JP2001174265A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an angular velocity sensor by which a stress is hard to concentrate in a connection part when the sensor is operated and when a disturbance acceleration is applied, by which the breakdown strength of a spring and that of comb teeth are enhanced and whose durability is high. SOLUTION: The angular velocity sensor is provided with a plurality of sensor constituent elements which are composed of at least a support frame 1. The elements are composed of a support substrate 10 which is fixed to the support frame 1. The elements are composed of two first vibrating bodies 2 which are coupled to the support frame 1 via suspension springs 3. The elements are composed of coupling springs 4 which couple the two first vibrating bodies 2. The elements are composed of second vibrating bodies 5 which are coupled to the first respective vibrating bodies 2 via vibrating springs 6. The elements are composed of moving comb teeth 9 which are coupled to the second vibrating bodies 5. The elements are composed of fixed electrodes 7 which are fixed to the support substrate 10. The elements are composed of fixed comb teeth 8 which are coupled to the fixed electrodes 7. In any of the sensor constituent elements, a part which is coupled to at least one other sensor constituent element is formed in an arc shape.

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 for detecting an angular velocity using a Coriolis force.

[0002]

2. Description of the Related Art FIG. 7 shows, for example, a document "A Pre
Ccision Yaw Rate Sensor in
Silicon Micromachining ”,
Digest of Transducers' 9
7 (1997 International Con
reference on Solid-State Se
nors and Actuators). 84
7-850. 1 shows a conventional angular velocity sensor described in Japanese Patent Application Laid-Open (Kokai) No. H11-27139.
In FIG. 7, reference numeral 101 denotes a frame for supporting the components of the sensor, 102 denotes a vibrating mass body, and 103 denotes a vibration loss
U-shaped spring 104 for suspending 2 from frame 101
Are acceleration sensors mounted on the vibrating mass body 102, 10
Reference numeral 5 denotes a connection spring that connects the angular vibration mass bodies 102.

The acceleration sensor 104 has two vibrating mass bodies 1
The oscillating mass 102 is mounted on the frame 101 by four U-shaped springs 103 respectively. Further, the two vibrating mass bodies 102 are connected by a connecting spring 105.

Since the thickness of the four U-shaped springs 103 and the connecting spring 105 in the Z direction is larger than the thickness in the X direction, the rigidity in the X direction is small, but the rigidity in other directions is large. That is, the vibrating mass body 102 has a structure that easily vibrates only in the X direction.

FIG. 8 is an enlarged view of the acceleration sensor 104 viewed from the Z direction. The acceleration sensor 104 includes a support spring 106, an acceleration sensor mass 107, a movable electrode comb 108 supported by the acceleration sensor mass 107, and a fixed electrode comb 10 with a movable electrode comb 109 interposed between the electrodes.
9. A fixed electrode 110 that supports the fixed electrode comb teeth 109. The hatched portion in FIG. 8 indicates the vibrating mass body 1
02, and the other structures are separated from the surface of the vibrating mass body 102 by a certain distance.

[0006] The acceleration sensor mass body 107 is
6 support both ends. The support spring 106 is y
Because the spring stiffness in the direction is configured to be small,
It is easy to move only in the y direction. The movable electrode comb teeth 108 are formed on the acceleration sensor mass, and the fixed electrode comb teeth 109 are formed on the fixed electrode 110.

Next, the operation will be described. The two vibrating mass bodies 102 are excited at a constant frequency in the direction of the arrow (x direction) by Lorentz force. The vibration frequencies of the two vibrating mass bodies 102 are the same, and the phases are shifted by 180 degrees. That is, the two vibrating mass bodies 102 vibrate in opposite phases. In this state, when an angular velocity ω is applied around the z-axis of the sensor (that is, when the sensor itself rotates), Coriolis acceleration a having a magnitude represented by the following equation (1) is generated in the y-axis direction.

A = 2vω (1) where v is the vibration speed of the excitation in the Y-axis direction.

