Sensor for force/acceleration/magnetism using piezoelectric element

• US 5,365,799 A
• Filed: 03/05/1993
• Issued: 11/22/1994
• Est. Priority Date: 07/17/1991
• Status: Expired due to Term

• Current Assignee: Kazuhiro Okada
• Original Assignee: Kazuhiro Okada
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): Chilcot, Jr., Richard E.
• Assistant Examiner(s): BIEGEL, RONALD L
• Application Number:
  US07/984,435
• Time in Patent Office: 627 Days
• Field of Search: 310/329, 73/567 R, 73/DIG. 4, 73/721, 73/727, 73/862.041, 73/862.042, 73/862.043, 73/862.628, 73/862.632, 73/862.637, 73/862.68
• US Class Current: 73/862.041
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: G01L 5/167 using piezoelectric means
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass

Abstract

A sensor for force, acceleration or magnetism is provided which can carries out high accuracy detection without temperature compensation and easily manufactured. The peripheral portion of a disk-shaped substrate (10) having flexibility is fixed to a sensor casing (60), and a working body (50) is connected to the center portion. With respect to the origin (O) within the substrate (10), an X, Y and Z three-dimensional coordinate system is defined, and four sets of detection elements (D1 to D4) are arranged. Respective detection elements are of a sandwich structure in which piezoelectric elements (21, 23) are put between upper electrodes (31 to 34) and lower electrodes (41 to 44). When a force Fx in the X-axis direction is applied to the working body (50) by application of an acceleration, the substrate (10) is bent, so positive or negative charges are produced in respective electrodes. How charges are produced depends upon the direction of an applied force, and a quantity of charges produced depends upon the magnitude of the applied force. Thus, it is possible to detect components in respective axial directions of an applied force on the basis of a pattern of charges produced.

Claims

1. A force sensor comprising:

a substrate (10) having a planar surface;

a working body (50);

a sensor casing (60);

four detection elements (D1, D2, D3, D4) on said planar surface of said substrate, each two of said detection elements comprising a piezoelectric element (21,

     23) in plate form;

at least two first electrodes (31, 32, 33,

     34) on a first surface of each of said piezoelectric elements;

at least two second electrodes (41, 42, 43,

     44) on an opposite second surface of each of said piezoelectric elements between said piezoelectric elements and said substrate; and

a first detection terminal (Ax) and a second detection terminal (Bx),

wherein an origin (O) is defined at a point within said substrate (10) and an X-axis is defined so that it passes through said origin and extends in a direction parallel to said surface of said substrate, said four detection elements being arranged along said X-axis in such a manner that one of said two of said detection elements (D3, D4) is located on one side of said origin and another of said two of said detection elements (D1, D2) is located on an opposite side of said origin,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate is flexible to said force,

whereby a first four of said electrodes (41, 32, 43,

     34) among said first and second electrodes provide charges of a first polarity when an X-axis component of said force is applied to said working body,

wherein said first four electrodes are connected to said first detection terminal (Ax),

whereby a second four of said electrodes (31, 42, 33,

     44) among said first and second electrodes produce charges of a second polarity when said X-axis component of said force is applied to said working body, and

wherein said second four electrodes are connected to said second detection terminal (Bx),

whereby to sense said X-axis component of said force applied to said working body on the basis of a potential difference between said first detection terminal and said second detection terminal.

2. A force sensor as set forth in claim 1, wherein a piezoelectric element (25) comprised of a single substrate is used commonly to a plurality of detection elements (D1-D12).

3. A sensor as set forth in claim 1, wherein a working body is caused to produce a force on the basis of an acceleration applied from the external, thereby permitting detection of acceleration.

4. A sensor as set forth in claim 1, wherein a working body is constituted with a magnetic material to allow said working body to produce a force on the basis of magnetism applied from the external, thereby permitting detection of magnetism.

5. A force sensor comprising:

a substrate (10) having a planar surface;

a working body (51);

a sensor casing (61);

four detection elements (D1, D2, D3, D4) on said planar surface of said substrate, each two of said detection elements comprising a piezoelectric element (21,

     23) in plate form;

at least two first electrodes (31, 32, 33,

     34) on a first surface of each of said piezoelectric elements;

at least two second electrodes (41, 42, 43,

     44) on an opposite second surface of each of said piezoelectric elements between said piezoelectric elements and said substrate; and

a first detection terminal (Ax) and a second detection terminal (Bx),

wherein an origin (O) is defined at a point within said substrate (10) and an X-axis is defined so that it passes through said origin and extends in a direction parallel to said surface of said substrate, said four detection elements being arranged along said X-axis in such a manner that one of said two of said detection elements (D3, D4) is located on one side of said origin and another of said two of said detection elements (D1, D2) is located on an opposite side of said origin,

wherein a portion of said substrate at said origin is fixed to said sensor casing (61),

wherein said working body (51) is fixed to a peripheral portion of said substrate so as to transmit a force applied to said working body to said peripheral portion of said substrate,

wherein said substrate is flexible to said force,

whereby a first four of said electrodes (41, 32, 43,

     34) among said first and second electrodes produce charges of a first polarity when an X-axis component of said force is applied to said working body,

wherein said first four electrodes are connected to said first detection terminal (Ax),

whereby a second four of said electrodes (31, 42, 33,

     44) among said first and second electrodes produce charges of a second polarity when said X-axis component of said force is applied to said working body, and

wherein said second four electrodes are connected to said second detection terminal (Bx),

whereby to sense said X-axis component of said force applied to said working body on the basis of a potential difference between said first detection terminal and said second detection terminal.

