U.S. patent application number 09/734465 was filed with the patent office on 2001-07-12 for piezoelectric actuatable valve.
Invention is credited to Itzhaky, Itzhak M..
Application Number | 20010007265 09/734465 |
Document ID | / |
Family ID | 26055764 |
Filed Date | 2001-07-12 |
United States Patent
Application |
20010007265 |
Kind Code |
A1 |
Itzhaky, Itzhak M. |
July 12, 2001 |
Piezoelectric actuatable valve
Abstract
In the case of a piezoelectrically operable valve (1) with at
least one valve channel (4, 5), which can be closed by means of a
sealing element (14, 16) held on a piezoelectric bending transducer
(7, 8), the bending transducer (7, 8) is held at both ends in the
valve housing (2) to increase the sealing effect of the closed
valve channel or valve channel to be closed (4, 5). In this case, a
first end (7a, 8a) of the bending transducer (7, 8) is fixed in the
valve housing (2), while the second end (7b, 8b) is guided movably
in the longitudinal direction (12) of the transducer in a housing
groove (11) on the opposite housing side (2b).
Inventors: |
Itzhaky, Itzhak M.; (New
York, NY) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
PATENT ATTORNEYS AND ATTORNEYS AT LAW
Post Office Box 2480
Hollywood
FL
33022-2480
US
|
Family ID: |
26055764 |
Appl. No.: |
09/734465 |
Filed: |
March 2, 2001 |
Current U.S.
Class: |
137/883 ;
251/129.06 |
Current CPC
Class: |
F16K 31/005 20130101;
F16K 31/004 20130101; Y10T 137/87877 20150401 |
Class at
Publication: |
137/883 ;
251/129.06 |
International
Class: |
F16K 011/22 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 1999 |
DE |
199 59 341.8 |
Dec 21, 1999 |
DE |
199 61 736.8 |
Claims
1. A piezoelectrically operable valve (1) with at least one valve
channel (4, 5), which can be closed by means of a sealing element
(14, 16) held on a piezoelectric bending transducer (7, 8), in
which arrangement the bending transducer (7, 8), having a first end
(7a, 8a) and a second end (7b, 8b), is fixed by the first end (7a,
8a) in the valve housing (2), and the second end (7b, 8b) of the
bending transducer (7, 8) is guided movably in the longitudinal
direction (12) of the transducer in a housing groove (11) on the
housing side (2b) lying opposite the first end (7a, 8a).
2. The piezoelectrically operable valve as claimed in claim 1,
characterized in that the first end (7a, 8a), fixed in the valve
housing (2), is configured as a connecting end of the bending
transducer (7, 8) which can be connected to an electric voltage
source (U.sub.1,2) for valve operation.
3. The piezoelectrically operable valve as claimed in claim 1 or 2,
characterized in that the bending transducer (7, 8) is concavely
bent in the direction of the valve channel (4, 5) in the
de-energized state.
4. The piezoelectrically operable valve as claimed in one of claims
1 to 3, characterized in that the sealing element (14, 16) is
arranged in the central region of the bending transducer (7,
8).
5. The piezoelectrically operable valve as claimed in one of claims
1 to 4, characterized in that, in the de-energized state, a first
valve channel (4) is closed by means of a first sealing element
(14), which is held on a first bending transducer concavely bent in
the direction of this valve channel (4), while a second valve
channel (5), lying opposite the first valve channel (4), is open,
said second valve channel having opposite it and at a distance from
it a second sealing element (16), which is held on a second bending
transducer (8) concavely bent in the direction (13) of this valve
channel (5).
6. The piezoelectrically operable valve as claimed in one of claims
1 to 5, characterized by an inlet channel (6) opening out into the
valve housing (2) transversely with respect to each valve channel
(4, 5).
7. The piezoelectrically operable valve as claimed in claim 1,
characterized in that, when a single bending transducer (7) is
used, in the de-energized state it is concavely bent in the
direction of a first valve channel (4) and convexly bent with
respect to a second valve channel, lying opposite it, the second
valve channel (5) extending within the valve housing (2) to within
the effective proximity of the bending transducer (7).
8. The piezoelectrically operable valve as claimed in claim 7,
characterized by a sealing element (14') that is effective on both
sides of the central region of the bending transducer (7).
