JPH0143841B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an actuator drive circuit that combines discharge pressure oil from a plurality of pumps as necessary and supplies the combined fluid to the actuator.

Conventionally, this type of circuit was shown in Figure 1 (Japanese Patent Application Laid-Open No.
55-135205).

This circuit includes a first circuit 3a in which a first actuator 2a is connected to a first switching valve 1a, and a second circuit 3b in which a second actuator 2b is connected to a second switching valve 1b. and second circuit 3
The pump includes a first pump 4a and a second pump 4b connected to the first switching valve 1a and the second switching valve 1b, respectively.

The first switching valve 1a is in a neutral position having a passage for carrying over the pressure oil of the first pump 4a.
1a1, a switching position 1a2 for forward rotation of the first actuator 2a, and a switching position 1a3 for reverse rotation, and the second switching valve 1b communicates the passage at the neutral position 1a1 of the first switching valve 1a with the tank T. a neutral position 1b1 and a second actuator 2b with a passageway for
Switching position 1b2 for forward rotation, switching position 1b3 for reverse rotation
The passage of the first switching valve 1a and the tank T are closed, and the switching position for forward rotation of the second actuator 2b is set.
1b4 and a switching position 1b5 for reverse rotation.

The discharge side of the first pump 4a includes a first switching valve 1a,
The second pump 4b is connected to the tank T via the second switching valve 1b, and is branched from between the first switching valve 1a and the second switching valve 1b via a first confluence circuit 5a equipped with a check valve. Connect to the discharge side of the Also the second
The discharge side of the pump 4b is connected to the second switching valve 1 and branched from the upstream side of the second switching valve 1b, via a second confluence circuit 5b in which a pressure compensation valve 6 and a check valve are connected in series. It is connected to the discharge side of the first pump 4a. Note that the pressure compensation valve 6 maintains a constant pressure difference between the upstream side and the downstream side of the second switching valve 1b.

In this circuit, when the first switching valve 1a and the second switching valve 1b are set to neutral positions 1a1 and 1b1 and the first pump 4a and the second pump 4b are driven, the discharge oil pressure of the first pump 4a is The pressure oil flows out to the tank T via the switching valve 1a and the second switching valve 1b, and the pressure oil discharged from the second pump 4b is discharged from the first pump 4a via the pressure compensating valve 6 of the second confluence circuit 5b and the check valve. It flows out from the side to the tank T together with the discharge pressure oil of the first pump 4a.

Next, when the second switching valve 1b is operated to the forward rotation switching position 1b2, the discharge pressure oil of the first pump 4a flows out to the tank T, but the second actuator 2b is switched to the second switching position 1b2.
Since the pump 4b is connected to the tank T, the discharge pressure oil of the second pump 4b acts on the second actuator 2b. This oil pressure simultaneously acts on one side of the pressure compensation valve 6, so the pressure compensation valve 6 operates and the second pressure compensation valve 6 operates.
The discharge hydraulic pressure of the pump 4b is controlled by the second actuator 2.
Increase the load pressure by a certain value higher than the load pressure of b. In this way, the second actuator 2b is operated by the pressure oil discharged from the second pump 4b. Subsequently, when the second switching valve 1b is operated to the forward rotation switching position 1b4, the space between the first pump 4a and the tank T is closed, so that the pressure oil discharged from the first pump 4a flows through the first confluence circuit 5a. The pressure oil flows into the second actuator 2b via the second switching valve 1b, so that the pressure oil flows into the second actuator 2b.
operates according to the sum of the pressure oil discharged from the first pump 4a and the second pump 4b.

Next, select only the first switching valve 1a and the switching position for forward rotation.
1a2, both the discharge sides of the first pump 4a and the second pump 4b are closed from communicating with the tank T, so that the first actuator 2a is connected to the discharge pressure oil of the first pump 4a and the second confluence circuit 5b. It is operated by a flow rate of pressure oil that is the sum of the flow rate of the pressure oil discharged from the second pump 4b and the flow rate of the second pump 4b.

