JP2003270265A - Multi-axis acceleration detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve detection accuracy of acceleration by reducing effect of acceleration of other axis in a multi-axis acceleration detector. <P>SOLUTION: A folded beam 130 of the multi-axis acceleration detector 301A has a going beam 130a, a returning beam 130c and a connection part 130b. The other end of the going beam 130a is connected to a fixed part 134. A linear beam 126 extends in y-axis direction in nearly parallel and one end of it is connected to a joint 128. A mass 112 is connected to the other end of linear beam 126 and is variable in x-axis direction and y-axis direction. An acceleration detection electrode 121 in x-axis direction has a movable electrode 121a connected to the mass 112 and a fixed electrode 121b. The acceleration detection electrode 140 in y-axis direction has a movable electrode 140a connected to the joint 128 and a fixed electrode 140b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-axis (typically 2-axis or 3-axis) acceleration detection device for detecting acceleration in at least an x-axis direction and a y-axis direction orthogonal thereto.

[0002]

2. Description of the Related Art FIG. 16 is a plan view of a biaxial acceleration detecting device 1 disclosed in Japanese Patent Laid-Open No. 4-232875. Figure 1
7 shows a sectional view taken along the line AA of FIG. 16, and FIG. 18 shows a sectional view taken along the line AA when acceleration is applied in the x-axis direction. The two-axis acceleration detection device 1 shown in FIGS. 16 to 18 is a device that detects acceleration in the x-axis direction and the y-axis direction orthogonal to the x-axis direction. 4 straight beams 22, 2 connected at one end
4, 26, 28 and four strain gauges 30, 32, 34, 36 formed on each beam 22, 24, 26, 28.
And the other end of each beam 22, 24, 26, 28 is connected to form a mass 20 that is displaceable in the x-axis direction and the y-axis direction. The beams 22 and the like and the mass 20 are floating on a substrate (not shown).

As shown in the sectional view of FIG. 17, since the mass 20 has a downwardly projecting shape, the center of gravity G1 of the mass 20 is located below the center of gravity of each linear beam 22, 24, 26, 28. To do. Therefore, for example, when an acceleration in the x-axis direction is applied to the mass 20, the mass 20 rotates around the y-axis about the center of gravity G1. As a result, the linear beam 22,
26 bends as shown in FIG. 18, and each linear beam 22, 2
The strain gauges 30, 34 on 6 are subjected to bending forces. Since the left linear beam 22 bends downward, the upper surface of the linear beam 22 is subjected to compressive stress. For this reason,
The strain gauge 30 formed on the linear beam 22 contracts. On the other hand, the straight beam 26 on the right side is bent upward, so that the upper surface of the straight beam 26 is subjected to tensile stress. Therefore, the strain gauge 34 formed on the linear beam 26 expands. Therefore, each strain gauge 30,
By measuring the voltage appearing across both ends of 34, the direction and magnitude of the acceleration applied to the mass 20 can be known.

[0004]

[Problems to be Solved by the Invention]
The acceleration in the x-axis direction is applied to 0, and the mass 20 moves to the center of gravity G1.
When it is rotated about the y-axis about the strain gauges 3 not only on the linear beams 30 and 34 extending in the x-axis direction but also on the linear beams 24 and 28 extending in the y-axis direction shown in FIG.
2, 36 also deform. That is, when the mass 20 rotates about the center of gravity G1 around the y-axis, a twisting force is applied to the linear beams 24 and 28 extending in the y-axis direction, which causes strain on the linear beams 24 and 28 extending in the y-axis direction. Gauge 3
2, 36 will also be deformed. That is, the strain gauges 32 and 36 originally for detecting the acceleration in the y-axis direction are also deformed by the acceleration in the x-axis direction.

When the acceleration in the x-axis direction is applied to the mass 20 as described above, the mass 20 not only rotates about the center of gravity G1 but also the position of the center of gravity becomes G2 as shown in FIG. Is displaced in the x-axis direction. As a result, the strain gauge 30 receives a tensile stress and the strain gauge 34 receives a compressive stress. These stresses are due to strain gauges 30, 3
4 causes a detection error when obtaining the acceleration from the voltage appearing at both ends. Further, when the mass 20 is displaced in the x-axis direction by applying the acceleration in the x-axis direction, the strain gauges 32, 36
Also receives tensile stress in the x-axis direction and deforms. Furthermore, z
When an angular velocity about the axis is applied, each beam 22, 24,
Torsional force is applied to 26, 28, which causes strain gauges 30, 32, 3 on each beam 22, 24, 26, 28.
4, 36 will be deformed.

As described above, the conventional biaxial acceleration detecting device 1
Then, for example, when acceleration is applied in the x-axis direction, x is also applied to the strain gauges 32 and 36 that originally detect the acceleration in the y-axis direction.
There has been a problem that the influence of the acceleration in the axial direction greatly affects. That is, there is a problem in that the influence of the acceleration of the other axis is large, and as a result, the accuracy of detecting the acceleration in the detection axis direction deteriorates. However, it is difficult to realize a multi-axis acceleration detecting device that can reduce the influence of such other-axis acceleration, and there has been a strong demand for its realization.

It is an object of the present invention to reduce the influence of other axis acceleration in a multi-axis acceleration detection device and improve the accuracy of acceleration detection.

[0008]

Means for Solving the Problems, Actions and Effects A multi-axis acceleration detecting device embodying the technical idea of the present invention is a fixed part, a first beam, a second beam, a mass, and an x-axis direction. Is an apparatus for detecting accelerations in at least the x-axis direction and the y-axis direction, and the acceleration detection electrode and the acceleration detection electrode in the y-axis direction orthogonal thereto. The first beam has a forward beam portion and a return beam portion that extend substantially parallel to the x-axis direction, one end of each of the beam portions is connected, and a connection portion having a bending rigidity equal to or higher than that of the both beam portions. The other end of the outgoing beam portion is connected to the fixed portion. The other ends of both beam parts are arranged on the same side with respect to the connection part. The second beam extends substantially parallel to the y-axis direction, and one end thereof is directly or indirectly connected to the other end of the return beam portion of the first beam.
The mass is directly or indirectly connected to the other end of the second beam and is displaceable in the x-axis direction and the y-axis direction. The acceleration detection electrode in the x-axis direction has a movable electrode provided directly or indirectly on the mass and a fixed electrode. The y-axis acceleration detection electrode has a movable electrode provided directly or indirectly at the other end of the return beam portion of the first beam, and a fixed electrode (claim 1).

[0009] Here, one part is "indirectly" to another part.
"Connected" means that one part and another part are connected via another member. For example, the other end of the return beam part of the first beam and one end of the second beam may be connected via a connecting part. Further, the phrase "indirectly provided with another portion on one portion" means that the other portion is provided on another member connected to a portion of the portion.
For example, the movable electrode of the acceleration detection electrode in the y-axis direction may be provided at the connecting portion connected to the other end of the return beam portion of the first beam.

The present inventors connect the second beam directly or indirectly to the other end of the return beam portion of the first beam having the above-mentioned structure, and directly or indirectly to the other end of the return beam portion of the first beam. By connecting the movable electrode of the acceleration detection electrode in the y-axis direction, the influence of the acceleration of the other axis is significantly reduced as compared with the conventional acceleration detection device, and as a result, the acceleration detection with the acceleration detection accuracy greatly improved. Realized the device. That is, due to the structure in which the first beam, the second beam, and the acceleration detection electrode in the y-axis direction having the above-described configuration are combined, the voltage is applied in one axial direction, which has been a big problem in the conventional multi-axis acceleration detection device. It has been found that an effective effect can be obtained in which the acceleration significantly reduces the effect of the acceleration of the other axis that affects the detected value of the acceleration in the other axis direction.

Here, the following two contents are included in the "influence of acceleration of another axis" in this specification. Firstly, "the detection value changes due to displacement of the movable electrode in the detection axis direction due to the other axis acceleration" is included. For example, when the acceleration detection electrode in the y-axis direction is used as a reference, "the movable electrode of the acceleration detection electrode in the y-axis direction is displaced in the y-axis direction by the acceleration in the x-axis direction among the applied accelerations. Changes in the acceleration detection value (for example, the electrostatic capacitance between the movable electrode and the fixed electrode). Secondly, "the detection value changes due to displacement of the movable electrode in a direction other than the detection axis due to the acceleration of the other axis" is included. For example, when the acceleration detection electrode in the y-axis direction is used as a reference, "the movable electrode of the acceleration detection electrode in the y-axis direction is displaced in the x-axis direction by the acceleration in the x-axis direction among the applied accelerations. That the detected value of the acceleration of “changes” is included.

In order to facilitate understanding of the function and effect of the present invention,
13 and 14 show a part of an acceleration detecting device 501 embodying one aspect of the present invention. This device 501
The fixed portion 536, the first beam 532, and the second beam 52
7 and a mass 512. The first beam 532 is
Forward beam portion 532a and return beam portion 532c having a length L extending in the x-axis direction, and both beam portions 532a and 532b.
Is connected to one end of both beam portions 532a,
The connection portion 532b has bending rigidity equal to or higher than that of the connection portion 532c. The other end of the outgoing beam portion 532a is connected to the fixed portion 536. The other ends of both beam portions 532a and 532c are arranged on the same side with respect to the connection portion 532b. The second beam 527 has a length M, extends in the y-axis direction, and one end thereof is connected to the other end (displacement end A) of the return beam portion 532c of the first beam 532. The mass 512 is the second
It is connected to the other end of the beam 527. The fixed portion 536 is fixed to a substrate (not shown), and the beams 532 and 527 float above the substrate.

As shown in FIG. 13, the acceleration detecting device 50
When acceleration is applied to the first mass 512 in the positive direction of the x-axis, the second beam 527 bends and the return beam portion 532c of the first beam 532 also bends slightly. However, the connecting portion 5 in which one end of the return beam portion 532c is connected
The bending rigidity of 32b is equal to or higher than that of the beam portions 532a and 532c. Further, in FIG. 13, the displacement end A and the connecting portion C are
Distance N between (connecting portion of mass 512 and second beam 527) N
1 is equal to or longer than the distance N2 between the fixed portion 536 and the displacement end A. Therefore, the displacement amounts of the displacement end A of the return beam portion 532c in the x-axis direction and the y-axis direction are much smaller than the displacement amounts of the mass 512 in the x-axis direction and the y-axis direction. In the aspect of the present invention, the movable electrode (not shown) of the acceleration detection electrode in the y-axis direction is not the mass 512 having a large displacement amount in the x-axis direction or the y-axis direction but the displacement end (the other end) of the return beam portion 532c. ) Directly or indirectly connected to A. Therefore, the displacement of the movable electrode of the acceleration detection electrode in the y-axis direction due to the acceleration in the x-axis direction can be greatly suppressed.
Therefore, according to the acceleration detection device 501, the influence of the acceleration applied in the x-axis direction on the detected value of the acceleration in the y-axis direction can be significantly reduced.

Although FIG. 13 shows a mode in which the displacement end A of the return beam 532c is slightly displaced, it is necessary to properly adjust the spring constant of each beam portion 532a, 532c and the bending rigidity of the connecting portion 532b. Then, if the acceleration applied in the x-axis direction is within a predetermined range, the displacement of the displacement end A of the return beam portion 532c is extremely small (nearly zero).
can do.

As shown in FIG. 14, the acceleration detecting device 50
If acceleration is applied to the first mass 512 in the negative direction of the y-axis, the mass 512 is displaced in the y-axis direction. At this time, the displacement in the x-axis direction is restricted by the connecting portion 532b. Further, the forward beam section 532a and the return beam section 532
Since the length of c is almost the same, each beam portion 532a,
532c is symmetrically displaced with respect to the connecting portion 532b, and
The connecting portion 532b is displaced parallel to the y-axis. Therefore, the displacement end A can be displaced only in the y-axis direction. Therefore, the fluctuation B in the x-axis direction due to the vibration of the mass 512 in the y-axis direction is very small. That is, according to the acceleration detecting device 501, the influence of the acceleration applied in the y-axis direction on the detected value of the acceleration in the x-axis direction can be significantly reduced.

