JP2015031377A - Hydraulic driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic driving device capable of suppressing vibration of piston occurring at the time of stop of a hydraulic cylinder, and capable of improving stop performance.SOLUTION: A hydraulic driving device includes a controller 16 that, in the case where an operation command for stopping a piston 7d of a boom cylinder 7a from being telescopically driven is input by an operation lever device 11, controls a pressure control device 40 to stop circulation of working fluid with respect to at least one of a bottom chamber 7e and a rod chamber 7f of the boom cylinder 7a, then controls pressure of at least the other of the bottom chamber 7e and the rod chamber 7f, and then makes load difference acting from both of the bottom chamber 7e and the rod chamber 7f to the piston 7d small.

Description

  The present invention relates to a hydraulic drive device used in, for example, a hydraulic excavator, and more particularly to a hydraulic drive device including a closed circuit hydraulic drive unit that drives a hydraulic cylinder with a hydraulic pump.

  In recent years, in construction machines such as hydraulic excavators, from the viewpoint of reducing the fuel consumption rate, the restriction of the hydraulic circuit for driving the hydraulic cylinder used in the working machine of the construction machine has been reduced. Development of a closed-circuit hydraulic drive device that connects the two in a closed circuit shape is underway. Further, as a hydraulic cylinder for driving a working device of a construction machine, a single rod type hydraulic cylinder is generally used.

  Patent Document 1 discloses a conventional technique related to this type of closed circuit hydraulic drive device. In Patent Document 1, when the hydraulic cylinder is suddenly stopped from a state where the hydraulic cylinder is driven to extend and contract, the hydraulic oil discharge flow rate of the hydraulic pump is set to zero in response to an operation command to stop the hydraulic cylinder from the operating device. That is, it is stopped. After that, the flow of hydraulic oil in the pipeline is shut off by an on / off valve provided in the closed circuit pipeline, and the flow of hydraulic fluid to the hydraulic cylinder is zero, that is, the hydraulic cylinder is expanded and contracted. Is stopped.

JP 2003-21104 A

  However, in the prior art disclosed in Patent Document 1 described above, when the amount of hydraulic oil flowing into and out of the hydraulic cylinder is suddenly reduced to zero, that is, when the hydraulic cylinder is stopped, the hydraulic cylinder mechanism causes inertia of the hydraulic cylinder. Since the piston cannot be stopped suddenly, the hydraulic oil in the oil chamber on the outflow side of the hydraulic cylinder is compressed and the pressure increases. At the same time, the hydraulic oil in the oil chamber on the inflow side of the hydraulic cylinder is pulled and the pressure drops. As a result, since the force in the direction opposite to the driving direction before stopping acts on the piston of the hydraulic cylinder, the piston vibrates greatly, and the piston cannot be stopped smoothly.

  The present invention has been made from the state of the prior art described above, and an object of the present invention is to provide a hydraulic drive device that can suppress the vibration of the piston that may occur when the hydraulic cylinder is stopped and can improve the stop performance. is there.

  In order to achieve this object, the present invention includes first and second inlets and outlets for sucking or discharging hydraulic oil, and a flow rate adjusting unit for controlling the flow rate and direction of the hydraulic oil with respect to the first and second inlets and outlets. A variable flow hydraulic pump having a piston capable of extending and contracting, a first hydraulic fluid chamber that extends by applying a hydraulic load to the piston, and a second hydraulic fluid chamber that contracts by applying a hydraulic load to the piston. A hydraulic cylinder having a first fluid passage connecting the first hydraulic oil chamber of the hydraulic cylinder to a first inlet / outlet of the variable flow hydraulic pump, and a second hydraulic oil chamber of the hydraulic cylinder having a second hydraulic oil chamber of the variable flow hydraulic pump. A closed circuit hydraulic drive unit having a second flow path connected to the inlet / outlet, an operation unit for instructing an expansion / contraction operation of the hydraulic cylinder, and outputting an instructed operation command; And a pressure control unit that controls the pressure of the second hydraulic oil chamber, and the pressure control unit is controlled when an operation command for stopping the piston of the hydraulic cylinder from a state in which the piston is extended and contracted is input from the operation unit. Then, after stopping the flow of the hydraulic oil to at least one of the first and second hydraulic oil chambers of the hydraulic cylinder, the pressure of at least one of the first and second hydraulic oil chambers is controlled. And a controller for reducing a load difference acting on the piston from the first and second hydraulic oil chambers.

  According to the present invention configured as described above, when an operation command for stopping the piston of the hydraulic cylinder from the state in which the piston of the hydraulic cylinder is driven to extend is input from the operation unit that instructs the expansion / contraction operation of the hydraulic cylinder to the controller, The controller controls a pressure control unit that controls the pressures of the first and second hydraulic oil chambers, and stops the flow of the hydraulic oil to at least one of the first and second hydraulic oil chambers of the hydraulic cylinder. Thereafter, the controller controls the pressure of at least one of the first and second hydraulic oil chambers to reduce the load difference acting on the piston of the hydraulic cylinder from the first and second hydraulic oil chambers. As a result, since the load difference between the first and second hydraulic fluid chambers of the hydraulic cylinder can be reduced, the vibration of the piston that can occur at the time of stopping from the state in which the piston of the hydraulic cylinder is driven to extend and contract can be suppressed. The stopping performance can be improved.

  In the invention described above, the pressure control unit may include a supply unit that supplies hydraulic oil to the first and second hydraulic oil chambers of the hydraulic cylinder, and first and second hydraulic oil chambers of the hydraulic cylinder. The controller includes a discharge unit that discharges hydraulic oil, and the controller is configured to output a first and a second of the hydraulic cylinder when an operation command to stop the piston of the hydraulic cylinder from being in a state of being driven to extend and contract is input from the operation unit. After stopping the flow of the hydraulic oil to any one of the two hydraulic oil chambers, the supply amount or discharge amount of the hydraulic oil to any one of the first and second hydraulic oil chambers is sent to the supply unit or the discharge unit. The load difference acting on the piston from the first and second hydraulic oil chambers is reduced.

  According to the present invention configured as described above, when an operation command for stopping the piston of the hydraulic cylinder from a state in which the piston is extended and contracted is input from the operation unit, one of the first and second hydraulic oil chambers of the hydraulic cylinder is provided. Stop the flow of hydraulic oil to Thereafter, the supply amount or the discharge amount of the hydraulic oil to one of the first and second hydraulic oil chambers is controlled by the supply unit or the discharge unit, so that the pistons can be moved from the first and second hydraulic oil chambers to the piston. The load difference acting on the can be reduced with a reliable and simple configuration.

  Further, the present invention is the above invention, wherein the pressure control unit includes a supply unit that supplies hydraulic oil to the first hydraulic oil chamber of the hydraulic cylinder, a discharge unit that discharges hydraulic oil from the first hydraulic oil chamber, and the A shut-off unit that stops the flow of hydraulic oil in the second hydraulic oil chamber of the hydraulic cylinder is provided, and the controller receives an operation command to stop the piston of the hydraulic cylinder from being driven to extend and contract from the operation unit. In this case, after the flow of the hydraulic cylinder to the second hydraulic oil chamber is stopped by the shut-off portion, the supply amount or the discharge amount of the hydraulic cylinder to the first hydraulic oil chamber is transferred to the supply portion or the discharge portion. The load difference acting on the piston from the first and second hydraulic oil chambers is reduced.

  The present invention configured as described above shuts off the flow of the hydraulic cylinder to the second hydraulic oil chamber when an operation command for stopping the piston of the hydraulic cylinder from the state in which the piston is extended and contracted is input from the operation unit to the controller. Stop at the part. Thereafter, the supply amount or discharge amount of the hydraulic cylinder to the first hydraulic oil chamber is controlled by the supply portion or the discharge portion, so that the load difference acting on the piston from the first and second hydraulic oil chambers can be further increased. It can be easily and reliably reduced, and vibration that can occur when the hydraulic cylinder is stopped can be more reliably suppressed.

  According to the present invention, there is provided a load equalizing portion for equalizing loads acting on the piston from the first and second hydraulic oil chambers of the hydraulic cylinder in the above invention, and the controller drives the piston of the hydraulic cylinder to extend and contract. When an operation command for stopping from the state of being operated is input from the operation unit, the pressure control unit is controlled to stop the flow of the hydraulic oil to the first and second hydraulic oil chambers of the hydraulic cylinder. Then, the load equalizing portion is controlled to reduce a load difference acting on the piston from the first and second hydraulic oil chambers.

