Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
1999-02-25
2001-06-05
Chapman, John E. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
C073S504140
Reexamination Certificate
active
06240780
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an angular velocity sensor to be suitably used to detect the angular velocity acting on, for example, a moving body, a rotating body, etc.
2. Description of the Related Art
The angular velocity sensor described in Japanese Unexamined Patent Publication No. 5-312576 is generally known as an angular velocity sensor of conventional technology.
The angular velocity sensor described in Japanese Unexamined Patent Publication No. 5-312576 is in substance composed of a board, a first vibrator supported on the board through a first supporting beam and arranged so as to be vibrated in the direction of a first axis, a second vibrator supported on the first vibrator through a second supporting beam and arranged so as to be vibrated in the direction of the first axis and in the direction of a second axis at a right angle to the direction of the first axis, a vibration generating means to make the first vibrator vibrate in the direction of the first axis, and a displacement detecting means to detect a displacement of the second vibrator in the direction of the second axis when an angular velocity has been applied around a third axis at right angles with the first and second axes and when the first vibrator vibrates in the direction of the first axis.
Further, the first supporting beam, first vibrator, and second vibrator constitute a vibration system to vibrate in the direction of the first axis, and this vibration system has a vibrating side resonance frequency. More, the second supporting beam, and second vibrator constitute a detection system to vibrate in the direction of the second axis, and this detection system has a detecting side resonance frequency.
In this angular velocity sensor, when the vibration generating means makes the first vibrator vibrate in the direction of a first axis horizontal to the board, the second vibrator supported on the first vibrator through the second supporting beam vibrates in the direction of the same axis at a frequency substantially equal to the resonance frequency of the second vibrator. When the second vibrator vibrates and when the whole of the sensor rotates around a rotational axis (the third axis) vertical to the board, the second vibrator is made to vibrate in the direction (the direction of the second axis)at a right angle to the vibrating direction of the first vibrator because of Coriolis force in proportion to the rotational force. And the displacement detecting means is able to detect the angular velocity applied to the whole of the sensor by detecting a displacement at the time when the second vibrator is vibrated.
In the above angular velocity sensor of conventional technology, the vibrating side resonance frequency of the vibration system is designed to be approximated to the detecting side resonance frequency of the detection system in order to heighten accuracy of the detection.
In general, the resonance frequency f of a spring vibration is defined in the following formula 1.
f
=
1
2
π
k
m
k
:
spring constant of supporting beam
m
:
weight of vibrator
Formula
1
Also, as shown in formula 1, the resonance frequency of each system is established by the width and length of the beam (spring constant) and the weight of the vibrator. However, as the angular velocity sensor of conventional technology is produced by using processes for silicon semiconductors, fluctuation of processed dimensions occurs and it is difficult to form vibrators, supporting beams, etc. precisely. Because of this, there is a problem that each vibrator cannot be vibrated at the same resonance frequency and the detection sensitivity of angular velocity cannot be increased.
In other conventional technology, e.g., in Japanese Unexamined Utility Model Publication No. 7-32514, Japanese Unexamined Patent Publication No. 7-43166, Japanese Unexamined Patent Publication No. 7-190784, and others, there is a method such in which the spring constant is seemingly changed and the resonance frequency of the vibrators is adjusted by adjustment of a tension applied :o the supporting beam. On the other hand, as in Japanese Unexamined Patent Publication No. 8-114460, and others, there is also a method in which the resonance frequency is adjusted by adding a weight to the vibrators and trimming the weight by a laser beam, a concentrated ion beam, etc.
However, the above-mentioned methods for adjustment of the resonance frequency are used where a vibrator is supported by a supporting beam and not to an angular velocity sensor having the construction of supporting a second vibrator on a first vibrator through a second beam. And the methods are not very effective to approximate resonance frequencies to each other by adjustment of the vibrating side resonance frequency of a vibration system or the detecting side resonance frequency of a detection system.
SUMMARY OF THE INVENTION
The present invention has been made considering the above problems of conventional technology, and the object of the present invention is to provide an angular velocity sensor in which, when an angular velocity is applied around a third axis, the vibrating amplitude of a second vibrator is increased and the detection sensitivity of the angular velocity is heightened by approximating the vibrating side resonance frequency of a vibration system vibrating in the direction of a first axis to the detecting side resonance frequency of a detection system vibrating in the direction of the second axis.
In order to solve the above-mentioned problems, an angular velocity sensor according to the present invention comprises a board, a first vibrator, a second vibrator, a vibration generating means, a displacement detecting means and a frequency adjustment means. The first vibrator is supported on the board through first supporting beams and arranged so as to be vibrated in the direction of a first axis. The second vibrator is supported on the first vibrator through second supporting beams and arranged so as to be vibrated in the direction of the first axis and in the direction of a second axis at a right angle to the direction of the first axis. The vibration generating means makes the first vibrator vibrate in the direction of the first axis. The displacement detecting means detects a displacement of the second vibrator in the direction to the second axis when an angular velocity has been applied around a third axis at right angles with the first and second axes in the state that the vibration generating means causes the first vibrator to vibrate in the direction of the first axis. The frequency adjustment means adjusts the vibrating side resonance frequency at the time when the first vibrator is vibrated in the direction of the first axis by the vibration generating means and the detecting side resonance frequency at the time when the second vibrator is vibrated in the direction of the second axis by an angular velocity applied around the third axis.
When thus constructed, the vibrating side resonance frequency can be approximated to the detecting side resonance frequency by the frequency adjustment means, and when an angular velocity is applied around the third axis, the second vibrator can be vibrated so as to give a high amplitude due to Coriolis force.
The frequency adjustment means may be made a vibration adding means to add a force in the direction of the first axis to the first vibrator in the state that the vibration generating means vibrates the first vibrator in the direction of the first axis. When thus constructed, the vibration adding means vibrates the first vibrator with a high amplitude in the direction of the first axis and the spring constant of the first beam is seemingly made small. As a result, the vibrating side resonance frequency can be decreased.
When an angular velocity is added around the third axis to make the second vibrator vibrate in the direction of the second axis, the frequency adjustment means may be made
Kobayashi Shinji
Konaka Yoshihiro
Moriya Kazufumi
Negoro Yosuhiro
Chapman John E.
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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