JPH0694908B2 - Directional control valve using piezoelectric element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a directional control valve using a piezoelectric element, and more particularly to a directional control capable of reducing a load on a piezoelectric element having a bimorph structure which constitutes a nozzle flapper structure. The technology is effective when applied to valves.

[Conventional technology]

As a directional control valve that controls the flow of fluid pressure, there is a structure that can control the flow by utilizing the displacement of the piezoelectric element.
For example, a working fluid chamber into which a fluid pressure flows, a piezoelectric element that opens and closes by coming into contact with an inflow path of the working fluid chamber, and a working member that is actuated by an increase in fluid pressure in the working fluid chamber. And a valve body for switching the flow path.

Further, as a driving method of the piezoelectric element, a method of displacing on one side by applying a continuous voltage and a method of displacing by alternating voltage are considered.

For example, in the case of a driving method in which the piezoelectric element is displaced on one side by applying a continuous voltage, a voltage is always applied to the one side, which is a bimorph structure, in the direction opposite to the polarization direction, and the piezoelectric element is displaced to one side to cause the working fluid chamber The inflow passage is opened and closed.

[Problems to be Solved by the Invention]

However, in the directional control valve based on the method of driving a piezoelectric element as described above, a voltage is always applied in the opposite direction to the polarization direction on one side of the bimorph structure that constitutes the piezoelectric element, so continuous voltage application does not occur for a long time. Then, polarization deterioration due to the polarization phenomenon occurs in the piezoelectric element having the bimorph structure.

Furthermore, since the displacement direction of the piezoelectric element is limited to one side,
Similarly, when the continuous voltage is applied for a long time, the piezoelectric element is deformed due to the creep phenomenon.

In particular, the piezoelectric element is apt to cause such a problem because its mechanical strength is relatively small.

A technique using such a piezoelectric element is, for example, a fuel injection nozzle described in Japanese Patent Publication No. 49-6043. This piezoelectric element has one end fixed and the other end configured as a free end. It is a laminated structure and is not a piezoelectric element having a bimorph structure as in the present invention. Therefore, the creep phenomenon and the polarization phenomenon are not generated.

Further, as an example of using a bimorph electrostrictive element similar to this piezoelectric element, there is an electric switching valve described in, for example, Japanese Utility Model Laid-Open No. 61-14269, which is a piezoelectric element having particularly weak mechanical strength. Is not used, and the control method is also different.

Further, in the PWM flow rate control method and apparatus disclosed in Japanese Patent Laid-Open No. 56-35223, a piezoelectric element having weak mechanical strength is not used as in the above case, and therefore creep phenomenon and polarization phenomenon are prevented. It is not a technology for.

Therefore, an object of the present invention is to reduce the load on the piezoelectric element of the bimorph structure that constitutes the nozzle flapper structure by driving by applying a pulse voltage, prevent leakage of fluid, and stabilize the operation and long the life. It is to provide a directional control valve using a piezoelectric element that has.

[Means for Solving the Problems]

A directional control valve using a piezoelectric element of the present invention includes an operating member that is displaced by the fluid pressure of an operating fluid chamber, a main shaft that forms a valve body that can control a flow path by the displacement of the operating member, and an operating member. It is applied to a directional control valve equipped with a pilot valve body having a nozzle flapper structure for controlling the fluid pressure in the working fluid chamber by opening and closing the inflow path to the working fluid chamber. As a source, a non-fixed side of the cantilever type structure is fixed to the pilot valve body, and a bimorph structure piezoelectric element that is displaced on one side for a pulse width time by application of a pulse voltage is used.

In particular, a directional control valve that uses a bimorph piezoelectric element to drive a nozzle flapper structure pilot valve body is provided with a working fluid chamber, a working member, and a pilot valve body on both sides in the axial direction of a valve body having a main shaft. The present invention is applied to a double pilot type directional control valve each provided with a drive unit having a.

[Action]

According to the above-mentioned means, the piezoelectric element of the bimorph structure to which the pulse voltage is applied is displaced on one side for the duration of the pulse width, and the pilot valve body of the nozzle flapper structure opens the inflow passage of the working fluid chamber to operate. As the fluid pressure in the working fluid chamber rises, the flow of the fluid pressure can be controlled by the main shaft that forms the valve element that is actuated via the actuating member.

