JPH04107305A - Directional control valve device - Google Patents

Abstract

PURPOSE:To secure a sufficient metering territory and to decrease pressure loss in the case of carrying out inching control by providing a pressure adjustment mechanism of pilot pressure to bypass a part of pressure oil supplied from a directional control valve to a pressure compensating mechanism to a tank. CONSTITUTION:First, when a directional control valve 109 is changed over to a change-over position 1, the secondary side of a throttle part 107 comes to be in the blocked state, and accordingly, pilot pressure Pb working upon the left side of a spool 41 of a pressure compensating mechanism 5 is as conventional. Next, in the case where the directional control valve 109 is changed over to a change-over position 11, the secondary side of a throttle part 107 comes to be in the state of being communicated with a tank 115, and a part of pressure oil supplied as the pilot pressure Pb through a circuit 101 is returned to the tank 115 and the pilot pressure Pb is lowered. Consequently, in the pressure compensating mechanism 5, force relationship with the pilot pressures Pa, Pb and a spring force of the compression coil spring 39 changes. That is, an increase rate of OUT flow rate supplied to an actuator 9 relative to the stroke of a directional control valve 7 comes to be low.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a directional control valve device, and particularly to one with an improved configuration of its pressure compensation mechanism.

(Prior Art) The configuration of a conventional directional control valve device will be described with reference to FIG. FIG. 10 is a hydraulic circuit diagram of the directional control valve device.

First, a hydraulic pump 1.3 is installed. The hydraulic pump 1 supplies pressure oil to the actuator 9 via the pressure compensation mechanism 5 and the directional switching valve 7, and returns the return oil to the tank 11.

The directional control valve 7 has operating positions a, b, C, d and a neutral position e, in which it is held by a compression coil spring 13.15. Further, by operating the operating lever 17, the operating position can be switched to any of the operating positions a, b, "c, and d."

On the other hand, the hydraulic pump 3 supplies and discharges pressure oil to the actuator 23.25 via the directional switching valve 1921, and also via the pressure compensation mechanism 27 and the directional switching valve 29.
It is supplied to and discharged from the actuator 31.

The single directional valve has operating positions f, g and a neutral position and is held in the neutral position by a compression coil spring 33,35.

Then, by operating the operating lever 37, the operating position is switched to either of the operating positions f and g.

Note that the directional switching valve 21 has a similar configuration, and the same parts in the drawings are denoted by the same reference numerals, and the explanation thereof will be omitted.

Also, regarding the directional switching valve 29, the above-mentioned directional switching valve 7
The pressure compensation mechanism 5 has the following structure, and the same parts in the drawings are denoted by the same reference numerals and the explanation thereof will be omitted. First, switching position i
, j, and is switched to the switching position i by biasing the spool 41 in one direction by three compression coil springs. Further, on the right side of the spool 41 in the figure, the pressure on the primary side of the directional control valve 7 acts as a pilot pressure P, and on the left side of the spool 41 in the figure, a shuttle valve 43 acts.
The pressure on the secondary side of the directional control valve 7 becomes the pilot pressure P through
It is designed to act as b. The spool 41 slides in an appropriate direction due to the force relationship between the differential pressure between the two pilot pressures p, , pb and the spring force of the three compression coil springs.

The pressure compensation mechanism 5 having such a configuration exhibits a compensation function as shown in FIG. 11. FIG. 11 is a characteristic diagram showing changes in the stroke of the directional control valve 7 on the horizontal axis and the OUT flow rate supplied to the actuator 9 on the vertical axis.

The pressure compensator 'Wi5 adjusts the stroke of the directional control valve 7 even if the IN flow rate from the hydraulic pump 1 changes large or small in a region exceeding the control flow rate with respect to a predetermined control flow rate. The actuator 9 is compensated for the corresponding controlled flow rate, and the excess flow rate is returned to the tank 1.

The same applies to the pressure compensation mechanism 27 side, and the same parts in the drawings are denoted by the same reference numerals, and the explanation thereof will be omitted.