As described above, the present invention is extremely significant in that it is possible to greatly suppress "the change in the detection value due to the displacement of the movable electrode in the detection axis direction due to the other axis acceleration" among the effects of the other axis acceleration. It is something. Of course, the present invention is y
Regarding the movable electrode of the acceleration detecting electrode in the axial direction, "The movable electrode of the acceleration detecting electrode in the y-axis direction is displaced in the x-axis direction by the acceleration in the x-axis direction (movable in a direction other than the detection axis by the other axis acceleration. It is also useful in that it is possible to greatly suppress "the detection value changes due to the displacement of the electrodes". However, when the movable electrode is displaced in a direction other than the detection axis due to the acceleration of the other axis, the influence thereof can be suppressed relatively easily, for example, by the aspect of claim 6 described later.

However, when "the movable electrode is displaced in the detection axis direction by the other axis acceleration", since the displacement direction is the positive detection axis direction, it is difficult to distinguish it from the displacement due to the acceleration to be detected. In addition, even a slight displacement is detected with high sensitivity, and it is difficult to suppress the influence. In that sense, as described above, the present invention significantly reduces the “change in the detection value due to the displacement of the movable electrode in the detection axis direction due to the other axis acceleration” in both the x-axis direction and the y-axis direction. Since it is possible, it has a very significant effect.

FIG. 19 shows a plan view of the angular velocity detecting device 2 described in Japanese Patent Application Laid-Open No. 10-170276, which was created by the present inventors. The angular velocity detection device 2 is a device that detects an angular velocity around the z-axis, and includes fixed portions 66, 68,
82, 84 and the first beams 62, 64, 78, 80,
Second beams 56, 58, 72, 74 extending in the y-axis direction
, Connecting portions 60 and 76, mass 50, and capacitance detection electrode 5
2 and excitation amplitude detection electrodes 70 and 86. The excitation amplitude detection electrodes 70 and 86 are connected to the coupling portions 60 and 76, respectively.
Movable electrodes 70a and 86a connected to the fixed electrode 70
b, 86b. The electrode fingers of the movable electrodes 70a and 86a and the fixed electrodes 70b and 86b extend in the y-axis direction. The fixed portions 66 and the like, the fixed electrode 70b and the like of each electrode are fixed to a substrate (not shown). The beams 62, the movable electrodes 70a of the electrodes, the connecting portions 60, and the mass 50 are
It floats on the substrate.

As described above, in the angular velocity detecting device 2,
Structures similar to those embodying one aspect of the invention are used. However, the implications of using this similar structure in the conventional angular velocity detecting device 2 and the implications of using the structure of the present invention in the acceleration detecting device of the present invention are as follows.
It is very different.

The angular velocity detector 2 shown in FIG. 19 utilizes the Coriolis force, and the Coriolis force acting on the mass 50 is the mass 5
It is proportional to a displacement velocity of zero. In order to increase the displacement speed of the mass 50, it is effective to increase the displacement of the mass 50 in the excitation direction (y-axis direction). Therefore, in the angular velocity detection device 2, the mass 50 is always kept in a vibrating state with a large amplitude. In the angular velocity detection device 2, as the excitation electrodes 70 and 86 for exciting the mass 50, the electrode fingers are fixed to the movable electrodes 70a and 86a extending in the excitation direction (y-axis direction) so as not to collide with each other even if the displacement is large. Electrode 70
b and 86b are used. When an angular velocity is applied to the large-amplitude vibrating mass 50, new Coriolis force causes new vibration in a direction perpendicular to the vibrating direction of the mass 50.
The angular velocity can be detected by detecting this vibration. As described above, the angular velocity detection device 2 needs a structure that generates a large-amplitude vibration state in the excitation direction and maintains the vibration state.

However, it is not necessary to maintain a large-amplitude vibration state in the acceleration detecting device, and conversely, in a structure that generates a large-amplitude vibration state, the influence of the acceleration of another axis appears significantly, and the response and linearity are high. Characteristics and temperature characteristics deteriorate, and it becomes difficult to detect acceleration. Therefore, in the acceleration detecting device, it is necessary to reduce the displacement of the mass in both the x-axis direction and the y-axis direction. That is, in the angular velocity detection device, since the angular velocity detection frequency is distributed around the excitation frequency which is relatively high, it is not necessary to consider the resonance characteristic from the DC component. However, the acceleration detection device needs to have flat vibration characteristics in the frequency range extending from the DC component to, for example, about 1 kHz. Therefore, when the resonance amplitude is large, the frequency characteristic is poor. Further, when the amplitude of the mass due to acceleration is large, the displacement from the electrode becomes too large and the linearity is greatly deteriorated. This causes deterioration of temperature characteristics.

As described above, the angular velocity detecting device and the multi-axis acceleration detecting device seem to be able to detect the angular velocity or the acceleration with the same structure at first glance, but actually, the required structures are greatly different.

In the angular velocity detecting device 2, [00
68], [0069], etc., a problem peculiar to the angular velocity detecting device that the above-described structure (especially the first beams 62, 64, 78, 80) generates a large-amplitude vibration state in the excitation direction. It is used to solve the problem. On the other hand, according to the present invention, the structure according to claim 1 has the effect of acceleration applied in one axial direction which is peculiar to the multi-axis acceleration detection device and is a very important subject, in the other axial directions. It is used to effectively solve the problem of appearing in the output. That is, the conventional angular velocity detecting device and the acceleration detecting device of the present invention have greatly different meanings from the above structure.

As described above, the present invention finds that a structure similar to the structure conventionally used for solving the problems peculiar to the angular velocity detecting device is applied to the acceleration detecting device, and the above-mentioned contracted claim 1 or Claims 2 to 15 described below
As a result of creating the configuration just suitable for the acceleration detecting device as described in (1), it is possible to find a great technical significance in that the problem peculiar to the acceleration detecting device can be effectively solved.

The apparatus according to claim 1 further comprises an acceleration detection electrode in the z-axis direction orthogonal to the x-axis direction and the y-axis direction, and detects the acceleration in the z-axis direction in addition to the x-axis direction and the y-axis direction. Is preferred. In this device, the mass can be displaced not only in the x-axis direction and the y-axis direction but also in the z-axis direction, and the acceleration detection electrode in the z-axis direction includes a movable electrode formed on the surface of the mass and a fixed electrode. It is preferable to have (Claim 2).

According to this aspect, it is possible to realize an acceleration detecting device capable of detecting acceleration in the z-axis direction in addition to the x-axis direction and the y-axis direction. Further, according to the above-described mass supporting structure of the first beam and the second beam, it is easy to prevent the mass from being displaced in the z-axis direction by the acceleration applied in the x-axis direction or the y-axis direction. Therefore, according to this aspect, it is possible to realize a multi-axis acceleration detection device in which the influence of the other-axis acceleration is small even in the z-axis direction. Note that "the mass (the movable electrode of the acceleration detection electrode in the z-axis direction) is displaced in the x-axis direction or the y-axis direction by the acceleration in the x-axis direction or the y-axis direction (in the direction other than the detection axis by the other-axis acceleration. With respect to "the detection value changes due to the displacement of the movable electrode)", its influence can be suppressed by, for example, an aspect of claim 6 described later.

In the apparatus of claim 1 or 2, at least two sets of beam units each having a fixed portion, a first beam and a second beam are provided, and each beam unit is arranged in parallel in the x-axis direction, The other end of the second beam of each beam unit is preferably directly or indirectly connected to the side portion of the mass extending in the x-axis direction (claim 3).

By providing at least two sets of beam units having the above structure as in this aspect, it is possible to further suppress the change in the detection value in the y-axis direction due to the acceleration in the x-axis direction. Further, it is possible to suppress the change in the detected value in the x-axis direction due to the acceleration in the y-axis direction. Further, when the acceleration in the z-axis direction is also detected, it is possible to suppress the change in the detected value in the z-axis direction due to the acceleration in the x-axis direction or the y-axis direction. That is, it is possible to make it less likely to be affected by the acceleration of the other axis.

In the apparatus according to the third aspect, a connecting portion is further provided, and the connecting portion has the other end of the return beam portion of the first beam of each beam unit arranged in parallel in the x-axis direction,
It is preferable that one ends of two or more second beams juxtaposed in the x-axis direction are connected to each other (claim 4).

By connecting the first beam and the second beam of each beam unit with the connecting portion as in this aspect, it is possible to suppress the displacement of each beam unit independently. It is possible to make it less susceptible to the influence of acceleration.

In the apparatus of claim 4, it is preferable that a movable electrode of the acceleration detecting electrode in the y-axis direction is further provided at the connecting portion (claim 5).

The connecting portion has the other end (displacement end) of the return beam portion of the first beam with a very small displacement amount in the x-axis direction and the y-axis direction even when acceleration in the x-axis direction is applied to the mass.
It is connected to the. Moreover, the connecting portion is the first beam and the second beam.
It is stably supported by the beam. For this reason, by providing the movable electrode of the acceleration detection electrode in the y-axis direction at this connecting portion, it is possible to more stably and less likely to be affected by the acceleration of another axis.

In the apparatus according to any one of claims 1 to 5, at least two sets of beam units each having a fixed portion, a first beam and a second beam are provided, and each beam unit is arranged so as to sandwich the mass. It is preferable that the other end of the second beam of the beam unit is directly or indirectly connected to both sides of the mass extending in the x-axis direction (claim 6).

Also according to this aspect, it is possible to make it more difficult to be affected by the acceleration of the other axis.

In the apparatus according to any one of claims 3 to 6, it is preferable that the first beams and the second beams are arranged at positions substantially line-symmetric with respect to a predetermined reference line (claim 7). .

By arranging the beams symmetrically as in this aspect, it is possible to further reduce the influence of the acceleration of the other axis.

In addition to the features of claim 1, claims 3 to 7
If at least two of the above modes are appropriately combined, the effect of the other-axis acceleration can be greatly reduced by the synergistic effect of the combination.

In the device according to any one of claims 1 to 7, the acceleration detecting electrode in one axial direction has a substantially constant facing area between the movable electrode and the fixed electrode even when the movable electrode is displaced in the other axial direction. It is preferable that the structure is such that (claim 8).

According to this aspect, among the influences of the accelerations of the other axes, "the detection values are changed by the displacements of the movable electrode in the directions other than the detection axis due to the accelerations of the other axes" can be significantly suppressed. That is, according to this aspect, even when the movable electrode is displaced in the other axial direction, the facing area between the movable electrode and the fixed electrode is substantially constant, and therefore the displacement causes a gap between the movable electrode and the fixed electrode of the acceleration detection electrode. It is possible to significantly suppress the change in capacitance. In this way, the influence of the acceleration of the other axis can be further reduced, so that the accuracy of detecting the acceleration can be further improved.

In the device according to any one of claims 1 to 8, it is preferable that the movable electrode of the acceleration detection electrode and the electrode finger of the fixed electrode in the detection axis direction extend in a direction substantially orthogonal to the detection axis direction ( Claim 9).

As described in comparison with the angular velocity detecting device, the acceleration detecting device is required to reduce the displacement of the mass. Then, it is required to realize a configuration for detecting this small displacement of the mass with high sensitivity. According to this aspect, even when the displacement of the mass due to the applied acceleration is small, the movable electrode of the acceleration detection electrode and the electrode finger of the fixed electrode in the detection axis direction (for example, the y-axis direction) are almost in the detection axis direction. Since it extends in the orthogonal direction (for example, the x-axis direction), compared with the case where the electrode fingers extend in the detection axis direction,
The change in capacitance between the movable electrode and the fixed electrode can be increased. Therefore, even when the applied acceleration is small and the displacement of the mass is small, the small acceleration can be detected with high sensitivity.

