U.S. patent number 3,635,016 [Application Number 04/870,715] was granted by the patent office on 1972-01-18 for electromechanical actuator having an active element of electroexpansive material.
This patent grant is currently assigned to Physics International Company. Invention is credited to Glendon M. Benson.
United States Patent |
3,635,016 |
Benson |
January 18, 1972 |
ELECTROMECHANICAL ACTUATOR HAVING AN ACTIVE ELEMENT OF
ELECTROEXPANSIVE MATERIAL
Abstract
An electromechanical transducer having an active module of
electroexpansive material, such as piezoelectric material. A
chamber filled with noncompressible fluid that is bounded by first
and second plungers or diaphragms, the first plunger being
operatively connected to the module. The area of the second plunger
is established at a size smaller than the first plunger so as to
provide for motion amplification of the relatively small mechanical
displacement of the electroexpansive module. An improved
electroexpansive module and a method for making the same are also
disclosed.
Inventors: |
Benson; Glendon M. (Danville,
CA) |
Assignee: |
Physics International Company
(San Leandro, CA)
|
Family
ID: |
24693012 |
Appl.
No.: |
04/870,715 |
Filed: |
July 16, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
671065 |
Sep 27, 1967 |
3501099 |
|
|
|
Current U.S.
Class: |
60/528; 60/545;
60/583; 91/459 |
Current CPC
Class: |
H02N
2/043 (20130101); H01L 41/053 (20130101); H01L
41/0833 (20130101); F02M 47/00 (20130101); F02M
57/025 (20130101); F02M 51/0603 (20130101) |
Current International
Class: |
F02M
47/00 (20060101); H01L 41/083 (20060101); H01L
41/00 (20060101); F02M 59/10 (20060101); F02M
59/00 (20060101); H01L 41/053 (20060101); F02M
51/06 (20060101); F01k 025/00 () |
Field of
Search: |
;60/23,54.5
;310/8.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schwadron; Martin P.
Assistant Examiner: Cohen; Irwin C.
Parent Case Text
This application is a divisional application of Ser. No. 671,065,
filed on Sept. 27, 1967 for ELECTROMECHANICAL ACTUATOR HAVING AN
ACTIVE ELEMENT OF ELECTROEXPANSIVE MATERIAL now U.S. Pat. No.
3,501,099.
Claims
What is claimed is:
1. Apparatus for actuating a load comprising:
an electroexpansive body having a surface,
means for forming walls that define in cooperation with said
surface a fluidtight chamber,
a plunger having a face communicating with said chamber, said face
having an area less than said surface of said electroexpansive
body,
noncompressive fluid in said chamber,
means for applying an electrical field across said electroexpansive
body, and
means for coupling said load to said plunger including a second
face on said plunger having an area which is larger than said first
plunger face,
means including said second face for defining a second fluidtight
chamber,
a noncompressible fluid in said second chamber, and
a rod coupled to said load having an end surface in said second
chamber that has an area less than said second plunger face.
2. Apparatus according to claim 1 wherein said electroexpansive
body comprises: a plurality of discs of ceramic electroexpansive
material having a thickness no greater than about one millimeter, a
plurality of conductive discs, one of said conducting discs being
interposed between each said ceramic disc, said discs and said
electrodes being bonded together in a unitary assembly, first
conductive means for electrically connecting together every
alternate conductive disc, second electric circuit means for
interconnecting all other conductive discs, whereby application of
an electric field between conductive circuit means places an equal
voltage across every disc in parallel so that the mechanical
expansion of each said disc is in series.
Description
This invention relates to electromechanical transducers or
actuators which have as the active element thereof an
electroexpansive module so arranged that accurate high speed
mechanical movement is generated in response to electrical
excitation. Such transducers are useful in any environment wherein
precise and rapid mechanical movement in response to an electric
signal is required.
An object of the present invention is to provide an
electromechanical transducer or actuator that has improved
precision of mechanical movement and response time. This object is
achieved by providing an actuator that employs as an active element
material that exhibits strain when subjected to an electric field,
such as piezoelectric material, in combination with a coupling or
linkage system for coupling a load to the active element.
The coupling or linkage affords substantial motion amplification so
that the relatively small magnitude of strain typical of such
electroexpansive elements as piezoelectric elements is multiplied
to a significant amount. In achieving such motion amplification
according to the present invention, a fluidtight chamber is
provided. The chamber contains noncompressible fluid, such as
mercury, and is bounded by a piston having a large surface area and
a piston having a small surface area. Attached in driving relation
to the large area piston is an electroexpansive module; attached to
the small area piston is a load. When the large area piston moves
in response to electrical excitation of the electroexpansive
module, the load attached to the small area piston moves a greater
amount. Because the unit forces developed by state-of-the-art
electroexpansive materials is high, the pressure of the fluid in
the chamber is adequate to drive the load.
Another object of the present invention is to provide an improved
method for making a piezoelectric module that constitutes the
active element of such actuator. The improved method lends itself
to automated production of the modules with a high degree of
reproducibility of characteristics and parameters.
Still another object is to provide an improved piezoelectric
module.
The foregoing as well as other objects will be more apparent after
referring to the following specification and accompanying drawings
in which:
FIG. 1 is a partially schematic side elevation view of an
electroexpansive actuator according to the present invention;
FIG. 2 is a view taken along line 2--2 of FIG. 1;
FIG. 3 is a fuel injection valve controlled by an actuator of the
present invention;
FIG. 4 is another form of injection valve controlled by an actuator
of the present invention;
FIG. 5 is still another form of injection valve exemplifying the
present invention;
FIG. 5A is a valve substantially identical to that shown in FIG. 5
with certain fluid sealing characteristics being modified;
FIG. 6 is yet another fuel injection valve exemplifying the present
invention;
FIG. 7 is yet another fuel injection valve illustrating the present
invention;
FIG. 8 is a further fuel injection valve that embodies this
invention;
FIG. 9 is a dual controlled injection valve illustrating this
invention;
FIG. 10 is a diagrammatic view illustrating a novel process for
making electroexpansive modules according to the present
invention;
FIG. 11 is a diagrammatic view of a module formed by the method;
and
FIG. 12 is a fragmentary perspective view of the module of FIG.
