Patent Application
20120125100
The present invention relates to a vibrating gyroscope including a piezoelectric film, in other words, a gyroscope utilizing vibrations, or an angular velocity sensor. More specifically, the present invention relates to a vibrating gyroscope that is capable of measuring variations in maximally triaxial angular velocity.
In recent years, there have been intensely developed vibrating gyroscopes including a piezoelectric material, in other words, gyroscopes utilizing vibrations, or angular velocity sensors. Conventionally developed is a gyroscope including a vibrating body that itself is made of a piezoelectric material, as disclosed in Patent Document 1. There is also a gyroscope including a piezoelectric film that is formed on a vibrating body. For example, Patent Document 2 discloses a technique for, by using a PZT film as a piezoelectric material, exciting a primary vibration of a vibrating body as well as for detecting partial deformation of a gyroscope, which is caused by a coriolis force generated to the vibrating body when an angular velocity is applied to the vibrating body.
Reduction in size of a gyroscope itself is also an important issue because a wide variety of devices including gyroscopes have been quickly reduced in size. In order to realize the reduction in size of a gyroscope, significant improvement is required to accuracy in processing each member of the gyroscope. Desired in the industry will be not only simple size reduction but also further improvement in performance of a gyroscope, namely, in accuracy of detecting an angular velocity. However, the configuration of the gyroscope disclosed in Patent Document 2 fails to satisfy the demands over the last few years for reduction in size and improvement in performance.
In view of the above technical issues, the applicant of the present invention has proposed a technical idea of performing all the manufacturing steps basically as dry processes so as to realize high processing accuracy as well as to satisfy the demand for high performance as a vibrating gyroscope (Patent Document 3).
In addition to the above technical issues, expectations are being increased for a vibrating gyroscope that also measures an angular velocity of multi rotational axes (Patent Document 4, for example). Nevertheless, satisfactory development has not yet been made to a vibrating gyroscope that has a simple and useful configuration to realize reduction in size.
As described above, it is very difficult to achieve reduction in size and high processing accuracy in a vibrating gyroscope including a piezoelectric film as well as to satisfy the demand for improvement in performance of the gyroscope. A gyroscope of a small size generally has a defect that, upon application of an angular velocity to a vibrating body, weakened is a signal to be detected by a detection electrode of the gyroscope. Therefore, in such a small vibrating gyroscope, the difference is decreased between the signal to be essentially detected and a signal generated due to a sudden external impact (disturbance), which results in difficulty in improving detection accuracy as a gyroscope.
There are various types of external impacts that are received suddenly. For example, the vibrating body in a ring shape, which is disclosed in Patent Document 2 already referred to, receives an impact that causes seesaw-like motions, about a fixed post at the center of the ring serving as an axis thereof, in a direction perpendicular to a plane including the ring. This impact excites a vibration in what is called a rocking mode. There is another impact by which the entire periphery of a ring-shaped member of the vibrating body supported by the fixed post is simultaneously bent upward or downward from the plane including the ring. This impact excites a vibration in what is called a bounce mode. It is quite difficult to achieve a technique for accurately detecting an angular velocity even in cases where the vibrating gyroscope receives some of these impacts.
The present invention solves the above technical problems to significantly contribute to reduction in size and improvement in performance of a vibrating gyroscope that includes a piezoelectric film and is capable of measuring an angular velocity of a single or multi rotational axes, in other words, a gyroscope utilizing vibrations, or an angular velocity sensor. The inventors initially worked on one of the above technical problems and adopted a vibrating gyroscope in a ring shape as a basic configuration, which is recognized as receiving a relatively small influence of a disturbance. The inventors then studied intensively to obtain a configuration for solving the respective technical problems by causing the piezoelectric film to excite a primary vibration as well as to detect a secondary vibration that is generated by a coriolis force. Found as a result is that accurate measurement of an angular velocity of a single rotational axis as well as an angular velocity of each of multi rotational axes is enabled by refining disposition of respective types of electrodes as well as electrical processing with use of the electrodes, even in a case with input causing an impact. Each of the electrodes of respective types causes the vibrating body to vibrate with use of the piezoelectric film or extracts, as a signal, deformation of the vibrating body with use of the piezoelectric film. Moreover, the inventors found out that, by devising the processing of an electrical signal related to the secondary vibration generated upon application of an angular velocity to the vibrating gyroscope, an S/N ratio is remarkably increased in comparison to the conventional cases, with no deterioration in responsiveness. The present invention was created in view of such a philosophy. It is noted that, in the present application, an “annular or polygonal vibrating gyroscope” is sometimes simply referred to as a “ring-shaped vibrating gyroscope”.
A vibrating gyroscope according to the present invention includes: a ring-shaped vibrating body having a uniform plane; leg portions flexibly supporting the ring-shaped vibrating body; a plurality of electrodes disposed on the plane of or above the ring-shaped vibrating body, and formed with at least one of an upper-layer metallic film and a lower-layer metallic film; and a piezoelectric film being sandwiched between the upper-layer metallic film and the lower-layer metallic film in a thickness direction thereof. Further, the plurality of electrodes include
Moreover, the driving electrodes are each disposed in the plane of the ring-shaped vibrating body and on a first electrode disposition portion that has at least one of a region from an outer peripheral edge of the ring-shaped vibrating body to a vicinity of the outer peripheral edge and a region from an inner peripheral edge thereof to a vicinity of the inner peripheral edge, and the detection electrodes and the suppression electrodes are each disposed on a second electrode disposition portion and are not electrically connected to any one of the driving electrodes.
In this vibrating gyroscope, since a piezoelectric element is formed as an electrode in the specific region described above on the plane of the ring-shaped vibrating body, the vibrating gyroscope functions as a uniaxial angular velocity sensor and is capable of exciting the primary vibration as well as detecting the secondary vibration. In other words, this vibrating gyroscope is configured to excite the primary vibration in a plane identical with the plane (an X-Y plane, for example) including the piezoelectric element on the ring-shaped vibrating body (hereinafter, also referred to as in plane) as well as to control the motions of the ring-shaped vibrating body, with no piezoelectric element being formed on a side surface of the ring-shaped vibrating body. As a result, it is possible to fabricate the electrodes and the ring-shaped vibrating body with a high degree of accuracy in accordance with the dry process technique. Further, it is recognized as significantly advantageous that this vibrating gyroscope is capable of detecting a uniaxial (the X axis, for example) angular velocity by adopting a vibration mode not in the plane including the piezoelectric element (hereinafter, also referred to as an out-of-plane vibration mode). Several examples of the vibration mode of cos Nθ are disclosed, for example, in Patent Documents 4 to 6 cited above or in Japanese Patent Application No. 2007-209014 that was filed by the applicant of the present application. The term “flexible” is used to mean “so as to allow the vibrating body to vibrate” in the entire invention of the present application. The present application also includes the expression “(angularly) apart from” an electrode as a reference, in order to recite the disposition of each electrode. The angle in this case refers to a value of an azimuth of each electrode, assuming that the reference electrode has an azimuth equal to zero degree. The azimuth of each electrode can be set as an azimuth of a linear line from an arbitrary point defined at the center portion of the circumference or of the annular shape of the ring-shaped vibrating body (for example, in a case where the ring-shaped vibrating body has a circular shape, the center of the circle or the like; hereinafter, this center is referred to as a “reference point”) to the corresponding electrode. This linear line can be arbitrarily defined such as to pass through each electrode. This linear line can be typically defined so as to include the reference point as well as the graphic center, the center of gravity, or one of vertices of each electrode. For example, an electrode disposed 30° apart from a reference driving electrode is to be located such that the center of this electrode and the center of the reference driving electrode form an angle of 30° from the azimuth of the reference electrode. Unless otherwise specified, angles are recited in a manner that values of the angles increase clockwise. However, even with an assumption that the values of the angles increase counterclockwise, the angles recited in such a manner fall within the scope of the present invention as long as these angles satisfy the conditions defined herein.
