JPH11148147A - Hydraulic driving device for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a pressure accumulated by a pressure accumulating means for a prolonged term when a prime mover is brought to a stopped state. SOLUTION: A pilot valve 25, an accumulator 26 and a changeover valve 30 are disposed on its midway to pilot piping 24 connecting the hydraulic pilot sections 22A, 22B of a directional control valve 22 and a pilot hydraulic pump 23. A switch 33 and a timer 36 are arranged between the electromagnetic pilot section 31 of the changeover valve 30 and a power supply 32. The switch 33 is closed and the changeover valve 30 is changed over to the place (a) of interruption when the stopped state of a prime mover 18 is detected by a pressure sensor 35 while the supply of a current is stopped by the timer 36 when the electromagnetic pilot section 31 is supplied with the current for a fixed time, and the changeover valve 30 is brought the state, in which changeover operation is carried out to a communicated place (b) by a lever 17 for getting-on-and-off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive device for a construction machine, which is provided in a construction machine such as a hydraulic shovel and can operate an actuator such as a hydraulic cylinder even after a motor stops.

[0002]

2. Description of the Related Art Generally, construction machines such as hydraulic excavators are provided with a main hydraulic pump driven by a prime mover.
Actuators such as a travel motor, a swing motor, a boom cylinder, an arm cylinder, and a bucket cylinder are driven by pressure oil discharged from the main hydraulic pump,
A control valve for controlling the flow of the pressure oil supplied from the main hydraulic pump to each actuator is provided, and the operation of each actuator is controlled by switching the control valve.

[0003] Further, such a construction machine is provided with an auxiliary hydraulic pump driven by a prime mover, and controls a hydraulic valve discharged from the auxiliary hydraulic pump to control each of the control valves, such as a pilot valve. It is known that an accumulator as pressure accumulating means is provided in the middle of an auxiliary pipe connecting a valve operating means and an auxiliary hydraulic pump to a control valve operating means (for example, Japanese Patent Application Laid-Open No. 6-235226).

In such prior art, if the control valve operating means is operated as needed even after the motor is stopped, the control valve can be switched by the pressure oil from the accumulator and the actuator can be driven. For this reason, for example, when the bucket of the working device is stopped in the air due to the stop of the prime mover, to lower this bucket to the ground,
This accumulator is used when driving an actuator.

[0005]

In the above-mentioned prior art, the pressure oil stored in the accumulator may leak from the pilot valve after the motor stops. For this reason, when the time of about 30 seconds to 1 minute usually elapses after the motor stops, there is a problem that the pressure in the accumulator decreases and the actuator cannot be driven.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to maintain the pressure accumulated by the pressure accumulating means for a long time when the prime mover is stopped. To provide a hydraulic drive for a construction machine.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention provides a motor, a main hydraulic pump driven by the motor, and a hydraulic oil discharged from the main hydraulic pump. An actuator, a control valve for controlling the flow of pressure oil supplied to the actuator from the main hydraulic pump, an auxiliary hydraulic pump driven by the prime mover, and controlling the pressure oil discharged from the auxiliary hydraulic pump to The present invention is applied to a hydraulic drive device of a construction machine comprising a control valve operating means for operating a control valve, and a pressure accumulating means provided in an auxiliary pipe connecting the auxiliary hydraulic pump and the control valve operating means.

The first aspect of the present invention is characterized in that stop detection means for detecting that the prime mover is in a stopped state, and the auxiliary position detecting means located between the pressure accumulating means and the control valve operating means. A switching valve provided in the middle of the conduit for communicating between and shutting off the pressure accumulating means and the control valve operating means, and switching the switching valve to a shut-off position when the stop detecting means detects that the motor is in a stopped state. Shut-off signal output means for outputting a shut-off signal; and when the shut-off signal is output by the shut-off signal output means for a predetermined period of time, the output of the shut-off signal is stopped, and the switching valve is switched to the communication position. There is provided a shut-off signal stopping means for enabling.

