Work machine

Abstract

To provide a work machine capable of detecting leakage from any on-off valve.SOLUTION: A work machine includes a hydraulic pump (1a), an actuator (5) driven by pressure oil from the hydraulic pump, a plurality of on-off valves (25a-25d), leak measurement means (6) that measures leaks from the plurality of on-off valves, a plurality of directional control valves (30a-30d), and a controller (20). Each directional control valve has a normal position (30a7), a first operating position (30a5), and a third operating position (30a8). The controller closes a specific on-off valve (25b) and opens the other on-off valves (25a, 25c, 25d), and also switches the directional control valve (30b) associated with the specific on-off valve to the first operating position (30b5) and switches the other directional control valves (30a, 30c, 30d) to their normal positions (30a7, 30c7, 30d7), thereby measuring the leaks from the specific on-off valve (25b).SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a work machine such as a hydraulic excavator, and more particularly to a technique for detecting the state of a hydraulic circuit. [Background technology]

[0002] In recent years, there has been a demand for even greater fuel economy in work machines such as hydraulic excavators. As a measure to reduce fuel economy in large models used in mining, etc., a circuit configuration has been studied in which multiple valves (on-off valves) can be assigned to one actuator and one pump, and the valves are only responsible for the on-off function (without metering control) (see Patent Document 1).

[0003] With such a circuit configuration, multiple valves will be connected to the actuator and pump, for example. If the leakage from one valve increases due to aging when it is closed, the amount of oil supplied to the actuator will decrease, which could lead to phenomena such as front end sinking.

[0004] As a means for solving this type of problem, there is known an abnormality detection method that calculates, from the operation of a hydraulic cylinder, the flow rate of hydraulic oil required for the hydraulic cylinder to operate as the cylinder supply flow rate, and also calculates, from the current value (control current) and discharge pressure of the hydraulic pump, the flow rate of hydraulic oil discharged from the hydraulic pump as the pump discharge flow rate, and then compares the cylinder supply flow rate with the pump discharge flow rate, and can detect leaks and the like in the hydraulic cylinder and the hydraulic circuit related to the hydraulic cylinder based on the comparison result (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2011 / 031851 [Patent Document 2] Patent No. 6005489 Summary of the Invention [Problem to be solved by the invention]

[0006] The conventional technology described in Patent Document 2 can detect leaks in the entire circuit, but cannot identify which of the multiple connected valves is leaking. As a result, if a leak occurs in the entire circuit, not only the valves that need to be replaced but also other valves (valves that do not need to be replaced) must be replaced, which poses the problem of unnecessary costs and work time during maintenance.

[0007] The present invention has been made in view of the current state of the prior art, and its object is to provide a work machine that can detect leakage from any on-off valve. [Means for solving the problem]

[0008] In order to achieve the above object, one aspect of the present invention comprises a hydraulic pump, an actuator driven by pressure oil from the hydraulic pump, a plurality of on-off valves that connect or block a flow path between the hydraulic pump and the actuator, a leak measurement means that measures leakage from the plurality of on-off valves, a plurality of directional control valves that are provided corresponding to the plurality of on-off valves, respectively, and a controller that controls the plurality of on-off valves and the plurality of directional control valves, wherein each of the directional control valves has a normal position that connects the flow path between the hydraulic pump and the on-off valve, connects the flow path between the on-off valve and the actuator, and blocks the flow path between the on-off valve and the leak measurement means, a first operating position that blocks the flow path between the hydraulic pump and the on-off valve, connects the flow path between the on-off valve and the actuator, and connects the flow path between the on-off valve and the leak measurement means, and a third operating position that blocks the flow path between the hydraulic pump and the on-off valve, connects the flow path between the on-off valve and the actuator, and blocks the flow path between the on-off valve and the leak measurement means. [Effects of the Invention]

