JP2010014510A - Sensing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To downsize a sensing apparatus for detecting a mechanical quantity. <P>SOLUTION: The sensing apparatus includes: a first oscillator 11 having a piezoelectric material; a second oscillator 12 having a piezoelectric material of which one end is mechanically connected to one end of the first oscillator 11; a weight 13 provided between the first and second oscillators 11, 12; a driving electrode 14 for providing at least one of the first and second oscillators 11, 12 with driving oscillation; and a detecting electrode 15 for detecting the amplitude of at least one of the first and second oscillators 11, 12. The mechanical quantity is detected within a range in which the first and second oscillators 11, 12 are in a degenerate state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sensing device such as an acceleration sensor or an inclination angle sensor used for automobiles, car navigation, and the like.

  Conventionally, in this type of sensing device, a vibrator 1 having a piezoelectric material as shown in FIG. 5 is arranged, for example, so that its longitudinal direction coincides with the traveling direction of an automobile, and one end 1A of the vibrator 1 is fixed. The weight 2 is disposed at the other end 1B, and a drive electrode for applying drive vibration to a part of the vibrator 1 and a detection electrode for detecting the vibration frequency are provided. For example, when the automobile is accelerated and acceleration is applied to the sensing device, the vibrator 1 expands and contracts accordingly, and the frequency detected by the detection electrode changes. This change is calculated as an acceleration or an inclination angle.

As prior art document information relating to this application, for example, Patent Document 1 is known.
JP 2004-251702 A

  In such a conventional sensing device, it has been a problem that miniaturization is difficult.

  That is, in the above-described conventional configuration, since the sensing signal is detected as a frequency, an F / V conversion circuit that converts the sensing signal into a voltage becomes indispensable, and as a result, downsizing becomes difficult.

  Therefore, an object of the present invention is to realize downsizing of the sensing device.

  In order to achieve this object, the present invention provides a first vibrator having a piezoelectric material, and a second vibrator having a piezoelectric material having one end mechanically coupled to one end of the first vibrator. A weight provided between the first and second vibrators, a drive electrode for applying drive vibration to at least one of the first and second vibrators, and the first and second vibrators And a detection electrode that detects the amplitude of at least one of the first and second transducers, and a sensing device that detects a mechanical quantity within a range where the first and second vibrators are in a degenerated state.

  With this configuration, not the frequency but the amplitude of the vibrator can be detected as a sensing signal, so that an F / V conversion circuit is not required, and as a result, downsizing can be realized.

(Embodiment 1)
Hereinafter, the sensing device according to Embodiment 1 of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a first vibrator 11 having a piezoelectric material, a second vibrator 12 having a piezoelectric material having one end mechanically coupled to one end of the first vibrator 11, and the first vibrator A weight 13 provided between the first and second vibrators 11 and 12, a drive electrode 14 for applying drive vibration to at least one of the first and second vibrators 11 and 12, and the first and second vibrators. And a detection electrode 15 for detecting the amplitude of at least one of the two vibrators 11 and 12.

  Specifically, the detection electrode 15 includes a first detection electrode 15A and a second detection electrode 15B, the first detection electrode 15A is provided at the other end of the first vibrator 11, and the first Two detection electrodes 15B are provided at the other end of the second vibrator 12, and the drive electrode 14 is provided at one end of the first and second vibrators 11 and 12, respectively. The drive electrode 14B is provided. Then, a mechanical quantity such as acceleration is detected in a range where the first and second vibrators 11 and 12 are in a degenerated state.

  Here, the degenerated state will be described.

  First, the total length of the first vibrator 11 in FIG. 1 is x, the total length of the second vibrator 12 is (1-x), and the total length of the first and second vibrators 11 and 12 is variable. Suppose you are in a state. The other end of the first vibrator 11 and the other end of the second vibrator 12 are fixed. For example, in a car, the longitudinal direction of the two vibrators coincides with the traveling direction of the car. Suppose that they are arranged. Here, if acceleration is applied in the direction of the arrow in FIG. 1, the weight 13 moves toward the second vibrator 12 according to the law of inertia, so that the frequency changes.

  FIG. 2 shows the change in the frequency. In FIG. 2, the horizontal axis represents x which is the total length of the first vibrator 11, and the vertical axis represents frequency. When the first vibrator 11 is not mechanically coupled to the second vibrator 12, the frequency of the first vibrator 11 increases as the total length x of the vibrator 11 increases as shown by the straight line A. Lower. On the other hand, since the total length (1-x) of the second vibrator 12 decreases as the total length x of the first vibrator 11 increases, the frequency of the second vibrator 12 is as shown in FIG. As shown by the straight line B, the total length x of the first vibrator 11 increases as the length increases.

  Here, when the first and second vibrators 11 and 12 are mechanically coupled, the straight line A and the straight line B shown in FIG. Then, the frequency of the first vibrator 11 and the second vibration are within a certain range in which the full length x of the first vibrator 11 and the full length (1-x) of the second vibrator 12 are close to each other. The frequency of the child 12 is constant. This is a degenerate state.

  As for this degenerate state, refer to page 261 of “Electromechanical vibrator and its application” written by Kenzo Nagai and Shoji Imano.