9. The piezoelectrically operable valve as claimed in one of claims
1 to 8, characterized in that the sealing element (14') has a
sealing curvature (14a, 14b) directed toward the respective valve
channel (4, 5).
Description
[0001] The invention relates to a piezoelectrically operable valve
with at least one valve channel, which can be closed by means of a
sealing element held on a piezoelectric bending transducer.
[0002] DE 36 08 550 A1 discloses a piezoelectrically operable
valve, into the valve housing of which at least three valve
channels open out to form a three-way valve. The valve, which can
be used as a pneumatic valve or hydraulic valve, has within its
valve housing at least one piezoelectric bending transducer, the
connecting end of which, for connecting an electric voltage source,
is fixed in a narrow side of the housing. The free end of the
bending transducer, protruding into the interior space of the
housing, carries on its side facing the respective valve channel a
sealing element for closing this valve channel.
[0003] In order, in an initial state or state of rest with an
outflow channel open, to close an inflow channel lying opposite
said outflow channel, the corresponding bending transducer is
mechanically prestressed and/or pressed against the valve seat of
the inflow channel by means of spring force. In this state, the
opposite outflow channel is opened by a sealing element which is
held by the same or a further bending transducer, that is fixed in
the housing on the connection side, being situated opposite the
valve seat of the outflow channel at a distance from it.
[0004] In the operating state, the connecting end of the bending
transducer or of each bending transducer is connected to a voltage
source, the free end of the bending transducer being deflected in
the direction of the respective valve channel or in the opposite
direction, depending on the polarity. As a result, the sealing
element moved along with the free end of the bending transducer
closes the outflow channel while the inflow channel is at the same
time opened. As a result, a medium flowing into the valve housing
via the inflow channel is carried away via a working channel,
whereas in the state of rest, with the inflow channel closed, a
medium flowing in via the working channel flows out of the valve
housing via the outflow channel.
[0005] In the case of this known piezoelectrically operated valve
there is the problem, in particular under extreme operating
conditions, of inadequate tightness of the valve channel closed
according to the operating state. Consequently, when a medium is
passed via the valve at a high pressure and/or high flow rate,
undesirably high leakage rates may occur as a result of inadequate
sealing, in particular of the valve channel that is open in the
state of rest and is to be closed by means of the excited bending
transducer.
[0006] A piezoelectrically operated valve known from U.S. Pat. No.
5,630,440 has a bending transducer that is clamped in the housing
at both ends and is consequently fixed by both its ends. As a
result, a comparatively high restoring force or working force is
admittedly achieved in comparison with fixing of just one end of
the bending transducer. However, the fixing of the bending
transducer at both ends has the considerable disadvantage of an
only small, and therefore generally inadequate, deflection
displacement or bending excursion.
[0007] The invention is therefore based on the object of specifying
a piezoelectric valve, in particular a pneumatic valve, in which
the valve channel to be blocked is reliably closed, while the
disadvantages mentioned are avoided.
[0008] This object is achieved according to the invention by the
features of claim 1. For this purpose, the second end of the
bending transducer, lying opposite the fixed first end, is guided
in a longitudinal groove provided in the valve housing. This
guidance, and the mobility of the bending transducer in the excited
state achieved as a result, permits a longitudinal movement of the
bending transducer, while a lateral movement of the free end is
prevented by the groove side walls forming stops on both sides for
the free end when the bending transducer is excited.
[0009] In this case, the fixed end is expediently configured as a
connecting end which can be connected to an electric voltage source
for valve operation.
[0010] The invention is in this respect based on the idea that a
reliable closing of the valve channel to be blocked, and
consequently deactivated in each case, can be achieved even under
extreme operating conditions, in particular in the case of a high
pressure and a high flow rate of a medium flow to be controlled, by
increasing the force, with at the same time a deflection
displacement or bending excursion that is as great as possible.
This increased pressing force with which the sealing element is
pressed against the valve seat of the corresponding valve channel
by means of the respective bending transducer can be produced by
the bending transducer itself, with at the same time an adequate
deflection displacement, if said bending transducer is held at both
ends within the valve housing and at the same time is fixed only at
one end, while the other end is merely supported in the manner of
an abutment. As a result, an improvement in the operating behavior
of the bending transducer and an increase overall in the operating
reliability of the valve are achieved.
