Load detecting device

• US 7,409,868 B2
• Filed: 03/13/2006
• Issued: 08/12/2008
• Est. Priority Date: 03/18/2005
• Status: Expired due to Fees

• Current Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Inventors: Kogure, Shunsuke, Shirai, Katsuyoshi, Ando, Mitsuhiro
• Primary Examiner(s): Lefkowitz; Edward
• Assistant Examiner(s): Kirkland, III; Freddie
• Application Number:
  US11/373,212
• Publication Number:
  US 20060207341A1
• Time in Patent Office: 883 Days
• Field of Search: 737/78, 738/620.41, 738/626.26
• US Class Current: 73/778
• CPC Class Codes: G01G 19/4142 for controlling activation of safety devices, e.g. airbag systems electrical circuits for triggering safety arrangements in case of vehicle accidents B60R21/015
• CPC Class Codes: G01G 3/13 having piezoelectric or piezoresistive properties
• CPC Class Codes: G01G 3/165 Constructional details
• CPC Class Codes: G01L 1/162 using piezoelectric resonators

Abstract

A load detecting device includes a sensor element including a function for generating and detecting a vibration within a single element, the sensor element converting a load or an acceleration into a detection signal, a driving portion for outputting a driving signal for vibrating the sensor element, a vibration detecting portion for extracting the detection signal from the sensor element and for detecting a vibration characteristic value of the sensor element, a wiring for electrically connecting the sensor element, the driving portion and the vibration detecting portion to one another, and for transmitting a superimposed signal constituted by superposition of the driving signal from the driving portion and the detection signal from the sensor element, and a calculating portion for calculating one of or both of a load and an acceleration applied to the sensor element based on the vibration characteristic value from the vibration detecting portion.

Claims

1. A load detecting device comprising:

a sensor element arranged on a supporting member to effect both vibration-generation and vibration-detection, the sensor element including only one piezoelectric member, and first and second electrodes on opposite surfaces of the only one piezoelectric member, respectively, the sensor element converting a load or an acceleration applied to the supporting member into a detection signal;

a driving portion for outputting a driving signal for vibrating the sensor element;

a vibration detecting portion for extracting the detection signal from the sensor element and for detecting a vibration characteristic value of the sensor element based on the detection signal extracted;

a wiring for electrically connecting the sensor element, the driving portion and the vibration detecting portion to one another, and for transmitting a superimposed signal constituted by superposition of the driving signal from the driving portion and the detection signal from the sensor element; and

a calculating portion for calculating one of or both of a load and an acceleration applied to the sensor element based on the vibration characteristic value from the vibration detecting portion.

2. A load detecting device according to claim 1, wherein a cycle of the superimposed signal is divided into a driving period in association with the driving signal and a detection period in association with the detection signal.

3. A load detecting device according to claim 1, wherein a cycle of the superimposed signal is divided into a driving period in association with the driving signal and a detection period in association with the detection signal.

4. A load detecting device according to claim 1, wherein the driving portion periodically applies as the driving signal a driving voltage at a predetermined level between the first electrode and the second electrode of the sensor element.

5. A load detecting device according to claim 4, wherein the vibration detecting portion extracts as the detection signal a voltage between the first electrode and the second electrode obtained when the driving voltage is not applied to the sensor element.

6. A load detecting device according to claim 5, wherein a frequency of the driving voltage corresponds to a resonance frequency of the sensor element.

7. A load detecting device according to claim 4, wherein a frequency of the driving voltage corresponds to a resonance frequency of the sensor element.

8. A load detecting device comprising:

a plurality of sensor elements arranged on a supporting member, each sensor element effecting both vibration-generation and vibration-detection, each sensor element including only one piezoelectric member, and first and second electrodes on opposite surfaces of the only one piezoelectric member, respectively, each of the sensor elements converting a load and an acceleration applied to the supporting member into a detection signal;

a driving portion for outputting a driving signal for vibrating each of the sensor elements;

a vibration detecting portion for extracting the detection signal from each of the sensor elements and for detecting a vibration characteristic value of each of the sensor elements based on the detection signal extracted;

a calculating portion for calculating one of or both of a load and an acceleration applied to the sensor elements based on the vibration characteristic value from the vibration detecting portion, and for outputting a switching signal for switching an electric connection state with a predetermined sensor element;

a connection switching portion electrically connected to each sensor element by a first wiring and for switching an electric connection state with the first wiring based on the switching signal from the calculating portion;

a second wiring for electrically connecting the connection switching portion, the driving portion and the vibration detecting portion to one another and for transmitting a superimposed signal constituted by the driving signal from the driving portion and the detection signal from the sensor element; and

a third wiring for electrically connecting the calculating portion and the connection switching portion to each other.

9. A load detecting device according to claim 8, wherein a cycle of the superimposed signal is divided into a driving period in association with the driving signal and a detecting period in association with the detection signal.

10. A load detecting device according to claim 8, wherein a cycle of the superimposed signal is divided into a driving period in association with the driving signal and a detection period in association with the detection signal.

11. A load detecting device according to claim 8, wherein the driving portion applies as the driving signal a driving voltage at a predetermined level between the first electrode and the second electrode of each sensor element.

12. A load detecting device according to claim 11, wherein the vibration detecting portion extracts as the detection signal a voltage between the first electrode and the second electrode obtained when the driving voltage is not applied to the sensor element.

13. A load detecting device according to claim 12, wherein a frequency of the driving voltage corresponds to a resonance frequency of the sensor element.

14. A load detecting device according to claim 11, wherein a frequency of the driving voltage corresponds to a resonance frequency of the sensor element.