The apparatus according to any one of claims 1 to 9 further comprises a capacitance detection circuit for detecting a change in the positional relationship between the movable electrode and the fixed electrode of the acceleration detection electrode due to the applied acceleration as a change in electrostatic capacitance. It is preferable (claim 10).

According to this aspect, since the change in the positional relationship between the movable electrode and the fixed electrode can be electrically processed as the change in electrostatic capacitance, it is suitable for the processing by the electronic circuit, so that the acceleration detection accuracy can be further improved. it can.

In the device according to any one of claims 1 to 10, a differential circuit is further provided, and the acceleration detection electrode has two sets of movable electrodes and fixed electrodes, and one set of movable electrodes and fixed electrodes is provided. When the distance is increased by a predetermined value, the distance between the movable electrode and the fixed electrode of the other set is decreased by almost the same value as the predetermined value, and the difference circuit is fixed to the two sets of movable electrodes detected by the capacitance detection circuit. It is preferable to take the difference in the change in capacitance between the electrodes (claim 11).

According to this aspect, noise and the like can be significantly removed, compared with the case where a change in electrostatic capacitance is detected between a pair of movable electrode and fixed electrode of the acceleration detection electrode, and about Acceleration can be detected with twice the sensitivity.

According to a tenth or eleventh aspect of the present invention, a feedback circuit and a feedback electrode are provided, and when the output value of the capacitance detection circuit is input, the feedback circuit applies a voltage according to the output value to the feedback electrode. It is preferable that it is configured as follows (claim 1
2).

According to the feedback circuit of this aspect,
It is possible to generate an electrostatic attraction force between the feedback electrodes, which has substantially the same magnitude as the inertial force due to the acceleration component corresponding to the output value of the capacitance detection circuit and which is in the opposite direction. As a result,
The displacement of the mass can be kept almost zero in the direction in which the forces are balanced. If the displacement of the mass can be kept substantially zero even when the acceleration is applied, the influence of the acceleration applied to the mass in the one axial direction on the output in the other axial direction can be reduced. In addition, the problems associated with displacement of the mass can be solved or largely eliminated. For example, the response characteristics of the beam can be improved, the linearity of the beam can be improved, the temperature characteristics can be improved, and the collision between the electrode fingers of the movable electrode and the fixed electrode can be prevented.

In the apparatus according to any one of claims 1 to 12, it is preferable that the detuning rate is equal to or more than a predetermined value (claim 13). In this case, it is particularly preferable that the detuning rate is 1% or more (claim 14). Detuning rate of 3% or more is 10
Even more preferably, it is at most 00%. here,
The "detuning rate" is a value obtained by dividing the absolute value of the difference between the resonance frequency f1 in one axial direction and the resonance frequency f2 in the other axial direction by the resonance frequency f1 in one axial direction, that is, | f1-f2. | / F1.

According to this aspect, it is possible to further suppress the change in the detected value of the acceleration in the other axial direction due to the acceleration applied in the one axial direction. In this way, the influence of the acceleration of the other axis can be further reduced, so that the accuracy of detecting the acceleration can be further improved.

In the apparatus according to any one of claims 2 to 14, the mass has a first mass part, a second mass part, and a third beam, and the first mass part uses the third beam to form the second mass part. Preferably, the first mass part is displaceable in the z-axis direction with respect to the second mass part, and the second mass part is connected to the other end of the second beam. 15).

According to this aspect, the sensitivity in the z-axis direction may be adjusted mainly by the third beam. For this reason, the first beam and the second beam may be designed with the sensitivity in the x-axis direction or the y-axis direction taken into consideration, with little consideration given to the sensitivity in the z-axis direction. For this reason, the degree of freedom in designing each beam is increased, so that acceleration can be detected with more appropriate sensitivity in each axial direction.

[0052]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 15 shows a two-axis acceleration detection device that embodies one aspect of the present invention. This acceleration detecting device includes fixed portions 134 and 136, first beams (and curved beams) 166 and 168, second beams (straight beams) 126 and 127, a mass 120, and acceleration detection in the x-axis direction. The device includes an electrode 710 and an acceleration detection electrode 700 in the y-axis direction orthogonal to the electrode 710, and is a device that detects accelerations in the x-axis direction and the y-axis direction. The second beams 126 and 127 are
One end of the return beam portion 1 of the first beams 166, 168
It is connected to the other ends of 66c and 168c via a connecting portion 128a (corresponding to claim 4). The mass 120 is connected to the other ends of the second beams 126 and 127. Square 12
0 can be displaced in the x-axis direction and the y-axis direction. The acceleration detection electrode 710 in the x-axis direction has a movable electrode 710a provided on the right side surface of the mass 120 and a fixed electrode 710b. The acceleration detection electrode 700 in the y-axis direction is the movable electrode 70.
0a and fixed electrode 700b. Movable electrode 700a
Is a return beam portion 166 of the first beams 166, 168.
It is provided on the upper side surface of the connecting portion 128a connected to the other ends of the c and 168c (corresponding to claim 5).

In this acceleration detecting device, a first portion composed of a fixed portion 134, a first beam 166 and a second beam 126 is provided.
A beam unit and a second beam unit including the fixing portion 136, the first beam 168, and the second beam 127 are provided. The beam units are arranged in parallel in the x-axis direction. The other ends of the second beams 126 and 127 of each beam unit are connected to the upper side surface of the mass 120 (corresponding to claim 3). The first beams 166, 168 and the second beams 126, 127 are arranged at positions symmetrical with respect to the center line L of the mass 120 (corresponding to claim 7). Even when the movable electrodes 700a and 710a are displaced in the other axial directions, the acceleration detection electrodes 700 and 710 in the respective axial directions are movable electrodes 700a and 710a and the fixed electrode 700.
The facing areas of b and 710b are configured to be substantially constant (corresponding to claim 8).

Both ends of the upper side surface of the mass 120 are respectively x
It is connected to the lower ends of the second beams 126 and 127 arranged in parallel in the axial direction. Both the second beams 126 and 127 are arranged at positions symmetrical with respect to the center line L of the mass 120. Further, the upper ends of these second beams 126 and 127 are connected via one connecting portion 128a extending in the x-axis direction,
Return beams 166c, 1 of the first beams 166, 168
It is connected to the other end of 68c. As a result, the connecting portion 12
8a lower side, mass 120a upper side, two second
A box-shaped structure is formed by the beams 126 and 127. Further, the two second beams 126 and 127 have a parallel leaf spring structure. Further, the first beams 166, 1
As described in Paragraph No. [0014] of this specification, 68 itself has a structure capable of significantly reducing the influence of the acceleration acting in the x-axis direction on the detected value of the acceleration in the y-axis direction. Therefore, when acceleration in the x-axis direction is applied to the mass 120 due to the synergistic effect of these structures,
The mass 120 is displaced only in the x-axis direction, and displacement or rotational movement in the y-axis direction is almost prohibited. The movable electrode 700a of the y-axis direction detection electrode 700 is provided on the connecting portion 128a that is displaced in association with the mass 120. Therefore, displacement of the movable electrode 700a (coupling portion 128a) in the y-axis direction due to acceleration in the x-axis direction is almost prohibited. Therefore, the amount of change in the detected value due to the displacement of the movable electrode 700a in the direction of the detection axis (y-axis direction) due to the acceleration of the other axis (x-axis) can be made extremely small.

Further, as described in paragraph number [0015] of the present specification by the first beams 166 and 168 themselves, the influence of the acceleration acting in the y-axis direction on the detected value of the acceleration in the x-axis direction is significantly increased. It has a structure that can be reduced. Therefore, when the y-axis direction acceleration is applied to the mass 120 by the synergistic action of this structure and the above-mentioned structure,
The connecting portion 128 that is displaced in conjunction with the mass 120 is displaced only in the y-axis direction, and displacement or rotational movement in the x-axis direction is almost prohibited. The movable electrode 710 a of the x-axis direction detection electrode 710 is provided on the right side surface of the mass 120.
Therefore, displacement of the movable electrode 710a in the x-axis direction due to acceleration in the y-axis direction is almost prohibited. Therefore, the amount of change in the detection value due to the displacement of the movable electrode 710a in the direction of the detection axis (x-axis direction) due to the acceleration of the other axis (y-axis) can be made extremely small.

The first beams 166 and 168 have low rigidity in the y-axis direction but high rigidity in the x-axis direction. Therefore, the first
Return beams 166c and 168 of the beams 166 and 168
The other end of c is easily displaced in the y-axis direction, but difficult to be displaced in the x-axis direction. Further, the two first beams 166 and 168 are arranged in parallel in the x-axis direction.
The connecting portion 128a is connected to the other ends of the return beam portions 166c, 168c of the reference numerals 6, 168. Moreover, these first beams 166 and 168 are arranged at positions symmetrical with respect to the center line L of the mass 120. With this configuration, the connecting portion 128a is easily displaced in the y-axis direction, but displacement in the x-axis direction is almost prohibited. The movable electrode 700a of the y-axis direction detection electrode 700 is provided on the connecting portion 128a. For this reason, the movable electrode 700a is easily displaced in the y-axis direction by the acceleration in the y-axis direction, but it is almost prohibited to be displaced in the x-axis direction by the acceleration in the x-axis direction. Therefore, the amount of change in the detected value due to the displacement of the movable electrode 700a in the direction other than the detection axis (x-axis direction) due to the acceleration of the other axis (x-axis) can be made extremely small.

Fixed electrode 700 of y-axis direction detection electrode 700
The detection surface (lower side surface) of b and the detection surface of the movable electrode 700a provided on the upper side surface of the connecting portion 128a are in a position facing each other in parallel to each other with a minute gap. Both electrodes 700
The capacitance between a and 700b is
It is determined by the distance between b and the facing area. Here, the area of the detection surface of the fixed electrode 700b is smaller than the area of the detection surface of the movable electrode 700a. Therefore, as described above, the connecting portion 1
28a has a structure in which the displacement in the x-axis direction is strongly restricted, but even if the connecting portion 128a is displaced in the x-axis direction, the facing area between the electrodes 700a and 700b does not change and remains constant. is there. Therefore, the movable electrode 700a is moved in a direction other than the detection axis (x-axis direction) by the acceleration of the other axis (x-axis).
All measures are taken against the change in the detected value due to the displacement of.

Fixed electrode 710 of x-axis direction detection electrode 710
The detection surface (the right side surface) of b and the detection surface of the movable electrode 710a provided on the right side surface of the mass 120 are also opposed to each other in parallel to each other with a minute gap. The mass 120 is displaced in the x-axis direction when the acceleration in the x-axis direction is applied as described above. The x-axis direction detection electrode 710 is for detecting this acceleration. However, the mass 120 is displaced in the y-axis direction when acceleration in the y-axis direction is applied. As a result, the movable electrode 710a of the x-axis direction detection electrode 710 provided on the right side surface of the mass 120 is also displaced in the y-axis direction. However, since the area of the detection surface of the movable electrode 710a is larger than the area of the detection surface of the fixed electrode 710b, even if the movable electrode 710a is displaced in the y-axis direction, both electrodes 7
The facing area between 10a and 710b does not change and is constant.
Therefore, the movable electrode 710a of the x-axis direction detection electrode 710 is
Even if is displaced in the y-axis direction, its effect on acceleration detection in the x-axis direction is very small. Therefore, the other axis (y
The amount of change in the detection value due to the displacement of the movable electrode 710a in the direction other than the detection axis (y-axis direction) due to the acceleration of the axis) can be made extremely small.

As described above, according to the above-described acceleration detecting device, it is possible to remarkably reduce the influence of the other-axis acceleration. Therefore, the accuracy of detecting the acceleration can be greatly improved.