[0009] According to the present invention, it is possible to detect leaks in any on-off valve. Therefore, only on-off valves that need replacement can be replaced, improving work efficiency during maintenance. Note that problems, configurations, and effects other than those described above will become clear from the description of the following embodiments. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an overall perspective view of a hydraulic excavator according to a first embodiment of the present invention. [Figure 2A] FIG. 2 is a hydraulic circuit diagram of the hydraulic excavator shown in FIG. [Figure 2B] FIG. 2 is an electrical configuration diagram of the hydraulic excavator shown in FIG. [Figure 3] FIG. 2(a) is a detailed view of a directional control valve according to a first embodiment, and FIG. 2(b) is a detailed view of a directional control valve according to a second embodiment. [Figure 4A] 10 is a flowchart showing a procedure for measuring leakage from an on-off valve. [Figure 4B] 10 is a flowchart showing a procedure for measuring leakage from an on-off valve. [Figure 5] 10 is a diagram illustrating the operation of a hydraulic circuit when measuring the amount of leakage of an on-off valve with respect to pressure oil flowing from a pump to an actuator. FIG. [Figure 6] 10 is a diagram illustrating the operation of a hydraulic circuit when measuring the amount of leakage of an on-off valve with respect to pressure oil flowing from an actuator to a pump. FIG. [Figure 7] FIG. 10 is a diagram illustrating the operation of the hydraulic circuit when measuring the amount of leakage of an on-off valve with respect to pressure oil flowing from a pump to an actuator in the second embodiment. [Figure 8] FIG. 10 is a diagram illustrating the operation of the hydraulic circuit when measuring the amount of leakage of an on-off valve with respect to pressure oil flowing from an actuator to a pump in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a hydraulic excavator will be described as an embodiment of a work machine according to the present invention with reference to the drawings.

[0012] (First embodiment) FIG. 1 is an overall perspective view of a hydraulic excavator 1. As shown in FIG. 1, the hydraulic excavator 1 includes a running body 101, and a rotating body 102 is provided on the running body 101. The running body 101 and the rotating body 102 form a main body. The running body 101 includes tracks provided on the left and right sides of the main body, and traveling motors 10a and 10b that are hydraulic actuators and provide traveling power to the left and right tracks. The rotating body 102 is rotatable relative to the running body 101 by a bearing mechanism (not shown) interposed between the running body 101 and the running body 101, and a swing motor (not shown) that is a hydraulic actuator. The rotating body 102 has a working device 103 mounted on the front of a main frame 105, a counterweight 108 mounted on the rear, and a cab 104 mounted on the left front. An engine 106 serving as a prime mover and a drive system 107 driven by the drive output from the engine 106 are housed in front of the counterweight 108.

[0013] The working implement 103 is a front working machine in which a structure consisting of a boom 111, an arm 112, and a bucket 113 is connected by a link mechanism, and each rotates about a link axis to perform work such as excavation. The working implement 103 is equipped with a boom cylinder 7a, an arm cylinder 7b, and a bucket cylinder 7c as hydraulic actuators that rotate the boom 111, the arm 112, and the bucket 113.

[0014] Next, an example of the configuration of a drive unit provided in the hydraulic excavator 1 will be described. Fig. 2A is a hydraulic circuit diagram of the hydraulic excavator 1, and Fig. 2B is an electrical configuration diagram of the hydraulic excavator 1. The drive circuit shown in Fig. 2A is composed of closed circuit pumps 1a and 1b (hereinafter abbreviated as pumps 1a and 1b) connected in a closed circuit, an actuator 5, and directional control valves 30a, 30b, 30c, and 30d which have on-off valves 25a, 25b, 25c, and 25d provided between the closed circuit pumps 1a and 1b and the actuator 5 and can open / close oil passages between the closed circuit pumps 1a and 1b and the on-off valves 25a, 25b, 25c, and 25d, open / close oil passages between the on-off valves 25a, 25b, 25c, and 25d and the actuator 5, and open / close oil passages between the on-off valves 25a, 25b, 25c, and 25d and the leak amount measuring device 6. The pumps 1a and 1b are bi-directional tilting pumps. The actuator 5 is a collective term for the travel motors 10a and 10b, the swing motor, the boom cylinder 7a, the arm cylinder 7b, the bucket cylinder 7c, and the like.

[0015] On-off valves 25a, 25b, 25c, and 25d connect or disconnect the oil passages between pumps 1a, 1b and actuator 5. In the normal position, they are closed by the force of springs 25a1, 25b1, 25c1, and 25d1 attached to them, i.e., they block the oil passages. Meanwhile, solenoids 25a2, 25b2, 25c2, and 25d2 are attached to the opposite sides of springs 25a1, 25b1, 25c1, and 25d1, respectively, and are connected to controller 20 by electrical wiring so that electrical signals from controller 20 can be input (see FIG. 2B). When an electrical signal is input from controller 20, on-off valves 25a, 25b, 25c, and 25d open to connect the oil passages between pumps 1a, 1b and actuator 5.

