JP4316293B2 - Driving method of tuning fork type angular velocity sensor element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a driving method of a tuning fork type angular velocity sensor element (hereinafter referred to as an angular velocity sensor element) using Coriolis force, and more particularly to a driving method in which a noise component due to oblique vibration is electrically reduced.
[0002]
[Prior art]
BACKGROUND OF THE INVENTION Tuning fork type angular velocity sensor elements are applied to position control and guidance devices such as cameras and car navigation systems. One of these is a piezoelectric material, particularly one using a bonded crystal, and further high sensitivity and productivity are required.
[0003]
(Example of Prior Art) FIG. 7 is a view of an angular velocity sensor element for explaining one conventional example.
[0004]
The angular velocity sensor element is configured on the basis of a tuning fork type crystal resonator (referred to as a tuning fork resonator) 1. The tuning fork vibrator 1 is composed of a Z-cut plate whose principal surface is orthogonal or substantially orthogonal to the Z axis of the crystal axis (XYZ), and extends a pair of tuning fork arms 3 (ab) from the tuning fork base 2. Here, two tuning-fork crystal pieces 1 (ab) having ± X axes in opposite directions are bonded together by direct bonding.
[0005]
Each of the pair of tuning fork arms 3 (ab) is provided with electrodes 4 and 5 for detecting Coriolis force by driving tuning fork vibration. Here, as shown in the connection diagram of FIG. 8, the first electrodes 4a and 5a provided on the inner surfaces of the pair of tuning fork arms 3 (ab) are connected, and the second electrodes 4b provided on the outer surfaces. 5b are connected to derive the first and second sensor terminals S1 and S2, respectively.
[0006]
Further, the third electrode 4c provided on the surface of one tuning fork arm 3a (right side in the figure) and the fourth electrode 5d provided on the back surface of the other tuning fork arm 3b (left side in the figure) are connected in common. One drive terminal D1 is derived. The second drive terminal D2 is derived from the fourth electrode 4d provided on the back surface of one tuning fork arm 3a. Further, the monitor terminal M is led out from the third electrode 5c provided on the surface of the other tuning fork arm 3b.
[0007]
In such a case, a direct current reference voltage E0 is applied to the first and second sensor terminals S1 and S2 as shown in FIG. 9, and the potentials on both sides of each tuning fork arm 3 (ab) are kept constant. To. The first and second drive terminals D1 and D2 are applied with AC voltages V1 and V2 having opposite phases with the reference voltage E0 as the center value. As a result, since the X-axis polarity is reversed, the outer surface of one tuning fork arm 3a expands (contracts) in the Y-axis direction due to the electric field generated between the front and back surfaces and the inner and outer surfaces. It contracts (extends) and bends and vibrates in the left-right direction.
[0008]
In the other tuning fork arm 3b, either one of the inner and outer surfaces is bent by being expanded or contracted by an AC voltage applied to the back surface, and since it has a tuning fork structure, it is reversed in response to one tuning fork arm 3a. Bends and vibrates. Therefore, the pair of tuning fork arms 3 (ab) vibrate in the horizontal direction opposite to each other.
[0009]
When a rotational force about the Y axis is applied during tuning fork vibration, the pair of tuning fork arms 3 (ab) are bent in opposite directions perpendicular to the plate surface, that is, opposite to each other perpendicular to horizontal vibration. Cause vertical vibration. Then, charges corresponding to the rotational force are generated on both side surfaces of each tuning fork arm 3 (ab). In addition, the sign of the electric charge between the both side surfaces of each tuning fork arm 3 (ab) is reversed. Specifically, the first electrodes 4a and 5a on the inner surface of each tuning fork arm 3 (ab) have the same polarity, and the second electrodes 4b and 5b on the outer surface have the same polarity.
[0010]
The first and second electrodes 4 (ab) and 5 (ab) of each tuning fork arm 3 (ab) collects continuously changing charges and superimposes them on the reference voltage E0 as an AC component. Detected at the second sensor terminals S1 and S2. Then, the AC component (charge amount) is detected by synchronous detection (not shown) in response to the vibration frequency, and the rotation angle is measured. The monitor terminal M is provided to detect the amount of charge induced by the tuning fork vibration and to set the vibration amplitude amount (displacement amount) as a constant reference value.
