JP2008139054A - Angular velocity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angular velocity sensor capable of detecting precisely an angular velocity, even when an angle of a detection axis of the angular velocity sensor to an actual rotation applied axis is great, without inclining a piezoelectric oscillator to be fixed. <P>SOLUTION: This angular velocity sensor using vibration of a piezoelectric oscillation piece has the first axis for detecting the angular velocity and the second axis set along a direction orthogonal to the first axis, and a detection sensitivity of the second axis is 15-55% of detection sensitivity of the first axis. Sensitivity correction of 15% or less is enough in attaching wherein an angle of the detection axis of the angular velocity sensor to the actual rotation applied axis is up to 40°, and an output sensitivity caused by the attaching angle can be corrected by computation processing based on a software. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an angular velocity sensor, and more particularly to an angular velocity sensor having two angular velocity detection axes.

In recent years, navigation devices that detect the position of a vehicle using GPS (Global Positioning System) and assist the movement of the vehicle to a destination or the like are widely used. In this navigation device, a method of autonomously measuring the moving direction of the vehicle from the reference point is used, and the moving direction is obtained by detecting an angular velocity applied to the vehicle by an angular velocity sensor provided in the navigation device.
Usually, the navigation device is attached to a vehicle by being installed in an indoor center console. For example, as shown in FIG. 11, a navigation device 101 is mounted in a center console in the vehicle 100. At this time, in order to improve the visibility of the navigation device 101 and the operability of the operation unit, the navigation device 101 is mounted so that the operation panel surface faces upward. In this case, the navigation device 101 is attached at an angle of θ ° from the direction perpendicular to the ground plane of the vehicle.
In a state in which the navigation device 101 is attached to the vehicle 100, as shown in FIG. 12, the angular velocity sensor 104 provided in the navigation device has an angle θ from the axis 108 perpendicular to the ground contact surface of the vehicle on the circuit board 105. ° tilted. An axis 108 is a rotation axis when the vehicle rotates, and does not coincide with the angular velocity detection axis (Z axis) 109 of the sensor element 106 incorporated in the angular velocity sensor 104, and is held in a state having an inclination of θ °. Has been. As described above, the conventional angular velocity sensor 104 has one rotation detection axis, and generally does not detect rotation about an axis in a direction orthogonal to the detection axis.

The angular velocity sensor 104 has a characteristic that the output sensitivity decreases as the tilt angle θ increases, and it is desirable to use the tilt angle θ as small as possible. Further, in the navigation device, it is possible to correct the output sensitivity due to the mounting angle by a calculation process based on software, but when the reduced output sensitivity is amplified by correction, the noise contained in it is also amplified, There is a problem that the accuracy deteriorates, and the tilt angle that can be corrected is limited to 30 ° (± 15% sensitivity change).
In order to solve these problems, there has been proposed an angular velocity sensor in which a sensor element (piezoelectric vibrator) incorporated in an angular velocity sensor is attached with an inclination corresponding to the attachment angle in advance (Patent Document 1,). 2).

JP 2005-331448 A JP 2003-227844 A

However, navigation devices that are less frequently operated than audio devices and the like are often attached to the lower part of the center console, and the attachment angle θ may be about 30 ° to 40 °.
In this case, it is not preferable in terms of accuracy to correct the output sensitivity due to the mounting angle by a calculation process based on software, and tilting and fixing the sensor element (piezoelectric vibrator) increases the size of the package. There are problems such as. The present invention has been made in order to solve the above-mentioned problems, and its purpose is to increase the angle between the detection axis of the angular velocity sensor and the axis to which the actual rotation is applied without tilting and fixing the sensor element. Another object of the present invention is to provide an angular velocity sensor capable of detecting an angular velocity with high accuracy.

  In order to solve the above-described problems, the present invention provides an angular velocity sensor that uses vibration of a piezoelectric vibrator, and includes a first axis that detects angular velocity and a second axis that is set in a direction orthogonal to the first axis. And the detection sensitivity of the second axis is 15 to 55% with respect to the detection sensitivity of the first axis.

  According to this configuration, the angular velocity sensor is provided in the navigation device or the like, and even if the angular velocity sensor is tilted up to 40 ° by being attached in a tilted state, the first axis and the second axis that detect the angular velocity are detected. By detecting and using this output, it is possible to cope with a sensitivity change of ± 15%, which is a sensitivity that enables correction by software. An accurate angular velocity sensor can be obtained by this correction.

