Hydraulic systems for industrial machinery

Abstract

To detect the degree of contamination of the hydraulic fluid in a hydraulic system. [Solution] The hydraulic system 20 of the work machine includes a pressure reducing valve 24 that reduces the pressure of the hydraulic fluid discharged from the hydraulic pump 21, an output channel through which the hydraulic fluid from the pressure reducing valve flows, and a contamination sensor 60 that detects the degree of contamination of the hydraulic fluid flowing through the output channel.

Description

Technical Field

[0001] The present disclosure relates to a hydraulic device for a working machine.

Background Art

[0002] In the technical field related to hydraulic devices for working machines, a method for determining the soundness of a hydraulic pump, as disclosed in Patent Document 1, is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] If a large amount of foreign matter is present in the hydraulic fluid, the hydraulic device may malfunction. Therefore, a technique for detecting the contamination level of the hydraulic fluid is desired.

[0005] The present disclosure aims to detect the contamination level of the hydraulic fluid in a hydraulic device.

Means for Solving the Problems

[0006] [[ID=4(5)]] According to the present disclosure, a hydraulic device for a working machine is provided. The hydraulic device includes a pressure reducing valve that reduces the pressure of the hydraulic fluid discharged from a hydraulic pump, an output flow path through which the hydraulic fluid from the pressure reducing valve flows, and a contamination level sensor that detects the contamination level of the hydraulic fluid flowing through the output flow path.

Effects of the Invention

[0007] According to the present disclosure, the contamination level of the hydraulic fluid in the hydraulic device can be detected.

Brief Description of the Drawings

[0008] [Figure 1] Note: There seems to be a minor formatting issue in the original text where "(32)" and "4(5)" are likely incorrect notations. I've translated them as they are but they might need to be corrected in the source.Figure 1 shows a working machine according to an embodiment. [Figure 2] Figure 2 is a block diagram of the controller according to the embodiment. [Figure 3] Figure 3 shows the hydraulic system of a work machine according to an embodiment. [Figure 4] Figure 4 is a schematic diagram showing a contamination level sensor according to an embodiment. [Figure 5] Figure 5 is a schematic diagram showing a contamination level sensor according to an embodiment. [Figure 6] Figure 6 shows the hydraulic system of a work machine according to an embodiment. [Figure 7] Figure 7 shows the hydraulic system of a work machine according to an embodiment. [Modes for carrying out the invention]

[0009] [Working machinery] Figure 1 is a side view showing a work machine 1 according to an embodiment. The work machine 1 operates at a work site. In this embodiment, the work machine 1 is a hydraulic excavator. The work machine 1 comprises a traveling body 2, a rotating body 3, a work machine 4, a hydraulic cylinder 5, a controller 6, an operating device 7, and a monitor 8.

[0010] The running body 2 supports the rotating body 3. The running body 2 has a pair of tracks 2A. The working machine 1 moves as the tracks 2A rotate.

[0011] The slewing body 3 is positioned above the traveling body 2. The slewing body 3 is rotatably supported by the traveling body 2. The slewing body 3 has a cab. The operator of the work machine 1 is seated in the cab. An operating device 7 and a monitor 8 are located in the cab. The operating device 7 is operated by the operator. The operating device 7 includes at least a work lever that is operated to operate the work machine 4. When the operating device 7 is operated, an operation signal is generated. The operation signal generated in the operating device 7 is transmitted to the controller 6. The monitor 8 provides output data to the operator. The monitor 8 includes a display device and an audio output device. The monitor 8 provides the operator with display data or audio data as output data.

[0012] The work implement 4 is rotatably connected to the slewing body 3. The work implement 4 includes a boom 4A, an arm 4B, and a bucket 4C. The boom 4A is rotatably connected to the front of the slewing body 3. The arm 4B is rotatably connected to the tip of the boom 4A. The bucket 4C is rotatably connected to the tip of the arm 4B.