A different vibrating gyroscope according to the present invention includes: a ring-shaped vibrating body having a uniform plane; leg portions flexibly supporting the ring-shaped vibrating body; a plurality of electrodes disposed on the plane of or above the ring-shaped vibrating body, and formed with at least one of an upper-layer metallic film and a lower-layer metallic film; and a piezoelectric film being sandwiched between the upper-layer metallic film and the lower-layer metallic film in a thickness direction thereof. Further, the plurality of electrodes include
Moreover, the driving electrodes are each disposed in the plane of the ring-shaped vibrating body and on a first electrode disposition portion that has at least one of a region from an outer peripheral edge of the ring-shaped vibrating body to a vicinity of the outer peripheral edge and a region from an inner peripheral edge thereof to a vicinity of the inner peripheral edge, and the detection electrodes and the suppression electrodes are each disposed on a second electrode disposition portion and are not electrically connected to any one of the driving electrodes.
Also in this vibrating gyroscope, since a piezoelectric element is formed as an electrode in the specific region described above on the plane of the ring-shaped vibrating body, the vibrating gyroscope functions as a uniaxial angular velocity sensor and is capable of exciting the primary vibration as well as detecting the secondary vibration. In other words, this vibrating gyroscope is configured to excite the primary vibration in a plane identical with the plane (an X-Y plane, for example) including the piezoelectric element on the ring-shaped vibrating body as well as to control the motions of the ring-shaped vibrating body, with no piezoelectric element being formed on a side surface of the ring-shaped vibrating body. As a result, it is possible to fabricate the electrodes and the ring-shaped vibrating body with a high degree of accuracy in accordance with the dry process technique. Further, it is recognized as significantly advantageous that this vibrating gyroscope is capable of detecting a uniaxial (the Y axis, for example) angular velocity by adopting an out-of-plane vibration mode.
A different vibrating gyroscope according to the present invention includes: a ring-shaped vibrating body having a uniform plane; leg portions flexibly supporting the ring-shaped vibrating body; a plurality of electrodes disposed on the plane of or above the ring-shaped vibrating body, and formed with at least one of an upper-layer metallic film and a lower-layer metallic film; and a piezoelectric film being sandwiched between the upper-layer metallic film and the lower-layer metallic film in a thickness direction thereof. Further, the plurality of electrodes include
Moreover, the driving electrodes are each disposed in the plane of the ring-shaped vibrating body and on a first electrode disposition portion that has at least one of a region from an outer peripheral edge of the ring-shaped vibrating body to a vicinity of the outer peripheral edge and a region from an inner peripheral edge thereof to a vicinity of the inner peripheral edge, and the detection electrodes and the suppression electrodes are each disposed on a second electrode disposition portion and are not electrically connected to the first electrode disposition portion.
Also in this vibrating gyroscope, since a piezoelectric element is formed as an electrode in the specific region described above on the plane of the ring-shaped vibrating body, the vibrating gyroscope functions as a uniaxial angular velocity sensor and is capable of exciting the primary vibration as well as detecting the secondary vibration. In other words, this vibrating gyroscope is configured to excite the primary vibration in a plane identical with the plane (an X-Y plane, for example) including the piezoelectric element on the ring-shaped vibrating body as well as to control the motions of the ring-shaped vibrating body, with no piezoelectric element being formed on a side surface of the ring-shaped vibrating body. As a result, it is possible to fabricate the electrodes and the ring-shaped vibrating body with a high degree of accuracy in accordance with the dry process technique. Further, it is recognized as significantly advantageous that this vibrating gyroscope is capable of detecting a uniaxial (the X axis, for example) angular velocity by adopting an out-of-plane vibration mode.
A different vibrating gyroscope according to the present invention includes: a ring-shaped vibrating body having a uniform plane; leg portions flexibly supporting the ring-shaped vibrating body; a plurality of electrodes disposed on the plane of or above the ring-shaped vibrating body, and formed with at least one of an upper-layer metallic film and a lower-layer metallic film; and a piezoelectric film being sandwiched between the upper-layer metallic film and the lower-layer metallic film in a thickness direction thereof. The plurality of electrodes include
Moreover, the driving electrodes are each disposed in the plane of the ring-shaped vibrating body and on a first electrode disposition portion that has at least one of a region from an outer peripheral edge of the ring-shaped vibrating body to a vicinity of the outer peripheral edge and a region from an inner peripheral edge thereof to a vicinity of the inner peripheral edge, and the detection electrodes and the suppression electrodes are each disposed on a second electrode disposition portion and are not electrically connected to the first electrode disposition portion.
Also in this vibrating gyroscope, since a piezoelectric element is formed as an electrode in the specific region described above on the plane of the ring-shaped vibrating body, the vibrating gyroscope functions as a uniaxial angular velocity sensor and is capable of exciting the primary vibration as well as detecting the secondary vibration. In other words, this vibrating gyroscope is configured to excite the primary vibration in a plane identical with the plane (an X-Y plane, for example) including the piezoelectric element on the ring-shaped vibrating body as well as to control the motions of the ring-shaped vibrating body, with no piezoelectric element being formed on a side surface of the ring-shaped vibrating body. As a result, it is possible to fabricate the electrodes and the ring-shaped vibrating body with a high degree of accuracy in accordance with the dry process technique. Further, it is recognized as significantly advantageous that this vibrating gyroscope is capable of detecting a uniaxial (the Y axis, for example) angular velocity by adopting an out-of-plane vibration mode.
A different vibrating gyroscope according to the present invention includes: a ring-shaped vibrating body having a uniform plane; leg portions flexibly supporting the ring-shaped vibrating body; a plurality of electrodes disposed on the plane of or above the ring-shaped vibrating body, and formed with at least one of an upper-layer metallic film and a lower-layer metallic film; and a piezoelectric film being sandwiched between the upper-layer metallic film and the lower-layer metallic film in a thickness direction thereof. The plurality of electrodes include
Moreover, the driving electrodes are each disposed in the plane of the ring-shaped vibrating body and on a first electrode disposition portion that has at least one of a region from an outer peripheral edge of the ring-shaped vibrating body to a vicinity of the outer peripheral edge and a region from an inner peripheral edge thereof to a vicinity of the inner peripheral edge, and the first detection electrodes, the second detection electrodes, the first suppression electrodes, and the second suppression electrodes are each disposed on a second electrode disposition portion and are not electrically connected to any one of the driving electrodes.
