Angular velocity sensor element, angular velocity sensor and angular velocity sensor unit both using angular velocity sensor element, and signal detecting method for angular velocity sensor unit

Abstract

TheAn angular velocity sensor of the present invention has one end connected to a holding section and the other another end connected to a weighting section. According to the angular velocity sensor, a driving arm has a dog-leg bent structure of arms extending in a direction perpendicular to a connecting direction of the holding section and the weighting section.

The invention claimed is: 
     
       1. An angular velocity sensor element comprising:
 a driving arm having a first end and a second end opposite to the first end; 
 a holding section connected to the first end of the driving arm; 
 a weighting section connected to the second end of the driving arm; 
 a driving electrode that is disposed on the driving arm and configured to vibrate the weighting section; and 
 a detecting electrode that is disposed on the driving arm and is configured to detect angular velocity of the driving arm, 
 wherein, the driving arm is disposed between the holding section and the weighting section, 
 a length of the driving arm in a first direction from the first end to the second end is shorter than a length of the driving arm in a second direction substantially perpendicular to the first direction, and 
 the driving arm comprises a first driving arm and a second driving arm, 
 the driving arm has a continuous space defined between the first driving arm and the second driving arm, 
 each of the first driving arm and the second driving arm is substantially surrounded on at least three sides by the holding section and the weighting section, 
 each of the first driving arm and the second driving arm comprises a first arm member, a second arm member and a third arm member, 
 the first arm member and the second arm member extend in the first direction, 
 the third arm member extends in the second direction perpendicular to the first direction, and 
 the weighting section is connected to the first driving arm and the second driving arm. 
 
     
     
       2. The angular velocity sensor element of  claim 1 , wherein
 the driving arm has arm members extending in the second direction, and 
 the detecting electrode is disposed on one arm member of the arm members so as to be offset from a central axis of the one arm member in an extending direction. 
 
     
     
       3. The angular velocity sensor element of  claim 2 , wherein the detecting electrode has a symmetrical shape in the extending direction of the arm members with respect to a changing point of deflection of the arm members. 
     
     
       4. The angular velocity sensor element of  claim 1 , wherein
 the driving arm is composed of comprises a first third driving arm and a second fourth driving arm, 
 the first driving arm has first and second arm members extending in the second direction, 
 the holding section is disposed between the first driving arm and the second third driving arm, and, 
 the driving electrode is disposed on the first arm member and the detecting electrode is disposed on the second arm member, and the driving electrode is disposed so as to be offset from a central axis of the first arm member in an extending direction. 
 
     
     
       5. The angular velocity sensor element of  claim 4 , wherein the driving electrode is divided into two sections and the first arm member is divided into four areas on a vertical axis parallel to the second direction and on a horizontal axis parallel to the first direction of the first arm member, and the divided sections of the driving electrode are disposed in diagonal areas of the four areas. 
     
     
       6. An angular velocity sensor comprising:
 an angular velocity sensor element of  claim 1 ; 
 a driving control circuit that applies configured to apply a driving signal to a the driving electrode disposed on the angular velocity sensor element; and 
 a detecting circuit that processes configured to process a detecting signal fed from a the detecting electrode disposed on the angular velocity sensor element. 
 
     
     
       7. The angular velocity sensor element of  claim 1 , wherein
 the driving arm has a dog-leg bent structure of arm members extending in a direction perpendicular to a vibrating direction of the weighting section. 
 
     
     
       8. The angular velocity sensor element of  claim 7 , wherein each corner of the dog-leg bent structure of the arm members has fillet geometry. 
     
     
       9. The angular velocity sensor element of  claim 1 , wherein
 the driving electrode has a lower electrode, piezoelectric substrate, and an upper electrode stacked in this order  piezoelectric substrate stacked on a lower electrode, and an upper electrode stacked on the piezoelectric substrate. 
 
     
     
       10. The angular velocity sensor element of  claim 1 , wherein
 the driving arm has an air gap disposed between the first end of driving arm and the second end of the driving arm.   
     
     
       11. The angular velocity sensor element of  claim 1 , wherein
 the holding section is separated into two portions at a center of the holding section. 
 
     
     
       12. The angular velocity sensor element of  claim 1 , wherein
 the first end of the driving arm is connected to the holding section at a center of the holding section in the second direction substantially perpendicular to the first direction from the first end to the second end.   
     
     
       13. The angular velocity sensor element of  claim 1 , wherein
 the driving arm has a first driving arm and a second driving arm,   the holding section is disposed between the first driving arm and the second driving arm, and   a length between the first driving arm and the second driving arm in the first direction is shorter than a length of the driving arm in the second direction.   
     
     
       14. An angular velocity sensor element comprising:
 a driving arm having a first end and a second end opposite to the first end;   a holding section connected to the first end of the driving arm;   a weighting section connected to the second end of the driving arm;   a driving electrode disposed on the driving arm and being configured to vibrate the weighting section; and   a detecting electrode disposed on the driving arm and configured to detect angular velocity of the driving arm,   wherein, the driving arm has a first driving arm and a second driving arm,   the holding section is disposed between the first driving arm and the second driving arm, and
 a length of the driving arm in a first direction from the first end to the second end is shorter than a length of the driving arm in a second direction substantially perpendicular to the first direction, 
 a length between the first driving arm and the second driving arm in the first direction is shorter than a length of the driving arm in the second direction, and 
 the driving arm is substantially surrounded on at least three sides by the holding section and the weighting section. 
   