6. A force sensor comprising a substrate (10), a working body (50), a sensor casing (60) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form, a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and a second electrode (41, 42, 43, 44) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Z-axis is defined so that it passes through said origin and extends in a direction perpendicular to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface, said four detection elements being arranged along said X-axis in such a manner that a first detection element (D1) is in a negative region of said X-axis in said outside area, a second detection element (D2) is in the negative region of said X-axis in said inside area, a third detection element (D3) is in a positive region of said X-axis in said inside area, and a fourth detection element (D4) is in the positive region of said X-axis in said outside area, and the respective second electrodes (41, 42, 43, 44) of said respective detection elements are fixed on said substrate,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

wherein potentials of said first electrodes (31, 32, 33, 34) with respect to said second electrodes (41, 42, 43, 44) fixed on said substrate in said respective detection elements are obtained,

to detect a force in said X-axis direction applied to said working body on the basis of a difference between a sum of a potential on said first detection element and a potential on said third detection element and a sum of a potential on said second detection element and a potential on said fourth detection element, and

to detect a force in said Z-axis direction applied to said working body on the basis of a difference between a sum of a potential on said first detection element and a potential on said fourth detection element and a sum of a potential on said second detection element and a potential on said third detection element.

7. A force sensor comprising a substrate (10), a working body (51), a sensor casing (61) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form, a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and a second electrode (41, 42, 43, 44) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Z-axis is defined so that it passes through said origin and extends in a direction perpendicular to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface, said four detection elements being arranged along said X-axis in such a manner that a first detection element (D1) is in a negative region of said X-axis in said outside area, a second detection element (D2) is in the negative region of said X-axis in said inside area, a third detection element (D3) is in a positive region of said X-axis in said inside area, and a fourth detection element (D4) is in the positive region of said X-axis in said outside area, and the respective second electrodes (41, 42, 43, 44) of said respective detection elements are fixed on said substrate,

wherein a portion in a vicinity of said origin of said substrate is fixed to said sensor casing (61),

wherein said working body (51) is fixed to said substrate so as to transmit a force applied to said working body to a peripheral portion of said substrate,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

wherein potentials of said first electrodes (31, 32, 33, 34) with respect to said second electrodes (41, 42, 43, 44) fixed on said substrate in said respective detection elements are obtained,

to detect a force in said X-axis direction applied to said working body on the basis of a difference between a sum of a potential on said first detection element and a potential on said third detection element and a sum of a potential on said second detection element and a potential on said fourth detection element, and

to detect a force in said Z-axis direction applied to said working body on the basis of a difference between a sum of a potential on said first detection element and a potential on said fourth detection element and a sum of a potential on said second detection element and a potential on said third detection element.

8. A force sensor comprising a substrate (10), a working body (50), a sensor casing (60) and eight detection elements (D1-D8), each of said detection elements comprising a piezoelectric element (21-24) in a plate form, a first electrode (31-38) formed on a first surface of said piezoelectric element, and a second electrode (41-48) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Y-axis is defined so that it is perpendicular to said X-axis at said origin and it extends in a direction parallel to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface,

wherein first, second, third and fourth detection elements (D1-D4) of said eight detection elements are respectively arranged along said X-axis in such a manner that said first detection element (D1) is in a negative region of said X-axis in said outside area, said second detection element (D2) is in the negative region of said X-axis in said inside area, said third detection element (D3) is in a positive region of said X-axis in said inside area, and said fourth detection element (D4) is in the positive region of the X-axis in said outside area, and the respective second electrodes (41-44) of said first to fourth detection elements are fixed on said substrate,

wherein fifth, sixth, seventh and eighth detection elements (D5-D8) of said eight detection elements are respectively arranged along said Y-axis in such a manner that said fifth detection element (D5) is in a negative region of said Y-axis in said outside area, said sixth detection element (D6) is in the negative region of said Y-axis in said inside area, said seventh detection element (D7) is in a positive region of said Y-axis in said inside area, and said eighth detection element (D8) is in the positive region of said Y-axis in said outside area, and the respective second electrodes (45-48) of said fifth to eighth detection elements are fixed on said substrate,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

wherein potentials of said first electrodes (31-38) with respect to said second electrodes (41-48) fixed on said substrate in said respective detection elements are obtained,

to detect a force in said X-axis direction applied to said working body on the basis of a difference between a sum of a potential on said first detection element and a potential on said third detection element and a sum of a potential on said second detection element and a potential on said fourth detection element, and

to detect a force in said Y-axis direction applied to said working body on the basis of a difference between a sum of a potential on said fifth detection element and a potential on said seventh detection element and a sum of a potential on said sixth detection element and a potential on said eighth detection element.