  In the present invention configured as described above, when an operation command for stopping the piston of the hydraulic cylinder from being extended and contracted is input from the operation unit to the controller, the controller controls the pressure control unit to The flow of the hydraulic oil to the first and second hydraulic oil chambers of the cylinder is stopped. Thereafter, the load equalizing portion for equalizing the load acting on the piston from the first and second hydraulic oil chambers of the hydraulic cylinder is controlled to reduce the load difference acting on the piston from the first and second hydraulic oil chambers. . Thus, the load difference acting on the piston from the first and second hydraulic oil chambers can be reliably reduced with a simpler configuration than when the supply amount or discharge amount of the hydraulic cylinder to the first hydraulic oil chamber is controlled. Therefore, vibration that can occur when the hydraulic cylinder is stopped can be reliably suppressed with a simpler configuration.

  The present invention provides a pressure control for controlling the pressures of the first and second hydraulic fluid chambers of a hydraulic cylinder when an operation command for stopping the piston of the hydraulic cylinder from being driven to extend and contract is input from the operation unit to the controller. The controller is controlled by a controller to stop the flow of hydraulic oil to at least one of the first and second hydraulic oil chambers of the hydraulic cylinder. Thereafter, the controller controls the pressure of at least one of the first and second hydraulic fluid chambers to reduce the load difference acting on the piston of the hydraulic cylinder from the first and second hydraulic fluid chambers. It is. With this configuration, the present invention can reduce the load difference between the first and second hydraulic fluid chambers of the hydraulic cylinder, and therefore can suppress vibration that may occur when stopping from a state in which the piston of the hydraulic cylinder is driven to extend and contract, The stopping performance of the hydraulic cylinder can be improved. Problems, configurations, and effects other than those described above will be made clear from the following description of embodiments.

1 is a hydraulic circuit diagram illustrating a hydraulic drive device according to a first embodiment of the present invention. It is a schematic block diagram which shows the hydraulic excavator by which the said hydraulic drive device is mounted. FIG. 6 is a time chart showing control signals at the time of a single boom raising operation of the hydraulic drive device, where (a) is an input signal of the operating lever device 11, (b) is a discharge flow rate of the first hydraulic pump 14, and (c) is a second signal. The discharge flow rate of the hydraulic pump 15, (d) is the operation of the on / off valve 20, (e) is the operation of the on / off valve 19, (f) is the operation of the on / off valve 36, and (g) is the operation of the control valve 31. It is a hydraulic circuit diagram which shows the flow of the hydraulic fluid at the time of the independent boom raising operation | movement of the said hydraulic drive device. FIG. 6 is a time chart showing control signals at the time of a single boom raising operation of the hydraulic drive device, where (a) is an input signal of the operating lever device 11, (b) is a stop of the first hydraulic pump 14, an on / off valve 19 is shut off; 2 shows the pressure change when the hydraulic pump 15 is controlled in the order of stop, and (c) shows the pressure change when the stop of the first and second hydraulic pumps 14 and 15 and the shut-off of the on / off valve 19 are controlled simultaneously. FIG. 6 is a time chart showing a control signal during a single boom lowering operation of the hydraulic drive device, where (a) is an input signal of the operating lever device 11, (b) is a discharge flow rate of the first hydraulic pump 14, and (c) is a second signal. The discharge flow rate of the hydraulic pump 15, (d) is the operation of the on / off valve 20, (e) is the operation of the on / off valve 19, (f) is the operation of the on / off valve 36, and (g) is the operation of the control valve 31. It is a hydraulic circuit diagram which shows the flow of the hydraulic fluid at the time of the independent boom lowering operation | movement of the said hydraulic drive device. FIG. 6 is a time chart showing control signals during the single boom lowering operation of the hydraulic drive device, where (a) is an input signal of the operation lever device 11, (b) is a stop of the first hydraulic pump 14, and shut-off of the on / off valves 19 and 20. , (C) is a pressure change when the stop of the first hydraulic pump 14 and the shutoff of the on / off valves 19, 20, and 36 are simultaneously controlled. It is a hydraulic circuit diagram which shows the hydraulic drive device which concerns on 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a hydraulic circuit diagram showing a hydraulic drive apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing a hydraulic excavator on which the hydraulic drive device is mounted.

<Configuration>
As a construction machine on which the hydraulic drive device 10 according to the present invention is mounted, a hydraulic excavator 1 will be described as an example. As shown in FIG. 2, the excavator 1 includes a lower traveling body 2 having a crawler type traveling device 2 a and an upper revolving body 3 as a main body pivotably attached on the lower traveling body 2. I have. A cab 4 is provided on the upper swing body 3, and the lower traveling body 2 and the upper swing body 3 are attached via a swing device 5 so as to be swingable.

  On the front side of the upper swing body 3, for example, a base end portion of a front work machine 6 which is an operating device for performing excavation work or the like is rotatably attached. Here, the front side refers to a direction (right direction in FIG. 2) in which an operator who rides on the cab 4 faces. The front work machine 6 includes a boom 7 whose base end is connected to the front side of the upper swing body 3 so as to be able to move up and down. The boom 7 operates via a boom cylinder 7a which is a hydraulic cylinder as a hydraulic actuator driven by hydraulic oil (pressure oil) as a supplied fluid. In the boom cylinder 7a, the tip of the rod 7b of the boom cylinder 7a is connected to the boom 7, and the base end of a cylinder tube 7c as a cylinder of the boom cylinder 7a is connected to the upper swing body 3.

  Further, as shown in FIG. 1, the boom cylinder 7a is located on the base end side of the cylinder tube 7c and is supplied with hydraulic oil to press the piston 7d attached to the base end portion of the rod 7b, thereby operating hydraulic pressure. Is provided with a bottom chamber 7e as a head chamber which is a first hydraulic oil chamber on the head side, that is, the bottom side, which extends the rod 7b. The boom cylinder 7a is located on the distal end side of the cylinder tube 7c and is supplied with hydraulic oil, thereby pressing the piston 7d and applying a load by the hydraulic pressure to move the rod 7b in a contracted manner. A rod chamber 7f as an oil chamber is provided.

  Moreover, the base end part of the arm 8 is connected to the front-end | tip part of the boom 7 so that raising / lowering is possible. The arm 8 operates via an arm cylinder 8a which is a hydraulic cylinder as a hydraulic actuator driven by supplied hydraulic oil. Specifically, the tip of the rod 8 b of the arm cylinder 8 a is connected to the arm 2, and the cylinder tube 8 c of the arm cylinder 8 a is connected to the boom 7.

  Further, the arm cylinder 8a is located on the base end side of the cylinder tube 8c and is supplied with hydraulic oil to press the piston 8d attached to the base end portion of the rod 8b, thereby extending the rod 8b. The bottom chamber 8e which is the first hydraulic oil chamber is provided. The arm cylinder 8a is located on the distal end side of the cylinder tube 8c and is supplied with hydraulic oil, thereby pressing the piston 8d and causing the rod 8b to retract and move to the rod chamber 8f which is a rod-side second hydraulic oil chamber. It has.

  Further, the base end portion of the bucket 9 is connected to the tip end portion of the arm 8 so as to be able to move up and down. The bucket 9 operates via a bucket cylinder 9a which is a hydraulic cylinder as a hydraulic actuator driven by supplied hydraulic oil. Specifically, the tip of the rod 9 b of the bucket cylinder 9 a is connected to the bucket 9, and the base end of the cylinder tube 9 c of the bucket cylinder 9 a is connected to the arm 8. Each of the boom cylinder 7a, the arm cylinder 8a, and the bucket cylinder 9a is a hydraulic single rod cylinder that expands and contracts by supplied hydraulic oil.

  The hydraulic drive device 10 is mounted on the upper swing body 3 of the hydraulic excavator 1 and is a hydraulic drive control device for driving the hydraulic excavator 1. The hydraulic drive device 10 is used for driving hydraulic actuators such as the turning device 5 and the traveling device 2a in addition to the boom cylinder 7a, the arm cylinder 8a, and the bucket cylinder 9a that constitute the front working machine 6. The hydraulic drive device 10 drives the boom cylinder 7a, the arm cylinder 8a, the bucket cylinder 9a, the turning device 5 and the traveling device 2a according to the operation of the operation lever device 11 as an operation unit installed in the cab 4. . Here, the expansion / contraction operation of the boom cylinder 7a, the arm cylinder 8a, and the bucket cylinder 9a, that is, the operation direction and the operation speed are instructed by the operation direction and operation amount of the predetermined lever 11a of the operation lever device 11. Although FIG. 1 shows only the hydraulic circuit related to the boom cylinder 7a and the arm cylinder 7b, the hydraulic circuit of the bucket cylinder 9a has the same configuration.

