Hydraulic system for work equipment, and work equipment

Abstract

The response delay of a proportional solenoid valve (45 (145)) is suppressed without excessive increase in power consumption.　A hydraulic system (HS (HS1)) of a work machine (1) is provided with a hydraulic actuator (AC) driven by a hydraulic oil, a control valve (V) that performs switching operation for switching the flow volume of the hydraulic oil supplied to the hydraulic actuator (AC), and a control device (70) for controlling the control valve (V), wherein: the control valve (V) is provided with a solenoid (S) and performs the switch operation on the basis of a current supplied to the solenoid (S); and the control device (70) supplies to the solenoid (S) a shift current (101) for causing the control valve (V) to perform the switching operation and, when the shift current (101) is not being supplied, intermittently supplies a standby current (100), which is lower than the shift current (101) and has a current value (Is) within a range where the control valve (V) does not perform the switching operation.

Description

[Technical Field]

[0001] The present invention relates to a hydraulic system for a work machine such as a rotary excavator (backhoe), and to the work machine. [Background technology]

[0002] Conventionally, known working machines equipped with a hydraulic system include a rotary excavator (backhoe) and the like disclosed in Patent Document 1. The hydraulic system of the working machine disclosed in Patent Document 1 includes a hydraulic actuator, an electromagnetic control valve that controls the flow rate of hydraulic oil supplied to the hydraulic actuator, an operating member operated by an operator, and a control device that controls the current value of a solenoid excitation current supplied to the electromagnetic control valve in accordance with the amount of operation of the operating member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-188825 Summary of the Invention [Problem to be solved by the invention]

[0004] In the work machine disclosed in Patent Document 1, a control device controls an electromagnetic control valve in accordance with the amount of operation of an operating member to operate a hydraulic actuator. However, under low-temperature conditions, such as in cold regions, the temperature of the hydraulic oil drops and the viscous resistance of the hydraulic oil increases. This causes a problem: it takes time from when the operating member is operated and the solenoid of the electromagnetic control valve is excited until the electromagnetic control valve changes position and switches the supply state of hydraulic oil to the hydraulic actuator, resulting in a response delay. For this reason, it is conceivable to supply a weak current while the electromagnetic proportional valve is in an inactive state, thereby improving the response when the electromagnetic proportional valve is subsequently switched.

[0005] However, if such a current is constantly supplied to a non-operating proportional solenoid valve, there are problems in that power consumption increases and a large load is placed on the control device and the like.

[0006] The present invention has been made to solve the problems of the prior art, and has an object to suppress the response delay of a proportional solenoid valve without excessively increasing power consumption. [Means for solving the problem]

[0007] A hydraulic system for a work machine according to one aspect of the present invention includes a hydraulic actuator driven by hydraulic oil, a control valve that performs a switching operation to switch the flow rate of hydraulic oil supplied to the hydraulic actuator, and a control device that controls the control valve, wherein the control valve has a solenoid and performs the switching operation in response to a current supplied to the solenoid, and the control device controls the solenoid to cause the control valve to perform the switching operation. With dither amplitude A shift current is supplied, and when the shift current is not supplied, a current value smaller than the shift current is supplied within a range in which the control valve does not perform the switching operation. and dither amplitude The standby current having The standby current is supplied to the control valve periodically and repeatedly, so that a supply time during which the standby current is supplied to the control valve and a non-supply time during which the standby current is not supplied to the control valve are alternately repeated. Supply intermittently.

[0008] The hydraulic system of the work machine may include a plurality of hydraulic actuators and a plurality of control valves corresponding to the plurality of hydraulic actuators, and the control device may supply the standby current to the solenoids of each of the plurality of control valves at different times. The control device may set the supply time and the non-supply time for each of the plurality of control valves so that, within the non-supply time for each of the plurality of control valves, the supply of the standby current to the solenoids of all of the other control valves is performed at different times without overlapping. The control device may also set the supply time and the non-supply time so that the supply time is shorter than the non-supply time.

[0009] The control valve may include a directional control valve that switches the flow rate of hydraulic oil supplied to the hydraulic actuator, and an electromagnetic proportional valve having the solenoid that operates the directional control valve in response to the shift current.

[0010] The solenoid of the control valve may include a first solenoid that acts to switch the control valve to one side and a second solenoid that acts to switch the control valve to the other side, and the control device may intermittently supply the standby current to one of the first solenoid and the second solenoid that is not supplied with the shift current.

[0011] The control device may simultaneously supply the standby current to the first solenoid and the second solenoid in the control valve when neither the first solenoid nor the second solenoid receives the supply of the shift current.

[0012] The control device may supply the standby current to the first solenoid and the second solenoid at different timings when neither the first solenoid nor the second solenoid in the control valve receives the supply of the shift current.

[0013] The control valve may comprise a directional control valve having a first pressure receiving portion and a second pressure receiving portion, and performing the switching operation in response to a pilot pressure acting on the first pressure receiving portion and the second pressure receiving portion; a first proportional valve that controls the pilot pressure acting on the first pressure receiving portion by the action of the first solenoid; and a second proportional valve that controls the pilot pressure acting on the second pressure receiving portion by the action of the second solenoid; and the control device may intermittently supply the standby current to one of the first proportional valve and the second proportional valve to which the pilot pressure for causing the directional control valve to perform the switching operation is not being supplied.

[0014] A work machine may include the hydraulic system.

[0015] According to the hydraulic system for the work machine, the response delay of the electromagnetic proportional valve can be suppressed without excessively increasing power consumption. [Brief explanation of the drawings]

[0016] [Figure 1]FIG. 1 is a side view of an excavation machine (backhoe) that is an example of a work machine. [Figure 2] 1 is a schematic diagram of a hydraulic system of a work machine that drives various hydraulic actuators in a first embodiment. [Figure 3] FIG. 2 is a hydraulic circuit diagram relating to a boom control valve, an arm control valve, a bucket control valve, and a swing control valve in the first embodiment. [Figure 4] FIG. 2 is a hydraulic circuit diagram relating to a dozer control valve, a swing control valve, a first traveling control valve, a second traveling control valve, and an SP control valve in the first embodiment. [Figure 5] FIG. 3 is a diagram illustrating a standby current supplied by a control device to an electromagnetic proportional valve (solenoid). [Figure 6A] FIG. 3 is a time chart illustrating an example of a pattern relating to the timing at which the control device supplies standby current to each electromagnetic proportional valve (each solenoid). [Figure 6B] FIG. 3 is a time chart showing an example of a pattern relating to the timing at which the control device supplies standby current to the electromagnetic proportional valves (solenoids) of the plurality of control valves. [Figure 6C] FIG. 10 is a time chart showing another example of a pattern relating to the timing at which the control device supplies standby current to the electromagnetic proportional valves (solenoids) of the plurality of control valves. [Figure 7] FIG. 10 is a schematic diagram of a hydraulic system of a work machine that drives various hydraulic actuators in a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.