With this configuration, when the motor stops, the stop detecting means detects that the motor is in a stopped state, and the shut-off signal is output by the shut-off signal output means, thereby setting the switching valve to the shut-off position. Can be switched. Thereby, it is possible to prevent the pressure in the pressure accumulating means from leaking from the control valve operating means,
The pressure in the pressure accumulating means can be kept constant.

The output of the shutoff signal is stopped by the shutoff signal stopping means when a predetermined time has elapsed, and the switching valve is held at the shutoff position, but can be switched to the communication position. Therefore, when the operator wants to drive the actuator, the switch valve is switched to the communication position and the control valve operating means is operated to control the control valve and drive the actuator.

Further, according to a second aspect of the present invention, the switching valve includes:
It is configured by a manual switching valve with an electromagnetic switching function that switches between the communication position and the cutoff position by operating the manual operation unit, and switches from the communication position to the cutoff position when a cutoff signal is input to the electromagnetic pilot unit. .

In this case, during operation of the prime mover, the switching valve can be switched between the communication position and the shut-off position by the manual operation unit, and when the prime mover is stopped, a current is input to the electromagnetic pilot unit to automatically switch the switching valve. It can be switched to the blocking position.

The invention according to claim 3 is configured such that the shut-off signal output means and the shut-off signal stopping means are provided in series between the switching valve and a power supply.

With this configuration, the start of the current supply from the power supply to the electromagnetic pilot unit can be controlled by the cutoff signal output means, and the stop of the current supply can be controlled by the cutoff signal stop means.

Further, the invention according to claim 4 is configured such that the switching valve is switched between a communication position and a blocking position by a lock lever that prohibits and permits a worker to ascend and descend to a driver's seat of a construction machine. .

According to the above configuration, when the operator wants to drive the actuator, the switching valve can be switched to the communication position by operating the lock lever to a position where the worker is prohibited from moving up and down to the driver's seat. By operating the control valve operating means, the control valve can be controlled and the actuator can be driven.

According to a fifth aspect of the present invention, a manual switching valve is provided between the switching valve and the control valve operating means in the middle of the auxiliary pipeline, and the manual switching valve is used for operating a construction machine. A lock lever that prohibits and permits the worker to move up and down the seat is switched between a communication position and a blocking position.

Thus, the auxiliary pipeline can be cut off by the two switching valves, and the pressure by the pressure accumulating means can be maintained for a longer period. When the operator wants to drive the actuator, the operator operates the lock lever to a position where the operator is prohibited from moving up and down to the driver's seat, thereby switching the manual switching valve to the communicating position and switching the switching valve. Is switched to the communication position. At this time, by operating the control valve operating means, the control valve can be controlled and the actuator can be driven.

Further, in the invention according to claim 6, the fixed time is a time for switching the switching valve from the communicating position to the shut-off position.

Therefore, when the prime mover stops, the switching valve can be reliably switched to the shut-off position, and it is possible to prevent the pressure accumulated by the pressure accumulating means from being reduced by stopping the switching valve at the communication position.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description will be given of an example in which a hydraulic drive device for a construction machine according to an embodiment of the present invention is applied to a hydraulic shovel.

FIGS. 1 to 4 show a first embodiment of the present invention, wherein 1 is a lower traveling body, and 2 is a working machine main body mounted on the lower traveling body 1 so as to be pivotable. The upper revolving unit 2 includes an operator cab 3, a machine room 4, and the like, and a work device 5 that performs excavation work and the like is provided to be able to move up and down.

The working device 5 includes a boom 6 pin-connected to the upper swing body 2, an arm 7 serving as a support member pin-connected to the distal end of the boom 6, and a boom 6 connected to the distal end of the arm 7. It is roughly composed of a bucket 8 and the like that are pin-connected. These boom 6, arm 7 and bucket 8 are respectively connected to boom cylinder 9, arm cylinder 10 and bucket cylinder 1 as actuators.
1 and the like.

Reference numeral 12 denotes a driver's seat provided in the driver's cab 3 of the upper swing body 2. In front of the driver's seat 12, a traveling operation pedal 13 provided on the floor of the driver's cab 12 is provided. A travel operation lever 14 that operates in conjunction with the pedal 13 is provided.

