JPS6177712A - Angular speed sensor - Google Patents

Abstract

PURPOSE:To make it possible to detect an angle accurately, by offsetting the lead of an AC driving voltage caused by capacity coupling between a driving part and a detecting part by the action of a phase inverting circuit, thereby extremely reducing a voltage generated between output terminals. CONSTITUTION:An AC driving voltage is applied to a driving piezoelectric bimorph 1' through a phase inverting circuit 6 so that the phase of an AC driving voltage, which is applied to a driving piezoelectric bimorph 1, is different by 180 deg. from the phase of an AC driving voltage, which is applied to a driving piezoelectric bimorph 2'. The polarizing directions of the piezoelectric bimorphs 1 and 1' are the directions shown by dotted arrow lines in the figure so that they are vibrated in 180 deg. out of phase even if the AC driving voltage is applied. The phase of each AC driving voltage, which leaks through coupling capacitor C3 or C3', is shifted by 180 deg. because the phase inverting circuit 6 is provided. The voltages are synthesized and offset. Thus the offset voltage generated between output terminals (a) and (b) can be reduced to the extremely small value.

Description

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

[Conventional technology]

Conventionally, as this type of device, there is a piezoelectric vibration type angular velocity sensor shown in FIG.

To explain the structure of this device, there is a driving piezoelectric bimorph 1.1' (driver) made of two piezoelectric materials pasted together, and a sensing piezoelectric bimorph 1.1' made of two piezoelectric materials pasted together like this driving piezoelectric bimorph 1.1'. Piezoelectric bimorphs 2 and 2' (sensing portions) are glued together with adhesive 3 and 3' so as to be perpendicular to each other. Further, the piezoelectric bodies inside the drive piezoelectric bimorphs 1, 1' are fixed to metal terminals 4 with adhesive, solder, etc., and are grounded via the gold M 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). And drive piezoelectric bimorph 1
, 1', the driving piezoelectric bimorphs 1, 1' have a phase of 18 in the direction of the solid arrow in the figure.
It vibrates with a deviation of 0° (symmetrical vibration), and during the vibration, the bending state of the detection piezoelectric bimorphs 2, 2' in the vertical direction is detected to obtain the angular velocity. That is, measurement axis A
When an angular velocity occurs around the sensor, the detection piezoelectric bimorph 2.2' bends due to the Coriolis force, so the angular velocity is obtained by detecting the bending state. Note that the dotted arrows in the drive piezoelectric bimorph 1.1' indicate the polarization directions of the respective piezoelectric bodies, and the corresponding piezoelectric bodies (inside and inside, outside and outside) in each drive piezoelectric bimorph 1.1' piezoelectric materials) have opposite polarization directions. Therefore, by applying AC drive voltages of the same phase, each drive piezoelectric bimorph has a phase of 18
It vibrates with a 0° deviation. (In addition, instead of providing two piezoelectric bodies in the driving part, it is possible to vibrate by attaching one piece to the substrate, shifting the piezoelectric body by 18 degrees in the same way as above. In this case, both can be placed on the outside or inside of the substrate. ) Also, piezoelectric bimorph 2゜2 for detection
The dotted arrows at ′ indicate the polarization directions of the respective piezoelectric bodies, and the polarization directions are opposite to each other. When subjected to a certain angular velocity, the drive piezoelectric bimorph 1
．． 1' vibrates symmetrically, the detection piezoelectric bimorphs 2 and 2' also vibrate symmetrically, so that the phases of the detection signals from each detection piezoelectric bimorph 2 and 2' are aligned. be.

However, in this case, the driving voltage leaks through the adhesive 3.3' from the driving piezoelectric bimorph 1.1' to the sensing piezoelectric bimorph 2.2' due to capacitive coupling, so that the angular velocity detection signal Therefore, a very large offset voltage is generated, making it impossible to accurately detect angular velocity. To explain this in detail, the equivalent circuit of the one shown in FIG. 1 is shown in FIG. 2, and the drive piezoelectric bimorph 1, 1'
and the detection piezoelectric bimorphs 2, 2', respectively, due to the adhesives 3, 3'. Capacitive coupling occurs at C3'. Therefore, AC drive voltage leaks from the AC drive power supply 5 to the detection side through the capacitors C3 and C3', and since the phases of the leaked AC drive voltages are the same, both are combined and output terminals a and b. A large offset voltage occurs between the two.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above problems, and an object of the present invention is to provide an angular velocity sensor that can accurately detect angular velocity by preventing the generation of offset voltage due to capacitive coupling between the driving section and the sensing section. It is about providing.

