JP2018169004A - Hydraulic control device for work machine - Google Patents

Abstract

To efficiently perform warm-up operation immediately after start up with a simple circuit configuration, and to enable warm-up even during operation of a machine without interrupting work.SOLUTION: A pilot pressure control device 21 includes: first electromagnetic proportional pressure reduction valves 22 and 23 for performing changeover control of a directional control valve 14 by selectively connecting first output ports 22C and 23C to first pump ports 22A and 23A or first tank ports 22B and 23B according to an electric signal from a controller 30; a second electromagnetic proportional pressure reduction valve 25 for selectively connecting the second output port 25C to either the second pump port 25A or the second tank port 25B according to the electric signal; a pilot pressure supply conduit 26; and a tank conduit 27. The second electromagnetic proportional pressure reduction valve 25 returns pressure oil, flowing from the second pump port 25A to the second output port 25C, to the tank conduit 27 to increase an oil temperature of hydraulic oil.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a hydraulic control device for a work machine that is suitably used for excavating work such as earth and sand.

  In general, a hydraulic circuit of a work machine represented by a large hydraulic excavator has a main hydraulic pump with a large discharge flow rate as a main hydraulic pressure source, and includes a high-pressure actuator including an actuator such as a hydraulic cylinder and a directional control valve for controlling the actuator. The main circuit and a low-pressure pilot circuit that includes a pilot pump having a discharge flow rate smaller than that of the hydraulic pump and switches and controls the direction control valve of the main circuit according to the lever operation amount of the cab. .

  In the pilot circuit, an electric signal corresponding to the lever operation amount is input to the controller from an electric operation device represented by an electric lever, and the controller outputs a control current corresponding to the signal to the electromagnetic proportional pressure reducing valve. The electromagnetic proportional pressure reducing valve controls the operation of the hydraulic actuator by supplying a pilot pressure proportional to the control current to the direction control valve on the main circuit and switching the direction control valve.

  Conventionally, work machines operating in cold regions have a high viscosity of the hydraulic oil when the oil temperature falls below a predetermined temperature, and the hydraulic oil and pilot pumps are poor in the ability to absorb the hydraulic oil, making the operation of the work machine smooth. Difficult to do. For this reason, a heater (hydraulic oil heater) is installed in the hydraulic oil tank or in the middle of the piping around the main hydraulic equipment, etc., and kept warm so that the temperature of the hydraulic oil does not drop below the predetermined temperature while the machine is parked. Yes. In addition, warm-up operation is performed at the start of the work machine at low temperatures, and work is started after warming hydraulic devices such as actuators. Proposals have been made (see Patent Documents 1 to 4).

JP 2003-184827 A Japanese Patent Laid-Open No. 2003-166502 JP 7-279908 A Japanese Utility Model Publication No. 4-34304

  By the way, the prior arts according to Patent Documents 1 and 2 are both techniques for recirculating oil in the pilot circuit and warming the circuit during the warm-up operation immediately after the engine cold start. However, during the operation of the work machine after the warm-up operation, the oil circulation in the pilot circuit may be stopped, and at this time, the oil temperature continues to decrease due to the influence of the ambient atmosphere temperature even during the operation of the machine. Therefore, if the work is not interrupted periodically and the warm-up operation is not performed when working in a cold region, the oil viscosity increases and the fluidity decreases, so the responsiveness during machine operation decreases greatly. There is.

  The prior art disclosed in Patent Document 3 describes a technique in which a throttle is provided in the middle of a return line to a tank in a pilot circuit, and the pilot circuit is warmed by energy of oil circulation. In this prior art, the pilot circuit can be warmed up during the lever operation, but cannot be warmed up when the lever is not operated. For this reason, the same problem as in Patent Documents 1 and 2 occurs.

  On the other hand, in the prior art according to Patent Document 4, it is possible to warm up the pilot circuit when the lever is operated and when the lever is not operated by providing a dedicated flow control valve and a pipe line. However, in this case, it is necessary to install a dedicated flow control valve and pipe. For this reason, when the working machine becomes large, there is a problem that the circuit configuration becomes complicated and the manufacturing cost increases accordingly.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to enable efficient warm-up operation immediately after start-up with a simple circuit configuration and to interrupt the operation even during operation of the machine. An object of the present invention is to provide a hydraulic control device for a work machine including a heat system that can warm up a pilot circuit without causing the pilot circuit to warm up.

  In order to solve the above-described problems, the present invention provides a main hydraulic pump and a pilot pump that are driven by a prime mover of a work machine and suck in hydraulic oil from a tank and discharge the pressure oil. A hydraulic actuator driven by pressure oil supplied from a pump, and provided between the hydraulic pump and the hydraulic actuator, and a pilot pressure from the pilot pump is supplied to a hydraulic pilot unit to the hydraulic actuator. A control valve for controlling the supply of pressure oil, an electric operation device for switching the control valve and controlling the operation of the hydraulic actuator to output an electric signal according to an external operation, and the electric operation device The pilot pressure supplied to the hydraulic pilot part of the control valve in accordance with the electrical signal from A pilot pressure control device for varying controlled, is applied to the working machine hydraulic control device provided with a.

  A feature of the configuration adopted by the present invention is that the pilot pressure control device includes a pilot pressure supply line connected to a discharge side of the pilot pump, a tank line connected to the tank, and the pilot pressure. A first pump port connected to a supply line, a first tank port connected to the tank line, and a first output port connected to a hydraulic pilot part of the control valve; A first solenoid valve that selectively connects one output port to the first pump port or the first tank port and performs switching control of the control valve; a second pump port connected to the pilot pressure supply line; A second tank port connected to the tank line and a second output port, and the second output port is connected to the second pump port or the second tank according to the electric signal; A second solenoid valve selectively connected to the port, wherein the second solenoid valve is connected to the second pump port in order to raise the temperature of the hydraulic fluid flowing through the pilot pressure control device. The pressure oil flowing through the second output port is returned to the tank pipe.

  As described above, according to the present invention, the second solenoid valve recirculates the pressure oil flowing from the second pump port to the second output port to the tank line, thereby allowing the hydraulic oil flowing in the pilot pressure control device to flow. Can raise the temperature. For this reason, the heat system of the pilot pressure control device (pilot circuit) can be realized with a simple circuit configuration, and the warm-up operation immediately after the start-up of the prime mover can be efficiently performed. Further, even during operation of the work machine, the pilot circuit can be warmed up without interrupting a desired excavation work or the like by switching and controlling the first electromagnetic valve and the second electromagnetic valve.

1 is an overall view showing a large hydraulic excavator as a work machine according to a first embodiment. FIG. 2 is a hydraulic circuit diagram for driving a hydraulic cylinder mounted on the hydraulic excavator in FIG. 1. FIG. 3 is a hydraulic circuit diagram for driving a hydraulic cylinder showing a state in which a heat circuit in FIG. 2 is operated. It is a flowchart which shows the control process of warm-up operation mode. It is a flowchart which shows the control processing in a work mode. It is a characteristic diagram which shows the characteristic of the heat circuit opening area, the operation circuit pressure, and the hydraulic oil temperature in warm-up operation mode and work mode. It is a general view which shows the large sized hydraulic excavator by 2nd Embodiment. FIG. 8 is a hydraulic circuit diagram for driving a hydraulic cylinder mounted on the hydraulic excavator in FIG. 7.

  Hereinafter, a case where a hydraulic control device for a working machine according to an embodiment of the present invention is applied to a large-sized hydraulic excavator will be described as an example and described in detail with reference to the accompanying drawings.

  Here, FIG. 1 thru | or FIG. 6 has shown 1st Embodiment. In FIG. 1, a large excavator 1 is used when excavation work is performed at various work sites (for example, a quarry such as a mine). The hydraulic excavator 1 is a self-propelled crawler-type lower traveling body 2, and is mounted on the lower traveling body 2 through a turning device 3 so as to be capable of turning. The body 4 is configured to include a working device 10 described later provided on the front side of the upper revolving body 4 so as to be able to move up and down.

  The upper swing body 4 includes a swing frame 5, a building cover 6, a cab 7, a counterweight 8, and the like. The swing frame 5 constitutes a support structure for the upper swing body 4. The turning frame 5 is attached on the lower traveling body 2 via the turning device 3. The revolving frame 5 is provided with a cab 7 on the front side and a counterweight 8 on the rear side. The revolving frame 5 is provided with a building cover 6 positioned between the cab 7 and the counterweight 8, and an engine 9 as a prime mover is provided in the building cover 6. The building cover 6, together with the turning frame 5, the cab 7 and the counterweight 8, defines a space (machine room) in which the engine 9 and the like are accommodated.

  The cab 7 is mounted on the front side of the revolving frame 5. The cab 7 defines a cab in which an operator is boarded. Inside the cab 7, a driver's seat on which an operator is seated, various operation levers (for example, the operation lever 20A shown in FIG. 2), and the like are disposed. The counterweight 8 constitutes a part of the upper swing body 4. The counterweight 8 is located on the rear side of the engine 9 and is attached to the rear end portion of the turning frame 5 to balance the weight with the work device 10.

  The working device 10 performs excavation work of, for example, earth and sand, with a boom 10A whose base end side is attached to the revolving frame 5 so as to be able to move up and down, and an arm 10B attached to the tip side of the boom 10A so as to be able to move up and down. The arm 10B is roughly constituted by a bucket 10C as a work tool that is rotatably provided on the distal end side of the arm 10B. The boom 10A of the work device 10 is lifted up and down with respect to the revolving frame 5 by the boom cylinder 10D, and the arm 10B is lifted up and down by the arm cylinder 10E on the tip side of the boom 10A. Further, the bucket 10C as the work tool is rotated up and down by the bucket cylinder 10F as the work tool cylinder on the distal end side of the arm 10B.

  As shown in FIG. 2, a main hydraulic pump 11 driven by an engine 9 as a prime mover discharges hydraulic oil sucked from the tank 12 as high-pressure pressure oil. The main hydraulic pump 11 is composed of, for example, a variable displacement axial piston type or radial piston type hydraulic pump, and constitutes a main hydraulic source together with the tank 12. The hydraulic pump 11 may be a fixed displacement hydraulic pump.

  The working hydraulic cylinder 13 shows a typical example of a hydraulic actuator. The hydraulic cylinder 13 constitutes, for example, a boom cylinder 10D, an arm cylinder 10E, or a bucket cylinder 10F provided in the work device 10. The hydraulic cylinder 13 includes a tube 13A, a piston 13B, a rod 13C, and the like. In particular, the hydraulic cylinder 13 used in the large excavator 1 has a large cylinder diameter, and the amount of hydraulic oil (operating oil amount) supplied to and discharged from the hydraulic pump 11 to the hydraulic cylinder 13 is also large.

  In the hydraulic cylinder 13, the inside of the tube 13A is defined by the piston 13B into two oil chambers 13D and 13E, and the base end side of the rod 13C is fixed to the piston 13B. The distal end side of the rod 13C protrudes outside the tube 13A, and is expanded and contracted by the pressure oil supplied and discharged into the tube 13A. The hydraulic actuator is not limited to the hydraulic cylinder 13, and may be a hydraulic motor for turning or traveling the hydraulic excavator 1, for example.

  The direction control valve 14 as a control valve is a control valve for the hydraulic cylinder 13 and is provided between the hydraulic pump 11, the tank 12 and the hydraulic cylinder 13. This directional control valve 14 is composed of, for example, a 4-port 3-position hydraulic pilot type directional control valve, and hydraulic pilot portions 14A and 14B are provided on both the left and right sides. Hydraulic pilot portions 14A and 14B of the directional control valve 14 are connected to a pilot pressure control device 21 described later via pilot pipelines 15A and 15B.

  The directional control valve 14 is switched from the neutral position (I) to one of the switching positions (II) and (III) by supplying pilot pressure from the pilot pressure control device 21 to the hydraulic pilot portions 14A and 14B. As a result, the hydraulic oil from the hydraulic pump 11 is supplied to and discharged from the oil chambers 13D and 13E of the hydraulic cylinder 13 via the pair of main pipelines 16A and 16B, and the rod 13C of the hydraulic cylinder 13 extends and contracts from the tube 13A ( Driven). At this time, the flow rate of the pressure oil supplied to and discharged from the bottom side oil chamber 13D and the rod side oil chamber 13E of the hydraulic cylinder 13 is determined by the stroke amount of the direction control valve 14 (that is, the tilt of the operation lever 20A described later). It is variably controlled according to the operation amount.

  The pilot pump 17 constitutes a pilot hydraulic pressure source together with the tank 12. The pilot pump 17 is driven to rotate together with the main hydraulic pump 11 by the engine 9. A low pressure relief valve 18 is provided between the pilot pump 17 and the tank 12 on the discharge side. The low-pressure relief valve 18 suppresses the discharge pressure of the pilot pump 17 below a predetermined relief setting pressure.

  The main hydraulic pump 11 is provided with a high-pressure relief valve 19 between the discharge pipe 11 </ b> A and the tank 12. The high-pressure relief valve 19 keeps the discharge pressure of the hydraulic pump 11 below a predetermined relief setting pressure in order to prevent an excessive pressure from being generated in the hydraulic pump 11. This relief set pressure is set to a pressure sufficiently higher than that of the low pressure relief valve 18.

  The operation lever device 20 is an electric operation device, and is configured as an electric lever device that remotely operates the hydraulic cylinder 13. The operation lever device 20 includes an operation lever 20A that is manually tilted by an operator of the excavator 1. The operation lever device 20 outputs an electric signal corresponding to the operation direction (arrow A, B direction) of the operation lever 20A and the operation amount to the electromagnetic pilot pressure control device 21.

  Here, the operation lever device 20 is provided in the cab 7 of the excavator 1. On the other hand, the electromagnetic pilot pressure control device 21 is disposed at a position (for example, a position close to the directional control valve 14) that is largely separated from the cab 7. That is, since the operation lever device 20 is an electric operation device, the pilot pressure control device 21 may be connected to the pilot pressure control device 21 by electric wiring (signal line), and the distance between the two may be several meters or more as required. Can be extended. In the case of pilot hydraulic piping, the length is limited to, for example, 1 to 2 meters.

  The electromagnetic pilot pressure control device 21 includes two first electromagnetic proportional pressure reducing valves as first electromagnetic valves that supply pilot pressures corresponding to (proportional to) an electrical signal from the operation lever device 20 to the pilot pipe lines 15A and 15B. 22, 23, a second electromagnetic proportional pressure reducing valve 25 as a second electromagnetic valve provided in a valve housing 24 common to the first electromagnetic proportional pressure reducing valves 22, 23, and a discharge side of the pilot pump 17. A pilot pressure supply line 26 that extends into the valve housing 24, a tank line 27 that extends from the valve housing 24 toward the tank 12, and has a distal end connected to the tank 12, and a fixed throttle 33 that will be described later. It is comprised including.

  The two first electromagnetic proportional pressure reducing valves 22 and 23 are disposed in the valve housing 24 so as to be in parallel with each other, and are switched in electromagnetic proportion from the low pressure position (a) to the switching position (b) according to the electric signal. The two first electromagnetic proportional pressure reducing valves 22 and 23 are respectively connected to the first pump ports 22A and 23A connected to the pilot pressure supply line 26 in the valve housing 24 and to the tank line 27, respectively. The tank ports 22B and 23B and the first output ports 22C and 23C connected to the hydraulic pilot portions 14A and 14B of the direction control valve 14 are provided.