[0060]

Embodiments (First Embodiment) FIG. 1 shows an explanatory diagram of a triaxial acceleration detection device 301A of the first embodiment. FIG. 2 is an explanatory diagram of z-axis direction acceleration detection of this device 301A (AA in FIG. 1).
(Including line sectional views). FIG. 1 shows a plan view of a sensor unit 101A constituting a triaxial acceleration detection device 301A and a block diagram of a sensor circuit unit 201A. The triaxial acceleration detection device 301A is a device that detects acceleration in the x-axis direction, the y-axis direction orthogonal thereto, and the z-axis direction orthogonal to the xy plane.

The sensor portion 101A is formed on the silicon substrate 110, and has a mass 112, an upper beam unit 123 connected to the upper side surface 112a of the mass 112, and a lower beam unit connected to the lower side surface 120b of the mass 112. The unit 125, the two x-axis direction detection electrodes 121 and 122 connected to the right side surface 112d of the mass 112, the electrode connecting portion 138 connected to the upper beam unit 123, and the two connecting electrodes 138 connected to the electrode connecting portion 138. y-axis direction detection electrode 1
40, 141 and the mass 112 (inner mass part 1 shown in FIG.
18) is provided with two z-axis direction detection electrodes 180 and 182 arranged at positions sandwiching 18). Sensor circuit unit 201A
Is an x-axis direction circuit unit 202A and a y-axis direction circuit unit 220.
A and a z-axis direction circuit portion 240A shown in FIG.

The mass 112 includes an inner mass part (corresponding to a first mass part) 118, an outer mass part (corresponding to a second mass part) 120 arranged so as to surround the inner mass part 118, and an inner mass part 118. And eight mass connection beams (corresponding to a third beam) 114 and 116 for connecting the outer mass part 120 to each other.
The upper side surface 112a and the lower side surface 112b of the mass 112 (outer mass part 120) are arranged in the x-axis direction in the left side surface 112c and the right side surface 1.
12d extends in the y-axis direction. The inner mass portion 118 is formed in a flat plate shape, and has a rectangular shape in a plan view (when viewed from the z-axis direction). The mass 112 is the silicon substrate 1
Floating above 10.

The mass connecting beams 114, 116 are four beams 114a, 114b, 114 extending in the x-axis direction.
c, 114d and four beams 116 extending in the y-axis direction
a, 116b, 116c, 116d.
Of these, each pair of beam groups (114a, 116a),
(114b, 116b), (114c, 116c),
One end of (114d, 116d) is connected to the vicinity of each corner of the inner mass portion 118, and the other end of the beam group is connected to the periphery of each inner corner of the outer mass portion 120.

The upper beam unit 123 includes two fixing portions 134 and 136, two bent beams (corresponding to a first beam) 130 and 132, two linear beams (corresponding to a second beam) 126, 127 and the beam connecting portion 12
Have eight. The upper beam unit 123, except for the fixing portions 134 and 136 fixed to the silicon substrate 110,
It floats on the silicon substrate 110.

The bent beam 130 has two forward beam portions 130a and two return beam portions 130c extending parallel to the x-axis direction, and a connecting portion 130b. One end of each of the beam portions 130a and 130c is connected to the connecting portion 130b. The two forward beam portions 130a and the two return beam portions 130c are both made of silicon and have substantially the same length and width. Therefore, the spring constants are almost equal. Since the connecting portion 130b is wider than the forward and return beam portions 130a and 130c, both elongated beam portions 130a and 13c are formed.
Bending rigidity is higher than 0c. The other end of the outgoing beam portion 130a is connected to the fixed portion 134. That is, the other end of the outgoing beam portion 130a is a fixed end. The other end of the return beam portion 130c has a connecting portion 128 (auxiliary plate portion 1) described later.
28b). The other end of the return beam portion 130c is a displacement end that allows displacement in the y-axis direction. However, the displacement in the x-axis direction is restricted. The other end (fixed end) of the outgoing beam section 130a and the return beam section 130
The other end (displacement end) of c is arranged on the same side with respect to the connecting portion 130b.

The linear beams 126 and 127 are elongated beams extending in the y-axis direction. The beam connecting portion 128 is
It has an elongated main plate portion 128a extending in the x-axis direction and two substantially square auxiliary plate portions 128b and 128c. At both ends of the upper side surface of the long main plate 128a, the auxiliary plate 128
b and 128c are attached one by one. As described above, the bent beam 1 is formed on both ends of the upper surface of the beam connecting portion 128 via the auxiliary plate portions 128b and 128c.
The other ends (displacement ends) of 30, 132 (return beam portions 130c, 132c) are connected. On the other hand, the beam connection part 1
Each of the lower ends of the lower surface 28 is provided with a linear beam 12
One end of 6, 127 is connected. Straight beam 12
The other end of 6, 127 is the mass 112 (mass outer part 120)
It is connected to both ends of the upper side surface 112a.

As described above, the bent beams 130 and 132 and the linear beam 126 having the above structure are provided at both ends of the upper and lower side surfaces of the elongated beam connecting portion 128 extending in the x-axis direction.
127 is connected and the mass 112 is connected to the other ends of the linear beams 126 and 127, the mass 112 is firmly supported, and stable displacement with less blurring is possible, so that the acceleration of the other axis is reduced. The impact is extremely small.

In the acceleration detecting device, as described in comparison with the angular velocity detecting device 2 (see FIG. 19), the mass 11 is considered from the viewpoint of the influence of the acceleration of another axis, the responsiveness, the linearity, and the temperature characteristic.
It is necessary to reduce the displacement of 2. Therefore, it is necessary to reduce the displacement of the mass 112 in the y-axis direction due to the bent beam 130 and the like. In the present embodiment, the displacement of the mass 112 in the y-axis direction was successfully reduced by making the bent beam 130 and the like compact. Further, by disposing the bent beam 130 and the like in the space between the y-axis direction detection electrode 140 and the like and the mass 112, the acceleration detecting device 301A (sensor unit 101A) has been successfully downsized. These configurations are the configuration of the angular velocity detecting device 2 shown in FIG.
Further, it is significantly different from the configuration in which the bent beam 62 and the like are arranged around the four corners of the sensor section).

The lower beam unit 125 includes two fixing portions 150 and 152 and two bent beams 146 and 1.
48, two linear beams 142 and 143, and a beam connecting portion 144. The lower beam unit 125 is
It has almost the same structure as the upper beam unit 123.

Both beam units 123 and 125 (each beam constituting the beam unit, etc.) are arranged at positions substantially symmetrical with respect to a line that divides the mass 112 into two equal parts parallel to the x-axis direction. Also, both beam units 123, 12
The beams No. 5 are arranged substantially line-symmetrically with respect to a line that divides the beam into two equal parts in parallel with the y-axis direction of the mass 112. The bilaterally symmetric support structure of the mass 112 supports the mass 112 more firmly and enables stable displacement with less blurring, so that the influence of the other-axis acceleration is extremely small.

The center of gravity of the mass 112 and each beam unit 1
23, 125 linear beams 126, 127, 142,
143 and the bent beams 130, 132, 146, 14
The center of gravity of 8 is located at substantially the same height on the silicon substrate 110. According to this aspect, it is possible to suppress rotational movement of the mass 112 when acceleration is applied to the mass 112. As a result, the influence of the other axis acceleration can be greatly reduced.

The stopper portion 15 is provided at a position where the beam connecting portion 144 of the lower beam unit 125 is sandwiched in the y-axis direction.
6 is provided. By providing the stopper portion 156, a large acceleration is applied in the y-axis direction and the mass 1
Even if 12 is going to be displaced a lot, mass 1
Since 12 is prohibited from being displaced by a predetermined amount or more, it is possible to prevent the movable electrode such as the y-axis direction detection electrodes 140 and 141 connected to the mass 112 from colliding with the fixed electrode.

The provision of such a stopper portion 156 allows the electrode structure for detecting a small displacement due to a small acceleration with high sensitivity (for example, the movable electrodes 140a, 141a of the y-axis direction detecting electrodes 140, 141 as in this embodiment). And a structure in which the direction in which the electrode fingers of the fixed electrodes 140b and 141b extend is the direction (x-axis direction) orthogonal to the detection axis direction (y-axis direction), the electrode fingers collide with each other. It is particularly meaningful because it can be prevented from being destroyed. The position of the stopper portion 156 may be a position that sandwiches not only the connecting portion 156 described above but also the mass 112 and a displaceable portion such as a beam. In addition, the stopper portion 156 includes the connecting portion 156 and the mass 11
It is not always necessary to arrange the beam on both sides of the beam 2, and it may be arranged on only one side.

The x-axis direction detection electrodes 121 and 122 are movable electrodes 121a and 122a and fixed electrodes 121b and 122, respectively.
b, and fixed electrode terminals 121c and 122c. The movable electrodes 121a and 122a are the right side surface 112 of the mass 112.
It is floating while connected to d. Fixed electrode terminal 121
c and 122c are fixed to the silicon substrate 110,
The fixed electrode 121 is attached to the fixed electrode terminals 121c and 122c.
b and 122b are attached. FIG. 3 shows an enlarged plan view of the x-axis direction detection electrodes 121 and 122. As shown in FIG. 3, the movable electrode 121a includes two movable electrode fingers 121a-1 to 121a-6 at two positions at equal intervals in the x-axis direction, and two movable electrode fingers 121a-1 to 121a-6 extending in a direction away from the center in the y-axis direction. Have. The fixed electrodes 121b extend in the direction of approaching from the outside in the y-axis direction, two in each of the three fixed electrodes in the x-axis direction.
The book has fixed electrode fingers 121b-1 to 121b-6.

The movable electrode fingers 121a-1 to 121a-3 extending in the positive direction of the y-axis of the movable electrode 121a and the fixed electrode finger 121b extending in the negative direction of the y-axis of the fixed electrode 121b.
-1 to 121b-3 are arranged so as to mesh with each other. Movable electrode fingers 121a-4 to 121a-6 extending in the negative direction of the y-axis of the movable electrode 121a, and the fixed electrode 12.
Fixed electrode finger 121b-4 extending in the positive direction of the y-axis of 1b
.About.121b-6 are also arranged so as to mesh with each other.

As shown in FIG. 3, the x-axis direction detection electrode 12
2 is also connected to the right side surface 112d of the mass 112 and has a configuration similar to that of the left side y-axis direction detection electrode 121 described above. However, the n-th movable electrode finger 121a-n from the right of the upper movable electrode 121a (hereinafter referred to as "n-th from right").
Is omitted) is the fixed electrode finger 121 of the fixed electrode 121b.
The lower movable electrode 1 is arranged on the left side of b-n.
The movable electrode fingers 122a-n of 22a correspond to the fixed electrodes 122b.
It is different in that it is arranged on the right side of the fixed electrode fingers 122b-n.

Therefore, for example, when the mass 112 is displaced in the positive direction of the x-axis, the movable electrode fingers 121a-n of the upper movable electrode 121a connected to the mass 112 and the fixed electrodes of the upper fixed electrode 121b are connected. The distance between fingers 121b-n decreases. On the other hand, the distance between the movable electrode finger 122a-n of the lower movable electrode 122a connected to the mass 112 and the fixed electrode finger 122b-n of the fixed electrode 122b increases. That is, the two x-axis direction detection electrodes 121 and 12
2 has a structure complementary to each other.

Further, as shown in FIG.
The distance between the movable electrode finger 121a-n of a and the fixed electrode finger 121b-n of the fixed electrode 121b is between the movable electrode finger 121a-n of the movable electrode 121a and the fixed electrode finger 121b- (n + 1) of the fixed electrode 121b. Narrow compared to the distance. That is, the distance between the movable electrode finger 121a-n and the two fixed electrode fingers 121b-n and 121b- (n + 1) adjacent thereto is different. Therefore, the electrostatic capacitance between the movable electrode 121a and the fixed electrode 121b is determined by the movable electrode fingers 121a-n.
It may be considered that it is determined only by the sum of the electrostatic capacities between the fixed electrode fingers 121b-n and.

