JP4466124B2 - Capacitance type acceleration sensor, acceleration measuring device, acceleration measuring method and program - Google Patents

Description

  The present invention relates to a capacitance-type acceleration sensor that detects acceleration using a change in capacitance, and an acceleration measurement device, an acceleration measurement method, and a program that use the acceleration sensor.

  Conventionally, as a capacitance type acceleration sensor, a capacitance that accompanies displacement of a movable electrode by a switched capacitor circuit from a capacitance detection unit having a movable electrode and a fixed electrode arranged to face each other so as to change a separation interval according to input acceleration. It is known to provide a servo circuit that converts a change into a voltage change and detects it as an acceleration signal, and feeds back the acceleration signal to hold the movable electrode in a neutral position in order to widen the detection range (for example, Patent Documents). 1).

As another capacitive acceleration sensor, a movable electrode and a fixed electrode are provided on the surface of the substrate so that the facing area changes according to the input acceleration, and an electrostatic capacitance composed of the movable electrode and the fixed electrode is provided. A device that obtains an acceleration signal by detecting a change in capacitance accompanying displacement of a movable electrode from a capacitance is known (see, for example, Patent Document 2).
JP 7-260510 A Japanese Patent Laid-Open No. 10-206457

  According to the acceleration sensor provided with the servo circuit described above, since the movement of the movable electrode is limited in accordance with the output of the servo circuit, the detection range can be expanded as compared with the case where the servo circuit is not provided. However, since the range of acceleration that can stabilize the movable electrode by the servo circuit is limited by the electrostatic attraction and the weight of the movable electrode, it is not easy to expand the detection range.

  Also, according to the above-described facing area change type acceleration sensor, it is not easy to expand the detection range because there is only one type of facing area change characteristic according to the input acceleration.

  An object of the present invention is to provide a novel capacitive acceleration sensor capable of easily expanding the detection range. Another object of the present invention is to provide an acceleration measuring device, an acceleration measuring method and a program using such an acceleration sensor.

  A capacitance type acceleration sensor according to the present invention includes a plurality of capacitance detection units each having a movable electrode and a fixed electrode provided on a substrate surface so that a facing area changes according to input acceleration, and the plurality of capacitances The detection unit is configured to detect the change in capacitance between the movable electrode and the fixed electrode as an acceleration signal for each capacitance detection unit by varying the facing areas of the movable electrode and the fixed electrode when the input acceleration is zero. It is what.

  According to the acceleration sensor of the present invention, the capacitance area between the movable electrode and the fixed electrode is different for each capacitance detection unit by varying the facing areas of the movable electrode and the fixed electrode when the input acceleration is zero in the plurality of capacitance detection units. Since the change of the capacitance is detected by using an acceleration signal, the detection range can be easily expanded by increasing the number of capacitance detection units. Further, it is possible to detect with high sensitivity an acceleration in a range suitable for each capacitance detection unit.

  In the acceleration sensor according to the present invention, the movable electrodes of the plurality of capacitance detection units may be integrally formed. In this way, the degree of integration can be improved when the acceleration sensor is formed on the substrate using semiconductor manufacturing technology.

  In the acceleration sensor according to the present invention, the movable electrode is composed of the first and second movable electrodes and the fixed electrode is composed of the first and second fixed electrodes in each capacitance detection unit, and the first movable electrode is formed in each capacitance detection unit. The opposing area of the electrode and the first fixed electrode and the opposing area of the second movable electrode and the second fixed electrode have a relationship in which one increases when the other decreases according to the input acceleration, and each capacitance detection In the configuration, an acceleration signal corresponding to a ratio or difference between the capacitance between the first movable electrode and the first fixed electrode and the capacitance between the second movable electrode and the second fixed electrode is obtained. Also good. In this way, an acceleration signal corresponding to the ratio or difference between the capacitance on the opposing area decreasing side and the capacitance on the opposing area increasing side can be obtained for each capacitance detection unit, so that the detection sensitivity is improved. .

  In each capacitance detection unit, when the movable electrode is constituted by the first and second movable electrodes and the fixed electrode is constituted by the first and second fixed electrodes, the first and second movable electrodes of the plurality of capacitance detection units May be formed integrally. In this way, the degree of integration can be improved when the acceleration sensor is formed on the substrate using semiconductor manufacturing technology.