[0016] When the actuator 5 is a hydraulic cylinder such as the boom cylinder 7a, arm cylinder 7b, or bucket cylinder 7c, the volume of oil that can be supplied differs between the rod side and the bottom side. To compensate for this volume difference (volume difference due to the inserted rod), this embodiment provides a supply / discharge path 50 on the bottom side of the actuator 5, and is configured to supply and receive any excess or deficiency of oil in the circuit.

[0017] Make-up valves 3a1, 3a2, 3b1, 3b2 are provided so that oil can be sucked from tank 40 via makeup valves 3a1, 3a2, 3b1, 3b2 when pumps 1a, 1b are operated with the oil passages between on-off valves 25a, 25b, 25c, 25d and pumps 1a, 1b blocked by directional control valves 30a, 30b, 30c, 30d. The role of makeup valves 3a1, 3a2, 3b1, 3b2 is to prevent cavitation by sucking up oil from tank 40 when pumps 1a, 1b are driven with the suction side closed.

[0018] Relief valves 7a1, 7a2, 7b1, 7b2 are provided so that oil can be released to tank 40 via relief valves 7a1, 7a2, 7b1, 7b2 when pumps 1a, 1b are operated with the oil passages between on-off valves 25a, 25b, 25c, 25d and pumps 1a, 1b blocked by directional control valves 30a, 30b, 30c, 30d. The role of relief valves 7a1, 7a2, 7b1, 7b2 is to create leak measurement conditions (pressurized conditions) by adjusting the set pressure of relief valves 7a1, 7a2, 7b1, 7b2 when measuring leaks.

[0019] The leak amount measuring instrument 6, which is an example of a leak measuring means, is a measuring instrument that can detect the amount of leaked oil (minute flow rate) that has passed through, and for example, a minute flow meter is used. As another example, for example, to keep costs down, it is also possible to use a drain pressure sensor, etc., and estimate the flow rate from pressure data.

[0020] The check valves 4a and 4b are configured to select the oil flow passing through the leak amount measuring device 6 and prevent the flow from one side from flowing to the other side.

[0021] Displacement sensors 16a, 16b, 16c, and 16d are provided in on-off valves 25a, 25b, 25c, and 25d and connected to recording device 10 via electrical wiring (see FIG. 2B). While 16a, 16b, 16c, and 16d are displacement sensors, they are not limited to this and may be other types of valve open / close detection means. The displacement amounts of on-off valves 25a, 25b, 25c, and 25d detected by displacement sensors 16a, 16b, 16c, and 16d can be recorded in recording device 10. Based on the recorded displacement amounts, controller 20 performs various calculations and issues commands to directional control valves 30a, 30b, 30c, and 30d. Recording device 10 can be configured as a large-capacity memory such as a hard disk drive (HDD).

[0022] The pressure sensors 15a to 15p are provided to detect the pressure before and after the on-off valves 25a, 25b, 25c, and 25d, and are connected to the recording device 10 via electrical wiring. Each pressure data detected by the pressure sensors 15 to 15p can be recorded in the recording device 10, and the wiring configuration allows the controller 20 to perform various calculations based on the recorded data and issue commands to the directional control valves 30a, 30b, 30c, and 30d.

[0023] 2B, reference numerals 2a and 2b denote operating lever devices, which are connected to a controller 20 via electrical wiring. The controller 20 is further connected to on-off valves 25a, 25b, 25c, and 25d via electrical wiring. The operating lever devices 2a and 2b include operating levers 2a1 and 2b1 for extending and retracting the actuator 5, and are operated by the operator of the hydraulic excavator 1, for example.

[0024] The operating lever devices 2a, 2b are equipped with a detection device (not shown) that electrically detects the tilt amount of the operating levers 2a1, 2b1, i.e., the lever operation amount. The lever operation amount detected by the detection device is output to the controller 20 via electrical wiring as a lever operation amount signal. In response to this output signal, the controller 20 sends a command via electrical wiring to the on-off valves 25a, 25b, 25c, 25d, thereby opening and closing the on-off valves 25a, 25b, 25c, 25d. The controller 20 is configured, for example, by a microcomputer and is equipped with a CPU, ROM, RAM, user interface, etc., although not shown.

