JPH0726589A - Pilot operation oil pressure circuit of construction machine - Google Patents

Abstract

PURPOSE:To improve performance, by changing over the discharge hydraulic oil path of a pilot relief valve and supplying the most of discharge oil to a pilot circuit on warming up operation and cutting off the discharge oil supplied to a temperature rising valve after the oil temperature has been increased. CONSTITUTION:When a lock valve 10 is placed in its inoperative position and a changeover valve 21 is changed over to the circuit A-A', the whole discharge oil of a pilot relief valve 7 flows in the circuit A-A'. The hydraulic oil flows through a temperature rising valve 9 at the pressure of a full flow filter 11 plus a pressure equivalent to the pressure loss in the pipe from the temperature rising valve 9 to a filter 11 so as to heat a pilot valve 8 and a pilot pipe line in a short time. When the valve 21 is changed over to a circuit directly connected to a hydraulic oil tank 3 through the filter 11, the whole discharge oil flows to a circuit B and the hydraulic oil supply to the circuit A-A' is blocked. When the valve 10 is changed over to the working position, the inner pressure of the circuit from the valve 8 to the tank 3 is lowered down to the tank pressure. In this way, the warming up operation can be efficiently carried out and the back pressure of pilot valve can be decreased. And hence, the operational force can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pilot operated hydraulic circuit for a construction machine, and more particularly to a technique for preventing deterioration of operability of the pilot valve in a pilot operated hydraulic circuit provided with a temperature raising valve.

[0002]

2. Description of the Related Art A construction machine having a pilot-operated hydraulic circuit has a low hydraulic oil temperature immediately after the engine is started at a low temperature, and therefore has a high hydraulic oil viscosity. Stop delay is likely to occur when the operation of is stopped. In order to avoid such an inconvenience and improve operability and safety, a pilot operation hydraulic circuit of a construction machine has often been provided with a temperature raising device for supplying high-temperature working oil to the pilot circuit.

FIG. 6 shows a first example of a pilot operated hydraulic circuit with a temperature raising device which is conventionally mounted on a hydraulic excavator or the like. As shown in the figure, the pilot operation hydraulic circuit of this example includes a main pump 1, a pilot pump 2, a hydraulic oil tank 3, a main relief valve 4, a control valve 5, an actuator 6, and a pilot relief valve. 7
A pilot valve 8, a temperature raising valve 9, a lock valve 10,
It is mainly composed of a full flow filter 11.

The pilot valve 8 changes the flow path of the hydraulic oil supplied from the pilot pump 2 via the lock valve 10, and switches the control valve 5. Control valve 5
Is operated by the pilot valve 8 and the main pump 1
The actuator 6 is driven by changing the flow path of the hydraulic oil discharged from the. The lock valve 10 opens and closes a circuit from the pilot pump 2 to the pilot valve 8 and a circuit from the pilot valve 8 to the hydraulic oil tank 3.
By switching to the closed state, the supply of hydraulic oil from the pilot pump 2 to the pilot valve 8 is prohibited, and the pilot valve 8 is put into the operation prohibited state. The main relief valve 4 controls the discharge pressure of the main pump 1, and the pilot relief valve 7 controls the discharge pressure of the pilot pump 2. The full flow filter 11 filters the return oil to the hydraulic oil tank 3, and acts as a kind of throttle on the return pipe line.

The temperature raising valve 9 includes two check valves 9a and 9b.
And is provided in the pilot circuit that connects the pilot valve 8 and the control valve 5. The operating oil supply end of the temperature raising valve 9 is connected to the pilot pump 2 via the pilot relief valve 7, and the operating oil discharge end is connected to the operating oil tank 3 via the full flow filter 11. There is. Therefore, the hydraulic oil discharged from the pilot relief valve 7 passes through the temperature raising valve 9, flows into the full flow filter 11, and further flows into the hydraulic oil tank 3.

