Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
  • G01C19/56—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
  • G01C19/5607—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces using vibrating tuning forks

Definitions

• the present invention relates to an inertial force sensor that detects inertial force used in various electronic devices such as attitude control and navigation of a moving body such as an aircraft, automobile, robot, ship, and vehicle.
• attitude control and navigation of a moving body such as an aircraft, automobile, robot, ship, and vehicle.
• FIG. 8 is a perspective view of a vibrator used in a conventional inertial force sensor.
• the conventional inertial force sensor is a piezoelectric vibration type inertial force sensor, and has a vibrator 1 and a circuit for detecting the inertial force based on the vibrator 1.
• This vibrator 1 has two tuning fork arms 2 and 3 that face each other, and a base 4 that connects the two tuning fork arms 2 and 3.
• Fig. 8 shows the X, Y, and Z axes orthogonal to each other. Tuning fork arms 2 and 3 are designed to vibrate in the X-axis direction.
• each of the two tuning fork arms 2 and 3 is irradiated with laser to melt and remove a part of the vibrator 1 to form the trimming portion 8.
• the trimming portion is formed on the ridge portion 7 that is easily melted and removed.
• Patent Document 1 is known as prior art document information related to the invention of this application.
• a work-affected layer may be formed in the vicinity of the trimming part 8 of the tuning fork arms 2 and 3 due to the caustic heat. There was a problem that 3 could be damaged or cause unnecessary vibration.
• Patent Document 1 Japanese Unexamined Patent Application Publication No. 2004-93158 Disclosure of the invention
• the present invention solves the above-described problems, and an inertial force sensor that has a configuration in which a trimming portion is formed in a portion excluding the ridge portion of the arm and is less likely to cause damage to the tuning fork arm due to trimming. It is to provide.
• FIG. 1 is a perspective view of a vibrator used for an inertial force sensor according to an embodiment of the present invention.
• FIG. 2 is a cross-sectional view taken along the line AA of the arm of the same vibrator.
• FIG. 3 is a special graph showing the relationship between the arm width and the arm strength with respect to the formation position of the trimming portion.
• FIG. 4 is a characteristic diagram showing the relationship between the formation position of the trimming portion and the amount of unnecessary vibration.
• FIG. 5 is a front view of a vibrator in which a trimming portion is formed at the center of the arm width.
• FIG. 6A is a front view of a vibrator formed by shifting the trimming portion with respect to the center of the arm width.
• FIG. 6B is a front view of the vibrator formed by shifting the trimming portion with respect to the center of the arm width.
• FIG. 7 is a characteristic diagram showing the relationship between the formation position of the trimming portion and the amount of unnecessary vibration.
• FIG. 8 is a perspective view of a vibrator used in a conventional inertial force sensor.
• FIG. 1 is a perspective view of a vibrator used for an inertial force sensor according to an embodiment of the present invention.
• Fig. 2 is a cross-sectional view taken along the line AA of the arm of the same vibrator.
• the inertial force sensor includes a tuning-fork type vibrator 10 for detecting inertia and a processing circuit (not shown).
• the vibrator 10 has two tuning fork arms 12 and 13 and a base portion 14 connecting them.
• One surface of the tuning fork arms 12 and 13 is an electrode surface 16 on which an electrode 15 is formed, and the other surface on the back side is a trimming surface 18 on which a trimming portion 17 is formed.
• the material of the vibrator 10 is silicon (Si).
• the electrodes 15 on the arms 12 and 13 are provided with Au / Ti, Pt / Ti, etc. above and below a piezoelectric thin film made of lead zirconate titanate ( ⁇ ).
• the vibrator 10 When AC signals that have opposite phases are applied to the two electrodes 15, the vibrator 10 is driven to vibrate in the width direction (X-axis direction shown in FIG. 1) of the tuning fork arms 12 and 13. At this time, if the tuning fork arms 12 and 13 are symmetric with respect to the sectional force axis and symmetric with respect to the Z axis, the tuning fork arms 12 and 13 drive and vibrate in the X axis direction without stagnation in the Z axis direction. If it breaks down, it will also stagnate in the Z-axis direction in accordance with the drive vibration in the X-axis direction (unnecessary vibration).
• the cross-sectional shape of the tuning fork arms 12 and 13 is accurately set in the X-axis direction and the Z-axis direction. It is very difficult to process it symmetrically. Therefore, it is necessary to secure the mass balance and stabilize the tuning fork drive signal by mechanically trimming the tuning fork arms 12 and 13 so that the unnecessary signal is minimized after the shape of the vibrator 10 is formed.
• Fig. 3 is a characteristic diagram showing the relationship between arm width and arm strength with respect to the trimming position.
• the arm strength when the ridge is trimmed is represented by the point where the distance from the ridge to the arm width is 0%. It is probable that a damaged layer due to the heat of trimming was formed in the vicinity of the trimming part 17 and the strength of the base material decreased.