[0025] Next, the directional control valves 30a, 30b, 30c, and 30d will be described in detail. Fig. 3(a) is a detailed view of the directional control valve 30a. Here, since the directional control valves 30b, 30c, and 30d have the same configuration as the directional control valve 30a, the directional control valve 30a will be described below as an example.

[0026] The directional control valve 30a has four switching positions: a normal position 30a7, a first operating position 30a5, a second operating position 30a6, and a third operating position 30a8.

[0027] The normal position 30a7 is a position that connects the flow path between the pump 1a and the on-off valve 25a, connects the flow path between the on-off valve 25a and the actuator 5, and blocks the flow path between the on-off valve 25a and the leak amount measuring instrument 6.

[0028] The first operating position 30a5 is a position that blocks the flow path between the pump 1a and the on-off valve 25a, opens the flow path between the on-off valve 25a and the actuator 5, and opens the flow path between the on-off valve 25a and the leak amount measuring device 6.

[0029] The second operating position 30a6 is a position that connects the flow path between the pump 1a and the on-off valve 25a, blocks the flow path between the on-off valve 25a and the actuator 5, and connects the flow path between the on-off valve 25a and the leak amount measuring instrument 6.

[0030] The third operating position 30a8 is a position that blocks the flow path between the pump 1a and the on-off valve 25a, blocks the flow path between the on-off valve 25a and the actuator 5, and blocks the flow path between the on-off valve 25a and the leak amount measuring instrument 6.

[0031] In normal position 30a7, directional control valve 30a connects ports ci and dj (between pump 1a and on-off valve 25a) and ports ag and bh (between on-off valve 25a and actuator 5), while blocking ports e and f. Solenoids 30a1 and 30a3 are attached to the opposite sides of springs 30a2 and 30a4, respectively, and are connected to controller 20 by electrical wiring so that electrical signals from controller 20 can be input. Also, by changing the magnitude of the electrical signal input to solenoid 30a1, it is possible to control whether the valve is switched to first operating position 30a5 or second operating position 30a6.

[0032] When an electrical signal 12 is input from the controller 20 to the solenoid 30a1, the spring 30a2 is compressed by electromagnetic force, and the directional control valve 30a is switched to the second operating position 30a6. In the second operating position 30a6, the ports ci and dj (between the pump 1a and the on-off valve 25a) and the ports ae and bf (between the on-off valve 25a and the leak amount measuring device 6) are connected, and the ports g and h are blocked.

[0033] When an electrical signal I1 is input to the solenoid 30a1 by the controller 20, the spring 30a2 is compressed by electromagnetic force, and the directional control valve 30a is switched to a first operating position 30a5. In the first operating position 30a5, the ports ce and df (between the on-off valve 25a and the leak amount measuring device 6) are connected, the ports ag and bh (between the on-off valve 25a and the actuator 5) are connected, and the ports i and j are blocked.

[0034] When an electric signal is input from the controller 20 to the solenoid 30a3, the spring 30a4 is compressed by electromagnetic force, and the directional control valve 30a is switched to the third operating position 30a8. In the third operating position 30a8, all of the ports a to j are blocked.

[0035] Next, a method for measuring leakage from the on-off valves 25a, 25b, 25c, and 25d will be described. Figures 4A and 4B are flowcharts showing the procedure for measuring leakage, and Figures 5 and 6 are diagrams showing the operation of the hydraulic circuit during leakage measurement.

[0036] First, in the state shown in Fig. 2A, it is assumed that pressure oils from pumps 1a and 1b are joined and sent to actuator 5 to operate actuator 5. When an operator tilts control lever 2a1, a detection device in control lever device 2a outputs a signal corresponding to the amount of lever operation to controller 20. In response to this output signal, controller 20 provides current commands to solenoids 25a2 and 25c2 of on-off valves 25a and 25c, and the thrust of solenoids 25a2 and 25c2 exceeds the force of springs 25a1 and 25c1, thereby opening on-off valves 25a and 25c.

