JP3882972B2 - Angular velocity sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an angular velocity sensor including a vibrating body that is floatingly supported with respect to a substrate. In particular, although not intended to be limited to this, a floating semiconductor thin film formed by using a semiconductor microfabrication technique is formed with a comb-tooth electrode. The present invention relates to an angular velocity sensor that is electrically attracted / released and excited in the x direction.
[0002]
[Prior art]
A typical example of this type of angular velocity sensor is provided with one set of floating comb electrodes (left floating comb electrode and right floating comb electrode) on the left side and one set on the right side of the floating thin film, and fixed comb teeth. There are also two pairs of electrodes (left fixed comb electrode and right fixed comb electrode that are in contact with and in parallel with each set of floating comb electrodes) and between the left floating comb electrode / left fixed comb electrode and the right floating comb electrode. By alternately applying a voltage between the tooth electrode / right-side 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, a Coriolis force is applied to the floating thin film, and the floating thin film becomes elliptical vibration that vibrates in the y direction. If the floating thin film is a conductor or an electrode is joined, and a detection electrode parallel to the xz plane of the floating thin film is provided on the substrate, the electrostatic capacitance between the detection electrode and the floating thin film is reduced by elliptic vibration. It vibrates corresponding to the y component (angular velocity component). By measuring the change (amplitude) of the capacitance, the angular velocity can be obtained (for example, Japanese Patent Laid-Open Nos. 5-248882, 7-218268, 8-152327, and 9). -127148, JP-A-9-42973).
[0003]
[Problems to be solved by the invention]
In the conventional angular velocity sensor, the anchor portion is divided into multiple points, and since there is a distance between them, a compressive or tensile stress is applied when an external force such as a temperature change is applied to the beam spring portion that causes the vibrator to perform simple vibration. Therefore, the resonance frequency changes with temperature, and has a characteristic having hysteresis and discontinuity. That reduces the accuracy of the sensor. For example, such as disclosed in JP-A-7-218268, the conventional angle sensor anchor portion is divided into multiple points, vibrations during driving because of the distance between the anchors is also currently being on the vibration of the detection side, therefore the precision It is thought that it will decrease. Also, for example, as disclosed in Japanese Patent Application Laid-Open No. 7-218268, when the fixed points of the driving vibration mode and the detection vibration mode do not match, the angular velocity detection accuracy is improved if there is an influence of mutual vibration leakage and external force. It is thought to decline. If the vibration mode of the drive includes a vibration component that reduces vibration due to Coriolis force, the angular velocity detection output is small. The amplitude of a conventional vibrator is different between the + x direction and the −x direction, and the vibration may become unstable and may not be established as a sensor.
[0004]
It is an object of the present invention to stabilize the continuous vibration of a vibrator and increase the angular velocity detection accuracy.
[0005]
[Means for Solving the Problems]
(1) The angular velocity sensor of the present invention is a pair of x oscillators (2, 3) at symmetrical positions with respect to a point O on the x, y plane;
a connecting beam (1) distributed in the x, y plane, symmetrical with respect to the point O, continuous to each of the pair of x oscillators (2,3) and bent at least in the x direction;
A first support beam (4) symmetrical to point O, including a first flexible beam (41, 42) continuous to the connecting beam and deflected in the x and y directions between point O and the connecting beam;
Detecting oscillator symmetrical about point O (5/6);
A second support beam (7/8) symmetrical to point O, including a second flexible beam (71, 72/81, 82) which is continuous with the detection vibrator and bends in the y direction between point O ;
A loop (45) about point O, in which the first flexible beam (41, 42) and the second flexible beam (71, 72/81, 82) are continuous ;
An anchor (120) supporting the center of the loop (45) at point O;
Excitation means (10A, 10B) for oscillating and driving the pair of x vibrators (2, 3) in the opposite phase in the x direction; and
Means (111, 112) for detecting the y-direction vibration of the detection vibrator (5/6);
Is provided. In addition, in order to make an understanding easy, the code | symbol of the corresponding element of the Example shown in drawing and mentioned later is added to the parenthesis for reference.
