JPH06280289A - Safety device for automatic refrigerator operation - Google Patents

Abstract

PURPOSE:To prevent the supply of pressure oil from a main hydraulic pump to an actuator, and to maintain a stationary state by forcibly holding a direction changeover valve at a neutral position when a starting switch is turned off during automatic refrigerator operation. CONSTITUTION:When a key switch 5 is turned off from the state of the operation of an engine 1, whether or not a turbo timer switch 20 commanding automatic refrigerator operation is turned on is discriminated. When the timer switch 20 is turned on, an electromagnetic control valve 23 is changed over to a closed position by a driving signal. A timer starts its operation, and operation that the counted number is decreased by one and the result is compared is repeated, and a driving signal is output to an engine stop device 22 from a controller 21 and the engine 1 is stopped when the count reaches zero. The connection of a pilot hydraulic pump 10 and an operating device 11 is interrupted during automatic refrigerator operation, thus keeping the type of a hydraulic shovel at a time when the key switch 5 is changed over to off as it is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a hydraulic working machine such as a hydraulic excavator. When a starting switch for starting a prime mover is turned off, the prime mover is continuously driven for a predetermined time and then the prime mover is stopped. The present invention relates to a safety device for automatic cooling operation.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing a hydraulic drive system of a hydraulic excavator cited as an example of a hydraulic working machine provided with a conventional automatic cooling system, and FIG. 6 is provided in the hydraulic drive system shown in FIG. It is a flow chart which shows a procedure of processing performed by a control device.

A hydraulic drive system shown in FIG. 5 includes a prime mover, that is, an engine 1 and a motor 2 for operating the engine 1.
And a power switch 4 for the motor 2 and a start switch or key switch 5 provided in a signal line 3 connecting the power source 4 and the motor 2 for starting the engine 1.

Further, a main hydraulic pump 6 driven by the engine 1, a pilot hydraulic pump 10, an actuator driven by pressure oil supplied from the main hydraulic pump 6 through a main pipe 9, for example, a swing motor 7, and a main hydraulic pressure. A turning direction switching valve 8 having a neutral position N and operating positions X and Y, and an operating device for switching the turning direction switching valve 8 by controlling the flow of pressure oil supplied from the pump 6 to the turning motor 7. 11, pilot hydraulic pump 10 and operating device 1
1 and a gate lock valve 12 having a gate lock lever 12a. The operating device 11 described above is provided with the pilot conduit 14a.
Via the pressure reducing valve 11a for generating a pilot pressure applied to the drive portion 8a of the turning direction switching valve 8 and the pilot pressure applied to the driving portion 8b of the turning direction switching valve 8 via the pilot conduit 14b. A pressure reducing valve 11b for
It is composed of an operating lever 11c. The gate lock valve 12 described above includes two switching positions: a lock position c that keeps the operating device 11 inoperable and a lock release position d that keeps the operating device 11 in operable.

Further, it has an engine stop device 22 for stopping the operation of the engine 1, a turbo timer switch 20 for instructing an automatic cooling operation of the engine 1, a logical judgment, a storage and an arithmetic function, and a key switch 5 and a turbo timer. The control device 21 receives a signal from the switch 20 and outputs a drive signal for operating the engine stop device 22. The control device 21, the engine stop device 22, the key switch 5, and the turbo timer switch 20 described above, when the key switch 5 is turned off, continue driving the engine 1 for a predetermined time and then stop the engine 1. It constitutes an automatic cooling device that performs automatic cooling operation.

The gate lock valve 12 described above is used.
The pilot pressure from the pilot pump 10 is not supplied to the operating device 11 when the switch is switched to the lock position c shown in FIG. 5, and therefore the turning direction switching is performed even if the operating lever 11c is operated. The valve 8 is not switched, the turning direction switching valve 8 is kept neutral, pressure oil of the main hydraulic pump 6 is not supplied to the turning motor 7, and the turning motor 7 is kept stationary. Also, in FIG.
When it is switched to the lock release position d, the operating device 11 and the pilot pump 10 are connected, and the pressure reducing valve 11 is operated by operating the operating lever 11c.
a or the pressure reducing valve 11b is actuated, and the pilot pressure is transmitted through the pilot pipe line 14a or the pilot pipe line 14b to the drive unit 8a or the drive unit 8 of the turning direction switching valve 8.
b, the turning direction switching valve 8 is switched to the position X or the position Y, the pressure oil of the main hydraulic pump 6 is supplied to the turning motor 7, and the turning motor 7 can be driven.