  Furthermore, the hydraulic drive device 10 includes an engine 12 as a drive source. For example, a first hydraulic pump 14 and a second hydraulic pump 15 as variable flow hydraulic pumps are attached to the engine 12 via a power transmission device 13 constituted by, for example, predetermined gears. The power output from the engine 12 is appropriately distributed and supplied to the first and second hydraulic pumps 14 and 15 by the power transmission device 13.

  The first hydraulic pump 14 includes a pair of input / output ports 14a and 14b as first and second inlets and outlets for sucking or discharging the hydraulic oil, and hydraulic oil entering and leaving the input / output ports 14a and 14b. A bi-tilt swash plate mechanism is provided with a bi-tilt swash plate 14c for adjusting the amount and the entry / exit direction, and the discharge and suction directions of hydraulic oil from these input / output ports 14a and 14b can be switched. ing. The first hydraulic pump 14 is provided with a regulator 14d as a flow rate adjusting unit for adjusting the inclination angle of the both inclined swash plates 14c. The regulator 14d is connected to a controller 16 as a control device via a regulator signal line 14e. Specifically, the suction and discharge flow rates and the suction and discharge directions of the hydraulic oil from the input / output ports 14a and 14b of the first hydraulic pump 14 are output from the controller 16 and input to the regulator 14d via the regulator signal line 14e. Controlled by a typical control signal.

  Further, one input / output port 14 a of the first hydraulic pump 14 is connected to the pipe line 17, and the other input / output port 14 b is connected to the pipe line 18. An on / off valve 19 is attached to the pipe line 17 connected to the one input / output port 14a. The on / off valve 19 is connected to the bottom chamber 7e of the boom cylinder 7a via a conduit 21. That is, the bottom chamber 7 e of the boom cylinder 7 a is connected to one input / output port 14 a of the first hydraulic pump 13 via the pipe line 21, the on / off valve 19 and the pipe line 17. Therefore, the pipes 17 and 21 constitute a first flow path that connects the bottom chamber 7e of the boom cylinder 7a to one input / output port 14a of the first hydraulic pump 14.

  Further, an on / off valve as a shut-off portion is provided in a pipe line 18 connected to the other input / output port 14b of the first hydraulic pump 14 to stop and shut off the flow of hydraulic oil to the rod chamber 7f of the boom cylinder 7a. 20 is attached. The on / off valve 20 is connected to the rod chamber 7f of the boom cylinder 7a through a pipe line 22. That is, the rod chamber 7 f of the boom cylinder 7 a is connected to the other input / output port 14 b of the first hydraulic pump 14 via the pipe line 22, the on / off valve 20 and the pipe line 18. Therefore, the pipes 18 and 22 form a second flow path that connects the rod chamber 7f of the boom cylinder 7a to the other input / output port 14b of the first hydraulic pump 14. Further, the boom cylinder 7a and the first hydraulic pump 14 are closed circuits connected in a closed circuit shape by pipe lines 17, 18, 20, and 21 as a closed circuit hydraulic drive device 29 as a closed circuit hydraulic drive unit. It is configured.

ing.

  Here, the boom cylinder 7 a is expanded and contracted by the hydraulic oil supplied from the first hydraulic pump 14. The expansion / contraction direction of the boom cylinder 7a, that is, the extension direction and the contraction direction, correspond to the discharge direction of the hydraulic oil discharged from the first hydraulic pump 14. Furthermore, the pressure in the bottom chamber 7e and the rod chamber 7f of the boom cylinder 7a acts on the pressure receiving surface on the bottom side or the rod side of the piston 7d of the boom cylinder 7a, and the piston 7d receives a load due to the hydraulic pressure. receive. The load difference acting on the piston 7d becomes a driving force for driving the piston 7d. The arm cylinder 8a and the bucket cylinder 9a are also configured in the same manner as the boom cylinder 7a, and the principle that a load is generated by the pressure in the bottom chamber 8e and the rod chamber 8f is the same.

  Next, the on / off valve 19 is an electromagnetically driven two-wheel drive having a switching position 19a for passing hydraulic oil, a switching position 19b for blocking the passage of hydraulic oil, and a single solenoid 19c for switching the switching positions 19a and 19b. This is a position switching valve. Specifically, the on / off valve 19 connects the pipeline 17 to the pipeline 21 when switched to the switching position 19a, and shuts off the pipeline 17 and the pipeline 21 when switched to the switching position 19b. It is considered to be a part. On the other hand, the on / off valve 20 also, like the on / off valve 19, is a switching position 20a for passing hydraulic oil, a switching position 20b for blocking the passage of hydraulic oil, and a single solenoid 20c for switching the switching positions 20a and 20b. Is an electromagnetically driven two-position switching valve. Specifically, the on / off valves 19 and 20 are connected to the controller 16 via the switching signal lines 23 and 24, and are output from the controller 16 and input to the single solenoids 19c and 20c via the switching signal lines 23 and 24. Is controlled by a control signal.

  On the other hand, the second hydraulic pump 15 is a supply / discharge source of hydraulic oil, and is used to adjust the input / output amount of hydraulic oil from the input port 15a to the output port 15b. The unidirectional swash plate mechanism is provided with the unidirectional swash plate 15c so that the minimum inclination is not zero. The second hydraulic pump 15 is provided with a regulator 15d that adjusts the inclination angle of the unidirectionally inclined swash plate 15c. The regulator 15d is connected to the controller 16 via a regulator signal line 15e. Specifically, the hydraulic oil suction / discharge flow rate by the second hydraulic pump 15 is controlled by a control signal output from the controller 16 and input to the regulator 15d via the regulator signal line 15e.

  The output port 15b of the second hydraulic pump 15 is connected to the pipe 26, the input port 15a of the second hydraulic pump 15 is connected to the pipes 27 and 30, and the pipes 27 and 30 are connected to the hydraulic oil tank. 28. The pipe line 26 is connected to the rod chamber 8f of the arm cylinder 8a through a control valve 31 and a pipe line 29 as a control unit. The pipe line 27 is connected to the bottom chamber 8e of the arm cylinder 8a through the pipe line 30, the control valve 31, and the pipe line 32. In addition, a throttle 34 is provided in the pipe line 30, and the flow rate of the hydraulic oil passing through the throttle 34 is reduced.

  Further, the control valve 31 includes a switching position 31a for blocking the passage of hydraulic oil, a switching position 31b for connecting the pipeline 26 to the pipeline 29 and connecting the pipeline 32 to the pipeline 30, and the pipeline 26 to the pipeline. This is an electromagnetically driven three-position proportional switching valve having a switching position 31c that connects to the pipe 32 and connects the pipe line 29 to the pipe line 30 and a solenoid 31d that switches the switching positions 31a, 31b, and 31c. Specifically, when the control valve 31 is switched to the switching position 31a, each of the pipelines 26, 29, 30, and 32 is blocked. When the control valve 31 is switched to the switching position 31b, the pipeline 26 and the pipeline 29 are connected, and the pipeline 30 and the pipeline 32 are connected. Further, when the control valve 31 is switched to the switching position 31c, the pipeline 26 and the pipeline 32 are connected, and the pipeline 30 and the pipeline 29 are connected. The control valve 31 is connected to the controller 16 via a switching signal line 33, and is controlled by a control signal output from the controller 16 and input to both solenoids 31d via the switching signal line 33. .

  The pipeline 26 is branched by connecting a pipeline 25 serving as a supply circuit, and the pipeline 25 is connected to the pipeline 21. Therefore, the hydraulic fluid discharged from the second hydraulic pump 15 is supplied to the pipeline 25 via the pipeline 26 and the pipeline 25, and the pipeline 25 is merged with the hydraulic oil passing through the pipeline 21. It functions as a hydraulic oil supply mechanism. In other words, the second hydraulic pump 15 functions as a supply unit that supplies hydraulic oil to the bottom chamber 7e and the rod chamber 7f of the boom cylinder 7a.

  Further, a pipe 35 serving as a discharge circuit is connected to the pipe 26 and branched, and the pipe 35 is connected to the pipe 30. The pipe 35 is provided with an on / off valve 36 as a blocking portion. The on / off valve 36 is an electromagnetically driven two-position having a switching position 36a for passing hydraulic oil, a switching position 36b for blocking the passage of hydraulic oil, and a single solenoid 36c for switching the switching positions 36a and 36b. It is a switching valve. The on / off valve 36 is connected to the controller 16 via a switching signal line 37, and is controlled by a control signal output from the controller 16 and input to the single solenoid 36c via each switching signal line. .