[0011]
[Problems to be solved by the invention]
However, in the angular velocity sensor element having the above configuration, the pair of tuning fork arms 3 (ab) does not necessarily vibrate in the horizontal direction indicated by the arrow PP in FIG. Due to the asymmetry of the cross-sectional shape resulting from the manufacture, so-called oblique vibrations occur in the oblique direction indicated by the arrow QQ. Therefore, electric charges are generated by the vertical vector component in the oblique vibration irrespective of the Coriolis force, and are detected as unnecessary signals at the sensor terminals S1 and S2. As a result, even when the angular velocity does not reach, an erroneous signal that the angular velocity reaches is generated.
[0012]
For this reason, normally, an unnecessary signal due to oblique vibration is detected for each angular velocity sensor element. Then, the pair of tuning fork arms 3 (ab) are repeatedly ground (trimmed) several times and adjusted to suppress oblique vibration. However, in this case, the trimming process takes a lot of time and there is a problem in that the productivity is lowered.
[0013]
(Object of the Invention) An object of the present invention is to provide a method of driving an angular velocity sensor element capable of reducing the influence of an unnecessary signal due to a processing error of a tuning fork.
[0014]
[Means for Solving the Problems]
According to the first aspect of the present invention, electrodes are provided on at least one of the tuning fork arms made of a tuning fork-shaped crystal piece, and the other electrode is used as a reference voltage from the front and back electrodes of both main surfaces. The AC voltage based on the monitor voltage based on the amplitude of the tuning fork vibration detected by the front or back electrode of the tuning fork arm is applied to vibrate the one and the other tuning fork arms and vibrate the electric charges generated by the Coriolis force. In the method for driving a tuning fork type angular velocity sensor element that detects at least the other tuning fork arm by means of sensor electrodes provided on both side surfaces, the alternating voltage applied from the surface electrode to the both side surfaces reduces the monitor voltage to the monitor voltage. An asymmetric voltage obtained by adding the rectified voltage to the AC voltage applied to the both side surfaces from the back electrode has the phase of the asymmetric voltage different by 180 °. And symmetric voltage, a structure having different magnitude of the AC voltage applied to the electrodes on both sides from the surface electrode and the rear electrode of the tuning fork arms. Thereby, the electric field which goes to both sides from both principal surfaces of a tuning fork arm, and the amount of bending of the surface side and the back side also differ. Therefore, the tuning fork arm generates oblique vibration. From this, it is possible to electronically cancel (suppress) the oblique vibration by changing the magnitude of the AC voltage according to the mechanical oblique vibration caused by the machining error.
[0015]
In the invention of claim 2, the tuning fork type angular velocity sensor element is formed by bonding two tuning fork crystal pieces with the ± X axes of crystal axes (XYZ) opposite to each other, and from both main surfaces of the tuning fork arm. The AC voltages applied to both sides are opposite in phase. Thereby, diagonal vibration can be suppressed by the angular velocity sensor element in which two tuning-fork crystal pieces are bonded together.
[0016]
In the invention of claim 3, the tuning fork type angular velocity sensor element is composed of a single tuning fork crystal piece, and AC voltages applied to both side surfaces from both main surfaces of the tuning fork arm are in phase with each other. Thereby, diagonal vibration can be suppressed with the angular velocity sensor element which consists of a single plate. In the fourth aspect of the invention, the method of varying the magnitude of the AC voltage is a condition that can cancel or suppress the oblique vibration generated in the tuning fork due to the tuning fork processing error.
[0017]
[First embodiment]
FIG. 1 is a top view showing a connection diagram of an angular velocity sensor element for explaining a driving method of a first embodiment of the present invention. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.
[0018]
As described above, the angular velocity sensor element is composed of a tuning fork vibrator having a tuning fork base 2 and a pair of tuning fork arms 3 (ab). (See figure). Each tuning fork arm 3 (ab) has first and second electrodes 4 (ab) and 5 (ab) to which a reference voltage E0 is applied on the inner and outer surfaces thereof, and the first and second electrodes 4a, 5a and 4b. 5b are connected in common and lead to sensor terminals S1 and S2.
[0019]
Further, the front and back surfaces of one tuning fork arm 3a have third and fourth electrodes 4 (cd) connected to drive terminals D1 and D2 and applied with AC voltages V1 and V2 having opposite phases to each other. A third electrode 5c connected to the monitor terminal M is provided on the surface of the tuning fork arm 3b, and a fourth electrode 5d connected to the third electrode 4c on the surface of one tuning fork arm 3a is provided on the rear surface (same as in FIG. 8). ).
