JP2871886B2 - Hydraulic circuit of excavator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a hydraulic shovel capable of running straight ahead during simultaneous operation of front operation or turning and running, and more particularly to the use of a hydraulic motor for running when the mud is dropped. The present invention relates to a hydraulic circuit of a hydraulic shovel capable of preventing rotation.

[0002]

2. Description of the Related Art As a hydraulic circuit of a conventional hydraulic excavator of this kind, a back pressure is applied to a traveling straight-ahead valve, and the back pressure is cut off only when a control valve for the most upstream hydraulic motor is operated. Some are designed to prevent rotation.

FIG. 4 is a circuit diagram showing a hydraulic circuit of the conventional hydraulic shovel. This hydraulic circuit has a first main hydraulic pump 1 and a second main hydraulic pump 2, and a discharge circuit of the first main hydraulic pump 1 has a first control valve for one traveling motor 5. A control valve 9 for the front actuator 7 such as a boom cylinder or an arm cylinder is connected in cascade with 3 as the most upstream side, and the discharge circuit of the second main hydraulic pump 2 is connected to the other. A control valve for a plurality of actuators, for example, a control valve 10 for a front actuator 8 such as a boom cylinder or an arm cylinder, with the second control valve 4 for the traveling motor 6 as the most downstream side.
Are cascaded. Each of the control valves 3, 4,
9 and 10 are pilot valves 13 and 14, respectively.
By the operations of 15 and 16, the pilot pressure supplied from the pilot pump 12 is given to each drive unit,
Is switched.

[0004] A connecting line 21 for connecting the upstream pump circuit of the first control valve 3 and the upstream pump circuit of the second control valve 4, and a traveling straight valve 11 for communicating and cutting off the connecting line 21. The pilot pump 12 and the pilot conduit 22 for guiding the pilot pressure of the pilot pump 12 apply a force for switching the traveling straight valve 11 to the communicating position to one drive unit of the traveling straight valve 11. It constitutes a force means. In addition, the straight traveling valve 1
The other one of the driving units is biased by a spring and is connected to the tank 25 via a conduit 28. Also,
The connection pipe 21 is provided with a check valve 35 for preventing backflow to the pump 1 side. Further, a detection circuit 23 for detecting operation signals of the control valves 9 and 10 and a detection circuit 33 for detecting operation signals of the first control valve 3 and the second control valve 4 are provided. The detection circuit 33 is connected to the braking devices of the traveling motors 5 and 6 via the conduit 31. That is, when either the first control valve 3 or the second control valve 4 is switched, a pressure builds up in the conduit 31 and the brakes of the traveling motors 5 and 6 are released. Detection circuits 23 and 33 described above
Are communicated to various devices (not shown) as necessary. When the control valves 3, 4, 9, and 10 are in neutral, the detection circuits 23 and 33 communicate with the tank 25 via the pipe 24.

[0005] In this conventional hydraulic circuit,
As means for applying a back pressure to the other drive unit of the above-mentioned straight traveling valve 11, a two-position switching valve 19 provided in a pipe 28 and a pilot pump 17 connected to the two-position switching valve 19 are provided. . One drive unit 19a of the two-position switching valve 19
Is a pilot line 2 that guides the pilot pressure generated by the pilot valve 13 to the drive unit of the first control valve 3.
The shuttle valve 18 is connected to 9 and 30,
The other drive section of the two-position switching valve 19 is biased by a spring.

