JPS61215916A - Angular velocity sensor - Google Patents

Abstract

PURPOSE:To decrease an off-set voltage and to execute the correct angular velocity detection by detecting the voltage of the difference between the alternating current voltage outputted from the second piezoelectric element and the alternating current outputted from the third piezoelectric element. CONSTITUTION:Capacities 4 and 5 respectively exist among piezoelectric elements 2-1 and 2-1' for driving, piezoelectric elements 1-1 and 1-1' for detecting and piezoelectric elements 1-2 and 1-2' for non-polarization. Consequently, part of the alternating driving voltage to drive elements 2-1 and 2-1' is applied from an alternating current electric power source 3 through the capacities 4 and 5 to the elements 1-1 and 1-1' and the elements 1-2 and 1-2'. The leaking alternating current voltage goes to be an off-set voltage of the elements 1-1 and 1-1'. Though there is a little difference between the amplitude values, both go to be the same phase similar voltage waveforms. Consequently, when the difference of the voltages of the two is obtained by a detecting circuit 100, the influence of the voltage, which leaks from the electric power source 3 through a capacity 4 to the elements 1-1' and 1-1, can be decreased.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a piezoelectric vibration type angular velocity sensor.

(Prior Art) Conventionally, in this type of device, a driving part having a driving piezoelectric element and a detecting part having a detecting piezoelectric element are coupled so as to be orthogonal to each other, and an AC driving voltage is applied to the driving piezoelectric element. The angular velocity is detected by receiving an alternating current voltage generated by the detection piezoelectric element due to the vibration action of the detection unit in a direction orthogonal to the vibration direction when the driving unit and the detection unit are vibrated by applying it to the element. Some are equipped with a detection circuit.

(Problem to be Solved by the Invention) However, in the above configuration, the AC driving voltage applied to the driving piezoelectric body leaks to the sensing part due to capacitive coupling between the driving part and the sensing part, There is a problem in that an offset voltage is generated from the piezoelectric element, and angular velocity cannot be detected accurately due to this offset voltage.

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 reducing the offset voltage generated by capacitive coupling between the driving section and the sensing section. .

(Means for Solving the Problems) In order to achieve the above object, the present invention connects and arranges a driving section having a first piezoelectric element and a detecting section having a second piezoelectric element so as to be perpendicular to each other. , when an AC drive voltage is applied to the first piezoelectric element to vibrate the drive section and the detection section, the second piezoelectric element is moved by the vibration action of the detection section in a direction orthogonal to the vibration direction. In the angular velocity sensor, the angular velocity sensor is provided with a detection means for detecting angular velocity by receiving an alternating current voltage generated by the drive unit, and detects an alternating current voltage leaking from the drive unit to the detection unit based on capacitive coupling between the drive unit and the detection unit. A third piezoelectric element to be detected is provided in the detection section, and the detection means further detects a voltage difference between the AC voltage output from the second piezoelectric element and the AC voltage output from the third piezoelectric element. It is characterized in that it includes a differential voltage detecting means for detecting the voltage difference, and obtains an angular velocity signal from an output signal from the differential voltage detecting means.

(Function) In the above configuration, the first piezoelectric element receives an AC drive voltage from an AC power supply and vibrates the drive section and the detection section. When an angular velocity occurs during this vibration, the detection section is influenced by the angular velocity and vibrates in a direction perpendicular to the direction of vibration caused by the drive section. This vibration generates an alternating current voltage from the second piezoelectric element.

This AC voltage includes leakage voltage due to capacitive coupling between the drive section and the detection section. Further, the detection section is provided with a third piezoelectric element to detect the leakage voltage.

and in the detection means, the leakage voltage is offset by detecting a voltage difference between the AC voltage output from the second piezoelectric element and the AC voltage output from the third piezoelectric element, Obtain an angular velocity signal with reduced offset voltage.

(Effects of the Invention) Therefore, according to the present invention, there is an excellent effect that accurate angular velocity detection can be performed while reducing the influence of offset voltage.

(Example) FIG. 1 shows the configuration of the angular velocity sensor used in this example.

In this FIG. 1, l is a detection section, 2 is a drive section,
A and A' are metal plates (0.5 mm thick Fe-Co'
-Ni alloy), and piezoelectric elements 1-1, 1-1', 2-1 are mounted on one side of the detection section 1 and drive section 2.
．． 2-1' (each 0.2 mm thick PZT
A ceramic material that has been polarized to give it piezoelectricity) is bonded to it. Piezoelectric element 1-1. 1-
1' is a piezoelectric element for detection, piezoelectric element 2-1.2-1''
is a driving piezoelectric element. Further, for the detection unit 1, unpolarized piezoelectric elements 1-2. 1-2' is formed.

FIG. 2 is an electrical wiring diagram of what is shown in FIG. 1.

