JPH0854238A - Oscillator drive circuit - Google Patents

Abstract

PURPOSE:To prevent the oscillation frequency from being shifted from the resonance frequency due to the phase shift in a phase shifter circuit or a low- pass filter caused by fluctuation in the oscillation frequency. CONSTITUTION:A analog integration circuit 40 is substituted for a 90 deg. phase shift circuit. A rectangular wave is fed to the integration circuit 40 to produce a triangular wave having phase shift of 90 deg.. The triangular wave signal is applied to excitation electrodes 5a, 5b through a low-pass filter 14. An integration circuit 40 is inserted between the excitation electrodes 5a, 5b and one input of a PLL circuit 20 or between feedback electrodes 4a, 4b and the other input of the PLL circuit 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrator driving circuit,
For example, it can be used for an angular velocity detection device.

[0002]

2. Description of the Related Art For example, a technique relating to a device for detecting a rotational angular velocity using a vibrator is disclosed in Japanese Patent Application Laid-Open Nos. 5-240649, 5-288555, and GB2266149A.

In the apparatus for detecting the rotational angular velocity as described above, a vibrator such as a piezoelectric element is driven at a resonance point so as to vibrate at a frequency matching its natural frequency, and the driving terminal of the vibrator is driven. The angular velocity is detected by measuring the phase difference between the signal and the signal at the detection terminal.

By the way, the natural frequency of the oscillator fluctuates due to the influence of ambient temperature and the like. Therefore, when the vibrator is driven at a constant frequency in an environment where the temperature changes, the vibration state of the vibrator cannot be maintained at the resonance point. When the vibration state of the vibrator deviates from the resonance point, the amplitude of vibration fluctuates or an error occurs in the relationship between the phase difference and the angular velocity.

Then, for example, British Patent Application Publication GB226.
In the 6149A, a PLL (Phase Synchronous Loop) circuit is used to control the vibration state of the vibrator so as to maintain it at the resonance point. That is, the phase difference between the signal at the drive voltage application terminal of the vibrator and the signal at the return voltage extraction terminal of the vibrator is 90
The oscillation frequency of the VCO (voltage controlled oscillator) is automatically adjusted so that the frequency becomes constant.

[0006]

In order to control the phase difference between the signal at the drive voltage application terminal of the vibrator and the signal at the return voltage take-out terminal of the vibrator to 90 degrees by using the PLL circuit. Shifts the phase of one signal by 90 degrees,
The phase difference between the two signals applied to the phase comparator of the circuit must be zero in the steady state.

The phase shift circuit that shifts the phase of a signal can be formed by a time constant circuit including, for example, a capacitor and a resistor. However, the phase shift amount of this type of phase shift circuit changes according to the frequency. Therefore, if the driving frequency of the vibrator fluctuates significantly with changes in the ambient temperature, the PLL circuit will not function properly and the driving frequency will deviate significantly from the resonance frequency of the vibrator.

The VCO used in the PLL circuit is
Generally, a square wave signal containing various harmonics is output, so if the VCO output signal is applied to the vibrator as it is, it can be used in various vibration modes other than the mode used by the vibrator to measure angular velocity. Because of the vibration, the noise included in the detected signal increases and the measurement error increases. Therefore, in general, connect a low-pass filter to the output of the VCO,
The oscillator is driven by a signal having a waveform close to a sine wave. However, since the low-pass filter is a time constant circuit, the amount of phase change of the signal passing through it changes according to the frequency of the signal. That is, when the drive frequency of the vibrator fluctuates due to the change in ambient temperature, the PLL circuit does not function properly due to the phase change in the low-pass filter, and the drive frequency deviates from the resonance frequency of the vibrator.

Therefore, according to the present invention, even when the natural vibration frequency of the vibrator fluctuates due to fluctuations in the ambient temperature, etc., the vibration state of the vibrator is prevented from shifting from the resonance state, and the vibration state is detected from the vibrator. It is an object to prevent an increase in noise included in a signal that is generated.

