JP2000046560A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detection precision of an angular velocity by making the continuous vibration of a vibrator stable. SOLUTION: This sensor is equipped with a couple of (x) vibrators 2 and 3 at positions symmetrical about a point O, coupling beams 11 and 14 which connect with the (x) vibrators 2 and 3 and bend at least in an (x) direction, a support beam 4 which connects with the coupling beams 11 and 14 and is symmetrical about the point O between the point O and coupling beams, detecting vibrators 5 and 6 which are distant from the point O in the (x) direction and symmetrical about the point O, and reinforcing beams 7 and 8 which connect with the detection vibrators 5 and are provided in the (x) vibrators and symmetrical about the point O, and an anchor which supports the support beam 4 at the point O.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor having a vibrating body floatingly supported on a substrate.
Although not intended to be limited to this, the floating semiconductor thin film formed using the semiconductor microfabrication technology is electrically attracted or released by applying a voltage to the comb-teeth electrode, and x
The present invention relates to an angular velocity sensor which is excited in a direction and detects an angular velocity based on a displacement of a vibrator.

[0002]

2. Description of the Related Art A typical type of angular velocity sensor has a pair of floating comb electrodes (a left floating comb electrode and a right floating comb electrode) on the left side and one set on the right side of a floating thin film. And two sets of fixed comb electrodes (a left fixed comb electrode and a right fixed comb electrode that mesh with and are parallel to each set of floating comb electrodes in a non-contact manner) as left floating comb electrodes / left fixed comb electrodes. By alternately applying a voltage between the space and the right floating comb electrode / the right fixed comb electrode, the floating thin film vibrates in the x direction. When an angular velocity of rotation about the z-axis is applied to the floating thin film, Coriolis force is applied to the floating thin film, and as a result, the floating thin film also oscillates in the y direction, resulting in elliptical vibration. If the floating thin film is used as a conductor or electrodes are joined, and a detection electrode parallel to the xz plane of the floating thin film is provided on the substrate,
The capacitance between the detection electrode and the floating thin film vibrates according to the y component (angular velocity component) of the elliptical vibration. By measuring the change (amplitude) of the capacitance, the angular velocity can be obtained (for example, JP-A-5-248872, JP-A-7-218268, and JP-A-8-152).
327, JP-A-9-127148 and JP-A-9-42973).

[0003]

In the conventional angular velocity sensor, the anchor portion is divided into multiple points, and furthermore, since there is a distance between the anchor portions, an external force such as a temperature change is applied to the beam spring portion which makes the vibrator simple vibration. , Compressive or tensile stress is applied. As a result, the resonance frequency changes with temperature, resulting in a characteristic having hysteresis and discontinuous points, which lowers the sensor accuracy.

For example, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-218268, in a conventional angle sensor in which the anchor portion is divided into multiple points, the vibration at the time of driving leaks to the vibration on the detection side due to the distance between the anchors. Therefore, accuracy may be reduced. Further, for example, in the one disclosed in Japanese Patent Application Laid-Open No. 7-218268, in which the fixed points of the driving vibration mode and the detection vibration mode do not match, the angular velocity detection accuracy is reduced due to mutual vibration leakage and external force. It is thought that.
Further, if the driving vibration mode includes a vibration component that reduces vibration due to Coriolis force, the output of angular velocity detection is small.
In some cases, the amplitude of the conventional vibrator is different between the + x direction and the −x direction, and the vibration is unstable, and the vibration may not be established as a sensor.

Accordingly, it is a technical object of the present invention to stabilize continuous vibration of a vibrator and to increase angular velocity detection accuracy.

[0006]

(1) An angular velocity sensor according to the present invention includes a pair of x vibrators (2/3) and x, y planes symmetrically positioned with respect to a point O on the x, y plane. Distributed, symmetric with respect to the point O, connected to each of the paired x-vibrators (2/3), and connected to the connecting beams (11,14) and (11,14) which bend at least in the x-direction. A support beam (4) that is continuous and symmetrical with respect to the point O, including a flexible beam (41, 42, 43, 44) that bends in the x and y directions between the point O and the connecting beam. , The detection oscillator (5/6), which is symmetrical about the point O, continues to the detection oscillator (5/6), and x
It includes a reinforcing beam (7, 8/17, 18) provided in the vibrator (2/3) and symmetrical with respect to the point O, and an anchor (120) supporting the supporting beam (43, 44) at the point O.