The automatic cooling operation in this prior art will be described with reference to the flow chart shown in FIG. Control device 2
In step 1, first, as shown in step S21, it is determined whether the engine 1 is in operation, that is, whether the key switch 5 is ON. If this determination is not satisfied, the engine 1 is not in operation. When this determination is satisfied, the engine 1 is in the operating state, and the standby state is formed for the automatic cooling operation. As shown in step S22, the key switch 5
When a signal for turning OFF is input, the process proceeds to step S23. In this step S23, it is determined whether the turbo timer switch 20 for instructing the automatic cooling operation is ON. If this determination is not satisfied, it means that the automatic cooling operation is not intended, the process moves to step S24, and a drive signal is output from the control device 21 to the engine stop device 22 in order to immediately stop the engine 1. When the determination in step S23 described above is satisfied, it means that the automatic cooling operation is intended, and the process proceeds to step S25. In step S25, the timer built in the control device 21 and having the count number corresponding to the cooling machine operation time set in advance is activated, and the process proceeds to step S26. This step S26
Then, a calculation is performed to decrease the count number once, and it is determined whether or not the count number obtained by the calculation is zero. If the determination is not satisfied, the above-described calculation of decreasing the count number once and the determination of whether or not the count number obtained by the calculation is 0 are repeated until the count number becomes 0.
Then, when the count number becomes 0, the process proceeds to step S24, and a drive signal is output from the control device 21 to the engine stop device 22 in order to stop the engine 1.

As described above, in the operating state of the engine 1 when the turbo timer switch 20 is ON, the key switch 5 is turned off to stop the engine 1.
When switched to FF, the engine 1 is stopped after the cooling operation is executed for a predetermined time,
As a result, the components of the engine 1 are gradually cooled to eliminate the adverse effects of heating.

[0009]

By the way, according to the above-mentioned prior art, the key is held with the gate lock valve 12 in the unlocked position d while the turbo timer switch 20 is turned on for the automatic cooling operation. A situation may occur in which the operator turns off the switch 5 and the operator gets out of the cab of the hydraulic excavator. In such a case, when the operation lever 11c of the operation device 11 is moved due to some vibration applied to the vehicle body of the hydraulic excavator or mischief of a child during execution of the automatic cooling operation, the turning direction switching is performed. There is a concern that the valve 8 is switched and the swing motor 7 is driven, the swing body (not shown) swings, and the initial form of the hydraulic excavator changes, which may cause a trouble in work.

The present invention has been made in view of the above-mentioned situation in the prior art, and an object thereof is to provide a safety device for automatic cooling operation which can prevent a situation where an actuator operates in an automatic cooling operation state. It is in.

[0011]

In order to achieve this object, the invention described in claim 1 of the present invention is a prime mover, a hydraulic pump driven by this prime mover, and a discharge from this hydraulic pump. Provided in a hydraulic working machine having an actuator driven by pressure oil, a direction switching valve for controlling the flow of pressure oil supplied from the hydraulic pump to the actuator, and an operating device for switching the direction switching valve. Turn on the start switch that starts the above prime mover.
In FF, in a safety device for automatic cooling operation that stops the driving of the prime mover after continuing the driving of the prime mover for a predetermined time, the OF of the start switch during the automatic cooler operation
The structure is provided with holding means for forcibly holding the directional control valve at the neutral position in conjunction with the F operation.

The invention described in claim 2 is such that a prime mover, a hydraulic pump driven by the prime mover, an actuator driven by pressure oil discharged from the hydraulic pump, and the actuator supplied from the hydraulic pump. Directional control valve for controlling the flow of pressure oil, an operating device for switching the directional control valve, a lock position for keeping the operating device inoperable, and an unlocked position for keeping the operating device operable. Provided in a hydraulic working machine having a gate lock valve including two switching positions of
When the start switch for starting the prime mover is turned off, the gate lock valve is switched to the unlocked position in an automatic cooling operation safety device for stopping the prime mover after continuing driving of the prime mover for a predetermined time. In this state, when the switch is turned off, the stopping means for immediately stopping the prime mover is provided.

[0013]

Since the invention according to claim 1 of the present invention is configured as described above, when the starting switch of the prime mover is turned off during the automatic cooling operation, the directional switching valve is forced by the holding means. Is kept in a neutral position, which prevents the supply of pressure oil from the main hydraulic pump to the actuator controlled by the directional valve, and ensures that the actuator remains stationary even during automatic cooling operation. can do.