[0006]
According to this, the anchor (120) at one point O supports the pair of x vibrators (2, 3) via the first support beam (4) and the connecting beam (1), and also the second support. Since the detection vibrator (5/6) is supported via the beam (7/8), that is, the stationary support point of the pair of x vibrators (2, 3) and the stationary support of the detection vibrator (5/6) Since the points are both one and the same, the following advantages are obtained:
1. In the conventional point support with multiple anchors, stress was 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 temperature of the support environment, self-heating of the x vibrator, or external force. However, in the present invention, since it is supported at one point O as described above, the stress as described above is not applied to the beam. Therefore, the discontinuous shift and hysteresis of the resonance frequency due to disturbance etc. are reduced.
2. Since the stationary point of the x oscillator system and the detection oscillator system is the point O and is supported at the point O, the vibration leakage between the x oscillator system and the detection oscillator system is reduced, so that the angular velocity is detected. Accuracy is improved, and
3. The first support beam (4) supported by the anchor at the point O includes the first flexible beam (41, 42/43, 44) which is bent in the x and y directions. The first support beam (4) includes Since the connecting beam (1) is continuous and the connecting beam is bent in the x direction and is continuous with the pair of x vibrators (2, 3), the pair of x vibrators (2, 3) is x Easy to vibrate in the direction. Thus, since the excitation means (10A, 10B) drives the pair of x vibrators (2, 3) that are symmetric with respect to the point O to vibrate in the opposite direction in the x direction, the x drive vibration is almost a single vibration. The vibration in the detection direction y is not applied to the detection vibrator, and therefore the angular velocity detection accuracy is improved.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
(2) The detection vibrators (5/6) are separated from each other in the x direction from the y axis and are symmetric with respect to the point O and make a pair. 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 pair of x vibrators (2, 3) becomes an elliptical vibration having a y vibration component. The connecting beam (1) generates torsional vibration around the z axis. This torsional vibration propagates to the second support beam (7, 8), and the torsional vibration causes the pair of detection vibrators (5, 6) to pass through the second flexible beam (71, 77/81, 87). Vibrates in opposite directions, but the detection transducers (5, 6) are separated from the y axis in the x direction, so their y amplitude due to torsional vibration is proportional to the distance from the y axis. Therefore, the y vibration of the detection vibrator (5, 6) with respect to the angular velocity value is large, and the angular velocity detection accuracy is high.
[0008]
(3) The second support beam (7, 8) surrounds the detection vibrator (5, 6) and the second flexible beam (71, 77/81, 87) distributed on the x, y plane and The reinforcing beam (74, 75/84, 85) is supported by the anchor (120) continuously to the flexible beam. With this reinforcing beam (74,75 / 84,85), the detection vibrator (5,6) is supported in the form of both ends (balanced support) via the second flexible beam (71,77 / 81,87). Therefore, the detection vibrator (5, 6) easily performs y-direction simple vibration, the y-direction vibration is stable, and the angular velocity detection accuracy and stability are high.
[0009]
(4) The connecting beam (1) has a loop shape with the point O as the center of the loop. As a result, sensor elements are arranged in a compact manner, such as placing the detection vibration system (or x vibration system) inside the loop (the space inside the loop of the connecting beam 1) and the x vibration system (detection vibration system) outside the loop. Yes. In addition, the excitation means (10A, 10B) drives the pair of x vibrators (2, 3) to vibrate in the opposite direction in the x direction, that is, the pair of x vibrators (2, 3) is used as a tuning fork. However, since the first support beam (4) includes the first flexible beam (41, 42/43, 44) which is bent in the x and y directions, the connecting beam (1) is easily bent in the y direction, and the x reverse The loop of the connecting beam (1) easily expands and contracts in the y direction due to the phase vibration, and the reverse phase x vibration of the pair of x vibrators (2, 3) is easy. For example, when an x driving external force is applied to the x vibrator (2, 3) by electrostatic driving by the excitation means (10A, 10B), the x vibrator (2, 3) is likely to resonate in a reverse phase.