[0037] When the on-off valves 25a, 25c open, pressure oil from the pumps 1a, 1b is sent to the actuator 5 via the directional control valves 30a, 30c, and the actuator 5 can be operated. At this time, the displacement sensors 16a, 16b, 16c, 16d provided in the on-off valves 25a, 25b, 25c, 25d detect the amount of displacement of the on-off valves 25a, 25b, 25c, 25d and send it to the recording device 10. The recording device 10 records the signal of the amount of displacement as a time history waveform and records the time (operation time) over which the on-off valves 25a, 25b, 25c, 25d are displaced from the waveform.

[0038] The recording device 10 outputs the operation times of the on-off valves 25a, 25b, 25c, and 25d to the controller 20. The controller 20 receives this history and, if the operation time exceeds a predetermined value ST1, issues a command to switch the directional control valve and performs leak measurement on the on-off valve being measured. The predetermined value ST1 is determined taking into consideration the timing of vehicle maintenance, and in this embodiment is set to, for example, 2000 hours.

[0039] At this time, the controller 20 makes a switching decision according to the flowchart of Figure 4A. In accordance with step 42a, the operating times T1, T2, T3, and T4 of the on-off valves 25a, 25b, 25c, and 25d are acquired from the recording device 10, and then a threshold decision is made in step 42b. Here, it is assumed that the operating time T1 of the on-off valve 25b has reached a predetermined value ST1, and a leak measurement is performed on the on-off valve 25b. In this case, in accordance with step 42c, the operator or the like is prompted to decide whether to switch to the leak measurement mode.

[0040] The operator checks this using an indicator (not shown) in the cab and decides to switch to the leak measurement mode. Switching to the leak measurement mode can be done using a button (not shown) in the cab, and when the operator operates the button, an electrical signal is sent to the controller 20, causing the mode to switch to the leak measurement mode.

[0041] When the mode is switched to leak measurement mode, the amount of leakage is first measured when the valve is closed, blocking the flow of pressurized oil from the pump 1a (P) to the actuator 5 (A) (Fig. 5).

[0042] In accordance with step 42d, the controller 20 turns off the command to the on-off valve 25b to close the specific on-off valve 25b that is the leak measurement target. Thereafter, in accordance with step 42e, the controller 20 issues a command to the directional control valve 30b associated with the on-off valve 25b to switch the directional control valve 30b to the second operating position 30b6. That is, the flow path (L11 → L12) between the on-off valve 25b and the pump 1a is opened via the directional control valve 30b, the flow path (L14 → L18 → L19) between the on-off valve 25b and the leak amount measuring instrument 6 is also opened via the directional control valve 30b, and the flow paths (L16, L25) between the on-off valve 25b and the actuator 5 are blocked via the directional control valve 30b.

[0043] Furthermore, in accordance with step 42f, in order to shut off the on-off valves 25a, 25c, 25d that are not the object of leak measurement from the actuator 5, the controller 20 issues a command to the directional control valves 30a, 30c, 30d, and switches the directional control valves 30a, 30c, 30d to the third operating positions (30a8, 30c8, 30d8) (see FIG. 5). Thereafter, in accordance with step 42g, pressure is applied by the pump 1a, and the amount of oil leaking from the on-off valve 25b is measured by the leak amount measuring instrument 6.

[0044] When measuring leaks, pressurized conditions for measuring leaks from the on-off valve 25b can be created by sucking up oil from the tank 40 via the makeup valve 3a2 and releasing the pressurized oil via the relief valve 7a1. This allows leak measurements to be performed on only the on-off valve 25b, and based on the results, it can be determined whether or not to replace only the on-off valve 25b.

[0045] Furthermore, if the on-off valve 25b is leaking, by appropriately replacing the on-off valve 25b, it is possible to prevent the amount of pressurized oil supplied from the pump 1a to the actuator 5 from decreasing due to the leak, thereby preventing problems such as the operating speed of the working device 103 being slow or the working device 103 not operating at all.

[0046] Next, the flow moves to flow 2 in FIG. 4B, and the leakage amount is measured when the valve is closed to block the pressure oil flowing (returning) from the actuator 5(A) to the pump 1a(P) (FIG. 6).

[0047] In step 42h, the controller 20 displays on the monitor in the cab a message instructing the operator to perform a predetermined lever operation. The lever operation is an operation that stabilizes the pressure in the actuator 5, for example, a single operation that operates the actuator 5 to the cylinder end and relieves the pressure.