Reference numeral 15 denotes control boxes (only one is shown) disposed on both the left and right sides of the driver's seat 12, and a control lever 16 is provided on the upper front side of each control box 15. Then, the operator operates the control lever 16 to control the switching of a pilot valve 25, which will be described later, to control the raising / lowering movement of the working device 5 and the turning of the upper swing body 2.

Reference numeral 17 denotes a lift lever as a lock lever attached near the control box 15, and the lift lever 17 is connected to a switching valve 30 described later. Further, the switching valve 30 is a pilot pipe 24 for pilot pressure which is switched and controlled by the operation pedal 13 or the like.
Communication and shut off.

Therefore, the getting on / off lever 17 is operated to a position A close to the driver's seat 12 as shown by a solid line in FIG. Cut off. As a result, the lower traveling unit 1 is operated by the operation pedal 13 or the traveling operation lever 14.
Is prohibited, and the control lever 16 prohibits the working device 5 from elevating.

On the other hand, the getting on / off lever 17 is moved to the position B near the floor plate away from the driver's seat 12 as shown by the phantom line in FIG. The pipe 24 is connected. This allows
The lower traveling body 1 is permitted to travel by the operation pedal 13 or the traveling operation lever 14, and the working device 5 is permitted to be raised and lowered by the control lever 16.

Next, a hydraulic drive device for a construction machine according to an embodiment of the present invention will be described with reference to a hydraulic circuit diagram of FIG.

Reference numeral 18 denotes a prime mover such as a diesel engine mounted in the machine room 4 of the upper swing body 2.
8 includes a hydraulic pump 19 and a pilot hydraulic pump 2 which will be described later.
3 is connected, and hydraulic oil is discharged from the hydraulic pump 19 and the pilot hydraulic pump 23 by driving the prime mover 18.

Numeral 19 denotes a hydraulic pump which is driven to rotate by a motor 18. The hydraulic pump 19 is composed of main pipelines 20A and 20A.
0B connects to, for example, the boom cylinder 9, the arm cylinder 10, and the bucket cylinder 11 (only the boom cylinder 9 is shown). The hydraulic pump 19 discharges hydraulic oil in the tank 21 toward the boom cylinder 9.

A directional control valve 22 controls the flow of hydraulic oil supplied from the hydraulic pump 19 to the boom cylinder 9. The directional control valve 22 connects between the hydraulic pump 19 and the tank 21. It is provided in the middle of the main pipelines 20A and 20B. The directional control valve 22 is provided with a pair of hydraulic pilot portions 22A and 22B, and the pilot pressure from the pilot valve 25 is supplied to the hydraulic pilot portions 22A and 22B. The switching positions (b) and (c) are switched from (a) to (b), and the hydraulic oil from the hydraulic pump 19 is supplied to and discharged from the boom cylinder 9.

Reference numeral 23 denotes a pilot hydraulic pump as an auxiliary hydraulic pump. The pilot hydraulic pump 23 is connected to pilot portions 22A and 22B by a pilot pipe 24, and the pilot portions 22A and 22B of the direction switching valve 22.
Is supplied with pilot pressure.

Reference numeral 25 denotes a pressure reducing valve type pilot valve as control valve operating means.
The output side is connected to pilot portions 22A and 22B of the directional control valve 22. And
The pilot valve 25 increases or decreases the pilot pressure supplied to the pilot portions 22A and 22B in accordance with the amount of tilting operation of the control lever 16 in the operator's cab 3, and accordingly sets the direction switching valve 22 in the neutral position (a). To the switching positions (b) and (c).

Numeral 26 denotes an accumulator as pressure accumulating means. The accumulator 26 is located between the pilot valve 25 and the pilot hydraulic pump 23 and is connected to the pilot pipe 2.
4 is provided at the tip of a branch pipe 27 which forms a part of the branch pipe 4. The accumulator 26 is connected to the pilot hydraulic pump 2 when the pilot hydraulic pump 23 is rotationally driven.
3, and when the pilot hydraulic pump 23 is stopped, the accumulated hydraulic oil flows out to cause the pilot portions 22A and 22A of the directional control valve 22 to flow out.
The pilot pressure is supplied to 2B.

