Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2000-04-12
2002-04-09
Chapman, John E. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
active
06367326
ABSTRACT:
TECHNICAL FIELD
This invention relates to an angular velocity sensor, and more particularly to an angular velocity sensor suitable for mass-production utilizing micromachining technology and semiconductor technology.
BACKGROUND ART
In the automobile industry or machinery industry, etc., there has been increased demand for sensors capable of precisely detecting acceleration or angular velocity of a moving object. In regard to an acceleration, sensors of various types have been conventionally proposed, and small-sized sensors capable of two-dimensionally or three-dimensionally detecting an applied acceleration have been put into practical use. For example, in the International Publication No. W088/08522 based on the Patent Cooperation Treaty (U.S. Pat. Nos. 4,967,605, 5,182,515), an acceleration sensor utilizing changes of resistance values of piezo resistance elements formed on a semiconductor substrate is disclosed. Moreover, in the International Publication No. W092/17759 based on the Patent Cooperation Treaty (U.S. Pat. No. 5,492,020), there is disclosed an acceleration sensor in which electrostatic capacitance elements or piezoelectric elements are used to detect an applied acceleration in every respective coordinate axis direction. In the International Publication No. W093/02342 based on the Patent Cooperation Treaty (U.S. Pat. No. 5,365,799), there is disclosed a multi-axial acceleration sensor using piezoelectric elements of different type.
On the other hand, there are a relatively few publications in connection with the angular velocity sensor. Particularly, publications in regard to angular velocity sensors capable of simultaneously detecting angular velocity about multi-axes can be hardly seen. Ordinarily, angular velocity sensors are utilized for the purpose of detecting an angular velocity of a power shaft, etc. of vehicle, and only have a function to detect an angular velocity about a specific one axis. In such a case that a rotational speed of the power shaft as described above is measured, it is sufficient to use a one-dimensional angular velocity sensor. However, as a sensor for detecting angular velocity with respect to an object which carries out free movement within a three-dimensional space, multi-axial velocity sensors capable of simultaneously detecting angular velocity components about two-axes or three-axes are expected.
In order to meet with such demand, the inventor of this application has proposed novel multi-axial angular velocity sensors in the International Publication No. W094/23272 based on the Patent Cooperation Treaty (U.S. patent application Ser. No. 08/366,026) and the Japanese Patent Application No. 7-56690/1995 specification (U.S. patent application Ser. No. 08/601,794). Such novel angular velocity sensors utilize the principle that when an angular velocity is applied about the second coordinate axis to the object moving in the first coordinate axial direction in the XYZ three-dimensional rectangular coordinate system, Coriolis force is produced in the third coordinate axial direction, and the sensors detect the Coriolis force applied to the object so as to indirectly detect an angular velocity. For detecting Coriolis force, the technologies which have been fostered in the conventional acceleration sensors are applied. That is, a piezo resistance element, a capacitance element and a piezoelectric element, etc. are utilized.
SUMMARY OF THE INVENTION
An object of this invention is to provide a concrete and more practical mechanism of the angular velocity sensor based on the above-described principle, particularly to provide a novel technique for manufacturing a multi-axial angular velocity sensor utilizing micromachining technology and semiconductor technology, According to this invention, mass-production of small and high accuracy multi-axial angular velocity sensors is realized.
(1) The first feature of the present invention resides in an angular velocity sensor comprising:
a substrate having an upper surface along an XY plane in an XYZ three-dimensional coordinate system;
a weight body for carrying out rotational movement in a non-contact state with respect to the upper surface with a Z-axis perpendicular to the upper surface being an axis of rotation; energy supply means for delivering energy to the weight body so that the weight body carries out the rotational movement while maintaining a fixed distance with respect to the upper surface of the substrate when no external force is applied; and
“distance above X-axis measurement means” for measuring a distance between the upper surface and the weight body at a time when the weight body passes above the X-axis;
thus to detect an angular velocity about the X-axis on the basis of a distance measured by the distance above X-axis measurement means.
(2) The second feature of the present invention resides in an angular velocity sensor as in the first feature: and
wherein there are provided a first weight body and a second weight body which carry out the rotational movement in a non-contact state with respect to the upper surface of the substrate with the Z-axis being as an axis of rotation;
wherein the first weight body and the second weight body can be rotated in a state where their phases are shifted relative to each other by 180 degrees so that when the first weight body is positioned above the positive X-axis, the second weight body is positioned above the negative X-axis; and
the “distance above positive X-axis measurement means” serves for measuring the distance between the upper surface of the substrate and either of the weight bodies at a time when the weight body passes above the positive X-axis;
the “distance above negative X-axis measurement means” serves for measuring a distance between the upper surface of the substrate and either of the weight bodies at a time when the weight body passes above the negative X-axis; and
difference calculation means for obtaining a difference between the distance measured by the “distance above positive X-axis measurement means” and the distance measured by the “distance above negative X-axis measurement means”,
thus to detect an angular velocity about the X-axis applied to the substrate on the basis of a difference obtained by the difference calculation means.
(3) The third feature of the present invention resides in an angular velocity sensor according to the first feature:
wherein there is further provided “distance above Y-axis measurement means” for measuring a distance between the upper surface of the substrate and the weight body at a time point when the weight body passes above the Y-axis;
thus to detect an angular velocity about the X-axis applied to the substrate on the basis of the distance measured by the “distance above X-axis measurement means”, and to detect an angular velocity about the Y-axis applied to the substrate on the basis of the distance measured by the “distance above Y-axis measurement means”.
(4) The fourth feature of the present invention resides in an angular velocity sensor according to the third feature:
wherein there are provided a first weight body and a second weight body which carry out rotational movement in a non-contact state with respect to the upper surface of the substrate with the Z-axis being as an axis of rotation;
wherein the first weight body and the second weight body can be rotated in a state where their phases are shifted relative to each other by 180 degrees so that when the first weight body is positioned above the positive X-axis, the second weight body is positioned above the negative X-axis and when the first weight body is positioned above the positive Y-axis, the second weight body is positioned above the negative Y-axis;
wherein there are provided;
“distance above positive X-axis measurement means” for measuring a distance between the upper surface of the substrate and either of the weight bodies at a time point when the weight body passes above the positive X-axis;
“distance above negative X-axis measurement means” for measuring the distance between the upper surface of the substrate and either
Chapman John E.
Ladas & Parry
Wacoh Corporation
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