Patent ID: 6269697
Filing Date: 2001-08-07
Classification: G01C,G01P

Abstract:
An angular velocity sensor for detecting an angular velocity component in an XYZ three-dimensional coordinate system having an X-axis, a Y-axis and a Z-axis, comprising a piezoelectric element in a plate form, four upper electrodes formed on an upper surface of the piezoelectric element and at least one lower electrode formed at a position facing the respective upper electrodes on a lower surface of the piezoelectric element; wherein an origin of the XYZ three-dimensional coordinate system is defined substantially at a central position of the upper surface of the piezoelectric element;wherein the piezoelectric element extends along an XY plane and includes a central portion around the origin, a flexible portion with flexibility surrounding the central portion and a peripheral portion surrounding the flexible portion, so that said central portion and said peripheral portion are caused to undergo displacement relative to each other by bending of the flexible portion;wherein either one of the central portion and the peripheral portion is fixed to a sensor casing as a fixed portion, and the other is supported as a working portion in a state to be displaced by force applied in respective coordinate axis directions; andwherein the four upper electrodes are constituted as a first upper electrode formed in a negative region with respect to the X-axis, a second upper electrode formed in a positive region with respect to the X-axis, a third upper electrode formed in a negative region with respect to the Y-axis and a fourth upper electrode formed in a positive region with respect to the Y-axis, at least each portion of these respective upper electrodes being located on the flexible portion;said angular velocity sensor further comprising;excitation means for applying an a.c. voltage across the first upper electrode and the lower electrode and across the second upper electrode and the lower electrode to oscillate the working portion in the X-axis direction,force detecting means for detecting a force in the Y-axis direction applied to the working portion on the basis of charges produced in the third and the fourth upper electrodes; andan electric circuit for outputting a detected value by the force detecting means as an electric signal indicative of an angular velocity component around the Z-axis.