  Further, the on / off valve 36 switches the hydraulic oil flowing out from the bottom chamber 7e of the boom cylinder 7a to the pipeline 21, the pipeline 25, the pipeline 26, the pipeline 35, and the pipeline 27 by switching to the switching position 36a. It functions as a discharge mechanism for the hydraulic oil that is discharged to the hydraulic oil tank 28 through the hydraulic oil. Here, hydraulic oil is supplied to or discharged from the bottom chamber 7e of the boom cylinder 7a by the second hydraulic pump 15, the pipeline 25, the pipeline 35, and the on / off valve 36, and the pressure of the hydraulic fluid in the bottom chamber 7e is reduced. A pressure control device 40 is configured as a pressure control unit to be controlled. That is, the pressure control device 40 controls the hydraulic pressure for the bottom chamber 7e and the rod chamber 7f of the boom cylinder 7a. In other words, the second hydraulic pump 15 functions as a discharge unit that discharges hydraulic oil from the bottom chamber 7e and the rod chamber 7f of the boom cylinder 7a.

  Furthermore, a relief valve 38a is provided in the pipeline 38 branched from the pipeline 26 and connected to the pipeline 30 to form a relief circuit. Relief valves 38b and 38c are attached to a conduit 39 branched from the conduits 29 and 32 and connected to the hydraulic oil tank 28 to form a relief circuit. Relief valves 38d and 38c are provided in a conduit 41 branched from the conduits 21 and 22 and connected to the hydraulic oil tank 28 to form a relief circuit. Furthermore, relief valves 38f and 38g are also provided in the pipeline 42 branched from the pipelines 17 and 18 and connected to the hydraulic oil tank 28 to form a relief circuit.

  That is, these relief valves 38a, 38b,..., 38g are configured so that the pressure of hydraulic oil (working hydraulic pressure) acting on the relief valves 38a, 38b,. When the pressure exceeds the relief pressure, the hydraulic oil is released from the relief valves 38a, 38b, ..., 38g to the hydraulic oil tank 28 to protect the hydraulic circuit. Here, the relief pressure of these relief valves 38a, 38b,..., 38g is defined by the spring pressure of a spring (not shown) attached to these relief valves 38a, 38b,. Yes.

  On the other hand, a check valve 39a, 39b is provided in a pipe line 43 branched from the pipe lines 17 and 18 and connected to the hydraulic oil tank 28 to form a supply circuit. The pipe 43 is connected to the pipe 42 at a position between the relief valves 38f and 38g. Further, check valves 39d and 39c are also provided in the pipe 44 branched from the pipes 21 and 22 and connected to the hydraulic oil tank 28 to form a supply circuit. This pipe 44 is also connected to the pipe 41 at a position between the relief valves 38d and 38e. These check valves 39a, 39b, 39c, and 39d are opened when the pipes 17, 18, 21, and 22 to which the attached pipe lines 17, 18 and 22 become negative pressure, the check valves 39a, 39b, 39c, and 39d are opened. The hydraulic oil is sucked into the pipes 17, 18, 21 and 22.

  Next, the controller 16 receives an operation signal corresponding to the expansion / contraction operation of the boom cylinder 7a or the arm cylinder 8a from the operation lever device 11, and converts the command value corresponding to the operation of the boom cylinder 7a or the arm cylinder 8a into an analog signal for control. As a signal, the on / off valves 19, 20, 36, the control valve 31, the regulator 14d of the first hydraulic pump 14, and the regulator 15da of the second hydraulic pump 15 are driven. Furthermore, when the controller 16 is operated by the lever 11a of the operation lever device 11 so as to stop from the state in which the boom cylinder 7a is extended and retracted, the operating oil is supplied to the bottom chamber 7e side of the boom cylinder 7a. The supply or discharge amount is appropriately controlled by the on / off valve 36 and the second hydraulic pump 15 to reduce the load difference acting on the piston 7d by the pressure of the hydraulic oil in the bottom chamber 7e and the rod chamber 7f of the boom cylinder 7a. . In other words, the controller 16 controls the pressure applied to the bottom chamber 7e side and the rod chamber 7f side to be equal to the piston 7d of the boom cylinder 7a.

<Single arm operation>
Next, the operation of the excavator 1 according to the first embodiment will be described as an example of the operation.

  First, when the arm cylinder 8a is extended, in FIG. 1, when the lever 11a of the operation lever device 11 is extended so as to extend the arm cylinder 8a, an operation command corresponding to the extension operation is sent to the controller 16. Entered. Then, the hydraulic oil is discharged from the second hydraulic pump 15 by the controller 16. At the same time, the controller 16 gives a control signal to the control valve 31 to switch the control valve 31 to the switching position 31c. As a result, the hydraulic oil discharged from the second hydraulic pump 15 flows into the bottom chamber 8e of the arm cylinder 8a via the pipelines 26 and 32, so that the arm cylinder 8a is extended. Further, the hydraulic oil that has flowed out of the rod chamber 8 f of the arm cylinder 8 a flows out to the hydraulic oil tank 28 via the pipe line 29, the throttle 34, and the pipe line 30.

<During single boom raising operation>
Next, as an example of the operation of the hydraulic excavator 1, a so-called single boom raising operation from when the boom cylinder 7a is stopped to when the boom cylinder 7a is stopped after the boom raising operation is described will be described.

  3A and 3B are time charts showing control signals during the single boom raising operation of the hydraulic drive device 10, wherein FIG. 3A is an input signal of the operating lever device 11, FIG. 3B is a discharge flow rate of the first hydraulic pump 14, and FIG. ) Is the discharge flow rate of the second hydraulic pump 15, (d) is the operation of the on / off valve 20, (e) is the operation of the on / off valve 19, (f) is the operation of the on / off valve 36, and (g) is the operation of the control valve 31. It is. That is, FIG. 3 shows that the controller 16 controls the discharge flow rate Qcp1 of the first hydraulic pump 14 and the discharge flow rate Qop1 of the second hydraulic pump 14 according to the operation amount of the lever 11a of the operation lever device 11 during the single boom raising operation. The time history response of the control signal given to the valves 19, 20, 36 and the control valve 31 is shown.

(When stopped)
In FIG. 1, when the lever 11 a of the operation lever device 11 is not operated at all, no operation command is input to the controller 16. In this case, the controller 16 drives and controls the regulators 14d and 15d so that the discharge flow rates of the first and second hydraulic pumps 14 and 15 become 0 (zero), and the on / off valves 19, 20, 36 and the control valve. 31 is drive-controlled to switching positions 19b, 20b, 36b, 31a that block the pipes 21, 22, 26, 30, 35. Therefore, the boom cylinder 7a and the arm cylinder 8a are each held in a stopped state.

(Boom raising operation)
FIG. 4 is a hydraulic circuit diagram showing the flow of hydraulic oil during the single boom raising operation of the hydraulic drive device 10. Here, the pipelines 17, 18, 21, 22, 25, 26, and 27 shown in bold lines in FIG. 4 indicate the pipelines that are in a circulating state.

  In FIG. 4, when the lever 11 a of the operation lever device 11 is extended so as to extend the boom cylinder 7 a, an operation command corresponding to the extension operation is input to the controller 16. Then, the controller 16 gives a control signal to the regulator 14d of the first hydraulic pump 14 via the regulator signal line 14e, and the inclination angle of the both inclined swash plates 14c of the first hydraulic pump 14 is controlled. The hydraulic oil is discharged toward the pipe line 17 and the hydraulic oil is sucked from the pipe line 18 side.

  At the same time, the on / off valves 19, 20, and 36 are controlled by the controller 16 to the switching positions 19a, 20a, and 36b through the switching signal lines 23, 24, and 37. Further, the controller 16 gives a control signal to the regulator 15d of the second hydraulic pump 15 via the regulator signal line 15e, and the inclination angle of the unidirectionally inclined swash plate 15c of the second hydraulic pump 15 is controlled. The hydraulic fluid with the discharge flow rate Qop1 is discharged toward the pipe line 26 side. As a result, the hydraulic oil discharged to the pipeline 26 joins the pipeline 21 via the pipelines 26 and 25 and flows into the bottom chamber 7e of the boom cylinder 7a.

