JPH044419B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a simultaneous operation circuit for a two-pump system that operates a predetermined actuator using two pumps, such as a control circuit for a power shovel.

(Conventional Operation Circuit) As this type of circuit, an operation circuit for a power shovel shown in FIG. 1 has been known in the past.

The operating circuit shown in FIG. 1 includes two circuit systems, and pumps 1 and 2 are connected to each circuit system.

A plurality of directional switching valves 3 to 6 and 7 to 10 are connected to each of the above circuit systems, and each of the directional switching valves is configured to control a predetermined actuator connected to it. The directional switching valve 3 of the circuit system controls one traveling motor 11, the directional switching valve 7 of the other circuit system controls the other traveling motor 12, and the directional switching valve 6 controls the earth removal plate cylinder 13. ing.

When the directional control valves configured as described above are held in the neutral position shown in the figure, their tandem passages 14 and 15 are all in communication, and the oil from the pumps 1 and 2 is returned to the tank 16.

When the directional control valve is switched, the pumps 1 and 2 are fed through the parallel feeders 17 and 18.
The structure is such that the oil is supplied.

Therefore, only the direction switching valve 6 that controls the earth removal plate cylinder 13 is switched to either the left or right, and
When all the other directional control valves are held at the neutral position, oil from the pump 1 flows into the earth removal plate cylinder 13 through the parallel feeder 17 and operates it.

Also, by switching the directional control valves 3 and 7, the travel motor 1
When the directional control valve 6 is switched while the vehicle is running with the wheels 1 and 12 rotated, the oil from the pump 1 is distributed between the travel motor 11 and the earth removal plate cylinder 13.

(Problem to be Solved by the Invention) In the conventional operation circuit as described above, the discharge amount of the pump 1 of the one circuit system is the same as that of the traveling motor 11.
and the earth removal plate cylinder 13, one of the traveling motors 1
1 rotation speed drops. For this reason, this conventional operating circuit has a drawback that if the earth removal plate cylinder 13 is operated to level the ground while the power shovel is running, the power shovel cannot travel straight.

An object of the present invention is to provide an operation circuit that does not affect straight traveling even if a specific actuator is operated.

(Means for Solving the Problem) This invention connects a pump to each of two circuit systems, and one circuit system has a directional switching valve that controls one travel motor and a directional switching valve that controls the other actuator. and the other circuit system is also provided with a directional switching valve for controlling a travel motor other than the above and a directional switching valve for controlling another actuator, and by controlling these directional switching valves,
In addition to controlling a predetermined actuator, when the directional switching valve is switched, oil is supplied from the pump via a parallel feeder, and a specific directional switching valve that controls a specific actuator is switched. In some cases, a simultaneous operation circuit for a two-pump system that allows simultaneous operation of this particular actuator and the travel motor is assumed.

Based on the above operating circuit, this invention
A check valve connected to each parallel feeder is provided in the path that communicates a specific directional control valve that controls a specific actuator with the parallel feeders of both circuit systems, and an orifice is provided downstream of this check valve. The present invention is characterized in that a pilot passage communicating with the spring chamber of each of the check valves is further provided on the downstream side of the orifice.

(Function) Since the present invention is configured as described above, when a specific directional control valve is switched in order to operate a specific actuator, a pressure difference is generated before and after the orifice, so the pressure in the spring chamber of the check valve is becomes lower. For this purpose, the check valve opens, and the discharge oil from the pumps in both circuit systems is supplied to a specific actuator via the respective parallel feeders, merging upstream of the check valve. That is, in this case, the discharge oil of the pumps of both circuit systems is simultaneously supplied to a specific actuator.

Further, unless the specific directional switching valve is switched, no differential pressure will be generated across the orifice, so the check valve will remain closed. Therefore,
The discharge amount of the pumps in both circuit systems is not supplied to a specific actuator.

(Effects of the Invention) According to the operation circuit of the present invention, when a specific actuator is operated, the discharge amount of the pumps of both circuit systems is equally supplied to this specific actuator, so that the actuator can be driven straight ahead. Even if this particular actuator is operated at times, it does not affect straight-line travel.

Also, as long as a specific directional control valve that controls a specific actuator is kept in the neutral position, the check valve is closed, and the check valve opens only when this specific directional control valve is switched. This prevents the check valve from opening accidentally.

(Embodiments of the present invention) An embodiment of the present invention will be described below, and elements that are the same as those of the prior art will be described using the same reference numerals while omitting details.

