JP2012167735A - Hydraulic driving device of working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic driving device of a working machine, which is capable of ensuring good operability during a normal operation and during a minor operation and reducing energy loss during the minor operation.SOLUTION: The present invention has a configuration in which a controller 31 includes: a pump discharge amount control unit 40 which performs control processing in which when the operation mode of a working element operation device is an operation mode regarded as a minor operation, a control signal for making the displacement of a variable capacity hydraulic pump 10 smaller than a displacement corresponding to a normal operation is output to a control unit of an electromagnetic proportional pressure reducing valve 21; and a center bypass valve control unit 50 which performs control processing in which when the operation mode is an operation mode regarded as the minor operation and the load pressure of a working element actuator is low, a control signal for making the amount of opening relatively larger while a center bypass valve 22 is in a state of switching between a fully open position and a fully closed position is output to a control unit of a proportional electromagnetic valve 23.

Description

  The present invention includes a working machine such as a hydraulic excavator including a working device including a working element such as a boom and an arm and capable of performing a normal operation and a fine operation performed at a smaller operation amount and a slower operation speed than the normal operation. The present invention relates to a hydraulic drive device for a work machine that includes an open center type directional control valve and positively controls a variable displacement hydraulic pump.

  As a prior art comprising this kind of open center positive control system, there is one disclosed in Patent Document 1. In this prior art, an open center type directional control valve for a boom, an directional control valve for an arm, etc. are arranged on a center bypass line connecting a variable displacement hydraulic pump and a tank, and the displacement volume of the variable displacement hydraulic pump is increased. In addition, the direction control valve for the boom, the direction control valve for the arm, and the like are variably controlled according to the operation amount of the operation device that performs the switching operation.

Japanese Patent Laid-Open No. 11-82416

  In the above-described prior art, when the system is set in consideration of ensuring good operability during normal work such as excavation work, the operation amount of the operation device is reduced or the operation speed is reduced. In the fine operation performed at a slower speed, the excess pump flow easily flows to the tank via the direction control valve and the center bypass line. That is, energy that is not utilized for work increases and energy loss is likely to occur. In addition, when the system is set in consideration of reducing the excessive flow rate that flows into the tank during the fine operation as described above, the operability during normal work is deteriorated. As described above, in the prior art, it has been difficult to achieve both reduction of energy loss during fine operation and ensuring good operability during normal work.

  In general, even if the work is performed by a fine operation, the load is high and the load is heavy, such as the crane work performed in a hydraulic excavator, or the earth and sand leveling work performed in a hydraulic excavator. In some cases, the load pressure is low and the load is light. In the past, sufficient consideration has not been given to control for such work with different loads in fine operations. Therefore, energy loss due to high and low loads during fine operation and operability are likely to deteriorate.

  The present invention has been made from the above-described prior art, and its purpose is to ensure good operability during normal operation and fine operation and to reduce energy loss during fine operation. An object of the present invention is to provide a hydraulic drive device for a working machine.

  In order to achieve this object, the present invention is provided in a work machine having a work device capable of normal operation and fine operation performed at a smaller operation amount and slower operation speed than the normal operation. A displacement hydraulic pump, a working element actuator that is driven by pressure oil discharged from the variable displacement hydraulic pump and drives a working element included in the working device, and a center bypass that connects the variable displacement hydraulic pump and the tank An open center type work element direction control valve provided on the line for controlling the flow of pressure oil supplied from the variable displacement hydraulic pump to the work element actuator, and the work element direction control valve are switched. A hydraulic drive device for a work machine comprising a work element operating device, wherein the displacement displacement control system controls a displacement volume of the variable displacement hydraulic pump. An apparatus, a center bypass valve provided in the center bypass line portion located downstream of the work element direction control valve, and capable of controlling a flow rate returned to the tank via the center bypass line, and the center bypass valve A center bypass valve control device for controlling, a displacement displacement control device, and a controller for controlling the center bypass valve control device, wherein the controller considers that the operation mode of the operation element operating device is the normal operation. A control signal for setting the displacement volume of the variable displacement hydraulic pump to a displacement volume corresponding to the normal operation is output to the displacement volume control device, and the work element operation device When the operation mode is an operation mode regarded as the fine operation, the variable displacement hydraulic pump is pushed away. A pump discharge amount control unit for performing a control process for outputting a control signal for making the product smaller than a displacement volume corresponding to the normal operation to the displacement controller, and an operation mode of the work element operation device is the normal operation. A control signal for controlling opening and closing of the center bypass valve, and an operation mode of the work element operation device is an operation mode considered as the fine operation. The control process for outputting the control signal for controlling the center bypass valve to the switching state between the fully open position and the fully closed position to the center bypass valve control device, respectively, and the operation mode of the work element operation device include: When the operation mode is regarded as the fine operation and the load pressure of the working element actuator is high, the center bypass valve is set to the fully open position and the fully closed position. A control signal for reducing the opening amount in a switching state between positions, and an operation mode in which the operation mode of the operation element operating device is regarded as the fine operation. A center bypass valve control unit that performs control processing to output a control signal for making the center bypass valve an opening amount larger than the opening amount to the center bypass valve control device when the load pressure is low. It is characterized by that.

  In the present invention configured as described above, when the work element operation device is operated during normal work, the displacement control unit of the variable displacement hydraulic pump is set to the normal operation by pushing away from the pump discharge amount control unit of the controller. A control signal with a corresponding relatively large displacement volume is output. As a result, a large flow rate is supplied from the variable displacement hydraulic pump to the work element actuator via the work element direction control valve. During this time, a control signal for controlling opening and closing of the center bypass valve is output from the center bypass valve control unit of the controller to the center bypass valve control device. Accordingly, a large flow rate can be returned from the working element actuator to the tank via the center bypass line and the center bypass valve. By these operations, it is possible to ensure good normal operability that allows the working element to be driven at a high operating speed.

  In addition, the present invention provides a variable displacement control device that moves away from the pump discharge amount control unit of the controller when the work element operation device is operated at a small operation amount or at a low operation speed during work performed by fine operation. A control signal is output to make the displacement of the hydraulic pump smaller than the displacement corresponding to normal operation. As a result, a small flow rate is supplied from the variable displacement hydraulic pump to the work element actuator via the work element direction control valve as compared with the normal operation. During this time, a control signal for controlling the center bypass valve to be switched between the fully open position and the fully closed position is output from the center bypass valve control unit of the controller to the center bypass valve control device. As a result, the flow rate returning from the work element actuator to the tank via the center bypass line and the center bypass valve can be kept small. By these operations, it is possible to ensure good fine operability capable of driving the work element at a low operating speed. Further, at this time, the output of the variable displacement hydraulic pump can be suppressed, and the energy loss can be reduced.