Note that when each of the first switching valve 1a and the second switching valve 1b is operated in the opposite direction to that described above, only the first actuator 2a and the second actuator 2b operate in the opposite direction to that described above, and the others operate in the opposite direction. Since they are similar, detailed explanation will be omitted.

Now, when such a circuit is used for construction machinery, for example, the first actuator 2a,
A third circuit (not shown) having a third switching valve to which a third actuator other than the second actuator 2b is connected is provided. Therefore, for example, the second pump 4b and the second actuator 2
A third switching valve is provided in parallel between the pumps 4b and 4b, and when this third switching valve, the first switching valve 1a, and the second switching valve 1b are operated simultaneously, the pressure oil discharged from the second pump 4b changes to the third switching valve.
It will be supplied to both the actuator and the second actuator 2b, and the second actuator 2b
The operating speed of the second actuator 2b becomes extremely low, or in some cases (when the third actuator consumes the entire discharge pressure oil of the second pump 4b), the second actuator 2b stops. Then, such a circuit is used in a crane truck to connect the first actuator 2a and the second actuator.
When the actuator 2b is used for hoisting and the third actuator is used for turning, if the load for hoisting is large, the second actuator
Part or all of the discharge flow rate of the pump 4b flows into the swinging actuator, which causes the hoisting actuator to slow down or stop with the load suspended, resulting in a dangerous situation. have

Therefore, a technical problem of the present invention is to operate an actuator regardless of the usage state of a plurality of pumps.

Means of the present invention for solving the above problems are as follows:
The first actuator is connected to the first switching valve.
a second circuit in which a second actuator is connected to a second switching valve; and a third circuit in which a third actuator is connected to a third switching valve; The discharge side is connected to the tank via the first switching valve and the second switching valve, and the discharge side of the second pump is connected via a confluence circuit, and the discharge side of the second pump is connected to the tank via the first switching valve and the second switching valve. connected to the first switching valve and the second switching valve;
Each of the switching valve and the second switching valve is provided with a switching position that communicates with a switching position that closes the discharge side of the first pump, and the first switching valve and the second switching valve are provided between the discharge side of the diversion valve and the tank. A pressure compensation valve is provided to maintain the pressure difference between the upstream side and the downstream side of each switching valve at a constant value.

The present invention having the above means includes a first circuit, a second circuit,
Even if each switching valve in the third circuit is operated simultaneously,
The first actuator of the first circuit and the second actuator of the second circuit.
The discharge hydraulic pressure of the second pump is supplied to the actuator via the diversion valve, and the discharge hydraulic pressure of the first pump is supplied to the third actuator of the third circuit, so all actuators can be operated. . In addition, when operating only the second circuit, the first switching valve,
When the connection between the discharge side of the first pump and the tank is closed with either of the second switching valves, the discharge pressure oil of the first pump is transferred to the discharge side of the second pump through the confluence circuit. Because it can be merged with
The first actuator and the second actuator can be operated at increased speeds.

Furthermore, the present invention having such a basic configuration has the following unique effects.

That is, the technical problem of the present invention is to provide, for example, a third circuit between the second pump and the second circuit in the conventional circuit shown in FIG. Assuming that the second and third actuators of the second and third circuits are driven, the amount of pressure oil discharged from the second pump is set to the second and third actuators.
This problem can be solved by setting the maximum working condition that acts on the actuator, using a pump that meets that condition, and making the second and third circuits parallel circuits. However, constantly driving a large pump causes a power loss in the engine, and furthermore, it is necessary to connect the second circuit and the third circuit in parallel, and it is not possible to use other circuits, such as a tandem circuit. be. However, in the present invention, since the discharge side of the second pump is connected to the first circuit and the second circuit via the flow dividing valve, the third pump is provided between the first pump and the first circuit.
The first circuit and the second circuit can each be driven independently of the circuit. Therefore, the first pump does not need to be particularly large, and there are no restrictions on the circuit configuration. In addition, since the discharge side of the diverter valve is connected to the tank via the pressure compensation valve, the operating speed of each actuator in the first circuit and the second circuit can be controlled by the first switching valve and the second switching valve. Each has an effect that can be adjusted depending on the amount of operation.