[0013] The hydraulic cylinder 5 operates the work machine 4. The hydraulic cylinder 5 is an example of a hydraulic actuator installed on the work machine 1. The operating device 7 is operated by an operator to operate the hydraulic cylinder 5. The hydraulic cylinder 5 is operated by hydraulic fluid. The hydraulic cylinder 5 includes a boom cylinder 5A, an arm cylinder 5B, and a bucket cylinder 5C.

[0014] The boom cylinder 5A operates the boom 4A. The operation of the boom 4A includes raising and lowering movements. When the boom cylinder 5A extends, the boom 4A moves upward. When the boom cylinder 5A retracts, the boom 4A moves downward.

[0015] The arm cylinder 5B operates the arm 4B. The operation of the arm 4B includes digging and dumping operations. When the arm cylinder 5B extends, the arm 4B performs the digging operation. When the arm cylinder 5B retracts, the arm 4B performs the dumping operation.

[0016] The bucket cylinder 5C operates the bucket 4C. The operation of the bucket 4C includes a digging operation and a dumping operation. When the bucket cylinder 5C extends, the bucket 4C performs a digging operation. When the bucket cylinder 5C contracts, the bucket 4C performs a dumping operation.

[0017] The controller 6 communicates with the server 10 via the communication system 9. The server 10 includes a computer arranged outside the working machine 1. The communication system 9 may include a public communication line or a dedicated communication line. As the communication system 9, a mobile phone communication network or a satellite communication network is exemplified. Note that the communication system 9 may include the Internet or a local area network. The server 10 can communicate with the working machine 1 via the communication system 9. The server 10 collects the operation data of the working machine 1.

[0018] [Controller] FIG. 2 is a block diagram showing a controller 6 according to an embodiment. The controller 6 includes a computer. The controller 6 has a processor 6A, a main memory 6B, a storage 6C, an input / output interface 6D, and a communication interface 6E. The processor 6A includes a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The main memory 6B includes a non-volatile memory such as a ROM (Read Only Memory) or a volatile memory such as a RAM (Random Access Memory). The storage 6C is a non-temporary tangible storage medium. Examples of the storage 6C include a magnetic disk, a magneto-optical disk, or a semiconductor memory. The input / output interface 6D includes an input / output circuit. The communication interface 6E includes a communication circuit. The functions of the controller 6 are stored in the storage 6C as a computer program. The processor 6A reads the computer program from the storage 6C and expands it in the main memory 6B, and executes processing according to the computer program. Note that the computer program may be distributed to the controller 6 via a network.

[0019] The processor 6A is connected to each of the operating device 7, the contamination sensor 60, and the monitor 8 via the input / output interface 6D. The processor 6A communicates with the server 10 via the communication interface 6E and the communication system 9. The operating device 7 and the contamination sensor 60 will be described later.

[0020] [Hydraulic device] Figure 3 shows a hydraulic system 20 of a work machine 1 according to an embodiment. The hydraulic system 20 includes a hydraulic pump 21, a directional control valve 22, an operating device 7, a pressure reducing valve 24, a flow control valve 25, an oil cooler 26, a filter 27, a hydraulic oil tank 28, a swashplate control valve 29, a suction passage 30, a pump passage 31, a bottom passage 32, a head passage 33, a tank passage 34, a branch passage 35, a first control passage 36, a second control passage 37, a third control passage 38, a first drain passage 41, a second drain passage 42, and a third drain passage 43. The hydraulic system 20 also includes a controller 6, which was described with reference to Figure 2.

[0021] The hydraulic pump 21 discharges hydraulic fluid drawn in from the hydraulic fluid tank 28. The hydraulic pump 21 is a swashplate type variable displacement pump. The capacity [cc / rev] of the hydraulic pump 21 is changed by changing the angle of the swashplate of the hydraulic pump 21. The hydraulic pump 21 has a suction port 212 for drawing in hydraulic fluid and a discharge port 211 for discharging hydraulic fluid. The suction passage 30 is connected to the suction port 212. The hydraulic pump 21 draws hydraulic fluid from the hydraulic fluid tank 28 through the suction passage 30. The pump passage 31 is connected to the discharge port 211. The hydraulic pump 21 discharges hydraulic fluid into the pump passage 31. The hydraulic fluid discharged from the hydraulic pump 21 flows through the pump passage 31.