  In the acceleration sensor according to the present invention, among the plurality of capacitance detection units, the capacitance detection unit having a relatively small facing area between the movable electrode and the fixed electrode detects an acceleration signal according to a relatively small input acceleration and the movable electrode. In addition, the capacitance detection unit having a relatively large opposed area of the fixed electrode may be configured to detect an acceleration signal according to a relatively large input acceleration. This makes it possible to detect acceleration with high sensitivity over a wide range.

The acceleration measuring device according to the present invention is:
First and second capacitance detectors each having a movable electrode and a fixed electrode provided on the surface of the substrate so that the opposing area changes according to input acceleration are provided, and the first and second capacitance detectors are compared to the first capacitance detector. A capacitance type acceleration sensor having a large opposing area between the movable electrode and the fixed electrode when the input acceleration is zero;
First detection means for detecting, as first acceleration information, a change in capacitance between the movable electrode and the fixed electrode in the first capacitance detection unit;
Second detection means for detecting a change in capacitance between the movable electrode and the fixed electrode in the second capacitance detection unit as second acceleration information;
Determining means for determining whether the first acceleration information exceeds a predetermined detection upper limit for the first capacity detector;
Output means for transmitting the first acceleration information if the determination result by the determination means is negative, and for transmitting the second acceleration information if the determination result by the determination means is affirmative. It is a thing.

  According to the acceleration measuring apparatus of the present invention, it is determined whether or not the first acceleration information exceeds the detection upper limit value. If the determination result is negative, the first acceleration information is transmitted, and the determination result is positive. If so, the second acceleration information is transmitted, so that the acceleration can be measured with high accuracy in a wide range. Further, since the detection upper limit value can be determined so as to exclude a region where the change is steep in the capacitance change characteristic according to the input acceleration, it is possible to prevent erroneous detection due to noise mixing.

The acceleration measuring method according to the present invention includes first and second capacitance detection units each having a movable electrode and a fixed electrode provided on the surface of the substrate so that the facing area changes according to the input acceleration. A capacitance-type acceleration sensor in which the opposing area of the movable electrode and the fixed electrode is set larger when the input acceleration is zero in the second capacitance detection unit, and the first capacitance detection unit. A first detecting means for detecting a change in capacitance between the movable electrode and the fixed electrode in the first acceleration information, and a capacitance between the movable electrode and the fixed electrode in the second capacitance detector. An acceleration measurement method using second detection means for detecting a change as second acceleration information,
Taking in the first and second acceleration information from the first and second detection means, respectively;
A determination step of determining whether or not the first acceleration information acquired in this acquisition step exceeds a predetermined detection upper limit value with respect to the first capacity detection unit;
If the determination result in this determination step is negative, the first acceleration information acquired in the acquisition step is transmitted. If the determination result in the determination step is positive, the first acceleration information is transmitted. And an output step for sending the second acceleration information.

The program according to the present invention includes first and second capacitance detection units each having a movable electrode and a fixed electrode provided on a substrate surface so that the facing area changes according to input acceleration, and the first capacitance Compared to the detection unit, the second capacitance detection unit has a capacitance type acceleration sensor in which the opposing area of the movable electrode and the fixed electrode is set large when the input acceleration is zero, and the first capacitance detection unit is movable. A first detection means for detecting a change in capacitance between the electrode and the fixed electrode as first acceleration information; and a change in capacitance between the movable electrode and the fixed electrode in the second capacitance detector. A program used in an acceleration measuring apparatus comprising a second detection means for detecting second acceleration information and a computer, the computer comprising:
Capture means for capturing first and second acceleration information from the first and second detection means, respectively;
Determining means for determining whether the first acceleration information captured by the capturing means exceeds a predetermined detection upper limit for the first capacity detector;
If the determination result by the determination means is negative, the first acceleration information acquired by the acquisition means is transmitted, and if the determination result by the determination means is positive, the first acquisition is performed by the acquisition means. It is made to function as an output means for sending out the second acceleration information.

  According to the acceleration measuring method and program of the present invention, acceleration can be measured with high accuracy over a wide range as described above with respect to the acceleration measuring apparatus of the present invention, and erroneous detection due to noise mixing can be prevented.

  According to the present invention, the plurality of capacitance detection units having different facing areas of the movable electrode and the fixed electrode when the input acceleration is zero are provided on the substrate surface, and the input acceleration in a range suitable for each capacitance detection unit is detected. Since the configuration is adopted, it is possible to easily expand the detection range by increasing the number of capacitance detection units, and to obtain an effect of enabling highly sensitive acceleration detection in a wide range.

