JP2012241742A - Hydraulic driving device of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic driving device having a variable displacement main pump that carries out a load sensing control, in which a pilot pressure can be generated by using discharged oil of the main pump without adding a special valve such as a sequence valve, a target differential pressure can be set for the load sensing control in accordance with a rotational speed of a motor, and wasteful energy consumption by a pilot relief valve can be suppressed.SOLUTION: A second pressure oil supply passage 31 connecting to a main pump 2 includes a pressure reducing valve 32, a check valve 34 and an accumulator 35, and in a downstream side of these components, provided with a switching valve 37 that is switched by a gate lock lever 36. A pilot oil pressure source is formed in upstream and downstream sides of the switching valve 37. An original pressure is supplied from the upstream side pilot oil pressure source to a LS (load sensing) control valve 12b, and the original pressure is supplied from the downstream side pilot oil pressure source to an engine rotation detecting valve unit 13. A signal pressure output by the valve unit 13 is guided to the LS control valve 12b and an unload valve 15.

Description

  The present invention relates to a hydraulic drive device for a construction machine such as a hydraulic excavator, and more particularly to a hydraulic drive device for a construction machine configured to ensure a pilot hydraulic power source without using a pilot pump.

  In a hydraulic drive device for a construction machine such as a hydraulic excavator, a pilot hydraulic power source is required to drive various hydraulic devices such as a flow control valve. As the pilot hydraulic power source, a fixed displacement type pilot pump is generally used.

  In the hydraulic drive device described in Patent Document 1, it has been proposed to eliminate the pilot pump and generate the pilot pressure from the discharge oil of the main pump using a pressure reducing valve. In this hydraulic drive apparatus, a bypass sequence valve is separately provided in the base hydraulic circuit in order to ensure the necessary pilot pressure.

  Some hydraulic drive devices for construction machines such as hydraulic excavators control the capacity of the hydraulic pump so that the discharge pressure of the hydraulic pump (main pump) is higher than the maximum load pressure of multiple actuators by the target differential pressure. This is called load sensing control.

  Such a hydraulic drive device for load sensing control is described in Patent Document 2, for example.

  The hydraulic drive device described in Patent Document 2 is connected to a supply oil passage of a pilot pump and outputs an engine speed detection valve unit that outputs an absolute pressure according to a discharge flow rate of the pilot pump, and downstream of the engine speed detection valve unit. The pilot pressure source is connected to the pilot oil source and has a pilot relief valve that keeps the pilot oil passage pressure constant, and the pilot pressure that is connected to the pilot oil passage and operates the flow control valve using the pilot oil pressure as the source pressure. And a plurality of operation lever devices including a remote control valve (pressure reducing valve) for generating

  The engine speed detection valve unit has a variable throttle valve that has a characteristic that the throttle amount is variable according to the flow rate supplied from the pilot pump, and a differential pressure reducing valve that outputs the differential pressure across the variable throttle valve as an absolute pressure. The output pressure of the differential pressure reducing valve (the differential pressure across the variable throttle valve) is used as the target differential pressure for load sensing control via the signal oil path, and the load sensing control unit provided in the pump control unit is switched. Guided to the valve 12b, the capacity of the main pump is controlled so that the discharge pressure of the main pump is higher than the maximum load pressure by the target differential pressure. This makes it possible to set the target differential pressure for load sensing control according to the engine speed, adjust the discharge flow rate of the main pump according to the engine speed, and control the actuator speed according to the engine speed. Become.

Japanese Patent No. 3692004 JP 2001-193705 A

  In the conventional general technique, in order to generate a pilot pressure, pressure oil discharged from a fixed displacement type pilot pump is guided to a pilot relief valve to constitute a pilot hydraulic pressure source. In this case, the pilot pump is driven by the engine, and the pilot relief valve always functions and generates a constant pressure regardless of whether or not the operation lever of the operation lever device is operated. As a result, for example, even when all the operation levers are not operated, the pilot pump consumes useless energy by the pilot relief valve.

  In the hydraulic drive device described in Patent Document 1, the pilot pump is eliminated, and the pilot pressure is generated from the main pump using a pressure reducing valve. However, it is necessary to provide a sequence valve in order to ensure the necessary pilot pressure.

  In addition, in the load sensing control hydraulic drive device described in Patent Document 2, a pilot pump and a pilot relief valve are used to obtain a pilot hydraulic pressure source, as in the conventional general technique. Wasted energy from the valve. In particular, in the configuration described in Patent Document 2, since the pilot relief valve is connected to the downstream side of the engine speed detection valve unit to form a pilot hydraulic pressure source, the discharge pressure of the pilot pump is detected by the engine speed detection. It becomes the sum of the passage resistance (pressure loss) of the pressure oil in the valve unit and the set pressure of the pilot relief valve, and consumption of useless energy further increases.

  Therefore, even in the load sensing control hydraulic drive device described in Patent Document 2, it is conceivable to eliminate the pilot pump as described in Patent Document 1.

  However, in load sensing control hydraulic drive devices, energy consumption may not be reduced as expected unless the method of extracting the source pressure for generating signal pressure for flow control of the main pump is devised. .

  For example, when the control lever is neutral and the gate lock lever is in the raised position, that is, in the shut-off position where pilot pressure cannot be generated, the main pump is not held at the minimum flow rate. There is a problem that the energy consumption reduction effect cannot be obtained as expected.

  A first object of the present invention is to provide a pilot pressure that uses oil discharged from a main pump without adding a special valve such as a sequence valve in a hydraulic drive apparatus having a variable displacement main pump that performs load sensing control. A hydraulic drive device for a construction machine that can set a target differential pressure for load sensing control in accordance with the rotational speed of the prime mover and suppress wasteful energy consumption by a pilot relief valve. It is to provide.

  A second object of the present invention is to provide a hydraulic drive apparatus having a variable displacement main pump that performs load sensing control, and further, when the gate lock lever is in a position that disables the operation of a plurality of actuators. It is an object of the present invention to provide a hydraulic drive device for a construction machine that can minimize the discharge flow rate of the main pump, reduce the discharge pressure of the main pump, and suppress unnecessary energy consumption by the main pump.

  (1) In order to achieve the first object, the present invention includes a prime mover, a variable capacity main pump driven by the prime mover, and a plurality of actuators driven by pressure oil discharged from the main pump. And a plurality of flow rate control valves for controlling the flow rate of pressure oil supplied from the main pump to the plurality of actuators, and the discharge pressure of the main pump is higher than the maximum load pressure of the plurality of actuators by a target differential pressure. And a pump control device having a load sensing control unit for controlling the capacity of the main pump, and when the discharge pressure of the main pump becomes higher than the maximum load pressure by a target unload pressure or more, the pump is opened and discharged from the main pump. An unload valve for returning the pressure to the tank and restricting further increase in the discharge pressure of the main pump; An operating lever device having a plurality of pressure reducing valves for generating a command pilot pressure for operating the valve, a rotational speed detector for detecting the rotational speed of the prime mover, and a first signal pressure corresponding to the rotational speed of the prime mover A rotation speed signal pressure generating device having a signal pressure generating valve to be generated, wherein the load sensing control unit inputs the first signal pressure generated by the signal pressure generating valve and sets the target differential pressure The hydraulic drive apparatus for a machine further includes a pilot pressure generation circuit that generates a pilot pressure using the discharge oil of the main pump, and the pilot pressure generation circuit includes a first pressure oil supply oil connected to the main pump. A second pressure oil supply oil passage branched from the passage; a pressure reducing valve provided in the second pressure oil supply oil passage; a check valve provided in a first oil passage downstream of the pressure reducing valve; An accumulator connected to a third oil passage branched from a second oil passage downstream of the check valve; and a pilot hydraulic source including the second oil passage downstream of the check valve; and a plurality of operating lever devices A source pressure when the pressure reducing valve generates a command pilot pressure for operating the plurality of flow control valves, and a signal pressure generating valve when generating the first signal pressure corresponding to the rotational speed of the prime mover The plurality of pressure reducing valves and the signal pressure generating valve are connected to the pilot hydraulic power source so that the original pressure is supplied from the pilot hydraulic power source.

  In the present invention configured as described above, the hydraulic drive device is a load sensing control hydraulic drive device including an unload valve. When the unload valve is provided, even when the operation lever device is neutral, The discharge pressure is maintained at a certain pressure by the unload valve. Therefore, it is possible to generate a pilot pressure using the discharge oil of the main pump without adding a special valve such as a sequence valve described in Patent Document 1.

  In addition, a pilot pressure generating circuit that generates pilot pressure using the discharge oil of the main pump is provided, and when a plurality of pressure reducing valves of the operation lever device generate a command pilot pressure for operating a plurality of flow control valves. A plurality of pressure reducing valves and signal pressures are supplied so that the source pressure and the source pressure when the signal pressure generating valve generates the first signal pressure corresponding to the rotational speed of the prime mover are supplied from the pilot hydraulic pressure source of the pilot pressure generating circuit. By connecting the generator valve to the pilot hydraulic pressure source, not only the command pilot pressure but also the first signal pressure is generated, and it becomes possible to set the target differential pressure for load sensing control according to the rotational speed of the prime mover.

  In addition, since a pilot hydraulic pressure source can be formed without providing a pilot relief valve as in the prior art, useless energy consumption by the pilot relief valve can be suppressed.

  Thus, in the present invention, in a hydraulic drive device having a variable displacement main pump that performs load sensing control, the pilot pressure that uses the discharge oil of the main pump is added without adding a special valve such as a sequence valve. The target differential pressure of load sensing control can be set according to the rotational speed of the prime mover, and wasteful energy consumption by the pilot relief valve can be suppressed.