On the other hand, the piezoelectric element returns to the normal state except during the pulse width time, and the voltage is not continuously applied to the piezoelectric element having the bimorph structure for a long time.

This makes it possible to obtain a directional control valve using a piezoelectric element that prevents fluid leakage and has stable operation and a long life.

〔Example〕

FIG. 1 is a cross-sectional view of a directional control valve using a piezoelectric element according to an embodiment of the present invention, and FIG. 2 is a timing diagram in the case of using a booster circuit of a DC power supply as a supply voltage power supply of this embodiment, FIG. 3 is a timing diagram when a full-wave rectifier circuit of an AC power supply is used as the supply voltage power supply of this embodiment.

A directional control valve using the piezoelectric element of the present embodiment is, for example,
It is an air-operated double pilot type directional control valve, in which the valve body 1 and the drive units 2a and 2b sandwiching the valve body 1 are coaxially coupled to each other, and serve as a voltage source for the drive units 2a and 2b. The power supply unit 3 is connected.

An input port 4 connected to a fluid pressure source (not shown) and discharge ports 5a and 5b are provided on the lower side surface of the valve body 1, and an output port 6a is provided on the upper side surface of the valve body 1. , 6
b is open.

A flow passage 7 is formed inside the valve body 1 along the axial direction thereof, and valve seats 8a to 8d are formed on the inner peripheral surface of the flow passage 7 at predetermined intervals along the axial direction. Are installed around.

A main shaft 9 is provided in the flow path 7 so as to be displaceable along the axial direction thereof, and main shaft 9 is provided with main shaft valve bodies 10a to 10d which are respectively brought into contact with and separated from valve seats 8a to 8d. Formed at intervals.

Pistons 11a and 11b as operating members of the main shaft 9 are provided on both end faces of the main shaft 9 in a fixed or non-fixed manner with respect to the end faces of the main shaft 9, and the pistons 11a and 11b have two working fluid chambers. Partitioned into 12a and 12b, these working fluid chambers 12
It is accommodated in a and 12b so as to be displaceable along the axial direction.

Of these working fluid chambers 12a, 12b, the working fluid chamber 12a on the left side in FIG. 1 is communicated with the outside through the bleed hole 13a and through the through hole 14a.
Is in communication with.

Further, in the fluid chamber 15a, the piezoelectric element 16a having a bimorph structure is provided.
The piezoelectric element 16a has a cantilever structure in which one end (lower end in FIG. 1) is fixed and the other end is not fixed.

The pilot valve body 17a is fixed to one side surface (the right side surface in FIG. 1) of the non-fixed side end of the piezoelectric element 16a to have a nozzle flapper structure, and the other side surface (the left side surface in the figure). 1 is provided with a spring 20a for urging the pilot valve body 17a to the right in FIG.

The pilot valve body 17a is biased by the spring 20a,
Normally, the nozzle 19 of the inflow passage 18 communicating with the input port 4
Block a.

On the other hand, the pilot valve body 17a includes the piezoelectric element 16a in the power supply unit 3.
The nozzle 19a is opened by bending the piezoelectric element 16a to the left side in FIG. 1 by driving the piezoelectric element 16a against the biasing force of the spring 20a.

Piston 11a, piezoelectric element 16a, pilot valve body 17a
The above-mentioned structure is the same for the piston 11b similarly provided on the right end side of the main shaft 9 as seen in FIG. 1, the piezoelectric element 16b as the nozzle flapper structure, and the pilot valve body 17b. The description is omitted by adding the suffix b to the same numbers as the former.

Further, in the power supply unit 3, a supply voltage E is applied to the one-shot pulse circuit 22 by a one-shot pulse circuit 22 having a switch 21 for driving the circuit.

And the switch 21 of this one-shot pulse circuit 22
When turned on or off, a drive voltage as a pulse voltage is applied from the one-shot pulse circuit 22 to the piezoelectric element 16a or 16b having a bimorph structure.

Next, the operation of the present embodiment will be described with respect to the case where the booster circuit of the DC power supply is used as the power supply voltage of the supply voltage E to the one-shot pulse circuit 22 and the case where the full-wave rectification circuit of the AC power supply is used. Each will be described with reference to FIGS. 2 and 3.

First, FIG. 2 is a timing diagram when a booster circuit of a DC power supply is used.

