JP2009074826A - Multifunctional tuning fork type vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tuning fork type vibrator capable of detecting an acceleration with a simple constitution in addition to an angular velocity detection function. <P>SOLUTION: This tuning fork type vibrator having a pair of tuning fork arms extended from a tuning fork base part, and equipped with at least a driving electrode for oscillating tuning fork vibration on the tuning fork arm is constituted as follows: the tuning fork base part includes the first base part from which the tuning fork arm is extended and the second base part elongated from the first base part; a notch penetrating in the thickness direction from the outer peripheral side toward the inside along the main surface direction is provided on the second base part; a movable rod is extended from a root part inside the notch; and an acceleration detection function based on a change of each capacity value of the first and second capacitors caused by displacement of the movable rod is provided, having the first and second electrodes on both opposite main surfaces along the main surface direction of the second base part of the movable rod, and having the third and fourth electrodes forming the first and second capacitors oppositely to the first and second electrodes on each inner peripheral surface of the notch facing to both main surfaces of the movable rod. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a tuning fork vibrator that generates at least a tuning fork vibration, and more particularly to a multi-function tuning fork vibrator that has an acceleration detection function in addition to an angular velocity detection function.

(Background of the Invention)
A tuning fork vibrator (so-called angular velocity detection element) having an angular velocity detection function is incorporated in, for example, a guidance device (navigator) such as an automobile or a camera shake prevention device of a camera, and is known as an element that detects angular velocity. In recent years, especially in automobiles, not only an angular velocity detecting element for navigators but also an acceleration detecting element is mounted to distinguish, for example, a highway and a side road.

(Example of conventional technology)
FIG. 4 is a diagram of a tuning fork type vibrator having an angular velocity detecting function for explaining a conventional example. FIG. 4 (a) is an external view of the tuning fork type vibrator (tuning fork crystal piece), and FIG. It is the connection diagram seen from.

  The tuning fork vibrator includes a tuning fork crystal piece 3 having a pair of tuning fork arms 2 (ab) extending in the length direction from the tuning fork base 1 and having a Z-cut, for example. The tuning fork crystal piece 3 is formed by directly joining two crystal pieces 3 (ab) with the X axis ± direction in the crystal axis (XYZ) reversed. The length of the tuning fork crystal piece is the Y axis, the width is the X axis, and the thickness is the Z axis direction.

  The pair of tuning fork arms 2 (ab) of the tuning fork crystal piece 3 have drive electrodes (D ±, D0) and monitor electrodes (M). The drive electrode (D0) also serves as the sensor electrode (S ±) and functions as a reference electrode for the drive electrode (D ±). Hereinafter, the drive electrode (D0) is also referred to as a reference electrode (D0) or a sensor electrode (S ±). Then, from each electrode (D ±, D0, M), a lead-out portion 4 extends to, for example, one main surface of the tuning-fork crystal piece 3, and becomes an electrode pad (not shown) for external connection.

  Of the drive electrodes (D ±), (D−) is formed on one main surface of one tuning fork arm 2a and the other main surface of the other tuning fork arm 2b and connected in common, and (D +) is one tuning fork arm. 2a is formed on the other main surface. The drive electrode (D0) that also serves as the sensor electrode (S ±) is formed on both side surfaces of each tuning fork arm 2 (ab), and is applied with a reference voltage Eo (DC). The inner side surfaces are commonly connected as sensor electrodes (S +) and the outer side surfaces are commonly connected as sensor electrodes (S−). The monitor electrode (M) is formed on one main surface of the other tuning fork arm 2b.

  In such a case, as shown in FIG. 5, inverted and non-inverted signals are applied from the drive circuit 5 to the drive electrode (D ±). Then, the tuning fork vibration is excited by an electric field indicated by an arrow (solid line) generated between the reference electrode (D0) and "FIG. 4 (b)". As a result, an electric field (dotted line) due to tuning fork vibration is generated between the monitor electrode (M) and the reference electrode (D0), and electric charges based on the electric field are amplified by the charge amplifier (op-amp, current / voltage conversion circuit) 6. .