[0018] [First embodiment] <Overall structure> 1 is a side view showing the overall configuration of a work machine 1. In this embodiment, the work machine 1 is exemplified by an excavation work machine (backhoe), which is a swivel work machine.

[0019] As shown in Fig. 1, the work machine 1 includes a machine body (swivel) 2, a left traveling unit 3L disposed on the left side of the machine body 2, a right traveling unit 3R disposed on the right side of the machine body 2, and a work device 4 attached to the front of the machine body 2. A driver's seat 6 is provided on the machine body 2 where a driver (operator) sits.

[0020] In this embodiment, the direction in which a driver seated in the driver's seat 6 of the work machine 1 faces (the direction of arrow A1 in FIG. 1) is referred to as the forward direction for the work machine 1, and the opposite direction (the direction of arrow A2 in FIG. 1) is referred to as the rear direction. Furthermore, the left side for the work machine 1 is the direction corresponding to the left side as seen by a driver facing forward along arrow A1 (the near side in FIG. 1), and the right side for the work machine 1 is the direction corresponding to the right side as seen by a driver facing forward similarly (the far side in FIG. 1).

[0021] 1 is the longitudinal direction (the longitudinal direction of the aircraft body). Also, the horizontal direction perpendicular to the longitudinal direction K1 is called the transverse direction (the left-right direction) of the aircraft body.

[0022] In this embodiment, the left traveling unit 3L and the right traveling unit 3R are configured as crawler-type traveling units. The left traveling unit 3L is driven by a traveling motor ML, and the right traveling unit 3R is driven by a traveling motor MR.

[0023] The travel motors ML and MR are hydraulic motors. A dozer 7 is attached to the front of the travel frame 11 to which the left travel unit 3L and the right travel unit 3R are attached. The dozer 7 has a blade that is raised and lowered by extending and retracting a dozer cylinder C1.

[0024] The machine body 2 is supported on a traveling frame 11 via a slewing bearing 8 so as to be rotatable about an axis (hereinafter referred to as the "vertical axis") extending in the vertical direction. The machine body 2 is driven to rotate by a slewing motor MT, which is a hydraulic motor (hydraulic actuator AC).

[0025] The machine body 2 has a swivel base plate 9 that swivels around a vertical axis, and a weight 10 supported at the rear of the swivel base plate 9. The swivel base plate 9 is made of a steel plate or the like, and is connected to a swivel bearing 8. A prime mover E1 is mounted at the rear of the machine body 2.

[0026] In this embodiment, the prime mover E1 is an engine, but the prime mover E1 may be an electric motor or a hybrid power system having an engine and an electric motor.

[0027] The machine body 2 has a support bracket 13 at the front. A swing bracket 14 is attached to the support bracket 13 so as to be swingable about a vertical axis. The working device 4 is attached to the swing bracket 14.

[0028] The work device 4 has a boom 15, an arm 16, and a bucket 17 as a work implement. The boom 15 has a base end pivotally attached to the swing bracket 14 so as to be rotatable about an axis (hereinafter referred to as the "horizontal axis") extending in the width direction of the machine body, and a tip end capable of swinging up and down. The arm 16 has a base end pivotally attached to the tip end of the boom 15 so as to be rotatable about the horizontal axis, and a tip end capable of swinging in the fore-and-aft direction K1 or up and down.

[0029] The bucket 17 is provided at the tip of the arm 16 so as to be capable of scooping and dumping. The scooping operation of the bucket 17 is a swing of the bucket 17 relative to the tip of the arm 16 in a direction toward the boom 15, and the dumping operation of the bucket 17 is a swing of the bucket 17 relative to the tip of the arm 16 in a direction away from the boom 15.

[0030] Instead of or in addition to the bucket 17, the work machine 1 can be equipped with another work implement, which is a hydraulic attachment that can be driven by a hydraulic actuator AC.

[0031] The swing bracket 14 is swingable by extension and retraction of a swing cylinder C2 provided in the machine body 2. The boom 15 is swingable by extension and retraction of a boom cylinder C3. The arm 16 is swingable by extension and retraction of an arm cylinder C4.

[0032] The bucket 17 can perform scooping and dumping operations by extending and retracting a bucket cylinder C5 serving as a work tool cylinder. The scooping operation is a movement of the bucket 17 toward the boom 15 relative to the arm 16, and the dumping operation is a movement of the bucket 17 away from the boom 15 relative to the arm 16.

[0033] The dozer cylinder C1, the swing cylinder C2, the boom cylinder C3, the arm cylinder C4, and the bucket cylinder C5 are each a hydraulic cylinder (hydraulic actuator AC).

[0034] As described above, the work machine 1 is equipped with a plurality of hydraulic actuators AC, which include hydraulic motors as the travel motors ML, MR and the swing motor MT, as well as hydraulic cylinders as the dozer cylinder C1, swing cylinder C2, boom cylinder C3, arm cylinder C4, and bucket cylinder C5.

[0035] <Hydraulic system for work equipment> As described above, Fig. 2 shows a schematic configuration of the hydraulic system HS of the work machine 1 for operating the plurality of hydraulic actuators AC (MT, ML, MR, C1 to C5) equipped on the work machine 1. As shown in Fig. 2, the hydraulic system HS of the work machine 1 includes a pressure oil supply unit 20 and a control valve unit CV.

[0036] The pressure oil supply unit 20 is equipped with a first pump 21, which is a main pump for supplying hydraulic oil to operate the hydraulic actuator AC, and a second pump 22, which is a pilot pump for supplying signal pressure oil such as pilot pressure and detection signals.

[0037] The first pump 21 and the second pump 22 are driven by a prime mover E1. The first pump 21 is a variable displacement hydraulic pump, and the second pump 22 is a fixed displacement hydraulic pump. The first pump 21 is, for example, a swash plate-type axial pump whose discharge amount can be changed by changing the angle of the swash plate, and the second pump 22 is, for example, a gear pump. In the following description, the second pump 22 may be referred to as the "hydraulic pump."