  Furthermore, the present invention provides the center bypass valve from the center bypass valve control unit of the controller to the center bypass valve control device at the fully open position and the fully closed position when the load pressure of the actuator for the work element is high, even during fine operation. A control signal for further reducing the opening amount of the center bypass valve is output. As a result, the discharge pressure of the variable displacement hydraulic pump increases, and it is possible to ensure good operability during this fine operation / heavy load operation.

  In addition, the present invention provides the center bypass valve from the center bypass valve control unit of the controller to the center bypass valve control device in the fully open position and the fully closed position when the load pressure of the working element actuator is low, even during fine operation. And a control signal for increasing the opening amount of the center bypass valve as compared with the opening amount at the time of the heavy load described above. As a result, the discharge pressure of the variable displacement hydraulic pump can be kept low, and good operability can be ensured during this fine operation / light load operation. Further, at this time, the output of the variable displacement hydraulic pump can be suppressed and energy loss can be reduced.

  Further, according to the present invention, in the above invention, the controller regards the operation mode of the work element operation device as a fine operation based on the operation amount or the operation speed or operation acceleration of the work element operation device. It is characterized by executing a process for calculating the operation mode.

  According to the present invention, in the above invention, the work machine includes a hydraulic excavator, the work element includes a boom and an arm, and the work element actuator operates a boom cylinder that operates the boom and an arm cylinder that operates the arm. The directional control valve for the working element includes a directional control valve for the boom that controls the boom cylinder, and a directional control valve for the arm that controls the arm cylinder. It includes a boom operating device for switching the direction control valve and an arm operating device for switching the arm direction control valve.

  According to the present invention, in the above invention, a discharge pressure sensor that detects a discharge pressure of the variable displacement hydraulic pump, or a bottom pressure sensor that detects a bottom pressure of the boom cylinder and a rod pressure sensor that detects a rod pressure of the arm cylinder. The center bypass valve control unit of the controller includes an operation amount of at least one of an operation amount of the boom operation device and an operation amount of the arm operation device, and a discharge pressure detected by the discharge pressure sensor. Or at least one of the operation amount of the boom operation device and the operation amount of the arm operation device, the bottom pressure detected by the bottom pressure sensor, and the rod pressure detected by the rod pressure sensor. Accordingly, the operation mode of the work element operation device is an operation mode regarded as the fine operation, and the work element actuator is When the load pressure of the motor is in a low state, it is characterized by performing a control process of outputting a control signal to a relatively large opening of the center bypass valve.

  The present invention relates to a pump discharge amount control unit in which a controller outputs a control signal for controlling a displacement volume of a variable capacity hydraulic pump to a displacement volume control device for controlling a displacement volume of a variable displacement hydraulic pump according to a normal operation and a fine operation. And a control signal for making the center bypass opening amount different from each other according to the normal operation and the fine operation is output to the center bypass valve control device for controlling the center bypass valve, and the actuator of the work element actuator at the time of the fine operation is provided. The center bypass valve control unit is configured to output a control signal for making different center bypass opening amounts to the control unit of the proportional solenoid valve according to the level of the load pressure. With this configuration, it is possible to ensure good operability during normal operation and secure good operability according to the load pressure of the work element actuator during fine operation, and energy during fine operation. Loss can be reduced. Accordingly, it is possible to realize a highly reliable operability that is more accurate than the conventional one, and that is economical and practical and highly reliable.

It is a side view which shows the hydraulic shovel mentioned as an example of a working machine. FIG. 2 is an electric / hydraulic circuit diagram showing the hydraulic drive device according to the first embodiment provided in the hydraulic excavator shown in FIG. 1. It is a block diagram which shows the structure of the pump discharge amount control part contained in the controller with which the hydraulic drive device which concerns on 1st Embodiment shown in FIG. 2 is equipped. It is a block diagram which shows the structure of the center bypass valve control part contained in the controller with which the hydraulic drive device which concerns on 1st Embodiment shown in FIG. 2 is equipped. It is a figure which shows the control implemented with the hydraulic drive device which concerns on 1st Embodiment. It is a figure which shows the control implemented with the hydraulic drive device which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the principal part structure of the pump discharge amount control part contained in the controller with which the hydraulic drive unit in 3rd Embodiment of this invention is equipped. It is a block diagram which shows the principal part structure of the center bypass valve control part contained in the controller with which the hydraulic drive unit in 3rd Embodiment of this invention is equipped.

  Embodiments of a hydraulic drive device for a work machine according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a side view showing a hydraulic excavator cited as an example of a work machine.

  The hydraulic drive device according to the first embodiment is provided, for example, in a hydraulic excavator. The traveling body 1, the swiveling body 2 disposed on the traveling body 1, and the swiveling body 2 are rotated in the vertical direction. And a work device 3 that can be attached. The work device 3 includes a boom 4, an arm 5, and a bucket 6 that constitute a work element, a work element actuator, for example, a boom cylinder 7 that operates the boom 4, an arm cylinder 8 that operates the arm 5, and a bucket cylinder that operates the bucket 6 9 is included.

  FIG. 2 is an electric / hydraulic circuit diagram showing the hydraulic drive device according to the first embodiment provided in the hydraulic excavator shown in FIG. 1, and FIG. 3 is a controller provided in the hydraulic drive device according to the first embodiment shown in FIG. FIG. 4 is a block diagram showing a configuration of a center bypass valve control unit included in a controller provided in the hydraulic drive apparatus according to the first embodiment shown in FIG. 2. .

  As shown in FIG. 2, the hydraulic drive device according to the first embodiment controls the variable displacement hydraulic pump 10, the servo valve 20 and the control actuator 20 a included in the regulator of the variable displacement hydraulic pump 10, and the servo valve 20. In other words, a displacement displacement control device for controlling displacement displacement of the variable displacement hydraulic pump 10, for example, an electromagnetic proportional pressure reducing valve 21 is provided.

  Further, in the present embodiment, in addition to the boom cylinder 7 and the arm cylinder 8 that are operated by the pressure oil discharged from the variable displacement hydraulic pump 10 and constitute the working element actuator, the variable displacement hydraulic pump 10 and the tank 34 Open center type work element directional control valve for controlling the flow of pressure oil supplied from the variable displacement hydraulic pump 10 to the boom cylinder 7 and the arm cylinder 8, that is, for the boom. A direction control valve 14 and an arm direction control valve 15 are provided. Further, a working element operating device for switching the boom direction control valve 14 and the arm direction control valve 15, that is, a boom operating device 12 and an arm operating device 13 are provided.

  Further, the first embodiment is provided in a center bypass line 60 portion located downstream of the boom direction control valve 14, and a center bypass valve 22 capable of controlling the flow rate returned to the tank 34 via the center bypass line 60. A center bypass valve control device for controlling the center bypass valve 22, for example, a proportional electromagnetic valve 23 is provided. Further, the first embodiment includes a controller 31 that controls the electromagnetic proportional pressure reducing valve 21 via a signal line 32 and controls the proportional electromagnetic valve 23 via a signal line 33.