9. A force sensor comprising a substrate (10), a working body (51), a sensor casing (61) and eight detection elements (D1-D8), each of said detection elements comprising a piezoelectric element (21-24) in a plate form, a first electrode (31-38) formed on a first surface of said piezoelectric element, and a second electrode (41-48) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Y-axis is defined so that it is perpendicular to said X-axis at said origin and it extends in a direction parallel to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface,

wherein first, second, third and fourth detection elements (D1-D4) of said eight detection elements are respectively arranged along said X-axis in such a manner that said first detection element (D1) is in a negative region of said X-axis in said outside area, said second detection element (D2) is in the negative region of said X-axis in said inside area, said third detection element (D3) is in a positive region of said X-axis in said inside area, and said fourth detection element (D4) is in the positive region of the X-axis in said outside area, and the respective second electrodes (41-44) of said first to fourth detection elements are fixed on said substrate,

wherein fifth, sixth, seventh and eighth detection elements (D5-D8) of said eight detection elements are respectively arranged along said Y-axis in such a manner that said fifth detection element (D5) is in a negative region of said Y-axis in said outside area, said sixth detection element (D6) is in the negative region of said Y-axis in said inside area, said seventh detection element (D7) is in a positive region of said Y-axis in said inside area, and said eighth detection element (D8) is in the positive region of said Y-axis in said outside area, and the respective second electrodes (45-48) of said fifth to eighth detection elements are fixed on said substrate,

wherein a portion in a vicinity of said origin of said substrate is fixed to said sensor casing (61),

wherein said working body (51) is fixed to said substrate so as to transmit a force applied to said working body to a peripheral portion of said substrate,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

wherein potentials of said first electrodes (31-38) with respect to said second electrodes (41-48) fixed on said substrate in said respective detection elements are obtained,

to detect a force in said X-axis direction applied to said working body on the basis of a difference between a sum of a potential on said first detection element and a potential on said third detection element and a sum of a potential on said second detection element and a potential on said fourth detection element, and

to detect a force in said Y-axis direction applied to said working body on the basis of a difference between a sum of a potential on said fifth detection element and a potential on said seventh detection element and a sum of a potential on said sixth detection element and a potential on said eighth detection element.

10. A force sensor comprising a substrate (10), a working body (50), a sensor casing (60) and twelve detection elements (D1-D12), each of said detection elements comprising a piezoelectric element in a plate form, a first electrode formed on a first surface of said piezoelectric element, and a second electrode formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Y-axis is defined so that it is perpendicular to said X-axis at said origin and it extends in a direction parallel to said substrate surface, a Z-axis is defined so that it passes through said origin and extends in a direction perpendicular to said substrate surface, a W-axis is defined so that it intersects with said respective axes of X, Y and Z at said origin and extends in a direction parallel to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface,

wherein first, second, third and fourth detection elements (D1-D4) of said twelve detection elements are respectively arranged along said X-axis in such a manner that said first detection element (D1) is in a negative region of said X-axis in said outside area, said second detection element (D2) is in the negative region of said X-axis in said inside area, said third detection element (D3) is in a positive region of said X-axis in said inside area, and said fourth detection element (D4) is in the positive region of said X-axis in side outside area, and the respective second electrodes of said first to fourth detection elements are fixed on said substrate,

wherein fifth, sixth, seventh and eighth detection elements (D5-D8) of said twelve sets of detection elements are respectively arranged along said Y-axis in such a manner that said fifth detection element (D5) is in a negative region of said Y-axis in said outside area, said sixth detection element (D6) is in the negative region of said Y-axis in said inside area, said seventh detection element (D7) is in a positive region of said Y-axis in said inside area, and said eighth detection element (D8) is in the positive region of said Y-axis in said outside area, and the respective second electrodes of said fifth to eighth detection elements are fixed on said substrate,

wherein ninth, tenth, eleventh and twelfth detection elements (D9-D12) of said twelve detection elements are respectively arranged along said W-axis in such a manner that said ninth detection element (D9) is in a negative region of said W-axis in said outside area, said tenth detection element (D10) is in the negative region of said W-axis in said inside area, said eleventh detection element (D11) is in a positive region of said W-axis in said inside area, and a twelfth detection element (D12) is in the positive region of said W-axis in said outside area, and the respective second electrodes of said ninth to twelfth detection elements are fixed on said substrate,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

wherein potentials of said first electrodes with respect to said second electrodes fixed on said substrate in said respective detection elements are obtained,

to detect a force in said X-axis direction applied to said working body on the basis of a difference between a sum of a potential on said first detection element and a potential on said third detection element and a sum of a potential on said second detection element and a potential on said fourth detection element,

to detect a force in said Y-axis direction applied to said working body on the basis of a difference between a sum of a potential on said fifth detection element and a potential on said seventh detection element and a sum of a potential on said sixth detection element and a potential on said eighth detection element, and

to detect a force in said Z-axis direction applied to said working body on the basis of a difference between a sum of a potential on said ninth detection element and a potential on said twelve detection element and a sum of a potential on said tenth detection element and a potential on said eleventh detection element.

11. A force sensor comprising a substrate (10), a working body (51), a sensor casing (61) and twelve detection elements (D1-D12), each of said detection elements comprising a piezoelectric element in a plate form, a first electrode formed on a first surface of said piezoelectric element, and a second electrode formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Y-axis is defined so that it is perpendicular to said X-axis at said origin and it extends in a direction parallel to said substrate surface, a Z-axis is defined so that it passes through said origin and extends in a direction perpendicular to said substrate surface, a W-axis is defined so that it intersects with said respective axes of X, Y and Z at said origin and extends in a direction parallel to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface,

wherein first, second, third and fourth detection elements (D1-D4) of said twelve detection elements are respectively arranged along said X-axis in such a manner that said first detection element (D1) is in a negative region of said X-axis in said outside area, said second detection element (D2) is in the negative region of said X-axis in said inside area, said third detection element (D3) is in a positive region of said X-axis in said inside area, and said fourth detection element (D4) is in the positive region of said X-axis in side outside area, and the respective second electrodes of said first to fourth detection elements are fixed on said substrate,