In this conventional hydraulic circuit, when the first control valve 3 is in the neutral state, the two-position switching valve 19 is maintained at the switching position shown in FIG. Is supplied as back pressure to the other drive unit of the straight-travel valve 11 via a pipe 28, and one drive unit of the straight-run valve 11 is connected to a tank 25 via a pilot pipe 22, a detection circuit 23, and a pipe 24. Contacted,
As a result, the connection pipeline 21 is cut off.
Here, a combined drive of the traveling motors 5 and 6 and the actuator 7 or 8 is intended. When the control valve 9 or 10 and the first and second control valves 3 and 4 are switched, the shuttle valve 18 is used. As a result, the pilot pressure is applied to one drive unit 19a of the two-position switching valve 19, and the two-position switching valve 19 is switched to the left position in FIG. Accordingly, the supply of the pilot pressure of the pilot pump 17 to the other drive section of the two-position switching valve 19 is prevented, and the other drive section of the two-position switching valve 19 communicates with the tank 25 via the pipe 28. I do. Further, by switching the control valve 9 or 10, a pressure builds up in the pilot line 22, and the straight traveling valve 11 is switched to the left position in FIG. 4, and the connection line 21 is connected. As a result, a part of the pressure oil discharged from the pump 1 is supplied to the second control valve 4 side via the connection pipe line 21, and a large flow rate to the traveling motor 5 is suppressed. Over rotation is prevented.

[0007]

In the above-mentioned prior art, as means for applying a back pressure to the other driving portion of the two-position switching valve 19, a two-position switching valve 19, a pilot pump 17, and a shuttle valve are provided. 18 and the number of parts is large, the structure is complicated, and the manufacturing cost is high.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and has as its object to provide a hydraulic circuit of a hydraulic shovel capable of applying a back pressure to a straight traveling valve without providing a two-position switching valve or the like. Is to provide.

[0009]

In order to achieve this object, the present invention has a first main hydraulic pump and a second main hydraulic pump, and a discharge circuit of the first main hydraulic pump includes: A plurality of actuator control valves are connected in cascade with one traveling first control valve being the most upstream side, and the other traveling second control valve is disposed in the discharge circuit of the second main hydraulic pump. A plurality of control valves for actuators are connected in cascade as a downstream side, and a connecting line connecting an upstream pump circuit of the first control valve and an upstream pump circuit of the second control valve is communicated with the connecting line. A traveling straight valve to be shut off, an urging means for applying a force for switching the traveling straight valve to a communication position to one drive unit of the traveling straight valve, and an operation signal of the first control valve and the second control valve. And a detection circuit for output, said first
In the hydraulic circuit of a hydraulic shovel configured to prohibit the switching of the traveling straight valve to the communication side when the control valve is not operated, the detection circuit and the other drive opposing one drive unit of the traveling straight valve are provided. It has a configuration in which a back pressure induction circuit for communicating with the section is provided.

[0010]

The hydraulic circuit of the hydraulic shovel according to the present invention has the above-described configuration. Therefore, when the front actuator is driven, the front control valve is switched.
Even if one of the drive units of the straight travel valve is biased by the biasing means, when only the second travel control valve is switched, that is, when the first travel control valve is not operated, the travel is stopped. The back pressure generated in the detection circuit by switching the first control valve is guided to the other drive unit of the traveling straight valve via the back pressure induction circuit so as to oppose the urging force of the urging means. Thus, the straight travel valve is not switched to the communication position, and can be maintained at the shutoff position.

Further, when the first control valve is switched from the above state, the supply of the back pressure is blocked by the cutoff of the detection circuit, and the urging force of the urging means provided to the straight traveling valve is provided. Overcomes the force due to the back pressure, and the straight travel valve is switched to the communicating position, whereby a part of the pressure oil discharged from the first main hydraulic pump is transferred to the second control valve side through the connection pipe. The flow, and thus the supply of a large flow rate to the travel motor driven and controlled by the first control valve, is suppressed, and the overrun of the travel motor is prevented.

Such an operation can be realized only by providing a back pressure induction circuit connected to the detection circuit, and there is no need to provide a two-position switching valve or the like.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the hydraulic circuit of a hydraulic shovel according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing one embodiment of a hydraulic circuit of a hydraulic shovel of the present invention, and FIGS. 2 and 3 are circuit diagrams showing the operation of the embodiment of the present invention shown in FIG.