An embodiment of the present invention shown in FIG. 2 will be described below.

In FIG. 2, the first circuit 3a connects the first actuator 2a to the first switching valve 1a,
The second circuit 3b connects the second actuator 2b to the second switching valve 1b. 3c is a third circuit, and a third circuit is connected to each of the third actuators 2c and 2c'.
It is formed by connecting switching valves 1c and 1c'.

Since the first switching valve 1a and the second switching valve 1b have the same configuration, the first switching valve 1a
The second switching valve 1b will be described as necessary.

The first switching valve 1a has a neutral position 1a1 having an unload passage and a closing port, and a switching position for forward rotation and reverse rotation in which the closing port is connected to the actuator.
1a2, 1a3, and forward rotation and reverse rotation switching positions 1a4 and 1a5 that close the unload passage. Further, the third switching valves 1c, 1c' are provided with an unload passage, and have a neutral position 1c1, 1c1' and a switching position 1c2, 1c2, for normal rotation and reverse rotation of the third actuator 2c, 2c'.
It has 1c2′, 1c3, and 1c3′.

The discharge side of the first pump 4a has a third switching valve 1c,
1c', connected to the tank T via each unload passage of the first switching valve 1a and the second switching valve 1b, and branched from the upstream side of the first switching valve 1a through a merging circuit 5c having a check valve. It is connected to the discharge side of the second pump 4b.

The discharge side of the second pump 4b is connected to a flow dividing valve 7, and each of the discharge sides of the flow dividing valve 7 is connected to the closing port of the first switching valve 1a and the second switching valve 1b, and the first switching valve A pressure compensation valve 8a that controls the difference in oil pressure between the upstream side and the downstream side of the valve 1a to a constant value, and a pressure compensation valve 8b that controls the difference in the oil pressure between the upstream side and the downstream side of the second switching valve 1b to a constant value. Connect to tank T via.

The diverter valve 7 includes metering orifices 7a, 7.
a', the metering orifices 7a and 7a' are provided downstream of the pressure compensating valve position 7b1, switching positions 7b2 and 7b3, and pilot portions 7b4 and 7b.
4′, and the first actuator 2
a, a pilot valve 7c which is connected and operated when the first switching valve 1a is operated, and a pilot valve 7c' which is connected and operated when the second switching valve 1b is operated to the second actuator 2b. Therefore, each of the pilot valves 7b4, 7b4' has a pilot valve 7c, 7c', a first switching valve 1a, and a second switching valve 1b which branch from between the metering orifices 7a, 7a' and the valve 7b. Through each tank T
This is a configuration in which pilot circuits 7d and 7d' are connected to each other. In addition, metering orifice 7
The circuits 7e, 7e' that bypass the valves 7a, 7a'
b is closed when it is in the pressure compensation position 7b1, and when it is in the switching position 7b2 the circuit 7e' is closed and the circuit 7e is connected to the second switching position 1a. Further, when the valve 7b is in the switching position 7b3, the circuit 7e is closed and the circuit 7e' is connected to the second switching valve 1b.

In the circuit of this embodiment, as shown in FIG.
1c' is not operated, the discharge pressure oil of the first pump 4a is transferred to the tank T via the unload passages of the third switching valves 1c, 1c', the first switching valve 1a, and the second switching valve 1b. The pressure oil discharged from the second pump 4b flows out into the tank T via the diversion valve 7 and the pressure compensation valves 8a and 8b.

Next, move the first switching valve 1a to the switching position 1a2 for forward rotation.
When operated, the unload passage remains formed, but the closed port and the pilot circuit 7d are connected to the first actuator 2a, so the hydraulic pressure in the pilot circuit 7d is transferred to the first actuator 2a.
It increases due to the load pressure of a, and the pilot valve 7
c operates and closes the space between the pilot part 7b4 and the first actuator 2a, so the pilot part 7
The hydraulic pressure of b4 switches the valve 7b to the switching position 7b2, and the pressure oil discharged from the second pump 4b flows only into the first switching valve 1a via the circuit 7e and the metering orifice 7a. Since the load pressure of the first actuator 2a also acts on the pressure compensating valve 8a, the pressure of the pressure oil supplied to the first switching valve 1a is controlled by the pressure compensating valve 8a to a constant level lower than the load pressure of the first actuator 2a. value is held higher. Therefore, the first actuator 2a has an operating speed that corresponds to the operation amount of the first switching valve 1a.

