JPS6240562B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is suitable for use in drive circuits of construction machinery such as truck cranes and hydraulic excavators, and includes two pumps and four flow control valves. and 3
The present invention relates to a fluid circuit for a construction machine, in which the speed of three actuators can be controlled using three pressure compensation valves in an optimal manner for the construction machine as described above.

<Prior Art> For example, the truck crane shown in FIG.
A boom actuator 104 for tilting the wire 103 and a hoisting actuator 106 for hoisting the wire 105 are provided.

In such a truck crane, since the swing of the base 101 is the basis of operation, even if another actuator is operated while the swing actuator 102 is in operation, the swing actuator 1
02 is required to be speed controlled without being affected by these factors and regardless of the magnitude of the load. Further, when winding up or lowering the wire 105, there is a demand for supplying the discharge amount of the entire pump to the winding actuator 106 to operate it at high speed. In addition, in the case of inching operation, etc., the swing actuator 102 and the boom actuator 10
4 and the hoisting actuator 106 are required to perform accurate slow speed control without being affected by the operation of other actuators and regardless of the magnitude of the load.

By the way, as a fluid circuit in which these three actuators are driven by two pumps, there is, for example, Japanese Patent Laid-Open No. 54-93778. As shown in FIG. 3, this fluid circuit is connected to parallel circuits 116a and 116b branched from the discharge path 117 of the first pump 140 in order to drive the first and second actuators 114a and 114b by the first pump 140, respectively. The pressure reduction type pressure compensation valves 120a, 120b and the flow rate direction control valves 110a, 110b are connected in sequence, and the discharge path 142 of the second pump 141 is provided with a flow rate type pressure compensation valve 147 and a flow rate direction control valve 146, so that the three actuators 114a, 114b,
148 are driven simultaneously.

<Problems to be Solved by the Invention> However, in this fluid circuit, when the required flow rate of the first and second actuators 114a, 114b exceeds the discharge amount of the first pump 140, the first pump 140 As the discharge pressure decreases,
Both pressure reducing type pressure compensation valves 120a and 120b no longer perform pressure compensation. For this reason, the first pump 140
The discharge fluid is supplied to any lightly loaded actuator and not to any heavily loaded actuator. That is, two actuators 114
When driving actuators a and 114b at the same time, the load conditions of both actuators are not constant but vary.
For example, it is not possible to specify an important actuator, such as the swing actuator of the truck crane shown in FIG. 1, and prioritize its operation. To give a specific example, if the operation of the swing actuator 102 is more important than the operation of the boom actuator 104, but the pump discharge rate is insufficient, oil will flow only to the boom actuator 104, which has a lower load. As a result, fluid is not supplied to the heavily loaded swing actuator 102, making it impossible to perform the most important swing operation. That is, the conventional fluid circuit has a defect in that when the discharge amount of the first pump 140 is insufficient, fluid cannot be supplied preferentially to a specific actuator regardless of load conditions.

This invention was invented in view of the above points, and the purpose is to be able to simultaneously drive three actuators at very low speeds without mutual interference, while still being able to operate independently of load conditions even when the discharge volume of the first pump is insufficient. It is an object of the present invention to provide a fluid circuit for construction machinery that can supply fluid preferentially to a specific actuator.

<Means for Solving the Problems> As illustrated in FIG. The fourth flow control valve 12 for the first actuator 3 is connected to the pressure reduction port 17 of the priority type pressure compensation valve 11 to preferentially compensate the pressure of the first flow rate control valve 12, and the priority type pressure compensation valve 11 The second flow control valve 13 for the second actuator 4 is connected to the bypass port 19 of the second actuator 4 via a line 20 to which a bypass type pressure compensation valve 14 is connected in the middle to compensate the pressure of the second flow control valve 13. A third flow rate control valve 62 and a fourth flow rate control valve 63 are connected in parallel to the pump line 65 of the two pumps 5, and the third or fourth flow rate is controlled by the bypass type pressure compensation valve 61 connected to the pump line 65. In addition to pressure compensating the control valves 62 and 63, the third actuator 7 is connected to the third flow control valve 62, and the load lines 84 and 85 of the fourth flow control valve 63 are connected to the load lines 84 and 85 of the second flow control valve 13. connected to the lines 53 and 54, and further connected to the fourth flow control valve 63 and the second flow control valve 1.
3 in conjunction with each other to delay the outflow timing of the fluid from the fourth flow rate control valve 63 from the outflow timing of the second flow rate control valve 13, thereby giving priority to the first actuator over the second actuator. When the speed can be controlled regardless of the size of the load and the speed of the first, second, and third actuators are all controlled at very low speed, the first, second, and third actuators can all be controlled independently of the load. An object of the present invention is to provide a new fluid circuit for construction machinery that can control speed regardless of fluctuations and can drive a second actuator at high speed by merging the discharge fluids of two pumps. It is.