(Problem to be solved by the invention) The conventional configuration described above has the following problems.

For example, fine control may not be performed in a state where the OUT flow rate to the actuator 9.31 is reduced (the stroke of the directional control valve 7.2 is reduced) (hereinafter referred to as inching control). In such a case, the IN flow rate from the hydraulic pump 1.3 is usually reduced significantly compared to the control flow rate in consideration of erroneous operation.

However, as shown in FIG. 12, even if the IN flow rate from hydraulic pump], 3 is small, the directional control valve 7.2
O to actuator 9.31 for 90 strokes
The rate of increase in UT flow rate ((El) is the same, so
There was a problem that the metering range δ was small and the desired fine adjustment could not be made.
This is due to the fact that the initial spring force of the compression coil spring 39 of the pressure compensation mechanism 5.27 is constant regardless of whether the flow rate is large or small.

Also, even when the IN flow rate is small, the pressure compensation mechanism 5.27
The switching pressure corresponding to the spring force of the compression coil spring 39 results in a pressure loss, and since the pressure loss cannot be reduced below the spring force, a large pressure loss is unavoidable.

The present invention has been made based on these points, and its purpose is to ensure a sufficient metering range and reduce pressure loss when inching control is performed by reducing the IN flow rate. It is an object of the present invention to provide a directional control valve device equipped with a pressure compensation mechanism capable of

(Means for Solving the Problems) In order to achieve the above object, the directional switching valve device according to the present invention has an operating position and a neutral position, and switches the IN flow rate from the hydraulic pump to the OUT actuator by appropriately switching the operating position and the neutral position.
A directional control valve is inserted between the hydraulic pump and the directional control valve, which supplies and discharges the flow as flow, and biases the spool in one direction with a compression coil spring. a pressure compensation mechanism that acts on both sides of the spool using the pressure on the side as a pilot pressure, and compensates for an OUT flow rate according to the opening degree of the directional control valve; and a pressure compensation mechanism on the secondary side of the directional control valve. A pressure adjustment mechanism is provided between the directional control valve and the pressure adjustment mechanism that bypasses a part of the pressure oil supplied from the secondary side of the directional control valve to one end side of the spool of the pressure compensation mechanism to the tank to adjust the pilot pressure. It is characterized by the following:

(Function) First, we will explain the case where the pilot pressure is reduced by using the pressure adjustment mechanism to divert part of the pressure oil supplied from the secondary side of the directional control valve to one end of the spool of the pressure compensation mechanism to the tank. .

In this case, in the force relationship between the pilot pressure acting on both sides of the spool of the pressure compensation mechanism and the compression coil splinter, the pressure effect on the compression coil spring side is reduced.

Therefore, the rate of increase of the OUT flow rate supplied to the actuator with respect to the stroke of the directional control valve becomes gradual, and for example, when performing inching control, it is possible to secure a sufficient metering range and reduce pressure loss. On the other hand, if the restriction of the pilot pressure by the pressure adjustment mechanism is relaxed or stopped, the force relationship between the pilot pressure acting on both sides of the spool of the pressure compensation mechanism and the compression coil spring will reduce the compression. This increases the pressure effect on the coil spring side.

Therefore, in this case, the O supplied to the actuator
The rate of increase of the UT flow rate with respect to the stroke of the directional control valve remains the same as before.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 4 to 7.

Incidentally, the same parts as in the prior art are denoted by the same reference numerals, and the explanation thereof will be omitted.

A circuit 10 that causes the pressure on the secondary side of the directional switching valve 7 to act on the spool 41 of the pressure compensation mechanism 5 as a pilot pressure Pb
1 is provided with a pressure adjustment mechanism 102. That is, a constriction section 103 is provided, and a circuit 105 is branched on the secondary side of this constriction section 103.
Another constriction section]07 is inserted into this circuit 105.

A switching valve 109 is connected to the secondary side of the throttle section 107 . This switching valve 109 has a switching position I and a switching position ■, and normally operates with a compression coil spring 1.
11, it is switched to the switching position ■. In this switching position (2), the secondary side of the throttle portion 107 is in a closed state.