[0010]
Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.
[0011]
【Example】
FIG. 1 shows a mechanism element according to an embodiment of the present invention. The silicon substrate 100 on which the insulating layer is formed has a floating anchor 120 made of polysilicon containing impurities for making it conductive (hereinafter referred to as conductive polysilicon), and anchors of a large number of drive electrodes 91 to 94 and a large number of anchors. Anchors of the detection electrodes 111 and 112 are joined, and these anchors are connected to connection electrodes (not shown) by wiring formed on the insulating layer on the silicon substrate 100.
[0012]
Using a lithographic semiconductor process, a conductive polysilicon floating x from the silicon substrate 100 and continuing to the floating anchor 120, a central x-beam 46 extending in the x-direction and a rectangular shape centered on the anchor 120 and continuous thereto. A first loop 45 is formed.
[0013]
The first support beam 4 (y arms 43 and 44 and flexible rectangular loops 41 and 42) extends in the y direction from the intersection of the first loop 45 with the y axis passing through the center O of the anchor 120, and the loop 41, The rectangular second loop 1 (x parallel sides 11 and 12 and y parallel sides 13 and 14) is continuous with the first support beam 4 at the intersection of 42 and the y axis. At the intersection of the y parallel sides 13 and 14 with the x axis, the first x vibrators 21 and 22 and the second x vibrators 31 and 32 that are continuous to them are continuous. These elements also float from the silicon substrate 100 and are the same conductive polysilicon as the first loop 45, are supported by the anchor 120 at the center O, and float from the substrate 100.
[0014]
The first x oscillators 21 and 22 are symmetrical with respect to the y parallel side 13 of the second loop 1 and are in a symmetrical position. The second x oscillators 31 and 32 are the first x oscillators 31 and 32 with respect to the y axis. It is symmetrical with the x vibrators 21 and 22 and is in a symmetrical position. These x vibrators 21, 22, 31 and 32 are also symmetric with respect to the x axis passing through the center O.
[0015]
These x vibrators 21, 22/31, 32 have comb-like movable electrodes 23, 33 distributed at equal pitches in the y direction and projecting in the x direction. The silicon drive electrodes 10A and 10B (91 to 94) and the drive detection electrodes 9A and 9B (101 to 104) also have comb-like fixed electrodes protruding into the space of the movable electrodes 23 and 33 in the y-direction distribution. Distributed in the direction.
[0016]
By alternately applying a voltage higher than the potential of the x vibrator 2 (substantially the device ground level) to the drive electrodes 10A, 10B 91, 93 and 92, 94, the x vibrator 2 vibrates in the x direction. Due to this x vibration, the electrostatic capacitance between the x vibrator 2 and the drive detection electrodes 9A, 9B 101, 103 vibrates, and between the x vibrator 2 and 102, 104 in an opposite phase to the capacitive vibration. Oscillates.
[0017]
The x vibrator 3 has a shape and position that is symmetric with respect to the x vibrator 2 with respect to the y axis, and a drive electrode for driving the x vibrator 3 (one that is symmetrical with 10A and 10B with respect to the y axis) By applying a drive pulse having a phase opposite to that of the x vibrator 2 drive pulse, the x vibrator 3 vibrates in the x direction with a phase opposite to that of the x vibrator 2, and the x vibrator 3 and the drive detection electrode (9A with respect to the y axis) , 9B, which is symmetrically located) vibrates. By setting the drive pulse to the resonance frequency of the vibrators 2 and 3, the x vibrators 2 and 3 generate resonance tuning fork vibration, and perform x vibration with high energy consumption efficiency.