  When the operation mode of the boom operation device 12 and the arm operation device 13 is an operation mode regarded as a normal operation, the controller 31 sets the displacement volume of the variable displacement hydraulic pump 10 to a displacement volume corresponding to the normal operation. Is output to the control unit of the electromagnetic proportional pressure reducing valve 21 via the signal line 32, and the operation mode of the boom operation device 12 and the arm operation device 13 is regarded as a fine operation. At some time, a control process for outputting a control signal for making the displacement volume of the variable displacement hydraulic pump 10 smaller than the displacement volume corresponding to the normal operation to the control unit of the electromagnetic proportional pressure reducing valve 21 via the signal line 32 is described later. The pump discharge amount control unit 40 is provided.

  The controller 31 also outputs a control signal for opening and closing the center bypass valve 22 when the operation mode of the boom operation device 12 and the arm operation device 13 is an operation mode regarded as a normal operation, and the boom operation mode. When the operation mode of the device 12 and the arm operation device 13 is an operation mode regarded as a fine operation, the center bypass valve 22 is switched to a predetermined switching state between the fully open position and the fully closed position (center bypass valve 22). A center bypass valve control unit 50 (to be described later) that performs a control process of outputting a control signal to the control unit of the proportional solenoid valve 23 via the signal line 33. . The center bypass valve control unit 50 is an operation mode in which the operation mode of the boom operation device 12 and the arm operation device 13 is regarded as a fine operation, and the load pressure of the boom cylinder 7 and the arm cylinder 8 is high. The control signal for further reducing the opening amount in a predetermined switching state between the fully open position and the fully closed position of the center bypass valve 22, and the operation of the boom operation device 12 and the arm operation device 13. When the mode is regarded as a fine operation and the load pressure of the boom cylinder 7 and the arm cylinder 8 is low, the center bypass valve 22 is switched between a fully open position and a fully closed position. A control process for outputting a control signal for increasing the opening amount as compared to the opening amount when the load pressure is high to the control unit of the proportional solenoid valve 23 via the signal line 33 is performed. Than is.

  The first embodiment also includes a pilot pump 11 that supplies pilot pressure to the boom operation device 12 and the arm operation device 13, and a discharge pressure sensor 24 that detects the discharge pressure of the variable displacement hydraulic pump 10. . Further, a boom raising pressure sensor 25 that detects a pilot pressure generated in response to a boom raising operation by the boom operation device 12, and a boom lowering that detects a pilot pressure generated in response to a boom lowering operation by the boom operation device 12. Pressure sensor 26, arm dump pressure sensor 27 that detects a pilot pressure generated by an arm dumping operation by arm operating device 13, and pilot pressure generated by an arm cloud operation by arm operating device 13 And an arm cloud pressure sensor 28 for detection.

  The first embodiment also includes a bottom pressure sensor 29 that detects the bottom pressure of the boom cylinder 7 and a rod pressure sensor 30 that detects the rod pressure of the arm cylinder 8.

  As shown in FIG. 3, the pump discharge amount control unit 40 of the controller 31 described above is a variable displacement hydraulic pressure corresponding to a signal output from the boom raising pressure sensor 25 in accordance with the boom raising operation amount of the boom operation device 12. The boom raising function generator 40a1 for calculating the displacement of the pump 10 and the variable displacement hydraulic pump 10 according to the signal output from the boom lowering pressure sensor 26 in accordance with the boom lowering operation amount of the boom operating device 12. A boom function generation unit 40a including a boom lowering function generation unit 40a2 for calculating the displacement volume is provided. The boom function generator 40a is configured to generate a displacement volume that increases as the lever operation amount of the boom operation device 12 increases.

  The pump discharge amount control unit 40 calculates the displacement volume of the variable displacement hydraulic pump 10 according to the signal output from the arm cloud pressure sensor 28 according to the arm cloud operation amount of the arm operation device 13. Function generation unit 40b1 and arm dump function generation for calculating the displacement volume of the variable displacement hydraulic pump 10 according to the signal output from the arm dump pressure sensor 27 according to the arm dump operation amount of the arm operation device 13 And an arm function generator 40b including the unit 40b2. The arm function generator 40b is also configured to generate a displacement volume that increases as the lever operation amount of the arm operation device 13 increases.

  The pump discharge amount control unit 40 also includes a displacement volume output from the boom raising function generation unit 40a1 of the boom function generation unit 40a and a displacement volume output from the boom lowering function generation unit 40a2. A maximum value selection unit 40c for selecting the maximum value is provided. Further, the pump discharge amount control unit 40 includes a displacement volume output from the arm cloud function generation unit 40b1 in the arm function generation unit 40b and a displacement volume output from the arm dump function generation unit 40b2. A maximum value selection unit 40d for selecting the maximum value is provided.

  Further, the pump discharge amount control unit 40 adds the displacement volume output from the maximum value selection unit 40c and the displacement volume output from the maximum value selection unit 40d, and outputs from the addition unit 40e. And a control function generator 40f for outputting a control signal corresponding to the displacement volume to the controller of the electromagnetic proportional pressure reducing valve 21. The control function generator 40f is configured to output a control signal having a smaller value to the controller of the electromagnetic proportional pressure reducing valve 21 as the displacement value output from the adder 40e increases.

  Further, as shown in FIG. 4, the center bypass valve control unit 50 of the controller 31 described above is a target value of the differential pressure between the pump discharge pressure and the boom bottom pressure in accordance with the boom raising operation of the boom operation device 12. A first differential pressure generator 50a that outputs a target differential pressure is provided. The first differential pressure generator 50a is configured to output a larger target differential pressure as the pressure output from the boom raising pressure sensor 25 increases.

  Further, the center bypass valve control unit 50 subtracts the pressure output by the bottom pressure sensor 29 of the boom cylinder 7 from the pressure output by the discharge pressure sensor 24, and the difference between the actual pump discharge pressure and the actual boom bottom pressure. A first subtractor 50b that calculates an actual differential pressure that is a pressure, and a second subtractor that subtracts the actual differential pressure output by the first subtractor 50b from the target differential pressure output by the first differential pressure generator 50a. 50c.

  Further, the center bypass valve control unit 50 outputs a second differential pressure generating unit 50d that outputs a target differential pressure that is a target value of the pump discharge pressure, the arm rod pressure, and the differential pressure in response to the arm dump operation of the arm operating device 13. It has. The second differential pressure generator 50d is also configured to output a large target differential pressure as the pressure output from the arm dump pressure sensor 27 increases.