wherein fifth, sixth, seventh and eighth detection elements (D5-D8) of said twelve sets of detection elements are respectively arranged along said Y-axis in such a manner that said fifth detection element (D5) is in a negative region of said Y-axis in said outside area, said sixth detection element (D6) is in the negative region of said Y-axis in said inside area, said seventh detection element (D7) is in a positive region of said Y-axis in said inside area, and said eighth detection element (D8) is in the positive region of said Y-axis in said outside area, and the respective second electrodes of said fifth to eighth detection elements are fixed on said substrate,

wherein ninth, tenth, eleventh and twelfth detection elements (D9-D12) of said twelve detection elements are respectively arranged along said W-axis in such a manner that said ninth detection element (D9) is in a negative region of said W-axis in said outside area, said tenth detection element (D10) is in the negative region of said W-axis in said inside area, said eleventh detection element (D11) is in a positive region of said W-axis in said inside area, and a twelfth detection element (D12) is in the positive region of said W-axis in said outside area, and the respective second electrodes of said ninth to twelfth detection elements are fixed on said substrate,

wherein a portion in a vicinity of said origin of said substrate is fixed to said sensor casing (61),

wherein said working body (51) is fixed to said substrate so as to transmit a force applied to said working body to a peripheral portion of said substrate,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

wherein potentials of said first electrodes with respect to said second electrodes fixed on said substrate in said respective detection elements are obtained,

to detect a force in said X-axis direction applied to said working body on the basis of a difference between a sum of a potential on said first detection element and a potential on said third detection element and a sum of a potential on said second detection element and a potential on said fourth detection element,

to detect a force in said Y-axis direction applied to said working body on the basis of a difference between a sum of a potential on said fifth detection element and a potential on said seventh detection element and a sum of a potential on said sixth detection element and a potential on said eighth detection element, and

to detect a force in said Z-axis direction applied to said working body on the basis of a difference between a sum of a potential on said ninth detection element and a potential on said twelve detection element and a sum of a potential on said tenth detection element and a potential on said eleventh detection element.

12. A force sensor comprising a substrate (10), a working body (50), a sensor casing (60) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form, a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and a second electrode (41, 42, 43, 44) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Z-axis is defined so that it passes through said origin and extends in a direction perpendicular to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface, said four detection elements being arranged along said X-axis in such a manner that a first detection element (D1) is in a negative region of said X-axis in said outside area, a second detection element (D2) is in the negative region of said X-axis in said inside area, a third detection element (D3) is in a positive region of said X-axis in said inside area, and a fourth detection element (D4) is in the positive region of said X-axis in said outside area, and the respective second electrodes (41, 42, 43, 44) of said respective detection elements are fixed on said substrate,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

said force sensor further comprising a first detection terminal (Ax), a second detection terminal (Bx), a third detection terminal (Az) and a fourth detection terminal (Bz),

wherein four electrodes (41, 32, 43, 34) among said first and second electrodes, on which charges of a first polarity are produced when an X-axis component of force is applied to said working body, are connectable to said first detection terminal (Ax),

wherein four electrodes (31, 42, 33, 44) among said first and second electrodes, on which charges of a second polarity are produced when an X-axis component of force is applied to said working body, are connectable to said second detection terminal (Bx),

wherein four electrodes (41, 32, 33, 44) among said first and second electrodes, on which charges of the first polarity are produced when an Z-axis component of force is applied to said working body, are connectable to said third detection terminal (Az),

wherein four electrodes (31, 42, 43, 34) among said first and second electrodes, on which charges of the second polarity are produced when an Z-axis component of force is applied to said working body, are connectable to said fourth detection terminal (Bz),

to detect said X-axis component of force applied to said working body on the basis of a potential difference (Vx) across said first and second detection terminals, and to detect said Z-axis component of force applied to said working body on the basis of a potential difference (Vz) across said third and fourth detection terminals.

13. A force sensor comprising a substrate (10), a working body (51), a sensor casing (61) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form, a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and a second electrode (41, 42, 43, 44) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Z-axis is defined so that it passes through said origin and extends in a direction perpendicular to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface, said four detection elements being arranged along said X-axis in such a manner that a first detection element (D1) is in a negative region of said X-axis in said outside area, a second detection element (D2) is in the negative region of said X-axis in said inside area, a third detection element (D3) is in a positive region of said X-axis in said inside area, and a fourth detection element (D4) is in the positive region of said X-axis in said outside area, and the respective second electrodes (41, 42, 43, 44) of said respective detection elements are fixed on said substrate,

wherein a portion in a vicinity of said origin of said substrate is fixed to said sensor casing (61),

wherein said working body (51) is fixed to said substrate so as to transmit a force applied to said working body to a peripheral portion of said substrate,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

said force sensor further comprising a first detection terminal (Ax), a second detection terminal (Bx), a third detection terminal (Az) and a fourth detection terminal (Bz),

wherein four electrodes (41, 32, 43, 34) among said first and second electrodes, on which charges of a first polarity are produced when an X-axis component of force is applied to said working body, are connectable to said first detection terminal (Ax),

wherein four electrodes (31, 42, 33, 44) among said first and second electrodes, on which charges of a second polarity are produced when an X-axis component of force is applied to said working body, are connectable to said second detection terminal (Bx),

wherein four electrodes (41, 32, 33, 44) among said first and second electrodes, on which charges of the first polarity are produced when an Z-axis component of force is applied to said working body, are connectable to said third detection terminal (Az),

wherein four electrodes (31, 42, 43, 34) among said first and second electrodes, on which charges of the second polarity are produced when an Z-axis component of force is applied to said working body, are connectable to said fourth detection terminal (Bz),

to detect said X-axis component of force applied to said working body on the basis of a potential difference (Vx) across said first and second detection terminals, and to detect said Z-axis component of force applied to said working body on the basis of a potential difference (Vz) across said third and fourth detection terminals.