  At this time, the controller 16 determines the discharge flow rate Qop1 of the second hydraulic pump 15 to be the difference between the flow rate on the bottom chamber 7e side of the boom cylinder 7a and the flow rate on the rod chamber 7f side. Specifically, the pressure receiving area on the bottom chamber 7e side of the boom cylinder 7a is Ah, the pressure receiving area on the rod chamber 7f side of the boom cylinder 7a is Ar, the discharge flow rate of the first hydraulic pump 14 is Qcp1, and the second hydraulic pump 15 When the discharge flow rate is Qop1, the flow rate on the bottom chamber 7e side of the boom cylinder 7a is (Qcp1 + Qop1), the flow rate on the rod chamber 7f side is {(Qcp1 + Qop1) × Ar / Ah}, and the difference between these discharge flow rates is { (Qcp1 + Qop1) × (1−Ar / Ah)}. That is, the discharge flow rate of the second hydraulic pump 14 relative to the discharge flow rate Qcp1 of the first hydraulic pump 14 is controlled by the controller 16 so that the flow rate Qop1 of the second hydraulic pump 15 becomes {Qcp1 × (Ah / Ar-1)}. Qop1 is determined.

  On the other hand, the controller 16 controls the control valve 31 to the switching position 31a. That is, the pipe line 26 is blocked from the pipe line 29 and the pipe line 32. Therefore, the hydraulic oil discharged from the second hydraulic pump 15 does not flow into the bottom chamber 8e and the rod chamber 8f of the arm cylinder 8a, and the arm cylinder 8a is held in a stopped state.

(When driving is stopped)
Next, when the lever 11a of the operation lever device 11 is operated to stop driving the boom cylinder 7a, an operation command corresponding to the stop operation is input to the controller 16 as shown in FIG. . Then, the controller 16 controls the inclination angle of the both inclined swash plates 14c of the first hydraulic pump 14, and the discharge and suction of the hydraulic oil of the first hydraulic pump 14 are stopped. Further, after the controller 16 stops discharging the hydraulic oil from the first hydraulic pump 14, the on / off valves 19, 20 are controlled to be switched to the switching positions 19b, 20b via the switching signal lines 23, 24, respectively. The path 18 and the pipeline 22 are blocked, and the pipeline 17 and the pipeline 21 are blocked. Furthermore, after the on / off valves 19 and 20 are switched by the controller 16, the inclination angle of the unidirectionally inclined swash plate 15c of the second hydraulic pump 15 is controlled, and the discharge of the hydraulic oil from the second hydraulic pump 15 is stopped. Is done.

  That is, the controller 16 outputs a control signal for stopping the discharge and suction of the hydraulic oil of the first hydraulic pump 14 when the operation lever device 11 is stopped to stop the driving of the boom cylinder 7a, and then on / off. A control signal for switching the valves 19 and 20 to the switching positions 19b and 20b is output, and then a control signal for stopping the discharge of the hydraulic oil from the second hydraulic pump 15 is output. Therefore, as shown in FIG. 3, the controller 16 outputs an output timing 61a for outputting a control signal for stopping the first hydraulic pump 14, an output timing 61b for outputting a control signal for switching the on / off valves 19 and 20, and a second The output timing 61c for outputting a control signal for stopping the hydraulic pump 15 is shifted in steps and outputted.

(Function and effect)
5A and 5B are time charts showing control signals during a single boom raising operation of the hydraulic drive device 10, where FIG. 5A is an input signal of the operation lever device 11, and FIG. 5B is a stop of the first hydraulic pump 14 and an on / off valve 19. Is a pressure change when the second hydraulic pump 15 is controlled in this order, and (c) is a pressure change when the first and second hydraulic pumps 14 and 15 are stopped and the on / off valve 19 is simultaneously controlled. is there.

  As described above, during the single boom raising operation, when the boom cylinder 7a is stopped from the extended operation state, the controller 16 stops the discharge of the hydraulic oil from the first hydraulic pump 14 and then the on / off valve. 19 and 20 are switched to the switching positions 19b and 20b, respectively, and the pipeline 18 and the pipeline 22 are shut off, and the pipeline 17 and the pipeline 21 are shut off.

  As a result, the flow of the hydraulic oil to the rod chamber 7f and the pipe line 22 of the boom cylinder 7a is stopped. Therefore, due to the inertia of the mechanism generated when the boom cylinder 7a is stopped while being extended, The hydraulic oil in the rod chamber 7f of the boom cylinder 7a is compressed, and the pressure in the rod chamber 7f increases. At this time, since the second hydraulic pump 15 is discharging hydraulic oil, the hydraulic oil flows into the bottom chamber 7e of the boom cylinder 7a via the pipelines 26, 25 and 21, and the inside of the bottom chamber 7e The pressure is rising.

  In this state, the controller 16 stops the discharge of the hydraulic oil from the second hydraulic pump 15 so that the pressure in the bottom chamber 7e of the boom cylinder 7a is maintained in an increased state. Both the pressure in the rod chamber 7f and the pressure in the bottom chamber 7e are maintained in a high pressure state.

  Therefore, as shown in FIG. 5B, the bottom of the boom cylinder 7a is compared with the case where the stop of the first and second hydraulic pumps 14 and 15 and the shut-off of the on / off valve 19 shown in FIG. The pressure difference between the chamber 7e side and the rod chamber 7f side is reduced, and the load difference acting on the piston 7d of the boom cylinder 7a is reduced. As a result, when the boom cylinder 7a is stopped driving, the vibration of the piston 7d, which may occur when the pressure difference between the pressure in the bottom chamber 7e and the pressure in the rod chamber 7f is large, is less likely to occur. It is possible to obtain good stopping performance that is fast and stable.

<Single boom lowering operation>
Next, as an operation example of the hydraulic excavator 1, a so-called single boom lowering operation from when the boom cylinder 7a is stopped to when the boom cylinder 7a is stopped after the boom lowering operation will be described.

  6A and 6B are time charts showing control signals during the single boom lowering operation of the hydraulic drive device 10, wherein FIG. 6A is an input signal of the operating lever device 11, FIG. 6B is a discharge flow rate of the first hydraulic pump 14, and FIG. ) Is the discharge flow rate of the second hydraulic pump 15, (d) is the operation of the on / off valve 20, (e) is the operation of the on / off valve 19, (f) is the operation of the on / off valve 36, and (g) is the operation of the control valve 31. It is. That is, FIG. 6 shows that during the single boom lowering operation, the controller 16 controls the discharge flow rate Qcp2 of the first hydraulic pump 14, the discharge flow rate Qop2 of the second hydraulic pump 14, on / off according to the operation amount of the lever 11a of the operation lever device 11. The time history response of the control signal given to the valves 19, 20, 36 and the control valve 31 is shown.

(When stopped)
In FIG. 1, when the lever 11a of the operation lever device 11 is not operated, the discharge flow rate of the first and second hydraulic pumps 14 and 15 is controlled to be zero as in the above-described single boom raising operation. The on / off valves 19, 20, 36 and the control valve 31 are controlled to the switching positions 19b, 20b, 36b, 31a.

(During boom lowering operation)
FIG. 7 is a hydraulic circuit diagram showing the flow of hydraulic oil during the single boom lowering operation of the hydraulic drive device 10. Here, the pipelines 17, 18, 21, 22, 25, 26, and 35 shown by the thick lines in FIG. 7 indicate the pipelines in a circulating state.

  In FIG. 7, when the lever 11 a of the operating lever device 11 is retracted so as to retract the boom cylinder 4, an operation command corresponding to the retracting operation is input to the controller 16. Then, the controller 16 gives a control signal to the regulator 14d of the first hydraulic pump 14 via the regulator signal line 14e, and the inclination angle of the both inclined swash plates 14c of the first hydraulic pump 14 is controlled. The hydraulic oil is discharged toward the pipe line 18 and the hydraulic oil is sucked from the pipe line 17 side.

  At the same time, the on / off valves 19, 20, and 36 are controlled by the controller 16 to the switching positions 19a, 20a, and 36a through the switching signal lines 23, 24, and 37. As a result, the hydraulic oil discharged from the bottom chamber 7e of the boom cylinder 7a is discharged to the hydraulic oil tank 28a via the pipe lines 21, 25, 26, the on / off valve 36, and the pipe line 30. The flow rate of the hydraulic oil discharged from the bottom chamber 7e of the boom cylinder 7a is the difference between the flow rate on the bottom chamber 7e side of the boom cylinder 7a and the flow rate on the rod chamber 7f side. Therefore, the flow rate Qv2 discharged from the bottom chamber 7e of the boom cylinder 7a is equal to the flow rate during the above-described single boom raising operation, and becomes {Qcp2 × (Ah / Ar−1)}.

  On the other hand, the control valve 31 is controlled to be switched to the switching position 31 a by the controller 16, and the pipe line 26 is blocked from the pipe line 29 and the pipe line 32. For this reason, the hydraulic fluid discharged from the bottom chamber 7e of the boom cylinder 7a does not flow into the bottom chamber 8e and the rod chamber 8f of the arm cylinder 8a, and the arm cylinder 8a is held in a stopped state.