[0010]

In order to solve the above-mentioned problems, the vibrator drive circuit of the present invention has a first terminal (5a, 5b) to which a drive voltage is supplied and the first terminal in a resonance state. A vibrator (2) including a second terminal (4a, 4b) in which a signal whose phase is shifted by approximately 90 degrees with respect to the signal of the terminal appears; the signal applied to the first terminal of the vibrator and the second terminal
Phase comparing means (21) for outputting a signal corresponding to the phase difference from the signal appearing at the terminal of the loop, and loop filter means (2) for generating a voltage corresponding to the signal output by the phase comparing means.
2), PLL control means (20) for supplying a signal to the first terminal of the vibrator, including a voltage controlled oscillation means (23) for generating a signal having a frequency corresponding to the voltage output from the loop filter means. And between the output of the PLL control means and the first terminal of the oscillator, between the output of the PLL control means and the first input of the phase comparison means, and the second terminal of the oscillator. And an integrator circuit means (40) interposed in at least one position between and the second input of the phase comparison means.

The symbols shown in the above parentheses are the reference numerals of the corresponding elements in the embodiments described later, but each component of the present invention is a specific element in the embodiments. It is not limited to only.

[0012]

In the present invention, the phase comparison means (21), the loop filter means (22) and the voltage controlled oscillation means (2).
The PLL control means (20) including 3) is applied to the first terminals (5a, 5b) of the oscillator (10) so that the phases of the signals applied to the two input terminals of the phase comparison means match. Automatically control the frequency of the signal. Further, at the second terminal (4a, 4b) of the vibrator, a signal whose phase is shifted by approximately 90 degrees with respect to the signal at the first terminal appears in the resonance state.

In order to maintain the resonator in a resonance state, it is necessary to input two signals having the same frequency and phase to the two input terminals of the phase comparison means in that state.
Since there is a phase difference of about 90 degrees in the resonance state between the signals applied to the first terminals (5a, 5b) and the signals appearing at the second terminals (4a, 4b) of the vibrator, they are different from each other. In order to perform PLL control with reference to a signal, it is necessary to use a phase shift circuit to phase shift at least one signal by substantially 90 degrees.

In the present invention, integrator circuit means (40) is provided to phase shift the signal by approximately 90 degrees. That is, since the sin function is integrated into a cos function, for example, when a sine wave signal is input to the integration circuit, a sine wave (cosine wave) whose phase is theoretically delayed by 90 degrees from the input is obtained at the output. To be Further, for example, when the input signal is a rectangular wave, a triangular wave whose phase is theoretically delayed by 90 degrees compared with the input is obtained at the output of the integrating circuit. The amount of phase shift by the integrating circuit means is always about 90 regardless of the frequency of the signal.
Therefore, even if the vibration frequency of the vibrator fluctuates, there is no phase shift in the output signal of the integrating circuit means. Therefore, the drive signal output from the PLL control means allows the vibrator to vibrate in a constantly resonant state.

In order to minimize the vibration component of the unnecessary mode, it is desirable that the vibrator vibrate in a perfect resonance state. However, even if it is vibrated at a frequency slightly deviated from the perfect resonance condition, noise will occur. The occurrence of unnecessary mode vibration is relatively small, and there is no problem in practical use. Further, there is a possibility that the phase shift amount of the integrating circuit means may be slightly deviated from 90 degrees due to the delay of the circuit element used, but the deviation is slight.

A triangular wave can be obtained by inputting a rectangular wave into the integrating circuit means, for example, but the proportion of harmonic components contained in the triangular wave is much smaller than that of the rectangular wave.
That is, since the harmonic component of the signal can be reduced by passing through the integrating circuit means, it becomes possible to reduce noise even if the filter is omitted by using the integrating circuit means. Omission of the filter can reduce the occurrence of phase shift when the signal frequency fluctuates.