11;
FIG. 13 is a sectional view of another form of electromechanical
actuator according to the present invention;
FIG. 14 is a cross-sectional view of a reciprocal-to-rotary motion
converter for operative association with the structure of FIG.
13;
FIG. 15 is a sectional top view taken along line 15--15 of FIG. 14;
and
FIG. 16 is a cross-sectional view of an electromechanical actuator
according to the invention that develops a rotary output.
Referring more particularly to the drawings, reference numeral 12
indicates an electroexpansive module having one end thereof secured
to an end plate 14 of a cylindric housing 16. In the present
specification and claims the term "electroexpansive" denotes the
characteristic of exhibiting or producing a strain in response to
excitation by an electric field. In this sense, piezoelectric
material is electroexpansive. Thus, when module 12 is electrically
excited, strain is produced at the lower end thereof with respect
to the upper end thereof, i.e., with respect to end plate 14.
Secured to the lower end of module 12 is a piston 18. A manifold
housing 19 is threadedly joined to casing 14 and is formed to
define a chamber 20 below piston 18. Piston 18 is provided with a
peripheral elastomer seal 22 so that chamber 20 is fluidtight.
Communicating with chamber 20 is a valve compartment 24 in which is
slidably carried a primary valve body 26. At the entry end of
compartment 24, valve body 26 is provided with an elastomer seal 28
for preventing the fluid in chamber 20 from passing the valve body
into the compartment. In FIG. 1 valve body 26 is shown in a neutral
position, a position obtaining when module 12 is in a discharged or
deenergized state. At the right-hand end of valve compartment 24 is
a coil spring 30 which is balanced by an equal force on the
left-hand side of the valve body from fluid within chamber 20.
Thus, it will be seen that when piston 18 moves downwardly in
response to expansion of module 12, valve body 26 is moved
rightwardly against the force of spring 30. Conversely, when piston
18 is moved upwardly, decrease of pressure within chamber 20 will
permit the force stored in spring 30 to move the valve
leftwardly.
It can be seen in the drawing that the area of piston 18 that is
exposed to chamber 20 is much greater than the exposed area of
valve body 26. This disparate area relationship accomplishes motion
amplification to a degree that is proportional to the ratio of the
two surface areas. Because such electroexpansive material as
piezoelectric material has a high unit force when expanded in
response to electrical excitation, adequate pressure is present in
chamber 20 for moving valve body 26 through its desired travel.
Manifold housing 19 includes a fluid inlet opening 32 and a fluid
outlet opening 34. Connected to inlet opening 32 is a pump (not
shown) of conventional form which supplies pressurized fluid from a
reservoir (not shown) which is connected to outlet opening 34.
Inlet 32 communicates with compartment 24 at the central region
thereof and outlet opening 34 communicates with the compartment at
the lateral regions thereof. Intermediate the central and lateral
regions of the compartment are transfer passages 36 and 38 through
which fluid is transferred between compartment 24 and a secondary
valve compartment 40. Within secondary compartment 40 is a
secondary valve body 42 which is moved rightwardly in response to
delivery of fluid through passage 36 and leftwardly in response to
delivery of fluid through passage 38. Fluid inlet opening 32
communicates with the central region of compartment 40 from which
fluid can be transferred through one or the other of a pair of
lower transfer passages 44 and 46 which communicate to opposite
sides of an actuator piston 48 carried in a piston chamber 50. The
piston is moved laterally in a direction determined by the position
of secondary valve 42. An actuator rod 52 is attached to piston 48
and extends exterior of manifold housing 19 so as to afford
attachment of a load to the actuator.
In operation, the embodiment of FIGS. 1 and 2 actuates a load in
response to expansion and/or contraction of electroexpansive module
12. Upon application of an electrical signal of appropriate
polarity to the electroexpansive module, piston 18 is driven
downwardly, as a consequence of which valve body 26 is driven
rightwardly against the force of spring 30. In such position, inlet
opening 32 communicates with transfer passage 36 so that the
pressure on the left side of valve body 42 is increased, thereby
driving the valve body rightwardly. As a consequence of such
rightward movement, fluid inlet 32 communicates fluid through
transfer passage 44 to the left side of piston 48 so as to move the
piston rightwardly; the load attached to piston rod 52 is moved in
a corresponding direction. When electroexpansive module 12 is
discharged, piston 18 moves upwardly, and the pressure on the left
side of primary valve body 26 is removed, thereby permitting spring
30 to move the valve body to a central neutral position so as to
interrupt delivery of fluid through transfer passage 36. Further
rightward movement of valve body 42 is terminated, but the valve is
not returned to the central neutral position until module 12 is
energized with a signal of the opposite polarity.
On energization of the module with a signal of opposite polarity,
piston 18 is moved upwardly thereby permitting compression spring
30 to move valve body 26 leftwardly in compartment 24. Responsive
to such movement, fluid entering inlet 32 is admitted to transfer
passage 38 thus moving valve body 42 toward a central position at
which movement of piston 48 is terminated. It can be seen that very
precise movement of actuator rod 52 is possible because the
response time of the electroexpansive module is very fast, and
further because the physical expansion and contraction of the
module is amplified by the relatively small cross-sectional area of
valve body 26 as compared with the cross-sectional area of piston
18. Because the structure is symmetrical rod 52 can be moved in
either direction, thus providing a double acting device.
Referring now to FIG. 3, wherein an embodiment of the present
invention is shown in driving relation to a fuel injection valve,
there is provided an electroexpansive module 54 which is drivably
connected as described hereinabove to a piston 56 below which is
defined a chamber 58. In direct communication with chamber 58 is a
control valve body 60. The area of valve body 60 that is exposed to
the fluid in chamber 58 is substantially less than the area of
piston 56 that is exposed to the chamber so that the valve body
experiences a relatively large amount of movement in response to a
relatively small amount of movement by piston 56.