On the other hand, the switching position ■
, the primary side of the throttle section 107 is the tank]
15, and a part of the pressure oil flowing through the throttle part 107 is returned to the tank 1]5.

It should be noted that the pressure compensation mechanism 27 side has a similar configuration, and the same parts are denoted by the same reference numerals and the explanation thereof will be omitted.

The operation will be explained based on the above configuration.

First, a case where the switching valve 109 is switched to the switching position I will be described. In this case, since the secondary side of the constriction portion 107 is closed, the pilot pressure Pb acting on the left side of the spool 41 of the pressure compensation mechanism 5 in the drawing remains the same as before.

Therefore, the relationship between the 0tJT flow rate supplied to the actuator 9 and the stroke of the directional control valve 7 is as shown in FIGS.
The result will be as shown in the figure. FIG. 4 shows a case where the I and N flow rates from the hydraulic pump 1 are large, and FIG. 5 shows a case where the IN flow rate from the hydraulic pump 1 is small.

Next, the case where the switching valve ], 09 is switched to the switching position H will be explained. In this case, the secondary side of the throttle part 107 is in communication with the tank 15, and a part of the pressure oil supplied as the pilot pressure Pb via the circuit 101 is returned to the tank 115, and the pilot pressure Pl , decreases.

Therefore, in the pressure compensation mechanism 5, the pilot pressure Pa,
The force relationship between Pb and the three spring forces of the compression coil spring changes.

Therefore, the relationship between the OUT flow rate supplied to the actuator 9 and the stroke of the directional control valve 7 is as shown in FIGS. 6 and 7. Figure 6 shows the hydraulic pump 1
Fig. 7 shows a case where the IN flow rate from the hydraulic pump 1 is small.

That is, the rate of increase (α) of the OUT flow rate supplied to the actuator 9 with respect to the stroke of the directional control valve 7 becomes gradual, making it possible to obtain a sufficient metering range δ− and reducing pressure loss. can.

Note that the same effect can be achieved on the pressure compensation mechanism 27 side as well.

According to this embodiment, the following effects can be achieved.

First, by switching the switching valve 109 to the switching position (2), a part of the pressure oil supplied as the pilot pressure P is returned to the tank 115, thereby reducing the pressure effect on the pressure compensation mechanism 5.27.

Therefore, the rate of increase of the OUT flow rate to the actuator 9.31 relative to the stroke of the directional control valve 7.2 can be made gentle, and a sufficient metering range δ' can be secured. This is the I from hydraulic pump 1.3
This is the same regardless of whether the N flow rate is large or small.

Therefore, for example, it is possible to make fine adjustments when performing inching control by reducing the IN flow rate from the hydraulic pump 1.3, thereby improving fine operability.

In addition, when the IN flow rate from the hydraulic pump 1.3 is small, the force acting on the pressure compensation mechanism 5.27 is set small, so the pressure for switching the pressure compensation mechanism 5.27 is small. Pressure loss can be reduced.

Next, a second embodiment will be described with reference to FIG. In this case, in the configuration of the first embodiment, the aperture portion 117
is further added.

This throttle portion 117 exerts a buffering function against the sliding movement of the spool 41 of the pressure compensation mechanism 5.27, and the spool 4 due to the switching operation of the switching valve 109.
This is to prevent hunting of No. 1.

Next, a third embodiment will be described with reference to FIG.

In this embodiment, a variable throttle part 119 is branch-connected to the secondary side of the throttle part 103, and a part of the pressure oil supplied as the pilot pressure Pb is returned to the tank 115 at an arbitrary flow rate.

In this case, characteristics as shown in FIGS. 8 and 9 can be obtained. Figure 8 shows the IN flow rate from the hydraulic pump 13 is large, and Figure 9 shows the IN flow rate from the hydraulic pump 1.3.
First, when the variable throttle section 119 is closed (showing the case where the flow rate is small), all the pressure oil is supplied as the pilot pressure Pb. (diagram shown).