The integrating circuit means is between the output of the PLL control means and the first terminal of the vibrator, between the output of the PLL control means and the first input of the phase comparison means, and the second terminal of the vibrator. It is inserted in at least one place between the terminal and the second input of the phase comparison means.

[0018]

FIG. 1 shows the configuration of a rotational angular velocity detection device according to an embodiment.
2 shows the detailed structure of a part of the blocks shown in FIG. 1, and FIG. 3 shows the appearance of the sensor element 10 shown in FIG. In FIG. 1, the sensor element 10 has shown the 1A-1A line cross section of FIG. The cylindrical piezoelectric body 2 of the sensor element 10 is fixed to the element base 1 whose lower end is a disk and whose upper end is a disk and whose lower surface is a round bar-shaped leg. The upper half of the outer peripheral surface of the cylindrical piezoelectric body 2 is covered with the reference potential electrode 3 connected to the equipment ground, but the lower half area of the outer peripheral surface has a pitch of 45 degrees and eight identical electrodes. Shaped electrode segments are joined. In the electric circuit connection shown in FIG. 1, of the eight electrode segments, a pair of electrode segments 4a and 4b opposed to each other in the first diametrical direction D1 is a feedback electrode and a second electrode segment.
A pair of electrode segments 5a and 5b facing each other in the diametrical direction D2 are excitation electrodes, and one facing each other in the third diametrical direction D3.
The pair of electrode segments 6a and 6b are detection electrodes.
In this example, the pair of electrode segments 7a and 7b facing each other in the fourth diametrical direction D4 are not used.

The AC voltage generated by the oscillator circuit is
It is applied to the excitation electrodes 5a and 5b of the sensor element 10, whereby the cylindrical piezoelectric body 2 is deformed and vibrates. Further, due to the vibration of the cylindrical piezoelectric body 2, the feedback electrodes 4a and 4b are provided.
The signal appearing at is fed back to the oscillator circuit.
Using the signal fed back, the oscillator circuit automatically adjusts the frequency of the output signal so that the cylindrical piezoelectric body 2 vibrates at a frequency matching its resonance frequency fm.

When the oscillation circuit is powered on, a certain voltage is applied between the excitation electrodes 5a and 5b and the reference potential electrode 3, whereby the cylindrical piezoelectric body 2 spreads in the second diameter direction D2. Or reduce. Due to this deformation, a certain voltage is generated between the feedback electrodes 4a and 4b and the reference potential electrode 3. The cylindrical piezoelectric body 2 at the resonance frequency fm and in the reduction peak of vibration when expanding / reducing vibration in the second diameter direction D2 is exaggerated in FIG. 4 and shown by a dotted line 2B. ,
The cylindrical piezoelectric body 2 in the enlarged peak is exaggeratedly shown in FIG. 4 by a chain double-dashed line 2A. As can be seen from FIG. 4, the enlargement / reduction in the second diametric direction D2 is the reduction / enlargement in the first diametric direction D1, and the enlargement peak in the D1 direction corresponds to the reduction peak in the D2 direction. Therefore, in this example, the cylindrical piezoelectric body 2 vibrates in the cross direction (D1 & D2).

As described above, when the cylindrical piezoelectric body 2 is vibrating in the cross direction (D1 & D2) (two-dot chain line 2 in FIG. 4).
A & dotted line 2B) and the detection electrodes 6a and 6b are located at the nodes of vibration, so that the voltage appearing between them and the reference potential electrode 3 is low. No voltage appears in the ideal state, but a certain amount of voltage is generated because the shape of the cylindrical piezoelectric body 2 is not a perfect cylinder.