The embodiment shown in FIG. 1 also includes the same devices and members as those of the hydraulic circuit shown in FIG. That is, a first main hydraulic pump 1, a second main hydraulic pump 2, a first control valve 3 for traveling connected to the first main hydraulic pump 1 and arranged at the most upstream position, And a plurality of actuator control valves exemplified by the actuator control valve 9 and a second traveling hydraulic valve connected to the second main hydraulic pump 2 and disposed at the most downstream position. A control valve 4 and a plurality of actuator control valves exemplified by an actuator control valve 10, which are arranged upstream of the second control valve 4, and traveling controlled by the first and second control valves 3 and 4. Motors 5, 6, actuators 7, 8 controlled by control valves 9, 10, control valves 3, 4, 9,
10 for switching pilot valves 13, 1
4, 15, 16 and the upstream side of the first control valve 3 connected to the first main hydraulic pump 1 and the upstream side of the second control valve 4 connected to the second main hydraulic pump 2 A connecting pipe 21 to be connected, a check valve 35 provided in the connecting pipe 21, a traveling straight valve 11, and a pilot for applying an urging force for biasing one drive unit of the traveling straight valve 11. The pump 12 and the pilot line 22 are connected to the pilot pump 12, and each control valve 3,
Detection circuits 23, 33 for detecting operation signals 4, 9, 10
And the traveling motor 5, which is connected to the pilot pump 12,
6, a line 36 connected to the braking device, the detection circuit 23,
And a conduit 24 that allows the 33 to communicate with the tank 25.

In this embodiment, a back pressure induction circuit for connecting a detection circuit 33 for detecting operation signals of the first control valve 3 and the second control valve 4 to the other drive unit of the straight travel valve 11. 40 are provided. The back pressure induction circuit 40 is connected to the tank 25 via the throttle 34. That is, in this embodiment, the two-position switching valve, the pilot pump, and the two-position switching valve as shown in FIG. No branch circuit and shuttle valve are required to guide pilot pressure.

The operation of the embodiment constructed as described above is as follows. When the front actuator 7 or 8 is being driven, the pilot valve 13 is operated to switch only the first control valve 3 as shown in FIG. . At this time, the detection circuit 2 is switched by switching the control valves 9 and 10 in accordance with the driving of the actuator 7 or 8.
3 and line 22 are cut off, and pilot pump 1
The pilot pressure of 2 is applied as an urging force to one drive unit of the straight traveling valve 11 through the pipe 22. Further, the pilot pump 1 is switched by switching the first control valve 3.
The supply of the pilot pressure 2 to the detection circuit 33 is blocked.
At this time, the detection circuit 33 is in communication with the tank 25 via the second control valve 4 and the pipe 24 as shown in FIG. Therefore, the back pressure is not guided to the other drive unit of the straight travel valve 11, and the straight travel valve 11 is switched to the communication position as shown in FIG. Thereby, a part of the pressure oil of the first main hydraulic pump 1 is guided to the second control valve 4 side through the connection pipe line 21, and an excessively large flow rate is supplied to the traveling motor 5 shown in FIG. Overrun of the traveling motor 5 can be prevented.

When the front actuator 7 or 8 is being driven, the pilot valve 14 is operated to operate the first control valve 4 as shown in FIG. Is switched. At this time, similarly to the above, the actuator 7 or 8
By switching the control valves 9 and 10 accompanying the drive of
The connection between the detection circuit 23 and the pipeline 22 is cut off, and the pilot pressure of the pilot pump 12 is applied via the pipeline 22 to one drive unit of the traveling straight valve 11 as an urging force. Further, the switching of the second control valve 4 cuts off the connection between the detection circuit 33 and the pipeline 24 shown in FIG. 1, and the pilot pressure guided from the pilot pump 12 to the detection circuit 33 via the first control valve 3. But back pressure induction circuit 4
The pressure is supplied to the other drive unit of the straight travel valve 11 as a back pressure via 0. Therefore, a force is applied to both driving portions of the straight traveling valve 11, and the straight traveling valve 11 is held at the right position shown in FIG. 3, and the connection pipeline 21 is kept in a disconnected state. In this case, it goes without saying that the straight traveling valve 11 is kept in the state shown in FIG. 3 even when the front actuator 7 or 8 is stopped.

