JP2000249556A - Triangular prismatic tripod tuning fork oscillator and angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the angular velocity detecting accuracy of an oscillator sensor. SOLUTION: Three regular triangular posts A, B, C are cut from piezoelectric elements 2, 3 each having a bimorph structure slightly chamfered at the top and arranged in a direction to form two pairs of tuning forks, exciting electrodes 4, 5 commonly using a Coriolis detection electrode are disposed on two adjacent faces of the regular triangular post, two monitor electrodes 6 serving as exciting electrodes are disposed on the other one face, and a sandwich electrode 7 is disposed on a bimorph intermediate surface. A voltage is applied to the exciting electrodes 4, 5 of the posts A, C to detect the Coriolis force from the electrodes 4, 5 of the post B wherein because the post B bends in the reverse direction to the posts A, C, the angular moment exerted on a fixed part due to the Coriolis force can be cancelled to raise the angular velocity detection accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrator and an angular velocity sensor for detecting an angular velocity, and more particularly to an angular velocity sensor effective for a vehicle navigation system and a vehicle body control system.

[0002]

2. Description of the Related Art FIG. 9 shows the structure of a conventional angular velocity sensor. In FIG. 9A, a U-shaped metal diaphragm 10
1 has two metal plates 102 and 102 ′ arranged at right angles to the upper portion of the U-shaped metal plate 101, a piezoelectric element 106 for excitation is provided on one surface of the U-shaped metal plate 101, and a monitor device is provided on the other surface. The piezoelectric element 107 and the metal plates 102 and 102 'are respectively connected to the Coriolis detecting piezoelectric elements 108 and 108'.
Is attached to the piezoelectric elements 106 and 107 at right angles to the tuning fork vibrator 103, and the base 105 is fixed via a fixed shaft 104.
It is fixed to. Piezoelectric elements 106, 107, 108,
108 ′ are lead wires 109, 110, and 11, respectively.
Lead pins 114, 115, 11
6,117. Lead pins 114 and 11
5, 116, 117 are insulators 1 such as glass.
18 and is electrically insulated from the base 105.

Next, the operation of the angular velocity sensor will be described. FIG. 9A shows the excitation state of the sensor.
(B) shows a state in which the Coriolis force of the sensor is detected. That is, in FIG. 9A, the tuning fork vibrator 103
By applying a voltage to the piezoelectric element 106 for excitation, 11
Tuning forks are excited in nine directions. The excitation frequency and the amplitude are monitored by the monitor piezoelectric element 107,
The voltage applied to the excitation piezoelectric element 106 is controlled so that excitation is always performed at a constant frequency and amplitude. When a rotational angular velocity ω is applied to the detection axis 120 of this sensor in the 121 direction as shown in FIG. 9B, Coriolis force generated in a direction perpendicular to the excitation direction 119 causes the metal plates 102, 10.
2 ′ bends in directions 122 and 123 opposite to each other. The Coriolis force FC generated at this time is FC = 2 mVω
Becomes m: mass of the tuning fork vibrator 103 V: excitation speed ω: applied rotational angular speed This Coriolis force FC is determined by the detection piezoelectric elements 108, 10
In order to generate distortions in opposite directions of expansion and contraction at 8 ′, the detection voltage is applied as a differential output to the lead pins 115,
117.

[0004]

