JP2003166502A - Warming-up system of hydraulic pilot circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently carry out warming-up operation by supplying the hydraulic pressure oil from a hydraulic pump to the tank drain port of a PPC valve, and fluidizing it to the tank port side in the inside of a directional changeover valve to return it to a tank, in the warming-up operation of the pilot circuit in the hydraulic circuit for actuating a working vehicle. <P>SOLUTION: A check valve allowing the flow of the hydraulic pilot oil from a pilot operation valve (PPC valve 4) directing the actuating direction of an actuator 1 and preventing a backward flow from a tank drain is installed in the spool of a directional changeover valve 3. A communication passage formed in the spool side and a communication passage formed in the directional changeover valve body side are arranged opposite to each other, the both communication passages are arranged at a position where they are closed before the pump port of the directional changeover valve 3 and the actuator circuit are opened at the moving time of the spool, and further, an electromagnetic changeover valve 7 changeable to branch pipe line 22 (22') of the hydraulic pump delivery circuit and a tank drain circuit 23 is installed on the tank drain circuit 23 of the PPC 4. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a warm-up system for a hydraulic pilot circuit, which can effectively start a hydraulically-operated working machine in a construction machine at a low temperature.

[0002]

2. Description of the Related Art Conventionally, in a construction machine, for example, a hydraulic working machine provided with a pilot-operated hydraulic circuit in a hydraulic excavator, the working oil temperature is low and the oil viscosity is accordingly high when the working machine is started at a low temperature. In addition, there is a delay in operating the pilot operated valve, resulting in poor operability.
The work machine cannot operate smoothly. In order to avoid such inconvenience and improve operability, many proposals have been made regarding means for supplying high-temperature working oil to the pilot operation circuit in the hydraulic circuit to raise the temperature. Regarding the temperature raising technology of the pilot operated hydraulic circuit at such low temperature,
The following prior art is known.

First, according to Japanese Patent Publication No. 4-29884, a pilot oil chamber for operating a spool of a pilot operated directional control valve for controlling the drive of an actuator,
It has a pilot conduit for connecting a pressure reducing valve (control operation valve) operated by an operation lever, and the pressure reducing valve is a secondary port connected to the pilot oil chamber and a tank port connected to a tank. Is provided in a pilot operation circuit formed so as to communicate at the time of neutrality, and from the pilot oil chamber to a communication path that connects the passage communicating with the return circuit formed in the directional control valve and the pilot oil chamber. The check valve is provided to prevent oil from flowing into the communication path. By doing so, when the pressure reducing valve is in the neutral position, the hydraulic pump is driven so that the hydraulic pressure discharged from the hydraulic pump is formed in the directional control valve through the passage, the connecting passage and the check valve. It is described that it is possible to increase the amount of oil that is guided to the passage and flows through the pilot pipe to increase the oil temperature of the pilot pipe and reduce the viscosity of the pressure oil that flows through the pilot operation circuit.

Further, in Japanese Unexamined Patent Publication No. 2001-182705, when the operation lever is in a neutral position, the discharge oil of the hydraulic pump is circulated from an opening / closing valve on a pilot circuit to a tank via a control operation valve (PPC valve) and There is disclosed a configuration including a circuit configured to return to the tank via a communication passage provided in a spool that is connected to both the pilot pressure receiving chamber of the direction switching valve and the drain chamber to the tank. In this configuration, when the opening / closing valve on the discharge side pilot circuit from the pump is "opened" by the operation signal in the controller during the low temperature operation, the discharge oil is heated by the passage resistance passing through the inside of the PPC valve and warmed up. At the same time, the pressure oil flowing into both pilot pressure receiving chambers of the directional control valve is warmed up by the passage resistance passing through the communication passage connected to the drain chamber provided in the spool of the directional control valve. Is.