When the first control valve 3 is switched by operating the pilot valve 13 shown in FIG. 1 while the second control valve 4 is switched as shown in FIG. The pilot pressure supplied to the detection circuit 33 is cut off by the first control valve 3, and the pressure in the detection circuit 33 is changed to a back pressure induction circuit 40,
The gas is released to the tank 25 through the throttle 34, and the traveling straight valve 1
The back pressure applied to one other drive is removed. Accordingly, the straight traveling valve 11 is in a state where it can be switched to the left position. In this state, the control valves 9 and 10 are switched for driving the front actuator 7 or 8 so that the straight travel valve 11 is driven as described above.
The pilot pressure is led to one of the drive sections of the
The straight-traveling valve 11 is switched to the left position to communicate with.

The throttle 34 provided between the back pressure induction circuit 40 and the tank 25 is connected to the other of the straight travel valve 11 when both the first control valve 3 and the second control valve 4 are switched. This is to prevent the back pressure from being trapped in the drive unit, and the throttle amount may be set so that the detection circuit 33 can hold the pressure oil when only the second control valve 4 is switched.

As described above, in the present embodiment, there is no need for a two-position switching valve, a pilot pump connected to the two-position switching valve, a shuttle valve, and the like.
The same operation as in the related art can be performed only by providing the back pressure induction circuit 40 that connects the detection circuit 33 and the other drive unit of the straight traveling valve 11.

[0021]

As described above, the hydraulic circuit of the hydraulic shovel of the present invention is constructed as described above, so that the back pressure is applied to the traveling straight valve in the same manner as in the prior art without providing a conventional two-position switching valve or the like. Therefore, the number of parts is smaller than that of the related art, the structure is simplified, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a hydraulic circuit of a hydraulic shovel according to the present invention.

FIG. 2 is a circuit diagram showing the operation of the embodiment of the present invention shown in FIG.

FIG. 3 is a circuit diagram showing an operation of the embodiment of the present invention shown in FIG. 1;

FIG. 4 is a circuit diagram showing a hydraulic circuit of a conventional hydraulic shovel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st main hydraulic pump 2 2nd main hydraulic pump 3 1st control valve 4 2nd control valve 5 Traveling motor 6 Traveling motor 7 Front actuator 8 Front actuator 9 Control valve 10 Control valve 11 Traveling straight valve 12 Pilot Pump 13 Pilot valve 14 Pilot valve 20 Pipe line 21 Connection pipe line 22 Pilot pipe line 23 Detection circuit 24 Pipe line 33 Detection circuit 34 Restrictor 35 Check valve

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E02F 9/22

Claims (1)

(57) [Claims] 1. A first main hydraulic pump having a first main hydraulic pump and a second main hydraulic pump. Actuator control valves are connected in cascade, and a plurality of actuator control valves are connected in cascade to the discharge circuit of the second main hydraulic pump with the other traveling second control valve being the most downstream side. A connecting pipe connecting the upstream pump circuit of the control valve and the upstream pump circuit of the second control valve, a traveling straight valve communicating and disconnecting the connecting pipe, and switching the traveling straight valve to a communicating position. A biasing means for applying a force to one of the drive units of the straight travel valve, and a detection circuit for detecting operation signals of the first control valve and the second control valve;
In the hydraulic circuit of a hydraulic shovel configured to prohibit the switching of the traveling straight valve to the communication side when the control valve is not operated, the detection circuit and the other drive opposing one drive unit of the traveling straight valve are provided. A hydraulic circuit for a hydraulic shovel, comprising a back pressure induction circuit that communicates with a section.