Numeral 28 is a check valve for preventing pressure oil from flowing backward from the accumulator 26 toward the pilot hydraulic pump 23. Reference numeral 29 denotes a constant pressure relief valve provided between the check valve 28 and the pilot hydraulic pump 23 for setting the discharge pressure of the pilot hydraulic pump 23 to a constant pressure.

Reference numeral 30 denotes a manual switching valve having an electromagnetic switching function (hereinafter, referred to as "switching valve 30") provided between the pilot valve 25 and the accumulator 26 and provided in the middle of the pilot pipe 24. The switch 30 is controlled by a boarding / alighting lever 17 as a manual switching unit. When the boarding / alighting lever 17 is operated to a position A in FIG. The pilot pipe 24 is shut off. On the other hand, the switching valve 30 is switched to the communication position (e) by operating the getting on / off lever 17 to the position B in FIG.
Is to communicate.

The switching valve 30 is provided with an electromagnetic pilot unit 31 such as an electromagnetic solenoid, and a power supply 32 is connected to the electromagnetic pilot unit 31. The electromagnetic pilot section 31 switches the switching valve 30 to the shut-off position (d) when a current serving as a shut-off signal is supplied from the power supply 32. On the other hand, when the current is not supplied from the power supply 32 to the electromagnetic pilot unit 31, the switching valve 30 can be switched between the shut-off position (d) and the communication position (e) by the getting-off lever 17.

Reference numeral 33 denotes a switch serving as a cutoff signal output means.
Is provided in the middle of a wiring 34 connecting the electromagnetic pilot section 31 and is normally opened to prohibit the supply of a current as a cutoff signal to the electromagnetic pilot section 31. Then, when the motor 18 stops and a detection signal is output from a pressure sensor 35 described later, the switch 33 is closed and the motor 18
When the detection signal is not output from the pressure sensor 35 as in the normal operation of the above, the switch 33 is opened. In the case of the present embodiment, as the switch 33, an electromagnetic switch including a coil and a contact is used.

Reference numeral 35 denotes a pressure sensor as stop detection means for detecting that the prime mover 18 is in a stopped state. The pressure sensor 35 is provided in the middle of the pilot pipe 24, and for example, a discharge pressure from the pilot hydraulic pump 23 is drained. When the pressure has decreased to about the pressure, it is detected that the prime mover 18 is in a stopped state, and a detection signal is output to the switch 33.
On the other hand, when the discharge pressure from the pilot hydraulic pump 23 is higher than a predetermined constant pressure, it is detected that the prime mover 18 is operating, and the output of the detection signal is stopped.

Reference numeral 36 denotes a timer serving as a shut-off signal stopping means. The timer 36 is connected to a wiring 34, and a switch 33
Are arranged in series. The timer 36 always connects the switch 33 and the power supply 32 electrically,
Is kept in a state where current can be supplied to the electromagnetic pilot unit 31 from the. When the switch 33 is closed and a current is supplied to the electromagnetic pilot unit 31 for a predetermined period of time T of, for example, about 1 second, the switch 33 and the power supply 32 are electrically cut off, This is to stop the supply of current from 32 to the electromagnetic pilot unit 31.

Here, the certain time T is determined as a time sufficient for the switching valve 30 to switch from the communication position (e) to the shut-off position (d). For this reason, the switching valve 30 is not provided until the fixed time T elapses after the motor 18 stops.
Switches to the shut-off position (d). After a certain time T has elapsed, the switching valve 30 can be switched to the communication position (e) by the getting on / off lever 17.

The hydraulic drive device according to the present embodiment has the above-described configuration, and its operation will be described next with reference to FIG.

First, when the prime mover 18 is driven, hydraulic oil is discharged from the hydraulic pump 19 toward the boom cylinder 9, and pilot pressure is supplied from the pilot hydraulic pump 23 to the hydraulic pilot portions 22A, 22B. Is done.

For this reason, the operator sits on the driver's seat 12 and
By operating the getting on / off lever 17 to the position A, the switching valve 30 is switched to the communication position (e). Next, by tilting the control lever 16 to operate the working device 5, the hydraulic pilot portions 22A, 22A,
By controlling the pilot pressure supplied to 22B, the direction switching valve 22 is switched from the neutral position (a) to the switching positions (b) and (c).