[0018]
Due to this x vibration, the midpoints of the y parallel sides 13 and 14 of the rectangular second loop 1 vibrate similarly to the x vibrators 2 and 3. As a result, the left and right ends of the x parallel sides 11 and 12 (continuous contact with the y parallel side) vibrate in the direction of about 45 degrees with respect to the x and y axes, but the midpoints of the x parallel sides 11 and 12 (y axis) The x parallel sides 11 and 12 are symmetrical with respect to each other, so that the vibration does not vibrate in the x direction and vibrates only in the y direction. However, since the flexible rectangular loops 41 and 42 absorb the y vibration, the y vibration hardly propagates to the y arms 43 and 44, and the x parallel side of the first loop 45 is slightly in the y direction even if it vibrates. And does not vibrate in the x direction. Since the center x beam 46 continues to the first loop 45 at the midpoint of the y parallel side of the first loop 45, even if the x parallel side of the first loop 45 vibrates in the y direction, the center x beam 46 is It does not vibrate in the x direction and of course does not vibrate in the y direction. Therefore, no x vibration is applied to the anchor 120. Regarding the x excitation of the x oscillators 2 and 3, the anchor 120 (center O) is a stationary point. As a result, the anchor 120 supports the x oscillators 2 and 3 at the stationary point.
[0019]
The y point of the y arm 73 of the beam 7 for supporting the detection vibrator is located at the midpoint of the above-mentioned parallel side of the first loop 45 that does not vibrate in the x and y directions with respect to the x excitation of the x vibrators 2 and 3. The center of the direction is continuous, the U-shaped flexible beams 71 and 72 are continuous with the y-direction end portion of the y arm 73, and the half pieces of the first detection vibrator 5 are connected to the flexible beams 71 and 72. 51 and 52 are continuous. These half pieces 51 and 52 are continuous with a trunk (y arm) 53 of the vibrator, and the first detection vibrator 5 has a symmetrical shape with respect to the x-axis. Further, with respect to the trunk 53, there are flexible beams 77 and 78 and y arms 76 that are symmetrical to the flexible beams 71 and 72 and the y arm 73, and these are also continuous with the half pieces 51 and 52. A y-arm 75 for reinforcement is continuous with the y-direction midpoint of the y-arm 76 (intersection with the x-axis), and the y-parallel side is continuous with the y-direction end of the y-arm 75. 74, the y arm 74 is continuous with the y parallel side of the first loop 45. These reinforcing members 75 and 74 also exist symmetrically with respect to the x axis.
[0020]
The second detection vibrator 6 and the support beam 8 are symmetrical to the first detection vibrator 5 and the support beam 7 with respect to the y axis, and are present at symmetrical positions. The detection vibrators 5 and 6 and the support beams 7 and 8 are point-symmetric with respect to the center O and distributed symmetrically with respect to both the x and y axes.
[0021]
The detection vibrators 5 and 6 and the beams 7 and 8 that support them are also made of conductive polysilicon and have substantially the same potential as the anchor 120. The half pieces 51, 52/61 and 62 of the detection vibrators 5 and 6 are roughly rectangular loops, but the movable electrode connecting beam connecting the opposite y parallel sides and parallel to the x axis is substantially in the y direction. There is a pair of conductive polysilicon fixed detection electrodes 111 and 112 distributed at an equal pitch and in each space between the crossing beams, and supported by and electrically connected to the respective anchors for the detection electrodes on the substrate 100. Continuous (in electrical connection). FIG. 2 shows an enlarged cross section taken along line A2-A2 of FIG.
[0022]
Referring to FIG. 1 again, the pair of detection electrodes 111 and 112 are insulated, but each counter electrode for detecting y movement of the first detection vibrator 5 is in a corresponding position between each pair. Some detection electrodes are connected in common. The same applies to each counter electrode for detecting y movement of the second detection transducer 6.
