JPS58160602A - Hydraulic device of control valve with logic valve - Google Patents

Abstract

PURPOSE:To restrain the energy loss at the minimum by connecting a logic valve which is under opening and closing control of the pilot pressure, and a pump discharge quantity control cylinder to the output side of a pilot valve which controls a selector valve. CONSTITUTION:A logic valve 12 which is placed under opening and closing control of the pilot pressure, and a pump discharge quantity control cylinder 29 are connected to the secondary side circuits 24, 25 of a pilot valve 8 controlling a selector valve 6, through a shuttle valve 27. From the above, in case an operational lever 23 of the pilot valve 8 is maintained unoperated, the discharge quantity of the pump 1 is maintained at the minimum flow rate, while in case said lever 23 is operated, the pump discharge quantity is controlled by displacement of the selector valve 6 corresponding to the pilot pressure obtained by the displacement of the lever 23 and by control of the logic valve. Therefore, smooth control of an actuator can be performed in proportion to the displacement of the selector valve 6, and only required quantity is discharged from a hydraulic pump. Accordingly, the energy loss can be restrained to the minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic system for a control valve, and more particularly to a hydraulic system for a control valve having a logic valve for controlling a variable displacement hydraulic pump and a control valve using a pilot valve.

The purpose is to provide a control valve hydraulic system having a logic valve that enables highly accurate flow control.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Diagrams showing one embodiment of the present invention will be described below. In the figure, l denotes a variable displacement hydraulic pump, and a control valve 4 that connects the center bypass passage 3 to the hydraulic pump 1 via a passage 2 has a valve body 4a that crosses the center bypass passage 3. A plurality of switching valves 5, 6.7 are incorporated as shown in FIG. The actuator 9 corresponding only to the switching valve 6 is shown).lQa and lQb are the first supply passages of the switching valve 6, and the valve body 4a has an inflow side center valve (4791 passage 3) with respect to the switching valve 5°6.7. A logic valve 12 is provided between the flow path 11 and the logic valve 1.
2 controls the bypass flow rate.

The logic valve 12 is slidably mounted on the outside between a cylindrical sleeve 13 that is fluid-tightly fitted to the valve body 4a and a protrusion 14a of a support member 14 that is fitted on one side of the sleeve 13. A poppet 15 is fitted, and this outer poppet 15 resists a spring 17 due to the pressure of a pyro chamber 16 formed on its end face and a stepped portion of the protrusion 14a, and connects the 7', ivy bypass passage 3 and tank. The center bypass passage 3 and the tank passage 11 are connected by a spring 17 when the pressure in the pilot chamber 16 is below a predetermined value.

The inner poppet 18 inserted into the protrusion 14a is adapted to release the pressure in the center bypass passage 3 to the tank passage 11 when the pressure in the chamber 19 reaches the relief set pressure. '20 is a tank, and the pilot pulp 8 operates the pressure of the primary side circuit 22 of the constant displacement hydraulic pump 21 and derives the pressure to the secondary side circuit 24 or 25 by displacement of the valve 23. Oh, this circuit 24 or 2
By introducing the displacement pressure 5 into the pilot chamber 26a or 26b provided on both sides of the switching valve 6, the switching valve 6 is displaced. In addition, there is a shuttle valve 2 in the circuit 24°25.
A signal path 28 connected via the logic valve 12
The valve is connected to the pilot chamber 16 of the variable displacement hydraulic pump 1 and the chamber 29a of the cylinder 29 that controls the variable displacement hydraulic pump 1. 6 displacement and logic.

The supply flow 1 to the shear actuator 9 is controlled by the control amount of the valve 12.
is configured to control.

Next, the operation of the present invention will be explained. First, when the operating lever 23 of the pilot pulp 8 is in the neutral position shown,
The pressure in the discharge side circuit 22 of the constant displacement hydraulic pump 21 is maintained by the pilot pulp 8, and the circuits 24 and 25 communicate with the tank 20 and are at tank pressure. Therefore, pilot room 2 connected to circuit 24.25
6a.