As described above, the electrode fingers 121a-n and 121b-n of the movable electrode 121a and the fixed electrode 121b extend in the y-axis direction orthogonal to the x-axis direction (detection axis direction).
In this case, the change in capacitance is detected by the change in the distance between the electrode fingers 121a-n and 121b-n of the movable electrode 121a and the fixed electrode 121b. If the electrode fingers of the movable electrode 121a and the fixed electrode 121b are configured to extend in the x-axis direction (detection axis direction), the movable electrode 12
The change in the capacitance is detected by the change in the area where the electrode fingers of 1a and the fixed electrode 121b overlap. Square 11
When the displacement of 2 is as small as 1 μm or less, the former has about 10 times greater acceleration detection sensitivity than the latter.

In addition, the movable electrode 121a and the fixed electrode 121
When the electrode fingers 121a-n and 121b-n of b extend in the y-axis direction orthogonal to the x-axis direction (detection axis direction),
The movable electrode fingers 121a-n are displaced and fixed electrode fingers 121b
-N, both electrode fingers 121a-n and 121b-n
A so-called squeeze effect occurs in which the gas sandwiched between is compressed. Therefore, a larger viscous damping effect can be obtained as compared with the case where the electrode fingers extending in the x-axis direction (detection axis direction) are meshed with each other. In addition, a spring effect that suppresses the displacement of the movable electrode 121a can be obtained. Therefore, mass 11
Even if a large acceleration is suddenly applied to 2,
It is possible to prevent the electrode fingers 121a-n and 121b-n from colliding with each other.

Further, since the movable electrodes 121a and 122a of the x-axis direction detection electrodes 121 and 122 are connected to the right side surface 112d of the mass 112 which is displaceable in the x-axis direction and the y-axis direction, only in the x-axis direction. Instead, it can also be displaced in the y-axis direction. When the movable electrode 121a is displaced in the positive direction of the y-axis, as shown in FIG.
1a-1, 121a-2, 121a-3 and fixed electrode 1
21b electrode fingers 121b-1, 121b-2, 121b
The opposing area of -3 increases. On the other hand, the movable electrode 121
a of the electrode fingers 121a-4, 121a-5, 121a-6
And the electrode fingers 121b-4 and 121b of the fixed electrode 121b.
The area where -5 and 121b-6 face each other decreases by the same amount as the above-mentioned increase in area.

Therefore, as a whole, the movable electrode 12
The area where the electrode fingers of 1a and fixed electrode 121b face each other is constant. That is, in principle, the effect of displacement of the mass 112 in the y-axis direction due to acceleration applied in the y-axis direction is x
It is configured so as not to appear in the output of the axial detection electrode 121. The same applies to the lower x-axis direction detection electrode 122.

However, in practice, the movable electrode 121
mass 112 due to a manufacturing error between a and the fixed electrode 121b.
The influence of the displacement in the y-axis direction affects the detection electrode 12 in the x-axis direction.
It may appear slightly in the output of 1. Therefore, x
In order to remove the influence of the displacement of the mass 112 in the y-axis direction, which slightly appears in the output of the axial detection electrode 121, the following method may be adopted.

First, the ratio A / B of the output value A of the x-axis direction detection electrode 121 when the mass 112 is displaced only in the y-axis direction and the output value B of the y-axis direction detection electrode 140 at that time is obtained. The accuracy of this ratio can be improved by plotting the relationship between the output value A and the output value B at a plurality of points and using the least square method or the like.
Then, from the output value C of the x-axis direction detection electrode 121 when the mass 112 is displaced in the x-axis direction and the y-axis direction to the output value D of the y-axis direction detection electrode 140 at that time and the ratio A of the output values. By subtracting the value multiplied by / B, the influence of the acceleration applied in the y-axis direction on the output of the x-axis direction detection electrode 121 can be removed. Note that the contribution of the x-direction displacement or the y-direction displacement of the inner mass portion 118 may be removed from the output values of the z-axis direction detection electrodes 180 and 182 in the same manner as the above method.

As shown in FIG. 1, the upper beam unit 1
A T-shaped electrode connecting portion 138 is connected to the center of the upper side surface of the beam connecting portion 128 (main plate portion 128a) of 23. The electrode connecting portion 138 is composed of an elongated first connecting rod 138a extending in the y-axis direction and an elongated second connecting rod 138b extending in the x-axis direction to which one end of the first connecting rod 138a is connected. ing. The movable electrodes 140a and 141a of the y-axis direction detection electrodes 140 and 141 are connected to both ends of the upper side surface of the second connecting rod 138b, respectively. The electrode connecting portion 138 and the movable electrodes 140a and 141a are floating on the silicon substrate 110. y-axis direction detection electrodes 140, 1
41 are the above-mentioned x-axis direction detection electrodes 121, 1 respectively.
22 has the same configuration as that of the movable electrodes 140a, 1a.
41a, fixed electrodes 140b and 141b, and fixed electrode terminals 140c and 141c.

X-axis direction circuit section 2 of sensor circuit section 201A
02A is the upper and lower x-axis direction detection electrodes 12 respectively.
The capacitance detection circuits 206 and 2 to which the outputs of 1 and 122 are input
08, a displacement calculation circuit 210 to which the outputs of both capacitance detection circuits 206 and 208 are input, and an acceleration display device 218 to which the output of the displacement calculation circuit 210 is input. The y-axis direction circuit unit 220A also includes the capacitance detection circuits 224 and 226.
It has a displacement calculation circuit 228 and an acceleration display device 236, and has the same configuration as the above-mentioned x-axis direction circuit unit 202A.

An acceleration detecting operation of the triaxial acceleration detecting device 301A will be described. In practice, it is usual to apply an acceleration that causes an acceleration component to appear in each direction of the three axes, and hence the following description will be made on the assumption that such an acceleration is applied.

First, the operation of detecting acceleration in the x-axis direction will be described. When acceleration is applied in the x-axis direction, the mass 112 floating in a state of being supported by the fixed portions 134 and 136 of the upper beam unit 123 and the fixed portions 150 and 152 of the lower beam unit 125 moves to the upper beam unit 1.
The linear beams 126 and 127 of 23 and the linear beams 142 and 143 of the lower beam unit 125 are deflected in the x-axis direction to vibrate in the x-axis direction.

When the mass 112 vibrates in the x-axis direction, the movable electrodes 12 of the x-axis direction detection electrodes 121 and 122 are moved.
Electrode fingers 1a and 122a and fixed electrodes 121b and 122b
The distance between the electrode fingers changes. When the distance between the electrode fingers changes, the capacitance detection circuits 206 and 208 respectively detect the change value of the electrostatic capacitance due to the change in the distance between the electrode fingers. When the capacitance change value is detected, the capacitance change value is input to the displacement calculation circuit 210.

As described above, the x-axis direction detection detection electrode 1
21 and 122, when one capacitance increases, the capacitance of the other decreases by the same amount as the increase amount. Change value and lower x-axis direction detection electrode 1
The difference of the capacitance change value detected from 22 is taken to cancel the influence of the parasitic capacitance and external noise which have a bad influence on the measurement.
The capacitance change value is detected with double sensitivity. Then, the displacement value of the mass 112 is calculated based on the detected capacitance change value.
The calculated displacement value is input to the acceleration display device 218 in the x-axis direction. The acceleration display device 218 calculates and displays the acceleration in the x-axis direction corresponding to the input calculated displacement value. As a result, the acceleration applied in the x-axis direction can be known.

As described above, even if the mass 112 is displaced (vibrated) in the x-axis direction due to the acceleration applied in the x-axis direction, the displacement (vibration) in the x-axis direction (according to the structure of the sensor portion 101A of the present embodiment). Vibration), the y-axis direction acceleration detection electrode 140,
Displacement of the movable electrodes 140a and 141a of 141 in both the y-axis direction and the x-axis direction can be extremely firmly regulated.

The operation of detecting the acceleration in the y-axis direction will be described.
When acceleration is applied in the y-axis direction, the mass 112 causes the bent beams 130 and 132 of the upper beam unit 123 to move.
And the bent beam 14 of the lower beam unit 125.
The bending of 6, 6 148 in the y-axis direction causes vibration in the y-axis direction. The subsequent operation is the same as the above-described operation of detecting the acceleration in the x-axis direction.

As described above, even if the mass 112 is displaced (vibrated) in the y-axis direction by applying the acceleration in the y-axis direction, the displacement (vibration) causes x in the structure of the sensor unit 101A according to the present embodiment. Displacement of the movable electrodes 121a and 122a of the axial acceleration detection electrodes 121 and 122 in the x-axis direction is extremely strongly restricted. In this case, the movable electrode 121
Although it cannot be restricted that the a and 122a are displaced in the y-axis direction, as described above, the x-axis direction acceleration detection electrodes 121, 1
Since 22 has a complementary structure that cancels the displacement in the y-axis direction, the accuracy of detecting the acceleration in the x-axis direction does not deteriorate. Further, according to the structure of the sensor unit 101A of the present embodiment, even if an angular velocity around the z-axis is applied, the effect of the angular velocity can be greatly suppressed from appearing in the x-axis direction or the y-axis direction. To be

A structure for detecting acceleration in the z-axis direction will be described with reference to FIG. FIG. 2 (a sectional view taken along the line AA in FIG. 1) shows an upper electrode 180, a lower electrode 182, and an inner mass portion 118 arranged between the electrodes 180 and 182.
And a z-axis direction circuit portion 240 connected to both electrodes 180, 182 is shown. Electrodes 118a and 118b are formed on the upper surface and the lower surface of the inner mass portion 118, respectively. Here, the surface area of both electrodes 180, 182 is smaller than the upper area and the lower area of the inner mass portion 118, and both electrodes 180, 182 are located in the region of the inner mass portion 118 when viewed from the z-axis direction. It is arranged. The z-axis direction circuit section 240A includes capacitance detection circuits 242 and 244 to which outputs of the upper electrode 180 and the lower electrode 182 are input, a displacement detection circuit 246 to which outputs of both capacitance detection circuits 242 and 244 are input, and displacement detection. It has an acceleration display device 248 to which the output of the circuit 246 is input.

The operation of detecting the acceleration in the z-axis direction will be described.
When acceleration is applied in the z-axis direction, the inner mass portion 1 of FIG.
18 is displaced in the z-axis direction. As described above, the inner mass portion 118 of FIG. 2 includes the eight mass connecting beam groups 11 of FIG.
4, 116 are connected to the outer mass part 120. The mass connection beam groups 114 and 116 play a role of displacing the inner mass part 118 in the z-axis direction with respect to the outer mass part 120 of FIG. 1 when acceleration is applied in the z-axis direction. These mass connection beam groups 114 and 116
Is easier to bend in the z-axis direction than the beams of the beam units 123 and 125. On the other hand, even when acceleration is applied in the x-axis direction or the y-axis direction, the inner mass portion 118 plays a role of restricting displacement of the inner mass portion 118 in the x-axis direction or the y-axis direction with respect to the outer mass portion 120.

As described above, the inner mass portion 118 for displacing in the z-axis direction and the mass connection beam group 11 which is easily bent in the z-axis direction.
By providing 4, 116, acceleration in the z-axis direction can also be detected with high sensitivity. However, the acceleration in the z-axis direction is calculated by using the inner mass portion 118 and the mass connection beam groups 114, 1
It is needless to say that the detection may be performed using a mass not provided with 16. Even when such a mass is used, the acceleration in the z-axis direction can be detected with a considerably high sensitivity.

