JP5209076B2 - Inertial force sensor - Google Patents

Description

  The present invention relates to an inertial force sensor that detects an inertial force used in various electronic devices such as attitude control and navigation of a moving body such as an aircraft, an automobile, a robot, a ship, and a vehicle.

  Hereinafter, a conventional inertial force sensor will be described with reference to the drawings.

  FIG. 5 is a perspective view of a vibrator used in a conventional inertial force sensor.

  In FIG. 5, the conventional inertial force sensor is a piezoelectric vibration type inertial force sensor, and includes a vibrator 1 and a circuit that detects the inertial force based on the vibrator 1. The vibrator 1 includes 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. As shown in FIG. 5, the vibrator 1 is arranged on the XY plane in the X axis, the Y axis, and the Z axis that are orthogonal to each other. The tuning fork arms 2 and 3 vibrate in the X-axis direction. However, in order to achieve ideal vibration (vibration in the X-axis direction), the cross-sectional shape of each tuning fork arm 2 and 3 is relative to the X-axis and Z-axis. A substantially rectangular shape that is symmetrical is preferred. However, since manufacturing variations occur in the manufacture of the vibrator 1, it is extremely difficult to process it into a substantially rectangular shape, and an unnecessary signal is superimposed on the vibration in the X-axis direction.

  Therefore, after processing the vibrator 1, the corner portions 7 of the two tuning fork arms 2 and 3 are irradiated with laser to trim the corner portions 7 to form trimming portions 8. As a result, the mass balance of the vibrator 1 is adjusted and appropriately oscillated in the X-axis direction.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

JP 2004-93158 A

  In the above-described configuration, a laser is used to process the tuning fork arms 2 and 3 with high precision when trimming. At this time, a damaged layer is formed in the vicinity of the trimming portion 8 of the tuning fork arms 2 and 3 due to machining heat, so that the strength of the base material is lowered, and the tuning fork arms 2 and 3 are damaged or unnecessary vibration is generated. There was a problem that there is a risk of.

  The present invention solves the above-described problems, and an object of the present invention is to provide an inertial force sensor that suppresses breakage of the tuning fork arm caused by trimming.

The present invention solves the above-described problems, and includes a vibrator having at least two arms and a base portion that connects the two arms, and the two arms have the same width. A trimming portion is formed at a portion separated from the corner on the same side by 1/20 or more in the width direction, and an axis parallel to the width direction of the two arms is an X axis. The distance from the corner / the arm width is the same in the two arms .

  With the above configuration, even if a work-affected layer is generated near the trimming portion due to the heat of trimming, the strength of the base material is reduced, and the reduction in arm strength and the occurrence of unnecessary vibration can be suppressed. Further, the mass balance of the vibrator can be adjusted, and the vibrator can be appropriately vibrated in the X-axis direction.

The perspective view of the vibrator | oscillator used for the inertial force sensor in one embodiment of this invention AA sectional view of the arm of the same vibrator Characteristic diagram showing the relationship between arm width and arm strength with respect to the trimming position Characteristic diagram showing the relationship between arm width and unnecessary vibration amount with respect to the trimming position A perspective view of a vibrator used in a conventional inertial force sensor

  Hereinafter, an inertial force sensor according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of a vibrator used in an inertial force sensor according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line AA of the arm of the vibrator, and FIG. FIG. 4 is a characteristic diagram showing the relationship between the arm width and the amount of unnecessary vibration with respect to the formation position of the trimming portion.

  1 and 2, the inertial force sensor according to the embodiment of the present invention includes a tuning fork type vibrator 10 for detecting the inertial force and a processing circuit (not shown). The vibrator 10 includes 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 is a trimming surface 18 on which a trimming portion 17 is formed.

  The vibrator 10 is made of silicon (Si), and the electrodes 15 on the arms 12 and 13 are made by providing Au / Ti, Pt / Ti, etc. above and below a piezoelectric thin film made of lead zirconate titanate (PZT).

  When alternating signals having opposite phases are applied to the two electrodes 15, the vibrator 10 vibrates in the width direction (X-axis direction) of the tuning fork arms 12 and 13. At this time, if the cross-sectional shape of the tuning fork arms 12 and 13 is symmetric with respect to the X 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 bending to the Z axis. If it collapses, it will also bend in the Z-axis direction in accordance with the drive vibration in the X-axis direction (unnecessary vibration).

  When the vibrator 10 bends in the Z-axis direction, an electric charge (unnecessary signal) is generated in the angular velocity detection electrode (not shown). This unnecessary signal is phase-shifted from the electric charge generated when the angular velocity is input. Is 90 °, the signal can be removed by performing synchronous detection processing in the processing circuit. However, if the phase of the reference signal and the unnecessary signal at the time of synchronous detection is slightly shifted, it is output as an angular velocity signal.

