JP2012137149A - Hydraulic drive unit of working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic drive unit of a working machine which can perform a boom-up operation irrespective of an output of a hydraulic pump without the need for performing complicated work by using a hydraulic circuit having a center bypass passage at a direction control valve as a fundamental factor.SOLUTION: The hydraulic drive unit of the working machine includes: a center bypass valve 10 which is arranged at the center bypass passage 12 located downstream of the boom direction control valve 7, and can open and close the center bypass passage 12; a proportional solenoid valve 17 which controls the switching of the center bypass valve 10; and a controller 19 which can output a control signal for controlling the proportional solenoid valve 17. The controller 19 is provided with a pump output calculation part which calculates the output of the hydraulic pump 6 when the boom-up operation is detected by a pressure sensor 20, and an opening amount calculation part which calculates an opening amount of the center bypass valve 10 corresponding to the output of the hydraulic pump 6 which is calculated by the pump output calculation part.

Description

  The present invention relates to a hydraulic drive device for a work machine such as a hydraulic excavator having a work device including a boom.

  Work machines such as hydraulic excavators are equipped with hydraulic actuators such as boom cylinders, arm cylinders, bucket cylinders, etc., and hydraulic pumps driven by the engine, and supply of hydraulic oil from the hydraulic pumps to the respective hydraulic actuators with direction control valves. To be controlled through. The direction control valve is driven via pilot pressure oil or the like whose spool is supplied according to the operation amount and operation direction of the operation lever, and controls the operating direction of the hydraulic actuator and the supply amount of pressure oil to the hydraulic actuator. .

  In this type of excavator, an open circuit having a center bypass passage in a directional control valve is generally used as a hydraulic circuit responsible for controlling the supply of pressure oil from a hydraulic pump to a hydraulic actuator. The center bypass passage opens the hydraulic pump to the hydraulic tank in the neutral state of the direction control valve (the neutral state of the operation lever). When the operation lever is operated from the neutral state and the spool of the directional control valve is displaced accordingly, the center bypass passage has an opening characteristic (a characteristic of the opening amount with respect to the operation amount of the operating lever) determined in advance by the profile of the spool. ) Changes the opening amount to the closed side.

  By the way, the working form in the hydraulic excavator is diverse from heavy load work to light load work. Also, attachments such as buckets are often exchanged as appropriate on site according to the work content and the like, and attachments heavier than standard ones are often mounted.

  In such a case, in the open circuit as described above, the operation characteristics of the hydraulic actuator overnight with respect to the operation of the operation lever are easily affected by the load of the hydraulic actuator and the weight of the attachment, and a favorable operability of the hydraulic actuator is obtained. There are many things that cannot be done. For example, when carrying out heavy load work or attaching a heavy attachment, the hydraulic actuator will not start unless the amount of operation from the neutral position of the swing lever is greater than normal, and the hydraulic actuator will not operate. The range of the operation amount of the operation lever capable of controlling the speed becomes narrow. In such a case, it is difficult to smoothly perform a desired operation.

  In order to solve such a problem, in the prior art disclosed in Patent Document 1, a hydraulic pump, a boom cylinder, and a boom from the hydraulic pump to control the supply of pressure oil from the hydraulic pump to the boom cylinder are disclosed. A directional control valve provided in a pipe line to the cylinder and having a center bypass passage, an operation lever for operating the directional control valve, and a flow rate of pressure oil flowing through the center bypass passage of the directional control valve; A center bypass valve provided in a flow path connected to the center bypass passage and capable of adjusting an opening amount; and a center bypass valve control means for controlling the opening amount of the center bypass valve. An operation volume for instructing the opening amount of the center bypass valve by a predetermined operation is provided. The center bypass valve control means is configured to operate the operation volume regardless of the operation amount of the operation lever when the operation lever is operated more than a predetermined operation amount as an operation amount before the center bypass passage of the direction control valve starts to close. The center bypass valve is controlled to the opening amount instructed by. In a situation where the load of the boom cylinder is determined to be relatively large, the boom is controlled by performing a predetermined operation on the operation volume so as to reduce the opening amount of the center bypass valve as the determined load increases. Even when the load on the cylinder is relatively large, the synthetic opening amount is controlled to be small when the supply of pressure oil to the boom cylinder is started, so the pressure oil on the upstream side (hydraulic pump side) of the direction control valve The pressure increases rapidly even with a relatively small operation amount of the operation lever. As a result, it is possible to quickly start (activate operation) the boom cylinder accompanying the operation of the operation lever regardless of the load of the boom cylinder.