(When driving is stopped)
Next, when the lever 11a of the operation lever device 11 is stopped so as to stop the driving of the boom cylinder 7a, as shown in FIG. 6, the first hydraulic pump as in the above-described single boom raising operation. The discharge and suction of the hydraulic fluid 14 are stopped. Thereafter, the on / off valves 19 and 20 are controlled to be switched to the switching positions 19b and 20b, respectively, the pipe 18 and the pipe 22 are shut off, and the pipe 17 and the pipe 21 are shut off. Furthermore, after the on / off valves 19 and 20 are switched by the controller 16, the on / off valve 36 is switched to the switching position 36b, and the discharge of the hydraulic oil from the bottom chamber 7e of the boom cylinder 7a to the hydraulic oil tank 28 is stopped. Is done.

  That is, the controller 16 switches the on / off valves 19 and 20 after outputting a control signal for stopping the first hydraulic pump 14 when the operation lever device 11 is operated to stop driving the boom cylinder 7a. A control signal is output, and then a control signal for switching the on / off valve 36 is output. Accordingly, as shown in FIG. 6, the controller 16 outputs an output timing 62a for outputting a control signal for stopping the first hydraulic pump 14, an output timing 62b for outputting a control signal for switching the on / off valves 19 and 20, and an on / off valve. The output timing 62c for outputting a control signal for switching 36 is shifted stepwise and output.

(Function and effect)
8A and 8B are time charts showing control signals during the single boom lowering operation of the hydraulic drive device 10, where FIG. 8A is an input signal of the operation lever device 11, and FIG. 8B is a stop of the first hydraulic pump 14 and an on / off valve 19. , 20 and pressure change when controlled in the order of shut-off of the on / off valve 36, (c) is pressure change when the stop of the first hydraulic pump 14 and the shut-off of the on / off valves 19, 20, 36 are controlled simultaneously. .

  As described above, during the single boom lowering operation, when the boom cylinder 7a is stopped from the retracted state, the controller 16 operates the first hydraulic pump 14 in the same manner as in the single boom raising operation described above. After the oil discharge is stopped, the on / off valves 19 and 20 are controlled to be switched to the switching positions 19b and 20b, the pipe 18 and the pipe 22 are cut off, and the pipe 17 and the pipe 21 are cut off.

  As a result, the flow of the hydraulic oil in the rod chamber 7f and the pipe line 22 of the boom cylinder 7a is stopped, and therefore, by the inertia of the mechanism generated when the boom cylinder 7a is stopped while being retracted, A pulling action is applied so that the hydraulic oil in the rod chamber 7f of the boom cylinder 7a is pulled out, and the pressure in the rod chamber 7f decreases. At this time, the on / off valve 36 is set to the switching position 36 a so that the hydraulic oil can pass through the pipeline 35. Therefore, since the hydraulic oil in the bottom chamber 7e of the boom cylinder 7a can flow out to the hydraulic oil tank 28 via the pipes 21, 25, 26, 35, 30, the pressure in the bottom chamber 7e is reduced. To do.

  In this state, the controller 16 switches the on / off valve 36 to the switching position 36b to shut off the pipe line 35 and stop the passage of hydraulic oil in the pipe line 35, whereby the bottom chamber 7f of the boom cylinder 7a. Therefore, the pressure in the rod chamber 7e of the boom cylinder 7a and the pressure in the bottom chamber 7f are both maintained in a low pressure state.

  Accordingly, as shown in FIG. 8B, the bottom chamber of the boom cylinder 7a is compared with the case where the stop of the first hydraulic pump 14 and the shut-off of the on / off valves 19, 20, and 36 shown in FIG. The pressure difference between the 7f side and the rod chamber 7e side is reduced, and the load difference acting on the piston 7d of the boom cylinder 7a is reduced. As a result, when the drive of the boom cylinder 7a is stopped, the vibration of the piston 7d, which may occur when the differential pressure between the bottom chamber 7e side and the rod chamber 7f side is large, can be hardly generated. As in the lifting operation, a good stopping performance with a quick settling can be obtained.

[Second Embodiment]
FIG. 9 is a hydraulic circuit diagram showing a hydraulic drive apparatus according to the second embodiment of the present invention. The second embodiment differs from the first embodiment described above in that the first embodiment is different from the first embodiment in the hydraulic drive device 10 that reduces the load difference of the boom cylinder 7a at the output timing of the control signal output from the controller 16. On the other hand, the second embodiment is a hydraulic drive device 10A provided with a load equalization circuit 70 for reducing the load difference of the boom cylinder 7a. In the second embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

<Configuration>
Specifically, in the second embodiment, a load equalization circuit 70 as a load equalization portion is attached between the pipeline 21 and the pipeline 22 of the closed circuit hydraulic drive device 29. The load equalization circuit 70 equalizes the load acting on the piston 7d from the bottom chamber 7e side of the boom cylinder 7a and the load acting on the piston 7d from the rod chamber 7f side of the boom cylinder 7a.

  As shown in FIG. 9, the load equalization circuit 70 includes a pair of relief valves 71 a and 71 b and a switching valve 72, and is attached to a pipeline 71 that is branched from the pipeline 21 and connected to the pipeline 22. ing. The relief valve 71 a is connected to the pipe line 22 and allows the hydraulic oil supplied from the switching valve 72 to pass through the pipe line 21. The relief valve 71 b is connected to the pipe line 21 and allows hydraulic oil supplied from the switching valve 72 to pass through the pipe line 22. Here, these relief valves 71a and 71b have a relief pressure lower than the relief pressure set by the relief valves 38a, 38b,..., 38g. These relief pressures are defined by spring pressures of springs (not shown) attached to the relief valves 71a and 71b.

  Next, the switching valve 72 switches the hydraulic oil through the switching position 72a, the switching position 72b through which the hydraulic oil passing through the pipeline 21 passes to the relief valve 71a, and the hydraulic oil passing through the pipeline 22 to the relief valve 71b. This is an electromagnetically driven three-position switching valve having a switching position 72c to be passed and both solenoids 72d for switching the switching positions 72a, 72b and 7c. Specifically, the switching valve 72 blocks the flow path through the load equalization circuit 70 from the pipe line 21 to the pipe line 22 when switching to the switching position 71a. When the switching valve 72 is switched to the switching position 71b, the pipe 71 branched from the pipe 21 is connected to the pipe 22 through the switching valve 72 and the relief valve 71a. Further, when the switching valve 72 is switched to the switching position 71c, the pipeline 71 branched from the pipeline 22 is connected to the pipeline 21 via the switching valve 72 and the relief valve 71b. The switching valve 72 is connected to the controller 16 via a switching signal line 73 and is controlled to be switched by a control signal output from the controller 16 and input to both solenoids 72d via the switching signal line 73.

<During single boom raising operation>
Next, a single boom raising operation will be described as an operation example of the hydraulic excavator 1 according to the second embodiment.

(When stopped)
When the lever 11a of the operation lever device 11 is not operated, the discharge flow rate of the first and second hydraulic pumps 14 and 15 is controlled to be zero and is turned on / off as in the case of the first embodiment described above. The valves 19, 20, 36 and the control valve 31 are controlled to the switching positions 19b, 20b, 36b, 31a. At this time, the switching valve 72 is controlled to be switched to the switching position 72a by the controller 16 via the switching signal line 73, so that the pipes 21 and 22 are blocked. Therefore, the boom cylinder 7a and the arm cylinder 8a are each held in a stopped state.

(Boom raising operation)
The flow state of the hydraulic oil during the boom raising operation according to the second embodiment is the state shown in FIG. 4 as in the case of the first embodiment described above. That is, when the lever 11a of the operation lever device 11 is extended so as to extend the boom cylinder 4, the inclination angle of the both inclined swash plates 14c of the first hydraulic pump 14 is controlled and directed toward the pipeline 17 side. Then, the hydraulic oil is discharged and the hydraulic oil is sucked from the pipe line 18 side. At the same time, the on / off valves 19, 20, 36 are controlled to be switched to the switching positions 19a, 20a, 36b.

  Further, the controller 16 gives a control signal to both solenoids 72d of the switching valve 72 of the load equalization circuit 70 via the switching signal line 73, and the switching valve 72 is controlled to be switched to the switching position 72a. Further, the controller 16 controls the unidirectionally inclined swash plate 15c of the second hydraulic pump 15, and the hydraulic oil having the discharge flow rate Qop1 is discharged toward the pipe line 26 side. At this time, the controller 16 causes the discharge flow rate Qop1 of the second hydraulic pump 15 to be the difference between the flow rate on the bottom chamber 7e side of the boom cylinder 7a and the flow rate on the rod chamber 7f side, and the first embodiment described above. A similar operation is performed and determined.

