JPH0329414Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pilot hydraulic circuit device for a hydraulic construction machine.

In the conventional hydraulic circuit device of this type, as shown in Fig. 1, a relief valve b is attached to the pilot pump circuit a to maintain the hydraulic pressure at P _R1 Kg/ ^cm2 .
Increase/decrease in pump discharge amount of main pumps c, d, e,
It was used as a pressure source for directional switching of main valve f.

However, since a large flow rate is temporarily required to increase/decrease the pump discharge amount and change the direction of the main valve f, the discharge flow rate Qpl/min from the pilot pump g is constantly relieved from the relief valve b, resulting in energy loss.

Furthermore, when the work equipment is operated in its natural state when the engine is stopped, it must be carried out immediately after the engine is stopped.

The present invention was developed in view of the above circumstances, and its purpose is to minimize energy loss in the pilot circuit, which conventionally usually flows from the relief valve to the tank, resulting in power loss. Not only is it possible to do this, but also when the engine stops due to an emergency or engine failure, it is possible to move the cylinder of a working machine that is stopped in the air in the direction of natural descent without restarting the engine. It is an object of the present invention to provide a pilot hydraulic circuit device for a hydraulic construction machine that can operate the actuator of a working machine or the like in its natural state at any time after the engine is stopped.

The present invention will be explained below with reference to FIG.

In the drawings, 1, 2, and 3 are main pumps, and 4 is a pilot pump. The first main pump 1 supplies hydraulic pressure to the first main valve group 5,
The second main pump 2 is connected to the second main valve group 6
supplying hydraulic pressure to the nth main pump 3
is for supplying hydraulic pressure to the n-th main valve group 7.

The n-th main valve group 7 includes a boom switching valve 8, a bottom switching valve 9, a left travel switching valve 10, and a bucket switching valve 11. It is equipped with electrohydraulic valve servos 8', 9', 10', and 11'.

The discharge side of the main pump 3 is connected to pump ports 8a and 8b of a boom switching valve 8 via first and second pipes 12 and 13, and a port 8c of the boom switching valve 8 is connected to a third pump port 8c. , fourth conduit 14,1
5 to ports 9a and 9b of the bottom switching valve 9.
is connected to port 9c of bottom switching valve 9.
are connected to the ports 10a, 10b of the left travel switching valve 10 via the fifth and sixth pipes 16, 17, and the port 10c of the left travel switching valve 10 is connected to the ports 11a, 11 of the bucket switching valve 11. 7th in 11b,
The port 11c of the bucket switching valve 11 is connected to the ninth pipe line 20.
It communicates with tank 21 via.

Connection ports 8d and 8e of the boom switching valve 8 are connected to a boom cylinder 23 as an actuator via ninth and tenth pipes 22 and 22',
The connection ports 9d and 9e of the bottom switching valve 9 are
11 and 12 are connected to the bottom cylinder as an actuator via pipes 24 and 25, and the connection ports 10d and 10e of the left travel switching valve 10 are
13, is connected to the left travel motor as an actuator via the 14th pipe line 26, 27, and the connection ports 11d, 11e of the bucket switching valve 11 are connected to the left travel motor as an actuator.
15 and 16 are connected to a bucket cylinder as an actuator via pipes 28 and 29.

Further, tank ports 8f, 9f, 10f, and 11f of the boom switching valve 8, the bottom switching valve 9, the left running switching valve 10, and the bucket switching valve 11 communicate with the tank 21.

The first main valve group 5 is an arm switching valve 3
0, switching valve for bucket 31, switching valve for boom 3
2. It is equipped with a switching valve 33 for swinging, and the second main valve group includes a switching valve 34 for swinging, a switching valve 35 for arm, a switching valve 36 for right travel, and a switching valve 3 for boom.
7.

The discharge side of the pilot pump 4 is connected to the port 39a of the first directional valve 39 via the 17th pipe 38, and the port 39b of the first directional valve 39 is connected to the port 39b of the first directional valve 39.
are the arm switching valve 30 and the bucket switching valve 3 as each main valve of the first main valve group 5.
1. Electrohydraulic valve servos 30', 31', 32' for boom switching valve 32 and swing switching valve 33,
33', a swing switching valve 34 as each main valve of the second main valve group 6, and an arm switching valve 3
5. Electrohydraulic valve servos 34', 35', 36' for right travel switching valve 36 and boom switching valve 37,
37' and the electrohydraulic servos 8', 9' of the boom switching valve 8, bottom switching valve 9, left running switching valve 10, and bucket switching valve 11 as main valves of the n-th main valve group 7. , 10', 11' via a pilot line 40. A check valve 4 is installed at the confluence section 41 of the pilot pipe 40.
2 is provided, and a check valve 4 of this confluence section 41 is provided.
An accumulator conduit 43 branches from the outlet side of No. 2, and the accumulator conduit 43 communicates with an accumulator 44.

A pilot line 45 branched from the accumulator line 43 is connected to a pilot port 39c of the first directional control valve 39.
Ports 39d and 39e of 9 are drain pipes 55 and 5.
6 to the tank 21, and a relief valve 57 is provided in the drain pipe line 55. Further, branch pipes 46, 47, and 48 branched from the outlet side of the check valve 42 of the confluence part 41 of the pilot pipe 40 are connected to the pump servo 49 of the first pump 1, the pump servo 50 of the second pump 2, and the n-th pump. 3 pump servos 51, respectively.

Further, a relief valve 52 is provided on the discharge side of the pilot pump 4.

53 in the drawing is an engine.

The set pressure P _R1 of the first relief valve 52 is set higher than the unload pressure P _P1 and the off-load pressure P _P2 .

