JPH09105633A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the bonding man-hour of a metal thin wire to an electrode formed at a vibrator, to reduce the unnecessary vibration of the vibrator due to the vibration of the metal thin wire, to enhance the S/N ratio of a detection signal and to increase the detection accuracy of an angular velocity in an angular velocity sensor which is provided with the vibrator composed of a piezoelectric body. SOLUTION: The angular velocity sensor is provided with a vibrator 2 in which driving electrodes 12a, 12b, monitoring electrodes 14a, 14b and a common electrode 19 are formed on a piezoelectric body. In the angular velocity sensor, a support implement 20 by which the vibrator 2 is fixed to a base is formed out of a conductive metal, the common electrode 19 is installed so as to be extended up to the bonding face of the vibrator 2 with the support implement 20, and the common electrode 19 and the support implement 20 are electrically conducted. As a result, the number of metal thin wires used to connect the respective electrodes is reduced, the bonding man-hour is reduced, and an unnecessary vibration by the metal thin wires can be reduced. In addition, the potential of the support implement 20 and that of the base to which the implement is attached can be held at the same reference potential as the common electrode 19, and it is possible to prevent the S/N ratio of the sensor from being dropped owing to the instability of the potentials of the parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor used for vehicle control of automobiles, navigation, video camera shake prevention, and the like.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 61-2943
As disclosed in Japanese Patent No. 11, a vibration formed by forming a drive electrode for excitation, a detection electrode for vibration detection, and a ground electrode corresponding to each of these electrodes on the sidewall of a tuning fork-shaped piezoelectric body. An angular velocity sensor including a child is known.

This angular velocity sensor detects the Coriolis force received by the vibrator when an angular velocity is input, and an AC voltage (driving voltage) is applied between the drive electrode and the ground electrode to vibrate the vibrator in a predetermined direction. (Drive vibration), and at the time of this drive vibration, by detecting the vibration state in a predetermined direction orthogonal to the excitation direction of the vibrator from the current flowing between the detection electrode and the ground electrode, Coriolis force and The angular velocity can be detected.

In this type of angular velocity sensor, the sensor main body can be manufactured only by providing the above-mentioned electrodes on the side wall of the piezoelectric body forming the vibrator, so that the vibrator which is generally used conventionally is made of metal. Compared with an angular velocity sensor of the type in which a piezoelectric body is formed and joined to the surface thereof, there are advantages in that the number of parts is small and the structure and, in turn, the manufacturing process are simple.

[0005]

However, in this type of angular velocity sensor, it is necessary to form at least four or more electrodes for detecting the angular velocity, and
These electrodes cannot be formed on the same surface of the piezoelectric body, but must be formed on at least two surfaces of the piezoelectric body. Therefore, a ground electrode or a common electrode in which the ground electrode is shared by the drive electrode and the detection electrode is held at the reference potential, a drive voltage is input to the drive electrode, and a detection signal is extracted from the detection electrode. A large number of signal lines (thin metal wires) are also required for each electrode, and such a large number of thin metal wires are connected to the electrode formation surface of the vibrator.

Therefore, in the angular velocity sensor using the vibrator made of a piezoelectric material, not only the number of man-hours for joining the thin metal wires, which is the most troublesome in manufacturing the sensor, but also the unnecessary vibration of the many thin metal wires is caused. S / of detection signal
There is a problem that N (signal to noise ratio) deteriorates.

Further, in this type of angular velocity sensor,
Since the sensitivity of the detection signal is mainly determined by the strength (amplitude, frequency) of the driving vibration, it is necessary to keep the driving vibration of the vibrator constant in order to improve the S / N. For this purpose, a metal support is used to support one end of the vibrator and fix it on a predetermined base so that the energy of drive vibration does not escape to the base side through the fixed end of the vibrator. Need to be formed.

However, in the case where the support tool is made of metal as described above, when the support tool and the base to which the support tool is joined are in an electrically floating state, these parts are antennad by an external electromagnetic field. , The potential of that part becomes unstable and affects the detection signal,
There was also a problem that / N worsened.

