JPH03199680A - Low noise type hydraulic device - Google Patents

Abstract

PURPOSE:To keep speed of an actuator constant by inserting a pressure compensation valve between a pump and a directional control valve, and providing, on an engine, a deceleration button which can lower engine speed with one touch. CONSTITUTION:A pump servo 5 which controls a pump swash plate is provided on a pump 2 in such a way that pressure difference between a pump outlet pressure P and a hydraulic cylinder inlet pressure P1 is kept always constant. A pressure compensation valve 6 is inserted between the hydraulic pump 2 and a directional control valve 3 in order that pressure difference between an inlet pressure P1' and the outlet pressure P of the directional control valve 3 is kept constant. A deceleration button 7 which lowers engine speed with one touch is additionally set on an engine 1. A flow rate acting on an actuator is not changed, is this way, and the speed thereof is kept constant.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a low-noise extraction device for operating a working device of a extraction shovel or the like.

(Prior Art) Fig. 5 and Fig. 6 are hydraulic circuit diagrams of a conventional hydraulic excavator.
FIG. 6 shows a case where a plurality of actuators are operated simultaneously.

In FIG. 5, oil discharged from a hydraulic pump 2 driven by an engine 1 is branched into two channels, one acting on a hydraulic cylinder 4 which is an actuator via a directional control valve 15, and the other acting directly on a hydraulic cylinder 4, which is an actuator. It has a 16-part structure.

here.

Q, Q^l + Q B l: Flow rate p at each position,
p,; Pressure At, Ill at each position: □, Km for each opening area of the directional control valve 15
+: When it is taken as the pressure loss coefficient at each opening of the directional control valve 15, the following linear relational expression is established.

Q=Q□ +q, ・ ・ ・
・ ・ −■ Therefore, when the engine rotation speed decreases, the pump discharge JIQ decreases, and the sum of 0□ and Qs+ also decreases from the formula ■, and the distribution is governed by the formula 0, so generally, O□, which has a large resistance, decreases significantly.

In addition, in FIG. 6 where the hydraulic cylinders 8 and 9, which are actuators, are operated simultaneously, Q, QA, QA, , +1. ,,Q,, :Flow rate at each position 1),P,,P, :Pressure at each position A+, As, B+,llz : Directional control valve 17.
18 opening areas KAl, Kam, Kar, Kax: Directional control valve 17.
Assuming the pressure loss coefficient at each of the 18 openings, the following linear relational expression holds true.

Q” QAI + Qllll +Q.
...■ Therefore, in this format 6, if the engine speed is reduced, the pump discharge amount will decrease, and from the formula ■, Q□.

Since the sum of Gs+ and Qsg also decreases, and their distribution is governed by the equation (2), the distribution ratio generally changes.

(Problem to be Solved by the Invention) In this type of hydraulic system, when the engine speed is reduced in order to reduce noise, the pump discharge amount decreases approximately in proportion to the rate of reduction, so the actuator speed decreases. Decrease.

Furthermore, in the case of simultaneous operation of multiple actuators, as the flow rate decreases, the distribution ratio, that is, the speed of the actuators, changes depending on the resistance of each circuit, resulting in a problem of reduced workability and operability. there were.

The present invention aims to solve this problem.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, in an extraction circuit that sends oil discharged from a hydraulic pump to an actuator via a directional control valve, the pump outlet pressure and the actuator population are In addition to attaching a pump servo to the pump to control the pump swash plate so that the pressure difference is always constant, the first method is to maintain a constant pressure difference between the inlet pressure and outlet pressure of the directional FIF well. A pressure 1 m compensating valve is inserted between the pump and the directional control valve.

A second method is to insert the pressure compensating valve between the directional control valve and the actuator instead of between the pump and the directional control valve.

Furthermore, the engine that drives the hydraulic pump is equipped with a deceleration button that lowers the engine speed with a single touch when low noise is required.

(Function) According to the above configuration, even if the engine rotational speed is reduced by imitating the deceleration button, as long as the differential pressure between the directional control valve inlet pressure and outlet pressure is maintained at a constant value by the action of the pressure compensation valve. , the amount of oil flowing into the actuator is constant due to the action of the pump servo.

(Example) The present invention will be explained below with reference to embodiments shown in the drawings.

FIG. 1 is a hydraulic circuit diagram showing an embodiment in which a single actuator is operated according to the first method of the present invention, and FIG. 2 is a hydraulic circuit diagram showing an embodiment in which a plurality of actuators are operated simultaneously. In FIG. 1, oil discharged from a hydraulic pump 2 driven by an engine 1 passes through a directional control valve 3 and acts on a hydraulic cylinder 4, which is an actuator.

In such a basic hydraulic circuit, the present invention includes a pump servo 5 that controls the pump swash plate so that the differential pressure between the pump outlet pressure P and the hydraulic cylinder inlet pressure P1 is always a constant value.
is attached to pump 2.

