JPH0599950A - Dynamics quantity detector - Google Patents

Abstract

PURPOSE:To enable diagnosing malfunctions of a dynamic quantity detection means properly without affecting the detection range oft he dynamic quantity by generating electricmotive force with electrostatic induction. CONSTITUTION:The electric charge obtained as a piezoelectric effect by acceleration give to an piezoelectric body 1 is output to an amplifier 7 as an acceleration signal. The signal from an oscillator 5 due to its driving is amplified in a booster coil 13, cut at the direct current signal part and impressed as a high frequency high voltage to an electrode 11 of a stage 5 and resultantly, a voltage with high inductance is induced between two electrodes of the piezoelectric body 1 by the alternating electric field. As this changes with the abnormality of the piezoelectric body 1 and the like, malfunction can be diagnosed. The acceleration signal mixed and output by the amplifier 7 and the malfunction diagnosing signal are separated with a low-pass filter 17 and a band-pass filter 9, respectively. Based on these signals, the malfunction diagnosis and dynamic quantity calculation are performed with an arithmetic processing means. Thus, using the induction voltage caused by electrostatic induction independent of the voltage generated by acceleration, proper malfunction diagnosis can be done.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical quantity detector having a fault diagnosis function.

[0002]

2. Description of the Related Art With the spread of control by microcomputers in recent years, development of mechanical quantity detectors for electrically detecting various mechanical quantities has been actively pursued. In this development, establishment of a failure diagnosis method for the mechanical quantity detector is one of the important themes in order to prevent inaccurate control due to an abnormal detected value due to a failure of the mechanical quantity detector. ..

As a mechanical quantity detector having a failure diagnosing function, there is one disclosed in, for example, Japanese Utility Model Laid-Open No. 1-5114. This mechanical quantity detector detects acceleration as a mechanical quantity in particular, but forcibly vibrates the beam portion at a predetermined frequency, separates the signal based on this vibration and extracts it, and the level of the signal is predetermined. It is configured to determine whether or not there is a failure by determining whether or not it is within the range.

[0004]

According to the mechanical quantity detector described above, an abnormality or failure such as deterioration of sensitivity or complete absence of signal detection can be detected, but it has the following problems to be improved. Was there. That is, a signal due to vibration applied to the beam portion for fault diagnosis appears in the frequency region for detecting acceleration, so that the detection frequency region is narrowed, and in order to suppress this narrowed region, the fault signal is separated and removed. Since a steep filter is required, the cost becomes high.
Further, there is a limit to the amount of amplitude of the beam, and the amount of amplitude due to the acceleration that should be originally detected is sacrificed by the amplitude that is always given for failure diagnosis, and the acceleration detection range becomes smaller.

The present invention has been made in view of the above, and an object thereof is to provide a mechanical quantity detector capable of performing accurate failure diagnosis without affecting the detection range of the mechanical quantity. is there.

[0006]

In order to achieve the above object, the present invention provides a mechanical quantity detecting means composed of a piezoelectric body for converting a mechanical quantity into an electric quantity and a static quantity detecting means for the mechanical quantity detecting means. Electromotive force generation means for generating electromotive force by electric induction and electromotive force generated by the electromotive force generation means output from the mechanical quantity detection means and electromotive force based on detection of the mechanical quantity are separated, and based on each electromotive force. And a processing unit for performing a failure diagnosis of the mechanical quantity detection means and a calculation of the mechanical quantity.

[0007]

In the mechanical quantity detector according to the present invention, an electromotive force is generated in the mechanical quantity detecting means by electrostatic induction, and the failure diagnosis is performed based on the response to the electromotive force.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an acceleration detector according to an embodiment when the present invention is applied to acceleration detection. In the figure, reference numeral 1 denotes a piezoelectric body that constitutes a mechanical quantity detecting means, and is bent by an acceleration being applied to generate an electric charge. As shown in FIG. 2, the piezoelectric body 1 is clamped and fixed by a pedestal 5 via a spacer 3 arranged on one end side thereof. Therefore, in this piezoelectric body 1, a vibration space due to acceleration is secured on the other end side, and it is a so-called cantilever. Although not shown, the structure including the piezoelectric body 1, the spacer 3 and the pedestal 5 described above is soaked in silicone oil for dipping and sealed in a case.

On the surface of the piezoelectric body 1, there is provided a comb-teeth-shaped electrode 9 as shown in FIG. 3 for outputting the generated charges to the amplifier 7 via the lead wire 6. An electrode 11 is provided on the surface of the base 5 on the piezoelectric body side.
1 is connected to the oscillator 15 via the boosting coil 13. In addition, the electrode 11, the boosting coil 13, and the oscillator 1
Reference numeral 5 constitutes an electromotive force generating means.

On the other hand, the output of the amplifier 7 is connected in parallel with a low-pass filter 17 and a band-pass filter 19 which constitute arithmetic processing means.

Next, the operation of this embodiment will be described.

When acceleration is applied to the piezoelectric body 1, a charge corresponding to the acceleration is obtained by the piezoelectric effect due to the vibration of the cantilever portion, and is output to the amplifier 7 as an acceleration signal. The frequency characteristic of the acceleration signal is determined by the rigidity of the cantilever and the damping effect of silicon oil, and the signal frequency (detection frequency) has a limit.