Since the viscosity of the hydraulic oil is high at low temperatures, the pressure loss of the full flow filter 11 and the pressure loss of the conduit from the temperature raising valve 9 to the full flow filter 11 are large. On the other hand, the tank port T of the pilot valve 8 is connected to the hydraulic oil tank 3 via the lock valve 10,
The hydraulic oil discharged from the pilot relief valve 7 has a pressure corresponding to the above-mentioned pressure loss, and the check valves 9a, 9
It flows into the pilot line from b and flows into the hydraulic oil tank 3 through the pilot valve 8 and the lock valve 10. Here, the hydraulic oil discharged from the pilot relief valve 7 is
It is heated for throttling, and the pilot valve 8 and the pilot line are warmed by the flow of the hydraulic oil.

FIG. 7 is a diagram showing a second example of a pilot operating hydraulic circuit with a temperature raising device which is conventionally mounted on a hydraulic excavator or the like, and the circuit of this example is the first conventional type shown in FIG. A pipeline directly connected to the full flow filter 11 is branched from an outlet pipeline of the pilot relief valve 7 in the circuit according to the example. Also in the pilot operated hydraulic circuit with the temperature raising device of the present example, the pressure loss of the full flow filter 11 has a large value at a stage where the viscosity of the hydraulic oil is large at low temperature, and therefore the pressure is discharged from the pilot relief valve 7. The hydraulic oil flows into the pilot conduit via the check valves 9a and 9b in the temperature raising valve 9, and the pilot valve 8 and the pilot conduit are warmed.

[0008]

However, in all of the temperature raising devices having the above-mentioned structure, the tank port T of the pilot valve 8 is used.
Since the lock valve 10 and the pipeline having a considerable length exist between the hydraulic oil tank 3 and the hydraulic oil tank 3, the hydraulic oil flowing from the temperature raising valve 9 to the hydraulic oil tank 3 causes a pressure loss. Therefore, even after the entire circuit is sufficiently warmed, this pressure acts as a back pressure of the pilot valve 8 during the switching operation of the pilot valve 8, and the lever operating force of the pilot valve 8 becomes heavy. In addition to the above-mentioned inconveniences, the device according to the second conventional example directly receives the exhaust oil from the pilot relief valve 7 directly into the full flow filter 11
The conduit B returning to the full-flow filter 1 is configured to return the residual oil discharged from the pilot relief valve 7 supplied to the temperature raising valve 9 to the full-flow filter 1
Since the resistance is smaller than that of the conduit A-A 'for returning to 1, the discharge oil from the pilot relief valve 7 mostly flows through the conduit B to the full flow filter 11 directly. In particular, the lower the temperature of the hydraulic oil becomes, the more remarkable such a phenomenon occurs, so that there is a disadvantage that the temperature raising efficiency of the pilot valve 8 and the pilot conduit is poor.

The present invention has been made in order to solve the inconveniences of the prior arts, and its purpose is to increase the temperature raising efficiency of the pilot valve and the pilot pipe line and to raise the oil temperature of the hydraulic oil. It is an object of the present invention to provide a pilot operating hydraulic circuit with a temperature raising device in which back pressure does not act on the pilot valve when the operation of 1 is started and therefore the lever operating force does not become heavy.

[0010]

In order to achieve the above object, the present invention provides a pilot valve, a control valve operated by the output pressure of the pilot valve, and a pilot pump having one end through a pilot relief valve. Temperature rise, which is connected and whose other end is provided in a circuit connected to a hydraulic oil tank through a filter and which supplies hydraulic oil discharged from the pilot relief valve to a circuit connecting the pilot valve and the control valve In a pilot operated hydraulic circuit provided with a valve, a switching valve is provided in the outlet circuit of the pilot relief valve, and the discharge oil from the pilot relief valve is connected to the hydraulic oil tank via the temperature raising valve and the filter, Alternatively, it is configured to selectively flow to a circuit directly connected to the hydraulic oil tank via the filter.

The switching valve may be a manual valve or an electromagnetic valve. When an electromagnetic valve is used as the switching valve, it can be switched by a manual switch arranged at a desired position, or a temperature sensor for detecting the temperature of the hydraulic oil flowing in the temperature raising valve. It is also possible to automatically switch by a signal from. Furthermore, it is possible to switch automatically by a signal from a temperature sensor that detects the temperature of the hydraulic oil stored in the hydraulic oil tank.

[0012]

By providing a switching valve in the outlet circuit of the pilot relief valve so that the oil discharged from the pilot relief valve is selectively flown to the temperature raising valve or the filter, the temperature of the switching valve is raised during the warming operation. By switching to the valve side, the exhaust oil from the pilot relief valve can be made to flow through the pilot pipe, so that the pilot valve and the pilot pipe are warmed.

When the switching valve is switched to the filter side at the stage of completion of warming up, the working oil discharged from the pilot relief valve flows to the working oil tank through the filter, so that the working oil is supplied to the temperature raising valve. Be refused. Therefore, the back pressure acting on the pilot valve is reduced, and the lever operating force of the pilot valve is reduced to the level of a circuit having no temperature increasing valve. Therefore, the operation of the actuator can be made smooth and reliable.

If the switching valve is manually switched, the construction machine can be started as needed regardless of the degree of warm air, which is convenient to use. Further, if the switching valve is automatically switched by the signal from the temperature sensor, it is not necessary to switch the switching valve after confirming whether warm-up is completed or not completed, which is convenient to use.

[0015]

【Example】

<First Embodiment> FIG. 1 shows the configuration of a pilot operation hydraulic circuit according to the first embodiment. As shown in the figure, the pilot operated hydraulic circuit circuit of this example is the pilot relief valve 7 in the conventional pilot operated hydraulic circuit circuit shown in FIG.
A manual switching valve 21 is provided at the outlet circuit of the circuit, and the oil discharged from the pilot relief valve 7 is connected to the hydraulic oil tank 3 via the temperature raising valve 9 and the full flow filter 11, or the hydraulic oil is supplied via the full flow filter 11. It is characterized in that the liquid is selectively flown to a circuit directly connected to the tank 3. Since the other parts are the same as those in the circuit of FIG. 4, corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

In the pilot operated hydraulic circuit circuit with the temperature raising device of the present embodiment, the lock valve 10 is switched to the inoperative position (state shown in the drawing) during warm-up operation, and the switching valve 21 is used for the temperature raising valve 9 and the full flow filter. It is switched to a position (state shown) through which the oil discharged from the pilot relief valve 7 flows to the circuit AA ′ connected to the hydraulic oil tank 3 via 11. At this time, the entire amount of the oil discharged from the pilot relief valve 7 flows to the circuit A-A ', and the hydraulic oil causes the pressure loss of the filter 11 and the pressure of the line pressure loss from the temperature raising valve 9 to the filter 11 to be the same. Flows to the temperature raising valve 9, and the pilot valve 8 and the pilot pipe are warmed. When the temperature of the hydraulic oil is low and therefore the viscosity of the hydraulic oil is high, most of the oil discharged from the pilot relief valve 7 flows to the pilot conduit via the temperature raising valve 9, so the pilot valve 8 and the pilot conduit Is heated in a short time. After completion of warming up, when the switching valve 21 is switched to a position where the exhaust oil from the pilot relief valve 7 flows to the circuit directly connected to the hydraulic oil tank 3 via the full flow filter 11, the exhaust oil from the pilot relief valve 7 becomes The entire amount flows to the circuit B, and the supply of hydraulic oil to the circuits A-A 'is cut off. After that, when the lock valve 10 is switched to the operating position, the internal pressure of the circuit from the pilot valve 8 to the hydraulic oil tank 3 drops to the tank pressure, so the back pressure acting on the pilot valve 8 drops, and the pilot valve 8 is operated. The rise of power is avoided.

As described above, the pilot operated hydraulic circuit circuit with the temperature raising device according to the present embodiment has the lock valve 1 during the warm-up operation.
0 is set in the inoperative position (usually this is done during warm-up operation), and the switching valve 21 is switched to the circuit A-A 'in the direction in which the oil discharged from the pilot relief valve 7 flows. The valve 8 and the pilot line can be efficiently heated, and after the warming-up operation is completed, the lock valve 10 is switched to the operating position, and the switching valve 21 is moved to the circuit B in the direction in which the oil discharged from the pilot relief valve 7 is made to flow. By switching, the lever operating force of the pilot valve 8 can be lightened.