(When driving is stopped)
Next, when the lever 11a of the operation lever device 11 is stopped so as to stop the driving of the boom cylinder 7a, an operation command corresponding to the stop operation is input to the controller 16. Then, after the discharge and suction of the hydraulic oil from the first hydraulic pump 14 are stopped, the discharge of the hydraulic oil from the second hydraulic pump 15 is stopped. Thereafter, the on / off valves 19 and 20 are controlled to be switched to the switching positions 19b and 20b, respectively, the pipe 18 and the pipe 22 are shut off, and the pipe 17 and the pipe 21 are shut off. Next, the controller 16 gives a control signal to both solenoids 72d of the switching valve 72 of the load equalization circuit 70 via the switching signal line 73, and the switching valve 72 is controlled to be switched to the switching position 72c.

(Function and effect)
As described above, in the above-described second embodiment, when the boom cylinder 7a is stopped from the state in which the boom cylinder 7a is extended during the single boom raising operation, the controller 16 causes the first and second hydraulic pumps 14 and 15 to move. After the discharge of the hydraulic oil is stopped, the on / off valves 19 and 20 are controlled to be switched to the switching positions 19b and 20b, respectively, and the pipeline 18 and the pipeline 22 are shut off, and the pipeline 17 and the pipeline 21 are shut off. .

  As a result, the flow of the hydraulic oil in the rod chamber 7f of the boom cylinder 7a and the conduit 22 is stopped, so that the hydraulic oil in the rod chamber 7f of the boom cylinder 7a is compressed by the inertia of the mechanism of the boom cylinder 7a. The pressure in the rod chamber 7f increases. At this time, the pressure in the rod chamber 7f acts on the relief valve 71b via the conduit 22 and the switching valve 72 of the load equalization circuit 70. Therefore, when the pressure in the rod chamber 7f that has risen when the boom cylinder 7a is stopped becomes higher than the preset relief pressure of the relief valve 71b, the relief valve 71b opens and opens. The hydraulic oil in the rod chamber 7f of the boom cylinder 7a flows into the bottom chamber 7e through the flow path 22, the switching valve 72, the relief valve 71b, and the flow path 21 of the load equalization circuit 70.

  That is, the load equalization circuit 70 functions as a hydraulic oil supply unit, and the hydraulic oil is supplied from the rod chamber 7f to the bottom chamber 7e. Therefore, the pressure drop due to insufficient supply of hydraulic oil to the bottom chamber 7e is reduced. Reduced. Accordingly, the pressure difference between the bottom chamber 7e side and the rod chamber 7f side of the boom cylinder 7a is surely reduced with a simpler configuration, and the load difference acting on the piston 7d of the boom cylinder 7a is reduced. As a result, when the boom cylinder 7a is stopped driving, the vibration of the piston 7d, which may occur when the pressure difference between the pressure in the bottom chamber 7e and the pressure in the rod chamber 7f is large, is less likely to occur. It is possible to obtain good stopping performance that is fast and stable.

<Single boom lowering operation>
Next, a single boom lowering operation will be described as an operation example of the excavator 1.

(When stopped)
When the lever 11a of the operation lever device 11 is not operated, the discharge flow rates of the first and second hydraulic pumps 14 and 15 are controlled to be zero, and the on / off valve 19, as in the case of the first embodiment described above. 20, 36 and the control valve 31 are controlled to be switched to the switching positions 19b, 20b, 36b, 31a. Further, the switching valve 72 of the load equalization circuit 70 is controlled to be switched to the switching position 72a, and each of the boom cylinder 7a and the arm cylinder 8a is held in a stopped state.

(During boom lowering operation)
The distribution state of the hydraulic oil during the boom lowering operation according to the second embodiment is the state illustrated in FIG. 7 as in the case of the first embodiment described above. That is, when the lever 11a of the operating lever device 11 is retracted so as to retract the boom cylinder 7a, the both inclined swash plates 14c of the first hydraulic pump 14 are controlled, and the hydraulic oil is directed toward the pipe 18 side. Is discharged, and hydraulic oil is sucked from the pipe 17 side. At the same time, the on / off valves 19, 20, 36 are controlled to be switched to the switching positions 19a, 20a, 36a.

  Further, the controller 16 gives a control signal to the switching valve 72 via the switching signal line 73, and the switching valve 72 is controlled to be switched to the switching position 72a. As a result, the hydraulic oil discharged from the bottom chamber 7e of the boom cylinder 7a is discharged to the hydraulic oil tank 28 via the pipe lines 21, 25, 26, the on / off valve 36, and the pipe line 30. The flow rate of the hydraulic oil discharged from the bottom chamber 7e is the difference between the flow rate on the bottom chamber 7e side of the boom cylinder 7a and the flow rate on the rod chamber 7f side. Accordingly, the controller 16 controls the discharge flow rate Qop1 of the second hydraulic pump 15 so as to be equal to the difference.

(When driving is stopped)
Next, when the lever 11a of the operation lever device 11 is stopped so as to stop the driving of the boom cylinder 7a, similarly to the above-described single boom raising operation, the discharge of the hydraulic oil from the first hydraulic pump 14 and Inhalation is stopped. Thereafter, the on / off valves 19 and 20 are controlled to be switched to the switching positions 19b and 20b, respectively, the pipe 18 and the pipe 22 are shut off, and the pipe 17 and the pipe 21 are shut off. Next, the on / off valve 36 is controlled to be switched to the switching position 36b, and the discharge of the hydraulic oil from the bottom chamber 7e of the boom cylinder 7a to the hydraulic oil tank 28 is stopped. Further, the controller 16 gives a control signal to the switching valve 72 via the switching signal line 73, and the switching valve 72 is controlled to be switched to the switching position 72c.

(Function and effect)
As described above, in the above-described second embodiment, after the boom cylinder 7a is stopped from the retracting state during the single boom lowering operation, the discharge of the hydraulic oil from the first hydraulic pump 14 is stopped. The on / off valves 19 and 20 are controlled to be switched to the switching positions 19b and 20b, respectively, and the pipeline 18 and the pipeline 22 are blocked, and the pipeline 17 and the pipeline 21 are blocked.

  As a result, the flow of the hydraulic oil in the rod chamber 7f of the boom cylinder 7a and the conduit 22 is stopped, so that the hydraulic oil in the rod chamber 7f of the boom cylinder 7a is compressed by the inertia of the mechanism of the boom cylinder 7a. The pressure in the rod chamber 7f increases. At this time, the pressure in the bottom chamber 7e of the boom cylinder 7a acts on the relief valve 71a via the flow path 21 and the switching valve 72 of the load equalization circuit 70. For this reason, when the pressure in the bottom chamber 7e that has risen when the boom cylinder 7a is stopped becomes higher than the preset relief pressure of the relief valve 71a, the relief valve 71a opens and opens. The hydraulic oil in the bottom chamber 7e of the boom cylinder 7a flows into the rod chamber 7f via the pipeline 21, the switching valve 72, the relief valve 71a, and the pipeline 22 of the load equalization circuit 70.

  That is, as in the case of the single boom raising operation described above, the load equalization circuit 70 functions as a hydraulic oil supply unit, and this hydraulic oil is supplied from the bottom chamber 7e to the rod chamber 7f. The pressure drop due to insufficient supply of hydraulic oil to is reduced. Therefore, the pressure difference between the bottom chamber 7e side and the rod chamber 7f side of the boom cylinder 7a is reduced, and the load difference acting on the piston 7d of the boom cylinder 7a is reduced. As a result, when the boom cylinder 7a is stopped driving, the vibration of the piston 7d, which may occur when the pressure difference between the pressure in the bottom chamber 7e and the pressure in the rod chamber 7f is large, is less likely to occur. Similarly to the first embodiment, even during the single boom lowering operation, it is possible to obtain a good stopping performance that is fast and stable.

[Others]
In addition, this invention is not limited to embodiment mentioned above, Various deformation | transformation aspects are included. For example, the above-described embodiments have been described in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those having all the configurations described.

  In each of the above embodiments, the case where the hydraulic drive device 10 is mounted on the hydraulic excavator 1 has been described as an example. However, the present invention is not limited to this, and for example, a hydraulic drive device such as a hydraulic crane or a wheel loader. If it is a construction machine provided with the drive device of the hydraulic cylinder which can drive by 10, it can apply also to construction machines other than a hydraulic shovel.