Japanese Patent No. 3804465

  In the prior art disclosed in Patent Document 1 described above, it is necessary for the operator to set the opening in advance by considering the actuator load by operating the operation volume, so that the work becomes complicated and the setting is good. There is a problem that it may not be done. Furthermore, there is a problem that a device such as an operation volume for setting is required, which increases costs.

  In addition, since the opening amount of the center bypass valve cannot be controlled even if the output of the hydraulic pump changes, the output of the hydraulic pump that supplies pressure oil to the boom cylinder decreases due to some conditions, and the boom is difficult to rise. There is a problem that it is not possible to deal with it when it is closed.

  The present invention has been made in view of such a background, and is based on a hydraulic circuit having a center bypass passage in a directional control valve, and does not require complicated work, and raises the boom regardless of the output of the hydraulic pump. It is an object of the present invention to provide a hydraulic drive device for a work machine that can be operated.

  In order to achieve the above object, a hydraulic drive device for a work machine according to the present invention is provided in a work machine having a work device including a boom, and supplies a boom cylinder for driving the boom and pressure oil to the boom cylinder. A boom direction control valve that includes a hydraulic pump, an engine that drives the hydraulic pump, and a center bypass type direction control valve that controls a flow of pressure oil supplied from the hydraulic pump to the boom cylinder, and the boom A center bypass valve which is provided in a center bypass passage located downstream of the directional control valve and which can open and close the center bypass passage, an electromagnetic valve which controls the switching of the center bypass valve, and a control signal which controls the electromagnetic valve. In a hydraulic drive device for a work machine having a controller capable of output, the solenoid valve is a proportional solenoid valve, and the boom The controller includes a detection unit that detects a lifting operation, and the controller includes a pump output calculation unit that calculates an output of the hydraulic pump when the boom raising operation is detected by the detection unit, and a pump output calculation unit. An opening amount calculation unit for calculating the opening amount of the center bypass valve according to the calculated output of the hydraulic pump, and the control signal corresponding to the opening amount calculated by the opening amount calculation unit is transmitted to the proportional electromagnetic Processing to output to the valve is performed.

  In the present invention, before the center bypass passage of the direction control valve begins to close by the operation of the operation lever, the opening amount of the center bypass valve is calculated by the pump output calculation unit of the controller and the boom raising operation pilot. Since the opening amount calculated by the opening amount calculation unit of the controller is controlled according to the pressure, the opening of the center bypass passage when the center bypass passage starts to close by the center bypass valve and the supply of pressure oil to the boom cylinder starts. The combined opening amount obtained by combining the amount and the opening amount of the center bypass valve becomes smaller as the indication value of the opening amount of the center bypass valve by the pump output calculation unit and the opening amount calculation unit of the controller is smaller.

  Therefore, in the present invention, even when the boom raising operation is performed when the output of the hydraulic pump is relatively small, the combined opening amount when the pressure oil supply to the boom cylinder is started is automatically set as the pump output. It is controlled to a small area suitable for the magnitude of the boom raising pilot pressure. As a result, the activation (operation start) of the boom cylinder accompanying the operation of the operation lever is quickly performed regardless of the load of the boom cylinder.

  In this way, it is possible to perform the pumping operation regardless of the output of the hydraulic pump without requiring complicated work.

  In the invention described above, the present invention includes a discharge pressure sensor that detects a discharge pressure of the hydraulic pump and a discharge amount sensor that detects a discharge amount of the hydraulic pump, and the pump output calculation unit of the controller includes: A process of calculating the output of the hydraulic pump based on the discharge pressure detected by the discharge pressure sensor and the discharge amount detected by the discharge amount sensor is performed.

  Further, the present invention is the above-described invention, further comprising a boom operation device for operating the boom direction control valve, wherein the detection means is a pilot generated when the boom operation device is operated to a boom raising operation side. It is characterized by comprising a pressure sensor that detects pressure.

  Further, the present invention is the above-described invention, wherein an attachment actuator that drives the attachment, another hydraulic pump that is driven by the engine and supplies pressure oil to the attachment actuator, and the attachment from the another hydraulic pump. And an attachment direction control valve for controlling the flow of pressure oil supplied to the actuator.