  Further, the center bypass valve control unit 50 subtracts the pressure output by the rod pressure sensor 30 of the arm cylinder 8 from the pressure output by the discharge pressure sensor 24 to obtain the actual pump discharge pressure and the actual arm rod pressure. A third subtractor 50e that calculates an actual differential pressure that is a differential pressure, and a fourth subtracter that subtracts the actual differential pressure output by the third subtractor 50e from the target differential pressure output by the second differential pressure generator 50d. Part 50f.

  Further, the center bypass valve control unit 50 includes the difference between the target differential pressure output from the second subtracting unit 50c and the actual differential pressure, and the difference between the target differential pressure output from the fourth subtracting unit 50f and the actual differential pressure. A maximum value selection unit 50g that selects the maximum value, a control signal calculation unit 50h that converts the difference output from the maximum value selection unit 50g into a control signal, and the current control signal converted by the control signal calculation unit 50h Is added to the previous control value to generate a new control signal. Note that the control signal calculation unit 50 performs a calculation process of outputting a control signal having a smaller value as the difference output from the maximum value selection unit 50g increases, for example. With such a configuration, the pump discharge pressure is controlled to be higher than the load pressure of the actuator by the difference between the target differential pressure selected by the maximum value selection unit 50g and the actual differential pressure.

  In the first embodiment configured as described above, for example, the boom operating device 12 and the arm operating device 13 are each operated with a large operation amount during excavation work of earth and sand, and the operation speed of the boom operating / arm dumping combined operation is increased. When a fast normal operation is to be performed, as shown in FIG. 3, a large operation amount of the boom operation device 12 is detected by the boom raising pressure sensor 25 and included in the pump discharge amount control unit 40 of the controller 31. This is input to the boom raising function generator 40a1. Further, a large operation amount of the arm operation device 13 is detected by the arm dump pressure sensor 27 and input to the arm dump function generation unit 40 b 2 included in the pump discharge amount control unit 40. Accordingly, a large displacement volume is output from each of the boom raising function generator 40a1 and the arm dump function generator 40b2 to the maximum value selectors 40c and 40d, and these values are added by the adder 40e for control purposes. It is output to the function generator 40f. From the control function generator 40f, a control signal having a small value is output to the electromagnetic proportional pressure reducing valve 21 shown in FIG. 2 in accordance with the displacement volume having a large value.

  Therefore, the electromagnetic proportional pressure reducing valve 21 tends to be switched to the upper side in FIG. 2 according to the spring force, and the control port of the servo valve 20 is connected to the boom operation device 12 via the electromagnetic proportional pressure reducing valve 21. The servo valve 20 connected to the arm operation device 13 is switched to the left position side in FIG. 2 according to the pilot pressure output according to the operation amount of the boom operation device 12 and the arm operation device 13. Tend to be. Thereby, the pilot pressure from the pilot pump 11 is supplied to the small diameter chamber of the control piston 20a via the servo valve 20, the large diameter chamber is connected to the tank 34, and the control piston 20a moves to the left in FIG. . As a result, the displacement of the variable displacement hydraulic pump 10 is controlled to increase, and a large flow rate is discharged from the variable displacement hydraulic pump 10.

  During this time, the boom direction control valve 14 is switched to the left position in FIG. 2 according to the boom raising operation of the boom operation device 12, and the arm direction control valve 15 is changed according to the arm dump operation of the arm operation device 13. It is switched to the right position in FIG. Therefore, a large amount of pressure oil discharged from the hydraulic pump 10 is supplied to the rod chamber of the arm cylinder 8 via the arm direction control valve 15 and is supplied to the bottom chamber of the boom cylinder 7 via the boom direction control valve 14. Supplied. As a result, the boom cylinder 7 is extended to perform the boom raising operation, and the arm cylinder 8 is contracted to perform the arm dump operation.

  Along with these operations, for example, a high pressure is detected from each of the bottom pressure sensor 29 that detects the bottom pressure of the boom cylinder 7 and the rod pressure sensor 30 that detects the rod pressure of the arm cylinder 8. Therefore, in the subtraction unit 50b included in the center bypass valve control unit 50 of the controller 31 shown in FIG. 4, the pressure detected by the bottom pressure sensor 29 is subtracted from the pressure detected by the discharge pressure sensor 24 to obtain the pump discharge pressure. The actual differential pressure with a small boom bottom pressure is calculated, and the small actual differential pressure is output to the subtractor 50c. On the other hand, according to the large boom raising operation amount output from the boom raising pressure sensor 25, the first differential pressure generating unit 50a outputs a large target differential pressure to the subtracting unit 50c. The subtracting unit 50c subtracts the actual differential pressure output by the subtracting unit 50b from the target differential pressure output by the first differential pressure generating unit 50a to obtain a difference between the target differential pressure and the actual differential pressure that is a relatively large value. Output to the maximum value selector 50g.

  Similarly, in the subtraction unit 50e included in the center bypass valve control unit 50, the pressure detected by the rod pressure sensor 30 is subtracted from the pressure detected by the discharge pressure sensor 24, so that the pump discharge pressure and the arm rod pressure are small. The differential pressure is calculated, and the small actual differential pressure is output to the subtracting unit 50f. On the other hand, the second differential pressure generating unit 50d outputs a large target differential pressure to the subtracting unit 50f in accordance with the large arm dump operation amount output from the arm dump pressure sensor 27. The subtracting unit 50f subtracts the actual differential pressure output by the subtracting unit 50e from the target differential pressure output by the second differential pressure generating unit 50d, and sets the difference between the relatively large target differential pressure and the actual differential pressure to the maximum value. The data is output to the selection unit 50g.

  The maximum value selection unit 50g selects the larger of the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50c and the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50f. Then, the selected relatively large difference is output to the control signal calculation unit 50h. The control signal calculation unit 50h converts the control signal into a control signal having a relatively small value corresponding to the relatively large difference output from the maximum value selection unit 50g, and outputs the control signal to the addition unit 50i. The adding unit 50i performs a correction calculation to generate a new control signal by adding the converted current control signal to the previous control value, and outputs the calculated value to the control unit of the proportional solenoid valve 23 shown in FIG. .

  As described above, as the value of the control signal supplied to the control unit of the proportional solenoid valve 23 is small, the proportional solenoid valve 23 tends to be switched to the lower side in FIG. 11 and the control port of the center bypass valve 22 are connected. As a result, the pilot pressure of the pilot pump 11 is applied to the control port of the center bypass valve 22 via the proportional solenoid valve 23, and the center bypass valve 22 enters a predetermined switching state between the fully open position and the fully closed position. Operates as follows. As a result, the amount of hydraulic oil escaping from the center bypass line 60 to the tank 34 is reduced, and the boom raising / arm dumping combined operation by the normal operation with a high operating speed is performed. The desired earth and sand excavation work can be carried out.

