Piezoelectric acceleration sensor and method of detecting acceleration and manufacturing method thereof

• US 6,263,734 B1
• Filed: 04/13/1999
• Issued: 07/24/2001
• Est. Priority Date: 04/13/1998
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Kanno, Isaku, Fujii, Satoru, Takayama, Ryoichi, Kamada, Takeshi
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/289,936
• Time in Patent Office: 833 Days
• Field of Search: 735/143.4, 735/141.6, 735/142.9, 735/140.1, 735/10, 310/311, 310/328, 310/329, 310/330, 310/340, 310/344, 310/368
• US Class Current: 73/514.34
• CPC Class Codes: G01P 15/0907 of the compression mode type
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

An acceleration sensor 201 comprises a longitudinal effect type detection unit 203 and a lateral effect type detection unit 204. The longitudinal effect type detection unit 203 comprises a longitudinal effect type piezoelectric element 211 comprising a piezoelectric body 211a of a thin film, an electrode 211b and an electrode 211c, which is formed on a deposition substrate 221 serving also as a weight. The lateral effect type detection unit 204 is constituted by providing a lateral effect type piezoelectric element 213 comprising a piezoelectric body 213a of a thin film, an electrode 213b and an electrode 213c, which is formed on the deposition substrate 221 and is cantilevered above a groovy recessed part 105a on a substrate 105. A detection circuit 116 detects an acceleration in a predetermined direction, based on an output of both the longitudinal effect type detection unit 203 and the lateral effect type detection unit 204. Consequently, it is possible to detect an acceleration in a predetermined direction and to make a wider dynamic range and a wider band.

Claims

1. A piezoelectric acceleration sensor comprising:

a longitudinal effect type piezoelectric element which has a first piezoelectric body and outputs a voltage according to an expansion and contraction and a shear deformation of said first piezoelectric body;

a lateral effect type piezoelectric element which has a second piezoelectric body and outputs a voltage according to a flexure of said second piezoelectric body; and

a sensor substrate on which said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element are fixed, wherein under an X-Y-Z three dimensional coordinate system including an X-Y plane having the sensor substrate thereon said longitudinal effect type piezoelectric element is fixed to output a voltage according to an acceleration component in a Z-axis direction added to a voltage according to an acceleration component in an X-Y plane direction, said lateral effect type piezoelectric element fixed to output a voltage according to an acceleration component in a Z-axis direction; and

a detecting means to output a detection signal according to an applied acceleration based on the voltage output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element.

2. A piezoelectric acceleration sensor according to claim 1, wherein:

said lateral effect type piezoelectric element has one of a structure of cantilever in which an end is fixed, a structure of a fixed beam at both ends in which both ends are fixed, a structure of a double cantilever in which a center is fixed, and a structure of a diaphragm in which a periphery is fixed.

3. A piezoelectric acceleration sensor according to claim 1, further comprising a deposition substrate;

wherein;

said first piezoelectric body and said second piezoelectric body are a piezoelectric body thin film which is deposited on said deposition substrate.

4. A piezoelectric acceleration sensor according to claim 3, wherein:

said longitudinal effect type piezoelectric element is fixed on said sensor substrate through said piezoelectric body thin film; and

said deposition substrate functions as a weight for expanding and contracting said piezoelectric body thin film composing said longitudinal effect type piezoelectric element, according to an applied acceleration.

5. A piezoelectric acceleration sensor according to claim 3, wherein:

a vibration body for giving a rigidity to said piezoelectric body thin film is provided on said lateral effect type piezoelectric element.

6. A piezoelectric acceleration sensor according to claim 1, wherein:

said detecting means is constituted so as to output a detection signal according to an acceleration component in a direction of causing a shear deformation in said longitudinal effect type piezoelectric element by generating a signal according to a difference in an output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element.

7. A piezoelectric acceleration sensor according to claim 1, wherein:

said detecting means is constituted so as to distinguish a direction of an applied acceleration by comparing an output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element.

8. A piezoelectric acceleration sensor according to claim 7, wherein:

said detecting means is constituted so as to decide that an acceleration in a direction of causing a shear deformation is applied on said longitudinal effect type piezoelectric element when an output from said longitudinal effect type piezoelectric element is larger than a predetermined value according to an output from said lateral effect type piezoelectric element.