When the inner mass portion 118 in FIG. 2 is displaced in the positive direction of the z-axis, the upper surface electrode 11 of the inner mass portion 118 is moved.
The distance between 8a and the upper electrode 180 becomes smaller. On the other hand, the distance between the lower surface electrode 118b of the inner mass portion 118 and the lower electrode 182 becomes large. Upper surface electrode 118a and upper electrode 18
The reduced value of the distance between 0 is that the lower electrode 118b and the lower electrode 1
It is the same as the increase value of the distance between 82. Therefore, the capacitance detection circuits 242 and 244 respectively detect the capacitance change, and by taking the difference between them, the influences of the parasitic capacitance and external noise, which have an adverse effect on the measurement, are canceled, and the capacitance change is detected by one electrode. The acceleration can be detected with a sensitivity about twice as high as that of the case. The calculated displacement value is the acceleration display device 2 in the z-axis direction.
It is input to 48, and the acceleration in the z-axis direction corresponding to the calculated displacement value is calculated and displayed. As a result, the acceleration applied in the z-axis direction can be known.

Even if the mass 112 is displaced (vibrated) in the x-axis direction or the y-axis direction due to the acceleration applied in the x-axis direction or the y-axis direction in addition to the z-axis direction, the sensor unit 101 of the present embodiment.
According to the structure A, the displacement of the mass 112 (the upper surface and the lower surface electrodes 118a and 118b of the inner mass 118) in the z-axis due to the displacement in the x-axis direction or the y-axis direction can be extremely strongly restricted. In this case, it is inevitable that the mass 112 is displaced (vibrated) to some extent in the x-axis direction or the y-axis direction as a whole, but as described above, the outer mass portion 12
Since displacement of the inner mass portion 118 with respect to 0 is restricted, large displacement of the inner mass portion 118 in the x-axis direction or the y-axis direction is suppressed. Inner mass part 11
Even if 8 is displaced to some extent in the x-axis direction or the y-axis direction, the upper and lower electrodes 180, 182 are arranged at the positions included in the upper and lower regions of the inner mass portion 118. 180, 182 and inner mass portion 11
8 does not change the size of the area where the upper and lower electrodes 118a and 118b overlap. Therefore, even if the inner mass portion 118 is slightly displaced in the x-axis direction or the y-axis direction, its effect is z.
It does not appear in the axial detection value. Therefore, according to the structure of the sensor unit 101A of the present embodiment, the influence of the acceleration of the other axis can be made extremely small also in the z-axis direction.

On the contrary, when the surface areas of both electrodes 180 and 182 are made larger than the upper area and the lower area of the inner mass portion 118, and viewed from the z-axis direction, the inner mass portion 118 has both electrodes 18.
Both electrodes 18 are placed at positions such that they are included in the region of 0 and 182.
The same effect can be obtained by arranging 0, 182 and the inner mass portion 118.

As described above, according to the structure of the triaxial acceleration detecting device 301A of the first embodiment, the x-axis direction, the y-axis direction,
In both the z-axis direction, the influence of the acceleration of the other axis can be greatly reduced. Therefore, the acceleration detection accuracy can be significantly improved. As described above, according to the device 301A, accelerations in the x-axis direction, the y-axis direction, and the z-axis direction can be simultaneously detected with high detection accuracy.

The structure of the sensor portion 101A of this embodiment is, for example, the mass 112 and the mass 11 formed on the silicon active layer of the SOI substrate by using the photolithography technique and the etching technique.
It can be formed by patterning a structure such as the linear beams 126 and 127 having a thickness smaller than two. Since the upper and lower surfaces of the inner mass portion 118 are used as the electrodes 118a and 118b, impurities may be added to reduce the resistance.

As described above, the mass 112 and the beam unit 12 are formed on the silicon active layer portion using the SOI substrate.
When a structure such as 3, 125 is formed, the physical properties of the material are constant, so that reliable and stable sensor characteristics can be obtained over a long period of time. Further, since the step of forming an oxide film or a silicon layer on the silicon substrate is unnecessary, the manufacturing process can be simplified. In addition, since the SOI substrate can be used to fabricate a multi-axis sensor unit by patterning a mass and each beam in a batch on the silicon active layer, a plurality of uniaxial acceleration sensor units can be formed. The beam orthogonality is high.

The mass 102 and the beam unit 12
3, 125, electrodes 121, 122, 140, 141, 1
The material of the structure such as 24 and 154 may be, for example, nickel, iron, or another metal other than the above-mentioned silicon.

(Second Embodiment) FIG. 4 shows an explanatory view of a triaxial acceleration detecting device 301B of the second embodiment. FIG. 5 is an explanatory diagram of the z-axis direction acceleration detection of this device 301B (A- in FIG. 4).
(A sectional view taken along line A is included). The second embodiment is characterized in that it has a sensitivity adjustment function and a self-diagnosis function as compared with the first embodiment. Hereinafter, the same parts as those in the first embodiment will be denoted by the same reference numerals, the description thereof will be omitted, and the differences from the first embodiment will be mainly described. The sensor unit 101B of the triaxial acceleration detection device 301B includes an x-axis direction sensitivity adjustment electrode 124 connected to the left side surface 112c of the mass 112,
The y-axis direction sensitivity adjustment electrode 154 connected to the lower beam unit 125 is provided. As shown in FIGS. 4 and 5, each axial circuit portion 202B of the sensor circuit portion 201B,
220B and 240B (see FIG. 5) are AC power sources 204,
222 and 250. This AC power source 204, 22
2, 250 and the capacitance detection circuits 206, 224, 242,
The selection switches 203, 221, 249 can be selectively connected to the detection electrodes 121, 140, 180 in each axial direction.

The sensor circuit section 201B further includes a sensitivity control circuit 238 and amplifiers 242 and 246 connected to the sensitivity control circuit 238. The sensitivity control circuit 238 outputs its output to the AC power source 20 of each of the axial direction circuit units 202B, 220B, 240B at "a", "b", and "c".
4, 222, 250. Also, the sensitivity control circuit 2
The outputs of the capacitance detection circuits 208, 226, and 244 are input to 38 at points “d”, “e”, and “f”, respectively. Further, the sensitivity control circuit 238 outputs its output to the amplifiers 242, 2
Enter in 46. The amplifiers 242 and 246 output their outputs,
It is input to the fixed electrode terminals 124c and 154c of the x-axis direction or y-axis direction sensitivity adjustment electrodes 124 and 154.

In the structure for detecting acceleration in the z-axis direction shown in FIG. 5, the sensitivity adjusting electrode is not provided, but in the z-axis direction, the capacitance detecting circuits 242, 244 act as the detecting electrodes 180, 182 in the circuit operation. The sensitivity is adjusted by adjusting the applied DC bias voltage. In this embodiment, the same DC bias voltage is applied from the capacitance detection circuits 242 and 244 to the upper and lower detection electrodes 180 by the control signal output from the position “g” of the sensitivity control circuit 238.
The sensitivity is adjusted by controlling the voltage applied to 182. As described above, when the same DC bias voltage is applied to the upper and lower detection electrodes 180 and 182, the inner mass portion 118 is pulled vertically with the same force. Therefore, the sensitivity adjustment electrodes 124 and 154 of the second embodiment shown in FIG. The spring constant can be adjusted by the electric spring effect similar to that using. Note that the same configuration can be adopted for the sensitivity adjustment in the x-axis direction or the y-axis direction.

FIG. 6 shows an enlarged plan view of the x-axis direction sensitivity adjusting electrode 124. The x-axis direction sensitivity adjustment electrode 124 includes a movable electrode 124a, a fixed electrode 124b, and a fixed electrode terminal 12
4c. The movable electrode 124a has four movable electrode fingers 124a-1 to 124a-4, each of which has two movable electrode fingers 124a-1 to 124a-4 extending in two directions at equal intervals in the x-axis direction and in a direction away from the center in the y-axis direction.
Have. The fixed electrodes 124b are arranged at equal intervals in the x-axis direction.
Two fixed electrode fingers 124b-1 to 124b-4 are provided at two locations, each extending from the outer side in the y-axis direction in a direction in which they approach each other.

The n-th movable electrode finger 124a-n from the left of the movable electrode 124a (hereinafter "n-th from the left" is omitted).
And the distance between the fixed electrode fingers 124b-n of the fixed electrode 124b is equal to the distance between the movable electrode fingers 124a-n of the movable electrode 124a and the fixed electrode fingers 124b- (n + 1) of the fixed electrode 124b. That is, the movable electrode fingers 124a-n and the two fixed electrode fingers 124b-n and 124b adjacent to the movable electrode fingers 124a-n.
The distance between-(n + 1) is equal. When the distance between adjacent electrode fingers is equal, when a DC voltage is applied to the fixed electrode terminal 154c by the DC power supply 244 shown in FIG.
An electric spring having a negative spring constant is generated between 54a and the fixed electrode 154b.

As shown in FIG. 4, the movable electrode 154a of the y-axis direction sensitivity adjusting electrode 154 is connected to the center of the lower side surface of the beam connecting portion 144 of the lower beam unit 125 described above. The y-axis direction sensitivity adjustment electrode 154 has the same configuration as the x-axis direction sensitivity adjustment electrode 124 described above, and has a movable electrode 154a, a fixed electrode 154b, and a fixed electrode terminal 154c. The y-axis direction sensitivity adjustment electrode 154 is provided on the upper surface 112 a or the lower surface 11 of the mass 112.
It may be directly connected to 2b.

(Sensitivity Adjustment Function) The spring constant of the beam is
Deviation from the design value may occur depending on processing accuracy and ambient temperature during use. Therefore, it is necessary to know the magnitude of this deviation, that is, the current spring constant of the beam before the acceleration is detected, and adjust the spring constant of the beam, that is, the sensitivity. The timing of sensitivity adjustment shall be performed at the start of use of the acceleration detection device or periodically after the start of use. For example, in the case of sensitivity adjustment in the x-axis direction, the changeover switch 203 shown in FIG. 4 is first set to the AC power supply 204 side at the start of sensitivity adjustment. Then, an AC voltage having a specified frequency and magnitude is applied to one x
It is applied to the axial direction detection electrode 121. This AC voltage generates a force that vibrates the mass 112 in the x-axis direction. Therefore, the mass 112 starts vibrating in the x-axis direction. The displacement value of the mass 112 in the x-axis direction generated at this time is detected by the other x-axis direction detection electrode 122 (capacitance detection circuit 208), whereby the current linear beams 126, 127, 142, 1
The magnitude of the spring constant of 43 can be estimated. For example, if the capacitance change value detected by the capacitance detection circuit 208 is smaller than the specified value, then the linear beams 126, 127, 142, 143.
It can be seen that the spring constant of is larger than the specified value.

Therefore, when the output value of the capacitance detection circuit 208 is input to the sensitivity control circuit 238 as indicated by the point "d", the sensitivity control circuit 238 applies a DC voltage to the sensitivity adjustment electrode 124 based on this value. To set. The DC voltage amplified by the amplifier 242 so as to have the set DC voltage is input to the sensitivity adjustment electrode 124. As a result, an electric spring having a negative spring constant −k2 is generated between the movable electrode 124a and the fixed electrode 124b. As a result, the total spring constant between the movable electrode 124a and the fixed electrode 124b is set to K.
And the spring constant of the linear beams 126, 127, 142, 143 is k1, the overall spring constant is K = k1−
k2. When the sensitivity is adjusted by such a method, the linear beams 126, 127, and 14 are formed by the electric spring effect.
The spring constant of 2,143 can be adjusted. When this sensitivity adjustment is completed, the changeover switch 203 is switched to the capacitance detection circuit 206 side, and the normal acceleration detection process is started. Even after the sensitivity adjustment is completed, the direct current voltage is applied to the sensitivity adjustment electrode 124 as it is.

As described above, the spring constant of the beam between the movable electrode 154a and the fixed electrode 154b can be adjusted by appropriately adjusting the value of the DC voltage applied to the fixed electrode terminal 154c by the sensitivity control circuit 238. . For this reason, it is possible to reduce variations in sensitivity of the spring constant due to processing accuracy and environmental temperature during use. Further, the spring constant K of the whole can be reduced to facilitate displacement of the mass 112.
Therefore, even if the applied acceleration is small,
The acceleration can be detected with high sensitivity.