14. A force sensor comprising a substrate (10), a working body (50), a sensor casing (60) and eight detection elements (D1-D8), each of said detection elements comprising a piezoelectric element (21-24) in a plate form, a first electrode (31-38) formed on a first surface of said piezoelectric element, and a second electrode (41-48) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Y-axis is defined so that it is perpendicular to said X-axis at said origin and it extends in a direction parallel to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface,

wherein first, second, third and fourth detection elements (D1-D4) of said eight detection elements are respectively arranged along said X-axis in such a manner that said first detection element (D1) is in a negative region of said X-axis in said outside area, said second detection element (D2) is in the negative region of said X-axis in said inside area, said third detection element (D3) is in a positive region of said X-axis in said inside area, and said fourth detection element (D4) is in the positive region of the X-axis in said outside area, and the respective second electrodes (41-44) of said first to fourth detection elements are fixed on said substrate,

wherein fifth, sixth, seventh and eighth detection elements (D5-D8) of said eight detection elements are respectively arranged along said Y-axis in such a manner that said fifth detection element (D5) is in a negative region of said Y-axis in said outside area, said sixth detection element (D6) is in the negative region of said Y-axis in said inside area, said seventh detection element (D7) is in a positive region of said Y-axis in said inside area, and said eighth detection element (D8) is in the positive region of said Y-axis in said outside area, and the respective second electrodes (45-48) of said fifth to eighth detection elements are fixed on said substrate,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

said force sensor further comprising a first detection terminal (Ax), a second detection terminal (Bx), a third detection terminal (Ay) and a fourth detection terminal (By),

wherein four electrodes (41, 32, 43, 34) among said first and second electrodes of said first to fourth detection elements, on which charges of a first polarity are produced when an X-axis component of force is applied to said working body, are connectable to said first detection terminal (Ax),

wherein four electrodes (31, 42, 33, 44) among said first and second electrodes of said first to fourth detection elements, on which charges of a second polarity are produced when an X-axis component of force is applied to said working body, are connectable to said second detection terminal (Bx),

wherein four electrodes (45, 36, 47, 38) among said first and second electrodes of said fifth to eighth detection elements, on which charges of the first polarity are produced when an Y-axis component of force is applied to said working body, are connectable to said third detection terminal (Ay),

wherein four electrodes (35, 46, 37, 48) among said first and second electrodes of said fifth to eighth detection elements, on which charges of the second polarity are produced when an Y-axis component of force is applied to said working body, are connectable to said fourth detection terminal (By),

to detect said X-axis component of force applied to said working body on the basis of a potential difference (Vx) across said first and second detection terminals, and to detect said Y-axis component of force applied to said working body on the basis of a potential difference (Vy) across said third and fourth detection terminals.

15. A force sensor comprising a substrate (10), a working body (51), a sensor casing (61) and eight detection elements (D1-D8), each of said detection elements comprising a piezoelectric element (21-24) in a plate form, a first electrode (31-38) formed on a first surface of said piezoelectric element, and a second electrode (41-48) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Y-axis is defined so that it is perpendicular to said X-axis at said origin and it extends in a direction parallel to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined in said substrate surface,

wherein first, second, third and fourth detection elements (D1-D4) of said eight detection elements are respectively arranged along said X-axis in such a manner that said first detection element (D1) is in a negative region of said X-axis in said outside area, said second detection element (D2) is in the negative region of said X-axis in said inside area, said third detection element (D3) is in a positive region of said X-axis in said inside area, and said fourth detection element (D4) is in the positive region of the X-axis in said outside area, and the respective second electrodes (41-44) of said first to fourth detection elements are fixed on said substrate,

wherein fifth, sixth, seventh and eighth detection elements (D5-D8) of said eight detection elements are respectively arranged along said Y-axis in such a manner that said fifth detection element (D5) is in a negative region of said Y-axis in said outside area, said sixth detection element (D6) is in the negative region of said Y-axis in said inside area, said seventh detection element (D7) is in a positive region of said Y-axis in said inside area, and said eighth detection element (D8) is in the positive region of said Y-axis in said outside area, and the respective second electrodes (45-48) of said fifth to eighth detection elements are fixed on said substrate,

wherein a portion in a vicinity of said origin of said substrate is fixed to said sensor casing (61),

wherein said working body (51) is fixed to said substrate so as to transmit a force applied to said working body to a peripheral portion of said substrate,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

said force sensor further comprising a first detection terminal (Ax), a second detection terminal (Bx), a third detection terminal (Ay) and a fourth detection terminal (By),

wherein four electrodes (41, 32, 43, 34) among said first and second electrodes of said first to fourth detection elements, on which charges of a first polarity are produced when an X-axis component of force is applied to said working body, are connectable to said first detection terminal (Ax),

wherein four electrodes (31, 42, 33, 44) among said first and second electrodes of said first to fourth detection elements, on which charges of a second polarity are produced when an X-axis component of force is applied to said working body, are connectable to said second detection terminal (Bx),

wherein four electrodes (45, 36, 47, 38) among said first and second electrodes of said fifth to eighth detection elements, on which charges of the first polarity are produced when an Y-axis component of force is applied to said working body, are connectable to said third detection terminal (Ay),

wherein four electrodes (35, 46, 37, 48) among said first and second electrodes of said fifth to eighth detection elements, on which charges of the second polarity are produced when an Y-axis component of force is applied to said working body, are connectable to said fourth detection terminal (By),

to detect said X-axis component of force applied to said working body on the basis of a potential difference (Vx) across said first and second detection terminals, and to detect said Y-axis component of force applied to said working body on the basis of a potential difference (Vy) across said third and fourth detection terminals.