• the trimming position to be trimmed moves away from the ridge of the tuning fork arm as shown by the point in FIG. Will go up.
• the strength increases monotonously up to about 5% of the distance from the edge of the trimming position to the arm width.
• the distance from the ridge at the trimming position to the arm width is greater than 5%, the strength is almost constant. This constant value is almost the same strength as when the trimming portion 17 is not formed.
• the trimming part 17 is formed with a distance of 5% or more from the ridge part 19, that is, 95% or less with respect to the other end, the tuning fork arms 12 and 13 in the driving vibration direction are Trimming is possible with almost no loss of strength.
• 4 and 7 are characteristic diagrams showing the relationship between the trimming portion formation position and the amount of unnecessary vibration.
• FIG. 4 is a front view of a vibrator in which a trimming portion is formed in the flat portion at the center of the arm width. Unnecessary vibration does not occur in the trimming at the position shown in Fig. 5.
• FIGS. 6A and 6B are front views of the vibrator formed by shifting the trimming portion with respect to the center of the arm width.
• the amount of unnecessary vibration changes linearly. That is, the mass balance is secured by determining the formation position of the trimming portion 17 based on the center of the width of the tuning fork arms 12 and 13 according to the amount of change in the unnecessary signal in the linear correlation. Generation of unnecessary signals can be suppressed. Therefore, depending on the size of the unwanted signal, the position where the trimming unit 17 is formed By adjusting the fork arms 12 and 13 in the width direction, unnecessary signals can be easily removed.
• the processing surface to be trimmed it is preferable to use the other surface on the back side where the electrodes 15 of the tuning fork arms 12 and 13 are not formed. This is because if the electrode surface 16 on which the electrode 15 is formed is processed, the processing position is restricted by the formation pattern of the electrode 15, so that an arbitrary position cannot be processed or the effect of the heat from the laser causes the electrode 15 to be processed. This is because there is a possibility that the characteristics of the PZT that constitutes.
• the reason for using a laser at the time of trimming is that the processing accuracy is high and the generation of debris melted and removed by processing can be reduced. Specifically, by using a wavelength of 355 nm, generation of molten waste due to laser irradiation can be suppressed. Of course, it is also possible to further reduce molten waste by shortening the wavelength. And the shorter the wavelength, the more precise processing is possible. However, the shorter the device, the more expensive the device and the higher the cost. Considering equipment cost and stability, 355 nm is preferable at the present time.
• the trimming unit 17 is preferably formed at the same position on the tuning fork arms 12 and 13. It is possible to trim only one of the two tuning fork arms 12 and 13 to reduce the tuning fork unnecessary signal. However, when such processing is performed, the amount of trimming (mass variation) is large. This is because, even if the tuning fork left and right arms become unbalanced and the tuning fork unnecessary signal can be reduced as an initial characteristic, output fluctuations may become large when temperature characteristics are taken into consideration. Therefore, it is desirable to perform it equally for all arms.
• the form in which trimming is individually performed on the vibrator 10 has been described.
• the unnecessary signal level of each vibrator 10 is measured in the wafer state, and the unnecessary signal level is not necessary.
• the position of the trimming unit 17 may be determined according to the signal level, and trimming by laser may be performed in the wafer state. By performing trimming in the wafer state, cleaning after trimming can be easily performed, so that processing waste generated during trimming can be easily removed.
• processing scraps from the trimming may enter the package. Does not occur.
• the mechanical strength is high, the semiconductor process
• Si silicon
• the Si surface is oxidized
• diamond fused quartz, alumina, GaA or the like.
• the inertial force sensor according to the present invention can prevent the tuning fork arm from being damaged due to trimming, and has high durability and accuracy applicable to various electronic devices.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Gyroscopes (AREA)
• Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

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Citations (4)

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• 2006
  • 2006-04-12 JP JP2006109507A patent/JP5208373B2/ja not_active Expired - Fee Related
• 2007
  • 2007-04-10 US US12/296,273 patent/US8215190B2/en not_active Expired - Fee Related
  • 2007-04-10 WO PCT/JP2007/057871 patent/WO2007117008A1/ja not_active Ceased
  • 2007-04-10 EP EP07741307A patent/EP1978330A4/en not_active Withdrawn
  • 2007-04-10 CN CN201210001632.0A patent/CN102589538B/zh not_active Expired - Fee Related
  • 2007-04-10 CN CN2007800096464A patent/CN101405569B/zh not_active Expired - Fee Related
• 2012
  • 2012-06-08 US US13/491,943 patent/US8590403B2/en not_active Expired - Fee Related

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