Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Patent
1991-08-27
1993-10-12
Chapman, John E.
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
G01P 904
Patent
active
052514838
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a sensor element intended for a gyro.
BACKGROUND OF THE INVENTION
It is previously known in this art to utilize rotating masses as sensor elements for gyros. However, such gyros are technically complex and, in recent years, various types of gyros based on torsion and vibration have, therefore, been designed.
Torsion-sensing gyros normally utilize vibrating tines connected to a transitional portion which, in turn, is secured to its ambient surroundings. The transitional portion plays an active part in the torsion oscillation generated by Coriolis forces. An example of such a torsion-sensing gyro is described in U.S. Pat. No. 4,524,619.
Vibration-sensing gyros are based either on a vibrating cylinder structure or on vibrating elongate bodies. For these types of gyros, the transitional portion primarily has a vibration-insulting effect.
There is a need in this art for gyros with sensor elements which display high g-force resistance. It is of the utmost importance that the various parts of the gyro withstand severe environmental stresses, in particular high acceleration stresses when the gyro is used in, for instance, ammunition units (missiles, projectiles, grenades etc.) with high muzzle velocities. The gyro must allow for a robust construction in which the gyro and its sensor elements may be of lightweight design in relation to the weakest point of each respective structure. It is essential, in respect of ammunition units, that the gyro may be capable of emitting an output signal even under the applied acceleration loads. There are also often demands on small external volumes.
SUMMARY OF THE INVENTION
The main object of the present invention is to propose a sensor element for gyros which affords a solution to the above outlined problems.
The novel sensor element is preferably designed as a tuning fork of quartz crystal. The base of the tuning fork is fixedly secured, while the tines of the tuning fork are allowed to vibrate freely. Drive electrodes are deposited on the crystal, these causing the tines of the crystal to vibrate in desired directions, with the aid of the piezoelectric effect. From the base of the crystal, it is possible to connect conductors (for example with the aid of wire bonding or TAB) and, by such means, establish contact with the surrounding electronics.
The sensor element is of a design which makes for production using conventional technology in quartz oscillator manufacture. The resonance frequencies of the tines of the sensor element may be adjusted by coating different parts of the tines with a mass, for example gold. Alternatively, the removal of mass may be employed, in which event such removal is best carried out with the aid of a laser. Mounting of the crystal in its associated capsule may be effected pursuant to prior art technology, using, for instance, glue.
Preferably, the electronics associated with the above-disclosed sensor element are placed as close to the sensor element as possible, since a quartz crystal is extremely sensitive to capacitive disturbances. Consequently, hybrid electronics are to be preferred, which makes it possible to keep the volume of the gyro to a minimum. The size of the sensor element need not be greater than that of a standard conventional watch crystal. The major portion of the volume will be taken up by the electronics, even though this is of hybrid design.
In addition to solving the above-outlined problems, the novel sensor element for gyros according to the present invention may be manufactured in economically favorable manufacturing processes. The gyro as such will be operationally highly reliable and robust, in that it will withstand such factors as high acceleration forces.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
One currently proposed embodiment of a sensor element displaying the characteristics significative of the present invention will be described in greater detail below with reference to the accompanying Drawings.
In the accompanying Drawings:
FIG. 1 is a horiz
REFERENCES:
patent: Re33479 (1990-12-01), Juptner et al.
patent: 4628734 (1986-12-01), Watson
patent: 4671112 (1987-06-01), Kimura et al.
patent: 4674331 (1987-06-01), Watson
Chapman John E.
Swedish Ordnance-FFV/Bofors AB
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