  Further, unlike the above-described excavation work of earth and sand, for example, in a crane operation performed by hanging a load on the bucket 6 portion by a combined boom raising / arm dump operation, the boom operation device 12 and the arm operation device 13 are used. , When the operation speed is slow and the fine operation / heavy load in which the actuator load pressure is high is to be performed, as shown in FIG. Detected by the pressure sensor 25 and input to the boom raising function generator 40a1 included in the pump discharge amount controller 40 of the controller 31, and a small operation amount of the arm operating device 13 is detected by the arm dump pressure sensor 27. Then, it is input to the arm dumping function generator 40b2 included in the pump discharge amount controller 40.

  Therefore, the displacement volume of a small value is output from the boom raising function generator 40a1 and the arm dump function generator 40b2 to the maximum value selectors 40c and 40d, respectively, compared to the above-described earth and sand excavation work. The values are added by the adder 40e and output to the control function generator 40f. From the control function generator 40f, a large value control signal is output to the electromagnetic proportional pressure reducing valve 21 shown in FIG. 2 in accordance with the small displacement volume.

  Therefore, the electromagnetic proportional pressure reducing valve 21 tends to be switched to the lower side in FIG. 2 against the spring force, and the control port of the servo valve 20 and the tank 34 tend to communicate with each other. 2 tends to be switched to the right position side in FIG. Thereby, the pilot pressure from the pilot pump 11 is also supplied to the large diameter chamber of the control piston 20a, and the control piston 20a moves rightward in FIG. 2 due to the area difference between the large diameter chamber and the small diameter chamber. As a result, the displacement volume of the variable displacement hydraulic pump 10 is controlled to be small, and a small flow rate is discharged from the variable displacement hydraulic pump 10.

  During this time, the boom direction control valve 14 is slightly switched to the left position side in FIG. 2 according to the boom raising operation with a small operation amount of the boom operation device 12, and the arm dump with a small operation amount of the arm operation device 13. In response to the operation, the arm direction control valve 15 is slightly switched to the right position side in FIG. Therefore, a small flow rate of pressure oil discharged from the hydraulic pump 10 is supplied to the rod chamber of the arm cylinder 8 via the arm direction control valve 15 and to the bottom chamber of the boom cylinder 7 via the boom direction control valve 14. Supplied.

  At this time, high pressure is detected by each of the bottom pressure sensor 29 for detecting the bottom pressure of the boom cylinder 7 and the rod pressure sensor 30 for detecting the rod pressure of the arm cylinder 8 along with the crane work in which the load increases. It is output to the controller 31. Therefore, in the subtracting unit 50b included in the center bypass valve control unit 50 of the controller 31 shown in FIG. 4, the high pressure detected by the bottom pressure sensor 29 is subtracted from the pressure detected by the discharge pressure sensor 24, thereby reducing a small actual difference. The pressure is calculated, and the small actual differential pressure is output to the subtraction unit 50c. On the other hand, according to the small boom raising operation amount output from the boom raising pressure sensor 25, the first differential pressure generating unit 50a outputs a small target differential pressure to the subtracting unit 50c. The subtracting unit 50c subtracts the actual differential pressure output by the subtracting unit 50b from the target differential pressure output by the first differential pressure generating unit 50a, and the difference between the target differential pressure and the actual differential pressure that is a relatively large value. Is output to the maximum value selector 50g.

  Similarly, in the subtraction unit 50e of the center bypass valve control unit 50, the high pressure detected by the rod pressure sensor 30 is subtracted from the pressure detected by the discharge pressure sensor 24 to calculate a small actual differential pressure. The differential pressure is output to the decompression unit 50f. On the other hand, the second differential pressure generator 50d outputs a small target differential pressure to the subtractor 50f in accordance with the small arm dump operation amount output from the arm dump pressure sensor 27. The subtracting unit 50f subtracts the actual differential pressure output by the subtracting unit 50e from the target differential pressure output by the second differential pressure generating unit 50d, and the difference between the target differential pressure and the actual differential pressure that is a relatively large value. Is output to the maximum value selector 50g.

  The maximum value selection unit 50g selects the larger of the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50c and the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50f. Then, the selected relatively large difference is output to the control signal calculation unit 50h. The control signal calculation unit 50h converts the control signal into a control signal having a small value corresponding to the relatively large difference output from the maximum value selection unit 50g and outputs the control signal to the addition unit 50i. The adder 50i performs a correction operation for adding the converted current control signal to the previous control value to generate a new control signal, and outputs the calculated value to the control unit of the proportional solenoid valve 23 shown in FIG. .

  As described above, as the control value given to the control unit of the proportional solenoid valve 23 is small, the proportional solenoid valve 23 tends to be switched to the lower side in FIG. 11 and the control port of the center bypass valve 22 are connected. As a result, the pilot pressure of the pilot pump 11 is applied to the control port of the center bypass valve 22, and the center bypass valve 22 is in a predetermined switching state between the fully open position and the fully closed position, and the opening amount is further reduced. Along with this, the center bypass line 60 tends to be closed. As a result, it is possible to perform a desired crane operation by performing a boom raising / arm dumping combined operation in which the operation speed is low and the actuator load pressure becomes high.

  Furthermore, unlike the above-described crane work, the first embodiment reduces the boom operation device 12 and the arm operation device 13 during the earth and sand leveling work performed through, for example, a boom raising / arm dump combined operation. There are cases where the operation speed is slow and the fine operation / light load is attempted to lower the actuator load pressure. At this time, control in the pump discharge amount control unit 40 of the controller 31 is the same as that in the above-described crane operation, but the center bypass valve control unit 50 performs control different from that during crane operation.

  That is, a small flow rate is supplied to each of the rod chamber of the arm cylinder 8 and the bottom chamber of the boom cylinder 7, and the bottom pressure of the boom cylinder 7 is detected along with the earth and sand leveling operation at which the actuator load pressure becomes low. A low pressure is detected by each of the bottom pressure sensor 29 and the rod pressure sensor 30 that detects the rod pressure of the arm cylinder 8, and is output to the controller 31. Therefore, in the subtraction unit 50b included in the center bypass valve control unit 50 of the controller 31 shown in FIG. 4, the low pressure detected by the bottom pressure sensor 29 is subtracted from the pressure detected by the discharge pressure sensor 24, resulting in a large actual difference. The pressure is calculated, and the large actual differential pressure is output to the subtracting unit 50c. On the other hand, according to the small boom raising operation amount output from the boom raising pressure sensor 25, the first differential pressure generating unit 50a outputs a small target differential pressure to the subtracting unit 50c. The subtracting unit 50c subtracts the actual differential pressure output by the subtracting unit 50b from the target differential pressure output by the first differential pressure generating unit 50a to obtain a difference between the target differential pressure and the actual differential pressure that is a relatively small value. Output to the maximum value selector 50g.