Thus, the boom cylinder 9, the arm cylinder 10, and the bucket cylinder 11 are driven, and the working device 5 can be raised and lowered. At this time, the pressure in the accumulator 26 is accumulated by the pressure oil discharged from the pilot hydraulic pump 23.

Next, a case where the prime mover 18 stops, for example, against the intention of the worker will be described. In this case,
When the motor 18 stops, the hydraulic pump 19 and the pilot hydraulic pump 23 also stop. At this time, the hydraulic pilot portions 22A, 2A of the direction switching valve 22
Since the supply of the pilot pressure to 2B is stopped, the directional control valve 22 stops at, for example, the neutral position (A), the boom cylinder 9 stops, and the working device 5 stops, for example, with the boom 6 raised. Become.

At this time, the discharge pressure from the pilot hydraulic pump 23 also drops to about the drain pressure. Therefore, the pressure is detected by the pressure sensor 35 and the switch 33 is closed. A current is supplied to the unit 31. As a result, the switching valve 30 is switched from the communication position (e) to the shut-off position (d), and the pressure oil in the accumulator 26 is prevented from leaking from the pilot valve 25, for example, for about 5 to 10 minutes. Thus, the pressure in the accumulator 26 can be maintained.

The power supply 32 supplies the electromagnetic pilot unit 31
Is supplied with the current, the timer 36 detects the supply of the current. The timer 36 controls the electromagnetic pilot unit 3 for a predetermined time T, for example, about 1 second.
1, when the current is supplied to the switch 33 and the power supply 3
2 is electrically cut off, and supply of current from the power supply 32 to the electromagnetic pilot unit 31 is stopped.

Here, the predetermined time T is determined as a time sufficient for the switching valve 30 to switch from the communication position (e) to the shut-off position (d), so that the switching valve 30 is reliably set in the shut-off position (d). ). After the elapse of the predetermined time T, the supply of the current to the electromagnetic pilot unit 31 is stopped, so that the switching valve 30 can be switched to the communication position (e) by the getting on / off lever 17.

For this reason, for example, when the motor 18 is stopped with the boom 6 lifted, when lowering the boom 6, the operator operates the getting on / off lever 17 to the position B,
The switching valve 30 is switched to the communication position (e). As a result, the pressure oil in the accumulator 26 is transferred to the hydraulic pilot unit 2.
2A and 22B, the operator tilts the control lever 16 and supplies the pilot pressure from the accumulator 26 to the hydraulic pilot sections 22A and 22B, thereby switching the switching valve 30 from the neutral position (A). It can be switched to the position (b). As a result, the boom cylinder 9 is reduced, so that the boom 6 can be lowered without restarting the prime mover 18.

Thus, in this embodiment, the power sensor 18 detects that the prime mover 18 is stopped by the pressure sensor 35, and supplies the current from the power source 32 to the electromagnetic pilot unit 31 by the operation of the switch 33 and the timer 36. The switching valve 30 is switched to the shut-off position (d). Next, when the current is supplied for a predetermined time T set in the timer 36, the supply of the current is stopped by the timer 36, and the switching valve 30 is brought into a state in which the switching operation can be performed by the getting on / off lever 17. It has a configuration.

Thus, even when the prime mover 18 is stopped against the intention of the operator, it is possible to prevent the pressure oil in the accumulator 26 from leaking from the pilot valve 25, for example, for about 5 to 10 minutes. The pressure in the accumulator 26 can be maintained over a period.

Therefore, 30 minutes after the motor 18 stops.
The boom cylinder 9 can be driven even after a time of about one second to one minute has elapsed. For example, even when the boom 6 or the like is lifted and the prime mover 18 is stopped in an unstable state, the prime mover 18 is not restarted. , The working device 5 can be lowered.