The present invention has been made in view of these problems, and in an angular velocity sensor provided with a vibrator made of a piezoelectric material, the man-hours for joining the metal thin wires to the electrodes formed on the vibrator and the vibration of the metal thin wires are accompanied. An object of the present invention is to reduce unnecessary vibration of the vibrator and improve the S / N of the detection signal to improve the angular velocity detection accuracy.

[0010]

The invention according to claim 1 made in order to achieve the above object corresponds to a piezoelectric body, a drive electrode for excitation, a detection electrode for vibration detection, and each of these electrodes. A vibrator formed by forming a ground electrode or a common electrode, a base for fixing the vibrator at a predetermined position, and a support joined to one end of the vibrator and fixing the vibrator on the base. An angular velocity sensor including a tool, wherein at least the support tool is made of a conductive metal, and the support tool is electrically connected to a ground electrode or a common electrode of the vibrator.

As described above, in the angular velocity sensor according to the first aspect of the invention, the support member that is joined to one end of the vibrator and fixes the vibrator on the base is made of a conductive metal, and is vibrated. It is electrically connected to the ground electrode or the common electrode of the child. Therefore, in order to hold the ground electrode or the common electrode formed on the vibrator at the reference potential, the support may be set to the reference potential. It is not necessary to connect a thin metal wire for applying a potential.

Therefore, according to the present invention, it is possible to reduce the number of metal thin wires bonded to the vibrator and the number of faces of the vibrator to which the metal thin wires are bonded, and to reduce the number of steps for bonding the metal thin wires to the vibrator. . Moreover, since the number of thin metal wires bonded to the vibrator can be reduced, it is possible to reduce unnecessary vibration due to the thin metal wires, and it is possible to suppress a decrease in S / N of the detection signal due to this unnecessary vibration.

Further, when the base to which the support is fixed has conductivity, the support can be made to have the same reference potential as the ground electrode or the common electrode of the vibrator, including the base. It is also possible to prevent the peripheral potential from fluctuating due to an external electromagnetic field or the like, and the detection signal being affected thereby. Therefore, according to the present invention, the S / N ratio of the detection signal can be improved and the angular velocity detection accuracy can be increased as compared with the conventional angular velocity sensor.

Next, a second aspect of the present invention is the first aspect.
In the angular velocity sensor described in the above item 1, the ground electrode or the common electrode is extended to a bonding surface of the vibrator to which the support tool is bonded. As described above, in the angular velocity sensor according to the second aspect, since the ground electrode or the common electrode is extended to the bonding surface of the vibrator to which the support tool is bonded, when the vibrator and the support tool are bonded, , The support can be electrically connected to the ground electrode or the common electrode only by pressing and bonding the joint portion and bringing the ground electrode or the common electrode into contact with the support, and the respective portions can be electrically connected very easily. be able to.

The invention according to claim 3 is the same as claim 1
In the angular velocity sensor described in (1), a conductive protrusion capable of contacting the ground electrode or the common electrode is formed in the vicinity of the joint surface of the support to which one end of the vibrator is joined. As described above, in the angular velocity sensor according to the third aspect, since the conductive protrusion capable of contacting the ground electrode or the common electrode is formed in the vicinity of the joint surface of the support tool with the vibrator, the vibrator is formed. The support and the ground electrode or the common electrode can be electrically connected only by bringing the protrusion into contact with the ground electrode or the common electrode when the support and the support are joined.
Similar to the angular velocity sensor described in (1), it is possible to make these parts conductive very easily.

On the other hand, the invention described in claim 4 is the same as claim 1.
In the angular velocity sensor according to, the vibrator and the support member are joined by using a conductive adhesive, and by protruding the conductive adhesive from the bonding surface, through the conductive adhesive, The support is electrically connected to the ground electrode or the common electrode.