  Similarly, in the subtraction unit 50e of the center bypass valve control unit 50, the low pressure detected by the rod pressure sensor 30 is subtracted from the pressure detected by the discharge pressure sensor 24 to calculate a large actual differential pressure. The differential pressure is output to the subtraction unit 50f. On the other hand, the second differential pressure generation unit 50d outputs a small target differential pressure to the subtraction unit 50f in accordance with a small boom raising operation amount output from the arm dump pressure sensor 27. The subtracting unit 50f subtracts the actual differential pressure output by the subtracting unit 50e from the target differential pressure output by the second differential pressure generating unit 50d to obtain a difference between the target differential pressure and the actual differential pressure that is a relatively small value. Output to the maximum value selector 50g.

  The maximum value selection unit 50g is the smaller but larger one of the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50c, and the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50f. The difference is selected, and the selected difference is output to the control signal calculator 50h. The control signal calculation unit 50h converts a small difference output from the maximum value selection unit 50g into a control signal and outputs the control signal to the addition unit 50i. The adding unit 50i performs a correction operation for adding the selected current control signal to the previous control value to generate a control signal in which the new value is slightly increased, and the calculated value is the proportional solenoid valve shown in FIG. It outputs to 23 control parts.

  As described above, as the value of the control signal given to the control unit of the proportional solenoid valve 23 is large, the proportional solenoid valve 23 tends to be switched to the upper stage side against the force of the spring. Thus, the pilot pump 11 and the control port of the center bypass valve 22 tend to be disconnected, while the control port of the center bypass valve 22 and the tank 34 tend to be connected. Thereby, the center bypass valve 22 is in a switching state between the fully open position and the fully closed position by the force of the spring, and slightly increases the opening amount. It tends to be more open than under load. As a result, the flow rate that flows to the tank 34 through the center bypass line 60 increases, and a fine operation with a slow operating speed is performed, and a boom raising / arm dumping combined operation in which the actuator load pressure is lowered is performed. Work can be carried out.

  FIG. 5 is a diagram illustrating control performed by the hydraulic drive device according to the first embodiment.

  In FIG. 5, the horizontal axis indicates the lever operation amount, for example, the lever operation amount of the boom operation device 12 and the lever operation amount of the arm operation device 13, and the vertical axis indicates the boom cylinder 7, the arm cylinder 8, and the like. It shows the load pressure of the actuator.

  As shown in FIG. 5, in the first embodiment, when the operation amount of the boom operation device 12 and the operation amount of the arm operation device are increased, the control of the normal operation area A in which the discharge amount of the hydraulic pump 10 is increased. For example, normal operations such as excavation of earth and sand can be performed as described above. In the above description, the case where the bottom pressure of the boom cylinder 7 and the rod pressure of the arm cylinder 8 are increased has been described. However, in the normal operation range A, it is originally limited by the difference in actuator load pressure such as light load and heavy load. Not receive.

  Further, when the operation amount of the boom operation device 12 and the operation amount of the arm operation device 13 are reduced, the discharge amount of the hydraulic pump 10 is reduced, the speed of the actuator is reduced, and fine operation can be performed. In this case, in the fine operation / heavy load operation region B where the load pressure of the actuator becomes high, for example, crane work can be performed as described above. Further, in the fine operation / light load operation region C in which the load pressure of the actuator becomes low, the soil leveling work or the like can be performed as described above.

  According to the first embodiment configured as described above, by increasing the operation amount of the boom operation device 12 and the arm operation device 13, the working elements such as the boom 4 and the arm 5 are driven at a high operating speed. It is possible to ensure good normal operability. Further, by reducing the amount of operation of the boom operation device 12 and the arm operation device 13, good fine operability capable of driving work elements such as the boom 4 and the arm 5 at a slow operating speed is ensured. be able to. Further, at this time, the output of the variable displacement hydraulic pump 10 can be suppressed, and the energy loss can be reduced. Furthermore, in the first embodiment, even during the fine operation, when the load pressure of the boom cylinder 7 and the arm cylinder 8 is high, the discharge pressure of the variable displacement hydraulic pump 10 is increased to increase the fine operation / heavy load. It is possible to ensure good operability during the work. Further, even during fine operation, when the load pressure of the boom cylinder 7 and the arm cylinder 8 is low, the discharge pressure of the variable displacement hydraulic pump 10 is lowered to perform the fine operation / light load operation. Good operability can be ensured. Further, at this time, the output of the variable displacement hydraulic pump 10 can be suppressed and energy loss can be reduced. Therefore, this embodiment can realize highly accurate operability and can realize a highly reliable hydraulic drive device that is economical and practical.

  In the above embodiment, only the configuration related to the combined operation of the boom raising and the arm dump is shown, but the same configuration as in the above embodiment related to the boom lowering operation and the arm cloud operation may be provided. . Moreover, you may provide the same structure in the said embodiment related to turning, operation of the bucket 6, and operation of the attachment attached instead of the bucket 6, if necessary.

  In the first embodiment, not only the combined operation of the boom 4 and the arm 5 but also the single operation of the boom 4 and the single operation of the arm 5 can be performed without any trouble in the above configuration.

  In the first embodiment, the control is performed in accordance with the operation amount of the boom operation device 12 and the operation amount of the arm operation device 13. For example, the bottom pressure sensor 29 provided in the boom cylinder 7 is used. On the basis of a signal output from the rod pressure sensor 30 provided on the arm cylinder 8 or a control speed of the lever of the boom operating device 12 in the controller 31 or on the lever of the arm operating device. The operation speed may be calculated, and control may be performed according to the calculated operation speed.

  FIG. 6 shows a case in the second embodiment in which control is performed at such an operation speed. In FIG. 6, A1 represents a normal operation area, B1 represents a fine operation / heavy load operation area, and C1 represents a fine operation / light load operation area. In general, when a fine operation is performed, the operation speed of the levers of the boom operation device 12 and the arm operation device 13 is lowered by an operator. Therefore, if the control is performed based on the operation speed in this way instead of the operation amount, it is possible to realize a highly accurate control according to the actual operation state. Instead of such control based on the operation speed, the controller 31 may perform calculation for obtaining the operation acceleration, and may perform control according to the calculated operation acceleration.

  FIG. 7 is a block diagram showing a main configuration of a pump discharge amount control unit included in a controller provided in the hydraulic drive apparatus according to the third embodiment of the present invention, and FIG. 8 shows the hydraulic drive apparatus according to the third embodiment of the present invention. It is a block diagram which shows the principal part structure of the center bypass valve control part contained in the controller with which it is provided.

