Measuring and testing – Speed – velocity – or acceleration – Structural installation or mounting means
Reexamination Certificate
1997-12-17
2001-02-06
Kwok, Helen C. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Structural installation or mounting means
C073S504160, C310S326000
Reexamination Certificate
active
06182508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to an angular rate sensor which may be used in an attitude control system for automotive vehicles, and a shake compensating system for video cameras, or a gyroscope of a navigation system for moving objects.
2. Background of Related Art
Japanese Patent First Publication No. 61-294311 teaches a conventional angular rate sensor which includes a base for installation on a moving object undergoing the angular rate and an tuning fork oscillator secured on the base. The oscillator is made of a piezoelectric element and responsive to an excitation input signal to oscillate in a direction perpendicular to an axis of rotation of the moving object. The angular rate sensor monitors the direction and status of oscillation of the oscillator to determine the angular rate of the moving object.
In such an angular rate sensor, an oscillator is mounted on a base using a metallic attachment. A variety of attachments are proposed, but they do not satisfy all angular rate sensor specifications perfectly.
SUMMARY OF THE INVENTION
It is therefore a principal object of the present invention to avoid the disadvantages of the prior art.
It is another object of the present invention to provide an improved structure of an angular rate sensor capable of optimizing the performance of the sensor.
According to one aspect of the present invention, there is provided an angular rate sensor apparatus which experiences a rotation around a given axis to determine an angular rate of the rotation which comprises: (a) an oscillator made of a piezoelectric element which is excited to oscillate; (b) a base for installation of the angular rate sensor on a moving object, the base having a reference surface for installation of the oscillator; and (c) a fixing member fixing a node of the oscillator to the base, the fixing member having a base attachment portion which is welded to the reference surface of the base so as to orient the oscillation of the oscillator substantially perpendicular to the given axis of rotation.
In the preferred mode of the invention, the fixing member has formed thereon an oscillator attachment surface to which the node of the oscillator is bonded. The oscillator attachment surface is geometrically oriented to the base attachment portion so that the oscillator oscillates substantially parallel to the reference surface of the base.
The base attachment portion of the fixing member has a base attachment surface in direct engagement with the reference surface of the base. The base attachment surface of the base attachment portion is oriented at right angles to the oscillator attachment surface.
The fixing member has first and second surfaces opposed to each other in a direction of the oscillation of the oscillator. The fixing member is welded to the reference surface of the base at the first and second surfaces.
Each of the first and second surfaces has formed thereon a chamfered surface facing the reference surface of the base. The chamfered surface has an edge welded to the reference surface of the base in direct contact therewith.
A spacer is further interposed between the base attachment portion of the fixing member and the reference surface of the base. The spacer has a thickness required to keep an interval between the oscillator and the reference surface of the base at a given value.
One of the base and the fixing member has a thinner walled portion smaller in thickness than a major portion thereof. The fixing member is welded to the base at the thinner walled portion.
The fixing member may have formed therein a recess to define the inner walled portion.
The reference surface of the base may have formed therein protrusions which engage the base attachment portion of the fixture with a given gap and which establishes a preselected orientation of the reference surface of the base to the fixing member. The protrusions may have lengths extending substantially parallel to each other in the direction of the given axis of rotation of the angular rate sensor apparatus.
The base attachment portion may have formed thereon protrusions which engage the reference surface of the base with a given gap and which establishes a preselected orientation of the fixing member to the reference surface of the base. The protrusions have lengths extending substantially parallel to each other in the direction of the given axis of rotation of the angular rate sensor apparatus.
The base attachment portion may be bonded at a plurality of portions thereof to the reference surface of the base by laser welding.
The base attachment portion may alternatively be bonded at a plurality of portions thereof to the reference surface of the base by projection welding.
The base attachment portion of the fixing member may be greater in area than the oscillator attachment surface. The base attachment portion of the fixing member has a length greater than that of the oscillator attachment surface in a direction of oscillation of the oscillator.
The oscillator attachment surface of the fixing member has an area bonded to the node of the oscillator. The bonded area may occupy the oscillator attachment surface symmetrically with respect to the center thereof. It is advisable that the bonded area occupy 80% or more of the oscillator attachment surface.
According to a second aspect of the invention, there is provided an angular rate sensor apparatus which experiences a rotation around a given axis to determine an angular rate of the rotation which comprises: (a) an oscillator having a given length which oscillates, when excited, in a first direction perpendicular to a longitudinal center line thereof and which is responsive to the rotation around the given axis to vibrate in a second direction perpendicular to the first direction during the oscillation in the first direction and provides an output signal indicative of the vibration for determining the angular rate; (b) a base for installation of the angular rate sensor on a moving object, the base having a reference surface; and (c) a fixing member fixing the oscillator to the reference surface of the base so that the longitudinal center line of the oscillator lies parallel to the reference surface of the base. The base has an orientation portion used to orient the oscillator relative to the base when the fixing member fixes the oscillator to the reference surface of the base so that the longitudinal center line of the oscillator coincides substantially with the given axis of rotation.
In the preferred mode of the invention, the orientation portion includes a protrusion formed on the reference surface of the base which has a reference orientation line for orienting the oscillator relative to the base. The reference orientation line may be defined by an outer profile of the protrusion.
The orientation portion may include a recess formed in the reference surface of the base which has a reference orientation line for orienting the oscillator relative to the base. The reference orientation line is defined by a profile of the recess. The recess has an area greater than a profile of the oscillator. The oscillator is arranged on a plane flush with the reference surface of the base.
The orientation portion may alternatively include an opening formed in the reference surface of the base to secure the oscillator on an inner wall of the opening through the fixing member.
The oscillator has attached thereon excitation and excitation monitor electrodes. The oscillator is a tuning fork oscillator including a pair of arms extending parallel to the reference surface of the base.
According to a third aspect of the present invention, there is provided an angular rate sensor apparatus for determining an angular rate of a moving object which comprises: (a) a mounting member for mounting the angular rate sensor on the moving object; (b) a sensor unit including a base and an oscillator, the oscillator being mounted on the base and excited to oscillate so as to output a signal indicating an angular rate when subje
Akimoto Katuhide
Hayashi Satoshi
Kanda Tomoyuki
Moriwaki Junji
Oda Shinro
Denso Corporation
Kwok Helen C.
Pillsbury Madison & Sutro LLP
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