Means for Solving Problems] In order to achieve the above object, the present invention provides two sets of vibrators in which a driving part having a driving piezoelectric body and a detecting part having a detecting piezoelectric body are orthogonally coupled. An angular velocity sensor that is arranged symmetrically and includes an AC drive power source for applying an AC drive voltage to each drive piezoelectric body, the drive piezoelectric body being connected to one vibrator from the AC drive power source to the drive piezoelectric body. An AC drive voltage is applied to the electrical path for extracting the detection signal from the detection piezoelectric body, and the phase of the input signal is set to 18.
A phase inversion circuit is provided to shift the driving piezoelectric body by 0°, and the polarization direction of each drive piezoelectric body is determined so that when the AC drive voltage is applied to each of the drive piezoelectric bodies, each drive part vibrates symmetrically. , and the polarization direction of each of the detection piezoelectric bodies is determined so that the detection signals from the respective detection piezoelectric bodies are combined 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 an excellent effect in that accurate angular velocity detection can be performed by preventing the generation of offset voltage due to capacitive coupling between the angular velocity and the angular velocity.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 3 is a configuration diagram showing an embodiment of the present invention, in which the polarization direction of the piezoelectric material in the driving piezoelectric material 1' is reversed from that shown in FIG. The difference is that the polarization directions of the corresponding piezoelectric bodies are the same) and that a phase inversion circuit 6 is provided. That is, the AC drive voltage applied to the drive piezoelectric bimorph 1 and the AC drive voltage applied to the drive piezoelectric bimorph 1' are 180° different in phase from each other. Apply AC drive voltage. The polarization direction of the piezoelectric bimorph 1°1' is set in the direction shown by the dotted arrow in the figure so that even when the above AC driving voltage is applied, the phase shifts by 180 degrees as shown by the solid 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 a driving voltage is applied, the piezoelectric bimorphs 1 and 1' vibrate with a phase shift of 180°, similar to that shown in FIG.

Moreover, the circuit of this circuit is as shown in FIG. Here, the coupling capacity ftc3. The AC drive voltage leaking to the detection unit via C3' has a phase shift of 180° due to the provision of the phase inversion circuit 6, and by combining them, they are canceled out and the output terminals a, It is possible to significantly reduce the offset voltage generated between b. 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 sensing piezoelectric bimorph 2' with respect to that shown in FIG.

Furthermore, in the embodiments shown in FIGS. 3 and 4, the electrical outputs of the detection piezoelectric bimorphs 2 and 2' are connected in parallel, but the angular velocity detection signal may also be obtained by connecting them in series. good.

Further, as shown in FIG. 7, each vibrator is integrally formed with metal plates 7 and 7', and a driving piezoelectric body 8 and 8' and a sensing piezoelectric body 8 and 8' are mounted on the metal plates 7 and 7'. A piezoelectric body 9,9' may be provided and the metal plates 7, 7' may be grounded via the fully bent terminal 4. In this one as well, the drive piezoelectric body 8,
A coupling capacitance using air or the like as a medium exists between the detection piezoelectric body 8' and the detection piezoelectric body 9, 9'. In this case, the driving piezoelectric bodies 8, 8'
It is also possible to provide a detection piezoelectric body 9,9' not only on one side of the metal plates 7, 7' but also on the opposite side so that the two piezoelectric bodies can drive or detect.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional angular velocity sensor, Fig. 2 is an equivalent circuit diagram of the one shown in Fig. 1, Fig. 3 is a block diagram of an angular velocity sensor according to the present invention, and Fig. 4 is a block diagram of the one shown in Fig. 3. FIG. 5 is an electrical connection diagram of the phase inversion circuit, FIG. 6 is an equivalent circuit diagram showing another embodiment, and FIG. 7 is a configuration diagram showing still another embodiment. 1.1'...Piezoelectric bimorph for driving, 2.2'...
Piezoelectric bimorph for detection, 5... AC drive power supply, 6.
...Phase inversion circuit.

Claims (3)

[Claims] (1) Two sets of vibrators are arranged symmetrically, with a driving part having a driving piezoelectric body and a detecting part having a detecting piezoelectric body orthogonally coupled, and an AC driving voltage is applied to each driving piezoelectric body. The angular velocity sensor is equipped with an AC drive power source for applying an AC drive voltage to one vibrator, and applies an AC drive voltage from the AC drive power source to the piezoelectric body for driving, and receives a detection signal from the piezoelectric body for detection. The phase of the input signal is set to 18 on the electrical path to be taken out.
A phase inversion circuit is provided to shift the driving piezoelectric body by 0°, and the polarization direction of each drive piezoelectric body is determined so that when the AC drive voltage is applied to each of the drive piezoelectric bodies, each drive part vibrates symmetrically. and an angular velocity sensor characterized in that the polarization direction of each of the detection piezoelectric bodies is determined so that the detection signals from the respective detection piezoelectric bodies are synthesized to obtain the 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 the driving piezoelectric body of 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.