9. A piezoelectric acceleration sensor according to claim 7, wherein:

said detecting means is constituted so as to decide that only an acceleration in a direction of causing a shear deformation is applied on said longitudinal effect type piezoelectric element when an acceleration is detected by only said longitudinal effect type piezoelectric element.

10. A piezoelectric acceleration sensor according to claim 1, wherein:

said detecting means is constituted so as to detect an acceleration in a frequency characteristic, into which a frequency characteristic of said longitudinal effect type piezoelectric element and a frequency characteristic of said lateral effect type piezoelectric element are compounded, by compounding an output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element.

11. A piezoelectric acceleration sensor according to claim 1, wherein:

said detecting means is constituted so as to detect an acceleration at a detectivity, into which a detectivity of said longitudinal effect type piezoelectric element and a detectivity of said lateral effect type piezoelectric element are compounded, by switching an output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element selectively.

12. A method of detecting an acceleration by using a piezoelectric acceleration sensor comprising:

a longitudinal effect type piezoelectric element which has a first piezoelectric body and outputs a voltage according to a expansion and contraction and a shear deformation of said first piezoelectric body; and

a lateral effect type piezoelectric element which has a second piezoelectric body and outputs a voltage according to a flexure of said second piezoelectric body;

wherein;

an applied acceleration is detected, based on an output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element.

13. A method of detecting an acceleration according to claim 12, wherein:

an acceleration component in a direction of causing a shear deformation in said longitudinal effect type piezoelectric element is detected according to a difference in an output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element.

14. A method of detecting an acceleration according to claim 12, wherein:

a direction of an applied acceleration is distinguished by comparing an output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element.

15. A method of detecting an acceleration according to claim 14, wherein:

it is decided that an acceleration in a direction of causing a shear deformation is applied on said longitudinal effect type piezoelectric element when an output from said longitudinal effect type piezoelectric element is larger than a predetermined value according to an output from said lateral effect type piezoelectric element.

16. A method of detecting an acceleration according to claim 14, wherein:

it is decided that only an acceleration in a direction of causing a shear deformation is applied on said longitudinal effect type piezoelectric element when an acceleration is detected by only said longitudinal effect type piezoelectric element.

17. A method of detecting an acceleration according to claim 12, wherein:

an acceleration is detected in a frequency characteristic, into which a frequency characteristic of said longitudinal effect type piezoelectric element and a frequency characteristic of said lateral effect type piezoelectric element are compounded, by compounding an output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element.

18. A method of detecting an acceleration according to claim 12, wherein:

an acceleration is detected at a detectivity, into which a detectivity of said longitudinal effect type piezoelectric element and a detectivity of said lateral effect type piezoelectric element are compounded, by switching an output from said longitudinal effect type piezoelectric element and said lateral effect type piezoelectric element selectively.

19. A piezoelectric acceleration sensor comprising:

a plurality of pairs of piezoelectric elements including a longitudinal effect type piezoelectric element which has a first piezoelectric body and produces a first output voltage according to an expansion and contraction and a shear deformation of the first piezoelectric body, and a lateral effect type piezoelectric element which has a second piezoelectric body and produces a second voltage output according to a flexure of the second piezoelectric body;

wherein said plurality of piezoelectric elements are located to detect acceleration components in different directions from each other.

20. A piezoelectric acceleration sensor according to claim 19, further comprising:

a detecting means for outputting a detection signal according to an acceleration component in a predetermined direction of an applied acceleration, based on an output from said plurality of pair of piezoelectric elements.

21. A piezoelectric acceleration sensor comprising:

a plurality of piezoelectric elements with a different frequency character of detecting an acceleration from each other; and

a detecting means for detecting an acceleration in a frequency characteristic, into which a frequency characteristic of each of said piezoelectric elements is compounded, based on an output from said plurality of piezoelectric elements.

22. A piezoelectric acceleration sensor comprising:

a plurality of piezoelectric elements with a different detectivity of an acceleration from each other; and

a detecting means for detecting an acceleration at a detectivity, into which a detectivity of each of said piezoelectric elements is compounded, based on an output from said plurality of piezoelectric elements.