  (2) In the above (1), preferably, the load sensing control unit of the pump control device includes a load sensing control valve having a first pressure receiving unit that sets the target differential pressure, and an output of the load sensing control valve. A load sensing actuator that is driven by pressure and controls the capacity of the main pump, and the pilot pressure generating circuit is further disposed in a cab of the construction machine to disable operation of the plurality of actuators A gate lock lever that is selectively operated between a first position and a second position that allows operation of the plurality of actuators; and a gate lock lever that is connected to the second oil passage downstream of the check valve; A switching valve that is switched by operation of a lever, and the switching valve is when the gate lock lever is in the first position. A fourth oil passage downstream of the switching valve is connected to the tank, and when the gate lock lever is in the second position, the fourth oil passage downstream of the switching valve is connected to the second oil upstream of the switching valve. The pilot hydraulic power source is configured to communicate with an oil passage, and the pilot hydraulic power source includes a first pilot pressure supply oil passage constituted by the second oil passage upstream of the switching valve, and the fourth oil passage downstream of the switching valve. A source pressure when the load sensing control valve generates the output pressure for driving the load sensing actuator is from the first pilot pressure supply oil passage. The load sensing control valve is connected to the first pilot pressure supply oil passage so as to be supplied, and a plurality of pressure reducing valves of the operation lever device are used to operate the plurality of flow control valves. A source pressure when generating a pilot pressure and a source pressure when the signal pressure generating valve generates the first signal pressure according to the rotational speed of the prime mover are supplied from the second pilot pressure supply oil passage. As described above, the plurality of pressure reducing valves and the signal pressure generating valve are connected to the second pilot pressure supply oil passage, and the first signal pressure generated by the signal pressure generating valve is the first signal pressure of the load sensing control valve. The signal pressure generating valve is connected to the first pressure receiving portion of the load sensing control valve so as to be guided to one pressure receiving portion.

  In this way, separate pilot pressure supply oil passages (first and second pilot pressure supply oil passages) are formed by selectively using the upstream and downstream of the switching valve, and the output for the load sensing control valve to drive the load sensing actuator. The source pressure when generating the pressure is supplied from the first pilot pressure supply oil passage, the source pressure when the pressure reducing valve of the operating lever device generates the command pilot pressure, and the signal pressure generating valve generates the first signal pressure. By connecting so that the original pressure is supplied from the second pilot pressure supply oil passage, not only the pressure reducing valve and the signal pressure generating valve of the operation lever device as described in (1) above, but also the load sensing control unit However, it is possible to provide a pilot hydraulic power source without providing a pilot relief valve, and to suppress wasteful energy consumption by the pilot relief valve.

  (3) In the above (2), preferably, the load sensing control valve further includes a third pressure receiving portion facing the first pressure receiving portion, and the discharge pressure of the main pump and the plurality of actuators A differential pressure reducing valve that converts the differential pressure from the maximum load pressure into an absolute pressure and outputs the absolute pressure as a second signal pressure is further provided, and the original pressure when the differential pressure reducing valve generates the absolute pressure is The differential pressure reducing valve is connected to the first pilot pressure supply oil passage so that the second signal pressure generated by the differential pressure reducing valve is supplied from the first pilot pressure supply oil passage. The differential pressure reducing valve is connected to the third pressure receiving portion of the load sensing control valve so as to be guided to the third pressure receiving portion of the control valve.

  As a result, even for the differential pressure reducing valve, a pilot hydraulic pressure source can be provided without providing a pilot relief valve, and wasteful energy consumption by the pilot relief valve can be suppressed.

  (4) Further, in order to achieve the second object, in the above (1), the load sensing control unit of the pump control device includes a first pressure receiving unit that sets the target differential pressure. A load sensing control valve; and a load sensing actuator that guides an output pressure of the load sensing control valve and controls a capacity of the main pump according to the output pressure. A second pressure receiving portion for setting a pressure and a spring; and the pilot pressure generating circuit is further disposed in a cab of the construction machine, the first position disabling operation of the plurality of actuators; A gate lock lever that is selectively operated between a second position that allows operation of a plurality of actuators, and a second oil passage downstream of the check valve. A switching valve that is switched by operating the gate lock lever, and the switching valve communicates a fourth oil passage downstream of the switching valve to the tank when the gate lock lever is in the first position. When the gate lock lever is in the second position, the fourth oil passage downstream of the switching valve is configured to communicate with the second oil passage upstream of the switching valve, and the pilot hydraulic pressure source is A pilot pressure supply oil passage constituted by the fourth oil passage downstream of the switching valve is included, and a plurality of pressure reducing valves of the operation lever device generates a command pilot pressure for operating the plurality of flow control valves. The plurality of pressure reductions so that the original pressure when the signal pressure generating valve generates the first signal pressure according to the rotational speed of the prime mover is supplied from the pilot pressure supply oil passage. valve The signal pressure generation valve is connected to the pilot pressure supply oil passage, and the first signal pressure generated by the signal pressure generation valve is the first pressure receiving portion of the load sensing control valve and the second pressure of the unload valve. The signal pressure generating valve is connected to the first pressure receiving portion of the load sensing control valve and the second pressure receiving portion of the unload valve so as to be guided to the pressure receiving portion, and the load sensing control valve is connected to the first pressure receiving portion. The target differential pressure is set by the first signal pressure guided to the pressure receiving portion, and the unload valve is configured to perform the target unloading by the first signal pressure guided to the second pressure receiving portion and the biasing force of the spring. Set the pressure.

  Thus, the pilot pressure supply oil passage is formed on the downstream side of the switching valve, and not only the original pressure when the plurality of pressure reducing valves of the operating lever device generates the command pilot pressure, but also the signal pressure generating valve is the first signal pressure. Is connected to the pilot pressure supply oil passage so that the first signal pressure generated by the signal pressure generating valve is generated between the first pressure receiving portion of the load sensing control valve and the unloading valve. It connects so that it may be guide | induced to a 2nd pressure receiving part, the target differential pressure | voltage of load sensing control is set with 1st signal pressure, and the target unload pressure of an unloading valve is set with 1st signal pressure and the urging | biasing force of a spring Thus, when the gate lock lever is in the first position where the operation of the plurality of actuators is disabled, the switching valve communicates the fourth oil passage downstream of the switching valve with the tank to supply the pilot pressure. Since road is tank pressure, the first signal pressure to the signal pressure generation valve for generating becomes the tank pressure, the target differential pressure of load sensing control also the tank pressure. As a result, the discharge flow rate of the main pump can be reliably controlled to the minimum. Further, since the target unload pressure of the unload valve becomes a pressure set by the biasing force of the spring, the discharge pressure of the main pump can be lowered to the set pressure of the spring.

  Thus, in the present invention, in a hydraulic drive device having a variable displacement main pump that performs load sensing control, when the gate lock lever is in a position that disables the operation of a plurality of actuators, the discharge flow rate of the main pump Since the discharge pressure of the main pump is reduced and wasteful energy consumption by the main pump can be suppressed.

  (5) In the above (1) to (4), preferably, the engine further includes a pilot pump driven by the prime mover, and the rotation speed detection unit of the rotation speed signal pressure generating device is configured such that a discharge oil of the pilot pump is The signal pressure generating valve is a differential pressure reducing valve that converts a differential pressure across the throttle valve into an absolute pressure and outputs the absolute pressure as the first signal pressure.

  As a result, the rotation speed signal pressure generating device has only a hydraulic element, and the entire hydraulic drive device can have a pure hydraulic configuration.

  (6) In the above (1) to (4), preferably, the rotation speed detection unit of the rotation speed signal pressure generator includes a rotation sensor that detects the rotation speed of the prime mover, and the rotation speed The signal pressure generating device further includes a controller that inputs a detection signal of the rotation sensor and outputs a control signal to the signal pressure generating valve, and the signal pressure generating valve is driven by a control signal output from the controller. And an electromagnetic proportional pressure reducing valve that outputs the first signal pressure.

  This eliminates the need for providing a pilot pump as a hydraulic pressure source of the rotation speed signal pressure generating device, so that the energy consumed by the pilot pump can be completely reduced to zero, and wasteful energy consumption can be further suppressed.

  According to the present invention, it is possible to set a target differential pressure for load sensing control in accordance with the rotational speed of the prime mover, and a pilot that uses the discharge oil of the main pump without adding a special valve such as a sequence valve. Pressure can be generated, and wasteful energy consumption by the pilot relief valve can be suppressed.

  Further, according to the present invention, in a hydraulic drive device having a variable displacement main pump that performs load sensing control, when the gate lock lever is in a position that disables the operation of a plurality of actuators, The discharge flow rate can be minimized, the discharge pressure of the main pump can be reduced, and unnecessary energy consumption by the main pump can be suppressed.

It is a figure which shows the system configuration | structure of the hydraulic drive unit in the 1st Embodiment of this invention. It is a figure which shows the external appearance of the hydraulic excavator by which the hydraulic drive device in this Embodiment is mounted. It is the figure which showed transition of the pressure of each part when starting an engine from an engine stop state and performing operation of (a)-(e). It is a figure which shows the discharge pressure of the pilot pump in the 1st Embodiment of this invention compared with the thing of a prior art. It is a figure which shows the system configuration | structure of the hydraulic drive unit in this Embodiment. It is a figure which shows the relationship between the engine speed for calculating the output of the proportional electromagnetic pressure reducing valve according to an engine speed, and the output pressure of a proportional electromagnetic pressure reducing valve in a controller. It is a figure which shows the system configuration | structure of the hydraulic drive unit in this Embodiment. It is a figure which shows the system configuration | structure of the hydraulic drive unit in this Embodiment.

<First Embodiment>
~Constitution~
FIG. 1 shows a system configuration of a hydraulic drive apparatus according to the first embodiment of the present invention. In the present embodiment, the present invention is applied to a hydraulic drive device of a front swing type hydraulic excavator.

  In FIG. 1, a hydraulic drive apparatus according to the present embodiment includes an engine 1, a variable displacement hydraulic pump 2 (hereinafter referred to as a main pump) as a main pump driven by the engine 1, and a fixed displacement pilot pump. 10, a plurality of actuators 3 a, 3 b, 3 c... Driven by pressure oil discharged from the main pump 2, a control valve unit 4 positioned between the main pump 2 and the actuators 3 a, 3 b, 3 c. A pump control unit 12 and an engine rotation detection valve unit 13 (rotation speed signal pressure generator) are provided.