  In the present invention, the solenoid valve is a proportional solenoid valve, and includes a detecting unit that detects a boom raising operation, and the controller calculates a hydraulic pump output when the boom raising operation is detected by the detecting unit. An output calculation unit, and an opening amount calculation unit that calculates the opening amount of the center bypass valve according to the output of the hydraulic pump calculated by the pump output calculation unit, the opening amount calculated by the opening amount calculation unit Since the process of outputting the corresponding control signal to the proportional solenoid valve is performed, the boom raising operation can be performed without requiring a complicated operation and regardless of the output of the hydraulic pump. Therefore, the apparatus configuration can be simplified as compared with the conventional case, and the manufacturing cost can be reduced. Moreover, even when the output of the hydraulic pump is small, the boom raising operation can be performed reliably. In this case, the operation amount of the operation lever for operating the boom direction control valve can be made equal regardless of whether the output of the hydraulic pump is large or small. Therefore, excellent boom raising operability can be ensured.

1 is a side view showing a hydraulic excavator having an attachment cited as an example of a work machine provided with an embodiment of a hydraulic drive device according to the present invention. It is a hydraulic circuit diagram which shows the hydraulic drive device which concerns on this embodiment. It is a block diagram which shows the structure of the controller part with which the hydraulic drive apparatus shown in FIG. 2 is equipped. It is a figure which shows the characteristic of the 1st function generator contained in the opening amount calculating part with which the controller shown in FIG. 3 is provided, and a 2nd function generator.

  A hydraulic drive device for a hydraulic working machine according to the present invention will be described with reference to FIGS. FIG. 1 is a side view showing a hydraulic excavator having an attachment as an example of a working machine provided with an embodiment of the hydraulic drive apparatus according to the present invention, and FIG. 2 is a hydraulic circuit diagram showing the hydraulic drive apparatus according to the present embodiment. 3 is a plotter diagram showing a configuration of a controller portion provided in the hydraulic drive apparatus shown in FIG. 2, and FIG. 4 is a first function generator and a second function included in the opening amount calculation unit provided in the controller shown in FIG. It is a figure which shows the characteristic of a generator.

  With reference to FIG. 1, first, an overall schematic configuration of a hydraulic excavator provided with the hydraulic drive device of the present embodiment will be described. In the figure, 1 is a traveling body, 2 is a revolving body, 3 is a boom, and the like is a working device that is attached to the revolving body 2 so as to be able to rotate in the vertical direction. The boom cylinder 5 to be driven is an attachment constituting the work device 3.

  Next, a schematic configuration of the hydraulic drive device for the work machine according to the present embodiment will be described with reference to FIG.

  In the figure, 6 is a variable displacement hydraulic pump, and 7 is a center bypass type directional control valve for controlling the supply of pressure oil to the boom cylinder 4, that is, a boom directional control valve.

  In this embodiment, a directional control valve 7 is connected to the discharge port of the hydraulic pump 6 via a pipe line 8, and pressure oil can be supplied from the hydraulic pump 6 to the boom cylinder 4 via the directional control valve 7. It is said.

  Since the basic mechanical structure of the hydraulic excavator is well known, detailed description and illustration are omitted here, but the traveling body 1 shown in FIG. An actuator for driving the turning device, an actuator for driving the arm on the arm constituting the work device 3, and an actuator for positioning the attachment 5 on the attachment 5 constituting the work device 3 are mounted. A directional control valve 9 for controlling the supply of pressure oil for driving the actuator is connected to the hydraulic pump 6 via a pipe 8.

  Reference numeral 10 denotes a center bypass valve whose opening amount can be changed from a fully open state to a fully closed state. The center bypass valve 10 is interposed in a center bypass conduit 12 from the boom direction control valve 7 to the oil tank 11. In this embodiment, the center bypass valve 10 is composed of a variable opening valve as will be described later.

  The boom cylinder 4 has a bottom side oil chamber 4 a connected to the boom direction control valve 7 via a conduit 13, and a rod side oil chamber 4 b connected to the boom direction control valve 7 via a conduit 14. Has been.