Further, in Japanese Patent Laid-Open No. 7-26590, in a hydraulic circuit including a pilot pump, a lock valve is provided between the pilot pump and the pilot valve (control operation valve), and a main control valve is provided downstream of the control operation valve. A temperature raising valve between the pilot pump and the pilot pump, and the temperature raising valve and the switching valve are installed via a relief valve, and the downstream side of the switching valve is connected to the tank via the temperature raising valve and the return circuit. A circulating branch circuit configuration is disclosed. In this configuration, when the lock valve and the switching valve operate integrally and the lock valve is inactive (locked state), the discharge oil of the pilot pump passes from the relief valve through the switching valve to the check valve of the temperature raising valve. Further, the temperature is raised and warmed up by the passage resistance while flowing back to the tank through the pilot valve and the lock valve. On the other hand, when the lock valve is switched to the operating position (unlocking-operation possible), the switching valve integrated with this lock valve is also switched, and the back pressure of the pilot valve drops because it escapes from the return circuit to the tank. The operation is a normal operation hydraulic circuit with a temperature raising device, which can be operated normally without any trouble.

Further, Japanese Patent Laid-Open No. 10-259809 discloses a circuit configuration in which a warm-up switching valve is installed on a discharge circuit between a pilot pump and a pilot valve (control operation valve). There is. The warm-up switching valve can switch between setting and releasing the throttle. This switching detects the circuit oil temperature with an oil temperature sensor, and when the temperature is below the set temperature, switches to the B position with the throttle. Therefore, when the temperature is equal to or lower than the set temperature, the discharge oil of the pilot pump is warmed up by the passage resistance passing through the throttle to raise the temperature of the pilot circuit in a short time. When the temperature exceeds the set temperature, the warm-up switching valve is configured to automatically switch to the A position without a throttle.

[0007]

The above-mentioned prior art has the following problems. That is, in the one disclosed in Japanese Patent Publication No. 4-29884, when the pressure reducing valve (PPC valve) of the pilot circuit is in the neutral position, the spool end of the directional control valve communicates with the return passage, and the spool end A connecting passage communicating with the pilot oil chamber is provided in the valve so that the set pressure of the spring for operating the check valve incorporated in the connecting passage is set to be slightly lower than the back pressure in the return passage of the directional control valve. Therefore, if the main hydraulic pump is operated without warming up (normally), there is a problem that pressure oil flows back to the pilot circuit from the return circuit side. The fact that the pressure oil flows into the pilot circuit in this manner affects the operation of the pilot circuit during normal operation, which is not preferable.

Further, in the system disclosed in Japanese Patent Laid-Open No. 2001-182705, during warm-up operation, the hydraulic pump (variable displacement type) is displaced by the maximum swash plate by the signal S2 from the controller, and is unloaded by the signal Sa. With the set pressure of the valve raised, the pump discharge is drained from the unload valve to the tank to raise the temperature,
And the signal S1 is used to open the on-off valve to open the oil whose temperature is rising to P
It is described that the warm-up effect is enhanced by introducing the temperature into the pilot valve by introducing it into the PC valve. However, during warm-up, the unload valve raises the source pressure of the pump to 4 MPa, so it is necessary to increase the pressure resistance of the pilot pressure receiving chamber of the on-off valve, PPC valve, and directional control valve (specifically, the pressure reducing valve). There is a problem that the set pressure is 3.3 MPa → the unload valve is 4 MPa, the weight is increased by about 20%, the weight and the installation volume are increased, and the cost is naturally increased.
In addition, to increase the temperature of the pilot circuit,
Since it is necessary to add circuits to a total of 12 ports on the secondary side of the valve (usually, 2 sets of ports for working machines and 2 sets for traveling), the number of pipes becomes excessive and the installation volume However, there is a problem in that the cost increases, the cost increases, and the assembly work becomes complicated. The reference numerals in the above description are the same as those in the publication.

Further, in the prior art disclosed in JP-A-7-26590, a temperature raising valve is required for each PPC valve, and a pipe is connected to the secondary side of the PPC valve. In addition, there is a problem that the number of pipes increases, the installation volume increases, the complexity of the assembling work occurs, and the cost increases. This technique is effective in raising the temperature of only the pilot circuit including the PPC valve, but does not actively raise the temperature by utilizing the control valve (direction switching valve).

Further, in the prior art disclosed in the above-mentioned Japanese Patent Laid-Open No. 10-259809, the above-mentioned Japanese Laid-Open Patent Publication No. 7-26590.
Similar to the one disclosed in the publication, the temperature of the pilot circuit including the PPC valve is raised, but this also requires piping for each PPC valve from the warm-up switching valve to each PPC valve,
There is a problem that the number of pipes increases, the installation volume increases, the complexity of the assembling work occurs, and the cost increases. Further, although the pilot circuit including the PPC valve alone has the effect of raising the temperature, it does not actively raise the temperature by utilizing the control valve (direction switching valve).

