Hydraulic system for work equipment, and work equipment

Abstract

The present invention suppresses a reduction in the response speed of an electromagnetic proportional valve (45) at low temperatures.　This hydraulic system (S) for a work machine (1) comprises: a hydraulic actuator (AC); a direction switching valve (41); an electromagnetic proportional valve (45); a control device (70) that controls current supplied to the electromagnetic proportional valve (45); an operation member (75) for a worker to operate the hydraulic actuator (AC); and a permission operating tool (77) that can switch between a permitting operation for permitting driving of the hydraulic actuator (AC) and a non-permitting operation for not permitting driving, wherein, when the permission operating tool (77) is performing the non-permitting operation and the temperature of hydraulic fluid is below a prescribed temperature, the control device (70) supplies, to the electromagnetic proportional valve (45), a first standby current of a first current value (Ia) defined in a range where a switching position of the direction switching valve (41) is not switched.

Description

[Technical Field]

[0001] The present invention relates to a hydraulic system for a work machine and to a work machine. [Background technology]

[0002] BACKGROUND ART A working machine disclosed in Patent Document 1 is known in the prior art.

[0003] The work machine disclosed in Patent Document 1 comprises a hydraulic actuator operated by hydraulic oil, an electromagnetic control valve that controls the flow rate of hydraulic oil flowing to the hydraulic actuator, an operating member that accepts operation of the hydraulic actuator by an operator (worker), and a control device that controls the opening degree of the electromagnetic control valve according to the amount of operation of the operating member, and the electromagnetic control valve is an electromagnetic three-position switching valve in which the position of a spool is switched by hydraulic oil (pilot oil). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-188825 Summary of the Invention [Problem to be solved by the invention]

[0005] In the work machine of Patent Document 1, the control device controls the opening degree of the electromagnetic control valve in accordance with the amount of operation of the operating member, thereby being able to operate the hydraulic actuator.

[0006] However, under low temperature conditions such as in cold regions, the temperature of the hydraulic oil becomes low and the viscosity resistance of the hydraulic oil increases, which causes a problem of delayed response.

[0007] The present invention has been made to solve the problems of the prior art, and has an object to suppress the decrease in the response speed of a proportional solenoid valve at low temperatures. [Means for solving the problem]

[0008] A hydraulic system for a work machine according to one aspect of the present invention comprises a hydraulic actuator driven by hydraulic oil, a directional control valve that controls the operation of the hydraulic actuator by changing the flow rate of the hydraulic oil supplied to the hydraulic actuator, an electromagnetic proportional valve that controls the switching position of the directional control valve by exciting a solenoid in response to a supplied current, a control device that controls the current supplied to the electromagnetic proportional valve, an operating member with which an operator operates the hydraulic actuator, and an enabling operation tool that can be switched between an enabling operation that enables operation of the hydraulic actuator and a disabling operation that does not enable operation, the electromagnetic proportional valve includes a first electromagnetic proportional valve for switching the switching position of the directional control valve to a first position, and a second electromagnetic proportional valve for switching the switching position of the directional control valve to a second position opposite to the first position, The control device is configured to, when the permitted operation tool is operated in the prohibited manner and the temperature of the hydraulic oil is lower than a predetermined temperature, generate a first standby current of a first current value defined within a range in which the switching position of the directional control valve does not switch. the first solenoid proportional valve and the second solenoid proportional valve Supply to When the permitting operation tool is permitted and the operating member is operated, a current having a current value corresponding to the operating direction and the operating amount of the operating member is supplied to the first electromagnetic proportional valve and the second electromagnetic proportional valve corresponding to the hydraulic actuator operated by the operating member. do.

[0009] When the temperature of the hydraulic oil is equal to or higher than the predetermined temperature, the control device outputs a second standby current having a second current value lower than the first current value to a hydraulic actuator that is not being operated by the operating member. the first solenoid proportional valve and the second solenoid proportional valve may be supplied to

[0010] The control device is configured to: when the permitted operation tool is permitted to perform the operation and the temperature of the hydraulic oil is lower than the predetermined temperature, the first solenoid proportional valve and the second solenoid proportional valve The first standby current or a second standby current having a second current value that is lower than the first current value may be supplied to the power supply.

[0011] The control device is configured to: When the temperature is lower than the predetermined temperature, the hydraulic actuator corresponding to the hydraulic actuator that is not being operated by the operating member is the first solenoid proportional valve and the second solenoid proportional valveand when the permitted operating tool is operated in the permitted manner and the temperature of the hydraulic oil is equal to or higher than the predetermined temperature, the second standby current may be passed to the electromagnetic proportional valve corresponding to the hydraulic actuator that is not being operated by the operating member.

[0012] When the permitted operation tool is operated in the prohibited manner and the temperature of the hydraulic oil is equal to or higher than the predetermined temperature, the first solenoid proportional valve and the second solenoid proportional valve It may be configured so that no current is supplied to the

[0013] The control device generates a dither current obtained by adding an oscillation component to the first current value as the first standby current. the first solenoid proportional valve and the second solenoid proportional valve may be supplied to

[0014] A hydraulic system for a work machine according to another aspect of the present invention includes a hydraulic actuator driven by hydraulic oil, a directional control valve that controls the operation of the hydraulic actuator by changing the flow rate of the hydraulic oil supplied to the hydraulic actuator, an electromagnetic proportional valve that controls the switching position of the directional control valve by exciting a solenoid in response to a supplied current, a control device that controls the current supplied to the electromagnetic proportional valve, an operating member with which an operator operates the hydraulic actuator, and an enabling operation tool that can be switched between an enabling operation that allows the hydraulic actuator to be driven and a disabling operation that does not allow the drive. a hydraulic oil tank that stores the hydraulic oil; a hydraulic pump that draws in and discharges the hydraulic oil from the hydraulic oil tank; a supply oil line connected to the hydraulic pump; a hydraulic oil line that is connected to the supply oil line and the electromagnetic proportional valve and supplies the hydraulic oil from the supply oil line to the electromagnetic proportional valve; and a warm-up oil line that circulates the hydraulic oil discharged by the hydraulic pump to the hydraulic oil tank via the hydraulic oil line when the permitted operating device is subjected to the unauthorized operation. and when the permitted operation tool is operated in the prohibited manner and the temperature of the hydraulic oil is lower than a predetermined temperature, the control device supplies to the solenoid proportional valve a first standby current having a first current value defined within a range in which the switching position of the directional control valve does not switch. .

[0015] The hydraulic system of the work machine may include an unloading valve that switches to a supply position to supply the hydraulic oil from the supply oil line to the hydraulic oil line when the permitted operating device is operated in the permitted manner, and switches to a suppression position to suppress the supply of hydraulic oil to the hydraulic oil line when the permitted operating device is operated in the unauthorized manner, and the warm-up oil line may connect the supply oil line and the hydraulic oil line in parallel to the unloading valve.

[0016] The permission operation tool may be a lever lock that can be swung to perform the permission operation or the non-permission operation.

[0017] A work machine may include the hydraulic system. [Effects of the Invention]

[0018] According to the hydraulic system for the work machine, it is possible to suppress a decrease in the response speed of the electromagnetic proportional valve at low temperatures. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. [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] 4 is a diagram showing the relationship between the magnitude (current value) of the current supplied to the electromagnetic proportional valve and the secondary pressure supplied from the electromagnetic proportional valve to the directional control valve. FIG. [Figure 5] 10 is a flowchart showing the definition of a predetermined current by a current control unit and the supply of the predetermined current by a control device. [Figure 6] FIG. 10 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 a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.

[0021] [First embodiment] 1 is a side view showing the overall configuration of a work machine 1. In this embodiment, a backhoe, which is a rotating work machine, is exemplified as the work machine 1.

[0022] 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 worker (operator) sits.