  In each of the above embodiments, the regulators 14d and 15d, the on / off valves 19, 20, and 36, the control valve 31, and the switching valve 72 are controlled by an electrical control signal output from the controller 16. As appropriate, these configurations may be configured as a hydraulic circuit having a similar function.

  Further, in each of the above embodiments, the stopping method during the expansion / contraction operation of the boom cylinder 7a has been described. However, the present invention is also applicable to other hydraulic cylinders such as the arm cylinder 8a and the boom cylinder 9a. That is, for example, even during the expansion / contraction operation of the arm cylinder 8a, a pressure change due to the inertia of the mechanism similar to that during the single boom raising operation and the single boom lowering operation described above can occur. It is also applicable when stopping.

  Further, the pressure control device 40 connected to the pipeline 21 on the bottom chamber 7e side of the boom cylinder 7a is used to control the pressure on the bottom chamber 7e side. However, the pressure control device 40 is connected to the rod chamber 7f side. It is possible to reduce the load difference acting on the piston 7f from the bottom chamber 7e side and the rod chamber 7f side.

  Further, a pressure sensor (not shown) capable of measuring the pressure in the bottom chamber 7e and the rod chamber 7f of the boom cylinder 7a is provided, and the pressure values in the bottom chamber 7e and the rod chamber 7f measured by these pressure sensors are controller. 16 to receive. The controller 16 controls the pressure control device 40 to control the pressure in the bottom chamber 7e so that the load difference acting on the piston 7d calculated from these two pressure values becomes zero. Vibration that can occur when the cylinder 7a is stopped can be more appropriately suppressed.

  Further, an electromagnetically driven two-position switching valve capable of switching between the flow and shut-off of the hydraulic oil on the pipe 25 for supplying the hydraulic oil discharged from the second hydraulic pump 15 to the pipe 21. An on-off valve (not shown) can also be provided. The on / off valve is controlled to be switched to the flow position when the boom cylinder 7a is driven, and is controlled to be switched to the shut-off position when the boom cylinder 7a is held, so that the boom cylinder 7a can be reliably held.

  Further, the hydraulic oil (pressure oil) discharged from the bottom chamber 7e or the rod chamber 7f of the boom cylinder 7a is collected by a collection device (not shown) such as an accumulator, and the collected hydraulic oil is collected in the boom cylinder 7a or It can also be set as the structure utilized when driving another hydraulic cylinder.

DESCRIPTION OF SYMBOLS 1 Hydraulic excavator 2 Lower traveling body 2a Traveling apparatus 3 Upper turning body 4 Cab 5 Turning apparatus 6 Front work machine 7 Boom 7a Boom cylinder (hydraulic cylinder)
7b Rod 7c Cylinder tube 7d Piston 7e Bottom chamber (first hydraulic oil chamber)
7f Rod chamber (second hydraulic oil chamber)
8 Arm (hydraulic cylinder)
8a Arm cylinder 8b Rod 8c Cylinder tube 8d Piston 8e Bottom chamber 8f Rod chamber 9 Bucket 9a Bucket cylinder 9b Rod 9c Cylinder tube 10, 10A Hydraulic drive device 11 Operation lever device (operation part)
11a lever 12 engine 13 power transmission device 14 first hydraulic pump (variable flow hydraulic pump)
14a I / O port (first entry / exit)
14b I / O port (second entry / exit)
14c Bi-slanting swash plate 14d Regulator (flow rate adjustment unit)
14e Regulator signal line 15 Second hydraulic pump (pressure control unit, supply unit, discharge unit)
15a Input port 15b Output port 15c One-side tilting swash plate 15d Regulator 15e Regulator signal line 16 Controller 17 Pipe line (first flow path)
18 Pipe line (second flow path)
19 On-off valve 19a, 19b Switching position 19c Single solenoid 20 On-off valve (blocking part)
20a, 10b Switching position 20c Single solenoid 21 Pipe line (first flow path)
22 Pipe line (second flow path)
23, 24 Switching signal line 25, 26, 27 Pipe line 28 Hydraulic oil tank 29 Closed circuit hydraulic drive device (closed circuit hydraulic drive unit)
30 Pipe line 31 Control valve (control part)
31a, 31b, 31c Switching position 31d Both solenoids 32 Pipe line 33 Switching signal line 34 Restriction 35 Pipe line 36 On-off valve (blocking part)
36a, 36b Switching position 36c Single solenoid 37 Switching signal line 38 Pipe line 38a, 38b, 38c, 38d, 38e, 38f, 38g Relief valve 39 Pipe line 39a, 39b, 39c, 39d Check valve 40 Pressure control device (pressure control unit) )
41 pipeline 43 pipeline 61a, 61b, 61c output timing 62a, 62b, 62c output timing 70 load equalization circuit (load equalization section)
71 Pipe 72 Switching valve 72a, 72b, 72c Switching position 72d Solenoid 73 Switching signal line

Claims (4)

A variable flow hydraulic pump having first and second inlets and outlets for sucking or discharging hydraulic oil and a flow rate adjusting unit for controlling the flow rate and direction of the hydraulic oil with respect to the first and second inlets and outlets, and a piston capable of extending and contracting A hydraulic cylinder having a first hydraulic fluid chamber that extends by applying a hydraulic load to the piston, and a second hydraulic fluid chamber that contracts by applying a hydraulic load to the piston, and the first hydraulic fluid of the hydraulic cylinder A first flow path connecting a chamber to a first inlet / outlet of the variable flow hydraulic pump, and a second flow path connecting a second hydraulic oil chamber of the hydraulic cylinder to a second inlet / outlet of the variable flow hydraulic pump. Closed circuit hydraulic drive,
An operation unit for instructing an expansion and contraction operation of the hydraulic cylinder and outputting the instructed operation command;
A pressure control unit for controlling the pressures of the first and second hydraulic oil chambers of the hydraulic cylinder;
When an operation command for stopping the piston of the hydraulic cylinder from being extended or contracted is input from the operation unit, the pressure control unit is controlled to control the first and second hydraulic oil chambers of the hydraulic cylinder. After stopping the flow of the hydraulic oil to at least one of them, the pressure of at least one of the first and second hydraulic oil chambers is controlled to act on the piston from these first and second hydraulic oil chambers. A controller that reduces the load difference
A hydraulic drive device comprising: In the hydraulic drive unit according to claim 1,
The pressure control unit includes a supply unit that supplies hydraulic oil to the first and second hydraulic oil chambers of the hydraulic cylinder, and a discharge unit that discharges the hydraulic oil from the first and second hydraulic oil chambers of the hydraulic cylinder. ,
The controller operates the hydraulic cylinder with respect to one of the first and second hydraulic fluid chambers when an operation command for stopping the piston of the hydraulic cylinder from a state in which the piston is extended and contracted is input from the operation unit. After stopping the circulation of the oil, the supply amount or discharge amount of the hydraulic oil to either one of the first and second hydraulic oil chambers is controlled by the supply unit or the discharge unit, and the first and first (2) A hydraulic drive device that reduces a load difference acting on the piston from the hydraulic oil chamber. In the hydraulic drive unit according to claim 1 or 2,
The pressure control unit includes: a supply unit that supplies hydraulic oil to the first hydraulic oil chamber of the hydraulic cylinder; a discharge unit that discharges hydraulic oil from the first hydraulic oil chamber; and a second hydraulic oil chamber of the hydraulic cylinder. Provided with a blocking part that stops the flow of hydraulic oil,
When the operation command for stopping the piston of the hydraulic cylinder from the state in which the piston of the hydraulic cylinder is driven to extend is input from the operation unit, the controller allows the hydraulic cylinder to flow to the second hydraulic oil chamber at the blocking unit. After stopping, the supply amount or discharge amount of the hydraulic cylinder to the first hydraulic oil chamber is controlled by the supply portion or discharge portion, and the load acting on the piston from the first and second hydraulic oil chambers A hydraulic drive device characterized in that the difference is reduced. In the hydraulic drive unit according to claim 1 or 2,
A load equalizing portion for equalizing the load acting on the piston from the first and second hydraulic oil chambers of the hydraulic cylinder;
The controller controls the pressure control unit to control the first and second of the hydraulic cylinder when an operation command for stopping the piston of the hydraulic cylinder from being driven to extend and contract is input from the operation unit. After stopping the flow of the hydraulic oil to the hydraulic oil chamber, the load equalizing portion is controlled to reduce the load difference acting on the piston from the first and second hydraulic oil chambers. Drive device.

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