[0038] The control valve unit CV is a unit configured by arranging a plurality of control valves V (V1 to V9) that control various hydraulic actuators AC (MT, ML, MR, C1 to C5) driven by hydraulic oil, an inlet block B1, and an outlet block B2 in a row or in a stack, interconnecting them, and connecting them to each other through internal oil passages. The plurality of control valves V can perform a switching operation to switch the flow rate of hydraulic oil supplied to the hydraulic actuators AC.

[0039] It should be noted that the plurality of control valves V do not have to be combined as a control valve unit CV, but may be arranged separately within the work machine 1 and connected by external oil passages.

[0040] 2, the hydraulic system HS of the work machine 1 includes a discharge oil passage 30 and a supply oil passage 31. The discharge oil passage 30 is an oil passage that connects the first pump 21 and the inlet block B1. Therefore, the oil discharged from the first pump 21 is supplied to the inlet block B1 via the discharge oil passage 30, and then supplied to each control valve V (V1 to V9).

[0041] The supply oil passage 31 is an oil passage connected to the second pump 22, and is an oil passage through which the hydraulic oil (discharged oil) discharged from the second pump 22 flows. That is, the discharged oil is supplied to the primary side of the control valve V via the supply oil passage 31 as a pilot source pressure.

[0042] Therefore, by changing the switching position, the multiple control valves V can switch the amount (output) of hydraulic oil discharged (supplied) from the control valve V to the hydraulic actuator AC from the discharge oil passage 30, and the direction of discharge (supply) of the hydraulic oil.

[0043] As shown in FIG. 2, the control valves V include a dozer control valve V1 that controls the dozer cylinder C1, a swing control valve V2 that controls the swing cylinder C2, a first travel control valve V3 that controls the travel motor ML of the left traveling unit 3L, a second travel control valve V4 that controls the travel motor MR of the right traveling unit 3R, a boom control valve V5 that controls the boom cylinder C3, an arm control valve V6 that controls the arm cylinder C4, a bucket control valve V7 that controls the bucket cylinder C5, a swing control valve V8 that controls the swing motor MT, and an SP control valve V9 that controls a hydraulic actuator AC equipped on a hydraulic attachment when the hydraulic attachment is attached as a working tool.

[0044] Although FIG. 2 shows an example in which the plurality of control valves V includes the SP control valve V9, the configuration may not include the SP control valve V9.

[0045] 3 and 4, the control valves V for controlling the hydraulic actuators AC in the control valve unit CV of this embodiment each have a spool and constitute a three-position directional control valve that can be switched to three positions by moving the spool. Note that the control valves V may be two-position or four-position changeover valves other than three-position changeover valves, and the number of changeover positions is not limited.

[0046] Of the multiple control valves V serving as three-position directional control valves, some of the control valves V are a combination of a directional control valve 41 and a pilot-operated electromagnetic proportional valve 45, as shown in Fig. 3. Other control valves V are non-electromagnetic pilot-operated directional control valves 51, as shown in Fig. 4.

[0047] The following describes the control valves V configured by the electromagnetic proportional valves 45 in Fig. 3. These are the boom control valve V5, arm control valve V6, bucket control valve V7, and swing control valve V8, and they configure the hydraulic circuit shown in Fig. 3.

[0048] 3 has a three-position directional control valve 41 that switches its position by moving a spool using the pilot pressure of the hydraulic oil. The directional control valve 41 changes the flow rate of the hydraulic oil supplied to the hydraulic actuator AC to control the operation of the hydraulic actuator AC.

[0049] 3 includes a pair of electromagnetic proportional valves 45 for controlling the switching position of the directional control valve 41. 45 includes a solenoid S, and the solenoid S is excited in response to a supplied current to operate (switch) the directional control valve 41. That is, a first proportional valve 46 serving as an electromagnetic proportional valve 45 is disposed on one side of the moving direction of the spool of the directional control valve 41, and a second proportional valve 47 serving as an electromagnetic proportional valve 45 is disposed on the other side. By receiving a supply of hydraulic oil having a pilot pressure by opening and closing these valves, the spool moves and the switching position of the directional control valve 41 is changed.

[0050] In the following description, the direction switching valve 41 provided in the boom control valve V5 will be referred to as the first switching valve 41A, and the direction switching valve 41 provided in the arm control valve V6 will be referred to as the second switching valve 41B. Furthermore, the direction switching valve 41 provided in the bucket control valve V7 will be referred to as the third switching valve 41C, and the direction switching valve 41 provided in the swing control valve V8 will be referred to as the fourth switching valve 41D. The term "direction switching valve 41" is used to represent the first to fourth switching valves 41A to 41D.

[0051] In the following description, the electromagnetic proportional valve 45 provided in the boom control valve V5 will be referred to as the first electromagnetic valve 45A, and the electromagnetic proportional valve 45 provided in the arm control valve V6 will be referred to as the second electromagnetic valve 45B. The electromagnetic proportional valve 45 provided in the bucket control valve V7 will be referred to as the third electromagnetic valve 45C, and the electromagnetic proportional valve 45 provided in the swing control valve V8 will be referred to as the fourth electromagnetic valve 45D. The electromagnetic proportional valve 45 is a representative name for these first to fourth electromagnetic valves 45A to 45D.

[0052] The direction switching valve 41 can be switched among a first position 41a, a second position 41b, and a neutral position 41c. The direction switching valve 41 is biased to the neutral position 41c by the biasing forces of a neutral spring on one side in the position switching direction (the direction of movement of the spool) and a neutral spring on the other side opposite to the one side, and is switched from the neutral position 41c to the first position 41a or the second position 41b by the pilot pressure of the hydraulic oil from the first proportional valve 46 or the second proportional valve 47, which is an electromagnetic proportional valve 45.

[0053] The directional control valve 41 has a first pressure receiving portion 42 on one side in the position switching direction (the direction of movement of the spool) and a second pressure receiving portion 43 on the other side. When the pilot pressure of the hydraulic oil supplied from the first proportional valve 46 acts on the first pressure receiving portion 42, the directional control valve 41 is switched from the neutral position 41c to the first position 41a. When the pilot pressure of the hydraulic oil supplied from the second proportional valve 47 acts on the second pressure receiving portion 43, the directional control valve 41 is switched from the neutral position 41c to the second position 41b.

[0054] This allows the direction switching valve 41 to switch the amount (output) of hydraulic oil discharged (supplied) from the discharge oil passage 30 to the hydraulic actuator AC and the direction of the hydraulic oil discharge (supply).

