JP2005291937A - Inertia sensor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein a conventional inertia sensor element cannot sufficiently damp the vibration of a tuning fork leg part at the tuning fork base part, in exciting the inflection vibration of the tuning fork leg part, and transmits it to a support part, and wherein the characteristics such as the temperature characteristic and the leakage of vibration extremely vary before and after assembling the inertia sensor element, and to improve the transmission of the vibration from the tuning fork leg part to the support part. <P>SOLUTION: In the inertia sensor element having a groove in the tuning fork base part, the inertia sensor element, composed of a piezoelectric material having at least a plurality of leg parts, the tuning fork base part, and the support part, is provided with a through hole or the groove having the dimension ≥0.3 times the distance between the outsides of the plurality of leg parts with respect to the X-axis direction and having the dimension ≤0.3 times the dimension of the tuning fork base part in the Y-axis direction, with respect to the Y-axis direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inertial sensor used for attitude control and position detection of an aircraft, a ship, an automobile, and the like.

There are various types of inertial sensors, and there is a vibration type angular velocity sensor that satisfies the requirement of being thin, small and lightweight for incorporation. A conventional vibration type inertial sensor detects a Coriolis force that works with rotation by vibrating a quadrangular prism.
As such a conventional inertial sensor, there is one using a tuning fork vibrator as shown in FIG. 2 (Patent Document 1).

  A conventional piezoelectric vibrator used for an inertial sensor includes two tuning fork legs 201 and 202, a tuning fork base 203 and a support 204 as shown in the perspective view of FIG. FIG. 2B is a cross-sectional view taken along the alternate long and short dash line on the leg portion of FIG. Further, the tuning fork legs 201 and 202 are provided with electrodes 211, 212, 213, 214 and electrodes 221, 222, 223, 224 as shown in the sectional view of FIG. In FIG. 2A, electrodes are omitted.

In the tuning fork leg 201, the electrode 211 and the electrode 213 are arranged opposite to each other with the tuning fork leg 201 interposed therebetween, and the electrode 212 and the electrode 214 are arranged to face each other across the tuning fork leg 201. The electrode 211 and the electrode 212 are formed on the same surface, and the electrode 213 and the electrode 214 are also formed on the same surface.
Further, as schematically shown in FIG. 9B, in the tuning fork leg 201, the electrode 211 and the electrode 214 have the same polarity, and the electrode 212 and the electrode 213 have different polarities.

  On the other hand, in the tuning fork leg 202, electrodes 221, 222, 223, and 224 are provided on each of the four side surfaces of the tuning fork leg 202, and the electrode 221 and the electrode 222 are disposed to face each other with the tuning fork leg 202 interposed therebetween. And the electrode 224 have different polarities.

  In the inertial sensor using the tuning fork type vibrator configured as described above, the tuning fork leg 202 serves as a vibrator excitation unit, and the terminals E3 and E4 serve as vibrator excitation terminals. The tuning fork leg 201 is an angular velocity detection unit, and the terminals E1 and E2 are angular velocity detection terminals.

  Here, when a DC voltage is applied so as to be positive at the terminal E3 and negative at the terminal E4, the electrolysis works as indicated by an arrow, the direction of the electrolytic component shown in the tuning fork leg 202 is reversed, and the tuning fork leg is bent. Therefore, when an AC voltage is applied to the terminals E3 and E4, the tuning fork legs 201 and 202 bend and vibrate in the XY plane.

In this state, when a rotational motion is generated around the Y axis to generate an angular velocity, a Coriolis force proportional to the angular velocity is generated in the Z axis direction perpendicular to the XY plane, and a component in the Z axis direction is generated. Causes bending vibration with At this time, if only the electric charge corresponding to the Z-axis direction generated in the tuning fork leg 201 is diverted to the electrodes 211, 212, 213, and 214, the magnitude of the angular velocity can be detected from the angular velocity detection terminals E1 and E2. Become.
JP-A-10-197253 JP 61-50031 A

  However, as the size of the inertial sensor element is reduced, the size of the tuning fork base is also reduced, so that the vibration propagating from the tuning fork leg to the support cannot be sufficiently attenuated by the tuning fork base. For this reason, when the inertial sensor element is assembled through the support portion, distortion is caused by the assembly, and characteristics such as vibration leakage and zero-point drift greatly vary before and after the inertial sensor element is assembled.