In this vibrating gyroscope, since a piezoelectric element is formed as an electrode in the specific region described above on the plane of the ring-shaped vibrating body, the vibrating gyroscope functions as a biaxial angular velocity sensor and is capable of exciting the primary vibration as well as detecting the secondary vibration. In other words, this vibrating gyroscope is configured to excite the primary vibration in a plane identical with the plane (an X-Y plane, for example) including the piezoelectric element on the ring-shaped vibrating body as well as to control the motions of the ring-shaped vibrating body, with no piezoelectric element being formed on a side surface of the ring-shaped vibrating body. As a result, it is possible to fabricate the electrodes and the ring-shaped vibrating body with a high degree of accuracy in accordance with the dry process technique. Further, it is recognized as significantly advantageous that this vibrating gyroscope is capable of detecting a biaxial (each of the X axis and the Y axis, for example) angular velocity by adopting an out-of-plane vibration mode.
In order to detect an angular velocity with respect to still another axis, when one of the driving electrodes is referred to as a reference driving electrode and S is equal to 0, 1, . . . , N, the detection electrodes, which detect a secondary vibration in a vibration mode of cos(N+1)θ generated when an angular velocity is applied to the ring-shaped vibrating body, and which are disposed at least any of [{360/(N+1)}×S]° apart from the reference driving electrode and [{360/(N+1)}×{S+(½)}]° apart from the reference driving electrode, are referred to as first detection electrodes. Further, the suppression electrodes, which are disposed at any angles detailed above, are referred to as first suppression electrodes, and the secondary vibration is referred to as the first secondary vibration. In this case, the plurality of electrodes further include the following (4), and the second detection electrodes and second suppression electrodes can be each disposed on the second electrode disposition portion:
Similarly, in order to detect an angular velocity of a different axis, when one of the driving electrodes is referred to as a reference driving electrode and S is equal to 0, 1, . . . , N, the detection electrodes, which detect a secondary vibration in a vibration mode of cos(N+1)θ generated when an angular velocity is applied to the ring-shaped vibrating body, and which are disposed at least any of [{360/(N+1)}×{S+(¼)}]° apart from the reference driving electrode and [{360/(N+1)}×{S+(¾)}]° apart from the reference driving electrode, are referred to as second detection electrodes. Further, the suppression electrodes, which are disposed at any angles detailed above, are referred to as second suppression electrodes, and the secondary vibration is referred to as a second secondary vibration. In this case, the plurality of electrodes further include the following (4), and first detection electrodes and the first suppression electrodes can be each disposed on the second electrode disposition portion:
A different vibrating gyroscope according to the present invention includes: a ring-shaped vibrating body having a uniform plane; leg portions flexibly supporting the ring-shaped vibrating body; a plurality of electrodes disposed on the plane of or above the ring-shaped vibrating body, and formed with at least one of an upper-layer metallic film and a lower-layer metallic film; and a piezoelectric film being sandwiched between the upper-layer metallic film and the lower-layer metallic film in a thickness direction thereof. The plurality of electrodes include
Moreover, the driving electrodes are each disposed in the plane of the ring-shaped vibrating body and on a first electrode disposition portion that has at least one of a region from an outer peripheral edge of the ring-shaped vibrating body to a vicinity of the outer peripheral edge and a region from an inner peripheral edge thereof to a vicinity of the inner peripheral edge, and
In this vibrating gyroscope, since a piezoelectric element is formed as an electrode in the specific region described above on the plane of the ring-shaped vibrating body, the vibrating gyroscope functions as a biaxial angular velocity sensor and is capable of exciting the primary vibration as well as detecting the secondary vibration. In other words, this vibrating gyroscope is configured to excite the primary vibration in a plane identical with the plane (an X-Y plane, for example) including the piezoelectric element on the ring-shaped vibrating body as well as to control the motions of the ring-shaped vibrating body, with no piezoelectric element being formed on a side surface of the ring-shaped vibrating body. As a result, it is possible to fabricate the electrodes and the ring-shaped vibrating body with a high degree of accuracy in accordance with the dry process technique. Further, it is recognized as significantly advantageous that this vibrating gyroscope is capable of detecting a biaxial (each of the X axis and the Y axis, for example) angular velocity by adopting an out-of-plane vibration mode.
A different vibrating gyroscope according to the present invention includes: a ring-shaped vibrating body having a uniform plane; leg portions flexibly supporting the ring-shaped vibrating body; a plurality of electrodes disposed on the plane of or above the ring-shaped vibrating body, and formed with at least one of an upper-layer metallic film and a lower-layer metallic film; and a piezoelectric film being sandwiched between the upper-layer metallic film and the lower-layer metallic film in a thickness direction thereof. The plurality of electrodes include
Moreover, the driving electrodes are each disposed in the plane of the ring-shaped vibrating body and on a first electrode disposition portion that has at least one of a region from an outer peripheral edge of the ring-shaped vibrating body to a vicinity of the outer peripheral edge and a region from an inner peripheral edge thereof to a vicinity of the inner peripheral edge,
the first detection electrodes and the second detection electrodes are each disposed on a second electrode disposition portion and are not electrically connected to any one of the driving electrodes, and
the third detection electrodes and the suppression electrodes are each disposed on the first electrode disposition portion and are not electrically connected to any one of the driving electrodes.
A different vibrating gyroscope according to the present invention includes: a ring-shaped vibrating body having a uniform plane; leg portions flexibly supporting the ring-shaped vibrating body; a plurality of electrodes disposed on the plane of or above the ring-shaped vibrating body, and formed with at least one of an upper-layer metallic film and a lower-layer metallic film; and a piezoelectric film being sandwiched between the upper-layer metallic film and the lower-layer metallic film in a thickness direction thereof. The plurality of electrodes include
Moreover, the driving electrodes are each disposed in the plane of the ring-shaped vibrating body and on a first electrode disposition portion that has at least one of a region from an outer peripheral edge of the ring-shaped vibrating body to a vicinity of the outer peripheral edge and a region from an inner peripheral edge thereof to a vicinity of the inner peripheral edge,
the first detection electrodes and the second detection electrodes are each disposed on a second electrode disposition portion and are not electrically connected to any one of the driving electrodes, and
the third detection electrodes and the suppression electrodes are each disposed on the first electrode disposition portion and are not electrically connected to any one of the driving electrodes.
In each of these vibrating gyroscopes, since a piezoelectric element is formed as an electrode in the specific region described above on the plane of the ring-shaped vibrating body, the vibrating gyroscope functions as a triaxial angular velocity sensor and is capable of exciting the primary vibration as well as detecting the secondary vibration. In other words, this vibrating gyroscope is configured to excite the primary vibration in a plane identical with the plane (an X-Y plane, for example) including the piezoelectric element on the ring-shaped vibrating body, to detect and suppress the secondary vibration of the ring-shaped vibrating body in the plane, as well as to detect the motions of the ring-shaped vibrating body in a direction not included in the plane, with no piezoelectric element being formed on a side surface of the ring-shaped vibrating body. As a result, it is possible to fabricate the electrodes and the ring-shaped vibrating body with a high degree of accuracy in accordance with the dry process technique. Further, this vibrating gyroscope is capable of detecting a biaxial (each of the X axis and the Y axis, for example) angular velocity by adopting an out-of-plane vibration mode. Moreover, detection can be made by the feedback of suppressing the secondary vibration generated by an angular velocity about the Z axis, and both the S/N ratio and the responsiveness are advantageously maintained at high levels.
