JPH05296209A - Pilot directional control valve - Google Patents

Abstract

PURPOSE:To provide a pilot directional control valve capable of controlling differential pressure of pilot pressure supplied to each pilot port of a control valve by one single valve and with favorable responsiveness for a command from outside. CONSTITUTION:This pilot directional control valve is constituted of a linear motor 15 with a rod 2 working by an input electric current to a coil 9 and a valve body 16 integrally connected by the rod 2 and a screw 12 and furnished with a spool 3 having a pressure system to receive pressure of control ports 43a, 43b on lands 3a, 3b. By balancing driving force of the linear motor 15 and pressing force of the spool 3, differential pressure between the control port 43a and the control port 43b is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pilot switching valve provided in, for example, a construction machine such as a hydraulic excavator, and more particularly to a pilot pressure driven control valve whose spool position is controlled by pilot pressure, The present invention relates to a pilot switching valve that supplies the pilot pressure to the control valve according to the command of.

[0002]

2. Description of the Related Art Conventionally, a pilot switching valve of this type feeds back pilot pressure and supplies a pressure corresponding to the operation amount of an operating lever to the control valve, as described in, for example, Japanese Patent Publication No. 62-42145. I was supposed to do it. This conventional technique will be described with reference to FIG.

FIG. 3 shows a hydraulic circuit diagram for driving a hydraulic cylinder, which is equipped with a pilot switching valve and a control valve operated by pilot pressure from the pilot switching valve. In this hydraulic circuit, the operating lever 101 and the pilot switching valves 102a and 102b whose spools move in response to the operation of the operating lever 101 and whose connection port positions are switched.
And a direction switching valve 103 as a control valve for supplying a flow rate corresponding to the pilot pressure supplied from the pilot switching valves 102a and 102b to a hydraulic cylinder 104 as an actuator, and an auxiliary pump 105 for supplying pressure oil for pilot. And a pump 106 for driving the actuator.

In the hydraulic circuit having the conventional pilot switching valve configured as described above, the spool of either the pilot switching valve 102a or the pilot switching valve 102b has the spring 10 depending on the operation amount of the operating lever 101.
2c or the spring 102d. For example, when the operation lever 101 is operated to the side of FIG. 3 (e), the spool of the pilot switching valve 102a is pressed against the spring 102c.
As a result, the pilot switching valve 102a switches the connection relationship of the input / output ports from the connection between the pipeline 108 and the pipeline 107a to the connection between the pipeline 109 and the pipeline 107a. As a result, the pressure oil from the auxiliary pump 105 flows out to the pipeline 107a. The pilot switching valve 102a has a variable throttle formed by the inflow port and the spool.
The pressure corresponding to the spool position is led to the conduit 107a. Further, since the discharge pressure is fed back by the pipe 107c branched from the pipe 107a, a reaction force corresponding to the operation amount of the operation lever 101 is generated.

Further, the discharge pressure of the pilot switching valve 102a is supplied to the pilot port 103a of the directional switching valve 103 via the conduit 107a. By the way, in this state, the pilot switching valve 102b is configured to connect the pipeline 108 and the pipeline 107b connected to the tank 110 via the pipeline 108a, and one pilot port 103b of the direction switching valve 103 is A pressure approximately equal to the tank pressure is applied. Therefore, the directional control valve 10
A pressing force corresponding to the pressure difference between the pilot pressure on the 103a side and the tank pressure is applied to the spool of No. 3. Due to this pressing force, the spool of the direction switching valve 103 moves from the neutral position (b) to the switching position (c), and the hydraulic cylinder 104
Is supplied with a flow rate of pressure oil proportional to the movement amount of the spool of the direction switching valve 103.

Therefore, the pilot pressure according to the operation amount of the operation lever 101 is supplied to the direction switching valve 103, and the hydraulic oil having the flow rate according to the pilot pressure is supplied to the hydraulic cylinder 10.
4 is supplied.