  In such a degenerate state, the frequency is constant as shown in FIG. 2, while the amplitude states of the first and second vibrators 11 and 12 change. When acceleration is applied in the direction of the arrow shown in FIG. 1 as in the present embodiment, the total length x of the first vibrator 11 becomes shorter and the amplitude thereof becomes smaller, and the second vibrator 12 is reduced. As the total length (1-x) of the plate increases, its amplitude increases. This change is detected by the first and second detection electrodes 15A and 15B and calculated as acceleration.

  As shown in FIG. 3, the acceleration is calculated by detecting the first amplitude corresponding to the first vibrator 11 from the first detection electrode 15A and corresponding to the second vibrator 12. If the method detects the second amplitude to be detected from the second detection electrode 15B, and calculates and outputs the difference between the first and second amplitudes by the differential amplifier 16, the acceleration can be calculated with higher accuracy. Can be made possible.

  In the present embodiment, the first detection electrode 15A is provided at the other end of the first vibrator 11, and the second detection electrode 15B is provided at the other end of the second vibrator 12. The drive electrode 14 is described as being configured as the first drive electrode 14A and the second drive electrode 14B at one end of the first and second vibrators 11 and 12, as shown in FIG. As described above, the first detection electrode 15A is provided at one end of the first vibrator 11, the second detection electrode 15B is provided at one end of the second vibrator 12, and the first drive electrode. 14A may be provided at the other end of the first vibrator 11, and the second drive electrode 14B may be provided at the other end of the second vibrator 12.

  Note that the first and second vibrators 11 and 12 may be piezoelectric materials themselves, or may be a material in which a vibrating member such as metal or ceramic and a piezoelectric material are integrated.

  In the present embodiment, the acceleration sensor has been described as an example, but the present invention can also be applied as a tilt angle sensor. Specifically, when the first vibrator 11 in FIG. 1 is at a high position on the slope and the second vibrator 12 is at a low position, the weight 13 is located on the second vibrator 12 side. Moving. Then, it is possible to calculate the value as the tilt angle from the amplitude change of the first and second vibrators 11 and 12 according to the principle described above.

  In addition, when this sensing device is mounted on an automobile and arranged such that the longitudinal direction of the sensing device coincides with the traveling direction of the automobile, when the automobile runs on a slope, acceleration information and inclination angle information However, since the acceleration from the start of the vehicle to the stop is 0 when integrated, only the inclination angle is extracted by offsetting the value. It is also possible to do.

  When combined with a travel sensor that measures the travel distance of an automobile, it can be applied as an altimeter by multiplying the travel distance by a value obtained by taking the sine of the inclination angle calculated as described above.

  The sensing device of the present invention has an effect that it can be miniaturized, and is useful in automobiles, car navigation devices, and the like.

The perspective view of the sensing apparatus in Embodiment 1 of this invention The figure which shows the relationship between the full length of the 1st vibrator | oscillator in the sensing apparatus of Embodiment 1 of this invention, and the frequency of a 1st, 2nd vibrator | oscillator. Electrical circuit diagram of sensing device in Embodiment 1 of the present invention The perspective view which shows the other Example of the sensing apparatus in Embodiment 1 of this invention. Top view of a transducer in a conventional sensing device

Explanation of symbols

11 First vibrator 12 Second vibrator 13 Weight 14 Drive electrode 15 Detection electrode

Claims (5)

A first vibrator having a piezoelectric material;
A second vibrator having a piezoelectric material having one end mechanically coupled to one end of the first vibrator;
A weight provided between the first and second vibrators;
A drive electrode for applying drive vibration to at least one of the first and second vibrators;
A detection electrode for detecting an amplitude of at least one of the first and second vibrators,
A sensing device that detects a mechanical quantity in a range where the first and second vibrators are in a degenerated state. The detection electrode comprises a first detection electrode and a second detection electrode;
The first detection electrode is provided at the other end of the first vibrator;
The second detection electrode is provided at the other end of the second vibrator;
The sensing device according to claim 1, wherein the drive electrode is provided at one end of at least one of the first and second vibrators. The amplitude includes a first amplitude corresponding to the first vibrator and a second amplitude corresponding to the second vibrator;
Detecting the first amplitude from the first detection electrode;
Detecting the second amplitude from the second detection electrode;
The sensing device according to claim 2, wherein the difference between the first and second amplitudes is calculated and output. The detection electrode comprises a first detection electrode and a second detection electrode;
The first detection electrode is provided at one end of the first vibrator;
The second detection electrode is provided at one end of the second vibrator;
The drive electrode comprises a first drive electrode and a second drive electrode;
The first drive electrode is provided at the other end of the first vibrator;
The sensing device according to claim 1, wherein the second drive electrode is provided at the other end of the second vibrator. The amplitude includes a first amplitude corresponding to the first vibrator and a second amplitude corresponding to the second vibrator;
Detecting the first amplitude from the first detection electrode;
Detecting the second amplitude from the second detection electrode;
The sensing device according to claim 4, wherein the difference between the first and second amplitudes is calculated and output.

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