  One of the first electromagnetic proportional pressure reducing valves 22 and 23 is switched to the low pressure position (a) or the switching position (b) according to the electrical signal, so that the first output port 22C becomes the first pump. It is selectively connected to the port 22A or the first tank port 22B. That is, while the operation lever 20A is in the neutral position, the electromagnetic proportional pressure reducing valve 22 is in the low pressure position (a) because the electrical signal is demagnetized (energization is stopped). At this time, the first output port 22C is connected to the first output port 22C. The pump port 22A is blocked and connected to the first tank port 22B. For this reason, the pilot pressure in the pilot line 15A is maintained at a low pressure state close to the tank pressure.

  However, when the operation lever 20A is tilted in the direction of arrow A, for example, and the electric signal is excited (energized), the electromagnetic proportional pressure reducing valve 22 is in a low pressure position (a) in proportion to the current value at this time. From the first to the switching position (b), and the first output port 22C is connected to the first pump port 22A. For this reason, the pilot pressure in the pilot line 15A is increased in response to the electric signal (that is, the control current) from the operation lever device 20, and the directional control valve 14 is neutral in proportion to the pilot pressure at this time. The position (I) is switched to the switching position (II).

  Of the first electromagnetic proportional pressure reducing valves 22 and 23, the other electromagnetic proportional pressure reducing valve 23 has a first output port 23C selectively connected to the first pump port 23A or the first tank port 23B in accordance with the electrical signal. The electromagnetic proportional pressure reducing valve 23 is in the low pressure position (a) while the operation lever 20A is returned to the neutral position and the electric signal is demagnetized. At this time, the first output port 23C is connected to the first tank port 23B. The For this reason, the pilot pressure in the pilot line 15B is maintained in a low pressure state close to the tank pressure.

  However, when the operation lever 20A is tilted in the direction of arrow B, for example, and the electric signal is excited, the electromagnetic proportional pressure reducing valve 23 is moved from the low pressure position (a) in proportion to the current value at this time. The first output port 23C is connected to the first pump port 23A at this time. For this reason, the pilot pressure in the pilot line 15B is increased in response to an electric signal (ie, control current) from the operation lever device 20, and the directional control valve 14 is neutral in proportion to the pilot pressure at this time. The position (I) is switched to the switching position (III).

  As described above, the directional control valve 14 is switched from the neutral position (I) to the switching position (II) or (III) when the pilot pressure is supplied to the hydraulic pilot portions 14A and 14B. For this reason, pressure oil from the hydraulic pump 11 is supplied to and discharged from the oil chambers 13D and 13E of the hydraulic cylinder 13 via the pair of main pipes 16A and 16B, and the rod 13C of the hydraulic cylinder 13 is expanded and contracted (driven). The As described above, the expansion and contraction of the hydraulic cylinder 13 is remotely operated by the operation lever device 20 via the electromagnetic pilot pressure control device 21 (first electromagnetic proportional pressure reducing valves 22 and 23) and the direction control valve 14.

  The second electromagnetic proportional pressure reducing valve 25 is provided in a common valve housing 24 so as to be in parallel with the two first electromagnetic proportional pressure reducing valves 22 and 23. The second electromagnetic proportional pressure reducing valve 25 constitutes a heat circuit of the pilot pressure control device 21 and is switched in electromagnetic proportion from the reflux stop position (c) to the reflux position (d) by an electric signal from the controller 30. The second electromagnetic proportional pressure reducing valve 25 includes a second pump port 25A connected to the pilot pressure supply line 26 in the valve housing 24 and a second tank port 25B connected to the tank line 27 in the valve housing 24. And a second output port 25C.

  The second electromagnetic proportional pressure reducing valve 25 is switched to the recirculation stop position (c) or the recirculation position (d) in accordance with the electrical signal from the controller 30, so that the second output port 25 C is set to the second pump port 25 A or the second tank port. 25B is selectively connected. That is, while the second electromagnetic proportional pressure reducing valve 25 is returned to the reflux stop position (c) by the electrical signal from the controller 30, the working oil flows (refluxs) in the valve housing 24 of the pilot pressure control device 21. Stop doing.

  However, when the second electromagnetic proportional pressure reducing valve 25 is switched from the reflux stop position (c) to the reflux position (d) by the electrical signal from the controller 30, the second output port 25C is connected to the second pump port 25A. . As a result, the second electromagnetic proportional pressure reducing valve 25 allows the pilot pressure oil discharged from the pilot pump 17 to flow through the pilot pressure supply line 26 and the valve housing 24 of the pilot pressure control device 21, while the second electromagnetic proportional pressure reducing valve 25. The 25 second pump port 25A is returned to the tank line 27 via the second output port 25C. At this time, the valve housing 24 of the pilot pressure control device 21 rises in temperature by receiving thermal energy from the pilot pressure oil (hydraulic oil) flowing through the inside, and the oil temperature of the hydraulic oil is maintained at a high temperature in the valve housing 24. can do.

  In other words, the second electromagnetic proportional pressure reducing valve 25 heats the pilot circuit (particularly, the first electromagnetic proportional pressure reducing valves 22, 23) that switches the direction control valve 14 including the pilot pressure control device 21. It is provided as a heat circuit. That is, the second electromagnetic proportional pressure reducing valve 25 circulates warm oil in the tank 12 (hydraulic oil always heated by a heater 31 described later) in the valve housing 24 of the pilot pressure control device 21, thereby The circuit (that is, the hydraulic circuit in the valve housing 24 including the first electromagnetic proportional pressure reducing valves 22 and 23) can be warmed up. The valve housing 24 has a common heat that allows heat due to an increase in the oil temperature of the hydraulic oil to be transmitted between the first electromagnetic proportional pressure reducing valves 22 and 23, the second electromagnetic proportional pressure reducing valve 25, and a fixed throttle 33 described later. It constitutes a conductor.

  The temperature sensor 28 is, for example, a temperature detector provided in the middle of the tank pipe line 27, and returns oil (hydraulic oil) returned from the valve housing 24 of the pilot pressure control device 21 to the tank 12 through the tank pipe line 27. ) Temperature. The pressure sensors 29A and 29B are detectors that individually detect the pilot pressure in the pilot pipes 15A and 15B. The pressure sensor 29A is provided in the middle of the pilot line 15A between the first output port 22C of the first electromagnetic proportional pressure reducing valve 22 and the hydraulic pilot portion 14A of the direction control valve 14. The pressure sensor 29B is provided in the middle of the pilot line 15B between the first output port 23C of the first electromagnetic proportional pressure reducing valve 23 and the hydraulic pilot portion 14B of the direction control valve 14. Detection signals from the temperature sensor 28 and the pressure sensors 29A and 29B are output to the controller 30.

  The controller 30 is constituted by, for example, a microcomputer. The controller 30 includes first electromagnetic proportional pressure reducing valves 22 and 23 and second electromagnetic proportional pressure reducing valves in accordance with drive information of the engine 9, electric signals from the operating lever device 20, and detection signals from the temperature sensor 28 and the pressure sensors 29A and 29B. The control means which controls switching to 25 is comprised. The controller 30 is connected at its input side to the operating lever device 20, temperature sensor 28, pressure sensors 29A and 29B, a control device (not shown) for the engine 9, and the like, and its output side is a first electromagnetic proportional pressure reducing valve. 22 and 23 and the second electromagnetic proportional pressure reducing valve 25 and the like.

  The controller 30 has a memory 30A composed of, for example, a nonvolatile memory, ROM, RAM, or the like. In this memory 30A, for example, a program (see FIG. 4) for performing control processing in the warm-up operation mode, a program for performing control processing in the work mode (see FIG. 5), and the temperature T of the hydraulic oil are within an appropriate temperature range. The first temperature Ta, the second temperature Tb (Ta> Tb) and the pilot pressure in the pilot lines 15A and 15B for switching the direction control valve 14 (ie, The pressure value and the like for determining whether or not the operation circuit pressure has reached the required set pressure P1 are stored.

  For example, the first temperature Ta is set to a temperature similar to the target temperature during the warm-up operation. The second temperature Tb is a temperature lower than the first temperature Ta by a predetermined temperature, and is set to a limit temperature at which a decrease in responsiveness due to an increase in the viscosity of the hydraulic oil does not occur. That is, the second temperature Tb is set to a temperature just before the response of the pilot pressure generated in the pilot pipes 15A and 15B is lowered with respect to, for example, the tilting operation of the operation lever 20A.