[0007]

In the above-described conventional pilot hydraulic circuit for pilot-driven control valves, two pilot switching valves 102a and 102b depending on the operating direction of the operating lever 101 are indispensable. For this reason,
In forming the pilot hydraulic circuit, a space for arranging two pilot switching valves is required. Along with this, a large number of pipes connected to the two pilot switching valves are required, and a large space is required for the pilot hydraulic circuit.

Further, when the operating direction of the operating lever 101 is switched, the pilot pressure is switched and set by the springs 102c, 1 provided on the pilot switching valves 102a, 102b.
02d, the response to the operation of the operation lever 101 is delayed. In particular, during fine operation of the actuator 104, poor operability becomes apparent due to this response delay, which is one of the causes of lowering work efficiency.

The object of the present invention is to control the differential pressure of the pilot pressure supplied to each pilot port of the control valve with one valve, and to switch the pilot with good response to an external command. To provide a valve.

[0010]

In order to achieve the above object, the present invention provides a control valve driven by pilot pressure,
In a pilot switching valve that supplies pilot pressure according to a command signal from the outside, a linear motor, a plate member provided on a plunger of the linear motor, and the plate member and a spool provided in the valve body are integrally connected. A connection mechanism, two or more control ports and a fluid supply port, and a pressure receiving mechanism that balances the spool pressing force due to the pressure of the fluid flowing through each control port and the driving force by the linear motor. ..

[0011]

Since the present invention is configured as described above, when a command signal from the outside is input, the plate member provided on the plunger of the linear motor moves, and the plate member and the connecting mechanism integrally move the plate member. The spool of the connected valve element also moves. As the spool moves, pilot pressure is supplied from each control port to the control valve. At that time, the fluid flowing through each control port has a pressure corresponding to the clearance between the spool and each control port. When the pressure receiving mechanism receives the pressure of the fluid flowing through each control port, a pressing force that opposes the driving force of the linear motor is generated on the spool,
The spool is held at a position where the linear motor driving force and the spool pressing force are balanced. As a result, the pilot pressure supplied to each pilot port of the control valve becomes a pressure corresponding to the spool movement amount, that is, the movement amount of the plunger of the linear motor.

Therefore, each pilot port of the control valve is supplied with pressure according to a command signal from the outside by one pilot switching valve, and the fluid flowing through the control valve is controlled according to the pressure difference between these. You can

Since the setting of the spool position of the pilot switching valve is controlled by the control of the plunger position of the linear motor, that is, the command current to the linear motor and the magnetic circuit based on this current signal, a response to the command is obtained. It will be extremely fast.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view of a first embodiment of the pilot switching valve according to the present invention, and is a diagram showing the structure of the pilot switching valve of the first embodiment and the connection relationship with the control valve.

The pilot switching valve 17 according to the first embodiment comprises a linear motor 15 which operates by a signal from an external command means (not shown), and a valve body 16 which supplies pilot pressure to the main valve 13. In the first embodiment, the main valve 13 and the pilot switching valve 17 have an integrated structure.

The linear motor 15 has a plunger 1 having a rod 2 and a plate 12 made of a non-magnetic material, and a pair of permanent magnets 7a and 7b installed on the outer periphery of the plunger 1.
A magnetic ring 8a installed between the pair of permanent magnets,
8b and a coil 9a installed on the outer periphery of the pair of permanent magnets,
9b, a pair of permanent magnets 7a, 7b and a coil 9a,
It is composed of a pair of yokes 4a and 4b fixed to the outer peripheral portions of both ends of the rod 2 and a casing 6 fixing these.

The valve body 16 includes a spool 3, pump ports 42a and 42b, control ports 43a and 43b, a tank port 44, and a sleeve body 40 surrounding them.
Consists of. The control ports 43a and 43b are connected to the pilot ports 13a and 13b of the main valve 13 to operate the spool 13c of the main valve 13. Further, the control port 4 is provided on the lands 3a and 3b of the spool 3.
A step is provided to receive the fluid pressure of 3 a and 43 b and to apply a reaction force against the driving force of the spool 3 by the linear motor 15 to the spool 3. The valve element 16 and the linear motor 15 are separated by a sealing material 41.
Further, the plate member 12 and the spool 3 are the spigot 3c provided on the spool 3 and the end 12a of the plate member 12 processed into a spherical shape.
And are integrated by press fitting. That is, the spigot 3c and the end 12a of the plate 12 form a connection mechanism between the plate 12 and the spool 3. Both ends of the rod 2 of the linear motor 15 are supported by the leaf springs 10a and 10b.