When the cylindrical piezoelectric body 2 rotates, for example, as shown in FIG.
When it is rotated clockwise as indicated by, the rotation and the vibration of the cylindrical piezoelectric body 2 generate Coriolis forces F1 to F4,
As a result, the vibration direction (D2) of the cylindrical piezoelectric body 2 is twisted (rotated) in the third diametrical direction D3 (or the fourth diametrical direction D4) as shown by the solid line 2C in FIG. As the voltage appearing at 6a and 6b increases, the phase of the voltage (AC) shifts. This phase shift amount is
It corresponds to the rotational angular velocity applied to the cylindrical piezoelectric body 2.
Therefore, the apparatus shown in FIG. 1 is equipped with a circuit for measuring the amount of phase shift of the signals appearing on the detection electrodes 6a and 6b.

An oscillating circuit for exciting the cylindrical piezoelectric body 2 will be described with reference to FIG. PLL (Phase synchronization rule
The signal SE is respectively applied to the two input terminals of the circuit 20.
And SF are applied. The signal (triangular wave) output from the PLL circuit 20 is applied to the frequency divider 18, the integrating circuit 40, and the low frequency wave.
It passes through the pass filter 14 and is applied as a drive signal SA to the excitation electrodes 5a and 5b.

As shown in FIG. 7, the signal SD output from the frequency divider 18 is a rectangular wave, and since this signal is input to the integrating circuit 40, the signal SO appearing at the output of the integrating circuit 40.
Becomes a triangular wave. Further, the phase of the output signal SO is delayed by 90 degrees with respect to the input signal SD. That is, the integrating circuit 40
Functions as a 90-degree phase shift circuit. Even if the frequency of the signal fluctuates, the phase shift amount of the integrating circuit 40 is always 90 degrees, and no phase shift occurs. Further, the rectangular wave has a large proportion of harmonic components contained therein, whereas the triangular wave has a relatively small proportion of harmonic components contained therein. As can be seen from the fact that if the sine function is integrated into a cos function, the input signal waveform is not limited to a rectangular wave as a condition for the integration circuit 40 to function as a 90-degree phase shift circuit.

In order to suppress the vibration in the unnecessary mode, it is desirable to use a sine wave as a signal for exciting the cylindrical piezoelectric body 2. Therefore, in this example, the low-pass filter 14 is connected to the output of the integrating circuit 40 to remove the harmonic component, and only the sine wave component is used as the signal SA for the excitation electrodes 5a, 5a.
It is configured to be applied to b. However, it is also possible to omit the low-pass filter 14. Further, since the harmonic components included in the triangular wave which is the input signal are relatively small, even when the low pass filter 14 is used, the harmonic attenuation rate required for the low pass filter 14 is relatively small. Therefore, the amount of phase shift caused by the low-pass filter 14 is slightly suppressed.

The signal SD output from the frequency divider 18 is input to the inverter 17 with a Schmitt trigger via the low pass filter 13. The binary signal SD obtained at the output of the inverter 17 is applied to one input terminal of the PLL circuit 20. The signals appearing on the feedback electrodes 4a and 4b pass through the low pass filter 12 and are input to the inverter 16 with a Schmitt trigger. The binary signal SF obtained at the output of the inverter 16 is the PLL circuit 20.
Applied to the other input terminal of.

The low pass filters 12, 13 and 14 are
The harmonic component contained in the input signal is removed, and only the fundamental wave (sine wave having a frequency matching the resonance frequency of the cylindrical piezoelectric body 2) component is extracted. Low-pass filter 13
Are provided to cancel the influence of the phase shift caused by the low-pass filters 12 and 14. The low-pass filters 12, 13 and 14 have cutoff frequencies slightly higher than the resonance frequency of the cylindrical piezoelectric body 2. Cylindrical piezoelectric body 2
Although the resonance frequency of 1 changes somewhat with a change in temperature, it does not change significantly, so the cutoff frequencies of the low-pass filters 12, 13 and 14 are fixed.