  The set pressure P1 is a pressure value for determining whether or not the operation lever 20A is tilted in one of the directions indicated by arrows A and B, for example, and the first electromagnetic proportional pressure reducing valves 22 and 23. Is set to a sufficiently low pressure value (for example, a pressure value of 1/2 or less) with respect to the maximum pressure value MAX of the pilot pressure (that is, the operation circuit pressure shown in FIG. 6) supplied to the pilot pipe lines 15A and 15B. Has been. The set pressure P1 is set to a minimum pressure within a range that does not affect the operation so that the switching operation of the direction control valve 14 (operation of the hydraulic excavator 1) cannot be performed due to insufficient pilot pressure, for example. preferable.

  In the excavator 1 that operates in a cold region or the like, for example, a heater 31 is provided in a tank 12. The heater 31 warms the hydraulic oil in the tank 12 to have an appropriate viscosity, and keeps the oil temperature within a required temperature range. This temperature range is determined based on, for example, a target temperature during warm-up operation. The relief valve 32 is provided in the middle of the main pipe line 16 </ b> A between the oil chamber 13 </ b> D of the hydraulic cylinder 13 and the tank 12 in order to prevent excessive pressure from being generated in the oil chamber 13 </ b> D on the bottom side of the hydraulic cylinder 13. ing.

  Here, a fixed throttle 33 is provided in the valve housing 24 of the pilot pressure control device 21 in the middle of the tank conduit 27. This is because when the proportional control of the first electromagnetic proportional pressure reducing valves 22 and 23 and the second electromagnetic proportional pressure reducing valve 25 is performed without the fixed throttle 33, the pressure is not stabilized due to the pressure regulation of the pressure reducing valve. For example, hunting may occur in the second electromagnetic proportional pressure reducing valve 25 or the like. In the case where the fixed throttle 33 is not provided, the second electromagnetic proportional pressure reducing valve 25 is preferably not on proportional control but on-off control.

  The large excavator 1 according to the first embodiment has the above-described configuration, and the operation thereof will be described next.

  First, the operator of the hydraulic excavator 1 gets on the cab 7 of the upper swing body 4, starts the engine 9, and drives the hydraulic pump 11 and the pilot pump 17. Thereby, the pressure oil is discharged from the hydraulic pump 11 toward the discharge pipe 11A, and this pressure oil is supplied to the hydraulic cylinder 13 (for example, the boom cylinder 10D shown in FIG. 1) via the direction control valve 14. Further, other directional control valves (not shown) are supplied to other hydraulic actuators (for example, arm cylinder 10E, bucket cylinder 10F, turning hydraulic motor, traveling hydraulic motor, etc. shown in FIG. 1). .

  When an operator boarding the cab 7 operates the operation lever 20A, the pilot pressure control device 21 causes the first electromagnetic proportional pressure reducing valve 22 or 23 to be switched from the low pressure position (a) to the switching position (b), and the operation lever A pilot pressure corresponding to (proportional to) the electrical signal from the apparatus 20 is supplied to the pilot line 15A or 15B. Therefore, the directional control valve 14 is switched from the neutral position (I) to any one of the switching positions (II) and (III), and the pressure oil from the hydraulic pump 11 is supplied to the hydraulic cylinder via the directional control valve 14. 13 is supplied. Thus, the hydraulic cylinder 13 can perform soil excavation work and the like by moving the working device 10 up and down by extending or reducing the rod 13C from the tube 13A.

  By the way, in the hydraulic excavator 1 operating in a cold region, when the temperature of the hydraulic oil is lowered to a low temperature, the viscosity of the hydraulic oil increases, and the hydraulic oil suction performance by the hydraulic pump 11 and the pilot pump 17 is deteriorated. It becomes difficult to smoothly operate the machine. For this reason, a heater 31 is provided in the tank 12 or the like for storing hydraulic oil, and the temperature of the hydraulic oil is kept so as not to fall below a predetermined temperature during the rest of the machine. Further, when the engine 9 is started at a low temperature, a warm-up operation is performed, and the operation is started after the hydraulic equipment such as a hydraulic actuator is warmed.

  However, during the operation of the hydraulic excavator 1 after the warm-up operation, the oil circulation in the pilot circuit (that is, the pilot pressure control device 21) may be stopped. At this time, the ambient temperature is affected even during the operation of the machine. As a result, the oil temperature drops. For this reason, unless the valve housing 24 or the like of the pilot pressure control device 21 is heated, the viscosity of the hydraulic oil increases and the responsiveness during operation decreases.

  In particular, in an ultra-large hydraulic excavator 1 having a body weight of 100 t or more, the pipe length from the discharge side of the pilot pump 17 to the first electromagnetic proportional pressure reducing valves 22 and 23 installed at the end of the pilot circuit becomes long. Since it is further away from the heat source of the vehicle body (for example, the position of the engine 9), it is more susceptible to the influence of the ambient temperature. In addition, when the flow rate circulating through the pilot pressure control device 21 (pilot circuit) is small, the oil temperature in the pipe line is easily affected by the ambient temperature, and the viscosity of the hydraulic oil flowing through the pilot circuit is high in a cold region environment. Thus, for example, the reaction speed until the first electromagnetic proportional pressure reducing valves 22 and 23 start to move from the input of the electric signal becomes slow, and the operation responsiveness on the pilot circuit side tends to be lowered.

  Therefore, in the first embodiment, the second electromagnetic proportional pressure reducing valve 25 is provided in parallel with the two first electromagnetic proportional pressure reducing valves 22 and 23 in the valve housing 24 of the pilot pressure control device 21. . When the second electromagnetic proportional pressure reducing valve 25 is switched to the return position (d) by the electric signal from the controller 30, the pilot pressure oil discharged from the pilot pump 17 is supplied to the pilot pressure supply line 26, pilot pressure control. While flowing into the valve housing 24 of the device 21, it is refluxed from the tank line 27 to the tank 12.

  As a result, the second electromagnetic proportional pressure reducing valve 25 can circulate the warm oil in the tank 12 (the hydraulic oil that is always heated by the heater 31) in the valve housing 24 of the pilot pressure control device 21. The circuit (that is, the first electromagnetic proportional pressure reducing valves 22 and 23) can be warmed up to maintain the pilot pressure oil supplied to the pilot lines 15A and 15B at a proper temperature and oil viscosity.

  FIG. 4 shows a control process in the warm-up operation mode of the second electromagnetic proportional pressure reducing valve 25 by the controller 30.

  That is, when the control process in the warm-up operation mode is started, it is determined in step 1 whether or not the engine 9 has been started. While it is determined as “NO” in step 1, the engine 9 is not started, so the control process is terminated. When it is determined as “YES” in step 1, the temperature T of the hydraulic oil in the tank pipe line 27 detected by the temperature sensor 28 in the next step 2 is the first temperature Ta (for example, the set temperature for the warm-up operation). ) Is determined.

  When “YES” is determined in step 2, since the temperature T of the hydraulic oil has not reached the first temperature Ta, the valve housing of the pilot pressure control device 21 is set to the maximum heat circuit opening in the next step 3. 24, the second electromagnetic proportional pressure reducing valve 25 is switched from the reflux stop position (c) to the reflux position (d). As a result, the second electromagnetic proportional pressure reducing valve 25 sets the flow rate of the working oil recirculated from the second pump port 25A to the tank line 27 via the second output port 25C to the maximum flow rate.

  For this reason, the second electromagnetic proportional pressure reducing valve 25 can circulate the warm oil in the tank 12 (the hydraulic oil that is always heated by the heater 31) in the valve housing 24 of the pilot pressure control device 21. 1 The pilot pressure oil supplied to the pilot lines 15A and 15B can be maintained at an appropriate temperature and viscosity by warming up the electromagnetic proportional pressure reducing valves 22 and 23. In the next step 4, the process returns, and the processes after step 1 are repeated.

