JP4344712B2 - Hydraulic drive - Google Patents

Description

  The present invention relates to a hydraulic drive device that is provided in a work machine such as a hydraulic excavator and includes an engine, a variable displacement main pump that is driven by the engine, and a pilot pump.

  There exists a thing shown by patent document 1 as this type of prior art. FIG. 3 is a hydraulic circuit diagram corresponding to the main part of the conventional hydraulic drive shown in Patent Document 1. In FIG.

  The prior art shown in FIG. 3 is provided with, for example, a hydraulic excavator, and includes a hydraulic drive equipped with a load sensing control system that controls a discharge pressure of a main pump to be higher by a target differential pressure than a maximum load pressure of a plurality of actuators. Device.

  As shown in FIG. 3, this prior art includes an engine 1, a variable capacity main pump 2 driven by the engine 1, and a pilot pump 3. In addition, a pump regulator that controls the tilt angle of the main pump 2 is provided. The pump regulator includes a horsepower control tilt actuator 4 that is driven by the discharge pressure of the main pump 2 and load sensing control (hereinafter referred to as “LS control”). .) The tilt actuator 5 and the LS control valve 6 for controlling the drive of the LS tilt actuator 5 are provided. When a load sensing target differential pressure is applied to one control chamber 6a of the LS control valve 6, the LS control valve 6 causes the LS tilt actuator 5 to increase the tilt angle of the main pump 2. The drive of the rolling actuator 5 is controlled. When the load sensing actual differential pressure corresponding to the current maximum load pressure is applied to the other control chamber 6b that opposes the control chamber 6a described above, the LS tilt actuator 5 is connected to the main pump 2 by the LS control valve 6. The drive of the LS tilt actuator 5 is controlled so as to reduce the tilt angle of the LS.

  Further, as shown in FIG. 3, a plurality of actuators such as an actuator 7 such as a turning motor driven by pressure oil discharged from the main pump 2 and an actuator 8 such as a boom cylinder are provided. In FIG. 3, only two actuators 7 and 8 are shown for ease of explanation, but actually, more actuators are provided.

In addition, flow control valves 9 and 10 for controlling the flow of pressure oil supplied from the main pump 2 to the actuators 7 and 8 and the like are provided. For example, on the upstream side of each of these flow control valves 9, 10, pressure compensation valves 11, 12, etc. that are driven according to the differential pressure across the throttle portion built in the flow control valves 9, 10 are provided. Yes. Further, on the upstream side of these pressure compensation valves 11, 12, etc., there is a differential pressure between the discharge pressure of the main pump 2 and the maximum load pressure of the plurality of actuators 7, 8 taken out from the shuttle valve 16. A differential pressure reducing valve 13 that is driven in response and supplies the load sensing actual differential pressure to the above-described pressure compensating valves 11 and 12 is provided.

  Further, a flow rate detection valve 14 for detecting a flow rate discharged from the pilot pump 3 in accordance with the rotational speed of the engine 1, that is, a flow rate corresponding to the rotational speed of the engine 1, and the flow rate detection valve 14 are controlled by the load sensing target. A differential pressure reducing valve 15 that outputs a differential pressure is provided. The load sensing target differential pressure output from the differential pressure reducing valve 15 is given to one control chamber 6a of the LS control valve 6 described above.

  Further, an unload valve 17 that is driven according to a differential pressure between the discharge pressure of the main pump 2 and the maximum load pressure, a main relief valve 18 that regulates the discharge pressure of the main pump 2, and a pilot discharged from the pilot pump 3 A pilot relief valve 19 that regulates pressure and an oil filter 20 are provided.

  The above-described main pump 2 is held at the minimum tilt angle so as to discharge a predetermined minimum flow rate when the engine 1 is driven and all of the flow control valves 9 and 10 are held neutral. When the engine 1 is stopped due to the structural relationship, the maximum tilt angle is maintained.

  By the way, in a working machine that works outdoors, such as a hydraulic excavator equipped with the hydraulic drive device shown in FIG. 3, in an environment where the ambient temperature is extremely low, such as in a cold winter, While the machine is stopped, the temperature of the hydraulic oil also decreases and its viscosity increases. In this state, the engine 1 is started. This engine starting operation is performed by continuously rotating the starter, that is, the operation unit of the engine starting device for a predetermined time. At this time, as described above, since the tilt angle of the main pump 2 is maximized for structural reasons, the output torque is high.