  The angular velocity sensor of the present invention is characterized in that the angular velocity sensitivity output is Q, the angle between the first axis and the direction of the rotation axis is θ, and the sensitivity ratio of the sensitivity change due to the angle between the first axis and the rotation axis. The sensitivity output is calculated by the equation of Q = A cos θ + B sin θ, where A is the sensitivity ratio of the sensitivity change due to the angle between the second axis and the rotation axis.

According to this angular velocity sensor, the sensitivity output from the first axis and the second axis for detecting the angular velocity is converted into the component force with respect to the axis to which the rotation is applied and added to obtain the sensitivity output on the axis to which the rotation is applied. be able to.
Here, when the detection axis in the angular velocity sensor is inclined with respect to the axis on which the actual rotation is applied, the sensitivity output is reduced, and the sensitivity ratios A and B depending on the inclination angle are determined.

  In the angular velocity sensor according to the present invention, the piezoelectric vibrating piece extends from the base and the connecting arm connected to the base or the base to be parallel to the second axis and is orthogonal to the first axis and the second axis. And a detection arm parallel to the drive arm extending from the base, and detecting the angular velocity of the first axis in the detection arm is detection of flexural vibration, The detection of the angular velocity of the second axis in the detection arm is detection of torsional vibration.

  In this so-called WT type angular velocity sensor, the vibration component of the first axis is flexural vibration, the vibration component of the second axis orthogonal to the first axis is torsional vibration, and the respective vibration modes are different. Angular velocity can be detected with minimal signal influence.

  In the angular velocity sensor according to the present invention, the piezoelectric vibrating piece includes two vibrating arm portions that extend in parallel to the second axis, and two double tuning fork support portions that respectively support both ends of the vibrating arm portion. And two support fixing portions disposed in the vicinity of the double tuning fork support portion, and two extending between the support fixing portion and the double tuning fork support portion and extending parallel to the second axis. And detecting the angular velocity of the first axis is detection of bending vibration in the direction perpendicular to the first axis direction and the second axis of the detection unit, and detecting the angular velocity of the second axis. The detection is a detection of a bending vibration in the first axial direction of the double tuning fork support part.

In this so-called double tuning fork type angular velocity sensor, detection of the vibration component of the first axis is detection of bending vibration of the detection unit, and detection of the vibration component of the second axis is detection of bending vibration of the double tuning fork support unit. . Further, the directions of these bending vibrations vibrate in directions orthogonal to each other.
As described above, the angular velocity sensor according to the present invention has different detection units for detecting the angular velocity, and the directions of the bending vibrations are different. Therefore, the angular velocity can be detected while minimizing the influence of the mutual detection signals.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings.
(First embodiment)

  FIG. 1 is a perspective view showing the structure of an angular velocity sensor according to an embodiment of the present invention. In FIG. 1, an angular velocity sensor 1 according to this embodiment includes a piezoelectric vibrating piece 10, a detection circuit (not shown) as detection means, and an oscillation circuit as excitation means. The piezoelectric vibrating piece 10 can be formed of a known piezoelectric material, but in the present embodiment, a quartz vibrating piece is exemplified.

In the present embodiment, the piezoelectric vibrating piece 10 is made of quartz and is cut out into a plane including an X axis and a Y axis among an X axis called an electric axis, a Y axis called a mechanical axis, and a Z axis called an optical axis. It is formed of a cut quartz substrate.
The planar shape of the piezoelectric vibrating piece 10 is developed on the XY plane in accordance with the crystal axis of the crystal, and is 180 ° point-symmetric with respect to the gravity center position G.

The piezoelectric vibrating piece 10 has a rectangular base 20 having end faces parallel to the X-axis direction and the Y-axis direction, respectively, and extends in parallel to the X-axis from the center of the two end faces parallel to the Y-axis of the base 20. The pair of drive arms 40 and 50 parallel to the Y axis from the distal ends of the first connecting arm 31 and the second connecting arm 32 and the center of the two end faces parallel to the X axis of the base 20 are parallel to the Y axis. A detection arm 60 extending on a straight line is formed.
The drive arm 40 includes a first connecting arm 31 extending from the end face of the base portion 20 in the X-axis direction, and two driving arms 40 extending in the Y-axis direction and the minus Y-axis direction perpendicular to the first connecting arm 31. The vibration parts 41 and 42 are comprised. Similarly, the drive arm 50 includes two vibrating portions 51 and 52 that are orthogonal to the second connecting arm 32 extending in the minus X-axis direction from the base portion 20 and extend in the Y-axis direction and the minus Y-axis direction. Has been.

At the tips of the vibration parts 41, 42, 51, 52, substantially square weight parts 43, 44, 53, 54 wider than the respective vibration parts are formed.
The detection arm 60 includes detection arm portions 61 and 62 extending from the two end portions of the base portion 20 on the straight lines in the Y-axis direction and the negative Y-axis direction, and each of the detection arm portions 61 and 62 formed at the tips of the detection arm portions 61 and 62. It is composed of substantially rectangular weight parts 63 and 64 that are wider than the detection arm part.
The reason why the weight portions 63 and 64 are provided in this way is to efficiently generate torsional vibration of the detection arm 60 in the angular velocity detection of the Y-axis rotation system described later.

A concave groove 45, 46, 55, 56, 65, 66 is formed in the thickness direction at the center in the width direction of each of the vibration parts 41, 42, 51, 52 and the detection arm parts 61, 62.
The weights 43, 44, 53, 54, 63, 64 and the grooves 45, 46, 55, 56, 65, 66 are provided to reduce the size of the piezoelectric vibrating piece 10. The invention is not particularly limited.

The drive arms 40 and 50 have the widths and lengths of the vibration parts 41, 42, 51, and 52, the dimensions of the weight parts 43, 44, 53, and the grooves 45 and 46 so that the drive vibration of a predetermined frequency is generated. , 55 and 56 are set. In addition, the width and length of the detection arm portions 61 and 62, the dimensions of the weight portions 63 and 64, and the dimensions of the grooves 65 and 66 are set in the detection arm 60 so that predetermined detection vibration is generated.
The piezoelectric vibrating piece 10 having the shape as described above is generally called a WT type piezoelectric vibrating piece and is advantageous for downsizing and high accuracy. The width of the detection arm portions 61 and 62 and the weight portion 63, Except for the relationship with the width of 64, the configuration is the same as that of the WT type (double T type) piezoelectric vibrating piece already proposed.

  The drive arms 40 and 50 and the detection arm 60 are formed with drive electrodes and detection electrodes (not shown), respectively. These drive electrodes and detection electrodes are connected from the back surface of the base 20 to a detection circuit and an oscillation circuit (not shown). The base 20 is connected to and supported by the substrate via leads or bonding wires. The substrate is fixed inside the package. With such a configuration, when an external impact is applied, the lead or the bonding wire absorbs the impact, so that the generation of noise can be suppressed. Alternatively, the drive electrode and the detection electrode may be electrically connected to the drive circuit or the detection circuit via a lead or a bonding wire. The detection circuit and the oscillation circuit have the same configuration as that adopted in the conventional WT type angular velocity sensor. Further, each drive electrode and detection electrode are formed symmetrically with respect to the gravity center position G by 180 °.

Next, the vibration mode of the Z-axis rotation system and the rotation system around the Y-axis (hereinafter sometimes simply referred to as the Y-axis rotation system), which is the operation of the piezoelectric vibrating piece 10 of the present embodiment described above, will be described.
FIG. 2 is an explanatory view schematically showing a drive mode (state in which rotation is not applied) of the piezoelectric vibrating piece of the present embodiment, and FIG. 3 is an explanatory view schematically showing a Z-axis detection mode. 2 and 3, the drive arms 40 and 50 and the detection arm 60 are simplified and represented by lines in order to easily express the vibration form. The same components as those in FIG. 1 are denoted by the same reference numerals, and the description of the structure is omitted.

  First, the drive mode (vibration mode when no rotational acceleration is applied) of the piezoelectric vibrating piece 10 will be described. In FIG. 2, the drive vibration is a bending vibration indicated by an arrow A of the vibration parts 41, 42, 51, 52, and a vibration state indicated by a solid line and a vibration state indicated by a two-dot chain line are repeated at a predetermined frequency. . At this time, the balance between the vibrating portions 41 and 42 and the vibrating portions 51 and 52 is adjusted, and vibration is performed in line symmetry with respect to the Y axis passing through the gravity center position G. Therefore, the base portion 20, the first connecting arm 31, The second connecting arm 32 and the detection arm portions 61 and 62 hardly vibrate.

Next, the detection mode when the rotational angular velocity ω around the Z axis is applied will be described. In FIG. 3, in the Z-axis rotation system, the detected vibration repeats a vibration state indicated by a solid line and a vibration state indicated by a two-dot chain line. The detected vibration is applied to the drive arms 40 and 50 when a rotational angular velocity ω about the Z-axis is applied to the piezoelectric vibrating piece 10 in a state where the piezoelectric vibrating piece 10 performs the driving vibration (bending vibration) shown in FIG. It is generated by the Coriolis force in the direction indicated by arrow B.
Due to the Coriolis force in the direction of arrow B, the driving arms 40 and 50 vibrate in the circumferential direction with respect to the gravity center position G. At the same time, as shown by an arrow C, the detection arm portions 61 and 62 perform bending vibration in the direction opposite to the arrow B in response to the vibration of the arrow B.

The drive electrode and the detection electrode formed on the piezoelectric vibrating piece 10 are electrically connected to the detection circuit and the oscillation circuit (both mounted on the semiconductor device) via the connection electrode formed on the base 20. (Both not shown). As a result, the piezoelectric vibrating piece 10 bends and vibrates by the oscillation circuit, and outputs a detection signal corresponding to the angular velocity from the detection arm 60 to the detection circuit. Then, an electrical signal corresponding to the angular velocity is output by the semiconductor device.
In the Z axis rotation system, the detection sensitivity of the Y axis rotation system or the X axis rotation system perpendicular to the Z axis can be ignored.

Next, the Y axis detection mode will be described with reference to the drawings.
4 to 6 show vibration modes of the Y-axis rotation system, FIG. 4 is a perspective view, and FIGS. 5 and 6 are upper side views showing a state viewed from above (in the direction of arrow A) in FIG. When a rotational angular velocity ω is applied around the Y axis in a state in which the drive arms 40 and 50 are flexurally vibrated, the drive arms 40 and 50 cause the flexural vibration in the X direction and the Z direction by the Coriolis force as shown in FIG. Vibrates in a vibration mode that combines axial bending vibrations.
In other words, due to the Coriolis force, the driving arm 40 bends and vibrates in the Z direction with the first connecting arm 31 as the axis of vibration and the driving arm 50 has the second connecting arm 32 in the opposite phase with respect to the axis of vibration. To do. Then, torsional vibration in the direction of arrow T is generated in the detection arm 60. By detecting this torsional vibration, a detection signal corresponding to the angular velocity is output to the detection circuit. Then, an electrical signal corresponding to the angular velocity is output by the semiconductor device.

  The relationship between Coriolis force and torsional vibration (detected vibration) in the Y-axis rotation system will be described in more detail with reference to FIGS. FIG. 5 illustrates a case where the driving arms 40 and 50 vibrate in the outer direction (indicated by an arrow + V in the drawing). The driving arm 40 is moved in the + Z direction by the Coriolis force F, and the driving arm 50 is moved in the −Z direction. Transforms into Then, the detection arm 60 is twisted and deformed in a direction (+ T direction) to cancel the Coriolis force F.

FIG. 6 illustrates a case where the driving arms 40 and 50 vibrate in the inner direction (indicated by an arrow −V in the figure). The driving arm 40 is moved in the −Z direction by the Coriolis force F, and the driving arm 50 is + Z. Vibration deformation in the direction. Then, the detection arm 60 is twisted and deformed in a direction (-T direction) to cancel the Coriolis force F.
In this way, the detection arm 60 repeats torsional vibrations as shown in FIGS. 5 and 6 due to the Coriolis force F, and outputs a detection signal to detect the angular velocity of the Y-axis rotation system.
In the case of the X-axis rotating system, no detection signal is output to the detection arm 60 because no Coriolis force is generated.

As described above, the bending vibration in the X-axis direction of the detection arm 60 can be detected as a detection signal for the Z-axis rotation system, and the torsional vibration of the detection arm 60 can be detected as a detection signal for the Y-axis rotation system. Can do.
Note that the detection arm on the Y-axis (+ Y-axis) side and the detection arm on the negative Y-axis side are visually oscillated in the opposite directions when viewed from the base 20. Therefore, each detection arm outputs a detection signal having an antiphase, and by synthesizing this detection signal, the output becomes twice the output from one detection arm, and the detection sensitivity is increased.

When the navigation apparatus including the angular velocity sensor 1 as described above is mounted on the vehicle as described above with reference to FIG. 11, the angular velocity sensor is perpendicular to the ground plane of the vehicle on the circuit board as shown in FIG. Is inclined from the axis 108 by an angle θ °.
When rotation is applied to the vehicle in this state, angular velocities are detected on the respective axes as shown in FIG.
Shaft 108 in the vertical direction with respect to the ground surface of the vehicle but is angular velocity omega occurs and the rotation shaft of the vehicle, the angular velocity sensor because the inclined theta ° from the axis 108, the angular velocity omega _Z, is omega _Y applied to the Z-axis and Y-axis In this way, the Z axis sensitivity output Q _Z and the Y axis sensitivity output Q _Y are detected. Then, sensitivity outputs Q1 and Q2 are obtained by decomposing the Z axis sensitivity output Q _Z and the Y axis sensitivity output Q _{Y in} the direction of the axis 108, and the sum of the sensitivity outputs Q1 and Q2 is applied to the axis 108. Output Q. This can be expressed by the following formula (1).
Q = Q1 + Q2 = A cos θ + B sin θ (1)
Here, A and B are sensitivity ratios representing a sensitivity change by an inclination angle between an angular velocity detection axis (Z axis, Y axis) of the angular velocity sensor and an axis (rotation axis) to which rotation is actually applied.

In this embodiment, the Y-axis detection sensitivity is referred to as other-axis sensitivity with respect to the Z-axis detection sensitivity, and the other-axis sensitivity is set within a range of 15 to 55%.
FIG. 8 shows that the sensitivity output when the tilt angle between the Z axis and the actual rotation axis is 0 ° is 100%, and the relative output when the other axis sensitivity is 0, 15, 35, and 55% when the tilt angle is 0 to 90 °. It is the graph which showed the sensitivity. As can be seen from this graph, when the other-axis sensitivity is 0%, that is, when the detection axis is only the Z-axis, the relative sensitivity decreases as the tilt angle increases, and calculation based on software at a tilt angle of 30 °. The relative sensitivity, which is the limit of correction by processing, exceeds 85%, and the relative sensitivity decreases to approximately 77% at an inclination angle of 40 °.
On the other hand, when the other-axis sensitivity is 15%, the relative sensitivity decreases as the tilt angle increases, but the relative sensitivity is 85% at the tilt angle of 40 °.
When the other-axis sensitivity is 55%, the relative sensitivity increases as the tilt angle increases until the tilt angle reaches approximately 30 °, and the value indicates approximately 115%. And it has a relative sensitivity of about 112% at an inclination angle of 40 °.
Further, the relative sensitivity once increases to about 106% at the other axis sensitivity of 35%, but has a relative sensitivity of 100% at an inclination angle of 40 °.

Thus, when the other-axis sensitivity is within a range of 15% to 55%, the relative sensitivity fluctuation, which is a range that can be corrected by a calculation process based on software, is within ± 15%, and the inclination angle is 0 to 40. Soft correction between ° is possible.
The other axis sensitivity is adjusted by adjusting the detuning frequency in the Y axis detection vibration. Adjusting the detection frequency away from the drive frequency is referred to as detuning, and has a characteristic that the sensitivity decreases as the detection frequency moves away from the drive frequency. By utilizing this fact, it is possible to adjust the other axis sensitivity by selecting the detuning frequency.
For example, when the piezoelectric vibrating piece is 2 mm in the Y-axis direction and 1.9 mm in the X-axis direction and the other-axis sensitivity is 15%, the driving frequency is 53 kHz, the Z-axis detuning frequency is 1000 Hz, and the Y-axis detuning frequency is 1500 Hz. Further, when the other-axis sensitivity is 35%, the driving frequency is 53 kHz, the Z-axis detuning frequency is 1000 Hz, and the Y-axis detuning frequency is 700 Hz. Further, when the other-axis sensitivity is 55%, the driving frequency is 53 kHz, the Z-axis detuning frequency is 1000 Hz, and the Y-axis detuning frequency is 400 Hz.