The acceleration a excites the acceleration sensor mass 107 in the y direction, and its amplitude is proportional to the acceleration a. That is, if the amplitude of the vibration velocity v is constant,
The amplitude of the acceleration sensor mass 107 is proportional to the angular velocity ω. Due to the vibration of the acceleration sensor mass 107, the distance between the movable electrode comb teeth 108 and the fixed electrode comb teeth 109 changes, and the capacitance between the comb teeth changes. By converting this change in capacitance into a change in voltage, the angular velocity ω can be measured.

FIG. 9 is a schematic sectional view of a conventional angular velocity sensor (see FIG. 7) disclosed in the above-mentioned document. In the figure, 112 indicates a cap wafer, 113 indicates a glass wafer, and 114 indicates sealing glass.

[0011]

As described above, the conventional angular velocity sensors are mainly used for vehicles, and are used for attitude control of automobiles and navigation systems. For this reason, there is a demand for a small-sized one having high sensitivity as a performance. In order to increase the sensitivity of the angular velocity sensor, it is necessary to increase the change in the capacitance between the comb teeth or to increase the capacitance itself.
In order to increase the change in the capacitance between the comb teeth, there are a method of increasing the Coriolis acceleration a and a method of increasing the vibration amplitude of the acceleration sensor mass 107 with respect to the same Coriolis acceleration a.

For the former, a method of increasing the amplitude of the vibration velocity v shown in the above equation (1) is adopted. That is, this is a method of increasing the amplitude of the excitation by the Lorentz force as much as possible. For this reason, the spring 103 and the connection spring 10
5 has a problem that large strain is generated, and in particular, a large stress concentration occurs near the fixed ends of these springs, and the spring is easily broken.

For the latter, a method has been adopted in which the rigidity of the support spring 106 of the acceleration sensor is reduced to increase the displacement in the y direction. Therefore, as in the former case, there is a problem that large distortion occurs in the support spring 106 and the support spring 106 is easily broken.

On the other hand, in order to increase the capacitance itself,
It is necessary to reduce the interval between the comb teeth and increase the area where the comb teeth face each other. For this reason, a method of packing a large number of comb teeth by reducing the thickness of the comb teeth itself or increasing the length of the comb teeth has been adopted. Therefore, there is a problem that the comb teeth are easily broken from the fixed end of the comb teeth when an acceleration impact is applied.

Furthermore, in the conventional angular velocity sensor,
As shown in the cross-sectional view of FIG. 9, the vibrating mass body 102 is suspended from the spring 103 and is in a state of floating from the glass wafer. Therefore, when an acceleration impact is applied in the Z direction and the vibrating mass body 102 is largely displaced in the Z direction, the spring 10
3 has a problem that a stress exceeding the breaking stress is generated and the spring 103 is broken.

The present invention has been made to solve the above-described problems, and has as its object to obtain an angular velocity sensor having excellent durability and high reliability.

[0017]

An angular velocity sensor according to the present invention comprises at least a support frame, a support substrate fixed to the support frame, and two second frames connected to the support frame via suspension springs. One vibrating body, a connecting spring for connecting the two first vibrating bodies, a second vibrating body connected to each of the first vibrating bodies via a vibrating spring, and the second vibrating body And a plurality of sensor components comprising a fixed electrode fixed to the support substrate and a fixed comb tooth connected to the fixed electrode, wherein at least one of the sensor components is at least The part connected to the other one of the sensor constituent elements is formed in an arc shape. Further, in the angular velocity sensor according to the present invention, the connection portion of the suspension spring connected to the support frame and the first vibrator has an arc shape. Further, the angular velocity sensor according to the present invention is the angular velocity sensor according to the present invention, wherein a connection portion of a vibration spring connected to the first vibrator and the second vibrator has an arc shape. In the angular velocity sensor according to the present invention, a portion where the first vibrator and the connection spring are connected has an arc shape. Further, in the angular velocity sensor according to the present invention, the connection portion of the fixed comb tooth connected to the fixed electrode has an arc shape. Further, in the angular velocity sensor according to the present invention, a connection portion of the movable comb tooth connected to the second vibrator has an arc shape. Further, in the angular velocity sensor according to the present invention, the thickness of the fixed comb tooth is made thicker toward the connection portion from the tip portion. Further, the angular velocity sensor according to the present invention is a mechanism for limiting a displacement amount of the second vibrating body in a direction perpendicular to both the vibration direction of the first vibrating body and the vibration direction of the second vibrating body. Was provided on the surface of the second vibrator facing the support substrate.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an angular velocity sensor according to Embodiment 1 of the present invention will be described with reference to the accompanying drawings. FIG. 1A is a plan view of the angular velocity sensor according to the first embodiment. FIG. 1B is a cross-sectional view taken along the line aa ′ in FIG.

