, and the control unit 30, and the hydraulic pressure is increased. The fluid leakage detection device 100 can be easily assembled to the cylinder 1.

Further, the first load detection units 21 and 121 are integrally formed with the main seal 13, and the second load detection units 22 and 122 are integrally formed with the sub seal 14.

In this configuration, the first load detection units 21 and 121 are integrally formed with the main seal 13, and the second load detection units 22 and 122 are integrally formed with the sub seal 14. Therefore, by assembling the main seal 13 and the sub-seal 14 to the hydraulic cylinder 1, the first load detection units 21, 121 and the second load detection units 22, 122 are also assembled to the hydraulic cylinder 1, so that the hydraulic cylinder 1 can be attached. The efficiency of the work of assembling the fluid leakage detection devices 100 and 200 can be improved.

Further, the first load detecting units 21, 121 and the second load detecting units 22, 122 each have a pair of electrodes 25 and a pressure-sensitive conductive rubber 24 sandwiched between the pair of electrodes 25, and are main components. The resistance value between the pair of electrodes 25 of the first load detection units 21 and 121 changes according to the load acting on the seal 13, and the pair of second load detection units 22 and 122 changes according to the load acting on the sub-seal 14. The resistance value between the electrodes 25 changes.

In this configuration, the first load detecting units 21, 121 and the second load detecting units 22, 122 each have a pair of electrodes 25 and a pressure-sensitive conductive rubber 24 sandwiched between the pair of electrodes 25. As described above, since the first load detecting units 21 and 121 and the second load detecting units 22 and 122 have extremely simple configurations, their molding can be easily performed. Therefore, even when the first load detection units 21, 121 and the second load detection units 22, 122 are widely provided along the main seal 13 and the sub seal 14, strain gauges, piezoelectric elements, and the like are arranged in a wide range. It is possible to suppress an increase in the manufacturing cost of the fluid leakage detection devices 100 and 200 as compared with the case where

Further, the first load detection units 21, 121 and the second load detection units 22, 122 are provided in an annular shape along the main seal 13 and the sub seal 14, respectively.

In this configuration, the first load detection units 21, 121 and the second load detection units 22, 122 are provided in an annular shape along the main seal 13 and the sub seal 14, respectively. Therefore, in the first load detecting units 21 and 121 and the second load detecting units 22 and 122, even if the pressure of the hydraulic oil acting on the seals 13 and 14 varies in the circumferential direction, they act on the seals 13 and 14. The average load is detected. For example, if the direction in which the weight of the piston rod 3 acts changes due to a change in the posture of the hydraulic cylinder 1, the pressure acting on the seals 13 and 14 may also partially increase or decrease. However, since the first load detecting units 21 and 121 and the second load detecting units 22 and 122 detect the average load acting on the seals 13 and 14, external factors such as a change in the posture of the hydraulic cylinder 1 are detected. It is possible to detect the load from which the influence of is removed. Then, in the fluid leakage detection devices 100 and 200, the deterioration of the sealing function in the sealing region 12 is determined based on the average load detected in this way, so that the determination accuracy can be improved. Further, since the number of wirings connected to the first load detection units 21 and 121 and the second load detection units 22 and 122 is small and the structure is simple, assembling work such as wiring can be easily performed. The manufacturing cost of the fluid leakage detection devices 100 and 200 can be reduced.

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. Absent.

For example, the modification in the first embodiment may be applied to the second embodiment. Further, by combining the first embodiment and the second embodiment, both the axial load and the radial load acting on the seals 13 and 14 are detected, and the main seal 13 is based on these loads. The presence or absence of fluid leakage may be determined.

100, 200 ... Fluid leak detector, 1 ... Hydraulic cylinder (fluid pressure device), 3 ... Piston rod (shaft), 5 ... Rod side chamber 5 (sealed space), 7 ... Cylinder Head (housing), 8 ... 1st annular groove, 9 ... 2nd annular groove, 12 ... Seal area, 13 ... Main seal, 14 ... Sub seal, 21,21a-21d, 121 ... 1st load detection unit, 22, 122 ... 2nd load detection unit, 24 ... Pressure-sensitive conductive rubber, 25 ... Pair of electrodes, 30 ... Control unit, 32 ... Judgment unit

Claims (7)

A fluid leakage detection device that detects fluid leakage in the first sealing portion that seals the sealed space to which fluid pressure is applied.
A first load detection unit that detects the first load acting on the first seal unit, and
A second load detection unit that detects a second load acting on the second seal portion that seals the sealed space at a position outside the first seal portion with respect to the sealed space.
A determination unit for determining fluid leakage in the first seal unit based on the first load detected by the first load detection unit and the second load detected by the second load detection unit is provided. A fluid leak detection device characterized in that. In the determination unit, when the difference between the first load detected by the first load detection unit and the second load detected by the second load detection unit is less than a predetermined reference value. The fluid leakage detection device according to claim 1, wherein the fluid leakage of the first seal portion is determined. The first seal portion and the second seal portion seal between the shaft and the housing that slides and supports the shaft.
The first load detecting unit detects an axial or radial load of the shaft acting on the first sealing unit, and the second load detecting unit is a load detected by the first load detecting unit. The fluid leakage detection device according to claim 1 or 2, wherein the load in the same direction detects the load acting on the second seal portion. The housing has a first annular groove for accommodating the first seal portion and a second annular groove for accommodating the second seal portion.
The first load detection unit is housed in the first annular groove together with the first seal part, and the second load detection part is housed in the second annular groove together with the second seal part. The fluid leak detection device according to any one of claims 3. Claims 1 to 4, wherein the first load detection unit is integrally formed with the first seal portion, and the second load detection unit is integrally formed with the second seal portion. The fluid leakage detection device according to any one of the above. The first load detection unit and the second load detection unit each have a pair of electrodes and a pressure-sensitive conductive rubber sandwiched between the pair of electrodes.
The resistance value between the pair of electrodes of the first load detection unit changes according to the load acting on the first seal portion, and the second load detection unit of the second load detection unit responds to the load acting on the second seal portion. The fluid leakage detection device according to any one of claims 1 to 5, wherein the resistance value between the pair of electrodes changes. The first load detection unit and the second load detection unit are provided in an annular shape along the first seal portion and the second seal portion, respectively, according to any one of claims 1 to 6. The described fluid leak detector.

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