The switching valve 30 is switched between the communicating position (e) and the shut-off position (d) by operating the getting on / off lever 17, and when the electric current is input to the electromagnetic pilot section 31, the communicating position (e) is changed. ) Is switched to the shut-off position (d) by a manually operated valve having an electromagnetic switching function.
0 can be switched between the communication position (e) and the shut-off position (d), and when the prime mover 18 is stopped, a current is input to the electromagnetic pilot unit 31 to automatically switch the switching valve 30 to the shut-off position (d). Can be switched.

Since the switch 33 and the timer 36 are connected in series between the power source 32 and the electromagnetic pilot unit 31, the start of current supply from the power source 32 to the electromagnetic pilot unit 31 can be controlled by the switch 33. The stop of the current supply can be controlled by the timer 36.

Further, since the switching valve 30 is configured to be switched between the communication position (e) and the shut-off position (d) by the getting on / off lever 17, the getting on / off lever 17 is operated to the position A.
When getting on / off to the driver's seat 12 is permitted, the pilot pipe 24 is shut off, the lever 17 for getting on / off is operated to the position B, and when getting on / off to the driver's seat 12 is prohibited, the pilot pipe 24 can be connected. . Therefore, even if the prime mover 18 is stopped, the accumulator 2
In a state where the working device 5 or the like can be operated by the pressure oil in the inside 6, it is possible to prohibit the worker from leaving the driver's seat 12.

The predetermined time T is determined as a time sufficient for the switching valve 30 to switch from the communication position (e) to the shut-off position (d). Therefore, when the motor 18 stops, the switching valve 30 is turned off. The switching to the shut-off position (d) can be surely performed, and a decrease in the pressure of the accumulator 26 from the switching valve 30 can be suppressed.

In the first embodiment, the stop sensor is constituted by the pressure sensor 35. However, the present invention is not limited to this. For example, the stop sensor is constituted by the crank angle sensor 37 shown in FIG. Detection means may be configured. In this case, the rotation speed of the prime mover 18 is detected by the crank angle sensor 37, and is compared with, for example, a predetermined rotation speed sufficiently lower than the rotation speed of the prime mover 18 during steady operation, and the rotational speed of the prime mover 18 is determined. Is lower than a predetermined rotation speed, it is detected that the prime mover 18 is stopped.

Next, FIG. 6 shows a second embodiment of the present invention. This embodiment is characterized in that a manual switching valve which is operated by a lever for getting on and off is provided in the middle of a pilot pipe, and a current is supplied from a power source. Is provided with an electromagnetic switching valve that is switched by supplying the solenoid valve. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, reference numeral 41 denotes a manual switching valve which is provided between the pilot valve 25 and the accumulator 26 and is provided in the middle of the pilot pipe 24. The manual switching valve 41 is connected to the communication position (e) by the lever 17 for getting on and off. ) And the switching position (d).

An electromagnetic switching valve 42 is provided between the first switching valve 41 and the accumulator 26 and is provided in the middle of the pilot pipe 24 as a switching valve.
Is an electromagnetic pilot section 42A made of an electromagnetic solenoid or the like,
42B. The electromagnetic switching valve 42 is switched to the communication position (g) while the prime mover 18 is driven. Further, the electromagnetic switching valve 42 is provided with an electromagnetic pilot section 42.
When the current is supplied to A, the switch is switched to the cut-off position (F), and when the current is supplied to the electromagnetic pilot portion 42B, the switch is switched to the communication position (G).

The electromagnetic pilot section 42A has a first
The power supply 32, the switch 33, and the timer 36 described in the first embodiment are connected via the wiring 34. The switch 33 is connected to a pressure sensor 35.

On the other hand, the power supply 32 is also connected to the electromagnetic pilot portion 42 B of the electromagnetic switching valve 42 via a wiring 43, and a manual operation switch 44 is connected in the middle of the wiring 43. The manual operation switch 44 is normally opened to prohibit current from being supplied to the electromagnetic pilot section 42B. When the electromagnetic switching valve 42 is switched to the shut-off position (f), the operator operates the switch 44.
Is closed, the current is supplied to the electromagnetic pilot section 42B, and the electromagnetic switching valve 42 is switched from the shut-off position (f) to the communication position (g).