In FIGS. 1A and 1B, reference numeral 1 denotes a support frame made of silicon, 10 denotes a support substrate made of silicon or glass, and the support frame 1 is fixed on the support substrate 10. 2 is a first vibrator. A hatched spring 3 is provided for connecting the support frame 1 and the first vibrating body 2. Reference numeral 4 provided with a mark “○” denotes a connection spring provided for connecting the two left and right first vibrators 2.

As shown in FIG. 1B, the cross sections of the suspension spring 3 and the connecting spring 4 are formed thicker in the Z direction than in the Y direction, so that the rigidity in the Y direction is higher than the rigidity in other directions. Small. Therefore, the first vibrating body 2 supported by these springs 3 and 4 easily vibrates only in the Y direction. 5 is a second vibrator.

In FIG. 1A, reference numeral 6 denotes a vibration spring provided for connecting the first vibrator 2 and the second vibrator 5. Since the cross section of the vibration spring 6 is formed thicker in the Z direction than in the X direction, the rigidity in the X direction is smaller than the rigidity in other directions. Therefore, the second vibrator 5 easily vibrates only in the X direction.

A fixed electrode 7 is fixed on the support substrate 10. Reference numeral 8 denotes a fixed comb formed integrally with the fixed electrode 7. Reference numeral 9 denotes a movable comb formed integrally with the movable electrode. A groove 12 is formed in the support substrate 10 so that the vibrator and the spring can move.

Next, the outline of the operation of the angular velocity sensor according to the present embodiment will be described. The two first vibrators 2 are excited at a constant frequency in the Y direction by Lorentz force. The vibration frequencies of the two first vibrators 2 are the same, and the phase is 18
It is shifted by 0 degrees. That is, the two first vibrators 2 vibrate in opposite phases. As a matter of course, since the vibration spring 6, the second vibration body 5, and the movable comb tooth 9 are also connected to the first vibration body 2, they vibrate in the Y direction in the same vibration state. In this state, when an angular velocity ω is applied around the Z axis of the sensor (that is, when the sensor itself rotates), a Coriolis acceleration a having a magnitude represented by the following equation (2) is generated in the X axis direction.

A = 2vω (2) where v is the vibration speed of the excitation in the Y-axis direction.

The acceleration a excites the second vibrating body 5 in the X direction, and its amplitude is proportional to the acceleration a. That is, if the amplitude of the vibration velocity v is constant, the amplitude of the second vibrator 5 is proportional to the angular velocity ω.

The vibration of the second vibrating body 5 causes the fixed comb teeth 8
The distance between the movable comb teeth 9 changes, and the capacitance between the comb teeth changes. By converting this change in capacitance into a change in voltage, the angular velocity ω can be measured.

Further, features of the first embodiment will be described in detail with reference to FIG. In FIG. 1A, the portions A and B encircled by ○ indicate the fixed end portion of the suspension spring 3 connected to the support frame 1 and the first vibrator 2. FIG.
(A) and (b) of FIG. 2 show enlarged views of these fixed end portions. As shown in the enlarged views of FIGS. 2A and 2B, the connection portion is characterized by being formed in an arc shape with a radius of curvature R.