As described above, in the angular velocity sensor according to the fourth aspect, the conductive adhesive is used for joining the vibrator and the supporting member, and the conductive adhesive is extruded from the joint surface, whereby the supporting member and the ground electrode or Since it is electrically connected to the common electrode,
As described in claim 2, the ground electrode or the common electrode is extended to the joint surface of the vibrator with the support tool, or the protrusion is provided on the joint surface of the support tool as described in claim 3. In order to establish electrical connection between the support and the ground electrode or the common electrode, it is not necessary to separately process the vibrator and the support, and these parts can be electrically connected more easily.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is an explanatory view showing a configuration of a vibrator 2 of an angular velocity sensor to which the present invention is applied. (A) is a front view, (b) is a left side view, (c) is a right side view, ( d)
Is a back view and (e) is a top view.

As shown in FIG. 2, the vibrator 2 of this embodiment is
The piezoelectric body is formed into a tuning fork shape having a pair of left and right arm portions 4 and 6 and a connecting portion 8 that connects one end of each arm portion 4 and 6. The arm portions 4, 6 and the connecting portion 8 are each in the shape of a quadrangular prism. Further, a ceramic piezoelectric body such as PZT, crystal, or the like can be used as the piezoelectric body forming the vibrator 2, but the vibrator 2 of this embodiment can be manufactured by arbitrarily setting the polarization direction. Easy PZT is used.

Next, X1 which is the surface of each arm 4, 6
On the surface, as shown in FIG. 2A, from the connecting portion 8 side,
Drive electrodes 12a, 12b, monitor electrodes 14a, 14b,
Preliminary electrodes 14c and 14d, and electrode 16 for polarization treatment
2 (b) and 2 (c) are formed on the Y1 surface and the Y2 surface, which are the left and right outer side surfaces of the arm portions 4 and 6, respectively.
2, the detection electrodes 18a and 18b are formed at positions corresponding to the electrodes 16a and 16b, and the X2 surface, which is the back surface of each arm portion 4 and 6, has the drive electrodes 12a and 18b, as shown in FIG. 12b, the monitor electrodes 14a to 14d, and the common electrode 1 serving as a reference electrode for the detection electrodes 18a and 18b.
9 are formed.

Further, the drive electrodes 12a and 12b pass through the connecting portion 8 and the outer surface side (Y1, Y) of each arm portion 4, 6.
2 surface side) and the opposing surface sides of the arm portions 4 and 6 that face each other, and the monitor electrodes 14a and 14b are
Preliminary electrodes 14c and 14d are formed on the outer surface sides of the arm portions 4 and 6, respectively, and detection electrodes 18a and 18b are formed on the outer surface sides of the arm portions 4 and 6, respectively. In the Y1 surface and the Y2 surface of the above, they are respectively formed at positions deviated to the X2 surface side.

Then, the X1 surface and X of each arm 4, 6
By performing the polarization process using the electrodes provided on the two surfaces, the arm portions 4 and 6 have x-axis (see FIG. 3) orthogonal to the X1 surface and the X2 surface as shown by arrows in FIG. (Reference), and is polarized in the direction from the X1 plane to the X2 plane.

The vibrator 2 of this embodiment having the above-mentioned structure
In the above, by using the common electrode 19 as a reference potential and applying alternating voltages having phases different by 180 degrees to the drive electrodes 12a and 12b, the y-axis along the arrangement direction of the arm portions 4 and 6 (see FIG. 3). The arm portions 4 and 6 can be excited in the direction, and the excited state is monitored by the monitor electrodes 14a,
It can be monitored from the current flowing between 14b and the common electrode 19. In this state, the detection electrodes 18a,
By detecting the current flowing between 18b and the common electrode 19, it is possible to detect the vibration of each arm portion 4, 6 in the x-axis direction, and from the detection signal, the center position of each arm portion 4, 6 can be detected. At, the angular velocity Ωz about the z-axis (see FIG. 3) parallel to the arm portions 4 and 6 can be obtained. The spare electrode 1
4c and 14d are used for noise cancellation and the like.