  In this case, the charge (current) from the monitor electrode (M) flows into one input terminal of the charge amplifier 6, and the reference voltage (E0) is applied to the other input terminal. Thereby, a monitor voltage is output. Then, the AGC 7 functions according to the amplitude of the tuning fork vibration (monitor voltage), and a voltage that makes the monitor voltage constant is applied to the drive circuit 5. Reference symbol Rf is a feedback resistor.

The sensor electrode (S ±) generates charges having different signs by vertical vibration perpendicular to the plate surface based on the Coriolis force (angular velocity). These charges having different signs are amplified by a charge amplifier 6 and added by a differential amplifier (synthesizer) 8. The electric charge generated in the sensor electrode (S ±) has the same AC component as the vibration frequency of the tuning fork vibration. Then, it is detected as a direct current component through the synchronous detection circuit 9 and the low-pass filter (LPF) 10.
JP 2004-347398 A Japanese Patent Laying-Open No. 2005-098841

(Problems of conventional technology)
However, although the tuning fork vibrator having the above configuration has an angular velocity detection function by providing the sensor electrode S (±), it does not yet have an acceleration detection function. In this regard, there are many tuning fork vibrators having both angular velocity and acceleration detection functions, but there are no tuning fork vibrators having an acceleration detection function with a simple configuration.

(Object of invention)
An object of the present invention is to provide a tuning fork vibrator capable of detecting acceleration as a simple configuration in addition to an acceleration detection function.

  The present invention is a tuning fork type vibrator having at least two tuning fork arms extending from a tuning fork base and having a drive electrode for exciting at least tuning fork vibrations, as indicated in the claims. The tuning fork base includes a first base extending from the tuning fork arm and a second base extending from the first base. The second base has a thickness direction from the outer peripheral side to the inside along the main surface direction. A through-cut is provided, a movable bar extends from the inner root of the cut, and the first and second main surfaces of the movable bar facing each other along the main surface direction of the second base are first and second. Third and fourth electrodes having electrodes and forming first and second capacitors facing the first and second electrodes on the inner peripheral surfaces of the cuts facing both the main surfaces of the movable rod And the first and second connectors by displacement of the movable rod A structure in which an acceleration detecting function based on the change of the capacitance value of the capacitor.

  With such a configuration, a simple configuration acceleration detection function is provided at the tuning fork base of the tuning fork vibrator. That is, the second base is extended from the conventional tuning fork base (first base) to provide a cut, and the movable rod having the weight is extended from the base of the cut. And the 1st and 2nd capacitor | condenser by between the both main surfaces of a movable rod and each inner peripheral surface of a notch | incision is formed.

  Thereby, when acceleration is applied from the outer peripheral side surface including the bottom surface of the tuning fork base, particularly when acceleration in the orthogonal direction is applied to both main surfaces of the movable rod, the movable rod is displaced according to the acceleration. Thereby, the capacitance values of the first and second capacitors change according to the acceleration. Therefore, by detecting the change in the capacitance value, it is possible to detect the acceleration particularly from both main surface directions of the movable rod.

(Embodiment section)
According to a second aspect of the present invention, in the first aspect, the tuning fork arm is provided with a sensor electrode for detecting an angular velocity due to a Coriolis force. Thereby, both angular velocity and acceleration can be detected by a single tuning fork vibrator.

  In the third aspect of the present invention, in the first aspect, the notch has a wide portion on the outer peripheral side of the second tuning fork base portion, a narrow portion on the inside of the second base portion, and a weight portion on the distal end side of the movable rod. . Thereby, the displacement of the front end side is facilitated by the wide portion, and the detection sensitivity to the acceleration can be enhanced by the weight portion.

  In the fourth aspect of the present invention, in the third aspect, the weight portion is wide corresponding to the wide portion. Thereby, the front end side of a movable rod can be made into a weight part easily.

  In the fifth aspect of the present invention, in the third or fourth aspect, the weight portion is provided in the wide portion. Thereby, since the movable bar is in the second base, the tuning fork vibrator can be kept small.