[0022] The directional control valve 22 is connected to the pump passage 31. The directional control valve 22 controls the flow rate and direction of the hydraulic fluid supplied from the hydraulic pump 21 to the hydraulic cylinder 5. The directional control valve 22 has a pump port 221 connected to the pump passage 31, a bottom port 222 connected to the bottom passage 32, a head port 223 connected to the head passage 33, and a tank port 224 connected to the tank passage 34. The pump port 221 is connected to the discharge port 211 of the hydraulic pump 21 via the pump passage 31. The bottom port 222 is connected to the bottom chamber 51 of the hydraulic cylinder 5 via the bottom passage 32. The head port 223 is connected to the head chamber 52 of the hydraulic cylinder 5 via the head passage 33. The tank port 224 is connected to the hydraulic fluid tank 28 via the tank passage 34. The oil cooler 26 and the filter 27 are each located in the tank passage 34. The oil cooler 26 is located in the tank passage 34 between the directional control valve 22 and the filter 27. The hydraulic fluid that flows out from the tank port 224 passes through the oil cooler 26 and the filter 27 before being discharged into the hydraulic fluid tank 28.

[0023] The spool of the directional control valve 22 is movable to a first position A, a second position B, and a neutral position N. When the spool of the directional control valve 22 is positioned at the first position A, the hydraulic fluid discharged from the hydraulic pump 21 flows into the pump port 221 via the pump passage 31, then flows out from the bottom port 222, and is supplied to the bottom chamber 51 via the bottom passage 32. As the hydraulic fluid is supplied to the bottom chamber 51, the hydraulic cylinder 5 extends. When the hydraulic cylinder 5 extends, the hydraulic fluid flows out from the head chamber 52. The hydraulic fluid that flows out from the head chamber 52 flows into the head port 223 via the head passage 33, then flows out from the tank port 224, and is discharged to the hydraulic fluid tank 28 via the tank passage 34.

[0024] When the directional control valve 22 is positioned in the second position B, the hydraulic fluid discharged from the hydraulic pump 21 flows into the pump port 221 via the pump passage 31, then flows out from the head port 223, and is supplied to the head chamber 52 via the head passage 33. As hydraulic fluid is supplied to the head chamber 52, the hydraulic cylinder 5 retracts. When the hydraulic cylinder 5 retracts, hydraulic fluid flows out from the bottom chamber 51. The hydraulic fluid that flows out from the bottom chamber 51 flows into the bottom port 222 via the bottom passage 32, then flows out from the tank port 224, and is discharged into the hydraulic fluid tank 28 via the tank passage 34.

[0025] When the directional control valve 22 is positioned in the neutral position N, the hydraulic fluid does not pass through the directional control valve 22. The hydraulic cylinder 5 does not extend or retract.

[0026] The operating device 7 generates a control pressure to move the spool of the directional control valve 22. Here, an example using a PPC (Pressure Proportional Control) valve as the operating device 7 is described, but the operating device 7 is not limited to this, and an EPC (Electromagnetic Proportional Control) valve or the like can also be used. The operating device 7 includes a first operating device 7A and a second operating device 7B. When the first operating device 7A applies control pressure to the directional control valve 22, the directional control valve 22 moves to the first position A. When the second operating device 7B applies control pressure to the directional control valve 22, the directional control valve 22 moves to the second position B.

[0027] The branch channel 35 branches off from the pump channel 31 between the hydraulic pump 21 and the directional control valve 22. At least a portion of the hydraulic fluid flowing through the pump channel 31 flows into the branch channel 35 and flows through the branch channel 35.

[0028] The pressure reducing valve 24 is connected to the branch passage 35. The pressure reducing valve 24 reduces the pressure of the hydraulic fluid discharged from the hydraulic pump 21. The pressure reducing valve 24 reduces the pressure of the hydraulic fluid that branches off from the pump passage 31 and flows through the branch passage 35. The pressure reducing valve 24 has an inlet port 241 connected to the branch passage 35, an outlet port 242 connected to the first control passage 36, and a drain port 243 connected to the first drain passage 41. The hydraulic fluid discharged from the outlet port 242 of the pressure reducing valve 24 flows through the first control passage 36.