[0023] In this embodiment, the direction in which an operator 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, and the opposite direction (the direction of arrow A2 in FIG. 1) is referred to as the rearward direction. The left side of the operator (the near side in FIG. 1) is referred to as the left side, and the right side of the operator (the far side in FIG. 1) is referred to as the right side. Therefore, the K1 direction in FIG. 1 is the fore-and-aft direction (the fore-and-aft direction of the machine body). The horizontal direction perpendicular to the fore-and-aft direction K1 is referred to as the width direction of the machine body.

[0024] 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. The traveling motors ML and MR are configured by hydraulic motors (hydraulic actuators AC). A dozer unit 7 is mounted on the front of the traveling frame 11 to which the left traveling unit 3L and the right traveling unit 3R are mounted. The dozer unit 7 can be raised and lowered (raised and lowered its blade) by extending and contracting a dozer cylinder C1.

[0025] The machine body 2 is supported on a traveling frame 11 so as to be rotatable about a vertical axis (an axis extending in the up-down direction) via a slewing bearing 8. The machine body 2 is driven to rotate by a slewing motor MT consisting of a hydraulic motor (hydraulic actuator AC).

[0026] 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 formed from 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. The prime mover E1 is an engine. The prime mover E1 may be an electric motor, or may be a hybrid type 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 working implement. The boom 15 has a base pivotally attached to the swing bracket 14 so as to be rotatable about a horizontal axis (an axis extending in the width direction of the machine body), and is capable of swinging up and down. The arm 16 has a base pivotally attached to the tip of the boom 15 so as to be rotatable about a horizontal axis, and is capable of swinging in the fore-and-aft direction K1 or up and down. The bucket 17 is provided on the tip of the arm 16 so as to be able to perform scooping and dumping operations. Instead of or in addition to the bucket 17, the work machine 1 can be equipped with another working implement (hydraulic attachment) that can be driven by a hydraulic actuator AC.

[0029] 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. The bucket 17 is capable of scooping and dumping operations by extension and retraction of a bucket cylinder C5 serving as a work tool cylinder. The dozer cylinder C1, swing cylinder C2, boom cylinder C3, arm cylinder C4, and bucket cylinder C5 are configured as hydraulic cylinders (hydraulic actuators AC).

[0030] Fig. 2 shows a schematic configuration of a hydraulic system S of the work machine 1 for operating the various hydraulic actuators AC (MT, ML, MR, C1 to C5) described above (equipped on the work machine 1). As shown in Fig. 2, the hydraulic system S of the work machine 1 includes a pressure oil supply unit 20 and a control valve CV.

[0031] The pressure oil supply unit 20 is equipped with a first pump (main pump) 21 for supplying hydraulic oil to operate the hydraulic actuator AC, and a second pump (pilot pump) 22 for supplying signal pressures such as pilot pressure and detection signals. The first pump 21 and the second pump 22 are driven by a prime mover E1 and draw in and discharge hydraulic oil from a hydraulic oil tank T. The first pump 21 is configured as a variable displacement hydraulic pump (swash plate type variable displacement axial pump) whose discharge rate can be changed by changing the angle of the swash plate. The second pump 22 is configured as a fixed displacement gear pump. In the following description, the second pump 22 may be referred to as the "hydraulic pump."

[0032] The control valve CV is composed of 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, which are arranged (stacked) in one direction and interconnected, and are connected to each other by internal oil passages.

[0033] 2, the hydraulic system S 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).

[0034] 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 (discharge oil) discharged from the second pump 22 flows. In other words, the discharge oil is supplied as a pilot source pressure to the primary side of the control valve V via the supply oil passage 31. Therefore, by changing the switching positions, the multiple control valves V can switch the discharge amount (output) and discharge direction of the hydraulic oil supplied from the discharge oil passage 30. In this way, the multiple control valves V control the hydraulic actuator AC.

[0035] 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 a hydraulic attachment is attached as a working tool. Note that while FIG. 2 shows an example in which the control valve V includes the SP control valve V9, the control valve V may be configured not to include the SP control valve V9.

[0036] 3 shows a schematic configuration of a hydraulic circuit related to the boom control valve V5, arm control valve V6, bucket control valve V7, and swing control valve V8 in the first embodiment. At least one of the multiple control valves V is an electromagnetic three-position switching valve in which the position of a spool is switched according to the value of current I supplied thereto. Specifically, at least one of the multiple control valves V has a directional control valve 41 and an electromagnetic proportional valve 45, and by changing the opening of the electromagnetic proportional valve 45 according to the value of current I supplied thereto, the pressure of pilot oil acting on the spool of the directional control valve 41 can be changed, thereby changing the position of the spool.

[0037] 3, in this embodiment, the boom control valve V5, arm control valve V6, bucket control valve V7, and swing control valve V8 are electromagnetic three-position switching valves incorporating the above-mentioned electromagnetic proportional valve 45. In other words, the boom control valve V5, arm control valve V6, bucket control valve V7, and swing control valve V8 each have a directional control valve 41 and an electromagnetic proportional valve 45.

[0038] In the following description, the direction switching valve 41 of the boom control valve V5 is referred to as the first switching valve 41A, and the direction switching valve 41 of the arm control valve V6 is referred to as the second switching valve 41B. Furthermore, the direction switching valve 41 of the bucket control valve V7 is referred to as the third switching valve 41C, and the direction switching valve 41 of the swing control valve V8 is referred to as the fourth switching valve 41D.

[0039] 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. Furthermore, 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.

[0040] The directional control valve 41 is a direct acting spool type switching valve that controls the operation of the hydraulic actuator AC by changing the flow rate of hydraulic oil supplied to the hydraulic actuator AC, and can change its switching position using hydraulic oil supplied from the solenoid proportional valve 45. The spool of the directional control valve 41 is moved in proportion to the flow rate of hydraulic oil supplied from the solenoid proportional valve 45, and an amount of hydraulic oil proportional to the amount of movement of the spool is supplied to the hydraulic actuator AC to be operated.

[0041] 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 held in the neutral position 41c by the biasing force 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 41c to the first position 41a or the second position 41b by the pressure of the hydraulic oil output from the electromagnetic proportional valve 45.

[0042] The direction switching valve 41 has a first pressure receiving portion 42 on one side in the switching direction and a second pressure receiving portion 43 on the other side. Therefore, when the hydraulic oil supplied from the electromagnetic proportional valve 45 acts on the first pressure receiving portion 42, the direction switching valve 41 is switched from the neutral position 41c to the first position 41a. When the hydraulic oil supplied from the electromagnetic proportional valve 45 acts on the second pressure receiving portion 43, the direction switching valve 41 is switched from the neutral position 41c to the second position 41b. This allows the direction switching valve 41 to switch the discharge amount (output) of the hydraulic oil supplied from the discharge oil passage 30 and the discharge direction of the hydraulic oil.

[0043] The electromagnetic proportional valve 45 controls the switching position of the directional control valve 41 by exciting a solenoid (not shown) in response to the current supplied. Specifically, when current is supplied to the electromagnetic proportional valve 45, the solenoid is excited and changes its opening, thereby changing the flow rate of hydraulic oil acting on the pressure receiving parts 42 and 43. The current supplied to the electromagnetic proportional valve 45 has a dither amplitude. In other words, the current supplied to the electromagnetic proportional valve 45 is a dither current to which an oscillation component has been added. The dither amplitude causes the solenoid to vibrate slightly, and the hydraulic oil acting on the pressure receiving parts 42 and 43 of the directional control valve 41 from the electromagnetic proportional valve 45 also pulsates.

[0044] 3, the solenoid proportional valve 45 has a first proportional valve 46 that supplies hydraulic oil to the first pressure receiving portion 42 of the directional control valve 41, and a second proportional valve 47 that supplies hydraulic oil to the second pressure receiving portion 43 on the opposite side of the directional control valve 41 from the first pressure receiving portion 42. 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.

