GB2262343A

GB2262343A - A vibrator for use in a vibratory gyroscope

Info

Publication number: GB2262343A
Application number: GB9301204A
Authority: GB
Inventors: Takeshi Nakamura; Keiichi Okano; Yoshiko Morishita
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 1988-08-12
Filing date: 1993-01-22
Publication date: 1993-06-16
Also published as: GB9301204D0; GB9301203D0; GB2262342A; GB2262343B; GB2262342B

Abstract

A vibrator, 14, having a polygonal section is supported by two support members 24a, 24b mounted at or near the nodal points of the body, said support members being equally spaced from the ends of the body e.g. at a distance 0.224 x the length of the body in the case of the figure shown. The body having associated with it piezo electric elements 16 for maintaining vibration and or measuring deflection due to a rotational force. <IMAGE>

Description

SPECIFICATION TITLE OF THE INVENTION Vibrator and Vibratory gyroscope using the same BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a vibrator and a bibratory gyroscope using the same, more particularly, it relates to the vibratory gyroscope used, for example, in a navigation system installed on a motor vehicle and the vibrator which may be used therein.

Description of the Prior Art Fig. 50 is an illustrative view showing one example of a conventional vibratory gyroscope comprising a background of the present invention, Fig. 51 is a perspective view showing a vibrator of the vibratory gyroscope and Fig. 52 is a sectional view taken along the line LII-LII of Fig. 51. The vibrator 2 of the vibratory gyroscope 1 includes a quadrangular prism shaped vibrating body 3 of a constant elastic metal material or the like.

On a pair of opposing side faces of the vibrating body 3, detecting piezoelectric elements 4, 4 are formed respectively, As shown in Fig. 52, the detecting piezoelectric element 4 comprises electrodes 4b formed on both surfaces of a piezoelectric ceramics 4a.

Meanwhile, on a pair of side faces of the vibrating body 3 whereon the detecting piezoelectric element 4 is not formed, driving piezoelectric elements 5, 5 are formed respectively. The driving piezoelectric element 5 also comprises electrodes 5b on both surfaces of the piezoelectric ceramics Sa as same as the detecting piezoelectric element 4.

The vibratory gyroscope 1 is supported by supporting members 6, 6 extending through nodal points of the vibrating body 3.

A differential amplifier 7 is connected to the detecting piezoelectric element 4 of the vibrator 2, and an oscillator 8 is connected to the driving piezoelectric element 5. Thus, when the driving signal is given to the driving piezoelectric element 5, the vibrating body 3, as shown exaggeratively in Fig. 53, makes bending vibration in the direction perpendicular to the main surface of the driving piezoelectric element 5.

In such a state, if the vibratory gyroscope 1 is rotated, for example, about its axis, a Coriolis force is exerted in the direction perpendicular to the vibrating direction. Thus, as shown exaggeratively in Fig. 54, the vibrating direction of the vibrating body 3 is changed by the Coriolis force, and the output voltage is produced in the detecting piezoelectric element 4. Since the output voltage is proportional to a bending quantity in the direction perpendicular to the main surface of the detecting piezoelectric element 4, by measuring the output voltage, the rotational angular velocity of the vibratory gyroscope 1 can be known. It is also same even when the vibratory gyroscope 1 is rotated about any axis along its axis.

In such conventional vibratory gyroscope, when it is rotataed the bending direction of the vibrating body or the detecting piezoelectric element (a direction of a resultant vector of a bending vibration direction vector at nonrotation and a deviation vector by the Coriolis force) is in the direction deviating from the direction perpendicular to its main surface, so that the output voltage generated in the detecting piezoelectric element 5 was small. It was, therefore, difficult to measure the rotational angular velocity applied to the vibratory gyroscope from the output voltage Accordingly, it was difficult to adjust the output voltage to zero, although required for earning the S/N ratio.

SUMMARY OF THE INVENTION It is, therefore, a primary object of the present invention to provide a vibratory gyroscope in which the output voltage at rotation can be increased, thus it is not necessarily brought to zero at non-rotation, and to provide a vibrator used in such vibratory gyroscope.

The vibrator according to the present invention comprises a vibrating body having a polygonal section and piezoelectric elements formed, at least, on two side faces of the vibrating body. The vibratory gyroscope according to the present invention utilizes the vibrator described above.

When a driving signal is applied to the piezoelectric element, the vibrating body makes bending vibration in the direction perpendicular to the main surface of the piezoelectric element.

When the vibratory gyroscope is rotated about its axis, though the vibrating direction is changed by a Coriolis force, side faces having the main surfaces in the direction substantially perpendicular to the vibrating direction present on the vibrating body. Thus, when the piezoelectric element on this surface is used for detection, a large output voltage can be produced thereon.

According to the present invention, since the bending direction of the vibrating body and the main surfaces of the detecting piezoelectric elements are substantially at right angles relative to each other at rotation of the vibratory gyroscope, output voltages generated in the detecting piezoelectric elements are larger as compared with the prior art vibratory gyroscope. Accordingly, it is simple to detect the rotational angular velocity in this vibratory gyroscope.

Thus, a delicate operation for earning the S/N ratio is not necessary.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiment taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing one embodiment of the present invention.

Fig. 2 is a sectional view taken along the line II-II of the embodiment of Fig. 1.

Fig. 3 is a block diagram showing a circuit for using a vibratory gyroscope shown in Figs. 1 and 2.

Fig. 4 is an illustrative view showing the vibration when the vibratory gyroscope shown in Figs. 1 and 2 is not rotating.

Fig. 5 is an illustrative view showing the vibration when the vibratory gyroscope shown in Figs. 1 and 2 is rotating.

Fig. 6 is a perspective view showing a modified example of the embodiment shown in Figs. 1 and 2.

Fig. 7 is a perspective view showing another modified example of tahe embodiment shown in Figs. 1 and 2.

Fig. 8 is a circuit diagram showing a differential amplifier used in a vibratory gyroscope of the present invention.

Fig. 9 is a circuit diagram showing an example enabling the gain control in the differential amplifier of Fig. 8.

Fig. 10 is a circuit diagram showing a modified example of the differential amplifier of Fig. 9.

Fig. 11 is a perspective view showing another embodiment of the present invention, and Fig. 12 is a sectional view taken along the line XII-XII of Fig. 11.

Fig. 13 is a circuit diagram showing an example of gyroscope means using the vibratory gyroscope shown in Figs.

11 and 12.

Fig 14 and 15 are graphs respectively showing outputs at respective portions of the circuit of Fig. 13, wherein Fig. 14 shows the output at non-rotation of the vibratory gyroscope and Fig. 15 shows the output at rotation thereof.

Fig. 16 is a graph showing the relationship between the rotational angular velocity of the vibratory gyroscope and the output voltage of a differential amplifier in a circuit of Fig. 1 3.

Fig. 17 is a sectional view showing a modified example of the embodiment of Figs. 11 and 12.

Fig. 18 is a perspective view showing an example of a supporting structure of a vibrator of the present invention, and Fig. 19 is a front view thereof.

Fig. 20 is a perspective view showing a modified example of the embodiment of Figs. 18 and 19, and Fig. 21 is a front view thereof.

Fig. 22 is a perspective view showing another modified example of the embodiment of Figs. 18 and 19, and Fig. 23 is a front view thereof.

Fig. 24 is a perspective view showing another example of a supporting structure of a vibrator of the present invention, and Fig. 25 is a front view thereof.

Fig. 26 is a side view showing a modified example of the embodiment of Figs. 24 and 25, and Fig. 27 is a front view thereof.

Fig. 28 is a perspective view showing still another embodiment of the present invention, and Fig. 29 is a sectional view taken along the line XXIX-XXIX of Fig. 28.

Fig. 30 is a block diagram showing an example of a vibratory gyroscopic means using the vibratory gyroscope shown in Figs. 28 and 29.

Fig. 31 and 32 respectively show the state of output voltages of the vibratory gyroscope shown in Figs. 28 and 29, wherein Fig. 31 is an illustrative view at non-rotation and Fig. 32 is an illustrative view at rotation.

Fig. 33 is a graph showing frequency characteristics before the resonance frequency on the driving side is coincided with those on the detecting side in the vibratory gyroscope shown in Figs. 28 and 29.

Fig. 34 is a graph showing frequency characteristics when the resonance frequency on the driving side is coincided with those on the detecting side in the vibratory gyroscope shown in Figs. 28 and 29.

Fig. 35 is a graph showing output voltage characteristics representing the relationship between the rotational angular velocity and the output voltage when a vibratory gyroscope is erected in the vibratory gyroscopic means shown in Fig. 30.

Fig. 36 is a graph showing output voltage characteristics representing the relationship between the tilt angle of the vibratory gyroscope and the output voltage in the vibratory gyroscopic means shown in Fig. 30.

Fig. 37 is a graph showing frequency temperature characteristics when a vibrating body is formed by an annealed material in the vibratory gyroscope shown in Figs.

28 and 29.

Fig. 38 is a sectional view showing a modified embodiment of Figs. 28 and 29.

Fig. 39 is an illustrative view showing another modified embodiment of Figs. 28 and 29.

Fig. 40 is an illustrative view showing a separate embodiment of the present invention.

Fig. 41 is an illustrative view showing a modified embodiment of Fig. 40.

Fig. 42 is an illustrative view showing another modified embodiment of Fig. 40.

Fig. 43 is an illustrative view showing a modified embodiment of Fig. 42.

Fig. 44 is an illustrative view showing still another modified embodiment of Fig. 40.

Fig. 45 is an illustrative view showing a modified embodiment of Fig. 44.

Fig. 46 is an illustrative view showing another modified embodiment of Fig. 44.

Fig. 47 is an illustrative view showing a separate example of a vibrator according to the present invention.

Fig. 48 is an illustrative view showing a modified embodiment of Fig 47.

Fig. 49 is an illustrative view showing another modified embodiment of Fig. 47.

Fig. 50 is an illustrative view showing an example of the conventional vibratory gyroscope comprising a background of the present invention.

Fig. 51 is a perspective view of a vibrator of the vibratory gyroscope of Fig. 50.

Fig. 52 is a sectional view taken along the line LII-LII of Fig. 51.

Fig. 53 is an illustrative view showing the vibration when the conventional vibratory gyroscope shown in Fig. 50 is not rotating.

Fig. 54 is an illustrative view showing the vibration when the conventional vibratory gyroscope shown in Fig. 50 is rotating.