[0029] The swash plate control valve 29 is connected to the first control flow path 36. The swash plate control valve 29 controls the swash plate of the hydraulic pump 21 based on the hydraulic fluid discharged from the outlet port 242 of the pressure reducing valve 24. The swash plate control valve 29 controls the angle of the swash plate of the hydraulic pump 21.

[0030] The second control channel 37 branches off from the first control channel 36 between the pressure reducing valve 24 and the swashplate control valve 29. At least a portion of the hydraulic fluid that flows out from the outlet port 242 of the pressure reducing valve 24 and through the first control channel 36 flows into the second control channel 37 and flows through the second control channel 37.

[0031] The flow control valve 25 is connected to the second control passage 37. The flow control valve 25 controls the flow rate of hydraulic fluid supplied to the operating device 7. The flow control valve 25 includes an on / off valve. The flow control valve 25 and the operating device 7 are connected via a third control passage 38. The hydraulic fluid that flows through the second control passage 37 and passes through the flow control valve 25 flows through the third control passage 38 and is then supplied to the operating device 7. The operating device 7 generates a control pressure to move the spool of the directional control valve 22 based on the hydraulic fluid from the flow control valve 25.

[0032] The first drain passage 41 is provided to return the hydraulic fluid leaking from the pressure reducing valve 24 back to the hydraulic fluid tank 28. The first drain passage 41 is connected to the drain port 243. Hydraulic fluid may leak internally from the gap between the valve body and spool of the pressure reducing valve 24. The leaked hydraulic fluid is discharged from the drain port 243 into the first drain passage 41.

[0033] The second drain passage 42 is provided to return the hydraulic fluid leaking from the directional control valve 22 back to the hydraulic fluid tank 28. The second drain passage 42 connects the directional control valve 22 and the hydraulic fluid tank 28. There is a possibility that hydraulic fluid may leak from the gap between the valve body and the spool of the directional control valve 22. The hydraulic fluid that leaks from the directional control valve 22 is discharged into the second drain passage 42. After flowing through the second drain passage 42, the hydraulic fluid that leaks from the directional control valve 22 is returned to the hydraulic fluid tank 28.

[0034] In this embodiment, the first drain passage 41 is connected to a second drain passage 42 between the directional control valve 22 and the hydraulic fluid tank 28. The hydraulic fluid that leaks from the pressure reducing valve 24 flows through the first drain passage 41, then through a portion of the second drain passage 42, and is returned to the hydraulic fluid tank 28.

[0035] The third drain passage 43 is provided to return the hydraulic fluid leaking from the hydraulic pump 21 back to the hydraulic fluid tank 28. The third drain passage 43 connects the hydraulic pump 21 and the hydraulic fluid tank 28. There is a possibility that hydraulic fluid may leak internally from the sliding parts of the hydraulic pump 21. The hydraulic fluid that leaks internally from the hydraulic pump 21 flows through the third drain passage 43 and is then returned to the hydraulic fluid tank 28.

[0036] The contamination level sensor 60 detects the degree of contamination of the hydraulic fluid. The degree of contamination of the hydraulic fluid refers to the amount of particles P present in the hydraulic fluid per unit volume. The contamination level sensor 60 is a type of particle counter. The amount of particles P present in the hydraulic fluid refers to the number of particles P that are larger than a predetermined size (e.g., 6 μm).

[0037] The contamination level sensor 60 detects the degree of contamination of the hydraulic fluid in the first control channel 36 through which the hydraulic fluid from the pressure reducing valve 24 flows. The first control channel 36 is an example of an output channel through which the hydraulic fluid from the pressure reducing valve 24 flows. The contamination level sensor 60 detects the degree of contamination of the hydraulic fluid flowing through the first control channel 36. The flow rate of the hydraulic fluid flowing through the first control channel 36, which is an output channel, is between 1 L / min and 5 L / min.