As shown in FIG. 2, the PLL circuit 20 is composed of a phase comparator 21, a loop filter 22 and a VCO (voltage controlled oscillator) 23. The phase comparator 21 is
It outputs a pulse signal having a pulse width corresponding to the phase difference between the pulse signals input to its two input terminals. The loop filter 22 outputs an analog voltage signal corresponding to the pulse width of the signal output by the phase comparator 21. This signal is input to the VCO 23. The VCO 23 outputs a triangular wave signal having a frequency according to the input voltage. Therefore, the PLL circuit 20 automatically adjusts the frequency of the triangular wave signal output from the PLL circuit 20 so that the phase difference between the pulse signals input to its two input terminals becomes zero.

The description will be continued with reference to FIG. 1 again. When the cylindrical piezoelectric body 2 is vibrating at its resonance frequency, the signals appearing on the feedback electrodes 4a and 4b have a phase difference of 90 degrees with respect to the signals applied to the excitation electrodes 5a and 5b. However, when the frequency of the signal deviates from the resonance frequency, the phase difference changes. The signal SA applied to the excitation electrodes 5a and 5b is 9 times that of the signal SE applied to one input terminal of the PLL circuit 20 due to the function of the integration circuit 40.
0 degrees out of phase. Also, the feedback electrode 4
Since the signals appearing at a and 4b have a phase difference of 90 degrees with respect to the signal SA applied to the excitation electrodes 5a and 5b, the phase of the signal SF applied to the other input terminal of the PLL circuit 20 is , Signal SE. Therefore, when the cylindrical piezoelectric body 2 vibrates at its resonance frequency, PL
The L circuit 20 is in a locked state and the vibration frequency is constant. However, if the resonance frequency deviates from the vibration frequency due to a temperature change, for example, the two input signals of the PLL circuit 20 are out of phase, so that the deviation is eliminated. , PLL circuit 20 adjusts the vibration frequency. Therefore, the cylindrical piezoelectric body 2
Is always driven to oscillate at its resonant frequency.

By the way, each of the low-pass filters 12, 13, and 14 is a time constant circuit, and a phase difference occurs between the input and the output. Moreover, this phase difference changes according to the frequency of the signal. However, in this example, the low-pass filter 12
Since the characteristics are determined so that the influence of the phase shift caused by the signals 14 and 14 on the signal SF and the influence of the phase shift caused by the low-pass filter 13 on the signal SE are substantially the same, the influence of the both influences the PLL circuit 20. On the other hand, they offset each other. That is, since the phase shift caused by the low-pass filters 12, 13 and 14 does not substantially affect the PLL circuit 20, the cylindrical piezoelectric body 2 is always maintained in the resonance state even if the vibration frequency changes. It

Next, a circuit for measuring the rotational angular velocity will be described. The signals appearing at the detection electrodes 6a and 6b of the cylindrical piezoelectric body 2 pass through the low pass filter 11 and are applied to the inverter 15 with a Schmitt trigger to be converted into a binary signal SG. This signal SG is
Applied to one input terminal of the switch 51. The signal SF generated from the signals appearing at the feedback electrodes 4a and 4b is applied to the other input terminal of the exclusive-overgate 51. The output signal SH of the exclusive gate 51 is applied to one input terminal of the NAND gate 52. To the other input terminal of the NAND gate 52,
The output signal SI of the multiplication circuit 30 is applied. Multiplier circuit 3
The output signal of the frequency divider 56 is applied to the 0 input. The output signal SN of the PLL circuit 20 is applied to the input terminal of the frequency divider 56. Further, this signal SN is supplied to the counter 5
5 is applied as a clock pulse. The carry signal SJ output from the counter 55 is applied to the clear terminal of the counter 53 and the clock terminal of the latch 54. The output signal SK of the NAND gate 52 is applied to the counter 53 as a clock pulse (count signal). The count value SL of the counter 53 is applied to the input terminal of the latch 54.

In this embodiment, the frequency divider 18 outputs a signal whose period is 32 times that of the input signal. Also divider 56
Outputs a signal whose period is 31 times that of the input signal.
The frequency of the frequency multiplier circuit 30 is 102 with respect to the input signal.
Outputs 4 times the signal. The counter 55 is a 992 binary counter. Therefore, assuming that the period and frequency of the signal SA are T and f, respectively, the period and frequency of each signal are as follows.