DESCRIPTION OF THE PREFFERED EMBODIMENTS Fig. 1 is a perspective view showing one embodiment of the present invention, and Fig. 2 is a sectional view taken along the line Il-Il of Fig. 1. A vibratory gyroscope 10 comprises a vibrator 12, which includes, for example, a regular triangular prism shaped vibrating body 14. The vibrating body 14 is made of a constant elastic metal material such as Ni, Fe, Cr and Ti alloys.

In the embodiment, on one side face of the vibrating body 14, two driving piezoelectric elements 16ai and 16a2 are formed in the longitudinal center. The piezoelectric elements 16al and 6a2 are formed in parallel laterally of the side face of the vibrating body 14.

As shown in Fig. 2, one piezoelectric element 16al includes a piezoelectric layer 18al consisting, for example, of ceramics, and on both surfaces of the piezoelectric layer 18al, electrodes 20al and 22al are formed respectively. One electrode 20al is bonded to the vibrating body 14.

Similarly, the other piezoelectric element 16a2 also includes a piezoelectric layer 18a2, on both surfaces of which, electrodes 20a2 and 22a2 are formed. One electrode 20a2 is bonded to the vibrating body 14. In the embodiment, the piezoelectric layers 18al and 18a2 are formed integrally, and the electrodes 20al and 20a2 bonded to the vibrating body 14 are also formed integrally.

Meanwhile, in the embodiment, for the practical reason, in the center of remaining two side faces of the vibrating body 14, detecting piezoelectric elements 16b and 16c are formed respectively.

One detecting piezoelectric element 16b, as showing in Fig. 2, comprises a piezoelectric layer 18b provided with electrodes 20b and 22b on both surfaces thereof. One electrode 20b is bonded to the side face of the vibrating body 14.

Similarly, the other detecting piezoelectric element 16c also comprises a piezoelectric layer 18c provided with electrodes 20c and 22c on both surfaces thereof. One electrodes 20c is bonded to the vibrating body 14.

Accordingly, in the embodiment, the driving piezoelectric elements 16al and 16a2 are formed on the side faces of the vibrating body 14 whereon the detecting piezoelectric elements 16b and 16c are not formed.

Though the vibrating body 14 makes bending vibration by applying the driving signal between the driving piezoelectric elements 16al and 16a2, supporting members 24a and 24b are secured to its nodal point. The supporting members 24a and 24b are secured by welding, for example, a metal wire and the like to the vibrating body 14. The vibratory gyroscope 10 is used in a circuit configuration as shown in Fig. 3.

That is, the input side of an oscillator 50 is connected to one driving piezoelectric element 16al of the vibratory gyroscope 10, and the output side thereof is connected to the other driving piezoelectric element 16a2 via a phase circuit 52 and an AGC circuit 54. Thus, the signal amplified in the oscillator 50 is phase controlled in the phase circuit 52 and applied to the driving piezoelectric element 16a2 after gain controlled in the AGC circuit 54. Then, the stable driving signal given at resonance frequencies of the vibrator 14 is applied to the vibratory gyroscope 10 by these oscillator 50, phase circuit 52 and AGC circuit 54.

Meanwhile, the detecting piezoelectric elements 16b and 16c are connected to the input side of the differential amplifier 60, through which the output voltage difference between the detecting piezoelectric elemesnts 16b and 16c is measured. The differential amplifier 60 is connected to a synchronizing detection circuit 90, which is connected to the oscillator 50 to detect the output of the differntial amplifier 60 in synchronism with the vibration frequencies of the oscillator 50. The signal detected by the synchronizing detection circuit 90 is smoothed by a smoothing circuit 92, and further amplified to the output signal by a DC amplifier 94.

When the vibratory gyroscope 1G is not rotated, as shown exaggeratively in Fig. 4, it makes bending vibration in the direction perpendicular to the main surfaces of the driving piezoelectric elements 16al and 16a2. In this case, since bending quantities of the surfaces of the vibrating body 14 provided with the detecting piazoelectric elements 16b and 16c are same, the output voltages generated in the detecting piezoelectric elements 16b and 16c are equal. Thus, the output voltages of the detecting piezoelectric elements 16b and 16c are canceled each other in the differential amplifier 60 and the output of which becomes zero. That is, in the vibratory gyroscope 10, the output at nonrotation can be simply brought to zero.

Furthermore, when the vibratory gyroscope 10 is rotated about its axis, a Coriolis force is exerted in tt direction perpendicular to the vibrating direction of the vibrating body 14. In this case, as shown exaggeratively in Fig. 5, the vibrating direction of the vibrating body 14 deviates from the vibrating direction at non-rotation. At this time, for example, the detecting piezoelectric element 16c makes bending motion in a direction nearly perpendicular to its main surface, and the detecting piezoelectric element 16b makes bending mothion in direction nearly in parallel to its main surface. Therefore, the output voltage generated in the detecting piezoelectric element 16c increases, and the output voltage generated in the detecting piezoelectric element 16b decreases.Accordingly, a larger output can be obtained from the differential amplifier 60 as compared with the conventional vibratory gyroscope. Thus, when this vibratory gyroscope 10 is used, the rotational angular velocity is more easily detected than the case using the conventional vibratory gyroscope.

In the embodiment described above, though the output voltage difference between the two detecting piezoelectric elements 16b and 16c was measured, either of the two output voltages may be measured to detect the rotational angular velocity.

Also, in the aforesaid embodiment, though the vibrating body 14 is formed into a regular triangular prism, it may be formed into an isosceles triangular prism. In this case, the detecting piezoelectric elements 16b and 16c may be formed on each side face of the vibrating body 14 having the same area.

Moreover, the vibrating body 14 may be formed into a triangular prism other than the isosceles triangular prism,or into polygonal prisms such as pentagonal or hexagonal prisms.

In this case, the detecting piezoelectric element may be formed, at least, on one side face of the vibrating body whereon the driving piezoelectric element is not formed.

In the embodiment aforementioned, though the supporting members 24a and 24b are connected respectively to the vibrating body 14 at one point, as shown in Fig. 6, they may be connected respectively at two points. That is, the supporting members 24a and 24b may just be connected to the nodal points of the vibrating body 14.

Furthermore, as shown in Fig. 7, the driving piezoelectric elements l6al and 16a2 may be formed at a distance lengthwise of the vibrating body 14.

Fig. 8 is a circuit diagram showing an example of the differential amplifier 60 shown in Fig. 3. The differential amplifier 60 includes two input ends 62, 64 and one output end 66. The differential amplifier 60 also includes an operating amplifier 68. One input end 62 is connected to an inversion input terminal of the operating amplifier 68 via a resistance 70. The inversion input terminal of the operating amplifier 68 is earthed via a resistance 72.

The other input end 64 of differential amplifier 60 is connected to a non-inversion input terminal of the operating amplifier 68 via a resistance 74. The non-inversion input terminal of the operating .ampifier 68 is earhted via a resistance 76. Ratio R2/R1 of the resistance values R1 and R2 of the two resistances 74 and 76 connected to the noninversion input terminal of the operating amplifier 68 is set to become generally equal to the ratio R4/R3 of the resistance values R3and R4 of the two resistances 70 and 72 connected to the inversion input terminal of the operating amplifier 68.

An output terminal of the operating amplifier 68 is connected to the output end 66 of the differential amplifier 60, and the output terminal and inversion input terminal of the operating amplifier 68 are connected via a resistance 78.

In such differential amplifier 60, its amplification is represented by the ratio R5/R3 of the resistance values R3 and R5 of the resistance 70 between the input end 62 and inversion input terminal of the operating amplifier 68, and the resistance 78 between the inversion input terminal and the output terminal of the operating amplifier 68. Thus, when the input voltage V1 is applied to the input end 62 and the input voltage V2 is applied to the input end 64, the output voltage V generated at the output end 66 is represented as follows; V = (V1 - V2) R5/R3 In such differential amplifier 60, in order to control gains on the non-inversion input side, as shown, for example, in Fig 9, a variable resistance 80 is connected to the noninversion input terminal of the operating amplifier 68. In this case, one fixed terminal of the variable resistance 80 is connected to the input end fi4 and the other fixed terminal thereof is earhted. Then, a movable terminal of the variable resistance 80 is connected to the non-inversion input terminal of the operating amplifier 68.

In order to obtain, for example, the amplification of ten times by using such differential amplifier 60, for example, the resistance values R3 and R4 of the resistances 70 and 72 connected to the inversion input terminal of the operating amplifier 68 are set respectively at lk#, and the resistance value R5 of the resistance 78 is set at 10kSX The resistance value betweeen the two fixed er-.inals of the varible resistance 80 is set, for example, at 2k). In such a case, since the resistance values R3 and ?t of te resistances 70 and 72 connected to the inversion input terminal of the operating amplifier 68 are set respectively at ik#, the movable terminal of the variable resistance 80 is controlled substantially near the center between the two fixed terminals. That is, the movable terminal of the variable resistance 80 is controlled in the proxi::iity of lScS.

from the two fixed terminals.

In the conventional differential amplifier without the resistance 72, though the proximity of one end of the variable resistance 80 had to be controlled for gain control, in the differential amplifier 60 shown in Fig. 9, the gain control is very simple since it can be effected substantially near the center of the variable resistance 80.

In the prior art differential amplifier, in order to enable the gain control near the center of the variable resistance, a fixed resistance was connected to the variable resistance in series. In such case, since the resistance temperature coefficients of the variable resistance and fixed resistance are unequal, a drift is produced by atmospheric temperature. On the contrary, in the differential amplifier 60 shown in Fig. 9, the fixed resistance is not needed to be connected to the variable resistance 80, thus a drift is hardly produced by atmospheric temperature.

That is, in this differential amplifier, the inversion input terminal of the operating amplifier is earthed via a resistance.

Therefore, the ratio of the resistance between the input end of the differential amplifier and the inversion input terminal of the operating amplifier, and the resistance between the inversion input terminal of the operating amplifier and the earth, and the ratio of the resistance between the input end and the non-inversion input terminal of the operating amplifier, and the resistance between the non-inversion input terminal of the operating amplifier and the earth are set substantially equally.

Accordingly, by suitably selecting the ratio of the resistance between the input end of the differential amplifier and the inversion input terminal of the operating amplifier, and the resistance between the input terminal of the operating amplifier and the earth, the ratio of the resistance between the input end and the non-inversion input terminal of the operating amplifier, and the resistance between the non-inversion input terminal of the operating amplifier and the earth can be changed optionally. Thus, if a variable resistance is connected to the input terminal of the operating amplifier for gain control on the non-inversion input side of the differential amplifier, it can be controlled near the center of the variable resistance and a fixed resistance is not needed to be connected to the variable resistance.Therefore, the gain control on the noninversion input side of the differential amplifier can be simply accomplished and a drift due to atmospheric temperature hardly occurs.