16. A force sensor comprising a substrate (10), a working body (50), a sensor casing (60) and twelve detection elements (D1-D12), each of said detection elements comprising a piezoelectric element in a plate form, a first electrode formed on a first surface of said piezoelectric element, and a second electrode formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Y-axis is defined so that it is perpendicular to said X-axis at said origin and it extends in a direction parallel to said substrate surface, a Z-axis is defined so that it passes through said origin and extends in a direction perpendicular to said substrate surface, a W-axis is defined so that it intersects with said respective axes of X, Y and Z at said origin and extends in a direction parallel to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface,

wherein first, second, third and fourth detection elements (D1-D4) of said twelve sets of detection elements are respectively arranged along said X-axis in such a manner that said first detection element (D1) is in a negative region of said X-axis in said outside area, said second detection element (D2) is in the negative region of said X-axis in said inside area, said third detection element (D3) is in a positive region of said X-axis in said inside area, and said fourth detection element (D4) is in the positive region of said X-axis in said outside area, and the respective second electrodes of said first to fourth detection elements are fixed on said substrate,

wherein fifth, sixth, seventh and eighth detection elements (D5-D8) of said twelve detection elements are respectively arranged along said Y-axis in such a manner that said fifth detection element (D5) is in a negative region of said Y-axis in said outside area, said sixth detection element (D6) is in the negative region of said Y-axis in said inside area, said seventh detection element (D7) is in a positive region of said Y-axis in said inside area, and said eighth detection element (D8) is in the positive region of said Y-axis in said outside area, and the respective second electrodes of said fifth to eighth detection elements are fixed on said substrate,

wherein ninth, tenth, eleventh and twelfth detection elements (D9-D12) of said twelve detection elements are respectively arranged along said W-axis in such a manner that said ninth detection element (D9) is in a negative region of said W-axis in said outside area, said tenth detection element (D10) is in negative region of said W-axis in said inside area, said eleventh detection element (D11) is in a positive region of said W-axis in said inside area, and a twelfth detection element (D12) is in the positive region of said W-axis in said outside area, and the respective second electrodes of said ninth to twelfth detection elements are fixed on said substrate,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

said force sensor further comprising a first detection terminal (Ax), a second detection terminal (Bx), a third detection terminal (Ay) a fourth detection terminal (By), a fifth detection terminal (Az) and a sixth detection terminal (Bz),

wherein four electrodes (41, 32, 43, 34) among said first and second electrodes of said first to fourth detection elements, on which charges of a first polarity are produced when an X-axis component of force is applied to said working body, are connectable to said first detection terminal (Ax),

wherein four electrodes (31, 42, 33, 44) among said first and second electrodes of said first to fourth detection elements, on which charges of a second polarity are produced when an X-axis component of force is applied to said working body, are connectable to said second detection terminal (Bx),

wherein four electrodes (45, 36, 47, 38) among said first and second electrodes of said fifth to eighth detection elements, on which charges of the first polarity are produced when an Y-axis component of force is applied to said working body, are connectable to said third detection terminal (Ay),

wherein four electrodes (35, 46, 37, 48) among said first and second electrodes of said fifth to eighth detection elements, on which charges of the second polarity are produced when an Y-axis component of force is applied to said working body, are connectable to said fourth detection terminal (By),

wherein four electrodes among said first and second electrodes of said ninth to twelfth detection elements, on which charges of the first polarity are produced when an Z-axis component of force is applied to said working body, are connectable to said fifth detection terminal (Az),

wherein four electrodes among said first and second electrodes of said ninth to twelfth detection elements, on which charges of the second polarity are produced when an Z-axis component of force is applied to said working body, are connectable to said sixth detection terminal (Bz),

to detect said X-axis component of force applied to said working body on the basis of a potential difference across said first and second detection terminals, to detect said Y-axis component of force applied to said working body on the basis of a potential difference across said third and fourth detection terminals, and to detect said Z-axis component of force applied to said working body on the basis of a potential difference across said fifth and sixth detection terminals.

17. A force sensor comprising a substrate (10), a working body (51), a sensor casing (61) and twelve detection elements (D1-D12), each of said detection elements comprising a piezoelectric element in a plate form, a first electrode formed on a first surface of said piezoelectric element, and a second electrode formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10), an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, a Y-axis is defined so that it is perpendicular to said X-axis at said origin and it extends in a direction parallel to said substrate surface, a Z-axis is defined so that it passes through said origin and extends in a direction perpendicular to said substrate surface, a W-axis is defined so that it intersects with said respective axes of X, Y and Z at said origin and extends in a direction parallel to said substrate surface, and an inside area including said origin and an outside area surrounding said inside area are defined on said substrate surface,

wherein first, second, third and fourth detection elements (D1-D4) of said twelve sets of detection elements are respectively arranged along said X-axis in such a manner that said first detection element (D1) is in a negative region of said X-axis in said outside area, said second detection element (D2) is in the negative region of said X-axis in said inside area, said third detection element (D3) is in a positive region of said X-axis in said inside area, and said fourth detection element (D4) is in the positive region of said X-axis in said outside area, and the respective second electrodes of said first to fourth detection elements are fixed on said substrate,