[0045] Specifically, the hydraulic system S 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 that stores hydraulic oil. The hydraulic oil passage 32 has a first end connected to the supply oil passage 31, and a second end opposite the first end branching into multiple parts that are connected to primary ports (primary ports) of the electromagnetic proportional valves 45 (first proportional valve 46 and second proportional valve 47). 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 (first proportional valve 46 and 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.

[0046] 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 branching into multiple parts that are connected to the electromagnetic proportional valve 45 and the directional control valve 41. Specifically, the second end of the drain oil passage 33 is connected to an oil passage between a discharge port of the electromagnetic proportional valve 45 and pressure receiving parts (first pressure receiving part 42 and second pressure receiving part 43) of the directional control valve 41, and to a discharge port (a port for discharging return oil from the hydraulic actuator AC) of the directional control valve 41. A throttle 33b is provided in a portion (discharge oil passage 33a) of the drain oil passage 33 that joins a port (secondary port) on the secondary side of the electromagnetic proportional valve 45 and the pressure receiving parts (first pressure receiving part 42 and second pressure receiving part 43) of the directional control valve 41.

[0047] 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 parts (first pressure receiving part 42 and second pressure receiving part 43) of the directional switching valve 41, and the hydraulic oil discharged from the directional switching valve 41, to the hydraulic oil tank T. As a result, the electromagnetic proportional valve 45 can change its opening depending on the magnitude of the current supplied, 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 switching valve 41, and discharge it to the drain oil passage 33.

[0048] Although this embodiment shows an electromagnetic three-position switching valve incorporating the electromagnetic proportional valve 45 and the directional control valve 41, the electromagnetic proportional valve 45 may be configured separately from the directional control valve 41. Furthermore, the configuration is not limited to switching the operation of the directional control valve 41 using pilot hydraulic oil, and the electromagnetic proportional valve 45 may directly drive the spool of the directional control valve 41. Furthermore, the multiple control valves V may be two-position switching valves, four-position switching valves, etc. other than three-position switching valves, and are not limited thereto.

[0049] As shown in FIG. 3, the hydraulic system S of the work machine 1 includes a control device 70. The control device 70 is a device configured from electric and electronic circuits, programs stored in a CPU, an MPU, etc. 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 of the prime mover E1 (prime mover rotation speed). The control device 70 also includes a memory unit 70a. The memory unit 70a is a non-volatile memory or the like, and stores various information related to the control of the control device 70.

[0050] The solenoid of the electromagnetic proportional valve 45 is connected to the control device 70, and the electromagnetic proportional valve 45 changes its opening depending on the magnitude of the current (current value I, command signal) supplied from the control device 70, and switches each directional control valve 41 using a pilot pressure according to the current value I. In addition, a first operating member 75 that operates each directional control valve 41 is connected to the control device 70.

[0051] The first operating member (operating member) 75 is an operating tool used by an operator to operate the hydraulic actuator AC. The first operating member 75 has a sensor 76 that detects the operating direction and amount. 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 operating direction and amount as a detection signal. In the following description, the first operating member 75 may be simply referred to as the "operating member."

[0052] The control device 70 supplies a current of a current value I corresponding to the amount of operation of the first operating member 75 to the solenoid of the electromagnetic proportional valve 45 to be operated. Specifically, as shown in Fig. 3, the control device 70 has a current control unit 70b that controls (defines) the current supplied to the electromagnetic proportional valve 45 (solenoid) according to the direction and amount of operation of the first operating member 75.

[0053] The current control unit 70b is composed of electric and electronic components provided in the control device 70, and a program installed in the memory unit 70a. The current control unit 70b defines the current (current value I) to be supplied to the electromagnetic proportional valve 45 (solenoid) based on the detection signal output by the sensor 76 to the control device 70 and a control map or a predetermined calculation formula pre-stored in the memory unit 70a. As a result, the control device 70 supplies the current defined by the current control unit 70b to the solenoid of the electromagnetic proportional valve 45 to be operated. Note that the current supplied by the control device 70 to the solenoid of the electromagnetic proportional valve 45 to be operated has a dither amplitude, as described above.

[0054] In this embodiment, the first operating member 75 includes a first operating tool 75A and a second operating tool 75B. The first operating tool 75A can operate two operation targets provided on the work implement 1, for example, the first selector valve 41A and the third selector valve 41C. In other words, the first operating tool 75A can swing the boom 15 and the bucket 17. The first operating tool 75A also has a first sensor 76a as the sensor 76 that detects the direction and amount of operation of the first operating tool 75A. Therefore, the current control unit 70b defines the currents to be supplied to 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 the currents to the first solenoid valve 45A and the third solenoid valve 45C.

[0055] 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 first solenoid valve 45A based on the detection signal output from the first sensor 76a, and the control device 70 supplies current to the first solenoid valve 45A. On the other hand, when the first operating device 75A is operated in the width direction of the aircraft body, the current control unit 70b defines the current to be supplied to 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 third solenoid valve 45C. In this way, the control device 70 controls the first selector valve 41A and the third selector valve 41C based on the operation of the first operating device 75A.

[0056] The second operating device 75B can operate two operating objects provided on the work implement 1, for example, the second switching valve 41B and the fourth switching valve 41D. In other words, the second operating device 75B can swing the arm 16 and rotate the swing motor MT. The second operating device 75B also has, as the sensor 76, a second sensor 76b that detects the direction and amount of operation of the second operating device 75B. Therefore, the current control unit 70b defines the current to be supplied to 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 the current to the second solenoid valve 45B and the fourth solenoid valve 45D.

[0057] 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 second solenoid valve 45B based on the detection signal output from the second sensor 76b, and the control device 70 supplies the current to the second solenoid valve 45B. On the other hand, when the second operating device 75B is operated in the width direction of the aircraft body, the current control unit 70b defines the current to be supplied to 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 fourth solenoid valve 45D. In this way, 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.

[0058] The first operating tool 75A and the second operating tool 75B are configured by operating levers that are gripped and operated by an operator seated in the driver's seat 6, for example.

[0059] In this embodiment, as shown in FIG. 3, the boom control valve V5, arm control valve V6, bucket control valve V7, and swing control valve V8 are electromagnetic three-position switching valves incorporating the aforementioned electromagnetic proportional valve 45. Meanwhile, the dozer control valve V1, swing control valve V2, first travel control valve V3, second travel control valve V4, and SP control valve V9 are configured as pilot-operated switching valves that are pilot-operated by an operating device (not shown). The operating device has a pilot valve that outputs pilot pressure (pilot oil) to the control valves V (V1 to V4, V9) and a second operating member that operates the pilot valve. The second operating member is configured, for example, by an operating lever or pedal arranged around the operator's seat 6.

[0060] In the hydraulic system S of the work machine 1, at least one of the multiple control valves V may be 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, arm control valve V6, bucket control valve V7, and swing control valve V8. For example, the control valve V incorporating an 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.

[0061] As shown in Fig. 3, the hydraulic system S of the work machine 1 includes an enabling operation device 77 and an unloading valve 60. The enabling operation device 77 is an operation device that can be switched between an enabling operation that enables operation of the hydraulic actuator AC and a disabling operation that does not enable operation. Specifically, the enabling operation device 77 is a lever lock 77 that can be swung to enable or disable operation.

[0062] As shown in Fig. 1, lever lock 77 is provided to the side of driver's seat 6 at a position corresponding to the accessway (boarding / alighting path) 5 through which workers get on and off. Lever lock 77 is supported so as to be swingable between a lowered state (lowered position) 77a, which is a first direction, and a raised state (raised position) 77b, which is a second direction opposite to the first direction. More specifically, lever lock 77 can be permitted by swinging it to lower position 77a, and when lever lock 77 is swung to lower position 77a, it closes accessway 5 to driver's seat 6, disabling ingress and egress.