  The present invention relates to an inertial sensor element composed of a piezoelectric material having at least a plurality of legs, a tuning fork base, and a support, and the tuning fork base includes a groove in the tuning fork base. An opening part that is a hole or a groove is formed, and the dimension of the opening part is 0.3 times or more the distance Wf between the outer sides of the two leg parts facing the dimension Wh in the X-axis direction. The dimension Lh in the Y-axis direction is provided at the center of the tuning fork base excluding the support part 0.3 times or less of the distance L2 in the Y-axis direction of the tuning fork base excluding the support part.

  In this inertial sensor, by providing the tuning fork base with a through hole or groove, it is possible to significantly reduce the vibration propagating from the tuning fork leg to the support. In particular, it has a great effect on the vibration of the Y-axis direction component and the vibration of the Z-axis direction component. When comparing the structure of the present invention with a through hole in the tuning fork base and the structure of the conventional structure without a through hole or groove, the structure of the present invention has a tuning fork up to about 1/10 of the conventional structure. The vibration propagating from the leg part to the support part could be reduced.

Therefore, before and after assembling the inertial sensor element, the amount of fluctuation in characteristics such as vibration leakage and zero-point drift can be made significantly smaller than the conventional one.
Further, since the vibration propagating from the tuning fork leg part to the support part can be sufficiently suppressed without enlarging the tuning fork base part, the element can be miniaturized.

An inertial sensor element composed of a piezoelectric material having at least a plurality of legs, a tuning fork base, and a support part, wherein the tuning fork base includes a groove,
In the through hole or groove of the tuning fork base, the opening size of the through hole is not less than 0.3 times the distance Wf between the outer sides of the two legs facing the dimension Wh in the X-axis direction. Yes, the dimension Lh in the Y-axis direction is 0.3 times or less the distance L2 in the Y-axis direction of the tuning fork base excluding the support part, and the through hole is the center of the tuning fork base excluding the support part It is an inertial sensor element provided with.

  FIG. 1 is a perspective view (a) showing a configuration example of an inertial sensor in the embodiment of the present invention and a cross-sectional view (b) showing a cross section of a leg portion. FIG.1 (b) is sectional drawing of the dashed-dotted line shown on the leg part of Fig.1 (a). This inertial sensor is a tuning fork type vibrator made of quartz and provided with two tuning fork legs 101 and 102. The tuning fork legs 101 and 102 have a dimension Wx of 0.38 mm, a dimension Wz in the Z-axis direction of 0.45 mm, and a length L1 in the Y-axis direction of 4.7 mm, including the tuning fork base 103 and the support 104. The length of is 6.5 mm. The length L2 of the tuning fork base in the Y-axis direction is 1.2 mm.

  The dimension Wh in the X-axis direction of the through hole 130 is 1.2 mm, and the dimension Lh in the Y-axis direction is 0.2 mm. The distance Dh in the Y-axis direction between the tuning fork leg base and the center of the through hole was 0.6 mm. In the tuning fork leg 101, the electrodes 111 and 114 have the same polarity and are connected to the terminals E1 and E2. The electrodes 112 and 113 have the same polarity and are connected to the terminal E2.

  On the other hand, in the tuning fork leg 102, the electrodes 121 and 122 have the same polarity and are connected to the terminal E3. The electrodes 123 and 124 have the same polarity and are connected to the terminal E4.

  In the inertial sensor using the tuning fork type vibrator configured as described above, the tuning fork leg 102 serves as a vibrator excitation unit, and the electrodes 121 and 122 and the electrodes 123 and 124 serve as vibrator excitation electrodes. The tuning fork leg 101 is an angular velocity detection unit, and the electrodes 111 and 114 and the electrodes 112 and 113 serve as angular velocity detection electrodes. In the XYZ orthogonal coordinate system shown in FIG. 1, the X axis indicates the electric axis of the crystal constituting the inertial sensor, the Y axis is the mechanical axis, and the Z axis is the optical axis.