  The boom direction control valve 7 has its pilot ports 7x and 7y connected to a boom operation device 15 having a swingable operation lever 15a for boom operation. The boom operation device 15 applies a pilot pressure proportional to the operation amount of the operation lever 15a to the pilot port 7x when the operation lever 15a is swung from the neutral position to the right in FIG. 2, for example. In addition, when the operation lever 15a is swung from the neutral position, for example, to the left in FIG. 2, a pilot pressure proportional to the operation amount of the operation lever 15a is applied to the pilot port 7y. Here, the operation of the operation lever 15a in the right direction in FIG. 2 is an operation for performing a boom raising operation (extension operation of the boom cylinder 4), and the operation in the left direction in FIG. This is an operation for performing a shortening operation of the boom cylinder 4).

  The boom direction control valve 7 is a valve in which an operating state is switched by moving a spool (not shown) to the pilot port 7x or 7y according to the pilot pressure applied from the boom operating device 15, and from the hydraulic pump 6 side. A center bypass passage 7a is provided for returning excess oil of the supplied pressure oil to the oil tank 11 via the pipe line 12 on the center bypass valve 10 side.

  And the direction control valve 7 for booms has the A position, B position, and C position of illustration as the basic operation position.

  The B position is a neutral position of the boom direction control valve 7 in a state where the operation lever 15a is in the neutral position (a state where the pilot pressure is not applied to any of the pilot ports 7x and 7y). The main pipe 8 on the hydraulic pump 6 side is opened to the center bypass passage 12 on the center bypass valve 10 side via the center bypass passage 7a, and is connected to the bottom side oil chamber 4a and the rod side oil chamber 4b of the boom cylinder 4 respectively. The continuous pipelines 13 and 14 are closed. Accordingly, in this neutral position B, the boom cylinder 4 is disabled.

  Further, the A position is the operating position of the boom direction control valve 7 corresponding to the state in which the operation lever 15a is fully operated in the right direction (boom raising side) in FIG. 2, and at the A position, the center bypass passage 7a is operated. Is closed, the branch line 8 a branched from the main line 8 is opened to the line 13, and the line 14 is opened to the oil tank 11 via the line 16. Therefore, at the position A, the discharge hydraulic oil of the hydraulic pump 6 is supplied to the bottom side oil chamber 4a of the boom cylinder 4, and the boom cylinder 4 can be operated to the extension side (the boom raising side). Become.

  The C position is an operating position of the boom direction control valve 7 corresponding to a state in which the operation lever 15a is fully operated in the left direction (boom lowering side) in FIG. 2, and at the C position, the center bypass passage 7a is operated. , The branch pipe 8 a is opened to the pipe 14, and the pipe 13 is opened to the oil tank 11 via the pipe 16. Therefore, at this position C, the discharge pressure oil of the hydraulic pump 6 is supplied to the rod side oil chamber 4b of the boom cylinder 4, and the boom cylinder 4 can be operated to the shortening side (the boom lowering side). .

  The center bypass passage 7a has a pilot pressure between the neutral position B and the A position, the opening amount of which is applied from the boom operating device 15 to the pilot port 7x according to the spool profile of the boom direction control valve 7. It changes according to. In general, the opening amount decreases as the pilot pressure increases.

  The center bypass valve 10 as a variable opening valve in the present embodiment has a pilot port 10 x connected to an electromagnetic valve, that is, a proportional electromagnetic valve 17. The proportional solenoid valve 17 generates a pilot pressure proportional to the energization current to the solenoid 17 x from the discharge pressure oil of the pilot pump 18 and applies it to the pilot port 10 x of the center bypass valve 10. The opening amount of the center bypass valve 10 changes according to the pilot pressure applied to the pilot port 10x, and the opening amount increases as the pilot pressure increases (the energization current of the proportional solenoid valve 17 increases). Get smaller.

  In the present embodiment, in addition to the above-described hydraulic circuit configuration, a controller 19 (electronic circuit unit) for controlling energization of the proportional solenoid valve 17 and, consequently, the opening amount of the center bypass valve 10, and a boom direction control valve 7 for detecting the boom raising pilot pressure applied from the boom operating device 15 to the pilot port 7x as a parameter indicating the operation amount of the operation lever 15a, for example, the pressure sensor 20 and the discharge pressure of the hydraulic pump 6 are detected. And a discharge amount sensor 22 for detecting the discharge amount of the hydraulic pump 6. The pressure sensor 20, the discharge pressure sensor 21, the discharge amount sensor 22, and the solenoid 17 x are electrically connected to the controller 19. Connected.