Further, it is a preferred aspect to add monitor electrodes configured according to (8) described below to the plurality of electrodes of the above uniaxial, biaxial, or triaxial vibrating gyroscope, since the disposition of other electrode groups and/or the metal tracks is facilitated in a limited planar region of a ring-shaped vibrating body that is particularly reduced in size:
In a vibrating gyroscope according to the present invention, since a piezoelectric element is formed as an electrode in the specific region described above on the plane of the ring-shaped vibrating body, the vibrating gyroscope functions as a uniaxial and/or triaxial angular velocity sensor and is capable of exciting the primary vibration, detecting the secondary vibration, as well as suppressing at least the uniaxial secondary vibration. In other words, this vibrating gyroscope is configured to excite the primary vibration in a plane identical with the plane (an X-Y plane, for example) including the piezoelectric element on the ring-shaped vibrating body as well as to control the motions of the ring-shaped vibrating body, with no piezoelectric element being formed on a side surface of the ring-shaped vibrating body. As a result, it is possible to fabricate the electrodes and the ring-shaped vibrating body with a high degree of accuracy in accordance with the dry process technique. This vibrating gyroscope is capable of detecting a uniaxial to triaxial angular velocity by adopting a detector for a secondary vibration inclusive of an out-of-plane vibration mode.
Embodiments of the present invention are described below in detail with reference to the accompanying drawings. In this disclosure, common parts are denoted by common reference symbols in all the drawings unless otherwise specified. Further, in these drawings, the elements of these embodiments are not necessarily illustrated in accordance with the same scale.
As shown in
In the present embodiment, a primary vibration of the ring-shaped vibrating gyroscope 100 is excited in an in-plane vibration mode of cos 2θ as indicated in
Thus, the plurality of electrodes 13a to 13h are categorized as follows. Firstly, two driving electrodes 13a, 13a are disposed 180° apart from each other in a circumferential direction. In a case where one of the above two driving electrodes 13a, 13a (for example, the driving electrode 13a disposed in the direction of twelve o'clock in
The ring-shaped vibrating gyroscope 100 is further provided with second detection electrodes 13d, 13e that are disposed 30°, 90°, 150°, 210°, 270°, and 330° respectively apart from the reference electrode in the circumferential direction. Each of the second detection electrodes 13d, 13e detects a secondary vibration generated when an angular velocity about the Y axis is applied. In addition, third detection electrodes 13f, 13g are disposed, each of which detects a secondary vibration generated when an angular velocity about the Z axis, that is, an axis perpendicular to the plane on which the ring-shaped vibrating gyroscope 100 shown in
In the present embodiment, the lower-layer metallic film 30 and the upper-layer metallic film 50 are 100 nm thick, respectively, and the piezoelectric film 40 is 3 μm thick. Further, the silicon substrate 10 is 100 μm thick.
In the present embodiment and other embodiments to be described later, there are two categorized portions in which the respective electrodes are disposed. One of the portions is referred to as a first electrode disposition portion, in which the driving electrodes 13a and the third detection electrodes 13f, 13g are respective disposed. The first electrode disposition portion includes a region from the outer peripheral edge of the upper surface of the ring-shaped vibrating body 11 to the vicinity of the outer peripheral edge and/or a region from the inner peripheral edge thereof to the vicinity of the inner peripheral edge. Another one of the two portions is referred to as a second electrode disposition portion, in which the first detection electrodes 13b, the first suppression electrodes 13j, the second detection electrodes 13d, 13e, and the third detection electrodes 13f, 13g are disposed. The second electrode disposition portion is located on the upper surface of the ring-shaped vibrating body 11 so as not to be electrically connected to the first electrode disposition portion. More specifically, the first detection electrodes 13b, the first suppression electrodes 13j, the second detection electrodes 13d, 13e, and the third detection electrodes 13f, 13g are disposed so as not to be electrically connected to any one of the two driving electrodes 13a, 13a.
A second structural portion includes leg portions 15, . . . , 15 that are each connected to a part of the ring-shaped vibrating body 11. These leg portions 15, . . . , 15 are also formed with the silicon substrate 10. Formed on the entire upper surfaces of the leg portions 15, . . . , 15 are the silicon oxide film 20, the lower-layer metallic film 30, and the piezoelectric film 40 described above, which are provided continuously to the portions of the respective films on the ring-shaped vibrating body 11. Further formed on the upper surface of the piezoelectric film 40 is the upper-layer metallic film 50 which configures metal tracks 14, . . . , 14 of approximately 8 μm wide.
In the present embodiment, the plurality of metal tracks 14 are formed on four leg portions 15, . . . , 15 out of the sixteen leg portions 15, . . . , 15. These metal tracks 14 are formed to obtain paths to electrode pads 18 on a post 19 from the respective electrodes that are disposed in the region from the outer peripheral edge of the ring-shaped vibrating body 11 to the vicinity of the outer peripheral edge. Particularly in the present embodiment, the metal tracks 14, 14 are provided from both ends of each of the second detection electrodes 13d, 13e so as to eliminate variations in electrical signals from the second detection electrodes 13d, 13e. The function of the vibrating gyroscope is not affected even in a case where the metal tracks 14, 14 are provided only from either of the ends of the respective second detection electrodes 13d, 13e.
A third structural portion includes the post 19 that is formed with the silicon substrate 10 provided continuously to the portions of the above leg portions 15, . . . , 15. In the present embodiment, the post 19 is connected to a package portion (not shown) of the ring-shaped vibrating gyroscope 100 and serves as a fixed end. The post 19 is provided with the electrode pads 18, . . . , 18. As shown in
Described next with reference to
Firstly, as shown in
The upper-layer metallic film 50 is then partially etched. In the present embodiment, there is formed a known resist film on the upper-layer metallic film 50, and dry etching is then performed on the basis of a pattern formed in accordance with the photolithographic technique, so that the respective electrodes shown are formed as in
Thereafter, as shown in
Then, as shown in
In the present embodiment, the resist film is formed to be approximately 4 μm thick so that the silicon oxide film 20 and the silicon substrate 10 are then continuously etched with the above resist film having formed again serving as an etching mask. However, even in a case where this resist film disappears during etching the silicon substrate 10, the selectivity of the etching rate relative to an etchant applied to the silicon substrate 10 functions advantageously. Therefore, the performance of any one of the upper-layer metallic film 50, the piezoelectric film 40, and the lower-layer metallic film 30 is not substantially affected by the above etching. In other words, in the present embodiment, since the ring-shaped vibrating body 11 is formed with the silicon substrate, it is possible to apply the known silicon trench etching technique with an adequately high selectivity also relative to the resist film. Even in a case where the resist film disappears, there is provided an adequate selectivity such that the upper-layer metallic film or the piezoelectric film layered therebelow serves as a mask for etching silicon.
Thereafter, as shown in
As described above, the silicon substrate 10 and the respective films laminated on the silicon substrate 10 are etched to form the principal structure of the ring-shaped vibrating gyroscope 100. Subsequently performed are the step of accommodating the principal structure into the package by known means as well as the step of wiring. As a result, there is obtained the ring-shaped vibrating gyroscope 100. Therefore, this vibrating gyroscope 100, which has no piezoelectric element on a side surface of the ring-shaped vibrating body 11, realizes excitation of an in-plane primary vibration as well as detection of maximally triaxial out-of-plane and in-plane secondary vibrations only with use of the piezoelectric element formed on the plane of the ring-shaped vibrating body 11. As a result, it is possible to manufacture the vibrating gyroscope 100 in accordance with the above dry process technique that realizes low cost mass production with a high degree of accuracy.