In the hydraulic drive apparatus according to the present embodiment having the above-described configuration, when the prime mover 18 is stopped against the intention of the operator, the prime mover is controlled by the pressure sensor 35 as in the first embodiment. When the switch 18 is detected to be in the stop state and the switch 33 is closed, the current from the power supply 32 is supplied to the electromagnetic pilot unit 42A. Further, when a current is supplied to the electromagnetic pilot unit 42A for a predetermined time T, the wiring 34 is electrically cut off by the timer 36, and the supply of the current is stopped.

When driving the boom 6 or the like with the motor 18 stopped, the operator closes the manual operation switch 44 and switches the electromagnetic switching valve 42 from the shut-off position (f) to the communication position (g). . At this time, the manual switching valve 41
Also, by switching to the communication position (e), the pressure oil in the accumulator 26 can be supplied to the hydraulic pilot portions 22A and 22B of the direction switching valve 22. Therefore, by tilting the control lever 16, the direction can be changed. Switching valve 22
Can be switched to drive the boom cylinder 9 and the like. For example, the boom 6 and the like in a raised state can be lowered.

Thus, in the present embodiment having the above-described configuration, the same operation and effect as those of the first embodiment can be obtained. Since the valve 41 is provided, the pilot pipe 24 can be shut off by the manual switching valve 41 and the electromagnetic switching valve 42, and the pressure in the accumulator 26 can be maintained for a longer period.

Although the electromagnetic switching valve 42 is provided in the middle of the pilot pipe 24 in the second embodiment, the present invention is not limited to this. May be provided in the middle of the process.

[0069]

As described in detail above, according to the first aspect of the present invention, when the stop detection means detects that the prime mover is in the stopped state, the shut-off signal for switching the switching valve to the shut-off position from the shut-off signal output means. Is output, and when the shut-off signal is output for a predetermined period of time, the shut-off signal is stopped by the shut-off signal stopping means, and the switching valve can be switched. Thereby, even when the prime mover stops against the intention of the operator, it is possible to prevent the pressure accumulated by the accumulator from leaking from the control valve operating means or the like.
It can be maintained for about 10 minutes.

For this reason, 30 seconds after the motor stops.
Even after a lapse of about one minute, the control valve can be switched, and the actuator can be driven without restarting the prime mover.

According to the second aspect of the present invention, the switching valve is switched between the communication position and the cutoff position by operating the manual operation unit, and is cut off from the communication position when a current is input to the electromagnetic pilot unit. Since the motor is operated by a manual switching valve with an electromagnetic switching function that switches to a position, the switching valve can be switched between a communication position and a shut-off position by a manual operation unit during operation of the prime mover. To automatically switch the switching valve to the shut-off position.

According to the third aspect of the present invention, since the shutoff signal output means and the shutoff signal stopping means are provided in series between the switching valve and the power supply, the electromagnetic pilot of the switching valve is switched from the power supply by the shutoff signal output means. The start of current supply to the unit can be controlled, and the stop of current supply can be controlled by the cutoff signal stopping means.

According to the fourth aspect of the invention, the switching valve is configured to be switched between the communication position and the shut-off position by the lock lever. The auxiliary line connecting the pump and the pressure accumulating means to the control valve operating means is shut off, and when the lock lever prohibits getting on and off the driver's seat, the auxiliary line can be communicated. For this reason, even when the prime mover is stopped, in a state where the actuator can be operated by the pressure of the pressure accumulating means,
It is possible to prohibit the worker from leaving the driver's seat.

According to the fifth aspect of the present invention, since a manual switching valve is provided in the middle of the auxiliary pipeline in addition to the switching valve, the auxiliary pipeline can be shut off by the two switching valves. Can be maintained for a longer period of time.

Furthermore, since the manual switching valve is configured to be switched between the communication position and the blocking position by the lock lever, when the operator wants to drive the actuator,
By operating the lock lever to a position where the worker is prohibited from ascending and descending to the driver's seat, the manual switching valve is switched to the communicating position and the switching valve is switched to the communicating position. At this time, by operating the control valve operating means, the control valve can be controlled and the actuator can be driven.

