JPH0141841B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is applicable to two pumps and two pumps, such as a control circuit for each actuator of a power shovel.
The present invention relates to a hydraulic circuit having a set of control valve units.

(Prior Art) The hydraulic circuit of the conventional power shovel shown in Fig. 1 consists of two sets of control valve units 2 and 3.
, one unit 2 is connected to the pump 4,
The other unit 3 is connected to a pump 5.

Each of these units 2 and 3 has four switching valves 6-9 and 10-13 as main elements, and each of these switching valves controls the next actuator.

That is, the switching valve 6 of one unit 2 controls the left traveling motor, the switching valve 7 controls the bucket cylinder, the switching valve 8 controls the boom cylinder, and the switching valve 9 controls the arm cylinder.

Further, the switching valve 10 of the other unit 3 controls the swing motor, the switching valve 11 controls the arm cylinder, the switching valve 12 controls the boom cylinder, and the switching valve 13 controls the right travel motor.

The switching valve 9 on one unit 2 side functions to increase the speed of the arm cylinder, and the switching valve 11 on the other unit 3 side functions to increase the speed of the boom cylinder. In other words, these arm cylinders and boom cylinders are simultaneously supplied with oil discharged from both pumps 4 and 5 as needed, so that their operating speeds can be increased.

Then, one control valve unit 2
On the side, switching valves 6 to 8 are connected in parallel, and a switching valve 9 controls the arm cylinder.
are connected in tandem to the other upstream switching valves 6 to 8.

Also, in the other control valve unit 3, the switching valve 11 that controls the arm cylinder is
Only one of the switching valves 12 and 13 is connected in tandem to the switching valve 10 controlling the swing motor, and the other switching valves 12, 13 are connected in parallel by a bypass 14.

The reason why the switching valves 9 and 11 for controlling the arm cylinders are connected in tandem with the other switching valves as described above is as follows. That is, usually
Since the load on this arm cylinder is small, for example, if pressure oil is supplied to the swing motor and arm cylinder at the same time, the pressure oil is preferentially supplied to the arm cylinder with a small load, making it impossible to operate the swing motor with a large load. Therefore, as described above, both switching valves are connected in tandem, and the switching valve that controls an actuator such as a swing motor with a large load is connected in tandem with the switching valve on the downstream side that controls an arm cylinder with a small load. When the side switching valve is switched, pressure oil is not supplied to the arm cylinder with a small load.

Therefore, when the switching valve 10 is switched to operate the swing motor and any of the switching valves 6 to 8 is switched to a position other than the neutral position,
Even if the switching valve 9 or 11 is switched, pressure oil cannot be supplied to the arm cylinder.

Therefore, in order to operate the actuator with a large load and the arm cylinder with a small load at the same time, this conventional hydraulic circuit is configured as follows.

That is, the pump 4 that supplies pressure oil to one control valve unit 2 is
It also communicates with the port 16 of this unit 2 via a branch passage 15 passing through the outside of the unit 2, and this passage 15 is provided with a selector valve 1. A shuttle valve 18 is provided in the swing motor circuit 17 so that the load pressure of the swing motor acts as a pilot pressure on the selector valve 1, and the branch passage 15 is opened and closed by switching the selector valve 1. There is.

When the switching valve 10 is switched to either the left or right position to drive the swing motor, the load pressure acts on the selector valve 1 as pilot pressure, switching it to the open position. When the branch passage 15 is opened in this way, the switching valve 9 is connected to the other switching valve 6.
-8, and pressure oil from the pump 4 flows into the port 16 via the branch passage 15, and the pressure oil is supplied to the arm cylinder via the switching valve 9.

Therefore, in this conventional hydraulic circuit, the arm cylinder can be operated simultaneously while the swing motor is operated.

(Problems to be Solved by the Invention) In the conventional hydraulic circuit as described above, the selector valve 1 and the branch passage 15 must be provided outside the control valve units 2 and 3, so that the control valves are controlled accordingly. There was a problem that the entire mechanism became larger.

An object of the present invention is to provide a hydraulic circuit in which the control mechanism does not become large and does not require a conventional check valve.

(Means for Solving Problems) This invention includes two pumps and two control valve units, one control valve unit has an upstream switching valve that controls an actuator with a large load, and an upstream switching valve that controls an actuator with a small load. The downstream switching valve that controls the actuator is connected in tandem, and the other control valve unit is also connected to the upstream switching valve that controls the actuator with a large load, and the same control valve unit that has a small load as the one control valve unit mentioned above. This is based on a hydraulic circuit that is connected in tandem with a downstream switching valve that controls the actuator.

Based on the above-mentioned device, the present invention connects a selector valve between both switching valves of one control valve unit, and transfers the load pressure of the actuator with a large load of the other control valve unit to the selector valve. When the actuator with a large load of the other control valve unit is driven, the selector valve switches the switching valve that controls the actuator with a small load of one control valve unit to the parallel feeder. It is characterized by a structure in which it is configured to communicate with the pump via the pump.

(Operation of the present invention) Since the present invention is configured as described above, by switching the switching valve that controls the actuator with a large load of the other control valve unit,
The selector valve is switched, and the switching valve that controls the actuator with a small load of one control valve unit is connected to the pump via the parallel feeder.

Therefore, the pump connected to one control valve unit can operate the actuator with a small load, and the pump connected to the other control valve unit can operate the actuator with a large load.

(Effects of the Present Invention) According to the hydraulic circuit of the present invention, one of the control valve units is provided with a selector valve, so there is no need to provide an external selector valve as in the prior art. Therefore, this hydraulic circuit can be made smaller than conventional ones.