[0011] The invention is based here on the finding that, with the
given connected voltage or operating voltage and accordingly with a
constant bending moment of the piezoelectric transducer, the force
produced by the latter increases with a decreasing lever arm. If
the bending transducer is consequently held at both ends, the
pressing force exerted by the sealing element on the valve seat of
the corresponding valve channel as a result of a bending deflection
of the bending transducer is distinctly greater in comparison with
a bending transducer that is clamped at one end and freely movable
at the free end. If in this case one of the ends of the bending
transducer is guided in an axially movable manner, the deflection
displacement is at the same time greater than in the case of a
bending transducer fixed at both ends. Therefore, it is expedient
to arrange the sealing element in the central region of the bending
transducer, preferably with at least approximately the same
distance both from the fixed end and from the movably guided
end.
[0012] In order to achieve reliable closing of a valve channel
already when it is in the initial state or state of rest in a
particular simple and effective way, in an advantageous development
the bending transducer is concavely bent in the direction of this
valve channel in the de-energized state. The bending profile of the
bending transducer in the de-energized or excitation-free state of
rest is expediently achieved by the bending transducer itself being
prestressed in the manner of a leaf spring. Such prestressing is in
turn expediently achieved by a suitable production process. In this
respect, a laminated bending transducer with a layer structure
having at least one electrically conductive backing layer and a
piezoceramic layer is taken as a basis and, by heating and
subsequent cooling, leads to layers prestressed to varying degrees
(prestressed layers) as a result of material-dependently different
contraction properties. The different prestressing of the layers in
turn leads to a bending deflection of the flat bending transducer
about a bending axis running transversely with respect to its
longitudinal sides and lying parallel to its narrow sides.
[0013] In a particularly preferred embodiment, two bending
transducers are arranged running essentially parallel to each other
within the valve housing. Their respective connecting end, which
can be connected to an electric voltage source, for valve operation
is in turn expediently the end that is held fixedly on the housing,
while the respective free end is in turn held movably in the
longitudinal direction. With respect to a central axis of the
housing, the two bending transducers are convexly curved in the
direction of the valve channel respectively assigned to them. In
the de-energized state, a first valve channel is in this case
closed by means of a sealing element, carried by a first bending
transducer, while an opposite second valve channel is open. Lying
opposite this second valve channel, at a distance from it, there is
then a sealing element carried by the second bending
transducer.
[0014] By applying the operating voltage with appropriate polarity,
both bending transducers are excited, so that the first valve
channel is opened and the second valve channel is closed. A medium
flowing into the valve housing via an additional inflow channel is
consequently led out of the valve housing via the second channel in
the state of rest and via the first channel in the operating state.
Depending on the mode of operation, a medium flowing in via the
open second valve channel can flow away out of the valve housing
via the inflow channel.
[0015] When a single bending transducer is used, in the
de-energized state it is concavely bent in the direction of a first
valve channel, a second valve channel, lying opposite said first
valve channel, extending within the valve housing to within the
effective proximity of the concave side of the bending transducer.
In particular in this embodiment with only a single bending
transducer, the latter carries a sealing element that is effective
on both sides of its central region.
[0016] Exemplary embodiments of the invention are explained in more
detail below with reference to a drawing, in which:
[0017] FIG. 1 shows in a sectional representation a first
configurational variant of a piezo-electrically operable valve with
two bending transducers held at both ends,
[0018] FIG. 2 shows a second configurational variant of the valve
according to FIG. 1,
[0019] FIG. 3 shows in a representation according to FIGS. 1 and 2
a piezoelectrically operable valve with a single bending transducer
that is held at both ends, and
[0020] FIG. 4 shows in representations A and B trial constructions
of a piezoelectric bending transducer held at one end and at both
ends in the excited state and excitation-free state.
[0021] The same parts are provided with the same reference numerals
in all the figures here.
[0022] The piezoelectrically operable valve 1 according to FIGS. 1
and 2 has a valve housing 2, which preferably consists of plastic
and is cuboidal, with a likewise cuboidal or else
circular-cylindrical interior space 3. Two diametrically opposed
valve channels 4 and 5 open out into the interior space 3. A
further valve channel or inlet channel 6, opening out into the
interior space 3 of the valve housing 2, runs transversely with
respect to the two valve channels 4 and 5. Arranged in the interior
space 3 of the valve housing 2 are two platelet-shaped bending
transducers 7 and 8. Each bending transducer 7, 8 has a connecting
end 7a, 8a and a free end 7b, 8b. The respective connecting end 7a,
8a of the bending transducer 7 and 8, respectively, is held in the
region of a narrow side 2a of the valve housing 2 on the connection
side and is fixed there. Connecting contacts 9, which are connected
to a respective voltage source U.sub.1 and U.sub.2 via connecting
lines 10, are led to the respective connecting end 7a, 8a of the
bending transducer 7 and 8, respectively. The voltage sources
supply a DC voltage of, for example, 200 V.
