JPH08304075A - Angular velocity sensor - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to prevent deterioration of detection accuracy in an angular velocity sensor. The present invention includes a piezoelectric body 3, detection electrodes 7 and 8 and a drive electrode 6 provided on the piezoelectric body 3, and a first power source connected to the drive electrode 6, A cancel electrode is provided, and the cancel electrode is connected to a second power supply that supplies a signal having a phase difference of approximately 180 degrees from the signal supplied from the first power supply to the drive electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor used for car navigation and vehicle attitude control.

[0002]

2. Description of the Related Art This type of vibrating angular velocity sensor has a tuning-fork-shaped piezoelectric body provided with a detection electrode and a drive electrode, and vibrates the piezoelectric body by supplying a signal from a power source to the drive electrode. When the angular velocity is applied during this vibration, the Coriolis force causes the piezoelectric body to bend in a direction orthogonal to the vibration direction, and the electric charge generated at that time is derived through the detection electrode.

[0003]

In the conventional angular velocity sensor described above, a part of the signal supplied from the drive electrode to the piezoelectric body flows into the detection electrode that is capacitively coupled to the drive electrode. As a result, there is a problem that the detection accuracy is lowered. That is, since the piezoelectric body, which is also a dielectric body, is provided with the detection electrode and the drive electrode as described above, capacitive coupling cannot be avoided even if the two are separated from each other. It would flow into the sensing electrode dielectrically.

The angular velocity sensor of the present invention is intended to improve the detection accuracy.

[0005]

To achieve this object, the present invention provides a piezoelectric body, a detection electrode and a drive electrode provided on the piezoelectric body, and a first power source connected to the drive electrode. The piezoelectric body is provided with a cancel electrode, and the cancel electrode is connected to a second power supply for supplying a signal having a phase difference of approximately 180 degrees from the signal supplied from the first power supply to the drive electrode. is there.

[0006]

With the above arrangement, the signal supplied from the second power supply to the cancel electrode is approximately 180 degrees out of phase with the signal supplied from the first power supply to the drive electrode. A signal that tries to inductively flow from the drive electrode to the sensing electrode is canceled by a signal that tries to dielectrically flow from the cancel electrode to the sensing electrode, and as a result, the sensing electrode has these first, The signal based on the angular velocity is correctly derived without being affected by the signal from the second power source, and the detection accuracy thereof is extremely high.

[0007]

【Example】

(Embodiment 1) In FIGS. 4 and 5, reference numeral 1 denotes a bottom plate made of stainless steel, and a case 2 in the shape of a metal square tube is mounted on the bottom plate 1, whereby the inside of the case 2 is a sealed space. A tuning fork-shaped piezoelectric body 3 is provided in the sealed space, and a lower end surface of the piezoelectric body 3 is supported by a pin 4 on a bottom plate 1 via a base 5. As shown in FIGS. 1 to 3, the piezoelectric body 3 has tuning fork arms 3a and 3b on the left and right, and each standing wall surface has three electrodes.

Of these, detection electrodes 7 and 8 are provided on the front side of the tuning fork arm 3a on the left and right sides of the drive electrode 6, and on the back side thereof, the detection electrodes 1 and 8 are centered on the drive electrode 9.
0 and 11 are provided, detection electrodes 7 and 10 are provided on the left side face around the drive electrode 12, and detection electrodes 7 and 10 are provided on the right side face around the drive electrode 13.
1 is provided.

A sine wave signal of 8 kHz is supplied to the drive electrodes 12 and 13 via a terminal 14 as shown in FIG. A sine wave signal of 8 kHz is also applied to the drive electrodes 6 and 9 via a terminal 15, but the phase is different by 180 degrees from that supplied to the drive electrodes 12 and 13. Further, the diagonal detection electrodes 7 and 11 are connected to the terminal 16 and the detection electrodes 8 and 10 are connected to each other.
Is connected to terminal 19 and the angular velocity signal is
6 and 19 are derived.