According to this, the anchor of one point O (120)
Supports the pair of x-vibrators (2/3) via the supporting beams (4) including the flexible beams (41, 42, 43, 44) and the connecting beams (11, 14),
Fixed support point of paired x oscillator (2/3) and detection oscillator (5/6)
Since the fixed support points are both one and the same point, the following advantages are obtained: In the conventional point support by a plurality of anchors, stress was conventionally applied to the beam portion of the x-vibrator due to the influence of the deflection of the base supporting the anchor due to the supporting environment temperature or self-heating of the x-vibrator and external force. However, the above-described stress is not applied to the beam supporting the x-vibrator due to the configuration of supporting at one point O. Therefore, discontinuous shift of resonance frequency and hysteresis due to disturbance or the like are reduced.

[0008] 2. Since the stationary point of the x-vibrator system and the detection vibrator system is the point O and is supported only at the point O, the leakage of vibration between the x-vibrator system and the detection vibrator system is reduced. And the angular velocity detection accuracy is improved.

3. The supporting beam supported by the anchor at the point O is continuous with the supporting beam including the flexible beam that bends in the x and y directions, the connecting beam bends in the x direction, and the connecting beam undergoes x vibration. Since the vibrators are provided at positions symmetrical with respect to the point O, the paired x vibrators are likely to vibrate in the x direction with respect to each other. Thus, the x drive vibration is close to a simple vibration, and the vibration in the detection direction y is not given to the detection vibrator, and the accuracy of detecting the angular velocity is improved.

Further, since the detecting vibrators (5/6) are separated from the y-axis in the x-direction, their y-amplitude due to the torsional vibration is large in proportion to the distance from the y-axis, and the detection relative to the value of the angular velocity. The y-vibration of the vibrator (5/6) is increased, and the accuracy of detecting the angular velocity is further improved.

(2) The detecting oscillator (5/6) has a substantially x shape and is supported by the reinforcing beams (7, 8/17, 18) on the x axis passing through the point O, and the reinforcing beams are detected. Provided on the outer periphery of the vibrator (5, 6), x
Since it is connected to the vibrator (2, 3), when an angular velocity about the z axis passing through the point O and perpendicular to the x and y axes is applied to the sensor, each x vibration of the x vibrator (2/3) becomes Elliptical vibration having a y-vibration component occurs, and the connecting beams (11, 14) generate torsional vibration around the z-axis. The pair of detection transducers (5, 6), which form a substantially x shape due to this torsional vibration, are opposite to each other with respect to the x transducer (2/3) in the reinforcing beam (7, 8/17, 18) (−y Vibrates in a stable state.

(3) The connecting beam (11, 14) has a symmetrical shape around the point O, and the length L of the connecting beam (11, 14) in the y-axis is equal to the connecting beam (11, 14). ), The length of the beam from the support beam (4) to the anchor (120) is the same as that of the beam, so that the detection transducers (5, 6) are supported in a double-supported (balanced support) state. The detection vibrator (5, 6) is easy to make simple vibration in the y direction, the vibration in the y direction is stable, the angular velocity detection accuracy and stability are high, and the length of the above beam is the same. This makes the vibration more stable.

(4) Exciting means (91, 92) for driving a pair of x vibrators (2/3) in opposite phases in the x direction, and a detecting vibrator (5 /
6) If the detecting means (111, 112) for detecting the vibration in the y-direction is provided, the pair of x-vibrators (2/3) are driven by the exciting means (91, 92) in opposite phases in the x-direction. It becomes possible to use a pair of x vibrators (2/3) as a tuning fork by vibrating drive. In this case, since the supporting beam (4) includes the flexible beams (41, 42) that bend in the y direction, the connecting beams (11, 14) are also easily bent in the y direction, and are expanded and contracted in the y direction by x-phase reverse vibration. X oscillators (2,3)
X vibration of the opposite phase becomes easier. For example, excitation means (91, 92)
External force by applying a voltage to the
When added to (2,3), the x-vibrator (2,3) tends to resonate in opposite phase.

