Method for determining the state of a piezoelectric element and sensor apparatus with a piezoelectric element

Patent metadata

Field	Value
Publication number	US-12535366-B2
Application number	US-202217981662-A
Country	US
Kind code	B2
Filing date	Nov 7, 2022
Priority date	Nov 5, 2021
Publication date	Jan 27, 2026
Grant date	Jan 27, 2026

Abstract

A method for determining the state of a piezoelectric element, in particular the piezoelectric element of a sensor apparatus, it is provided. The piezoelectric element is a component of a resonant circuit. The resonant circuit is excited to natural vibrations. The period durations of the natural vibrations of the resonant circuit are captured, and conclusions are drawn regarding the state of the piezoelectric element base on the period durations of the natural vibrations. A sensor apparatus with at least one piezoelectric element is provided. The sensor apparatus has at least one resonant circuit and that the piezoelectric element is a component of the resonant circuit. The sensor apparatus includes at least one evaluator for capturing and evaluating the natural vibrations of the resonant circuit. The evaluator includes at least one storage device for storing reference resonance frequencies that have been determined in advance.

First claim

The invention claimed is:

1 . A method for determining a state of at least one piezoelectric element, in particular the at least one piezoelectric element of a sensor apparatus, wherein
the at least one piezoelectric element is a component of a resonant circuit, the resonant circuit is excited to natural vibration, the period durations of the natural vibrations of the resonant circuit are captured, and conclusions are drawn about the state of the at least one piezoelectric element from a period durations of the natural vibrations.

2 . The method according to claim 1 , wherein the state of the piezoelectric element is a temperature of the piezoelectric element and/or a functional state of the piezoelectric element.

3 . The method according to claim 1 , wherein the resonant circuit is a component of an oscillator circuit, the oscillator circuit includes a phase-inverting and signal amplifying element, and the piezoelectric element is excited to natural vibrations by the phase-inverting and signal amplifying element.

4 . The method according to claim 3 , wherein the phase-inverting and signal amplifying element is a Schmitt trigger.

5 . The method according to claim 1 , wherein captured period durations of the natural vibrations of the resonant circuit are compared with period duration reference values, wherein the period duration reference values of a associated state of the piezoelectric element are known, and conclusions are drawn about the state of the piezoelectric element from the comparison.

6 . The method according to claim 1 , wherein individual reference resonance frequencies are calculated in advance, each of which is assigned to a state of the piezoelectric element, the resonant circuit is excited in a frequency range of each of reference resonance frequencies calculated in advance, the period durations of the natural vibrations of the resonant circuit are captured.

7 . The method according to claim 6 , wherein the resonant circuit is excited exclusively with natural frequencies determined in advance.

8 . The method according to claim 1 , wherein the resonant circuit is excited with a frequency mix, in particular with noise, and the period durations of the natural vibrations of the resonant circuit are captured.

9 . The method according to claim 8 , wherein the period durations of the natural vibrations at high frequency are captured.

10 . The method according to claim 1 , wherein the state of the piezoelectric element is calculated from the period durations of the natural vibrations using a capacitance of the piezoelectric element.

11 . The method according to claim 1 , wherein a captured natural vibrations of the resonant circuit are converted into binary square pulses.

12 . The method according to claim 11 , wherein the captured natural vibrations are converted into square pulses with aid of the Schmitt trigger circuit.

13 . The method according to claim 11 , wherein the square pulses are evaluated with aid of a microcontroller.

14 . The method according to claim 11 , wherein a development of the square pulses over time is captured, time-dependent changes in the period durations are captured, and conclusions are drawn regarding a change of state of the piezoelectric element on the basis of the time-dependent change in the period duration.

15 . The method according to claim 1 , wherein natural vibrations of the resonant circuit have a different frequency range from the vibrations captured in a measurement operation with the piezoelectric element.

16 . The method according to claim 1 , wherein the capture of the state of the piezoelectric element and a measurement operation are executed in parallel by means of the piezoelectric element.

17 . The method according to claim 1 , wherein the sensor apparatus is arranged on a motor vehicle, the sensor apparatus is a sensor apparatus for detecting liquid on a road on which the vehicle is travelling, and conclusions are drawn about a temperature of the liquid from the period durations of the natural vibrations.

18 . The method according to claim 17 , wherein conclusions regarding a temperature of the piezoelectric element are first drawn on the basis of the period durations of the natural vibrations, and conclusions regarding the temperature of the liquid on the basis of the temperature of the piezoelectric element.

19 . A sensor apparatus having a piezoelectric element,
wherein; the sensor apparatus includes at least one resonant circuit, the piezoelectric element is a component of the resonant circuit, the sensor apparatus includes at least one evaluator for capturing and evaluating natural vibrations of the resonant circuit, and the evaluator includes at least one storage device for storing reference resonance frequencies determined in advance.

20 . The sensor apparatus according to claim 19 , wherein the resonant circuit is a component of an oscillator circuit, the oscillator circuit includes a phase-inverting and signal amplifying element, and the phase-inverting and signal amplifying element is designed to excite the resonant circuit to natural vibrations.

21 . The sensor apparatus according to claim 20 , wherein the phase-inverting and signal amplifying element is a Schmitt trigger circuit, and the Schmitt trigger circuit is connected to microcontroller to allow a transmission of signals.

Assignees

• Hella Gmbh & Co Kgaa

Inventors

• Baumgärtel Hauke
• Horst Carsten

Classifications

• H03K5/07 Primary

  by the use of resonant circuits · CPC title

• H03K3/3565

  Bistables with hysteresis, e.g. Schmitt trigger · CPC title

• H03H9/545

  including active elements · CPC title

• G01K11/26 Primary

  of resonant frequencies · CPC title

• G01K7/32

  using change of resonant frequency of a crystal · CPC title