On the other hand, the tuning fork arm 3b side has the same electrode arrangement, and the same reference numeral as that of the tuning fork arm 3a side is given. However, since this tuning fork arm 3b is on the drive amplitude monitor side, The terminals connected to the electrodes 12, 13, 6, 9 are different from the tuning fork arm 3a. That is, the tuning fork arm 3b
The electrodes 12 and 13 are connected to the monitor terminal 17, and the electrodes 6 and 9 are connected to the monitor terminal 18.

A current detector 20 is connected to the terminal 18, and the terminal 14 is connected to the current detector 20 via an AGC adjuster 21. Further, the charge detector 22, the synchronous detector 23, and the integrator 2 are connected to the terminal 19.
An output terminal 25 is connected via 4. Further, the current detector 20 is connected to an AGC adjuster 21 via an AGC comparator 26. Furthermore, this AGC adjuster 21
The terminal 15 is connected to the output side of the resistor 27 via the resistor 27, the negative terminal of the operational amplifier 28, and the output thereof. A variable resistor 29 is connected in parallel between the negative terminal and the output terminal of the operational amplifier 28.

In the above structure, a drive signal of a sinusoidal wave of 8 kHz is applied from the terminal 14 to the drive electrodes 12 and 13, and at the same time, a drive having a 180 ° phase difference inverted by the operational amplifier 28 from the terminal 15 is applied. A signal is applied. This state is shown in FIG.
2 and 13 are shown as D +, and the drive electrodes 6 and 9 are shown as D- (minus). When a drive signal is applied to the tuning fork arm 3a, since the tuning fork arm 3a itself has a self-excited resonance point of 8 kHz, it vibrates left and right in FIG. That is, as shown in FIG. 2, the drive electrodes 12, 13, 6, 9 of the tuning fork arm 3a are provided with D +, D-.
6 is applied, an electric force line like an arrow from the D + side to the D− side is formed as shown in FIG. 6, and in response to this, the tuning fork arm 3a contracts on the drive electrode 13 side (in the figure, Chi "
That is, the drive electrode 12 side extends (expressed as “no” in the figure), that is, the drive electrode 12 is curved outward. Figure 6
7 and 7 respectively show only the drive electrodes and the detection electrodes in an easy-to-understand manner. In reality, both electrodes are arranged on the tuning fork arms 3a and 3b.

To further explain this point, in the tuning fork, strain or stress in the axial direction (vertical direction in FIG. 1) and electric flux density or electric field in the width direction (horizontal direction in FIG. 1) are mutually converted with polarity. As shown in FIG. 6, in the tuning fork arm 3a, when an electric force line is generated from the drive electrode 13 toward the drive electrodes 6 and 9, an axial contraction phenomenon occurs at this portion. When (electric field → distortion conversion) occurs and electric lines of force on the opposite side from the above are generated from the drive electrode 12 toward the drive electrodes 6 and 9, an axial elongation phenomenon (electric field → distortion) occurs in this portion. (Conversion) occurs, and as a result, the tuning fork arm 3a bends outward.

Along with this, a displacement current phenomenon (distortion → electric flux density conversion) in the width direction occurs opposite to the tuning fork arm 3a in the axial extension and contraction of the tuning fork arm 3b due to the resonance phenomenon of the tuning fork. A current signal is picked up from the electrodes 6, 9, 12, and 13, and the terminal 1 is based on the terminal 17.
8. Positive feedback is applied through the self-excited oscillation loop of the current detector 20, the AGC adjuster 21, and the resonance phenomenon is induced and amplified.

The AGC comparator 26 is the current detector 2
Negative feedback is applied to the AGC regulator 21 in order to keep the output of 0 constant. In this way, the tuning fork arms 3a and 3b vibrate regularly with a constant amplitude.

In this way, when the tuning fork arms 3a and 3b vibrate regularly, when an angular velocity is applied,
The Coriolis force causes the tuning fork arms 3a and 3b to vibrate in directions opposite to each other in a direction orthogonal to the tuning fork vibration direction. Then, the angular velocity signal is the tuning fork arm 3a, shown in FIG.
It is derived from the detection electrodes 8, 10, 7, 11 of 3b, and is output from the output terminal 25 via the terminal 19, the charge detector 22, the synchronous detector 23, and the integrator 24 with reference to the terminal 16.

