Acceleration sensor, an acceleration detection apparatus, and a positioning device

• US 6,629,462 B2
• Filed: 07/20/2001
• Issued: 10/07/2003
• Est. Priority Date: 07/24/2000
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Koike, Takafumi, Taniguchi, Fumihiko, Otsuchi, Tetsuro
• Primary Examiner(s): Kwok, Helen
• Application Number:
  US09/908,635
• Publication Number:
  US 20020011111A1
• Time in Patent Office: 809 Days
• Field of Search: 735/143.4, 735/143.5, 735/143.6, 735/141.6, 735/041.2, 735/041.5, 310/329, 310/331, 310/332, 360/103, 360/106, 360/109, 360/104
• US Class Current: 73/514.34
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type

Abstract

An acceleration sensor housed in a confined space can detect rotational acceleration with great accuracy. The acceleration sensor has first and second piezoelectric elements with electrodes for outputting a charge produced by strain deformation. Each of the first and second piezoelectric elements has at least one piezoelectric body and a support block for supporting the piezoelectric body. The electrodes are provided on opposite sides of the piezoelectric body. One surface of the first piezoelectric element and one surface of the second piezoelectric element are substantially parallel to each other.

Claims

1. An acceleration sensor comprising:

first piezoelectric element having first electrodes for outputting a charge produced by strain deformation, said first piezoelectric element including at least one first piezoelectric body and a first support block supporting said first piezoelectric body, said first electrodes being provided on opposite surfaces of said first piezoelectric element; and

second piezoelectric element having second electrodes for outputting a charge produced by strain deformation, said second piezoelectric element including at least one second piezoelectric body and a second support block supporting said second piezoelectric body, said second electrodes being provided on opposite surfaces of said second piezoelectric element,

wherein one surface of said first piezoelectric element and one surface of said second piezoelectric element are substantially parallel to each other,

wherein said first support block is firmly held to provide a first cantilevered piezoelectric body,

wherein said second support block is firmly held to provide a second cantilevered piezoelectric body,

wherein the longitudinal axis of said first piezoelectric element is aligned with the longitudinal axis of said second piezoelectric element, and a free end portion of said first cantilevered piezoelectric body and a free portion of said second cantilevered piezoelectric body are pointing to each other.

2. An acceleration sensor comprising:

first piezoelectric element having first electrodes for outputting a charge produced by strain deformation, said first piezoelectric element including at least one first piezoelectric body and a first support block supporting said first piezoelectric body, said first electrodes being provided on opposite surfaces of said first piezoelectric element; and

second piezoelectric element having second electrodes for outputting a charge produced by strain deformation, said second piezoelectric element including at least one second piezoelectric body and a second support block supporting said second piezoelectric body, said second electrodes being provided on opposite surfaces of said second piezoelectric element,

wherein one surface of said first piezoelectric element and one surface of said second piezoelectric element are substantially parallel to each other, and

wherein said first support block is separated from said second support block.

3. An acceleration sensor as described in claim 2, wherein said first piezoelectric element includes one first piezoelectric body, and said second piezoelectric element includes one second piezoelectric body,

wherein a direction of polarization of said first piezoelectric body and a direction of polarization of said second piezoelectric body are opposite.

4. An acceleration sensor as described in claim 2, wherein said first piezoelectric element includes one first piezoelectric body, and said second piezoelectric element includes one second piezoelectric body,

wherein a direction of polarization of said first piezoelectric body and a direction of polarization of said second piezoelectric body are the same.

5. An acceleration sensor as described in claim 2, wherein said first piezoelectric element includes a first plurality of layered piezoelectric bodies, and said second piezoelectric element includes a second plurality of layered piezoelectric bodies.

6. An acceleration sensor as described in claim 5, wherein a direction of polarization of each of said first plurality of layered piezoelectric bodies is the same and a direction of polarization of each of said second plurality of piezoelectric bodies is the same.

7. An acceleration sensor as described in claim 6, wherein the direction of polarization of each of said first plurality of layered piezoelectric bodies and the direction of polarization of each of said second plurality of layered piezoelectric bodies are opposite.