The present invention has been made in view of the above circumstances, and when warming up the pilot circuit in the hydraulic circuit for operating the working machine, the pressure oil from the hydraulic pump is supplied to the tank drain port of the pilot operated valve. It is an object of the present invention to provide a warm-up system of a hydraulic pilot circuit that can be efficiently supplied and flowed to the tank port side inside the directional control valve and returned to the tank to efficiently perform warm-up operation.

[0012]

In order to achieve the above-mentioned object, a hydraulic pilot circuit warm-up system according to a first aspect of the present invention is provided in a hydraulic pilot circuit warm-up system of a construction machine. On the tank drain circuit of the pilot operated valve that indicates the operating direction, a switching valve that can switch between the discharge circuit of the hydraulic pump and the tank drain circuit is provided.

According to the present invention, in the existing hydraulic circuit for operating the working machine, a switching valve is interposed between the discharge circuit of the hydraulic pump and the tank drain circuit of the pilot operated valve to provide a new connecting line. As a result, the warm-up function can be enhanced, and by configuring the tank drain circuits of the pilot operated valves so that they can pass through the switching valve, the piping can be made smaller, so the installation space can be reduced and the assembly work It is also easy and does not increase the cost. In other words, it is possible to construct the warm-up system of the hydraulic pilot circuit with a simple system.

A warm-up system for a hydraulic pilot circuit according to a second aspect of the present invention is a warm-up system for a hydraulic pilot circuit for construction machinery in which a directional control valve for switching the operating direction of an actuator is provided with a pilot for instructing the operating direction of the actuator. A check valve is provided in a direction that allows the flow of pilot pressure oil from the operation valve and prevents reverse flow from the tank drain, and a communication passage provided on the spool side and a communication passage provided on the direction switching valve body side. When the spool moves, the two communication passages are provided so as to be closed before the pump port of the directional control valve and the actuator circuit are opened.

According to the present invention, when the spool is in the neutral state, the pressure oil from the pilot operated valve is transferred from the pilot pressure receiving chamber of the directional control valve through the check valve in the spool to the communication passage in the spool and the directional control valve. Passing resistance (pressure loss) due to the flow by flowing back from the tank port to the tank through the drain circuit through the communication passage in the body
Can be used for heat conversion to enhance the temperature raising effect. And, when the directional control valve operates in normal time,
Simultaneously with the movement of the spool, the communication passage provided on the spool and the communication passage provided on the valve body side are immediately closed, so that the pilot operation circuit side quickly switches to normal spool operation and operates the direction switching valve normally. You can do it.

In the first invention or the second invention, the pilot operation circuit connected from the secondary side of the pilot operation valve to the pilot pressure receiving chamber of the directional control valve is further provided in the spool of the directional control valve and in the directional control valve. It is preferable that the valve is connected to the tank drain circuit via a communication passage provided in the body of the valve and connected to the neutral state (third invention). By doing so, the discharge oil from the hydraulic pump connected to the tank drain port of the pilot operated valve generates heat due to passage resistance occurring while flowing from the pilot operated pipeline to the internal communication passage of the directional control valve. By utilizing this fact, the temperature of the pressure oil can be raised, and at the same time, the warm-up of the pilot operation circuit and the directional control valve can be promoted.

Further, a warm-up system for a hydraulic pilot circuit according to a fourth aspect of the present invention is the warm-up system for a hydraulic pilot circuit for construction machinery, which has a pilot operation valve for instructing an operating direction of an actuator, A check valve is provided inside the spool in a direction that allows the flow of pilot pressure oil from the pilot operated valve that directs the operating direction of the actuator and prevents the reverse flow from the tank drain. And the communication passage provided on the direction switching valve body side face each other, and when the spool moves, both the communication passages are provided at positions that are closed before the pump port of the direction switching valve and the actuator circuit are opened. , On the tank drain circuit of the pilot operated valve, switchable between a hydraulic pump discharge circuit and a tank drain circuit Valve is characterized in that is provided.