[0063] On the other hand, the lever lock 77 can be operated to prohibit access by swinging it to the raised position 77b, and when the lever lock 77 is swung to the raised position 77b, it opens the boarding and alighting passage 5 to allow boarding and alighting.

[0064] 3, the lever lock 77 has a permission switch 78. The permission switch 78 is a switch that can be switched between two positions, and detects the switching operation (permission operation and non-permission operation) of the lever lock 77. The permission switch 78 is also connected to the control device 70, and outputs a detection signal to the control device 70 when the switching operation is detected.

[0065] The unloading valve 60 is a valve that permits or prohibits the operation of the hydraulic actuator AC in response to the operation of an enabling operating device (lever lock) 77. The unloading valve 60 is provided between the supply oil passage 31 and the hydraulic oil passage 32. Specifically, as shown in FIG. 2, the unloading valve 60 has a primary side port (primary port) 60a connected to the supply oil passage 31, a secondary side port (secondary port) 60b connected to the hydraulic oil passage 32, and a discharge port 60c connected to the hydraulic oil tank T.

[0066] The unloading valve 60 is a two-position selector valve that can be switched between a supply position (load position) 61 that permits the operation of the hydraulic actuator AC and a suppression position (unload position) 62 that suppresses the operation of the hydraulic actuator AC. When the lever lock 77 is operated to permit, the unloading valve 60 switches to the supply position 61 that supplies hydraulic oil from the supply oil passage 31 to the hydraulic oil passage 32. In the supply position 61, the unloading valve 60 connects the supply oil passage 31 to the starting end of the hydraulic oil passage 32.

[0067] On the other hand, when the lever lock 77 is operated to the unauthorized position, the unloading valve 60 is switched to a suppression position 62 which suppresses the supply of hydraulic oil to the hydraulic oil passage 32, i.e., stops the supply of hydraulic oil from the supply oil passage 31 to the hydraulic oil passage 32. In the suppression position 62, the unloading valve 60 cuts off communication between the supply oil passage 31 and the start end of the hydraulic oil passage 32, and connects the start end of the supply oil passage 31 to the discharge port 60c.

[0068] The unloading valve 60 is biased by a spring in a direction that switches it to the suppression position 62, and is switched to the suppression position 62 when the solenoid is de-energized, and is switched to the supply position 61 when the solenoid is energized. The switching control of the unloading valve 60 is performed by a control device 70.

[0069] The control device 70 controls the current supplied to the solenoid of the unloading valve 60 based on the detection signal output from the permission switch 78, in other words, the switching operation of the lever lock 77. Specifically, when the permission switch 78 detects the permission operation of the lever lock 77 (when the lever lock 77 is in the down position 77a), the control device 70 supplies current to the solenoid of the unloading valve 60 to excite the solenoid and switch the unloading valve 60 to the supply position 61.

[0070] On the other hand, when the permission switch 78 detects an unauthorized operation of the lever lock 77 (when the lever lock 77 is in the up position 77b), the control device 70 stops supplying current to the solenoid of the unloading valve 60, activates the solenoid, and switches the unloading valve 60 to the suppression position 62.

[0071] As a result, when the lever lock 77 is switched (permitted) to the lowered position 77a, the unloading valve 60 switches to the supply position 61, and the hydraulic oil (pilot oil) discharged by the second pump 22 is supplied to the solenoid proportional valve 45 and the primary side port of the pilot-operated switching valve via the supply oil passage 31, the unloading valve 60, and the hydraulic oil passage 32, making it possible to operate the hydraulic actuators AC (MR, ML, MT, C1 to C5).

[0072] On the other hand, when the lever lock 77 is switched to the up position 77b (non-permitted operation), the unloading valve 60 switches to the suppression position 62, and hydraulic oil is no longer supplied to the primary side ports of the solenoid proportional valve 45 and the pilot-operated switching valve, making it impossible to operate the hydraulic actuators AC (MR, ML, MT, C1 to C5).

[0073] In the hydraulic system S of the work machine 1, when the permitted operating device 77 is in an unauthorized operation and the temperature of the hydraulic oil is below a predetermined temperature (threshold value), the control device 70 supplies to the electromagnetic proportional valve 45 a current (first standby current) of a first current value Ia defined within a range in which the switching position of the directional control valve 41 does not switch.

[0074] It is preferable that the first current value Ia is defined as a current value I that is as large as possible within a range in which the switching position of the directional control valve 41 does not change.

[0075] Furthermore, when the permitted operation device 77 is in an unauthorized operation state and the temperature of the hydraulic oil is equal to or higher than a predetermined temperature (threshold value), the control device 70 continuously or intermittently supplies a current (second standby current) of a second current value Ib smaller than the first current value Ia to each solenoid proportional valve 45. This makes it possible to improve the response speed of the solenoid proportional valve 45.

[0076] Furthermore, when the permitted operation of the operating device 77 is permitted and the temperature of the hydraulic oil is below a predetermined temperature (threshold), the control device 70 continuously or intermittently supplies a current of a first current value Ia (first standby current) or a current of a second current value Ib (second standby current) to the solenoid proportional valve 45 that is not being operated by the operating member (first operating member) 75. In this embodiment, when the permitted operation of the operating device 77 is permitted and the temperature of the hydraulic oil is below a predetermined temperature (threshold), the control device 70 supplies the first standby current to the solenoid proportional valve 45 that is not being operated by the first operating member 75.

[0077] In addition, when the permission operating device 77 is operated in a permission manner and the temperature of the hydraulic oil is above a predetermined temperature (threshold value), the control device 70 continuously or intermittently supplies a current of the second current value Ib (second standby current) to the electromagnetic proportional valve 45 that is not being operated by the operating member (first operating member) 75.

[0078] In the following description, the first standby current and the second standby current may be simply referred to as "standby current." The current control unit 70b determines whether the conditions for flowing a standby current to the electromagnetic proportional valve 45 are met, and if the current control unit 70b determines that the conditions are met, it defines the current to be supplied to the electromagnetic proportional valve 45 (solenoid).

[0079] The current control unit 70b determines whether the temperature of the hydraulic oil detected by a detection device 79 provided in the hydraulic system S of the work machine 1 is lower than a predetermined temperature (threshold value). The detection device 79 is a device that detects the temperature (oil temperature) of the hydraulic oil such as pilot oil in the hydraulic system S of the work machine 1. The detection device 79 is made up of an oil temperature sensor, and is provided at one of the ports of the second pump 22 to which the hydraulic oil tank T is connected.

[0080] As shown in FIG. 3, the detection device 79 is connected to the control device 70 and outputs the detected oil temperature as a detection signal to the control device 70. The threshold value is defined in advance and stored in the memory unit 70a. The control device 70 determines whether the oil temperature acquired from the detection device 79 is lower than the threshold value stored in the memory unit 70a. The threshold value is defined as a value within a range of 25°C to 35°C, for example. Note that the threshold value is not limited to the range of 25°C to 35°C. The threshold value may be defined as a fixed value, or may be changeable using an operating tool (not shown) provided on the work machine 1 or a mobile terminal connected to the control device 70 so as to be able to communicate with the work machine 1.

[0081] Furthermore, the current control unit 70b determines whether the prime mover E1 is operating based on a signal for starting the prime mover E1 that is output to the control device 70. Specifically, the current control unit 70b determines whether the prime mover E1 is operating based on a signal that is output from the ignition switch 71 to the control device 70.

[0082] The ignition switch 71 is a switch for starting the prime mover E1. The ignition switch 71 is connected to the control device 70, which starts and stops the prime mover E1 based on signals (start signal and stop signal) output from the ignition switch 71. Specifically, when the ignition switch 71 is turned ON, it outputs a start signal to the control device 70, and the control device 70 starts the prime mover E1 through predetermined processing. On the other hand, when the ignition switch 71 is turned OFF, it outputs a stop signal to the control device 70, and the control device 70 stops driving the prime mover E1. Note that the ignition switch 71 is not limited to a mechanical type (key cylinder type) that is operated by inserting an engine key into a key cylinder, but may be a smart entry type that permits or prohibits prime mover starting via wireless communication.