<Second Embodiment> FIG. 2 shows the configuration of a pilot operating hydraulic circuit according to the second embodiment. As shown in the figure, in the pilot operated hydraulic circuit of this example, a solenoid valve 22 is provided in the outlet circuit of the pilot relief valve 7 in place of the manual switching valve, and the solenoid valve 22 is manually operated at a desired position. The switch 23 is used for switching. Since the other parts are the same as those in the circuit of FIG. 1, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

In the pilot operated hydraulic circuit with the temperature raising device of this embodiment, the switching valve 22 and the lock valve 10 are also operated in the same procedure as described above.
It is possible to raise the temperature of the pilot valve 8 and the pilot pipe line and recover the operability of the pilot valve 8 by switching. The pilot operated hydraulic circuit with the temperature raising device of this example has the same effects as the circuit of the first embodiment, and since the solenoid valve is used as a switching valve for switching the flow path of the oil discharged from the pilot relief valve 7, There is an advantage that the degree of freedom of the setting position of the switching valve is increased and the design of the construction machine is facilitated.

<Third Embodiment> FIG. 3 shows the configuration of a pilot operation hydraulic circuit according to the third embodiment. As shown in the figure, in the pilot operation hydraulic circuit of this example, the solenoid valve 22 provided in the outlet circuit of the pilot relief valve 7 is connected to the temperature raising valve 9
It is characterized in that it is automatically switched by a signal a from a temperature sensor 24 for detecting the temperature of the working oil flowing therein. Since the other parts are the same as those in the circuit of FIG. 1, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

In the pilot operating hydraulic circuit with the temperature raising device of this embodiment, the temperature of the hydraulic oil flowing through the temperature raising valve 9 is a preset temperature, for example, an operation delay when the pilot valve 8 is operated or the pilot valve 8 is operated. When the temperature reaches the level at which the stop delay when the operation of the
4 outputs the signal a, and the solenoid valve 22 automatically makes the circuit B
The discharge oil from the pilot relief valve 7 is switched to the flow direction, and the supply of the discharge oil to the pilot line is stopped. Therefore, after the solenoid valve 22 is switched, the operability of the pilot valve 8 can be recovered by switching the lock valve 10 to the operating position. The pilot operated hydraulic circuit with the temperature raising device of the present example has the same effects as the circuit of the first example, and the solenoid valve is automatically switched by the signal a from the temperature sensor 24. There is an advantage that the operation is facilitated.

<Fourth Embodiment> FIG. 4 shows the configuration of a pilot operation hydraulic circuit according to the fourth embodiment. As shown in the figure, in the pilot operation hydraulic circuit of this example, a solenoid valve 22 provided in the outlet circuit of the pilot relief valve 7 is provided with a temperature sensor 25 for detecting the temperature of the working oil stored in the working oil tank 3. It is characterized in that it is automatically switched by the signal b from the. Since the other parts are the same as those in the circuit of FIG. 1, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

In the pilot operated hydraulic circuit with the temperature raising device of this embodiment, when the temperature of the hydraulic oil stored in the hydraulic oil tank 3 reaches a preset temperature, a signal b is issued from the temperature sensor 25 and the electromagnetic wave is generated. The valve 22 is automatically switched to the direction in which the oil discharged from the pilot relief valve 7 flows in the circuit B, and the supply of the oil discharged to the pilot line is stopped. Therefore, after the solenoid valve 22 is switched, the operability of the pilot valve 8 can be recovered by switching the lock valve 10 to the operating position. The pilot operated hydraulic circuit with the temperature raising device of the present example has the same effects as the circuit of the first example, and the solenoid valve is automatically switched by the signal a from the temperature sensor 24. There is an advantage that the operation is facilitated.

<Fifth Embodiment> FIG. 5 shows the configuration of a pilot operation hydraulic circuit according to the fifth embodiment. As shown in the figure, the pilot operation hydraulic circuit of the present embodiment discharges from the pilot relief valve 7 not only to the conduit B but also to the conduit A-A 'when switching to the outlet circuit of the pilot relief valve 7. A switching valve 26 for supplying oil is provided.
Since the other parts are the same as those in the circuit of FIG. 1, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted. The switching valve 26 may be a manual valve or a solenoid valve.