According to the present invention, when performing warm-up operation,
Operate the switching valve between the hydraulic pump discharge circuit and the tank drain circuit to supply the hydraulic pump discharge oil from the tank drain circuit to the pilot operated valve, and then from the pilot operated circuit connected to the secondary side of the pilot operated valve. After passing through the pilot pressure receiving chamber of the directional control valve, open the check valve in the spool end and pass through the communication channel, and from the communication channel provided in the directional control valve body that opens at the neutral position to correspond to the communication channel to the tank. By returning to the tank via the drain port, a large amount of pressure oil can be made to flow and the heat generated by the passage resistance in the passage can be used to increase the efficiency of warm-up.
It is possible to warm up quickly and shift to normal operation in a short time. Of course, when shifting to the normal operation, the directional switching valve is switched by the pilot operating valve by returning the switching valve on the tank drain circuit in the pilot operating circuit to the steady state, and the oil discharged from the hydraulic pump reaches the required actuator. Supplied. Further, in the direction switching valve, the pilot passageway is supplied with the pilot pressure oil, and the communication passage is closed immediately after the spool is moved. Absent.

In the first to fourth aspects of the invention, the switching valve for switching between the hydraulic pump discharge circuit and the tank drain circuit is formed by collecting the tank drain circuits of pilot operated valves that direct each directional switching valve into one. , Is preferably provided on the assembled tank drain circuit (fifth invention). In this way, the piping can be simplified and the directional control valves and their pilot operation circuits can be reliably warmed up all at once.

In the first to fourth inventions, the hydraulic circuit causes the controller to output a command signal for executing warm-up to the switching valve on the basis of a warm-up command from an operating means to raise the temperature to a prescribed oil temperature. Then, the warm-up cancellation command is preferably output from the controller to the switching valve as a command signal (sixth invention). In this case, for example, based on the operator's intention, the operating means arranged near the driver's seat such as a lever switch or a monitor switch is operated, and the oil temperature sensor provided in the hydraulic circuit detects the oil temperature to detect that the temperature is below the specified oil temperature. In this case, the warm-up command is automatically output, and the warm-up function is automatically released when the temperature exceeds the specified oil temperature.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Next, specific embodiments of a warm-up system for a hydraulic pilot circuit according to the present invention will be described with reference to the drawings.

FIG. 1 shows a hydraulic circuit diagram of an embodiment constituting a warm-up system of a hydraulic pilot circuit according to the present invention. FIG. 2 is a schematic view (a) showing a cross section of a main portion of a pilot operating portion of a directional control valve incorporated in the hydraulic circuit shown in FIG. 1 and a cross-sectional view taken along line AA in the drawing (b). There is.

In the warm-up system of the hydraulic pilot circuit of the present embodiment, as shown in FIG. 1, the discharge circuit 20 of the hydraulic pump 2 for operating the actuator 1 has the directional switching valves 3 ... Connected to the
From the direction switching valves 3 ...
Connected to (represented by one actuator 1 in the figure). Those directional control valves 3 ...
The pilot operation circuits 21 and 21 ′ for switching operation of the pilot operation circuit 21 and 21 ′ are provided with an operation lever 5.
It is connected to the pilot pressure receiving chambers 3a and 3b on both sides of the direction switching valve 3 via pressure reducing valves 4a and 4b (referred to as valve 4). A pressure reducing valve 6 is provided near the discharge portion of the hydraulic pump 2 on the pressure oil supply line 22 to the pilot operation circuits 21 and 21 ′, and the discharge circuit 20 to the actuator 1 is provided.
It is designed to supply pressure oil that has been further reduced in pressure. The pilot operating circuits 21 and 21 'are shown as one circuit for the sake of explanation. In addition, the pressure oil supply line 22
Although not shown, each PPC valve 4 is connected via a branching device, and the drain circuit 23 of each PPC valve 4 is likewise connected to the tank 8 by a single conduit via an aggregator (not shown).

