JPH06174476A - Rotation angular velocity sensor - Google Patents

Abstract

PURPOSE:To provide a small-sized rotation angular velocity sensor with high precision at a low cost. CONSTITUTION:A piezoelectric thin film 12 and a dielectric thin film 13 are formed on a silicon substrate 11 in multiple layers, and electrodes 14, 15 for propagating Lamb waves are formed on the piezoelectric thin film 12 to constitute an oscillating circuit. The silicon at the propagation portion of the Lamb waves is etched from the back face to form a thin plate having the wavelength lower than that of the Lamb waves. When rotation is applied to a rotation angular velocity sensor (a semiconductor element formed on the substrate 11) centering on the Z-axis, the propagation speed of the Lamb waves is changed in response to the rotating direction and the angular velocity OMEGA by the effect of the Coriolis force. The change of the oscillation frequency proportional to the angular velocity OMEGA is outputted as the electric signal (a). This output is detected by a counter 17, the frequency difference is obtained by an arithmetic device 18, and the rotation angular velocity of the rotation angular velocity sensor is calculated from the obtained frequency difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational angular velocity sensor (piezoelectric vibrating gyro).

[0002]

2. Description of the Related Art A conventional rotary angular velocity sensor (piezoelectric vibrating gyro) has a structure in which a piezoelectric ceramic is bonded to a tuning fork type or a tuning piece type vibrator, and the piezoelectric vibrator for excitation is bonded to the vibrator via an adhesive layer. The applied vibration is converted into a voltage via the adhesive layer and the piezoelectric ceramic for detection to obtain a detection signal. The basic principle of this operation is that the displacement of the oscillator is modulated by the Coriolis force proportional to the rotational angular velocity of the oscillator, and the modulation component due to the Coriolis force is extracted from the detection signal to obtain the angular velocity.

FIG. 4 is a perspective view and a block diagram showing a configuration of a rotational angular velocity sensor using an equilateral triangular sound piece type vibrator which is currently in practical use and an example of a peripheral device thereof. Figure 4
As shown in (A), the piezoelectric vibrating gyro 40 has a structure in which an exciting and detecting piezoelectric ceramic 42 is attached to three sides of an equilateral triangular sound piece type oscillator 41 made of a constant elastic metal material with an adhesive. ing.

As a circuit configuration, as shown in FIG. 4B, the piezoelectric ceramics 42 on the left and right sides of the equilateral triangular sound piece type gyro 40.
The -42 is used for driving, and the remaining one side of the piezoelectric ceramic 42 is used for feedback together with the oscillation circuit 43 and the phase correction circuit 45 to form an oscillation circuit by self-excitation. The left and right piezoelectric ceramics 42-42 are also used for detection, and the differential output of the differential circuit 44 is processed by the synchronous detection circuit 46 and the DC amplifier 47 to extract the Coriolis signal.

[0005]

However, the conventional rotary angular velocity sensor having a structure in which the piezoelectric ceramic is bonded to the sound piece type vibrator requires a step of adhering the piezoelectric ceramic to the vibrator with an adhesive. There is a problem in mechanical precision such as misalignment.Therefore, the reproducibility of sensor performance is poor, and it is difficult to improve productivity such as yield, reduce cost, and reduce size. It was

The present invention has been made to solve the above problems, and an object of the present invention is to provide a highly accurate, small-sized, low-cost rotation angular velocity sensor.

When the soot that propagates the elastic waves (SAW, Lamb waves) makes a rotational motion (the rotation vector is perpendicular to the traveling direction of the wave and the depth direction of the substrate), Coriolis force works and the propagation velocity of the wave changes. To do. Detecting the rotational angular velocity from the change in the propagation velocity is the operating principle of the vibration gyro using SAW and Lamb waves. Conventionally, the displacement of the oscillator is modulated by the Coriolis force, and the rotational angular velocity is detected by this, but in the present invention, the propagation velocity is modulated.