  On the other hand, when “NO” is determined in Step 2, the temperature T of the hydraulic oil has reached the first temperature Ta. Therefore, in the next Step 5, the second electromagnetic proportional pressure reducing valve 25 is set so as to close the heat circuit. Return to the reflux stop position (c). As a result, the hydraulic oil is stopped from flowing (refluxing) in the valve housing 24 of the pilot pressure control device 21, and the temperature T of the hydraulic oil is prevented from becoming excessively higher than the first temperature Ta. The process returns at step 4, and the processes after step 1 are repeated.

  As indicated by characteristic lines 34 to 36 in FIG. 6, during the time 0 to t1 in the warm-up operation mode, the second electromagnetic proportional pressure reducing valve 25 is driven by the electrical signal from the controller 30 as the engine 9 starts. The switching is controlled, and the heat circuit opening area is set to the maximum (MAX) as described above (see the characteristic line 34). As a result, the temperature T of the hydraulic oil detected by the temperature sensor 28 gradually increases between time 0 and time t1 as indicated by the characteristic line 36, and rises to the first temperature Ta (set temperature for warm-up operation). .

  In the warm-up operation mode, the second electromagnetic proportional pressure reducing valve 25 is switched to the reflux position (d) and the two electromagnetic proportional pressure reducing valves 22 and 23 are switched from the low pressure position (a) to the switching position (b). It is good also as a structure. At this time, the pilot pressure oil discharged from the pilot pump 17 is returned to the tank 12 through the pilot pressure supply line 26, the second electromagnetic proportional pressure reducing valve 25, and the tank line 27. For this reason, even if the two electromagnetic proportional pressure reducing valves 22 and 23 are switched from the low pressure position (a) to the switching position (b), the pilot pressures in the pilot lines 15A and 15B are both low, and the direction control valve 14 Is not inadvertently switched from the neutral position (I). However, it is possible to raise the temperature of the hydraulic oil introduced into the pilot pipelines 15A and 15B.

  Next, work mode control processing by the controller 30 will be described with reference to FIG. That is, when the work mode control process is started, it is determined in step 11 whether or not the engine 9 is in operation. While it is determined as “NO” in step 11, the engine 9 is not operating, so the control process is terminated.

  If "YES" is determined in the step 11, the process proceeds to the next step 12, and whether or not the temperature T of the hydraulic oil in the tank pipe line 27 detected by the temperature sensor 28 is lower than the second temperature Tb (that is, Then, it is determined whether or not the temperature of the pilot pressure generated in the pilot pipes 15A and 15B has dropped to a temperature at which the response of the pilot lever 15A is lowered. For example, as indicated by the characteristic line 36 in FIG. 6, the hydraulic oil temperature T is equal to or higher than the second temperature Tb during the time t1 to t2 of the work mode. Is done. In this case, the process returns at the next step 13, and the processing after step 11 is continued.

  On the other hand, when “YES” is determined in Step 12, the temperature T of the hydraulic oil is lower than the second temperature Tb. Therefore, in step 14, in order to increase the opening amount of the heat circuit, the second electromagnetic proportional pressure reducing valve 25 is switched from the reflux stop position (c) to the reflux position (d), and the opening amount at the reflux position (d) is gradually increased. Let Thereby, for example, as indicated by a characteristic line 36 between times t2 and t3 in FIG. 6, the temperature T of the hydraulic oil is raised to the second temperature Tb or higher.

  In the next step 15, it is determined whether or not the operation lever 20 </ b> A has been tilted. If it is determined “NO” in step 15, the operation lever 20 </ b> A has not been tilted. Move. If “YES” is determined in the step 15, the process proceeds to the next step 16. In step 16, the operating circuit pressure P detected by the pressure sensors 29A and 29B (that is, the pilot pressure in the working mode supplied from the first electromagnetic proportional pressure reducing valves 22 and 23 to the pilot lines 15A and 15B) is set to the set pressure P1 ( It is determined whether it is lower than the characteristic line 35 in FIG. If “NO” is determined in the step 16, the process returns to the step 14 to increase the opening amount of the heat circuit as described above. On the other hand, when “YES” is determined in step 16, the process proceeds to the next step 17 to perform control to reduce the heat circuit opening amount.

  In the pilot pressure control device 21 shown in FIGS. 2 and 3, the second electromagnetic proportional pressure reducing valve 25 is switched from the recirculation stop position (c) to the recirculation position (d) to greatly increase the opening amount at the recirculation position (d). The pilot pressure oil discharged from the pilot pump 17 circulates into the pilot pressure supply line 26 and the valve housing 24 of the pilot pressure control device 21, and most of it returns to the tank 12 from the tank line 27. Is done. Therefore, even if the first electromagnetic proportional pressure reducing valves 22 and 23 are switched from the low pressure position (a) to the switching position (b), the pilot supplied from the first electromagnetic proportional pressure reducing valve 22 to the hydraulic pilot portion 14A of the direction control valve 14 is supplied. The pressure (or the pilot pressure supplied from the first electromagnetic proportional pressure reducing valve 23 to the hydraulic pilot portion 14B of the direction control valve 14) does not increase. In this case, the pilot pressure oil in the pilot lines 15A and 15B tends to be insufficient, and in some cases, the switching operation of the directional control valve 14 becomes difficult, and the expansion / contraction operation of the hydraulic cylinder 13 becomes impossible.

  Therefore, in such a case, it is determined as “YES” in the step 16, and the operation state in which the operation circuit pressure P detected by the pressure sensors 29A and 29B is not equal to or higher than the set pressure P1 (that is, the first electromagnetic proportionality). Since either one of the pressure reducing valves 22 and 23 is in the operation state in which the low pressure position (a) is switched to the switching position (b)), the opening amount of the heat circuit is decreased in the next step 17. In other words, the opening amount of the second electromagnetic proportional pressure reducing valve 25 at the reflux position (d) is decreased. Thereby, the flow volume of the pilot pressure oil recirculated from the 2nd electromagnetic proportional pressure reducing valve 25 to the tank 12 via the tank pipe line 27 is decreased. For this reason, the pilot pressure oil (that is, the operation circuit pressure P) supplied from the first electromagnetic proportional pressure reducing valve 22 or 23 to the hydraulic pilot portion 14A or 14B of the direction control valve 14 can be increased, and a required pilot pressure is secured. It can be so.

  In the next step 18, it is determined whether or not the temperature T of the hydraulic oil is lower than the first temperature Ta, and when “YES” is determined in step 18, the process returns to step 16 and the subsequent processing is continued. To do. However, when it is determined “NO” in step 18, the process proceeds to the next step 19 in order to avoid that the temperature T of the hydraulic oil becomes equal to or higher than the first temperature Ta and becomes excessively high (overheat). Control to close the heat circuit. That is, by returning the second electromagnetic proportional pressure reducing valve 25 from the recirculation position (d) to the recirculation stop position (c), the heat circuit is closed and the recirculation of the pilot pressure oil is stopped. .

  In this way, the work mode control process by the controller 30 is executed as shown in steps 12 to 19 in FIG. For this reason, the opening area of the heat circuit is variably controlled between the times t1 and t7 as shown by the characteristic 33 in FIG. As a result, the temperature T of the hydraulic oil in the tank line 27 detected by the temperature sensor 28 is, as indicated by the characteristic line 36, a temperature range between the first temperature Ta and the second temperature Tb (that is, The temperature is controlled so as to be within the range of the warm-up temperature.

  Further, the operation circuit pressure P detected by the pressure sensors 29A and 29B is controlled in a stepwise manner as indicated by a characteristic line 35 in FIG. The pilot pressure supplied from 22 or 23 to the hydraulic pilot part 14A or 14B of the direction control valve 14 can be secured. For this reason, the pilot pressure oil supplied from the first electromagnetic proportional pressure reducing valve 22 or 23 to the hydraulic pilot portion 14A or 14B of the direction control valve 14 tends to be insufficient while the temperature of the hydraulic oil is kept warm in the work mode. The expansion / contraction operation of the hydraulic cylinder 13 (the operation required during work) can be continued.