<Operation> According to the above configuration, the first flow control valve for the first actuator is connected to the pressure reducing pump of the priority type pressure compensation valve, and the flow control valve for the second actuator is connected to the bypass port. Therefore, even if the discharge amount of the first pump is insufficient,
The speed of the first actuator is controlled in priority over the second actuator regardless of load fluctuations.

Further, a bypass type pressure compensation valve is connected between the second flow rate control valve and the bypass port of the priority type pressure compensation valve, so that the second flow rate control valve is pressure compensated, while a third flow rate control valve is connected to the second pump. 3rd for actuator
The flow control valve and the fourth flow control valve are connected in parallel via a pump line with a bypass type pressure compensation valve connected between them, and one of them is selectively pressure compensated. Further, the fourth flow rate control valve and the second flow rate control valve are linked to each other so that the timing at which the fluid starts flowing from the fourth flow rate control valve is made later than the timing at which fluid starts flowing from the second flow rate control valve.
Therefore, when controlling the speed of all the first, second, and third actuators at a very slow speed, the first, second, and third flow control valves, which are pressure-compensated, are used to
The speed of the second and third actuators is controlled independently and accurately without being affected by the operation of other actuators and regardless of load fluctuations.

Further, the load line of the fourth flow control valve is connected to the second flow control valve.
It is connected to the load line of the flow control valve, and the discharge fluids of the first and second pumps are combined and supplied to the second actuator, so that the second actuator is driven at high speed.

<Example> Hereinafter, an example in which the present invention is applied to a drive circuit for a truck crane will be described in detail.

In FIG. 2, 1 is a fixed displacement first pump;
2 is a first control valve unit connected to the first pump 1; 3 and 4 are a first swing actuator and a second hoist actuator connected to the first control valve unit 2, respectively.
Actuator, 5, fixed displacement second pump, 6
7 is a second control valve unit connected to the second pump 5, and 7 is a third boom actuator connected to the second control valve unit 6.

The first control valve unit 2 includes a priority type pressure compensation valve 11, a first flow rate directional control valve 12 and a second flow rate directional control valve 13, which are a type of flow rate control valve, and a bypass type pressure compensation valve 14. .

The first flow rate directional control valve 12 and the second flow rate directional control valve 13 have exactly the same structure, and each ABT has the functions of a flow rate control valve and a directional control valve.
It is a connection type throttle switching valve, with pilot ports m,
n. The pilot ports m and n communicate in the neutral position, and in the switching position, the pilot port m communicates with the load port A or B which communicates with the pump port P.

On the other hand, the primary port 15 of the priority pressure compensation valve 11 is connected to the first pump 1 via a pump line 16.
The pressure reduction port 17 of the preferential pressure compensation valve 11 is connected to the pump port P of the first flow directional control valve 12 via line 18, and the bypass port 19 of the preferential pressure compensation valve 11 is connected to ,
It is connected to the pump port P of the second flow direction control valve 13 via a line 20 . The line 20 is connected to a tank 22 via a line 21 having a bypass type pressure compensating valve 14 installed therebetween.

The spring chamber of the above-mentioned priority type pressure compensation valve includes a throttle 26,
It is connected to the pilot port m of the first flow directional control valve 12 through the center port of the shuttle valve 25 and a port at one end thereof, and is connected to the pilot port n of the first flow directional control valve 12 and the shuttle valve 25. The port at the other end is connected to tank 22 via line 27. Therefore,
The priority type pressure compensation valve 11 has a differential pressure before and after a flow rate adjusting section (not shown) of the first flow rate directional control valve 12;
That is, pump port P and load port A or B
The pressure on the pressure reduction port 17 side is preferentially controlled so as to maintain the differential pressure between the pressure and the pressure at a constant level in response to the spring force of the spring 11a in the spring chamber.
Further, a pilot relief valve 3 is provided in the middle between the spring chamber of the priority type pressure compensation valve 11 and the throttle 26.
It is connected to the tank 22 via a line 31 equipped with 0, and the maximum pressure on the decompression port 17 side is regulated.