The detuning frequency adjustment of the Y-axis rotation system is performed by adding or removing mass in the weight parts 63 and 64 (see FIG. 1). Here, an example of removing mass will be described.
Au layers are formed in advance on both the front and back surfaces of the weight parts 63 and 64. This Au layer has an additional mass, and this Au layer is removed using a laser so as to have a predetermined detuning frequency.
At this time, the weights 63 and 64 are removed linearly in the longitudinal direction from the outer end or inner end in the width direction and gradually removed toward the inner end. As described above, since the detection of the Y-axis rotation system detects the torsional vibration component, the detuning frequency can be adjusted efficiently by removing the mass from the outside in the width direction of the weight part that easily affects the torsional vibration.

Further, when the detuning frequency is adjusted by removing the mass of the weights 63 and 64, the Au layer is formed so that the detected detuning frequency is in the minus direction with respect to the target frequency.
On the other hand, the detailed description of the adjustment of the detected detuning frequency by adding mass is omitted, but it is possible by applying the above-described concept of mass removal. That is, the Y-axis detuning frequency may be set to the plus side in advance, and mass may be added to the weights 63 and 64 by sputtering or vapor deposition.

As described above, in the so-called WT type angular velocity sensor 1, the angular velocity sensor 1 is provided in a navigation device or the like, and the angular velocity sensor 1 is detected even when the angular velocity sensor 1 is tilted by attaching the device in an inclined state. The angular velocity applied to the actual rotation axis can be detected using the output from the axis and the Y axis. At this time, by setting the Y-axis detection sensitivity to 15 to 55% with respect to the Z-axis detection sensitivity of the angular velocity sensor 1, the fluctuation of the relative sensitivity is suppressed within ± 15% until the tilt angle is 40 °. It is possible to correct the output sensitivity resulting from the mounting angle by a calculation process based on software. Further, in the angular velocity sensor 1, the Z-axis vibration component is flexural vibration, and the Y-axis vibration component orthogonal to the Z-axis is torsional vibration, and the respective vibration modes are different. The angular velocity can be detected.
(Second Embodiment)

Next, another angular velocity sensor having two detection axes will be described.
9A and 9B are configuration diagrams showing the structure of another angular velocity sensor according to the embodiment of the present invention. FIG. 9A is a plan view, and FIG. 9B is a side view of FIG.
In FIG. 9, the angular velocity sensor 2 of the present embodiment includes a piezoelectric vibrating piece 70, a detection circuit (not shown) as detection means, and an oscillation circuit as excitation means. The piezoelectric vibrating piece 70 can be formed of a known piezoelectric material, but in this embodiment, a quartz vibrating piece is exemplified.

The piezoelectric vibrating piece 70 is formed in a double tuning fork shape by a Z-cut quartz substrate. The piezoelectric vibrating piece 70 has a pair of vibrating arm portions 71a and 71b formed extending in the Y-axis direction, double tuning fork support portions 72a and 72b supported at both ends of the vibrating arm portions 71a and 71b, and a double tuning fork. Detection parts 73a and 73b that are connected to the support parts 72a and 72b and detect vibrations of the vibrating arm parts 71a and 71b, and support fixing parts 74a that support one ends of the detection parts 73a and 73b and are fixed to the pedestal with an adhesive or the like. , 74b.
A drive electrode and a second detection electrode (not shown) are formed on the vibrating arm portions 71a and 71b, and a first detection electrode is formed on the detection portions 73a and 73b. These drive electrodes and detection electrodes are pulled out to the support fixing portions 74a and 74b and connected to an oscillation circuit and a detection circuit (not shown).