[0023]
When the x vibrators 2 and 3 vibrate in the x direction with opposite phases, for example, when an angular velocity about an axis parallel to the z axis passing through the center O is applied, the vibrations of the x vibrators 2 and 3 become y components. The torsional vibration around the z-axis appears in the second loop 1, and the torsional vibration around the z-axis also appears in the first loop 45. As a result, the arms 73, 76/83, and 86 vibrate in the y direction, and the detection vibrators 5 and 6 vibrate in the y direction. However, the y vibrations of the detection vibrators 5 and 6 are in opposite phases.
[0024]
FIG. 3 shows an electric circuit connected to the angular velocity sensor shown in FIG. The timing signal generator TSG generates a driving pulse signal for driving the x vibrators 2 and 3 in the x direction in the opposite phase at the resonance frequency, and supplies the driving pulse signals to the driving circuits a1 to a4 and b1 to b4. The signal is given to the synchronous detection circuits e1 to e5.
[0025]
FIG. 4 shows voltages applied to the drive electrodes (10A, 10B: 91 to 94) by the drive circuits a1 to a4 and b1 to b4 in synchronization with the drive pulse signal. As a result, the x vibrators 2 and 3 perform the tuning fork vibration in the opposite phase in the x direction.
[0026]
Due to the x vibration of the x vibrator 2, the capacitance of the drive detection electrodes (9 </ b> A) opposite to each other (101 and 103) vibrates in the opposite phase. The differential amplifiers c1 to c8 (c1) differentially amplify the electrostatic capacity signal generated by the preamplifier, which represents the vibration of the electrostatic capacity, and substantially reduce the amplitude of the electrostatic capacity signal generated by one preamplifier. A differential signal that is doubled to cancel the noise is generated and applied to the differential amplifiers d1 to d4. One differential amplifier (d1) is provided with differential signals of two differential amplifiers (c1, c2) having opposite phases to each other, and these differential signals are supplied to the differential amplifier (d1). Is provided to the synchronous detection circuits e1 to e4 (e1). The synchronous detection circuits e1 to e4 (e1) detect the differential signal provided by the differential amplifier (d1), that is, the x vibration detection voltage representing the x vibration in synchronization with the synchronous signal in phase with the drive pulse signal, and drive pulse A signal representing a phase shift of x vibration with respect to the signal is generated and applied to the feedback processing circuit FCR.
[0027]
The feedback processing circuit FCR sends to the drive circuits a1 to a4, b1 to b4 (a1, b1) phase shift signals for adjusting the phase shift signal levels given by the synchronous detection circuits e1 to e4 (e1) to the set values. The drive circuit that receives the signal shifts the phases of the output drive voltages V1 to V8 (V1, V2) with respect to the drive pulse signal in response to the phase shift signal. The resonance tuning fork vibrations of the x vibrators 2 and 3 become stable in a state where all the phase shift signal levels of the synchronous detection circuits e1 to e4 are substantially set values.
[0028]
When an angular velocity about an axis parallel to the z axis passing through the center O is applied during stable resonance tuning fork vibration, a negative y vibration appears in the detection vibrators 5 and 6, and the amplitude becomes the absolute value of the angular velocity. Correspondingly, the sign of the phase difference (± 180 degrees) between the detection vibrators 5 and 6 corresponds to the direction of the angular velocity.
[0029]
The capacitance of the pair of detection electrodes (111, 112) for detecting the y vibration of the detection vibrators 5, 6 (5) vibrates in a relatively opposite phase due to the y vibration, and a capacitance signal representing this is obtained. The differential amplifiers c9 and c10 (c9) generated by the preamplifier have the differential signal of both signals, that is, the differential signal in which the amplitude of the electrostatic capacitance signal generated by one preamplifier is approximately doubled to cancel the noise, Is supplied to the differential amplifier d5.