On the collecting conduit of the drain circuit 23 connected to the tank drain port T of the PPC valve 4 in the pilot operation circuits 21 and 21 'and returned to the tank 8,
An electromagnetic switching valve 7 is provided, and by this electromagnetic switching valve 7, P
A conduit 22 'branched from a pressure oil supply conduit 22 connected to the input side port P of the PC valve 4 and the drain circuit 23 are switchable. The electromagnetic switching valve 7
Is, for example, an operation switch 10 provided at an appropriate place in the driver's cab.
When the input signal from the controller 11 is output as a switching signal via the controller 11, the solenoid operates and the conduit 22 'connecting the normal drain circuit 23 to the pressure oil supply conduit 22 from the hydraulic pump 2 is connected to the train circuit 23. It has a configuration that can be switched to connect to. In the figure, reference numeral 9 is an oil cooler, 10 is a relief valve, and 12 is an oil temperature sensor.

On the other hand, in the directional control valve 3, as shown in FIG. 2, a valve chamber 33 is formed on the axial center line at both ends of the spool 32, and the valve chamber 33 opens to the outer peripheral surface of the spool 32. A communication passage 34 is formed. In the valve chamber 33, the pilot pressure receiving chamber 3a is normally provided.
A check valve 35 acting in a closing direction toward the side is provided, and a communication passage 36 is provided on the body 31 side of the directional control valve 3 so as to be in communication with the communication passage 34 of the spool 32 so as to communicate with the T port side. Is provided. Incidentally, such a structure is also provided at the opposite end of the spool 3 (not shown).

The check valve 35 in the valve chamber 33 provided at the end of the spool 32 is opposed to the valve seat 35b provided on the inner surface of the cap 37 which is screwed and fixed so as to cover the valve chamber 33 at the end of the spool 32. The valve element 35a is fitted in the back and pressed by a coil spring 35c that applies an urging force, and is slidably inserted in the axial direction, and an oil pressure that overcomes the thrust by the coil spring 35c is applied from the pilot pressure receiving chamber 3a side. It is designed to open when opened. A small-diameter pressure oil inflow hole 38 is provided in the center of the cap 37, and a plurality of grooves 35d are formed in the axial direction on the outer peripheral surface of the valve element 35a, as shown in FIG. 2B. An oil passage is formed.

The positional relationship between the communication passage 34 provided at the end of the spool 32 and the communication passage 36 to the T port provided on the body 31 side of the directional control valve 3 is determined by the spool 3
Both communication passages 34 and 36 in the state where 2 is stopped at the neutral position.
When the spool 32 moves by the switching operation, the communication passages 34 and 36 are closed so that the openings of the above are substantially aligned with each other. The communication passages 34 and 36 are closed at a position slightly before the spool 32 is moved and the P port is switched to communicate with the actuator 1. In the figure, reference numeral 39 is a case cover that forms the pilot pressure receiving chamber 3a, 40 is a spring receiver that is fitted on the end of the spool 32 to apply a biasing force, 41 is a coil spring, and 42 is an inlet for pilot operating oil.

In the present embodiment configured as described above,
When the warm-up operation is performed at a low temperature, after operating the hydraulic pump 2, the operation switch 10 provided at a position suitable for the operator to operate in a driver's cab (not shown) is turned on.
The controller 11 switches the switching solenoid valve 7 from the normal time to the warm-up operation by a program stored in advance, and the drain circuit 23 connected to the tank drain port T of the PPC valve 4 and the pressure connected to the discharge side of the hydraulic pump 2. The oil supply line 22 'is connected. When the pilot operation circuit is warmed up, the PPC valve 4 is kept in a neutral state.

Then, the pressure oil discharged from the hydraulic pump 2 is sent to the drain circuit 23 from the pressure oil supply pipe line 22 'through the pressure reducing valve 6, and the pressure reducing valves 4a and 4b of the PPC valve 4 are supplied.
From the T port through the inside to flow into the pilot operation circuits 21 and 21 'all at once. Pilot operation circuit 2
The pressure oil flowing into 1, 21 'pushes the end of the spool 32 at the neutral position in the pilot pressure receiving chamber 3a of the directional control valve 3, but is urged on both sides to maintain the neutral state. Pressure oil inflow hole 38 provided in the cap 37 at the end
The valve element 35a of the check valve 35 is pushed open to enter the valve chamber 33, and the direction is passed from the communication passage 34 inside the valve chamber 33 through the communication passage 36 on the body 31 side through the groove portion 35d provided around the check valve 35. It flows to the T port of the switching valve 3 and is returned to the tank 8 via the drain circuit 25.