In the pilot switching valve 17 of the first embodiment configured as described above, when a current signal is input to the coils 9a and 9b of the linear motor 15 by an instruction means from the outside (not shown), the magnitude of the current, And, a magnetic field corresponding to the polarity is generated. The plunger 1, the yokes 4a and 4b, and the casing 6 installed in this magnetic field are made of a magnetic material, and a magnetic circuit is formed by the generation of the magnetic field. With this magnetic circuit, one end of the plunger 1 is magnetized to the S pole and the other end is magnetized to the N pole. The magnetic force of this magnetic field imparts a propulsive force to the plunger 1 in the lateral direction with respect to FIG. 1. Further, the propulsive force is also given from the magnetic circuit by the pair of permanent magnets 7a and 7b installed on both sides of the plunger 1. Be done. Since the current input to the coils 9a and 9b is proportional to the strength of the magnetic field due to this current, the plunger 1 obtains a propulsive force proportional to the input current to the coils 9a and 9b.

On the other hand, the plunger 1 and the spool 3 of the valve body 16 are integrated via the plate member 12, and the plunger 1
The spool 3 also moves laterally with respect to FIG. When the spool 3 moves, the pump port 42a and the control port 43a of the valve body 16 or the pump port 42b and the control port 43b communicate with each other, and the fluid supplied from a pump (not shown) is controlled by the control port 43a or controlled. It flows out to the port 43b. As described above, the land 3a and the land 3b of the spool 3 are provided with steps having different diameters as a pressure receiving mechanism. Let d and D be the respective diameters of this step, and the area difference A = (D **
2-d ** 2) × π / 4, the pressing force of Fa = A × Pca (1) is applied to the land 3a in the left direction in FIG.

A pressing force of Fb = A × Pcb (2) is applied to the land 3b in the right direction in FIG.

Here, Pca and Pcb are control ports 43
The fluid pressures flowing through a and 43b are shown. In addition, ** represents the square. From the above formulas (1) and (2), the pressing force of F = (Pca−Pcb) × A (3) acts on the spool 3 in the leftward direction. The spool 3 moves at a position where the sum of the pressing force F and the spring force of the leaf springs 10a and 10b supporting the spool 3 and the rod 2 and the driving force of the linear motor 15 described above is balanced, that is, the plate material 12, the plunger. The movement of 1 stops.

By the way, the control port 43a or 4
As for the fluid pressure flowing through 3b, the fluid pressure supplied to the pump port is considered to be constant, so the land 3a and the control port 4
3a or opening area with land 3b and control port 4
3b and the opening area. That is, it is determined by the movement amount of the spool 3. Therefore, the spool 3
A pressure corresponding to the amount of movement of the control ports 43a and 43b is generated, and the pressing force F corresponding to this differential pressure acts on the spool 3. That is, the pressure difference between the control port 43a and the control port 43b can be controlled by the current input to the linear motor 15. This control port 4
The differential pressure (Pc) of the pilot pressure supplied from 3a and 43b.
a-Pcb) drives the spool of the main valve 13,
The flow rate corresponding to the differential pressure is further supplied to the hydraulic cylinder 14 in the direction corresponding to the differential pressure.

Therefore, according to the pilot switching valve 17 of the first embodiment, the differential pressure of the pilot pressure can be controlled to the main valve 13 by one valve. As a result, the space for installing the pilot switching valve can be made narrower than before. Further, since the position of the spool 3 included in the pilot switching valve 17 is controlled by the current signal to the coils 9a and 9b, the pilot pressure can be changed quickly in response to a command from the outside.