As shown in this figure, the drive piezoelectric element 2-1.2-1"
and detection piezoelectric element 1-1. 1-1' and unpolarized piezoelectric element 1-2. There is a capacity of 4.5 between each
exists.

Therefore, from the AC power source 3 to the drive piezoelectric body 2-1゜2-1''
A part of the AC drive voltage for driving is applied to the sensing piezoelectric element 1-1.1-1'' and the unpolarized piezoelectric element 1-2.1-2'' via a capacitor 4.5. This leakage AC voltage becomes the offset voltage of the detection piezoelectric element 1-1°1-1′.

According to experiments, the sensing piezoelectric elements i-i,
The voltage leaking to t-io is as shown by the solid line in Figure 3, and the voltage leaking to the unpolarized piezoelectric element 1-2, 1-2' via capacitor 5 is as shown by the dotted line in Figure 3. Although there is a slight difference in the amplitude values of the two, they have quite similar voltage waveforms with the same phase.

Therefore, if the detection circuit 100 detects the difference in voltage between the two, the detection piezoelectric element 1-1°,
The influence of the voltage leaking to 1-1 can be reduced.

FIG. 4 is an electrical wiring diagram showing the detailed configuration of the detection circuit 100. Piezoelectric element for detection 1-1. The output voltage from 1-1' is applied to amplifier 6 via voltage follower 7. Further, the output voltage from the unpolarized piezoelectric elements i-2, 1-2' is also applied via the voltage follower 8. The amplifier 6 includes an operational amplifier 6a and four resistors 6b, 6c,
It is composed of 6d and 6e. Here, the output voltage from the detection piezoelectric element 1-L 1-1' is Va, and the output voltage from the unpolarized piezoelectric element 1-2.1-2' is vb.

The resistance values of resistors 6b, 6c, 6d, and 6e are R+
, R2, R3, Ra (where R+ = R3, R2=
R4), the output of the operational amplifier 6a is (Va-V
b) X Rt / R+. That is, this amplifier 6 operates as a differential amplifier (differential voltage detection means), and detects the unpolarized piezoelectric elements 1-2. 1-2' output voltage, that is, unpolarized piezoelectric element 1 from AC power source 3 through capacitor 5.
-2.1-2' voltage (corresponding to the voltage leaking to the detection piezoelectric element 1-1.1-1° via the capacitor 4) is removed.

The output voltage of this amplifier 6 is applied to a synchronous detection circuit 10 via a bandpass filter 9, and synchronously detected based on the AC drive voltage from the AC power supply 3. The synchronously detected voltage is converted into a DC voltage by the smoothing amplifier circuit 11.

In addition, in the above embodiment, the piezoelectric element 1-2.1-
Although the piezoelectric element 2' is used to detect the leakage voltage via the capacitor 5, polarization may be applied to the piezoelectric element 1-2 and 1-2'. In this case, since the amplifier 6 operates in a dynamic amplifying manner, the piezoelectric elements 1-L 1-1° and 1
-2. The polarization directions of the piezoelectric elements 1-2' are set in opposite phases, for example, as shown by the dotted lines in Figure 1. )There is a need. In this case, since the leakage voltage is not affected by the polarization of the piezoelectric element, it can be removed in the same manner as in the above embodiment.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an angular velocity sensor showing an embodiment of the present invention, Fig. 2 is an electrical wiring diagram of the angular velocity sensor shown in Fig. 1, Fig. 3 is a waveform diagram showing leakage voltage, and Fig. 4 is a diagram of the angular velocity sensor shown in Fig. 1. FIG. 3 is an electrical wiring diagram showing the detailed configuration of the detection circuit in FIG. 2; 1-1.1-1', 1-2.1-2°, 2-1°2-
1°...piezoelectric element, 3...AC power supply, 6...amplifier. Representative Patent Attorney Takashi Okabe Figure 1 Figure 2

Claims (1)

[Claims] A driving section having a first piezoelectric element and a detecting section having a second piezoelectric element are coupled and arranged so as to be perpendicular to each other, and
When an AC drive voltage is applied to the first piezoelectric element to vibrate the drive section and the detection section, the vibration of the detection section in a direction orthogonal to the vibration direction causes the second piezoelectric element to move. In an angular velocity sensor provided with a detection means for detecting angular velocity in response to a generated alternating current voltage, the alternating current voltage leaking from the drive section to the detection section is detected based on capacitive coupling between the drive section and the detection section. A third piezoelectric element is provided in the detection section, and the detection means detects a voltage difference between an AC voltage output from the second piezoelectric element and an AC voltage output from the third piezoelectric element. An angular velocity sensor comprising differential voltage detection means for detecting an angular velocity, and obtaining an angular velocity signal from an output signal from the differential voltage detection means.