  That is, in a low-temperature environment, the suction resistance of the hydraulic pumps 2 and 3 due to the increase in the viscosity of the hydraulic oil and the pipe resistance when flowing in the pipe are increased. If it is circulated in the circuit, the load acting on the engine 1 becomes extremely high. Moreover, at a low temperature, the output horsepower itself of the engine 1 is reduced due to an increase in engine oil viscosity, a decrease in battery capacity, and the like, and therefore the engine 1 cannot be started smoothly and quickly. When the temperature is extremely low, the starting operation must be continued for, for example, one minute or more.

  As a conventional technique for solving such a problem, a technique disclosed in Patent Document 2 has been proposed. In this other prior art, a bypass flow path for returning to the hydraulic oil tank is connected to a discharge port of a hydraulic pump driven by the engine, and when the engine is started, a switching valve arranged in the bypass flow path is switched. The oil discharged from the hydraulic pump is directly returned to the hydraulic oil tank to suppress the load resistance of the engine at the start.

When the idea shown in Patent Document 2 is applied to a hydraulic drive apparatus including the variable displacement main pump 2 and the pilot pump 3 as shown in FIG. 3, the main pump 2 and Since each discharge pressure and flow rate when the pilot pump 3 is operated are different from each other, each of these two pumps is provided with a bypass passage as described above and a switching valve disposed in the bypass passage. It will be necessary.
JP 2003-113804 A Japanese Patent Laid-Open No. 10-18968

  As described above, in the conventional hydraulic drive device including the variable displacement main pump 2 and the pilot pump 3 as shown in FIG. Since it is necessary to provide a bypass flow path and a switching valve corresponding to each of the pump 2 and the pilot pump 3, the structure of the entire apparatus is complicated. In particular, since the main pump 2 directly drives the actuators 7, 8, etc., the maximum discharge pressure is extremely high. A switching valve that can withstand such a maximum discharge pressure, that is, a switching valve provided in the bypass flow path is large. That is, the entire apparatus becomes large. Such complication and enlargement of the structure of the entire apparatus cause an increase in manufacturing cost, which is problematic in terms of practicality.

  The present invention has been made from the above-described prior art, and its object is to reduce the engine load at the start of the engine while suppressing the complication and enlargement of the structure of the entire apparatus, and the rapid engine associated therewith. An object of the present invention is to provide a hydraulic drive device that can realize a starting operation.

To achieve the above object, the present invention provides an engine, a variable displacement main pump and a pilot pump driven by the engine, a tilting actuator for controlling a tilting angle of the main pump, and the tilting actuator. A pump regulator including a control valve for controlling the driving of the motor, a plurality of actuators driven by pressure oil discharged from the main pump, and a flow rate for controlling the flow of pressure oil supplied from the main pump to each of the actuators In the hydraulic drive apparatus including the control valve, when the engine is started, the control oil is used as the control pressure for driving the control valve so that the tilting angle of the main pump becomes small. a control pressure supply means for supplying to the control chamber, the control pressure supply means, the control pressure is given A pilot line that can connect the control chamber of the control valve and the pilot pump, and a switching unit that is provided in the pilot line and that can supply pressure oil of the pilot pump to the control chamber of the control valve A solenoid valve having a position, a battery connectable to the solenoid valve, a switch for connecting and disconnecting the solenoid valve and the battery, and a gate lock lever for switching the switch is provided .

  In the present invention configured as described above, when the engine is started, the control pressure supply means supplies the pilot pump pressure oil that rises up to the maximum pressure faster than the main pump to the control valve of the pump regulator, and this control valve is supplied to the main pump. The tilt angle is driven so as to be small. Therefore, when the engine is started, the tilt angle of the main pump that has been maintained at the maximum tilt angle can be immediately changed to a small tilt angle. Thereby, the engine load at the time of engine start can be reduced, and the quick engine start operation associated therewith can be performed. In particular, according to the present invention, the control pressure supply means for driving the control valve so as to reduce the tilt angle of the main pump when the engine is started only needs to be provided in association with only the pilot pump. And increase in size can be suppressed.

Further , for example, when the engine is started in a state in which the switch is turned off and the connection between the solenoid valve provided in the pilot line and the battery is cut off and the engine is started, the pilot pump is connected via the solenoid valve and the pilot line. Pressure oil is supplied to the control chamber of the control valve included in the pump regulator. Thereby, this control valve is driven so that the tilt angle of the main pump becomes small. Therefore, when the engine is started, the tilt angle of the main pump that has been maintained at the maximum tilt angle immediately before becomes a small tilt angle. Thereafter, when the switch is turned on, the electromagnetic valve and the battery are connected, the electromagnetic valve is driven, the pilot line is shut off, and the supply of pressure oil from the pilot pump to the control chamber is stopped. That is, the hydraulic device such as the front work machine can be driven.

  In particular, the present invention is characterized in that the control pressure supply means includes a pilot line that communicates only with a pilot pump, that is, a pilot pump and a control chamber of a control valve of the pump regulator, and the pilot pressure line is provided in the pilot line. Since the electromagnetic valve provided, a battery connectable to the electromagnetic valve, and a switch for connecting / disconnecting the electromagnetic valve to the battery are included, the structure of the entire apparatus can be complicated and the increase in size can be suppressed.

In addition , a switch that enables driving of the solenoid valve included in the control pressure supply means is used as a gate lock lever that realizes permission to supply pressure oil from the main pump to the actuator that drives the front work machine, etc. Since the gate lock lever is not allowed to supply pressure oil from the main pump to the actuator that drives the front work machine etc. By setting the gate lock lever position and the switch operation relationship in advance so as to be shut off, the front working machine or the like is not erroneously driven when the engine is started.

  Further, the present invention is characterized in that in the above invention, a load sensing control system is provided for controlling the discharge pressure of the main pump so as to be higher than the maximum load pressure among the plurality of actuators by a target differential pressure.

  In the present invention, the control pressure supply means for driving the control valve of the pump regulator is provided in association with only the pilot pump so that the tilt angle of the main pump is reduced when the engine is started. While reducing the complexity and size, it is possible to reduce the engine load at the start of the engine, and to realize a quick engine start operation associated with this, and to reduce the manufacturing cost compared to what can be considered in the past, practicality Rich.

  The best mode for carrying out the hydraulic drive apparatus according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a hydraulic circuit diagram showing an embodiment of a hydraulic drive apparatus according to the present invention. In FIG. 1, the same components as those shown in FIG. 3 are denoted by the same reference numerals.

  That is, although the description overlaps with the above description, this embodiment is also provided in a hydraulic excavator, for example, as shown in FIG. 3, and the discharge pressure of the main pump 2 is the same as that of the actuators 7 and 8. It is equipped with a load sensing control system that controls the target differential pressure to be higher than the maximum load pressure.

  This embodiment also includes an engine 1, a variable displacement main pump 2 driven by the engine 1, and a pilot pump 3, and a pump regulator that controls the tilt angle of the main pump 2. The pump regulator includes a horsepower control tilt actuator 4 that is driven by the discharge pressure of the main pump 2, an LS control tilt actuator 5, and an LS control valve 6 that controls the drive of the LS control tilt actuator 5. Yes.

  As described above, when the load sensing target differential pressure is applied to one control chamber 6a of the LS control valve 6, the LS control valve 6 causes the LS control tilt actuator 5 to increase the tilt angle of the main pump 2. As described above, when the driving of the LS control tilting actuator 5 is controlled, and the other control chamber 6b that opposes the control chamber 6a is given a load sensing actual differential pressure generated in the circuit in accordance with the maximum load pressure. The LS control valve 6 controls the driving of the LS control tilt actuator 5 so that the LS control tilt actuator 5 reduces the tilt angle of the main pump 2.

  Further, in FIG. 1, only two actuators 7 and 8 are illustrated for ease of explanation, but actually, more actuators are provided.

Further, the flow rate control valves 9 and 10 etc. for controlling the flow of pressure oil supplied from the main pump 2 to the actuators 7 and 8 etc. and the flow rate control valves 9 and 10 etc. are arranged on the upstream side, for example. And pressure compensation valves 11 and 12 that are driven in accordance with the differential pressure across the throttle portion built in the flow control valves 9 and 10. Further, on the upstream side of these pressure compensation valves 11, 12, etc., there is a differential pressure between the discharge pressure of the main pump 2 and the maximum load pressure of the plurality of actuators 7, 8 taken out from the shuttle valve 16. A differential pressure reducing valve 13 that is driven in response and supplies the load sensing actual differential pressure to the above-described pressure compensating valves 11 and 12 is provided. Further, a flow rate detection valve 14 for detecting a flow rate discharged from the pilot pump 3 in accordance with the rotational speed of the engine 1, that is, a flow rate corresponding to the rotational speed of the engine 1, and the flow rate detection valve 14 are controlled by the load sensing target. A differential pressure reducing valve 15 that outputs a differential pressure is provided. The load sensing target differential pressure output from the differential pressure reducing valve 15 is given to one control chamber 6a of the LS control valve 6 described above.

  Further, an unload valve 17 that is driven according to a differential pressure between the discharge pressure of the main pump 2 and the maximum load pressure, a main relief valve 18 that regulates the discharge pressure of the main pump 2, and a pilot discharged from the pilot pump 3 A pilot relief valve 19 that regulates pressure and an oil filter 20 are provided.

  As described above, the main pump 2 is held at the minimum tilt angle so as to discharge a predetermined minimum flow rate when the engine 1 is driven and all of the flow control valves 9 and 10 are held neutral. However, when the engine 1 is stopped for structural reasons, the maximum tilt angle is maintained.

  The basic configuration in the present embodiment described above is the same as that shown in FIG. 3 as described above.

In particular, in the present embodiment, when the engine 1 is started, the pressure oil of the pilot pump 3 is used as a control pressure for driving the LS control valve 6 so that the tilt angle of the main pump 2 becomes small. Control pressure supply means for supplying the control chamber 6b is provided. This control pressure supply means includes, for example, a pilot line 21 that can connect the control chamber 6b of the LS control valve 6 and the pilot pump 3, an electromagnetic valve 22 provided in the pilot line 21, and the electromagnetic valve 22 A battery 23 that can be connected to the battery 23, a switch 24 that connects and disconnects the electromagnetic valve 22 and the battery 23, an engine starter 26 that is connected to the drive control unit of the engine 1 and the electromagnetic valve 22 and outputs a signal for starting the engine 1, Is included.

  The electromagnetic valve 22 described above allows the differential pressure reducing valve 13 and the control chamber 6b of the LS control valve 6 to communicate with each other, the switching position 22a for blocking the pilot line 21, the differential pressure reducing valve 13 and the LS control valve 6 to be connected. The control chamber 6b is shut off, and the pilot line 21 is connected, and a switching position 22b capable of supplying the pressure oil of the pilot pump 3 to the control chamber 6b of the LS control valve 6 is provided. The switch 24 described above is provided in association with the gate lock lever 25. When the gate lock lever 25 is held in the standing configuration shown by the solid line in FIG. 1, the switch 24 is turned off, the connection between the electromagnetic valve 22 and the battery 23 is cut off, and the electromagnetic valve 22 is switched to the switching position by the force of the spring. 22b. When the gate lock lever 25 is tilted as shown by the broken line in FIG. 1, the switch 24 is turned on, the electromagnetic valve 22 and the battery 23 are connected, and the electromagnetic valve 22 is switched to the switching position 22a against the force of the spring. Can be switched to.

  As is well known, the gate lock lever 25 is a lever that realizes permission and non-permission of supply of pressure oil from the main pump 2 to the actuators 7 and 8 that drive the front working machine and the like. It is arranged near the driver's seat (not shown) of the excavator. When the gate lock lever 25 is held upright as shown by the solid line in FIG. 1, an actuator that drives a front working machine or the like from the main pump 2 by a hydraulic control circuit (not shown) operated by the gate lock lever. The supply of pressure oil to 7, 8, etc. is not permitted, and when the gate lock lever 25 is tilted as shown by the broken line in FIG. Supply of pressure oil to the actuator to be driven is permitted.

  FIG. 2 is a diagram showing engine speed characteristics, main pump pressure characteristics, and pilot pump pressure characteristics at the time of engine start obtained in the present embodiment. As shown by the characteristic line 32 showing the characteristic of the pilot pump pressure in FIG. 2, the rise of the discharge pressure of the pilot pump 3 when the engine 1 is started is the rise of the discharge pressure of the main pump 2 shown by the characteristic line 31. Faster than This is because the volume of the pipe connected to the pilot pump 3 is smaller than the volume of the pipe connected to the main pump 2. Reference numeral 30 denotes a characteristic line of the engine speed at startup.

  In this embodiment configured as described above, when the front work machine and the like are stopped and the engine 1 is stopped, the flow control valves 9 and 10 are held neutral, and the gate lock lever 25 is operated in the front work. The switch 24 is turned off because it is held in a standing configuration in which the supply of pressure oil to the actuators 7 and 8 that drive the machine is not permitted. As a result, the connection between the electromagnetic valve 22 and the battery 23 is cut off, and the electromagnetic valve 22 is held at the switching position 22b by the force of the spring. Therefore, the pilot line 21 communicates and the pressure oil of the pilot pump 3 can be supplied to the control chamber 6 b of the LS control valve 6 via the electromagnetic valve 22 and the pilot line 21. In the state where the engine 1 is stopped as described above, the tilt angle is the maximum tilt angle because of the structure of the main pump 2 as described above.

