Measuring and testing – Speed – velocity – or acceleration – Acceleration determination utilizing inertial element
Patent
1997-01-22
1999-01-05
Williams, Hezron E.
Measuring and testing
Speed, velocity, or acceleration
Acceleration determination utilizing inertial element
7351438, G01P 15125
Patent
active
058566201
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an acceleration sensor and, more particularly, to an acceleration sensor suitable for detecting acceleration based on earthquake or collision of automotive vehicle.
BACKGROUND ART
In view of grasping movement of an object, detection of acceleration has important meaning. For this reason, various acceleration sensors have been conventionally proposed. Particularly, in recent years, the spotlight of attention upon multi-dimensional acceleration sensors capable of detecting two-dimensional or three-dimensional acceleration every respective directional components has been focused. For example, in the International Publication No. WO88/08522 based on the Patent Cooperation Treaty, a three-dimensional acceleration sensor using piezo resistance elements is disclosed. In this sensor, plural piezo resistance elements are formed at specific positions on a semiconductor substrate, thereby making it possible to respectively independently detect acceleration components in respective coordinate axes directions in the XYZ three-dimensional coordinate system. Moreover, in the International Publication No. WO91/10118 or the International Publication No. WO92/17759, a three-dimensional acceleration sensor using electrostatic capacitance elements is disclosed. In the International Publication No. WO93/02342, a three-dimensional acceleration sensor using piezoelectric elements is disclosed. In these sensors, plural electrodes are formed at specific positions, thereby making it possible to respectively independently detect acceleration components in respective coordinate axes directions in the XYZ three-dimensional coordinate system in a manner similar to the above.
In such three-dimensional acceleration sensors, since all of respective coordinate axes direction components of applied acceleration can be respectively independently detected by a single sensor, it is possible to specify an acceleration to be detected as a vector quantity within the three-dimensional space. Accordingly, such three-dimensional acceleration sensors can be widely utilized in use for precisely detecting acceleration exerted on an object moving within the three-dimensional space, e.g., a vehicle being traveled, or an air-plane being flown, etc. in a manner to include its direction. In future, it is expected that its utilization value will be increased.
On the other hand, the acceleration sensor can be utilized also as a seismometer or an impact detector. For example, in a control system for control valves of the city gas or a control system for control an elevator, an acceleration sensor functioning as a seismometer is included. In the case where an acceleration based on vibration of the earthquake exceeds a predetermined threshold value, the control system stops supply of gas, or stops an operation of the elevator. Moreover, in automotive vehicles with an air bag which begins being popularized rapidly in recent years, an acceleration sensor functioning as an impact detector is mounted, wherein there is employed a mechanism to momentarily swell the air bag to protect a driver in the case where an acceleration based on impact exceeds a predetermined threshold value. However, it is to be noted that the acceleration sensors used in seismometers or impact detectors are mainly mechanical type sensors which detect an acceleration by means of mechanical operation. For example, a mechanical sensor recognizes whether or not a steel ball is flown out from a bowl-shaped vessel, and judges whether or not an acceleration more than the threshold value is exerted.
As described above, the acceleration sensors utilized as seismometers or impact detectors are mainly mechanical type sensors for the present. However, such mechanical acceleration sensors have drawbacks that the detection accuracy or the reliability is low, and it is difficult to electrically take out detection results. On the other hand, three-dimensional acceleration sensors using piezo resistance elements, capacitance elements or piezoelectric elements have a
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Moller Richard A.
Wacoh Corporation
Williams Hezron E.
LandOfFree
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