On the other hand, the spring chamber of the bypass type pressure compensation valve 14 is connected to the pilot port m of the second flow rate directional control valve 13 via the throttle 38, the central port of the shuttle valve 37, and a port at one end thereof. A pilot port n of the second flow direction control valve 13 and a port at the other end of the shuttle valve 37 are connected to the tank 22 via a line 39. Therefore, the bypass type pressure compensation valve 14
is pressure compensated so that the differential pressure before and after the flow rate adjustment part of the second flow rate directional control valve 13, that is, the differential pressure between the pump port P and the load port A or B, corresponds to the spring force of the spring 14a of the spring chamber. People are starting to do this. Furthermore, a tank 22 is connected between the spring chamber of the bypass type pressure compensation valve 14 and the throttle 38 via a line 41 in which a pilot relief valve 40 is installed in the middle to regulate the maximum pressure in the line 20. are doing.

Each load port A, B of the first flow rate directional control valve 12 is connected to the first swing actuator 3 via each load line 51, 52, respectively. Further, each load port A, B of the second flow rate directional control valve 13 is connected to the second hoisting actuator 4 via each load line 53, 54, respectively.

On the other hand, the second control valve unit 6 includes a bypass type pressure compensation valve 61, a closed center type third flow rate directional control valve 62, and an ABT connection type fourth flow rate directional control valve 63.

The third and fourth flow rate directional control valves 62, 63
Each pump port P is connected to the second pump 5 in parallel via a pump line 65. 3rd above
A check valve 66 is provided on the primary side of the pump port P of the flow direction control valve 62 to prevent backflow from the load side of the third flow direction control valve 62 to the pump line 65.

A pump line 65 between the second pump 5 and the check valve 66 is connected to a tank 69 via a line 67 having a bypass type pressure compensating valve 61 installed in the middle.
is connected to.

The spring chamber of the bypass type pressure compensating valve 61 is connected to the pilot port m of the third flow direction control valve 62 via the throttle 71, the central port of the shuttle valve 72, and a port at one end thereof. The other end port of the shuttle valve 72 is connected to the center port of another shuttle valve 73.
One end port of 3 is connected to the pilot port n of the third flow rate directional control valve 62 and the pilot port m of the fourth flow rate directional control valve 63, while the port at the other end of the shuttle valve 73 and the fourth flow rate directional control valve 63
Pilot port n means pilot line 74.
It is connected to tank 69 via. Therefore, the maximum pressure of the load side pressure of the third or fourth flow direction control valves 62, 63 is selected and transmitted to the spring chamber of the bypass type pressure compensation valve 61 by the shuttle valves 72, 73. It's summery. Therefore, the bypass type pressure compensating valve 61 converts the differential pressure before and after the maximum load side flow rate adjusting section of the third or fourth flow rate directional control valve 62, 63 into the spring force of the spring 61a of the spring chamber. Pressure compensation is performed to correspond to this. Furthermore, a tank 69 is connected between the spring chamber of the bypass type pressure compensation valve 61 and the throttle 71 via a line 79 in which a pilot relief valve 78 is installed in the middle, so that the maximum pressure of the pump line 65 can be controlled. It is regulated.

Each load port A, B of the third flow rate directional control valve 62 is connected to the third boom actuator 7 via each load line 81, 82, respectively.
Further, each load port A, B of the fourth flow direction control valve 63 is connected to each load line 5 of the second flow direction control valve 13 via each load line 84, 85, respectively.
It is connected to 3,54.

Operation lever 63 of the fourth flow direction control valve 63
a is the operating lever 13 of the second flow direction control valve 13;
a via a signal transmission path 88 consisting of a link. And the fourth flow rate directional control valve 6
The timing at which the fluid starts flowing from the second flow direction control valve 13 is delayed from the timing at which the fluid starts flowing from the second flow direction control valve 13 due to the difference in the land width of the spool (not shown) and the lever ratio of the connecting link.

The fluid circuit configured as described above operates as follows.

Assume that this fluid circuit is now in the state shown in FIG. From this state, the first flow rate directional control valve 12 is positioned at the switching position _S1 , and the first swing actuator 3 is driven.

Then, the pilot port m of the first flow rate directional control valve 12 communicates with the load port A which communicates with the rear part of the flow rate adjustment section, that is, the pump port P, so that the spring chamber of the priority type pressure compensation valve 11 is connected to the pilot port m. Port m, shuttle valve 25, throttle 26
It communicates with the load port A through. Therefore, the priority type pressure compensation valve 11 operates to keep the differential pressure before and after the flow rate adjustment part of the first flow rate directional control valve 12 constant, and discharges excess fluid from the bypass port 19 to the line 20. ing. Therefore, the first
The flow rate directional control valve 12, regardless of load fluctuations,
To accurately control the speed of a first turning actuator 3.