Described next are the functions of the respective electrodes included in the ring-shaped vibrating gyroscope 100. As already described, excited in the present embodiment is a primary vibration in an in-plane vibration mode of cos 2θ. Because the fixed potential electrode 16 is grounded, the lower-layer metallic film 30, which is provided continuously to the portion on the fixed potential electrode 16, is uniformly set to 0 V.
As shown in
Then, each of the monitor electrodes 13h, 13h shown in
After the excitation of the primary vibration described above, upon application of an angular velocity about the perpendicular axis (the Z axis), in the present embodiment in the in-plane vibration mode of cos 2θ, generated by a coriolis force is a secondary vibration indicated in
This secondary vibration is detected by the two detection electrodes (third detection electrodes) 13f, 13f as well as by the two other detection electrodes (third detection electrodes) 13g, 13g. In the present embodiment, as shown in
Then, obtained in an arithmetic circuit functioning as a known difference circuit are differences between the electrical signals of the respective third detection electrodes 13f, 13g. Resulting detection signals of this case have approximately doubled detectability in comparison to the case with only one type of the detection electrodes.
Described below is a case where an angular velocity is applied about the X axis after the excitation of the primary vibration described above. Excited in this case is a secondary vibration in a vibration mode of cos 3θ as indicated in
This secondary vibration is detected by the three detection electrodes (first detection electrodes) 13b, 13b, 13b. In the present embodiment, as shown in
In the present embodiment, the respective detection electrodes 13b are formed outside or inside the center line in the upper surface of the ring-shaped vibrating body 11. However, the embodiments of the present invention are not limited to such a case. In different disposition of electrodes according to another aspect, the detection electrode 13b disposed in the direction of twelve o'clock out of the three detection electrodes 13b, 13b, 13b shown in
In further different disposition of electrodes according to still another aspect, the respective detection electrodes 13b can be disposed so as to include the center line in the plane of the ring-shaped vibrating body 11. This is one of more preferred aspects in comparison to the disposition of electrodes according to the above aspect because the piezoelectric film is least deformed by the in-plane primary vibration or the secondary vibration with respect to the Z axis.
Electrical signals of the respective detection electrodes 13b are detected by a known circuit that is capable of detecting voltages. In this case, the ring-shaped vibrating gyroscope 100 according to the present embodiment includes a first feedback control circuit 62 for suppressing a secondary vibration. The first feedback control circuit 62 instructs or controls to apply a voltage to each of the first suppression electrodes 13j, so as to cancel the voltage signals related to the secondary vibration detected by these first detection electrodes 13b, in other words, in order to set the values of these voltage signals to zero. The value of the voltage applied to each of the first suppression electrodes 13j, or a value corresponding to the voltage is used as a resultant output of the vibrating gyroscope on an angular velocity about the X axis. It is noted that, in the present application, the vibration axis has an azimuth that allows the recited vibration to have a largest amplitude, and such an azimuth is indicated by a direction on the ring-shaped vibrating body. In an exemplary case of the secondary vibration indicated in
Described below is a case where an angular velocity is applied about the Y axis after the excitation of the primary vibration described above. Excited in this case is a secondary vibration in a vibration mode of cos 3θ as indicated in
This secondary vibration is detected by the three detection electrodes (second detection electrodes) 13d, 13d, 13d as well as by the three other detection electrodes (second detection electrodes) 13e, 13e, 13e. In the present embodiment, as shown in
Thus, similarly to the above case, obtained in an arithmetic circuit functioning as a known difference circuit are differences between the electrical signals of the respective detection electrodes 13d, 13e. Resulting detection signals of this case have approximately doubled detectability in comparison to the case with only one type of the detection electrodes.
In the present embodiment, the first suppression electrodes 13j are provided for suppressing a secondary vibration on the basis of voltage signals outputted from the first detection electrodes 13b. The first feedback control circuit 62 for suppressing a secondary vibration applies, to each of the first suppression electrodes 13j, an electrical signal for suppressing a secondary vibration. Accordingly, the ring-shaped vibrating gyroscope 100 can exert the performance as a vibrating gyroscope with almost no secondary vibration being caused to the ring-shaped vibrating body 11 by an angular velocity about the X axis, in other words, a secondary vibration in a mode such as indicated in
In the first embodiment described above, for the purpose of easier description, the detection electrodes are referred to as the first detection electrodes to the third detection electrodes, each of which detects one axial component of a triaxial angular velocity to be detected. Alternatively, the detection electrodes for the respective axes may be each arbitrarily referred to as one of the first detection electrode to the third detection electrode so as to be differentiated from one another.
Described next is modification (1) of the first embodiment with reference to
The ring-shaped vibrating gyroscope 110 according to this modification includes third suppression electrodes 13p for suppressing a secondary vibration generated when an angular velocity about the Z axis is applied. It is noted that the ring-shaped vibrating gyroscope 110 does not include the first suppression electrodes 13j of the ring-shaped vibrating gyroscope 100 in the embodiment shown in
In the ring-shaped vibrating gyroscope 110, the third suppression electrodes 13p are disposed 135° and 315° respectively apart in the circumferential direction from the reference electrode disposed in the direction of twelve o'clock in the figure. These third suppression electrodes 13p respectively replace the third detection electrodes 13g that are included in the ring-shaped vibrating gyroscope 100 shown in
The third feedback control circuit 64 for suppressing a secondary vibration instructs or controls to apply a voltage to each of the third suppression electrodes 13p, so as to cancel the voltage signals related to the secondary vibration detected by the third detection electrodes 13f, in other words, in order to set the values of these voltage signals to zero. The value of the voltage applied to each of the third suppression electrodes 13p, or a value corresponding to the voltage is used as a resultant output of the vibrating gyroscope on an angular velocity about the Z axis.
In the case of this modification, similarly to the suppression of the secondary vibration in accordance with an angular velocity about the X axis in the first embodiment described above, suppressed is the secondary vibration (the secondary vibration indicated in
Described next is modification (2) of the first embodiment with reference to
Described first is disposition of electrodes on the plane of the ring-shaped vibrating body 11 in the ring-shaped vibrating gyroscope 120 according to this modification, by referring to arrangements modified from the ring-shaped vibrating gyroscope 100 according to the embodiment shown in
In the ring-shaped vibrating gyroscope 120 according to this modification, in addition to the first feedback control circuit 62 that is connected to the first suppression electrodes 13j and suppresses a secondary vibration, the third feedback control circuit 64 for suppressing a secondary vibration is connected to the third suppression electrodes 13p as in the ring-shaped vibrating gyroscope 110. There is further provided a second feedback control circuit 63 that is connected to the second suppression electrodes 13m and suppresses a secondary vibration. The first feedback control circuit 62 for suppressing a secondary vibration and the third feedback control circuit 64 for suppressing a secondary vibration operate similarly to those of the ring-shaped vibrating gyroscope 100 and the ring-shaped vibrating gyroscope 110, respectively.