(Self-Diagnosis Function) When a part of the sensor unit 101B (for example, the mass 112 or each beam) sticks to the substrate 110, the mass 112 cannot be displaced due to acceleration. That is, it becomes a failure state. Therefore, similar to the sensitivity adjustment operation described above, for example, the x-axis direction circuit unit 20.
The changeover switch 203 of 2B is switched to the side of the AC power source 204, and one fixed electrode terminal 12 of the x-axis direction detection electrode 121.
An alternating voltage is applied to 1c to vibrate the mass 112. Thus, when the capacitance detection circuit 208 that detects the output of the other detection electrode 122 does not detect a capacitance change, even if the mass 112 is oscillated,
Alternatively, if the expected capacitance change is not detected, a situation such as a part of the sensor unit 101B sticking to the substrate 110 may occur, and the mass 112 may not be displaced even if acceleration is applied or may not be displaced as planned. It can be detected that there is a failure. In this case, the sensitivity control circuit 238 outputs a diagnosis signal (fault detection signal) to the system side so that the triaxial acceleration detecting device 301B
The failure of can be detected.

In the triaxial acceleration detecting device 301B shown in FIG. 4, if the resonance frequency in the x-axis direction is f1 and the resonance frequency in the y-axis direction is f2, the detuning rate | f1-f2 | / f1 is 1% or more. Is adjusted so that If the resonance frequencies f1 and f2 in the x-axis direction and the y-axis direction are close to each other, for example, when acceleration is applied in the x-axis direction and the mass vibrates in the x-axis direction, the mass also vibrates in the y-axis direction. I will end up. That is, even if the acceleration is applied only in the x-axis direction, the output of the y-axis direction detection electrode is affected. Detuning rate | f1-f2
If | / f1 is set to 1% or more, it is possible to sufficiently suppress the influence of the acceleration in the y-axis direction when the acceleration is applied in the x-axis direction. However, if you increase the detuning rate too much,
If the resonance frequency in one axial direction becomes extremely high or low, there will be a large difference in the range of acceleration that can be detected in the x-axis direction and the y-axis direction. Therefore, the detuning rate |
f1-f2 | / f1 is preferably 1000% or less. Further, the detuning rate is more preferably 3% or more and 1000% or less. To adjust the resonance frequencies f1 and f2 in the x-axis direction and the y-axis direction, the value of the DC voltage applied to the sensitivity adjustment electrodes 124 and 154 in the x-axis direction and the y-axis direction is changed to adjust the spring constant. You can do that.

(Third Embodiment) FIG. 7 shows an explanatory view of a triaxial acceleration detecting device 301C according to a third embodiment. FIG. 8 is an explanatory diagram of the z-axis direction acceleration detection of this device 301C (A- in FIG. 7).
(A sectional view taken along line A is included). The third embodiment is characterized in that it has a feedback function as compared with the first embodiment. Hereinafter, the same parts as those in the first embodiment will be denoted by the same reference numerals, the description thereof will be omitted, and the differences from the first embodiment will be mainly described. This triaxial acceleration detection device 301C
The sensor section 101C of the two x-axis direction feedback electrodes 1 connected in parallel to the left side surface 112c of the mass 112.
90, 191, and two y-axis direction feedback electrodes 1 connected in parallel to the lower surface of the lower beam unit 125.
92, 193. Each axial feedback electrode 1
90, 191, 192, and 193 have the same configuration as the axial direction detection electrodes 122, 121, 141, and 140, respectively.

The x-axis direction or y-axis direction circuit portions 202C and 220C of the sensor circuit portion 201C have feedback circuits 212 and 230. Feedback circuit 212,
The outputs of the displacement calculation circuits 210 and 228 are input to 230. The outputs of the feedback circuits 212 and 230 are
It is input to each axial acceleration display device 218, 236.
Also, the outputs of the feedback circuits 212 and 230 are the axial feedback electrodes 190, 191 and 192,
Fixed electrode terminals 190c, 191c and 192 of 193
c, 193c.

As shown in FIGS. 7 and 8, also in the z-axis direction, the upper or lower feedback electrodes 184, 18 are arranged so as to surround the upper or lower detection electrodes 180, 181, respectively.
6 is formed. The z-axis direction circuit unit 240C has a feedback circuit 252. The output of the displacement calculation circuit 246 is also input to the feedback circuit 252. The output of the feedback circuit 252 is input to the acceleration display device 248 and also to the upper or lower feedback electrodes 184 and 186.

The feedback operation in the y-axis direction will be described as an example. Displacement detection circuit 2 of y-axis direction circuit section 220B
The displacement value calculated in 28 is input to the feedback circuit 230. The feedback circuit 230 applies a voltage of a desired magnitude to be applied to the feedback electrodes 192 and 193 based on the input displacement value. When a voltage is applied to the feedback electrodes 192 and 193, the mass 112, which is about to be displaced by the acceleration in the x-axis direction, has the same magnitude as the inertial force due to the acceleration, and the electrostatic attraction in the opposite direction to the direction of the acceleration. Pulled. In this way, the displacement of the mass 112 is controlled to be substantially zero. Such a control method is called a null method. In addition,
The feedback operations in the y-axis direction and the z-axis direction can be similarly performed. Further, in this embodiment, the x-axis direction detection electrodes 122 and 121 and the feedback electrodes 190 and 191 for performing the null method are provided separately, but they may be used in combination.

When the displacement of the mass 112 in the y-axis direction is controlled to be substantially zero, the x-axis direction detection electrodes 121, 1
It is possible to prevent the movable electrodes 121a and 122a of 22 from being displaced in the direction (y-axis direction) orthogonal to the detection axis direction (x-axis direction). That is, like the movable electrodes 140a and 141a of the y-axis direction detection electrodes 140 and 141, the y-axis direction detection electrodes 140 and 141 can be prevented from being displaced in the direction orthogonal to the detection axis direction. In this way, the influence of the y-axis direction acceleration applied to the mass 112 on the output in the x-axis direction or the z-axis direction can be greatly reduced. Further, the problem associated with the displacement of the mass 112 can be solved or largely eliminated. For example, the response characteristics of the beam can be improved, the linearity of the beam can be improved, the temperature characteristics can be improved, and the collision between the electrode fingers of the movable electrode and the fixed electrode can be prevented.

Another problem of the conventional acceleration detecting device 1 shown in FIG. 17 will be described. Each linear beam 22, 24, 26, 28 of the acceleration detecting device 1 has one end connected to the fixed portion 38 and the other end connected to the mass 20. However, if one end is connected to the fixed portion 38,
There is a problem that internal stress is accumulated and remains in the linear beams 22, 24, 26 and 28. Since the magnitude of this residual stress varies greatly due to, for example, changes in the manufacturing process, the spring constant varies between devices immediately after manufacturing or between beams within the device. Further, the magnitude of the residual stress greatly changes depending on the temperature change, so that the spring constant varies among the devices or between the beams in one device. This is because, in a linear beam whose one end is connected to the fixed portion, internal stress existing in the longitudinal direction of the beam is accumulated and cannot be released. In order to obtain a stable sensitivity, it is desirable that the spring constant of the linear beam does not vary and is almost constant. This is because the spring constant of the linear beam defines the displacement amount of the mass with respect to acceleration.

Thus, the linear beams 22, 24, 2
One end of 6, 28 is connected to the fixed portion 38, and the other end is connected to the mass 20.
Connection to the linear beam 22, 24, 2
The spring constants of 6 and 28 are not simply determined by their shapes such as width, thickness, and length, but are affected by residual stress and stress in the longitudinal direction generated when largely bent.
Therefore, there is a problem that stable sensitivity cannot be obtained.

Acceleration detecting device 301 of the first to third embodiments
Is a bent beam 130, 132, 14 whose one end is fixed by four fixing portions 134, 136, 150, 152.
6, 148 and the linear beams 126, 127, 142, 14 connected to them via connecting portions 128, 144.
By supporting the mass 112 by 3
This is a structure in which the acceleration of another axis is sufficiently reduced in the axial direction. Nevertheless, the linear beams 126, 127,
142, 143 with respect to the bent beams 130, 13
2, 146 and 148 have a buffer structure. Therefore,
Accumulation of stress in the beam is greatly suppressed. Therefore, the spring constant is stable, and stable sensitivity can be obtained.

The structure of the sensor section 101 of the first to third embodiments may be as follows. (First Modification) FIG. 9 shows a plan view of the sensor unit 102 of the first modification. In addition, in the following modified examples, members having the same configurations as the members of the sensor unit 101A of the first embodiment shown in FIG. First Modification Sensor Unit 102
Bending beams 162, 164 of the forward beam portion 162
a, 164a and the return beam portions 162b, 164b are
Each is composed of one beam. At this point, the outward beam portions 130a, 1a of the bent beams 130, 132
32a and the return beam sections 130b and 132b are different from those of the first to third embodiments in which each of them has two beams. Further, the bent beams 162 and 164 of the first modified example.
The connecting portions 162b and 164b are each formed in a rectangular shape. At this point, the bent beams 130, 13
This is different from the first to third embodiments in which the second connecting portions 130b and 132b are formed in a substantially square shape.

The movable electrode 121a of one x-axis direction detection electrode 121 is connected to the right side surface 120d of the mass 102, and the movable electrode 160a of the other x-axis direction detection electrode 160.
Is connected to the left side surface 120c of the mass 102. The x-axis direction detection electrodes 121 and 160 have the same configuration. In this respect, the two x-axis direction detection electrodes 121, 122
Of the two movable electrodes 121a and 122a are connected to the right side surface 120d of the mass 102, and the two x-axis direction detection electrodes 12
The configuration of Nos. 1 and 122 is slightly different from that of the first to third embodiments. Furthermore, the sensor unit 102 of the first modification is different from the first to third embodiments in that it does not have the lower beam unit.

(Second Modification) FIG. 10 shows a plan view of a sensor section 103 of a second modification. Sensor unit 1 of second modification
The bent beams 166 and 168 of No. 03 extend in directions away from each other. At this point the bent beam 162,
This is different from the sensor unit 102 and the like of the first modification in which 164 extend in the direction in which they approach each other.

(Third Modification) FIG. 11 shows a plan view of a sensor section 104 of a third modification. Sensor unit 1 of the third modification
04 is a bent beam 17 of the beam unit 169.
0 and 172 and the fixed portions 174 and 176 are the mass 102,
Two linear beams 126 and 127 and the beam connecting portion 1
It is arranged in a region surrounded by 28. In this respect, the sensor unit 1 of the first modification example in which the bent beams 162 and 164 and the fixing portions 134 and 136 are arranged outside the above-mentioned region.
Different from 02 etc.

(Fourth Modification) FIG. 12 shows a plan view of a sensor section 105 of a fourth modification. Sensor unit 1 of the fourth modification
05 differs from the sensor unit 102 of the first modification in the position and configuration of the y-axis direction detection electrode. Specifically, in the sensor unit 102 of the first modified example, as shown in FIG. 9, the y-axis direction detection electrodes 140 and 141 are lined up in the x-axis direction on the beam connecting unit 128 via the electrode connecting unit 140. On the other hand, in the sensor unit 105 of the fourth modified example, as shown in FIG.
The movable electrode 140a of the axial direction detection electrode 140 is connected,
The movable electrode 178a of the other y-axis direction detection electrode 178 is connected to the center of the lower surface. That is, they are arranged side by side in the y-axis direction.

Three-axis acceleration detecting device 3 of the first to third embodiments
01 may have the following configurations in addition to the configurations shown in the first to fourth variations.