In this case, if the state of the switch 21 connected to the one-shot pulse circuit 22 is turned on as shown in FIG. 2 (a), the booster circuit of the DC power supply causes 1
One-shot pulse circuit with pulse drive voltage of power supply unit 3
22 from, for example, the piezoelectric element 16 of one bimorph structure
applied to a.

At this time, the free end of the piezoelectric element 16a is curved and displaced to the left side in FIG. 1 for the time of one pulse width against the biasing force of the spring 20a.

As a result, the pilot valve body 17 of the nozzle flapper structure
a opens the nozzle 19a for a time corresponding to the width of one pulse as in the state shown in FIG. Fig. 1 Piezoelectric element 16a on the left side
[Fig. 6] is a state diagram in which a pulse voltage is applied.

Further, the nozzle 19a is opened for one pulse time and then immediately closed.

Therefore, one pulse of fluid pressure flows from the input port 4 into the working fluid chamber 12a through the inflow passage 18, the nozzle 19a, the fluid chamber 15a, and the through hole 14a.

As a result, the fluid pressure in the working fluid chamber 12a increases as shown in FIG. 2 (c) with a slight delay time due to the displacement of the piezoelectric element 16a, and the piston 11a is pushed to the right of the working fluid chamber 12a. Therefore, the spindle 9 moves to the right in FIG.

Further, as for the fluid pressure in the working fluid chamber 12a, one pulse of fluid pressure is released to the outside from the bleed hole 13a at the same time when the application of the driving voltage to the piezoelectric element 16a ends, so that FIG. 2 (c). Gradually decreases.

In addition, the piston 1 due to the increase in the fluid pressure in the working fluid chamber 12a
With a slight delay time between the displacement of 1a and the main shaft 9, the fluid flows from the input port 4 to the output port 6a, and the fluid thickness of the output port 6a increases as shown in FIG. It becomes saturated with the supply fluid pressure of.

At this time, since the fluid pressure is discharged from the output port 6b through the discharge port 5b, the fluid pressure at the output port 6b decreases as shown in FIG. 2 (g).

In addition, switch 21 is turned off as shown in Fig. 2 (a).
Then, by the booster circuit of the DC power supply to the piezoelectric element 16b,
One-shot pulse circuit 22 to 1 as shown in FIG. 2 (e)
A pulse drive voltage is applied.

At this time, the free end of the piezoelectric element 16b is displaced to the right in FIG. 1 for a time corresponding to the width of one pulse against the biasing force of the spring 20b, and the pilot valve element 17b opens the nozzle 19b. .

Furthermore, the nozzle 19b is opened for one pulse time and then immediately closed.

Therefore, the fluid pressure from the input port 4 is changed to the inflow path 18, the nozzle.
One pulse of fluid pressure is introduced into the working fluid chamber 12b through the fluid chamber 19b, the fluid chamber 15b, and the through hole 14b.

As a result, the fluid pressure in the working fluid chamber 12b increases as shown in FIG. 2 (f) with a slight delay time due to the displacement of the piezoelectric element 16b, and the piston 11b is moved in the working fluid chamber 12b to the left in FIG. Since it pushes in the direction, the spindle 9 also moves to the left in FIG.

Further, as for the fluid pressure in the working fluid chamber 12b, one pulse of fluid pressure is released from the bleed hole 13b to the outside at the same time when the application of the drive voltage to the piezoelectric element 16b ends, so that FIG. Gradually decreases.

Also, since the input port 4 is communicated with the output port 6b,
With a slight delay time of the displacement of the piston 11b and the main shaft 9 due to the fluid pressure in the working fluid chamber 12b, the fluid pressure at the output port 6b increases as shown in FIG. It becomes saturated.

At this time, since the output port 6a communicates with the discharge port 5a, the fluid pressure at the output port 6a decreases as shown in FIG. 2 (d).

Next, the operation of this embodiment when a full-wave rectification circuit of an AC power supply is used as the power supply circuit for the supply voltage E of the one-shot pulse circuit 22 will be described with reference to the timing diagram of FIG.

In this case, as shown in FIGS. 3 (b) and 3 (e), the driving voltage of the piezoelectric elements 16a and 16b of the bimorph structure is as shown in FIG. 2 (b),
When the fluid pressure in the working fluid chambers 12a and 12b increases as shown in FIGS. 3 (c) and 3 (f), in addition to the square wave as in (e), a full-wave rectified waveform of an AC wave is obtained. Although the rising waveform and the like of FIG. 2 are also different from those in FIGS. 2 (c) and 2 (f), basically the timing diagrams of FIGS. 3 (a) to 3 (g) are shown in FIGS. It corresponds to that of g).