8. An acceleration sensor as described in claim 6, wherein the direction of polarization of each of said first plurality of layered piezoelectric bodies and the direction of polarization of each of said second plurality of layered piezoelectric bodies are the same.

9. An acceleration sensor as described in claim 6, wherein said first piezoelectric element includes at least two first piezoelectric bodies, and said second piezoelectric element includes at least two second piezoelectric bodies,

wherein said at least two first piezoelectric bodies are bonded with surfaces of the same polarity of polarization and said at least two second piezoelectric bodies are bonded with surfaces of the same polarity of polarization, whereby a direction of polarization of one piezoelectric body and the direction of polarization of another piezoelectric body are opposite.

10. An acceleration sensor as described in claim 9, wherein the direction of polarization of said first plurality of layered piezoelectric bodies is opposite to the direction of polarization of said second plurality of layered piezoelectric bodies.

11. An acceleration sensor as described in claim 9, wherein the direction of polarization of said first plurality of layered piezoelectric bodies is the same as the direction of polarization of said second plurality of layered piezoelectric bodies.

12. An acceleration sensor as described in claim 5, wherein said first plurality of piezoelectric bodies comprises at least two first piezoelectric bodies bonded with a first intervening shim therebetween, and

wherein said second plurality of piezoelectric bodies comprises at least two second piezoelectric bodies bonded with a second intervening shim therebetween.

13. An acceleration sensor as described in claim 5, wherein said first plurality of piezoelectric bodies is formed by bonding plural first piezoelectric bodies by direct bonding, and

wherein said second plurality of piezoelectric bodies is formed by bonding plural second piezoelectric bodies by direct bonding.

14. An acceleration sensor as described in claim 13, wherein said first plurality of piezoelectric bodies is formed by bonding a plurality of first piezoelectric bodies by direct bonding by way of at least one of oxygen atoms and hydroxyl groups, and

wherein said second plurality of piezoelectric bodies is formed by bonding plural second piezoelectric bodies by direct bonding by way of at least one of oxygen atoms and hydroxyl groups.

15. An acceleration sensor as described in claim 2, further comprising an output terminal for each electrode of said first and said second piezoelectric elements.

16. An acceleration sensor as described in claim 2, further comprising:

at least one output terminal interconnecting a first electrode of said first piezoelectric element and a first electrode of said second piezoelectric element,

wherein a polarity of a charge generated on said first electrode of said first piezoelectric element and a polarity of a charge generated on said first electrode of said second piezoelectric element are different.

17. An acceleration sensor as described in claim 2, further comprising:

a first output terminal interconnecting a first electrode of said first piezoelectric element and a first electrode of said second piezoelectric element; and

a second output terminal from an electrode other than said first electrode of said first piezoelectric element or said first electrode of said second piezoelectric element,

wherein a polarity of a charge generated on said first electrode of said first piezoelectric element and a polarity of a charge generated on said first electrode of said second piezoelectric element are the same.

18. An acceleration sensor as described in claim 2, further comprising at least one output terminal set for outputting a charge generated at each electrode of said first and said second piezoelectric elements.

19. An acceleration sensor as described in claim 2, wherein said first piezoelectric element is substantially adjusted to the same sensitivity as said second piezoelectric element.

20. An acceleration sensor as described in claim 19, wherein said first piezoelectric element comprises a first cantilever portion, and

wherein a portion of the cantilever portion is removed.

21. An acceleration sensor as described in claim 19, wherein said first piezoelectric element comprises a first cantilever portion, and

wherein a sensitivity adjusting mass is affixed to the cantilever portion.

22. An acceleration sensor as described in claim 2, further comprising a package,

wherein said first piezoelectric element comprises a first cantilever portion, and

wherein said second piezoelectric element comprises a second cantilever portion, and

wherein said first piezoelectric element is fixed by said first support block portion inside said package and said second piezoelectric element is fixed by said second support block portion inside said package, whereby said first cantilever portion and said second cantilever portion can vibrate freely.