Further, a second directional switching valve 59 is provided at a confluence 58 of the branch pipes 46, 47, and 48, and a pilot port 59a of the second directional switching valve 59 is connected to a pilot pipe branched from the discharge side of the pilot pump 4. 60 is connected, and the tank port 59b of the second directional switching valve 59 communicates with the tank 21.

The relief valve 57 is provided to guarantee the minimum pilot pressure of the second directional control valve 59.
(Normally, the second directional switching valve 59 may or may not be operable due to the circuit resistance of the hydraulic pressure circuit, but this is to ensure the hydraulic pressure when the oil temperature rises, etc.) Set pressure of the relief valve 57 P _R2 is set to the minimum hydraulic pressure required for the second directional switching valve 59 to operate.

Next, the operation will be explained.

During operation, the second directional valve 59 is the relief valve 5.
7, and the pump servo _circuit , that is, the junction of branch circuits 46, 47, and 48 is open.

When the discharge pressure from the pilot pump 4 is stored in the accumulator 44 and the pressure inside the accumulator 44 reaches the unload pressure P _P1 , the directional control valve 39 is activated, and the discharge liquid from the pilot pump 4 is transferred to the tank 21.
and is unloaded.

1st, 2nd, nth main valve groups 5, 6,
Each of the main valves 7 uses the energy stored in the accumulator 44 to operate the valve servos 30' to 37',
8' to 11' and pump servos 49, 50, and 51 are operated to operate each actuator.

When the hydraulic pressure of the accumulator 44 decreases to the on-load pressure P _P2 , the spring 54 returns the position of the first directional control valve 39 to its original position, and the discharge pressure from the pilot pump 4 is accumulated in the accumulator 44 again after being on-loaded.

A check valve 42 is provided to prevent backflow of fluid during unloading.

The reason why the set P _R1 of the first relief valve 52 is made higher than the unload pressure P _P1 and the on-load pressure P _P2 is because the relief valve 5
2 does not operate, and the relief valve 5
This is to prevent power loss from 2. Therefore, although the relief valve 52 does not operate under normal conditions, the relief valve 52 is provided to prevent the circuit from becoming high pressure in the event of some abnormality in the circuit, such as malfunction of the first directional valve 39.

In an emergency or some kind of accident, engine 5
3 stops, no hydraulic pressure is discharged from the pilot pump 4, and the hydraulic pressure at the pump discharge portion decreases. In this case, the position of the second directional control valve 59 is changed to the position of the spring 63.
Since the circuit to the pump servos 49, 50, 51 returned by the pump servos 49, 50, 51 is closed, the hydraulic pressure stored in the accumulator 44 will not be released through the internal throttles of the pump servos 49, 50, 51.

Therefore, after checking the safety of the surrounding area or the situation of an accident, the actuator can be operated in a natural state (a state in which no holding pressure is applied to the cylinder of the working machine, etc.).

As described in detail above, the present invention operates the valve servo of the main valve provided in the work equipment operating circuit and the pump servo of the main pump of the work equipment operating circuit using the pilot pressure of the pilot circuit. An accumulator 44 that accumulates the discharge pressure of the pilot pump 4 in the circuit.
is provided in the pilot circuit, and is operated by the unload pressure P _P1 of the accumulator 44 to interlock the discharge side of the pilot pump 4 with the tank 21, and operates by the on-load pressure P _P2 to connect the discharge side of the pilot pump 4 to the accumulator 44. A check valve 42 is provided in the pilot circuit to allow fluid to flow only from the first directional valve 39 side to the accumulator 44 side. This is a pilot hydraulic circuit device for a hydraulic construction machine, characterized in that it is provided with a second directional switching valve 59 that switches over and closes the pump servo circuit.

Therefore, when the discharge pressure from the pilot pump 4 is stored in the accumulator 44 and the pressure of the accumulator 44 reaches the unload pressure P _P1 , the first directional control valve 39 is switched and the discharge side of the pilot pump 4 is communicated with the tank. and enters the unload state. Therefore, it is possible to minimize energy loss in the pilot circuit, which conventionally usually flows from the relief valve to the tank, resulting in power loss.

In addition, even if the engine stops due to an emergency or engine failure, the hydraulic pressure is stored in the accumulator 44, so the valve servo can be moved, and the cylinder of the work equipment that is stopped in the air can be moved. Since it can be moved in the direction of natural descent, danger can be avoided without restarting the engine.

Furthermore, since the pump servo circuit is closed by the second directional control valve 59 when the engine is stopped, the pressure in the accumulator is maintained for a long time, and the actuator of the work equipment can be operated in its natural state at any time after the engine has stopped, which is convenient. Become.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of a conventional pilot hydraulic circuit device for a hydraulic construction machine, and FIG. 2 is an explanatory diagram of the configuration of an embodiment of the present invention. 4 is a pilot pump, 39 is a first directional valve, 42 is a check valve, 44 is an accumulator,
59 is a second directional control valve.

Claims (1)

[Scope of utility model registration request] In a system in which the valve servo of the main valve provided in the work equipment operating circuit and the pump servo of the main pump of the work equipment operating circuit are operated by the pilot pressure of the pilot circuit, the discharge pressure of the pilot pump 4 is stored in the pilot circuit. An accumulator 44 is provided in the pilot circuit, and the pilot circuit is operated by switching the unload pressure P _P1 of the accumulator 44 to communicate the discharge side of the pilot pump 4 with the tank 21, and operates by the on-load pressure P _P2 to connect the discharge side of the pilot pump 4. A check valve 42 is provided in the pilot circuit to allow fluid to flow only from the first directional valve 39 side to the accumulator 44 side. A pilot hydraulic circuit device for a hydraulic construction machine, characterized in that a second directional switching valve 59 is provided which switches and closes a pump servo circuit when the pressure decreases.