The portions C and D encircled by ○ indicate the fixed end portions of the vibration spring 6 connected to the first vibrator 2 and the second vibrator 5. 2 (c) and 2 (d) show these enlarged views. As shown in the enlarged views of FIGS. 2C and 2D, the connection portion is characterized in that it is formed in an arc shape having a radius of curvature R.

The portion E surrounded by a circle indicates a fixed end portion of the first vibrating body 2 and the connecting spring 4. FIG. 2H shows an enlarged view of this portion. As shown in the enlarged view of FIG. 2H, the connection portion is characterized in that it is formed in an arc shape with a radius of curvature R.

The portions F and G surrounded by circles indicate a connection portion between the fixed comb teeth 8 and the fixed electrode 7 and a connection portion between the movable comb teeth 9 and the movable electrode 5. 2 (e) and 2 (g) show these enlarged views. As shown in the enlarged views of (e) and (g) of FIG. 2, the connection portion is characterized in that it is formed in an arc shape with a radius of curvature R.

FIG. 1B is a cross-sectional view of FIG.
The portion of H surrounded by indicates the cross section of the connection portion between the fixed comb tooth 8 and the fixed electrode 7. FIG. 2 (i) shows these enlarged views. As shown in the enlarged view of FIG. 2 (i), the connection portion is characterized by being formed in an arc shape.

The magnitude of the radius of curvature R of each connection portion is as follows:
When the width of the connection portion is 2S, it is preferably 0.1S or more, and more preferably S. This is because generally, when the radius of curvature R is smaller than 0.1 S, the stress concentration at the connection part rapidly increases. For example, the literature (Shokabo, Material Strength Data Book, 5th Edition, 776-
(Page 777) introduces a graph of the bending experiment formula.

FIG. 3 shows this graph. In FIG. 3, it can be said that h = S. In addition, judging from the shapes of the enlarged views in FIGS. 2A to 2I, D / d> 5 can be said in most cases. From FIG. 3, when ρ / h <0.1, Shape factor αk
(Ratio of the maximum stress to the nominal stress or the average stress of the part)
Can be seen to rise extremely. When ρ = R and h = S are substituted, it can be seen that the stress concentration sharply increases when R <0.1S.

According to the first embodiment, since the connecting portions of the springs and the comb teeth are formed in an arc shape, stress concentration hardly occurs in the connecting portions when the sensor is operated and when a disturbance acceleration is applied. . Therefore, the breaking strength of the spring and the comb teeth is improved, and a highly durable angular velocity sensor can be expected.

Embodiment 2 FIG. 4 is a sectional view of the vicinity of the fixed comb teeth 8 in the angular velocity sensor shown in FIG. As is clear from this cross-sectional view, Z
It is characterized in that the thickness in the direction is formed so as to gradually increase in thickness from the tip end portion A to the connection portion B. Such a shape can be realized by processing the fixed electrode constituent member from below the member by deep dry etching. With such a configuration, when an external force is applied to the fixed comb teeth 8 in the Z direction, stress concentration near the fixed end is reduced, and the breaking strength can be increased.

Embodiment 3 FIG. 5 is a diagram showing a configuration of an angular velocity sensor according to the third embodiment. 5A is a plan view of the angular velocity sensor according to the present embodiment, and FIG. 5B is a cross-sectional view taken along a line bb ′ in FIG. 5A. In FIGS. 5A and 5B, reference numeral 11 denotes a stopper provided to limit the amount of displacement of the second vibrating body 5 in the Z direction. Stopper 11
Is provided on the second vibrator 5, and its surface faces the surface of the support substrate 10 with the groove 12 interposed therebetween. In order to limit the amount of displacement of the second vibrating body 5 in the lower Z direction (downward in the drawing), the distance between the stopper 11 and the support substrate 10 needs to be set appropriately, and it depends on the structure. But usually 1μ
m to 50 μm is appropriate.

