U.S. patent application number 09/765031 was filed with the patent office on 2001-08-16 for vibration gyro sensor and method for producing vibration gyro sensor.
This patent application is currently assigned to NGK Insulators, Ltd.. Invention is credited to Namerikawa, Masahiko, Shibata, Kazuyoshi, Takeuchi, Yukihisa.
Application Number | 20010013252 09/765031 |
Document ID | / |
Family ID | 17510593 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013252 |
Kind Code |
A1 |
Namerikawa, Masahiko ; et
al. |
August 16, 2001 |
Vibration gyro sensor and method for producing vibration gyro
sensor
Abstract
Disclosed is a vibration gyro sensor comprising an annular frame
having an approximately square planar contour with a central
opening having an approximately circular planar configuration, an
annular section arranged in the opening of the annular frame and
having an approximately circular planar contour for constructing a
vibrator, and a plurality of resilient sections which span the
inner circumference of the annular frame and the outer
circumference of the annular section, wherein the annular frame,
the annular section, and the plurality of resilient sections are
constructed by an integrated fired product made of ceramics. The
vibration gyro sensor further comprises
piezoelectric/electrostrictive elements (driving
piezoelectric/electrostrictive elements and detecting
piezoelectric/electrostrictive elements) formed on upper surfaces
of the respective resilient sections. Each of the resilient
sections has a thickness in its direction of height designed to be
smaller than a thickness of the annular section, which is thus
thin-walled so that the rigidity in the direction of vibration of
the piezoelectric/electrostrict- ive elements is lowered to give a
large amplitude of vibration caused on the annular section
(vibrator).
Inventors: |
Namerikawa, Masahiko;
(Inazawa-City, JP) ; Shibata, Kazuyoshi;
(Mizunami-City, JP) ; Takeuchi, Yukihisa;
(Nishikamo-Gun, JP) |
Correspondence
Address: |
BURR & BROWN
PO BOX 7068
SYRACUSE
NY
13261-7068
US
|
Assignee: |
NGK Insulators, Ltd.
|
Family ID: |
17510593 |
Appl. No.: |
09/765031 |
Filed: |
January 18, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09765031 |
Jan 18, 2001 |
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09471993 |
Dec 23, 1999 |
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6240781 |
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09471993 |
Dec 23, 1999 |
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08944899 |
Oct 6, 1997 |
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6089090 |
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Current U.S.
Class: |
73/504.12 ;
73/504.13 |
Current CPC
Class: |
G01C 19/5677
20130101 |
Class at
Publication: |
73/504.12 ;
73/504.13 |
International
Class: |
G01P 003/44 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 15, 1996 |
JP |
8-272,206 |
Claims
What is claimed is:
1. A vibration gyro sensor comprising: an annular section for
constructing a vibrator; a support member for resiliently
supporting said annular section; a plurality of resilient sections
provided between said support member and said annular section; and
piezoelectric/electrostrictive elements formed on said annular
section, wherein: all of said annular section, said support member,
and said plurality of resilient sections are constructed by an
integrated fired product of ceramics; and portions of said annular
section, on which said piezoelectric/electrostrictive elements are
formed, are constructed by plate-shaped sections which are
thin-walled in their direction of height.
2. The vibration gyro sensor according to claim 1, wherein: said
annular section is integrated with element attachment sections
which are provided at positions opposite to positions for forming
said plurality of resilient sections and which have their principal
surfaces parallel to a plane perpendicular to an axial direction of
said annular section, said principal surfaces being used as
attachment surfaces for said piezoelectric/electrostrictive
elements; and portions of said element attachment sections, on
which said piezoelectric/electrostrictive elements are formed, are
used as said plate-shaped sections which are thin-walled in their
direction of height.
3. The vibration gyro sensor according to claim 1, wherein: said
plurality of resilient sections are arranged at positions separated
from each other by equal spacing distances and mutually
point-symmetrical respectively; and said
piezoelectric/electrostrictive elements are formed at positions
corresponding to positions at which said resilient sections are
arranged on said annular section.
4. The vibration gyro sensor according to claim 3, wherein one of
said two adjacent piezoelectric/electrostrictive elements is a
driving piezoelectric/electrostrictive element for vibrating said
annular section, and the other is a detecting
piezoelectric/electrostrictive element for detecting a strain
caused by vibration generated in a direction of 45.degree. with
respect to a direction of vibration of said annular section, upon
rotation about an axis of said annular section.
5. The vibration gyro sensor according to claim 1, wherein said
support member is formed to have an approximately circular planar
configuration with an outer diameter which is smaller than an inner
diameter of said annular section.
6. The vibration gyro sensor according to claim 1, wherein said
support member has an opening having an approximately circular
planar configuration with an inner diameter which is larger than an
outer diameter of said annular section, and said annular section is
supported in said opening through said plurality of resilient
sections.
7. The vibration gyro sensor according to claim 1, wherein each of
said resilient-sections has its contour which is constructed by a
ring section having an approximately elliptic planar configuration
with its minor axis directed in a radial direction on the basis of
a center of said annular section.
8. The vibration gyro sensor according to claim 1, wherein each of
said resilient sections has its contour which is constructed by a
ring section having an approximately elliptic planar configuration
with its major axis directed in a radial direction on the basis of
a center of said annular section.
9. A vibration gyro sensor comprising: an annular section for
constructing a vibrator; a support member for resiliently
supporting said annular section; resilient sections provided
between said support member and said annular section; and
piezoelectric/electrostrictive elements formed on said annular
section, wherein: all of said annular section, said support member,
and said resilient sections are constructed by an integrated fired
product of ceramics; and portions of said resilient sections, on
which said piezoelectric/electrostrictive elements are formed, are
constructed by plate-shaped sections which are thin-walled in their
direction of height.
10. The vibration gyro sensor according to claim 9, wherein said
plurality of resilient sections are arranged at positions separated
from each other by equal spacing distances and mutually
point-symmetrical respectively.
11. The vibration gyro sensor according to claim 9, wherein one of
said two adjacent piezoelectric/electrostrictive elements is a
driving piezoelectric/electrostrictive element for vibrating said
resilient section, and the other is a detecting
piezoelectric/electrostrictive element for detecting a strain
caused by vibration generated in a direction of 45.degree. with
respect to a direction of vibration of said resilient section, upon
rotation about an axis of said annular section.
12. The vibration gyro sensor according to claim 9, wherein said
support member is formed to have an approximately circular planar
configuration with an outer diameter which is smaller than an inner
diameter of said annular section.
13. The vibration gyro sensor according to claim 9, wherein said
support member has an opening having an approximately circular
planar configuration with an inner diameter which is larger than an
outer diameter of said annular section, and said annular section is
supported in said opening through said plurality of resilient
sections.
14. The vibration gyro sensor according to claim 9, wherein each of
said resilient sections has its contour which is constructed by a
ring section having an approximately elliptic planar configuration
with its minor axis directed in a radial direction on the basis of
a center of said annular section.
15. The vibration gyro sensor according to claim 9, wherein each of
said resilient sections has its contour which is constructed by a
ring section having an approximately elliptic planar configuration
with its major axis directed in a radial direction on the basis of
a center of said annular section.
16. The vibration gyro sensor according to claim 11, wherein: when
each of said resilient sections is constructed by a ring section
having an approximately elliptic planar configuration with its
minor axis directed in a radial direction on the basis of a center
of said annular section, said driving
piezoelectric/electrostrictive element is formed on said
plate-shaped section which spans said ring section in a direction
perpendicular to said radial direction on the basis of said center
of said annular section; and said detecting
piezoelectric/electrostrictive element is formed on said
plate-shaped section which spans said ring section in said radial
direction on the basis of said center of said annular section.
17. A vibration gyro sensor comprising: an annular section for
constructing a vibrator; an outer support member disposed outside
said annular section, for resiliently supporting said annular
section; an inner support member disposed inside said annular
section, for resiliently supporting said annular section; outer
resilient sections provided between said outer support member and
said annular section; inner resilient sections provided between
said inner support member and said annular section; and
piezoelectric/electrostrictive elements formed on said outer
resilient sections and said inner resilient sections, wherein: all
of said annular section, said outer support member, said inner
support member, said outer resilient sections, and said inner
resilient sections are constructed by an integrated fired product
of ceramics; and portions of said outer resilient sections and said
inner resilient sections, on which said
piezoelectric/electrostrictive elements are formed, are constructed
by plate-shaped sections which are thin-walled in their direction
of height.
18. The vibration gyro sensor according to claim 17, wherein: said
inner support member is formed to have an approximately circular
planar configuration with an outer diameter which is smaller than
an inner diameter of said annular section; said outer support
member has an opening having an approximately circular planar
configuration with an inner diameter which is larger than an outer
diameter of said annular section; and said annular section is
supported in said opening through said plurality of resilient
sections.
19. The vibration gyro sensor according to claim 17, wherein any
resilient section of said inner resilient sections and said outer
resilient sections has its contour which is constructed by a ring
section having an approximately elliptic planar configuration with
its minor axis directed in a radial direction on the basis of a
center of said annular section.
20. The vibration gyro sensor according to claim 17, wherein any
resilient section of said inner resilient sections and said outer
resilient sections has its contour which is constructed by a ring
section having an approximately elliptic planar configuration with
its major axis directed in a radial direction on the basis of a
center of said annular section.
21. The vibration gyro sensor according to claim 17, wherein said
plurality of inner and outer resilient sections are arranged at
positions separated from each other by equal spacing distances and
mutually point-symmetrical respectively.
22. The vibration gyro sensor according to claim 17, wherein said
piezoelectric/electrostrictive element formed on one resilient
section of said inner resilient sections and said outer resilient
sections is a driving piezoelectric/electrostrictive element for
vibrating said resilient section, and said
piezoelectric/electrostrictive element formed on the other
resilient section is a detecting piezoelectric/electrostrict- ive
element for detecting a strain caused by vibration generated in a
direction of 45.degree. with respect to a direction of vibration of
said resilient section, upon rotation about an axis of said annular
section.
23. A method for producing a vibration gyro sensor, comprising the
steps of: shaping a spacer layer, a substrate layer, and a thin
plate layer composed of green sheets respectively; stacking and
integrating said spacer layer, said substrate layer, and said thin
plate layer after said shaping respectively, followed by firing to
produce a fired product having, in an integrated manner, an annular
section, a support member for resiliently supporting said annular
section, and a plurality of resilient sections provided between
said support member and said annular section; forming at least
piezoelectric/electrostrictive elements at predetermined regions on
said thin plate layer in accordance with a film formation method;
applying a trimming treatment to electrodes of said
piezoelectric/electrostrictive elements to adjust electric
characteristics; and applying a trimming treatment to at least said
annular section and said resilient sections to adjust mechanical
characteristics.
24. A method for producing a vibration gyro sensor, comprising the
steps of: shaping a substrate layer and a spacer layer composed of
green sheets respectively; stacking and integrating said substrate
layer and said spacer layer after said shaping together with an
unshaped thin plate layer, followed by firing; shaping said thin
plate layer to produce a fired product having, in an integrated
manner, an annular section, a support member for resiliently
supporting said annular section, and a plurality of resilient
sections provided between said support member and said annular
section; forming at least piezoelectric/electrostrictive elements
at predetermined regions on said thin plate layer in accordance
with a film formation method; applying a trimming treatment to
electrodes of said piezoelectric/electrostrictive elements to
adjust electric characteristics; and applying a trimming treatment
to at least said annular section and said resilient sections to
adjust mechanical characteristics.
25. A method for producing a vibration gyro sensor, comprising the
steps of: shaping a substrate layer and a spacer layer composed of
green sheets respectively; stacking and integrating said substrate
layer and said spacer layer after said shaping together with an
unshaped thin plate layer, followed by firing; forming at least
piezoelectric/electrostrictiv- e elements at predetermined regions
on said thin plate layer in accordance with a film formation
method; applying a trimming treatment to electrodes of said
piezoelectric/electrostrictive elements to adjust electric
characteristics; shaping said thin plate layer to produce a fired
product having, in an integrated manner, an annular section, a
support member for resiliently supporting said annular section, and
a plurality of resilient sections provided between said support
member and said annular section; and applying a trimming treatment
to at least said annular section and said resilient sections to
adjust mechanical characteristics.
26. A method for producing a vibration gyro sensor, comprising the
steps of: shaping a substrate layer composed of a green sheet to
form connecting sections between a portion to be subsequently
formed into an annular section and a portion to be subsequently
formed into a support member; shaping a spacer layer composed of a
green sheet; stacking and integrating said substrate layer and said
spacer layer after said shaping together with an unshaped thin
plate layer, followed by firing; forming at least
piezoelectric/electrostrictive elements at predetermined regions on
said thin plate layer in accordance with a film formation method;
shaping said thin plate layer to produce a fired product having, in
an integrated manner, said annular section, said support member for
resiliently supporting said annular section, and a plurality of
resilient sections provided between said support member and said
annular section; cutting said connecting sections remaining in said
substrate layer; applying a trimming treatment to electrodes of
said piezoelectric/electrostrictive elements to adjust electric
characteristics; and applying a trimming treatment to at least said
annular section and said resilient sections to adjust mechanical
characteristics.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention:
[0002] The present invention relates to a vibration gyro sensor and
a method for producing the same. In particular, the present
invention relates to a vibration gyro sensor (scope) for detecting
the angular velocity of rotation by utilizing the Coriolis force
generated when a ring member (vibrator) vibrated with a driving
piezoelectric/electrostric- tive element is rotated while making
vibration.
[0003] 2. Description of the Related Art:
[0004] The gyro sensor (scope), which is a sensor for detecting the
angular velocity of rotation, has been hitherto used, for example,
for inertial navigation systems of aircraft and shipping. Recently,
the gyro sensor is used for vehicle-carried navigation systems and
for attitude control systems of automatically guided robot
vehicles. Further, the gyro sensor is also used, for example, for
picture blurring-preventive systems of VTR cameras. In such
circumstances, a compact type gyro sensor is required, which is
appropriately used in various fields as described above.
Accordingly, the vibration gyro sensor attracts attention.
[0005] As well-known, the vibration gyro sensor (scope) of this
type has a basic structure comprising a driving piezoelectric
element and a detecting piezoelectric element which adhere to a
vibrator formed of a constant resilience metal represented by the
elinvar alloy. In a rectangular coordinate system of X, Y, Z axes,
when the vibrator is rotated about the z axis while giving bending
vibration in the x axis direction to the vibrator by using the
driving piezoelectric element, the Coriolis force acts in the y
axis direction to the vibrator. Accordingly, a strain or distortion
is generated in the detecting piezoelectric element in accordance
with bending vibration in the y axis direction caused in the
vibrator by the Coriolis force. The strain is detected as a voltage
(or as an electric charge). The angular velocity is determined on
the basis of the detected voltage.
[0006] However, in the case of the conventional vibration gyro
sensor as described above, the amount of displacement of the
vibrator, which is based on the vibration induced by the driving
piezoelectric element, is small. Therefore, the voltage
(electromotive force), which is detected by the detecting
piezoelectric element, is small. As a result, the conventional
vibration gyro sensor involves a problem that the sensitivity is
low.
[0007] In addition, the driving piezoelectric element and the
detecting piezoelectric element are glued and fixed to the vibrator
by using an adhesive. Therefore, the adhesive intervenes between
the vibrator and the piezoelectric elements. As a result, the
stress is absorbed by the adhesive. Due to this fact, together with
other factors, if any, a problem arises in that the detection
sensitivity is lowered.
[0008] When the vibrator comprises a member which is composed of a
sound chip or a tuning fork formed of an elinvar alloy, a problem
arises in that the characteristics of the vibrator tend to be
affected by an ambient magnetic field, because the elinvar alloy is
a ferromagnetic material. Further, due to the shape or the material
of the vibrator as described above, there is an implicit problem
that it is difficult to perform processing or machining when the
resonance frequency of the vibrator is adjusted.
SUMMARY OF THE INVENTION
[0009] The present invention has been made taking such problems
into consideration, an object of which is to provide a vibration
gyro sensor made of ceramics wherein the characteristics of the
vibrator are scarcely affected by an ambient magnetic field,
processing or machining can be easily performed, and the electric
characteristics and the mechanical characteristics can be
advantageously adjusted, and a method for producing the vibration
gyro sensor.
[0010] Another object of the present invention is to provide a
vibration gyro sensor which is excellent in sensitivity in addition
to the foregoing objective advantages, and a method for producing
the vibration gyro sensor.
[0011] The above and other objects, features and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings in which a preferred embodiment of the present invention
is shown by way of illustrative example.
DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows a plan view illustrating a structure of a
vibration gyro sensor according to a first embodiment.
[0013] FIG. 2A shows a cross-sectional view taken along a line A-A
in FIG. 1.
[0014] FIG. 2B shows a cross-sectional view taken along a line B-B
in FIG. 1.
[0015] FIG. 3 shows a perspective view, with partial cutaway,
illustrating a structure of a piezoelectric/electrostrictive
element based on the use of the lateral effect of the electric
field-induced strain.
[0016] FIG. 4 shows a structure of a modified embodiment of the
vibration gyro sensor according to the first embodiment.
[0017] FIG. 5 shows a plan view illustrating a structure of a
vibration gyro sensor according to a second embodiment.
[0018] FIG. 6A shows a cross-sectional view taken along a line A-A
in FIG. 5.
[0019] FIG. 6B shows a cross-sectional view taken along a line B-B
in FIG. 5.
[0020] FIG. 7 shows a structure of a modified embodiment of the
vibration gyro sensor according to the second embodiment.
[0021] FIG. 8A shows a cross-sectional view taken along a line A-A
in FIG. 7.
[0022] FIG. 8B shows a cross-sectional view taken along a line B-B
in FIG. 7.
[0023] FIG. 9 shows a plan view illustrating a structure of a
vibration gyro sensor according to a third embodiment.
[0024] FIG. 10A shows a cross-sectional view taken along a line A-A
in FIG. 9.
[0025] FIG. 10B shows a cross-sectional view taken along a line B-B
in FIG. 9.
[0026] FIG. 11 shows a structure of a modified embodiment of the
vibration gyro sensor according to the third embodiment.
[0027] FIG. 12A shows a cross-sectional view taken along a line A-A
in FIG. 11.
[0028] FIG. 12B shows a cross-sectional view taken along a line B-B
in FIG. 11.
[0029] FIG. 13 shows a plan view illustrating a structure of a
vibration gyro sensor according to a fourth embodiment.
[0030] FIG. 14A shows a cross-sectional view taken along a line A-A
in FIG. 13.
[0031] FIG. 14B shows a cross-sectional view taken along a line B-B
in FIG. 13.
[0032] FIG. 15 shows a structure of a modified embodiment of the
vibration gyro sensor according to the fourth embodiment.
[0033] FIG. 16A shows a cross-sectional view taken along a line A-A
in FIG. 15.
[0034] FIG. 16B shows a cross-sectional view taken along a line B-B
in FIG. 15.
[0035] FIG. 17 shows a plan view illustrating a structure of a
vibration gyro sensor according to a fifth embodiment.
[0036] FIG. 18A shows a cross-sectional view taken along a line A-A
in FIG. 17.
[0037] FIG. 18B shows a cross-sectional view taken along a line B-B
in FIG. 17.
[0038] FIG. 19 shows a structure of a modified embodiment of the
vibration gyro sensor according to the fifth embodiment.
[0039] FIG. 20A shows a cross-sectional view taken along a line A-A
in FIG. 19.
[0040] FIG. 20B shows a cross-sectional view taken along a line B-B
in FIG. 19.
[0041] FIG. 21 shows a plan view illustrating a structure of a
vibration gyro sensor according to a sixth embodiment.
[0042] FIG. 22A shows a cross-sectional view taken along a line A-A
in FIG. 21.
[0043] FIG. 22B shows a cross-sectional view taken along a line B-B
in FIG. 21.
[0044] FIG. 22C shows a cross-sectional view taken along a line C-C
in FIG. 21.
[0045] FIG. 23 shows a structure of a modified embodiment of the
vibration gyro sensor according to the sixth embodiment.
[0046] FIG. 24A shows a cross-sectional view taken along a line A-A
in FIG. 23.
[0047] FIG. 24B shows a cross-sectional view taken along a line B-B
in FIG. 23.
[0048] FIG. 24C shows a cross-sectional view taken along a line C-C
in FIG. 23.
[0049] FIG. 25 shows a block diagram of production steps
illustrating a first method of methods for producing the vibration
gyro sensors according to the first to sixth embodiments (including
the respective modified embodiments).
[0050] FIG. 26 shows a block diagram of production steps
illustrating a second method of methods for producing the vibration
gyro sensors according to the first to sixth embodiments (including
the respective modified embodiments).
[0051] FIG. 27 shows a block diagram of production steps
illustrating a third method of methods for producing the vibration
gyro sensors according to the first to sixth embodiments (including
the respective modified embodiments).
[0052] FIG. 28 illustratively shows exemplary production steps for
the vibration gyro sensor according to the second embodiment
[0053] FIG. 29 illustratively shows exemplary production steps for
the vibration gyro sensor according to the first embodiment.
[0054] FIG. 30 shows a perspective view, with partial cutaway,
illustrating a structure of a piezoelectric/electrostrictive
element based on the use of the longitudinal effect of the electric
field-induced strain.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0055] Several illustrative embodiments of the vibration gyro
sensor according to the present invention will be described below
with reference to FIGS. 1 to 30.
[0056] At first, as shown in FIG. 1, a vibration gyro sensor
according to a first embodiment comprises an annular frame 12
having an approximately square planar contour with a central
opening 10 having an approximately circular planar configuration,
an annular section 14 arranged in the opening 10 of the annular
frame 12 and having an approximately circular planar contour for
constructing a vibrator, and a plurality of resilient sections 16
(16a to 16h) which span the inner circumference of the annular
frame 12 and the outer circumference of the annular section 14,
wherein the annular frame 12, the annular section 14, and the
plurality of resilient sections 16 are constructed by an integrated
fired product made of ceramics. The vibration gyro sensor further
comprises piezoelectric/electrostrictive elements 18 (driving
piezoelectric/electrostrictive elements 18A and detecting
piezoelectric/electrostrictive elements 18B) formed on upper
surfaces of the respective resilient sections 16a to 16h. The
resilient sections 16a to 16h will be simply referred to as the
resilient sections 16 when they are collectively described.
[0057] Each of the resilient sections 16 is formed to have a
rectangular planar configuration, having a thickness in its
direction of height designed to be smaller than a thickness of the
annular section 14 which constructs the vibrator. Namely, each of
the resilient sections 16 is thin-walled so that the rigidity in
the direction of vibration of the piezoelectric/electrostrictive
element 18 is lowered to give a large amplitude of vibration caused
on the annular section 14 (vibrator).
[0058] In the illustrative embodiment shown in FIG. 1, the entire
resilient sections 16 are thin-walled. However, only portions for
forming the piezoelectric/electrostrictive elements 18 thereon may
be thin-walled, and the other portions may be allowed to have the
same thickness as that of the annular section 14. Therefore, in the
following description, when the entire resilient section 16 is
indicated, it is referred to as "resilient section", while when the
portion of the resilient section 16, on which the
piezoelectric/electrostrictive element 18 is formed, is indicated,
it is referred to as "thin-walled region".
[0059] The plurality of resilient sections 16 (eight resilient
sections 16a to 16h in the illustrative embodiment shown in FIG. 1)
are arranged at positions at which they are separated from each
other by equal spacing distances (distance to give a central angle
of 45.degree.) and they are mutually point-symmetrical.
[0060] The piezoelectric/electrostrictive elements 18, which are
formed on the resilient sections 16, include the driving
piezoelectric/electrostric- tive elements 18A for vibrating the
annular section 14 to serve as the vibrator, and the detecting
piezoelectric/electrostrictive elements 18B for detecting the
strain caused by vibration generated in a direction of 45.degree.
with respect to the direction of vibration of the annular section
14 when the annular section 14 is rotated about its axis as a
center. In the vibration gyro sensor according to the first
embodiment, the mutually adjacent resilient sections 16 are divided
into two groups. One group of the resilient sections 16 are used,
for example, to form the driving piezoelectric/electrostrictive
elements 18A thereon, and the other group of the resilient sections
16 are used to form the detecting piezoelectric/electrostrictive
elements 18B. In the illustrative embodiment shown in FIG. 1, the
driving piezoelectric/electrostrictive elements 18A are formed on
the four resilient sections 16a, 16c, 16e, 16g arranged in
directions along the X and Y axes respectively, and the detecting
piezoelectric/electrostrictive elements 18B are formed on the other
four resilient sections 16b, 16d, 16f, 16h respectively.
[0061] Inwardly protruding projections 20 are provided in an
integrated manner on the inner circumference of the annular frame
12 between the mutually adjacent resilient sections 16. The
projections 20 are consequently formed when connecting sections are
cut and removed at outer circumferential portions of the annular
section 14, the connecting sections having been provided in order
to position the annular section 14 at a prescribed position in the
opening 10 of the annular frame 12 at the stage of production of
the vibration gyro sensor as described later on. Therefore, the
projections 20 may be omitted or removed at the stage in which the
vibration gyro sensor has been assembled.
[0062] As shown in FIG. 2, the vibration gyro sensor, which is
constructed by the integrated fired product of ceramics as
described above, may be grasped as an integrated stacked product
comprising a spacer layer 22 as a lowermost layer, a substrate
layer 24 as an intermediate layer, and a thin plate layer 26 as an
uppermost layer. Namely, the thin-walled resilient section 16 is
given by the thin plate layer 26, the annular section 14 and the
projections 20 are given by integrating and stacking the thin plate
layer 26 and the substrate layer 24, and the annular frame 12 is
given by integrating and stacking the thin plate layer 26, the
substrate layer 24, and the spacer layer 22.
[0063] The piezoelectric/electrostrictive element 18 is directly
formed on the resilient section 16 (thin plate layer 26) in a state
in which a thin film lower electrode 18a, a
piezoelectric/electrostrictive film 18b, and an upper electrode 18c
are stacked and integrated into one unit as shown in FIG. 3.
[0064] When an electric power is applied to the driving
piezoelectric/electrostrictive elements 18A of the vibration gyro
sensor according to the first embodiment constructed as described
above to operate the driving piezoelectric/electrostrictive
elements 18A, the operation causes the annular section 14 to make
deformation vibration in an alternating manner to form, for
example, an ellipse having its major axis parallel to the X axis
and an ellipse having its major axis parallel to the Y axis.
[0065] When an angular velocity is applied around the axis of the
annular section 14 in a state in which the annular section 14 is
vibrated as described above, a force directed in a certain
direction (Coriolis force) is generated in the annular section 14
in an alternating manner in accordance with the vibration. As a
result, the force acts in the certain direction on the regions 16b,
16d, 16f, 16h (detecting regions) formed with the detecting
piezoelectric/electrostrictive elements 18B, of the resilient
sections 16a to 16h. The force causes the detecting regions 16b,
16d, 16f, 16h to make vibration. The vibration is detected as an
electromotive force (voltage) by the detecting
piezoelectric/electrostric- tive elements 18B disposed on the
detecting regions 16b, 16d; 16f, 16h.
[0066] As described above, the vibration gyro sensor according to
the first embodiment includes the annular frame 12, the annular
section 14 (vibrator), and the resilient sections 16 all of which
are constructed by using the integrated fired product made of
ceramics. Therefore, there is no magnetic material such as the
conventional elinvar alloy in the materials for constructing the
vibration gyro sensor. As a result, the characteristics of the
sensor are not affected by any ambient magnetic field.
[0067] The portions, on which the piezoelectric/electrostrictive
elements 18A, 18B are formed, are constructed by the thin-walled
regions 16 which are thin-walled in their direction of height to
give the structure having low rigidity. Accordingly, large strain
is obtained at the detecting regions 16b, 16d, 16f, 16h, and the
detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly
improved.
[0068] The vibration gyro sensor has the structure to measure the
angular velocity about the axis of the annular section 14 which
constructs the vibrator. Therefore, the annular section 14
(vibrator), the annular frame 12, and the resilient sections 16 can
be made thin in their direction of height. Thus it is possible to
facilitate realization of a compact size and a light weight of the
sensor.
[0069] Next, a modified embodiment of the vibration gyro sensor
according to the first embodiment will be explained with reference
to FIG. 4. Components or parts corresponding to those shown in FIG.
1 are designated by the same reference numerals, duplicate
explanation of which will be omitted.
[0070] As shown in FIG. 4, a vibration gyro sensor according to
this modified embodiment has approximately the same structure as
that of the vibration gyro sensor according to the first
embodiment. However, the former is different from the latter in
that the annular frame 12 has an approximately circular planar
configuration, and in that the resilient sections 16 has the
following configuration.
[0071] Namely, each of the resilient sections 16a to 16h is formed
to comprise, in an integrated manner, an element-forming region 30
for forming the piezoelectric/electrostrictive element 18 thereon,
an outer connecting region 32 for connecting the element-forming
region 30 and the annular frame 12, and an inner connecting region
34 for connecting the element-forming region 30 and the annular
section 14.
[0072] The outer connecting region 32 has the same width as that of
the inner connecting region, 34. The width is set to be smaller
than a width of the element-forming region 30 to provide a
structure having low rigidity. A portion of the element-forming
region 30, on which the piezoelectric/electrostrictive element 18
is formed, has a thickness in its direction of height designed to
be smaller than those of other portions to give a thin-walled
region 36.
[0073] The vibration gyro sensor according to the modified
embodiment has the same advantage as that of the vibration gyro
sensor according to the first embodiment. Namely, the
characteristics of the sensor are not affected by an ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive element 18B is greatly improved, and
it is possible to facilitate realization of a compact size and a
light weight of the sensor.
[0074] Next, a vibration gyro sensor according to a second
embodiment will be explained with reference to FIGS. 5 and 6.
Components or parts corresponding to those shown in FIGS. 1 and 2
are designated by the same reference numerals, duplicate
explanation of which will be omitted.
[0075] As shown in FIG. 5, the vibration gyro sensor according to
the second embodiment has approximately the same structure as that
of the vibration gyro sensor according to the first embodiment.
However, the former is different from the latter in the following
points.
[0076] Namely, each of the resilient sections 16a to 16h is
composed of a ring section having an approximately elliptic planar
configuration with its minor axis directed in a radial direction on
the basis of the center of the annular section 14. Each of the
resilient sections 16a to 16h has a thickness in a direction of
height, the thickness being designed to be approximately the same
as a thickness of the annular section 14.
Piezoelectric/electrostrictive elements 18 are formed at
predetermined positions on the annular section 14.
[0077] The respective resilient sections 16a to 16h are arranged at
positions at which they are separated from each other by equal
spacing distances (distance to give a central angle of 45.degree.)
and they are mutually point-symmetrical, in the same manner as the
vibration gyro sensor according to the first embodiment. In the
illustrative embodiment shown in FIG. 5, the eight resilient
sections 16a to 16h are exemplarily arranged and separated from
each other by equal spacing distances.
[0078] Predetermined portions of the annular section 14, which
contact with the inner circumference thereof, are used as regions
for forming the piezoeleletric/electrostrictive elements 18
thereon. The regions are provided as thin-walled regions 36 (36a to
36h) each having a thickness in a direction of height designed to
be smaller than the thickness of the annular section 14. Namely,
the portions of the annular section 14, on which the
piezoelectric/electrostrictive elements 18 are formed, are
thin-walled so that the rigidity in the direction of vibration of
the piezoelectric/electrostrictive elements 18 is lowered. The
thin-walled regions 36 (36a to 36h) are provided as eight
individuals corresponding to the resilient sections 16a to 16h, and
they are arranged at positions at which they are separated from
each other by equal spacing distances (distance to give a central
angle of 45.degree.) and they are mutually point-symmetrical. When
the thin-walled regions 36a to 36h are collectively referred to,
they are simply described as the thin-walled regions 36.
[0079] The piezoelectric/electrostrictive elements 18, which are
formed on the respective thin-walled regions 36, include driving
piezoelectric/electrostrictive elements 18A for vibrating the
annular section 14, and detecting piezoelectric/electrostrictive
elements 18B for detecting the strain caused by vibration generated
in a direction of 45.degree.0 with respect to the direction of
vibration of the annular section 14 when the annular section 14 is
rotated about its axis as a center, in the same manner as the
vibration gyro sensor according to the first embodiment. As for the
mutually adjacent thin-walled regions 36, the driving
piezoelectric/electrostrictive elements 18A are formed, for
example, on one group of the thin-walled sections 36, and the
detecting piezoelectric/electrostrictive elements 18B are formed on
the other group of the thin-walled regions 36.
[0080] In the illustrative embodiment shown in FIG. 5, the driving
piezoelectric/electrostrictive elements 18A are formed on the four
thin-walled sections 36a, 36c, 36e, 36g arranged in directions
along the X and Y axes respectively, and the detecting
piezoelectric/electrostricti- ve elements 18B are formed on the
other four thin-walled regions 36b, 36d, 36f, 36h.
[0081] As shown in FIG. 6, the vibration gyro sensor according to
the second embodiment may be also grasped as an integrated stacked
product comprising a spacer layer 22 as a lowermost layer, a
substrate layer 24 as an intermediate layer, and a thin plate layer
26 as; an uppermost layer, in the same manner as the vibration gyro
sensor according to the first embodiment. The thin-walled regions
36a to 36h of the annular section 14 are given by the thin plate
layer 26, the annular section 14 (except for the thin-walled
regions 36a to 36h) and the resilient sections 16a to 16h are given
by integrating and stacking the thin plate layer 26 and the
substrate layer 24, and the annular frame 12 is given by
integrating and stacking the thin plate layer 26, the substrate
layer 24, and the spacer layer 22.
[0082] Each of the piezoelectric/electrostrictive elements 18 is
directly formed on the thin-walled region 36 (thin plate layer 26)
of the annular section 14 in a state in which a thin film lower
electrode 18a, a piezoelectric/electrostrictive film 18b, and an
upper electrode 18c are stacked and integrated, in the same manner
as the vibration gyro sensor according to the first embodiment.
[0083] When an electric power is applied to the driving
piezoelectric/electrostrictive elements 18A on the thin-walled
regions 36a, 36c, 36e, 36g of the vibration gyro sensor according
to the second embodiment constructed as described above to operate
the driving piezoelectric/electrostrictive elements 18A, the
operation causes the annular section 14 to make deformation
vibration in an alternating manner to form, for example, an ellipse
having its major axis parallel to the X axis and an ellipse having
its major axis parallel to the Y axis.
[0084] When an angular velocity is applied around the axis of the
annular section 14 in a state in which the annular section 14 is
vibrated as described above, a force directed in a certain
direction (Coriolis force) is generated in the annular section 14
in an alternating manner in accordance with the vibration. As a
result, the force acts in the certain direction on the regions 36b,
36d, 36f, 36h (detecting regions) formed with the detecting
piezoelectric/electrostrictive elements 18B, of the thin-walled
regions (36a to 36h) of the annular section 14. The force causes
the detecting regions 36b, 36d, 36f, 36h to make vibration. The
vibration is detected as an electromotive force (voltage) by the
detecting piezoelectric/electrostrictive elements 18B disposed on
the detecting regions 36b, 36d, 36f, 36h.
[0085] As described above, the vibration gyro sensor according to
the second embodiment includes the annular frame 12, the annular
section 14 (vibrator), and the resilient sections 16a to 16h all of
which are constructed by using the integrated fired product made of
ceramics. Therefore, there is no magnetic material such as the
conventional elinvar alloy in the materials for constructing the
vibration gyro sensor. As a result, the characteristics of the
sensor are not affected by any ambient magnetic field.
[0086] The portions of the annular section 14, on which the
piezoelectric/electrostrictive elements 18 are formed, are
constructed by the thin-walled regions 36 which are thin-walled in
their direction of height to give the structure having low
rigidity. Accordingly, large strain is obtained at the detecting
regions 36b, 36d, 36f, 36h, and the detection sensitivity on the
detecting piezoelectric/electrostrictive elements 18B is greatly
improved.
[0087] The vibration gyro sensor has the structure to measure the
angular velocity about the axis of the annular section 14 which
constructs the vibrator. Therefore, the annular section 14
(vibrator), the annular frame 12, and the resilient sections 16a to
16h can be made thin in their direction of height. Thus it is
possible to facilitate realization of a compact size and EL light
weight of the sensor.
[0088] Especially, the vibration gyro sensor according to the
second embodiment includes the resilient sections 16a to 16h each
constructed as the ring section having the approximately elliptic
planar contour. Accordingly, the minute vibration, which is
generated on the thin-walled regions 36a, 36c, 36e, 36g of the
annular section 14, can be transmitted to the entire annular
section 14 with high following performance. Thus it is possible to
greatly improve the amplitude of vibration of the annular section
14 caused by operating the driving piezoelectric/electrostrictive
elements 18A.
[0089] Next, a modified embodiment of the vibration gyro sensor
according to the second embodiment will be explained with reference
to FIGS. 7 and 8. Components or parts corresponding to those shown
in FIGS. 5 and 6 are designated by the same reference numerals,
duplicate explanation of which will be omitted.
[0090] As shown in FIG. 7, a vibration gyro sensor according to
this modified embodiment has approximately the same structure as
that of the vibration gyro sensor according to the second
embodiment. However, the former is different from the latter in
that in place of the annular frame 12, a support section 42 is
constructed by an integrated fired product of ceramics together
with the resilient sections 16a to 16h and the annular section 14,
the support section 42 having an outer diameter smaller than an
inner diameter of the annular section 14, and having a central hole
40, and in that the eight resilient sections 16a to 16h are
equivalently arranged between the inner circumference of the
annular section 14 and the outer circumference of the support
section 42.
[0091] Predetermined portions of the annular section 14, which
contact with the outer circumference, are used as regions for
forming piezoelectric/electrostrictive elements 18 thereon. Each of
the regions has a thickness in its direction of height which is
designed to be smaller than a thickness of the annular section 14
to provide the thin-walled regions 36 (36a to 36h), in the same
manner as the second embodiment described above.
[0092] As shown in FIG. 8, the vibration gyro sensor according to
the modified embodiment may be also grasped as an integrated
stacked product comprising a spacer layer 22 as a lowermost layer,
a substrate layer 24 as an intermediate layer, and a thin plate
layer 26 as an uppermost layer, in the same manner as the vibration
gyro sensor according to the second embodiment. The thin-walled
regions 36a to 36h of the annular section 14 are given by the thin
plate layer 26, the annular section 14 (except for the thin-walled
regions 36a to 36h) and the resilient sections 16a to 16h are given
by integrating and stacking the thin plate layer 26 and the
substrate layer 24, and the support section 42 is given by
integrating and stacking the thin plate layer 26, the substrate
layer 24, and the spacer layer 22.
