JP2012092925A - Hydraulic circuit and hydraulic shovel equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit which uses a multiple control valve and is excellent in responsiveness.SOLUTION: In the hydraulic circuit where pressure oil from a variable displacement hydraulic pump is supplied to each hydraulic actuator via two or more directional control valves connected in series, a shut-off valve is provided at the most downstream position of the two or more directional control valves and an accumulator is provided between the directional control valve at the most downstream position and the shut-off valve via a check valve.

Description

  Corresponds to the hydraulic circuit of construction machinery. It is particularly suitable for machines that require responsiveness, such as hydraulic excavators.

In recent construction machines, particularly hydraulic excavator circuits, a closed center circuit using a variable pump has been used to make an energy saving system. In the case of the conventional open center negative circuit, the pump must discharge the oil for negative control when the valve is neutral. This is because the power loss can be reduced in order to reduce the discharge of water.
However, in the case of a closed center circuit, the tilting of the variable displacement pump is controlled by the operation signal (hydraulic pilot pressure, electromagnetic proportional valve command, etc.) of the multiple control valve that is configured by stacking multiple control valves. Therefore, there is a problem that a delay in flow rate discharge at the start and a surge pressure at the stop are generated due to an influence on the response time of the pump. On the other hand, some improvement can be achieved by improving the response time of the pump, but the response time has a limit and is not a complete measure.
As this type of hydraulic circuit, for example, proposed in Patent Document 1, the circuit disclosed in the same document accumulates the pressure generated during inertial body braking in an accumulator and returns the pressurized oil to the main pipeline. Only a configuration is disclosed, and no proposal has been made for measures against surge pressure generated in the closed center circuit.

JP 2005-003183 A

  In view of this, an object of the present application is to provide a circuit with improved surge pressure and excellent energy saving effect in a closed center hydraulic circuit using multiple control valves.

In order to solve the above-mentioned problems, the invention according to claim 1 of the present application applies pressure oil from a variable displacement hydraulic pump to each hydraulic actuator via a plurality of closed center type directional control valves connected in series. In the hydraulic circuit to be supplied, a closing valve is provided on the most downstream side of the plurality of directional control valves, and an accumulator is provided between the directional control valve on the most downstream side and the closing valve via a check valve. .
The invention according to claim 2 is the invention according to claim 1, wherein the accumulator is connected between a discharge line from the hydraulic pump and the directional control valve on the most upstream side via a poppet type solenoid valve. It is connected.
According to a third aspect of the present invention, in the second aspect of the present invention, the poppet type electromagnetic valve is controlled by an electric signal for operating the direction control valve.
According to a fourth aspect of the present invention, the hydraulic excavator includes the hydraulic circuit according to any one of the first to third aspects.

In a hydraulic circuit with multiple control valves, when the valve is returned to neutral, the variable displacement pump reduces the tilt angle to reduce the discharge amount to 0, but surge pressure is generated in the pump discharge line due to the response delay However, according to the hydraulic circuit of the present invention, since the pump discharge line is connected to the bypass line when the multiple control valve is neutral, the surge pressure is accumulated in the accumulator through the check valve provided on the most downstream side. Can prevent excessive surge pressure.
When the multiple control valve is switched, the pump moves the tilt angle from zero to the maximum direction, but at the same time, the solenoid valve is turned on by the operation signal of the multiple control valve. Since the hydraulic pressure released from the accumulator is connected to the pump discharge line via the check valve, it is possible to improve the response delay when starting all the hydraulic actuators. Further, since the recovered energy can be returned to the operation of the actuator, more energy saving effect is possible.

Explanatory drawing of the hydraulic circuit of the hydraulic excavator of one embodiment of the present invention

Next, an embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a hydraulic circuit for a hydraulic excavator, which includes a bucket 1, a boom 2, an arm 3, a left traveling motor 4, a right traveling motor 5, and a turning motor 6 as hydraulic actuators. Closed center type directional control valves 11 to 16 are connected to the hydraulic actuators 1 to 3, respectively. These directional control valves 11 to 16 are connected in series to the discharge lines P1 and P2 of the variable displacement hydraulic pump, and are configured as so-called multiple control valves.

As shown in the drawing, in the flow path downstream of the most downstream directional control valve 16 among the directional control valves 11 to 16, the closing valves 17a and 17b are provided, and the most downstream directional control valve 16 and the closing valve 17a. , 17b, an accumulator 19 is provided via check valves 18a, 18b.
Thus, the accumulator 19 for pressure accumulation is provided in the most downstream of the multiple control valves 11 to 16, so that the generated surge pressure is accumulated in the accumulator 19 regardless of which section of the direction control valves 11 to 16 is switched. become.

  In the illustrated example, the discharge side of the accumulator 19 is connected via a poppet type valve 20 to a pump discharge line indicated by Z in the figure. Thus, the switching time can be shortened by using a poppet type solenoid valve.

  The poppet-type electromagnetic valve 20 is preferably controlled by an electric signal for operating the direction control valves 11 to 16. This is because the switching can be quickly performed together with the operation of the direction control valves 11 to 16.

1-6 Hydraulic actuator 11-16 Direction control valve 17a, 17b Stop valve 18a, 18b Check valve 19 Accumulator 20 Poppet type solenoid valve and check valve

Claims (4)

  In a hydraulic circuit that supplies hydraulic oil from a variable displacement hydraulic pump to a hydraulic actuator through a plurality of closed center type directional control valves connected in series, the hydraulic oil is closed to the most downstream of the directional control valves. A hydraulic circuit comprising a valve, wherein an accumulator is provided between the most downstream direction control valve and the closing valve via a check valve.   The hydraulic circuit according to claim 1, wherein the accumulator is connected between a discharge line from the hydraulic pump and the directional control valve on the most upstream side via a poppet type solenoid valve.   3. The hydraulic circuit according to claim 2, wherein the poppet type solenoid valve is controlled by an electric signal for operating the direction control valve.   A hydraulic excavator comprising the hydraulic circuit according to any one of claims 1 to 3.

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