Further, the invention according to claim 2 is in a state in which the automatic cooling operation is intended, and further, in a state in which the gate lock valve is switched to the unlocked position,
When the starting switch of the prime mover is turned off, the prime mover is immediately stopped by the stopping means without performing the automatic cooling operation. Therefore, the drive of the main hydraulic pump driven by the prime mover is also immediately stopped, whereby the supply of pressure oil from the main hydraulic pump to the actuator is blocked, and the actuator can be reliably maintained in a stationary state.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a safety device for automatic cooling operation according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a hydraulic drive system of a hydraulic excavator to which a first embodiment of a safety device for automatic cooling operation of the present invention corresponding to claim 1 is applied, and FIG. 2 is a first embodiment shown in FIG. It is a flow chart which shows the procedure of the processing performed by the control device with which an example is equipped.

FIG. 1 is drawn corresponding to FIG. 5 described above. Therefore, the same reference numerals as those in FIG. 5 described above indicate equivalent ones. That is, even in the hydraulic drive system shown in FIG. 1, a prime mover, that is, an engine 1, a motor 2 for operating the engine 1, a power source 4 for the motor 2, and a signal for connecting the power source 4 and the motor 2 to each other. A start switch or key switch 5 provided in the line 3 for starting the engine 1, and
A main hydraulic pump 6 driven by the engine 1, a pilot hydraulic pump 10, and an actuator driven by pressure oil supplied from the main hydraulic pump 6 via a main pipeline 9.
For example, a turning motor 7, a turning direction switching valve 8 for controlling the flow of pressure oil supplied from the main hydraulic pump 6 to the turning motor 7, and having a neutral position N and operating positions X and Y, and this turning direction switching. An operating device 11 for switching and operating the valve 8, and a conduit 1 for connecting the pilot hydraulic pump 10 and the operating device 11
3 and a gate lock valve 12 having a gate lock lever 12a.

The operating device 11 described above includes a pressure reducing valve 11a for generating a pilot pressure applied to the drive portion 8a of the turning direction switching valve 8 via the pilot conduit 14a, and a turning direction via the pilot conduit 14b. Pressure reducing valve 11 for generating pilot pressure applied to drive portion 8b of switching valve 8
b and an operating lever 11c, the gate lock valve 12 described above has a lock position c that keeps the operating device 11 inoperable and a lock release position d that keeps the operating device 11 operable. Includes two switching positions.

Further, the engine stop device 22 for stopping the operation of the engine 1, the turbo timer switch 20 for instructing the automatic cooling operation of the engine 1, the logical judgment, storage, and arithmetic functions are provided, and the key switch 5 and the turbo timer are provided. The control device 21, which receives the signal from the switch 20 and outputs a drive signal for operating the engine stop device 22, is provided. The control device 21, the engine stop device 22, the key switch 5, and the turbo timer switch 20 are provided. When the key switch 5 is turned off, the engine 1 is continuously driven for a predetermined time, and then the engine 1 is stopped to perform an automatic cooling operation.

The above-mentioned components are the same as those shown in FIG.

In particular, in the first embodiment, an electromagnetic control valve 23 capable of controlling the opening and closing of the pipeline 13 is provided in the pipeline 13 portion located between the pilot pump 10 and the gate lock valve 12. The electromagnetic control valve 23 is driven by a drive signal output from the control device 21. The electromagnetic control valve 23 forcibly neutralizes the turning direction switching valve 8 in synchronism with the OFF operation of the key switch 5 during the automatic cooling operation by the automatic cooling device including the control device and the turbo timer switch 20 described above. It constitutes a holding means for holding the position.

The operation of this first embodiment is as follows. First, general operations other than the cooling operation will be described, and the relationship of the cooling operation will be described later. When the key switch 5 is turned on while the engine 1 is stopped, the motor 2 is activated and the engine 1 is driven. Along with this, the main hydraulic pump 6 and the pilot hydraulic pump 10 are driven.
By the ON operation of the key switch 5 described above, the control device 21 outputs a drive signal, that is, a high level signal to the drive unit of the electromagnetic control valve 23. As a result, the electromagnetic control valve 23 is switched to the open position against the force of the spring. When the gate lock lever 12a is operated to switch the gate lock valve 12 to the unlocked position d in FIG. 1, the pilot hydraulic pump 10 and the operating device 11 are connected via the electromagnetic control valve 23 and the gate lock valve 12. The operated state, that is, the operating device 11 is in the operable state.