In this state, the hydraulic pump 2 is continuously passed through the drain circuit 23 on the pilot operation circuit side, and the PP
By flowing the pressure oil into the pilot pressure receiving chamber 3a of the directional control valve 3 by causing the reverse flow in the C valve 4, a large amount of the pressure oil passes through the narrow space, so that the passage resistance in the passage increases. The pressure oil that generates heat and flows in a short time rises in temperature. Particularly, in the directional control valve 3, the pilot pressure receiving chamber and the valve chamber 33 in which the check valve 35 is provided in the spool end portion adjacent to the pilot pressure receiving chamber and the communication passages 34 and 36 communicating with the T port are provided in the corresponding portion. Since the flow resistance of is higher than that of other parts, not only the flowing pressure oil but also a part of the valve is raised in temperature, which is useful for promoting the temperature raising effect to reach the state during normal operation.

Eventually, when the temperature of the recirculating oil reaches the specified temperature by the oil temperature sensor 12 provided in the tank 8, the oil temperature sensor 12 outputs a signal to the controller 11, and the controller 11 performs comparison calculation. If it is confirmed that the set temperature has been reached, the command to the electromagnetic switching valve 7 is released and the electromagnetic switching valve 7 is switched to the normal state. At the same time, the operator in the driver's seat is instructed to end the warm-up operation, and normal operation can be started. The instruction from the controller 11 to end the warm-up operation is, for example, when the operation switch 10 for starting the warm-up operation on the operation panel is turned on, the red lamp is turned on, and when the operation is finished, the red lamp is turned off or, for example, the green lamp is temporarily turned on. You should be able to recognize by.

When performing such a warm-up operation, in order to recirculate to the tank 8, the pilot pressure receiving chamber 3a portion of the direction switching valve 3 to the valve chamber 33 of the check valve 35 provided at the end of the spool 32. The pressure oil inflow hole 38 is provided with a small diameter, and the communication passage 34 for communicating the valve chamber 33 and the T port is formed with a small through hole. Even if a pilot pressure is applied to the pilot pressure receiving chamber 3a during normal operation from the pilot operating circuit, the valve element 3 of the check valve 35 is in the initial stage of start-up.
5a tries to open for a moment due to the pressure related to the pressure oil inflow hole 38, but the valve element 33a of the check valve 35 in the valve chamber 33 opens and the throttle resistance in the pressure oil inflow hole 38 and the valve chamber 33 Since the pressure loss due to the sum of the flow resistance and the resistance in the communication passage 34 is large, the pressing force acting on the end surface of the spool 32 is higher than the pressing force flowing in by pushing the valve element 35a, so that the spool 32 does not leak inside. Is moved to smoothly carry out the direction switching operation. The required amount spool 32 slides to close the T port and immediately before the P port opens, the communication passage 34 and the body 3 provided on the spool 32 side.
The opening with the communication passage 36 on the first side is closed so that switching is not hindered. Further, even if both the communication passages 34 and 36 are in the communicating state, the check valve 35 in the valve chamber 33 does not cause the pressure oil to flow backward from the T port side into the pilot pressure receiving chamber 3a.

FIG. 3 is a diagram showing a main part of a hydraulic circuit when a control hydraulic pump is used as another embodiment.

In this embodiment, the technical structure is basically the same as that of the above-mentioned embodiment, and the structure is different in the portion using the control hydraulic pump. Therefore, only different parts will be described in terms of structure, and the description of the same parts as those in the above structure will be omitted and only necessary parts will be denoted by reference numerals.

In the electromagnetic switching valve 7 provided on the drain circuit 23 of the PPC valve, a pipe branched from the pressure oil supply pipe line 22 to the PPC valve from the discharge side of the control hydraulic pump 15 via the relief valve 16. The path 22 'is connected to the controller 1 during the warm-up operation as in the above embodiment.
According to the command from 1, the drain circuit 23 switches the communication to the tank 8 side to the communication to the branched line 22 ′ from the pressure oil supply pipe line 22, and the pressure oil from the control hydraulic pump 15 is transferred to the PPC valve. The tank drain port is connected to the pilot pressure receiving chamber 3a of the directional control valve 3 so that the inside of the spool is returned to the tank via the T port of the directional control valve 3. Also in this method, the function and effect are the same as those in the above-described embodiment.