[0038] As shown in Figure 3, the second control channel 37 branches off from the first control channel 36 between the pressure reducing valve 24 and the contamination level sensor 60. The contamination level sensor 60 detects the degree of contamination of the hydraulic fluid flowing through the first control channel 36 between the connection point between the first control channel 36 and the second control channel 37 and the swashplate control valve 29.

[0039] [Contamination level sensor] Figure 4 is a schematic diagram showing a contamination level sensor 60 according to an embodiment. The contamination level sensor 60 has a light-emitting unit 61, a light-receiving unit 62, and a detection tube 63. The light-emitting unit 61 includes a light-emitting diode (LED). The light-receiving unit 62 includes a photodiode. The hydraulic fluid flows through the detection tube 63. The detection tube 63 is translucent. The detection tube 63 is a transparent tube, such as a glass tube. The detection tube 63 is positioned between the light-emitting unit 61 and the light-receiving unit 62. The light-emitting unit 61 and the light-receiving unit 62 are positioned so as to sandwich the detection tube 63. The light-emitting unit 61 irradiates the detection tube 63 with detection light. The light-receiving unit 62 receives at least a portion of the detection light that has passed through the detection tube 63. At least a portion of the detection light emitted from the light-emitting unit 61 passes through the detection tube 63 and then enters the light-receiving unit 62.

[0040] The detection tube 63 is connected to the first control flow path 36. The detection tube 63 is connected in series with the first control flow path 36. The inner diameter of the detection tube 63 is smaller than the inner diameter of the first control flow path 36. The hydraulic fluid flows inside the detection tube 63.

[0041] The hydraulic fluid may contain particles P. Examples of particles P include sand that has entered the hydraulic system 20 from outside the work machine 1, and metal powder generated by wear on at least a part of the hydraulic system 20. The contamination sensor 60 detects particles P. The contamination sensor 60 detects the degree of contamination of the hydraulic fluid in accordance with ISO 4406.

[0042] If particles P are present in the hydraulic fluid flowing inside the detection tube 63, the detection light from the light-emitting unit 61 is absorbed, scattered, or attenuated by the particles P. This absorption, scattering, or attenuation of the detection light by the particles P causes a change in the amount of light received by the light-receiving unit 62. The contamination sensor 60 can detect the amount of particles P based on the amount of light received by the light-receiving unit 62. The detection data from the contamination sensor 60 is transmitted to the controller 6. The detection data from the contamination sensor 60 includes the amount of light received by the light-receiving unit 62.

[0043] The controller 6 acquires detection data from the contamination sensor 60 when the spool of the directional control valve 22 is in the neutral position N. That is, the detection data from the contamination sensor 60 when the spool of the directional control valve 22 is in the neutral position N is treated as valid data. The controller 6 can determine, for example, whether or not the spool of the directional control valve 22 is in the neutral position N based on an operation signal from the operating device 7.

[0044] The controller 6 transmits the detection data from the contamination sensor 60, acquired when the spool of the directional control valve 22 is in the neutral position N, to the server 10. The server 10 stores contamination data related to the contamination level of the hydraulic fluid. If the contamination level of the hydraulic fluid (amount of particles P) exceeds a predetermined threshold, the controller 6 outputs output data to the monitor 8 indicating that the contamination level of the hydraulic fluid (amount of particles P) has exceeded the threshold.

[0045] [effect] As described above, in this embodiment, the hydraulic system 20 of the work machine 1 includes a pressure reducing valve 24 that reduces the pressure of the hydraulic fluid discharged from the hydraulic pump 21, a first control passage 36 which is an output passage through which the hydraulic fluid from the pressure reducing valve 24 flows, and a contamination sensor 60 that detects the degree of contamination of the hydraulic fluid flowing through the first control passage 36.

[0046] According to this embodiment, the contamination level of the hydraulic fluid is detected by the contamination level sensor 60. If a large amount of particles P are present in the hydraulic fluid, the hydraulic system 20 may malfunction. Since the contamination level of the hydraulic fluid is detected by the contamination level sensor 60, the user (operator or manager) of the work machine 1 can recognize the possibility of a malfunction in the hydraulic system 20 early on based on the detection data from the contamination level sensor 60.