The operation of such a piezoelectric vibrating piece 70 will be described.
FIG. 10 is an explanatory view schematically showing each vibration mode (drive mode, Z-axis detection mode, Y-axis detection mode) of the piezoelectric vibrating piece, and shows a plan view and a side view in each vibration mode.
FIG. 10A shows the vibration in the driving mode in a state where the piezoelectric vibrating piece 70 is not rotated, and the vibrating arm portions 71a and 71b bend and vibrate in the X-axis direction symmetrically to each other. This vibration is a bending vibration called an in-plane symmetrical bending primary vibration mode.
Next, rotation about the Z axis is given to the piezoelectric vibrating piece 70 vibrating in this drive mode. For example, in FIG. 10A, when clockwise rotation occurs, when the vibrating arm portions 71a and 71b vibrate away from each other, a downward Coriolis force acts on the left vibrating arm portion 71a in the drawing, An upward Coriolis force in the figure acts on the right vibrating arm 71b. Further, when the vibrating arm portions 71a and 71b vibrate in a direction approaching each other, an upward Coriolis force in the drawing acts on the left vibrating arm portion 71a, and a downward Coriolis force in the drawing is exerted on the right vibrating arm portion 71b. work. Accordingly, since the Coriolis forces act on the vibrating arm portions 71a and 71b in opposite directions so as to slide in the vertical direction (Y-axis direction) in the drawing, the vibrating arm portions 71a and 71b have a force as shown in FIG. Bending vibration occurs. This vibration is a bending vibration called an in-plane asymmetric bending secondary vibration mode. At this time, due to the bending vibration, moments are generated in the double tuning fork support portions 72a and 72b, respectively, and the detection portions 73a and 73b vibrate in the X-axis direction correspondingly.

Accordingly, the detection voltage is output from the detection electrodes provided in the detection units 73a and 73b in response to the vibration of the detection units 73a and 73b in the X-axis direction.
As a detection signal, a voltage proportional to the angular velocity ω _Z around the Z axis is obtained, but when the rotation direction around the Z axis is reversed, the direction of the Coriolis force acting on each of the vibrating arm portions 71a and 71b is reversed, Accordingly, the polarity of the detection signal is also inverted. Therefore, if the phase difference of the detection signal with respect to the drive signal is measured, the rotation direction with respect to the Z axis can be detected.

Next, rotation about the Y axis is given to the piezoelectric vibrating piece 2 vibrating in the drive mode. For example, in FIG. 10A, when rotation occurs in the Y-axis clockwise direction, when the vibrating arm portions 71a and 71b vibrate away from each other, the left vibrating arm portion 71a faces upward in the Z-axis direction, that is, In the drawing, a Coriolis force acts in a direction perpendicular to the paper surface, and a Coriolis force acts on the right vibrating arm portion 71b downward in the Z-axis direction.
Further, when the vibrating arm portions 71a and 71b vibrate in a direction approaching each other, a downward Coriolis force acts on the left vibrating arm portion 71a, and an upward Coriolis force acts on the right vibrating arm portion 71b. Work. As a result, bending vibration in the Z-axis direction as shown in FIG.

At this time, detection signals are generated from the detection electrodes formed on the vibrating arm portions 71a and 71b. Thereby, a detection signal corresponding to the rotation about the Y axis is output.
As a detection signal, a voltage proportional to the angular velocity ω _r around the Y axis is obtained, but when the rotation direction around the Y axis is reversed, the direction of the Coriolis force acting on each of the vibrating arm portions 71a and 71b is reversed, Accordingly, the polarity of the detection signal is also inverted. Therefore, if the phase difference of the detection signal with respect to the drive signal is measured, the rotation direction with respect to the Y axis can be detected.

Also in such a double tuning fork type angular velocity sensor 2, the Y-axis detection sensitivity is set to 15 to 55% with respect to the Z-axis detection sensitivity of the angular velocity sensor 2, so that it is shown in FIG. 8 of the first embodiment. The same relationship as the relationship between the tilt angle and the relative sensitivity is obtained, and the same effect as in the first embodiment is obtained.
That is, in the so-called double tuning fork type angular velocity sensor 2, the navigation device or the like is provided with the angular velocity sensor 2, and the Z-axis for detecting the angular velocity even if the posture of the angular velocity sensor 2 is inclined by attaching the device in an inclined state. The angular velocity applied to the actual rotation axis can be detected by using the output from the Y axis. At this time, by setting the Y-axis detection sensitivity to 15 to 55% with respect to the Z-axis detection sensitivity of the angular velocity sensor 2, the relative sensitivity can be suppressed within ± 15% up to an inclination angle of 40 °. It is possible to correct the output sensitivity due to the mounting angle by a calculation process based on software.
In this so-called double tuning fork type angular velocity sensor 2, the detection of the Z-axis vibration component is the detection of the bending vibration of the detection units 73a and 73b, and the detection of the Y-axis vibration component is the bending vibration of the vibration arm portions 71a and 71b. Detection. Further, the directions of these bending vibrations vibrate in directions orthogonal to each other. As described above, the angular velocity sensor 2 according to the present invention is different in the detection unit for detecting the angular velocity and in the direction of the bending vibration, so that it is possible to detect the angular velocity while minimizing the influence of the mutual detection signals. it can.