Next, in the vibrator 2, as shown in FIG. 3, the end surface (bottom surface) 2a of the connecting portion 8 on the side opposite to the arm portions 4 and 6 is
The plate-shaped base 2 is joined to the pedestal portion 20b of the support tool 20 with an adhesive or the like, and the main body side of the support tool 20 is welded or bonded.
By fixing to the surface of No. 2, the front and back surfaces (X1 and X2 surfaces) of the vibrator 2 are fixed to the base 22 so as to be parallel to the surface of the base 22.

The support 20 is mounted on a base 22 and a vibrator 2 is attached to the main body via a vibration absorbing neck 20a.
A pedestal portion 20b for joining the
For example, it is integrally formed of a conductive metal such as SUS. The base 22 is for fixing the vibrator 2 directly to the housing of the angular velocity sensor or the vehicle body or the like for which the angular velocity is to be detected, or via a vibration-proof rubber, and is substantially conductive such as SUS. It is made of a quadrangular metal plate, and has a shape in which a hole for screwing or attaching a vibration proof rubber is formed at each of four corners.

The base 22 has drive electrodes 12a, 12b and monitor electrodes 14a, 1 formed on the vibrator 2.
4b and the detection electrodes 18a, 18b via thin metal wires L1 to L6, respectively, and six terminals 24 to 29 for relaying these electrodes and a detection circuit (not shown).
Is erected. The base 22 and the terminal 24
To 29 are electrically insulated. In addition, thin metal wire L1
To L6 are connected to corresponding electrodes and terminals 24 to 29 by soldering or the like.

By the way, in order to detect the angular velocity, it is necessary to hold the common electrode 19 formed on the back surface (X2 surface) of the vibrator 2 at a predetermined reference potential. For this purpose, for example, as shown by the dotted line in FIG. 3, a terminal 30 for the common electrode 19 is provided on the base 22, and this and the common electrode 19 are connected by a thin metal wire L7, and the terminal 30 is connected. The reference potential may be applied from the outside.

However, as described above, since the common electrode 19 is formed on the back surface of the vibrator 2, connecting the metal wire L7 for applying the reference potential to the common electrode 19 requires a lot of man-hours in mass production. There is a manufacturing problem,
The increase in the number of the metal thin wires L connected to the vibrator 2 has a characteristic problem that the S / N of the sensor deteriorates due to unnecessary vibration of the metal thin wires L. Further, when the support tool 20 and the base 22 arranged around the vibrator 2 are in an electrically floating state, these parts act as antennas by an external electromagnetic field, and the potential thereof becomes unstable. And affects the detection signal of the angular velocity using a small electric signal, and the S / N of the sensor
Was also found to worsen.

Therefore, in the present embodiment, as shown in FIG. 1B, in the vibrator 2, the common electrode 19 is connected to the supporting member 20.
To the bottom surface 2a of the vibrator 2 by wrapping around the joint surface (that is, the bottom surface 2a of the vibrator 2) bonded to the base portion 20b of
An electrode 19a formed by extending the common electrode 19 is formed, and FIG.
As shown in (a), when the vibrator 2 and the support tool 20 are joined, the joint portion is pressure-bonded to form the common electrode 1
9 and the support 20 (then the base 22) are electrically connected.

As a result, according to the angular velocity sensor of this embodiment, the common electrode 19 can be held at the reference potential by connecting the base 22 to, for example, the ground terminal held at the reference potential in the detection circuit. , Common electrode 19
It is not necessary to connect a thin metal wire for applying a reference potential to.

Therefore, according to the present embodiment, the number of the metal thin wires L bonded to the vibrator 2 and the number of faces of the vibrator 2 bonded to the metal thin wires L are reduced so that the metal The number of man-hours for joining thin wires can be reduced. Moreover, since the number of the metal thin wires L bonded to the vibrator 2 can be reduced, it is possible to reduce unnecessary vibration due to the metal thin wires L, and it is possible to suppress a decrease in S / N of the detection signal due to the unnecessary vibration. Furthermore, since the support tool 20 and the base 22 can be set to the reference potential, the potentials of these parts do not fluctuate and affect the detection signal, and the S / N of the detection signal is improved to improve the angular velocity. The detection accuracy can be improved.