The induction of this angular velocity signal will be described in detail. As shown in FIG. 7, when the tuning fork arm 3a vibrates downward and the tuning fork arm 3b vibrates upward, the upper side of the tuning fork arm 3a in FIG. The side is contracted, and conversely, the upper side of the tuning fork arm 3b is contracted and the lower side is extended. At this time, the sensing electrodes 10 to 1
A displacement current phenomenon (strain → electric flux density conversion) from 1, 8 to 7 occurs. Therefore, the electrodes 8 and 10 at the starting point of the arrow are connected to the terminal 19 and the electrodes 7 and 11 at the ending point of the arrow are connected to the terminal 16 to form a circuit, and the terminal 16 is used as a reference to convert the current from the terminal 19 into a current. The angular velocity signal is integrated by the charge detector 22 and extracted as a charge signal.

In the present embodiment, as described above, the angular velocity signal is taken out from the detection electrodes 8 and 10 on the basis of the detection electrodes 7 and 11 of the tuning fork arms 3a and 3b. The drive electrodes 6, 9, 1
Drive signals are applied to the detection electrodes 8 and 10 due to capacitive coupling between the electrodes.
If the drive electrodes are not configured to have opposite polarities, the accuracy of the angular velocity signal may deteriorate as a result. However, since the drive electrodes 6 and 9 of the tuning fork arm 3b are set to the ground potential via the terminals 17 and 18, capacitive coupling to the detection electrodes 7 and 11 does not occur. This means that in the present embodiment in which the tuning fork arm is a piezoelectric body, the piezoelectric body is also a dielectric body, so that the capacitive coupling is large, and this decrease in accuracy becomes particularly remarkable.

However, in this embodiment, the drive electrodes 6, 9 and 12, 13 that are close to both sides of the detection electrodes 8 and 10 via the dielectric (piezoelectric material) have a phase of 1.
Drive signals of mutually opposite polarities different by 80 degrees are applied, and as a result, a cancellation phenomenon occurs,
As a result, the accuracy of the detection signal does not decrease. Although the operational amplifier 28 is used to apply the opposite phase of the drive signal, adjustment is performed by the variable resistor 29 in order to make the cancel phenomenon more accurate.

The position of the positive drive electrode or the negative drive electrode with respect to the detection electrode is designed so as to optimize the cancel phenomenon without adjustment by the variable resistor 29, and these electrodes are further trimmed with a laser or the like. It can also be adjusted.

(Embodiment 2) FIGS. 8 to 10 show another embodiment of the present invention. In this embodiment, a cancel electrode 30 dedicated to the tuning fork is provided on the side surface below the opening, and an inverted drive signal output from the operational amplifier 28 is applied to the cancel electrode 30 as a cancel signal as shown in FIG. Is.

That is, as shown in FIG. 10, the tuning fork arm 3b in this embodiment is different from that of the first embodiment in that a drive signal is supplied to the drive electrodes 6 and 9 thereof, and the drive signal is supplied to the drive electrode similarly to the first embodiment. A self-excited resonance driving force is generated together with the tuning fork arm 3 a supplied to the 12 and 13. Further, since the drive electrodes 6 and 9 of the tuning fork arm 3a and the drive electrodes 12 and 13 of the tuning fork arm 3b are set to the ground potential, it is not possible to cause the cancellation phenomenon of itself as in the first embodiment.

Therefore, in this embodiment, the cancel electrode 30 is separately provided, and the cancel signal whose phase is inverted by 180 degrees with respect to the drive signal supplied from the cancel electrode 30 is used to prevent the accuracy of the detection signal from deteriorating due to the intrusion of the drive signal. is there.

In this embodiment, the cancel electrode 30 is provided on the side surface below the opening 31, and
The width of the tuning fork arms 3a and 3b is made smaller than that of the opening 31 in order to make the electrodes of the vibrating tuning fork arms 3a and 3b as large as possible.
This is because inadvertent vibration is not induced in a and 3b. In other words, this is the fulcrum of vibration.

(Embodiment 3) FIG. 11 shows still another embodiment of the present invention, in which a cancel electrode 30 is horizontally provided near the lowermost side of the piezoelectric body 3 and the lower side portions of the left and right detection electrodes 7 are connected. Then, the cancel electrode 30 is horizontally opposed to the cancel electrode 30.

