Tuning-fork type vibration gyro and electrode trimming method therefor

Abstract

A tuning-fork type vibration gyro enables to suppress pyroelectric noise caused by temperature change and to obtain sensor output having high signal-to-noise ratio. The tuning-fork type vibration gyro includes a tuning-fork type vibration body having two arms mutually disposed in parallel and a base for commonly supporting one end of the each arm, wherein a longitudinal direction of the two arms is defined as a z-axis and a perpendicular direction thereto is defined as an x-axis; driving electrodes respectively formed on the two arms for generating vibration of the two arms in a direction parallel to the x-axis; detecting electrodes respectively formed on the two arms for detecting electromotive force generated when the tuning-fork type vibration body is rotated around the z-axis; and dummy electrodes formed on the two arms in respective areas different from the driving electrodes and the detecting electrodes.

1 . A tuning-fork type vibration gyro comprising: 
 a tuning-fork type vibration body having two arms mutually disposed in parallel and a base for commonly supporting one end of said each arm, wherein a longitudinal direction of said two arms is defined as a z-axis and a perpendicular direction thereto is defined as an x-axis;    driving electrodes respectively formed on said two arms for generating vibration of said two arms in a direction parallel to said x-axis;    detecting electrodes respectively formed-on said two arms for detecting electromotive force generated when said tuning-fork type vibration body is rotated around said z-axis; and    dummy electrodes formed on said two arms in respective areas different from said driving electrodes and said detecting electrodes.    
   
   
       2 . A tuning-fork type vibration gyro comprising: 
 a tuning-fork type vibration body having three or more arms mutually disposed in parallel and a base for commonly supporting one end of said each arm, wherein a longitudinal direction of said three or more arms is defined as a z-axis and a perpendicular direction thereto is defined as an x-axis;    driving electrodes formed on at least two arms of said three or more arms for generating vibration of said two arms in a direction parallel to said x-axis;    detecting electrodes formed on at least one arm of said three or more arms for detecting electromotive force generated when said tuning-fork type vibration body is rotated around said z-axis; and    dummy electrodes formed on said three or more arms in respective areas different from said driving electrodes and said detecting electrodes.    
   
   
       3 . The tuning-fork type vibration gyro according to  claim 1  or  claim 2  wherein said tuning fork type vibration body is formed of ferroelectric body.  
   
   
       4 . The tuning-fork type vibration gyro according to  claim 1 , wherein said dummy electrodes are formed on four side faces of said each arm, being connected so that each dummy electrode has an identical potential.  
   
   
       5 . The tuning-fork type vibration gyro according to  claim 2 , wherein said dummy electrodes are formed on four side faces of said each arm, being connected so that each dummy electrode has an identical potential.  
   
   
       6 . The tuning-fork type vibration gyro according to  claim 1 , wherein said dummy electrodes are electrically connected to said detecting electrodes.  
   
   
       7 . The tuning-fork type vibration gyro according to  claim 2 , wherein said dummy electrodes are electrically connected to said detecting electrodes.  
   
   
       8 . The tuning-fork type vibration gyro according to  claim 1 , wherein said driving electrodes and detecting electrodes are disposed in deviating positions in said z-axis direction.  
   
   
       9 . The tuning-fork type vibration gyro according to  claim 2 , wherein said driving electrodes and detecting electrodes are disposed in deviating positions in said z-axis direction.  
   
   
       10 . A tuning-fork type vibration gyro having a sensor circuit to which a sensor signal generated by a tuning-fork type vibration body is input, said sensor circuit comprising: 
 a differential amplifier to which said sensor signal is input; and    a capacitor or a voltage limiting element being connected to input terminals of said differential amplifier.    
   
   
       11 . The tuning-fork type vibration gyro according to  claim 10  wherein said voltage limiting element is a Zener diode, and said Zener diode, said capacitor and said differential amplifier are integrated into one piece.  
   
   
       12 . A tuning-fork type vibration gyro having a sensor circuit to which a sensor signal generated by a tuning-fork type vibration body is input, 
 wherein said sensor circuit comprises:    a differential amplifier to which said sensor signal is input; and    an inductor being connected to input terminals of said differential amplifier.    
   
   
       13 . The tuning-fork type vibration gyro according to  claim 10 , wherein said differential amplifier comprises: 
 a first stage transistor being differentially connected; and    a guard electrode for separating said first stage transistor from transistors in succeeding stages.    
   
   
       14 . The tuning-fork type vibration gyro according to  claim 12 , wherein said differential amplifier comprises: 
 a first stage transistor being differentially connected; and    a guard electrode for separating said first stage transistor from transistors in succeeding stages.    
   
   
       15 . A tuning-fork type vibration gyro comprising: 
 a tuning-fork type vibration body having two arms disposed in parallel and a base for commonly supporting one end of said each arm, wherein a longitudinal direction of said two arms is defined as a z-axis and a perpendicular direction thereto is defined as an x-axis; and    a sensor circuit to which a sensor signal generated by said tuning-fork type vibration body is input, wherein said tuning-fork type vibration body further comprises:    driving electrodes respectively formed on said two arms for generating vibration of said two arms in a direction parallel to said x-axis;    detecting electrodes respectively formed on said two arms for detecting electromotive force generated when said tuning-fork type vibration body rotates around said z-axis; and    dummy electrodes formed on said two arms in respective areas different from said driving electrodes and said detecting electrodes, and,    said sensor circuit comprises:    a differential amplifier to which said sensor signal is input; and    a capacitor or a voltage limiting element being connected to input terminals of said differential amplifier.    
   
   
       16 . An electrode trimming method for a tuning-fork type vibration gyro having two or more arms and a base for supporting said arms, driving electrodes and/or detecting electrodes respectively formed on said arms, and a support substrate for supporting said tuning-fork type vibration body on said base, said electrode trimming method comprising the steps of: 
 when defining a parallelly disposed direction of said arms as an x-axis, suppressing vibration of said support substrate while vibration of said arms in a direction parallel to said x-axis is excited by a predetermined drive power applied to said driving electrodes; and    adjusting areas of said detecting electrodes so that a sensor signal output from said detecting electrodes is decreased.    
   
   
       17 . The electrode trimming method for the tuning-fork type vibration gyro according to  claim 16 , 
 wherein said vibration of the support substrate is suppressed by a pressing jig formed of a rubbery elastic body.