  The third embodiment according to the present invention includes a signal output from the discharge pressure sensor 24 or a bottom pressure sensor 29 that detects the bottom pressure of the boom cylinder 7 and a rod pressure sensor 30 that detects the rod pressure of the arm cylinder 8. Based on the output signal, it is determined whether the work performed by the work device 3 is a heavy load work or a light load work. When it is determined that the work is a heavy load work, the pump discharge of the controller 31 shown in FIGS. The quantity control unit 40 and the center bypass valve control unit 70 do not function, and normal control is performed. As shown in FIG. 7, the pump discharge amount control unit 40 in the third embodiment is connected to an addition unit 40 e, and a signal output from the discharge pressure sensor 24 or a bottom pressure for detecting the bottom pressure of the boom cylinder 7. ON when the signal output from the sensor 29 and the rod pressure sensor 30 for detecting the rod pressure of the arm cylinder 8 is a signal corresponding to a light load, and OFF when the signal is corresponding to a heavy load. A switch unit 40g is provided. When the switch unit 40g is turned on, the addition value of the addition unit 40e is converted into a control signal, and the control function generation unit that controls the electromagnetic proportional pressure reducing valve 21 that adjusts the displacement volume of the variable displacement hydraulic pump 10 is controlled. 40f is output.

  In the third embodiment, the configuration of the center bypass valve control unit 70 of the controller 31 is different from that in the first embodiment. The center bypass valve control unit 70 according to the third embodiment includes a boom function generator 70 a that outputs an opening area of the center bypass valve 22 according to an operation amount of the boom operation device 12, and an operation of the arm operation device 13. And an arm function generator 70b for outputting the opening area of the center bypass valve 22 according to the amount.

  The boom function generation unit 70a includes a boom raising function generation unit 70a1 that outputs a large opening amount of the center bypass valve 22 as the boom raising operation amount decreases, that is, with a light load of fine operation. A boom lowering function generator 70a2 that outputs a large opening amount of the center bypass valve 22 as the operation amount decreases, that is, with a light load of fine operation is included. The relationship between the boom raising operation amount in the boom raising function generation unit 70a1 and the opening amount of the center bypass valve 22 and the relationship between the boom lowering operation amount in the boom lowering function generation unit 70a2 and the opening amount of the center bypass valve 22 are previously set. Is set. Since the boom tends to have a lower load pressure due to its own weight in the lowering direction, for example, the boom lowering function generator 70a2 is compared with the opening amount in the fine operation region set in the boom raising function generator 70a1. It is possible to set so that the opening amount in the same fine manipulation region set to be larger.

  Similarly, the arm function generation unit 70b outputs an opening amount of the center bypass valve 22 that increases as the arm cloud operation amount decreases, that is, with a light load of fine operation. The arm dump function generator 70b2 outputs a large opening amount of the center bypass valve 22 as the arm dump operation amount decreases, that is, with a light load of fine operation. The relationship between the arm cloud operation amount in the arm cloud function generation unit 70b1 and the opening amount of the center bypass valve 22, and the relationship between the arm dump operation amount in the arm dump function generation unit 70b2 and the opening amount of the center bypass valve 22 are previously set. Is set.

  Further, the center bypass valve control unit 70 includes the opening amount of the center bypass valve 22 output from the boom raising function generation unit 70a1 and the opening amount of the center bypass valve 22 output from the boom lowering function generation unit 70a2. Of the center bypass valve 22 output from the arm dump function generator 70b2 and the opening amount of the center bypass valve 22 output from the arm dump function generator 70b2. And a maximum value selection unit 70d for selecting the larger one of the quantities.

  The center bypass valve control unit 70 also adds an opening amount of the center bypass valve 22 output from the above-described maximum value selection unit 70c and an opening amount of the center bypass valve 22 output from the maximum value selection unit 70d. 70e.

  The center bypass valve control unit 70 is connected to the adding unit 70e, and a signal output from the discharge pressure sensor 24 or a bottom pressure sensor 29 for detecting a bottom pressure of the boom cylinder 7 and a rod pressure of the arm cylinder 8 is used. A switch portion 70f that is turned on when the signal output from the rod pressure sensor 30 to be detected is a signal corresponding to a light load and turned off when the signal is a signal corresponding to a heavy load is provided.

  Further, when the switch unit 70f is turned on, the center bypass valve control unit 70 converts an addition value related to the opening amount of the center bypass valve 22 of the addition unit 70e into a control signal, and A control function generator 70g for outputting to the proportional solenoid valve 23 to be controlled is provided. The control function generator 70g is preset with a relationship of control signal values that increase as the added value of the adder 70e increases. Other configurations in the third embodiment are the same as those in the first embodiment described above.

  In the third embodiment configured as described above, when a fine operation is performed by operating the boom operation device 12 and the arm operation device 13, the fine operation is performed by the boom function generation unit 40a and the arm function generation unit 40b. And the small value output from the boom function generator 40a and the small value output from the arm function generator 40b are added by the adder 40e via each selection process in the maximum value selectors 40c and 40d. Addition and output to the switch unit 40g. At this time, when the pressure value detected by the discharge pressure sensor 24 (or the bottom pressure sensor 29 or the rod pressure sensor 30) is high and it is detected that the load is heavy while being finely operated, the switch unit 40g is turned off. The output of the added value added by the adding unit 40e to the control function generating unit 40f is cut off. In this state, the processing operation corresponding to the heavy load work in the normal fine operation state is performed.

  Further, when the pressure value detected by the discharge pressure sensor 24 (or the bottom pressure sensor 29 or the rod pressure sensor 30) is low during the fine operation and the light load is detected by the fine operation, the switch The unit 40g is turned on, and the added value added by the adding unit 40e is output to the control function generating unit 40f. The control function generator 40f outputs a large control signal value corresponding to the relatively small value added by the adder 40e to the electromagnetic proportional pressure reducing valve 21. Accordingly, the proportional solenoid valve 21 tends to be switched to the lower position side in FIG. 2, and as a result, the displacement volume of the variable displacement hydraulic pump 10 is controlled to be small as described above. Is discharged.

  In the center bypass valve control unit 70 of the third embodiment, the pressure value detected by the discharge pressure sensor 24 (or the bottom pressure sensor 29 and the rod pressure sensor 30) is high during the fine operation, When it is detected that a heavy load is being applied, the switch unit 70f is turned off, and the output of the added value added by the adding unit 70e to the control function generating unit 70g is cut off. In this state, the processing operation corresponding to the heavy load work in the normal fine operation state is performed. At this time, the proportional solenoid valve 23 tends to be held on the lower position side in FIG. 2 so as to guide the pilot pressure of the pilot pump 11 to the control port of the center bypass valve 22. Accordingly, the center bypass valve 22 is controlled so that the opening amount is relatively small in a predetermined switching state between the fully open position and the fully closed position. As a result, pressure is generated in the center bypass line 60, and desired fine manipulation / heavy load work can be performed.