[0055] When a current is supplied to the electromagnetic proportional valve 45, the solenoid S is excited and the pilot pressure can be changed. The current supplied to the electromagnetic proportional valve 45 has a dither amplitude. The dither amplitude causes the solenoid S to move slightly, and the electromagnetic proportional valve 45 sends a pressure to the pressure receiving portion of the directional control valve 41. 42,43 The hydraulic oil acting on the valve also pulsates.

[0056] 3, the first proportional valve 46 (one of the electromagnetic proportional valves 45) supplies hydraulic oil to the first pressure-receiving portion 42 of the directional control valve 41, and the second proportional valve 47 (the other electromagnetic proportional valve 45) supplies hydraulic oil to the second pressure-receiving portion 43 opposite the first pressure-receiving portion 42 of the directional control valve 41. The first proportional valve 46 and the second proportional valve 47 are supplied with hydraulic oil discharged from the second pump 22 via the supply oil passage 31.

[0057] The first proportional valve 46 and the second proportional valve 47 each have a solenoid S, and when the solenoid S is excited, they open and supply hydraulic oil to the first pressure receiving portion 42 or the second pressure receiving portion 43 of the directional control valve 41, and apply the pilot pressure of this hydraulic oil to the spool to move the spool and control the switching position of the directional control valve 41.

[0058] The solenoid S of the first proportional valve 46 will be referred to as the first solenoid S1, and the solenoid S of the second proportional valve 47 will be referred to as the second solenoid S2. Furthermore, regardless of whether or not proportional valves 46, 47 are present, the solenoid that operates to switch the spool to one side may be referred to as the first solenoid S1, and the solenoid that operates to switch the spool to the other side may be referred to as the second solenoid S2. In other words, the first proportional valve 46 has a solenoid S (first solenoid S1) and controls the pilot pressure acting on the first pressure receiving portion 42 through the action of the first solenoid S1. The second proportional valve 47 has a solenoid S (second solenoid S2) and controls the pilot pressure acting on the second pressure receiving portion 43 through the action of the second solenoid S2.

[0059] Specifically, the hydraulic system HS of the work machine 1 includes a hydraulic oil passage 32 connected to a supply oil passage 31 and a drain oil passage 33 connected to a hydraulic oil tank T.

[0060] The hydraulic oil passage 32 has a first end connected to the supply oil passage 31, and a second end opposite the first end branches into multiple parts and is connected to the primary side ports (primary ports) of the electromagnetic proportional valve 45 (first proportional valve 46 and second proportional valve 47).

[0061] Therefore, the hydraulic oil passage 32 can supply the hydraulic oil flowing through the supply oil passage 31 to each of the electromagnetic proportional valves 45 (the first proportional valve 46 and the second proportional valve 47). That is, the oil discharged by the second pump 22 is supplied to the electromagnetic proportional valve 45 via the supply oil passage 31 and the hydraulic oil passage 32.

[0062] As shown in FIG. 3, the drain oil passage 33 has a first end connected to the hydraulic oil tank T, and a second end opposite the first end that branches into multiple parts and is connected to the electromagnetic proportional valve 45 and the directional control valve 41.

[0063] Specifically, the second end of the drain oil passage 33 is connected to the oil passage between the discharge side port of the electromagnetic proportional valve 45 and the pressure receiving portion (first pressure receiving portion 42 and second pressure receiving portion 43) of the directional control valve 41, and to the discharge port of the directional control valve 41 (a port for discharging return oil from the hydraulic actuator AC).

[0064] In addition, a throttle 33b is provided in the drain oil passage 33 at a portion (discharge oil passage 33a) that joins the secondary port (secondary port) of the electromagnetic proportional valve 45 and the pressure receiving portion (first pressure receiving portion 42 and second pressure receiving portion 43) of the directional control valve 41.

[0065] Therefore, the drain oil passage 33 can discharge a portion of the hydraulic oil supplied from the electromagnetic proportional valve 45 to the pressure-receiving section (first pressure-receiving section 42 and second pressure-receiving section 43) of the directional control valve 41, as well as the hydraulic oil discharged from the directional control valve 41, into the hydraulic oil tank T.

[0066] As a result, the electromagnetic proportional valve 45 can change its opening depending on the magnitude of the current supplied to it, and supply the hydraulic oil supplied from the hydraulic oil passage 32 to the pressure receiving parts (first pressure receiving part 42 and second pressure receiving part 43) of the directional control valve 41, and discharge it to the drain oil passage 33. In other words, the electromagnetic proportional valve 45 is a valve that controls the hydraulic actuator AC via the directional control valve 41 depending on the current supplied to it.

[0067] In this embodiment, the three-position directional control valve 41 is incorporated into the electromagnetic proportional valve 45, but the electromagnetic proportional valve for operating the spool of the directional control valve 41 may be configured separately from the directional control valve.

[0068] <Joystick operation> As shown in Fig. 3, the hydraulic system HS of the work machine 1 is equipped with a control device 70. The control device 70 is a device configured from electric and electronic circuits, programs stored in a CPU, an MPU, and the like.

[0069] The control device 70 controls various devices included in the work machine 1. For example, the control device 70 can control the prime mover E1 and the rotation speed (prime mover rotation speed) of the prime mover E1. The control device 70 also has a storage unit 70a. The storage unit 70a is a non-volatile memory or the like, and stores various information related to the control of the control device 70.

[0070] In each control valve V, the solenoids S1, S2 of the first proportional valve 46 and the second proportional valve 47, which are electromagnetic proportional valves 45, are connected to the control device 70, and in accordance with the magnitude of the current as a command signal supplied from the control device 70, i.e., the current value I, the electromagnetic proportional valve 45 receives a supply of hydraulic oil having a pilot pressure corresponding to the current value I, thereby switching each directional control valve 41.

[0071] A first operating member 75 that is manually operated by an operator to operate each directional control valve 41 is also connected to the control device 70.

[0072] The first operating member 75 has a sensor 76 that detects the direction and amount of operation. The configuration of the sensor 76 is not particularly limited, and a potentiometer, for example, can be used. The sensor 76 is connected to the control device 70, and outputs the detected direction and amount of operation as a detection signal.

[0073] The control device 70 supplies a current having a current value I corresponding to the amount of operation of the first operating member 75 to the solenoid S (S1, S2) of the electromagnetic proportional valve 45 in the control valve V to be operated. Specifically, as shown in Fig. 3, the control device 70 has a current control unit 70b that controls (defines) the current to be supplied to the solenoid S (S1, S2) of the electromagnetic proportional valve 45 in the control valve V to be operated, according to the direction and amount of operation of the first operating member 75.

[0074] The current control unit 70b is composed of electric and electronic components provided in the control device 70, and a program installed in the storage unit 70a.