(5) If the pair of x vibrators (2, 3) are driven to vibrate in opposite phases, the supporting beams (41, 42) can be supported at the fixed points of the connecting beams. The vibration of (11, 14) becomes stable, and the detection accuracy of the angular velocity improves.

[0015]

FIG. 1 shows a configuration of an angular velocity sensor 1 according to an embodiment of the present invention. On the silicon substrate 100 on which the insulating layer is formed, a floating body anchor (hereinafter, referred to as an anchor) 120 made of polysilicon (conductive polysilicon) containing impurities to make it conductive is symmetric with respect to a point O. Drive electrodes 91 and 92, drive detection electrode 10
1, 102, and the vibration detection electrodes 111, 112 are joined on the substrate. These are connected to connection electrodes (electrode pads) (not shown) via wires formed on the insulating layer on the silicon substrate 100.

Using a lithographic semiconductor process, a structure (vibrating body) made of conductive polysilicon is floated from the silicon substrate 100 and floated from the anchor 120. The vibrator is supported by the support beams 4 including the flexible beams 43 and 44 that bend in the x direction and the rectangular flexible beams 41 and 42 that easily bend in the y direction, passing through the point O from the anchor 120. The substantially U-shaped connecting beam 11 is supported by 41 and 42. The flexible beams 41, 42, 43, 4
Reference numeral 4 denotes a support beam 4 for supporting the vibrating body, and the anchor 1
It is formed symmetrically with respect to the x-axis with the center at 20.

The first x-vibrator 2 (21, 22) and the second x-vibrator 3
(31, 32) are supported. These x vibrators 2 and 3 also float from the silicon substrate 100 in the z direction perpendicular to the x and y axes, and are formed of the same conductive polysilicon.

The first x vibrators 21 and 22 are connected to the connecting beam 1
The first and second vibrators 31 and 32 are similarly symmetric with respect to the y-parallel sides of the connecting beams 11 and 14 and have x-axis and y-axis directions.
The structure is symmetric with respect to the axis and the point O.

These x vibrators 21, 22/31, 32
, Comb-shaped movable electrodes 23 and 33 that are distributed at equal pitches in the outer frame y direction and protrude in the x direction are formed on both sides of the parallel side of the outer frame y. Also, the drive electrodes 91 and 92 and the drive detection electrodes 101 and 102 made of conductive polysilicon also have comb-shaped fixed electrodes protruding into the space of the movable electrodes 23 and 33 in the y direction, and are distributed in the y direction. ing.

By alternately applying a voltage higher than the potential (ground level) of the x oscillator 2 to the drive electrodes 91 and 92, the x oscillator 2 is electrically attracted in the x direction by electrostatic force, Vibrates in the x direction. Due to this x-vibration, the capacitance between the x-vibrator 2 and the drive detection electrodes 101 and 102 fluctuates, and the capacitance change generated in the drive detection electrodes 101 and 102 is fed back and input to the feedback circuit bc. The drive circuit ac provides an accurate rectangular wave whose waveform has been shaped by the controller dc based on the signal, thereby causing the vibrator 2 to vibrate, thereby changing the capacitance between the x vibrator 2 and the drive detection electrodes 101 and 102. I do.

The x-vibrator 3 has an x-axis with respect to the y-axis passing through the point O.
The drive electrodes 91 and 92 on the x-vibrator 3 side for driving the x-vibrator 3 are symmetrical in shape and position to the vibrator 2.
By applying a drive pulse having a phase opposite to that of the x-vibrator 2 drive pulse,
Vibrating in the direction, the x-vibrator 3 and the drive detection electrodes 101 and 10
The capacitance between the two oscillates. Therefore, the driving pulses A to
By setting D to be the resonance frequency of the x vibrators 2 and 3, x
Since the vibrators 2 and 3 resonate to generate tuning fork vibration, x vibration with high energy consumption efficiency can be performed.

