Force detector and acceleration detector and method of manufacturing the same

• US 5,811,693 A
• Filed: 03/18/1997
• Issued: 09/22/1998
• Est. Priority Date: 10/12/1990
• Status: Expired due to Term

• Current Assignee: Kazuhiro Okada
• Original Assignee: Kazuhiro Okada
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): Oen, William L.
• Application Number:
  US08/819,357
• Time in Patent Office: 553 Days
• Field of Search: 73/862.043, 73/514.32, 73/DIG. 4
• US Class Current: 73/862.043
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 5/165 using variations in capacitance
• CPC Class Codes: G01L 5/167 using piezoelectric means
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: G01P 15/105 by magnetically sensitive devices
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• 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
• CPC Class Codes: Y10S 73/04 Piezoelectric
• CPC Class Codes: Y10T 29/43 Electric condenser making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer
• CPC Class Codes: Y10T 29/49007 Indicating transducer

Abstract

An electrode layer is formed on the upper surface of a first substrate, and a processing for partially removing the substrate is carried out in order to allow the substrate to have flexibility. To the lower surface of the first substrate, a second substrate is connected. Then, by cutting the second substrate, a working body and a pedestal are formed. On the other hand, a groove is formed on a third substrate. An electrode layer is formed on the bottom surface of the groove. The third substrate is connected to the first substrate so that both the electrodes face to each other with a predetermined spacing therebetween. Finally, the first, second and third substrates are cut off every respective unit regions to form independent sensors, respectively. When an acceleration is exerted on the working body, the first substrate bends. As a result, the distance between both the electrodes changes. Thus, an acceleration exerted is detected by changes in an electrostatic capacitance between both the electrodes.

Claims

1. An acceleration sensor using a piezoelectric element comprising:

a sensor casing;

a fixed substrate fixed on the sensor casing;

a displacement substrate facing the fixed substrate;

a working body fixed to the displacement substrate, said working body transmitting a force produced on the basis of an acceleration applied thereto to the displacement substrate to cause a displacement;

a fixed electrode formed on a surface, which faces to said displacement substrate, of said fixed substrate;

a displacement electrode formed on a surface, which faces to said fixed substrate, of said displacement substrate; and

a piezo electric element formed in a manner that it is put between said fixed electrode and said displacement electrode to transform an applied pressure to an electric signal, said electric signal being outputted from said electrodes;

wherein any one or both of said fixed electrode and said displacement electrode are constituted by two localized electrodes to form two detection elements by using said two localized electrodes, respectively, a first localized electrode to form a first detection element being located in a positive area with respect to a first axis of coordinates, a second localized electrode to form a second detection element being located in a negative area with respect to said first axis, said first axis and a second axis being perpendicular to each other on a surface where said localized electrodes are formed;

an acceleration component in said first axis direction being detected by a difference between electric signal values outputted from said first and second detection elements;

an acceleration component in a third axis direction perpendicular to said first axis and said second axis being detected by a sum of electric signal values outputted from said first and second detection elements.

2. An acceleration sensor using a piezoelectric element comprising:

a sensor casing;

a fixed substrate fixed on the sensor casing;

a displacement substrate facing the fixed substrate;

a working body fixed to the displacement substrate, said working body transmitting a force produced on the basis of an acceleration applied thereto to the displacement substrate to cause a displacement;

a fixed electrode formed on a surface, which faces to said displacement substrate, of said fixed substrate;

a displacement electrode formed on a surface, which faces to said fixed substrate, of said displacement substrate; and

a piezo electric element formed in a manner that it is put between said fixed electrode and said displacement electrode to transform an applied pressure to an electric signal, said electric signal being outputted from said electrodes;

wherein any one or both of said fixed electrode and said displacement electrode are constituted by four localized electrodes to form four detection elements by using said four localized electrodes, respectively, a first localized electrode to form a first detection element being located in a positive area with respect to a first axis of coordinates, a second localized electrode to form a second detection element being located in a negative area with respect to said first axis, a third localized electrode to form a third detection element being located in a positive area with respect to a second axis of coordinates, a fourth localized electrode to form a fourth detection element being located in a negative area with respect to said second axis, said first axis and said second axis being perpendicular to each other on a surface where said localized electrodes are formed;

an acceleration component in said first axis direction being detected by a difference between electric signal values outputted from said first and second detection elements;

an acceleration component in said second axis direction being detected by a difference between electric signal values outputted from said third and fourth detection elements.

3. An acceleration sensor using a piezoelectric element as set forth in claim 2:

wherein an acceleration component in a third axis direction perpendicular to the first axis and the second axis is detected by a sum of electric signal values outputted from said first to fourth detection elements.

4. An acceleration sensor using a piezoelectric element comprising:

a sensor casing;

a fixed substrate fixed on the sensor casing;

a displacement substrate facing the fixed substrate;

a working body fixed to the displacement substrate, said working body transmitting a force produced on the basis of an acceleration applied thereto to the displacement substrate to cause a displacement;

a fixed electrode formed on a surface, which faces to said displacement substrate, of said fixed substrate;

a displacement electrode formed on a surface, which faces to said fixed substrate, of said displacement substrate; and

a piezo electric element formed in a manner that it is put between said fixed electrode and said displacement electrode to transform an applied pressure to an electric signal, said electric signal being outputted from said electrodes;

wherein any one or both of said fixed electrode and said displacement electrode are constituted by five localized electrodes to form five detection elements by using said five localized electrodes, respectively, a first localized electrode to form a first detection element being located in a positive area with respect to a first axis of coordinates, a second localized electrode to form a second detection element being located in a negative area with respect to said first axis, a third localized electrode to form a third detection element being located in a positive area with respect to a second axis of coordinates, a fourth localized electrode to form a fourth detection element being located in a negative area with respect to said second axis, said first axis and said second axis being perpendicular to each other on a surface where said localized electrodes are formed, a fifth localized electrode to form a fifth detection element being located on the surface containing said first axis and said second axis, said fifth localized electrode having a substantially symmetrical shape with respect to an intersecting point of said first axis and said second axis;

an acceleration component in said first axis direction being detected by a difference between electric signal values outputted from said first and second detection elements;

an acceleration component in said second axis direction being detected by a difference between electric signal values outputted from said third and fourth detection elements;

an acceleration component in a third axis direction perpendicular to said first axis and said second axis being detected by an electric signal value outputted from said fifth detection element.