  In the sixth aspect of the present invention, in the first aspect, the cut is provided in a width direction or a height direction of the second base portion. Thereby, in particular, acceleration in a direction orthogonal to the width direction and the height direction can be detected.

  According to the seventh aspect, in the first aspect, the second base portion extends below the first base portion, and at least a lower end portion of the first base portion, which is a boundary region with the second base portion, is a fixing portion. Accordingly, since the lower end portion of the first base portion is a fixed portion, the acceleration detection mechanism can be substantially separated from the tuning fork vibrator, and the characteristics of the tuning fork vibrator can be maintained as they are.

  FIG. 1 is a diagram of a tuning fork vibrator for explaining an embodiment of the present invention. FIG. 1 (a) is an overview and FIG. 1 (b) is an enlarged view of a dotted frame. 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.

  As described above, the tuning fork vibrator “refer to FIG. 3 and FIG. 4” is formed by directly joining two tuning fork crystal pieces with the X-axis direction reversed, and a pair of tuning fork arms 2 ( ab) includes drive electrodes (D ±, D0), sensor electrodes (S ±), and monitor electrodes (M). Inverted and non-inverted signals are applied to the drive electrode (D ±) from the drive circuit 5, and the tuning fork vibration is excited by an electric field indicated by an arrow (solid line) generated between the drive electrode (D ±) and the reference electrode (D0).

  As a result, an electric field (dotted line) due to tuning fork vibration is generated between the monitor electrode (M) and the reference electrode (D0), and the charge based on this is amplified by the charge amplifier (op amp, current / voltage conversion circuit) 6. As described above, the monitor voltage is output. Then, the AGC 7 functions in accordance with the amplitude of the tuning fork vibration (monitor voltage) to keep the monitor voltage constant.

  On the sensor electrode (S ±), charges having different signs are generated by vertical vibration perpendicular to the plate surface based on Coriolis force (angular velocity). Then, it is amplified by the charge amplifier 5, added by the differential amplifier (synthesizer) 8, and detected as a DC component through the synchronous detection circuit 9 and the low-pass filter (LPF) 10.

  In this embodiment, the tuning fork base 1 includes a first base 1a and a second base 1b. The first base 1a corresponds to a conventional tuning fork base, and a pair of tuning fork arms 2 (ab) extend, and the second base 1b extends below the first base 1a. Let the lower end side of the 1st base 1a used as the boundary with the 2nd base 1b be a fixing part by an adhesive agent etc. In the width direction that is the X-axis of the second base portion 1b, a cut 11 is provided from the outer peripheral side (side surface on one end side) toward the inside.

  The notch 11 is formed into a squirrel shape that gradually narrows with the outer peripheral side being wide, and is narrow with a constant interval inside. Then, a movable rod 12 integrated with the second base portion 1b extends from the root portion inside the cut 11. The movable rod 12 extends from the root portion to the outer peripheral side with a narrow width, and has a triangular weight portion 12a corresponding to a wide sliver shape on the tip side.

  Both main surfaces of the narrow portion 12b inside the movable rod 12 have the first and second electrodes 13 (ab), and the third and fourth electrodes 13 are formed on the inner peripheral surfaces of the cuts 11 facing these. (Cd). Thus, the first and third electrodes 13 (ac) facing each other form a first capacitor C1, and the second and fourth electrodes 13 (bd) form a second capacitor C2. The first and second electrodes 13 (ab) on both main surfaces of the movable rod 12 are connected in common, and an electrode pad (not shown) on one main surface of the second base 1b together with the third and fourth electrodes 13 (cd). To extend.

  In such a case, as shown in FIG. 2, an AC voltage Vd based on, for example, tuning fork vibration is applied to the common connection point of the first and second electrodes 13 (ab) of the first and second capacitors C1, C2. Applied. The third and fourth electrodes 13 (cd) of the first and second capacitors C1 and C2 have first and second operational amplifiers (charge amplifiers) 6 (ab) having feedback resistors Rf as current-voltage converters. ) Connect.

