Surface potential sensor and copying machine

• US 10,073,127 B2
• Filed: 03/14/2012
• Issued: 09/11/2018
• Est. Priority Date: 11/15/2011
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Matsushita, Soichi
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): Russo, Raul Rios
• Application Number:
  US14/354,451
• Publication Number:
  US 20150028881A1
• Time in Patent Office: 2,372 Days
• Field of Search: 324 72, 324109, 324457, 324458
• CPC Class Codes: G01R 15/14 Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
• CPC Class Codes: G01R 15/165 measuring electrostatic potential, e.g. with electrostatic voltmeters or electrometers, when the design of the sensor is essential electrometers with passively moving electrodes G01R5/28; measuring electrostatic fields G01R29/12; measuring charge G01R29/24; measuring in circuits with high internal resistance G01R19/0023
• CPC Class Codes: G01R 19/0023 Measuring currents or voltages from sources with high internal resistance by means of measuring circuits with high input impedance, e.g. OP-amplifiers electrostatic instruments G01R5/28; measuring electrostatic potential G01R15/165; measuring electrostatic fields G01R29/12; amplifiers per se H03F
• CPC Class Codes: G01R 29/08 Measuring electromagnetic field characteristics
• CPC Class Codes: G01R 29/0814 Field measurements related to measuring influence on or from apparatus, components or humans EMC, EMI and similar testing in general G01R31/001, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning
• CPC Class Codes: G01R 29/0842 Measurements related to lightning, e.g. measuring electric disturbances, warning systems
• CPC Class Codes: G01R 29/12 Measuring electrostatic fields or voltage-potential
• CPC Class Codes: G01R 31/2642 Testing semiconductor operation lifetime or reliability, e.g. by accelerated life tests
• CPC Class Codes: G01R 5/28 Electrostatic instruments
• CPC Class Codes: G03G 15/5037 the characteristics being an electrical parameter, e.g. voltage

Abstract

This surface potential sensor is provided with an electret electrode (28), which is configured of a metal film (26) and an electret film (27), said electret electrode being provided on an upper surface of a diaphragm (25) of a semiconductor substrate. Four piezoresistors (29a, 29b, 29c, 29d) are formed on the diaphragm (25), and a distortion quantity detecting unit (32) is configured by forming a bridge circuit using the piezoresistors. Since an electrostatic force that operates between an object and the electret electrode (28) changes corresponding to potential of the object, and the electret electrode (28) warps corresponding to the change, the potential of the object can be detected by measuring a distortion quantity of the electret electrode (28) by means of the distortion quantity detecting unit (32). Consequently, not only the potential of the object but also a polarity thereof can be detected with reduced size and high sensitivity.

Claims

1. A surface potential sensor, comprising:

a thin-film electret electrode with flexibility, wherein the rear surface of the thin-film electret electrode is supported by an elastic material; and

an electrostatic force detector configured to detect a change in electrostatic force that operates on the thin-film electret electrode, wherein

the electrostatic force detector comprises;

a deformable member which deforms in response to deformation of the thin-film electret electrode; and

a distortion quantity detecting device configured to detect a distortion quantity of the deformable member,

wherein the deformable member and the distortion quantity detecting device are embedded in the elastic material without being exposed.

2. The surface potential sensor according to claim 1, wherein an electret film is formed on the surface of a metal film in the thin-film electret electrode.

3. The surface potential sensor according to claim 1, wherein

an outer peripheral portion of the thin-film electret electrode is supported by a support, and

an inner region thereof is floating in a space.

4. A copying machine, comprising:

the surface potential sensor according to claim 1.

5. The copying machine according to claim 4, wherein the surface potential sensor is arranged as opposed to the outer peripheral surface of a photosensitive drum.

6. The copying machine according to claim 5, wherein the surface potential sensor is configured to be capable of travelling along a width direction of the photosensitive drum.