  Incidentally, a piezoelectric material such as quartz has a piezoelectric-inverse piezoelectric effect. Also in the inertial sensor of the present embodiment, when electrolysis is applied in parallel to the electrical axis through the appropriately configured electrode, strain (extension or contraction) is generated in parallel to the mechanical axis (reverse piezoelectric effect). On the other hand, when mechanical external force strain (in this case, strain due to Coriolis force) is applied to the inertial sensor, a charge proportional to the magnitude is generated in the distorted portion (piezoelectric effect). If an appropriately configured electrode is disposed at a place where this charge is generated, the generated charge can be collected effectively.

  Here, when a DC voltage is applied so that the electrodes 121 and 122 are positive and the electrodes 123 and 124 are negative, the tuning fork leg is bent in the X-axis direction. Therefore, when an AC voltage is applied between the electrodes 121 and 122 and the electrodes 123 and 124, the tuning fork legs 101 and 102 cause bending vibration (excited) in the XY plane.

  In this state, when a rotational motion is generated around the Y axis, a Coriolis force proportional to the angular velocity is generated in the Z axis direction perpendicular to the XY plane, and bending vibration having a component in the Z axis direction. cause. Due to this bending vibration, electric charges are generated in the tuning fork leg 101 due to the piezoelectric effect, which are detected by the electrodes 111 and 114 and the electrodes 112 and 113 which are angular velocity detection electrodes and output from the terminals E1 and E2. Since the generated charge is in proportion to the angular velocity of the generated rotational motion, the magnitude of the angular velocity can be obtained from the electrical signal detected by the angular velocity detection electrode. Further, the direction of the angular velocity can also be detected by comparing the phases of the charge polarity, the excitation signal polarity and the excitation signal.

  According to the inertial sensor element shown in FIG. 1 configured as described above, vibrations generated in the X, Y, and Z axial directions generated in the tuning fork leg are attenuated by the through hole or groove provided in the tuning fork base. By doing so, propagation of vibration from the tuning fork base to the support can be significantly reduced.

Here, the result of considering the relationship between the dimension of the through hole in the X-axis direction, the dimension in the Y-axis direction, the insertion position and the vibration displacement at the support portion is shown below.
3 and 4, when the distance between the outsides of the two legs is Wf and the dimension of the through hole in the X-axis direction is Wh, the horizontal axis is Wh / Wf and the through-hole is in the X-axis direction. 1 shows the change in vibration displacement at points A and B in FIG. 1. FIGS. 5 and 6 show the Y-axis dimension of the tuning fork base portion excluding the support portion as L2. When the dimension in the Y-axis direction is Lh and the horizontal axis is Lh / L2 and the dimension Lh in the Y-axis direction of the through hole is changed, the change in vibration displacement at points A and B is shown in FIG. In FIG. 8, when the distance in the Y-axis direction between the tuning fork leg base and the center of the through hole is Dh, when the horizontal axis is Dh / L2 and the insertion position Dh of the through hole is changed, points A and B The change of vibration displacement is shown. The Y axis in FIGS. 3 to 8 is a ratio indicated by a numerical value when the vibration displacement without a through hole or groove is 1.

  3 and 4, when the vibration displacement at points A and B is Wh = (0.8 to 0.9) × Wf, the wave propagating from the tuning fork leg to the support is minimized, and Wh> 0. In the case of 3 × Wf, the vibration propagating from the tuning fork leg portion to the support portion is smaller than in the model having no through hole or groove. The two curves exist in the figure because the different forks such as the slit width of the tuning fork leg and the size of the tuning fork base are compared.

  5 and 6, the vibration displacement at points A and B when the dimension of the through hole in the Y-axis direction is changed is that the wave propagating from the tuning fork leg to the support when Lh is about 0.15 × L2. When Lh is smaller than 0.3 × L2, it is smaller than the model without through holes or grooves.