SA, SB, SC: T, f SN: T / 32, 32f SJ: 31T, f / 31 SI: 31T / (32 × 1024), (32 × 1024) f / 31 signal SA, SB, SC , SD, SE, SF, SG and S
An example of the timing of H is shown in FIG. The phase difference between the signals SA and SB is always maintained at 90 degrees by the control of the PLL circuit 20. The phase difference between the signal SB (SF) and the signal SC (SG) changes in proportion to the rotational angular velocity applied to the cylindrical piezoelectric body 2. Assuming that the pulse width of the signal SH output from the exclusive-original gate 51 is ΔT, ΔT / T changes in proportion to the phase difference between the signal SF and the signal SG, that is, the angular velocity. Therefore, if ΔT / T is measured, information indicating the angular velocity can be obtained.

As shown in FIG. 2, the multiplication circuit 30 is composed of a phase comparator 31, a loop filter 32, a VCO 33 and a frequency divider 34. The frequency division ratio N of the frequency divider 34 in the frequency multiplication circuit 30 is 1024. Therefore, at the output of the multiplication circuit 30, a signal having a frequency of 1024 times that of the input signal is obtained.

As shown in FIG. 6, the signal SH becomes a high level H by ΔT every cycle T. Then, a pulse of the signal SI appears in the signal SK while the signal SH is at a high level. The number of pulses of this signal SK, that is, the time corresponding to ΔT corresponding to the angular velocity is counted by the counter 53. Since the cycle of the signal SJ that clears the counter 53 is 31T,
The counter 53 calculates the time integrated value of ΔT × 31 during 31T, and the integrated value is held in the latch 54 and the signal S.
It is output as M.

In the circuit shown in FIG. 1, there is a special reason why the frequency division ratio of the frequency divider 18 and the frequency division ratio of the frequency divider 56 are set to different values. That is, the counter 53
By shifting the frequency of the signal SI which becomes the counting pulse of the above from an integer multiple of the vibration period number (1 / T) of the cylindrical piezoelectric body 2, it is possible to improve the measurement accuracy without raising the frequency of the signal SI very much. it can.

In the circuit shown in FIG. 1, it is assumed that the frequency divider 5
When the division ratio of 6 is changed to 1/32, the frequency of the signal SI becomes 1024f, so the resolution when measuring the phase difference (ΔT / T) becomes 1/1024, and a subtle change in angular velocity is measured. Can not do it. If the frequency of the signal SI is increased in order to increase the resolution, the measurement circuit such as the counter 53 must be configured by a special circuit that operates at high speed, which is very expensive.

In the actual circuit shown in FIG. 1, the signal S
Since the frequency of I is (32 × 1024) f / 31, the number of SI pulses during the time T is 32 × 1024/31, for example. In a digital circuit, the fractional part of the pulse number is usually rounded down or rounded up, which causes an error. However, in the circuit of FIG. 1, since the frequency division ratios of the frequency divider 18 and the frequency divider 56 are deviated, the phase in which the SI pulse appears in the time T is deviated little by little over time, and a certain period In, the fractional part of the SI pulse number counted in the time T is rounded down, but in another certain period, the fractional part of the SI pulse number counted in the time T is rounded up. Therefore, if the number of pulses counted in a plurality of cycles is averaged, the error is reduced.

Actually, since the period of the signal SJ that determines the counting period of the counter 53 is 31T, the measurement of the time with respect to ΔT is repeated 31 times, and the integrated value of ΔT in the period of 31T, that is, the error of rounding down and rounding up. The value obtained by smoothing is counted by the counter 53 and held in the latch 54. That is, the number of SI pulses in the period of 31T is 32 ×
Since it is 1024, the measurement resolution of the phase difference (ΔT / T) is 1 / (32 × 1024). Therefore, the frequency divider 18
And the resolution becomes 32 times as compared with the case where the frequency division ratio of the frequency divider 56 is the same. As a result, even if the frequency of the signal SJ is low, the angular velocity can be measured with high accuracy.