[0048] In response to this lever operation, as shown in step 42i, the on-off valves 25a, 25c, and 25d turn on their commands, and to communicate with the actuator 5, the controller 20 issues commands to the directional control valves 30a, 30c, and 30d, switching the directional control valves 30a, 30c, and 30d to their normal positions (30a7, 30c7, and 30d7) (see FIG. 6). That is, the flow path (L20 → L21) between the on-off valve 25a and the pump 1a is connected via the directional control valve 30a, the flow paths (L17 and L19) between the on-off valve 25a and the leak amount measuring device 6 are blocked via the directional control valve 30a, and the flow paths (L23 → L25 and L26 → L24) between the on-off valve 25a and the actuator 5 are connected via the directional control valve 30a. The same applies to the other flow paths.

[0049] Meanwhile, the controller 20 switches the directional control valve 30b to the first operating position (30b5). That is, the flow path (L11) between the on-off valve 25b and the pump 1a is blocked via the directional control valve 30b, the flow paths (L12 → L16 → L17, L13 → L18 → L19) between the on-off valve 25b and the leak amount measuring device 6 are connected via the directional control valve 30b, and the flow paths (L16 → L14, L25 → L15) between the on-off valve 25b and the actuator 5 are connected via the directional control valve 30b.

[0050] Then, in step 42j, a guidance on the lever holding time is displayed on the monitor inside the cab, and leakage measurement is performed within a predetermined time.

[0051] As a result, when the actuator 5 is operating at a predetermined relief pressure, pressure oil leaking from the on-off valve 25b, which is in a closed state, flows into the leak amount measuring instrument 6, making it possible to perform leakage measurement for only the on-off valve 25b, and based on the result, it can be determined whether or not to replace only the on-off valve 25b. In other words, if it is detected that return pressure oil from the actuator 5 to the pump 1a side is leaking via the on-off valve 25b, by appropriately replacing only the on-off valve 25b, it is possible to prevent problems with the actuator 5, such as problems such as the inability to maintain the operating positions of the boom 111, arm 112, and bucket 113 (the inability to maintain the pressure in the hydraulic cylinder).

[0052] Furthermore, since the leak measurement results are easily affected by the oil temperature, it is desirable to take into account the value of an oil temperature sensor (not shown) installed at a key point in the circuit, such as the tank 40, when measuring the leak, and use the results as information for management, replacement, and maintenance decisions.

[0053] As described above, according to the first embodiment, it is possible to measure leakage from only a specific on-off valve (on-off valve 25b in the above example) among the multiple on-off valves 25a, 25b, 25d, and 25d. Therefore, it is possible to replace only the on-off valve with the largest leakage amount, improving maintenance efficiency.

[0054] In Flow 1, the directional control valves 30a, 30c, and 30d are switched to their third operating positions 30a8, 30c8, and 30d8, and the directional control valve 30b is switched to its second operating position 30b6. Then, pressure oil is introduced into the on-off valve 25b from the pump 1a side, thereby measuring the leakage of pressure oil from flow path L12 to L14. That is, the leakage from one of the two ports of the on-off valve 25b can be measured. Furthermore, because the pump 1a is a bi-directional pump, the leakage from the other port of the on-off valve 25b can also be measured by reversing the rotation direction of the pump 1a. Thus, in Flow 1, by switching the rotation direction of the pump 1a between forward and reverse, the leakage of pressure oil introduced into the two ports of the on-off valve 25b from the pump 1a side can be accurately measured.

[0055] In flow 2, directional control valves 30a, 30c, and 30d are switched to normal positions 30a7, 30c7, and 30d7, and directional control valve 30b is switched to first operating position 30b5. Then, by introducing the pressure oil supplied from pumps 1a and 1b to actuator 5 via directional control valves 30a, 30c, and 30d and the pressure oil returned from actuator 5 via directional control valves 30a, 30c, and 30d into on-off valve 25b, it is possible to simultaneously measure the leakage of pressure oil from flow path L15 to flow path L13 and the leakage of pressure oil from flow path L14 to flow path L12. In this way, in flow 2, the return pressure oil from actuator 5 is introduced into on-off valve 25b, allowing the leakage of pressure oil from on-off valve 25b to be measured, thereby preventing the actuator 5 from losing its holding pressure and causing malfunction.