However, the first embodiment shown in FIG.
Check valves 19 and 2 are provided in the path communicating with the
0 is set.

Both check valves 19 and 20 are configured to allow oil from the parallel feeders 17 and 18 to flow only to a communication path 21 common to both.

Furthermore, the communication passage 21 is connected to the earth removal plate cylinder 1 through an oil passage 22 and a load check valve 23.
3 is configured to flow into the directional switching valve 6 that controls the directional control valve 3.

The oil passage 22 constructed as described above has an orifice 2.
4 is provided, and pilot passages 25 and 26 are connected to the downstream side of this orifice 24.

Each of the pilot passages 25 and 26 is
It is connected to the spring chambers 27, 28 of the check valves 19, 20 so that the pilot pressure from the pilot passages 25, 26 acts on the check valves 19, 20 as back pressure.

Therefore, when only the directional control valve 3 is switched to drive the earth removal plate cylinder 13, the oil from the pump 2 returns to the tank 16, while the oil from the pump 1 pushes open the check valve 19 and pushes the directional control valve 6 open. The soil flows into the earth discharge plate cylinder 13 from there.

Also, by switching the directional control valves 3 and 7, the travel motor 1
1 and 12 are being rotated, when the direction switching valve 6 that controls the earth removal plate cylinder 13 is switched, a pressure difference is generated before and after the orifice 24, and the pressure in the spring chambers 27 and 28 is lower than the pressure in the spring chambers 27 and 28. Since the pressure on the feeders 17 and 18 increases, both check valves 19 and 20 open.

If both check valves are opened as described above, the discharge amount of the pumps 1 and 2 will be equal to the discharge amount of the soil discharge plate cylinder 13.
flows into.

As mentioned above, in this embodiment, both pumps 1 and 2
The discharge amount flows into the earth removal plate cylinder 13 in equal parts, so unlike the conventional circuit where only the discharge amount of one pump flows into the earth removal plate cylinder 13, the rotation speed of both traveling motors is the same. This allows the power shovel to travel straight ahead.

The second embodiment shown in FIG. 3 has an oil passage 22 downstream of the pilot passages 25 and 26.
, an orifice 29 different from the orifice 24
The rest is the same as the first embodiment.

However, in this second embodiment, if the directional control valves 3 and 7 are switched to rotate the travel motors 11 and 12, and the directional control valve 6 that controls the earth removal plate cylinder 13 is switched, it is the same as in the first embodiment. Then, oil from both pumps 1 and 2 flows into the earth removal plate cylinder 13.

However, in this second embodiment, since the orifice 29 is provided downstream of the pilot passages 25 and 26 as described above, for example, when only oil from one pump 1 is supplied to the earth removal plate cylinder 13,
The other check valve 20 will not open inadvertently.

That is, when the soil discharge plate cylinder 13 is driven by only the oil from one of the pumps 1 as described above, since the orifice 29 is located downstream of the pilot passages 25 and 26, the spring chamber 27, The pressure flowing into 28 is higher than in the first embodiment. For that purpose check valve 20
The back pressure acting on the check valve 20 becomes high.
becomes difficult to open.

[Brief explanation of drawings]

FIG. 1 is a conventional circuit diagram, FIG. 2 is a circuit diagram of a first embodiment of the present invention, and FIG. 3 is a circuit diagram of a second embodiment. 1, 2...Pump, 3-10...Directional switching valve,
17, 18...parallel feeder, 19, 20...
...Check valve, 24...Orifice, 25, 26
...Pilot passage, 27, 28...spring chamber.

Claims (1)

[Claims] 1 A pump is connected to each of the two circuit systems, and one circuit system is provided with a directional switching valve that controls one travel motor and a directional switching valve that controls the other actuator, and the other circuit system is also equipped with the above-mentioned directional switching valve. is provided with a directional switching valve that controls another travel motor and a directional switching valve that controls another actuator, and by controlling these directional switching valves, a predetermined actuator is controlled and the directional switching valve is When switched, oil is supplied from the pump via the parallel feeder, and when a specific directional control valve that controls a specific actuator is switched, this specific actuator and travel motor can be operated simultaneously. made possible 2
In the simultaneous operation circuit of the pump system, a check valve connected to each parallel feeder is provided in a path that communicates the specific directional switching valve that controls the specific actuator with the parallel feeders of both circuit systems, A simultaneous operation circuit for a two-pump system comprising an orifice provided downstream of the check valve and a pilot passage communicating with the spring chambers of each of the check valves further downstream of the orifice.