[0075] The current control unit 70b defines the current (current value I) to be supplied to the solenoid S (S1, S2) of the electromagnetic proportional valve 45 based on the detection signal output by the sensor 76 to the control device 70 and a control map or a predetermined arithmetic expression pre-stored in the storage unit 70a. As a result, the control device 70 supplies the current defined by the current control unit 70b to the solenoid S (first solenoid S1 or second solenoid S2) of the electromagnetic proportional valve 45 (first proportional valve 46 or second proportional valve 47) in the control valve V to be operated.

[0076] As described above, the current supplied by the control device 70 to the solenoid S (first solenoid S1 or second solenoid S2) of the electromagnetic proportional valve 45 (first proportional valve 46 or second proportional valve 47) in the control valve V to be operated has a dither amplitude.

[0077] In this embodiment, the first operating member 75 includes a first operating tool 75A and a second operating tool 75B.

[0078] The first operating device 75A can operate two operating objects provided on the work implement 1, for example, the first switching valve 41A of the boom control valve V5 and the third switching valve 41C of the bucket control valve V7. In other words, the first operating device 75A can swing the boom 15 and the bucket 17.

[0079] The first operating device 75A also has a first sensor 76a that detects the operating direction and amount of the first operating device 75A as the sensor 76. Therefore, the current control unit 70b defines the current to be supplied to the solenoid S of each of the first solenoid valve 45A and the third solenoid valve 45C based on the detection signal output from the first sensor 76a, and the control device 70 supplies current to the solenoid S of the first solenoid valve 45A and the third solenoid valve 45C.

[0080] For example, when the first operating device 75A is operated in the forward / backward direction, the current control unit 70b defines the current to be supplied to the solenoid S of the first solenoid valve 45A based on the detection signal output from the first sensor 76a, and the control device 70 supplies the current to the solenoid S of the first solenoid valve 45A.

[0081] On the other hand, when the first operating device 75A is operated in the width direction (left-right direction) of the machine body, the current control unit 70b defines the current to be supplied to the solenoid S of the third solenoid valve 45C based on the detection signal output from the first sensor 76a, and the control device 70 supplies the current to the solenoid S of the third solenoid valve 45C. As a result, the control device 70 controls the first switching valve 41A and the third switching valve 41C based on the operation of the first operating device 75A.

[0082] The second operating tool 75B can operate two operating objects provided on the work implement 1, for example, the second switching valve 41B of the arm control valve V6 and the fourth switching valve 41D of the swing control valve V8. In other words, the second operating tool 75B can operate the swing of the arm 16 and the swing drive operation of the swing motor MT.

[0083] The second operating device 75B also has a second sensor 76b that detects the operating direction and amount of the second operating device 75B as the sensor 76. Therefore, the current control unit 70b defines the current to be supplied to the solenoid S of each of the second solenoid valve 45B and the fourth solenoid valve 45D based on the detection signal output from the second sensor 76b, and the control device 70 supplies current to the solenoid S of the second solenoid valve 45B and the fourth solenoid valve 45D.

[0084] For example, when the second operating device 75B is operated in the forward / backward direction, the current control unit 70b defines the current to be supplied to the solenoid S of the second solenoid valve 45B based on the detection signal output from the second sensor 76b, and the control device 70 supplies current to the solenoid S of the second solenoid valve 45B.

[0085] On the other hand, when the second operating device 75B is operated in the width direction (left-right direction) of the machine body, the current control unit 70b defines the current to be supplied to the solenoid S of the fourth solenoid valve 45D based on the detection signal output from the second sensor 76b, and the control device 70 supplies the current to the solenoid S of the fourth solenoid valve 45D. As a result, the control device 70 controls the second selector valve 41B and the fourth selector valve 41D based on the operation of the second operating device 75B.

[0086] The first operating device 75A and the second operating device 75B are configured, for example, by operating levers that are gripped and operated by the driver seated in the driver's seat 6. This operating lever may be one that can rotate (tilt) in the front-to-rear direction and in the vehicle width direction (left-to-right direction) as described above, or may be a joystick that can rotate (tilt) in all directions from a neutral position.

[0087] <Pilot Operation> The control valves V configured as the pilot-operated switching valve 51 in Fig. 4 will be described below. These are the dozer control valve V1, swing control valve V2, first travel control valve V3, second travel control valve V4, and SP control valve V9, and form a hydraulic circuit as shown in Fig. 4.

[0088] 4, the operating device 55 has a pilot valve 56 that supplies hydraulic oil (pilot oil) having pilot pressure to the control valves V (V1 to V4, V9), and a second operating member 57 that operates the pilot valve 56. The second operating member 57 is composed of, for example, an operating lever or pedal arranged around the driver's seat 6.

[0089] A pilot-operated switching valve 51 serving as a control valve V can be switched among a first position 51a, a second position 51b, and a neutral position 51c. The pilot-operated switching valve 51 is biased toward the neutral position 51c by the biasing forces of a neutral spring on one side of the switching direction and a neutral spring on the other side opposite the one side, and is switched from the neutral position 51c to the first position 51a or the second position 51b by the pressure of the hydraulic oil output from a pilot valve 56.

[0090] Furthermore, the pilot-operated switching valve 51 has a third pressure-receiving portion 52 on one side in the switching direction and a fourth pressure-receiving portion 53 on the other side. Furthermore, a primary-side port (primary port) of the pilot valve 56 is connected to a second end of the hydraulic oil passage 32, and the hydraulic oil supplied from the hydraulic oil passage 32 can be supplied from the secondary-side port (secondary port) to the pressure-receiving portions (third pressure-receiving portion 52 and fourth pressure-receiving portion 53) of the pilot-operated switching valve 51.

[0091] Therefore, when the hydraulic oil supplied from the pilot valve 56 acts on the third pressure receiving portion 52, the pilot operated switching valve 51 is switched from the neutral position 51c to the first position 51a. Furthermore, when the hydraulic oil supplied from the pilot valve 56 acts on the fourth pressure receiving portion 53, the pilot operated switching valve 51 is switched from the neutral position 51c to the second position 51b. This allows the pilot operated switching valve 51 to switch the amount (output) of hydraulic oil discharged (supplied) from the discharge oil passage 30 to the hydraulic actuator AC and the direction of the hydraulic oil discharge (supply).

[0092] In addition, the hydraulic system HS of the work machine 1 may be configured such that at least one of the multiple control valves V is a control valve V incorporating an electromagnetic proportional valve 45, and the control valves V incorporating an electromagnetic proportional valve 45 are not limited to the boom control valve V5, the arm control valve V6, the bucket control valve V7, and the swing control valve V8.