  Thus, according to the first embodiment, for example, when warming up the vehicle body that has cooled down immediately after the engine 9 starts cold in a cold region or the like, the heat circuit by the second electromagnetic proportional pressure reducing valve 25 is maximized. By making the opening and increasing the flow rate, it is possible to circulate warm oil in the tank 12 (hydraulic oil that is always heated by the heater 31) in the valve housing 24 of the pilot pressure control device 21. As a result, the pilot circuit (that is, the first electromagnetic proportional pressure reducing valves 22 and 23) can be warmed up and the pilot pressure oil supplied to the pilot lines 15A and 15B can be maintained at an appropriate temperature and viscosity state.

  Even in the work mode after the warm-up operation mode, the temperature of the pilot pressure oil is constantly monitored by the temperature sensor 28 provided on the tank line 27 side, and the opening area of the heat circuit by the second electromagnetic proportional pressure reducing valve 25 is determined. It can be adjusted according to the situation. As a result, the minimum pilot pressure (operation circuit pressure) necessary for the operation of the directional control valve 14 can be secured by the switching control of the first electromagnetic proportional pressure reducing valves 22 and 23, and the pilot pressure control device 21 Warm-up is possible and the oil temperature can be maintained at the required temperature.

  Further, switching between the warm-up operation mode and the work mode may be performed freely by an operator in the cab 7 (operating room) by an arbitrary operation using, for example, a switch (not shown). Further, in the warm-up operation mode, when the oil temperature detected by the temperature sensor 28 of the pilot pressure control device 21 reaches a set temperature such as the first temperature Ta, for example, the operator is notified by a monitor or the like. Thus, it is possible to smoothly shift to the work mode and start the field work.

  Therefore, according to the first embodiment, the second electromagnetic proportional pressure reducing valve 25 recirculates the pilot pressure oil flowing from the second pump port 25A to the second output port 25C to the tank line 27, thereby controlling the pilot pressure. The oil temperature of the working oil flowing through the valve housing 24 of the device 21 can be raised. For this reason, the heat system of the pilot pressure control device 21 (pilot circuit) can be realized with a simple circuit configuration, and the warm-up operation immediately after the engine 9 is started at a low temperature can be efficiently performed. Even during the operation of the hydraulic excavator 1, the pilot circuit can be warmed up without interrupting the operation by switching the first electromagnetic proportional pressure reducing valves 22, 23 and the second electromagnetic proportional pressure reducing valve 25.

  Moreover, the pilot pressure control device 21 employed in the first embodiment is provided with a fixed throttle 33 in the middle of the tank line 27 on the downstream side of the second electromagnetic proportional pressure reducing valve 25. As a result, the flow (kinetic) energy of the hydraulic oil (return oil) recirculated from the second pump port 25A of the second electromagnetic proportional pressure reducing valve 25 to the tank pipe line 27 via the second output port 25C has thermal energy. Is converted by the fixed aperture 33. Thereby, the oil temperature of the hydraulic fluid which distribute | circulates the inside of the valve housing 24 of the pilot pressure control apparatus 21 can be raised, and the pilot pressure control apparatus 21 can be warmed up satisfactorily.

  As described above, according to the first embodiment, the fixed throttle 33 is provided in the middle of the tank conduit 27 on the downstream side of the second electromagnetic proportional pressure reducing valve 25, so that the inside of the valve housing 24 of the pilot pressure control device 21. It is possible to increase the oil temperature of the hydraulic oil that circulates and maintain the pilot pressure control device 21 warm-up. Further, in this state, a pressure corresponding to the resistance of the fixed throttle 33 can be generated on the upstream side of the second electromagnetic proportional pressure reducing valve 25, and the operation becomes impossible due to insufficient pressure on the first electromagnetic proportional pressure reducing valves 22 and 23 side. Can be prevented. In other words, the fixed throttle 33 can serve as a safety device by setting a fixed throttle diameter that guarantees a minimum pressure that does not affect the operation of the machine and secures a flow rate.

  In the first embodiment, the case where the fixed throttle 33 is provided in the valve housing 24 of the pilot pressure control device 21 has been described as an example. However, the present invention is not limited to this. For example, the fixed throttle 33 may be provided outside the valve housing 24 of the pilot pressure control device 21 and provided in the middle of the tank conduit 27.

  Next, FIG. 7 and FIG. 8 show a second embodiment. In the present embodiment, the same components as those in the first and second embodiments described above are denoted by the same reference numerals, and the description thereof is omitted. However, the feature of the second embodiment is that the pilot pressure control device for switching the control valve is located away from the heat source of the upper swing body 4 (vehicle body) (for example, the boom 10A of the work device 10). The configuration is such that it is exposed to the outside.

  As shown in FIG. 8, a regeneration pipeline 51 is provided between the main pipelines 16A and 16B of the hydraulic cylinder 13 so as to short-circuit the bottom-side oil chamber 13D and the rod-side oil chamber 13E. Yes. A flow rate regeneration valve 52 and a check valve 53 as control valves are provided in the middle of the regeneration conduit 51. The flow rate regeneration valve 52 is constituted by, for example, a 2-port 2-position hydraulic pilot type switching valve, and is always placed at the cutoff position (e) by a spring 52B.

  When the pilot pressure is supplied to the hydraulic pilot portion 52A via the pilot pipe line 54, the flow rate regeneration valve 52 is switched from the cutoff position (e) to the flow rate regeneration position (f) against the spring 52B. At this time, the flow rate regenerating valve 52 is configured to remove a part of the pressure oil (return oil) discharged from the bottom oil chamber 13D of the hydraulic cylinder 13 to the main line 16A through the regenerating line 51 and the check valve 53. It joins and circulates to the 16B side, and supplies this to the oil chamber 13E on the rod side as regenerated oil. The flow rate regeneration valve 52 constitutes a control valve that controls the supply of pressure oil to the hydraulic cylinder 13.

  The electromagnetic pilot pressure control device 55 includes a first electromagnetic proportional pressure reducing valve 56 as a first electromagnetic valve that supplies pilot pressure to the hydraulic pilot portion 52A of the flow rate regeneration valve 52 via the pilot pipe line 54, and the first electromagnetic proportional pressure reducing valve 56. A second electromagnetic proportional pressure reducing valve 58 as a second electromagnetic valve provided in a valve housing 57 common to the electromagnetic proportional pressure reducing valve 56 and a discharge side of the pilot pump 17 are provided and extended into the valve housing 57. The pilot pressure supply line 59 and the tank line 60 extending from the valve housing 57 toward the tank 12 and having a distal end connected to the tank 12 are configured.

  The pilot pressure supply line 59 of the pilot pressure control device 55 is branched off from the pilot pressure supply line 26 of the pilot pressure control device 21, and both are connected to the discharge side of the pilot pump 17. The tank line 60 of the pilot pressure control device 55 is also provided so as to branch off from the tank line 27 of the pilot pressure control device 21, and both are connected to the tank 12.

  The first electromagnetic proportional pressure reducing valve 56 is disposed in the valve housing 57 so as to be in parallel with the second electromagnetic proportional pressure reducing valve 58, and is switched from the low pressure position (g) to the switching position (h) according to an electric signal from the controller 64 described later. Is switched in proportion to the electromagnetic field. The first electromagnetic proportional pressure reducing valve 56 includes a first pump port 56 </ b> A connected to the pilot pressure supply line 59 in the valve housing 57, a first tank port 56 </ b> B connected to the tank line 60, and a flow rate regeneration valve 52. And a first output port 56C connected to the hydraulic pilot portion 52A.