FIG. 2 is an explanatory view of the second embodiment of the present invention, showing the structure of the pilot switching valve. The same parts as those in the structural diagram of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 2, the pilot switching valve 53 according to the second embodiment comprises a linear motor 51 and a valve body 52 as in the first embodiment. The spool 55 of the valve body 52 is provided with flow paths 45a and 45b for guiding the pressure of the control ports 43a and 43b. further,
Pressure receiving bodies 50a and 50b for receiving the pressure guided by the flow paths 45a and 45b are provided. The pressure receiving body 50a and the pressure receiving body 50b are processed to have the same cross-sectional area.

In the pilot switching valve 53 according to the second embodiment thus constructed, the rod 2 of the linear motor 51 is used.
2, the spool 55 also moves laterally with respect to FIG. With the movement of the spool 55, the pump port 42a and the control port 43a, or the pump port 42b and the control port 43b are brought into communication with each other. As described above, the pressure of the control port 43a is guided to the pressure receiving body 50a, and the pressure of the control port 43b is guided to the pressure receiving body 50b. Assuming that the cross-sectional areas of the pressure receiving body 50a and the pressure receiving body 50b are A and the pressures of the control ports 43a and 43b are Pca and Pcb, respectively, Fa, b = A × Pca, b by the pressure receiving bodies 50a and 50b. The pressing force of only (4) acts on the spool 55 in the lateral direction of FIG.

That is, the pressing force Fa is to the right in FIG.
The pressing force Fb acts leftward.

Therefore, the difference between the pressing forces of Fa and Fb, that is, the pressing force of F = A × (Pca-Pcb) (5) acts on the spool 55 in the leftward direction in FIG. ..

The movement of the spool 55 is stopped at a position where the pressing force of the spool 55 represented by the equation (5) and the driving force of the linear motor 51 are balanced.

Therefore, according to the pilot switching valve 53 of the second embodiment, as in the first embodiment described above, the current input to the linear motor 51 causes a difference between the control port 43a and the control port 43b. The differential pressure can be controlled and the differential pressure of the pilot pressure to the main valve can be controlled by one valve. As a result, the space for installing the pilot switching valve can be made narrower than before. Further, the spool 55 included in the pilot switching valve 53
Since the position is controlled by the current signal to the coil 9, the pilot pressure can be changed quickly with respect to a command from the outside.

[0032]

As described above, according to the present invention, the differential pressure between the control ports can be controlled by the current input to the linear motor, and the differential pressure of the pilot pressure to the main valve can be controlled by one valve. Can be controlled. As a result, the space for installing the pilot switching valve can be made narrower than before. Further, since the position of the spool of the pilot switching valve is controlled by the current signal to the coil of the linear motor, the pilot pressure can be changed quickly in response to a command from the outside.

[Brief description of drawings]

FIG. 1 is a structural diagram of a first embodiment of a pilot switching valve according to the present invention.

FIG. 2 is a structural diagram of a second embodiment of the pilot switching valve according to the present invention.

FIG. 3 is a hydraulic circuit diagram for driving an actuator using a conventional pilot switching valve.

[Explanation of symbols]

 1 Plunger 2 Rod 3 Spool 12 Plate material 13 Main valve (control valve) 15 Linear motor 16 Valve body 17 Pilot switching valve 42a, 42b Pump port (fluid supply port) 43a, 43b Control port 45a, 45b Flow path 46 Flow path 47a, 47b Flow path 50a, 50b Pressure receiving body 51 Linear motor 52 Valve body 53 Pilot switching valve 55 Spool

Claims (1)

[Claims] 1. A pilot switching valve for supplying pilot pressure according to a command signal from the outside to a control valve driven by pilot pressure, a linear motor, a plate material provided on a plunger of this linear motor, and this plate material. And a spool provided in the valve body, a connecting mechanism that integrally connects the spool and a valve body, two or more control ports and a fluid supply port, a spool pressing force due to the pressure of fluid flowing through each control port, and a driving force by the linear motor And a pressure receiving mechanism that balances the