[0093] For example, the control valve V incorporating the electromagnetic proportional valve 45 may be any one of the dozer control valve V1, swing control valve V2, first travel control valve V3, second travel control valve V4, and SP control valve V9, and the combination thereof is not limited.

[0094] <Intermittent standby current> As shown in FIG. 5, in the hydraulic system HS of the work machine 1, the control device 70 controls the solenoid S of the electromagnetic proportional valve 45 for changing the position of the directional control valve 41 that controls each hydraulic actuator AC by supplying a standby current having a predetermined current value Is to the solenoid S. 100 The control device 70 intermittently supplies a standby current to the first proportional valve 46 and the second proportional valve 47 to which the pilot pressure for causing the directional control valve 41 to perform the switching operation is not supplied. 100 supply.

[0095] The standby current 100 is a weak current supplied to the solenoid S of the electromagnetic proportional valve 45 to suppress a decrease in the responsiveness of the electromagnetic proportional valve 45, for example, when the electromagnetic proportional valve 45 is switched from a neutral position that has been in place for a long time to an operating position.

[0096] Therefore, this standby current 100 is supplied to the solenoid S of the electromagnetic proportional valve 45 while the electromagnetic proportional valve 45 is in the neutral position, and when the first operating member 75 or the like is subsequently operated to move it from the position it had been holding, the electromagnetic proportional valve 45 responds favorably and operates to change the switching position of the directional control valve 41.

[0097] 5, the standby current 100 is intermittently supplied to the solenoid proportional valve 45. That is, periods when the standby current 100 is supplied and periods when it is not supplied are alternately repeated. This reduces the total current value used by the control device 70 compared to when the standby current 100 is constantly supplied, thereby suppressing heat generation by the control device 70 and reducing power consumption.

[0098] Preferably, as shown in FIG. 5, the total current value supplied by the control device 70 can be reduced by extending the time during which the standby current 100 is not supplied and shortening the time during which the standby current 100 is supplied.

[0099] These time settings are arbitrary, and the time during which the standby current 100 is supplied may be longer than the time during which the standby current 100 is not supplied, or the time during which the standby current 100 is supplied may be approximately the same as the time during which the standby current 100 is not supplied.

[0100] Furthermore, in order to prevent malfunction of the directional control valve 41, i.e., to prevent an erroneous change in switching position, the current value Is of the standby current 100 is set to be smaller than the minimum current value Imin of the shift current 101, which will be described later, required to start the spool, within a range in which the directional control valve 41 does not perform a switching operation, and is set to a value equal to or greater than the minimum current value required to ensure good responsiveness of the spool.

[0101] In other words, the current value Is of the standby current 100 supplied to the electromagnetic proportional valve 45 is a current value that is set so as not to change the current position of the directional control valve 41 while ensuring the good responsiveness desired for the electromagnetic proportional valve 45.

[0102] In the control valve unit CV of this embodiment, each control valve V constitutes one section, and the control valve unit CV is made up of a combination of multiple sections. More specifically, as shown in Fig. 3, the control valve unit CV is provided with multiple sections each made up of an electromagnetic proportional valve 45 including a directional control valve 41, and also with a section made up of a pilot-operated switching valve 51, as shown in Fig. 4. The supply of the standby current 100 described above is applied to the section made up of the electromagnetic proportional valve 45 shown in Fig. 3.

[0103] The first solenoid S1 of the first proportional valve 46 and the second solenoid S2 of the second proportional valve 47 each receive current supplied from the control device 70 and supply hydraulic oil as pilot pressure to the directional control valve 41 in the same section (control valve V) to change the switching position of the directional control valve 41.

[0104] The current supplied to each of the first solenoid S1 of the first proportional valve 46 and the second solenoid S2 of the second proportional valve 47 in order to supply pilot pressure (hydraulic oil) for performing the switching operation (position change) of the directional control valve 41 is referred to as a shift current 101. The shift current 101 has a current value equal to or greater than the minimum current value Imin.

[0105] 6A shows an example of a supply pattern of standby current 100 to the first solenoid S1 (first proportional valve 46) and the second solenoid S2 (second proportional valve 47) in each section (control valve V). When neither the first solenoid S1 (first proportional valve 46) nor the second solenoid S2 (second proportional valve 47) receives current, the directional control valve 41 is disposed in the neutral position 41c. At this time, both the first solenoid S1 (first proportional valve 46) and the second solenoid S2 (second proportional valve 47) are intermittently supplied with standby current 100.

[0106] In the pattern shown in FIG. 6A, the standby current 100 is supplied to the first solenoid S1 (first proportional valve 46) and the second solenoid S2 (second proportional valve 47) in the same section simultaneously, and the current supply time is also the same.

[0107] When the shift current 101 is supplied to the electromagnetic proportional valve 45 in an inoperative state in which neither the first solenoid S1 (first proportional valve 46) nor the second solenoid S2 (second proportional valve 47) receives the shift current 101 to change the switching position of the directional control valve 41, the shift current 101 is supplied to one of the first solenoid S1 (first proportional valve 46) and the second solenoid S2 (second proportional valve 47), and the other continues to not receive the shift current 101 but continues to receive the intermittent supply of the standby current 100.

[0108] 6A, a shift current 101 is supplied to the first solenoid S1 (first proportional valve 46) to switch the directional control valve 41 from the neutral position 41c to the first position 41a. During this time, a standby current 100 is intermittently supplied to the second solenoid S2 (second proportional valve 47), which is not supplied with the shift current 101 and is in an inactive state.

[0109] Since the second solenoid S2 (second proportional valve 47) has been in an inactive state since before the shift current 101 was supplied to the first solenoid S1 (first proportional valve 46), the second solenoid S2 continues to receive the standby current 100 while the first solenoid S1 (first proportional valve 46) is receiving the shift current 101, even after a set period of no current supply since the previous supply of the standby current 100.

[0110] 6B and 6C each show an example of a supply pattern of standby current 100 to the electromagnetic proportional valves 45 (45A, 45B, 45C, 45D) of the multiple control valves V in the control valve unit CV. In both examples, the standby current 100 is supplied to the multiple control valves V at different timings for each electromagnetic proportional valve 45 (solenoid S).

[0111] This reduces the total amount of current output from the control device 70 at one time compared to when the standby current 100 is applied to multiple electromagnetic proportional valves 45 simultaneously, contributing to improved durability of the control device 70.