[0093] The vibration gyro sensor according to the modified
embodiment has the same advantages as those provided by the
vibration gyro sensor according to the second embodiment. Namely,
the characteristics of the sensor are not affected by any ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly improved,
and it is possible to facilitate realization of a compact size and
a light weight of the sensor.
[0094] Especially, each of the resilient sections 16a to 16h is
constructed as the ring section having the approximately elliptic
planar contour. Accordingly, the minute vibration, which is
generated on the thin-walled regions 36a, 36c, 36e, 36g of the
annular section 14, can be transmitted to the entire annular
section 14 with high following performance. Thus it is possible to
greatly improve the amplitude of vibration of the annular section
14 caused by operating the driving piezoelectric/electrostrictive
elements 18A.
[0095] Next, a vibration gyro sensor according to a third
embodiment will be explained with reference to FIGS. 9 and 10.
Components or parts corresponding to those shown in FIGS. 5 and 6
are designated by the same reference numerals, duplicate
explanation of which will be omitted.
[0096] As shown in FIG. 9, the vibration gyro sensor according to
the third embodiment has approximately the same structure as that
of the vibration gyro sensor according to the second embodiment.
However, the former is different from the latter in the following
points.
[0097] Namely, eight projections 44a to 44h, which protrude toward
the center of the annular section 14, are formed on the inner
circumference of the annular section 14 in an integrated manner.
Each of the resilient sections 16a to 16h is composed of a ring
section having an approximately elliptic planar configuration with
its major axis directed in a radial direction on the basis of the
center of the annular section 14. Piezoelectric/electrostrictive
elements 18 are formed on the respective projections 44a to
44h.
[0098] Each of the projections 44a to 44h has an approximately
rectangular planar configuration, with a thickness in its direction
of height which is approximately the same as the thickness of the
annular section 14. However, the thickness in the direction of
height at the portion for forming the
piezoelectric/electrostrictive element 18 is designed to be smaller
than the thickness of the annular section 14. Namely, the portion
of each of the projections 44a to 44h, on which the
piezoelectric/electrostrictive element 18 is formed, is thin-walled
(thin-walled regions 36a to 36h) so that the rigidity in the
direction of vibration of the piezoelectric/electrostrictive
element 18 is lowered, and the amplitude of vibration is large at
the annular section 14 (vibrator).
[0099] The projections 44a to 44h are provided as eight individuals
corresponding to the resilient sections 16a to 16h, and they are
disposed at positions at which they are separated from each other
by equal spacing distances (distance to give a central angle of
45.degree.) and they are mutually point-symmetrical.
[0100] In the illustrative embodiment shown in FIG. 9, the driving
piezoelectric/electrostrictive elements 18A are formed on the
respective thin-walled regions 36a, 36c, 36e, 36g of the four
projections 44a, 44c, 44e, 44g arranged in directions along the X
and Y axes respectively, and the detecting
piezoelectric/electrostrictive elements 18B are formed on the
respective thin-walled regions 36b, 36d, 36f, 36h of the other four
projections 44b, 44d, 44f, 44h.
[0101] As shown in FIG. 10, the vibration gyro sensor according to
the third embodiment may be also grasped as an integrated stacked
product comprising a spacer layer 22 as a lowermost layer, a
substrate layer 24 as an intermediate layer, and a thin plate layer
26 as an uppermost layer, in the same manner as the vibration gyro
sensor according to the second embodiment. The thin-walled regions
36a to 36h of the projections 44a to 44h are given by the thin
plate layer 26, the annular section 14, the projections 44a to 44h
(except for the thin-walled regions 36a to 36h), and the resilient
sections 16a to 16h are given by integrating and stacking the thin
plate layer 26 and the substrate layer 24, and the annular frame 12
is given by integrating and stacking the thin plate layer 26, the
substrate layer 24, and the spacer layer 22.
[0102] Each of the piezoelectric/electrostrictive elements 18 is
directly formed on the thin-walled region 36 (thin plate layer 26)
of the projection 44 in a state in which a thin film lower
electrode 18a, a piezoelectric/electrostrictive film 18b, and an
upper electrode 18c are stacked and integrated, in the same manner
as the vibration gyro sensor according to the first embodiment.
[0103] The vibration gyro sensor according to the third embodiment
has the same advantages as those provided by the vibration gyro
sensor according to the second embodiment. Namely, the
characteristics of the sensor are not affected by any ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly improved,
and it is possible to facilitate realization of a compact size and
a light weight of the sensor.
[0104] Especially, each of the resilient sections 16a to 16h is
constructed as the ring section having the approximately elliptic
planar contour. Accordingly, the minute vibration, which is
generated on the thin-walled regions 36a, 36c, 36e, 36g of the
annular section 14, can be transmitted to the entire annular
section 14 with high following performance. Thus it is possible to
greatly improve the amplitude of vibration of the annular section
14 caused by operating the driving piezoelectric/electrostrictive
elements 18A.
[0105] Next, a modified embodiment of the vibration gyro sensor
according to the third embodiment will be explained with reference
to FIGS. 11 and 12. Components or parts corresponding to those
shown in FIGS. 9 and 10 are designated by the same reference
numerals, duplicate explanation of which will be omitted.
[0106] As shown in FIG. 11, a vibration gyro sensor according to
this modified embodiment has approximately the same structure as
that of the vibration gyro sensor according to the third
embodiment. However, the former is different from the latter in
that in place of the annular frame 12, a support section 42 is
constructed by an integrated fired product of ceramics together
with the resilient sections 16a to 16h and the annular section 14,
the support section 42 having an outer diameter smaller than an
inner diameter of the annular section 14, and having a central hole
40, in that the eight resilient sections 16a to 16h are
equivalently arranged between the inner circumference of the
annular section 14 and the outer circumference of the support
section 42, and in that eight projections 44a to 44h are formed so
that they protrude outwardly from the outer circumference of the
annular section 14.
[0107] As shown in FIG. 12, the vibration gyro sensor according to
the modified embodiment may be also grasped as an integrated
stacked product comprising a spacer layer 22 as a lowermost layer,
a substrate layer 24 as an intermediate layer, and a thin plate
layer 26 as an uppermost layer, in the same manner as the vibration
gyro sensor according to the third embodiment. The respective
thin-walled regions 36a to 36h of the projections 44a to 44h are
given by the thin plate layer 26, the annular section 14, the
projections 44a to 44h (except for the thin-walled regions 36a to
36h), and the resilient sections 16a to 16h are given by
integrating and stacking the thin plate layer 26 and the substrate
layer 24, and the support section 42 is given by integrating and
stacking the thin plate layer 26, the substrate layer 24, and the
spacer layer 22.
[0108] The vibration gyro sensor according to the modified
embodiment has the same advantages as those provided by the
vibration gyro sensor according to the third embodiment. Namely,
the characteristics of the sensor are not affected by any ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly improved,
and it is possible to facilitate realization of a compact size and
a light weight of the sensor.
[0109] Especially, the minute vibration, which is generated on the
thin-walled regions 36a, 36c, 36e, 36g of the annular section 14,
can be transmitted to the entire annular section 14 with high
following performance. Thus it is possible to greatly improve the
amplitude of vibration of the annular section 14 caused by
operating the driving piezoelectric/electrostrictive elements
18A.
[0110] Next, a vibration gyro sensor according to a fourth
embodiment will be explained with reference to FIGS. 13 and 14.
Components or parts corresponding to those shown in FIGS. 5 and 6
are designated by the same reference numerals, duplicate
explanation of which will be omitted.
[0111] As shown in FIG. 13, the vibration gyro sensor according to
the fourth embodiment has approximately the same structure as that
of the vibration gyro sensor according to the second embodiment.
However, the former is different from the latter in that eight
projections 46a to 46h, which protrude toward the center of the
annular section 14, are formed on the inner circumference of the
annular section 14 in an integrated manner, and in that
piezoelectric/electrostrictive elements 18 are formed on the
respective projections 46a to 46h.
[0112] Each of the projections 46a to 46h has an approximately
trapezoidal planar configuration, with a thickness in its direction
of height which is approximately the same as the thickness of the
annular section 14. However, the thickness in the direction of
height at the portion for forming the
piezoelectric/electrostrictive element 18 is designed to be smaller
than the thickness of the annular section 14. Namely, the portion
of each of the projections 46a to 46h, on which the
piezoelectric/electrostrictive element 18 is formed, is thin-walled
(thin-walled regions 36a to 36h) so that the rigidity in the
direction of vibration of the piezoelectric/electrostrictive
element 18 is lowered, and the amplitude of vibration is large at
the annular section 14 (vibrator).
[0113] The projections 46a to 46h are provided as eight individuals
corresponding to the resilient sections 16a to 16h, and they are
disposed at positions at which they are separated from each other
by equal spacing distances (distance to give a central angle of
45.degree.) and they are mutually point-symmetrical. In the
illustrative embodiment shown in FIG. 13, the driving
piezoelectric/electrostrictive elements 18A are formed on the
respective thin-walled regions 36a, 36c, 36e, 36g of the four
projections 46a, 46c, 46e, 46g arranged in directions along the X
and Y axes respectively, and the detecting
piezoelectric/electrostrictive elements 18B are formed on the
respective thin-walled regions 36b, 36d, 36f, 36h of the other four
projections 46b, 46d, 46f, 46h.
[0114] As shown in FIG. 14, the vibration gyro sensor may be
grasped as an integrated stacked product comprising a spacer layer
22 as a lowermost layer, a substrate layer 24 as an intermediate
layer, and a thin plate layer 26 as an uppermost layer. The
thin-walled regions 36a to 36h of the projections 46a to 46h are
given by the thin plate layer 26, the annular section 14, the
projections 46a to 46h (except for the thin-walled regions 36a to
36h), and the resilient sections 16a to 16h are given by
integrating and stacking the thin plate layer 26 and the substrate
layer 24, and the annular frame 12 is given by integrating and
stacking the thin plate layer 26, the substrate layer 24, and the
spacer layer 22.
[0115] Each of the piezoelectric/electrostrictive elements 18 is
directly formed on the thin-walled region 36 (thin plate layer 26)
of the projection 46 in a state in which a thin film lower
electrode 18a, a piezoelectric/electrostrictive film 18b, and an
upper electrode 18c are stacked and integrated, in the same manner
as the vibration gyro sensor according to the first embodiment.
[0116] The vibration gyro sensor according to the fourth embodiment
has the same advantages as those provided by the vibration gyro
sensor according to the second embodiment. Namely, the
characteristics of the sensor are not affected by any ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly improved,
and it is possible to facilitate realization of a compact size and
a light weight of the sensor.
[0117] Especially, each of the resilient sections 16a to 16h is
constructed as the ring section having the approximately elliptic
planar contour. Accordingly, the minute vibration, which is
generated on the thin-walled regions 36a, 36c, 36e, 36g of the
annular section 14, can be transmitted to the entire annular
section 14 with high following performance. Thus it is possible to
greatly improve the amplitude of vibration of the annular section
14 caused by operating the driving piezoelectric/electrostrictive
elements 18A.
[0118] Next, a modified embodiment of the vibration gyro sensor
according to the fourth embodiment will be explained with reference
to FIGS. 15 and 16. Components or parts corresponding to those
shown in FIGS. 13 and 14 are designated by the same reference
numerals, duplicate explanation of which will be omitted.
[0119] As shown in FIG. 15, a vibration gyro sensor according to
this modified embodiment has approximately the same structure as
that of the vibration gyro sensor according to the fourth
embodiment. However, the former is different from the latter in
that in place of the annular frame 12, a support section 42 is
constructed by an integrated fired product of ceramics together
with the resilient sections 16a to 16h and the annular section 14,
the support section 42 having an outer diameter smaller than an
inner diameter of the annular section 14, and having a central hole
40, in that the eight resilient sections 16a to 16h are
equivalently arranged between the inner circumference of the
annular section 14 and the outer circumference of the support
section 42, and in that eight projections 46a to 46h are formed so
that they protrude outwardly from the outer circumference of the
annular section 14.
[0120] As shown in FIG. 16, the vibration gyro sensor according to
the modified embodiment may be also grasped as an integrated
stacked product comprising a spacer layer 22 as a lowermost layer,
a substrate layer 24 as an intermediate layer, and a thin plate
layer 26 as an uppermost layer, in the same manner as the vibration
gyro sensor according to the fourth embodiment. The thin-walled
regions 36a to 36h of the projections 46a to 46h are given by the
thin plate layer 26, the annular section 14, the projections 46a to
46h (except for the thin-walled regions 36a to 36h), and the
resilient sections 16a to 16h are given by integrating and stacking
the thin plate layer 26 and the substrate layer 24, and the support
section 42 is given by integrating and stacking the thin plate
layer 26, the substrate layer 24, and the spacer layer 22.
[0121] Each of the piezoelectric/electrostrictive elements 18 is
directly formed on the thin-walled region 36 (thin plate layer 26)
of the projection 46 in a state in which a thin film lower
electrode 18a, a piezoelectric/electrostrictive film 18b, and an
upper electrode 18c are stacked and integrated, in the same manner
as the vibration gyro sensor according to the first embodiment.