  7 and 8, the vibration displacement at points A and B when the insertion position of the through hole into the tuning fork base is changed in the Y-axis direction has a through hole at the center of the tuning fork base excluding the support. In some cases, the wave propagating from the tuning fork leg part to the support part is minimized, and when a through hole is inserted at a position where Dh = (0.3 to 0.7) × L2, it is smaller than that without a through hole or groove. Become.

  As shown in FIGS. 3 to 8, by determining the optimum size and insertion position of the through hole or groove, it is possible to significantly reduce the vibration from the tuning fork leg portion to the support portion. Therefore, characteristic changes such as zero point drift and vibration leakage after assembly can be significantly reduced as compared with the conventional one. As a result, according to the present embodiment, the angular velocity can be detected with higher accuracy than in the past.

  In the embodiment described above, quartz is used. However, the present invention is not limited to this, and other piezoelectric materials such as crystals of lithium niobate and piezoelectric ceramics may be used.

  Application to inertial sensors capable of measuring acceleration and angular velocity, as well as angular velocity sensors used for video camera image correction, attitude control of aircraft, ships, automobiles, etc., position detection, or 2-axis or 3-axis The present invention can also be applied to an inertial sensor capable of measuring the angular velocity.

It is the perspective view (a) which shows the structural example of the inertial sensor element in embodiment of this invention, and sectional drawing (b) of a leg part. It is the perspective view (a) which shows the structural example of a conventional inertial sensor element, and sectional drawing (b) which shows the cross section of a leg part. It is a characteristic view which shows the change of the vibration displacement in the support part center part (A point in FIG. 1) produced when the dimension of the through-hole of the inertial sensor element by this invention is changed to the X-axis direction. It is a characteristic view which shows the change of the vibration displacement in the support part edge part (B point in FIG. 1) produced when the dimension of the through-hole of the inertial sensor element by this invention is changed to an X-axis direction. It is a characteristic view which shows the change of the vibration displacement in the support part center part (A point in FIG. 1) produced when the dimension of the through-hole of the inertial sensor element by this invention is changed to a Y-axis direction. It is a characteristic view which shows the change of the vibration displacement in the support part edge part (B point in FIG. 1) produced when the dimension of the through-hole of the inertial sensor element by this invention is changed to a Y-axis direction. It is a characteristic view which shows the change of the vibration displacement in the support part center part (A point in FIG. 1) produced when the insertion position of the through-hole of the inertial sensor element by this invention is changed to a Y-axis direction. It is a characteristic view which shows the change of the vibration displacement in the support part edge part (B point in FIG. 1) produced when the insertion position of the through-hole of the inertial sensor element by this invention is changed to a Y-axis direction.

Explanation of symbols

101, 102 ... tuning fork leg 103 ... tuning fork base 104 ... support 111, 112, 113, 114 ... angular velocity detection electrode 121, 122, 123, 124 ... vibrator excitation electrode 130 ... through holes
E1, E2 ... Angular velocity detection terminals
E3, E4 ... vibrator excitation terminals 201, 202 ... tuning fork legs 203 ... tuning fork base 204 ... support parts 211, 212, 213, 214 ... angular velocity detection electrodes 221, 222, 223, 224 ... Vibrator excitation electrode

Claims (2)

An inertial sensor element composed of a piezoelectric material having at least a plurality of legs, a tuning fork base, and a support part, wherein the tuning fork base includes a through hole or a groove,
The dimension of the through hole or groove is not less than 0.3 times the distance Wf between the outer sides of the two legs facing the dimension Wh in the X-axis direction, and the dimension Lh in the Y-axis direction. Is 0.3 times or less the distance L2 in the Y-axis direction of the tuning fork base excluding the support portion. The inertial sensor element according to claim 1,
The opening position of the through hole or groove to the tuning fork base is set such that the distance Dh from the root of the tuning fork to the center of the through hole or groove is 0 with respect to the dimension L2 of the tuning fork base excluding the support portion. Inertial sensor element characterized in that it is 3 to 0.7 times.

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