Considering the application to navigation, etc.,
The gyro can be regarded as a sensor that detects a relatively small rotational angular velocity. Therefore, it is considered that the low-frequency operation is essentially required for the vibration gyro using elastic waves.
When SAW is used, there is a concern that the element size may increase due to the low frequency. Focusing on antisymmetric Lamb waves as elastic waves, as shown in FIG. 5, there is a property that the propagation speed of the waves can be reduced by making the plate extremely thin, which is a great advantage in operating at low frequencies. is doing.

[0009]

In order to achieve the above-mentioned object, the rotational angular velocity sensor according to the first invention is a semiconductor formed by a dielectric film layer and a piezoelectric film layer provided on a predetermined substrate. An element and a pair of electrodes formed on the piezoelectric film layer for propagating an elastic wave of a predetermined mode,
It is characterized by including a detection device that detects a change in elastic wave in a predetermined mode due to rotation of the semiconductor element, and an arithmetic device that calculates a rotational angular velocity of the semiconductor element from a change in frequency detected by the detection device.

A second invention is characterized in that, in the rotational angular velocity sensor according to the first invention, the elastic wave in a predetermined mode is a Lamb wave.

The rotational angular velocity sensor according to the third aspect of the invention is a pair of semiconductor elements formed by a dielectric film layer and a piezoelectric film layer provided on a predetermined substrate, and a piezoelectric film layer on each semiconductor element. A pair of electrodes for propagating elastic waves of a predetermined mode in opposite directions, respectively, and a detection device for detecting the frequency of the elastic wave of a predetermined mode in each semiconductor element accompanying the rotation of the pair of semiconductor elements; ,
And an arithmetic unit for calculating the rotational angular velocities of the pair of semiconductor elements by obtaining the difference between the respective detected frequencies.

A fourth invention is characterized in that, in the rotational angular velocity sensor according to the second invention, the elastic wave of a predetermined mode is a Lamb wave.

[0013]

With the above structure, the rotational angular velocity sensor according to the first aspect of the invention propagates the elastic wave of a predetermined mode by the pair of electrodes formed on the piezoelectric film layer, and the detection device elastically moves in a predetermined mode as the semiconductor element rotates. The change in the wave is detected, and the rotational angular velocity of the semiconductor element is calculated from the frequency difference detected by the detection device by the arithmetic device.

In the rotational angular velocity sensor according to the third aspect of the invention, a pair of electrodes formed on the piezoelectric film layer on each semiconductor element causes elastic waves of a predetermined mode to propagate in opposite directions, and a detection device is used. The rotational angular velocity of the pair of semiconductor elements is calculated by detecting the frequency of the elastic wave in a predetermined mode in each semiconductor element due to the rotation of the pair of semiconductor elements and obtaining the difference between the frequencies detected by the arithmetic unit.

[0015]

【Example】

<Embodiment 1> FIG. 1 shows the structure of an embodiment of a rotational angular velocity sensor according to the present invention. In FIG. 1A, a dielectric thin film 13 is formed in multiple layers together with a piezoelectric thin film 12 on a silicon (Si) substrate 11, and electrodes 14 and 15 for propagating Lamb waves are formed on the piezoelectric thin film 12. , The amplifier 16 and the oscillation circuit 10 are configured. Here, the piezoelectric thin film 1
2. ZnO (zinc oxide) / SiN (silicon nitride) or the like can be considered as the combination of the dielectric thin film 13, but other thin film combinations are also possible. There is a possibility of improving performance by combining thin films.

Silicon in the Lamb wave propagation portion is etched from the back surface to form a thin plate having a Lamb wave wavelength or less. This is because an antisymmetric mode having a slow sound velocity is used as a propagation mode of Lamb waves. When the rotation angular velocity sensor (semiconductor element formed on the substrate 11) is rotated about the z-axis, the propagation velocity of the Lamb wave changes according to the rotation direction and the angular velocity due to the influence of the Coriolis force. This is the angular velocity Ω
A change in the oscillation frequency proportional to is output as an electric signal a. This output is detected by the counter 17, the frequency difference is obtained by the arithmetic unit 18, and the rotational angular velocity of the rotational angular velocity sensor is calculated from the obtained frequency difference. The output a is detected as a change in the oscillation frequency f. If the frequency when the rotation angular velocity sensor is not rotating is f0, and the deviation from the frequency f0 when rotating is Δf, the result is as shown in FIG. 1 (B).