An adhesive may be used to bond the vibrator 2 and the support 20 to each other. For this adhesive, an adhesive having a small damping coefficient after curing, for example, an epoxy thermosetting adhesive is used. It is desirable to use an adhesive or the like. Here, in the above-described embodiment, the common electrode 19 is extended on the bottom surface 2a of the vibrator 2 so that the common electrode 19 and the support tool 20 are electrically connected, but for example, as shown in FIG. As described above, the conductive adhesive 32 is used for joining the vibrator 2 and the support tool 20,
At the time of joining, the conductive adhesive 32 may be intentionally squeezed out to the back surface side on which the common electrode 19 is formed, so that the common electrode 19 and the support 20 are electrically connected. Then, in this way, the vibrator 2 and the support 20
The common electrode 19 and the supporting member 20 can be electrically connected to each other without performing any special processing for electrically connecting the common electrode 19 and the supporting member 20, and the same effect as that of the above-described embodiment can be obtained.

Further, for example, the vibrator 2 and the supporting member 20 are once joined with an adhesive or the like, and then a conductive adhesive or a conductive paste is applied and solidified, so that the common electrode 19 and the supporting member are made of these conductive materials. You may make it electrically connect with 20. In this case, although the work process for electrically connecting the common electrode 19 and the support tool 20 is increased, the common electrode 19 and the support tool 20 can be more reliably electrically connected, and
The same effects as in the above embodiment can be obtained.

Further, for example, as shown in FIG. 4 (b), the pedestal portion 20b of the support 20 is made of the same material as the support 20,
It is also possible to form a protrusion 20c that can come into contact with the common electrode 19 when the vibrator 2 is joined, and to electrically connect the common electrode 19 and the support tool 20 via this protrusion 20c. In this case, it is necessary to form the protrusion 20c on the support tool 20, but since the protrusion 20c can hold a part of the side wall of the vibrator 2, the support tool 20 can further support the vibrator 2. It can be firmly supported, and the same effect as in the above embodiment can be obtained.

Further, the common electrode 19 and the supporting tool 20 are further provided.
If the above-described methods are combined in order to make the electrical connection between and, the common electrode 19 and the support tool 20 can be electrically connected more reliably. The angular velocity sensor using the tuning-fork-shaped vibrator 2 has been described above as an example of the present invention. However, the angular velocity sensor includes a long vibrator in which electrodes for driving and detecting are formed on a rod-shaped piezoelectric body. However, the same effects as those of the above-described embodiment can be obtained by applying the present invention.

Further, in the above embodiment, the angular velocity sensor for detecting the angular velocity is explained by using the vibrator 2 having a common electrode common to the respective electrodes as the ground electrode for the drive electrode and the detection electrode. As shown in 5,
A tuning fork-shaped piezoelectric body composed of a pair of arm portions 4'and 6'and a connecting portion 8'for connecting them is provided, and a drive electrode 41 and a ground electrode 42 corresponding thereto are provided on one arm portion 6'side. And an angular velocity sensor for detecting the angular velocity by using a pair of detection electrodes 43, 44 on the side of the other arm 4 ′ and a vibrator 2 ′ having ground electrodes 45, 46 corresponding to the detection electrodes 43, 44. By applying the present invention, it is possible to obtain the same effect as that of the above embodiment.