However, the above-mentioned conventional angular velocity sensor has the following problems. 1) When the angular velocity ω is generated, Coriolis force is applied to the vibrator 103 and the vibrator 103 is moved in the direction (122, 122) in FIG.
Since the rotational moment 124 generated by the bending of the rotary shaft 123) is applied to the rotary shaft 104, the degree of fixation of the rotary shaft 104, the base 105, and the tuning fork vibrator 103 may cause a variation in the angular velocity detection accuracy of the sensor. . 2) The excitation piezoelectric element 106, the monitoring piezoelectric element 107, and the detection piezoelectric elements 108 and 108 'are the tuning fork vibrator 1
Since each of the metal plates 101, 102, and 102 'constituting the substrate 03 is bonded using an adhesive, variations in bonding and temperature characteristics of the adhesive may cause variations in sensor angular velocity detection accuracy. 3) In the excitation direction and the Coriolis detection direction, the tuning fork vibrator 1
Since the shapes of the metal plates 101, 102, and 102 'constituting 03 do not match, it is difficult to match the resonance frequency at the time of excitation with the resonance frequency at the time of Coriolis detection, and it is therefore difficult to increase the detection sensitivity. That is, it is difficult to make the resonance type angular velocity sensor as shown in FIG.
As a result, the sensitivity becomes lower than that of the resonance type. 4) Bending accuracy of tuning fork type vibrator 103, fixed shaft 104
Accuracy of fixing the tuning fork vibrator 103 and the base 105,
In addition, variations in assembly processing accuracy, such as the bonding accuracy of the piezoelectric elements 106, 107, 108, and 108 ', cause variations in the angular velocity detection accuracy of the sensor. 5) Since the lead wires 109, 110, 112, and 113 are connected to the vibrating body, the deflection of the lead wires 109, 110, 112, and 113 causes variation in the angular velocity detection accuracy of the sensor. An object of the present invention is to solve the problems related to the angular velocity sensor described above.

[0005]

According to the present invention, the following means are taken to solve the above-mentioned problems. 1) A tripod tuning fork structure is adopted to cancel the rotational moment applied to the fixed portion when Coriolis occurs, and the variation in the fixed degree of the fixed portion does not affect the angular velocity detection accuracy. 2) By forming the vibrator with a piezoelectric cut-out structure, the piezoelectric element itself can be made into a vibrator, and the detection sensitivity of the sensor is improved by eliminating the adhesive portion. 3) By adopting a tripod tuning fork structure composed of a regular triangular prism, an electrode is formed at an opposite position of 60 °, thereby sharing the excitation electrode and the detection electrode, thereby improving the angular velocity detection sensitivity. 4) Resonance frequency f01 at the time of excitation and resonance frequency f0 at the time of Coriolis detection by adopting a tuning fork structure of a regular triangular prism.
2 can be brought close to each other, and a resonance type angular velocity sensor has been realized to improve the detection sensitivity. According to the present invention, a high-sensitivity and small-sized angular velocity sensor can be realized by effectively implementing the above means.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, three triangular pillars each composed of a piezoelectric element having a bimorph structure with a chamfered apex are arranged in the directions constituting two pairs of tuning forks, respectively. With the adjacent two of the triangular columns
An angular velocity characterized by arranging an excitation electrode sharing a Coriolis detection electrode on each of two surfaces, arranging two monitor electrodes also serving as an excitation electrode on another surface, and arranging a sandwich electrode on a bimorph intermediate surface. This is a triangular prism tripod tuning fork vibrator for detection, and has a tripod tuning fork structure, so the rotational moment when Coriolis force is generated can be canceled, vibration loss can be minimized, and the influence on the detection accuracy of the fixed part can be eliminated. Therefore, angular velocity detection can be realized with high accuracy. .

According to a second aspect of the present invention, there is provided a triangular prism tripod tuning fork vibrator according to the first aspect, wherein three triangular columns are cut out from a plate-shaped piezoelectric element having a bimorph structure. By forming the vibrator with the piezoelectric cutout structure, the piezoelectric element itself can be made into a vibrator, and the detection sensitivity of the sensor can be improved by eliminating the adhesive portion.

According to a third aspect of the present invention, the triangular prism tripod according to the first or second aspect, wherein each electrode arranged on each surface of the triangular shape is led out to one side of the triangular prism base. Since it is a tuning fork vibrator and the connection of the signal line is performed not by the vibrator but by a fixed part, the detection accuracy can be stabilized without affecting the detection accuracy.

According to a fourth aspect of the present invention, there is provided a tripodal tripod tuning fork resonator according to the first, second or third aspect, wherein the arrangement pitch of the three triangular prisms is 1: 1 or 2: 1. And the two tuning forks can vibrate with maximum efficiency.