As described above, by providing the stopper and limiting the displacement of the second vibrating body 5 in the Z direction, the stress applied to the beam or the vibrating body when an external force is applied in the Z direction can be reduced. Therefore, an angular velocity sensor with improved breaking strength and high durability can be expected. In the present embodiment, the stopper 11
Are four for each second vibrating body 5 and are attached to the corners of the second vibrating body 5.
The number and position are not particularly limited as long as the function of limiting the amount of displacement in the direction is provided.

Embodiment 4 FIG. FIG. 6 is a sectional view of the angular velocity sensor according to the fourth embodiment. In FIG. 6, 13 is Z
The protection substrate is provided to limit the amount of displacement of the vibrating body and the beam in the direction, and the other configuration is the same as that of the third embodiment.

The protection substrate 13 is formed of silicon or glass, and is fixed on the support frame 1 by anodic bonding or sealing glass. By providing the protection substrate 13 in this manner, when an external force is applied in the Z direction and the vibrating body is displaced upward (upward in the drawing) in the Z direction, the surface of the groove 12 formed on the protection substrate 13 , The displacement of the vibrating body is limited. Therefore, in addition to the effect of the stopper shown in the third embodiment, the breaking strength of the vibrator is further improved, and a highly durable angular velocity sensor can be expected. The distance from the vibrator to the surface of the groove 12 depends on the structure.
m is appropriate.

[0040]

According to the present invention, at least a support frame, a support substrate fixed to the support frame, two first vibrators connected to the support frame via suspension springs, 2
A connecting spring for connecting the two first vibrators, a second vibrator connected to each of the first vibrators via a vibrating spring, and a movable comb tooth connected to the second vibrator And, a fixed electrode fixed to the support substrate, comprising a plurality of sensor components consisting of fixed comb teeth connected to the fixed electrode,
Since any one of the sensor components has at least a portion connected to the other sensor component formed in an arc shape, stress concentration occurs at the connection portion during operation of the sensor and when a disturbance acceleration is applied. It has the effect of being difficult. Furthermore, there is an effect that the breaking strength of the spring and the comb teeth is improved, and a highly durable angular velocity sensor can be realized. According to the present invention, since the connection portion of the suspension spring connected to the support frame and the first vibrator is formed in an arc shape, stress concentration occurs in the connection portion during operation of the sensor and when disturbance acceleration is applied. There is an effect that it hardly occurs. Further, there is an effect that the breaking strength of the spring and the comb teeth is improved, and a highly durable angular velocity sensor can be realized.

According to the present invention, since the connecting portion of the vibration spring connected to the first vibrating body and the second vibrating body is formed in an arc shape, when the sensor is operated and a disturbance acceleration is applied, the connection is made. There is an effect that stress concentration hardly occurs in the portion. Further, there is an effect that the breaking strength of the spring and the comb teeth is improved, and a highly durable angular velocity sensor can be realized.

According to the present invention, the portion where the first vibrator and the connection spring are connected is formed in an arc shape, so that stress concentration occurs at the connection portion when the sensor is operated and when a disturbance acceleration is applied. It has the effect of being difficult. Further, there is an effect that the breaking strength of the spring and the comb teeth is improved, and a highly durable angular velocity sensor can be realized.

According to the present invention, since the connection portion of the fixed comb tooth connected to the fixed electrode is formed in an arc shape, stress concentration hardly occurs at the connection portion during operation of the sensor and when a disturbance acceleration is applied. effective. Further, there is an effect that the breaking strength of the spring and the comb teeth is improved, and a highly durable angular velocity sensor can be realized.