The vibrations in the x direction cause the x vibrators 2, 3
, The sides 13 and 15 of the connecting beams 11 and 14 in the y direction are bent, and vibrate similarly to the x vibrators 2 and 3. As a result, the left and right ends of the x-parallel sides of the connecting beams 11 and 14 (connecting points with the y-parallel sides) vibrate in a direction substantially 45 degrees with respect to the x and y axes, and the x-parallel sides of the connecting beams 11 and 14 Vibrates in the y-direction in opposite phase. However, the connecting beams 11 and 14 are connected to flexible beams 41 and 42 for absorbing vibration in the y direction, and the flexible beams 41 and 42 bend in opposite directions in the y direction, respectively.
20 is pulled from both sides of the beams 43 and 44, and becomes a stationary point with respect to the x excitation of the x vibrators 2 and 3.

As described above, when the x-vibrators 2 and 3 are driven to excite and the connecting beams 11 and 14 are flexed and vibrated in the x and y directions, the x parallel sides of the connecting beams 11 and 14 are moved in the y direction. When the support beam 4 is pulled through the two extending beams 16 and 26,
Two fixed points appear in the vibration in the y direction. Therefore, if the connecting beams 13 and 14 and the supporting beam 4 are connected by the beams 16 and 26 to the position of the fixed point, the connecting beam 1
The vibrations of 1, 14 are stabilized.

Each of the x vibrators 2 and 3 has a comb-shaped movable electrode 23 or 33 on the y-parallel side of the outer periphery and has a substantially H shape. The x vibrators 2 and 3 are supported at both ends by the y parallel sides 13 and 15 of the connecting beams 11 and 14, and the x parallel sides connecting two y parallel sides 74 and 84 inside the x vibrator 2. The U-shaped ends of the connecting beams 11 and 14 are connected at the midpoint of 94. In this case, y of the connecting beams 11 and 14
If the length of the parallel sides 13 and 15 is set to the same length L as the length of the beam from the connecting beams 13 and 14 to the anchor 120 via the support beam 4, vibration of the x vibrators 2 and 3 is stabilized. And it is close to a simple vibration.

Two y-parallel sides 74, 8 inside the x-vibrator
4, reinforcing beams 7, 8 extending in the y-direction from the upper and lower positions in the frame of the x-vibrator 2 shown in FIG. The x-parallel sides of the reinforcing beams 7, 8 extend from the midpoint of the reinforcing beams 7, 8 (on the x-axis passing through the point O), and support the abdomen where the center of gravity of the x-shaped detection vibrator 5 is located. I have. Also, with respect to the x vibrator 3, the detection vibrator 6 is formed in a shape and position symmetrical with respect to the y axis passing through the point O.

The detecting vibrators 5, 6 and the reinforcing beams 7, 8 supporting them are also made of conductive polysilicon, and have substantially the same potential as the anchor 120. The pieces 51, 52, 61, and 62 of the detection oscillators 5 and 6 have a substantially x shape. The crossovers for the movable detection electrode parallel to the x-axis connecting the opposing y-parallel sides of the piece are distributed at substantially equal pitches in the y-direction, and thus windows are formed at several places in the y-direction. In each space (window) between the bridge beams, fixed detection electrodes 111, 11 each made of a pair of conductive polysilicon and fixed on the substrate are provided.
2 exist at equal intervals in the y direction, and are supported on the substrate 100 by the anchors for the detection electrodes.

Although the detection electrodes 111 and 112 are insulated from each other, each of the pair of detection electrodes 111 and 112 has a differential configuration in order to detect the y-movement of the first detection transducer 5. Are detected, and a detection signal is input to the detection circuit cc, and each of the pieces 51, 52,
A plurality of electrodes at corresponding positions between 61 and 62 are commonly connected. In addition, the second detecting vibrator 6 also has a symmetric structure with respect to the y-axis in order to similarly detect the y movement.