<Embodiment 2> FIG. 2 shows the structure of another embodiment of the rotational angular velocity sensor according to the present invention, and FIG. 3 is a characteristic diagram of the oscillation frequency. In FIG. 2A, a pair of oscillation circuits 21 and 22 having the same characteristics as the oscillation circuit shown in FIG. 1A and having the same characteristics are arranged so that the Lamb waves have opposite directions, and the z-axis Lamb propagates in the positive direction of x under the influence of the Coriolis force when a rotation in the positive direction about
The propagation velocity of b-wave becomes large. On the contrary, the propagation speed of the Lamb wave propagating in the negative direction of x becomes small.

The rotational angular velocity Ω can be detected as a frequency difference between the output 23 of the frequency f1 and the output 24 of the frequency f2. As shown in FIG. 2B, the output pulses 23 and 24 from the oscillation circuits 21 and 22 are counted by the counters 31 and 32, respectively.
Then, the arithmetic circuit 33 obtains the frequency difference to calculate the rotational angular velocity of the rotational angular velocity sensor. By using the frequency difference between the two outputs, it is possible to cancel the influence of frequency drift due to temperature changes and the like, and improve the sensor performance.

[0019]

As described above, according to the rotational angular velocity sensor of the present invention, the rotational angular velocity sensor utilizing the Lamb wave is used by using the structure in which the piezoelectric thin film and the dielectric thin film are formed in multiple layers on the silicon substrate. Can be realized. This makes it possible to manufacture using semiconductor process technology,
A low-cost rotation angular velocity sensor can be realized. Furthermore, it is possible to realize a high-performance sensor in which peripheral circuits are integrated on the same substrate.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of an embodiment of a rotational angular velocity sensor according to the present invention.

FIG. 2 is a diagram showing the structure of another embodiment of the rotational angular velocity sensor according to the present invention.

FIG. 3 is a characteristic diagram of an oscillation frequency.

FIG. 4 is an example of a conventional rotation angular velocity sensor.

FIG. 5 is a dispersion relation of Lamb waves.

[Explanation of symbols]

 10, 21 and 22 Oscillation circuit (semiconductor element) 12 Piezoelectric thin film (piezoelectric thin film layer) 13 Dielectric thin film (dielectric thin film layer) 14, 15 Electrode 17, 31, 32 Counter (detecting device) 18, 33 Arithmetic device

Claims (4)

[Claims] 1. A semiconductor element formed of a dielectric film layer and a piezoelectric film layer provided on a predetermined substrate, and a pair formed on the piezoelectric film layer for propagating elastic waves of a predetermined mode. An electrode, a detection device that detects a change in the elastic wave in the predetermined mode due to the rotation of the semiconductor element, and an arithmetic device that calculates the rotational angular velocity of the semiconductor element from the change in the frequency detected by the detection device, A rotational angular velocity sensor having: 2. The rotational angular velocity sensor according to claim 1, wherein the elastic wave in the predetermined mode is a Lamb wave. 3. A pair of semiconductor elements formed by a dielectric film layer and a piezoelectric film layer provided on a predetermined base, and a pair of semiconductor elements of a predetermined mode formed on the piezoelectric film layer on each of the semiconductor elements. A pair of electrodes for propagating the elastic waves in opposite directions, a detection device for detecting the frequency of the elastic wave in the predetermined mode in each semiconductor element accompanying the rotation of the pair of semiconductor elements, and the detected frequency A rotation angular velocity sensor, comprising: an arithmetic unit that calculates a rotation angular velocity of the pair of semiconductor elements by obtaining a difference. 4. The rotational angular velocity sensor according to claim 3, wherein the elastic wave in the predetermined mode is a Lamb wave.