[0122] The vibration gyro sensor according to the modified
embodiment has the same advantages as those provided by the
vibration gyro sensor according to the fourth embodiment. Namely,
the characteristics of the sensor are not affected by any ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly improved,
and it is possible to facilitate realization of a compact size and
a light weight of the sensor.
[0123] Especially, the minute vibration, which is generated on the
thin-walled regions 36a, 36c, 36e, 36g of the annular section 14,
can be transmitted to the entire annular section 14 with high
following performance. Thus it is possible to greatly improve the
amplitude of vibration of the annular section 14 caused by
operating the driving piezoelectric/electrostrictive elements
18A.
[0124] Next, a vibration gyro sensor according to a fifth
embodiment will be explained with reference to FIGS. 17 and 18.
Components or parts corresponding to those shown in FIGS. 5 and 6
are designated by the same reference numerals, duplicate
explanation of which will be omitted.
[0125] As shown in FIG. 17, the vibration gyro sensor according to
the fifth embodiment has approximately the same structure as that
of the vibration gyro sensor according to the second embodiment.
However, the former is different from the latter in that the
annular section 14 does not include the thin-walled regions 36a to
36h, and in that minor axes or major axes of the resilient sections
16a to 16h are spanned with thin-walled sections 36a to 36h. The
resilient sections 16a to 16h and the thin-walled regions 36a to
36h are formed of ceramics in an integrated manner.
[0126] In the illustrative embodiment shown in FIG. 17, the
respective major axes of the two resilient sections 16a, 16e
located along the Y axis and of the two resilient sections 16h, 16d
adjacent at the left side to the resilient sections 16a, 16e are
spanned with the thin-walled regions 36a, 36e, 36h, 36d. The
respective minor axes of the other four resilient sections 16b,
16c, 16f, 16g are spanned with the thin-walled regions 36b, 36c,
36f, 36g.
[0127] Driving piezoelectric/electrostrictive elements 18A are
formed on the thin-walled regions 36a, 36e, 36h, 36d which span the
major axes of the resilient sections 16a, 16e, 16h, 16d
respectively. Detecting piezoelectric/electrostrictive elements 18B
are formed on the thin-walled regions 36b, 36c, 36f, 36g which span
the minor axes of the resilient sections 16b, 16c, 16f, 16g
respectively.
[0128] As shown in FIG. 18, the vibration gyro sensor according to
the fifth embodiment may be also grasped as an integrated stacked
product comprising a spacer layer 22 as a lowermost layer, a
substrate layer 24 as an intermediate layer, and a thin plate layer
26 as an uppermost layer, in the same manner as the vibration gyro
sensor according to the second embodiment. The thin-walled regions
36a to 36h which span the major axes or the minor axes of the
resilient sections 16a to 16h are given by the thin plate layer 26,
the annular section 14 and the resilient sections 16a to 16h
(except for the thin-walled regions 36a to 36h) are given by
integrating and stacking the thin plate layer 26 and the substrate
layer 24, and the annular frame 12 is given by integrating and
stacking the thin plate layer 26, the substrate layer 24, and the
spacer layer 22.
[0129] Each of the piezoelectric/electrostrictive elements 18 is
directly formed on the thin-walled region 36 (thin plate layer 26)
of the resilient section 16 in a state in which a thin film lower
electrode 18a, a piezoelectric/electrostrictive film 18b, and an
upper electrode 18c are stacked and integrated, in the same manner
as the vibration gyro sensor according to the first embodiment.
[0130] With reference to FIG. 17, the driving
piezoelectric/electrostricti- ve elements 18A are formed on the two
thin-walled regions 36a, 36e arranged along the Y axis and on the
two thin-walled regions 36d, 36h arranged along an axis rotated
counterclockwise by 45.degree. from the Y axis respectively. The
detecting piezoelectric/electrostrictive elements 18B are formed on
the two thin-walled regions 36c, 36g arranged along the X axis and
on the two thin-walled regions 36b, 36f arranged along an axis
rotated counterclockwise by 45.degree. from the X axis
respectively.
[0131] Especially, the vibration gyro sensor according to the fifth
embodiment is operated by using the driving
piezoelectric/electrostrictiv- e elements 18A formed on the
thin-walled regions 36a, 36e. Characteristics (for example,
frequency and amplitude) of the driving vibration are monitored
(detected) by using the detecting piezoelectric/electrostrictiv- e
elements 18B formed on the thin-walled regions 36c, 36g. If any
characteristic of the driving vibration is deviated from a
prescribed characteristic (designed value), feedback control is
applied to the driving piezoelectric/electrostrictive elements 18A
formed on the thin-walled regions 36a, 36e so that the prescribed
characteristic is obtained. When the detection is performed, a
vibration based on the Coriolis force is detected by using the
detecting piezoelectric/electrost- rictive elements 18B on the
thin-walled regions 36b, 36f. Simultaneously, a driving signal is
fed to the detecting piezoelectric/electrostrictive elements 18B
formed on the thin-walled regions 36d, 36h so that the vibration
based on the Coriolis force is offset. Thus it is intended to
generate no vibration based on the Coriolis force.
[0132] The reason why the vibration based on the Coriolis force is
suppressed is as follows. In the case of the so-called resonance
type vibration gyro sensor in which the driving system has a
resonance frequency which is identical with that of the detecting
system, it takes a long time to stabilize the vibration based on
the Coriolis force. When the angular velocity changes in accordance
with passage of time, for example, in automobiles, it is impossible
to accurately measure the angular velocity by using such a sensor.
Namely, the problem of response performance as described above
disappears by suppressing the vibration based on the Coriolis
force, and thus it is possible to highly accurately detect the
angular velocity.
[0133] The foregoing discussion may be summarized as follows. The
driving piezoelectric/electrostrictive elements 18A formed on the
thin-walled regions 36a, 36e are active elements to serve for
vibration, which have the function as
piezoelectric/electrostrictive elements for generating the driving
vibration. The detecting piezoelectric/electrostrictive elements
18B formed on the thin-walled regions 36c, 36g are passive elements
to serve for vibration, which have the function as
piezoelectric/electrostrictive elements for monitoring the driving
vibration. The detecting piezoelectric/electrostrictive elements
18B formed on the thin-walled regions 36b, 36f are passive elements
to serve for detection, which have the function as
piezoelectric/electrostrictive elements for detecting the driving
caused by the Coriolis force. The driving
piezoelectric/electrostrictive elements 18A formed on the
thin-walled regions 36d, 36h are active elements to serve for
detection, which have the function as
piezoelectric/electrostrictive elements for suppressing the driving
caused by the Coriolis force.
[0134] The vibration gyro sensor according to the fifth embodiment
has the same advantages as those provided by the vibration gyro
sensor according to the second embodiment. Namely, the
characteristics of the sensor are not affected by any ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly improved,
and it is possible to facilitate realization of a compact size and
a light weight of the sensor.
[0135] Especially, in the vibration gyro sensor according to the
fifth embodiment, the resilient sections 16a to 16h are constructed
as the ring sections each having the approximately elliptic planar
contour. The major axes of the four resilient sections 16a, 16e,
16h, 16d are spanned with the thin-walled regions 36a, 36e, 36h,
36d on which the driving piezoelectric/electrostrictive elements
18A are formed respectively. Accordingly, the minute amplitude of
vibration in the direction of the major axis is converted into
large amplitude of vibration in the direction of the minor axis.
Thus it is possible to greatly improve the amplitude of vibration
of the annular section 14 caused by operating the driving
piezoelectric/electrostrictive elements 18A.
[0136] Next, a modified embodiment of the vibration gyro sensor
according to the fifth embodiment will be explained with reference
to FIGS. 19 and 20. Components or parts corresponding to those
shown in FIGS. 17 and 18 are designated by the same reference
numerals, duplicate explanation of which will be omitted.
[0137] As shown in FIG. 19, a vibration gyro sensor according to
this modified embodiment has approximately the same structure as
that of the vibration gyro sensor according to the fifth
embodiment. However, the former is different from the latter in
that in place of the annular frame 12, a support section 42 is
constructed by an integrated fired product of ceramics together
with the resilient sections 16a to 16h and the annular section 14,
the support section 42 having an outer diameter smaller than an
inner diameter of the annular section 14, and having a central hole
40, and in that the eight resilient sections 16a to 16h are
equivalently arranged between the inner circumference of the
annular section 14 and the outer circumference of the support
section 42.
[0138] Especially, in the illustrative embodiment shown in FIG. 19,
respective major axes of the two resilient sections 16a, 16e
located along the Y axis and of the two resilient sections 16b, 16f
adjacent at the right side to the resilient sections 16a, 16e are
spanned with thin-walled regions 36a, 36e, 36b, 36f. Respective
minor axes of the other four resilient sections 16c, 16d, 16g, 16h
are spanned with thin-walled regions 36c, 36d, 36g, 36h.
[0139] Driving piezoelectric/electrostrictive elements 18A are
formed on the thin-walled regions 36a, 36e, 36b, 36f which span the
major axes of the resilient sections 16a, 16e, 16b, 16f
respectively. Detecting piezoelectric/electrostrictive elements 18B
are formed on the thin-walled regions 36c, 36d, 36g, 36h which span
the minor axes of the resilient sections 16c, 16d, 16g, 16h
respectively.
[0140] As shown in FIG. 20, the vibration gyro sensor according to
the modified embodiment may be also grasped as an integrated
stacked product comprising a spacer layer 22 as a lowermost layer,
a substrate layer 24 as an intermediate layer, and a thin plate
layer 26 as an uppermost layer, in the same manner as the vibration
gyro sensor according to the fifth embodiment. The thin-walled
regions 36a to 36h which span the major axes or the minor axes of
the resilient sections 16a to 16h are given by the thin plate layer
26, the annular section 14 and the resilient sections 16a to 16h
(except for the thin-walled regions 36a to 36h) are given by
integrating and stacking the thin plate layer 26 and the substrate
layer 24, and the support section 42 is given by integrating and
stacking the thin plate layer 26, the substrate layer 24, and the
spacer layer 22.
[0141] With reference to FIG. 19, the driving
piezoelectric/electrostricti- ve elements 18A are formed on the two
thin-walled regions 36a, 36e arranged along the Y axis and on the
two thin-walled regions 36b, 36f arranged along an axis rotated
clockwise by 45.degree. from the Y axis respectively. The detecting
piezoelectric/electrostrictive elements 18B are formed on the two
thin-walled regions 36c, 36g arranged along the X axis and on the
two thin-walled regions 36d, 36h arranged along an axis rotated
clockwise by 45.degree. from the X axis respectively.
[0142] In this embodiment, the driving
piezoelectric/electrostrictive elements 18A formed on the
thin-walled regions 36a, 36e have the function as
piezoelectric/electrostrictive elements for generating the driving
vibration. The detecting piezoelectric/electrostrictive elements
18B formed on the thin-walled regions 36c, 36g have the function as
piezoelectric/electrostrictive elements for monitoring the driving
vibration. The detecting piezoelectric/electrostrictive elements
18B formed on the thin-walled regions 36d, 36h have the function as
piezoelectric/electrostrictive elements for detecting the driving
caused by the Coriolis force. The driving
piezoelectric/electrostrictive elements 18A formed on the
thin-walled regions 36b, 36f have the function as
piezoelectric/electrostrictive elements for suppressing the driving
caused by the Coriolis force.
[0143] The vibration gyro sensor according to the modified
embodiment has the same advantages as those provided by the
vibration gyro sensor according to the fifth embodiment. Namely,
the characteristics of the sensor are not affected by any ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly improved,
and it is possible to facilitate realization of a compact size and
a light weight of the sensor. Further, it is possible to greatly
improve the amplitude of vibration of the annular section 14 caused
by operating the driving piezoelectric/electrostrictive elements
18A.
[0144] Next, a vibration gyro sensor according to a sixth
embodiment will be explained with reference to FIGS. 21 and 22.
[0145] As shown in FIG. 21, the vibration gyro sensor according to
the sixth embodiment comprises an annular frame 52 having an
approximately square planar contour with a central opening 50 of an
approximately circular planar configuration, an annular section 54
arranged in the opening 50 of the annular frame 52 and having an
approximately circular planar contour for constructing a vibrator,
a support section 58 having an outer diameter smaller than an inner
diameter of the annular section 54 and having a central hole 56, a
plurality of outer resilient sections 60a to 60h which span the
inner circumference of the annular frame 52 and the outer
circumference of the annular section 54, and a plurality of inner
resilient sections 62a to 62h which span the inner circumference of
the annular section 54 and the outer circumference of the support
section 58, wherein the annular frame 52, the annular section 54,
the support section 58, and the plurality of outer resilient
sections 60a to 60h, and the plurality of inner resilient sections
62a to 62h are constructed by an integrated fired product made of
ceramics.