[0056] (Second embodiment) Next, a second embodiment of the present invention will be described. Fig. 7 and Fig. 8 are hydraulic circuit diagrams of a hydraulic excavator according to the second embodiment of the present invention. Fig. 7 is a diagram showing the operation of the hydraulic circuit when leak measurement is performed in flow 1, and Fig. 8 is a diagram showing the operation of the hydraulic circuit when leak measurement is performed in flow 2. As shown in these figures, the second embodiment is characterized by the combination of a closed circuit 60 and an open circuit 70. Therefore, the following will describe the characteristics of the second embodiment, and the same components as those in the first embodiment will be assigned the same reference numerals and will not be described again.

[0057] As shown in Figures 7 and 8, the hydraulic excavator according to the second embodiment is equipped with a closed circuit 60 and an open circuit 70 as hydraulic circuits for driving the actuator 5. The closed circuit 60 is a closed circuit between the pump 1a and the actuator 5, and is configured so that pressure oil circulates between the pump 1a and the actuator 5. On the other hand, the open circuit 70 is an open circuit between the pump 1b and the actuator 5, and is configured so that pressure oil supplied from the pump 1b to the actuator 5 returns to the tank 40. The actuator 5 is driven by pressure oil supplied from the pump 1a, and can also be driven by pressure oil supplied from the pump 1b.

[0058] When the mode switches to leak measurement mode (flow 1), the amount of leakage is measured first when the valve is closed, blocking the flow of pressure oil from pump 1b (P) to actuator 5 (A) (Fig. 7).

[0059] 4A, in accordance with step 42d, the controller 20 turns off the command to the on-off valve 25f to close the specific on-off valve 25f that is the leak measurement target. Then, in accordance with step 42e, the controller 20 issues a command to the directional control valve 30f associated with the on-off valve 25f to switch the directional control valve 30f to the second operating position 30f6 (see also FIG. 3(b)). That is, the flow path (L41 → L42) between the on-off valve 25f and the pump 1b is opened via the directional control valve 30f, the flow path (L43 → L44) between the on-off valve 25f and the leak amount measuring instrument 6 is opened via the directional control valve 30f, and the flow path (L45) between the on-off valve 25f and the actuator 5 is blocked via the directional control valve 30f.

[0060] Furthermore, in accordance with step 42f, a command is given from the controller 20 to the directional control valve 30e to switch the directional control valve 30e to the third operating position (30f8) in order to shut off the on-off valve 25e that is not the object of leakage measurement and the actuator 5. Thereafter, in accordance with step 42g, pressure is applied by the pump 1b, and the amount of oil leaking from the on-off valve 25f is measured by the leak amount measuring instrument 6.

[0061] When measuring leaks, pressurized conditions for measuring leaks from the on-off valve 25f can be created by sucking up oil from the tank 40 and releasing the pressurized oil through the relief valve 31. In this way, leak measurements can be performed on only the on-off valve 25f, and based on the results, it can be determined whether or not to replace only the on-off valve 25f.

[0062] Next, referring to FIG. 4, we move to flow 2, and measure the leakage amount when the valve is closed to block the pressure oil flowing (returning) from the actuator 5(A) to the pump 1b(P) (FIG. 8).

[0063] In step 42h, the controller 20 displays on the monitor in the cab a message instructing the operator to perform a predetermined lever operation. The lever operation is an operation that stabilizes the pressure in the actuator 5, for example, a single operation that operates the actuator 5 to the cylinder end and then relieves the pressure.

[0064] In response to this lever operation, as shown in step 42i, the on-off valve 25e turns on the command, and in order to further communicate with the actuator 5, the controller 20 issues a command to the directional control valve 30e, switching the directional control valve 30e to its normal position (30e7) (see FIG. 8). That is, the flow path (L46 → L47) between the on-off valve 25e and the pump 1b is communicated via the directional control valve 30e, the flow path (L49) between the on-off valve 25e and the leak amount measuring instrument 6 is blocked via the directional control valve 30e, and the flow path (L48 → L50) between the on-off valve 25e and the actuator 5 is communicated via the directional control valve 30e.

[0065] Meanwhile, the controller 20 switches the directional control valve 30f to the first operating position (30f5). That is, the flow path (L41) between the on-off valve 25f, which is the leakage measurement target, and the pump 1b is blocked via the directional control valve 30f, the flow path (L42 → L44) between the on-off valve 25f and the leak amount measuring instrument 6 is open via the directional control valve 30f, and the flow path (L45 → L43) between the on-off valve 25f and the actuator 5 is open via the directional control valve 30f.