[0112] Furthermore, in the embodiment of FIG. 6B, when neither the first solenoid S1 nor the second solenoid S2 in the electromagnetic proportional valve 45 of each control valve V is supplied with the shift current 101 for changing the position of the directional control valve 41, that is, when neither the first proportional valve 46 nor the second proportional valve 47 is supplied with the pilot pressure for causing the directional control valve 41 to perform a switching operation, a standby current 100 is simultaneously supplied to the first solenoid S1 and the second solenoid S2.

[0113] This makes it possible to simplify the control of the supply timing of the standby current 100, which tends to be complicated. Directional switching valve 41 On both ends of the spool simultaneous A standby current of 100 is supplied to Directional switching valve 41 This can reliably prevent malfunction.

[0114] On the other hand, in the embodiment of FIG. 6C, the first solenoid S1 and the second solenoid S2 in the electromagnetic proportional valve 45 of each control valve V are S2 When neither the first proportional valve 46 nor the second proportional valve 47 is supplied with the shift current 101 for changing the position of the directional control valve 41, that is, when neither the first proportional valve 46 nor the second proportional valve 47 is supplying the pilot pressure for causing the directional control valve 41 to perform a switching operation, the timing at which the standby current 100 is supplied to the first solenoid S1 and the second solenoid S2 is made to differ.

[0115] This further enhances the effect of reducing the total amount of current output from the control device 70 at one time.

[0116] [Second embodiment] FIG. 7 shows a hydraulic system HS1 for a work machine according to another embodiment (second embodiment).

[0117] The following description of the hydraulic system HS1 for a work machine of the second embodiment will focus on configurations that differ from those of the embodiment described above (first embodiment), and configurations that are common to the first embodiment will be given the same reference numerals and detailed description will be omitted.

[0118] The hydraulic system HS1 of the second embodiment differs from the hydraulic system HS of the first embodiment in that the control valve V, which in the first embodiment is constituted by a pilot-type electromagnetic proportional valve 45, is changed to a direct-acting electromagnetic proportional valve 145.

[0119] <Explanation of solenoid proportional valve> The direct acting electromagnetic proportional valve 145 is a valve that controls the flow of hydraulic oil to the hydraulic actuator AC by directly moving a spool with a solenoid without using a pilot valve.

[0120] That is, the electromagnetic proportional valve 145 shown in Fig. 7 has a first solenoid S1 disposed on one side of the spool movement direction and a second solenoid S2 disposed on the other side, without going through the proportional valves 46 and 47 as shown in Fig. 3. That is, the solenoid that acts to move the spool of the electromagnetic proportional valve 145 (directional switching valve 41) to one side is the first solenoid S1, and the solenoid that acts to move the spool to the other side is the second solenoid S2.

[0121] In this embodiment, the electromagnetic proportional valve 145 of the boom control valve V5 is referred to as a first electromagnetic valve 145A, the electromagnetic proportional valve 145 of the arm control valve V6 is referred to as a second electromagnetic valve 145B, the electromagnetic proportional valve 145 of the bucket control valve V7 is referred to as a third electromagnetic valve 145C, and the electromagnetic proportional valve 145 of the swing control valve V8 is referred to as a third electromagnetic valve 145C. 1 45 is referred to as a fourth solenoid valve 145D. The solenoid proportional valve 145 is a representative name for the first solenoid valve 145A to the fourth solenoid valve 145D.

[0122] 7 has a main valve portion that is a three-position switching type directional control valve like the directional control valve 41. The position of the electromagnetic proportional valve 145 is switched between the neutral position 45c and the first position 45a, or between the neutral position 45c and the second position 45b, by the movement of a spool caused by supplying a shift current 101 to the first solenoid S1 or the second solenoid S2.

[0123] More specifically, when the shift current 101 is supplied to the first solenoid S1, the first solenoid S1 is energized to move the spool of the electromagnetic proportional valve 145, and the electromagnetic proportional valve 145 switches from the neutral position 45c to the first position 45a. On the other hand, when the shift current 101 is supplied to the second solenoid S2, the second solenoid S2 is energized to move the spool of the electromagnetic proportional valve 145, and the electromagnetic proportional valve 145 switches from the neutral position 45c to the second position 45b.

[0124] The supply pattern of the standby current 100 to the solenoids S1, S2 of each electromagnetic proportional valve 145 shown in Fig. 7 and the supply pattern of the standby current 100 to the plurality of electromagnetic proportional valves 145 (145A, 145B, 145C, 145D) are the same as the supply pattern of the standby current 100 to the electromagnetic proportional valve 45 in the first embodiment. That is, the intermittent supply pattern of the standby current 100 described above with reference to Figs. 5, 6A, 6B, and 6C is adopted.

[0125] <Effects> The hydraulic system HS (HS1) of the work machine described above comprises a hydraulic actuator AC driven by hydraulic oil, a control valve V that performs a switching operation to switch the flow rate of hydraulic oil supplied to the hydraulic actuator AC, and a control device 70 that controls the control valve V. The control valve V has a solenoid S, and performs a switching operation in response to a current supplied to the solenoid S. The control device 70 supplies a shift current 101 to the solenoid S to cause the control valve V to perform a switching operation, and also controls the shift current 101 when the shift current 101 is not being supplied. 101 A standby current 100 having a current value Is smaller than the value I S and within a range in which the control valve V does not perform a switching operation is intermittently supplied.

[0126] According to the above configuration, the current supplied to the solenoid S of the control valve V is not interrupted for a long period of time. This solves the problem of delay in starting the operation of the control valve V when current is supplied again after the current has not been supplied to the solenoid S of the control valve V for a long period of time.

[0127] The hydraulic system HS (HS1) configured as described above includes a plurality of hydraulic actuators AC and a plurality of control valves V corresponding to the plurality of hydraulic actuators AC. The control device 70 supplies standby current 100 to the solenoids S of the plurality of control valves V at different timings.

[0128] According to the above configuration, the control device 70 does not supply the standby current 100 to a plurality of control valves V at one time, and therefore the load caused by the flow of the standby current 100 can be reduced.

[0129] In the hydraulic system HS having the above configuration, the control valve V includes a directional control valve 41 for switching the flow rate of hydraulic oil supplied to the hydraulic actuator AC, and a shift current 101 and an electromagnetic proportional valve 45 having a solenoid S that operates the directional control valve 41 in response to the pressure.

[0130] According to the above configuration, the above-mentioned effect due to the intermittent supply of the standby current 100 to the solenoid S can be achieved in the pilot type electromagnetic proportional valve 45.