That is, in this angular velocity sensor, as shown in FIG. 5 (a), a driving AC voltage VD is applied between the drive electrode 41 and the ground electrode 42, and one arm portion of the vibrator 2'is applied. The vibrator 2'is vibrated in the y-axis direction from the 6'side, and the detection electrodes 43, 44 and the ground electrode 4 provided on the other arm 4 '
By detecting the change in the current flowing between the armature 5 and 46 as a detection signal Vs, the vibration state of the arm portion 6'in the x-axis direction, and thus the angular velocity Ωz around the z-axis, is detected (Japanese Patent Laid-Open No. 61- 29431 (see FIG. 4), even in an angular velocity sensor equipped with such a vibrator 2 ',
As shown in FIG. 5 (b), a supporting member 50 for supporting the vibrator 2'and fixing it to a predetermined base is made of a conductive metal, and a pedestal portion 50b thereof has a bottom surface 2a of the vibrator 2 '. If the ground electrodes 42, 45, 46 on the side of the vibrator 2'and the pedestal portion 50b of the supporting member 50 are electrically connected to each other when joining the ', the same effect as that of the above embodiment can be obtained. The pedestal portion 50b is similar to the above embodiment in that the neck portion 5 is attached to the main body of the support tool 50.
It is provided via 0a.

Then, in order to make the respective ground electrodes 42, 45, 46 and the supporting member 50 electrically conductive, as in the above embodiment, as shown in FIG. 5 (c), the bottom surface 2a 'of the vibrator 2'is shown.
Electrodes 42a, 4 having ground electrodes 42, 45, 46 extended to
5a and 46a are respectively formed, and the electrode vibrator 2'and the support 5 are formed.
0 may be pressure-bonded to each other, and as shown in FIG. 5D, the vibrator 2 ′ and the supporting member 50 may be bonded to each other with the conductive adhesive 5.
2 and the conductive adhesive 52 may be protruded to the outside so that the ground electrodes 42, 45, 46 and the supporting member 50 are electrically connected to each other at the time of the bonding, as shown in FIG. As shown, each ground electrode 42, 45, 46 of the pedestal 50b
At the position corresponding to each ground electrode 42, 45, 46 at the time of joining.
The protrusions 50c, 50e, 50d that can come into contact with each other may be formed respectively, or these methods may be combined.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a method for joining a vibrator and a support according to an embodiment.

FIG. 2 is an explanatory view showing a state where the vibrator of the embodiment is viewed from the front, back, left and right, and from above.

FIG. 3 is a perspective view showing a state in which the vibrator of the example is joined to a base via a support.

FIG. 4 is an explanatory diagram illustrating a method of conducting the common electrode formed on the vibrator and the support tool.

FIG. 5 is an explanatory diagram illustrating a method of conducting the plurality of ground electrodes formed on the vibrator and the support tool.

[Explanation of symbols]

2 ... Transducer 2a ... Bottom surface 4, 6 ... Arm portion 8
... Connecting portions 12a, 12b, 41 ... Driving electrode 19 ... Common electrode
19a ... Electrodes 18a, 18b, 43, 44 ... Detection electrodes 42, 4
5, 46 ... Ground electrode 20, 50 ... Supporting tool 20a, 50a ... Neck 20
b, 50b ... Pedestal part 20c, 50c, 50d, 50e ... Protrusion part 22 ... Base 24-29 ... Terminal 32, 52 ... Conductive adhesive L1-L6 ... Metal fine wire

Claims (4)

[Claims] 1. A vibrator comprising a piezoelectric body on which a drive electrode for excitation, a detection electrode for vibration detection, and a ground electrode or a common electrode corresponding to each of these electrodes are formed, and the vibrator is provided at a predetermined position. An angular velocity sensor comprising: a base for fixing to the base and a supporting member joined to one end of the vibrator to fix the vibrator on the base, wherein at least the supporting member is made of a conductive metal. The angular velocity sensor is formed by electrically connecting the supporting member to the ground electrode or the common electrode of the vibrator. 2. The angular velocity sensor according to claim 1, wherein the ground electrode or the common electrode is extended to a bonding surface of the vibrator to which the supporting member is bonded. 3. A conductive protrusion capable of contacting the ground electrode or the common electrode is formed in the vicinity of a joint surface of the supporting member to which one end of the vibrator is joined.
The angular velocity sensor described in. 4. The support is joined to the vibrator via the conductive adhesive by bonding the vibrator and the support using a conductive adhesive and allowing the conductive adhesive to protrude from the bonding surface. The angular velocity sensor according to claim 1, wherein a tool is electrically connected to the ground electrode or the common electrode.