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Acceleration sensor

Inactive Publication Date: 2005-01-27
FUJITSU LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0014] A more specific object of the present invention is to provide a compact, thin, less-expensive acceleration sensor having improved sensitivity.

Problems solved by technology

Japanese Laid-Open Patent Application No. 11-51960 or the like needs a troublesome work of attaching the weight element to the piezoelectric element.
Thus, the acceleration sensor is heavy.
Therefore, it can be concluded that the acceleration sensor of this time has difficulty in realizing lightweight, thin acceleration sensors.
The laminated structure can be produced only by a very complex process and is thus expensive.

Method used

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Experimental program
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Effect test

first embodiment

[0063] (First Embodiment)

[0064] An acceleration sensor according to a first embodiment of the present invention has an arrangement, in which the detection electrode mentioned before is divided into two parts arranged side by side in the main-axis direction X in which acceleration α is applied in order to further improve sensitivity and reduce noise.

[0065]FIGS. 3A, 3B and 3C illustrate an acceleration sensor according to the first embodiment of the present invention. As shown in FIG. 3A, the detection electrode 11 is divided into two detection electrodes 11-1 and 11-2 arranged side by side in the width direction of the LNX-cut plate 1. As shown in FIG. 3B, electric signals respectively picked up via the detection electrodes 11-1 and 11-2 caused by acceleration α applied in the main-axis direction X are 180 degrees out of phase. As to the Y-axis direction perpendicular to the main-axis direction X, the electric signals respectively picked up via the detection electrodes 11-1 and 11-2...

second embodiment

[0066] (Second Embodiment)

[0067] An acceleration sensor according to a second embodiment of the present invention has an arrangement, in which the detection electrode mentioned before is divided into two parts arranged side by side in a Z-axis direction perpendicular to the direction in which acceleration α is applied in order to reduce the production cost.

[0068]FIG. 4 is a diagram of the acceleration sensor according to the second embodiment of the present invention. The detection electrode 11 is divided into parts 11-3 and 11-4 arranged side by side in the longitudinal direction Z of the LNX-cut plate perpendicular to the direction in which acceleration α is applied.

[0069] The detection electrodes 11-3 and 11-4 are arranged in parallel with the X-axis direction in which acceleration α is applied. Hence, it is possible to easily divide the detection electrode 11 into the parts 11-3 and 11-4 by batch processing at the time of dividing the LNX-cut plate into the individual LNX-cut ...

third embodiment

[0070] (Third Embodiment)

[0071] An acceleration sensor according to a third embodiment of the present invention has an arrangement in which the LNX-cut plate is supported in a position which does not include the center of gravity thereof.

[0072] Referring to FIG. 5A, the supporting area S is located in an end part of the LNX-cut plate 1. Thus, the effective length L of the weight part W can be lengthened, so that acceleration α can be sensed with higher sensitivity.

[0073]FIG. 5B is a graph showing a relationship between the supporting area S and normalized sensor output. The sensitivity depends on the supporting area S. More particularly, the sensitivity becomes worse as a supporting member 2 shown in FIG. 5A is positioned so as to become closer to the center of the LNX-cut plate 1. A normalized sensor output of 1 is defined when the supporting area S is located in the end part of the LNX-cut plate 1. The horizontal axis of the graph of FIG. 5B denotes the normalized supporting are...

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Abstract

An acceleration sensor includes a piezoelectric single-plate having a weight part and a detection part. The piezoelectric single-plate is, for example, an X-cut plate of LiNbO3.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention generally relates to an acceleration sensor which senses a shock or acceleration applied to an object. More particularly, the present invention is concerned with an acceleration sensor of a piezoelectric type that senses the amount of feature produced by inertia force caused in an object due to an acceleration. [0003] Recently, downsizing of electronic apparatuses has progressed and portable electronic apparatuses such as notebook-type personal computers have been spread. Usually, the portable electronic apparatuses are designed to sense a shock unexpectedly applied thereto and carry out a given process in order to maintain the reliability. For example, if a hard disk drive built in a notebook type personal computer gets a shock, the current write / reproduction operation is interrupted, and rather a process for avoiding occurrence of error is initiated. An acceleration sensor can be used to sens...

Claims

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Application Information

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IPC IPC(8): H01L41/08G01P15/09
CPCG01P15/0922G01H11/08G01P15/0915
Inventor TANAKA, HIROSHIISHIKAWA, HIROSHIIKATA, OSAMU
Owner FUJITSU LTD