  The first and second operational amplifiers 6 (ab) detect signals flowing through the first and second capacitors C1 and C2 due to the AC voltage Vd. Then, the outputs Vc1 and Vc2 of the first and second operational amplifiers 6 (ab) are combined by a differential amplifier 14 indicated by a dotted frame. The differential amplifier 14 is formed by the third operational amplifier 6c and each resistor R, and obtains a combined output Vc3. The synthesized output Vc3 is synchronously detected by a synchronization signal based on the AC voltage Vd, and a detection voltage Vsa corresponding to the acceleration converted to DC by being smoothed by the LPF 10 by an integration circuit or the like is obtained. Reference numeral 9 denotes a synchronous detection circuit.

  Accordingly, when the capacitance values of the first and second capacitors C1 and C2 are equal, the combined output Vc3 becomes substantially zero by the common-mode component removing function of the differential amplifier 14. When acceleration is applied and the first capacitors C1 and C2 become unbalanced, a signal is generated in the composite voltage Vc3. If the direction of acceleration is reversed, the phase of the composite output Vc3 is also reversed. Therefore, the magnitude and direction of acceleration can be detected.

  With such a configuration, the second base 1b is provided on the first base 1a corresponding to the conventional tuning fork base 1 of the tuning fork vibrator having the angular velocity detection function, and the first and second capacitors C1 and C2 are provided. An acceleration detection function can be obtained simply by forming the cut 11 and the movable rod 12 to be formed. Therefore, in addition to the angular velocity detection function, an acceleration detection function having a simple configuration can be obtained.

  Further, the notch 11 has a wide portion on the outer peripheral side of the second tuning fork base portion 1b, a narrow portion on the inside of the second base portion 1b, and a weight portion 12a corresponding to the wide portion on the distal end side of the movable rod 12. In this case, the weight 12a on the tip side facilitates the displacement of the movable rod 12 in the vertical direction, as indicated by the arrow.

  Thereby, the detection sensitivity with respect to acceleration can be improved by the weight part 12a. And the weight part 12a can be simply provided only by making the front end side of the movable rod 12 wide. Further, in this example, since the weight portion 12a is within the wide portion of the notch 11, the size of the tuning fork base 1 can be reduced by simply increasing the length (height) of the tuning fork base 1 while maintaining the width of the tuning fork vibrator as in the prior art. Can be planned.

  And since the notch | incision 11 here is provided in the width direction of the said 2nd base 1b, especially the acceleration of the height direction orthogonal to the width direction is detectable. Therefore, in the case of an automobile installed with the tuning fork main surface set in a direction perpendicular to the traveling direction, it is possible to detect the acceleration in the vertical direction and detect, for example, getting on and off the expressway.

  Further, since at least the lower end portion of the first base portion 1a that is a boundary region with the second base portion 1b is a fixed portion, the acceleration detection mechanism is substantially separated from the tuning fork vibrator. Accordingly, there is no buffering between the angular velocity detection function and the acceleration detection function, and a tuning fork vibrator that functions independently and detects the angular velocity and acceleration with high accuracy can be obtained.

(Other matters)
In the above embodiment, the cut 11 and the movable rod 12 are provided in the width direction of the second base 1b, but these may be provided from the bottom surface of the second base 1b toward the inside. In this case, acceleration in the width direction can be detected to sense, for example, a side shake of the car. In short, the notch 11 and the movable rod 12 are formed from the outer peripheral side to the inside along the direction of the main surface of the second base, and in particular, acceleration in a direction orthogonal to these can be detected.

  Moreover, although the movable rod 12 is in the plate surface of the second base portion 1b, it may protrude from the outer peripheral side surface of the second base portion 1b. In this case, since the movable rod 12 becomes longer, the displacement with respect to acceleration also increases, and the detection sensitivity can be increased. However, in order to maintain the miniaturization, it is better to place the second base portion 1b on the plate surface as in this embodiment.

  In addition, the wide weight portion 12a is provided on the distal end side of the movable rod 12. However, as shown in FIG. 3, for example, as the notch 11 that gradually spreads from the root portion of the second base portion 1b, the cut portion 11 is gradually increased accordingly. The movable rod 12 spreads out. Even in this case, the same effect as the provision of the weight portion 12a on the tip side can be obtained.