Next, in this state, the second flow rate directional control valve 13 is positioned at the switching position _S1 , and the second actuator 4 for hoisting is operated. At this time, the speed control of the first actuator 3 controlled by the first flow rate directional control valve 12 is not affected by the operation of the second actuator 4. I mean,
The priority type pressure compensation valve 11 compensates the pressure preferentially on the pressure reduction port 17 side and bypasses excess fluid to the bypass port 19.
This is because the first flow rate directional control valve 12 is connected to the pressure reduction port 17, and the second flow rate directional control valve 13 is connected to the bypass port 19. Further, the flow control of the first flow direction control valve 12, that is, the speed control of the first actuator 3, is also influenced by the operation of the third flow direction control valve 62 and the fourth flow direction control valve 63 to the switching position _S1 . You will not receive any. This is because the first flow rate directional control valve 12 is connected to the first pump 1 side, and the third flow rate directional control valve 62 and the fourth flow rate directional control valve 63 are connected to the second pump 5 side. Therefore,
The first flow direction control valve 12 is always pressure compensated,
Speed control of the first actuator 3 is absolutely ensured.

Next, the operating lever 1 of the first flow direction control valve 12
2a, the first flow direction control valve 1
2 is located at the switching position _S1 with a small opening, the first actuator 3 operates at a slow speed, and the second actuator 3 operates at a slow speed.
By slightly operating the operation lever 13a of the flow rate directional control valve 13, the second flow rate directional control valve 13 decreases its opening degree and is located at the switching position _S1 , which is interlocked with the second flow rate directional control valve 13. The fourth flow rate control valve 63 is still located at the neutral position _S0 , the second actuator 4 operates at a slow speed, and the operating lever 62a of the third flow rate directional control valve 62 is slightly operated to control the third flow rate. The directional control valve 62 is located at the switching position _S1 with a small opening degree, and the third actuator 7 is brought into a state where it operates at a slow speed.

At this time, the first flow rate directional control valve 12 is pressure compensated by the priority type pressure compensation valve 11 in the same manner as described above, and the opening degree of the first flow rate directional control valve 12 is small, so
Most of the fluid discharged from the first pump 1 is discharged through the bypass port 19 of the preferential pressure compensation valve 11. In addition, the spring chamber of the bypass type pressure compensation valve 14 is connected to the rear part of the flow rate adjustment section of the second flow rate directional control valve 13 via the pilot port m, the shuttle valve 37, and the throttle 38 of the second flow rate directional control valve 13. That is, since it communicates with the load port A, the bypass type pressure compensation valve 14 compensates the pressure of the line 20 so as to keep the differential pressure across the flow rate adjustment section constant. Therefore, the speed of the second actuator 4 is accurately controlled regardless of the magnitude of the load and without being affected by the operation of other actuators. On the other hand, at this time, the pump port P of the fourth flow rate directional control valve 63 is closed, and its pilot port m communicates with the tank 69 via the pilot port n and line 74. Therefore, the spring chamber of the bypass type pressure compensation valve 61 is connected to the third flow direction control valve 62 via the shuttle valve 72 and the throttle 71.
The pressure at the load port A communicating with the pilot port m, that is, the pressure downstream of the flow rate adjustment section is transmitted.
Therefore, the third flow rate directional control valve 62 is pressure compensated by the bypass type pressure compensation valve 61. Therefore, the speed of the third actuator is accurately controlled by the third flow control valve 62 regardless of load variations and without being affected by the operation of other actuators. That is, during slow-speed operation such as inching, the first, second, and third actuators 3, 4, and 7 are pressure-compensated first, second, and third actuators, respectively.
The third flow rate directional control valves 12, 13, and 62 accurately control the speed independently and independently of load fluctuations.

Next, the operating lever 1 of the second flow direction control valve 13
3a is further operated to maximize the opening degrees of both the second and fourth flow direction control valves 13, 63 and position them at the switching position _S1 .

Then, the maximum pressure of the load port A of the third or fourth flow direction control valve 62, 63 is selectively transmitted to the spring chamber of the bypass type pressure compensation valve 61 by the shuttle valves 72, 73. The bypass type pressure compensation valve 61 performs pressure compensation on the maximum load side of the third or fourth flow direction control valves 62, 63. At this time, the second actuator 4
At this time, fluid from the second and fourth flow control valves 13, 63 is supplied via the load lines 53, 84, and the second actuator 4 is driven at high speed. In this state, when the first and third flow rate directional control valves 12, 62 are positioned at the neutral position _S0 , no fluid passes through the first and third flow rate directional control valves 12, 62. In other words, the second actuator 4
can be driven at high speed by making maximum use of the fluid discharged from the first and second pumps 1 and 5. At this time, the second and fourth flow rate directional control valves 13 and 63 are
The pressure is compensated by the bypass type pressure compensation valves 14 and 61, respectively, and therefore the second actuator 4
The speed is accurately controlled regardless of load fluctuations.