[0066] Then, in step 42j, a guidance on the lever holding time is displayed on the monitor inside the cab, and leakage measurement is performed within a predetermined time.

[0067] As a result, when the actuator 5 is operating at a predetermined relief pressure, the pressurized oil leaking from the on-off valve 25f, which is in a closed state, flows into the leak amount measuring instrument 6, making it possible to perform leakage measurement on only the on-off valve 25f, and based on the results, it can be considered whether to replace only the on-off valve 25b.

[0068] The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments and includes various other modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of this embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of this embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of this embodiment with other configurations.

[0069] For example, in this embodiment, the configuration is such that leakage from the on-off valve can be measured both when pressure oil flows from the pump to the actuator and when pressure oil returns from the actuator to the pump, i.e., the configuration is such that both measurements shown in FIGS. 5 and 6 (or FIGS. 7 and 8) are possible. However, if leakage measurement is required only in one case, the directional control valve does not need to have the four operating positions described above. More specifically, in leakage measurement when pressure oil is returned from the actuator to the pump (as in FIGS. 6 and 8), the directional control valve only needs to be switchable between the first operating position and the normal position. On the other hand, in leakage measurement when pressure oil is supplied from the pump to the actuator (as in FIGS. 5 and 7), the directional control valve only needs to be switchable between the second operating position, the normal position, and the third operating position. [Explanation of symbols]

[0070] 1 Hydraulic excavator (work machine) 1a, 1b Hydraulic pump 5 Actuators 6. Leak measurement device (leak measurement means) 10 Recording Device 20 Controller 25a~25f On-off valve 30a~30f Directional valve

Claims

1. A hydraulic pump, an actuator driven by pressure oil from the hydraulic pump; a plurality of on-off valves that connect or block a flow path between the hydraulic pump and the actuator; a leak measurement means for measuring leaks from the plurality of on-off valves; a plurality of directional control valves provided corresponding to the plurality of on-off valves, respectively; a controller for controlling the plurality of on-off valves and the plurality of directional control valves, Each of the directional control valves is a normal position in which a flow path between the hydraulic pump and the on-off valve is communicated, a flow path between the on-off valve and the actuator is communicated, and a flow path between the on-off valve and the leak measurement means is blocked; a first operating position that blocks a flow path between the hydraulic pump and the on-off valve, communicates a flow path between the on-off valve and the actuator, and communicates a flow path between the on-off valve and the leak measurement means; a third operating position in which a flow path between the hydraulic pump and the on-off valve is blocked, a flow path between the on-off valve and the actuator is blocked, and a flow path between the on-off valve and the leak measurement means is blocked. A work machine characterized by:

2. 2. The work machine according to claim 1, The controller a specific on-off valve among the plurality of on-off valves is closed, and the on-off valves other than the specific on-off valve are opened; the directional control valve associated with the specific on-off valve is switched to the first operating position, and the directional control valves associated with the on-off valves other than the specific on-off valve are switched to the normal position, and leakage measurement of the specific on-off valve is performed. A work machine characterized by:

3. 2. The work machine according to claim 1, Each of the directional control valves is a second operating position that connects a flow path between the hydraulic pump and the on-off valve, blocks a flow path between the on-off valve and the actuator, and connects a flow path between the on-off valve and the leak measurement means, A work machine characterized by:

4. 4. The work machine according to claim 3, The controller a specific on-off valve among the plurality of on-off valves is closed, and the on-off valves other than the specific on-off valve are opened; the directional control valve associated with the specific on-off valve is switched to the second operating position, and the directional control valve associated with the on-off valves other than the specific on-off valve is switched to the third operating position, and leakage measurement of the specific on-off valve is performed. A work machine characterized by:

5. The work machine according to claim 1 or 3, The hydraulic pump is a double tilt pump. A work machine characterized by:

6. 5. The work machine according to claim 4, The hydraulic pump is a double-tilt pump, the controller detects leakage in one direction of the specific on-off valve based on forward rotation of the bi-directional rotary pump, and detects leakage in the other direction of the specific on-off valve based on reverse rotation of the bi-directional rotary pump. A work machine characterized by:

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