[0030]
The differential amplifier d5 is supplied with the differential signals of the two differential amplifiers c9 and c10 having opposite phases to each other, and the differential amplifier d5 supplies the differential signals to the synchronous detection circuit e5. The synchronous detection circuit e5 detects a differential signal provided by the differential amplifier d5, that is, a y vibration detection voltage representing y vibration in synchronization with a synchronization signal in phase with the drive pulse signal, and generates a signal representing an angular velocity. The polarity (±) of the angular velocity signal indicates the direction of the added angular velocity, and the absolute value of the signal level indicates the magnitude of the angular velocity.
[0031]
As described above, detection of x vibration (drive feedback) and detection of y vibration (yaw rate) include noise caused by voltage pulses applied to the drive electrodes by the drive circuits a1 to a4 and b1 to b4. And the differential amplifiers c1 to c8 and d1 to d5 calculate the difference between the signals of the detection electrodes at symmetrical positions, so that the differential output related to noise due to x excitation is As shown in the lowermost row of FIG. 4, only the noise appearing at the rising and falling points of the drive pulse is present and is removed by the fundamental detection circuits e1 to e5. Thereby, the S / N of the x vibration feedback signal that is the output of the synchronous detection circuits e1 to e4 is high, and the S / N of the angular velocity signal that is the output of the synchronous detection circuit e5 is high.
[0032]
FIG. 5 schematically shows the outline of the vibration system of the angular velocity sensor shown in FIG. 1, and the characteristics of the angular velocity sensor shown in FIG. 1 will be described with reference to this. The angular velocity sensor has a tuning fork structure, and an x oscillator. 2 and 3 are vibrated in the opposite direction in the x direction. This state is shown in FIG. When an angular velocity is applied to the x vibrators 2 and 3 and the detection vibrators 5 and 6, the x vibrators 2 and 3 vibrate in the x direction. Vibrates in the y-direction perpendicular to. Since the detection vibrators 5 and 6 are stopped, no Coriolis force is received.
[0033]
When a Coriolis force is applied, the x vibrators 2 and 3 vibrate in the y direction, and their displacement in the y direction is proportional to the angular velocity.
y displacement = (angular velocity × oscillator velocity × oscillator mass) / y displacement which is a spring constant in the y direction. In the vibrators 2, 3/5, and 6, the vibration mode at the time of resonance in the detection direction y is that the x vibrators 2 and 3 are out of phase with each other, and the detection vibrators 5 and 6 are out of phase with each other. Coincides with the center of gravity O of the entire floating body of the angular velocity sensor. As a result, when the x vibrators 2 and 3 receive Coriolis force, the detection vibrators 5 and 6 vibrate in the y direction as shown in FIG. Note that the resonance frequency of the x vibrators 2 and 3 and the resonance frequency of the detection vibrators 5 and 6 are higher than the resonance frequency of the x vibrators 2 and 3 from the balance of sensitivity and compatibility. The resonance frequency is set slightly higher. From the relationship between the masses of the x vibrators 2 and 3, the masses of the detection vibrators 5 and 6, and the spring constants in the respective detection directions y, the x vibrators 2 and 3 are configured to be hardly displaced in the y direction. Instead, the detection vibrators 5 and 6 are greatly displaced. As described above, the accuracy (S / N ratio) of this sensor can be improved because the leakage (crosstalk) between the vibrations of the drive (x) and the detection (y) is small in principle.
[0034]
In addition, unlike the conventional structure, this structure is not designed to forcibly suppress vibrations, and is therefore a structure that is resistant to the effects of stress and temperature changes. In addition, since the fixed point of vibration for driving and detection almost coincides with the center of gravity of the sensor, and when subjected to Coriolis force as described above, it does not involve any rotational movement at all, so the center of gravity does not have any support. In position, the support point is stationary. Therefore, since external vibration (when mounted on a vehicle or the like) hardly affects the driving vibration and detection vibration of the sensor, the S / N ratio is improved as compared with the conventional type. Further, since the support is as described above, there is little influence of thermal expansion due to temperature or the like, and temperature correction can be reduced. Therefore, the S / N ratio is improved as compared with the conventional type.