  Further, an attachment direction control valve 24 of the attachment 5 having the same structure as the boom direction control valve 7 is connected to a discharge port of another hydraulic pump 23 different from the hydraulic pump 6 via a pipe line 25. The hydraulic pump 23 can supply pressure oil to the actuator 5 a that drives the attachment 5 via the attachment direction control valve 24.

  The hydraulic pump 6, the pilot pump 18, and the hydraulic pump 23 are driven by the engine 26.

  Next, the configuration of the controller 19 will be described with reference to FIG. 27 calculates the pump output of the hydraulic pump 6 based on the discharge pressure detected by the discharge pressure sensor 21 and the discharge amount detected by the discharge amount sensor 22 when the boom raising operation is detected by the pressure sensor 20. A pump output calculation unit 28 is an opening amount calculation unit that calculates the opening amount of the center bypass valve 10 according to the pump output calculated by the pump output calculation unit 27. The opening amount calculation unit 28 includes a first function generator 29, a second function generator 30, and a maximum value selection unit 31 that selects the maximum value of the output values of the function generators 29 and 30. .

  In the first function generator 29, the opening amount of the center bypass valve 10 is determined according to the pump output calculated by the pump output calculation unit 27, and in the second function generator 30, the boom raising detected by the pressure sensor 20 is determined. The opening amount of the center bypass valve 10 corresponding to the pilot pressure is determined. The opening amount determined by the first function generator 29 and the second function generator 30 is selected to have a large opening amount by the maximum value selection unit 31, and the opening amount of the center bypass valve 10 is determined as the selected opening amount. The current value of the proportional solenoid valve 17 necessary for the calculation is calculated by the current calculation unit 32, and the calculated current value is output to the solenoid 17x of the proportional solenoid valve 17 so that the proportional solenoid valve 17 is controlled. become.

  As shown in FIG. 4, in the first function generator 29, the lower the pump output is, the smaller the opening area of the center bypass valve 10 is. In the second function generator 30, the higher the boom raising pilot pressure is, the higher the center bypass valve 10 is. The opening area is reduced.

Next, the operation of this embodiment will be described.
First, when performing the boom raising single operation, the discharge pressure and discharge amount of the hydraulic pump 6 that supplies pressure oil to the boom cylinder 4 are large, and the output of the hydraulic pump 6 calculated by the pump output calculation unit 27 of the controller 19 is The value in the first function generator 29 of the opening amount calculation unit 28 is large, this value is selected by the maximum value selection unit 31, a small current is calculated by the current calculation unit 32, and this small current is calculated by the proportional solenoid valve 17. Is output to the solenoid 17x. Therefore, the pilot pressure applied to the pilot port 10a of the center bypass valve 10 is small, and the center bypass valve 10 is open. However, since sufficient output is supplied from the engine 26 that drives the hydraulic pump 6, the boom can be raised without any problem.

  Next, when performing a combined operation of raising the boom and the attachment 5, pressure oil is supplied from the hydraulic pump 23 to the attachment actuator 5 a via the attachment direction control valve 24 by switching the attachment direction control valve 24. Drive. At this time, the output necessary for driving the actuator 5 is subtracted from the output supplied to the hydraulic pump 6 from the engine 26. At this time, the discharge pressure and the discharge amount of the hydraulic pump 6 become small, and the pump of the controller 19 The value in the first function generator 29 of the output calculation unit 28 becomes small, and the value output from the pressure sensor 20, that is, the operation amount of the operation lever 15a of the boom operation device 15 is large, and the second function is generated accordingly. The value in the vessel 30 is also reduced.

  Thus, the value selected by the maximum value selection unit 31 is small, and the current calculated by the current calculation unit 32 according to this value is a large current. This large current is output to the solenoid 17x of the proportional solenoid valve 17. Accordingly, the pilot pressure applied to the pilot port 10a of the center bypass valve 10 is large, and the center bypass valve 10 is closed. Thereby, it can be made easy to raise the boom.

  Further, when the boom raising single operation is performed with the engine speed being low, such as economy mode, the output supplied from the engine 26 to the hydraulic pump 6 is reduced, but the center bypass valve 10 is similarly closed by the controller 19. Therefore, it is easy to raise the boom.