According to a fifth aspect of the present invention, each of the excitation electrodes is connected to one of the poles of a drive power source, and two triangular prism monitor electrodes at both ends of the arranged triangular prisms are connected to the other end of the drive power source. 5. The method according to claim 1, wherein the electrode is connected to one of the poles, the monitor electrode of the middle triangular prism is connected to another power supply terminal, and the sandwich electrode is polarized to a lower potential than each of the excitation electrodes. This is a triangular prism tripod tuning fork vibrator as described, which can excite the Coriolis detection axis from both sides, so that the amplitude can be amplified and a highly sensitive angular velocity sensor can be realized.

The invention according to claim 6 of the present invention is the triangular prism tripod tuning fork vibrator according to any one of claims 1 to 5, wherein the three triangular prisms are equilateral triangular prisms, which are easy to manufacture and stable in performance. Angular velocity sensor can be realized.

According to a seventh aspect of the present invention, a fixing portion of the triangular prism tripod tuning fork vibrator according to any one of the first to sixth aspects is fixed to a base with a leaf spring and is insulated on the base. The lead pin and each electrode of the triangular prism tripod tuning fork vibrator are connected by wire bonding and hermetically sealed together with a printed circuit board including a detection and excitation circuit. Since it is implemented by wire bonding instead of attachment, it is possible to cope with ultra-small size and to have no influence on detection accuracy.

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment) FIGS. 1 and 2 show an angular velocity sensor vibrator having a triangular prism tripod tuning fork structure according to an embodiment of the present invention. FIG. 1A is a perspective view of the front side of the vibrator, and FIG.
FIG. 2 is a perspective view of the back side, FIG. 2A is a plan view of the same vibrator, and FIG. 2B is a front view. Triangular prisms A, B, and C are cut out from plate-shaped piezoelectric elements 2 and 3 each having a bimorph structure by laminating two triangular prisms in a plane indicated by reference numeral 1 and each vertex of an equilateral triangular cross section is 8a, 8a ', 8a. '' (8b, 8
b ', 8b ", 8c, 8c', 8c"). Also, the three faces 4, 5, 6,
(4 ', 5', 6 ', 4'',5'',6'')
As shown in FIG. 2A, the electrodes (4a, 5a,
6a, 6a '(4b, 5b, 6b, 6b', 4c, 5
c, 6c, 6c ') and the sandwich electrode 7a (7b, 7c).
c) shows the directions of the arrows a, a '(b, b', c, c ') and the arrows a ", a"' (b ", b '", c ",
c ″ ′) (the potential in the piezoelectric element due to the polarization is indicated by + and −). Three triangular prisms A, B, C
Constitutes a pair of tuning forks with A and B, and a pair of tuning forks with B and C, and the respective arrangement pitches are L1:
L2 and L2, such as L2 = 1: 1 or L1: L2 = 1: 2, so that the two tuning forks vibrate with maximum efficiency.
Has been determined. The size of the center of gravity means a pitch between centers of gravity or a pitch between centroids.

The part D is a triangular prism base, the front surface 9 and the back surface 1
At 0, an electrode is formed. That is, on the surface 9, the electrodes 5a and 6a '(5
b, 6b ', 5c, 6c') in the G portion and the electrode 4 on the F surface side.
a, 6 a (4 b, 6 b, 4 c, 6 c) are led to an H portion through an I portion on the back surface 10 and through holes 24, 25, 26, 27, 28, 29. Further, the sandwich electrodes 7a, 7b, 7c are integrally connected electrodes, and are also led out to the H section through the through holes 30. To describe the arrangement of the electrodes in more detail, the electrode 5a on the E side of the triangular prism A is connected to 12, the electrode 6a 'is connected to 11, and the electrode 4a on the F side is connected to the back electrode 18' and the through hole 25.
The electrode 6a has a back electrode 17 'and a through hole 24.
To 17 via. Similarly, E of triangular prism B
Side electrode 5b to 13; electrode 6b 'to 14; F side electrode 4b to 20 via back electrode 20' and through hole 26; electrode 6b to 21 via back electrode 21 'and through hole 27. The E-side electrode 5c of the triangular prism C goes to 16, the electrode 6c goes to 15, and the F-side electrode 4c goes to 23 through the back surface electrode 23 'and the through hole 29.
The electrode 6c has a back electrode 22 'and a through hole 28.
To 22. Further, the sandwich electrodes 7a, 7b, 7c are led out to the back electrode 19 ′ and 19 through the through hole 30. Part J is a fixing portion of the triangular prism tripod tuning fork vibrator.