In such a structure, as shown in FIG. 2, a driving electrode 91 for driving the x vibrators 2 and 3 to vibrate is
The drive signals A and B are supplied from the drive circuit ac, and the phase of the voltage applied to the drive electrode 91 with respect to the drive electrode 92 is 1
By giving the drive vibrations C and D deviated by 80 degrees from the drive circuit ac by the controller dc, the x vibrators 2 and 3
Are vibrated in the opposite phase. When a drive voltage is applied to the drive electrodes 91 and 92, respectively, and the x vibrators 2 and 3 are vibrating in the x direction with opposite phases, for example, when an angular velocity around the z axis is applied, Coriolis force acts on the vibrator. I do. When the Coriolis force acts, the vibrations of the x vibrators 2 and 3 become elliptical vibrations, and torsional vibrations around the z-axis are generated in the connecting beams 11 and 14, so that the x vibrators 2 and 3 receive the Coriolis force and y It vibrates in the direction. Further, in this case, the detection oscillator 5,
6 also oscillates in the y-direction, but the y-vibration of the detection oscillator 5 has a phase opposite to that of the x-vibrator 2, and the detection oscillator 6
Has a phase opposite to the vibration of the x vibrator 3.

From the above, the angular velocity sensor 1 of the present invention
Has a tuning fork structure to vibrate the x vibrators 2 and 3 in opposite phases in the x direction. When angular velocities are applied to the x vibrators 2 and 3 and the detecting vibrators 5 and 6, the x vibrators 2 and 3 vibrate in the x direction and receive Coriolis force proportional to the angular velocity, thereby detecting the vibration direction x and the angular velocity. Vibrates in the y direction perpendicular to the axis z. When the Coriolis force is applied, the x vibrators 2 and 3 respectively become y
And their displacement in the y direction is proportional to the angular velocity: y displacement = (angular velocity × vibrator velocity × vibrator mass) / y
The spring constant in the direction is y displacement, which is a constant.

The vibrators 2, 3, 5, and 6 have a vibration mode at resonance in the detection direction y of the x vibrators 2 and 3 opposite to each other, and the detection vibrators 5 and 6 also have opposite phases. The center of vibration coincides with the center of gravity O of the entire floating body of the angular velocity sensor. Accordingly, when the x vibrators 2 and 3 receive Coriolis force, the detection vibrators 5 and 6 vibrate in the y direction opposite to the direction in which the x vibrators 2 and 3 move. In addition, the resonance frequency of the x oscillators 2 and 3 and the resonance frequency of the detection oscillators 5 and 6 are determined by the resonance frequency of the x oscillators 2 and 3 based on the balance between sensitivity and correspondence. Is set slightly higher. From the relationship between the masses of the x oscillators 2 and 3 and the masses of the detection oscillators 5 and 6 and the spring constants in the respective detection directions y, the x oscillators 2 and 3 are set in the y direction. It has a configuration that hardly displaces. Instead, the detection oscillators 5 and 6 are displaced greatly.

From the above, the accuracy (S / N) of this sensor
Can be improved because, in principle, mutual leakage (crosstalk) of the vibration in the driving in the x direction and the vibration in the detection in the y direction is small.

Also, this structure is different from the conventional structure in that the vibration is not forcibly suppressed. Therefore, the structure is resistant to the influence of stress and temperature change, and the fixed point of driving and detecting vibration is almost at the center of gravity of the sensor. Since they coincide with each other, and when they receive Coriolis force as described above, they do not involve any rotational movement, so that the support points are stationary at the center of gravity even without support. Therefore, external vibration (when mounted on a vehicle, etc.) hardly affects the driving vibration and detection vibration of the sensor.
The S / N ratio is improved as compared with the related art. In addition, since the above-described support is used, the influence of thermal expansion due to temperature or the like is small, and the temperature correction can be reduced. Therefore, the S / N ratio is improved as compared with the conventional type.

The angular velocity sensor shown in FIG.
Since the connecting beams 11 and 14, which are spring portions, are continuously and floatingly supported at the center of mass of the vibrator 3, there is substantially no change in the spring effect due to the deformation of the vibrating mass itself. Becomes closer to a simple vibration.