  The control valve unit 4 includes a first pressure oil supply oil passage 5 connected to the main pump 2 and actuators 3a, 3b, 3c... Branched from the oil passage 5a connected to the first pressure oil supply oil passage 5. Are connected to the corresponding oil passages 8a, 8b, 8c... And connected to the oil passages 8a, 8b, 8c..., And control the flow rate and direction of the pressure oil supplied from the main pump 2 to the actuators 3a, 3b, 3c. Are connected to oil passages 8a, 8b, 8c... Upstream of the respective flow control valves 6a, 6b, 6c..., And throttles of the respective flow control valves 6a, 6b, 6c. The pressure compensation valves 7a, 7b, 7c... For controlling the differential pressure across the section and the highest pressure (maximum load pressure) among the load pressures of the actuators 3a, 3b, 3c. Shuttle valve that outputs to a, 9b, 9c (maximum load pressure detecting means) and the discharge pressure of the main pump 2 (hereinafter referred to as pump pressure as appropriate) are input from an oil passage 21 branched from the first pressure oil supply oil passage 5 of the main pump 2. The differential pressure reducing valve 11 that inputs the maximum load pressure from the signal oil passage 20a, generates a differential pressure between the two (pump pressure and maximum load pressure) as an absolute pressure, and outputs the absolute pressure to the signal oil passages 22a and 22b; A main relief valve 14 that is connected to the first pressure oil supply oil passage 5 of the pump 2 and limits the maximum discharge pressure (maximum circuit pressure) of the main pump 2, and the first pressure oil supply oil passage 5 of the main pump 2 is oiled. When the discharge pressure of the main pump 2 is higher than the maximum load pressure by a set pressure (target unload pressure) or more, the main pump 2 is opened and the discharge oil of the main pump 2 is returned to the tank. Further increase in the discharge pressure of And an unload valve 15 to restrict.

  The actuators 3a, 3b, and 3c are, for example, a swing motor, a boom cylinder, and an arm cylinder of a hydraulic excavator. The flow control valve 6a is for turning, the flow control valve 6b is for a boom, and the flow control valve 6c is for an arm. . For convenience of illustration, illustration of other actuators such as a bucket cylinder, a boom swing cylinder, a traveling motor, and circuit elements related to these actuators is omitted.

  The pressure compensation valves 7a, 7b, 7c,... Are pressure-receiving portions 24a, 24b, 24c, etc., which are operated in the opening direction, in which the output pressure of the differential pressure reducing valve 11 is guided as a target compensation differential pressure via the signal oil passage 22a. Have pressure receiving portions 25a, 25b, 25c,... And 26a, 26b, 26c,... That detect the differential pressure across the meter-in throttle portions of the valves 6a, 6b, 6c,. Control is performed so that the differential pressure across the throttle is equal to the output pressure of the differential pressure reducing valve 11 (the differential pressure between the pump pressure and the maximum load pressure). In this way, the differential pressure between the meter-in throttle portions of the flow control valves 6a, 6b, 6c,... Is controlled using the output pressure of the differential pressure reducing valve 11 (the differential pressure between the pump pressure and the maximum load pressure) as the target compensation differential pressure. Therefore, the differential pressures before and after the meter-in throttle portions of the flow control valves 6a, 6b, 6c,... Are all controlled to the same value, and the meter-in throttles of the flow control valves 6a, 6b, 6c,. Pressure oil can be supplied at a ratio corresponding to the opening area of the part. Thus, during the combined operation of simultaneously driving a plurality of actuators, depending on the opening area ratio of the meter-in throttle portions of the flow control valves 6a, 6b, 6c... Regardless of the load pressure of the actuators 6a, 6b, 6c. The discharge flow rate of the main pump 2 can be distributed to ensure composite operability.

  Further, by controlling the differential pressure across the meter-in throttle portions of the flow control valves 6a, 6b, 6c,... Using the output pressure of the differential pressure detection valve 11 (the differential pressure between the pump pressure and the maximum load pressure) as a target compensation differential pressure. Even when the discharge flow rate of the main pump 2 is in a saturation state where the required flow rate is less than the required flow rate, the output pressure of the differential pressure detection valve 11 (the differential pressure between the pump pressure and the maximum load pressure) depends on the degree of supply shortage. Accordingly, the differential pressure across the meter-in throttle portion of the flow control valves 6a, 6b, 6c... Decreases at the same rate, so that the passing flow rate of the flow control valves 6a, 6b, 6c. Thus, even in the saturation state, the main pump 2 discharge flow rate is distributed according to the ratio of the opening areas of the meter-in throttle portions of the flow rate control valves 6a, 6b, 6c.

  The pump control unit 12 drives the pump tilt changing unit 2a of the main pump 2 to control the tilt angle (capacity or displacement) of the main pump 2, and when the discharge pressure of the main pump 2 rises In addition, the torque control unit 12T that controls the absorption torque of the main pump 2 so as not to exceed a certain value, and the discharge pressure of the main pump 2 becomes higher by the target differential pressure than the maximum load pressure of the actuators 3a, 3b, 3c. The load sensing control unit 12L that controls the capacity (tilt angle) of the main pump 2 and the stopper 12S that defines the minimum tilt position of the main pump 2 are provided.

  The torque control unit 12T includes a tilt angle control piston 12a that controls the tilt angle of the main pump 2 to be reduced as the discharge pressure of the main pump 2 is introduced and the discharge pressure of the main pump 2 increases. I have. The load sensing control unit 12L is controlled so that the tilt angle of the main pump 2 is changed according to the control valve 12b for load sensing control and the output pressure of the control valve 12b. And a piston 12c (load sensing actuator) for turning angle control.

  In the control valve 12b, a signal pressure output from the engine rotation detection valve unit 13 is guided through a signal oil passage 27a, and a pressure receiving portion 12d that sets this signal pressure as a target differential pressure for load sensing control, and the pressure receiving portion 12d. And a pressure receiving portion 12e through which the signal pressure output from the differential pressure reducing valve 11 is guided to face the signal oil passage 22b. When the signal pressure output from the differential pressure reducing valve 11 becomes higher than the signal pressure output from the engine rotation detection valve unit 13 (target differential pressure for load sensing control), the control valve 12b increases the output pressure, and the differential pressure reducing valve 11 When the signal pressure output from the engine pressure becomes lower than the signal pressure output from the engine rotation detection valve unit 13, the control valve 12b decreases the output pressure. The tilt angle control piston 12c reduces the tilt angle of the main pump 2 to decrease the discharge flow rate of the main pump 2 when the output pressure of the control valve 12b increases, and reduces the discharge flow rate of the main pump 2 when the output pressure of the control valve 12b decreases. To increase the discharge flow rate of the main pump 2. Thereby, the control valve 12b and the tilt angle control piston 12c control the signal pressure output from the differential pressure reducing valve 11 to be equal to the signal pressure output from the engine rotation detection valve unit 13, and the discharge pressure of the main pump 2 is controlled. The discharge flow rate of the main pump 2 is controlled so that becomes higher by the signal pressure (target differential pressure of load sensing control) output from the engine rotation detection valve unit 13 than the maximum load pressure. The output pressure (target differential pressure of load sensing control) of the engine rotation detection valve unit 13 when the engine 1 is at the maximum rated speed is, for example, 2 MPa.

  The engine rotation detection valve unit 13 has a variable throttle valve 28 (rotational speed detection unit) having a characteristic that the throttle amount is variable according to the flow rate supplied from the pilot pump 10 and a differential pressure across the variable throttle valve 28. A differential pressure reducing valve 29 (signal pressure generating valve) that converts the absolute pressure into an absolute pressure and outputs the absolute pressure as a signal pressure (first signal pressure) is provided, and the signal pressure (the differential pressure across the variable throttle valve 28) is Via the signal oil passage 27a, the target differential pressure of the load sensing control is led to the pressure receiving part 12d of the control valve 12b of the load sensing control part 12L.

  When the rotational speed of the engine 1 increases, the discharge flow rate of the pilot pump 10 increases and the differential pressure across the variable throttle valve 28 also increases accordingly. Conversely, when the rotational speed of the engine 1 decreases, the discharge flow rate of the pilot pump 10 decreases, and the differential pressure across the variable throttle valve 28 also decreases accordingly. The differential pressure reducing valve 29 converts the differential pressure across the variable throttle valve 28 into an absolute pressure and outputs it. Thus, since the signal pressure output from the engine rotation detection valve unit 13 is a pressure that changes according to the engine speed, this pressure is received by the pressure receiving portion of the control valve 12b of the load sensing control unit 12L via the signal oil passage 27a. By leading to 12d and using it as a target differential pressure for load sensing control, the discharge flow rate of the main pump 2 can be increased or decreased according to the engine speed, and the actuator speed can be controlled according to the engine speed.

  The unload valve 15 includes a spring 15a that operates in the closing direction and a pressure receiving portion 15b as setting means for the target unload pressure, and the pressure receiving portion 15b rotates through a signal oil passage 27b that branches from the signal oil passage 27a. It is connected to the output side of the differential pressure reducing valve 29 of the detection valve unit 13. Further, the unload valve 15 is guided through the oil passage 20b by the pressure receiving portion 15c that operates in the opening direction to which the discharge pressure of the main pump 2 is guided, and the output pressure (maximum load pressure) of the shuttle valves 9a, 9b, 9c. And a pressure receiving portion 15d that is operated in the closing direction. As a result, the unload valve 15 detects the engine rotation in which the discharge pressure of the main pump 2 is guided to the biasing force of the spring 15a and the pressure receiving portion 15b rather than the output pressure (maximum load pressure) of the shuttle valves 9a, 9b, 9c. The discharge pressure of the main pump 2 is set to the maximum load pressure and the biasing force of the spring 15a and the pressure receiving portion 15b so as not to be higher than the pressure (target unload pressure) set by the signal pressure output from the valve unit 13. The rise in the discharge pressure of the main pump 2 is limited so as not to become higher than the pressure obtained by adding the set pressure (target unload pressure).

The target unload pressure is set to 3 MPa, for example, higher than the target differential pressure of load sensing control. The signal pressure (target differential pressure for load sensing control) output from the engine rotation detection valve unit 13 when the engine 1 is at the rated maximum speed is, for example, 2 MPa as described above, and the target pressure set by the pressure receiving portion 15b. The shared pressure of the load pressure is 2 MPa which is the same as the signal pressure output from the engine rotation detection valve unit 13. The shared pressure of the target unload pressure set by the biasing force of the spring 15a is, for example, 1 MPa, and the pressure obtained by adding this shared pressure and the shared pressure of the pressure receiving portion 15b (2 MPa) becomes the target unload pressure (3 MPa). .
-Characteristic configuration-
Next, a characteristic configuration of the hydraulic drive device according to the present embodiment will be described.