FIG. 3 shows a one-dimensional angular velocity sensor incorporating the triangular prism tripod tuning fork vibrator Z, and FIG. 4 shows a three-dimensional angular velocity sensor. The triangular prism tripod tuning fork vibrator Z has a fixed portion J of 32,
The base plate 48 is fixed to the base 48 by the leaf spring 31 spot-welded at 33, and the electrodes 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 2
3 and pads 35, 36, 3 formed on the circuit board 34
7, 38, 39, 40, 41, 42, 43, 44, 4
5, 46 and 47 are connected by bonding wires. Output from the triangular prism tripod tuning fork vibrator Z is led out from the circuit board 34 to the lead pins 50 and 51 insulated and fixed to the base 48 via the circuit board 49. The three-dimensional angular velocity sensor shown in FIG. 4 has vibrators Z, Z ′, and Z ″ arranged so as to be orthogonal to each other and detects angular velocities in the x, y, and z-axis directions. Omitted.

Next, the operation of the triangular prism tripod tuning fork vibrator Z will be described. In FIG. 5A, the electrodes 4a, 5a
(4b, 5b and 4c, 5c) are triangular prisms A (B,
C) is an excitation electrode for exciting the in-plane stress of arrow 70, and a Coriolis force is generated to generate triangular prisms A (B, C).
Also serves as a Coriolis detection electrode when it is bent in the direction perpendicular to the plane of the arrow 71. Electrodes 6a, 6a '(6b, 6b', 6
c, 6c ') are monitor electrodes (also serving as excitation electrodes) for monitoring the resonance frequency and amplitude of the excitation. Also, the sandwich electrodes 7a, 7b, 7c are excitation electrodes 4a, 5a (4b, 5b) also serving as Coriolis detection electrodes.
And 4c, 5c).

FIG. 5B shows a connection diagram of each electrode. The excitation electrodes 4b and 5b for detecting the Coriolis force include an amplifier 78.
Is connected, and a voltage change is output from the output terminal 79 by differential amplification. Each excitation electrode 4a, 5a, 4b, 5
b and 4c, 5c are connected to one pole of the drive power supply 80 via resistors, respectively, and are connected to the monitor electrodes 6a, 6c.
a 'and 6c, 6c' are connected to the other pole of the drive electrode 80. Also, the monitor electrodes 6b, 6b '
Is connected to another power supply terminal 81 and the sandwich electrode 7
a, 7b and 7c are connected to ground terminals 82 and 83, respectively. By applying a voltage to the excitation electrodes 4a, 5a and 4c, 5c, the Coriolis detection axis B becomes the excitation axis A,
The tuning fork is excited from both sides by C, and is also excited by applying a voltage to the excitation electrodes 4b and 5b. Therefore, the amplitude of the Coriolis detection axis B is amplified more than the excitation axes A and C, and the excitation direction at a certain moment is different from the excitation axes A and C (bending in the direction of 74) due to the tuning fork excitation. The direction is reversed (deflects to the direction of 75), and the excitation direction at the next instant is opposite to the directions of 74 and 75 due to the tuning fork excitation.

The mechanism by which the triangular prisms A, B, and C are excited in the in-plane direction of the arrow 70 will be described with reference to FIGS. Each electrode 4 of the excitation axis A
When voltages are alternately applied to the electrodes a, 5a, 6a, and 6a ', the internal charges (+) of the excitation electrodes 4a and 5a of the excitation axis A are inverted to (-) when the voltage of the polarity is applied, and the monitor electrodes (excitation) are applied. The same as the internal charge (+) on 6a and 6a ')
Is applied, the portion 72 contracts in the direction of 76, and the portion 73 extends in the direction of 77. Therefore, the excitation axis A is bent in the direction of arrow 74, and the Coriolis detection axis B is also bent in the direction of arrow 75 by the tuning fork configuration of the excitation axis A and the Coriolis detection axis B. Similarly, the Coriolis detection axis B is also deflected by the tuning fork of the excitation axis C in the direction of the arrow 75 by the pair of tuning forks of the excitation axis C and the Coriolis detection axis B, so that the amplitude is amplified. Thus, the triangular prisms A, B, and C which are always excited in the in-plane direction of the arrow 70
When an angular velocity 86 is applied to the detection shaft 85 shown in FIG. 7, a Coriolis force is generated in each of the triangular prisms A, B, and C in a direction perpendicular to the plane of the arrow 71, and the triangular prisms A, B, and C are shown in FIG. As described above, vibration occurs while bending in the direction perpendicular to the plane.