In the differential amplifier 60 described above, though the resistance values of the resistances 70 and 72 are made equally to control near the center of the variable resistance 80, if the resistance value ratio of the resistances 70 and 72 is set at 1:2, the movable terminal of the variable resistance 80 can also be controlled at the position dividing between the two fixed terminal into 1:2 responsive thereto.

Thus, by selecting suitably the resistance value of the resistance connected to the operating amplifier 68, the gain control can be effected at any position of the variable resistance 80. In this differential amplifier 60, the resistance value R3 of the resistance 70 connected to the inversion input terminal of the operating amplifier 68, and the resistance values R1 and R2 of the resistances 74 and 76 connected to the non-inversion input terminal can be set freely, and even when the both input terminal impedances have to be made equally, it can be easily set.

In the aforesaid differential amplifier 60, though the variable resistance 80 was connected to the non-inversion input terminal of the operating amplifier 68, as shown in Fig. 10, the variable resistance 82 may be connected to the inversion input terminal of the operating amplifier 68 for gain control. Moreover, it is also possible to control the gain by connecting the variable resistance to both of the inversion input terminal and non-inversion input terminal of the operating amlifier 68.

A vibrator 12 of a vibratory gyroscope 10 of the embodiment includes, for example, a regular triangular prism shaped vibrating body 14. The vibrating body 14 is formed with a material producing, in general, a mechanical vibration such as elinver, ferro-nickel alloy, quartz, glass, crystal, ceramics etc.

On the vibrating body 14, in the center of three side faces thereof, piezoelectric elements 16a, 16b and 16c are formed respectively. The piezoelectric element 16a includes a piezoelectric layer 18a consisting, for example, of ceramics, and on two main surfaces thereof, electrodes 20a and 22a are formed respectively. The electrodes 20a and 22a are made of an electrode material such as gold, silver, aluminum, nickel, copper-nickel alloy (Monel Metal) etc., and formed by thin film techniques such as sputtering and evaporation or depending upon the material, by printing techniques.

Similarly, the other piezoelectric elements 16b and 1Se include respectively piezoelectric layers 185 and 18c condidting of, for example, ceramics, and on both surfaces thereof, there are respectively, formed electrodes 20b, 22b and 20c, 22c. The electrodes 20a - 20c of the piezoelectric elements 16a - 16c are bonded to the vibrating body 14, for example, by conductive adhesives.

Meanwhile, the vibrating body 14 is supported by supporting members 24a and 24b consisting cf a metal wire the proximity of its nodal points. The su?portir.g members 24a and 24b are secured near the nodal points of the vibrating body 14, for example, by welding. The supporting members 24a and 24b may also be secured by a conductive paste. The supporting members 24a and 24b are used as an earthing terminal of the vibratory gyroscope 10.

in the vibratory gyroscope 10, if any one of piezoelectric elements 16a - 16c is used for driving, the remaining two piezoelectric elements may be used for detection. In this embodiment, for example, the piezoelectric element 16a is used for driving and the other piezoelectric elements 16b and 16c are used for detection.

When the driving signal is given to the driving piezoelectric element 16a, the vibrating body 14 is vibrated and the similar sine waves are outputted from the detecting piezoelectric elements 16b and 16c. When the vibratory gyroscope 10 is rotated about its axis under this condition, the output of one detecting piezoelectric element increases in accordance with the rotational angular velocity, and conversely, the output of the other detecting piezoelectric element decreases.

Referring now to Fig. 13, between the detecting piezoelectric elements 16b, 16c and the driving piezoelectric element 16a of the vibratory gyroscope 10, an oscillator 100 is connected as a feedback loop for self-oscillation driving the vibratory gyroscope 10.

That is, the oscillator 100 is designed to apply the outputs of the detecting piezoelectric elements 16b and 16c to the driving piezoelectric element 16a in the composite form, and includes a variable resistance 102 having two fixed terminals 102a and 102b as input ends. The fixed terminals 102a and 102b of the variable resistance 102 are connected respectively to the electrodes 22b and 22c of the piezoelectric elements 16b and 16c. The variable resistance 102 is designed to correct voltage errors and phase difference produced between the outputs from the piezoelectric elements 16b and lGc, and to compose those outputs. In place of the variable resistance 102, these outputs may be composed by two fixed resistances.

Furthermore, a movable terminal 102c of the variable resistance 102 is connected to an input side of an inversion amplifier 104. The inversion amplifier 104 includes an operating amplifier 106, and is designed to inverse the output phase from the variable resistance 102 and to amplify its signal.

An output side of the Inversion amplifier 104 is connected to an input side of a low-pass filter 108 which includes two-stage RC filters 110 and 112. Each of the RC filters 110 and 112 has, for example, a lagging power factor of 45 degree. The low-pass filter filter 108 108 is for lagging the output phase from the inversIon amplifier 104 by 90 degree and suppressing harmonic components included in the output.

An output side of the low-pass filter 108 is connected to the electrode 22a of the driving piezoelectric element 16a via a resistance 114.

Meanwhile, the outputs of the piezoelectric elements 16b and 16c of the vibratory gyroscope 10 are inputted respectively to two input ends of a differential amplifier 150 for detecting the output difference thereof.

That is, the differential amplifier 150 includes an ideal diode circuit 152, to an output side of which, the electrode 22b of one detecting piezoelectric element 16b is connected.

The ideal diode circuit 152 includes one operating amplifier 154 and two diodes 156 and 158 interconnected in a forward direction for half-wave rectification of the sine-wave output from the piezoelectric element 16b into the positive signal.

The electrode 22c of the other detecting piezoelectric element 16c is connected to an input side of another ideal diode circout 160 having the polarity different from the aforesaid ideal diode circuit 152. The ideal diode circuit 160 includes one operating amplifier 162 and two diodes 164 and 166 interconnected reversely for half-wave rectification of the sine-wave output from the piezoelectric element 16c into a negative signal.

Moreover, output sides of the ideal diode circuits 152 and 160 are connected respectivery to input sides of smoothing circuits 168 and 170 comprising, for example, RC filters. Output sides of the smoothing circuits 168 and 170 are connected respectively to fexed terminals 172a and 172b of a variable resistance 172 as composing means. The variable resistance 172 includes a movable terminal 172c.

In the following, the operation of respective circuits at non-rotation and at rotation of the vibratory gyroscope 10 will be described with reference to Figs. 13, 14 and 15. In Fig. 13, output wave forms of respective portions at nonrotation of the vibratory gyroscope 10 are shown together with the circuits. In Fig. 14, outputs of the detecting piezoelectric elements 16b and 16c, an output of the variable resistance 102 of the oscillator 100 and an output of the differential amplifier 150 at non-rotation of the vibratory gyroscope 10 are shown, and in Fig. 15, these outputs at rotation of the vibratory gyroscope 10 in one direction are shown. In this case, in Figs. 14 and 15, magnitudes and wave forms of those outputs are shown more or less correctly, but those phases are shown incorrectly.

At non-rotation of the vibratory gyroscope 10, it makes bending vibration in the direction perpendicular to the main surface of the driving piezoelectric element 16a, so that the piezoelectric elements 1Qb and 16c bend simlarly. Therefore, from the piezoelectic elements 16b and 16c, as particularly shown in Fig. 14, the similar sine waves are outputted.

In the oscillator 100, the outputs from the piezoelectric elements 16b and 16c are outputted from the movable terminal 102c of the variable resistance 102 in the composite form. In this case, the composite output of the piezoelectric elements 16b and lGc shows a predetermined sine wave having the phase of -90 on the basis of driving side of the vibratory gyroscope 10 in an ideal state. However, when the voltage errors and phase differences are produced betweeen the outputs of the piezoelectric elements 16b and 16c, a predetermined sine wave aforementioned can not be obtained just by merely composing the outputs of the piezoelectric elements 16b and 16c.

However, the voltage errors and phase differences between the outputs of the piezoelectric elements 16b and 16c can be corrected by controlling the variable resistance 102.

Thus, by controlling the variable resistance 102, the output from the movable terminal 102c can be corrected into a predetermined sine wave having the phase of -90 on the basis of driving side.

In the inversion amplifier 104, the sine-wave output phase from the variable resistance 102 is inversed and its signal is amplified. Thus, from the inversion amplifier 104, a signal having the phase of 900 on the basis of driving side of the vibratory gyroscope 10 is outputted.

In the low-pass filter 108, the output phase from the inversion amplifier 104 is lagged by 900 and harmonic wave components included in the output are suppressed. Thus, from the low-pass filter 108, a constant signal having no spurious due to the harmonic wave components is outputted always in the same phase as the driving side of the vibratory gyroscope 10.

The output from the low-pass filter 108 is applied to the electrode 22a of the driving piezoelectric element 16a via the coupling resistance 114. Thus, in this embodiment, the self-oscillation drive of the vibratory gyroscope 10 can be accomplished effidiently.

Meanwhile, in the differential amplifier 150, a halfwave rectification of the sine-wave output of the piezoelectric element 16b is effected in a forward direction by the ideal diode circuit 152. Therefore, a positive sinewave output signal from the piezoelectric element 16b is outputted from the ideal diode dircuit 152.

Also, a half-wave rectification of the sine-wave output from the piezoelectric element lGc is effected reversely by the other ideal diode circuit 160, and its negative sine-wave output signal is outputted.

By the smoothing circuits 168 and 170, the outputs from the ideal diode circuits 152 and 160 are smoothed into the postive and negative direct currents.

These DC outputs are given to the fixed terminals 172a and 172b of the variable resistance 172 as composing means.

Thus, from the movable terminal 172c of the variable resistance 172, the DC outputs from the smoothing circuits 168 and 170 are outputted in the composite form.

In the differential amplifier 150, the output of the piezoelectric element 16b is smoothed by half - wave rectification in a forward direction, and the output of the piezoelectric element 16c is smoothed by half-wave rectification in an opposite direction before composition, so that even if the phase difference exists between these outputs, errors due the phase difference will not occur.

Besides, even if the voltage errors exist between these outputs, by controlling the variable resistance 172 as composite means, these voltage errors may be corrected. In this embodiment, the output of the differential amplifier 150 at non-rotation of the vibratory gyroscope 10 is controlled to become zero. Thus, if it is confined that the output from the differential amplifier 150 is zero, it is known that the vibratorly gyroscope 10 is not rotating.