wherein fifth, sixth, seventh and eighth detection elements (D5-D8) of said twelve detection elements are respectively arranged along said Y-axis in such a manner that said fifth detection element (D5) is in a negative region of said Y-axis in said outside area, said sixth detection element (D6) is in the negative region of said Y-axis in said inside area, said seventh detection element (D7) is in a positive region of said Y-axis in said inside area, and said eighth detection element (D8) is in the positive region of said Y-axis in said outside area, and the respective second electrodes of said fifth to eighth detection elements are fixed on said substrate,

wherein ninth, tenth, eleventh and twelfth-detection elements (D9-D12) of said twelve detection elements are respectively arranged along said W-axis in such a manner that said ninth detection element (D9) is in a negative region of said W-axis in said outside area, said tenth detection element (D10) is in negative region of said W-axis in said inside area, said eleventh detection element (D11) is in a positive region of said W-axis in said inside area, and a twelfth detection element (D12) is in the positive region of said W-axis in said outside area, and the respective second electrodes of said ninth to twelfth detection elements are fixed on said substrate,

wherein a portion in a vicinity of said origin of said substrate is fixed to said sensor casing (61),

wherein said working body (51) is fixed to said substrate so as to transmit a force applied to said working body to a peripheral portion of said substrate,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements, and

said force sensor further comprising a first detection terminal (Ax), a second detection terminal (Bx), a third detection terminal (Ay) a fourth detection terminal (By), a fifth detection terminal (Az) and a sixth detection terminal (Bz),

wherein four electrodes (41, 32, 43, 34) among said first and second electrodes of said first to fourth detection elements, on which charges of a first polarity are produced when an X-axis component of force is applied to said working body, are connectable to said first detection terminal (Ax),

wherein four electrodes (31, 42, 33, 44) among said first and second electrodes of said first to fourth detection elements, on which charges of a second polarity are produced when an X-axis component of force is applied to said working body, are connectable to said second detection terminal (Bx),

wherein four electrodes (45, 36, 47, 38) among said first and second electrodes of said fifth to eighth detection elements, on which charges of the first polarity are produced when an Y-axis component of force is applied to said working body, are connectable to said third detection terminal (Ay),

wherein four electrodes (35, 46, 37, 48) among said first and second electrodes of said fifth to eighth detection elements, on which charges of the second polarity are produced when an Y-axis component of force is applied to said working body, are connectable to said fourth detection terminal (By),

wherein four electrodes among said first and second electrodes of said ninth to twelfth detection elements, on which charges of the first polarity are produced when an Z-axis component of force is applied to said working body, are connectable to said fifth detection terminal (Az),

wherein four electrodes among said first and second electrodes of said ninth to twelfth detection elements, on which charges of the second polarity are produced when an Z-axis component of force is applied to said working body, are connectable to said sixth detection terminal (Bz),

to detect said X-axis component of force applied to said working body on the basis of a potential difference across said first and second detection terminals, to detect said Y-axis component of force applied to said working body on the basis of a potential difference across said third and fourth detection terminals, and to detect said Z-axis component of force applied to said working body on the basis of a potential difference across said fifth and sixth detection terminals.

18. A force sensor comprising a substrate (10), a working body (50), a sensor casing (60) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form and a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and said substrate including four second electrodes (41, 42, 43, 44) formed on a surface thereof,

wherein an origin (O) is defined at a point within said substrate (10) and an X-axis is defined so that it passes through said origin and extends in a direction parallel to the surface of said substrate, said four second electrodes being arranged along said X-axis in such a manner that two of said detection elements (D3, D4) are located on one side of said origin and two of said detection elements (D1, D2) are located on an opposite side of said origin, and each of said four detection elements being arranged on each of said four second electrodes (41, 42, 43, 44), respectively, in such a manner that a second surface of each detection element is fixed to each second electrode,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements,

said force sensor further comprising a first detection terminal (Ax) and a second detection terminal (Bx),

wherein four electrodes (41, 32, 43, 34), among said first and second electrodes, on which charges of a first polarity are produced when an X-axis component of force is applied to said working body, are connected to said first detection terminal (Ax), and

wherein four electrodes (31, 42, 33, 44), among said first and second electrodes, on which charges of a second polarity are produced when said X-axis component of force is applied to said working body, are connected to said second detection terminal (Bx),

thus to detect said X-axis component of force applied to said working body on the basis of a potential difference between said first detection terminal and said second detection terminal.

19. A force sensor comprising a substrate (10), a working body (51), a sensor casing (61) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form and a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and said substrate including four second electrodes (41, 42, 43, 44) formed on a surface thereof,

wherein an origin (O) is defined at a point within said substrate (10) and an X-axis is defined so that it passes through said origin and extends in a direction parallel to the surface of said substrate, said four second electrodes being arranged along said X-axis in such a manner that two of said detection elements (D3, D4) are located on one side of said origin and two of said detection elements (D1, D2) are located on an opposite side of said origin, and each of said four detection elements being arranged on each of said four second electrodes (41, 42, 43, 44), respectively, in such a manner that a second surface of each detection element is fixed to each second electrode,

wherein a portion in a vicinity of said origin of said substrate is fixed to said sensor casing (61),

wherein said working body (51) is fixed to said substrate so as to transmit a force applied to said working body to a peripheral portion of said substrate,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements,

said force sensor further comprising a first detection terminal (Ax) and a second detection terminal (Bx),

wherein four electrodes (41, 32, 43, 34), among said first and second electrodes, on which charges of a first polarity are produced when an X-axis component of force is applied to said working body, are connected to said first detection terminal (Ax), and

wherein four electrodes (31, 42, 33, 44), among said first and second electrodes, on which charges of a second polarity are produced when said X-axis component of force is applied to said working body, are connected to said second detection terminal (Bx),

thus to detect said X-axis component of force applied to said working body on the basis of a potential difference between said first detection terminal and said second detection terminal.