On the other hand, the oscillator 15 driven by the oscillator 15
The signal from is amplified by the boosting coil 13 and the direct current signal is cut off, and becomes a high frequency high voltage and is applied to the electrode 11 of the pedestal 5. As a result, as shown in FIG. 4, an alternating electric field is created at the position where the piezoelectric body 1 is located, and the alternating electric field induces a voltage between both electrodes of the piezoelectric body 1 having a high dielectric constant.

By the way, as the induced voltage,
It depends on the material property such as the dielectric constant of the piezoelectric body 1, and does not depend on the structure of the cantilever or the Young's modulus. Further, since the frequency characteristic of the permittivity generally reaches the MHz order, the induced voltage signal can follow a higher frequency than the acceleration signal due to bending of the cantilever, which is a resonance frequency of about several KHz. Therefore, by setting the signal frequency from the oscillator 15 constant at, for example, several tens KHz or several hundreds KHz or more, a constant voltage is induced in the piezoelectric body 1 regardless of the resonance frequency of the cantilever, and the piezoelectric body 1 If 1 is broken, a wire is broken, or the amplifier 7 is abnormal, the constant induced voltage changes the output voltage of the amplifier 7 which should be constant (hereinafter referred to as "fault diagnosis signal"). The failure diagnosis can be performed by monitoring the change of the failure diagnosis signal.

Specifically, in the present embodiment, the acceleration signal and the failure diagnosis signal mixed and output from the amplifier 7 are separated by the low-pass filter 17 and the band-pass filter 19, respectively, and output to a processing unit (not shown). The low pass filter 17 and the band pass filter 1
As shown in FIG. 5, if only an acceleration signal and a failure diagnostic signal can be extracted from a signal in which an acceleration signal having a resonance frequency of about several KHz and a failure diagnostic signal of several tens KHz or several hundreds KHz or more are mixed, as shown in FIG. So good
For example, a first-order simple one having the characteristics shown in FIG. 6 is sufficient.

Therefore, according to this embodiment, a voltage irrelevant to the voltage generated in the piezoelectric body due to acceleration is induced in the piezoelectric body by electrostatic induction, and the failure diagnosis is performed based on the change in the induced voltage. Therefore, the failure diagnosis signal does not occur in the frequency region of the acceleration signal as in the conventional case (see FIG. 5), and the frequency characteristic of acceleration detection is not sacrificed. Moreover, since it is not necessary to vibrate the beam for failure diagnosis as in the conventional case, the detection range of acceleration is not reduced. Further, conventionally, in order to extract the failure diagnostic signal (see FIG. 5) generated in the frequency domain of the acceleration signal so as not to affect the acceleration signal as much as possible,
Although a steep filter having the characteristics shown in FIG. 7 is required and there is a risk of increasing the cost, in the present embodiment, a simple filter of the first order is sufficient, and the cost can be reduced.

FIG. 8 is a diagram showing another embodiment of the present invention. The feature is that the voltage applied to the electrode 11 of the pedestal 5 is made into a single pulse by using the DC-DC converter 21, and the failure diagnosis is performed by monitoring the fluctuation of the output signal when the pulse is applied. There is something I did.

Therefore, according to the present embodiment, it is particularly advantageous when controlled by the microcomputer 23. Even if the width of a single pulse to be applied is short, the output signal changes, and fault diagnosis is performed in a short time. be able to.

[0020]

As described above, according to the present invention, an electromotive force is generated in the mechanical quantity detection means by electrostatic induction,
Since the failure diagnosis is performed based on the response to the electromotive force, the accurate failure diagnosis can be performed without affecting the detection range of the mechanical quantity.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a diagram for explaining a configuration of the embodiment.

FIG. 3 is a diagram for explaining the configuration of a piezoelectric body.

FIG. 4 is a diagram for explaining the operation of the embodiment.

FIG. 5 is a diagram showing a relationship between an acceleration signal and a failure diagnosis signal with respect to frequency.

FIG. 6 is a diagram showing characteristics of a low-pass filter and a band-pass filter.

FIG. 7 is a diagram showing a conventional filter characteristic.

FIG. 8 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

 1 Piezoelectric body 3 Spacer 5 Pedestal 7 Amplifier 9 Electrode 11 Electrode 13 Booster coil 15 Oscillator 17 Low-pass filter 19 Band-pass filter 21 DC-DC converter 23 Microcomputer

Claims (1)

[Claims] 1. A mechanical quantity detecting means composed of a piezoelectric body for converting a mechanical quantity into an electric quantity; an electromotive force generating means for generating an electromotive force by electrostatic induction with respect to the mechanical quantity detecting means; The electromotive force generated by the electromotive force generating means output from the mechanical quantity detecting means and the electromotive force based on the detection of the mechanical quantity are separated, and the failure diagnosis of the mechanical quantity detecting means and the calculation of the mechanical quantity are performed based on each electromotive force. A mechanical quantity detector comprising: an arithmetic processing unit.