For example, the vibration frequency of the cylindrical piezoelectric body 2 is 8
In the case of KHz, in order to detect the phase difference with a resolution of 0.02 degrees, it is necessary to count 144 MHz clock pulses in a general circuit, and the circuit configuration is extremely difficult. In this case, since the frequency of the clock pulse (SI) can be lowered to about 4.8 MHz, the circuit configuration becomes very simple.

Next, a modified embodiment will be described. In the embodiment shown in FIG. 8, the signal SD output from the frequency divider 18
Is directly applied to the low-pass filter 14, and the output signal SA of the low-pass filter 14 is applied to the excitation electrodes 5a and 5b. Further, the signal SA is input to the integrating circuit 40, and the output signal SP of the integrating circuit 40 is input to the PLL circuit 20 as the signal SE via the low-pass filter 13 and the inverter 17. Therefore, when the cylindrical piezoelectric body 2 is in the resonance state, the signals SE and SF are in phase with each other, and the resonance state is maintained by the control of the PLL circuit 20.

In the embodiment shown in FIG. 8, since the signal input to the low-pass filter 14 is a rectangular wave containing many harmonics, the harmonic attenuation rate required for the low-pass filter 14 becomes large. Therefore, although the phase shift generated in the low-pass filter 14 is larger than that in the embodiment of FIG. 1, this phase shift has the same effect on both the signals SE and SF, and therefore the position between the signals SE and SF is large. There is no change in the phase difference.
The low-pass filter 13 produces the same phase shift as the signal S caused by the low-pass filter 12 in the signal S.
It is provided in order to cancel the phase shift between the two by causing it in E.

In the embodiment shown in FIG. 9, the frequency divider 18
The signal SD output by the above is applied to the excitation electrodes 5a and 5b as the signal SA through the low-pass filter 14, and
The signal SD is applied to one input terminal of the PLL circuit 20 as the signal SE through the low pass filter 13 and the inverter 17. An integrating circuit 40 is inserted between the output of the low-pass filter 12 and the input of the inverter 16. Therefore, the signal SQ obtained by phase-shifting the signal SB by 90 degrees is applied to the input of the inverter 16. That is, also in this embodiment, when the cylindrical piezoelectric body 2 is in the resonance state,
Since the phases of the signals SE and SF match, the PLL circuit 2
With the control of 0, the resonance state of the cylindrical piezoelectric body 2 is maintained.

In the embodiment shown in FIG. 9, since the signal input to the low-pass filter 14 is a rectangular wave containing many harmonics, the harmonic attenuation rate required for the low-pass filter 14 becomes large. Therefore, the phase shift generated in the low-pass filter 14 is larger than that in the embodiment of FIG. The low-pass filter 13 produces the same phase shift as the signal S caused by the low-pass filters 12 and 14 in the signal S.
It is provided in order to cancel the phase shift between the two by causing it in E.

In the above embodiment, in order to vibrate the cylindrical piezoelectric body 2 in the resonance state at all times, the excitation electrodes 5a,
The PLL circuit 20 controls the phase difference between the signal of 5b and the signals of the feedback electrodes 4a and 4b to be 90 degrees. However, in actuality, it is conceivable that the vibrator may reach the maximum resonance state when there is a phase difference slightly deviated from the theoretical value of 90 degrees due to variations in circuit constants and characteristics of the vibrator. Therefore, the phase difference may actually be controlled within the range of about 80 to 100 degrees. If the phase difference to be maintained is different from 90 degrees, it can be dealt with by adding an additional phase shift circuit to the integrating circuit 40. Even in that case, since the phase shift amount of the auxiliary phase shift circuit is sufficiently smaller than 90 degrees, even if the frequency changes, a large phase shift does not occur. Further, the vibration frequency of the vibrator does not have to completely match the resonance frequency thereof. It is most preferable to match the vibration frequency with the resonance frequency, but if the vibration frequency is in the vicinity of the resonance frequency, noise can be prevented from occurring to some extent, and there is no practical problem.

