US 7,523,665 B2
Angular velocity sensor and method for operating the same
Takashi Katsumata, Kariya (Japan); Takeshi Ito, Okazaki (Japan); Hirofumi Higuchi, Okazaki (Japan); Mutsuhito Ogino, Okazaki (Japan); and Tetsuya Morishima, Ichinomiya (Japan)
Assigned to DENSO CORPORATION, Kariya (Japan); and Nippon Soken, Inc., Nishio (Japan)
Filed on Jan. 16, 2007, as Appl. No. 11/653,344.
Claims priority of application No. 2006-052094 (JP), filed on Feb. 28, 2006; and application No. 2006-260603 (JP), filed on Sep. 26, 2006.
Prior Publication US 2007/0199377 A1, Aug. 30, 2007
Int. Cl. G01P 15/125 (2006.01)
U.S. Cl. 73—514.32  [73/504.02; 73/514.02; 361/280] 19 Claims
OG exemplary drawing
 
1. An angular velocity sensor comprising:
a support substrate; and
first and second vibrators disposed on the support substrate, wherein
each vibrator includes a movable portion and a fixed portion,
the movable portion of each vibrator has a driving purpose movable electrode and a detecting purpose movable electrode,
the movable portion is movably supported on the support substrate so that the movable portion is movable in a horizontal direction parallel to a surface of the support substrate,
the fixed portion of each vibrator has a driving purpose fixed electrode and a detecting purpose fixed electrode,
the fixed portion is fixed on the support substrate,
the driving purpose fixed electrode faces the driving purpose movable electrode, and the detecting purpose fixed electrode faces the detecting purpose movable electrode,
the first vibrator has a predetermined construction, which is symmetric to a construction of the second vibrator,
the movable portion of each vibrator has a part capable of vibrating in a vibration direction parallel to the horizontal direction by applying a driving voltage between the driving purpose fixed electrode and the driving purpose movable electrode,
the part of movable portion of each vibrator is capable of oscillating in an oscillation direction perpendicular to the vibration direction by a Coriolis force, which is generated by an angular velocity applied to the part of the movable portion,
a capacitance between the detecting purpose fixed electrode and the detecting purpose movable electrode is changeable in accordance with an oscillation of the part of the movable portion,
the angular velocity is detected based on a capacitance change between the detecting purpose fixed electrode and the detecting purpose movable electrode,
the driving purpose fixed electrode in the first vibrator includes a first side driving purpose fixed electrode and a second side driving purpose fixed electrode,
the driving purpose fixed electrode in the second vibrator includes a first side driving purpose fixed electrode and a second side driving purpose fixed electrode,
the driving voltage applied to the first side driving purpose fixed electrode in the first vibrator is defined as a first driving voltage, and the driving voltage applied to the second side driving purpose fixed electrode in the second vibrator is the first driving voltage,
the first driving voltage includes a direct voltage defined as A volts and an alternating voltage defined as B volts so that the first driving voltage is described as A+B volts,
the driving voltage applied to the second side driving purpose fixed electrode in the first vibrator is defined as a second driving voltage, and the driving voltage applied to the first side driving purpose fixed electrode in the second vibrator is the second driving voltage,
the second driving voltage includes a direct voltage defined as C volts and an alternating voltage defined as D volts so that the second driving voltage is described as C+D volts,
the alternating voltage of the first driving voltage has a predetermined phase, which is opposite to a phase of the alternating voltage of the second driving voltage, and
at least one of the direct voltages in the first and second driving voltages is controlled in such a manner that the first vibrator vibrates the movable portion with a predetermined phase, which is opposite to a phase of the movable portion in the second vibrator, at least one of the alternating voltages in the first and second driving voltages is controlled in such a manner that the first vibrator vibrates the movable portion with a predetermined phase, which is opposite to a phase of the movable portion in the second vibrator, or at least one of duty ratios of the first and second driving voltages that are set to be a rectangular wave is controlled with reference to a center value of the duty ratios of the rectangular waves in such a manner that the first vibrator vibrates the movable portion with a predetermined phase, which is opposite to a phase of the movable portion in the second vibrator.