In the above embodiment, a flow rate directional control valve is used as the flow rate control valve, but it goes without saying that a flow rate control valve may also be used.

Further, in the above embodiment, an example of application to a truck crane has been described, but the invention can also be applied to a hydraulic excavator. In this case, the first actuator can be used for a bucket or an arm, the second actuator can be used for a boom, and the third actuator can be used for turning.

Further, the load line of the fourth flow control valve may be connected only to the load line of the first flow control valve in accordance with requests from other construction machines and the like.

<Effects of the Invention> As is clear from the above description, according to the present invention, the first flow rate directional control valve for the first actuator is connected to the pressure reducing port of the priority type pressure compensation valve whose primary port is connected to the first pump. On the other hand, since the flow rate control valve for the second actuator is connected to the bypass port, even if the discharge amount of the first pump is insufficient, the speed of the first actuator is prioritized over the second actuator regardless of load fluctuations. Can be controlled.

Further, a bypass type pressure compensation valve is connected between the second flow rate control valve and the bypass port of the priority type pressure compensation valve to compensate the pressure of the second flow rate control valve, while a third actuator is connected to the second pump. The third flow control valve and the fourth flow control valve are connected in parallel via a pump line with a bypass type pressure compensation valve connected between them, and one of them is selected for pressure compensation. The fourth flow rate control valve and the second flow rate control valve are configured to be linked so that the timing at which the fluid starts flowing from the fourth flow rate control valve is later than the timing at which the fluid starts flowing from the second flow rate control valve. , second, and third actuators are all controlled at very low speeds, the first, second, and third flow rate control valves are pressure-compensated, respectively.
The speed of the third actuator can be accurately controlled independently without being affected by the operation of other actuators and without fluctuations in load.

Also, the load line of the fourth flow control valve is connected to the second flow control valve.
Since it is connected to the load line of the flow control valve and the discharge fluids of the first and second pumps are combined and supplied to the second actuator, the second actuator can be driven at high speed.

In addition, since the load line of the fourth flow control valve is connected to the load line of the second flow control valve connected to the bypass port of the priority type pressure compensation valve, pressure oil is preferentially supplied to the first actuator (for example, the entire amount). Even if the second actuator is operated, pressurized oil is supplied from the fourth flow control valve to the second actuator, and simultaneous operations can be performed without any trouble.

The fluid circuit for construction machinery of the present invention is versatile and can be used in truck cranes and hydraulic excavators.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the relationship between a truck crane and an actuator, FIG. 2 is a circuit diagram of a fluid circuit according to an embodiment of the present invention, and FIG. 3 is a circuit diagram of a conventional fluid circuit. 1...first pump, 3...first actuator, 4
...Second actuator, 5...Second pump, 7...Third actuator, 11...Priority type pressure compensation valve, 1
2...First flow rate directional control valve, 13...Second flow rate directional control valve, 14, 61...Bypass type pressure compensation valve, 62
...Third flow rate directional control valve, 63... Fourth flow rate directional control valve.

Claims (1)

[Claims] 1 Connect the primary port 15 of the priority pressure compensation valve 11 to the first pump 1 via the pump line 16,
And the first flow control valve 1 for the first actuator 3 is connected to the pressure reduction port 17 of the priority type pressure compensation valve 11.
2 is connected to preferentially compensate the pressure of the first flow control valve 12, and the second flow control valve 13 for the second actuator 4 is connected to the bypass port 19 of the priority type pressure compensation valve 11, and the bypass type pressure is connected to the bypass port 19 of the priority type pressure compensation valve 11. The second flow control valve 13 is pressure compensated by being connected via a line 20 to which the compensation valve 14 is connected;
A third flow control valve 6 is connected to the pump line 65 of the pump 5.
2 and a fourth flow control valve 63 are connected in parallel, and the third or fourth flow control valve 6 is controlled by a bypass type pressure compensation valve 61 connected to the pump line 65.
2 and 63, the third actuator 7 is connected to the third flow control valve 62, and the load lines 84 and 85 of the fourth flow control valve 63 are connected to the load line 53 of the second flow control valve 13. , 54, and the fourth flow control valve 63 and the second flow control valve 13 are connected to each other.
The second flow control valve 1 controls the timing of the flow of fluid.
A fluid circuit for construction machinery, characterized in that the fluid circuit is configured to delay the outflow timing of the fluid as described in item 3.