[0047] It is said that 70% to 80% of failures in the hydraulic system 20 are caused by foreign matter (particles P) contained in the hydraulic fluid. Contamination level and metal element concentration are used as indicators to quantitatively evaluate the particles P contained in the hydraulic fluid. Currently, this quantitative evaluation is performed by sampling the hydraulic fluid and having it analyzed at a specialized analytical institution using expensive analytical equipment. In addition, delays in judgment due to the analysis lead time of remote analysis may occur, and these delays in judgment may increase the risk of sudden failure of the hydraulic system 20. In this embodiment, a contamination level sensor 60, which is a particle counter, is installed in the hydraulic system 20 of the work machine 1, and the detection data of the contamination level sensor 60 is monitored. As a result, the user of the work machine 1 can recognize the risk of sudden failure of the hydraulic system 20 in real time.

[0048] The contamination level sensor 60 has a detection tube 63 through which hydraulic fluid flows. If the inner diameter of the detection tube 63 is large, the detection light from the light-emitting unit 61 may be excessively attenuated by the hydraulic fluid, potentially reducing the amount of light received by the light-receiving unit 62. A decrease in the amount of light received by the light-receiving unit 62 may reduce the detection accuracy of the contamination level sensor 60. For this reason, the inner diameter of the detection tube 63 of the contamination level sensor 60 is smaller than the inner diameter of the output flow path (first control flow path 36) of the hydraulic system 20. If the inner diameter of the detection tube 63 is small, pressure loss of the hydraulic fluid may occur in the detection tube 63.

[0049] For example, if the contamination level sensor 60 is located in the pump flow path 31, the operating performance of the hydraulic system 20 may deteriorate, such as the operation of the directional control valve 22 becoming sluggish due to pressure loss of the hydraulic fluid. In this embodiment, the contamination level sensor 60 is located in the output circuit (first control flow path 36) of the pressure reducing valve 24. Since the contamination level sensor 60 is located in the output circuit of the pressure reducing valve 24, the deterioration of the operating performance of the hydraulic system 20 is suppressed.

[0050] Furthermore, if the contamination level sensor 60 is located in the pump flow path 31, for example, the pressure of the hydraulic fluid acting on the contamination level sensor 60 may exceed the pressure resistance performance of the contamination level sensor 60. In this embodiment, the contamination level sensor 60 is located in the output circuit (first control flow path 36) of the pressure reducing valve 24. Since the contamination level sensor 60 is located in the output circuit of the pressure reducing valve 24, the high pressure of the hydraulic fluid acting on the contamination level sensor 60 is suppressed.

[0051] Furthermore, if the contamination level sensor 60 is located in the pump flow path 31, for example, the flow velocity of the hydraulic fluid flowing through the detection tube 63 may exceed the flow velocity of the hydraulic fluid at which the contamination level sensor 60 can detect particles P. In other words, if the flow velocity of the hydraulic fluid flowing through the detection tube 63 is excessively high, the contamination level sensor 60 may have difficulty detecting particles P. In this embodiment, the contamination level sensor 60 is located in the output circuit (first control flow path 36) of the pressure reducing valve 24. Since the contamination level sensor 60 is located in the output circuit of the pressure reducing valve 24, it is suppressed that the flow velocity of the hydraulic fluid flowing through the detection tube 63 becomes excessively high.

[0052] When the spool of the directional control valve 22 is positioned at the first position A or the second position B, the hydraulic fluid pressure in the hydraulic system 20 may fluctuate. When the hydraulic fluid pressure fluctuates, it may become difficult to detect the degree of contamination of the hydraulic fluid under the same conditions. In this embodiment, the controller 6 acquires detection data from the contamination sensor 60 when the spool of the directional control valve 22 is positioned at the neutral position N. Therefore, the contamination sensor 60 can detect the degree of contamination of the hydraulic fluid under the same conditions while suppressing fluctuations in the hydraulic fluid pressure.