According to the present invention, since the connecting portion of the movable comb tooth connected to the second vibrating body is formed in an arc shape, stress concentration occurs in the connecting portion when the sensor is operated and when a disturbance acceleration is applied. There is an effect that it hardly occurs. Further, there is an effect that the breaking strength of the spring and the comb teeth is improved, and a highly durable angular velocity sensor can be realized.

According to the present invention, the thickness of the fixed comb teeth is formed so as to gradually increase from the tip to the connection portion. Therefore, when an external force is applied to the fixed comb teeth, stress concentration near the connection portion is reduced. This has the effect of being relaxed and increasing the breaking strength.

According to the present invention, the mechanism for limiting the displacement of the second vibrating body in a direction perpendicular to both the vibration direction of the first vibrating body and the vibration direction of the second vibrating body. On the second vibrating body and on the surface facing the supporting substrate, the stress applied to the beam and the vibrating body when an external impact is applied can be reduced, and a highly durable sensor can be obtained. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an angular velocity sensor according to a first embodiment.

FIG. 2 is a diagram for describing an angular velocity sensor according to the first embodiment in detail;

FIG. 3 is a diagram for explaining the angular velocity sensor according to the first embodiment in more detail;

FIG. 4 is a diagram illustrating an angular velocity sensor according to a second embodiment;

FIG. 5 is a diagram for explaining an angular velocity sensor according to a third embodiment.

FIG. 6 is a diagram for explaining an angular velocity sensor according to a fourth embodiment.

FIG. 7 is a view for explaining a conventional angular velocity sensor.

FIG. 8 is a diagram for explaining a conventional angular velocity sensor in more detail.

FIG. 9 is a diagram for explaining a conventional angular velocity sensor in more detail.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 support beam, 2 first vibrator, 3 suspension spring, 4 connecting spring, 5 second vibrator, 6 vibrating spring, 7 fixed electrode, 8 fixed comb, 9 movable comb, 10 support substrate, 1
1 stopper, 12 groove, 13 protective substrate, 101
Frame, 102 vibrating mass, 103 spring, 104
Acceleration sensor, 105 connecting spring, 106 support spring, 107 acceleration sensor mass, 108 movable electrode comb, 109 fixed electrode comb, 110 fixed electrode, 111
Movable electrode.

Claims (8)

[Claims] At least a support frame, a support substrate fixed to the support frame, two first vibrators connected to the support frame via suspension springs, and two first vibrations A connecting spring for connecting the body, a second vibrating body connected to each of the first vibrating bodies via a vibrating spring, a movable comb tooth connected to the second vibrating body, and the support substrate A plurality of sensor components each including a fixed electrode fixed to the fixed electrode and fixed comb teeth connected to the fixed electrode, and any one of the sensor components is connected to at least the other sensor component. An angular velocity sensor characterized in that a part is formed in an arc shape. 2. The angular velocity according to claim 1, wherein a connection portion of the suspension spring connected to the support frame and the first vibrator is an arc shape among the sensor constituent elements. Sensor. 3. The angular velocity sensor according to claim 1, wherein a connecting portion of the vibration spring connected to the first vibrating body and the second vibrating body has an arc shape. 4. The angular velocity sensor according to claim 1, wherein a portion where the first vibrator and the connection spring are connected has an arc shape. 5. The angular velocity sensor according to claim 1, wherein a connection portion of the fixed comb tooth connected to the fixed electrode has an arc shape. 6. The connecting portion of the movable comb tooth connected to the second vibrating body has an arc shape.
2. The angular velocity sensor according to 1. 7. The angular velocity sensor according to claim 1, wherein the thickness of the fixed comb tooth is formed so as to gradually increase from a tip portion toward a connection portion. 8. A mechanism for limiting a displacement amount of a second vibrating body in a direction perpendicular to both of a vibration direction of the first vibrating body and a vibration direction of the second vibrating body, The angular velocity sensor according to any one of claims 1 to 6, wherein the angular velocity sensor is provided on a surface of the second vibrator that faces the support substrate.