26b, the switching valve 6 is in the neutral position shown, and
A signal circuit 28 connected via a shuttle valve 27 maintains tank pressure in the chamber 29a and the pilot chamber 16. Therefore, the outer poppet 15 of the logic valve 12 is positioned to the left of the illustrated position due to the elastic biasing force of the spring 17, and a very small amount of oil discharged from the variable displacement hydraulic pump 1 is transferred from the center bypass passage 3 to the outer poppet. , and is returned to the tank passage 11 via the port 15. Therefore, when the pyro valve 8 is not operated, the pump discharge amount can be reduced to the minimum flow rate.

Now, when the operating lever 23 is displaced leftward from the illustrated neutral position, the pressure in the circuit 22 becomes a predetermined pressure proportional to the displacement of the operating lever 23 and is led out to the circuit 24. The derived pressure of the circuit 24 acts on the pilot chamber 26a, and the pilot chamber 26b on the other side is at the tank pressure, so the switching valve 6 is displaced from the neutral position shown in the figure to the right. At the same time, the predetermined pressure of the circuit 240 acts on the cylinder chamber 29a from the signal circuit 28 via the shuttle valve 27 to operate the cylinder 29, so that the discharge amount of the variable displacement hydraulic pump 1 increases and the pressure is increased through the passage 25-. and is supplied to the center bypass passage 3 of the control valve 4. Further, since the pressure of the signal circuit 28 acts on the pyro chamber 16 of the logic valve 12, the outer poppet 15
7 to the right to disconnect the center bypass passage 3 and the tank passage 11. Therefore, the discharge flow rate of the center bypass passage 3 is supplied to the actuator 9 via the supply passage 10a. Therefore, by operating the pilot pulp 8, it is possible to control the supply of pump discharge oil to the actuator 9 in proportion to its displacement pressure.

Further, the operation and logic of the cylinder 29 is proportional to the pressure derived from the pilot pulp 8.

The opening degree of the outer poppet 15 of the valve 12 gradually decreases.

Further, when the operating lever 23 is displaced from the illustrated neutral position to the right position, the pressure in the circuit 22 becomes a predetermined pressure proportional to the displacement of the operating lever 23 and is led out to the circuit 25. This derived pressure of the circuit 25 acts on the pilot chamber 26b,
And since the pilot chamber 26a on the other side becomes the tank pressure,
The switching valve 6 is displaced from the neutral position to the left position. In addition, the operation of the cylinder 6-nder 29 and the opening of the logic valve 12 are controlled in the same manner as when the operating lever 23 is moved to the left, so the explanation thereof will be omitted.

As described above, according to the present invention, the pump discharge amount is maintained at the minimum flow rate when the operating lever of the pyro and valve is kept unoperated, and when the operating lever is operated, the displacement of the operating lever is maintained. Since the discharge flow rate is controlled by the displacement of the switching valve and the control of the logic valve, it is possible to smoothly control the actuator in proportion to the displacement of the switching valve. Since only the flow rate can be discharged from the hydraulic pump, it has the effect of minimizing energy loss.

[Brief explanation of the drawing]

The figure is a schematic sectional view showing an embodiment according to the present invention. DESCRIPTION OF SYMBOLS 1... Variable displacement hydraulic pump, 3... Center bypass passage, 4... Control valve, 5, 6.7... Switching valve, 8
...Pilot pulp, 9...Actuator, 1
1...tank passage, 12...logic valve, 29...
Cylinder, Applicant: Toshiba Machine Co., Ltd. 7-

Claims (1)

[Scope of Claims] A control valve having a plurality of switching valves connected to a variable displacement hydraulic pump, an actuator each controlled by the switching valves of the control valve, and a pilot valve controlling the switching valve. In the hydraulic system, a logic valve whose opening/closing is controlled by the pilot pressure is provided between the plurality of switching valves that are displaced by a pilot pressure proportional to the displacement of the pilot pulp, a center bypass passage, and a tank passage. The control valve is provided with discharge oil of a variable displacement hydraulic pump having a cylinder chamber that controls the pump discharge amount by the pilot pressure, and the pump discharge is adjusted to correspond to the displacement of the pilot pulp. A hydraulic system for a control valve having a logic valve, characterized in that the flow rate of oil supplied to a shear actuator is controlled by the displacement of a switching valve and the control amount of a logic valve.