[0053] [Differentiation] The following describes some modifications. Figure 5 shows a contamination level sensor 60 according to an embodiment. As shown in Figure 5, the contamination level sensor 60 may be connected in parallel to the first control channel 36. In the example shown in Figure 5, the detection tube 63 of the contamination level sensor 60 is connected to the first control channel 36 via a first branch channel 36A and a second branch channel 36B. The first branch channel 36A and the second branch channel 36B each branch off from the first control channel 36. At least a portion of the hydraulic fluid flowing through the first control channel 36 branches off to the first branch channel 36A and then flows through the detection tube 63. The contamination level sensor 60 detects particles P of the hydraulic fluid flowing through the detection tube 63. The hydraulic fluid that has flowed through the detection tube 63 is returned to the first control channel 36 via the second branch channel 36B.

[0054] By connecting the contamination level sensor 60 in parallel to the first control channel 36, the pressure loss of the hydraulic fluid flowing through the first control channel 36 is reduced. As described in the first embodiment above, by connecting the contamination level sensor 60 in series to the first control channel 36, the complexity of the hydraulic system 20 structure is suppressed. Since the required flow rate of hydraulic fluid for the swash plate control valve 29 is small, even if a pressure loss occurs in the hydraulic fluid flowing through the first control channel 36 due to the series connection of the contamination level sensor 60 to the first control channel 36, the swash plate control valve 29 can operate properly.

[0055] Figure 6 shows a hydraulic system 20 of a work machine 1 according to an embodiment. As shown in Figure 6, the contamination level sensor 60 may detect the degree of contamination of the hydraulic fluid flowing through the second control channel 37. The second control channel 37 is an example of an output channel through which hydraulic fluid from the pressure reducing valve 24 flows. The flow rate of the hydraulic fluid flowing through the second control channel 37, which is an output channel, is 1 L / min or more and 5 L / min or less. In the example shown in Figure 6, the contamination level sensor 60 is connected in parallel to the second control channel 37. By connecting the contamination level sensor 60 in parallel to the second control channel 37, the pressure loss of the hydraulic fluid flowing through the second control channel 37 is reduced. By reducing the pressure loss of the hydraulic fluid flowing through the second control channel 37, hydraulic fluid at the appropriate pressure is supplied to the flow control valve 25 and the operating device 7. The contamination level sensor 60 may also be connected in series to the second control channel 37.

[0056] Figure 7 shows a hydraulic system 20 of a work machine 1 according to an embodiment. As shown in Figure 7, the contamination level sensor 60 may detect the degree of contamination of the hydraulic fluid flowing through the second drain passage 42. The second drain passage 42 is an example of an output passage through which hydraulic fluid from the pressure reducing valve 24 flows. The flow rate of the hydraulic fluid flowing through the second drain passage 42, which is an output passage, is 1 L / min or more and 5 L / min or less. In the example shown in Figure 7, the contamination level sensor 60 is connected in parallel to the second drain passage 42. By connecting the contamination level sensor 60 in parallel to the second drain passage 42, the pressure loss of the hydraulic fluid flowing through the second drain passage 42 is reduced. Since the pressure of the hydraulic fluid flowing through the second drain passage 42 is low, if the pressure loss of the hydraulic fluid flowing through the second drain passage 42 is large, there is a possibility that the hydraulic fluid will backflow in the second drain passage 42. By connecting the contamination level sensor 60 in parallel to the second drain channel 42, backflow of hydraulic fluid in the second drain channel 42 is suppressed. Alternatively, the contamination level sensor 60 may be connected in series with the second drain channel 42.

[0057] [Other embodiments] In the above-described embodiment, the hydraulic actuator is defined as a hydraulic cylinder 5. The hydraulic actuator may also be a hydraulic travel motor for driving the track 2A, or a hydraulic slewing motor for slewing the slewing body 3.