The second feedback control circuit 63 for suppressing a secondary vibration instructs or controls to apply a voltage to each of the second suppression electrodes 13m, so as to cancel the voltage signals related to the secondary vibration detected by the second detection electrodes 13d (the secondary vibration indicated in
In this modification, an operation for the suppression of a secondary vibration is exerted with respect to an angular velocity about any one of the X, Y, and Z axes. Therefore, both the S/N ratio and the responsiveness can be maintained with respect to the angular velocity about an axis in an arbitrary direction.
The ring-shaped vibrating gyroscope 300 according to the present embodiment is configured identically with the ring-shaped vibrating gyroscope 100 of the first embodiment, except for the upper-layer metallic film 50 in the first embodiment. The manufacturing method therefor is identical with that of the first embodiment except for some steps. Further, the vibration modes of the primary vibration and the secondary vibration in the present embodiment are identical with those of the first embodiment. Accordingly, the description duplicating with that of the first embodiment will not be repeatedly provided.
As shown in
In this case, the second suppression electrode 13m is connected with the second feedback control circuit (not shown) for suppressing a secondary vibration. The second feedback control circuit for suppressing a secondary vibration receives a signal outputted from the second detection electrode 13d. The second feedback control circuit for suppressing a secondary vibration instructs or controls to apply a voltage to the second suppression electrode 13m in accordance with the output from the second detection electrode 13d, so as to cancel the voltage signals related to the secondary vibration (the secondary vibration indicated in
It is a preferred aspect in the present embodiment that the first detection electrodes 13b, 13c are disposed so as to include the center line, as in the ring-shaped vibrating gyroscope 300. This aspect is preferred because the piezoelectric film is least deformed by the primary vibration in the in-plane vibration mode and the secondary vibration. Furthermore, it is a more preferred aspect to dispose the respective first detection electrodes 13b, 13c so as to be symmetrical with respect to the center line, in which state each of the first detection electrodes 13b, 13c is deformed in directions opposite to each other with respect to the center line in the in-plane vibration mode.
Even in a case where the plurality of first detection electrodes 13b, 13c are not disposed symmetrically with respect to the center line, the respective first detection electrodes 13b, 13c may be disposed in various ways so as to be unlikely to detect a vibration in an in-plane vibration mode in accordance with the vibration mode to be adopted. Accordingly, as described earlier, the second electrode disposition portion including the respective detection electrodes 13b, 13c, 13d, 13m is defined as a portion on the upper surface of the ring-shaped vibrating body 11 not electrically connected to the first electrode disposition portion.
In the present embodiment, each of the first detection electrodes 13b, 13c occupies an area larger than that of the first embodiment. Each of the first detection electrodes 13b, 13c is preferably disposed symmetrically with respect to its vibration axis of the secondary vibration (the secondary vibration indicated in
Because the respective electrodes of the present embodiment are eccentrically located, some of the leg portions 15 are not provided with the metal tracks 14. However, the present invention is not limited to such a case. Effects similar to those of the present embodiment are exerted even in a case where the leg portion 15 not provided with the metal track 14 is removed. However, random absence of the leg portion 15 may cause an irregular vibration of the ring-shaped vibrating body 11. It is therefore preferred to remove only the leg portions 15 that are allocated at equal angles.
The ring-shaped vibrating gyroscope 310 according to the present embodiment is configured identically with the ring-shaped vibrating gyroscope 100 of the first embodiment, except for the upper-layer metallic film 50 in the first embodiment. In particular, the first detection electrode 13c in the ring-shaped vibrating gyroscope 300 is replaced with the first suppression electrode 13j. Accordingly, the first suppression electrode 13j is connected with the first feedback control circuit (not shown) for suppressing a secondary vibration. The first feedback control circuit for suppressing a secondary vibration receives a signal outputted from the first detection electrode 13b. The first feedback control circuit for suppressing a secondary vibration instructs or controls to apply a voltage to the first suppression electrode 13j in accordance with the output from the first detection electrode 13b, so as to cancel the voltage signals related to the secondary vibration (the secondary vibration indicated in
As shown in
Described above in each of the first embodiment and the modifications (1) to (5) thereof is the configuration of the vibrating gyroscope that is capable of detecting a triaxial angular velocity and includes the suppression electrodes for suppressing a secondary vibration with respect to the angular velocity about one, two, and three axes. Also obtained from the first embodiment is the disposition of respective detection electrodes for detecting a biaxial or uniaxial angular velocity.
For example, when only the first detection electrodes 13b, 13c used for measuring an angular velocity about the X axis and the second detection electrodes 13d, 13e used for measuring an angular velocity about the Y axis, out of the first to third detection electrodes 13b, 13c, 13d, 13e, 13f, 13g, are disposed on the ring-shaped vibrating body 11, manufactured is a vibrating gyroscope for detection of a biaxial angular velocity. More specifically, it is possible to obtain the vibrating gyroscope for detection of a biaxial angular velocity by selecting the detection electrodes with respect to two axes out of the first to third detection electrodes. Further, only one type (for example, the first detection electrode 13b) out of the first detection electrodes 13b, 13c may be disposed on the ring-shaped vibrating body 11, and the first suppression electrode 13j may be provided. In this case, with use of the output from the first detection electrode 13b, it is possible to suppress a secondary vibration generated by an angular velocity about the X axis.
An idea similar to the above is applicable to the configuration of a vibrating gyroscope that is capable of detecting a uniaxial angular velocity. For example, when only the first detection electrode 13b used for measuring an angular velocity about the X axis, out of the first to third detection electrodes 13b, 13c, 13d, 13e, 13f, 13g, is disposed on the ring-shaped vibrating body 11, manufactured is a vibrating gyroscope for detecting a uniaxial angular velocity. Similarly, a secondary vibration can be suppressed by the first suppression electrode 13j.
In comparison to the first embodiment, the ring-shaped vibrating gyroscope 500 according to the present embodiment is provided with a fixed end 60 around the ring-shaped vibrating body 11 by way of grooves or leg portions 17. Formed on the leg portions 17 and the fixed end 60 are the electrode pads 18 and the metal tracks 14 that are drawn from the driving electrodes 13a, 13a and the second detection electrodes 13d, 13e. Further, due to the provision of the metal tracks 14 on the leg portions 17, there are not provided the metal tracks 14 and the electrode pads 18 on the leg portions 15 and the fixed end 19, respectively. The ring-shaped vibrating gyroscope 500 according to the present embodiment is configured identically with that of the first embodiment except for the above points. The manufacturing method therefor is identical with that of the first embodiment except for some steps. The vibration modes of the primary vibration and the secondary vibration in the present embodiment are identical with those of the first embodiment. Accordingly, the description duplicating with that of the first embodiment will not be repeatedly provided. In the present embodiment, alternating-current power supplies to be connected with the driving electrodes 13a, 13a are not illustrated for easier comprehension of the figure.
Due to the provision of the fixed end 60 and the leg portions 17 connecting the fixed end 60 and the ring-shaped vibrating body 11 in the ring-shaped vibrating gyroscope 500 of the present embodiment, it is unnecessary to dispose the plurality of metal tracks 14 on the leg portions 15 inside the ring-shaped vibrating body 11. Thus remarkably decreased are risks of short circuiting among the metal tracks due to some defect in the manufacturing steps or the like. As shown in
The ring-shaped vibrating gyroscope 500 thus configured also includes the first suppression electrodes 13j, thereby achieving suppression of a secondary vibration generated by an angular velocity about the X axis.