  Further, in the center bypass valve control unit 70, the pressure value detected by the discharge pressure sensor 24 (or the bottom pressure sensor 29 and the rod pressure sensor 30) is low during fine operation, and the light load is obtained by fine operation. Is detected, the switch unit 70f is turned on, and the added value added by the adding unit 70e is output to the control function generating unit 70g. The control function generator 70g outputs a large control signal value to the proportional solenoid valve 23 according to the large addition value. Therefore, the proportional solenoid valve 23 tends to be switched to the upper position side in FIG. Along with this, the center bypass valve 22 is in a predetermined switching state between the fully open position and the fully closed position, and the opening amount is controlled to be larger than that during the fine operation / heavy load described above. Thereby, the flow volume which flows into the tank 34 through the center bypass line 60 increases, and a desired fine operation and light load work can be implemented.

  According to the third embodiment configured as described above, the same effect as that of the first embodiment can be obtained, and the discharge pressure sensor 24 is provided as the pressure sensor for detecting the load pressure of the actuator, or the bottom pressure sensor 29 is provided. And the rod pressure sensor 30 may be provided, and the number of pressure sensors can be reduced as compared with the first embodiment, and the apparatus configuration can be simplified.

3 Working device 4 Boom (working element)
5 Arm (working element)
7 Boom cylinder (work element actuator)
8 Arm cylinder (actuator for work element)
DESCRIPTION OF SYMBOLS 10 Variable displacement hydraulic pump 11 Pilot pump 12 Boom operation device (work operation device)
13 Arm operation device (work operation device)
14 Boom direction control valve (work element direction control valve)
15 Arm direction control valve (work element direction control valve)
20 Servo valve 20a Control piston 21 Electromagnetic proportional pressure reducing valve (push-away volume control device)
22 Center Bypass Valve 23 Proportional Solenoid Valve (Center Bypass Valve Control Device)
24 Discharge Pressure Sensor 25 Boom Raising Pressure Sensor 27 Arm Dump Pressure Sensor 29 Bottom Pressure Sensor 30 Rod Pressure Sensor 31 Controller 34 Tank 40 Pump Discharge Control Unit 40a Boom Function Generation Unit 40b Arm Function Generation Unit 40c Maximum Value Selection Unit 40d maximum value selection unit 40e addition unit 40f control function generation unit 40g switch unit 50 center bypass valve control unit 50a first differential pressure generation unit 50b first calculation unit 50c second calculation unit 50d second differential pressure generation unit 50e first 3 calculation unit 50f 4th calculation unit 50g maximum value selection unit 50h control signal calculation unit 50i addition unit 60 center bypass line 70 center bypass valve control unit 70a boom function generation unit 70b arm function generation unit 70c maximum value selection unit 70d maximum Value selector 70e Adder 70f Pitch portion 70g control function generator A normal control B fine operation, the heavy load control C fine operation and light load control A1 normal control B1 fine operation, the heavy load control C1 fine operation and light load control

Claims (4)

Provided in a work machine equipped with a working device capable of normal operation and fine operation performed at a smaller operation amount and slower operation speed than the normal operation,
A variable displacement hydraulic pump, a working element actuator that is operated by pressure oil discharged from the variable displacement hydraulic pump and drives a working element included in the working device, and a center that connects the variable displacement hydraulic pump and the tank. An open center work element direction control valve for controlling the flow of pressure oil supplied from the variable displacement hydraulic pump to the work element actuator, and a switching operation for the work element direction control valve. In a hydraulic drive device for a work machine provided with a work element operating device
A displacement displacement control device for controlling the displacement volume of the variable displacement hydraulic pump and a center bypass line portion located downstream of the work element direction control valve are provided and returned to the tank via the center bypass line. A center bypass valve capable of controlling the flow rate, a center bypass valve control device for controlling the center bypass valve, the displacement volume control device, and a controller for controlling the center bypass valve control device,
The above controller
When the operation mode of the operating device for the work element is an operation mode regarded as the normal operation, a control signal for setting the displacement volume of the variable displacement hydraulic pump as a displacement volume corresponding to the normal operation is described above. When the operation mode of the operating element operating device is an operation mode regarded as the fine operation, the displacement volume of the variable displacement hydraulic pump corresponds to the normal operation. A pump discharge amount control unit for performing a control process for outputting a control signal to be smaller than the displacement volume to the displacement volume control device;
When the operation mode of the work element operation device is an operation mode regarded as the normal operation, a control signal for controlling the opening and closing of the center bypass valve, and the operation mode of the work element operation device are A control process for outputting a control signal for controlling the center bypass valve to a switching state between a fully open position and a fully closed position to the center bypass valve control device when the operation mode is regarded as a fine operation. And when the operation mode of the work element operation device is regarded as the fine operation and the load pressure of the work element actuator is high, the center bypass valve is set to the fully open position. A control signal for reducing the opening amount in a switching state between the fully closed position, and an operation mode in which the operation mode of the operating device for the work element is regarded as the fine operation. Thus, when the load pressure of the working element actuator is low, a control process is performed to output a control signal for opening the center bypass valve to the center bypass valve control device, which makes the center bypass valve larger than the opening amount. A hydraulic drive device for a work machine, comprising a center bypass valve control unit. The hydraulic drive device for a work machine according to claim 1,
Based on the operation amount, the operation speed, or the operation acceleration of the work element operation device, the controller calculates that the operation mode of the work element operation device is regarded as a fine operation. A hydraulic drive device for a work machine, characterized in that The hydraulic drive device for a work machine according to claim 2,
The work machine consists of a hydraulic excavator,
The working element includes a boom and an arm;
The working element actuator includes a boom cylinder for operating the boom and an arm cylinder for operating the arm,
The working element direction control valve includes a boom direction control valve for controlling the boom cylinder, and an arm direction control valve for controlling the arm cylinder,
The working element operating device includes a boom operating device for switching the boom directional control valve, and an arm operating device for switching the arm directional control valve. apparatus. The hydraulic drive device for a work machine according to claim 3,
A discharge pressure sensor for detecting the discharge pressure of the variable displacement hydraulic pump, or a bottom pressure sensor for detecting the bottom pressure of the boom cylinder and a rod pressure sensor for detecting the rod pressure of the arm cylinder,
The center bypass valve control unit of the controller is
The operation amount of at least one of the operation amount of the boom operation device and the operation amount of the arm operation device and the discharge pressure detected by the discharge pressure sensor, or the operation amount of the boom operation device and the operation amount According to the operation amount of at least one of the operation amounts of the arm operation device, the bottom pressure detected by the bottom pressure sensor, and the rod pressure detected by the rod pressure sensor, the operation mode of the work element operation device is A control process for outputting a control signal for setting the center bypass valve to a relatively large opening amount when the operation element is regarded as a fine operation and the load pressure of the working element actuator is low. A hydraulic drive device for a working machine.

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