Control valve body 60, when in the lower or open position,
communicates fluid at an inlet port 62 to an outlet port 64 and,
when in the closed or upper position, interrupts such fluid flow to
outlet port 64. In the upper or closed position of the valve body,
port 64 is connected to a discharge port 66. Valve body 60 is
biased toward the upper or closed position by a compression spring
68 so that inlet port 62 is normally closed thereby permitting
maintenance of high pressure at inlet port 62.
Outlet port 64 communicates to an injection valve assembly
designated generally as 70, which valve typically has a nozzle
portion 72 for installation into communication with the cylinder of
an internal combustion engine. The valve has one or more injection
ports 74 through which fuel is injected when the valve is open. The
injection ports are normally closed by an injector needle 76 which
needle is biased downwardly by a spring 78 to so normally close the
injection ports. The needle is supported by an elastomer seal 80
below which fuel under high pressure enters through a fuel line 82
and above which outlet port 64 from control valve body 60
communicates. Above elastomer seal 80 a chamber 84 is defined;
within the chamber an actuator 86 is secured to injection needle 76
and has a downwardly-directed surface area so that when pressurized
fluid is conveyed through port 64 in response to downward movement
of control valve body 60, actuator 86 and needle valve 76 are
lifted upwardly against force of spring 78 so as to inject fuel
through injection port 74. Such action occurs in response to
energization of module 54 by an electric signal so as to drive
piston 56 downwardly. Fuel injection continues so long as the
module is strained or electrically charged. Chamber 84 is delimited
at the upper extremity thereof by a cup 88 above which resides
spring 78 and above which discharge port 66 communicates.
Communicating with the volume above cup 88 is an outlet fitting 90
which returns fuel to the low-pressure side of the fuel source.
In operation the device of FIG. 3 normally resides in the position
shown in the figure. In such position high-pressure fuel is
maintained at inlet opening 62 of the actuator valve and at the
lower end of injector needle 76, ready for injection through
injector ports 74. When an electrical signal is applied to module
54, piston 56 is driven downwardly thereby compressing the fluid in
chamber 58 to drive control valve body 60 downwardly against the
force of spring 68. This action moves the annular excision on valve
body 60 into interposition between inlet port 62 and outlet port 64
so as to apply high pressure fluid to chamber 84. Thus, piston 86
and injector needle 76 are lifted to permit injection of fuel
through ports 74 into the engine to which the device is installed.
Fuel injection continues for as long as module 54 is energized or
charged. When the application of an electrical signal is
interrupted and when the electroexpansive module is discharged so
as to move piston 56 upwardly, control valve body 60 experiences a
corresponding movement. Upward movement of the control valve body
interrupts the inflow of fuel through inlet port 62 and connects
outlet port 64 through the annular excision in the control valve
body to discharge port 66. Consequently, the fluid pressure within
chamber 84 and the upward force against piston 86 are abruptly
terminated so that the injector needle 74 is moved downwardly to
the closed position. Because the injector valve of FIG. 3 is very
fast acting and closes securely, over supply of fuel and/or nozzle
weep are avoided.
The valve of FIG. 3 illustrates the versatility of an injector
valve embodying the present invention. The distance that control
valve body 60 travels is proportional to the magnitude of the
voltage applied to electroexpansive module 54. If the magnitude of
the voltage applied to the module is large, control valve body 60
moves a relatively large distance and fuel is applied to chamber 84
rapidly. If the magnitude of the electric signal applied to the
module is of relatively low magnitude, control valve body 60
experiences a shorter travel so that outlet port 64 is not fully
opened. Accordingly, the time required for application of fluid
pressure to chamber 84 is lengthened. Because the time of opening
and closing injector needle 76 is proportional to the time required
for fuel pressure buildup within chamber 84, the actuating time of
the injector valve is proportional to the magnitude of the electric
signal applied to the electroexpansive module. Thus, it will be
seen that the injection characteristics of the valve can be
controlled by simple control devices capable of varying the voltage
applied to the electroexpansive module in proportion to operating
characteristics of the engine with which the device of FIG. 3 is
used.
It will be observed that the valve of FIG. 3 is driven by the
pressure present in the combustion fuel supply system. This
characteristic materially simplifies the control system without
sacrificing accuracy or versatility. In the valve of FIG. 3 the
fuel injection pressure is limited to the supply pressure of the
fuel. In the modification of the invention shown in FIG. 4,
mechanisms for materially increasing the pressure are provided.
In FIG. 4 an electroexpansive module 92 having characteristics
described hereinabove is mounted in a housing 94 and is provided
with a piston 96 which is driven downwardly in response to
electrical energization of the module. The piston 96 forms one side
of a fluid chamber 98 which chamber communicates with a control
valve body 100. The valve body is biased toward an upward position
by a compression spring 102, and when the valve body moves
downwardly in response to energization of the module 92, an inlet
fluid connection 104 is connected to a plunger chamber 106 by a
suitable annular excision in the control valve body. Below chamber
106 is carried a first plunger 108 which is resiliently biased in
an upward position by compression spring 110. Spring 110 resides
below the first plunger in a lower plunger chamber 112 in which is
also disposed a second plunger 114 of lesser diameter than first
plunger 108. Below second plunger 114 is a fuel compression chamber
116 which communicates at the lower end thereof with an injector
port 118. An injector needle 120 is biased by a spring toward a
position at which the needle closes port 118. Communicating with
fuel chamber 116 from inlet 104 is a fluid passage 124 having a
check valve 126 therein. The check valve affords one-way fuel flow
into chamber 116 and prevents backflow of fuel from the
chamber.
The operation of the embodiment of FIG. 4 can be appreciated by
assuming that chamber 116 is filled with fuel from inlet port 104.
When electroexpansive module 92 is energized by an electric pulse,
downward movement of piston 96 results, which in turn moves valve
body 100 down to admit fuel into plunger chamber 106. The pressure
applied to plunger 108 is equal to the supply pressure of the fuel.