  The hydraulic drive apparatus according to the present embodiment includes, as a characteristic configuration, a pilot pressure generation circuit 30 that constitutes a pilot hydraulic source for generating pilot pressure using the discharge oil of the main pump 2.

  The pilot pressure generating circuit 30 includes a second pressure oil supply oil passage 31 branched from the oil passage 5a in the control valve unit 4 connected to the first pressure oil supply oil passage 5 of the main pump 2, and the second pressure oil. A pressure reducing valve 32 provided in the supply oil passage 31, a check valve 34 provided in the first oil passage 33a downstream of the pressure reducing valve 32, and a third oil branched from the second oil passage 33b downstream of the check valve 34. An accumulator 35 connected to the path 33c, a shut-off position (first position) and an actuator disposed in the cab 108 (FIG. 2) of a hydraulic excavator (construction machine) and disabling the operation of the actuators 3a, 3b, 3c. 3a, 3b, 3c... Are provided in a gate lock lever 36 that is selectively operated between the release position (second position) and the second oil passage 33b downstream of the check valve 34. And is connected to the gate lock lever 36, the switching valve 37 is switched by the operation of the gate lock lever 36, and a fourth oil passage 33d downstream of the switching valve 37.

  The second oil passage 33 b constitutes a first pilot pressure supply oil passage 38, and the fourth oil passage 33 d constitutes a second pilot pressure supply oil passage 40.

  The first pilot pressure supply oil passage 38 is connected to the input side of the control valve 12b of the load sensing control unit 12L via the oil passage 44a, and supplies the original pressure (primary pressure) to the control valve 12b of the load sensing control unit 12L. To do. The first pilot pressure supply oil passage 38 is connected to the input side of the differential pressure reducing valve 11 via an oil passage 44a and an oil passage 44b branched from the oil passage 44a. (Primary pressure) is supplied. That is, the first pilot pressure supply oil passage 38 functions as a pilot hydraulic power source (first pilot hydraulic power source) for the control valve 12b and the differential pressure reducing valve 11.

  The second pilot pressure supply oil passage 40 has a plurality of remote control valves (pressure reducing valves) 42a1, 42a2, 42b1, which generate command pilot pressures for operating the flow control valves 6a, 6b, 6c. .. Are connected to 42b2... And supplies a primary pressure (primary pressure) to the remote control valves 42a, 42b. The remote control valves 42a1, 42a2, 42b1, 42b make a pair and are built in the operation lever devices 122, 123, and the operation lever device 123 containing the remote control valves 42a, 42b is for a boom, for example. The second pilot pressure supply oil passage 40 is connected to the input side of the differential pressure reducing valve 29 of the engine rotation detection valve unit 13 via the oil passage 43, and the original pressure (primary pressure) is supplied to the differential pressure reducing valve 29. Supply. That is, the second pilot pressure supply oil passage 40 functions as a pilot hydraulic power source (second pilot hydraulic power source) for the remote control valves 42a1, 42a2, 42b1, 42b2,.

  The output side of the differential pressure reducing valve 29 of the engine rotation detection valve unit 13 is connected to the pressure receiving part 12d of the control valve 12b of the load sensing control part 12L via the signal oil passage 27a, and the differential pressure reducing valve 29 is connected to the pressure receiving part 12d. The signal pressure output by is derived. As described above, the load sensing control unit 12L sets the target differential pressure for load sensing control using the signal pressure.

  The output side of the differential pressure reducing valve 29 of the engine rotation detection valve unit 13 is connected to the pressure receiving portion 15b of the unload valve 15 via a signal oil passage 27a and a signal oil passage 27b branched from the signal oil passage 27a. Then, the signal pressure output from the differential pressure reducing valve 29 is guided to the pressure receiving portion 15b. As described above, the unload valve 15 sets the target unload pressure by the signal pressure guided to the pressure receiving portion 15b and the urging force of the spring 15a.

  When the gate lock lever 36 is in the shut-off position (first position), the switching valve 37 is in the illustrated position, and the first pilot pressure supply oil passage 38 (second oil passage 33b) and the second pilot pressure supply oil. The communication with the passage 40 (fourth oil passage 33d) is blocked, and the second pilot pressure supply oil passage 40 is communicated with the tank. When the second pilot pressure supply oil passage 40 communicates with the tank, the pressure in the second pilot pressure supply oil passage 40 becomes substantially equal to the tank pressure (generally 0 MPa). When the gate lock lever 36 is switched to the release position (second position), the switching valve 37 is switched from the illustrated position, and the second pilot pressure supply oil passage 40 (fourth oil passage 33d) is supplied with the first pilot pressure supply. It communicates with the oil passage 38 (second oil passage 33b).

  The pressure reducing valve 32 has a setting spring 32a. The pressure reducing valve 32 reduces the pressure of the second pressure oil supply oil passage 31 to the pressure set by the spring 32a and outputs the pressure to the oil passage 33a. The set pressure of the spring 32a is preferably set to a value higher than the set pressure of the unload valve 15. As described above, when the set pressure of the unload valve 15 is 3 MPa, for example, the set pressure of the spring 32a is 4 MPa, which is higher than that.

  FIG. 2 is an external view of a hydraulic excavator on which the hydraulic drive device according to the present embodiment is mounted.

  The hydraulic excavator includes a lower traveling body 101, an upper revolving body 102 that is turnably mounted on the lower traveling body 101, and a top portion of the upper revolving body 102 that rotates in the vertical and horizontal directions via a swing post 103. And a front work machine 104 that is movably connected. The lower traveling body 101 is a crawler type, and a blade 106 for earth removal that can move up and down is provided on the front side of the track frame 105. The upper swivel body 102 includes a swivel base 107 having a basic lower structure, and a canopy type cab 108 provided on the swivel base 107. The front work machine 104 includes a boom 111, an arm 112, and a bucket 113. The base end of the boom 111 is pin-coupled to the swing post 103, and the base end of the arm 112 is pin-coupled to the tip of the boom 111. The tip of the arm 112 is pin-coupled.

  The upper turning body 101 is driven to turn by the turning motor 3a with respect to the lower traveling body 100, and the boom 111, the arm 112, and the bucket 113 are rotated by extending and retracting the boom cylinder 3b, the arm cylinder 3c, and the bucket cylinder 3d, respectively. To do. The lower traveling body 101 is driven by left and right traveling motors 3f and 3g. The blade 106 is driven up and down by a blade cylinder 3h. In FIG. 1, illustration of the bucket cylinder 3d, the left and right traveling motors 3f and 3g, the blade cylinder 3h, and their circuit elements is omitted.

  The driver's cab 108 is provided with a driver's seat 121, the above-described operation lever devices 122 and 123 (only the right side is shown in FIG. 2), and the gate lock lever 24.

  The gate lock lever 24 is disposed on the entrance / exit side of the driver's seat 121 and can be selectively operated by the operator between the shut-off position (first position) and the release position (second position) as described above. The blocking position of the gate lock lever 24 corresponds to the raised position, and the release position of the gate lock lever 24 corresponds to the lowered position.

When the gate lock lever 24 is in the shut-off position (raised position), the switching valve 37 is in the illustrated position, and as described above, the second pilot pressure supply oil passage 40 (fourth oil passage 33d) and the first pilot The communication with the pressure supply oil passage 38 (second oil passage 33b) is blocked, and the second pilot pressure supply oil passage 40 is communicated with the tank. At this time, the second pilot pressure supply oil passage 40 (fourth oil passage 33d) cannot supply the primary pressure, and the flow control valves 6a, 6b, 6c... Even if the operation levers of the operation lever devices 122, 123 are operated. Cannot be switched, and all actuators become inoperable. When the gate lock lever 24 is switched to the release position (lowering position), the switching valve 37 is switched from the position shown in FIG. 1, and the second pilot pressure supply oil passage 40 (fourth oil passage 33d) is supplied to the first pilot pressure supply. The oil passage 38 (second oil passage 33b) is communicated. At this time, the second pilot pressure supply oil passage 40 (fourth oil passage 33d) can supply the primary pressure, and when any one of the operation devices including the operation lever devices 122 and 123 is operated, the flow control valves 6a and 6b. , 6c... Switch, and the corresponding actuator can be operated. As a result, the front work machine 104 or the like can be operated to perform a desired work.
~ Operation ~
Next, the operation of this embodiment will be described with reference to FIG.

  FIG. 3 is a diagram showing changes in pressure of each part when the engine is started from the engine stopped state and the following operations (a) to (e) are performed.

(A) Gate lock lever shut-off position (b) Neutral control lever neutral at gate lock lever release position (c) Control lever neutral after boom raising control lever operation (d) Control lever neutral after fine operation of boom lowering control lever ( e) Gate lock lever blocking position The symbols relating to the pressure of each part in FIG. 3 mean the following values.

Pgr0: Signal pressure output from the engine rotation detection valve unit 13 when the engine 1 is at the rated maximum speed (target differential pressure for load sensing control)
Pp0 + Pgr0: Set pressure of the unload valve 15 when the engine 1 is at the maximum rated speed (target unload pressure)
Pp0: set pressure of the spring 15a of the unload valve 15 Pi0: set pressure of the pressure reducing valve 32 (set pressure of the spring 32b)
Pia: Pressure of first pilot pressure supply oil passage 38 Pib: Pressure of second pilot pressure supply oil passage 40 Pbmr: Load pressure of boom cylinder 3b during boom raising operation Ppbml: Discharge of main pump 2 during boom lowering fine operation Pressure (pressure in first pressure oil supply oil passage 5)
As described above, in the present embodiment, Pgr0 is 2 MPa, Pp0 + Pgr0 is 3 MPa, Pp0 is 1 MPa, and Pi0 is 4 MPa.

  Hereinafter, description will be made in the order of (a) to (e).