The ring-shaped vibrating gyroscope 600 according to the present embodiment is configured identically with the ring-shaped vibrating gyroscope 100 of the first embodiment except for the disposition of the driving electrodes 13a, the monitor electrodes 13h, the first detection electrodes 13b, the first suppression electrodes 13j, and some of the detection electrodes out of the second detection electrodes 13d, 13e and the third detection electrodes 13f, 13g in the first embodiment, as well as the disposition and the number of the alternating-current power supplies 12. The manufacturing method therefor is identical with that of the first embodiment. Accordingly, the description duplicating with that of the first embodiment will not be repeatedly provided. However, the primary vibration in the present embodiment has an in-plane vibration mode of cos 3θ as indicated in
As shown in
In the present embodiment, excited to the ring-shaped vibrating gyroscope 600 is a primary vibration in an in-plane vibration mode of cos 3θ. On the other hand, a secondary vibration in the present embodiment has vibration modes indicated in
Described below are the functions of the respective electrodes included in the ring-shaped vibrating gyroscope 600. As described earlier, excited in the present embodiment is a primary vibration in the in-plane vibration mode of cos 3θ. Because the fixed potential electrode 16 is grounded, the lower-layer metallic film 30, which is provided continuously to the portion on the fixed potential electrode 16, is uniformly set to 0 V.
Firstly, as shown in
Then, each of the monitor electrodes 13h, 13h, 13h shown in
After the excitation of the primary vibration described above, upon application of an angular velocity about the perpendicular axis (the Z axis), in the present embodiment in the in-plane vibration mode of cos 3θ, generated by a coriolis force is a secondary vibration indicated in
This secondary vibration is detected by the three detection electrodes (third detection electrodes) 13f, 13f, 13f as well as by the three other detection electrodes (third detection electrodes) 13g, 13g, 13g. In the present embodiment, similarly to the first embodiment, obtained in an arithmetic circuit functioning as a known difference circuit are differences between the electrical signals of the respective third detection electrodes 13f, 13g. Resulting detection signals of this case have approximately doubled detectability in comparison to the case with only one type of the detection electrodes.
Described below is a case where an angular velocity is applied about the X axis after the excitation of the primary vibration described above. Excited in this case is the secondary vibration in the out-of-plane vibration mode of cos 2θ indicated in
This secondary vibration is detected by the two detection electrodes (first detection electrodes) 13b. Output signals therefrom are received by the first feedback control circuit (not shown) for suppressing a secondary vibration, while each of the first suppression electrodes 13j receives an output from the first feedback control circuit for suppressing a secondary vibration. In the present embodiment, as shown in
Because of the disposition of the two first detection electrodes 13b in the present embodiment, the two first detection electrodes 13b generate electrical signals theoretically having completely identical waveforms, in accordance with the out-of-plane secondary vibration excited upon the application of an angular velocity. Nevertheless, in an actual ring-shaped vibrating gyroscope, erroneous alignment is caused in any way between the pattern in the formation of the respective electrodes and the pattern in the formation of the ring-shaped vibrating body 11. In such a case, the first detection electrode 13b disposed in the direction of twelve o'clock and the first detection electrode 13b disposed in the direction of six o'clock are shifted in directions opposite to each other with respect to the ring-shaped vibrating body 11. For example, if the first detection electrode 13b in the direction of twelve o'clock is shifted toward the outer peripheral edge of the ring-shaped vibrating body 11, the first detection electrode 13b in the direction of six o'clock is shifted toward the inner peripheral edge thereof. Accordingly, these first detection electrodes are shifted so as to cancel each other the displacement in position, particularly in the radial direction of the ring, on the plane of the ring-shaped vibrating body 11. This is a preferred feature because, upon extracting paralelly connected electrical signals to be detected by the first detection electrodes 13b, 13b, absolute values of the outputs will be less likely to be affected by the erroneous alignment.
Described below is a case where an angular velocity is applied about the Y axis after the excitation of the primary vibration described above. Excited in this case is the secondary vibration in the vibration mode of cos 2θ indicated in
This secondary vibration is detected by the two detection electrodes (second detection electrodes) 13d, 13d as well as by the two other detection electrodes (second detection electrodes) 13e, 13e. In the present embodiment, as shown in
Because of the disposition of the respective detection electrodes 13d, 13e in the present embodiment, the detection electrodes 13d, 13e generate electrical signals of positive/negative polarities inverse to each other in accordance with the out-of-plane secondary vibration excited upon application of an angular velocity. Thus, obtained in an arithmetic circuit functioning as a known difference circuit are differences between the electrical signals of the respective detection electrodes 13d, 13e. Resulting detection signals of this case have approximately doubled detectability in comparison to the case with only one type of the detection electrodes.
In the first embodiment described above, for the purpose of easier description, the detection electrodes are referred to as the first detection electrodes to the third detection electrodes, each of which detects one axial component of a triaxial angular velocity to be detected. Alternatively, the detection electrodes for the respective axes may be each arbitrarily referred to as one of the first detection electrode to the third detection electrode so as to be differentiated from one another.
Described next is modification (1) of the second embodiment with reference to
The ring-shaped vibrating gyroscope 610 according to this modification includes the third suppression electrodes 13p, 13p, 13p for suppressing a secondary vibration generated when an angular velocity about the Z axis is applied. It is noted that the ring-shaped vibrating gyroscope 610 does not include the first suppression electrodes 13j of the ring-shaped vibrating gyroscope 600 in the embodiment shown in
In the ring-shaped vibrating gyroscope 610, the third suppression electrodes 13p are disposed 90°, 210°, and 330° respectively apart in the circumferential direction from the reference electrode disposed in the direction of twelve o'clock in the figure. These third suppression electrodes 13p respectively replace the third detection electrodes 13g that are included in the ring-shaped vibrating gyroscope 600 shown in
The third feedback control circuit for suppressing a secondary vibration instructs or controls to apply a voltage to each of the third suppression electrodes 13p, so as to cancel the voltage signals related to the secondary vibration detected by the third detection electrodes 13f, in other words, in order to set the values of these voltage signals to zero. The value of the voltage applied to each of the third suppression electrodes 13p, or a value corresponding to the voltage is used as a resultant output of the vibrating gyroscope on an angular velocity about the Z axis.