The consequent downward force on the plunger is substantial because
the upper surface area of the plunger is large. Such force causes
downward movement of plunger 108 and secondary plunger 114 which
compresses the fuel in fuel chamber 116 to such an extent that
injector needle 120 is raised so as to open the valve and
forcefully inject fuel through ports 118.
The pressure at which the fuel is injected is very high, because
the surface area of lower plunger 114 is small compared to the
upper surface of plunger 106. Equal force transmission from the
upper plunger to the lower plunger renders inversely proportional
the pressure on the respective surfaces. In one valve designed
according to the present invention, a surface area ratio of 10 to 1
(upper plunger, 10; lower plunger, 1) affords a tenfold pressure
increase so that fuel will be injected to the engine cylinders at
10,000 p.s.i. in a system wherein the fuel supply pressure is 1,000
p.s.i.
Fuel injection terminates either when secondary plunger 114
completes its stroke or when electroexpansive module 92 is
discharged to permit upward movement of valve body 100 at which
time the force of spring 110 moves secondary plunger 114 upwardly.
Thus, it can be seen that the quantity of fuel injected through
injecting ports 118 can be established by selecting the appropriate
size secondary plunger 114 or in the alternative can be adjusted by
adjusting the timing of the signal applied to electroexpansive
module 92. A circuit suitable for so controlling the energization
of the module is shown in U.S. Pat. application, Ser. No. 671,060,
now U.S. Pat. No. 3,500,799 filed concurrently herewith and
entitled "Electromechanical Control System." Thus, the embodiment
of FIG. 4 combines extremely high injection pressure with
versatility in timing and quantity of fuel injection.
Still another form of the present invention is shown in FIG. 5
wherein the electroexpansive module is designated by reference
numeral 128, the module functioning to drive a piston 130
associated with a fluid chamber 132 which in turn drives an
actuator valve body 134 having an upper surface communicating with
the fluid in the chamber. The actuator valve body is slidably
supported in a valve chamber designated generally at 136; a spring
138 is provided for biasing the valve body upwardly to the position
shown in the drawing. In such upward position, an upwardly
converging valve face 140 on the valve body seats against a
corresponding seat portion of chamber 136 and prevents fuel
entering inlet opening 142 from passing. Below upwardly converging
valve face 140 a fuel compression chamber 143 is defined between an
annular excision 144 on valve body 134 and the wall of chamber 136.
Chamber 143 at its lower extremity is bounded by an annular face
146 formed on the valve body. Below annular face 146 the valve body
has a cylindric or tubular skirt portion 148 which in the position
shown in the figure closes a fluid outlet passage 150. Valve
chamber 136 at the bottom thereof includes an annular section 152
which also communicates with fuel outlet opening 150. At the lower
end of the structure a plurality of injection openings 154 are
provided and are normally closed by an injector needle valve 156
which is biased downwardly by a spring 158.
In operation, the embodiment of FIG. 5, when the electroexpansive
module is energized by an electric signal, injects fuel by the
following sequence of actions: the increase of pressure in chamber
132 moves the valve body 134 downwardly so as to retract converging
face 140 from its seat and thereby admit fuel therebelow.
Downward movement of valve body 134 moves tubular skirt portion 148
downward within annular chamber 152 so as to compress the fuel in
the annular chamber. Injector needle valve 156 is thereby loaded by
an upwardly directed force that is almost equal to the opposing
downward force of spring 158. When annular face 146 of valve body
134 passes below the upper extremity of fuel passage 150, a fuel
path from inlet opening 142 down to the lower end of injector
needle 156 is provided so that the needle is unseated and fuel is
injected through ports 154. As described hereinabove, the injection
continues until module 128 is discharged to permit piston 130 to
move upwardly.
As in the preceding embodiments, the quantity of fuel injected
depends upon the time between the energization of the
electroexpansive module and the discharge of the module. Moreover,
the physical geometry of plunger 134 can be modified to effect
variations in fuel injection quantity.
FIG. 5A depicts a valve identical in most respects to that shown in
FIG. 5. Because of the substantial identity, similar characters of
reference are used in many respects in the two figures.
Corresponding parts that are rearranged from FIG. 5 are primed in
FIG. 5A. It will be noted, however, that centrally of valve body
134' in FIG. 5A is a longitudinal passage 160 which affords a
drainage path for whatever minor amount of fuel may leak past the
relatively moving parts of the system. When module 128 is pulsed to
compress fluid in chamber 132 and drive valve body 134' downwardly,
converging valve face 140' is unseated so as to admit fluid below
the shoulders on needle valve 156. Pressure on the shoulders
unseats the valve and permits egress of fluid from ports 154 at a
pressure equal to that of the source applied at inlet 142. Such
pressure is less than that of FIG. 5; the lower pressure permits
simplification of valve body 134' (as compared with valve body 134)
and elimination of spring 138. The presence of longitudinal passage
160 unloads all downward force on needle valve 156 except that of
spring 158. Consequently, the needle valve is efficiently opened
because the upward force on the shoulders from fluid pressure
exceeds the downward force of spring 158. Such construction
shortens response time of the structure. For example, a device
designed according to FIG. 5A has a response time in the order of
100 microseconds, by which is meant the valve is opened and is
injecting fuel within 100 microseconds after electrical excitation
of module 128 occurs. This is approximately 100 times faster than
any known prior electrically driven valves.
Yet another modification of the present invention is shown in FIG.
6, wherein an electroexpansive stack 162 drives a piston 164 which
compresses fluid in a chamber 166. Communicating with chamber 166
is a plunger 168 having a downwardly-directed surface exposed to
the chamber interior. Connected to plunger 168 is an injection
needle 170 the lower end of which is adapted to normally close off
a fuel injection port 172. The injection needle is retained in such
normally closed condition by a compression spring 174 that exerts a
force on a collar 176 which is operatively connected to the
injector needle. The force of spring 174 is sufficient to move the
valve toward a closed position and retain it there even in the
presence of fuel supplied at significant pressures to a fuel inlet
opening 178.
In operation the valve of FIG. 6 opens in response to application
of an electric signal to an electroexpansive module 162, because on
such application the pressure within chamber 166 is increased so
that plunger 168 is lifted as is injector needle 170. When the
electroexpansive module is discharged, the force of spring 174 is
sufficient to reseat the injector needle to interrupt fuel
injection through port 172.
In FIG. 6, seal 165 is a metal bellows of Omega seal which prevents
fluid leakage from chamber 166 into the upper electroexpansive
module 162. Such seals are leaktight, reliable seals that easily
withstand the high pressures and the large number of operating
cycles experienced.
As shown in FIG. 7 the present invention can be embodied with an
electroexpansive module 180 of generally cylindric configuration.
The module has an outer face on which is disposed a conductive
layer 182 that defines an electrode. Another conductive layer 184
is provided on the inner face of the cylindric module 180 so that
connection of an electric signal across electrodes 182 and 184 will
effect a radial strain in the module. The axial ends of the module
are sealed off with respect to a housing 186 by an upper flexible
metallic seal member 188 and a lower flexible metallic seal member
190. Between the seal members is defined an annular chamber 191.
Housing 186 includes a rigid core member 186a that defines a radial
passage 192 communicating annular chamber 191 with a pressure
chamber 194. The top surface of pressure chamber 194 is defined by
the lower face of a plunger 196 which is biased downwardly by a
compression spring 198. The surface of plunger 196 that is exposed
to chamber 194 is less than the area of module 180 that is exposed
to annular chamber 191 so that motion amplification is achieved.
Attached to or integral with plunger 196 is an injector needle 200,
the lower end of which is adapted normally to close an injection
port 202. A suitable seal 204 is provided for isolating chamber 194
from fuel entering an inlet opening 206.
In operation, the embodiment of FIG. 7 is caused to open by
application of an electrical signal of suitable magnitude to the
electrodes 182 and 184. Module 180 expands inwardly in response to
such signal. Inward expansion of the module compresses the fluid in
chamber 194 which in turn exerts an upward force on plunger 196.
Valve needle 200 is thereby lifted so as to open port 202 and
permit injection of fuel therethrough.
Further demonstrating the versatility of the present invention is
the embodiment depicted in FIG. 8. An electroexpansive module 208
has at the lower end thereof a piston 210 that forms the upper wall
of a fluid chamber 212. Also forming a part of the chamber is a
plunger 214 to which is affixed a valve body 216. Plunger 214 has
an area less than piston 210. A compression spring 218 is provided
for biasing plunger 214 upwardly, it being understood that the
plunger 214 and valve body 216 will be driven downwardly in
response to electrical excitation of module 208. The valve body is
supported for slidable movement in a bore 220 which at the lower
end thereof has a plurality of outlet injection ports 222. It will
be noted that a port 222a is at a level higher than a port 222b
which in turn is higher than a port 222c. Opposite the ports, valve
body 216 is formed with a cylindric portion 224 that in the
uppermost position, as shown in the figures, closes all of
injection ports 222. Also in the uppermost position, a valve face
226 seats on a downwardly diverging seat 228 in bore 220 to arrest
fuel flow entering at inlet 230 from entering the lower region of
bore 220.
By employment of the structure of FIG. 8, rate of fluid delivery
can be controlled in proportion to the magnitude of voltage applied
to energize electroexpansive module 208.
When electroexpansive module 208 is deenergized, valve body 216
resides in the position shown in FIG. 8, a position in which
upwardly converging surface portion 226 seats against downwardly
diverging seat portion 228 so as to prevent entry of fuel below the
seat. Additionally, injection ports 222 are closed because
cylindric portion 224 of the valve body closes the inner terminus
of the ports. When the module is pulsed, the fluid in chamber 212
is compressed so as to move plunger 214 and valve body 216
downwardly. The amount of downward movement is proportional to the
voltage of the pulse applied to the module. The number of ports 222
uncovered in response to downward movement of the valve body is
proportional to the amount of downward travel of the valve body.
Because the rate of fuel injected is proportional to the number of
ports uncovered, the rate of fuel injected is proportional to the
amplitude of the voltage pulse applied to module 208. Accordingly,
the rate of fuel injected is very readily controlled since many
techniques are known in the art for controlling the magnitude of
the voltage applied to the module in proportion to engine speed or
like engine operating parameters. Several such techniques are
described in my copending application titled "Electromechanical
Control System," and filed concurrently herewith.
Illustrating the versatility of the present invention in an
extremely high speed accurate fuel injection actuator is the fuel
injection valve of FIG. 9. The valve includes an outlet opening 232
and a fuel inlet opening 234. Intermediate the openings is a
chamber 236 that defines a valve seat closable by either a central
valve body 238 or an outer valve body 240 which is concentric with
the central valve body and axially movable relative thereto. Valve
bodies 238 and 240 are driven independently of one another so that
the time duration of fluid flow from inlet opening 234 to outlet
opening 232 can be made extremely short without requiring high
valve body accelerations and excessive consumption of power
necessary for such acceleration. For controlling the valve bodies
independently an electroexpansive valve module is provided for each
valve body. A module 242 is associated with central valve body 238
and is connected in driving relation to a piston 244 below which is
a fluid chamber 246. The fluid chamber communicates with a
secondary piston 248 which is biased downwardly by compression
spring 250. Piston 248 is preferably integral with valve body 238
and has a fluid passage 252 therethrough for communicating fluid
from chamber 246 to the volume below the piston. Thus, when module
242 is electrically pulsed, the fluid in chamber 246 is compressed
and piston 248 as well as valve body 238 are lifted against the
force of spring 250.
Associated with valve body 240 is an electroexpansive module 254
which is connected in driving relation to a piston 256 that bounds
a fluid chamber 258. Chamber 258 communicates with the lower side
of a secondary piston 260 which is integral with outer valve body
240 and which is resiliently biased downwardly by a compression
spring 262. Thus, when module 254 is pulsed, thereby compressing
fluid in chamber 258, piston 260 is moved upwardly against the
force of spring 262 so as to lift outer valve body 240 from its
seat in chamber 236.
The operation of the form of my invention shown in FIG. 9 is as
follows: Voltage is applied to one of the electroexpansive modules,
e.g., module 242. The fluid in chamber 246 is compressed thereby
unseating central valve 238. Outer valve 240, in a down or seated
position, arrests fluid flow from inlet opening 234 to outlet
opening 232. In order to initiate a short injection of fluid, a
voltage pulse is applied to module 254, as a consequence of which
outer valve body 240 is lifted from its seat. A short interval
after such energization of module 254 module 242 is discharged,
thereby permitting central valve body 238 to seat and to arrest
fluid flow from outlet opening 232. In a specific valve designed
according to the invention as depicted in FIG. 9, a flow duration
of 100 microseconds (1.times.10.sup..sup.-4 seconds) is readily
achieved. It will be appreciated by those skilled in the art that
control circuitry for pulsing and discharging the modules in an
appropriate sequence is well within the competence of the present
state of the art. Moreover, examples of novel control circuitry can
be found in my concurrently filed copending application.
Thus, it will be seen that the present invention provides an
electromechanical actuator or transducer that is capable of being
driven electronically with great precision and speed. Because the
transducer is a solid state device it possesses the advantageous
characteristics inherent in such devices. Moreover, the operating
characteristics of the actuator can be readily predicted in view of
the simple relationship between the area of the piston driven by
the electroexpansive module and in the area of the follower or
secondary piston which communicates with the first mentioned
piston.
Further contributing to the excellent operating characteristics of
the actuator of the present invention is a method for making the
electroexpansive module which method permits automated production
of the modules. The method also affords a high degree of
predictability of characteristics, so that modules with desired
characteristics are readily reproducible. The steps of the method
can be more fully appreciated by reference to FIG. 10. A hopper 312
for ceramic material having desired electroexpansive,
piezoelectric, or ferroelectric properties is supported over an
endless conveyor 314. The particles of which the ceramic powder is
constituted are preferably in the diameter range of approximately 1
to 50 microns mean diameter. Oxides of lead, titanium, zirconium or
the like exemplify materials having the necessary electrical and
mechanical characteristics. A second hopper 316 is provided for
holding such additives as may be necessary to enhance the
electroexpansive character of the ceramic material. Such additives
are exemplified by the oxides of niobium, strontium, and the like.
Suitable mechanical blending and mixing equipment is identified
schematically at 318; the specific nature of such equipment forms
no part of the invention. Conveyor 314 is part of a hot rolling
mill, which according to the present invention, produces a
continuous sheet of ceramic material preferably in the thickness
range of about 5 to 50 mills. The hot rolling mill portion of the
apparatus includes a heat chamber 320 and opposed pinch rolls 322
and 324 between which the ceramic material is conveyed from
conveyor 314. Rolls 322 and 324 are designed so that the combined
effect of the pressure exerted by the rolls and the temperature
within chamber 320 cooperate to compact the ceramic material to a
degree that the density range of the ceramic material is about
80-99 percent of the theoretical density after the material exits
from the hot rolling segment of the apparatus. A second rolling
station formed by pinch rolls 326 and 328 is provided to further
compact the material so as to increase the density thereon. The
compacted ceramic material is fed in a continuous sheet by a
conveyor 330 to a punch station 332. At punch station 332 the
ceramic material is formed into discs or rings as desired for the
particular form of module desired. The excess sheet stock produced
from punch 332 is ground at a grinder indicated at 334 and returned
to hopper 312 for reuse by a conveyor line 335, in which is
interposed apparatus 335a for reprocessing the material.
The ceramic discs or rings, as the case may be, are conveyed from
punch 332 by a conveyor 336 to a cleaning bath 338. In bath 338 the
discs are cleaned and chemically treated so as to prepare the
surfaces thereof for bonding.
Simultaneous with the formation and preparation of the ceramic
discs or rings, conductive electrodes are prepared. A sheet or roll
of material such as nickel, platinum, tungsten or like compatible
material is provided as indicated schematically at 340. The
material preferably has a thickness of less than a mil. A punch 342
is provided to form the conductive material into discs or rings,
the specific configuration depending on the specific configuration
of the ceramic discs. Punch 342 is adapted so that the discs or
rings are continuously connected one to the other for electrical
continuity therebetween. The formed electrode rings or discs are
transported by a conveyor 344 to a cleaning bath 346 so as to
prepare the electrodes for bonding to the ceramic discs. From baths
338 and 346 are delivered respectively the disc and electrodes
along a conveyor indicated schematically at 348 to an assembly and
stacking station 350.
At assembly and stacking station 350 the ceramic discs are
assembled into stacks with the continuous disc electrodes
alternately disposed therebetween so that an electrode is disposed
between each adjacent ceramic disc and further so that alternate
sets of electrodes are electrically continuous. To each stack so
formed are applied ceramic end plates, one functioning as a plunger
or piston, for example the piston designated by reference numeral
18 in FIG. 1.
The formed assembly is then clamped as at 354 for mechanical
conveyance through succeeding steps in the process. The clamp
retains axial compression on the stack during subsequent hot
isostatic treatment thereof. The pressure from the clamp and the
extreme smoothness of the discs and electrodes can be combined with
a hard vacuum in a chamber at 352 to effect cold welding between
the parts.