[0146] Each of the outer resilient sections 60a to 60h is composed
of a ring section having an approximately elliptic planar
configuration with its minor axis directed in a radial direction on
the basis of the center of the annular section 54. Each of the
outer resilient sections 60a to 60h has a thickness in a direction
of height, the thickness being designed to be approximately the
same as a thickness of the annular section 54.
[0147] The respective outer resilient sections 60a to 60h are
arranged at positions at which they are separated from each other
by equal spacing distances (distance to give a central angle of
45.degree.) and they are mutually point-symmetrical, in the same
manner as the vibration gyro sensor according to the fifth
embodiment.
[0148] Major axes of the respective outer resilient sections 60a to
60h are spanned with thin-walled regions 64a to 64h each having a
thickness smaller than that of the annular section 54 respectively.
The outer resilient sections 60a to 60h and the thin-walled regions
64a to 64h are formed of ceramics in an integrated manner.
[0149] Each of the inner resilient sections 62a to 62h is formed to
have a rectangular planar configuration, having a thickness in its
direction of height designed to be smaller than the thickness of
the annular section 54. Namely, each of the inner resilient
sections 62a to 62h is thin-walled so that the rigidity in the
direction of vibration of the piezoelectric/electrostrictive
element 18 is lowered to give a large amplitude of vibration caused
on the annular section 54. The respective inner resilient sections
62a to 62h are provided as eight individuals corresponding to the
outer resilient sections 60a to 60h, and they are arranged at
positions at which they are separated from each other by equal
spacing distances (distance to give a central angle of 45.degree.)
and they are mutually point-symmetrical.
[0150] Driving piezoelectric/electrostrictive elements 18A are
formed on the thin-walled regions 64 of the plurality of outer
resilient sections 60 located at predetermined positions, of the
eight outer resilient sections 60. Detecting
piezoelectric/electrostrictive elements 18B are formed on the
plurality of inner resilient sections 62 (thin-walled regions)
located at predetermined positions, of the eight inner resilient
sections 62.
[0151] In the illustrative embodiment shown in FIG. 21, the driving
piezoelectric/electrostrictive elements 18A are formed on the
respective thin-walled regions 64a, 64e, 64b, 64f of the two outer
resilient sections 60a, 60e located along the direction of the Y
axis and of the two outer resilient sections 60b, 60f adjacent at
the right side to the outer resilient sections 60a, 60e
respectively. The detecting piezoelectric/electrostrictive elements
18B are formed on the two inner resilient sections 62c, 62g located
along the direction of the X axis and on the two inner resilient
sections 62d, 62h adjacent at the right side to the inner resilient
sections 62c, 62g respectively.
[0152] In this embodiment, the driving
piezoelectric/electrostrictive elements 18A formed on the
thin-walled regions 64a, 64e have the function as
piezoelectric/electrostrictive elements for generating the driving
vibration. The detecting piezoelectric/electrostrictive elements
18B formed on the inner resilient sections (thin-walled regions)
62c, 62g have the function as piezoelectric/electrostrictive
elements for monitoring the driving vibration. The detecting
piezoelectric/electrostri- ctive elements 18B formed on the inner
resilient sections (thin-walled regions) 62d, 62h have the function
as piezoelectric/electrostrictive elements for detecting the
driving caused by the Coriolis force. The driving
piezoelectric/electrostrictive elements 18A formed on the
thin-walled regions 64b, 64f have the function as
piezoelectric/electrost- rictive elements for suppressing the
driving caused by the Coriolis force.
[0153] Outwardly protruding projections 66 are provided in an
integrated manner on the outer circumference of the support section
58 between the mutually adjacent inner resilient sections 62. The
projections 66 are consequently formed when connecting sections are
cut and removed at inner circumferential portions of the annular
section 54, the connecting sections having been provided in order
to connect the support section 58 and the annular section 54 at
prescribed positions at the stage of production of the vibration
gyro sensor, in the same manner as the vibration gyro sensor
according to the first embodiment. Therefore, the projections 66
may be omitted or removed at the stage in which the vibration gyro
sensor has been assembled.
[0154] As shown in FIG. 22, the vibration gyro sensor according to
the sixth embodiment may be also grasped as an integrated stacked
product comprising a spacer layer 22 as a lowermost layer, a
substrate layer 24 as an intermediate layer, and a thin plate layer
26 as an uppermost layer. The thin-walled regions 64a to 64h which
span the major axes of the outer resilient sections 60a to 60h and
the inner resilient sections 62a to 62h (thin-walled regions) are
given by the thin plate layer 26, the annular section 54, the outer
resilient sections 60a to 60h (except for the thin-walled regions
64a to 64h), and the projections 66 are given by integrating and
stacking the thin plate layer 26 and the substrate layer 24, and
the annular frame 52 and the support section 58 are given by
integrating and stacking the thin plate layer 26, the substrate
layer 24, and the spacer layer 22.
[0155] The vibration gyro sensor according to the sixth embodiment
has the same advantages as those provided by the vibration gyro
sensor according to the second embodiment. Namely, the
characteristics of the sensor are not affected by any ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly improved,
and it is possible, to facilitate realization of a compact size and
a light weight of the sensor.
[0156] Especially, in the vibration gyro sensor according to the
sixth embodiment, the outer resilient sections 60a to 60h are
constructed as the ring sections each having the approximately
elliptic planar contour. The major axes of the four outer resilient
sections 60a, 60e, 60b, 60f are spanned with the thin-walled
regions 64a, 64e, 64b, 64f on which the driving
piezoelectric/electrostrictive elements 18A are formed
respectively. Accordingly, the minute amplitude of vibration in the
direction of the major axis is converted into large amplitude of
vibration in the direction of the minor axis, in the same manner as
the vibration gyro sensor according to the fifth embodiment. Thus
it is possible to greatly improve the amplitude of vibration of the
annular section 54 caused by operating the driving
piezoelectric/electrostrictive elements 18A.
[0157] Next, a modified embodiment of the vibration gyro sensor
according to the sixth embodiment will be explained with reference
to FIGS. 23 and 24. Components or parts corresponding to those
shown in FIGS. 21 and 22 are designated by the same reference
numerals, duplicate explanation of which will be omitted.
[0158] As shown in FIG. 23, a vibration gyro sensor according to
this modified embodiment has approximately the same structure as
that of the vibration gyro sensor according to the sixth
embodiment. However, the former is different in structure from the
latter in the following points.
[0159] Namely, each of eight outer resilient sections 60a to 60h is
formed to have a rectangular planar configuration to be
thin-walled, having a thickness of its direction of height designed
to be smaller than the thickness of the annular section 54. Each of
inner resilient sections 62a to 62h is composed of a ring section
having an approximately elliptic planar configuration with its
minor axis directed in a radial direction on the basis of the
center of the annular section 54, having a thickness in its
direction of height designed to be approximately the same as the
thickness of the annular section 54. Major axes of the respective
inner resilient sections 62a to 62h are spanned with thin-walled
regions 64a to 64h respectively. Detecting
piezoelectric/electrostrictive elements 18B are formed on the four
outer resilient sections 60c, 60d, 60g, 60h located at
predetermined positions respectively. Driving
piezoelectric/electrostrictive elements 18A are formed on the
respective thin-walled regions 64a, 64b, 64e, 64f of the four inner
resilient sections 62a, 62b, 62e, 62f located at predetermined
positions respectively.
[0160] In this embodiment, the driving
piezoelectric/electrostrictive elements 18A formed on the
thin-walled regions 64a, 64e have the function as
piezoelectric/electrostrictive elements for generating the driving
vibration. The detecting piezoelectric/electrostrictive elements
18B formed on the outer resilient sections (thin-walled regions)
60c, 60g have the function as piezoelectric/electrostrictive
elements for monitoring the driving vibration. The detecting
piezoelectric/electrostri- ctive elements 18B formed on the
thin-walled regions 64d, 64h have the function as
piezoelectric/electrostrictive elements for detecting the driving
caused by the Coriolis force. The driving piezoelectric/electrost-
rictive elements 18A formed on the outer resilient sections
(thin-walled regions) 60b, 60f have the function as
piezoelectric/electrostrictive elements for suppressing the driving
caused by the Coriolis force.
[0161] Inwardly protruding projections 66 are provided in an
integrated manner on the inner circumference of the annular frame
52 between the mutually adjacent outer resilient sections 60. The
projections 66 are consequently formed when connecting sections are
cut and removed at outer circumferential portions of the annular
section 54, the connecting sections having been provided in order
to support the annular section 54 at a prescribed position in the
opening 50 of the annular frame 52 at the stage of production of
the vibration gyro sensor, in the same manner as the vibration gyro
sensor according to the sixth embodiment. Therefore, the
projections 66 may be omitted or removed at the stage in which the
vibration gyro sensor has been assembled.
[0162] As shown in FIG. 24, the vibration gyro sensor according to
the modified embodiment may be also grasped as an integrated
stacked product comprising a spacer layer 22 as a lowermost layer,
a substrate layer 24 as an intermediate layer, and a thin plate
layer 26 as an uppermost layer. The outer resilient sections 60a to
60h and the thin-walled regions 64a to 64h which span the major
axes of the inner resilient sections 62a to 62h are given by the
thin plate layer 26, the annular section 54, the inner resilient
sections 62a to 62h (except for the thin-walled regions 64a to
64h), and the projections 66 are given by integrating and stacking
the thin plate layer 26 and the substrate layer 24, and the annular
frame 52 and the support section 58 are given by integrating and
stacking the thin plate layer 26, the substrate layer 24, and the
spacer layer 22.
[0163] The vibration gyro sensor according to the modified
embodiment has the same advantages as those provided by the
vibration gyro sensor according to the sixth embodiment. Namely,
the characteristics of the sensor are not affected by any ambient
magnetic field, the detection sensitivity on the detecting
piezoelectric/electrostrictive elements 18B is greatly improved,
and it is possible to facilitate realization of a compact size and
a light weight of the sensor. Further, it is possible to greatly
improve the amplitude of vibration of the annular section 54 caused
by operating the driving piezoelectric/electrostrictive elements
18A.
[0164] Any of the vibration gyro sensors according to the first to
sixth embodiments is constructed by the integrated fired product
made of ceramics, except for the driving
piezoelectric/electrostrictive elements 18A, the detecting
piezoelectric/electrostrictive elements 18B, and wiring.
Specifically, the vibration gyro sensors are produced as
follows.
[0165] At first, concerning the vibration gyro sensors according to
the first to sixth embodiments (including the respective modified
embodiments), their main sensor bodies are provided. Each of the
main sensor bodies typically comprises the annular frame 12 (52),
the annular section 14 (54), the support section 42 (58), and the
resilient sections 16 (60, 62). Those usable, without any problem,
as materials for forming the integrated fired product of ceramics
for providing the main sensor body include any of ceramic materials
composed of oxide and any of ceramic materials composed of those
other than oxide, provided that the material is an insulative
material or a dielectric material having large mechanical strength,
which can be subjected to a heat treatment at about 1400.degree. C.
as described later on, and which can be stacked and integrated with
the piezoelectric/electrostrictive element 18 and other components
without using any adhesive or the like.
[0166] Especially, those preferably adopted include materials
comprising a major component of at least any one of aluminum oxide,
magnesium oxide, zirconium oxide, aluminum nitride, and silicon
nitride, in order to obtain excellent operation characteristics,
i.e., large displacement, large generated force, and quick response
speed. In particular, it is recommended to use ceramic materials
comprising, as a major component or major components, aluminum
oxide and/or zirconium oxide.
[0167] More specifically, those advantageously used include
materials comprising a major component of zirconium oxide
stabilized with at lease one compound selected from the group
consisting of yttrium oxide, ytterbium oxide, cerium oxide, calcium
oxide, and magnesium oxide, because they exhibits features such as
high toughness and high mechanical strength obtained even when the
plate thickness is thin.
[0168] In order to stabilize zirconium oxide, the foregoing
compound is preferably added in man amount of 1 mole % to 30 mole %
in the case of yttrium oxide and ytterbium oxide, 6 mole % to 50
mole % in the case of cerium oxide, or 5 mole % to 40 mole % in the
case of calcium oxide and magnesium oxide. Especially, it is
desirable to use yttrium oxide as a stabilizer. In this case,
yttrium oxide is desirably added in an amount of 1.5 mole % to 6
mole %, more preferably 2 mole % to 4 mole %.
[0169] When yttrium oxide is added to zirconium oxide in the
foregoing range of addition, the crystal phase is partially
stabilized, thus giving excellent characteristics for the main
sensor body.
[0170] When stabilized or partially stabilized zirconia is used for
the thin plate layer 26, it is preferable to contain an auxiliary
shown in the following table. An equivalent effect can be obtained
even when the piezoelectric/electrostrictive element 18 contains
the following auxiliary.
1TABLE 1 Type of Preferable More applicable content preferable
electric range range field-induced Auxiliary (% by weight) (% by
weight) Effect strain alumina 0.1.about.5.0 0.2.about.2.0 *1
lateral effect titania 0.1.about.5.0 0.2.about.2.0 *2 longitudinal
effect *1: Stress itself or dispersion of stress of the
piezoelectric layer is reduced by avoiding conglutination (fusion)
of the thin plate layer and the piezoelectric layer. *2: Sufficient
joining is ensured between the thin plate layer and the
piezoelectric layer to obtain high reliability.