[0083] Therefore, when a start signal is output from the ignition switch 71 to the control device 70, the current control unit 70b determines that the prime mover E1 is operating, and when a stop signal is output, it determines that the prime mover E1 is stopped.

[0084] The standby currents (first standby current and second standby current) defined by the current control unit 70b will be described in detail below. The current control unit 70b defines the first standby current as the standby current to be passed through the solenoid proportional valve 45 when the temperature of the hydraulic oil is below a predetermined temperature (threshold value). Specifically, the current control unit 70b defines the first standby current for both the first proportional valve 46 and the second proportional valve 47. Specifically, when the temperature of the hydraulic oil is below the predetermined temperature (threshold value) and the permitted operation of the permitted operating device 77 is in the prohibited operation (when the unloading valve 60 is in the suppression position 62), the current control unit 70b defines the first standby current for both the first proportional valve 46 and the second proportional valve 47 of each solenoid proportional valve 45. In addition, when the temperature of the hydraulic oil is below a predetermined temperature (threshold value) and the permission operating device 77 is in a permission operation (when the unload valve 60 is in the supply position 61), the current control unit 70b defines a first standby current for the electromagnetic proportional valves 45 that are not operated by the first operating member 75, among the electromagnetic proportional valves 45 provided in the hydraulic system S of the work machine 1.

[0085] On the other hand, when the temperature of the hydraulic oil is equal to or higher than a predetermined temperature (threshold), the current control unit 70b defines a second standby current, which is a current with a second current value Ib lower than the first current value Ia of the first standby current, as the standby current to be passed through the solenoid proportional valve 45. Specifically, when the temperature of the hydraulic oil is equal to or higher than the predetermined temperature (threshold) and the permitted operation device 77 is in an unauthorized state (when the unloading valve 60 is in the suppression position 62), the current control unit 70b defines the second standby current for both the first proportional valve 46 and the second proportional valve 47 of each solenoid proportional valve 45. Furthermore, when the temperature of the hydraulic oil is equal to or higher than the predetermined temperature (threshold) and the permitted operation device 77 is in an authorized state (when the unloading valve 60 is in the supply position 61), the current control unit 70b defines the second standby current for the solenoid proportional valve 45 that is not operated by the first operating member 75, among the solenoid proportional valves 45 provided in the hydraulic system S of the work machine 1.

[0086] The magnitudes of the standby currents (first current value Ia, second current value Ib) for the first solenoid valve 45A to the fourth solenoid valve 45D may be the same for each solenoid valve, or may be different for each solenoid valve.

[0087] When the permitted operation of the operating device 77 is permitted (when the unloading valve 60 is in the supply position 61), the current control unit 70b identifies the first proportional valve 46 and the second proportional valve 47 that are not being operated based on the detection signal output from the sensor 76. The current control unit 70b defines a standby current for the identified first proportional valve 46 and second proportional valve 47. That is, in this embodiment, for example, when neither the first operating device 75A nor the second operating device 75B is being operated, the standby current is defined for all of the first solenoid valve 45A, the second solenoid valve 45B, the third solenoid valve 45C, and the fourth solenoid valve 45D that are not being operated by the first operating device 75A and the second operating device 75B.

[0088] Furthermore, for example, when the first operating device 75A is operated only in the forward and backward directions and the second operating device 75B is not operated, the current control unit 70b defines a current to be supplied to the first solenoid valve 45A operated by the first operating device 75A in accordance with the amount of operation of the first operating device 75A based on the detection signal output from the first sensor 76a, and defines a standby current for the second solenoid valve 45B, the third solenoid valve 45C, and the fourth solenoid valve 45D that are not operated by the first operating device 75A and the second operating device 75B.

[0089] Hereinafter, with reference to FIG. 4, the magnitude Ia of the first standby current defined by the current control unit 70b will be described in detail. FIG. 4 is a diagram showing the relationship between the magnitude (current value) I of the current supplied to the electromagnetic proportional valve 45 and the secondary pressure supplied from the electromagnetic proportional valve 45 to the direction switching valve 41. FIG. 4 shows a case where the unloading valve 60 is switched to the supply position 61 and the hydraulic oil discharged by the second pump 22 is supplied to the electromagnetic proportional valve 45 as the primary pressure. In the graph of FIG. 4, the horizontal axis represents the magnitude (current value, command signal) I of the current supplied by the control device 70 to the electromagnetic proportional valve 45, and the vertical axis represents the secondary pressure of the hydraulic oil supplied to the pressure receiving portions (first pressure receiving portion 42, second pressure receiving portion 43) of the direction switching valve 41 when the electromagnetic proportional valve 45 is supplied with current and the solenoid is excited to change the opening degree.

[0090] As shown in FIG. 4, when the current supplied to the electromagnetic proportional valve 45 is within a predetermined range (Is ≦ I < Imax), the secondary pressure output by the electromagnetic proportional valve 45 increases as the current increases. When the current supplied to the electromagnetic proportional valve 45 is less than Is (I < Is), the secondary pressure output by the electromagnetic proportional valve 45 becomes zero and is constant. When the current supplied to the electromagnetic proportional valve 45 is Imax or more (I ≧ Imax), the secondary pressure output by the electromagnetic proportional valve 45 becomes Pmax and is constant.

[0091] Also, in FIG. 4, the minimum value (starting pressure) of the pressure of the hydraulic oil whose switching position of the direction switching valve 41 changes is indicated by Pmin. When the electromagnetic proportional valve 45 outputs the starting pressure Pmin, the current value (starting current value) of the current supplied to the electromagnetic proportional valve 45 is Imin. That is, when the current value I of the current supplied to the electromagnetic proportional valve 45 is less than the starting current value Imin, the pressure of the pilot hydraulic oil acting on the direction switching valve 41 becomes less than the starting pressure Pmin, and the switching position of the direction switching valve 41 does not change.

[0092] The current control unit 70b defines a current of a first current value Ia that is smaller than Imin as the first standby current. For example, when Imin is 1.0 A, the current control unit 70b defines the first current value Ia to be less than 1.0 A. The first standby current is a dither current obtained by adding an oscillation component to the first current value Ia.

[0093] As shown in FIG. 4, the first current value Ia and the second current value Ib are current values I that are smaller than the starting current value Imin (Ia < Imin, Ib < Imin). Also, the second current value Ib is a current value I that is lower than the first current value Ia (Ib < Ia). The second standby current is a dither current obtained by adding an oscillation component to the second current value Ib.

[0094] Therefore, when the prime mover E1 is driven, the temperature of the working oil is less than a predetermined temperature (threshold value), the permission operating tool 77 is not permitted to operate, and the unloading valve 60 is in the suppression position 62, the current control unit 70b defines a first standby current (a current of the first current value Ia) for the first proportional valve 46 and the second proportional valve 47. Thereby, the control device 70 supplies the first standby current to the first proportional valve 46 and the second proportional valve 47, and the solenoids of the first proportional valve 46 and the second proportional valve 47 supplied with the first standby current vibrate according to the dither amplitude. Also, the first proportional valve 46 and the second proportional valve 47 supplied with the first standby current supply the working oil of the first secondary pressure Pa to the pressure receiving portions (the first pressure receiving portion 42 and the second pressure receiving portion 43) of the direction switching valve 41. Since the first secondary pressure Pa is smaller than the starting pressure Pmin of the direction switching valve 41, the switching position of the direction switching valve 41 is not changed, and the working oil flowing from the first proportional valve 46 and the second proportional valve 47 toward the pressure receiving portions 42 and 43 of the direction switching valve 41 is discharged through the discharge oil passage 33a and the throttle 33b. Therefore, by the vibration of the solenoid and the circulation of the working oil, the electromagnetic proportional valve 45 and the working oil inside thereof can be warmed up.