Next, when the variable throttle section 119 is opened with a small opening degree, a small portion of the pressure oil supplied as the pilot pressure Pb is returned to the tank 115 via the variable throttle section 119.

Therefore, the characteristic shown by the slope β in the figure can be obtained.

When the variable throttle section 119 is opened to a larger opening degree, most of the pressure oil supplied as the pilot pressure Pb is transferred to the variable throttle section 1.
19 and is returned to tank 115. Therefore, the characteristic shown by the slope α in the figure can be obtained.

In this way, desired characteristics can be obtained by appropriately adjusting the aperture opening of the variable aperture section 119.

Note that the present invention is not limited to the above embodiment.

The configuration of the directional switching valve device is not limited to that shown in the figure, and various configurations can be considered for the number of directional switching valves, the number of pressure compensation mechanisms, etc.

In addition, various configurations other than the one shown in the drawings can be considered as the pressure adjustment mechanism, and the key point is the pilot pressure P.

It is sufficient that the pilot pressure Pb can be adjusted by diverting a part of the pressure oil supplied to the tank to the tank.

(Effects of the Invention) As detailed above, according to the directional control valve device according to the present invention, the flow rate of pressure oil supplied to the pressure compensation mechanism from the secondary side of the directional control valve, and thus the pilot pressure, is adjusted by the pressure adjustment mechanism. I did it like that.

Therefore, for example, when performing inching control by reducing the IN flow rate from the axial pressure pump, the flow rate of pressure oil supplied from the secondary side of the directional control valve to the pressure compensation mechanism is reduced by the flow rate adjustment mechanism. , lower the pilot pressure.

As a result, the pressure effect on the compression coil spring side of the pressure compensation mechanism is set to a small value, making it possible to secure a sufficient metering range, improving fine controllability, and reducing pressure loss. can be reduced.

[Brief explanation of the drawing]

Figures 1, 4 to 7 are diagrams showing an embodiment of the present invention, in which Figure 1 is a hydraulic circuit diagram of a directional control valve device, and Figures 4 to 7 are OUTs that are supplied to the actuator. A characteristic diagram showing changes in flow rate with respect to stroke; FIG. 2 is a hydraulic circuit diagram of a directional control valve device showing the second embodiment; FIGS. 3 and 8.
9 and 9 are diagrams showing the third embodiment, FIG. 3 is a hydraulic circuit diagram of a directional valve device showing the third embodiment, and FIGS. 8 and 9 are diagrams of the OUT flow rate supplied to the actuator. Characteristic diagrams showing changes with respect to stroke, Figures 10 to 12
The figures show a conventional example, in which Fig. 10 is a hydraulic circuit diagram of a directional control valve device, and Figs. 11 and 12 are characteristic diagrams showing changes in the OUT flow rate supplied to the actuator with respect to the stroke. 1.3... Hydraulic pump, 5.27... Pressure compensation mechanism, 7. Two... Directional switching valve, 9, 31... Actuator, 41... Spool, 102... Pressure adjustment Mechanism, P□, Pb...Pilot pressure. Applicant's representative Patent attorney Nobuyuki Shima

Claims (1)

[Scope of Claims] A directional control valve that has an operating position and a neutral position and supplies and discharges an IN flow rate from a hydraulic pump to an actuator as an OUT flow rate by switching as appropriate, and between the hydraulic pump and the directional control valve. The spool is biased in one direction by a compression coil spring, and the pressure on the primary and secondary sides of the directional control valve is used as pilot pressure to act on both sides of the spool. A pressure compensation mechanism that compensates the OUT flow rate according to the opening degree, and a pressure compensation mechanism provided between the secondary side of the directional switching valve and the pressure compensation mechanism, and from the secondary side of the directional switching valve to one end of the spool of the pressure compensation mechanism. A directional control valve device comprising: a pressure adjustment mechanism that adjusts pilot pressure by diverting a portion of pressure oil supplied to the tank to a tank;