<(A) Gate lock lever blocking position>
When the engine 1 is started in a state where the engine 1 is stopped and the gate lock lever 36 is in the shut-off position (position where all the actuators cannot be operated), the discharge oil of the main pump 2 driven by the engine 1 Is supplied to the first pressure oil supply oil passage 5. At this time, the flow rate control valves 6a, 6b, 6c,... Further, the pressure oil in the first pressure oil supply oil passage 5 is guided to the pressure reducing valve 32 through the second pressure oil supply oil passage 31 to be depressurized, and is guided to the first pilot pressure supply oil passage 38.

  Here, the set pressure (target unload pressure) of the unload valve 15 includes the urging force of the spring 15a and the signal pressure output to the pressure receiving portion 15b and output from the engine rotation detection valve unit 13 (hereinafter referred to as Pgr pressure as appropriate). Is set by.

  The engine rotation detection valve unit 13 is guided to the pressure of the second pilot pressure supply oil passage 40 downstream of the switching valve 37 as the original pressure, the gate lock lever 36 is in the cutoff position, and the switching valve 37 is Since it is in the illustrated position, the pressure Pib of the second pilot pressure supply oil passage 40 is equal to the tank pressure, and the Pgr pressure output from the engine rotation detection valve unit 13 is also equal to the tank pressure. Therefore, the tank pressure (approximately 0 MPa) is guided to the pressure receiving portion 15b of the unload valve 15, and the set pressure of the unload valve 15 is the pressure Pp0 (1 MPa) set only by the spring 15a.

  In this case, as shown in “(a) gate lock lever blocking position” in FIG. 3, the discharge pressure of the main pump 2 (pressure of the first pressure oil supply oil passage 5) is unloaded when the engine 1 is started. The pressure Pp0 (1 MPa) set by the spring 15a is maintained by the action of the valve 15.

  The first pilot pressure supply oil passage 38 is supplied with the pressure oil depressurized by the pressure reducing valve 32 from the first pressure oil supply oil passage 5 through the pressure reducing valve 32. As shown in FIG. Since the pressure (1 MPa) of the first pressure oil supply oil passage 5 is lower than the pressure Pi0 (4 MPa) set by the spring 32b of the valve 32, the pressure (1 MPa) of the first pressure oil supply oil passage 5 remains as it is. The pressure Pia of the first pilot pressure supply oil passage 38 is the same as the pressure of the first pressure oil supply oil passage 5 (1 MPa). Yes.

  On the other hand, as the original pressure of the differential pressure reducing valve 11 provided in the control valve unit 4 having a plurality of flow control valves 6a, 6b, 6c... That outputs the differential pressure between the discharge pressure of the main pump 2 and the maximum load pressure. The pressure Pia (1 MPa) of the first pilot pressure supply oil passage 38 is introduced.

  Accordingly, as shown in “(a) gate lock lever cutoff position” in FIG. 3, the tank pressure is supplied to the differential pressure reducing valve 11 via the shuttle valves 99a, 9b, 9c. Since the set pressure Pp0 (1 MPa) is also introduced to the spring 15a as the discharge pressure of the pump 2, the signal pressure (hereinafter referred to as Pls pressure as appropriate) output from the differential pressure reducing valve 11 is the discharge pressure of the main pump 2. The set pressure Pp0 (1 MPa) of the spring 15a is output.

  A Pgr pressure (in this case, approximately 0 MPa of tank pressure) is guided to the pressure receiving portion 12d on the left side of the control valve 12b of the load sensing control unit 12L of the pump control unit 12, and the pressure receiving portion 12e on the right side of the control valve 12b in the drawing is shown. Is the Pls pressure (in this case, 1 MPa of Pp0).

  Therefore, the relationship of Pls pressure (= Pp0)> Pgr pressure (= tank pressure) is established, and the control valve 12 of the load sensing control unit 12L switches to the left in the figure, and the first pilot pressure supply oil passage 38 The pressure is guided to the piston 12c of the load sensing control unit 12L, and operates to reduce the tilt of the main pump 2 that is a variable displacement pump, and the main pump 2 is held at the minimum tilt position defined by the stopper 12S. .

  With the above operation, the discharge flow rate of the main pump 2 is kept at the minimum flow rate.

<(B) At the gate lock lever release position, all control levers are neutral>
When the gate lock lever 36 is switched to the release position (position where the actuator can be operated), the switching valve 37 is switched from the illustrated position by the gate lock lever 36, and the pressure oil in the first pilot pressure supply oil passage 38 is It is guided to the second pilot pressure supply oil passage 40. As a result, the pressure oil decompressed by the pressure reducing valve 32 from the first pressure oil supply oil passage 5 is supplied to both the first pilot pressure supply oil passage 38 and the second pilot pressure supply oil passage 40.

  Further, the pressure oil in the second pilot pressure supply oil passage 40 is supplied to the engine rotation detection valve unit 13, and the engine rotation detection valve unit 13 outputs a Pgr pressure using the pressure as a source pressure. The Pgr pressure changes according to the engine speed, and is set to increase when the engine speed is high and to decrease when the engine speed is low. For example, assuming that the Pgr pressure when the engine speed is at the rated maximum speed is Pgr0, Pgr0 is, for example, 2 MPa as described above.

  The Pgr pressure output from the engine rotation detection valve unit 13 acts on the pressure receiving portion 12d on the left side of the control valve 12b of the load sensing control portion 12L of the pump control unit 12 of the main pump 2. Further, the Pgr pressure is also guided to the pressure receiving portion 15b of the unload valve 15 of the control valve unit 4, and the Pgr pressure acts on the pressure receiving portion 15b, whereby the set pressure of the unload valve 15 is “(a It becomes higher by the amount of Pgr pressure (when the engine speed is at the rated maximum speed, Pgr0 = 2 MPa) than in the case of “) gate lock lever cutoff position”. That is, the target unload pressure of the unload valve 15 increases from Pp0 (1 MPa) to Pp0 + Pgr0 (3 MPa).

  As a result, as shown in FIG. 3, the discharge pressure of the main pump 2 is maintained at the pressure (3 MPa) of Pp0 + Pgr0 by the action of the unload valve 15, and the pressure of the first pressure oil supply oil passage 5 is also Pp0 + Pgr0. (3 MPa).

  At this time, the first pilot pressure supply oil passage 38 is supplied with the pressure oil depressurized by the pressure reduction valve 32 from the first pressure oil supply oil passage 5 through the pressure reduction valve 32. FIG. As shown, since the pressure (3 MPa) of the first pressure oil supply oil passage 5 is lower than the pressure Pi0 (4 MPa) set by the spring 32b of the pressure reducing valve 32, the pressure of the first pressure oil supply oil passage 5 is shown. (3 MPa) is supplied as it is to the first pilot pressure supply oil passage 38 on the downstream side of the pressure reducing valve 32, and the pressure Pia of the first pilot pressure supply oil passage 38 is the same as the pressure of the first pressure oil supply oil passage 5 ( 3 MPa).

  On the other hand, the pressure oil in the second pilot supply oil passage 40 is supplied to the differential pressure reducing valve 11 of the control valve unit 4, and the differential pressure reducing valve 11 uses the pressure as a source pressure and the discharge pressure of the main pump 2 and the maximum load. The differential pressure from the pressure is converted into an absolute pressure, and the Pls pressure is output.

  At this time, the discharge pressure of the main pump 2 is maintained at a pressure of Pp0 + Pgr0 (3 MPa). Further, since all the operation levers are neutral, the maximum load pressure detected by the shuttle valves 9a, 9b, 9c... Is the tank pressure. For this reason, the Pls pressure output by the differential pressure reducing valve 11 is maintained at a pressure (3 MPa) of Pp0 + Pgr0 equal to the discharge pressure of the main pump 2.

  The Pgr pressure (Pgr0 = 2 MPa) output from the engine rotation detection valve unit 13 and the Pls pressure (Pp0 + Pgr0 = 3 MPa) output from the differential pressure reducing valve 11 are respectively controlled by the load sensing control unit 12L of the main pump 2. It is led to pressure receiving portions 12d and 12e on both sides of 12b.

  In this case, since Pls (= Pp0 + Pgr0)> Pgr (= Pgr0), the control valve 12b remains switched to the left in the figure, and the first pilot pressure supply oil passage 38 is load sensed via the control valve 12b. It acts on the control piston 12c and operates to reduce the tilt of the main pump 2. As a result, the tilt of the main pump 2 remains held at the minimum tilt position.

  As described above, the discharge flow rate of the main pump 2 is kept at the minimum flow rate.

<(C) Neutral operation lever after boom raising operation lever operation>
For example, when the boom raising operation is performed by operating the operation lever of the operation lever device 123, the pilot pressure supplied from the second pilot pressure supply oil passage 40 is used as the original pressure, and the boom raising operation remote control valve 42b1 is operated with the pilot pressure. The pilot pressure acts on the pressure receiving portion on the left side of the flow control valve 6b, and the flow control valve 6b is switched to the right in the figure.

  Pressure oil in the first pressure oil supply oil passage 5 from the main pump 2 passes through the flow rate control valve 6b via the pressure compensation valve 7b and is supplied to the bottom side of the boom cylinder 3b.

  At this time, the load pressure of the boom cylinder 3b is guided to the differential pressure reducing valve 11 as the maximum load pressure via the internal passage of the flow rate control valve 6b and the shuttle valves 9b and 9c, and at the same time, the unload valve. 15 pressure receiving portions 15d. The differential pressure reducing valve 11 outputs a differential pressure between the discharge pressure of the main pump 2 and the maximum load pressure (in this case, the load pressure of the boom cylinder 3b) as a Pls pressure.

  At the beginning of the movement of the boom cylinder 3b, the load pressure of the boom cylinder 3b is determined to be a certain value (Pbmr) by the load of the boom cylinder 3b, but the pressure of the first pressure oil supply oil passage 5 of the main pump 2, that is, the main pump Since the pressure oil in the first pressure oil supply oil passage 5 flows out into the boom cylinder 3b, the discharge pressure of 2 decreases for a moment. For this reason, at this time, the Pls pressure, which is the output pressure of the differential pressure reducing valve 11, decreases.