[0023] On the opposite narrow side 2b of the housing of the valve
1, the free ends 7b, 8b of the respective bending transducer 7 and
8, respectively, lie in housing grooves 11. Within these housing
grooves 11, the free ends 7b, 8b of the bending transducers 7 and 8
are held movably in the longitudinal direction 12 of the
transducer, which also corresponds to the longitudinal direction of
the housing. The housing grooves 11 in this case form lateral stops
for the respective free end 7b, 8b, in or counter to the transverse
direction of the housing illustrated by the arrow 13.
[0024] In the state of rest or initial state represented in the
exemplary embodiment, the bending transducers 7, 8 are de-energized
and consequently excitation-free. In this state of rest, the
right-hand valve channel 4 in the exemplary embodiment according to
FIGS. 1 and 2 is closed. For this purpose, the bending transducer 7
carries in the central region of the outer side facing this valve
channel 4 a sealing element 14, preferably consisting of plastic or
rubber. This sealing element bears against the valve seat 15 of the
valve channel 4 and seals the latter off on the inner side of the
housing. The pressing force F.sub.1 required for this purpose is
applied by the bending transducer 7 itself, in that, in the state
of rest, the latter is concavely curved in the direction of the
valve seat 15 and thereby prestressed in the manner of a leaf
spring by being fitted in a corresponding position.
[0025] The bending and curving profile represented of the
respective bending transducer 7, 8 is achieved by a special
production process, in which a layer structure with an electrically
conductive backing layer, preferably in the form of a flat
sheet-metal strip, and with a piezoceramic layer adhesively held on
it is prestressed in a way not represented in any more detail by
heating and subsequent cooling along the longitudinal direction 12
of the transducer.
[0026] The bending transducer 8 assigned to the (left-hand) valve
channel 5, which transducer corresponds with respect to its shape
and structure to the bending transducer 7, likewise carries a
sealing element 16 in its central region. In the open state of the
valve channel 5 represented, this sealing element is arranged at a
distance a from the valve seat 17 of said valve channel. In the
de-energized state of rest, this bending transducer 8 is also
convexly curved in the direction of the valve seat 17 and
consequently in the direction of the valve channel 5.
[0027] For operating the valve 1, the two bending transducers 7 and
8 are excited with appropriate polarity of the voltage sources
U.sub.1 and U.sub.2. When this happens, the two bending transducers
7, 8 move in the direction or bending direction of the arrow 13, so
that the sealing element 14 carried by the bending transducer 7 is
lifted off the valve seat 15 and consequently opens the valve
channel 4, while the sealing element 16 carried by the bending
transducer 8 is pressed against the valve seat 17 and consequently
closes the valve channel 5. The free ends 7b and 8b of the two
bending transducers 7 and 8 can be displaced thereby in the
longitudinal direction 12 on account of being secured within the
housing grooves 11. In this arrangement, the free ends 7b and 8b
are extended into the housing grooves 11 to such a depth that they
cannot come out of the housing grooves 11 when there is a bending
deflection of the bending transducers 7, 8 in the excited
state.
[0028] Whereas in the state of rest the prestressing of the bent
bending transducer 7 has the effect that the sealing element 14
carried by the latter is already pressed with an adequately high
pressing force F.sub.1 against the valve seat 15, the pressing
force F.sub.2 required for closing the valve channel 5, which is
open in the state of rest, is achieved by the securement of the
bending transducer 8 at both ends in combination with the central
arrangement of the sealing element 16. The reason for this is an
increase in force brought about by a particularly favorable lever
arm effect with a constant bending moment.