  Therefore, it is desirable that the vibrator 10 does not generate an unnecessary signal. However, as described above, the cross-sectional shapes of the tuning fork arms 12 and 13 are processed so as to be symmetric in the X-axis direction and the Z-axis direction. Is very difficult. Therefore, normally, the tuning fork arms 12 and 13 are mechanically trimmed so that the unnecessary signal is minimized after the processing of the vibrator 10, thereby securing the mass balance and stabilizing the tuning fork drive signal.

  In trimming, the most efficient portion is the corner portion 19 at the base of the tuning fork arms 12 and 13 (near the base portion 14). If this portion is processed, the tuning fork arm 12 and The strength of 13 is reduced.

  However, as shown in FIG. 3, an interval of 1/20 or more with respect to the width of the tuning fork arms 12 and 13 from the corner portion 19 in the width direction of the tuning fork arms 12 and 13 (an angle with respect to the width of the tuning fork arms 12 and 13). If the trimming portion 17 is formed with a distance of 5% or more from the portion 19), the strength of the tuning fork arms 12 and 13 in the driving vibration direction is maintained at the same strength as when the trimming portion 17 is not formed. it can.

  That is, since the trimming portion 17 is formed in the tuning fork arms 12 and 13 except for the corner portion 19, a work-affected layer caused by the processing heat of trimming is formed in the vicinity of the trimming portion 17, and the strength of the base material is increased. Even if it falls, the arm strength reduction can be suppressed.

  In addition, as shown in FIG. 4, when the trimming length in the longitudinal direction and the trimming length in the width direction of the tuning fork arms 12 and 13 are fixed, the formation position of the trimming portion 17 in the width direction and the amount of change in unnecessary signals are There is a linear correlation. Therefore, the formation position of the trimming portion 17 can be adjusted in the width direction of the tuning fork arms 12 and 13 according to the magnitude of the unnecessary signal, and can be easily adjusted.

  Further, as the processed surface to be trimmed, it is preferable to use the surfaces of the tuning fork arms 12 and 13 on which the electrode 15 is not formed. This is because when 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 electrode 15 is affected by the heat of the laser. This is because there is a possibility that the characteristics of the PZT constituting the change may change.

  Furthermore, the reason for using a laser at the time of trimming is that the processing accuracy is high and the generation of scraps due to 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 possible to further reduce the melting waste by further shortening the wavelength, but 355 nm is realistic considering the apparatus cost and stability.

  Further, it is desirable that the trimming portion 17 is formed at the same location on all the tuning fork arms 12 and 13. For example, it is possible to trim only one of the two tuning fork arms 12 and 13 to reduce a tuning fork unnecessary signal. However, when such processing is performed, if the trimming amount (mass change) is large, This is because the mass of the tuning fork left and right arms becomes unbalanced, and even if the tuning fork unnecessary signal can be reduced as an initial characteristic, there is a possibility that the output fluctuation becomes large in consideration of the temperature characteristic. Therefore, it is desirable to perform it equally for all arms.

  In the embodiment of the present invention, the form in which trimming is individually performed on the vibrator 10 has been described. However, an unnecessary signal level of each vibrator 10 is measured in a wafer state, and according to the unnecessary signal level. Then, the position of the trimming unit 17 may be determined, and trimming by a laser may be performed in a wafer state. By performing trimming in the wafer state, cleaning after trimming can be easily performed, and thus processing waste generated during trimming can be easily removed. In addition, when trimming after incorporating a vibrator or IC as a sensor, there is a possibility that processing scraps from the trimming may enter the package. do not do.

  Further, in one embodiment of the present invention, silicon (Si) is used for the structure of the vibrator 10 in terms of mechanically high strength and easy high-precision processing by semiconductor process technology. Although the example has been described, as long as it is a non-piezoelectric material, for example, an oxidized Si surface, diamond, fused quartz, alumina, GaAs, or the like can be used.

  The inertial force sensor according to the present invention can suppress damage to the tuning fork arm caused by trimming, and can be applied to various electronic devices.

10 vibrator 12 tuning fork arm 13 tuning fork arm 14 base 15 electrode 16 electrode surface 17 trimming portion 18 trimming surface 19 corner portion

Claims (6)

Comprising at least two arms, a vibrator having a base portion for connecting the two arms, the width of the two arms are the same, said two arms toward the respective corner portions in the width direction 1 When the trimming part is formed in a part separated by 20 / more and the axis parallel to the width direction of the two arms is the X axis, the distance / arm width from the corner on the positive side of the X axis is the two arms Inertial force sensor that is the same in The inertial force sensor according to claim 1, wherein masses of the two arms are equal to each other. 2. The inertial force sensor according to claim 1, wherein the two arms have electrodes formed on one surface, and the trimming portions are formed on the other surface of the two arms, respectively. The inertial force sensor according to claim 1, wherein the trimming portion is formed by a laser. The inertial force sensor according to claim 4, wherein the wavelength of the laser is shorter than 355 nm. The inertial force sensor according to claim 1, wherein the trimming portion is formed by performing trimming in a wafer state.

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