Piezoelectric valve

Details Piezoelectric valve Piezoelectric valve

1999-08-12

2001-02-20

Shaver, Kevin (Department: 3754)

Valves and valve actuation

Electrically actuated valve

Having element dimensionally responsive to field

C251S335200

Reexamination Certificate

active

06189858

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a piezoelectric valve which displaces a diaphragm under the bending action of a piezoelectric element, controls the inflow and outflow of the fluid, and controls the flow rate.
BACKGROUND ART
Up to now, a piezoelectric valve which is used to control the inflow and outflow of the fluid or the flow rate is disclosed in U.S. Pat. No. 5,628,411, for example. As shown in
FIG. 13
, this piezoelectric valve
1
is configured so that a diaphragm
3
whereon a piezoelectric element
2
is provided can be brought near or separated from a valve seat
5
of an output port
4
. In this case, if the pressure of compressed air is introduced into a pressure chamber
6
from an input port
7
is P, a force Fp applied to the output port
4
is expressed by:
Fp=&pgr;/
4
×D
2
×P
(D: Diameter of opening of output port
4
)
On the other hand, a recovering force Fs of the diaphragm
3
when the diaphragm
3
is displaced by an amount of displacement of x
1
to close up the output port
4
is expressed by:
Fs=k
i
×x
1
(k
1
: Spring constant)
And, with this piezoelectric valve
1
, by setting the pressure P of the compressed air so that Fp=Fs, a closed state is maintained.
On the other hand, when the output port
4
is to be opened, drive power is applied to the piezoelectric element
2
to change the amount of bending of the piezoelectric element
2
for separating the diaphragm
3
from the valve seat
5
. This results in that the compressed air is allowed to flow from the pressure chamber
6
to the output port
4
.
However, with the above prior art, there is a possibility of that, if the pressure P of the compressed air is varied, the force Fp applied to the diaphragm
3
is varied, as shown in
FIG. 14
, and when the recovering force Fs is larger than the force Fp, the diaphragm
3
is separated from the valve seat
5
, resulting in the compressed air being allowed to leak from the output port
4
.
The present invention has been provided to solve the above stated problem, being intended to offer a piezoelectric valve with which there is no possibility of the fluid leaking from the pressure chamber with a variation in the pressure of the supplied fluid.
DISCLOSURE OF THE PRESENT INVENTION
To accomplish the above purpose, the piezoelectric valve according to the present invention comprises a diaphragm which is disposed in diaphragm chambers whereto a fluid is supplied from an input port, and constitutes a valve body;
a piezoelectric element which is provided on one surface of the diaphragm, and displaces the diaphragm;
a cushioning member which is opposed to the piezoelectric element, and provided on a housing forming the diaphragm chambers; and
a valve seat which is provided for an output port opening in the housing, and wherewith the other surface of the diaphragm can be contacted;
wherein, when no drive power is applied to the piezoelectric element, the diaphragm is contacted with the valve seat with no elastic energy being built up therein for closing up the output port.
According to the present invention, when no drive power is applied to the piezoelectric element, a variation in the pressure of the supplied fluid will not cause the diaphragm to be separated from the valve seat, thus leakage of the fluid from the output port resulting from the pressure variation is prevented. In addition, if the piezoelectric element is excessively deformed, the piezoelectric element is contacted with the cushioning member, which can prevent the piezoelectric element itself being damaged.
In this case, if, between the diaphragm and the housing, a clearance connecting the diaphragm chambers to each other which is partitioned by the diaphragm is formed, and a fluid introduced into the diaphragm chambers can freely flow through the clearance, there is no need for providing another passage to introduce the fluid to both the one side and the other side of the diaphragm, which allows the construction of this piezoelectric valve to be simplified, which is favorable.
In addition, if the portion of the valve seat which contacts with the diaphragm is formed flat and smoothly, while the diaphragm is formed with a metallic sheet, and the portion of the diaphragm which contacts with the valve seat is formed flat and smoothly, the strength of the diaphragm can be improved, and when the diaphragm is contacted with the valve seat, the fluid can be prevented from leaking from the valve seat, which is more favorable.
Further, if grooves are formed in the surface of the cushioning member which is opposed to the piezoelectric element, the piezoelectric element can be prevented from adhering to the cushioning member, which is preferable.
Still further, if, between the piezoelectric element and the housing, an elastic member which energizes the diaphragm toward the valve seat is provided, while, on the piezoelectric element, a seating member whereon the elastic member is seated is provided, the piezoelectric element can be prevented from adhering to the cushioning member by means of the elastic member, and when the diaphragm is contacted with the valve seat, the output port can be positively closed up by means of the elastic member.
In addition, the present invention comprises a plurality of diaphragms which are disposed in diaphragm chambers whereto a fluid is supplied from an input port, for constituting a valve body;
piezoelectric elements which are provided on the diaphragms, respectively, and displace the diaphragms; and
valve seats which are provided for a plurality of output ports opening in a housing forming the diaphragm chambers, and wherewith the diaphragms can be contacted, respectively, wherein:
when no drive power is applied to the piezoelectric elements, the diaphragms are contacted with the valve seats with no elastic energy being built up in the diaphragms for closing up the output ports, and by selectively or simultaneously displacing the plurality of diaphragms, the fluid being selectively or simultaneously introduced to the plurality of output ports.
According to the present invention, the flow rates of the compressed air introduced to a plurality of output ports can be controlled by means of a single piezoelectric valve, which eliminates the need for providing a plurality of piezoelectric valves, and thus allows simplifying the construction of a device using this piezoelectric valve.


REFERENCES:
patent: 4254938 (1981-03-01), Inada et al.
patent: 4581624 (1986-04-01), O'Connon
patent: 4903732 (1990-02-01), Allen
patent: 5029805 (1991-07-01), Albarda et al.
patent: 5628411 (1997-03-01), Mills et al.
patent: 5638862 (1981-03-01), Miller
patent: 62-28585 (1987-06-01), None
patent: 62-224780 (1987-06-01), None

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