Meanwhile, when the vibratory gyroscope 10 is rotated in one direction about its axis, a Coriolis force is exerted in the direction perpendicular to its vibrating direction.

Therefore, the vibrating direction of the vibratory gyroscope 10 is deviated from the vibrating direction at non-rotation.

At this time, for example, one detecting piezoelectric element 1Gb makes bending vibration in the direction substantially perpendicular to its main surface, and the other detecting piezoelectric element 16c makes bending vibration in the direction substantially in parallel to its main surface In this case, as particularly shown in Fig. 15, the output from one detecting piezoelectric element 16b increases, and conversely the output from the other detecting piezoelectric element 16c decreases by the output increment of the piezoelectric element 16b. Thus, also in this case, the putput from the variable resistance 102 of the oscillator 100 becomes as same as the output at non-rotation.

The output from the variable resistance 102 is, as same as the case of non-rotation, given to the driving piezoelectric element 16a via the Inversion amplifier 104, the low-pass filter 108 and so on. Thus, also at rotation of the vibratory gyroscope 10, as same as at non-rotation, salf- oscillation drive of the vibratory gyroscope 10 can be accomplished efficiently.

On the other hand, in the differential amplifier 150, since the output of the piezoelectric element 16b becomes larger than that of the piezoelectric element 16c, the absolute output value of the smoothing circuit 168 becomes larger than that of the other smoothing circuit 170. Thus, as shown in Fig. 15, the positive direct current is outputted from the variable resistance 172 as composite means, thereby it is known that the vibratory gyroscope 10 is rotating in one direction.

Since the output difference between the piezoelectric elements 16b and 16c becomes larger as the rotational angular velocity of the vibratory gyroscope 10 increases, the output from the differential amplifier 150 also increases. Thus, from the magnitude of the output from the differential amplifier 150, the rotational angular velocity of the vibratory gyroscope 10 can be known. Also in this case, in the differential amplifier 150, the output of the piezoelectric element 16b is smoothed by half-wave rectification in a forward direction, and the output of the piezoelectric element 16c is smoothed by half-wave rectificatlon in an opposite direction before composition, so that even if the phase difference exists between these outputs, errors due to the phase difference will not occur.

When the vibratory gyroscope 10 is rotating reversely, since the outputs of the piezoelectric elements 16b and 16c are reversed, the negative direct current is outputted from the differential amplifier 150. Thus, by the output polarity from the differential amplifier 150, the rotating direction of the vibratory gyroscope 10 can be known.

According to experiments made by the inventor, in this embodiment, the rotational angular velocity of the vibratory gyroscope 10 and the output voltage of the differential amplifier ISO, as shown in Fig. 16, have an accurate linear relationship, and having a high S/N ratio.

In the embodiment described above, for self-oscillation drive of the vibratory gyroscope 10, though, the outputs of the two detecting piezoelectric elements 16b and 16c are given to the driving piezoelectric element 16c in the composite form by the special oscillator 100, in place thereof, these outputs may be given to the driving piezoelectric element in the composite form by a usual cumulative amplifier. In short, for self-oscillation drive of the vibratory gyroscope 10, the outputs of the two detecting piezoelectric elements may be given to the driving piezoelectric element in the composite form.

In the embodiment described above, though the output difference of the two detecting piezoelectric elements 16b and 16c was detected by the special differential amplifier 150 for measuring the rotational angular velocity of the vibratory gyroscope 10, in lieu of the special differential amplifier 1SO, a usual differential amplifier may be used to detect the output difference. In this case, the Output difference is obtained in a sine wave. In short, in order to measure the rotational angular velocity of the vibratory gyroscope 10, the output difference of the two detecting piezoelectric elements may be detected.

In the aforesaid oscillator 100, though the fixed terminals 102a and 102b of the variable resistance 102 are used as input ends, and the movable terminal 102c thereof is connected directly to the input side of the inversion amplifier 104, the input ends and the fixed terminals 102a, 102b of the variable resistance 102, and the movable terminal 102c thereof and the input side of the inversion amplifier 104 may be connected respectively via resistances.

In short, the oscillator may consist of two input ends, and include a resistance connected between the two input ends and an amplifier whose input side is connected to the midwway of the resistance. When the two input ends of such oscillator are connected respectively to two detecting piezoelectric elements of a vibrator of a vibratory gyroscope, and an output end of the oscillator is connected to a driving piezoelectric element of the vibrator, the outputs from the two detecting piezoelectric elements are given to the driving piezoelectric element in the composite form. In this case, by adjusting the connecting point between the input side of the amplifier of the oscillator and the midway of the resistance, voltage errors and phase differences produced between the outputs of the two detecting piezoelectric elements can be corrected.Therefore, an optimum driving signal is applied to the driving piezoelectric element of the vibrator. Thus, selfoscillation drive of the vibrator can be accomplished efficiently.

Fig. 17 is a sectional view showing the modified embodiment of Figs. 11 and 12. In the vibratory gyroscope 10 of the embodiment, in particular, a vibrating body 14 is formed with a vibration material consisting of a metal such as elinver, ferro-nickel alloy etc. On three side faces of the vibrating body 14, piezoelectric layers 18a - 18c of piezoelectric elements lGa - 16e are formed with a piezoelectric material such as PZT and ZnO by thin-film techniques such as sputtering and evaporation. Thus, between these piezoelectric layers 18a - 18c and the vibrating body 14, electrodes 20a - 20c in the embodiment shown in Figs. 11 and 12 are not formed. It is because that the vibrating body 14 serves as the electrodes 20a - 20c.

Meanwhile, on the surfaces of the piezoelectric layers 18a - 18c, electrodes 22a - 22c are formed with an electrode material such as gold, silver, aluminum, nickel, coppernickel alloy (Monel Metal) etc. by thin-film techniques such as sputtering and evaporation.

In the embodiment, supporting members 24a and 24b are secured at two points near the nodal points of the vibrating body 14.

This embodiment is also used similarly as the embodiment of Figs. 11 and 12.

In each of the embodiments shown in Figs. 11, 12 and l7, though the vibrating body 14 is formed into a regular triangular prism, in the present invention, it may be formed into an isosceles triangular prism. In this case, the piezoelectric elements formed on the side faces of the vibrating body 14 having the same area may be used for detection. The vibrating body 14 may also be formed into a triangular prism other than the isosceles triangular prism, or into polygonal prisms such as a quadrangular prism, pentagonal prism, hexagonal prism etc. In this case, piezoelectric elements may be formed, at least, on three side faces of the vibrating body. Either of these piezoelectric elements may be used for driving and the remaining piezoelectric elements for detection.When the driving signal is given to the driving piezoelectric element, the vibrating body is vibrated. Then, when the vibratory gyroscope is rotated about its axis, though its vibrating direction is changed by a Coriolis force, the side face having the main surface in the direction substantially perpendicular to the vibrating direction of the vibrating body exist thereon. Therefore, if the piezoelectric element formed on the side face is used for detection, a large output can be obtained.Thus the rotational angular velocity of the vibratory gyroscope can be known accurately by the large output from the piezoelectric element Besides, since the piezoelectric elements are just needed to be formed respectively on, at least, three side faces of the vibrating body, and it is not necessary to form two piezoelectric elements on one side face of the vibrating body as compared with the embodiment shown in Figs. 1 and 2, results in simple construction and low cost.

Fig. 18 is a perspective view showing an example of a supporting construction ef a vibrator of the present invention, and Fig. 19 is a front view thereof. In this embodiment, a vibratory gyroscope using the vibrator will be described. The vibratory gyroscope 10 includes a vibrator 12, which includes a vibrating body 14 and driving piezoelectric elements 16a and 16b for vibrating the vibrating body 14. The vibrating body 14 is formed, for example, into a regular triangular prism.

In the center of two side faces of the vibrating body 14, the driving piezoelectric elements 16a and 16c are formed respectively. As shown in Fig. 19, one piezoelectric element 16a is provided with electrodes 20a and 22a on both surfaces of a piezoelectric layer l8a. The electrode 20a is bonded to the side face of the vibrating body 14.Similarly, the other piezoelectric element 16b includes a piezoelectric layer 16b and electrodes 20b, 22b formed on both surfaces thereof, the electrode 20b is bonded to the side face of the vibrating body 14. By applying the driving signal to the piezoelectric elements 55a and 16b, the vibrating body 14 makes bending vibration in the direction perpendicular to the face whereon the piezoelectric elements 16a, 16b are not formed.

Meanwhile, in the center of the other side face of the vibrating body 14, a detecting piezoelectric element 16c is formed. The piezoelectric element 1 6c includes a piezoelectric layer 18c and electrodes 20c, 22c formed on both surfaces thereof, the electrode 20c is bonded to the side face of the vibrating body 14. By detecting the output signal from the piezoelectric element 16c, the rotational angular velocity applied to the vibratory gyroscope 10 can be detected The vibrating body 14 is supported by two supporting member 24a and 24b, which are connected to an edge between two faces whereon the driving piezoelectric elements 16a, 16b of the vibrating body 14 are formed.The supporting members 24a, 24b are connected near the nodal points ot the vibrating body 14. In this embodiment, if the length of the vibrating body 14 is represented by L, connecting points will be 0.224L from opposite ends of the vibrating body 14.

In the vibratory gyroscope 10, the driving signal is given to the driving piezoelectric elements 16a, 16b, thereby the vibrating body 14 makes bending vibration in the direction perpendicular to the face whereon the piezoelectric elements 16a, 16b are not formed. At this time, vibrating conditions of the faces of the vibrating body 14 whereon the piezoelectric elements 16a, 16b are formed, are symmetrical on both sides of the edge which the supporting membaers 24a, 24b are connected. Accordingly, connecting portions of the vibrating body 14 and the supporting members 24a, 24b are free from torsion and vibrations of the vibrating body 14 hardly attenuate.When such a supporting construction of the vibrator as the vibratory gyroscope 10 is employed, through holes or the like are not necessary to be formed in the vibrating body 14, and the supporting members 24a, 24b can be connected by welding, so that a good operability can be obtained at manufacturing. Moreover, since the through hole is not needed in the vibrating body 14, the vibrator 12 can be made in compact size.