[0029] During the operation of the pneumatic valve 1, configured in
the exemplary embodiment as a three-way valve, air L flowing into
the valve housing 2 at a given pressure p and at a given flow rate
v via the inlet channel 6 is carried away out of the valve housing
2 via the valve channel 5, which is open in this de-energized state
of rest. The inflow channel 6 may in this case be led into the
interior space 3 in the way according to FIG. 1 through a
longitudinal side of the valve housing 2 at least approximately at
the same height as the two diametrically opposed valve channels 4
and 5. Alternatively, the inlet channel 6 may be led into the
interior space 3 in the way according to FIG. 2 through the narrow
side 2b of the valve housing 2, provided with the housing grooves
11. In the case of this embodiment, the inlet channel 6 expediently
runs between the two housing grooves 11 and consequently opens out
between the two bending transducers 7 and 8 into the interior space
3.
[0030] For switching over the valve 1, the two bending transducers
7 and 8 are excited by applying an operating voltage U with
appropriate polarity of the voltage sources U.sub.1 and U.sub.2 and
are deflected in the same direction (bending direction) 13. As this
happens, the valve channel 4, which is closed in the state of rest,
is opened, while the valve channel 5, which is open in the state of
rest, is closed. The air L flowing into the valve housing 2 via the
inlet channel 6, is consequently carried away via the valve channel
4. Appropriate polarity of the voltage sources U.sub.1 and U.sub.2
also allows both valve channels 4 and 5 to be opened or closed.
[0031] In the case of the variant represented in FIG. 3 without
voltage connections 9, 10, with a single bending transducer 7,
which in turn is held at both ends in the valve housing 2, in the
exemplary embodiment the central region of said transducer is
curved or bent in the direction of the valve channel 4 in the state
of rest. The valve channel 5 lying opposite the valve channel 4 is
lengthened in the interior space 3 in the direction toward the
sealing element 14' and consequently extends to within the
effective proximity of the bending transducer 7. The sealing
element 14' which is placed on or applied to the bending transducer
7 and is effective both on the convex side and on the concave side
of the latter is expediently configured in such a way that it is
curved on both sides. Sealing curvatures 14'a, 14'b directed
counter to each other are in this case expediently of a
hemispherical design. As a result, a particularly reliable sealing
effect is achieved even with a comparatively small clear width or a
comparatively small inside diameter of the valve channels 4, 5.
[0032] During the operation of the pneumatic valve 1 according to
FIG. 3, in the de-energized state--or else with appropriate
polarity of the voltage U (not represented)--the sealing element
14' is pressed against the valve seat 15, and consequently the
valve channel 4 is closed, while the valve channel 5 is open, by
means of the pre-stressed, bent bending transducer 7. By polarity
reversal of the voltage U, the valve channel 5 is closed, and at
the same time the valve channel 4 is opened, as a result of a
bending deflection of the bending transducer 7 counter to the
bending direction 13 represented.
[0033] FIG. 4 illustrates trial structures A and B with a single
bending transducer 7 restrained on the connection side, the
following statements applying analogously to the bending transducer
8 according to FIGS. 1 and 2. Whereas according to trial A the free
end 7b of the bending transducer 7 is freely movable in the manner
of a boom, according to trial B its free end 7b is held such that
it is merely longitudinally displaceable. In both trials A and B
the same bending transducer 7 was used, the piezoceramic layer of
which had the dimensions 38.00.times.12.70.times.0.- 20 and the
backing layer of which had the dimensions
63.4.times.13.7.times.0.15 (length, width and thickness in mm).
Measuring parameters were the required restoring force F to return
the bending transducer 7 excited with a voltage U=200 V (DC) at the
respective point P.sub.A, P.sub.B from the deflected position
A.sub.a, B.sub.a into the excitation-free rest or neutral position
A.sub.b or B.sub.b, respectively.
[0034] In trial A, the restoring force F was registered at the free
end 7b of the bending transducer at the measuring point P.sub.A,
while in trial B this was determined in the central region of the
bending transducer 7 at the measuring point P.sub.B. The restoring
force F corresponding to the pressing force F.sub.1,2 was measured
in trial A at 0.2 N (corresponds to 20 g) and in trial B at 1.25 N
(corresponds to 125 g).
[0035] This means that the arrangement according to the invention
of a bending transducer 7, 8 held at both ends, with a sealing
element 14, 16 arranged in its central region, within a
piezoelectrically operated valve 1 achieves an increase many times
over of the force F.sub.1,2 for closing a valve channel 4 or 5 in
comparison with a piezo element restrained at one end.
* * * * *