When the operating lever 11c of the operating device 11 is operated from such a state, the pressure reducing valve 11a or the pressure reducing valve 11b is driven, and pilot pressure is generated in the pilot conduit 14a or the pilot conduit 14b. It is given to the drive unit 8a or the drive unit 8b of the switching valve 8. As a result, the turning direction switching valve 8 is switched to the position X or the position Y, and the pressure oil discharged from the main hydraulic pump 6 is supplied to the turning motor 7 via the turning direction switching valve 8. As a result, the swing motor 7 is driven, and the swing body (not shown) is driven.

When the gate lock lever 12a is operated to switch the gate lock valve 12 to the lock position c shown in FIG. 1 from the above state, the connection between the pilot hydraulic pump 10 and the operating device 11 is cut off, Operating device 1
The pilot pressure is not supplied to 1. That is, the operating device 11 is in an inoperable state in which it does not operate even if the operating lever 11c is operated. At this time, the turning direction switching valve 8 is switched to the neutral position N by the force of the springs provided on both sides, and the connection between the main hydraulic pump 6 and the turning motor 7 is cut off. Therefore, no pressure oil is supplied to the turning motor 7, and the turning motor 7 is held stationary. Along with this, the revolving structure (not shown) is also held stationary.

Next, the operation of the first embodiment included in the hydraulic drive system shown in FIG. 1, that is, the related operation of the automatic cooling operation will be described.

First, the control device 21 determines whether the engine 1 is in operation, that is, whether the key switch 5 is ON, as shown in step S1. If this determination is not satisfied, the engine 1 is not in operation. When this determination is satisfied, the engine 1 is in the operating state, and the standby state is formed for the automatic cooling operation. As shown in step S2, when a signal for turning off the key switch 5 is input from the operating state of the engine 1, the process proceeds to step S3. In this step S3, it is determined whether or not the turbo timer switch 20 for instructing the automatic cooling operation is ON. If this determination is not satisfied, it means that the automatic cooling operation is not intended, the process moves to step S4, and a drive signal is output from the control device 21 to the engine stop device 2 in order to immediately stop the engine 1. The steps S1, S2, S3, and S4 described above are the same as those shown in FIG.

When the determination in step S3 shown in FIG. 2 is satisfied, it means that the automatic cooling operation is intended, and the process proceeds to step S5. In this step S5, a signal of 0, that is, a low level signal is output to the drive unit of the electromagnetic control valve 23. As a result, the electromagnetic control valve 23 shown in FIG. 1 is switched to the closed position by the force of the spring. Procedure S described above
After 5, the procedure moves to step S6. In step S6, the timer built in the control device 21 and having the count number corresponding to the cooling machine operating time set in advance becomes the operation start state, and the process proceeds to step S7. In this step S7, a calculation is performed to decrease the count number once, and it is determined whether the count number obtained by the calculation is 0 or not. If the determination is not satisfied, the above-described calculation of decreasing the count number once and the determination of whether or not the count number obtained by the calculation is 0 are repeated until the count number becomes 0. Then, when the count number becomes 0, the process moves to the above-described step S4, and a drive signal is output from the control device 21 to the engine stop device 22 in order to stop the engine 1.

In the first embodiment thus constructed, as in the prior art shown in FIG. 5, the engine 1 is operated in the operating state when the turbo timer switch 20 is ON. When the key switch 5 is turned off to stop the engine 1, the engine 1 is stopped after the cooling operation is performed for a predetermined time, whereby the components of the engine 1 are gradually cooled, and the adverse effects of heating are eliminated. be able to. And, in particular, since the electromagnetic control valve 23 is switched to the closed position during the automatic cooling operation, the connection between the pilot hydraulic pump 10 and the operating device 11 is cut off, and therefore the gate lock lever 12 is switched to the unlocked position d. The operating device 11 due to vibrations given to the vehicle body or mischief of a child while in a standing state.
Even if the operating lever 11c of No. 3 is moved, the operating device 11 is kept in the inoperative state, and the turning direction switching valve 8 is in the neutral position N.
Therefore, the swing motor 7 does not operate, and accordingly, the swing body (not shown) also does not swing. That is, the form of the hydraulic excavator when the key switch 5 is turned off can be maintained as it is,
There is no concern that work will be hindered due to the above-mentioned change in form.