[0046]

In the present invention, the integrating circuit means (40) is used to shift the phase of the signal by about 90 degrees. Since the amount of phase shift by the integrating circuit means is always about 90 degrees regardless of the frequency of the signal, even if the vibration frequency of the oscillator fluctuates due to temperature change, the output of the integrating circuit means There is no phase shift in the signals. Therefore PL
The drive signal output from the L control means allows the vibrator to vibrate in a constant resonance state.

A triangular wave can be obtained by inputting a rectangular wave to the integrating circuit means, for example, but the proportion of harmonic components contained in the triangular wave is much smaller than that of the rectangular wave.
That is, since the harmonic component of the signal can be reduced by passing through the integrating circuit means, it becomes possible to reduce noise even if the filter is omitted by using the integrating circuit means. Omission of the filter can reduce the occurrence of phase shift when the signal frequency fluctuates.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a rotation angular velocity detection device according to an embodiment.

FIG. 2 is a block diagram showing a detailed configuration of some blocks of the device shown in FIG.

FIG. 3 is a front view showing an external appearance and a partial cross section of the sensor element 10.

FIG. 4 is a plan view showing a vibrating state of the cylindrical piezoelectric body 2.

5 is a time chart showing an example of signals of respective parts of the circuit of FIG. 1. FIG.

FIG. 6 is a time chart showing an example of signals of respective parts of the circuit of FIG.

FIG. 7 is a time chart showing an example of signals of respective parts of the circuit of FIG.

FIG. 8 is a block diagram showing a configuration of a rotation angular velocity detection device of a modified example.

FIG. 9 is a block diagram showing a configuration of a rotation angular velocity detection device of another modification.

[Explanation of symbols]

1: Element stage 2: Cylindrical piezoelectric body 3: Reference potential electrode 4a, 4b: Feedback electrode 5a, 5b: Excitation electrode 6a, 6b: Detection electrode 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b : Electrode segment 10: Sensor element 12, 13, 14: Low-pass filter 16, 17: Inverter 18, 56: Divider 20: PLL circuit 30: Multiplier circuit 21, 31: Phase comparator 22, 32, 42: Loop filter 23, 33: VCO (voltage controlled oscillator) 34, 56: Frequency divider 40: Integrator circuit 51: Exclusion-sive or agate 52: Nandgate 53, 55: Counter 54: Latch SA, SB, SC, SD, SE, SF, SG, SH, S
I, SJ, SK, SL, SM, SN, SO, SP, S
Q, S41, S42, S43: Signal Patent applicant Aisin Seiki Co., Ltd. Attorney Attorney
Nobuoki Sugi

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Kobayashi 2-1-1 Asahi-cho, Kariya city, Aichi Aisin Seiki Co., Ltd.

Claims (1)

[Claims] 1. A vibrator comprising: a first terminal to which a drive voltage is supplied; and a second terminal in which a signal whose phase is shifted by approximately 90 degrees with respect to the signal of the first terminal appears in a resonance state; Phase comparing means for outputting a signal according to the phase difference between the signal applied to the first terminal of the vibrator and the signal appearing at the second terminal, and to generate a voltage according to the signal output by the phase comparing means. PLL control means for supplying a signal to the first terminal of the vibrator, including loop filter means and voltage controlled oscillating means for generating a signal having a frequency corresponding to the voltage output by the loop filter means; and the PLL. Between the output of the control means and the first terminal of the oscillator, between the output of the PLL control means and the first input of the phase comparison means, and between the second terminal of the oscillator and the phase comparison. At least one of the second inputs of the means Integrating circuit means inserted at a location;
A vibrator driving circuit including.