[0020]
In this embodiment, as shown particularly in FIG. 2, the first and second drive terminals D1 and D2 are connected to the third and fourth electrodes (front and back electrodes) 4 (cd) of one tuning fork arm 3a. The AC voltages V1 and V2 to be applied are centered on the reference voltage E0 and have opposite phases as described above, and here the voltage levels (amplitude levels) are further different.
[0021]
In such a case, first, a large voltage of a half cycle from the drive terminal D1 is applied to the third electrode (front surface electrode) 4c of one tuning fork arm 3a, and a small reverse phase is applied to the fourth electrode (back surface electrode) 4d. When a voltage is applied, as shown in FIG. 3A, the bending amount of the front surface side crystal 1b due to bonding is large, and the bending amount of the back surface side crystal 1a is small. Therefore, since the expansion and contraction amounts of the two crystal pieces 1 (ab) to be bonded differ in the previous half cycle, the tuning fork arm 3a is displaced in an oblique direction with a component biased toward the electrode 4c, for example.
[0022]
Next, when a small voltage of the next half cycle is applied to the third electrode (front surface electrode) 4c of one tuning fork arm 3a, and a large voltage in reverse phase is applied to the fourth electrode (back surface electrode) 4d, As shown in FIG. 3 (b), the amount of bending of the front surface side crystal 1b due to bonding is small, and the amount of bending of the back surface side crystal 1a is large. Therefore, in the next half cycle, for example, a displacement in an oblique direction with a component biased toward the electrode 4d side is performed. From these things, as shown in FIG. 4, it vibrates in an oblique direction in one cycle of the AC voltage.
[0023]
In such a driving method, if alternating voltages of different magnitudes are applied to the drive terminals D1 and D2 so as to cancel out the charge amount due to the oblique vibration of the tuning fork vibrator based on the processing error, the drive terminals D1 and D2 are inclined. The horizontal vibration can be maintained by suppressing the vibration. In short, mechanical oblique vibration can be suppressed electronically. For example, the AC voltage V1 applied to the drive terminal D1 is formed as follows.
[0024]
That is, first, as shown in FIG. 5 (a), an AC voltage V0 having a constant amplitude of tuning fork vibration is generated from the charge amount of the monitor terminal M. Next, an adjustment voltage A0 in which the amplitude level of the AC voltage V0 is reduced is obtained (FIG. 2B). Next, a rectified voltage A1 obtained by inverting the negative side of the adjustment voltage A0 is obtained (FIG. 3C). Finally, the rectified voltage A1 is added to the AC voltage V0 to obtain an asymmetrical AC voltage V1 having a different amplitude between the positive and negative "(d)".
[0025]
The amplitude of the adjustment voltage A0 (rectified voltage A1) is determined according to the oblique vibration. The AC voltage V2 applied to the drive terminal D2 is obtained by shifting the phase of the AC voltage V1 by 180 degrees. From these facts, an angular velocity sensor element that is less affected by unnecessary signals due to processing errors can be obtained. In addition, compared with trimming such as grinding, the time required for electronic control is shortened, so that productivity can be improved.
[0026]
[Second embodiment]
FIG. 6 is a top view showing a connection diagram of the angular velocity sensor element for explaining the driving method of the second embodiment of the present invention. In addition, description of the same part as 1st Example is simplified or abbreviate | omitted.
[0027]
In the first embodiment, an example of a tuning fork type vibrator in which two crystal pieces 1 (ab) are bonded is described. However, in the second embodiment, a tuning fork type consisting of a single (single plate) tuning fork crystal piece is described. It is an example with a vibrator. In this example, one tuning fork arm 3a is used for driving tuning fork vibration, and the other tuning fork arm 3b is used for detecting vertical vibration due to Coriolis force.
[0028]
That is, the reference voltage E0 is applied by commonly connecting both side electrodes of one tuning fork arm 3a. Then, AC voltages V1 and V2 having different magnitudes are applied to the front and back electrodes from the drive terminals D1 and D2. Further, the inner side electrode of the other tuning fork arm 3b is set to, for example, a reference voltage E0 (or ground potential), and charges due to vertical vibration are detected by the sensor terminals S1 and S2 between the divided electrodes provided on the outer side. Note that M provided on the front and back surfaces is a monitor terminal, and charges are detected by tuning fork vibration to make the amplitude constant as described above.
