JPH0516522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric vibration type angular velocity sensor.

[Background of the invention]

Conventionally, an angular velocity sensor is known in which a piezoelectric body is attached to a tuning fork-shaped moving body and vibrated.

Here, an angular velocity sensor (not known to the public), which is one of this type of angular velocity sensor and which was developed by the inventors before the invention was proposed, will be described.

To explain the structure of this device, there is a drive piezoelectric bimorph 1, 1' (drive part) made of two piezoelectric materials pasted together, and a sensing piezoelectric bimorph made of two piezoelectric materials pasted together like the drive piezoelectric bimorph 1, 1'. Piezoelectric bimorphs 2 and 2' (sensing parts) are adhered to each other with adhesives 3 and 3' so as to be perpendicular to each other. Further, the piezoelectric bodies inside the driving piezoelectric bimorphs 1, 1' are fixed to metal terminals 4 with adhesive, solder, etc., and are grounded via the metal terminals 4. An AC driving voltage is applied to the driving piezoelectric bimorphs 1, 1' by an AC driving power source 5 (a self-oscillation type one may be used). When an AC driving voltage is applied to the driving piezoelectric bimorphs 1, 1', the driving piezoelectric bimorphs 1, 1'
1' vibrates with a phase shift of 180° in the direction of the solid arrow in the figure (symmetrical vibration), and at the time of the vibration, detects the bending state of the detection piezoelectric bimorphs 2, 2' in the vertical direction and calculates the angular velocity. I'm trying to get it. That is, when an angular velocity occurs around the measurement axis A, the detection piezoelectric bimorphs 2, 2' are bent by the Coriolis force, so the angular velocity is obtained by detecting the bent state. Note that the dotted arrows in the driving piezoelectric bimorphs 1 and 1' indicate the polarization direction of each piezoelectric body, and the corresponding piezoelectric bodies (inside and inside, outside and outside) in each drive piezoelectric bimorph 1 and 1' piezoelectric materials) have opposite polarization directions. Therefore, by applying AC drive voltages of the same phase, each driving piezoelectric bimorph vibrates with a phase shift of 180°. (In addition, it is possible to vibrate by shifting 180 degrees in the same way as above even if the piezoelectric body in the drive part is not provided with two pieces but one piece is pasted on the board. In this case, both can be attached to the outside or inside of the board. ) Also, piezoelectric bimorph 2 for detection,
The dotted arrows at 2' indicate the polarization directions of the respective piezoelectric bodies, which are opposite to each other. This is because when receiving a certain angular velocity, the drive piezoelectric bimorphs 1 and 1' vibrate symmetrically, so the detection piezoelectric bimorphs 2 and 2' also vibrate symmetrically, and each detection piezoelectric bimorph 2 This is to match the phases of the detection signals from , 2'.

However, in this case, the adhesive 3, 3'
Because the drive voltage easily leaks from the drive piezoelectric bimorphs 1, 1' to the detection piezoelectric bimorphs 2, 2' through the coupling, a very large offset voltage is generated with respect to the angular velocity detection signal, making it difficult to accurately detect angular velocity. I can't do it. To explain this in detail, the equivalent circuit of the one shown in FIG. 1 is as shown in FIG. , 3' are capacitively coupled by capacitances C ₃ and C ₃ '. Therefore, from the AC drive power source 5, the capacity C ₃ ,
The AC drive voltage leaks to the detection side through C ₃ ', and since the phases of the leaked AC drive voltages are the same, both are combined and a large offset voltage is generated between the output terminals a and b.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems, and its purpose is to prevent the generation of offset voltage due to capacitive coupling between the driving part and the sensing part, and to improve accuracy. An object of the present invention is to provide an angular velocity sensor capable of detecting angular velocity.

[Means for solving problems]

In order to achieve the above object, the present invention symmetrically arranges two sets of vibrators in which a driving part having a piezoelectric body for driving and a detecting part having a piezoelectric body for sensing are orthogonally coupled, and An angular velocity sensor equipped with an AC drive power source for applying an AC drive voltage to a piezoelectric body, the AC drive voltage being applied from the AC drive power source to the drive piezoelectric body for one vibrator, and the detection In the electrical path for extracting the detection signal from the piezoelectric material,
A phase inversion circuit that shifts the phase of the input signal by 180° is provided, and the drive piezoelectric bodies are arranged so that when the AC drive voltage is applied to the respective drive piezoelectric bodies, the respective drive parts vibrate symmetrically. The polarization direction of each of the detection piezoelectric bodies is determined such that the polarization direction of each of the detection piezoelectric bodies is determined, and the detection signals from the respective detection piezoelectric bodies are synthesized to obtain an angular velocity.