  In the control valve 12b and the piston 12c of the load sensing control unit 12L of the pump control unit 12, the Pls pressure, which is the difference between the discharge pressure of the main pump 2 and the maximum load pressure, is the output pressure of the engine rotation detection valve unit 13. The tilt of the main pump 2 is controlled to be equal to the Pgr pressure, but when the boom cylinder 3b starts to move, the Pls pressure becomes smaller than the Pgr pressure (Pgr> Pls) as described above. For this reason, the control valve 12b of the pump control unit 12 switches to the right in the figure, and operates to increase the tilt of the main pump 2 by returning the pressure oil of the tilt angle control piston 12c to the tank.

  As the tilt of the main pump 2 increases, the discharge flow rate of the main pump 2 increases and the flow rate supplied to the boom cylinder 3b also increases. When the flow rate supplied to the boom cylinder 3 b increases, the Pls pressure (the differential pressure between the pump pressure and the maximum load pressure) output from the differential pressure reducing valve 11 increases, and the Pls pressure is output from the engine rotation detection valve unit 13. When the pressure reaches the Pgr pressure, the increase in the discharge flow rate of the main pump 2 stops.

  Thus, the discharge flow rate of the main pump 2 is controlled so that the Pls pressure becomes equal to the Pgr pressure (= Pgr 0) that is the output pressure of the engine rotation detection valve unit 13.

  Here, from the relationship of Pls pressure = pump pressure−maximum load pressure, when the boom raising operation is performed, the relationship of Pls pressure = pump pressure−boom cylinder load pressure (Pbmr) is established.

  In other words, since pump pressure = boom cylinder load pressure + Pls pressure, the pump pressure is maintained at Pbmr + Pgr0 (see FIG. 3).

  The first pilot pressure supply oil passage 38 is supplied with pressure oil from the first pressure oil supply oil passage 5 via the pressure reducing valve 32. In this case, the discharge pressure (Pbmr + Pgr0) of the main pump 2 is supplied. ) Is higher than the pressure Pi0 (4 MPa) set by the spring 32b of the pressure reducing valve 32, the pressure of the first pilot pressure supply oil passage 38 is set to the set pressure Pi0 ( 4 MPa).

  When the operation lever of the boom operation lever device 123 is returned to the neutral position, the state becomes the same as the state of “(b) Operation lever neutral at the gate lock lever release position”.

<(D) Control lever neutral after fine operation of boom lowering control lever>
For example, when a boom lowering operation is performed by operating the operation lever of the operation lever device 123, the pilot pressure supplied from the second pilot pressure supply oil passage 40 is used as the base pressure, and the remote control valve 42b2 for boom lowering operation has the pilot pressure. The pilot pressure acts on the pressure receiving portion on the right side of the flow control valve 6b in the figure, and the flow control valve 6b is switched in the left direction in the figure.

  The pressure oil in the first pressure oil supply oil passage 5 from the main pump 2 is supplied to the rod side of the boom cylinder 3b through the flow rate control valve 6b via the pressure compensation valve 7b.

  At this time, the load pressure of the boom cylinder 3b is guided to the differential pressure reducing valve 11 as the maximum load pressure via the internal passage of the flow rate control valve 6b and the shuttle valves 9b and 9c, and at the same time, the unload valve. 15 pressure receiving portions 15d. The differential pressure reducing valve 11 outputs a differential pressure between the discharge pressure of the main pump 2 and the maximum load pressure (in this case, the load pressure of the boom cylinder 3b) as a Pls pressure. At this time, in an operation in which the actuator is pulled by the load's own weight, such as a fine operation for lowering the boom, the load pressure of the cylinder hardly occurs and becomes almost equal to the tank pressure. For this reason, the Pls pressure output from the differential pressure reducing valve 11 is substantially equal to the discharge pressure of the main pump 2.

  On the other hand, the pressure of the first pressure oil supply oil passage 5 of the main pump 2, that is, the discharge pressure of the main pump 2, decreases to Ppbml as shown in FIG. 3 because the pressure oil flows out to the boom cylinder 3b.

  When the boom lowering operation is a fine operation, the flow rate flowing out to the boom cylinder 3b is slight, and the discharge pressure Ppbml of the main pump 2 is, as shown in FIG. 3, the Pgr pressure (= Balance with a value larger than (Pgr0 = 2 MPa).

  In the control valve 12b and the piston 12c of the load sensing control unit 12L of the pump control unit 12, the Pls pressure, which is the difference between the discharge pressure of the main pump 2 and the maximum load pressure, is the output pressure of the engine rotation detection valve unit 13. The tilt of the main pump 2 is controlled so as to be equal to the Pgr pressure. However, in the case of fine operation for lowering the boom, Pls pressure (= Ppbml)> Pgr pressure (= Pgr0), and the Pls pressure is higher than the Pgr pressure. Increased (Pls> Pgr). For this reason, the control valve 12b of the pump control unit 12 switches to the left in the figure, guides the pressure oil of the first pilot pressure supply oil passage 38 to the piston 12c for tilt angle control, and reduces the tilt of the main pump 2. Operates to When the tilt of the main pump 2 is reduced to the minimum value, the discharge flow rate of the main pump 2 is maintained at the minimum flow rate.

  Further, the first pilot pressure supply oil passage 38 and the second pilot pressure supply oil passage 40 are also supplied with the decompressed pressure oil from the first pressure oil supply oil passage 5 of the main pump 2 through the pressure reducing valve 32. However, in this case, since the discharge pressure Ppbml of the main pump 2 is lower than the pressure Pi0 (4 MPa) set by the spring 32b, the pressure Ppbml remains as it is at the first pilot pressure supply oil passage on the downstream side of the pressure reducing valve 32. 38.

  As described above, in the boom lowering fine operation, the pump pressure is lower than the discharge pressure (Pp0 + Pgr0) of the main pump 2 when the operation lever is neutral, but the pressure oil accumulated in the accumulator 42 As shown in FIG. 3, the pressure in the first pilot pressure supply oil passage 38 on the downstream side is maintained at the pump pressure (Pp0 + Pgr0) of the immediately preceding operation.

  When the boom operation lever is returned to the neutral position, the state becomes the same as the state of “(b) Operation lever neutral at the gate lock lever release position”.

<(E) Gate lock lever blocking position>
This is the same as “(a) Gate lock lever blocking position”.
~effect~
According to the present embodiment, the following effects can be obtained.

  (1) In the present embodiment, the hydraulic drive device is a load sensing control hydraulic drive device including an unload valve 15. When the unload valve 15 is provided, the “(a) gate lock lever blocking position” and As described in “(b) Neutral operation lever at the gate lock lever release position”, the discharge pressure of the main pump 2 is a constant pressure by the unload valve 15 even when the operation lever devices 122 and 123 are neutral. Retained. Therefore, it is possible to generate a pilot pressure using the discharge oil of the main pump 2 without adding a special valve such as a sequence valve described in Patent Document 1.

  In addition, a pilot pressure generating circuit 30 that generates pilot pressure using the oil discharged from the main pump 2 is provided, and the pressure reducing valves 42a1, 42a2, 42b1, 42b2 of the operation lever devices 122, 123 are flow control valves 6a, 6b, 6c. ... And a differential pressure reducing valve 29 (signal pressure generating valve) of the engine rotation detection valve unit 13 is a signal pressure (first pressure) corresponding to the number of revolutions of the engine 1. The pressure reducing valves 42a1, 42a2, 42b1, so that the original pressure when generating the signal pressure is supplied from the pilot hydraulic power sources (first and second pilot pressure supply oil passages 38, 40) of the pilot pressure generating circuit 30. 42b2 and the differential pressure reducing valve 29 are connected to a pilot hydraulic pressure source. For this reason, not only the command pilot pressure but also the signal pressure corresponding to the rotational speed of the engine 1 is generated, and the target differential pressure of the load sensing control corresponding to the rotational speed of the engine 1 can be set.

  Moreover, since a pilot hydraulic pressure source can be formed without providing a pilot relief valve on the downstream side of the engine rotation detection valve unit 13 in the path through which the supply flow rate from the pilot pump 10 flows as in the prior art, the pilot relief valve can be formed. The discharge pressure of the pilot pump 10 can be reduced as compared with the case where the is provided, and wasteful energy consumption by the pilot relief valve can be suppressed.

FIG. 4 is a diagram showing the discharge pressure of the pilot pump 10 in comparison with the conventional technique as described in Patent Document 1 and the present embodiment. In a conventional hydraulic drive device that performs load sensing control as described in Patent Document 1, a pilot relief valve is provided on the downstream side of the engine rotation detection valve unit 13 to constitute a pilot hydraulic pressure source. When the pressure of this pilot hydraulic power source is set to the same pressure as the pilot hydraulic power source (first and second pilot pressure supply oil passages 38 and 40) in the present embodiment, the set pressure of the pilot relief valve is set to the pressure reducing valve 32a. The pressure must be the same as the pressure Pi0, and the set pressure Pi0 is, for example, 4 MPa as described above. When the differential pressure reducing valve 29 of the engine rotation detection valve unit 13 outputs a signal pressure of Pgr0, the signal pressure is equal to the differential pressure across the variable throttle valve 28, and the supply flow rate from the pilot pump 10 flows. In the path, a pressure loss equal to Pgr0 occurs. Pgr0 is, for example, 2 MPa as described above.

  Therefore, in the conventional hydraulic drive device that performs load sensing control as described in Patent Document 1, the discharge pressure of the pilot pump 10 is obtained by adding the set pressure of the pressure reducing valve 32a and the signal pressure output by the differential pressure reducing valve 29. Pi0 + Pgr0 (6 MPa).

  On the other hand, in the present embodiment, the downstream side of the engine rotation detection valve unit 13 can be directly connected to the tank, so that the discharge pressure of the pilot pump 10 is Pgr0 of the signal pressure output by the differential pressure reducing valve 29. (2 MPa).

  Thus, in the present invention, in a hydraulic drive device having a variable displacement main pump 2 that performs load sensing control, a pilot that uses the discharge oil of the main pump 2 without adding a special valve such as a sequence valve. The pressure can be generated, the target differential pressure of the load sensing control according to the rotational speed of the engine 1 can be set, and wasteful energy consumption by the pilot relief valve can be suppressed.

