# US 8,770,025 B2 · Physical quantity sensor

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- Number: US 8,770,025 B2
- Document ID: US8770025B2
- Status: Granted
- Kind: B2
- Application number: 13/321,980
- Filed: 2010-05-26
- Published: 2012-03-22
- Granted: 2014-07-08
- Earliest claimed: 2009-05-27
- Assignees: Panasonic Corporation
- Applicants: Tsutomu Nakanishi; Yasunobu Kobayashi; Koumei Hujita
- Inventors: Tsutomu Nakanishi; Yasunobu Kobayashi; Koumei Hujita
- Web page: https://patentgrep.com/patent/US8770025B2

## CPC

- G01L 9/0016: {of a diaphragm}
- G01L 1/162: {using piezoelectric resonators}
- G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G)

## Abstract

A physical quantity sensor includes a beam-like vibrating body and a fixing part supporting both ends of the beam-like vibrating body. A driving element is formed on a central portion of the beam-like vibrating body, and feedback elements are formed on both ends. A physical quantity acting on the beam-like vibrating body is detected by causing natural vibration in the beam-like vibrating body and detecting a natural frequency of the vibrating body. This enables reliable detection of a physical quantity, such as a strain or load, acting on an object.

## Claims

### Claim 1

A physical quantity sensor comprising:
a beam-like vibrating body;
a fixing part supporting both ends of the vibrating body;
a first piezoelectric element formed on a central portion of the vibrating body;
a second piezoelectric element formed on one end of the vibrating body; and
a third piezoelectric element formed on an other end of the vibrating body, wherein
at least the vibrating body has a first surface and a second surface opposite to the first surface; and
the first piezoelectric element, the second piezoelectric element and the third piezoelectric element are on the first surface.

### Claim 2 (depends on 1)

The physical quantity sensor of claim 1, wherein
the second piezoelectric element and the third piezoelectric element are formed at symmetrical positions relative to a center of the vibrating body.

### Claim 3 (depends on 1)

The physical quantity sensor of claim 1, wherein
the first piezoelectric element acts as a driving element; and
the second piezoelectric element and the third piezoelectric element act as feedback elements.

### Claim 4 (depends on 1)

The physical quantity sensor of claim 1, wherein
the first piezoelectric element acts as a feedback element; and
the second piezoelectric element and the third piezoelectric element act as driving elements.

### Claim 5 (depends on 1)

The physical quantity sensor of claim 1, wherein
a physical quantity acting on the vibrating body can be detected by causing natural vibration in the vibrating body and measuring a natural frequency of the vibrating body.

### Claim 6 (depends on 1)

The physical quantity sensor of claim 1, wherein
the vibrating body has a first end and a second end and
the fixing part supports the first end and the second end.

### Claim 7 (depends on 6)

The quantity sensor of claim 6, wherein
the second piezoelectric element is formed on the first end; and
the third piezoelectric element is formed on the second end.

### Claim 8 (depends on 1)

The physical quantity sensor of claim 1, wherein the first surface is planar.

### Claim 9

A physical quantity sensor comprising:
a beam-like vibrating body;
a fixing part supporting both ends of the vibrating body;
a first piezoelectric element formed on a central portion of the vibrating body;
a second piezoelectric element formed on one end of the vibrating body;
a third piezoelectric element formed on an other end of the vibrating body;
a fourth piezoelectric element formed near the second piezoelectric element; and
a fifth piezoelectric element formed near the third piezoelectric element,
wherein
at least the vibrating body has a first surface and a second surface opposite to the first surface; and
the first piezoelectric element, the second piezoelectric element and the third piezoelectric element are on the first surface.

### Claim 10 (depends on 9)

The physical quantity sensor of claim 9, wherein
the fourth piezoelectric element and the fifth piezoelectric element are formed at symmetrical positions relative to a center of the vibrating body.

### Claim 11 (depends on 9)

The physical quantity sensor of claim 9, wherein
the second piezoelectric element and the third piezoelectric element are formed at symmetrical positions relative to a center of the vibrating body.

### Claim 12 (depends on 9)

The physical quantity sensor of claim 9, wherein
the first piezoelectric element acts as a detecting element;
the second piezoelectric element and the third piezoelectric element act as driving elements; and
the fourth piezoelectric element and the fifth piezoelectric element act as feedback elements.

### Claim 13 (depends on 9)

The physical quantity sensor of claim 9, wherein
a physical quantity acting on the vibrating body is detected by causing natural vibration in the vibrating body by driving the second piezoelectric element and the third piezoelectric element with a same amplitude in a same phase;
feeding back a vibration state by the fourth piezoelectric element and the fifth piezoelectric element; and
detecting a natural frequency of the vibrating body by the first piezoelectric element.

### Claim 14 (depends on 9)

The physical quantity sensor of claim 9, wherein
the vibrating body has a first end and a second end; and
the fixing part supports the first end and the second end.

### Claim 15 (depends on 14)

The quantity sensor of claim 14, wherein
the second piezoelectric element is formed on the first end; and
the third piezoelectric element is formed on the second end.