23. An acceleration sensor as described in claim 22, wherein said first piezoelectric element is mounted inside said package with said first cantilever portion inclined relative to the surface of said package, and said second piezoelectric element is mounted inside said package with said second cantilever portion inclined relative to the surface of said package.

24. An acceleration sensor as described in claim 23, wherein said first piezoelectric element is mounted to said package, and said second piezoelectric element is mounted to said package, whereby a first angle of inclination between said first cantilever portion and the surface is different than a second angle of inclination between said second cantilever portion and the surface.

25. An acceleration sensor comprising:

first piezoelectric element having first electrodes for outputting a charge produced by strain deformation, said first piezoelectric element including at least one first piezoelectric body and a first support block supporting said first piezoelectric body, said first electrodes being provided on opposite surfaces of said first piezoelectric element; and

second piezoelectric element having second electrodes for outputting a charge produced by strain deformation, said second piezoelectric element including at least one second piezoelectric body and a second support block supporting said second piezoelectric body, said second electrodes being provided on opposite surfaces of said second piezoelectric element,

third piezoelectric element having third electrodes for outputting a charge produced by strain deformation, said third piezoelectric element including at least one third piezoelectric body and a third support block supporting said third piezoelectric body, said third electrodes being provided on opposite surfaces of said third piezoelectric element; and

fourth piezoelectric element having fourth electrodes for outputting a charge produced by strain deformation, said fourth piezoelectric element including at least one fourth piezoelectric body and a fourth support block supporting said fourth piezoelectric body, said fourth electrodes being provided on opposite surfaces of said fourth piezoelectric element,

wherein one surface of said first piezoelectric element and one surface of said second piezoelectric element are substantially parallel to each other,

wherein first set of piezoelectric elements is mounted to the package, and second set of piezoelectric elements is mounted to the package with the cantilever portions thereof perpendicular to a package surface,

wherein one surface of said third piezoelectric element and one surface of said fourth piezoelectric element are substantially parallel to each other,

wherein third set of piezoelectric elements is mounted to the package, and fourth set of piezoelectric elements to the package with the cantilever portions thereof parallel to the package surface.

26. An acceleration detection apparatus comprising:

an acceleration sensor comprising an first piezoelectric element and a second piezoelectric element; and

a signal processing circuit for processing output signals from said first and second piezoelectric elements,

wherein said first piezoelectric element has first electrodes for outputting a charge produced by strain deformation, said first piezoelectric element including at least one first piezoelectric body and a first support block supporting said first piezoelectric body, said first electrodes being provided on opposite surfaces of said first piezoelectric element,

wherein said second piezoelectric element has second electrodes for outputting a charge produced by strain deformation, said second piezoelectric element including at least one second piezoelectric body and a second support block supporting said second piezoelectric body, said second electrodes being provided on opposite surfaces of said second piezoelectric element, and

wherein one surface of said first piezoelectric element and one surface of said second piezoelectric element are substantially parallel to each other.

27. An acceleration detection apparatus as described in claim 26, wherein said first and second piezoelectric elements are connected to said signal processing circuit to output same-polarity output signals for acceleration in the same direction, and

wherein said signal processing circuit is operable to determine the difference between the output signals.

28. An acceleration detection apparatus as described in claim 26, wherein said first and second piezoelectric elements are connected to said signal processing circuit to output opposite-polarity output signals for acceleration in the same direction, and

wherein said signal processing circuit is operable to determine the sum of the output signals.

29. An acceleration detection apparatus as described in claim 26, wherein said signal processing circuit includes a circuit operable to detect angular acceleration from the difference of an output from said first piezoelectric element and an output from said second piezoelectric element.

30. An acceleration detection apparatus as described in claim 26, wherein said signal processing circuit is operable to adjust an output thereof so that a sensitivity of said first piezoelectric element and a sensitivity of said second piezoelectric element are substantially equal.

31. An acceleration detection apparatus as described in claim 26, wherein said signal processing circuit comprises:

one impedance converting circuit operable to convert an output signal impedance from said first piezoelectric element and said second piezoelectric element; and

an amplifier circuit operable to amplify the converted output signals.