  (2) In the present embodiment, separate pilot pressure supply oil passages (first and second pilot pressure supply oil passages 38, 40) are formed by selectively using the upstream and downstream of the switching valve 37, and load sensing is performed. The original pressure when the control valve 12b generates an output pressure for driving the piston 12c (load sensing actuator) is supplied from the first pilot pressure supply oil passage 38, and the pressure reducing valves 42a1, 42a2 of the operation lever devices 122, 123 are supplied. , 42b1 and 42b2 are supplied from the second pilot pressure supply oil passage 40 as the original pressure when the command pilot pressure is generated and the original pressure when the differential pressure reducing valve 29 (signal pressure generating valve) generates the signal pressure. It is set as the structure connected so that. For this reason, not only the pressure reducing valves 42a1, 42a2, 42b1, 42b2 and the differential pressure reducing valve 29 of the operating lever devices 122, 123 as described in (1) above, but also the load sensing control unit 12L of the above (1). As described above, a pilot relief valve is provided not only for the pressure reducing valves 42a1, 42a2, 42b1, 42b2 and the differential pressure reducing valve 29 (signal pressure generating valve) of the operation lever devices 122, 123 but also for the load sensing control unit 12L. A pilot hydraulic power source can be provided without wasteful energy consumption by the pilot relief valve.

  (3) In the present embodiment, a pilot hydraulic pressure source is provided for the differential pressure reducing valve 11 without providing a pilot relief valve, and further circuit configuration is achieved while suppressing wasteful energy consumption by the pilot relief valve. Can be further simplified.

  (4) Furthermore, in the present embodiment, the second pilot pressure supply oil passage 40 is formed on the downstream side of the switching valve 37, and the plurality of pressure reducing valves 42 a 1, 42 a 2, 42 b 1, 42 b 2 of the operation lever devices 122, 123 are instructed. Connected so that not only the original pressure when generating the pilot pressure but also the original pressure when the differential pressure reducing valve 29 (signal pressure generating valve) generates the signal pressure is supplied from the second pilot pressure supply oil passage. In addition, the signal pressure generated by the differential pressure reducing valve 29 is connected so as to be guided to the pressure receiving portion 12d (first pressure receiving portion) of the load sensing control valve 12b and the pressure receiving portion 15b (second pressure receiving portion) of the unload valve 15. The target differential pressure for load sensing control is set by the signal pressure, and the target unload pressure of the unload valve 15 is set by the signal pressure and the biasing force of the spring.

  Therefore, as described in “(a) Gate lock lever blocking position”, when the gate lock lever 36 is in the first position where the operation of the plurality of actuators 3a, 3b, 3c. Since the fourth oil passage 33d downstream of the switching valve 37 is communicated with the tank and the second pilot pressure supply oil passage 40 becomes the tank pressure, the signal pressure generated by the differential pressure reducing valve 29 also becomes the tank pressure, and the load sensing control. The target differential pressure is also the tank pressure. Thereby, the discharge flow rate of the main pump 2 can be reliably controlled to the minimum. Further, since the target unload pressure of the unload valve 15 becomes a pressure set by the urging force of the spring 15a, the discharge pressure of the main pump 2 can be lowered to the set pressure Pp0 (for example, 1 MPa) of the spring 15a.

  As described above, in the present embodiment, in the hydraulic drive apparatus having the variable displacement main pump 2 that performs load sensing control, the position at which the gate lock lever 36 disables the operation of the plurality of actuators 3a, 3b, 3c. In this case, since the discharge flow rate of the main pump 2 is minimized and the discharge pressure of the main pump 2 is reduced, wasteful energy consumption by the main pump 2 can be suppressed.

(5) Further, in the present embodiment, the engine rotation detection valve unit 13 (rotation speed signal pressure generating device) has only a hydraulic element, and the entire hydraulic drive device can have a pure hydraulic configuration.
<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIGS.
~Constitution~
FIG. 5 is a diagram showing a system configuration of the hydraulic drive apparatus according to the present embodiment.

  The hydraulic drive apparatus in the present embodiment shown in FIG. 5 includes an electromagnetic switching valve 37A instead of the switching valve 37 in the first embodiment shown in FIG. 1, and an engine instead of the engine rotation detection valve unit 13. A rotation sensor 51 (rotation number detection unit) that detects the number of rotations of 1; a switch 53 that is provided between the electromagnetic switching valve 37A and the battery 52 and is switched by the gate lock lever 24; and load sensing of the pump control unit 12. An electromagnetic proportional pressure reducing valve 54 (signal pressure generating valve) whose output side is connected to the pressure receiving portion 12d of the control valve 12b of the control portion 12L via the signal oil passage 27c and the output of the rotation sensor 51 are input, and the electromagnetic proportional pressure reducing valve And a controller 55 for controlling the output of 54. The input side of the electromagnetic proportional pressure reducing valve 54 is connected to the second pilot pressure supply oil passage 40 via the oil passage 43, and the second pilot pressure supply oil passage 40 supplies the original pressure (primary pressure) to the electromagnetic proportional pressure reducing valve 54. To do.

  Further, as a result of not including the engine rotation detection valve unit 13, the hydraulic drive device in the present embodiment also does not include the fixed displacement type pilot pump 10 provided as a pilot hydraulic pressure source of the engine rotation detection valve unit 13. .

The rest is the same as the first embodiment shown in FIG.
~ Activation ~
The operation of the present embodiment will be described again with reference to FIG.

  When the rotational speed of the engine 1 is detected by the rotational speed sensor 51 and input to the controller 55, the controller 55 calculates the output pressure of the proportional electromagnetic pressure reducing valve 54 corresponding to the engine rotational speed, and the current value corresponding to the output pressure. And the current value is output to the proportional electromagnetic pressure reducing valve 54 as an electric signal.

  The controller 55 stores the relationship between the engine speed and the output pressure of the proportional electromagnetic pressure reducing valve 230 as shown in FIG. 6 in order to calculate the output of the proportional electromagnetic pressure reducing valve 54 according to the engine speed. This relationship is set so that the Pgr pressure, which is the output pressure of the proportional electromagnetic pressure reducing valve 230, increases from Pgr0min to Pgr0 as the engine speed increases. In the figure, High is the rated maximum speed of the engine 1 and Low is the low speed idle speed of the engine 1.

  As described above, the controller 55 controls the output pressure of the proportional electromagnetic pressure reducing valve 54 in accordance with the rotational speed sensor 51, so that the operation similar to that of the engine rotation detecting valve unit 13 in the first embodiment shown in FIG. can get.

Other operations are the same as those in the first embodiment.
~effect~
According to the present embodiment, in addition to the effects (1) to (4) of the first embodiment, since the fixed displacement pilot pump is not provided, the energy consumed by the pilot pump is completely reduced to 0. And wasteful energy consumption can be further suppressed.
<Third Embodiment>
A third embodiment of the present invention will be described with reference to FIG.

  FIG. 7 is a diagram showing a system configuration of the hydraulic drive apparatus according to the present embodiment.

  The hydraulic drive apparatus according to the present embodiment includes an unload valve 15B instead of the unload valve 15 according to the first embodiment shown in FIG. The difference between the unload valve 15 and the unload valve 15B is that the unload valve 15 has a closing direction operation spring 15a and a pressure receiving portion 15b as means for setting the target unload pressure. Whereas the target unload pressure of the unload valve 15 is set by the signal pressure output from the engine rotation detection valve unit 13 guided to the pressure receiving portion 15b, the unload valve 15B serves as a setting means for the target unload pressure. The target unloading pressure of the unloading valve 15 is set only with the biasing force of the spring 15e. The target unload pressure set by the urging force of the spring 15e is, for example, the output pressure (target differential pressure of load sensing control) of the engine rotation detection valve unit 13 when the engine 1 is at the rated maximum speed as described above. When set to 2 MPa, it is, for example, 3 MPa which is equal to or higher than the target differential pressure of the load sensing control.

  The rest is the same as the first embodiment shown in FIG.

Also according to the present embodiment, the effects (1) to (3) and (5) of the first embodiment can be obtained.
<Fourth embodiment>
A fourth embodiment of the present invention will be described with reference to FIG.

  FIG. 8 is a diagram showing a system configuration of the hydraulic drive apparatus according to the present embodiment.

  The difference between the hydraulic drive device of the present embodiment and the first embodiment shown in FIG. 1 is that the differential pressure reducing valve 11 in the first embodiment is not provided, and the control valve 12b of the pump control unit is provided. It is the point which comprised so that the discharge oil of the main pump 2 might be utilized as a source pressure of.

  That is, in the hydraulic drive apparatus according to the present embodiment, the pressure compensation valves 7Ca, 7Cb, 7Cc,..., As means for setting the target compensation differential pressure, the pressure receiving portions 58a, 58b, 58c,. Of the main pump 2 through the oil passage 5a in the control valve unit 4 communicating with the first pressure oil supply oil passage 5 to the pressure receiving portions 58a, 58b, 58c. The discharge pressure is guided, and the maximum load pressure selected by the shuttle valves 9a, 9b, 9c... Is guided to the pressure receiving portions 59a, 59b, 59c. Control is performed so that the differential pressure across the meter-in throttle 6c... Is equal to the Pls pressure which is the differential pressure between the pump pressure and the maximum load pressure.

  The control valve 12Cb of the load sensing control unit 12L of the pump control unit 12C includes a pressure receiving unit 12f located on the opposite side to the pressure receiving unit 12d that sets a target differential pressure for load sensing control, and a pressure receiving unit 12i located on the same side. The discharge pressure of the main pump 2 is guided to the pressure receiving portion 12f via the oil passage 61 communicating with the first pressure oil supply oil passage 5, and the shuttle valve is connected to the pressure receiving portion 12i via the signal oil passages 30a and 20d. The maximum load pressure selected by 9a, 9b, 9c,... Is derived, and the Pls pressure, which is the differential pressure between the pump pressure and the maximum load pressure, is set in the pressure receiving unit 12d as the target differential pressure of the load sensing control. To be equal to.

  The first pressure oil supply oil passage 5 is connected to the input side of the switching valve 12Cb via the oil passage 61, and supplies the discharge pressure of the main pump 2 to the switching valve 12Cb as a source pressure (primary pressure).