[0058] In the above embodiment, the working machine 1 is assumed to be a hydraulic excavator. The working machine 1 only needs to have a working implement. The working machine 1 may be a bulldozer or a wheel loader. [Explanation of Symbols]

[0059] 1...Working machine, 2...Traction unit, 2A...Track, 3...Slewing unit, 4...Working machine, 4A...Boom, 4B...Arm, 4C...Bucket, 5...Hydraulic cylinder, 5A...Boom cylinder, 5B...Arm cylinder, 5C...Bucket cylinder, 6...Controller, 6A...Processor, 6B...Main memory, 6C...Storage, 6D...Input / output interface, 6E...Communication interface, 7...Operating device, 7A...First operating device, 7B...Second operating device, 8...Monitor, 9...Communication system, 10...Server, 20...Hydraulic system, 21...Hydraulic pump, 22...Directional control valve, 24...Pressure reducing valve, 25...Flow control valve, 26...Oil cooler, 27...Filter, 28...Hydraulic oil tank, 29...Swashplate control valve, 30...Suction passage , 31...Pump channel, 32...Bottom channel, 33...Head channel, 34...Tank channel, 35...Branch channel, 36...First control channel, 36A...First branch channel, 36B...Second branch channel, 37...Second control channel, 38...Third control channel, 41...First drain channel, 42...Second drain channel, 43...Third drain channel, 51...Bottom chamber, 52...Head chamber, 60...Contamination level sensor, 61...Light-emitting part, 62...Light-receiving part, 63...Detection tube, 211...Discharge port, 212...Suction port, 221...Pump port, 222...Bottom port, 223...Head port, 224...Tank port, 241...Inlet port, 242...Outlet port, 243...Drain port, A...First position, B...Second position, N...Neutral position, P...Particle.

Claims

1. A hydraulic system for a work machine, A pressure reducing valve that reduces the pressure of the hydraulic fluid discharged from the hydraulic pump, The output channel through which the hydraulic fluid from the pressure reducing valve flows, The system includes a contamination sensor for detecting the degree of contamination of the hydraulic fluid flowing through the output channel. Hydraulic systems for industrial machinery.

2. A pump passage through which the hydraulic fluid discharged from the hydraulic pump flows, A directional control valve that controls the flow rate and direction of the hydraulic fluid connected to the pump flow path and supplied to the hydraulic actuator, The pump flow path includes a branch flow path that branches off from the pump flow path, The pressure reducing valve is connected to the branched flow path, A hydraulic system for a work machine as described in claim 1.

3. The aforementioned hydraulic pump is a swashplate type variable displacement pump, A first control channel through which the hydraulic fluid discharged from the outlet port of the pressure reducing valve flows, The system includes a swash plate control valve connected to the first control channel and controlling the swash plate of the hydraulic pump, The output channel includes the first control channel, A hydraulic system for a work machine according to claim 2.

4. A second control channel through which the hydraulic fluid discharged from the outlet port of the pressure reducing valve flows, A flow control valve connected to the second control channel, The system comprises an operating device connected to an operating device for operating a hydraulic actuator, which generates a control pressure for moving the spool of the directional control valve based on the hydraulic fluid from the flow control valve, The output channel includes the second control channel, A hydraulic system for a work machine according to claim 2.

5. The system is equipped with a drain channel for returning the hydraulic fluid leaked from the pressure reducing valve back to the hydraulic fluid tank. The output channel includes the drain channel, A hydraulic system for a work machine according to claim 2.

6. Equipped with a controller, The controller acquires the detection data from the contamination level sensor when the spool of the directional control valve is in the neutral position. A hydraulic system for a work machine according to claim 2.

7. The contamination level sensor comprises a light-transmitting detection tube through which the hydraulic fluid flows, a light-emitting unit that irradiates the detection tube with detection light, and a light-receiving unit that receives at least a portion of the detection light that has passed through the detection tube, wherein the inner diameter of the detection tube is smaller than the inner diameter of the output flow path. A hydraulic system for a work machine as described in claim 1.

8. The flow rate of the hydraulic fluid flowing through the output channel is 1 L / min or more and 5 L / min or less. A hydraulic system for a work machine as described in claim 1.

Images