[0095] On the other hand, when the prime mover E1 is operating and the temperature of the hydraulic oil is equal to or higher than a predetermined temperature (threshold value), the current control unit 70b defines a second standby current (current with a second current value Ib) for the not-operated first proportional valve 46 and second proportional valve 47. As a result, the control device 70 supplies the second standby current to the not-operated first proportional valve 46 and second proportional valve 47, and the solenoids of the first proportional valve 46 and second proportional valve 47 to which the second standby current is supplied vibrate. This makes it possible to warm up the solenoid proportional valve 45 and the hydraulic oil therein.

[0096] According to the above configuration, when the temperature of the hydraulic oil is below a predetermined temperature (threshold value), the permitting operation device 77 is operated to prohibit the operation, and the unloading valve 60 is in the inhibiting position 62, the control device 70 supplies a first standby current to the solenoid of the electromagnetic proportional valve 45, thereby vibrating the solenoid with the first standby current, thereby warming up the electromagnetic proportional valve 45 and the hydraulic oil therein. On the other hand, when the temperature is relatively high, the control device 70 supplies a second standby current, which has a current value lower than the first standby current, to the first proportional valve 46 and the second proportional valve 47, thereby suppressing a response delay of the electromagnetic proportional valve 45 and reducing the load.

[0097] In the above-described embodiment, the control device 70 supplies the second standby current to each solenoid proportional valve 45 when the permitted operation device 77 is in an unauthorized operation and the temperature of the hydraulic oil is equal to or higher than a predetermined temperature (threshold value). However, it is also possible not to supply current to each solenoid proportional valve 45. This improves the response speed of the solenoid proportional valve 45 at low temperatures, and suppresses the current at times other than low temperatures, thereby reducing power consumption and suppressing heat generation in the control device 70. Furthermore, a standby current may be supplied to the first proportional valve 46 and the second proportional valve 47 that are not being operated, regardless of the temperature of the hydraulic oil.

[0098] In the above-described embodiment, the current control unit 70b defines a constant current of the first current value Ia or the second current value Ib in accordance with the operation (permitted operation or non-permitted operation) of the permitted operating device 77. The magnitude of the current may be at least less than the current value (starting current value) Imin corresponding to the starting pressure Pmin, and may be decreased as the temperature of the hydraulic oil increases, for example. In other words, the standby current value Iw may be increased as the temperature of the hydraulic oil decreases. The magnitude Iw of the first current value Ia and the second current value Ib may be changeable using an operating device (not shown) provided on the work machine 1 or a mobile terminal connected to the control device 70 so as to be able to communicate with the work machine 1.

[0099] The flow of how the current control unit 70b defines the current value I will be described below with reference to the flowchart shown in FIG.

[0100] The current control unit 70b monitors whether the prime mover E1 is operating or not based on a signal (start signal) output from the ignition switch 71 to the control device 70 (S1).

[0101] When the current control unit 70b determines that the prime mover E1 is operating (S1, Yes), it determines whether the permission operating device 77 is being operated in a permission manner based on the detection signal output from the permission switch 78 to the control device 70 (S2).

[0102] If it is determined in S2 that operation is permitted (S2, Yes), the current control unit 70b determines whether there is an electromagnetic proportional valve 45 being operated by the first operating member 75 based on the detection signal output from the sensor 76 to the control device 70 (S3).

[0103] When it is determined in S3 that there is an operated solenoid proportional valve 45 (S3, Yes), the current control unit 70b defines the current value I to be supplied to the operated solenoid proportional valve 45 in accordance with the operation direction and operation amount of the first operating member 75 (S4). The current control unit 70b defines the current value I to be supplied to the solenoid proportional valve 45 based on, for example, the operation direction and operation amount of the first operating member 75 and a control map or a predetermined arithmetic expression stored in advance in the memory unit 70a.

[0104] If it is determined in S3 that there is no electromagnetic proportional valve 45 being operated (S3, No), or after defining the current value I to be supplied to the electromagnetic proportional valve 45 being operated in S4, the current control unit 70b determines whether there is any electromagnetic proportional valve 45 that is not being operated by the first operating member 75 based on the detection signal output from the sensor 76 to the control device 70 (S5).

[0105] If it is determined in S5 that there is an electromagnetic proportional valve 45 that is not being operated (S5, Yes), the current control unit 70b determines whether the temperature of the hydraulic oil is below a threshold value (predetermined temperature) based on the detection signal output from the detection device 79 (S6).

[0106] If it is determined in S6 that the temperature of the hydraulic oil is below the threshold value (S6, Yes), the current control unit 70b defines the current value I supplied to the non-operated solenoid proportional valve 45 as the first current value Ia (S7a). On the other hand, if it is determined in S6 that the temperature of the hydraulic oil is not below the threshold value (S6, No), the current control unit 70b defines the current value I supplied to the non-operated solenoid proportional valve 45 as the second current value Ib (S7b). Note that the processing of S6 may be omitted, and the current control unit 70b may define the current value I supplied to the non-operated solenoid proportional valve 45 as the second current value Ib regardless of the temperature of the hydraulic oil.

[0107] If it is determined in S2 that no permitted operation has been performed (S2, No), the current control unit 70b determines whether the temperature of the hydraulic oil is below a threshold value (predetermined temperature) based on the detection signal output from the detection device 79 (S8).

[0108] If it is determined in S8 that the temperature of the hydraulic oil is below the threshold value (S8, Yes), the current control unit 70b defines the current value I to be supplied to each solenoid proportional valve 45 as a first current value Ia (S9a). On the other hand, if it is determined in S8 that the temperature of the hydraulic oil is not below the threshold value (S8, No), the current control unit 70b defines the current value I to be supplied to each solenoid proportional valve 45 as a second current value Ib (S9b). Note that the processing of S8 may be omitted, and a standby current of the first current value Ia may be supplied to each solenoid proportional valve 45 when it is determined in S2 that a permitted operation has not been performed.

[0109] If it is determined in S5 that there are no electromagnetic proportional valves 45 that are not being operated (S5, No), after defining the current value I to be supplied to the electromagnetic proportional valves 45 that are not being operated in S7a or S9a as the first current value Ia, or after defining the current value I to be supplied to the electromagnetic proportional valves 45 as the second current value Ib in S7b or S9b, the control device 70 supplies current to each electromagnetic proportional valve 45 based on the current value I defined by the current control unit 70b (S10).

[0110] After supplying current to each solenoid proportional valve 45 in S10, the current control unit 70b determines whether or not the prime mover E1 has stopped (S11) based on a signal (start signal) output from the ignition switch 71 to the control device 70. If it is determined in S11 that the prime mover E1 has stopped, the process ends, and if it is determined in S11 that the prime mover E1 has not stopped, the process from S2 onwards is repeated.

[0111] In addition, in a modified example in which the control device 70 does not supply current to each electromagnetic proportional valve 45 when the permitted operating device 77 is operated in an unauthorized manner and the temperature of the hydraulic oil is above a predetermined temperature (threshold value), the control device 70 omits S9b, does not define the current value I, and proceeds to S11.

[0112] The hydraulic system S of the above-mentioned work machine 1 includes a hydraulic actuator AC driven by hydraulic oil, a directional control valve 41 that controls the operation of the hydraulic actuator AC by changing the flow rate of hydraulic oil supplied to the hydraulic actuator AC, an electromagnetic proportional valve 45 that controls the switching position of the directional control valve 41 by exciting a solenoid in accordance with a supplied current, a control device 70 that controls the current supplied to the electromagnetic proportional valve 45, an operation member (first operation member) 75 with which an operator operates the hydraulic actuator AC, and an authorization operation device 77 that can be switched between an authorization operation that permits operation of the hydraulic actuator AC and a non-authorization operation that does not permit operation, and when the authorization operation device 77 is in the non-authorization operation and the temperature of the hydraulic oil is below a predetermined temperature, the control device 70 supplies to the electromagnetic proportional valve 45 a first standby current of a first current value Ia that is defined within a range in which the switching position of the directional control valve 41 does not switch.