32. An acceleration detection apparatus as described in claim 26, wherein said signal processing circuit comprises:

two impedance converting circuits for converting output signal impedance from said first and second piezoelectric elements; and

an adding circuit for adding signals from said two impedance converting circuits.

33. An acceleration detection apparatus as described in claim 26, wherein said signal processing circuit comprises:

two impedance converting circuits for converting output signal impedance from said first and second piezoelectric elements; and

a differential amplifier circuit for detecting and amplifying a difference between signals from said two impedance converting circuits.

34. An acceleration detection apparatus as described in claim 26, further comprising a plurality of output terminals operable to simultaneously externally output impedance-converted piezoelectric element output signals and amplified output of converted output after impedance conversion.

35. An acceleration detection apparatus as described in claim 26, further comprising a package,

wherein said first piezoelectric elements comprises a first cantilever portion, and

wherein said second piezoelectric element comprises a second cantilever portion, and

wherein said first piezoelectric element is fixed, at said first support block, in said package, and said second piezoelectric element is fixed, at said second support block, in said package, whereby said first and second cantilever portions can vibrate freely, and

wherein said signal processing circuit is housed inside said package.

36. A positioning apparatus comprising:

an acceleration detection apparatus comprising an acceleration sensor, including a first piezoelectric element and a second piezoelectric element, and a signal processing circuit for processing output signals from said first and second piezoelectric elements;

an object mover operable to move an object; and

a controller operable to control said object mover to move and position the object based on an output signal from said acceleration detection apparatus corresponding to detected acceleration,

wherein said first piezoelectric element has first electrodes for outputting a charge produced by strain deformation, said first piezoelectric element including at least one first piezoelectric body and a first support block supporting said first piezoelectric body, said first electrodes being provided on opposite surfaces of said first piezoelectric element,

wherein said second piezoelectric element has second electrodes for outputting a charge produced by strain deformation, said second piezoelectric element including at least one second piezoelectric body and a second support block supporting said second piezoelectric body, said second electrodes being provided on opposite surfaces of said second piezoelectric element, and

wherein one surface of said first piezoelectric element and one surface of said second piezoelectric element are substantially parallel to each other.

37. A position apparatus as described in claim 36,

wherein said first piezoelectric element comprises a first cantilever portion, and

wherein said second piezoelectric element comprises a second cantilever portion, and

wherein said cantilever portions of said first and second piezoelectric elements of said acceleration detection apparatus are provided substantially parallel to an object supporter operable to support the object.

38. A disk recording and reading apparatus comprising:

an acceleration detection apparatus comprising an acceleration sensor, including a first piezoelectric element and a second piezoelectric element, and a signal processing circuit for processing output signals from said first and second piezoelectric elements;

a head mover operable to move a head for recording to and reading from a disk; and

a controller operable to control said head mover,

wherein said first piezoelectric element has first electrodes for outputting a charge produced by strain deformation, said first piezoelectric element including at least one first piezoelectric body and a first support block supporting said first piezoelectric body, said first electrodes being provided on opposite surfaces of said first piezoelectric element,

wherein said second piezoelectric element has second electrodes for outputting a charge produced by strain deformation, said second piezoelectric element including at least one second piezoelectric body and a second support block supporting said second piezoelectric body, said second electrodes being provided on opposite surfaces of said second piezoelectric element,

wherein one surface of said first piezoelectric element and one surface of said second piezoelectric element are substantially parallel to each other, and

wherein said controller is operable to calculate movement of said head based on an output signal from said acceleration detection apparatus corresponding to detected acceleration, and to move and position said head via said head mover.

39. A disk recording and reading apparatus as described in claim 38,

wherein said first piezoelectric element comprises a first cantilever portion, and

wherein said second piezoelectric element comprises a second cantilever portion, and

wherein said cantilever portion of said first and second piezoelectric elements of said acceleration detection apparatus are provided substantially parallel to an arm supporting said head.