[0029]
In such a configuration, first, due to the half-cycle AC voltage V1> V2, the surface side of one tuning fork arm 3a has a high electric field strength and a large amount of bending, and the back side has a low electric field strength and a small amount of bending. . Then, by the next half-cycle AC voltage V1 <V2, similarly, the amount of bending on the front surface side is small and the back surface side is large. Accordingly, oblique vibration is generated as in the first embodiment. From this, it is possible to electronically cancel and suppress mechanical oblique vibration due to processing errors.
[0030]
【The invention's effect】
According to the present invention, the means for solving the above-described problem (paragraph 0014) is driven by changing the magnitude of the AC voltage applied to both side surfaces from both main surfaces of the tuning fork arm to drive the tuning fork vibration. The electric field from both main surfaces of the tuning fork arm to both sides and the amount of bending on the front side and the back side are also different, and the tuning fork arm generates oblique vibration. This makes it possible to electronically cancel and suppress mechanical oblique vibration caused by machining errors, so that an angular velocity sensor element that is less affected by machining errors and has high productivity can be obtained.
[Brief description of the drawings]
FIG. 1 is a top view showing a connection diagram of an angular velocity sensor element for explaining a driving method of a first embodiment of the present invention.
FIG. 2 is a drive voltage diagram for explaining the first embodiment of the present invention;
FIG. 3 is a top view of one tuning fork arm for explaining the operation of the first embodiment of the present invention.
FIG. 4 is a top view of one tuning fork arm for explaining the operation of the first embodiment of the present invention.
FIG. 5 is a diagram of a method for forming a drive voltage for explaining the first embodiment of the present invention;
FIG. 6 is a top view showing a connection diagram of an angular velocity sensor element for explaining a driving method of a second embodiment of the present invention.
FIG. 7 is a diagram of a tuning fork type angular velocity sensor for explaining a conventional example.
FIG. 8 is a top view showing a connection diagram of an angular velocity sensor element for explaining a conventional example.
FIG. 9 is a drive voltage diagram illustrating a conventional example.
FIG. 10 is a top view of a tuning fork arm for explaining a conventional example.
[Explanation of symbols]
1 tuning fork crystal piece, 2 tuning fork base, 3 tuning fork arm, 4, 5 electrodes.

Claims (4)

On both sides electrodes and reference voltage electrodes provided on four sides of the at least one of the tuning fork arms consisting tuning fork shaped crystal pieces from the surface electrode and the rear electrode on both main surfaces, the surface electrode or the backside electrode of the other tuning fork arm applying an AC voltage based on the monitor voltage by the amplitude of the tuning fork vibration detected, the tuning fork arms of the one and the other as well as tuning fork,
In a driving method of a tuning fork type angular velocity sensor element for detecting charges generated by Coriolis force by sensor electrodes provided on both side surfaces of at least the other tuning fork arm,
The alternating voltage applied to the both side surfaces from the surface electrode is an asymmetric voltage obtained by adding a rectified voltage obtained by reducing the monitor voltage to the monitor voltage,
The alternating voltage applied to the both side surfaces from the back electrode is an asymmetric voltage in which the phase of the asymmetric voltage is different by 180 °,
A driving method of a tuning fork type angular velocity sensor element characterized in that the magnitude of the AC voltage applied to the electrodes on both sides from the front and back electrodes of the tuning fork arm is varied.   The tuning fork angular velocity sensor element is formed by bonding two tuning fork crystal pieces with the ± X axes of crystal axes (XYZ) opposite to each other, and is applied to the electrodes on both sides from the electrodes on both main surfaces of the tuning fork arm. 2. The tuning-fork type angular velocity sensor element according to claim 1, wherein the AC voltages applied are in opposite phases to each other.   2. The tuning fork type angular velocity sensor according to claim 1, wherein the tuning fork type angular velocity sensor element is composed of a single tuning fork crystal piece, and AC voltages applied to electrodes on both side surfaces from electrodes on both main surfaces of the tuning fork arm are in phase with each other. element.   2. The method of driving a tuning fork type angular velocity sensor element according to claim 1, wherein the method of varying the magnitude of the AC voltage is a condition that can cancel or suppress an oblique vibration generated in the tuning fork due to a processing error of the tuning fork.

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