For example, the number of the forward beam portions 130a or the return beam portions 130c forming the bent beam 130 may be more than two. In this case, in order to further reduce the influence of the other-axis acceleration and make the spring constant of the beam linear, it is preferable that the number of the forward beam portions 130a and the number of the return beam portions 130c be the same. Further, it is preferable that the forward beam portion 130a and the return beam portion 130c have the same shape when deformed. That is, it is preferable that the forward beam portion 130a and the return beam portion 130c have the same length and width. With this configuration, when the beam portions 130a and 130c are deformed by the displacement of the mass 120 in the y-axis direction, the stress distributions generated inside the beam portions 130a and 130c are substantially the same. Therefore, both beam units 130
a, 130c bending, both beam portions 130a,
The end portion of the connecting portion 130b on the side of the connecting portion 130b can be uniformly displaced in the x-axis direction. Therefore, there is almost no nonuniformity of the force applied to the beam portions 130a and 130c, and the spring constant can be made more linear. That is, in the relationship of F = kx, the spring constant k can be made constant even if the displacement x is larger. In addition, since the lengths of both beam portions 130a and 130c are the same, both beam portions 130a and 130c due to temperature change.
The change in 0c is the same, and the effect of temperature change on the spring constant can be greatly improved.

Further, the shape of the connecting portion 130b constituting the bent beam 130 is not particularly limited. Connection 1
The shape of 30b may be, for example, curved, semicircular, or linear as long as it has bending rigidity equal to or higher than that of the forward beam portion and the return beam portion. The material may be different from that of the return beam portion. The bent beam is the bent beam 13 of this embodiment.
A structure in which a plurality of 0s are combined may be used. For example,
The structure may be such that the displacement ends of the two bent beams 130 are connected to each other and the two fixed ends are connected to the fixed portion.

Each of the beam units 123 and 125 may have one linear beam or one bent beam. Further, for example, the straight beam and the bent beam may be directly connected without connecting the straight beam and the bent beam via the connecting portion. When the linear beam and the bent beam of the beam unit are combined into one and both beams are directly connected, for example, in the beam unit 123, one end of the linear beam is connected to the vicinity of the center of the upper side surface 112a of the mass 112. It is preferable to connect a bent beam to the other end of the linear beam. According to this configuration, even if there is only one linear beam and one bent beam, the mass 112 can be supported relatively stably, and the influence of the acceleration of the other axis can be reduced.
Further, for example, the number of linear beams or bent beams forming the beam unit 123 may be more than two. Also in this case, it is preferable that the number is even.

The connection points of the sensitivity adjustment adjustments 124 and 154 in FIG. 4 may be other points. Although the x-axis direction sensitivity adjustment electrode 124 is connected to the mass 120 in FIG. 4, it may be connected to, for example, a portion between the connecting portion 128a and the mass 120. For example, it may be connected to the middle portion of the second beam 126. Further, in FIG. 4, the y-axis direction sensitivity adjusting electrode 154 is connected to the connecting portion 144, but for example, the fixing portion 150.
It may be connected to a place between and the connecting portion 144. For example,
The folded beam 146 may be connected to a connecting portion connecting the forward beam and the return beam.

In the sensitivity adjusting electrode 124 (the same applies to the sensitivity adjusting electrode 154), the electrode fingers of the fixed electrode 124b are located on both sides of the electrode finger of the movable electrode 124a. When the electrode fingers of the movable electrode 124a are located substantially in the middle of the electrode fingers of the fixed electrodes 124b on both sides, the fixed electrodes 12 on both sides are
The electrostatic attraction from the electrode fingers of 4b is evenly applied, and the operation is most stable. However, if excessive acceleration is applied,
The position of the electrode finger of the movable electrode 124a is the fixed electrode 12 on one side.
The electrode finger of 4b may be approached. In this case, the electrostatic attraction from the electrode fingers of the fixed electrodes 124b on both sides becomes uneven. As a result, the movable electrode 124a receives a strong electrostatic attraction force from the electrode finger of the fixed electrode 124b on one side. Therefore, the electrode finger of the movable electrode 124a is one of the fixed electrodes on one side.
There is a phenomenon in which the electrode fingers of 24b are attracted and fixed, or do not return to the intermediate position.

Therefore, as described above, the sensitivity adjusting electrode 12
By connecting 4 and 154 to a portion with a small displacement instead of a portion with a large displacement, even when an excessive acceleration is applied, the fixed electrodes 124a on both sides are attached to the electrode fingers of the movable electrodes 124a and 154a. A substantially uniform electrostatic attraction can be applied from the electrode fingers of 154a. Therefore, stable sensitivity adjustment operation is possible.

The three-axis acceleration detecting devices of the first to third embodiments and the other modified examples have been described above. However, in order to facilitate understanding of the device configuration, particularly in the first to third embodiments. It is divided into the first to third embodiments for the sake of convenience, and actually,
It is preferable to use the configurations of the first to third embodiments in combination. By appropriately combining and using the configurations of the first to third embodiments and the configurations of other modified examples, (1) the influence of the acceleration of the other axis is extremely reduced, and the acceleration in the detection axis direction to be originally detected is very accurately. It can detect (2) small displacement due to small acceleration with very high sensitivity, (3) between devices or 1
It is possible to realize an acceleration detection device in which variations and deviations of the spring constant of the beam are small in one device and very stable sensitivity is obtained.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. Further, the technical elements described in the present specification or the drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Further, the technique illustrated in the present specification or the drawings can simultaneously achieve a plurality of purposes, and achieving the one purpose among them has technical utility.

[Brief description of drawings]

FIG. 1 shows an explanatory diagram of a triaxial acceleration detection device according to a first embodiment.

FIG. 2 is an explanatory diagram of acceleration detection in the z-axis direction of the triaxial acceleration detection device according to the first embodiment.

FIG. 3 is an enlarged plan view of an x-axis direction detection electrode of the triaxial acceleration detection device according to the first embodiment.

FIG. 4 is an explanatory diagram of a triaxial acceleration detecting device according to a second embodiment.

FIG. 5 is an explanatory diagram of acceleration detection in the z-axis direction of the triaxial acceleration detection device according to the second embodiment.

FIG. 6 is an enlarged plan view of an x-axis direction sensitivity adjustment electrode of the triaxial acceleration detection device of the second embodiment.

FIG. 7 shows an explanatory diagram of a triaxial acceleration detecting device of a third embodiment.

FIG. 8 is an explanatory diagram of acceleration detection in the z-axis direction of the triaxial acceleration detection device according to the third embodiment.

FIG. 9 shows a plan view of a sensor unit of a first modified example.

FIG. 10 shows a plan view of a sensor section of a second modification.

FIG. 11 shows a plan view of a sensor section of a third modification.

FIG. 12 shows a plan view of a sensor section of a fourth modified example.

FIG. 13 shows a diagram to assist in understanding the present invention (1).

FIG. 14 shows a diagram to assist in understanding the present invention (2).

FIG. 15 is an explanatory diagram of an acceleration detection device that embodies one aspect of the present invention.

FIG. 16 is a plan view of a conventional biaxial acceleration detecting device.

FIG. 17 is a sectional view taken along line AA of FIG. 16 (1).

FIG. 18 is a sectional view taken along line AA of FIG. 16 (2).

FIG. 19 shows a plan view of a conventional angular velocity detecting device.

[Explanation of symbols]

301: 3-axis acceleration detection device 101: Sensor section 201: Sensor circuit section 120: Trout 121, 122: x-axis direction detection electrodes 126 and 127: linear beam 128: Beam connection part 130, 132: Bent beam 134, 136: Fixed part 138: Electrode connection part 140, 141: y-axis direction detection electrode

Claims (15)

[Claims] 1. A fixed part, a first beam, a second beam, a mass, an acceleration detection electrode in the x-axis direction, and an acceleration detection electrode in the y-axis direction orthogonal thereto, and at least in the x-axis direction. The first beam is a device that detects acceleration in the y-axis direction, and the first beam has a forward beam portion and a return beam portion that extend substantially parallel to the x-axis direction, one end of each of the beam portions is connected, and both beam portions are bent. It has a connecting part with equal or higher rigidity, the other end of the forward beam part is connected to the fixed part, the other ends of both beam parts are arranged on the same side with respect to the connecting part, and the second beam is It extends substantially parallel to the y-axis direction, one end of which is directly or indirectly connected to the other end of the return beam section of the first beam, and the mass is directly or indirectly connected to the other end of the second beam. It is displaceable in the x-axis direction and the y-axis direction. The acceleration detection electrode has a movable electrode provided directly or indirectly on the mass and a fixed electrode, and the acceleration detection electrode in the y-axis direction is provided directly or indirectly on the other end of the return beam portion of the first beam. Multi-axis acceleration detection device having fixed movable electrode and fixed electrode. 2. A device for detecting acceleration in the z-axis direction in addition to the x-axis direction and the y-axis direction, the device further comprising an acceleration detection electrode in the z-axis direction orthogonal to the x-axis direction and the y-axis direction. , The x-axis direction and the y-axis direction can be displaced in the z-axis direction, and the acceleration detection electrode in the z-axis direction has a movable electrode formed on the surface of the mass and a fixed electrode. Axial acceleration detector. 3. A fixed part, a first beam, and at least two sets of beam units having a second beam, each beam unit being arranged in parallel in the x-axis direction, the side extending in the x-axis direction of the mass. 2nd of each beam unit
3. The multi-axis acceleration detecting device according to claim 1, wherein the other end of the beam is directly or indirectly connected. 4. A connecting portion is further provided, and the connecting portion has the other end of the return beam portion of the first beam of each beam unit arranged in parallel in the x-axis direction and two juxtaposed in the x-axis direction. The multi-axis acceleration detecting device according to claim 3, wherein one end of the second beam is connected. 5. The multi-axis acceleration detection device according to claim 4, wherein a movable electrode of an acceleration detection electrode in the y-axis direction is further provided at the connecting portion. 6. A fixing unit, a first beam, and at least two sets of beam units having a second beam are provided, and each beam unit is arranged so as to sandwich the mass, and both side parts extending in the x-axis direction of the mass are provided. 6. The multi-axis acceleration detecting device according to claim 1, wherein the other ends of the second beams of the beam units are directly or indirectly connected to each other. 7. The multiaxial acceleration detecting device according to claim 3, wherein the first beams and the second beams are arranged at positions substantially line-symmetric with respect to a predetermined reference line. 8. The acceleration detecting electrode in one axial direction is configured such that the facing area between the movable electrode and the fixed electrode is substantially constant even when the movable electrode is displaced in the other axial direction. The multi-axis acceleration detection device according to claim 1. 9. The movable electrode of the acceleration detection electrode and the electrode finger of the fixed electrode in the detection axis direction extend in a direction substantially orthogonal to the detection axis direction. Axial acceleration detector. 10. The capacitance detection circuit according to claim 1, further comprising a capacitance detection circuit that detects a change in the positional relationship between the movable electrode and the fixed electrode of the acceleration detection electrode due to the applied acceleration as a change in electrostatic capacitance. Any multi-axis acceleration detection device. 11. A differential circuit is further provided, and the acceleration detection electrode has two sets of movable electrodes and fixed electrodes,
When the distance between the movable electrode and the fixed electrode of one set increases by a predetermined value, the distance between the movable electrode and the fixed electrode of the other set decreases by about the same value as the predetermined value. 11. The multi-axis acceleration detection device according to claim 10, wherein the difference in the change in electrostatic capacitance between the two sets of the movable electrode and the fixed electrode, which is detected in step 3, is taken. 12. A feedback circuit and a feedback electrode are provided, and the feedback circuit is configured to apply a voltage according to the output value of the capacitance detection circuit to the feedback electrode when the output value is input. The multi-axis acceleration detection device according to claim 10 or 11. 13. The multiaxial acceleration detecting device according to claim 1, wherein the detuning rate is equal to or more than a predetermined value. 14. The multi-axis acceleration detection device according to claim 13, wherein the detuning rate is 1% or more. 15. The mass has a first mass part, a second mass part and a third beam, and the first mass part is connected to the second mass part by the third beam. The part is displaceable in the z-axis direction with respect to the second mass part, and the second mass part is connected to the other end of the second beam. Acceleration detection device.