Since the angular velocity sensor shown in FIG. 1 employs a bi-resonant x-vibration system, the amplitudes of the x-vibrators 2 and 3 are amplified and a large change can be obtained. As a result, driving can be performed with a small amount of energy, so that cost can be reduced. Since a large displacement output can be obtained, the S / N is improved.

Further, the fixed point of each vibration mode of the bi-resonance is the center of gravity O, and the x vibrators 2 and 3 are the center of gravity O
Since it is supported at (single point), vibration leakage of x vibration does not occur in principle, so that a large amplification factor of the detected vibration y can be obtained. Since unnecessary vibration is not induced in the detected vibration y, the S / N of the angular velocity signal is improved. Unnecessary vibration is not induced in the driving vibration, the driving can be performed with a single vibration, and the S / N is improved.

Since the center of gravity of the x-vibration system and the y-vibration system are at the point O and at the same point, a stress load is applied to the spring portions (1, 4, 7, 8) due to thermal expansion due to temperature. It does not occur and the temperature characteristics are improved. In particular, the reliability (stability) of detecting the angular velocity is high when the device is used in an environment with a large temperature change such as a vehicle.

Further, since the connecting beams 11 and 14 are provided with the flexible beams 41 and 42 for relaxing the stress, the nonlinearity of the x-drive vibration is improved, and the vibration is caused by a single vibration.
/ N is improved.

Further, the detecting vibrators 5, 6 are supported by reinforcing beams 7, 8 which are close to rigid bodies, and the detecting vibrators 5, 6 are not in the mode of torsional rotation but in parallel with each other and in the opposite phase.
When the detection vibration in the y direction is detected by the capacitance, an ideal sine output is obtained and the S / N of the angular velocity signal is improved.

The above-described angular velocity sensor 1 can be formed on a silicon wafer by a semiconductor process using a lithography and can be manufactured by a conventional semiconductor process, so that it can be manufactured at low cost. The floating body is formed by a single film, can be easily formed by a semiconductor process, and can be produced at low cost.

[Brief description of the drawings]

FIG. 1 is a plan view of one embodiment of the present invention.

FIG. 2 is a diagram illustrating a driving voltage applied to a driving electrode of FIG. 1;

[Explanation of symbols]

 1: angular velocity sensor 2, 3: x vibrator 4: supporting beam 5, 6: detecting vibrator 7, 8: reinforcing beam 11, 14: connecting beam 41, 42, 43, 44 flexible beam 91, 92: drive electrode 101, 102: drive detection electrode 100: substrate 120: floating body anchor

Claims (5)

[Claims] 1. A pair of x oscillators, which are symmetrical with respect to a point O on the x, y plane, distributed on the x, y plane, symmetric with respect to the point O, A connecting beam that is continuous and deflects at least in the x-direction, a support beam that is continuous with the connecting beam, and that includes a flexible beam that deflects in the x and y directions between point O and the connecting beam; , A detection oscillator that is distant in the x-direction, is symmetric with respect to the point O, is continuous with the detection oscillator, is provided in the x oscillator, and is a reinforcing beam that is symmetric with respect to the point O, and an anchor that supports the support beam at the point O. An angular velocity sensor comprising: 2. The detecting oscillator has a substantially x shape, is supported by a reinforcing beam on an x-axis passing through a point O, and the reinforcing beam is provided on the outer periphery of the detecting oscillator and connected to the x oscillator. The angular velocity sensor according to claim 1. 3. The connecting beam has a symmetrical shape about a point O, and the length of the connecting beam in the y-axis is the same as the length of the connecting beam to the anchor via the supporting beam. The angular velocity sensor according to claim 2, wherein: 4. Exciting means for driving a pair of x vibrators in opposite phases in the x direction, and detecting means for detecting y-direction vibration of the detecting vibrator.
The angular velocity sensor according to claim 1. 5. The angular velocity sensor according to claim 4, wherein the supporting beam is supported at a fixed point of the connecting beam when the pair of x vibrators are driven to vibrate in opposite phases.