Further, the main shaft 9 and the pistons 11a and 11b of the embodiment of FIG. 1, the piezoelectric elements 16a and 16b as the nozzle flapper structure, and the pilot valve bodies 17a and 17b at the respective timings of FIGS. The operation of FIG.
Since it is similar to the case of (g), it is shown in FIGS.
A duplicate description of the above will be omitted.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Nor.

For example, in this embodiment, the piezoelectric element 16 having a bimorph structure is used.
Although the pistons 11a and 11b are used as the actuating members for the displacement of the main shaft 9 by the a and 16b, a diaphragm may be used instead of the pistons 11a and 11b.

〔The invention's effect〕

The following is a brief description of the effects obtained by the representative one of the inventions disclosed in the present application.

(1). The bimorph piezoelectric element is driven by the application of a pulse voltage, and the piezoelectric element is used to open and close the pilot valve body of the nozzle flapper structure, so that the voltage can be applied to the piezoelectric element continuously for a long time. Since it does not exist, it is possible to prevent the occurrence of polarization deterioration due to the polarization phenomenon.

(2). Since the piezoelectric element having the bimorph structure is only displaced on one side for the duration of the pulse width by the application of the pulse voltage, it is possible to prevent the deformation due to the creep phenomenon.

(3). According to the above (1) and (2), it is possible to obtain a directional control valve using a piezoelectric element that has no fluid leakage, stability of operation, and long life.

(4). A bimorph piezoelectric element needs only to have an effective cross-sectional area that can control the fluid pressure in the working fluid chamber, so the load on the piezoelectric element can be reduced, so the shape of the directional control valve must be small. Is possible.

(5). Since the double pilot type directional control valve has a lower minimum operating pressure than the single pilot type valve, the double pilot type directional control valve can be driven by a drive voltage for a pulse width time like a one-shot pulse circuit. It can be controlled.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a directional control valve using a piezoelectric element according to an embodiment of the present invention, and FIG. 2 is a timing diagram in the case of using a booster circuit of a DC power supply as a supply voltage power supply of this embodiment, FIG. 3 is a timing diagram when a full-wave rectifier circuit of an AC power supply is used as the supply voltage power supply of this embodiment. 1 ... Valve body, 2a, 2b ... Drive, 3 ... Power supply, 4 ... Input port, 5a, 5b ... Discharge port, 6a, 6b ... Output port, 7 ... Flow path, 8a ～ 8d …… Valve seat, 9 …… Spindle, 10a ～ 10d …… Spindle valve body, 11a, 11b …… Piston (operating member), 12a, 12b …… Operating fluid chamber, 13a, 13b …… Bleed hole, 14a, 14b ... through hole, 15a, 15b ... fluid chamber, 16a, 16b ... piezoelectric element, 17a, 17b ... pilot valve body, 18 ... inflow passage, 19a, 19b ... nozzle, 20a, 20b ...... Spring, 21 …… Switch, 22 …… One-shot pulse circuit, E …… Supply voltage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-35223 (JP, A) Actually developed 61-14269 (JP, U) JP-B Sho-49-6043 (JP, B1)

Claims (1)

[Claims] 1. An actuating member that is displaced by the fluid pressure of an actuating fluid chamber, a main shaft that forms a valve body whose flow path can be controlled by the displacement of the actuating member, and an inflow path into the actuating fluid chamber. And a pilot valve body having a nozzle flapper structure for opening and closing to control the fluid pressure in the working fluid chamber,
A double pilot type directional control valve in which a drive unit having the working fluid chamber, the working member and the pilot valve body is provided on both sides in the axial direction of a valve main body unit having the main shaft, wherein As a drive source of the pilot valve element, a non-fixed side of the cantilever structure is fixed to the pilot valve element, and a bimorph structure piezoelectric element that is unilaterally displaced by a pulse width time by application of a pulse voltage is used. A directional control valve using a piezoelectric element, wherein the pilot valve body is driven by the displacement of the piezoelectric element only in the pulse width time to open the inflow passage to the working fluid chamber.