Fig. 20 is a perspective view of the modified embodiment of Figs. 18 and 19, and Fig. 21 is a front view thereof. In this embodiment, a vibrating body 14 is formed into a regular quadrangular prism. Driving piezoelectric elements 16a, 16b are formed in the center of adjusting side faces of the vibrating body 14, and detecting piezoelectric elements 16e, 16d are formed in the center of the other side faces of the vibrating body 14. Supporting members 24a, 24b are connected to an edge between the faces of the vibrating body 14 whereon the driving piezoelectric elements 16a, 15b are formed. The supporting members 24a, 24b are connected near the nodal points of the vibrating body 14 as same as the embodiment shown in Figs. 18 and 19.

As shown in Figs. 22 and 23, the vibrating body 14 may be formed into a hexagonal prism by shaving off edge portions of the vibrating body 14 shown in Figs. 18 and 19. In this case, to the plane between the faces of the vibrating body 14 whereon the driving piezoelectric: elements 16a, 16b are formed, the supporting members 24a, 24b are connected. At this time, the supporting members 24a, 24b are connected on the center line of the plane between the faces of the vibrating body 14 whereon the driving piezoelectric elements 16a, 16b are formed. It is to be understood that, also in this embodiment, the supporting members 24a, 24b are connected near the nodal points.

Also in the embodiments of Figs. 20, 21 and Figs. 22, 23, vibrations of the vibrating body 14 are harly attenuated due to the supporting members 24a, 24b, and a good operability can be obtained at manufacturing and the vibrator can be made in compact size.

That is, each of the supporting constructions of the vibrator is designed to support the vibrator including the polygonal prism shaped vibrating body, and the driving piezoelectric elements for vibrating the vibrating body formed on two side faces of the vibrating body which are not in parallel, and supported near the nodal point of the vibrating body at two points on a longitudinal straight line of the vibrating body and at an equally spaces relation form two faces of the vibrating body whereon the driving piezoelectric elements are formed.

Therefore, vibrating conditions of the vibrating body faces whereon the driving piezoelectric elements are formed are symmetrical on both sides of a straight line connecting the two supporting points.

Accordingly, since the vibrating conditions of the faces of the vibrating body whereon the driving piezoelectric elements are formed are symmetrical on both sides of the straight line connecting the two supporting points, torsion of the vibrating body is hardly occurred at the supporting points. Thus vibrations of the vibrating body are hardly attenuated due to the supporting members.

Also, since the supporting points are on the surface of the vibrating body, through holes or the like are not necessary to be formed in the vibrating body as in the past results in a good operability at manufacturing. Moreover, since it is not necessary to form the through holes in the vibrating body, the vibrator can be formed in a compact size.

Fig. 24 is a perspective view showing another supporting construction of a vibrator according to the present invention, and Fig. 25 is a front view thereof.

The vibrator 12 includes a regular triangular prism shaped vibrating body 14.

On the vibrating body 14, piezoelectric elements 16a, 16b and 16c are formed respectively in the center of three side faces.

Furthermore, to the vibrating body 14, if the longitudinal length thereof is represented by L, on the edge portion between the faces whereon the piezoelectric elements 16a and 16b are formed, at portions 0.224L inward from its opposite ends, the center portions of U-shaped supporting members 24a and 24b made of, for example, a wire material are secured respectively, for example, by means of welding or bonding.

In the vibrator 12, when the driving signal is given to the piezoelectric elements 16a and 16b or to the piezoelectric element 16c, the vibrating body 14 is vibrated in the direction perpendicular to the main surface of the piezoelectric element 16c. In this case, the nodal points of the vibrator 12, if the longitudinal length of the vibrating body 14 is represented by L, exist on the center axis of the vibrating body 14 at points 0.224L inward from its opposite ends. Therefore, the two supporting members 24a and 24b bend reversely each other axialy of the vibrating body 14.

The supporting construction of the present embodiment includes a rectangular plate supporting base 200 consisting of a material such as metal or ceramics. On one main surface of the supporting base 200, a buffer 202 consisting of an elastic material such as rubber, sponge and the like is bonded On one main surface of the buffer 202, two substrates 204 and 206 divided longitudinally thereof are bonded. On one main surface of one substrate 204, five electrodes 208a, 208b, 208c, 208d and 208e are formed laterally in spaced relation. On the main surface of the other substrate 206, electrodes 210a and 210b are formed respectively on opposite ends laterally thereof.

To the electrodes 208a and 208e of the substrate 204, opposite ends of the supporting member 24a of the vibrator 12 are secured respectively, for example, by welding or the like. Similarly, both ends of the other supporting member 24b are secured respectively to the electrodes 210a and 210b of the other substrate 206.

Meanwhile, to the electrodes 208b, 208d and 208c of the substrate 204, piezoelectric elements 16a, 16b and 16e are electrically connected respectively, for example, by lead wires.

In the embodiment, when the driving signal is given to the electrodes 208b and 208d on the substrate 204, namely, to the piezoelectric elements 16a and 1gob, or to the electrode 208c namely, to the piezoelectrle element 16c, the vibrator 12 is driven. In this case, though the supporting members 24a and 24b bend reversely each other longitudinally of the vibrating body 14, the divided substrates 204 and 206 are displaced separately alike. Therefore, the supporting members 24a and 24b are not interfered each other, thus vibrations of the vibrator 12 are not suppressed by the supporting members 24a and 24b. Accordingly, a stable vibrating attitude of the vibrator 12 can be assurec.

Also, in this embodiment, since the buffer 202 is formed between the supporting base 200 and the substrates 204, 206, a bad influence by external vibrating noises can be minimized Fig. 26 is a side view showing the modified embodiment of Figs. 24 and 25, and Fig. 27 is a front view thereof.

In the embodiment, as compared with the embodiment of Figs. 24 and 25, in particular, a vibrating body 14 of a vibrator 12 being supported is formed into a quadrangular prism. Piezoelectric elements 16a and 16b are formed in the center of two opposing upper and lower side faces of the vebrating body 14. Two supporting members 24a and 24b are secured as extending through the center laterally of the side faces of the vibrating body 14 whereon piezoelectric elements not formed.

Meanwhile, on one main surface of the substrate 204, four electrodes 208a, 208b, 208c and 208d are formed in spaced relation laterally thereof. Both ends of the supporting member 24a are secured respectively to the electrodes 208a and 208d on the poppsite sides. To the center electrodes 208b and 208c, the piezoelectric elements 16a and 16b are connected electrically respectively by lead wires In this embodiment, when the driving signal is given to the center electrode 208b or 208c of the substrate 204, the vibrator 12 is driven.In this case, also in this embodiment, though the two supporting members 24a and 24b bend reversely each other longitudinally of the vibrating body 14, the substrates 204 and 206 onto which these supporting members 24a and 24b are secured are displaced separately, so that a stable vibrating attitude of the vibrator 12 can be assured, In the embodiment, since the buffer 202 is formed also between the supporting base 200 and the substrates 204, 206, external vibrating noises can be absorbed.

In each of the embodiments shown in Figs. 24 through 27, though the substrate is divided into two, in the present invention, the substrate may be divided more than the number of supporting members of the vibrator.

That L5 , the supporting construction of a vibrator according to the present invention is designed to support the vibrator provided with a plurality of supporting neners, and including a supporting base, a buffer formed thereon and substrates which are divided and formed on the buffer and to which a plurality of supporting members are secured separately.

Therefore, when the vibrator makes bending vibration1 though the plurality of supporting members are also bent, in this case, they are displaced together with the divided substrates independently.

Thus, since the plurality supporting members are displayed independently, vibrations of the vibrator are not suppressed due to the supporting members. Accordingly, a stable vibrating attitude of the vibrator is assured.

A vibrator 12 of a vibratory gyroscope 10 includes, for example, a regular triangular prism shaped vibrating body 14.

On the vibrating body 14, pizoelectric elements 16a, 16b and 16c are formed respectively in the center of three side faces thereof.

The piezoelectric element 16a includes a piezoelectric layer 18a consisting of, for example, ceramics, and on one surface thereof, a mouting electrode 2Ga is formed. The mounting electrode 20a is bonded to the side face of te vibrating body 14, for example, by adhesives Moreover, on the other main surface of the piezoelectric layer l8a, connecting electrodes 22al, 22a2 and 22a3 divided into three laterally of the side face of the vibrating body 14 are formed.

Similarly, the other piezoelectric elements 16b and 16c also include piezoelectric layers 18b and 18c consisting of, for example, ceramics, and on one surfaces thereof, also mounting electrodes 20b and 20c are formed respectiverly.

These mounting electrodes 20b and 20c are also bonded to the side faces of the vibrating body 14, for example, by adhesives. Meanwhile, on the other main surface of the piezoelectric layer 18b, connecting electrodes 22bl, 22b2 and 22b3 divided into three laterally of the side face of the vibrating body 14 are formed, and on the other main surface of the piezoelectric layer l8c, connecting electrodes 22cl, 22c2 and 22c3 divided into three laterally of the side face of the vibrating body 14 are also formed.

Each of the electrodes descrbed above are made of an electrode material such as gold, silver, aluminum, nickel, copper-neckal alloy (Monel Metal) and the like, and formed by thin-film techniques such as squttering, evaporation and the like, or by printing techniques depending on the material.

If the vibrating body 14 is formed with a vibrating material comprising a metal such as elinver, ferro-nickel alloy, the electrodes 20a - 20c of the piezoelectric elements 16a - 16c may not be formed. It is because that, the vibrating body 14 serves as these electrodes 20a - 20c. In this case, the piezoelectric layers 18a - 18c may be made with a piezoelectric material such as PZT, ZnO etc. and formed by thin film techniques such as sputtering, evaporation etc.

In the vibratory gyroscope 10, for example, the piezoelectric element 16a is used for driving and the remaining two piezoelectric elements 16b and 16c for detection.

Therefore, in the embodiment, to the connecting electrodes 22al, 22a2 and 22a3 of the driving piezoelectric element 16a, a driving terminal 230 is connected. To the connecting electrodes 22b3 and 22c3 of the detecting piezoelectric elements 16b and 16c which are located extremely far away from the driving piezoelectric element 16a, a feedback terminal 232 is connected. Moreover, to the two connecting electrodes 22bl and 22b2 among the connecting electrodes of the detecting piezoelectric element 16b which are colse to the driving piezoelectric element 16a, one detecting terminal 234 is connected. Similarly, to the two connecting electrodes 22cl and 22c2 of the other detecting pXezoelectric element 16c, another detecting terminal 236 is connected.

Meanwhile, in the vibratory gyroscope 10, by shaving off an edge portion between the side faces of the vibrating body 14, the resonance frequency on the driving side and respective resonance frequencies on the detecting side are brought in coincidence.