     
     
       15. The angular velocity sensor element of  claim 14 , wherein
 the driving electrode has a lower electrode, piezoelectric substrate, and an upper electrode stacked in this order.   
     
     
       16. The angular velocity sensor element of  claim 14 , wherein
 the holding section is separated into two portions at a center of the holding section.   
     
     
       17. The angular velocity sensor element of  claim 14 , wherein
 the first end of the driving arm is connected to the holding section at a center of the holding section in the direction substantially perpendicular to the direction from the first end to the second end.   
     
     
       18. The angular velocity sensor element of  claim 14 , wherein
 each of the first driving arm and the second driving arm has arm members extending in the second direction, and   the detecting electrode is disposed on one arm member of the arm members so as to be offset from a central axis of the one arm member in the second direction.   
     
     
       19. The angular velocity sensor element of  claim 14 , wherein
 each of the first driving arm and the second driving arm has arm members extending in the second direction, and   the detecting electrode has a symmetrical shape in the second direction with respect to a changing point of deflection of the arm member.   
     
     
       20. The angular velocity sensor element of  claim 1 , wherein the driving arm has a first driving arm and a second driving arm,
 the holding section is disposed between the first driving arm and the second driving arm, and 
 a shape of the first driving arm is symmetric to a shape of the second driving arm with respect to the holding section. 
 
     
     
       21. The angular velocity sensor element of  claim 20 , wherein the holding section is separated into two portions at a center of the holding section. 
     
     
       22. An angular velocity sensor element comprising:
 a first arm, a second arm, a third arm and a fourth arm;   a holding section connected to the first arm, the second arm, the third arm and the fourth arm;   a first weighting section connected to the first arm and the second arm;   a second weighting section connected to the third arm and the fourth arm;   driving electrodes configured to vibrate the first weighting section and the second weighting section; and   detecting electrodes configured to detect angular velocity,   wherein,   each of the first arm and the second arm is disposed between the holding section and the first weighting section,   each of the third arm and the fourth arm is disposed between the holding section and the second weighting section,   the first arm and the second arm are surrounded on at least three sides by the holding section and the first weighting section,   the third arm and the fourth arm are surrounded on at least three sides by the holding section and the second weighting section,   each of the first arm and the second arm comprises a first arm member, a second arm member and a third arm member,   the first arm member and the second arm member extend in a first direction, and   the third arm member extends in a second direction perpendicular to the first direction.   
     
     
       23. The angular velocity sensor element of claim 22, wherein
 each of the third arm and the fourth arm comprises a first arm member, a second arm member and a third arm member,   the first arm member and the second arm member extend in the first direction,   the third arm member extends in the second direction perpendicular to the first direction, and,   the driving electrodes are disposed on the first arm members and the detecting electrodes are disposed on the second arm members, and the driving electrodes are disposed so as to be offset from a central axis of a respective one of the first arm members.   
     
     
       24. An angular velocity sensor comprising:
 an angular velocity sensor element of claim 22;   a driving control circuit configured to apply a driving signal to the driving electrodes disposed on the angular velocity sensor element; and   a detecting circuit configured to process a detecting signal fed from the detecting electrodes disposed on the angular velocity sensor element.   
     
     
       25. The angular velocity sensor element of claim 22, wherein
 each of the first arm, the second arm, the third arm and the fourth arm has a bent structure of arm members extending in a direction perpendicular to a vibrating direction of a respective one of the weighting sections.   
     
     
       26. The angular velocity sensor element of claim 25, wherein each corner of the bent structure of the arm members has fillet geometry. 
     
     
       27. The angular velocity sensor element of claim 22, wherein
 the driving electrodes have a piezoelectric substrate stacked on a lower electrode, and an upper electrode stacked on the piezoelectric substrate.   
     
     
       28. The angular velocity sensor element of claim 22, wherein
 a continuous space is defined between the first arm and the second arm.   
     
     
       29. The angular velocity sensor element of claim 22, wherein
 the holding section is separated into two portions at a center of the holding section.   
     
     
       30. The angular velocity sensor element of claim 22, wherein
 a continuous space is defined between the third arm and the fourth arm.   
     
     
       31. The angular velocity sensor element of claim 22, wherein
 the holding section comprises a connection section and a supporting arm, and   the supporting arm is disposed between the first arm member of the first arm and a first arm member of the third arm.   
     
     
       32. The angular velocity sensor element of claim 22, wherein
 a length of the first arm in the first direction from is shorter than a length of the first arm in the second direction substantially perpendicular to the first direction.   
     
     
       33. The angular velocity sensor element of claim 22, wherein
 a length between the first arm member or the second arm member in the first direction is shorter than a length of the third arm member in the second direction.