[0035]
In the angular velocity sensor shown in FIG. 1, the loop 1 which is a spring portion continuously floats and supports the center of the mass of the x vibrators 2 and 3, so that the spring effect due to the deformation of the vibration mass (2, 3) itself. Is substantially unchanged, and the x vibrations of the x vibrators 2 and 3 are close to simple vibrations. The overall size can be reduced without changing the length of the spring (1). Since the driving force of x excitation applied to the x vibrators 2 and 3 is applied to the connection point (one point) with the loop 1, components such as torsion are hardly generated in the vibration mode, and the x vibration becomes a single vibration.
[0036]
Further, since the angular velocity sensor shown in FIG. 1 is a bi-resonant x vibration system, the amplitude of the x vibrators 2 and 3 is amplified and a large change can be obtained. Thereby, since it can drive with little energy, it can reduce cost. Since the displacement output can be increased, S / N is improved.
[0037]
Furthermore, the fixed point of each vibration mode of the dual resonance of the angular velocity sensor shown in FIG. 1 is the center of gravity O, and the x vibrators 2 and 3 are supported by the center of gravity O (single point). Thereby, since the vibration leakage of x vibration does not occur in principle, the amplification factor of the detected vibration y can be increased. 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 drive vibration, and the drive can be driven with a single vibration. Therefore, S / N is improved.
[0038]
In addition, since each of the gravity centers of the x vibration system and the y vibration system of the angular velocity sensor shown in FIG. 1 is one point O, which is the same point, the spring portions (1, 4, 7, 8) No stress is applied and the temperature characteristics are improved. In particular, the reliability (stability) of angular velocity detection is high when used in an environment with a large temperature change, such as in-vehicle.
[0039]
Further, since the spring portions (1, 4, 7, 8) of the angular velocity sensor shown in FIG. 1 are all formed in a bent shape, no stress load is generated on the spring portion due to the influence of thermal expansion due to temperature. The temperature characteristics are improved. Compared with the same resonance frequency, the outer shape can be reduced, so that the cost is low.
[0040]
In addition, springs (41, 42) for stress relaxation are added to the x-drive vibration springs. As a result, the non-linearity of the x drive vibration is improved, and the S / N is improved because the vibration is caused by a single vibration.
[0041]
When the angular velocity is not applied, the detection vibrators 5 and 6 are substantially stationary, and the detection vibration y does not resonate with the drive vibration x. Therefore, the detection vibration y singly vibrates and the S / N of the angular velocity signal is reduced. improves.
[0042]
Since the y detection displacement of the detection vibrators 5 and 6 is designed to be larger than the detection displacement of the detection directions y of the x vibrators 2 and 3 (the masses of 5 and 6 are smaller than those of 2 and 3), The influence of the y detection vibration on the x drive vibration is relatively reduced, and the S / N of the angular velocity signal is improved. Since the x distance of the mass centers (53, 63) of the detection vibrators 5, 6 with respect to the fixed point O can be increased, and the displacement in the y direction of the detection vibrators 5, 6 can be increased by the lever principle, the S of the angular velocity detection signal / N can be increased.
[0043]
The detection vibrators 5 and 6 of the angular velocity sensor shown in FIG. 1 are supported by frames (74 and 75) close to a rigid body via flexible beams 71 and 72 having high spring property (flexibility) in the y direction. . Since the detection vibrators 5 and 6 are not in the torsional rotation mode but are vibrated in parallel with each other and in opposite phases, an ideal sine output is obtained when the detected vibration y is detected by capacitance, and the angular velocity signal S / N is improved.