  The first electromagnetic proportional pressure reducing valve 56 is switched to the low pressure position (g) or the switching position (h) according to the electric signal, so that the first output port 56C is selectively used as the first pump port 56A or the first tank port 56B. Connected to. That is, while the electrical signal from the controller 64 is demagnetized (energization is stopped), the first electromagnetic proportional pressure reducing valve 56 is in the low pressure position (g). At this time, the first output port 56C is connected to the first pump port 56A. On the other hand, it is blocked and connected to the first tank port 56B. For this reason, the pilot pressure in the pilot line 54 is maintained at a low pressure state close to the tank pressure.

  However, when the electrical signal from the controller 64 is in an excited (energized) state, the first electromagnetic proportional pressure reducing valve 56 is electromagnetically proportional from the low pressure position (g) to the switching position (h) in proportion to the current value at this time. At this time, the first output port 56C is connected to the first pump port 56A. For this reason, the pilot pressure in the pilot line 54 is increased in response to the electric signal (that is, the control current), and the flow rate regenerating valve 52 flows from the shut-off position (e) in proportion to the pilot pressure at this time. The playback position (f) is switched.

  The flow rate regeneration valve 52 is switched from the cutoff position (e) to the flow rate regeneration position (f) by supplying the pilot pressure to the hydraulic pilot unit 52A in this way. For this reason, when the rod 13C of the hydraulic cylinder 13 is contracted into the tube 13A, a part of the pressure oil (return oil) discharged from the bottom side oil chamber 13D of the hydraulic cylinder 13 to the main pipeline 16A is regenerated. It is possible to circulate through the check valve 53 to the main pipe line 16B side and supply it to the oil chamber 13E on the rod side as recycled oil. Thereby, the operation of reducing the rod 13C of the hydraulic cylinder 13 can be accelerated by the regenerated flow rate.

  The second electromagnetic proportional pressure reducing valve 58 is provided in a common valve housing 57 so as to be in parallel with the first electromagnetic proportional pressure reducing valve 56. The second electromagnetic proportional pressure reducing valve 58 constitutes a heat circuit of the pilot pressure control device 55 and is switched in electromagnetic proportion from the reflux stop position (j) to the reflux position (k) by an electric signal from the controller 64. The second electromagnetic proportional pressure reducing valve 58 includes a second pump port 58A connected to the pilot pressure supply line 59 in the valve housing 57 and a second tank port 58B connected to the tank line 60 in the valve housing 57. And a second output port 58C.

  The second electromagnetic proportional pressure reducing valve 58 is switched to the recirculation stop position (j) or the recirculation position (k) according to the electric signal from the controller 64, so that the second output port 58C becomes the second pump port 58A or the second tank port. 58B is selectively connected. That is, while the second electromagnetic proportional pressure reducing valve 58 is returned to the recirculation stop position (j) by the electrical signal from the controller 64, the working oil flows (recirculates) in the valve housing 57 of the pilot pressure control device 55. Stop doing.

  However, when the second electromagnetic proportional pressure reducing valve 58 is switched from the reflux stop position (j) to the reflux position (k) by the electrical signal from the controller 64, the second output port 58C is connected to the second pump port 58A. . As a result, the second electromagnetic proportional pressure reducing valve 58 allows the pilot pressure oil discharged from the pilot pump 17 to flow through the pilot pressure supply line 59 and the valve housing 57 of the pilot pressure control device 55, while the second electromagnetic proportional pressure reducing valve 58. The second pump port 58A is returned to the tank line 60 via the second output port 58C. At this time, the valve housing 57 of the pilot pressure control device 55 rises in temperature by receiving thermal energy from the pilot pressure oil (hydraulic oil) flowing inside, and the oil temperature of the hydraulic oil is maintained at a high temperature in the valve housing 57. can do.

  In other words, the second electromagnetic proportional pressure reducing valve 58 heats the pilot circuit (particularly, the first electromagnetic proportional pressure reducing valve 56) including the pilot pressure control device 55 that switches the flow rate regeneration valve 52. It is provided as a circuit. That is, the second electromagnetic proportional pressure reducing valve 58 circulates the warm oil in the tank 12 (the working oil that is always heated by the heater 31) into the valve housing 57 of the pilot pressure control device 55, thereby piloting the pilot oil. The circuit (ie, the first electromagnetic proportional pressure reducing valve 56) can be warmed up. The valve housing 57 constitutes a common heat conductor that allows heat due to an increase in the oil temperature of the hydraulic oil to be transferred between the first electromagnetic proportional pressure reducing valve 56 and the second electromagnetic proportional pressure reducing valve 58.

  Further, the pilot pressure control device 55 is fixed between the second output port 58 </ b> C of the second electromagnetic proportional pressure reducing valve 58 and the tank pipeline 60 to limit the flow rate of the return oil returned to the tank pipeline 60. A diaphragm 61 is provided. The fixed throttle 61 is configured in the same manner as the fixed throttle 33 described in the second embodiment, but is different from the second embodiment in that it is arranged outside the valve housing 57. doing. The fixed throttle 61 may be arranged inside the valve housing 57, and such a design change can be made as necessary.

  Here, in the pilot pressure control device 55 employed in the second embodiment, the first electromagnetic proportional pressure reducing valve 58 and the second electromagnetic proportional pressure reducing valve 58 arranged in parallel in the valve housing 57 are common. Along with the valve housing 57, the boom 10 </ b> A of the work apparatus 10 is provided. Thereby, the pipe line length of the pilot pipe line 54 connecting the hydraulic pilot part 52A of the flow rate regeneration valve 52 and the first electromagnetic proportional pressure reducing valve 56 can be shortened. As shown in FIG. 7, the first electromagnetic proportional pressure reducing valve 56, the second electromagnetic proportional pressure reducing valve 58 and the valve housing 57 of the pilot pressure control device 55 are provided in a state of being exposed to the outside of the boom 10A.

  The temperature sensor 62 is, for example, a temperature detector provided in the middle of the tank pipeline 60, and returns oil (hydraulic fluid) returned from the valve housing 57 of the pilot pressure control device 55 to the tank 12 via the tank pipeline 60. ) Temperature. The pressure sensor 63 is a detector that detects the pilot pressure in the pilot pipe line 54. The pressure sensor 63 is provided in the middle of the pilot conduit 54 between the first output port 56C of the first electromagnetic proportional pressure reducing valve 56 and the hydraulic pilot portion 52A of the flow rate regeneration valve 52. Detection signals from the temperature sensor 62 and the pressure sensor 63 are output to the controller 64.

  The controller 64 is configured in substantially the same manner as the controller 30 described in the first embodiment. However, the controller 64 determines the first electromagnetic proportional pressure reducing valve 56 and the second electromagnetic proportional pressure reducing valve 58 according to the drive information of the engine 9, the electric signal from the operation lever device 20, and the detection signals from the temperature sensor 62 and the pressure sensor 63. Is different from the first embodiment in that switching control is performed. On the input side of the controller 64, the operation lever device 20, the temperature sensors 28 and 62, the pressure sensors 29 </ b> A, 29 </ b> B and 63, a control device (not shown) for the engine 9, and the like are connected. The output side of the controller 64 is connected to the pilot pressure control device 55 in addition to the first electromagnetic proportional pressure reduction valves 22 and 23 and the second electromagnetic proportional pressure reduction valve 25 of the pilot pressure control device 21 described in the first embodiment. The first electromagnetic proportional pressure reducing valve 56 and the second electromagnetic proportional pressure reducing valve 58 are connected.

  The controller 64 has a memory 64A composed of, for example, a nonvolatile memory, a ROM, a RAM, and the like. In the memory 64A, for example, the warm-up operation mode control process (see FIG. 4) described in the first embodiment, the work mode control process program (see FIG. 5), and the first temperature are stored. In addition to Ta, second temperature Tb, required set pressure P1, etc., a program (not shown) for switching control of flow rate regeneration valve 52, and a program for warming up pilot pressure control device 55 (Not shown) and the like are stored.