Since the directions of the plane perpendicular deflection of the triangular prisms A, B, and C due to the Coriolis force are determined by the direction of the excitation, the triangular prisms A and C flex in the same direction (the direction of 87), and the triangular prism B moves in the opposite direction (the direction of 88). ). When the triangular prism B is bent in the direction of 88 in FIG. 7, the Coriolis detection electrode (also serving as an excitation electrode) 4b expands and 5b contracts in FIGS. Further, since the potential between the sandwich electrode 7b and the Coriolis detection electrode 5b changes, the voltage change can be output by differential amplification with the terminal 79 via the amplifier 78. At this time, since the Coriolis detection electrodes 4b and 5b are arranged at a right angle to the Coriolis force generation direction, the detection sensitivity is increased. Further, the triangular prisms A or C and the triangular prisms B are used to take advantage of the surface vertical deflection in the opposite direction.
Alternatively, a differential output from the triangular prism B can be taken out, and further improvement in output sensitivity can be expected (not shown).

As described above, according to this embodiment, since the vibrator Z has a tripod tuning fork structure, the rotational moment M applied to the triangular prism tripod tuning fork vibrator Z when Coriolis force is generated is shown in FIG. As shown, opposite moments of + M and −M are obtained, the shape is canceled in the triangular prism base D, and almost no moment is generated in the fixed portion J. Therefore, when the triangular prism tripod tuning fork vibrator Z is fixed by the fixing portion J, the accuracy of Coriolis force detection is not affected by the degree of fixing, and the detection accuracy is extremely high. The triangular prism tripod tuning fork vibrator Z
Has a cut-out structure from the piezoelectric material, so there is no bonded part with the adhesive, and there is no influence of the adhesive variation and the temperature characteristics of the adhesive.Moreover, the dimensional variation is determined by the processing accuracy. Variations are not superimposed, and variations in angular velocity detection accuracy can be minimized. Furthermore, because of the equilateral triangular prism configuration, it is easy to match the resonance frequencies in the excitation direction and the Coriolis detection direction, and a resonance-type angular velocity sensor with extremely high sensitivity can be realized. In addition, since the signal lines are routed on the triangular prism base where the influence of vibration is small, the deflection of the wire does not affect the angular velocity detection accuracy. In addition, the triangular prisms A, B, and C do not necessarily need to be regular triangular prisms, and may have any shape as long as they are triangular prisms.

[0021]

The present invention has the following effects. 1) With a tripod tuning fork structure, the rotational moment when Coriolis force is generated can be canceled, the vibration loss can be minimized, and the influence on the detection accuracy of the fixed part can be eliminated. it can. 2) Due to the tripod tuning fork structure, the Coriolis detection axis can be excited from both sides, and the amplitude can be amplified to realize a small and highly sensitive angular velocity sensor. 3) Because of the triangular prism structure, the detection electrodes can be arranged almost perpendicular to the direction in which the Coriolis force is generated, and the detection sensitivity can be increased. 4) Because of the triangular prism structure, the excitation electrode and the detection electrode can be shared, the structure can be simplified, and the resonance frequency in the excitation direction and the resonance direction in the Coriolis detection direction are easily matched, realizing a very sensitive and small angular velocity sensor. it can. 5) Since the triangular prism has a tripod tuning fork structure, the Coriolis detection axis itself can simultaneously perform excitation and output (differential) detection, and output amplification by a tuning fork configuration with another axis is also possible. Can be realized. 6) Since the vibrator is formed by cutting out the piezoelectric material, there is no bonding portion, and the detection accuracy can be improved. 7) Since the connection of the signal line is performed not by the vibrator but by the fixed portion, the detection accuracy is not affected and the detection accuracy can be stabilized. 8) Since the extraction of the signal line is performed by wire bonding instead of soldering, it is possible to cope with ultra-small size and to have no influence on detection accuracy. 9) Since the electrodes arranged on each surface of the triangular prism are led out to only one surface of the triangular prism base that is less affected by vibration, connection work of the signal lines can be facilitated.