(Embodiment of the present invention) The first embodiment shown in FIG.
0, 21 and two sets of control valve units 2
2 and 23, one pump 20 supplies pressure oil to one unit 22, and the other pump 21 supplies pressure oil to the other unit 23.

And one control valve unit 22
The main elements are switching valves 24 to 27 and a selector valve 28.

Also, the other control valve unit 23
The main elements are switching valves 29 to 32, and each of these switching valves 24 to 32 operates an actuator (not shown) of the power shovel, and their correspondence is as follows.

Switching valve 24 → Motor for left movement 〃 32 → Motor for right movement 〃 25 → Bucket cylinder 〃 26 〃 31〓 → Boom cylinder 〃 27 〃 30〓 → Boom cylinder 〃 29 → Motor for swing Note: Boom cylinder and arm cylinder The pressure oil of both pumps 20 and 21 can be supplied to the pumps at the same time.

However, one control valve unit 2
2, the selector valve 28 is interposed between the switching valves 26 and 27, and when the respective valves are in the illustrated neutral position, the pump 20
Pressure oil from the tank 3 passes through the tank passage 33.
Return to 4.

Moreover, the switching valves 24 to 26 are connected to the parallel feeder 35.
Since the actuators are connected in parallel through the actuators, each of the corresponding actuators can be operated independently.

Further, the selector valve 28 is normally located at the position shown in the figure to close the parallel feeder 35 and to connect the switching valves 26 and 27 in tandem. And this selector valve 2
8 is switched to the left side position in the drawing, the parallel feeder 35 and the switching valve 27 are connected.

Therefore, for example, when the selector valve 28 is in the illustrated position, the other switching valves 24 to
26, when either of them is switched to a position other than the neutral position, pressure oil from the pump 20 will no longer flow into the switching valve 27.

On the other hand, when the selector valve 28 is switched to the left side position in the drawing, the parallel feeder 35 opens and is connected to the switching valve 27, so that the switching valve 27 is also connected in parallel like the other switching valves 24 to 26.

In the other control valve unit 23, when the switching valves 29 to 32 are in the neutral position shown, the pressure oil from the pump 21 is transferred to the tank passage 4.
1 and returns to the tank 34.

The switching valve 29 for operating the swing motor and the switching valve 30 for operating the arm cylinder are connected in tandem, while the switching valves 31 and 32 are connected in parallel via a parallel feeder 36.

Therefore, when the swing motor is operated, in other words, when the switching valve 29 is switched to a position other than the neutral position, pressure oil does not flow into the switching valve 30, and no pressure oil flows into the arm cylinder from the pump 21. Pressure oil will not flow.

On the other hand, a shuttle valve 38 that takes out only the high pressure is connected to the swing motor circuit 37, which is opened and closed by the switching valve 29, and the circuit pressure that flows into the shuttle valve 38 is used as pilot pressure to control the selector valve. It leads to 28 pilot operation pressure chambers.

Therefore, when driving the swing motor,
The circuit pressure acts as pilot pressure on the selector valve 28, switching the valve 28 from the illustrated state to the left position.

When the selector valve 28 is switched, the switching valve 27 is connected in parallel as described above.
Even if the swing motor is driven and any of the switching valves 24 to 26 is set to a position other than the neutral position, the switching valve 27 can be switched to operate the arm cylinder.

Note that the reference numeral 39 in FIG. 2 is an engine.

Next, a second embodiment shown in FIG. 3 will be described. In this second embodiment, the same elements as in the first embodiment are designated by the same reference numerals.

In this second embodiment, the shuttle valve 38 of the first embodiment is omitted, and accordingly, the selector valve 40 is provided in three positions.

That is, the A and B circuits of the swing motor 31 are respectively guided to the pilot operation pressure chambers on both sides of the selector valve 40, and the
The selector valve 40 is switched to a position where it performs the same function depending on the pressure on either side.

The other configurations are completely the same as the first embodiment.

Although the above embodiments are all for power shovels, the present invention is not limited to these embodiments. In short, the present invention can be applied to any device equipped with two pumps and two sets of control valve units.

As is clear from the above description, according to the hydraulic circuit of the present invention, there is no need to provide an external selector valve unlike in the past, and the piping is simplified accordingly, and the entire control mechanism has the advantage of being compact. be.

[Brief explanation of drawings]

FIG. 1 is a conventional circuit diagram, and FIGS. 2 and 3 are circuit diagrams of first and second embodiments of the present invention. 20, 21... Pump, 22, 23... Control valve unit, 28, 40... Selector valve, 36... Parallel feeder, 37...
A swing motor circuit which is an actuator circuit of this invention.

Claims (1)

[Claims] 1 Equipped with two pumps and two control valve units, one control valve unit has an upstream switching valve that controls an actuator with a large load, and a downstream switching valve that controls an actuator with a small load. In addition to connecting in tandem, the other control valve unit also includes an upstream switching valve that controls an actuator with a large load, and a downstream switching valve that controls the same actuator with a small load as the one control valve unit mentioned above. In a hydraulic circuit connected in tandem, a selector valve is connected between the two switching valves of one control valve unit, and the load pressure of the actuator with a large load of the other control valve unit is
When the selector valve is guided into the pilot chamber of the selector valve and the actuator with a large load of the other control valve unit is driven, the selector valve switches to control the actuator with a small load of the one control valve unit. A hydraulic circuit configured to communicate with the pump via a parallel feeder.