  The rest is the same as the first embodiment shown in FIG.

Also according to the present embodiment, the effects (1) and (3) to (5) of the first embodiment can be obtained.
<Others>
Various modifications can be made to the above embodiment within the spirit of the present invention. For example, in the above embodiment, the engine 1 (diesel engine) is used as the prime mover, but an electric motor may be used instead of the engine 1, or the engine and the electric motor may be used in combination.

1 Engine 2 Variable displacement hydraulic pump (Main pump)
3a, 3b, 3c ... Actuator 4 Control valve unit 5 First pressure oil supply oil passages 6a, 6b, 6c ... Flow rate control valves 7a, 7b, 7c ... Pressure compensation valves 9a, 9b, 9c ... Shuttle valve 10 Pilot pump 11 Difference Pressure reducing valve 12, 12C Pump control unit 12L Load sensing controller 12T Torque controller 12S Stopper 12a Tilt angle control piston 12b, 12Cb Load sensing control valve 12c Tilt control piston (load sensing actuator)
12d Pressure receiving part 12e Pressure receiving part 12h Pressure receiving part 12i Pressure receiving part 13 Engine rotation detection valve unit 14 Main relief valve 15, 15B Unload valve 15a Spring 15b Pressure receiving part 15e Spring 20a, 20b, 20c, 20d Signal oil path 22a, 22b Signal oil Paths 27a, 27b Signal oil path 28 Variable throttle valve (Rotation speed detector)
29 Differential pressure reducing valve (Signal pressure generating valve)
30 pilot pressure generating circuit 31 second pressure oil supply oil passage 32 pressure reducing valve 32a spring 33a first oil passage 33b second oil passage 33c third oil passage 33d fourth oil passage 35 accumulator 36 gate lock lever 37 switching valve 38 first Pilot pressure supply oil passage 40 First pilot pressure supply oil passage 42a1, 42a2, 42b1, 42b2 Remote control valve (pressure reducing valve)
43 Oil passages 44a, 44b Oil passage 51 Rotation sensor (rotation speed detection unit)
52 Battery 53 Switch 54 Proportional pressure reducing valve (signal pressure generating valve)
55 Controllers 58a, 58b, 58c ... Pressure receiving portions 59a, 59b, 59c ... Pressure receiving portions 61 Oil passage 101 Lower traveling body 102 Upper turning body 103 Swing post 104 Front work machine 106 Soil plate 107 Swing stand 108 Operator's cab 111 Boom 112 Arm 113 buckets

Claims (6)

Prime mover,
A variable displacement main pump driven by this prime mover;
A plurality of actuators driven by pressure oil discharged from the main pump;
A plurality of flow rate control valves for controlling the flow rate of pressure oil supplied from the main pump to the plurality of actuators;
A pump control device having a load sensing control unit for controlling a capacity of the main pump so that a discharge pressure of the main pump is higher than a maximum load pressure of the plurality of actuators by a target differential pressure;
When the discharge pressure of the main pump becomes higher than the target unload pressure by more than the target unload pressure, the main pump is opened and the discharge oil of the main pump is returned to the tank to restrict further increase of the discharge pressure of the main pump. A load valve,
An operation lever device comprising a plurality of pressure reducing valves for generating a command pilot pressure for operating the plurality of flow control valves;
A rotation speed detection unit that detects the rotation speed of the prime mover, and a rotation speed signal pressure generation device that includes a signal pressure generation valve that generates a first signal pressure corresponding to the rotation speed of the prime mover,
The load sensing control unit receives the first signal pressure generated by the signal pressure generation valve, and sets the target differential pressure in a hydraulic drive device for a construction machine,
A pilot pressure generating circuit that generates pilot pressure using the discharge oil of the main pump;
The pilot pressure generation circuit includes:
A second pressure oil supply oil passage branched from the first pressure oil supply oil passage connected to the main pump;
A pressure reducing valve provided in the second pressure oil supply oil passage;
A check valve provided in a first oil passage downstream of the pressure reducing valve;
An accumulator connected to a third oil passage branched from a second oil passage downstream of the check valve;
A pilot hydraulic source including the second oil passage downstream of the check valve;
The source pressure when the plurality of pressure reducing valves of the operation lever device generates a command pilot pressure for operating the plurality of flow control valves, and the signal pressure generating valve according to the number of rotations of the prime mover. The hydraulic drive of a construction machine, wherein the plurality of pressure reducing valves and the signal pressure generating valve are connected to the pilot hydraulic source so that a source pressure when generating the signal pressure is supplied from the pilot hydraulic source apparatus. The hydraulic drive device for a construction machine according to claim 1,
The load sensing control unit of the pump control device is driven by a load sensing control valve having a first pressure receiving unit for setting the target differential pressure, and an output pressure of the load sensing control valve, and controls the capacity of the main pump. A load sensing actuator that
The pilot pressure generation circuit further includes:
A gate lock lever that is disposed in a cab of the construction machine and is selectively operated between a first position in which operation of the plurality of actuators is disabled and a second position in which operation of the plurality of actuators is enabled. When,
A switching valve connected to the second oil passage downstream of the check valve and switched by operation of the gate lock lever;
The switching valve communicates a fourth oil passage downstream of the switching valve with the tank when the gate lock lever is in the first position, and the switching valve when the gate lock lever is in the second position. The fourth oil passage downstream is connected to the second oil passage upstream of the switching valve,
The pilot hydraulic pressure source includes a first pilot pressure supply oil passage constituted by the second oil passage upstream of the switching valve and a second pilot pressure supply constituted by the fourth oil passage downstream of the switching valve. Including oil passages,
The load sensing control valve is configured to supply the original pressure when the load sensing control valve generates the output pressure for driving the load sensing actuator from the first pilot pressure supply oil passage. Connect to the pilot pressure supply oil passage,
The source pressure when the plurality of pressure reducing valves of the operation lever device generates a command pilot pressure for operating the plurality of flow control valves, and the signal pressure generating valve according to the number of rotations of the prime mover. The plurality of pressure reducing valves and the signal pressure generating valve are connected to the second pilot pressure supply oil passage so that the original pressure when generating the signal pressure is supplied from the second pilot pressure supply oil passage,
The signal pressure generating valve is connected to the first pressure receiving portion of the load sensing control valve so that the first signal pressure generated by the signal pressure generating valve is guided to the first pressure receiving portion of the load sensing control valve. A hydraulic drive device for a construction machine. The hydraulic drive device for a construction machine according to claim 2,
The load sensing control valve further includes a third pressure receiving portion facing the first pressure receiving portion,
A differential pressure reducing valve that converts a differential pressure between the discharge pressure of the main pump and the maximum load pressure of the plurality of actuators into an absolute pressure, and outputs the absolute pressure as a second signal pressure;
Connecting the differential pressure reducing valve to the first pilot pressure supply oil passage so that a source pressure when the differential pressure reducing valve generates the absolute pressure is supplied from the first pilot pressure supply oil passage;
The differential pressure reducing valve is connected to the third pressure receiving portion of the load sensing control valve so that the second signal pressure generated by the differential pressure reducing valve is guided to the third pressure receiving portion of the load sensing control valve. A hydraulic drive device for a construction machine. The hydraulic drive device for a construction machine according to claim 1,
The load sensing control unit of the pump control device has a load sensing control valve having a first pressure receiving unit for setting the target differential pressure, and an output pressure of the load sensing control valve is guided, and the load sensing control unit according to the output pressure A load sensing actuator that controls the capacity of the main pump,
The unload valve has a second pressure receiving portion and a spring for setting the target unload pressure,
The pilot pressure generation circuit further includes:
A gate lock lever that is disposed in a cab of the construction machine and is selectively operated between a first position in which operation of the plurality of actuators is disabled and a second position in which operation of the plurality of actuators is enabled. When,
A switching valve connected to the second oil passage downstream of the check valve and switched by operation of the gate lock lever;
The switching valve communicates a fourth oil passage downstream of the switching valve with the tank when the gate lock lever is in the first position, and the switching valve when the gate lock lever is in the second position. The fourth oil passage downstream is connected to the second oil passage upstream of the switching valve,
The pilot hydraulic pressure source includes a pilot pressure supply oil passage configured by the fourth oil passage downstream of the switching valve,
A source pressure when a plurality of pressure reducing valves of the operating lever measure generates a command pilot pressure for operating the plurality of flow control valves, and the signal pressure generating valve corresponds to the number of rotations of the prime mover. The plurality of pressure reducing valves and the signal pressure generating valve are connected to the pilot pressure supply oil passage so that the original pressure when generating the signal pressure is supplied from the pilot pressure supply oil passage,
The signal pressure generating valve is connected to the load so that the first signal pressure generated by the signal pressure generating valve is guided to the first pressure receiving portion of the load sensing control valve and the second pressure receiving portion of the unload valve. Connected to the first pressure receiving portion of the sensing control valve and the second pressure receiving portion of the unloading valve;
The load sensing control valve sets the target differential pressure by the first signal pressure guided to the first pressure receiving unit,
The hydraulic drive device for a construction machine, wherein the unload valve sets the target unload pressure by the first signal pressure guided to the second pressure receiving portion and the biasing force of the spring. The hydraulic drive device for a construction machine according to any one of claims 1 to 4,
A pilot pump driven by the prime mover;
The rotation speed detection unit of the rotation speed signal pressure generator has a throttle valve through which the discharge oil of the pilot pump passes,
The hydraulic pressure drive device for a construction machine, wherein the signal pressure generating valve is a differential pressure reducing valve that converts a differential pressure across the throttle valve into an absolute pressure and outputs the absolute pressure as the first signal pressure. . The hydraulic drive device for a construction machine according to any one of claims 1 to 4,
The rotation speed detection unit of the rotation speed signal pressure generator includes a rotation sensor that detects the rotation speed of the prime mover,
The rotation speed signal pressure generation device further includes a controller that inputs a detection signal of the rotation sensor and outputs a control signal to the signal pressure generation valve,
The hydraulic drive device for a construction machine, wherein the signal pressure generating valve is an electromagnetic proportional pressure reducing valve that is driven by a control signal output from the controller and outputs the first signal pressure.

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