  Thus, in the second embodiment configured as described above, the heat system of the pilot pressure control device 21 (pilot circuit) is realized with a simple circuit configuration as in the first and second embodiments described above. The engine 9 can be efficiently warmed up immediately after the cold start, and the first electromagnetic proportional pressure reducing valve 25 and the second electromagnetic proportional pressure reducing valve 25 are switched while the hydraulic excavator 1 is being operated. By doing so, the pilot circuit can be warmed up without interrupting the work.

  Moreover, in the second embodiment, a second electromagnetic proportional pressure reducing valve 58 and the like are additionally provided to the first electromagnetic proportional pressure reducing valve 56 of the pilot pressure control device 55 that controls the flow rate regeneration valve 52 with the pilot pressure. Thus, the heat system of the pilot pressure control device 55 can be realized with a simple configuration, and the operation can be performed by switching the first electromagnetic proportional pressure reducing valve 56 and the second electromagnetic proportional pressure reducing valve 58 even during the operation of the hydraulic excavator 1. The pilot line 54 and the like can be warmed up without interruption.

  As shown in FIG. 7, the first electromagnetic proportional pressure reducing valve 56, the second electromagnetic proportional pressure reducing valve 58, and the valve housing 57 of the pilot pressure control device 55 are provided in a state of being attached to the boom 10A from the outside. Thereby, there is an advantage that the pipeline length of the pilot pipeline 54 connecting the hydraulic pilot portion 52A of the flow rate regeneration valve 52 and the first electromagnetic proportional pressure reducing valve 56 can be shortened. However, since the valve housing 57 of the pilot pressure control device 55 is located away from the heat source of the upper swing body 4 (vehicle body) and exposed to the outside of the boom 10A, the valve housing 57, the pilot The oil temperature in the pressure supply line 59 and the tank line 60 is particularly susceptible to the ambient temperature in cold regions.

  Therefore, for example, when warming up the vehicle body and the boom 10A side of the working device 10 immediately after the low temperature start of the engine 9 in a cold region or the like, the heat circuit by the second electromagnetic proportional pressure reducing valve 58 is opened to the maximum. By increasing the flow rate, it is possible to circulate the warm oil in the tank 12 (the hydraulic oil that is always heated by the heater 31) in the valve housing 57 of the pilot pressure control device 55. As a result, the pilot circuit (that is, the first electromagnetic proportional pressure reducing valve 56 and the valve housing 57) is warmed up by the second electromagnetic proportional pressure reducing valve 58, and the pilot pressure oil supplied to the pilot line 54 is supplied with an appropriate temperature and viscosity. Can be kept in a state.

  Therefore, in the second embodiment, even when the valve housing 57 of the pilot pressure control device 55 is provided at a position where it is blown away at a position away from the heat source of the upper swing body 4 (vehicle body), the warming in the tank 12 is maintained. By circulating the oil in the valve housing 57, the oil temperature in the valve housing 57, the pilot pressure supply pipe 59 and the tank pipe 60 can be raised, and it is also necessary at a place where it is easily affected by the ambient temperature particularly in a cold region. Warm-up can be performed efficiently.

  In the second embodiment, the pilot pressure control device 21 and another pilot pressure control device 55 are provided on the discharge side of the pilot pump 17 via the pilot pressure supply lines 26 and 59 as an example. Explained. However, the present invention is not limited to this. For example, the pilot pressure control device 21 may be omitted, and only another pilot pressure control device 55 may be provided.

  In the first embodiment, the case where the pilot pressure control device 21 is provided with the first electromagnetic proportional pressure reducing valves 22 and 23 and the second electromagnetic proportional pressure reducing valve 25 has been described as an example. However, the present invention is not limited to this. For example, instead of the second electromagnetic proportional pressure reducing valve 25, an electromagnetic valve capable of more inexpensive ON-OFF control may be used.

  Further, in the pilot pressure control device 55 described in the second embodiment, the second electromagnetic proportional pressure reducing valve 58 may be constituted by an electromagnetic valve capable of inexpensive ON-OFF control.

  Furthermore, in each said embodiment, the large sized hydraulic excavator 1 was mentioned as an example and demonstrated as a working machine. However, the present invention is not limited to this, and may be applied to, for example, a medium-sized hydraulic excavator. Furthermore, it can be widely applied to work machines such as hydraulic cranes, wheel loaders, and dump trucks.

1 Excavator (work machine)
DESCRIPTION OF SYMBOLS 2 Lower traveling body 4 Upper revolving body 5 Turning frame 7 Cab 8 Counterweight 9 Engine 10 Working apparatus 11 Main hydraulic pump 12 Tank 13 Hydraulic cylinder (hydraulic actuator)
14 Directional control valve (control valve)
15A, 15B, 54 Pilot pipeline 17 Pilot pump 20 Operation lever device (electric operation device)
20A Operation lever 21, 55 Pilot pressure control device 22, 23, 56 First electromagnetic proportional pressure reducing valve (solenoid valve)
22A, 23A, 56A First pump port 22B, 23B, 56B First tank port 22C, 23C, 56C First output port 24, 57 Valve housing 25, 58 Second electromagnetic proportional pressure reducing valve (solenoid valve)
25A, 58A Second pump port 25B, 58B Second tank port 25C, 58C Second output port 26, 59 Pilot pressure supply line 27, 60 Tank line 28, 62 Temperature sensor 29A, 29B, 63 Pressure sensor 30, 64 Controller 31 Heater 33, 61 Fixed throttle 51 Regeneration line 52 Flow rate regenerative valve (control valve)

Claims (5)

A main hydraulic pump and a pilot pump that are driven by the prime mover of the work machine and suck in hydraulic oil from the tank and discharge the pressure oil;
A hydraulic actuator provided in the work machine and driven by pressure oil supplied from the hydraulic pump;
A control valve which is provided between the hydraulic pump and the hydraulic actuator, and controls supply of pressure oil to the hydraulic actuator by supplying pilot pressure from the pilot pump to a hydraulic pilot unit;
An electric operation device that outputs an electric signal in accordance with an external operation to control the operation of the hydraulic actuator by switching the control valve;
A pilot pressure control device that variably controls the pilot pressure supplied to the hydraulic pilot portion of the control valve in accordance with the electrical signal from the electric operation device;
In the hydraulic control device for work machines provided with
The pilot pressure control device
A pilot pressure supply line connected to the discharge side of the pilot pump;
A tank line connected to the tank;
A first pump port connected to the pilot pressure supply line; a first tank port connected to the tank line; and a first output port connected to a hydraulic pilot part of the control valve; A first solenoid valve that selectively connects the first output port to the first pump port or the first tank port to perform switching control of the control valve,
A second pump port connected to the pilot pressure supply line; a second tank port connected to the tank line; and a second output port. The second output port is connected to the second pump according to the electrical signal. A second solenoid valve selectively connected to the port or the second tank port;
Comprising
The second solenoid valve has a configuration in which pressure oil flowing from the second pump port to the second output port is recirculated to the tank pipe line in order to increase the temperature of hydraulic oil flowing through the pilot pressure control device. A hydraulic control device for a work machine, characterized in that   A fixed restrictor is provided between the second output port of the second solenoid valve and the tank pipe to limit the flow rate of return oil returned to the tank pipe. Item 2. A hydraulic control device for a work machine according to Item 1. A temperature sensor that detects the temperature of the return oil that is returned from the tank line to the tank;
A pressure sensor provided between a first output port of the first solenoid valve and a hydraulic pilot part of the control valve for detecting the pilot pressure;
A controller for controlling the first and second electromagnetic valves in accordance with drive information of the prime mover, an electrical signal from the electric operation device, and detection signals from the temperature sensor and pressure sensor. The hydraulic control device for a work machine according to claim 1.   The said pilot pressure control apparatus has a common valve housing in which the heat by the oil temperature rise of the said hydraulic fluid is transmitted between the said 1st, 2nd solenoid valves. Hydraulic control device for work machines.   The pilot pressure control device includes a common valve housing to which heat due to a rise in oil temperature of the hydraulic oil is transmitted between the first and second electromagnetic valves and the fixed throttle. Item 3. A hydraulic control device for a work machine according to Item 2.

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