  When the operator sitting on the driver's seat (not shown) of the hydraulic excavator operates the operation unit of the engine starter 26 in an attempt to start excavation work by the front work machine, for example, from the state where the engine 1 is stopped as described above. As shown in FIG. 2, the engine 1 is started. When the engine 1 is started, the main pump 2 and the pilot pump 3 are driven. At this time, as shown in FIG. 2, the pressure rise of the pilot pump 3 is faster than the pressure rise of the main pump 2. The pressure oil of the pilot pump 3 whose pressure rises quickly is supplied to the control chamber 6b of the LS control valve 6 through the switching position 22b of the electromagnetic valve 22 held in the state shown in FIG. . As a result, the LS control valve 6 is switched to the left position in FIG. 1, and the LS control tilt actuator 5 causes the tilt angle of the main pump 2 to be smaller than the maximum tilt angle so far. To drive.

  Accordingly, when the engine is started, the main pump 2 can be changed so that the tilt angle immediately becomes a small tilt angle, that is, as shown in FIG. Thereby, reduction of the load of the engine 1 at the time of engine starting, and the rapid engine starting operation | movement accompanying this can be implement | achieved.

Thereafter, when the operator tilts the gate lock lever 25 as shown by the broken line in FIG. 1, the switch 24 is turned on. When the engine starter 26 is operated, the switch 24 is turned on in this way, and when the electromagnetic valve 22 and the battery 23 are connected, the electromagnetic valve 22 is switched to the switching position 22a. As a result, the differential pressure reducing valve 13 and the control chamber 6 b of the LS control valve 6 communicate with each other, the pilot pipe line 21 is shut off, and the pressure oil of the pilot pump 3 is not supplied to the control chamber 6 b of the control valve 6. Moreover, by tilting the gate lock lever 25 as described above, the pressure oil from the main pump 2 is allowed to be supplied to the actuators 7 and 8 that drive the front working machine.

  Accordingly, when an operating lever of an operating device (not shown) that operates the actuators 7 and 8 is operated, the corresponding one of the flow control valves 9 and 10 is switched, and the corresponding actuator of the actuators 7 and 8 is switched. Operates and drives the front work machine. As a result, desired work such as excavation work can be performed. During this time, the load sensing actual differential pressure corresponding to the current maximum load pressure is given to the pressure compensation valves 11 and 12 and the control chamber 6 b of the LS control valve 6 by the differential pressure reducing valve 13. Further, the flow rate of the pilot pump 3 corresponding to the rotational speed of the engine 1 is detected by the flow rate detection valve 14, and a load sensing target differential pressure corresponding to the detected flow rate is given to the control chamber 6 a of the LS control valve 6. In the LS control valve 6 included in the pump regulator, the load sensing target differential pressure is given to the control chamber 6a, and the load sensing actual differential pressure is given to the control chamber 6b. Drive so that the differential pressure becomes the load sensing target differential pressure. That is, the LS control tilt actuator 5 is driven in accordance with the drive of the LS control valve 6, and the differential pressure between the discharge pressure of the main pump 2 and the maximum load pressure is caused by the LS control tilt actuator 5. Load sensing control is performed in which the tilt angle of the main pump 2, that is, the discharge amount of the main pump 2 is appropriately changed so as to achieve a differential pressure.

  In addition, when all the operation levers of an operation device (not shown) for operating the actuators 7 and 8 are returned to the neutral position in order to temporarily stop the excavation work and the like, all the flow control of the flow control valves 9 and 10 and the like are performed. The valve is in the neutral position, and the operation of the actuators 7 and 8 is stopped. As a result, the pressure applied to the control chamber 6b of the LS control valve 6 becomes the tank pressure, and the load sensing target differential pressure applied to the control chamber 6a also decreases, so that the LS control valve 6 is tilted at the tilt angle of the main pump 2. The LS control tilt actuator 5 is driven so that becomes the minimum tilt angle. That is, a predetermined minimum flow rate is discharged from the main pump 2.