[0113] According to the above configuration, when the permitted operating device 77 is in an unauthorized operation and the temperature of the hydraulic oil is below a predetermined temperature, the control device 70 supplies a first standby current to the electromagnetic proportional valve 45, thereby suppressing a decrease in response speed when the electromagnetic proportional valve 45 is subsequently driven, even at low temperatures.

[0114] Furthermore, when the temperature of the hydraulic oil is equal to or higher than a predetermined temperature, the control device 70 supplies a second standby current of a second current value Ib, which is lower than the first current value Ia, to the solenoid proportional valve 45 corresponding to the hydraulic actuator AC that is not being operated by the first operating member 75. This makes it possible to improve the response speed while suppressing the load and power consumption of the control device 70 when the temperature of the hydraulic oil is relatively high.

[0115] Furthermore, when the permitted operation of the permitted operating device 77 is permitted and the temperature of the hydraulic oil is below a predetermined temperature, the control device 70 supplies the first standby current or a second standby current having a second current value that is lower than the first current value to the solenoid proportional valve 45 corresponding to the hydraulic actuator AC that is not being operated by the first operating member 75. As a result, even when the permitted operation of the permitted operating device 77 is permitted, by supplying a standby current to the solenoid proportional valve 45 corresponding to the hydraulic actuator AC that is not being operated by the first operating member 75 at low temperatures, it is possible to suppress a decrease in response speed.

[0116] Furthermore, the control device 70 may be configured to pass a first standby current to the solenoid proportional valve 45 corresponding to the hydraulic actuator AC that is not being operated by the first operating member 75 when the permitted operation of the operating device 77 is permitted and the temperature of the hydraulic oil is below a predetermined temperature, and to pass a second standby current to the solenoid proportional valve 45 corresponding to the hydraulic actuator AC that is not being operated by the first operating member 75 when the permitted operation of the operating device 77 is permitted and the temperature of the hydraulic oil is equal to or higher than the predetermined temperature. This makes it possible to suppress a decrease in response speed at low temperatures, and to suppress the load and power consumption of the control device 70 when the temperature of the hydraulic oil is relatively high.

[0117] Furthermore, the control device 70 may be configured not to supply current to the proportional solenoid valve 45 when the permitted operation device 77 is in an unauthorized operation state and the temperature of the hydraulic oil is equal to or higher than a predetermined temperature. This makes it possible to reduce the load and power consumption of the control device 70 when the temperature of the hydraulic oil is relatively high.

[0118] Furthermore, the control device 70 supplies a dither current, which is the first current value Ia plus an oscillation component, as the first standby current to the solenoid proportional valve 45. This causes the solenoid to vibrate slightly, reducing sliding resistance and improving response speed.

[0119] The work machine 1 also includes the above-described hydraulic system S for the work machine 1. This makes it possible to realize the work machine 1 that provides the above-described excellent effects.

[0120] [Second embodiment] FIG. 6 shows another embodiment (second embodiment) of the hydraulic system S of the work machine 1.

[0121] The following description of the hydraulic system S of the work machine 1 of the second embodiment will focus on configurations that differ from those of the above-described embodiment (first embodiment). Configurations that are common to the first embodiment are assigned the same reference numerals and will not be described in detail. Unlike the first embodiment, the hydraulic system S of the work machine 1 of the second embodiment includes a warm-up oil passage 65 for warming up the hydraulic oil in the hydraulic oil passage 32 when the permitting operation device 77 is in the prohibiting operation and the unloading valve 60 is in the suppression position 62. The warm-up oil passage 65 is an oil passage that circulates the hydraulic oil discharged by the second pump 22 to the hydraulic oil tank T via the hydraulic oil passage 32 when the unloading valve 60 is in the suppression position 62. The hydraulic oil is discharged to the hydraulic oil tank T via the hydraulic oil passage 32 and the secondary port 60b and discharge port 60c of the unloading valve 60. In other words, the discharge port 60c discharges the hydraulic oil that flows through the warm-up oil passage 65 and into the hydraulic oil passage 32 when the unloading valve 60 is in the suppression position 62. Therefore, when the unloading valve 60 is in the suppression position 62, the hydraulic oil circulates through the second pump 22, the warm-up oil passage 65, the hydraulic oil passage 32, the unloading valve 60, and the hydraulic oil tank T.

[0122] Specifically, for example, the warm-up oil passage 65 is an oil passage that connects the supply oil passage 31 and the hydraulic oil passage 32 in parallel with the unloading valve 60. The warm-up oil passage 65 also has a connecting oil passage 66 that connects a midpoint of the supply oil passage 31 to a terminal end of the hydraulic oil passage 32, and a throttle section 67 provided in the connecting oil passage 66. The throttle section 67 limits the flow rate of hydraulic oil flowing from the second pump 22 to the hydraulic oil passage 32 via the connecting oil passage 66 so that the hydraulic actuators AC (MT, ML, MR, C1 to C5) to be operated will not be activated even if the solenoid proportional valve 45 and the pilot valve are operated when the unloading valve 60 is switched to the suppression position 62. In other words, the throttle section 67 limits the flow rate of hydraulic oil flowing to the hydraulic oil passage 32 so that a pressure that operates the directional control valve 41 is not generated in the secondary port of the solenoid proportional valve 45, and a pressure that operates the pilot-operated changeover valve is not generated in the secondary port of the pilot valve.

[0123] Therefore, when the permission operating device 77 is operated to prohibit the unloading valve 60 to the suppression position 62, the hydraulic oil discharged from the second pump 22 is supplied from the supply oil passage 31 to the terminal end of the hydraulic oil passage 32 via the warm-up oil passage 65. In addition, the hydraulic oil that has flowed into the terminal end of the hydraulic oil passage 32 flows toward the starting end of the hydraulic oil passage 32 and is discharged from the starting end to the hydraulic oil tank T via the unloading valve 60. As a result, the hydraulic oil pumped up from the hydraulic oil tank T by the second pump 22 is supplied to the primary port of the electromagnetic proportional valve 45 and the primary side port of the pilot valve.

[0124] The following describes a case in the hydraulic system S of the work machine 1 of the second embodiment where the prime mover E1 is driven, the temperature of the hydraulic oil is below a predetermined temperature (threshold value), the permission operating device 77 is in the non-permission operation, and the unloading valve 60 is in the suppression position 62. In this case, the control device 70 supplies a first standby current to the first proportional valve 46 and the second proportional valve 47, and hydraulic oil at the second secondary pressure Pb is supplied to the pressure receiving parts (the first pressure receiving part 42 and the second pressure receiving part 43) of the directional control valve 41. Here, because the second secondary pressure Pb is lower than the starting pressure Pmin of the directional control valve 41, the switching position of the directional control valve 41 is not changed, and the hydraulic oil flowing from the first proportional valve 46 and the second proportional valve 47 toward the pressure receiving parts 42, 43 of the directional control valve 41 is discharged through the discharge oil passage 33a and the throttle 33b. In other words, in the hydraulic system S for hydraulic oil in the second embodiment, even when the permitted operating device 77 is operated in an unauthorized manner, in addition to the vibration of the solenoid, the hydraulic oil inside the electromagnetic proportional valve 45 can be consumed (circulated), thereby further improving the warming of the electromagnetic proportional valve 45 and the hydraulic oil inside it.