  Then, for example, the first to fourth electrodes 13 (abcd) are provided on both the main surfaces of the movable rod 1 and the opposing surfaces. In this case, since the facing area of the electrodes 13 (ac) and 13 (bd) is increased, the detection sensitivity is further increased. In addition, it does not necessarily need to be the weight part 12a and the structure corresponding to this, but it basically operates even if there is no weight part with the movable rod 12 having the same width.

  Although the tuning fork type vibrator has been described as a junction type composed of two crystal pieces 3 (ab), the present invention can be similarly applied even when the tuning fork type crystal vibrator is formed from a single crystal piece. However, in this case, the arrangement structure of the sensor electrodes S ± is particularly different. Furthermore, the present invention can be applied to a tuning fork type crystal resonator having an existing angular velocity detection function or a tuning fork type resonator that generates a simple tuning fork vibration.

  In addition, the tuning fork vibrator has been described using quartz as a material. However, the tuning fork vibrator can be applied even when other materials such as silicon are used. Further, although a pair of tuning fork arms (two) is used, the present invention can be applied to a case where three or more tuning fork arms are used.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the tuning fork type | formula vibrator explaining one Embodiment of this invention, The figure (a) is a general-view figure, The figure (b) is an enlarged view of a dotted-line frame part. It is a schematic circuit diagram of the acceleration detection function explaining one Embodiment of this invention. FIG. 5 is a partially enlarged front view of a tuning fork vibrator (second base) for explaining another example of the present invention. FIG. 2 is a diagram of a tuning fork type vibrator having an angular velocity detecting function for explaining the prior art. FIG. 1A is an external view of the tuning fork type vibrator (tuning fork crystal piece), and FIG. is there. It is a schematic circuit diagram of an angular velocity detection function for explaining a conventional example.

Explanation of symbols

  1 tuning fork base, 2 tuning fork arm, 3 tuning fork crystal piece (tuning fork type vibrator), 5 drive circuit, 6 operational amplifier, 7 AGC, 8 differential amplifier, 9 synchronous detection circuit, 10 low pass filter, 11 cut, 12 movable bar , 13 electrodes.

Claims (7)

  A tuning fork type vibrator having at least two tuning fork arms extending from a tuning fork base and having a drive electrode for exciting at least tuning fork vibration on the tuning fork arm, wherein the tuning fork base extends from the first tuning fork arm. It comprises a base and a second base extending from the first base, and the second base is provided with a notch penetrating in the thickness direction from the outer peripheral side to the inside along the main surface direction, and the inner root of the notch A movable rod extends from the portion, and both the main surfaces of the movable rod facing each other along the main surface direction of the second base have first and second electrodes, and are opposed to both the main surfaces of the movable rod. Each of the inner peripheral surfaces of the cut has third and fourth electrodes that form first and second capacitors facing the first and second electrodes, and the first and second electrodes are displaced by displacement of the movable rod. Acceleration detector based on change in capacitance value of second capacitor The multifunctional fork vibrator that is characterized by providing.   The multi-function tuning fork vibrator according to claim 1, wherein the tuning fork arm includes a sensor electrode that detects an angular velocity due to Coriolis force.   2. The multi-function tuning fork type according to claim 1, wherein the incision has a wide portion on the outer peripheral side of the second tuning fork base and a narrow portion on the inside of the second base, and a weight on the tip side of the movable rod. Vibrator.   4. The multifunctional tuning fork vibrator according to claim 3, wherein the weight portion is wide corresponding to the wide portion.   5. The multifunctional tuning fork vibrator according to claim 3, wherein the weight portion is provided in the wide portion.   2. The multifunctional tuning fork vibrator according to claim 1, wherein the cut is provided in a width direction or a height direction of the second base portion.   The multifunctional tuning fork type vibration according to claim 1, wherein the second base portion extends below the first base portion, and at least a lower end portion of the first base portion which is a boundary region with the second base portion is a fixed portion. Child.

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