[0131] In the hydraulic system HS (HS1) configured as described above, the solenoid S of the control valve V includes a first solenoid S1 that acts to switch the control valve V to one side, and a second solenoid S2 that acts to switch the control valve V to the other side. The control device 70 intermittently supplies a standby current 100 to either the first solenoid S1 or the second solenoid S2 that is not supplied with a shift current 101.

[0132] According to the above configuration, the control device 70 supplies the standby current 100, thereby improving the response of the solenoid S1 or S2 that is not receiving the supply of the shift current 101 when it subsequently receives the supply of the shift current 101, while the standby current 100 is not supplied to the solenoid S1 or S2 that is receiving the supply of the shift current 101, so that the hydraulic actuator AC can be more reliably prevented from operating unintentionally.

[0133] Furthermore, in the hydraulic system HS (HS1) configured as described above, when neither the first solenoid S1 nor the second solenoid S2 in the control valve V is supplied with the shift current 101, the control device 70 simultaneously supplies the standby current 100 to the first solenoid S1 and the second solenoid S2.

[0134] According to the above configuration, it is possible to simplify the control of the supply timing of the standby current 100, which tends to be complicated.

[0135] Alternatively, in the hydraulic system HS (HS1) configured as described above, when neither the first solenoid S1 nor the second solenoid S2 in the control valve V is supplied with the shift current 101, the control device 70 supplies the standby current 100 to the first solenoid S1 and the second solenoid S2 at different timings.

[0136] According to the above configuration, the control device 70 does not supply the standby current 100 to the first solenoid S1 and the second solenoid S2 at the same time, so that the load caused by the flow of the standby current 100 can be reduced.

[0137] Furthermore, in the hydraulic system HS having the above configuration, the control valve V is provided with a directional control valve 41 having a first pressure receiving portion 42 and a second pressure receiving portion 43, and performing a switching operation in response to the pilot pressure acting on the first pressure receiving portion 42 and the second pressure receiving portion 43, and an electromagnetic proportional valve 45 having a first proportional valve 46 that controls the pilot pressure acting on the first pressure receiving portion 42 by the action of a first solenoid S1, and a second proportional valve 47 that controls the pilot pressure acting on the second pressure receiving portion by the action of a second solenoid S2, and the control device 70 intermittently supplies standby current 100 to one of the first proportional valve 46 and the second proportional valve 47 that does not receive the pilot pressure for causing the directional control valve 41 to perform a switching operation.

[0138] According to the above configuration, the above-mentioned effect obtained by intermittently supplying the standby current 100 to the first solenoid S1 and the second solenoid S2 can be achieved in the first proportional valve 46 and the second proportional valve 47, which are pilot type electromagnetic proportional valves.

[0139] The work machine 1 also includes the hydraulic system HS (HS1) configured as described above.

[0140] According to the above configuration, the above-mentioned effects due to the intermittent supply of standby current 100 can be achieved in work machine 1.

[0141] Although the present invention has been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0142] 1: Work equipment 41: Directional valve 45: Solenoid proportional valve 46: First proportional valve 47: Second proportional valve 70: Control device 100: Standby current 101: Shift current 145: Solenoid proportional valve AC: Hydraulic actuator I: Current value Imin: Minimum current value (of the shift current) Is: (Standby current) current value HS: Hydraulic system HS1: Hydraulic system S: Solenoid S1: First solenoid S2: Second solenoid V: Control valve

Claims

1. a hydraulic actuator driven by hydraulic oil; a control valve that performs a switching operation to switch the flow rate of hydraulic oil supplied to the hydraulic actuator; a control device that controls the control valve; Equipped with the control valve includes a solenoid, and performs the switching operation in response to a current supplied to the solenoid; The control device supplies, to the solenoid, a shift current having a dither amplitude for causing the control valve to perform the switching operation, and, when the shift current is not being supplied, periodically and intermittently supplies a standby current having a current value and dither amplitude smaller than the shift current and within a range in which the control valve does not perform the switching operation, so that a supply time in which the standby current is supplied to the control valve and a non-supply time in which the standby current is not supplied to the control valve alternately and repeatedly. Hydraulic system of the implement.

2. A plurality of the hydraulic actuators are provided, a plurality of the control valves respectively corresponding to the plurality of hydraulic actuators; The hydraulic system for a work machine according to claim 1 , wherein the control device supplies the standby current to the solenoids of the plurality of control valves at different timings.

3. A hydraulic system for a work machine as described in Claim 2, wherein the control device sets the supply time and the non-supply time for each of the plurality of control valves so that, within the non-supply time for each of the plurality of control valves, the supply of the standby current to the solenoids of all other control valves is performed at different times without overlapping.

4. A hydraulic system of a work machine described in any one of claims 1 to 3, wherein the control device sets the supply time and the non-supply time so that the supply time is shorter than the non-supply time.

5. 4. The hydraulic system for a work machine according to claim 1, wherein the control valve comprises a directional control valve that switches the flow rate of hydraulic oil supplied to the hydraulic actuator, and an electromagnetic proportional valve having the solenoid that operates the directional control valve in accordance with the shift current.

6. The solenoid of the control valve includes a first solenoid that operates to switch the control valve to one side and a second solenoid that operates to switch the control valve to the other side, The hydraulic system of a work machine according to any one of claims 1 to 3, wherein the control device intermittently supplies the standby current to one of the first solenoid and the second solenoid that is not receiving the supply of the shift current.

7. 7. The hydraulic system of a work machine according to claim 6, wherein the control device simultaneously supplies the standby current to the first solenoid and the second solenoid in the control valve when neither the first solenoid nor the second solenoid receives the supply of the shift current.

8. 7. The hydraulic system of a work machine according to claim 6, wherein the control device supplies the standby current to the first solenoid and the second solenoid at different timings when neither the first solenoid nor the second solenoid in the control valve receives the supply of the shift current.

9. The control valve is a directional control valve having a first pressure receiving portion and a second pressure receiving portion, and performing the switching operation in response to a pilot pressure acting on the first pressure receiving portion and the second pressure receiving portion; an electromagnetic proportional valve including a first proportional valve that controls a pilot pressure acting on the first pressure receiving portion by the action of the first solenoid, and a second proportional valve that controls a pilot pressure acting on the second pressure receiving portion by the action of the second solenoid, 7. The hydraulic system for a work machine according to claim 6, wherein the control device intermittently supplies the standby current to one of the first proportional valve and the second proportional valve to which a pilot pressure for causing the directional control valve to perform the switching operation is not supplied.

10. A work machine comprising the hydraulic system for a work machine according to any one of claims 1 to 3.

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