〔Effect of the invention〕

As described above, in the present invention, leakage of AC drive voltage due to capacitive coupling between the drive section and the detection section in each vibrator is canceled out by the action of the phase inverting circuit, so that the drive section and the detection section are offset. This has the excellent effect of preventing the generation of offset voltage due to capacitive coupling between the two parts and allowing accurate angular velocity detection.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings. FIG. 3 is a configuration diagram showing an example thereof,
The polarization direction of the piezoelectric body in the drive voltage body 1' is reversed from that shown in FIG. The difference is that a phase inversion circuit 6 is provided. That is, the AC driving voltage applied to the driving piezoelectric bimorph 1' is applied to the driving piezoelectric bimorph 1' through the phase inversion circuit 6 so that the phases of the AC driving voltage applied to the driving piezoelectric bimorph 1' are 180 degrees different from each other. Apply AC drive voltage. Even when the above AC drive voltage is applied, the phase remains unchanged as shown by the solid arrow in the figure.
A piezoelectric bimorph 1,
The polarization direction of 1' is shown by the dotted arrow in the figure.

Therefore, according to the above configuration, the polarization direction of the piezoelectric material in the piezoelectric bimorph 1' is reversed to that shown in FIG.
Since the alternating current drive voltage is applied through the phase inversion circuit 6 which shifts the phase by 180 degrees, the piezoelectric bimorphs 1 and 1' vibrate with a phase shift of 180 degrees, similar to that shown in FIG.

The equivalent circuit of this device is as shown in FIG. Here, the AC drive voltage leaking to the detection unit via the coupling capacitances C ₃ and C ₃ ' has a phase shift of 180° due to the provision of the phase inversion circuit 6, and by combining them, These cancel each other out, and the offset voltage generated between output terminals a and b can be significantly reduced. Note that as the phase inverting circuit 6, as shown in FIG. 5, an inverting amplifier using an operational amplifier can be used.

In the above embodiment, the phase inversion circuit 6 is provided between the AC drive power source 5 and the drive voltage bimorph 1', but as shown in FIG. It may also be provided. In this case, it is necessary to reverse the polarization direction of the detection piezoelectric bimorph 2' with respect to that shown in FIG.

Furthermore, in the embodiments shown in FIGS. 3 and 4,
Although the electrical outputs of the detection piezoelectric bimorphs 2 and 2' are connected in parallel, they may be connected in series to obtain an angular velocity detection signal.

Further, as shown in FIG. 7, each vibrator is integrally formed with metal plates 7, 7', and piezoelectric bodies 8, 8' for driving and piezoelectric bodies 8' for detection are placed on the metal plates 7, 7'. The piezoelectric bodies 9, 9' may be provided and the metal plates 7, 7' may be grounded via the metal terminals 4. In this case as well, there is a coupling capacitance using air or the like as a medium between the drive piezoelectric bodies 8, 8' and the detection piezoelectric bodies 9, 9'. In this case, the drive piezoelectric bodies 8, 8' and the detection piezoelectric bodies 9, 9' are provided not only on one side of the metal plates 7, 7' but also on the opposite side, and the two piezoelectric bodies are used for driving or sensing. You may do so.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an angular velocity sensor developed by the inventors before the invention was proposed, Fig. 2 is an equivalent circuit diagram of the one shown in Fig. 1, and Fig. 3 is a block diagram of an angular velocity sensor according to the present invention. Fig. 4 is an equivalent circuit diagram of the one shown in Fig. 3, Fig. 5 is an electrical wiring diagram of a phase inverting circuit, Fig. 6 is an equivalent circuit diagram showing another embodiment, and Fig. 7 is a still further embodiment. FIG. 1, 1'... Drive piezoelectric bimorph, 2, 2'...
...Piezoelectric bimorph for detection, 5...Power source for AC drive, 6...Phase inversion circuit.

Claims (1)

[Scope of Claims] 1. Two sets of vibrators are arranged symmetrically, in which a driving part having a driving piezoelectric body and a detecting part having a detecting piezoelectric body are orthogonally coupled, and An angular velocity sensor equipped with an AC drive power supply for applying an AC drive voltage, the AC drive voltage being applied to one of the vibrators from the AC drive power supply to the drive piezoelectric body, and the detection piezoelectric body In the electrical path that extracts the detection signal from
A phase inversion circuit that shifts the phase of the input signal by 180° is provided, and the drive piezoelectric bodies are arranged so that when the AC drive voltage is applied to the respective drive piezoelectric bodies, the respective drive parts vibrate symmetrically. An angular velocity sensor characterized in that the polarization direction of each of the detection piezoelectric bodies is determined so that the polarization direction of each of the detection piezoelectric bodies is determined, and the detection signals from the respective detection piezoelectric bodies are synthesized to obtain an angular velocity. 2. The angular velocity sensor according to claim 1, wherein the phase inversion circuit is provided between the AC drive power source and a driving piezoelectric body in one of the vibrators. 3. The angular velocity sensor according to claim 1, wherein the phase inversion circuit is provided at an output portion of the detection signal of the detection piezoelectric body in the one vibrator.