The stacked and clamped assembly enters a continuous oven having an
oxidizing atmosphere therein. Preferably the oven has a temperature
gradient therein so that as the clamped stack progresses, it is
gradually brought up to the appropriate temperature. The
temperature desired is in the range of about
1,000.degree.-1,400.degree. C. The stacks are accumulated at the
downstream or outlet end of 356 for admission as a group or batch
into a pressurization chamber 358. The pressure within chamber 358
is rapidly increased to several thousand p.s.i., as a consequence
of which the entire stack is subjected to uniform radial loading as
well as axial loading additional to that provided by clamping
structure 354. However, such pressure does not cause ambient gas to
be diffused into the stack because a gas impervious glaze is formed
only on the outer surface of the stack as a result of the elevated
temperature in oven 356. From pressurization chamber 358 the batch
of stacks is transferred to a high temperature pressurized chamber
360 in which the batch is maintained at the same temperature and
pressure for a required time interval. After the transfer,
pressurization chamber 358 is decompressed and is ready to accept
another batch of stacks from oven 356.
The elevated temperature and pressure in chamber 360 effect bonding
together of the elements of the stacks. When the stacks within
chamber 360 have assumed the requisite bonding characteristics
between the individual elements and after the ceramic has assumed
the required domain structure, the batch is moved to a
depressurization chamber 362 which is gradually reduced to ambient
pressure. Thereafter, the batch is transferred to a cool-down
chamber 364 for controlled cooling to ambient temperature. At the
outlet end of cool-down chamber 364 clamp 354 is released so that a
formed stack, indicated at 356 in FIG. 10, is deposited onto a
conveyor 358 for further processing.
Conveyor 358 first delivers the stack to a lead attaching station
360 at which a common lead is connected to one group of electrodes
formed by alternate electrodes and another lead is attached to
another group of electrodes formed by the remaining electrodes.
Accordingly, the leads permit establishment of electric field
across each ceramic disc between the electrodes. An appropriately
polarized DC voltage is applied across the leads in an electric
polling station 362 which includes an insulative liquid bath, for
example peanut oil, that is maintained at a temperature of about
100.degree.-200.degree. C.
Electric polling unit 362 operates by first raising the temperature
of the stack by immersion in the hot insulating liquid and then by
applying a DC voltage across the previously attached leads. The
magnitude of the DC voltage is established in accordance with such
parameters as the specific composition of the ceramic material, the
temperature of the bath, and the thickness of the individual
ceramic discs that constitute the stack. A skilled artisan will
appreciate the specific voltage magnitude required, a typical
magnitude being approximately 100 volts per mil (0.001 inch)
thickness of the discs across which the voltage is established.
Duration of voltage application also depends on the above mentioned
parameters, 10 to 50 minutes being a typical time range. When
electric polarizing is completed in unit 362, the module is cleaned
and dried after which it is transferred to an encapsulating station
364. Exemplary of suitable encapsulating material is a plastic
insulative cover such as silicon rubber or urethane, the
encapsulation being performed so that the end pieces of the module
are exposed. In an automated production line the encapsulation
material can be most expeditiously applied by continuous extrusion
of insulative material concentrically with the stack.
The encapsulated unit is then subjected to testing procedures at a
test station 366 and is then discharged at the output of the
apparatus, a completed module being indicated at 368. Module 368
can then be incorporated into the piezoelectric actuators described
hereinabove.
A completed module 368 is depicted, partially schematically, in
FIGS. 11 and 12. The module includes an upper end plate 370 and a
lower end plate 372. The upper end plate serves to support the
electrical terminations to the electrodes, and the lower end plate
acts as a piston, for example, see piston 18 of FIG. 1. Alternate
electrodes are interconnected to one another to form one group by
straps 374 which as described hereinabove are integral with the
electrodes which they interconnect. The group of interconnected
electrodes is terminated at a ground connection 376. Alternate
electrodes are interconnected by straps 378 so as to form a second
group of electrodes, which second group of electrodes is terminated
at a high voltage terminal 380 located centrally of upper end plate
370. Ceramic discs or rings of electroexpansive material are
indicated at 382. An exemplary ground electrode is indicated at 384
and an exemplary high voltage electrode is indicated at 386. The
assembly is completed, as described above, by enclosure in a
insulative encapsulation layer 388. Accordingly, the module is
self-contained and is readily mountable into an electroexpansive
actuator or transducer housing.
An alternate electrode design employs a thin electrode deposited on
each ceramic by conventional techniques in such a manner that the
electrode covers the flat surface of the disc except for a narrow
margin or border that exists for approximately 330.degree., with
the remaining 30.degree. having the electrode extend to the edge.
The processing is identical to that described above except that in
lead attaching station 360, a thin strip electrode is placed on
each side of the stack in such a manner as to connect the tabs of
the individual electrodes to the strip electrode thereby forming
two integral electrode systems, one for ground and the other for
voltage application.
Employment of the foregoing method for producing electroexpansive
ceramic stacks results in increased performance measured in terms
of dielectric constant, coupling coefficient, loss factors, and
other piezoelectric coefficients.
Construction of electroexpansive modules by employing a plurality
of extremely thin discs or like bodies affords increased stack
performance measured in terms of dielectric constant, coupling
coefficients, loss factor, and other piezoelectric coefficients.
Using the methods of this invention on advanced ceramic
compositions produces even greater performance. As an example,
producing, by piezoelectric action, axial strains of over 0.5 per
centum in large stacks is presently feasible while the attainment
of one per centum unit strain appears achievable.
Modules or stacks produced by the method can be incorporated into
many forms of actuators. For example, in FIG. 13 there is shown an
electroexpansive stack 402 fixed at its upper end to a housing 404
and at its lower end to a primary piston 406. The piston is sealed
within body 404 by an elastomer seal 408. Such seal permits primary
piston 406 to move in response to electrical excitation of stack
402. The lower face of piston 406 defines one surface of a fluid
tight chamber 410. A secondary piston 412 has a surface 414
communicating with chamber 410; the area of surface 414 is small
with respect to the area of piston 406 so that the amount of
movement of secondary piston 412 is greater than the amount of
movement of piston 406. Secondary piston 412 has a lower face 416
that bounds a second fluid tight chamber 418. The piston 412 is
supported in housing 404 by an upper elastomer seal 420 and a lower
elastomer seal 422 so that both chambers 410 and 418 are fluid
tight. A rod 424 is supported for slidable movement in body 404 and
has a surface 426 communicating with chamber 418. The area of
surface 426 is much less than surface 416 of secondary piston 412
so that the rod moves a greater distance than does secondary piston
412. Rod 424 is supported in fluidtight relationship to chamber 418
by a Bellowfram or rolling bellows seal 428 or the like and is
supported for reciprocal movement by guide extension 430 that
extends from main body 404 and is integral therewith.