In the case of this modification, similarly to the suppression of the secondary vibration in accordance with an angular velocity about the X axis in the first embodiment described above, suppressed is the secondary vibration (the secondary vibration indicated in
Described next is modification (2) of the second embodiment with reference to
Described is disposition of electrodes on the plane of the ring-shaped vibrating body 11 in the ring-shaped vibrating gyroscope 620 according to this modification, by referring to arrangements modified from the ring-shaped vibrating gyroscope 600 according to the embodiment shown in
Also in the ring-shaped vibrating gyroscope 620 according to this modification, the first, second, and third feedback control circuits for suppressing a secondary vibration are connected to the first, second, and third suppression electrodes 13j, 13m, and 13p, respectively. the first, second, and third feedback control circuits for suppressing a secondary vibration receive signals outputted from the first, second, and third detection electrodes 13b, 13d, and 13f, respectively. In this configuration, a voltage is applied to each of the first, second, and third suppression electrodes so as to cancel the voltage signals related to the secondary vibrations (the secondary vibrations indicated in
In each of the first embodiment and the modifications (1) to (7) thereof as well as the second embodiment and the modifications (1) and (2) thereof, the monitor electrodes 13h, 13h are disposed at the identical positions or in the identical regions. However, the embodiments of the present invention are not limited to such a case. When N is a natural number of 2 or more or a natural number of 3 or more, and M is equal to 0, 1, . . . , N−1 (hereinafter, always true in this paragraph), in a case where one of the driving electrodes 13a is referred to as a reference driving electrode, the monitor electrodes 13h are not necessarily disposed [(360/N)×{M+(½)}]° apart from the reference driving electrode 13a in the circumferential direction. For example, in a vibration mode of cos Nθ, when L is equal to 0, 1, . . . , 2N−1 (hereinafter, always true in this paragraph), the monitor electrodes 13h are disposed so as not to be (180/N)×{L+(½)}° apart from the reference driving electrode in the circumferential direction, or are disposed so as not to be axisymmetrical with respect to the above angular positions. Moreover, the respective monitor electrodes 13h are disposed so as not to be symmetrical with respect to the center line in the width direction of the ring. Because of the disposition of the respective monitor electrodes 13h, the effects of the first embodiment or any one of the modifications thereof are substantially exerted.
One specific example of the above case is a ring-shaped vibrating gyroscope 700 shown in
Another example of the above case is a ring-shaped vibrating gyroscope 720 shown in
Still another example of the above case is a ring-shaped vibrating gyroscope 740 shown in
Further, a different example of the above case is a ring-shaped vibrating gyroscope 760 shown in
Moreover, a different example of the above case is a ring-shaped vibrating gyroscope 780 shown in
As shown in each of the examples described above, in any one of the ring-shaped vibrating gyroscopes according to the present invention, excited is a primary vibration in the in-plane vibration mode. Thus, the monitor electrodes may be disposed on the plane of the ring-shaped vibrating body 11 with a high degree of flexibility. However, for example, in a vibration mode of cos Nθ, when L is equal to 0, 1, . . . , 2N−1 (hereinafter, always true in this paragraph), the respective monitor electrodes 13h are disposed so as not to be (180/N)×{L+(½)}° apart from the reference driving electrode in the circumferential direction, or are disposed so as not to be axisymmetrical with respect to the above angular positions. The monitor electrodes are not disposed at such former positions since deformation of the ring-shaped vibrating body 11 is eliminated (zero) at the former positions. The monitor electrodes are not disposed at such latter positions since the electrodes are deformed in directions opposite to each other so as to cancel the deformations each other. Moreover, the respective monitor electrodes 13h are disposed so as not to be symmetrical with respect to the center line. The monitor electrodes are not disposed at such positions since the monitor electrodes are deformed in directions opposite to each other so as to cancel the deformations each other at the positions. In a limited planar region of the ring-shaped vibrating body 11 that is particularly reduced in size, the disposition of the monitor electrodes 13h as in the first embodiment will facilitate the disposition of the other electrode groups and/or the metal tracks. More specifically, when N is a natural number of 2 or more or a natural number of 3 or more and M is equal to 0, 1, . . . , N−1 (hereinafter, always true in this paragraph), in a case where one of the driving electrodes 13a is referred to as a reference driving electrode, it is a preferred aspect to dispose the monitor electrodes 13h so as to be [(360/N)×{M+(½)}]° apart from the reference driving electrode 13a in the circumferential direction.
Described with reference to
In the ring-shaped vibrating body 11 of the ring-shaped vibrating gyroscope 900, the electrodes are disposed also in the planar region including the center line. In the annular portion of the ring-shaped vibrating body, the electrodes are disposed in three regions, namely, the region from the inner peripheral edge to the vicinity of the inner peripheral edge, the region including the center line, and the region from the outer peripheral edge to the vicinity of the outer peripheral edge. In this ring-shaped vibrating gyroscope 900, suppressed is a secondary vibration generated by an angular velocity about every one of the X, Y, and Z axes.
In the disposition described above, the driving electrodes 13a, the monitor electrodes 13h, the third detection electrodes 13f, and the third suppression electrodes 13p, which are related to an in-plane vibration (an exited vibration, that is, a secondary vibration generated by an angular velocity about the Z axis), can be disposed in the region from the inner peripheral edge to the vicinity of the inner peripheral edge and the region from the outer peripheral edge to the vicinity of the outer peripheral edge. On the other hand, the first and second detection electrodes 13b, 13d, and the first and second suppression electrodes 13j, 13m, which are related to an out-of-plane vibration (a secondary vibration generated by an angular velocity about each of the X and Y axes), can be disposed in the region including the center line. Therefore, in the ring-shaped vibrating gyroscope 900 shown in
Such disposition allows the electrodes to be expanded, in other words, expands the lengths of the electrodes in the angular direction. Therefore, a primary vibration can be exited easily, and a secondary vibration generated by an angular velocity about the Z axis can be detected and suppressed easily. Therefore, both the S/N ratio and the responsiveness are advantageously maintained at high levels in the detection of an angular velocity about each of the X and Y axes, as well as the detection of an angular velocity about the Z axis.
Applicable to the second embodiment are respective modifications similarly to those of the first embodiment as described above. Therefore, there are exerted advantageous effects in accordance with the respective configurations thereof.
Each of the embodiments described above refers to the vibrating gyroscope including the ring-shaped vibrating body. However, the ring-shaped vibrating body may be replaced with a polygonal vibrating body. There are exerted effects substantially similar to those of the present invention even with use of a vibrating body in a regular polygonal shape such as a regular hexagonal shape, a regular octagonal shape, a regular dodecagonal shape, or a regular icosagonal shape. Further alternatively, there may be adopted a vibrating body such as a dodecagonal vibrating body 111 of a ring-shaped vibrating gyroscope 800 shown in
Moreover, adopted in each of the embodiments described above is the ring-shaped vibrating gyroscope that is mainly made of silicon. However, the present invention is not limited to such a case. Alternatively, the base material for the vibrating gyroscope may be germanium or silicon germanium, for example. By particularly adopting silicon or silicon germanium among the above materials, it is possible to apply the known anisotropic dry etching technique, which leads to significant contribution to the improvement in processing accuracy of the entire gyroscope including the vibrating body.
In each of the embodiments described above, the upper-layer metallic film is patterned to form the respective electrodes. However, the present invention is not limited to this case. There will be exerted effects similar to those of the present invention even in a case where only the lower-layer metallic film, or both the upper-layer metallic film and the lower-layer metallic film, are patterned to form the respective electrodes. Nevertheless, in view of the facilitation in the manufacturing steps, it is a preferred aspect to pattern only the upper-layer metallic film as in each of the embodiments described above. As having been described so far, modifications made within the scope of the present invention, inclusive of other combinations of the respective embodiments, will be also included in the scope of the patent claims.
The present invention is applicable, as a vibrating gyroscope, to portions of various types of devices.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-173972 | Jul 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/058096 | 5/13/2010 | WO | 00 | 1/26/2012 |