[0044]
The angular velocity sensor shown in FIG. 1 can be constructed on a silicon wafer by a semiconductor process using a lithograph and can be manufactured by a conventional semiconductor process, so that it can be produced at a low cost. A floating body (4, 1-3 / 5 to 8) is formed from a single plate, can be easily shaped by a semiconductor process, and can be produced at low cost.
[0045]
FIG. 6 shows a structure of a modification of the angular velocity sensor shown in FIG. 1 different from that shown in FIG. In this modification, an additional loop 47 and a y beam 48 are interposed between the floating anchor 120 and the x beam 46 shown in FIG. 1, and the x beam 46 is connected to the anchor 120 by these.
[0046]
FIG. 7 schematically shows the outline of the vibration system of this modification. In this modification, since the loop 47 is added, the torsional vibration is effectively propagated similarly to the embodiment of FIG. 1, and the excitation vibration x is cut off more effectively than the embodiment of FIG. . That is, the effect of not transmitting the x vibration of the x vibrators 2 and 3 to the detection vibrators 5 and 6 and the substrate 100 is high.
[Brief description of the drawings]
FIG. 1 is a plan view of an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view taken along line A2-A2 of FIG.
FIG. 3 is a block diagram showing an electric circuit for exciting the embodiment shown in FIG. 1 and obtaining an angular velocity signal.
4 is a time chart showing voltages applied to drive electrodes 91 to 94 for x excitation by drive circuits a1 to a4 and b1 to b4 shown in FIG.
5 is a plan view schematically showing a configuration outline of a vibration system of the angular velocity sensor shown in FIG. 1. FIG. 5 (a) shows a state where no angular velocity is applied, and FIG. 5 (b) shows a state where an angular velocity is added. .
6 is a plan view showing a changing portion of the angular velocity sensor shown in FIG. 1. FIG.
FIG. 7 is a plan view schematically showing a configuration outline of a vibration system of an angular velocity sensor showing a change unit in FIG. 6;
[Explanation of symbols]
1: 2nd loops 11-14: x, y parallel sides 2, 3: x vibrators 21, 22, 31, 32: x vibrators 4: first support beams 41, 42: flexible rectangular loops 43, 44 : Y arm 45: first loop 46: x beam 47: additional loop 48: y beam 5, 6: detection vibrator 51, 52/61, 62: half piece 7, 8: beam 9A for supporting the detection vibrator, 9B, 91-94: Drive detection electrodes 10A, 10B, 101-104: Drive electrode 100: Substrate 120: Floating body anchor

Claims (4)

a pair of x oscillators at positions symmetrical about a point O on the x, y plane;
a connecting beam distributed in the x, y plane, symmetrical about the point O, continuous to each of the pair of x-vibrators and deflected at least in the x direction;
A first support beam that is symmetric with respect to point O and includes a first flexible beam continuous to the connecting beam and deflected in the x and y directions between point O and the connecting beam;
A detection oscillator symmetric with respect to point O;
A second support beam that is symmetric with respect to point O and includes a second flexible beam that is continuous with the detection transducer and that deflects in the y direction between point O and the point O;
A loop centered at point O, the first flexible beam and the second flexible beam being continuous;
An anchor supporting the center of the loop at point O;
An anchor supporting the first support beam and the second support beam at point O;
Excitation means for oscillating and driving a pair of x-oscillators in opposite directions in the x direction;
Means for detecting vibration in the y direction of the detection vibrator;
An angular velocity sensor comprising:   2. The angular velocity sensor according to claim 1, wherein the detection vibrators are separated from each other in the x direction from the y axis and are in a symmetrical position with respect to the point O and are paired.   The second support beam includes a detection vibrator distributed on the x, y plane and a reinforcing beam surrounding the second flexible beam and supported by an anchor continuously to the second flexible beam. Angular velocity sensor.   The angular velocity sensor according to claim 1, wherein the connecting beam has a loop shape with the point O as a center of the loop.

Images