Angular rate sensor and method of improving output characteristic thereof

• US 6,415,643 B2
• Filed: 03/23/2001
• Issued: 07/09/2002
• Est. Priority Date: 03/24/1997
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Watarai, Takehiro
• Primary Examiner(s): Muller, Richard A.
• Application Number:
  US09/814,952
• Publication Number:
  US 20010010169A1
• Time in Patent Office: 473 Days
• Field of Search: 73/18.2, 735/040.2, 735/041.2, 735/041.4, 735/041.5, 735/041.6, 310/311, 310/312, 310/368, 310/370
• US Class Current: 73/1.82
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

A method of improving an output characteristic of an angular rate sensor including, for example, a fork oscillator and an improved structure of an angular rate sensor are provided. The improvement of the output characteristic is achieved by adjusting a physical structure of the oscillator to minimize unwanted vibrations of the oscillator or noises of a sensor output. The adjustment of the physical structure is achieved by trimming away an edge portion of the oscillator or a supporter for supporting the oscillator on a base.

Claims

1. A method of adjusting an oscillation characteristic of an oscillator of an angular rate sensor, the oscillator having a given length and being shaped to have a plurality of longitudinal edges, the oscillator being excited by input of an excitation signal to oscillate in a first direction perpendicular to the length of the oscillator and, when the angular rate sensor undergoes an angular rate during excitation of the oscillator, oscillating in a second direction perpendicular to the length of the oscillator to provide an output indicative of the angular rate, comprising the steps of:

applying to the oscillator an ac voltage having a resonant frequency, at which the oscillator resonates in the first direction, to oscillate the oscillator;

monitoring an output signal of the oscillator during oscillation of the oscillator by application of the ac voltage; and

adjusting the oscillation characteristic of the oscillator so as to decrease an amplitude of the monitored output signal of the oscillator to minimize undesired oscillations of the oscillator in the second direction when excited by the input of the excitation signal.

2. A method as set forth in claim 1, wherein said adjusting step removes a portion of the oscillator to adjust the oscillation characteristic of the oscillator.

3. A method as set forth in claim 2, wherein the removed portion of the oscillator is one of the longitudinal edges of the oscillator.

4. A method as set forth in claim 1, wherein the oscillator is a fork oscillator including a pair of arms and a connecting portion connecting ends of the arms, and wherein said adjusting step removes a portion of at least one of longitudinal edges of the arms to adjust the oscillation characteristic of the oscillator.

5. A method as set forth in claim 1, wherein the oscillator is a fork oscillator including a pair of arms and a connecting portion connecting ends of the arms, and wherein said adjusting step removes at least one of an longitudinal edge portion of one of the arms leading to the connecting portion, an edge portion of the connecting portion extending in a lengthwise direction of the arms, and a portion of the longitudinal edges of the oscillator extending over a connection between one of the arms and the connecting portion.

6. A method as set forth in claim 1, wherein said oscillator includes a single oscillating portion made of a polygonal rod member whose end is fixed on the angular rate sensor, and wherein said adjusting step removes a portion of the oscillating portion leading to the fixed end to adjust the oscillation characteristic of the oscillator.

7. A method as set forth in claim 1, wherein said oscillator includes a single oscillating portion made of a polygonal rod member, the oscillating portion having formed at an end thereof a node portion supported on the angular rate sensor, and wherein said adjusting step removes a central portion of a longitudinal edge of the oscillating portion to adjust the oscillation characteristic of the oscillator.

8. A method as set forth in claim 1, wherein said adjusting step machines a portion of the oscillator in a lengthwise direction to adjust the oscillation characteristic of the oscillator.

9. A method as set forth in claim 1, wherein said adjusting step machines a portion of the oscillator in a depthwise direction to adjust the oscillation characteristic of the oscillator.

10. A method as set forth in claim 1, wherein said oscillator is made of a piezoelectric element.

11. A method of adjusting an output characteristic of an angular rate sensor which includes a first oscillator having a given length, shaped to have a plurality of longitudinal edges, excitation means responsive to input of an excitation signal for exciting the first oscillator to oscillate in an excitation-axis direction perpendicular to a longitudinal center line of the first oscillator, and a second oscillator having a given length, shaped to have a plurality of longitudinal edges having pickup means for picking up oscillations of the second oscillator in a pickup-axis direction perpendicular to a longitudinal center line of the second oscillator, comprising the steps of:

applying an ac voltage having a resonant frequency, at which the first oscillator resonates in the excitation-axis direction, to the excitation means to oscillate the oscillating portion of the first oscillator;

monitoring an output of the pickup means during oscillation of the first oscillator by application of the ac voltage; and

adjusting oscillation characteristics of the first and second oscillators so as to decrease an amplitude of the monitored output of the pickup means to minimize undesired oscillations of the second oscillator in the pickup-axis direction produced during oscillation of the first oscillator by the excitation means.

12. A method as set forth in claim 11, wherein said adjusting step removes portions of the first and second oscillators to adjust the oscillation characteristics of the first and second oscillators.

13. A method as set forth in claim 12, wherein each of the removed portions of the first and second oscillators is one of the longitudinal edges of corresponding one of the first and second oscillators.

14. A method as set forth in claim 11, wherein each of the first and second oscillator is a fork oscillator including a pair of arms and a connecting portion connecting ends of the arms, and wherein said adjusting step removes a portion of at least one of longitudinal edges of the arms of each of the first and second oscillators to adjust the oscillation characteristic of the oscillator.

15. A method as set forth in claim 11, wherein each of the first and second oscillators is a fork oscillator including a pair of arms and a connecting portion connecting ends of the arms, and wherein said adjusting step removes at least one of an longitudinal edge portion of one of the arms leading to the connecting portion of each of the first and second oscillators, an edge portion of the connecting portion extending in a lengthwise direction of the arms of each of the first and second oscillators, and a portion of the longitudinal edges extending over a connection between one of the arms and the connecting portion of each of the first and second oscillators.