That is, if the edge portion 13a opposing the driving piezoelectric element 16a is shaved off, the resonance frquency in the direction perpendicular to the main surface of the driving piezoelectric element 16a is controlled without influencing the vibrating direction of the vibrating body 14. Similarly, if the edge portion 13b or 13c opposing the detecting piezoelectric elements 16b or 16c is shaved off, the resonance frepuency in the direction perpendicular to the main surface of the piezoelectric element 16b or 16c is controlled without influencing the vibrating direction of the vibrating body 14.In this case, if the edge portion is shaved off at the longitudinal center, in particular, thickness T1, T2 or T3 in the vibrating direction shown in Fig. 29 is substantially thinned, as the result, the resonance frequency is reduced, and if longitudinal ends of the edge potion are shaved off, additional mass is substantially reduced and conversely the resonance frequency increases.

In the vibratory gyroscope 10, waken al resonance frequencies in three directions per?encicv31ar to the main surfaces of the piezoelectric elements lEa, 16b and 16e are different, these resonance frequencies are coinceded by shaving off at least two edge portions, and when the resonance frequency in one direction is different from the other resonance frequency in two directions, at least one edge portion is shaved off to coincide these resonance frequencies. Thereby, the resonance frequency on the driving side is coincided with respective resonance frequencies on the detecting side.

When coinciding the resonance frequency on the driving side with those on the detecting sides, the longitrdinal center of the edge portions of the vibrating body 14 are preferably shved off. When coinciding the resonance frequencies by shaving off the center of the edge portions of the vibrating body 14, the edge portion associated with the highest resonance frequency may be shved off first.

In the vibratory gyroscope 10, as particularly shown in Fig. 30, to the feedback terminal 232 and the driving terminal 230, an oscillator 250 as a feedback loop is connected. Thus, the vibratory gyroscope 10 makes selfoscillation drive. In this case, the vibrating body 14 is vibrated in the direction perpendicular to the main surface of the driving piezoelectric element 16a, and the output signal is obtained from the detecting pieazoelectric elements 16b and 16c or the detecting terminals 234 and 236.

Meanwhile, as shown in Fig. 30, the detecting terminals 234 and 236 are connected to an inversion input end and a non-inversion input end of a differential amplifier 252. An outut end of the differential amplifier 252 is connected to an input end of a synchronizing detection circuit 254, to which the aforesaid oscillation circuit 250 is connected via a phase circuit 256. In this case, the phase circuit 256 is controlled such that, the signal on the positive or negative side of the output difference between the detecting terminals 234 and 236 can be obtained from an output end of the synchronizing detection circuit 254. Meanwhile, the output end of the synchronizing detection circuit 254 is connected to an input end of DC amplifier 258 for rectifying the signal therefrom.

In the following, the operation of the vibratory gyroscope 10 will be particularly described.

thirst, t is ass'jmed that, hen the vibratory gyroscope 10 is not rotated, opposite ends of the vibrating body 14 bend, for example, in the direction shown by the arrow in Fig. 31, or reversely to the face whereon the driving piezoelectric c element 16a is formed. In this case, since the bending conditions of the piezoelecteic layer 18b of the detecting piezoelectric element 16b at portions close to and apart fron the driving piezoelectric element 16a are different, voltages generated are not equal. Therefore, if the positive voltage is outputted from the connecting electrode 22b1 close to the driving piezoelectric element 16a, the negative voltage is outputted from the connecting electrode 22b2 apart therefrom.Thus, the voltages of the connecting electrodes 22b1 and 22b2 are cancelled each other, and the putput voltage taken out from the detecting terminal 234 is deteriorated. Similarly, the positivse voltage is outputted from the connecting electrode 22cl of the other detecting piezoelectric element 16c, and the negative voltage is outputted from the connecting electrode 22c2. Thus, these voltages are cancelled each other, and the output voltage outputted from the other detecting terminal 236 is also deteriorated. When opposite ends of the vibrating body 14 bend in the direction in which the driving piezoelectric element 16a is formed, the output voltage signals from these connecting electrodes are inverse.

When considering the case whore the vibratory gyroscope 10 is rotated about its axis, sv vector composition of the vibration direction at non-rotation and a Coriolis force due to rotation, for example, as shown in Fig. 32, bending vibration takes place in the direction perpendicular to the face whereon the detecting piezoelectric element 16b is formed.In this case, assuming that opposite ends of the vibrating body 14, as shown by the arrow in Fig. 32, bend in the direction in which the detecting piezoelectric element 16b is fromed, the negative voltage is outputted fro te connecting electrodes 22bl and 22b2 of the detecting piezoelectric element 16b, and the positive voltage is outputted from the connecting electrodes 22cl and 22c2 of the detecting pieaoelectric element 16c. Thus, from one detecting terminal 234, a large value negative voltage is outputted, and from the other detecting terminal 23E, a large value positive voltage is outputted.When opposite ends of the vibrating body 14 bend reversely to the face whereon the detecting piezoelectric element 16b is formed, the output voltage signals outputted from these connecting electrdes are inversed.

In the vibratory gyroscope 10, since the resonance frequencies on the driving and detecting sides are coincided, the outputs from the detecting piezoelectric elements 1Sb and 16c or the detecting terminals 234 and 236 are obtained efficiently, as the result the rotational angular velocity can be detected efficiently. That is, frequency characteristics in the vibratory gyroscope 10 before coinciding the resonance frequencies on the driving and detecting sides are shown in Fig. 33 and those at coincidence of the resonance frepuencies are shown in Fig.

34.

Furthermore, in the vibratory gyroscope 10, the output voltage difference at non-rotation and rotation is large, results in a good S/N ratio. Besides, since the output signal difference between the detecting terminals 234 and 236 is detected, the output voltage at non-rotation becomes still smaller and that at rotation becomes still larger.

Output voltage characteristics representing the relationship between the rotational angular velocity (DEC;/SEC) and the output voltagae (V) when te vibratory gyroscope 10 is erected is shown in Fig. 35, and those representing the relationship between the tilt angle (degree) and the output voltage (V) thereof is shown in Fig. 36 When elinver annealed at 6000C for two hours was used as a material of the vibrating body 14, in the vibrating gyroscope 10, as shown in Fig. 37, a good frequencytemperature characteristics having a low frequency variation factor (%) against the temperature (OC) variation was obtained Fig 38 is a sectional view showing the modified embodiment of Figs. 28 and 29.In the embodiment, as compared with the embodiment of Figs. 28 and 29, in particular, entirely on the other main surfaces of the piezoelectric layers 18a, 18b and 18c, connecting electrodes 22a, 22b and 22c are formed respectively. Accordingly, in the embodiment, the driving terminal 230 is connected to one connecting electrode 22a and the detecting terminals 234 and 236 are connected respectively to the connecting electrodes 22b and 22c. In the embodiment, the outputs from the detecting terminals 234 and 236 are fed back to the driving terminal 230 in the composite form for self-oscillation drive.

Also, in this embodiment, as same as the embodiment of Figs. 28 and 29, the edge portion 13a, 13b or 13c of the vibrating body 14 is shaved off to coincide the resonance frequencies on the driving and detecting sides, so that the rotational angular velocity can be detected efficiently.

Fig. 39 is an illustrative view showing another modified embodiment of Figs. 28 and 29. In the embodiment, in particular, a vibrating body 14 is formed into a regular quadrangular prism, and on four side faces thereof, piezoelectric elements 16a, 16b, 16c and 16d are formed respectively. In this embodiment, two adjoining piezoelectric elements 16a and 1Sb are used for driving and the remaining two piezoelectric elements 15c and 16c are used for detection. Thus, to the driving piezoelectric elements 16a and 16b, driving terminals 230a and 230S are connected respectively, and to the detecting piezoelectric elements 16c and lEd, detecting terminals 234 and 236 are connected respectively.

Moreover, in the embodiment, the edge portion between the side faces of the vibrating body 14 are shaved off to coincide the resonance frequncies on the driving and detecting sides. In this case, by shaving off the edge portion 13a between the side faces whereon the driving piezoelectric elements 16a and 1Gb are formed, or the edge portion 13c between the side faces whereon the detecting piezoelectric elements 16c and lEd are formed, the thickness T and additional mass of the vibrating body 14 associated with the resonance frequency on the driving side can be changed, and the resonance frequency on the driving side is mainly controlled without influencing the vibrating direction of the vibrating body 14.Also, by shaving off the other edge portion 13b or 13d, the resonance frequency on the detecting side can be controlled without influencing the vibrating direction and the resonance frequency in the driving side.

Accordingly, also in this embodiment, the output from the detecting piezoelectric element is obtained efficiently and the rotational angular velocity can be detected efficiently.

Though the vibrating body 14 is formed into a regular triangular prism or a quadrangular prism in each of the embodiments shown in Figs. 28 through 39, it may be formed into other polygonal prism. In this case, the piezoelectric elements may be formed respectively on at least, three or more side faces of the vibrating body. The piezoelecWric elements formed on the side faces which are not n parallel may be used for one of driving and detection, and the other piezoelectric elements may be used for the other of driving and detection. Moreover, the resonance frequencies on the driving and detecting sides may be coincided by shaving off the edge portion between the side faces of the vibrating body.

If the edge portion between the side faces of the vibrating body is shaved off to coincide the resonance frequencies on the driving and detecting sides, since the piezoelectric elements formed on the side faces of the vibrating body which are not in parallel are used for one driving and detection, even when the edge portion between the side faces of the vibrating body is shaved off, the vibrating direction of the vibrating body is not deviated, thus detecting errors can be eliminated.

Thus, the output from the detecting piezoelectric element is obtained efficiently and the rotational angular velocity of the vibratory gyroscope can be detected efficiently.

In the vibrator 12, any two of piezoelectric elements 1Sa - 16c are used for driving and the remaining one is used for feedback. In the embodiment, for example, the piezoelectric elements 16a and 16b are used for driving and the other piezoelectric element 1Çe is used for feedback.

An electrode 22c of the feedback piezoelectric element 15c is connected to an input end of an oscillator 272 via a feedback terminal 270. An output end of the oscillator 272 is connected to a driving terminal 274, which is then connected to an electrode 22a of the driving piezoelectric element 16a via a fixed resistance 276a, and to an electrode 22b of the driving piezoelectric element 16b via a fixed resistance 276b. Therefore, the output of the feedback piezoelectric element 16c is fed back to the two driving piezoelectric elements 16a and 16b via the oscillator 272 and so on, and the vibrator 12 makes self-oscillation drive.In this case, the vibrating body 14 of the vibrator 12 is vibrated in the direction composed of two driving directions by the two driving piezoelectric elements 16a and 16b. Thus, in the embodiment, amplitudes of the vibrating body 14 are larger as compared with the case driven by one driving piezoelectric element. In addition, the vibrating attitude of the vibrating body 14 is stable against mechanical state variations such as variation with time, temperature variation, variation of mounting angle and variation of gravity (position of center of gravity).