In the pilot operated hydraulic circuit with the temperature raising device of this embodiment, when the switching valve 26 is switched, the exhaust oil from the pilot relief valve 7 is supplied not only to the conduit B but also to the conduit A-A '. Therefore, most of the hydraulic oil flows to the pipe B due to the difference in pressure loss between the pipe B and the pipe A-A ', but a part of the hydraulic oil flows to the pipe A-A', and even after the switching valve 26 is switched, The temperature rise of the pilot valve 8 and the pilot circuit is continued. Therefore, the pilot operated hydraulic circuit with the temperature raising device of the present example has the same effect as the circuit of the first embodiment, and can start using the construction machine even when the warm air is insufficient to some extent. Has the advantage of increasing the practicality of.

In each of the above embodiments, the full-flow filter is used as the filter for filtering the return oil, but other types of filters may be used.

[0027]

As described above, according to the present invention,
Since a switching valve is provided in the outlet circuit of the pilot relief valve and the flow path of the hydraulic oil discharged from the pilot relief valve is controlled by operating this switching valve,
During warm-up operation, most of the oil discharged from the pilot relief valve can be supplied to the pilot circuit, enabling efficient warm-up operation. Also, by switching the switching valve, it is possible to cut off the oil discharged from the pilot relief valve that is supplied to the temperature raising valve.Therefore, by switching the lock valve to the operating state, the back pressure acting on the pilot valve can be reduced. Therefore, the lever operating force of the pilot valve can be reduced. Therefore, the operating force of the pilot valve can be reduced and the operation of the actuator can be smoothly performed without impairing the temperature raising effect of the temperature raising device.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a pilot operated hydraulic circuit according to a first embodiment.

FIG. 2 is a circuit diagram of a pilot operated hydraulic circuit according to a second embodiment.

FIG. 3 is a circuit diagram of a pilot operated hydraulic circuit according to a third embodiment.

FIG. 4 is a circuit diagram of a pilot operating hydraulic circuit according to a fourth embodiment.

FIG. 5 is a circuit diagram of a pilot operated hydraulic circuit according to a fifth embodiment.

FIG. 6 is a circuit diagram of a pilot operation hydraulic circuit according to a first conventional example.

FIG. 7 is a circuit diagram of a pilot operated hydraulic circuit according to a second conventional example.

[Explanation of symbols]

 1 main pump 2 pilot pump 3 hydraulic oil tank 4 main relief valve 5 control valve 6 actuator 7 pilot relief valve 8 pilot valve 9 temperature raising valve 10 lock valve 11 full flow filter 21 manual switching valve 22 solenoid valve 23 switch 24, 25 temperature sensor 26 Switching valve

Claims (6)

[Claims] 1. A pilot valve, a control valve operated by the output pressure of the pilot valve, one end connected to a pilot pump via a pilot relief valve, and the other end connected to a hydraulic oil tank via a filter. In a pilot operated hydraulic circuit having a temperature raising valve that is provided in a circuit that supplies hydraulic oil discharged from the pilot relief valve to a circuit that connects the pilot valve and the control valve, A switching valve is provided in the outlet circuit, and the discharge oil from the pilot relief valve is selected to a circuit connected to the hydraulic oil tank via the temperature raising valve and a filter, or a circuit directly connected to the hydraulic oil tank via the filter. It is a pilot operated hydraulic circuit for construction machinery, which is designed to flow normally. 2. The pilot operated hydraulic circuit according to claim 1, wherein the switching valve is a manual valve. 3. The pilot operated hydraulic circuit according to claim 1, wherein the switching valve is a solenoid valve. 4. The pilot operated hydraulic circuit according to claim 3, wherein the solenoid valve is configured to be switched by a manual switch arranged at a desired position. Pilot operated hydraulic circuit. 5. The pilot operated hydraulic circuit according to claim 3, wherein the solenoid valve is automatically switched by a signal from a temperature sensor that detects a temperature of hydraulic oil flowing in the temperature raising valve. A pilot operated hydraulic circuit for construction machinery, which is characterized in that 6. The pilot operated hydraulic circuit according to claim 3, wherein the electromagnetic valve is automatically switched by a signal from a temperature sensor that detects a temperature of hydraulic oil stored in the hydraulic oil tank. A pilot-operated hydraulic circuit for a construction machine, which is configured as follows.