In this way, the electric field from the cancel electrode 30 to the detection electrode 7 is applied to the tuning fork arm 3a of the piezoelectric body 3,
It will be below 3b and in the axial direction. This is suitable when quartz is used as the piezoelectric body, and since this electric field is oriented in the machine axis direction, no mechanical driving force is generated. Therefore, there is no disturbance of the tuning fork drive.

The upper side of the cancel electrode 30 is left as it is, and both sides are inclined so as to widen downward so that the electric field vectors on both sides toward the drive electrode 6 and the detection electrode 8 are oriented in the axial direction. Maybe,
On the contrary, the upper side may be left as it is, and both side sides may be narrowed downward to significantly reduce the electric field components on both sides toward the drive electrode 6 and the detection electrode 8.

[0028]

As described above, the present invention includes the piezoelectric body, the detection electrode and the drive electrode provided on the piezoelectric body, and the first power source connected to the drive electrode, and the piezoelectric body is canceled. An electrode is provided and a second power supply for supplying a signal having a phase difference of approximately 180 degrees from the signal supplied from the first power supply to the drive electrode is connected to the cancel electrode.

Therefore, since the signal supplied from the second power source to the cancel electrode is approximately 180 degrees out of phase with the signal supplied from the first power source to the drive electrode,
The signal flowing from the drive electrode to the detection electrode is canceled by the signal flowing from the cancel electrode to the detection electrode, and as a result, the detection electrode is affected by the signals from the first and second power supplies. The signal based on the angular velocity is correctly derived, and the detection accuracy is extremely high.

[Brief description of drawings]

FIG. 1 is a front view of an angular velocity sensor according to an embodiment of the present invention.

FIG. 2 is a top view of the same angular velocity sensor.

FIG. 3 is an electric circuit diagram of the same angular velocity sensor.

FIG. 4 is a front sectional view showing the entire angular velocity sensor.

FIG. 5 is a side sectional view showing the entire same angular velocity sensor.

FIG. 6 is a diagram showing the operating principle of the same angular velocity sensor.

FIG. 7 is a diagram showing an operating principle of the same angular velocity sensor.

FIG. 8 is a front view of an angular velocity sensor according to another embodiment of the present invention.

FIG. 9 is a top view of the same angular velocity sensor.

FIG. 10 is an electric circuit diagram of the same angular velocity sensor.

FIG. 11 is a front view of an angular velocity sensor according to still another embodiment of the present invention.

[Explanation of symbols]

 3 Piezoelectric body 3a Tuning fork arm 3b Tuning fork arm 6 Driving electrode (cancelling electrode) 7 Detecting electrode 8 Detecting electrode 30 Canceling electrode

Claims (8)

[Claims] 1. A piezoelectric body, a detection electrode and a drive electrode provided on the piezoelectric body, and a first power source connected to the drive electrode, wherein a cancel electrode is provided on the piezoelectric body and the cancel electrode is provided on the cancel electrode. Is an angular velocity sensor connected to a second power supply for supplying a signal having a phase difference of approximately 180 degrees from the signal supplied to the drive electrode from the first power supply. 2. The angular velocity sensor according to claim 1, wherein the second power source is constructed by inverting a signal supplied from the first power source. 3. The angular velocity sensor according to claim 1, wherein the piezoelectric body has a tuning fork shape, and at least one of the tuning fork arms of the piezoelectric body is provided with a detection electrode, a drive electrode, and a cancel electrode. 4. The angular velocity sensor according to claim 1, wherein the piezoelectric body has a tuning fork shape, and a cancel electrode is provided on a surface below the opening of the tuning fork shape. 5. The angular velocity sensor according to claim 4, wherein the cancel electrode is smaller than the width of the opening of the piezoelectric body. 6. The angular velocity sensor according to claim 4, wherein the cancel electrode is horizontally arranged below the tuning fork-shaped piezoelectric body. 7. The angular velocity sensor according to claim 6, wherein both sides of the cancel electrode arranged in the horizontal direction are inclined. 8. The angular velocity sensor according to claim 1, wherein the cancel electrode is also used as a drive electrode.