20. A force sensor comprising a substrate (10), a working body (50), a sensor casing (60) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form, a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and a second electrode (41, 42, 43, 44) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10) and an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, said four detection elements being arranged along said X-axis in such a manner that two of said detection elements (D3, D4) are located on one side of said origin and two of said detection elements (D1, D2) are located on an opposite side of said origin, and the respective second electrodes (41, 42, 43, 44) of said respective detection elements are fixed on said substrate,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements,

wherein potentials of said first electrodes (31, 32, 33, 34) with respect to said second electrodes (41, 42, 43, 44) fixed on said substrate in said respective detection elements are obtained, and

wherein an X-axis component of force applied to said working body is detected on the basis of a difference between a first sum (V1+V3) of potentials on two of said four detection elements having a first polarity and a second sum (V2+V4) of potentials on the other two of said four detection elements having a second polarity.

21. A force sensor comprising a substrate (10), a working body (51), a sensor casing (61) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form, a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and a second electrode (41, 42, 43, 44) formed on a second surface of said piezoelectric element,

wherein an origin (O) is defined at a point within said substrate (10) and an X-axis is defined so that it passes through said origin and extends in a direction parallel to a substrate surface of said substrate, said four detection elements being arranged along said X-axis in such a manner that two of said detection elements (D3, D4) are located on one side of said origin and two of said detection elements (D1, D2) are located on an opposite side of said origin, and the respective second electrodes (41, 42, 43, 44) of said respective detection elements are fixed on said substrate,

wherein a portion in a vicinity of said origin of said substrate is fixed to said sensor casing (61),

wherein said working body (51) is fixed to said substrate so as to transmit a force applied to said working body to a peripheral portion of said substrate,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements,

wherein potentials of said first electrodes (31, 32, 33, 34) with respect to said second electrodes (41, 42, 43, 44) fixed on said substrate in said respective detection elements are obtained, and

wherein an X-axis component of force applied to said working body is detected on the basis of a difference between a first sum (V1+V3) of potentials on two of said four detection elements having a first polarity and a second sum (V2+V4) of potentials on the other two of said four detection elements having a second polarity.

22. A force sensor comprising a substrate (10), a working body (50), a sensor casing (60) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form and a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and said substrate including four second electrodes (41, 42, 43, 44) formed on a surface thereof,

wherein an origin (O) is defined at a point within said substrate (10) and an X-axis is defined so that it passes through said origin and extends in a direction parallel to the surface of said substrate, said four second electrodes being arranged along said X-axis in such a manner that two of said detection elements (D3, D4) are located on one side of said origin and two of said detection elements (D1, D2) are located on an opposite side of said origin, and each of said four detection elements being arranged on each of said four second electrodes (41, 42, 43, 44), respectively, in such a manner that a second surface of each detection element is fixed to each second electrode,

wherein a peripheral portion of said substrate is fixed to said sensor casing (60),

wherein said working body (50) is fixed to said substrate so as to transmit a force applied to said working body to said origin,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements,

wherein potentials of said first electrodes (31, 32, 33, 34) with respect to said second electrodes (41, 42, 43, 44) fixed on said substrate in said respective detection elements are obtained, and

wherein an X-axis component of force applied to said working body is detected on the basis of a difference between a first sum (V1+V3) of potentials of two of said four detection elements having a first polarity and a second sum (V2+V4) of potentials of the other two of said four detection elements having a second polarity.

23. A force sensor comprising a substrate (10), a working body (51), a sensor casing (61) and four detection elements (D1, D2, D3, D4), each of said detection elements comprising a piezoelectric element (21, 23) in a plate form and a first electrode (31, 32, 33, 34) formed on a first surface of said piezoelectric element, and said substrate including four second electrodes (41, 42, 43, 44) formed on a surface thereof,

wherein an origin (O) is defined at a point within said substrate (10) and an X-axis is defined so that it passes through said origin and extends in a direction parallel to the surface of said substrate, said four second electrodes being arranged along said X-axis in such a manner that two of said detection elements (D3, D4) are located on one side of said origin and two of said detection elements (D1, D2) are located on an opposite side of said origin, and each of said four detection elements being arranged on each of said four second electrodes (41, 42, 43, 44), respectively in such a manner that a second surface of each detection element is fixed to each second electrode,

wherein a portion in a vicinity of said origin of said substrate is fixed to said sensor casing (61),

wherein said working body (51) is fixed to said substrate so as to transmit a force applied to said working body to a peripheral portion of said substrate,

wherein said substrate having enough flexibility to transmit a force applied to said working body to said detection elements,

wherein potentials of said first electrodes (31, 32, 33, 34) with respect to said second electrodes (41, 42, 43, 44) fixed on said substrate in said respective detection elements are obtained, and

wherein an X-axis component of force applied to said working body is detected on the basis of a difference between a first sum (V1+V3) of potentials of two of said four detection elements having a first polarity and a second sum (V2+V4) of potentials of the other two of said four detection elements having a second polarity.