In the above description, it is premised that the warm-up operation is decided and performed by the operator's intention. However, if the engine is started in the driver's cab on the basis of the outside air temperature, this can be dealt with. It is also possible to make it possible to perform warm-up operation.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment constituting a warm-up system of a hydraulic pilot circuit according to the present invention.

FIG. 2 is a schematic view (a) showing a main section of a pilot operating portion of a directional control valve incorporated in the hydraulic circuit shown in FIG. 1 in section and a sectional view taken along line AA in the figure (b). Is.

FIG. 3 is a diagram showing a main part of a hydraulic circuit when a control hydraulic pump is used as another embodiment.

[Explanation of symbols]

1 actuator 2 hydraulic pump 3-way switching valve 3a Pilot pressure receiving chamber 4 PPC valve (pilot operated valve) 6 Pressure reducing valve 7 Solenoid switching valve 8 tanks 10 Operation switch 11 Controller 12 Oil temperature sensor 15 Control hydraulic pump 16 relief valve 20 discharge circuit 21,21 'Pilot operation circuit 22 Pressure oil supply line 22 'Branch line of pressure oil supply line 23 Drain circuit 31 Directional valve body 32 spools 33 valve chamber 34,36 communication passage 35 Check valve 35a valve 37 cap 38 Pressure oil inlet

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2D003 AA00 AB07 BA01 DA03 EA00                 2D015 BA04 CA01                 3H082 AA08 BB17 CC02 DA17 DB02                       EE01                 3H089 AA50 CC01 DA03 DB43 DB45                       DB48 DB75 EE35 EE36 GG02                       HH09 HH16 JJ01

Claims (6)

[Claims] 1. In a warm-up system for a hydraulic pilot circuit of a construction machine, a switch capable of switching between a discharge circuit of a hydraulic pump and the tank drain circuit on a tank drain circuit of a pilot operated valve that directs an operating direction of an actuator. A warm-up system for the hydraulic pilot circuit, which is equipped with a valve. 2. In a warm-up system for a hydraulic pilot circuit of a construction machine, a flow of pilot pressure oil from a pilot operated valve that indicates the operating direction of the actuator is allowed inside the directional switching valve that switches the operating direction of the actuator. Then, a check valve is provided in a direction to prevent backflow from the tank drain, and the communication passage provided on the spool side and the communication passage provided on the direction switching valve body side face each other, and A warm-up system for a hydraulic pilot circuit, wherein the two communication passages are provided at positions that are closed before the pump port and the actuator circuit of the directional control valve are opened during movement. 3. A pilot circuit connected from the secondary side of the pilot operated valve to the pilot pressure receiving chamber of the directional control valve is further provided in the spool of the directional control valve and in the body of the directional control valve when the neutral position is established. The warm-up system for the hydraulic pilot circuit according to claim 1 or 2, wherein the warm-up system is connected to the tank drain circuit through a connecting communication path. 4. A warm-up system for a hydraulic pilot circuit of a construction machine, comprising a pilot operation valve for instructing an operating direction of an actuator, and a pilot for instructing an operating direction of the actuator inside a spool of the directional control valve. A check valve is provided in a direction that allows the flow of pilot pressure oil from the operation valve to prevent backflow from the tank drain, and a communication passage provided on the spool side and a communication passage provided on the direction switching valve body side are provided. When the spools are moved so as to face each other, the two communication passages are provided at positions that are closed before the pump port of the directional control valve and the actuator circuit are opened, and the hydraulic pressure is provided on the tank drain circuit of the pilot operated valve. A hydraulic pilot circuit characterized in that a switching valve capable of switching between the pump discharge circuit and the tank drain circuit is provided. Warm-up system. 5. A switching valve for switching between the hydraulic pump discharge circuit and the tank drain circuit is a collection of tank drain circuits of pilot operated valves that direct each directional switching valve, and the assembled tank drain circuit. The warm-up system for the hydraulic pilot circuit according to any one of claims 1 to 4, which is provided above. 6. The hydraulic circuit causes a controller to output a command signal for executing warm-up to the switching valve based on a warm-up command from an operating means, and when the temperature rises to a prescribed oil temperature, a warm-up cancellation command is issued from the controller. The warm-up system for the hydraulic pilot circuit according to claim 1, wherein the switching valve outputs the command signal as a command signal.