According to the sixth aspect of the present invention, the fixed time of the cutoff signal stopping means is determined as a time sufficient for the switching valve to switch from the communication position to the cutoff position.
When the prime mover stops, the switching valve can be reliably switched to the shut-off position, and a decrease in the pressure of the pressure accumulating means from the switching valve can be suppressed.

[Brief description of the drawings]

FIG. 1 is an external view showing a hydraulic shovel to which a hydraulic drive device according to a first embodiment of the present invention is applied.

FIG. 2 is a longitudinal sectional view showing a cab according to the first embodiment.

FIG. 3 is a hydraulic circuit diagram showing a hydraulic drive device according to the first embodiment.

FIG. 4 is a characteristic diagram illustrating an operation of the hydraulic drive device according to the first embodiment.

FIG. 5 is a hydraulic circuit diagram showing a modified example of the hydraulic drive device according to the first embodiment.

FIG. 6 is a hydraulic circuit diagram showing a hydraulic drive device according to a second embodiment.

[Explanation of symbols]

 Reference Signs List 9 boom cylinder (actuator) 10 arm cylinder 11 bucket cylinder 17 lever for getting on and off (lock lever) 18 prime mover 19 hydraulic pump (main hydraulic pump) 22 direction switching valve (control valve) 23 pilot hydraulic pump (auxiliary hydraulic pump) 24 pilot piping (Auxiliary pipeline) 25 Pilot valve (control valve operating means) 26 Accumulator (pressure accumulating means) 30 Switching valve 33 Switch (cut-off signal output means) 35 Pressure sensor (stop detecting means) 36 Timer (cut-off signal stopping means) 37 Crank angle Sensor (stop detection means) 41 Manual switching valve 42 Solenoid switching valve 44 Manual operation switch

Claims (6)

[Claims] 1. A motor, a main hydraulic pump driven by the motor, an actuator driven by pressure oil discharged from the main hydraulic pump, and a flow of pressure oil supplied from the main hydraulic pump to the actuator. A control valve for controlling, an auxiliary hydraulic pump driven by the prime mover, control valve operating means for controlling hydraulic oil discharged from the auxiliary hydraulic pump to operate the control valve, and operating the auxiliary hydraulic pump and control valve A hydraulic drive device for a construction machine comprising a pressure accumulating means provided in the middle of an auxiliary pipe connecting the means, a stop detecting means for detecting that the prime mover is in a stopped state, the pressure accumulating means and a control valve operation. A switching valve which is provided between the pressure accumulating means and the control valve operating means and is provided between the pressure accumulating means and the control valve operating means. Shut-off signal output means for outputting a shut-off signal for switching the switching valve to the shut-off position when it is detected that the prime mover is in a stopped state, and outputting the shut-off signal by the shut-off signal output means for a predetermined period of time. And a shut-off signal stopping means for stopping the output of the shut-off signal when the switch is made, and enabling the switching valve to be switched to the communication position. 2. The electromagnetic switching device according to claim 1, wherein the switching valve switches between a communication position and a shut-off position by operating a manual operation unit, and switches from the communication position to the shut-off position when a shut-off signal is input to the electromagnetic pilot unit. The hydraulic drive device for a construction machine according to claim 1, wherein the hydraulic drive device is a manual switching valve with a function. 3. The hydraulic drive device for a construction machine according to claim 2, wherein said shutoff signal output means and shutoff signal stop means are provided in series between said switching valve and a power supply. 4. The switching valve is configured to be switched between a communication position and a blocking position by a lock lever that prohibits and permits a worker to move up and down to a driver's seat of a construction machine. 3. A hydraulic drive for a construction machine according to claim 1. 5. A manual switching valve is provided between the switching valve and the control valve operating means in the middle of the auxiliary pipeline, and the manual switching valve moves an operator up and down to a driver's seat of a construction machine. 2. The hydraulic drive device for a construction machine according to claim 1, wherein the lock lever is configured to be switched between a communication position and a blocking position by a lock lever that prohibits and permits the operation. 6. The fixed time is a time for switching a switching valve from a communication position to a shut-off position.
6. The hydraulic drive device for a construction machine according to 4 or 5.