[Brief description of the drawings]

FIG. 1A is a front perspective view of an angular velocity sensor vibrator according to an embodiment of the present invention. FIG. 1B is a perspective view of a rear surface side of the angular velocity sensor vibrator according to an embodiment of the present invention.

2A is a plan view of the same vibrator. FIG. 2B is a front view of the same vibrator.

FIG. 3 is a perspective view showing a one-dimensional angular velocity sensor structure incorporating the same vibrator.

FIG. 4 is a perspective view showing a three-dimensional angular velocity sensor structure incorporating the vibrator.

FIG. 5A is a plan view showing an electrode arrangement of the same vibrator. FIG. 5B is a plan view showing an electrode connection of the same vibrator.

FIG. 6 is a front view showing the operation of the vibrator at the time of excitation.

FIG. 7 is a perspective view showing a bending direction of the vibrator when Coriolis occurs.

FIG. 8A is a plan view showing a moment generated when a Coriolis force is applied to the vibrator. FIG. 8B is a front view showing a moment generated when a Coriolis force is applied to the vibrator.

9A is a perspective view showing a conventional angular velocity sensor (during normal excitation). FIG. 9B is a perspective view showing a conventional angular velocity sensor (when Coriolis occurs).

10A is a characteristic diagram showing a resonance point of a non-resonant angular velocity sensor. FIG. 10B is a characteristic diagram showing a resonance point of a resonance angular velocity sensor.

[Explanation of symbols]

 2, 3 plate-shaped piezoelectric element 4, 5 excitation electrode (shared with Coriolis detection electrode) 6 monitor electrode (also used as excitation electrode) 7 sandwich electrode A, B, C triangular prism D triangular prism base J fixing part

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toru Fukuda 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama-shi, Kanagawa F-term (reference) 2F105 AA02 BB02 BB04 BB13 CC01 CC05 CD02 CD06 CD13

Claims (7)

[Claims] 1. Three triangular columns each composed of a piezoelectric element having a bimorph structure with a chamfered apex are arranged in directions respectively forming two pairs of tuning forks, and two triangular columns are respectively arranged on two adjacent surfaces of the triangular column. A triangular prism for angular velocity detection, wherein an excitation electrode sharing a Coriolis detection electrode is arranged, two monitor electrodes also functioning as an excitation electrode are arranged on another surface, and a sandwich electrode is arranged on a bimorph intermediate surface. Tripod tuning fork vibrator. 2. The triangular prism tripod tuning fork vibrator according to claim 1, wherein three triangular columns are cut out from a plate-shaped piezoelectric element having a bimorph structure. 3. The triangular prism tripod tuning fork vibrator according to claim 1, wherein each electrode arranged on each surface of the triangular prism is led out to one surface of the triangular prism base. 4. The triangular prism tripod tuning fork resonator according to claim 1, wherein the arrangement pitch of the three triangular prisms is 1: 1 or 2: 1. 5. An excitation electrode is connected to one pole of a drive power supply, and monitor electrodes of two triangular prisms at both ends of the arranged triangular prisms are connected to the other pole of the drive power supply.
5. The triangular prism tripod fork resonator according to claim 1, wherein the monitor electrode of the middle triangular prism is connected to another power supply terminal, and the sandwich electrode is polarized to a lower potential than each of the excitation electrodes. 6. The three triangular prisms are equilateral triangular prisms.
6. The triangular prism tripod tuning fork vibrator according to any one of items 1 to 5, above. 7. The fixing portion of the triangular prism tripod tuning fork vibrator according to claim 1 is fixed to a base with a leaf spring, and a lead pin and a triangular prism tripod tuning fork vibrator arranged insulated on the base are provided. An angular velocity sensor wherein each electrode is connected by a wire bonding method and hermetically sealed together with a printed circuit board including a detection and excitation circuit.