Meanwhile, to the electrodes 22a and 22b on the input side of the driving piezoelectric elements 16a and 16b, detecting terminals 278a and 278b are connected respectively.

The detecting terminals 278a and 278b are designed to detect impedance variations of the driving piezoelectric elements 16a and 16b which change responsive to the rotational angular velocity of the vibratory gyroscope 10.

The detecting terminals 278a and 278b are connected respectively to two input ends of the differential amplifier 280. In the differential amplifier 280, impedance variations of the driving piezoelectric elements lEa and 16b are detected as potential differences between the electrodes 22a and 22b. Thus, the rotational angular velocity of the vibratory gyroscope 10 can be known by the output from the differential amplifier 280.

In the vibratory gyroscope 10, since the vibrator 12 having a large amplitude is use, the sensibility of the rotational angular velocity is improved. Besides, as the vibrating attitude of the vibrating body 14 is stable against the mechanical state variation such as the variation with time, the rotational angular velocity can be detected stably.

Furthermore, in the vibratory gyroscipe 10, since the rotational angular velocity is measured by detecting the potential difference between the electrodes 22a and 22b of the driving piezoelectric elements 16a and 16b, or the potential difference on the input side of the driving piezoelectric element without using the exclusive detecting piezoelectric element, even if characteristic variations, variations with time and temperature variations occur in the piezoelectric elements 16a - 16c, the rotational angular velocity can be measured accurately as the driving voltage is communized and stabilized, without being influenced by the characteristics of the piezoelectric elements or their resonance frequency deviation.

Fig. 41 is an illustrative view showing the modified embodiment of Fig. 40. In the embodiment, in particular, a vibrating body 14 is formed into a regular quadrangular prism, and piezoelectric elements 16a, 16b, 16c and 16d are formed respectively on four side faces of a vibrating body 14. The two adjoining piezoelectric elements 16a and 16b are used for driving, and the remaining two piezoelectric elements 16e and 16d are used for feedback.Therefore, the two feedback piezoelectric elements 16c and 16d are connected respectively to two fixed terminals 282a and 282b of a variable resistance 282, a movable terminal 282c of which is connected to the input end of an oscillator 272 via a feedback terminal 270. Thus, in this embodiment, outputs from the two feedback piezoelectric elements 16e and 16d are fed back to the two driving piezoelectric elements 16a and 16b in tahe composite form.

In each of the vibrators shown in Figs. 40 and 41, though the vibrator 14 is formed into a regular triangular prism or a regular quadrangular prism, it may be formed into a isosceles triangular prism. In this case, piezoelectric elements formed on the two identical side faces are used for driving and a piezoelectric element formed on the other side face is used for feedback. The vibrating body 14 may also take the form of a polygonal prism besides the isosceles triangular prism and regular quadrangular prism. In this case, the piezoelectric elements are formed respectively on, at least, three side faces of the vibrating body, and two or ore piezoelectric elements may be used for driving and one or more remaining piezoelectric elements may be used for feedback.In such a vibrator, when outputs from one or more feedback piezoelectric elements are fed back to two or more driving piezoelectric elements, the vibrator is driven by these driving piezoelectric elenents and the vibrating body is vibrated in the composite direction of the driving directions. Since the vibrating jod is vibrated as such by two or ore driving piezoelectric elements, amplitude of the vibrating body is larger as compared with the case wherein the vibrating bod is driven oy on driving piezoelectric element. Accordingly, a high sensitive vibratory gyroscope wnich is hardly influenced by external unnecessary vibrations can we obtained.Since the vibrating body is driven from two directions anc can be vibrated in tne composite direction of te criving direction, a stable vibrating attitude can obtained against mechanical state variation such as variation with time and variaticns of temperature, mounting angle and gravity (center of gravity) of the vibrating bod and its supporting member or supporting base, as compared with the case driven by one driving piezoelectric element so-called a one-way driving.Accordingly, such a vibrators can be preferably used in an apparatus whose basic vibrating attitude must be stable for detecting fine vibrations such as vibratory gyroscope.

Fig. 42 is an illustrative view showing another modified embodiment of Fig. 40. In the embodiment, a vibrating body 14 is formed into a regular triangular prism, and on two side faces thereof, piezoelectric elements 16a and 16b are formed respectively. One piezoelectric element 16a is used for driving and the other piezoelectric element 15b is used for feedback. Accordingly, to an electrode 22a cn the inpJt side of the driving piezoelectric element 16a, a detecting terminal 278 for detecting the rotational angular velocity is connected.

In the embodiment, an electrode 22b of tne feedback piezoelectric element 16b is connected to an input end of an oscillator 272, an output end of which is connected to the electrode 22a of the driving piezoelectric element 15a via fixed resistance 276.

Fig. 43 is an illustrative vie showin the odified embodiment of Fig. 42. In this embodiment, a vibrating bodi 14 is formed into a regular uadrangular prism, and on the two opposing side faces thereof, piezoelectric elements lEa and 16b are formed respectively. One piezoelectric element 16a is used for driving and the other piezoelectric element 16b is used for feedback. Therefore, also in this embodinent, as same as the embodiment shown in Fig. 42, to an electrode 22a on the input side of the drving piezoelectric element 16a, a detecting terminal 278 for detecting the rotational angular velocity is connected, and between te feedback piezoelectric element 16b and the driving piezoelectric element 16a, an oscillator 272 and a fixed resistance 276 connected in series are connected.

In such of the embodiments shown in Figs. 40 through 43, though the vibrating body 14 is formed into a regular triangular prism or a regular quadrangular prism it may take the form of polygonal prism other than the regular triangular an uadrangular prisms. Also in this case, if a detecting terminal is connected to the input side of a driving piezoelectric element formed on the side face of the vibrating body, the output corresponding to the rotational angular velocity can be obtained from the detecting terminal without passing through the piezoelectric element.

Accordingly, since the output corresponding to the rotational angular velocity can be obtained without passing through the piezoelectric element, even if characteristic deviations, variations with time and temperature variations occur in the piezoelectric element, the rotational angular velocity can be measured accurately without being influenced b y characteristics of the piezoelectric element.

Fig. 44 is an illustrative view showing still another modified embodiment of Fig. 40, In the vibratory gyroscope 10, to electrodes 22a and 22b of two driving piezoelectric elements 16a and 16b, fixed terminals 284a and 2 ;s of a variable resistance 294 are connected respectively. To a :novable terminal 234c of the variable resistance 284, a driving terminal 274 is connected When the vibrating gyroscope 10 is driven, fro the detecting terminal 278a and 278b, the output voltage corresponding to the rotational angular velocity is obtained.

In tis case, if the variable resistance 284 is controlled to make the product Cl?l of the electrostatic capacity value C1 c- tne driving piezoelectric element 16a and the resistance value R1 fror. one fixed terminal 284a to the movable terminal 234c of the variable resistance 284, and the product C2 . 2 of the electrostatic capacity value C2 of the driving piezoelectric element 165 and the resistance value R2 from the other fixed terminal 284b to the movable terminal 284c of the variable resistance 284 substantially equally, the in hase output voltage can be obtained from the detecting ~er..l ,.als 278a ant 278b without being influenced hy dispersions of the electrostatic capacity values of the driving piezoelectric elements 16a and 16b, and deviations of the resonance frequencies associated therewith.

In the vibratory gyroscope 10, even if the dispersions of the electrostatic capacity values or the deviations of the resonance frequencies associated therewith occur in the piezoelectric element, output voltages from te detecting terminals 278a and 278b nay be put in phase. Accordingly, the potential difference between the detecting term in s a 278a and 276b or the output from the differential amplifier 280 at standstill (at non-rotation) can be made zero.At rotation, by detecting the potential difference between the detecting terminals 278a and 27b by a svnchronizing detection circuit, a positive or negative signal corresponding to the rotational angular velocity can te obtained. Thus, in the the gyroscope 10, the rotational angular velocity can ce measured accurately.

Fig. 45 is an illustrative vie show =e embodiment of Fig. 44. n tne embodiment, as the embodiment shown in Fig. 44, in particular, though the construct ions of a vibratingbody 14, plezoelectric elements 16a - 16C ano a variable resistance 2; are same, it is cl different in that two piezoelectric elements 16a an 5^ are used or feedback an te remaining piezoelectric element 16c is used for driving.

Therefore, in this embodiment, driving terminal 274 is connected to ar. electrode 22e of the piezoelectric element 16c, Neanwhile, a feedback terminal 270 is connected tca movable terminal 284c of the variable resistance 284.

Also, in this embodiment, since the output voltage corresponding to the rotational angular velocity is obtained fro: the feedback piezelectric elements lEa and 16b, to electrodes 22a and cf the piezoelectric elements 16a ann 16b, detecting terminals 278a and 278b are connected respectively.

In the embodiment, if the variable resistance 284 is controlled so as to makt the product Cl.r-.l of the electrostatic capacity value C1 of the piezoelectric element 16a and the resistance value R1 fro one fixed terminal 284a to the movable terminal 234c of the variable resistance 284, and the product C2R2 of the electrostatic capacity value C2 of the piezoelectric element 16b and the resistance value ?.2 from the other fixed terminal 284S to the movable terminal 284c of the variable resistance 23e substantially equally, in-phase output voltages can be obtained from the detectng terminals 278a and 278b without being influenced by dispersions of the electrostatic capacity value of t he piezoelectric elements 16a and 16b, and deviations of the resonance frequencies associated therewith.

Fig. a6 is an illustrative view showing another :nodified embodiment of Fig. 44. In the embodiment, in particular, a vibrating body 14 is formed into a regular quadrangular prism, and on four side faces thereof, piezoelectric elements 16a, 16b, 16c and lEd are formed respectively. The two adjoining piezoelectric elements 16a and 16b are used for driving, and the remaining two piezoelectric elements 1Se and 16d. are used for feedback.