When the second switching valve 1b is operated to the switching position 1b2 while the first switching valve 1a is operated to the switching position 1a2, both the pilot circuit 7d' and the closing port are connected to the second actuator, but the unload passage is Not closed. Since the load pressure of the second actuator 2b acts on the pilot circuit 7d' connected to the second actuator 2b, the pilot valve 7c' closes the space between the pilot portion 7b4' and the second actuator. Therefore, the pilot parts 7b4 and 7b4' have the same pressure, the valve 7b switches to the pressure compensation position 7b1, and the pressure oil discharged from the second pump 4b is transferred to each of the first switching valve 1a and the second switching valve 1b. The flow is divided into a value corresponding to the amount of restriction of the metering orifices 7a, 7a'. At the same time, the load pressure of the second actuator 2b acts on the pressure compensation valve 8b, so the pressure of the pressure oil supplied to the second switching valve 1b is
The second actuator 2b is controlled by the pressure compensation valve 8b.
is held at a value higher than the load pressure by a certain value.
Therefore, the second actuator 2b has an operating speed that corresponds to the operation amount of the second switching valve 1b.

In the above operation, the pressure oil discharged from the first pump 4a flows out to the tank T because the unload passages of the first switching valve 1a and the second switching valve 1b are secured.

Next, when the first switching valve 1a is operated to the switching position 1a4, the unload passage of the first switching valve 1a is closed, so the discharge pressure oil of the first pump 4a is transferred from the confluence circuit to the discharge pressure oil of the second pump. The water flows into the first actuator 2a and the second actuator 2b via the first switching valve 1a and the second switching valve 1b.

Note that while the first switching valve 1a is operated to the switching position 1a4, the second switching valve 1b is set to the switching position.
1b2, the pressure compensating valve 8b causes a part of the pressure oil to flow out from the diversion valve 7 to the tank T.

Furthermore, even if either the third switching valve 1c or 1c' of the third circuit 3c is operated before operating the first switching valve 1a or the second switching valve 1b, the first actuator 2
a, the second actuator 2b includes a second pump 4;
The discharge pressure oil of b is supplied by the flow dividing valve 7.

Furthermore, regarding the operation of the first switching valve 1a and the second switching valve 1b opposite to that described above, the first actuator 2a and the second actuator 2b are both driven in the opposite direction to that described above, and the other operations are the same. Therefore, detailed explanation will be omitted.

[Brief explanation of drawings]

FIG. 1 is a conventional circuit diagram, and FIG. 2 is a circuit diagram according to an embodiment of the present invention. 1a...first switching valve, 1b...second switching valve, 2
a...first actuator, 2b...second actuator, 3a...first circuit, 3b...second circuit, 4a...first pump, 4b...second pump,
7...Diversion valve, 8a, 8b...Pressure compensation valve.

Claims (1)

[Claims] 1 A first circuit in which a first actuator is connected to a first switching valve, a second circuit in which a second actuator is connected to a second switching valve, and a third circuit in which a third actuator is connected to a third switching valve. provision, said third
The discharge side of the first pump connected to the switching valve is connected to the tank via the first switching valve and the second switching valve, and is also connected to the discharge side of the second pump via the merging circuit, and the second pump is connected to the tank via the first switching valve and the second switching valve. The discharge side of the pump is connected to the first switching valve and the second switching valve via a flow divider valve, and each of the first switching valve and the second switching valve has a switching position that closes the discharge side of the first pump. , and a communicating switching position, and a pressure that maintains a pressure difference between the upstream side and the downstream side of each of the first switching valve and the second switching valve at a constant value between the discharge side of the branch valve and the tank. An actuator drive circuit characterized by being provided with a compensation valve.