Moreover, between the hydraulic pump 2 and the direction control valve 3, there is a direction fl
The pressure that acts so that the differential pressure between the population pressure P+' of the ill m valve 3 and the outlet pressure of the directional control valve, that is, the inlet pressure P1 of the hydraulic cylinder 4, becomes a constant value? +tl fR valve 6 is inserted.

Furthermore, if low noise is required for the engine,
It is equipped with a deceleration button 7 that can reduce the engine speed with one touch.

In the extraction circuit with such a configuration, q''1: Flow rate at each position p, p, ', p: Pressure at each position [11 Opening area of the two-way control valve 3 xl Pressure loss of the two-way control valve 3 If it is a coefficient,
pressure? +tl ('As long as the following equation (2) holds true due to the action of the R valve 6, if the opening surface mu is constant, the flow ff1
Q,, b becomes constant.

Δp,=p,'-p+=(mouth a+/B+
l ” , the engine rotational speed decreases, and the action of the pressure ? The flowing oil flow ff1Q, is constant.

Next, in FIG. 2, the pump swash plate is controlled so that the differential pressure between the outlet pressure P of the hydraulic pump 2 and the higher of the inlet pressures P1 or h of the hydraulic cylinders 8 or 9 is a constant value. A servo 5 is attached to the pump 2.

In order to supply this pilot pressure, a shuttle valve lo is inserted between the hydraulic cylinders 8 and 9, which outputs the larger pressure of P and P2.

Furthermore, between the hydraulic pump 2 and the directional control valves 11 and 12, there is an inlet pressure Pl of the directional control valves, respectively.

Or the pressure that acts so that the differential pressure between P, ° and the outlet pressure of the directional control valve, that is, the inlet pressure P or P2 of the hydraulic cylinder, becomes a constant value? 111 compensation valves 13 and 14 are inserted.

Furthermore, the engine 1 is equipped with a deceleration button 7 as in the case of a single conversion.

In a hydraulic circuit with such a configuration, Q, Q, , Q, : Flow rate p, p at each position
,,p,°,P-,Pa°: Pressure B,,I at each position
1. , the opening area of the directional control valve 11.12,
□ If the pressure loss coefficient of two-way control valve 11.12 is the pressure? As long as the following equation (■) holds true due to the action of the itl m valve 13.14, the opening area and B! If Qa+ and q are constant, then Qa+ and q are also constant.

ΔP,=　P,“-P,=　P,’-P.

= fast/n+)”x K11l = (Q
ll□/口zl''
Since P-n+ax (P+°, h゛) is controlled to be constant, even if the engine speed decreases by operating the deceleration button 7, the operation of the pressure 9m compensating valves 13 and 14 is guaranteed.
Therefore, since △P6 is held constant, the oil flow ff flowing into the hydraulic cylinders 8 and 9 is determined by equation (2).
1a, and Q are constant.

As a second method, as shown in Figures 3 and 4,
Even if the positions of the pressure fill compensation valve and the direction control valve are swapped,
Its operation is similar to that in FIGS. 1 and 2.

(Effects of the Invention) As stated above, in the hydraulic system of the present invention, even if the engine speed is lowered to reduce noise and the pump discharge amount is reduced, the load remains within a certain range relative to the engine output. , the flow rate acting on the actuator does not change and therefore its speed also remains constant.

Also, in the case of combined operations, a similar function also holds the relative speed of both actuators constant, so that
Workability and operability do not deteriorate even if the engine speed is reduced.

[Brief explanation of drawings]

1 to 4 are circuit diagrams of a hydraulic system according to the present invention;
Further, FIGS. 5 and 6 are circuit diagrams of a conventional general hydraulic system. l...Engine 2...Hydraulic pump 3.11,
12.15.17.18 Directional control valve 4. 8.・Hydraulic cylinder pump servo 6. 13゜Pressure compensation valve/deservokun/shuttle valve tank.

Claims (2)

[Claims] (1) In the hydraulic circuit that sends oil discharged from the hydraulic pump to the actuator via the directional control valve, the pump swash plate is controlled so that the differential pressure between the pump outlet pressure and the actuator inlet pressure is always a constant value. Attaching a pump servo to the pump, and inserting a pressure compensation valve between the pump and the directional control valve so that the differential pressure between the inlet pressure and the outlet pressure of the directional control valve becomes a constant value, This low-noise hydraulic system is characterized by the fact that the engine that drives the hydraulic pump is equipped with a deceleration button that can reduce the engine speed with one touch. (2) A pressure compensation valve that acts so that the differential pressure between the inlet pressure and outlet pressure of the directional control valve remains constant is inserted between the directional control valve and the actuator instead of between the pump and the directional control valve. The low-noise hydraulic system according to claim 1, characterized in that: