Multiaxial acceleration sensor using a piezoelectric element

An acceleration sensor for detecting acceleration components in plural coordinate axis directions in an XYZ three-dimensional coordinate system having an X-axis, a Y-axis and a Z-axis, comprising piezoelectric element in a plate form, five upper electrodes formed on an upper surface of the piezoelectric element, at least one lower electrode formed at a position facing the respective upper electrodes on a lower surface of the piezoelectric element and a strain generative body in a plate form for supporting said at least one lower electrode from below;

• wherein an origin of the XYZ three-dimensional coordinate system is defined substantially at a central position of an upper surface of the strain generative body;
• wherein the strain generative body 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;
• wherein the upper surface of the strain generative body and a lower surface of said at least one lower electrode are fixed in such a state where a plate surface of the piezoelectric element is substantially in parallel to a plate surface of the strain generative body so that when bending takes place in the flexible portion of the strain generative body, said bending is transmitted to the piezoelectric element, while when bending takes place in the piezoelectric element, said bending is transmitted to the flexible portion of the strain generative body;
• and
• wherein the five 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, a fourth upper electrode formed in a positive region with respect to the Y-axis and a fifth upper electrode formed in a region surrounding a periphery of the origin, at least each portion of these respective upper electrodes being located on the flexible portion;
• said acceleration sensor further comprising;
• excitation means for applying an a.c. voltage across a predetermined pair of upper and lower electrodes to thereby oscillate the working portion;
• force detecting means for detecting a force in an axis direction applied to the working portion on the basis of charges produced in the upper electrodes;
• and
• circuit means having a first function to output a detected value by the force detecting means with respect to a particular axis direction under the condition that the working portion is not oscillated thus to carry out detection of acceleration in said particular axis direction, and a second function to output a detected value by the force detecting means with respect to a first axis direction under the condition that the working portion is oscillated in a second axis direction perpendicular to the first axis direction thus to carry out detection of an angular velocity about a third axis perpendicular to the first axis and the second axis;
• thus making it possible to detect angular velocity components about plural coordinate axes along with acceleration components in plural coordinate axes directions.

An acceleration sensor for detecting acceleration components in plural coordinate axis directions 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, five upper electrodes formed on an upper surface of the piezoelectric element, and a strain generative body in a plate form for supporting the piezoelectric element from below, at least an upper surface portion of the strain generative body being constituted by conductive material so that a lower electrode facing the respective upper electrodes is constituted by the conductive material;

• wherein an origin of the XYZ three-dimensional coordinate system is defined substantially at a central position of an upper surface of the strain generative body;
• wherein the strain generative body 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;
• the upper surface of the strain generative body and a lower surface of the piezoelectric element are fixed in such a state where a plate surface of the piezoelectric element is substantially parallel to a plate surface of the strain generative body so that when bending takes place in the flexible portion of the strain generative body, said bending is transmitted to the piezoelectric element, while when bending takes place in the piezoelectric element, said bending is transmitted to the flexible portion of the strain generative body;
• and
• wherein the five 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, a fourth upper electrode formed in a positive region with respect to the Y-axis and a fifth upper electrode formed in a region surrounding a periphery of the origin, at least each portion of these respective upper electrodes being located on the flexible portion;
• said acceleration sensor further comprising;
• excitation means for applying an a.c. voltage across a predetermined pair of upper and lower electrodes to thereby oscillate the working portion;
• force detecting means for detecting a force in an axis direction applied to the working portion on the basis of charges produced in the upper electrodes;
• and
• circuit means having a first function to output a detected value by the force detecting means with respect to a particular axis direction under the condition that the working portion is not oscillated thus to carry out detection of acceleration in said particular axis direction, and a second function to output a detected value by the force detecting means with respect to a first axis direction under the condition that the working portion is oscillated in a second axis direction perpendicular to the first axis direction thus to carry out detection of an angular velocity about a third axis perpendicular to the first axis and the second axis;
• thus making it possible to detect angular velocity components about plural coordinate axes along with acceleration components in plural coordinate axis directions.

An acceleration sensor for detecting acceleration components in plural coordinate axis directions 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, five 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;
• and
• wherein the five upper electrodes are constituted as a first upper electrode disposed in the first quadrant of the XY coordinate system, a second upper electrode disposed in the second quadrant thereof, a third upper electrode disposed in the third quadrant thereof, a fourth upper electrode disposed in the fourth quadrant thereof and a fifth upper electrode disposed in a peripheral region of the origin, at least each portion of these respective upper electrodes being located on the flexible portion;
• said acceleration sensor further comprising;
• force detecting means for detecting a force in a particular axis direction applied to the working portion on the basis of charges produced in the upper electrodes;
• and
• circuit means for outputting a detected value by the force detecting means with respect to the particular axis direction as an electric signal so as to carry out detection of acceleration in the particular axis direction.

An acceleration sensor for detecting acceleration components in plural coordinate axis directions 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, five upper electrodes formed on an upper surface of the piezoelectric element, at least one lower electrode formed at a position facing the respective upper electrodes on a lower surface of the piezoelectric element and a strain generative body in a plate form for supporting said at least one lower electrode from below;

• wherein an origin of the XYZ three-dimensional coordinate system is defined substantially at a central position of an upper surface of the strain generative body;
• wherein the strain generative body 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;
• wherein the upper surface of the strain generative body and a lower surface of said at least one lower electrode are fixed in such a state where a plate surface of the piezoelectric element is substantially parallel to a plate surface of the strain generative body so that when bending takes place in the flexible portion of the strain generative body, said bending is transmitted to the piezoelectric element, while when bending takes place in the piezoelectric element, said bending is transmitted to the flexible portion of the strain generative body;
• and
• wherein the five upper electrodes are constituted as a first upper electrode disposed in the first quadrant of the XY coordinate system, a second upper electrode disposed in the second quadrant thereof, a third upper electrode disposed in the third quadrant thereof, a fourth upper electrode disposed in the fourth quadrant thereof and a fifth upper electrode disposed in a peripheral region of the origin, at least each portion of these respective upper electrodes being located on the flexible portion;
• said acceleration sensor further comprising;
• excitation means for applying an a.c. voltage across a predetermined pair of upper and lower electrodes to thereby oscillate the working portion;
• force detecting means for detecting a force in an axis direction applied to the working portion on the basis of charges produced in the upper electrodes;
• and
• circuit means having a first function to output a detected value by the force detecting means with respect to a particular axis direction under the condition that the working portion is not oscillated thus to carry out detection of acceleration in said particular axis direction, and a second function to output a detected value by the force detecting means with respect to a first axis direction under the condition that the working portion is oscillated in a second axis direction perpendicular to the first axis direction thus to carry out detection of an angular velocity about a third axis perpendicular to the first axis and the second axis;
• thus making it possible to detect angular velocity components about plural coordinate axes along with acceleration components in plural coordinate axis directions.

An acceleration sensor for detecting acceleration components in plural coordinate axis directions 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, five upper electrodes formed on an upper surface of the piezoelectric element, and a strain generative body in a plate form for supporting the piezoelectric element from below, at least an upper surface portion of the strain generative body being constituted by conductive material so that a lower electrode facing the respective upper electrodes is constituted by the conductive material;

• wherein an origin of the XYZ three-dimensional coordinate system is defined substantially at a central position of an upper surface of the strain generative body;
• wherein the strain generative body 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;
• the upper surface of the strain generative body and a lower surface of the piezoelectric element are fixed in such a state where a plate surface of the piezoelectric element is substantially parallel to a plate surface of the strain generative body so that when bending takes place in the flexible portion of the strain generative body, said bending is transmitted to the piezoelectric element, while when bending takes place in the piezoelectric element, said bending is transmitted to the flexible portion of the strain generative body;
• and
• wherein the five upper electrodes are constituted as a first upper electrode disposed in the first quadrant of the XY coordinate system, a second upper electrode disposed in the second quadrant thereof, a third upper electrode disposed in the third quadrant thereof, a fourth upper electrode disposed in the fourth quadrant thereof and a fifth upper electrode disposed in a peripheral region of the origin, at least each portion of these respective upper electrodes being located on the flexible portion;
• said acceleration sensor further comprising;
• excitation means for applying an a.c. voltage across a predetermined pair of upper and lower electrodes to thereby oscillate the working portion;
• force detecting means for detecting a force in an axis direction applied to the working portion on the basis of charges produced in the upper electrodes;
• and
• circuit means having a first function to output a detected value by the force detecting means with respect to a particular axis direction under the condition that the working portion is not oscillated thus to carry out detection of acceleration in said particular axis direction, and a second function to output a detected value by the force detecting means with respect to a first axis direction under the condition that the working portion is oscillated in a second axis direction perpendicular to the first axis direction thus to carry out detection of an angular velocity about a third axis perpendicular to the first axis and the second axis;
• thus making it possible to detect angular velocity components about plural coordinate axes along with acclearation components in plural coordinate axis directions.