FIG. 3 is a circuit diagram showing a hydraulic drive system for a hydraulic excavator to which the second embodiment of the present invention is applied, and FIG. 4 is shown in FIG.
6 is a flowchart showing a procedure of processing executed by a control device provided in the second embodiment shown in FIG.

In the second embodiment shown in FIG. 3, instead of providing the electromagnetic control valve 23 as in the first embodiment, a gate lock switch 18 interlocking with the gate lock lever 12a is provided. The gate lock switch 18 is connected to the control device 21, and the gate lock valve 12
Gate lock lever 12a so that
Is turned off when is operated, and gate lock valve 1
It is configured to be turned on when the gate lock lever 12a is operated so that 2 is in the unlocked position d. In the control means 21, the gate lock switch 18 is turned on.
At this time, when the key switch 5 is switched from the ON state to the OFF state, even if the turbo timer switch 20 is ON and the automatic cooling operation is intended, the engine stop device 22 is provided to immediately stop the engine 1. The drive signal is output to the. That is, the control device 21 and the gate lock switch 18 are a stop means for immediately stopping the engine 1 when the key switch 5 is turned off in the state where the gate lock valve 12 is switched to the unlock position d. Are configured. For other configurations, the first configuration shown in FIG.
It is equivalent to the embodiment of.

Regarding the formation of the inoperative state and the operable state of the operating device 11 due to the drive of the turning motor 7 by the operation of the operating device 11 and the switching of the gate lock valve 12 in the second embodiment thus constructed, The description is omitted because it is the same as the first embodiment.

In the second embodiment, the related operation of the automatic cooling operation is controlled as follows. That is, as shown in FIG. 4, in the control device 21, first, in step S11, it is determined whether the engine 1 is in operation, that is, the key switch 5
Is determined to be ON, and when this determination is satisfied, the engine 1 is in the operating state, and the standby state is formed for the automatic cooling operation. As shown in step S12, the key switch 5 is turned off from the operating state of the engine 1.
When the signal for setting F is input, the process proceeds to step S13. In this step S13, it is determined whether or not the turbo timer switch 20 for instructing the automatic cooling operation is ON. If this determination is not satisfied, it means that the automatic cooling operation is not intended, the process moves to step S14, and a drive signal is output from the control device 21 to the engine stop device 2 to immediately stop the engine 1. When the determination in step S13 described above is satisfied, it means that the automatic cooling operation is intended, and the process proceeds to step S15. In this step S15, a timer built in the control device 21 and having a preset number of counts corresponding to the cooling machine operating time is activated, and the process moves to step S16. In this step S16,
It is determined whether the gate lock switch 18 is OFF, that is, whether the gate lock valve 12 is switched to the lock position c. If this determination is not satisfied, the gate lock valve 12 is in the unlocked position d and the operating device 11 is operable, and the procedure S1 is performed.
Go to 4. In step S14, as described above, the drive signal is output from the control device 21 to the engine stop device 2 in order to stop the engine 1.

When the gate lock switch 18 is determined to be OFF in the determination in step S16 described above, the process proceeds to step S17. In this step S17, a calculation for reducing the count number by one is performed, and it is determined whether or not the count number obtained by the calculation is 0. If the determination is not satisfied, steps S16 and S1
The processing of 7 is repeated, and until the count number becomes 0, the above-described calculation for reducing the count number by 1 and determination as to whether or not the count number obtained by the calculation is 0 are performed. During such processing, the gate lock lever 1
When the gate lock valve 12 is switched to the unlocked position d by operating 2a, the determination in step S16 is satisfied, so the process proceeds to step S14, and the control for immediately stopping the engine 1 is performed. When it is determined in step S17 that the count number has reached 0, the process proceeds to step S4, and a drive signal is output from the control device 21 to the engine stop device 22 to stop the engine 1.

In the second embodiment thus constructed, the gate lock valve 12 is switched to the lock position c,
When the key switch 5 is turned off in order to stop the engine 1 while the turbo timer switch 20 is turned on, the engine is run after the cooling operation is performed for a predetermined time as in the first embodiment. 1 is stopped, whereby the components of the engine 1 are gradually cooled, and the adverse effects of heating can be eliminated. Then, in particular, when the gate lock valve 12 is switched to the unlocked position d and the operation device 11 is operable and the key switch 5 is switched to OFF, the control device 21
A drive signal is immediately output from the engine stop device 22 to stop the engine 1. Further, even during the automatic cooling operation, when the gate lock valve 12 is switched to the unlocked position d, a drive signal is immediately output from the control device 21 to the engine stop device 22 and the engine 1 is stopped. Therefore, the operation device 11 does not accidentally operate during the cooling operation, and the revolving structure (not shown) does not revolve accordingly. That is,
Similar to the first embodiment, the form of the hydraulic excavator when the key switch 5 is turned off can be maintained as it is, and there is no concern that work problems will occur due to the change in the form.