[0125] 6 is merely an example, and the warm-up oil passage 65 is not limited to the above-described configuration as long as it can supply the hydraulic oil discharged by the second pump 22 to the hydraulic oil passage 32 when the unloading valve 60 is in the suppression position 62. For example, when the unloading valve 60 is in the suppression position 62, the unloading valve 60 may block communication between the hydraulic oil passage 32 and the hydraulic oil tank T, and the hydraulic oil supplied from the warm-up oil passage 65 to the hydraulic oil passage 32 may circulate to the hydraulic oil tank T via the electromagnetic proportional valve 45 and the drain oil passage 33.

[0126] The hydraulic system S of the work machine 1 described above includes a hydraulic oil tank T that stores hydraulic oil, a hydraulic pump 22 that draws in and discharges hydraulic oil from the hydraulic oil tank T, a supply oil passage 31 connected to the hydraulic pump 22, a hydraulic oil passage 32 that is connected to the supply oil passage 31 and the solenoid proportional valve 45 and supplies hydraulic oil from the supply oil passage 31 to the solenoid proportional valve 45, and a warm-up oil passage 65 that circulates hydraulic oil discharged by the hydraulic pump 22 to the hydraulic oil tank T via the hydraulic oil passage 32 when the permitted operating device 77 is in an unauthorized operation. With the above configuration, the hydraulic oil passage 32 can be warmed up when the permitted operating device 77 is in an unauthorized operation, and a decrease in response speed at low temperatures can be more effectively suppressed.

[0127] Furthermore, the hydraulic system S of the work machine 1 is provided with an unloading valve 60 that switches to a supply position 61 where hydraulic oil from the supply oil passage 31 is supplied to the hydraulic oil passage 32 when the permitting operation device 77 is operated to permit, and to a suppression position 62 where hydraulic oil supply to the hydraulic oil passage 32 is suppressed when the permitting operation device 77 is operated to prohibit, and a warm-up oil passage 65 connects the supply oil passage 31 and the hydraulic oil passage 32 in parallel to the unloading valve 60. According to the above configuration, when the permitting operation device 77 is operated to prohibit, hydraulic oil can be circulated from the supply oil passage 31 to the hydraulic oil passage 32, bypassing the unloading valve 60. This makes it possible to more effectively suppress a decrease in response speed at low temperatures.

[0128] 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]

[0129] 1. Work equipment (swivel work equipment) 22 Second pump (hydraulic pump) 31 Oil supply line 32 Hydraulic oil passage 41 Directional valve 45 Solenoid proportional valve 60 Unloading valve 61 Supply position 62 Suppression position 65 Warm-up oil path 70 Control device 75 Operating member (first operating member) 77 Permission operating device (lever lock) AC Hydraulic Actuator Ia First current value S Hydraulic System T Hydraulic oil tank

Claims

1. a hydraulic actuator driven by hydraulic oil; a directional control valve that changes the flow rate of the hydraulic oil supplied to the hydraulic actuator to control the operation of the hydraulic actuator; an electromagnetic proportional valve that controls a switching position of the directional control valve by exciting a solenoid in response to a supplied current; a control device for controlling the current supplied to the electromagnetic proportional valve; an operating member for an operator to operate the hydraulic actuator; an enabling operation tool that can be switched between an enabling operation that enables driving of the hydraulic actuator and a disabling operation that does not enable driving; Equipped with the electromagnetic proportional valve includes a first electromagnetic proportional valve for switching the switching position of the directional control valve to a first position, and a second electromagnetic proportional valve for switching the switching position of the directional control valve to a second position opposite to the first position, When the permitted operating device is operated in the prohibited manner and the temperature of the hydraulic oil is below a predetermined temperature, the control device supplies to the first solenoid proportional valve and the second solenoid proportional valve a first standby current of a first current value defined within a range in which the switching position of the directional control valve does not switch, and when the permitted operating device is operated in the permitted manner and the operating member is operated, supplies to the first solenoid proportional valve and the second solenoid proportional valve corresponding to the hydraulic actuator operated by the operating member a current of a current value according to the operating direction and operation amount of the operating member.

2. 2. The hydraulic system of claim 1, wherein the control device supplies a second standby current having a second current value that is lower than the first current value to the first electromagnetic proportional valve and the second electromagnetic proportional valve corresponding to a hydraulic actuator that is not being operated by the operating member when the temperature of the hydraulic oil is equal to or higher than the predetermined temperature.

3. When the permitting operation tool is permitted to perform the permitting operation and the temperature of the hydraulic oil is lower than the predetermined temperature, the control device supplies the first standby current or the second standby current to the first electromagnetic proportional valve and the second electromagnetic proportional valve corresponding to the hydraulic actuator that is not operated by the operating member. The hydraulic system for a work machine according to claim 1 , wherein a second standby current having a second current value that is lower than the first current value is supplied.

4. The control device When the permitting operation tool is permitted to perform the permitting operation and the temperature of the hydraulic oil is lower than the predetermined temperature, the first standby current is passed to the first electromagnetic proportional valve and the second electromagnetic proportional valve corresponding to the hydraulic actuator that is not being operated by the operating member, A hydraulic system for a work machine as described in claim 3, wherein when the permission operating tool is operated in the permission mode and the temperature of the hydraulic oil is equal to or higher than the predetermined temperature, the second standby current is passed through the electromagnetic proportional valve corresponding to the hydraulic actuator that is not being operated by the operating member.

5. 2. A hydraulic system for a work machine as described in claim 1, wherein the control device does not supply current to the first electromagnetic proportional valve and the second electromagnetic proportional valve when the permitted operating tool is operated in the prohibited manner and the temperature of the hydraulic oil is equal to or higher than the predetermined temperature.

6. 2. The hydraulic system of the work machine according to claim 1, wherein the control device supplies a dither current obtained by adding an oscillation component to the first current value to the first electromagnetic proportional valve and the second electromagnetic proportional valve as the first standby current.

7. A hydraulic actuator driven by hydraulic oil; a directional control valve that changes the flow rate of the hydraulic oil supplied to the hydraulic actuator to control the operation of the hydraulic actuator; an electromagnetic proportional valve that controls a switching position of the directional control valve by exciting a solenoid in response to a supplied current; a control device for controlling the current supplied to the electromagnetic proportional valve; an operating member for an operator to operate the hydraulic actuator; an enabling operation tool that can be switched between an enabling operation that enables driving of the hydraulic actuator and a disabling operation that does not enable driving; a hydraulic oil tank that stores the hydraulic oil; a hydraulic pump that draws in and discharges the hydraulic oil from the hydraulic oil tank; a supply oil passage connected to the hydraulic pump; a hydraulic oil passage connected to the supply oil passage and the electromagnetic proportional valve, for supplying the hydraulic oil from the supply oil passage to the electromagnetic proportional valve; a warm-up oil passage that circulates the hydraulic oil discharged by the hydraulic pump to the hydraulic oil tank via the hydraulic oil passage when the permitted operation tool is operated in the unauthorized manner; Equipped with The control device is a hydraulic system of a work machine that supplies a first standby current of a first current value defined within a range in which the switching position of the directional control valve does not switch to the electromagnetic proportional valve when the permitted operating tool is operated in the unauthorized manner and the temperature of the hydraulic oil is below a predetermined temperature.

8. an unloading valve that is switched to a supply position to supply the hydraulic oil from the supply oil passage to the hydraulic oil passage when the permission operating device is operated in the permission manner, and is switched to a suppression position to suppress the supply of the hydraulic oil to the hydraulic oil passage when the permission operating device is operated in the non-permission manner; 8. The hydraulic system for a work machine according to claim 7, wherein the warm-up oil passage connects the supply oil passage and the hydraulic oil passage in parallel with respect to the unloading valve.

9. 2. The hydraulic system for a work machine according to claim 1, wherein the permission operation tool is a lever lock that can be swung to perform the permission operation or the non-permission operation.

10. A work machine comprising the hydraulic system for a work machine according to any one of claims 1 to 9.

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