The operation of the embodiment of FIG. 13 is as follows: An
electric pulse is applied to stack 402 so as to cause the stack to
expand and drive piston 406 downwardly. Fluid in chamber 410 is
compressed thereby applying pressure to surface 414 of secondary
piston 412 so as to urge the secondary piston downwardly by an
amount proportional to the ratio of areas between piston 406 and
surface 414. Consequently, fluid in chamber 418 is compressed so
that a force is applied against surface 426 of rod 424. The rod is
thus driven downwardly. A load attached to the rod is driven
correspondingly. Because rod surface 426 is smaller than surface
416, substantial motion amplification is achieved by the device.
When the stack 402 is electrically discharged, piston 406 moves
upwardly, piston 412 moves upwardly, and rod 424 and load attached
thereto is moved upwardly.
An exemplary load device for attachment to the rod 424 of FIG. 13
is shown in FIGS. 14 and 15. The device functions to change
reciprocal movement of rod 424 to rotary movement. Attached to the
outer end of plunger rod 424 is a swivel connection 432 which joins
to the actuator rod for axial movement therewith a shaft 434 and
which permits shaft 434 to rotate relative to the actuator rod.
Shaft 434 extends into a motion converter housing 436. Housing 436
includes a helical ramp 438 that has an upper surface 440 and a
lower surface 442. Radiating from shaft 434 is one or more upper
arms 444. Each arm has at its outer extremity an antifriction
member, such as a ball bearing 446, for affording rolling contact
with upper ramp surface 440. Also radiating from shaft 434 is one
or more lower arms 448, each of which is provided with a ball
bearing 450 for bearing on lower ramp surface 442. Shaft 434 has a
fitting 452 that extends exterior of housing 436 to permit
attachment of a load to the device.
The structure of FIGS. 13-15 operates as follows: electrical
excitation of module 402 effects axial movement of rod 424 as
previously described. Such movement is transmitted through swivel
432 to shaft 434 which in turn forces upper arm 444 down ramp
surface 440. Swivel 432 permits shaft 434, and load fitting 452, to
rotate. The load attached to the outlet portion 452 is
correspondingly rotatively driven. When module 402 is discharged
and rod 424 moves in the opposite axial direction, rotative
movement in the opposite sense is effected because ball bearings
450 move up ramp surface 442 so as to apply torque to shaft 434
through arm 448.
FIG. 16 depicts a somewhat more sophisticated rotary actuator or
motor in which a main housing 454 supports axially opposed
right-hand electroexpansive modules 456a and 456b, and lower
axially opposed left-hand electroexpansive modules 458a and 458b.
Because each module has a substantially identical plunger
structure, only the plunger structure associated with the module
458b will be explained in detail, it being understood that the
plunger structures associated with the other modules are
substantially identical. A piston 460 is attached to one end of
module 458b and is supported for movement with respect to housing
454 by a peripheral elastomer seal 462 so that a fluid tight
chamber 464 is formed above the piston. A secondary plunger 466 is
supported in housing 454 and has a surface portion 468 in
communication with chamber 464. The area of surface portion 468 is
much smaller than the area of piston 460 so that on movement of
piston 460 resulting from expansion or contraction of module 458b,
plunger 466 will move a greater amount.
Mounted centrally of housing 454 is a shaft 470. The shaft is
supported for rotation on bearings 472. Mounted on the shaft is a
generally wedge shaped body 474 which has annular faces 476
thereon, body 474 being so constructed that annular faces 476 are
spaced axially from one another by a large distance at one point,
are spaced close to one another at a point 180.degree. from the
first mentioned point, and converge smoothly from the first
mentioned point to the last mentioned point. The surface 476 forms
one race of a roller bearing that has rollers 478. The other race
is formed by a disc 480 that, on the outer surface thereof, has a
depression 482 for engaging each plunger 466 associated with the
electroexpansive modules. Each of the modules 456a, 456b, 458a and
458b is connected through an electrical wire harness 484 to
external control circuitry not shown.
The operation of this embodiment of the invention can be understood
by assuming that shaft 470 resides in the position shown in the
drawing and by further assuming that left-hand modules 458a and
458b are pulsed. When the modules are so pulsed, they expand so
that each plunger 466 associated with the modules is moved inwardly
toward member 474. Forces are thereby applied to the portion of
surface 476 that are separated from one another by the greatest
amount, and because of the gradual taper inwardly from such point,
member 474 and shaft 470 will be rotatively driven as a consequence
of such force. Simultaneously with such action modules 468a and
468b are discharged so that the plungers 466 associated with the
latter modules are urged away from member 474. When the shaft has
been rotatably driven through approximately 180.degree., modules
458a and 458b are discharged and modules 456a and 456b are supplied
with electric pulses. Consequently, the rotative force on shaft 470
is continued and the shaft continues to rotate.
The device described above is simplified for convenience of
description; an actual device made in accordance with this
invention has more than two pairs of electroexpansive modules so
that torque can be delivered smoothly and continuously to shaft 470
by appropriate charging and discharging of the modules in sequence.
The speed of rotation of shaft 470 can be controlled by controlling
the frequency at which the modules are charged and discharged.
Thus, it will be seen that the present invention provides an
improved electromechanical actuator that has characteristics not
heretofore achievable. The excellent electromechanical
characteristics of the device are achieved in part by employing a
novel method for producing a module that constitutes the active
part of the actuator.
Although several embodiments of the invention have been shown and
described, it will be apparent that other adaptations and
modifications can be made without departing from the true spirit
and scope of the invention.
* * * * *