In the above embodiment, the turning motor 7 is used as the actuator and the turning direction switching valve 8 is used as the direction switching valve. However, the present invention is not limited to this, and the actuator may be a traveling motor, a boom cylinder, or an arm. It may be a cylinder, a bucket cylinder, or the like, and the direction switching valve may be a traveling direction switching valve, a boom direction switching valve, an arm direction switching valve, or a bucket direction switching valve.

Further, in the above embodiment, the pilot operation system in which the turning direction switching valve 8 is switched by the pilot pressure is illustrated, but the direction switching valve is formed by an electromagnetic switching valve.
The electromagnetic switching valve may be switched by an electric operation method.

[0036]

Since the present invention is configured as described above, it is possible to prevent the actuator from operating in the automatic cooling operation state and to keep the form of the hydraulic working machine when the start switch is OFF. In addition, there is no fear of causing a trouble in the work due to a change in the form of the hydraulic working machine due to a malfunction of the actuator during the operation of the conventional automatic cooling machine.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a hydraulic drive system of a hydraulic excavator to which a first embodiment of a safety device for automatic cooling operation according to the present invention is applied.

FIG. 2 is a flowchart showing a procedure of processing executed by a control device provided in the first embodiment shown in FIG.

FIG. 3 is a circuit diagram showing a hydraulic drive system for a hydraulic excavator to which a second embodiment of the present invention is applied.

FIG. 4 is a flowchart showing a procedure of processing executed by a control device provided in the second embodiment shown in FIG.

FIG. 5 is a circuit diagram showing a hydraulic drive device of a hydraulic excavator taken as an example of a hydraulic working machine provided with a conventional automatic cooling machine operating device.

6 is a flowchart showing a procedure of processing executed by a control device provided in the hydraulic drive system shown in FIG.

[Explanation of symbols]

 1 Engine (Motor) 2 Motor 3 Signal Line 4 Power Supply 5 Key Switch (Start Switch) 6 Main Hydraulic Pump 7 Swing Motor (Actuator) 8 Swing Directional Change Valve 8a Drive 8b Drive 9 Main Pipeline 10 Pilot Hydraulic Pump 11 Operating Device 11a Operating lever 11b Pressure reducing valve 11c Pressure reducing valve 12 Gate lock valve 12a Gate lock lever 13 Pipe line 14a Pilot line 14b Pilot line 18 Gate lock switch 20 Turbo timer switch 21 Control device 22 Engine stop device 23 Electromagnetic control valve

Claims (2)

[Claims] 1. A prime mover, a hydraulic pump driven by the prime mover, an actuator driven by pressure oil discharged from the hydraulic pump, and a direction for controlling the flow of pressure oil supplied from the hydraulic pump to the actuator. A hydraulic working machine having a switching valve and an operating device for switching the directional switching valve is provided, and when a start switch for starting the prime mover is turned off, after continuing driving of the prime mover for a predetermined time, A safety device for an automatic cooling operation for stopping a prime mover, comprising: holding means for forcibly holding the directional switching valve in a neutral position in conjunction with an OFF operation of the start switch during the automatic cooling operation. Safety device for automatic cooling operation. 2. A prime mover, a hydraulic pump driven by the prime mover, an actuator driven by pressure oil discharged from the hydraulic pump, and a direction for controlling the flow of pressure oil supplied from the hydraulic pump to the actuator. A gate lock including a switching valve, an operating device for switching and operating the directional switching valve, a lock position for keeping the operating device in an inoperable state, and a lock release position for keeping the operating device in an operable state. In a safety device for automatic cold machine operation, which is provided in a hydraulic working machine having a valve, and when the start switch for starting the prime mover is turned off, after continuing driving of the prime mover for a predetermined time, the prime mover is stopped. With the gate lock valve switched to the unlocked position, switch the switch to OFF. Safety device for an automatic cold operation, characterized in that it comprises a stopping means for immediately stopping the motor when.