Accordingly, fixed terminals 284a and 284b of a variable resistance 23e are connect respectively to the driving piezoelectric element 16a and 16b, and to a movable terminal 284c of the variable resistance 284, a driving terminal 272 is connected. Meanwhile, to the feedback piezoelectric elements 15c and 16d, two fixed terminals 286a and 286b of a separate variable resistance 286 are connected respectively, and to a movable terminal 286c thereof, a feedback terminal 270 is connected.

isO, in this embodiment, as same as each of the embodiments of tigs. 44 and 5, an oscillator 272 is connected to the feedback terminal 270 and the driving terminal 272. Thus, the vibratory gyroscope 10 also makes self-oscillation crive. In this case, output voltages corresponding to te rotational angular velocity are generated in tahe driving piezoelectric elements 16a and lEb Therefore, in the embodiment, the detecting terminals 278a an an are connected te the driving piezoelectric elements 16a and 16b. The detecting terminals 278a and 278b are connected to the input side of a differential amplifier 280.

Also, in this embodiment, as same as the embodiment shown in Fig. 44, b controlling the variable resistance 284 connected to the driving piezoelectric elelments, in-phase output voltages can be obtained from the detecting terminals 27a and 2787^.

In the embodiment, since the output voltages corresponding to the rotational angular velocity is generated also from the feedback piezoelectric elements 16c and 16a, the detecting terminals 278a and 278b may be connected respectively to the feedback piezoelectric elements 16c and 16c. In this case, by controlling the separate variable resistance 236, in-phase output voltages are obtained from the detecting terminals 278a and 273b.

In each of the embodiments shown in Figs. 4 through 46, though the vibrating body 14 is forrned into a regular triangular or regular quadrangular prisms, it may take the form of polygonal prism other than the regular triangular or regular quadrangular prisms. -n this case, piezoelectric elements may be formed respectively on, at least, three sice faces of the vibrating body, respectively connecting to fixed terminals of the variable resistance to the two piezoelectric elements, connecting two detecting terminals resr,ectively to the two iezoelectric elements and using the movable terminal of the variable resistance for one of driving and feedback.

In this case, if the driving signal is applied to the movable terminal of the variable resistance to give the driving signal to the two piezoelectric elements connected to the two fixed terminals of the variable resistance, cr the output signal from these two piezoelectic elements is applied to the other piezoelectric elements through the movable terminal of the variable resistance, the vibratory gyroscope is driven, and the output voltages corresponding to the rotational angular velocity are obtained from the two detecting terminals.In this case, if the variable resistance value is controlled so as to make the product Cl.Rl of the electrostatic capacity value C1 of one of the two piezoelectric elements and the resistance value R1 ton one fixed terminal connected to the piezoelectric events to the movable terminal, and the product C 22 of the electrostatic capacity value C2 of te other piezoelectric elements and the resistance value 22 from te otter fixed terminal connected to te piezoelectric element to the rcvable terminal substantially equally, output voltages obtained from th two detecting; terminals are in phase.

Accordingly, since the output voltage - ... he two detecting elements can be put in 'phase without - influenced by despersions of the electrostatic capacity value of the piezoelectric element an deviations of the resonance frequencies associated therewith, the rotational angular velocity can be measured accurately.

Fig. 47 is an illustrative view showing a separate example of vibrator according to the present invention. he vibrator 12 includes a regular tri angular prism shapec vibrating body 14.

On the vibrating body 14, piezoelectric elements 16a, 15b and 16c are formed respectively in the center of three side faces thereof.

To electrodes 22a, 22b and 22c of the piezoelectric elements, three terminals 300a, 300b and 300c are connected respectively. Moreover, to the electrodes 22a and 22b of the oiezoelectric elements lóa and 15b, opposite ends 302a and '02b of a fixed resistance 302 are connected respectively.

The fixes resistance r02 is designed to balance characteristics between the piezoelectric elements 16a and 15b. That is, in the vibrator to which such a resistance is not connected, the characteristics between the piezoelectric elements may be unbalanced by dispersions of the electrostatic capacity value of the piezoelectric element and deviations o the resonance frequencies associated therewith, but in this embodiment, the characteristics between the piezoelectric elements 16a and lEb are ell balanced.

In the vibrator 12, the two piezoelectric elements 16a and lEb provided with the fixed resistance 302 are used for one of driving and detection, and the other piezoelectric element 16c is used for the other of driving and detection.

Thus, in the vibrator 12, if the driving signal is applied to the terminals 300a and 300b or the piezoelectric elements 15a and lEb, a stable output signal is obtained fro te piezoelectric element 16c or the t~~...inal 300c Conversely, if the drivin signal is applied to the terminal 300e of the piezoelectric element 16c, stable output signals are obtained from the piezoelectric elments 16a and 16b or the terminals 300a and 300.

For using the vibrator 12 in vibrator gyroscope, the driving signal may be applied to te piezoelectic element as aforementioned to measure the rotation angular velocity by tne output signal obtained from the other piezoelectric element under this condition.At this time, when the output signals are obtained from the two iezoelectric elements 16a and 16b, the rotational angular velocity may be measured from the output signal defference, for e:.m?le, by a differential amplifier.

A is is an illustrative view showing , the embodiment of Fig. 47. In this embodiment, in particular, a vibrating bod 14 is formec into a regular cuadrangular prsm, and on tour side faces thereof, piezoelectric elements 16a, 16b, lEc and 16d are formed respectively. To the piezoelectric elements 15a, 16b, 16c and 16c, terminals 300a, 300b, 300c and 300d are connected respectively.

Meanwhile, to the two adjoining piezoelectric elements 15a and 15b, opposite ends 302a and 302b of a fixed resistance 302 are connected respectively for improving the c h a r a c t e r i s b a l a n c e t h e r e b e t w e e n. Thus, t h e characteristics between te piezoelectric elements 16a and 16b are well balanced by the fixed resistance 302.

Similarly, to the other adjoining piezoelectric elements 16c and 16d, opposite ends 304a and 304b of another fixed resistance 304 are connected respectively, and the characteristic balance between the piezoelectiric elements 16c and 16d is improved by the fixed resistance 304.

In the vibrator 12, the two piezoe1ectric elements 15a and lSb provided with the fixed resistance 302 are used for one of driving and detection, ano the piezoelectric elements 16c and 16d provided with the other fixed resistance 304 are used for the other of driving and detection.

In the vibrator 12, if the driving signal is applied to the piezoelectric elements 15a and 16b, stable output signals are outputted from the piezoelectric elements 16e and 16d, and conversely if the driving signal is applied to the piezoelectric elements 16e and 16d, stable output srnals are obtained from the piezoelectric elements 16a and 15.

Accordingly, the vibrator 12 can also be preferably used in an apparatus utilizing fine variations of the vibrator such as vibratory gyroscope.

Fig. 49 is an illustratlive view showing another modified embodiment of Fig. 47. In the embodiment, a vibrating body 14 is formed into a regular hexagonal prism and to three side faces thereof not adjoined, piezoelectric elements 16a - 16c are formed respectively. To the piezoelectric elements 16a - 16c, terminals 300a - 'S0c are connected respectively. '-!oreover, to the piezoelectric elements 16a and 16b, opposite ends 302a and 302b of a fixed resistance 302 are connected respectively.

In this embodiment, as same as the embodiment shown Fig. 47, te two piezoelectric elements 16a and 15j are used for one o driving and detection, and the other piezoelectrc elements 16c is use for the other of driving and detection.

Also in this embodiment, since the characteristics balance between the two piezoelectric elements 16a and lEb is imoroved, it is preferably used in an apparatus suc as a vibratory gyroscope.

In each of the embodiments shown in Figs. 27 through 49, though the vibrating body 14 is formed into a regular triangular prism, a regular quadrangular prism or a regular hexagonal prism, it may be take the form of Isosceles triangular prism. In this case, che resistance is connected to the piezoelectric elements formed on the two identical side faces of the vibrating body 14 and the piezoelectric elements may be used for driving or detection.The vibrating body 14 may also be formed into a polygonal prism other than the isosceles triangular prism, regular quadrangular prism or regular hexagonal prism. In this case, piezoelectric elements may be formed, at least, on three side faces of the vibrating body Then, a resistance may be connected =o the two piezoelectric elements so as to be used for one of driving and detection, and the other piezoelectric element may be used for the other of driving and detection.

In this arrangement, the characteristic balance between the two piezoelectric elements connected thereto is improved by the resistance.

Accordingly, such a vibrator involves stable characteristics without being influenced by dispersions of the electrostatic capacity values of the two piezoelectric elements used for driving or detection and the resonance frequencies associated therewith.

Thus, the vibrator is preferably used in an apparatus utilizing fine variations of the vibrator such as a vibratory gyroscope. For example, when the vibrator is used in the vibratory gyroscope, a rotational angular velocity can be measured accurately.

tl hile the present invention has been particularly described and illustrated, it will be obvious that it is merely illustrative and restrictive, the spirit and scope of the present invention is therefore limited solely by the appended and claims.

Claims

CLAIMS:

1. A vibrator comprising: a vibratable body having a polygonal section; piezoelectric elements associated with two side faces of said vibratable body which are not in parallel; and two supporting members for supporting said vibratable body, wherein said vibratable body is supported by said supporting members near nodal points thereof a) at an equally spaced relation from two faces of said vibratable body whereon said piezoelectric elements are associated, and b) at two points on a longitudinal straight line of said vibratable body.

2. A vibrator in accordance with claim 1, wherein said supporting members are extended in a direction crossing a vibrating direction of said vibratable body,

3. A vibrator in accordance with claim 1, wherein said supporting members are connected to an edge of said vibratable body between two faces where said piezoelectric elements are associated.

4. A vibrator in accordance with claim 1, wherein said vibratable body is triangular in cross section.

5. A vibrator in accordance with claim 1, wherein said vibratable body is quadrangular in cross section.

6. A vibrator in accordance with claim 1, wherein said vibratable body is hexagonal in cross section and said supporting members are connected to said vibratable body on a centreline of a plane between faces of the vibratable body where the piezoelectric elements are formed.

6. A vibrator in accordance with claims 1, wherein said vibratable body is hexagonal in cross section and said supporting members are connected on a centreline of a plane between faces of the vibratable body where the piezoelectric elements are formed Amendments to the claims have been filed as follows 1. A vibrator comprising: a vibratable body having a polygonal section; piezoelectric elements associated with two side faces of said vibratable body which two faces are disposed obliquely to the plane of vibration.

two supporting members for supporting said vibratable body, wherein said vibratable body is supported by said supporting members near nodal points thereof a) at an equally spaced relation from two opposed end faces of said vibratable body whereon said piezoelectric elements are associated, and b) at two points on a longitudinal straight line of said vibratable body.

2. A vibrator in accordance with claim 1, wherein said supporting members are extended in a direction crossing a vibrating direction of said vibratable body.