[0171] As shown in FIG. 2, for example, the integrated fired
product of ceramics, which constructs the main sensor body as
described above, comprises the thin plate layer 26, the substrate
layer 24, and the spacer layer 22. However, it is preferable to
contain silicon oxide (SiO, SiO.sub.2) at least in the material to
give the thin plate layer 26. The content of silicon oxide is
preferably not less than 0.5% by weight and not more than 5% by
weight, and especially desirably not less than 1% by weight and not
more than 3% by weight.
[0172] When silicon oxide is contained in the foregoing ratio, it
is possible to avoid any excessive reaction with the
piezoelectric/electrost- rictive element 18 during the heat
treatment for the piezoelectric/electrostrictive element 18 formed
on the thin plate layer 26. Accordingly, good actuator
characteristics can be obtained in relation to the driving
piezoelectric/electrostrictive element 18A, and good detection
characteristics can be obtained in relation to the detecting
piezoelectric/electrostrictive element 18B.
[0173] Further, in order to obtain quick response and large
displacement in the vibration gyro sensors according to the first
to sixth embodiments (including the respective modified
embodiments), the thickness of the thin plate layer 26 on which the
piezoelectric/electrostrictive elements 18 are formed in the
integrated manner, i.e., the thickness of the thin-walled region 36
(64) is generally not more than 50 .mu.m, preferably not more than
30 .mu.m, and more preferably not more than 15 .mu.m.
[0174] On the other hand, the thickness of the substrate layer 24
is appropriately determined. However, the thickness of the
substrate layer 24 is generally not less than 30 .mu.m, preferably
not less than 50 .mu.m, and more preferably not less than 100
.mu.m.
[0175] In order to obtain large displacement and large generated
force in the actuator or the detecting region, at least the thin
plate layer 26 preferably has an average particle diameter of
crystals of 0.1 to 2 .mu.m. More preferably, the thin plate layer
26 is desirably composed of a ceramic material having an average
particle diameter of not more than 1 .mu.m.
[0176] Those usable to obtain the integrated fired product of
ceramics to give the main sensor body comprising the thin plate
layer 26, the substrate layer 24, and the spacer layer 22 as
described above include, for example, a green sheet stacking method
for stacking, in a state of green sheets, the thin plate layer 26,
the substrate layer 24, and the spacer layer 22, as well as various
molding methods based on the use of a mold, such as pressure
molding, casting molding, and injection molding, and processing or
machining methods for forming, for example, the annular frame 12
(52), the support section 42 (58), the annular section 14 (54), and
the resilient sections 16 (60, 62) by means of machining processing
such as ultrasonic, cutting, and grinding processing methods.
Especially, it is preferable to use the green sheet stacking method
as a method in which no processing stress remains, and the accuracy
for the thickness of the thin plate layer 26 is high.
[0177] The green sheet stacking method is preferably based on the
use of first, second, and third green sheets for providing the thin
plate layer 26, the substrate layer 24, and the spacer layer 22
respectively. A method is adopted, in which the first, second, and
third green sheets are stacked by means of thermal adhesion under a
pressure, and then they are integrated with each other by firing.
It is preferable to use, as the first to third green sheets, green
sheets which at least have the same degree of percentage of
contraction by firing, upon the firing and integration.
[0178] The green sheet stacking method, which is used to produce
the vibration gyro sensors according to the first to sixth
embodiments, specifically includes three methods. The respective
methods are shown in FIGS. 25 to 27 respectively, as illustrated in
block diagrams of production steps.
[0179] The first method will be described with reference to FIG.
25. First, second, and third green sheets are prepared, and they
are formed to have shapes corresponding to the thin plate layer 26,
the substrate layer 24, and the spacer layer 22 respectively (Step
S1). This shaping step is performed by using the laser processing,
the mold press working, or the ultrasonic processing.
[0180] Subsequently, the thin plate layer 26, the substrate layer
24, and the spacer layer 22 after the shaping step are stacked and
integrated (Step S2), followed by firing to obtain an integrated
fired product (Step S3).
[0181] Subsequently, the driving piezoelectric/electrostrictive
elements 18A, the detecting piezoelectric/electrostrictive elements
18B, and wiring are formed at predetermined regions on the thin
plate layer 26 (Step S4). This step for forming the driving
piezoelectric/electrostricti- ve elements 18A, the detecting
piezoelectric/electrostrictive elements 18B, and wiring is
performed by using, for example, screen printing, dipping, ion
beam, sputtering, vacuum vapor deposition, ion plating, CVD
(chemical vapor deposition), and plating methods.
[0182] Subsequently, the respective upper electrodes 18c of the
driving piezoelectric/electrostrictive elements 18A and the
detecting piezoelectric/electrostrictive elements 18B are subjected
to a trimming treatment to adjust electric characteristics of the
respective piezoelectric/electrostrictive elements 18A, 18B (Step
S5). The trimming treatment is performed, for example, by means of
laser processing or plasma etching such as RIE.
[0183] Subsequently, the annular section 14 (54), the resilient
sections 16 (60, 62), the projections 20 (66), and the thin-walled
regions 36 (64) are subjected to a trimming treatment to adjust
mechanical characteristics of the main sensor body (Step S6). The
trimming treatment is performed, for example, by means of laser
processing or ultrasonic processing.
[0184] According to the method described above, the vibration gyro
sensors according to the first to sixth embodiments (including the
respective modified embodiments) can be easily produced with high
reliability.
[0185] The electric characteristics of the
piezoelectric/electrostrictive elements 18 can be conveniently
adjusted by performing the trimming treatment for the upper
electrodes 18c of the piezoelectric/electrostrict- ive elements 18.
Further, the mechanical characteristics of the vibrator or other
components can be conveniently adjusted by performing the trimming
treatment for the annular section 14 (54) and the resilient
sections 16 (60, 62). Accordingly, this method is advantageous in
that the number of production steps can be reduced.
[0186] Vibration gyro sensors, which have been hitherto used,
employ the elinvar alloy for the vibrator in many cases, and the
bulky piezoelectric/electrostrictive element formed with the
electrode is fixed to the vibrator by means of adhesion. Therefore,
it is necessary to use solder or Ag paste for connecting external
wiring to the electrode of the piezoelectric/electrostrictive
element. In this procedure, for example, the solder, the Ag paste,
and the external wiring itself behave as added weights to greatly
affect the vibration characteristics of the vibrator, making it
difficult to produce the gyro sensors.
[0187] Vibration gyro sensors of another type is also known, in
which a piezoelectric ceramic is used for the vibrator. However,
such vibration gyro sensors are not essentially different from the
foregoing conventional vibration gyro sensor in that the lead wire
is connected to the part which is used to make vibration Problems
arise in that (a) the connecting section to the external wiring is
less reliable, and (b) the dispersion in production is large.
[0188] However, the vibration gyro sensors according to the first
to sixth embodiments (including the respective modified
embodiments) described above are advantageous in that external
wiring can be easily connected to the pair of electrodes of the
respective piezoelectric/electrostrictive elements 18.
[0189] In the present invention, the annular frame 12 (52), the
annular section 14 (54), the resilient sections 16 (60, 62), the
support section 42 (58), and other components are constructed as a
whole by the integrated fired product composed of ceramics
(non-conductive substances) represented by zirconia oxide.
Accordingly, the present invention is advantageous in that external
wiring can be directly wired and formed on the foregoing components
by means of the film formation method. In addition to this
advantage, the film formation method such as screen printing is
used for forming the electrodes of the driving
piezoelectric/electrostrictive elements 18A and the detecting
piezoelectric/electrostrictive elements 18B. Accordingly, the
present invention is also advantageous in that when the electrodes
of the piezoelectric/electrostrictive elements 18 are formed, the
wiring for these electrodes can be simultaneously extended up to
the annular frame 12 (52) or the support section 42 (58) so that
the vibration characteristics are not affected. Therefore, it is
possible to realize improvement in yield and easy production of the
vibration gyro sensor.
[0190] Next, the second method will be described with reference to
FIG. 26. First, second, and third green sheets are prepared, of
which the second and third green sheets are formed to have shapes
corresponding to the substrate layer 24 and the spacer layer 22
respectively (Step S101).
[0191] Subsequently, the substrate layer 24 and the spacer layer 22
after the shaping step are stacked and integrated together with the
first green sheet (unshaped thin plate layer 26) (Step S102),
followed by firing to obtain an integrated fired product (Step
S103). After that, the thin plate layer 26 disposed as the
uppermost layer is shaped to give a shape corresponding to the thin
plate layer 26 (Step S104).
[0192] Subsequently, the driving piezoelectric/electrostrictive
elements 18A, the detecting piezoelectric/electrostrictive elements
18B, and wiring are formed at predetermined regions on the thin
plate layer 26 (Step S105). After that, the respective upper
electrodes 18c of the driving piezoelectric/electrostrictive
elements 18A and the detecting piezoelectric/electrostrictive
elements 18B are subjected to a trimming treatment to adjust
electric characteristics of the respective
piezoelectric/electrostrictive elements 18 (Step S106). Further,
the annular section 14 (54), the resilient sections 16 (60, 62),
the projections: 20 (66), and the thin-walled regions 36 (64) are
subjected to a trimming treatment to adjust mechanical
characteristics of the main sensor body (Step S107).
[0193] According to the second method, the vibration gyro sensors
according to the first to sixth embodiments (including the
respective modified embodiments) can be also easily produced with
high reliability, in the same manner as the first method described
above. Further, the electric characteristics of the
piezoelectric/electrostrictive elements 18 can be conveniently
adjusted, and the mechanical characteristics of the vibrators or
other components can be conveniently adjusted. Accordingly, the
second method is advantageous in that the number of production
steps can be reduced.
[0194] Further, the annular frame 12 (52), the annular section 14
(54), the resilient sections 16 (60, 62), the support section 42
(58), and other components are constructed as a whole by the
integrated fired product composed of ceramics (non-conductive
substances) represented by zirconia oxide. Accordingly, the present
invention is advantageous in that the external wiring can be
directly wired and formed on the foregoing components by means of
the film formation method. In addition to this advantage, the film
formation method such as screen printing is used for forming the
electrodes of the driving piezoelectric/electrostric- tive elements
18A and the detecting piezoelectric/electrostrictive elements 18B.
Accordingly, the present invention is also advantageous in that
when the electrodes of the piezoelectric/electrostrictive elements
18 are formed, the wiring for these electrodes can be
simultaneously extended up to the annular frame 12 (52) or the
support section 42 (58) so that the vibration characteristics are
not affected. Therefore, it is possible to realize improvement in
yield and easy production of the vibration gyro sensor.
[0195] Next, the third method will be described with reference to
FIG. 27. First, second, and third green sheets are prepared, of
which the second and third green sheets are formed to have shapes
corresponding to the substrate layer 24 and the spacer layer 22
respectively (Step S201).
[0196] Subsequently, the substrate layer 24 and the spacer layer 22
after the shaping step are stacked and integrated together with the
first green sheet (unshaped thin plate layer 26) (Step S202),
followed by firing to obtain an integrated fired product (Step
S203).
[0197] After that, the driving piezoelectric/electrostrictive
elements 18A, the detecting piezoelectric/electrostrictive elements
18B, and wiring are formed at predetermined regions on the first
green sheet disposed as the uppermost layer (unshaped thin plate
layer 26) (Step S204). Subsequently, the first green sheet is
shaped to give a shape corresponding to the thin plate layer 26
(Step S205).
[0198] Subsequently, the respective upper electrodes 18c of the
driving piezoelectric/electrostrictive elements 18A and the
detecting piezoelectric/electrostrictive elements 18B are subjected
to a trimming treatment to adjust electric characteristics of the
respective piezoelectric/electrostrictive elements 18 (Step S206).
Further, the annular section 14 (54), the resilient sections 16
(60, 62), the projections 20 (66), and the thin-walled regions 36
(64) are subjected to a trimming treatment to adjust mechanical
characteristics of the main sensor body (Step S207).
[0199] According to the third method, the vibration gyro sensors
according to the first to sixth embodiments (including the
respective modified embodiments) can be also easily produced with
high reliability, in the same manner as the first method described
above. Further, the electric characteristics of the
piezoelectric/electrostrictive elements 18 can be conveniently
adjusted, and the mechanical characteristics of the vibrators or
other components can be conveniently adjusted. Accordingly, the
third method is advantageous in that the number of production steps
can be reduced.
[0200] Further, the annular frame 12 (52), the annular section 14
(54), the resilient sections 16 (60, 62), the support section 42
(58), and other components are constructed as a whole by the
integrated fired product composed of ceramics (non-conductive
substances) represented by zirconia oxide. Accordingly, the present
invention is advantageous in that the external wiring can be
directly wired and formed on the foregoing components by means of
the film formation method. In addition to this advantage, the film
formation method such as screen printing is used for forming the
electrodes of the driving piezoelectric/electrostric- tive elements
18A and the detecting piezoelectric/electrostrictive elements 18B.