  Further, for example, when the engine 1 is turned off from such a state, as described above, the main pump 2 has the maximum tilt angle due to its structural reason. Here, in order for the operator to get out of the driver's seat, when the gate lock lever 25 is set in the standing state shown by the solid line in FIG. 1, the supply of pressure oil from the main pump 2 to the actuators 7 and 8 is not permitted. It becomes possible. Further, by returning the gate lock lever 25 to the standing state, the switch 24 is turned off, the connection between the electromagnetic valve 22 and the battery 23 is cut off, and the electromagnetic valve 22 is switched to the switching position 22b by the force of the spring. That is, it becomes a standby mode before starting the engine 1.

  According to this embodiment configured as described above, as described above, when the engine 1 is started, the pressure oil from the pilot pump 3 is supplied to the control chamber 6b of the LS control valve 6 via the electromagnetic valve 22 and the pilot pipe line 21. And by driving the LS control tilt actuator 5 accompanying the driving of the LS control valve 6, the tilt angle of the main pump 2 that has been held at the maximum tilt angle immediately before becomes a small tilt angle. Thus, it is possible to reduce the engine load at the time of starting the engine and to realize a quick engine starting operation associated therewith. In particular, since the control pressure supply means for driving the LS control valve 6 so as to reduce the tilt angle of the main pump 2 when the engine is started only needs to be provided in association with only the pilot pump 3, Complexity and enlargement can be suppressed. This makes it possible to reduce the manufacturing cost and is practical.

  Further, a switch 24 that enables driving of the electromagnetic valve 22 included in the control pressure supply means is provided in association with the gate lock lever 25, and the gate lock lever 25 drives the front working machine from the main pump 2. The relationship between the position of the gate lock lever 25 and the operation of the switch 24 is set in advance so that the connection between the electromagnetic valve 22 and the battery 23 is cut off in the state where the supply of pressure oil to the actuators 7 and 8 is not permitted. Therefore, when the engine is started, the pressure oil of the main pump 2 is not supplied to the actuators 7 and 8 that drive the front working machine and the like. That is, it is possible to surely prevent an unexpected movement of the front work machine or the like when starting the engine, and to ensure excellent safety.

1 is a hydraulic circuit diagram showing an embodiment of a hydraulic drive device according to the present invention. It is a figure which shows the engine speed characteristic at the time of the engine start obtained by this embodiment, a main pump pressure characteristic, and a pilot pump pressure characteristic. It is a hydraulic circuit diagram equivalent to the principal part of the conventional hydraulic drive unit.

Explanation of symbols

1 Engine 2 Main Pump 3 Pilot Pump 5 LS Control Tilt Actuator 6 LS Control Valve 6a Control Room 6b Control Room 7 Actuator 8 Actuator 9 Flow Control Valve 10 Flow Control Valve 11 Pressure Compensation Valve 12 Pressure Compensation Valve 13 Differential Pressure Reduction Valve 14 Flow detection valve 15 Differential pressure reducing valve 16 Shuttle valve 17 Unload valve 21 Pilot pipe (control pressure supply means)
22 Solenoid valve (control pressure supply means)
23 battery (control pressure supply means)
24 switch (control pressure supply means)
25 Gate lock lever 26 Engine starter

Claims (2)

An engine, a variable displacement main pump and a pilot pump driven by the engine,
A tilting actuator for controlling the tilting angle of the main pump, and a pump regulator including a control valve for controlling the driving of the tilting actuator;
In a hydraulic drive device comprising a plurality of actuators driven by pressure oil discharged from the main pump, and a flow rate control valve for controlling the flow of pressure oil supplied from the main pump to each of the actuators,
There is provided control pressure supply means for supplying pressure oil of the pilot pump to the control chamber of the control valve as control pressure for driving the control valve so that the tilt angle of the main pump becomes small when starting the engine. ,
The control pressure supply means is
A pilot line capable of connecting the control chamber of the control valve to which the control pressure is applied and the pilot pump, and provided in the pilot line, pressure oil of the pilot pump is supplied to the control chamber of the control valve. An electromagnetic valve having a switching position that can be supplied to the battery, a battery connectable to the electromagnetic valve, and a switch that connects and disconnects the electromagnetic valve and the battery,
A hydraulic drive device comprising a gate lock lever for switching the switch . In the invention of claim 1,
A hydraulic drive apparatus comprising a load sensing control system for controlling the discharge pressure of the main pump to be higher than a maximum load pressure among a plurality of actuators by a target differential pressure .

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