The perspective view which shows the structure of the angular velocity sensor which concerns on the 1st Embodiment of this invention. Explanatory drawing which shows typically the vibration mode when the rotational acceleration of the piezoelectric vibrating piece which concerns on the 1st Embodiment of this invention is not added. Explanatory drawing which shows typically the vibration mode of the Z-axis | shaft rotation system which concerns on the 1st Embodiment of this invention. The perspective view which shows the vibration mode of the Y-axis rotation system which concerns on the 1st Embodiment of this invention. The upper side view which shows the state visually recognized from the upper direction (arrow A direction) of FIG. The upper side view which shows the state visually recognized from the upper direction (arrow A direction) of FIG. Explanatory drawing explaining the sensitivity output in 1st Embodiment. The graph which shows the relationship between the inclination angle of an angular velocity sensor, and relative sensitivity. The structure of the angular velocity sensor which concerns on the 2nd Embodiment of this invention is shown, (a) is a top view, (b) is a side view. The schematic diagram which shows the mode of the bending vibration of the angular velocity sensor which concerns on the 2nd Embodiment of this invention. The schematic diagram which shows the state which attached the navigation apparatus to the vehicle. The schematic diagram which shows the state of an angular velocity sensor, when a navigation apparatus is attached to the vehicle.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2 ... Angular velocity sensor, 10 ... Piezoelectric vibration piece, 20 ... Base part, 40, 50 ... Drive arm, 60 ... Detection arm, 61, 62 ... Detection arm part, 63, 64 ... Weight part, 70 ... Piezoelectric vibration piece, 71a, 71b ... vibrating arm portions, 72a, 72b ... double tuning fork support portions, 73a, 73b ... detection portions, 74a, 74b ... support fixing portions.

Claims (4)

An angular velocity sensor using vibration of a piezoelectric vibrating piece,
A first axis for detecting an angular velocity and a second axis set in a direction orthogonal to the first axis;
An angular velocity sensor, wherein the detection sensitivity of the second axis is 15 to 55% with respect to the detection sensitivity of the first axis. The angular velocity sensor according to claim 1,
The angular velocity sensitivity output is Q, the angle between the first axis and the axis of rotation is θ, the sensitivity ratio of the sensitivity change due to the angle between the first axis and the axis of rotation is A, and the second axis. When the sensitivity ratio of the sensitivity change due to the angle with the rotating axis is B,
Q = A cos θ + B sin θ
A sensitivity output is calculated by the following formula. The angular velocity sensor according to claim 1 or 2,
The piezoelectric vibrating piece extends from the base and a connecting arm connected to the base or the base to be parallel to the second axis and is capable of bending vibration in a direction perpendicular to the first axis and the second axis And a detection arm parallel to the drive arm extending from the base,
Detection of the angular velocity of the first axis in the detection arm is detection of bending vibration,
An angular velocity sensor, wherein the detection of the angular velocity of the second axis in the detection arm is detection of torsional vibration. The angular velocity sensor according to claim 1 or 2,
The piezoelectric vibrating piece includes two vibrating arm portions extending in parallel to the second axis, two double tuning fork support portions that respectively support both ends of the vibrating arm portion, and the vicinity of the double tuning fork support portion. Two supporting and fixing portions disposed in the two, and two detecting portions connected between the supporting and fixing portion and the double tuning fork supporting portion and extending in parallel with the second axis,
Detection of the angular velocity of the first axis is detection of bending vibration in the direction perpendicular to the first axis direction and the second axis of the detection unit;
The angular velocity sensor, wherein the detection of the angular velocity of the second axis is detection of bending vibration of the double tuning fork support portion in the first axis direction.

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