Accordingly, the present invention is also advantageous in that
when the electrodes of the piezoelectric/electrostrictive elements
18 are formed, the wiring for these electrodes can be
simultaneously extended up to the annular frame 12 (52) or the
support section 42 (58) so that the vibration characteristics are
not affected. Therefore, it is possible to realize improvement in
yield and easy production of the vibration gyro sensor.
[0201] In the first to third methods described above, the shapes of
the thin plate layer 26, the substrate layer 24, and the spacer
layer 22 are preferably realized and established by adopting, for
example, the laser processing, the press working with a mold, and
the ultrasonic processing applied to the first, second, and third
green sheets. Especially, it is advantageous to use the press
working with a mold, because this method is excellent in
performance of mass production and performance concerning stacking
and integration.
[0202] FIG. 28 illustratively shows exemplary production steps for
producing, for example, the vibration gyro sensor according to the
second embodiment (see FIG. 5) in accordance with the third
method.
[0203] In this procedure, a first green sheet 70 for giving the
thin plate layer 26 is not processed into the shape of the thin
plate layer 26 at all. The first green sheet 70 is merely used as
one thin plate having a rectangular configuration. A second green
sheet 72 for giving the substrate layer 24 is processed into the
shape corresponding to the shape of the substrate layer 24. A third
green sheet 74 for giving the spacer layer 22 is also processed
into the shape corresponding to the shape of the spacer layer
22.
[0204] The first, second, and third green sheets 70, 72, 74 are
stacked, and then they are fired and integrated into one unit.
After that, the piezoelectric/electrostrictive elements 18 are
formed in an integrated manner on the predetermined regions on the
unshaped thin plate layer 26 of the obtained fired product 76 in
accordance with the film formation method.
[0205] Subsequently, cutting processing is applied to predetermined
portions of the unshaped thin plate layer 26 of the integrated
fired product 76 by means of, for example, laser processing or
ultrasonic processing. Thus the vibration gyro sensor according to
the second embodiment shown in FIG. 5 is completed.
[0206] In the case of the second method described above (FIG. 26),
the order of the step of forming the driving
piezoelectric/electrostrictive elements 18A and the detecting
piezoelectric/electrostrictive elements 18B and the step of
processing the thin plate layer 26 is inverted, and the
piezoelectric/electrostrictive elements 18A, 18B are formed in an
integrated manner. Thus the vibration gyro sensor shown in FIG. 5
is completed.
[0207] As clarified from FIGS. 1 and 2, in the case of the
structure of the vibration gyro sensor according to the first
embodiment shown in FIG. 1, the resilient sections 16 which span
the annular frame 12 and the annular section 14 are formed only by
the thin plate layer 26 given by the first green sheet 70.
Therefore, there is an implicit problem in that deformation tends
to occur upon firing and upon heat treatment performed when the
piezoelectric/electrostrictive elements 18 are formed, in addition
to the fact that it is difficult to position the annular section 14
at the prescribed position in the opening 10 of the annular frame
12, when the second green sheet 72 and the third green sheet 74 are
processed into the prescribed shapes.
[0208] Accordingly, as shown in FIG. 29, for example, the following
method is preferably adopted. Namely, when the second green sheet
72 is shaped and processed, a plurality of connecting sections 80
are allowed to exist between a portion for forming the annular
frame 12 and a portion for forming the annular section 14. After
stacking and integration, or after firing and integration, the
connecting sections 80 are cut.
[0209] The method shown in FIG. 29 is illustrative of one of
effective methods for producing the vibration gyro sensor according
to the first embodiment shown in FIG. 1. As shown in FIG. 29, the
second green sheet 72 for giving the substrate layer 24 is formed
and shaped so that the plurality of connecting sections 80 exist
between the portion for forming the annular frame 12 and the
portion for forming the annular section 14. At this stage, the
first green sheet 70 for giving the thin plate layer 26 is not
processed into the shape of the thin plate layer 26 at all, which
is merely provided as one thin plate having a rectangular
configuration. The third green sheet 74 for giving the spacer layer
22 has been processed into the shape corresponding to the shape of
the spacer layer 22.
[0210] The first, second, and third green sheets 70, 72, 74 are
stacked, and then they are fired and integrated into one unit.
After that, the piezoelectric/electrostrictive elements 18 are
formed in an integrated manner on the predetermined regions on the
thin plate layer 26 of the obtained fired product 76 in accordance
with the film formation method.
[0211] Subsequently, cutting processing is applied to predetermined
portions of the thin plate layer 26 of the integrated fired product
76 by means of, for example, laser processing or ultrasonic
processing. Thus the resilient sections 16 based on the thin plate
layer 26 are formed. Further, the projections 20 are formed by
cutting the connecting sections 80 by means of, for example, laser
processing or ultrasonic processing. Consequently, the vibration
gyro sensor according to the first embodiment shown in FIG. 1 is
completed.
[0212] The production method shown in FIG. 29 can be also applied
to the vibration gyro sensor according to the sixth embodiment and
the vibration gyro sensor according to the modified embodiment
thereof, in addition to the vibration gyro sensor according to the
first embodiment.
[0213] In the first to third methods described above, the
piezoelectric/electrostrictive elements 18 are formed on the
predetermined regions on the thin plate layer 26 as follows.
[0214] At first, in order to form the upper electrode 18c, the
lower electrode 18a, and the piezoelectric/electrostrictive film
18b on the predetermined regions on the thin plate layer 26, it is
possible to appropriately adopt various film formation methods
including, for example, thick film methods such as screen printing,
application methods such as dipping, and thin film methods such as
ion beam, sputtering, vacuum vapor deposition, ion plating, CVD,
and plating. However, there is no limitation thereto at all. In
order to form the piezoelectric/electrostrictive film 18b, it is
preferable to adopt techniques based on, for example, screen
printing, dipping, and application.
[0215] In the foregoing film formation methods, the film can be
formed on the thin plate layer 26 by using a paste or a slurry
comprising, as major components, ceramic particles and a metal for
constructing the piezoelectric/electrostrictive element 18, in
which good operation characteristics can be obtained. When the
piezoelectric/electrostrictive element 18 is formed in accordance
with the film formation method as described above, the element can
be integrated with the thin plate layer 26 without using any
adhesive. Accordingly, the use of the film formation method
provides such effects that the reliability and the reproducibility
are excellent, and it is easy to achieve integration.
[0216] The shape of the stacked film for constructing the
piezoelectric/electrostrictive element 18 is formed by means of
pattern formation by using, for example, the screen printing method
and photolithography. Alternatively, the pattern may be formed by
removing unnecessary portions by using mechanical processing
methods such as laser processing, slicing, and ultrasonic
processing.
[0217] The shape of the film and the structure of the
piezoelectric/electrostrictive element 18 formed integrally on the
predetermined region on the thin plate layer 26 in accordance with
the film formation method are not limited at all, to which those
hitherto known may be appropriately adopted. For example, other
than the structure based on the use of the lateral effect of the
electric field-induced strain as shown in FIG. 3, it is possible to
appropriately adopt those having a structure based on the use of
the longitudinal effect of the electric field-induced strain as
shown in FIG. 30. No problem occurs concerning the shape of the
film. The shape of the film may be any of polygonal configurations
such as triangles and rectangles, circular configurations such as
circles, ellipses, and rings, comb-shaped configurations,
lattice-shaped configurations, and special configurations obtained
by combining the foregoing configurations.
[0218] The stacked films 18a, 18b, 18c, which are formed on the
thin-walled region 36 (64) given by the thin plate layer 26, may be
heat-treated every time when each film is formed so that the
integrated structure is established together with the thin-walled
region 36 (64). Alternatively, all of the films may be formed to
give the stacked films, and then they may be collectively
heat-treated so that the respective films may be simultaneously
joined with the thin-walled region 36 (64) in an integrated
manners. Incidentally, when the electrode film is formed by means
of the thin film formation technique, the heat treatment is not
necessarily indispensable to achieve integration in some cases.
[0219] As for the heat treatment temperature to integrate the
stacked films formed on the thin-walled region 36 (64) and the
underlying thin-walled region 36 (64), a temperature of about
800.degree. C. to 1400.degree. C. is generally adopted, and
preferably, a temperature within a range of 1000.degree. C. to
1400.degree. C. is advantageously selected. When the
piezoelectric/electrostrictive film 18b is heat-treated, it is
preferable to perform the heat treatment while controlling the
atmosphere by using an evaporation source composed of a
piezoelectric/electrostrictive material together so that the
composition of the piezoelectric/electrostrictive film 18b is not
unstable at a high temperature.
[0220] The material for the electrode films 18a, 18c for
constructing the piezoelectric/electrostrictive element 18 produced
in accordance with the foregoing method is not specifically limited
provided that the material is a conductor which can withstand the
oxidizable atmosphere at a high temperature of a degree of the heat
treatment temperature and the firing temperature. For example, the
material may be a simple substance of metal or an alloy. The
material may be a mixture of a metal or an alloy and an additive
such as an insulative ceramic and glass. Further, no problem occurs
when the material is a conductive ceramic. More appropriately, it
is preferable to use electrode materials comprising major
components of high melting point metals such as platinum,
palladium, and rhodium, and alloys such as silver-palladium,
silver-platinum, and platinum-palladium.
[0221] As for the mixture described above, it is desirable to use,
as the ceramic to be added to the metal and the alloy, the same
material as the material for constructing the thin plate layer 26
(thin-walled region) or the piezoelectric/electrostrictive material
described later on. The same material as the material for the thin
plate layer 26 is preferably added in an amount of 5 to 30% by
volume. The same material as the piezoelectric/electrostrictive
material is preferably added in an amount of about 5 to 20% by
volume. Namely, the mixtures which is obtained by mixing the metal
or the alloy described above with the material for constructing the
thin plate layer 26 or the piezoelectric/electrostrictiv- e
material, is advantageously used to form the objective electrode
film.
[0222] The electrodes 18a, 18c, which are formed by using the
material as described above, are allowed to have appropriate
thicknesses depending on the use or application. As shown in FIG.
3, in the case of the type based on the use of the lateral effect
of the electric field-induced strain, the electrode is generally
formed to have a thickness of not more than 15 .mu.m, more
preferably not more than 5 .mu.m. As shown in FIG. 30, in the case
of the type based on the use of the longitudinal effect of the
electric field-induced strain, the electrode is appropriately
formed to have a thickness of not less than 3 .mu.m, preferably not
less than 10 .mu.m, and more preferably not less than 20 .mu.m.
[0223] Any material may be used as the
piezoelectric/electrostrictive material to give the
piezoelectric/electrostrictive film 18b for constructing the
driving piezoelectric/electrostrictive elements 18A and the
detecting piezoelectric/electrostrictive elements 18B, provided
that the material exhibits the electric field-induced strain such
as the piezoelectric or electrostrictive effect. The material may
be crystalline materials, or amorphous materials. No problem occurs
when the material is any of semiconductor materials, dielectric
ceramic materials, or ferroelectric ceramic materials. The material
may be materials which require the polarization treatment, or
materials which do not require the polarization treatment.
[0224] Specifically, those preferably used as the
piezoelectric/electrostr- ictive material employed for the
vibration gyro sensors according to the first to sixth embodiments
include, for example, materials comprising a major component of
lead zirconate titanate (PZT system), materials comprising a major
component of lead magnesium niobate (PMN system), materials
comprising a major component of lead nickel niobate (PNN system),
materials comprising a major component of lead zinc niobate,
materials comprising a major component of lead manganese niobate,
materials comprising a major component of lead antimony stannate,
materials comprising a major component of lead titanate, materials
comprising a major component of barium titanate, and composite
materials thereof. No problem occurs when the material comprising
the major component of the PZT system is appropriately added with
predetermined additives to give materials, for example, those of
the PLZT system containing, as additives, oxides of lanthanum,
barium, niobium, zinc, nickel, and manganese, or other types of
compounds thereof.
[0225] It is desirable that the thickness of the
piezoelectric/electrostri- ctive element 18 constructed as
described above is generally not more than 100 .mu.m, preferably
not more than 50 .mu.m, and more preferably not more than 30
.mu.m.
[0226] It is noted that the following system may be adopted.
Namely, the relative arrangement of the driving
piezoelectric/electrostrictive elements 18A and the detecting
piezoelectric/electrostrictive elements 18B in the vibration gyro
sensors according to the first to fourth embodiments is converted
into the same relative arrangement as that in the vibration gyro
sensor according to the fifth embodiment or the modified embodiment
thereof so that the driving vibration characteristics offered by
the driving piezoelectric/electrostrictive elements 18A are
feedback-controlled to obtain prescribed characteristics while
suppressing the vibration based on the Coriolis force.
[0227] The present invention has been specifically described above
on the basis of the first to sixth embodiments (including the
respective modified embodiments). However, the present invention
should not be interpreted at all as one which is limited by the
foregoing respective embodiments. It should be understood that
various changes, modifications, and improvements may be added to
the present invention on the basis of the knowledge of those
skilled in the art without deviating from the scope of the present
invention.
* * * * *