  In this embodiment, the opening amount of the center bypass valve 10 is calculated by the pump output calculation unit 27 of the controller 19 before the center bypass passage 7a of the boom direction control valve 7 starts to close by the operation of the boom raising operation lever 15a. Since the opening amount calculated by the opening amount calculation units 29 and 30 of the controller 19 is controlled according to the output of the hydraulic pump 6 and the boom raising operation pilot pressure, the center bypass valve 12 starts to close by the center bypass valve 10. The combined opening amount of the opening amount of the center bypass passage 7a and the opening amount of the center bypass valve 10 when the supply of pressure oil to the boom cylinder 4 is started is determined by the pump output calculation unit 27 of the controller 19 and the opening amount. The smaller the instruction value of the opening amount of the center bypass valve 10 by the arithmetic units 29 and 30 is, the smaller it is.

  Therefore, in this embodiment, even when the boom raising operation is performed when the output of the hydraulic pump 6 is relatively small, the combined opening amount when the pressure oil supply to the boom cylinder 4 is started is automatically pumped. A small opening amount suitable for the output and the boom raising pilot pressure is controlled. As a result, the activation (start of operation) of the boom cylinder 4 accompanying the operation of the operation lever 15a is quickly performed regardless of the load of the boom cylinder 4.

  In this manner, the boom raising operation can be performed regardless of the output of the hydraulic pump 6 without requiring complicated work. Therefore, the apparatus configuration can be simplified and the manufacturing cost can be reduced. Further, even when the output of the hydraulic pump 6 is small, the boom raising operation can be performed reliably. In this case, the operation amount of the operation lever 15a for operating the boom direction control valve 7 can be made equal regardless of whether the output of the hydraulic pump 6 is large or small. Therefore, excellent boom raising operability can be ensured.

DESCRIPTION OF SYMBOLS 3 Working device 4 Boom cylinder 5 Attachment 5a Attachment actuator 6 Hydraulic pump 7 Boom direction control valve 10 Center bypass valve 12 Center bypass passage 15 Boom operating device 17 Proportional solenoid valve 19 Controller 20 Pressure sensor 21 Discharge pressure sensor 22 Discharge amount Sensor 27 Pump output calculation unit 28 Opening amount calculation unit 23 Hydraulic pump 24 Direction control valve for attachment 26 Engine

Claims (4)

Provided in a work machine having a work device including a boom;
A boom cylinder that drives the boom, a hydraulic pump that supplies pressure oil to the boom cylinder, an engine that drives the hydraulic pump, and a center bypass type directional control valve, which is supplied from the hydraulic pump to the boom cylinder Direction control valve for the boom for controlling the flow of the pressurized oil, a center bypass valve provided in a center bypass passage located downstream of the direction control valve for the boom and capable of opening and closing the center bypass passage, and the center bypass valve In a hydraulic drive device for a work machine including a solenoid valve that controls switching of a valve and a controller that can output a control signal for controlling the solenoid valve,
The solenoid valve comprises a proportional solenoid valve;
Detecting means for detecting the boom raising operation;
The controller includes a pump output calculation unit that calculates an output of the hydraulic pump when the boom raising operation is detected by the detection unit, and a response to the output of the hydraulic pump calculated by the pump output calculation unit. And an opening amount calculation unit that calculates the opening amount of the center bypass valve, and performs processing for outputting the control signal corresponding to the opening amount calculated by the opening amount calculation unit to the proportional solenoid valve. Hydraulic drive device for work machines. In the invention of claim 1,
A discharge pressure sensor that detects a discharge pressure of the hydraulic pump; and a discharge amount sensor that detects a discharge amount of the hydraulic pump,
The pump output calculation unit of the controller performs a process of calculating an output of the hydraulic pump based on a discharge pressure detected by the discharge pressure sensor and a discharge amount detected by the discharge amount sensor. Hydraulic drive device for work machines. In the invention of claim 2,
A boom operation device for operating the boom direction control valve;
The hydraulic drive device for a working machine, wherein the detecting means includes a pressure sensor that detects a pilot pressure generated when the boom operating device is operated to a boom raising operation side. In the invention of claim 3,
The work machine has an attachment,
An attachment actuator that drives the attachment, another hydraulic pump that is driven by the engine and supplies pressure oil to the attachment actuator, and a flow of pressure oil supplied from the other hydraulic pump to the attachment actuator A hydraulic drive device for a work machine, comprising an attachment direction control valve for controlling the movement.

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