  FIG. 1 shows an electrode arrangement of a capacitance detection unit used in a capacitive acceleration sensor according to the present invention. (A) shows an electrode arrangement on the opposite area decreasing side, and (B) shows an increase in the opposed area. Each side electrode arrangement is shown. The principle of the acceleration sensor of the present invention will be described with reference to FIG.

1A and 1B, each of the movable electrodes M _{1 to} M ₄ is a rectangular shape having a length of 2L and a constant width. The movable electrodes M ₁ and M ₃ are juxtaposed at a predetermined interval so as to align the center in the length direction with the straight line L ₁ , and the movable electrodes M ₂ and M ₄ are arranged in the length direction with respect to the straight line L _2. Are aligned in parallel with the movable electrodes M ₁ and M ₃ so as to be aligned with each other. The straight lines L ₁ and L ₂ are parallel to each other. The movable electrodes M ₁ and M ₂ are juxtaposed at an electrode pitch 4L, and the movable electrodes M ₃ and M ₄ are juxtaposed at an electrode pitch 4L. The movable electrodes M _{1 to} M ₄ have a weight action, and can be integrally displaced in the left-right direction in parallel to the paper surface in accordance with the input acceleration in a state where the illustrated positional relationship is maintained.

Fixed electrodes S _1, S ₂ has been disposed below the movable electrodes M _1, M ₂ so that each faces the portion of the movable electrode M _1, the left half of M ₂ length L, a convenience of explanation The movable electrodes M ₁ and M ₂ are illustrated so as not to overlap with each other. The fixed electrodes S ₃ and S ₄ are arranged below the movable electrodes M ₃ and M ₄ so as to face the length L of the right half of the movable electrodes M ₃ and M ₄ , respectively. For convenience, the movable electrodes M ₃ and M ₄ are illustrated so as not to overlap with each other.

When the input acceleration is 0 G (G is gravitational acceleration [9.8 m / sec ² ]), the movable electrode-fixed electrode (M ₁ -S ₁ , M ₂ -S ₂ , M ₃ -S ₃ , Assume that the capacitance between M _{4 and} S ₄ ) is C ₀ . Next, when 1G acts as an input acceleration on the movable electrodes M _{1 to} M ₄ and the movable electrodes M _{1 to} M ₄ are displaced by a distance d in the right direction as indicated by arrows, the movable electrode-fixed electrode (M capacitance between _{1 -S 1, M 2 -S 2} ) counter electrode in both opposing area decreases, both with decreases from _{C 0} to _{C D,} opposing the movable electrode - the fixed electrode (M ₃ capacitance between -S _{3, M 4} -S 4) the counter electrode in both the facing area increases are all increases from _{C 0} to _{C U.} When a large input acceleration than 1G is applied to the movable electrode _M 1 ~M _4, the capacitance _{C D} is more reduced, the electrostatic capacitance _{C U} is further increased.

FIG. 2 shows the relationship between the input acceleration and the capacitance change rate C _U / C _D when the electrode overlap amount L (corresponding to the electrode facing area) is set to various values in the acceleration sensor of FIG. It is. In FIG. 2, curves K ₁ , K ₂ , K ₃ , K ₄ , K ₅ , K ₆ , K ₇ , K ₈ have electrode overlap amounts L of 0.5 [μm], 0.75 [μm], Input acceleration when set to 1.0 [μm], 1.25 [μm], 1.5 [μm], 2.0 [μm], 2.5 [μm], and 5.0 [μm], respectively The relationship with the capacitance change rate C _U / C _D is shown.

  As can be seen from FIG. 2, the larger the electrode overlap amount L, the larger the input acceleration can be detected. Therefore, the present invention employs a configuration in which a plurality of capacitance detection units having different electrode overlap amounts L are provided and input acceleration in a range suitable for each capacitance detection unit is detected. In this way, for example, for a relatively small input acceleration, acceleration detection is performed using a capacitance detection unit having a small electrode overlap amount, and for a relatively large input acceleration, a capacitance detection unit having a large electrode overlap amount is used. Acceleration can be detected, and high-sensitivity acceleration can be detected over a wide range.

In each curve, such as K _1, to prevent said detection due to noise mixing, rate of change in capacitance C _{U /} C _D is large (the change is steep) to avoid using the region is desirable.

  FIG. 3 shows a capacitive acceleration sensor 10 according to an embodiment of the present invention.

In the acceleration sensor 10, for example on the surface of the substrate such as a silicon substrate, the support member H ₁ to H ₄ as the movable member MB is displaceable in a direction DS parallel to the substrate surface having a weight acts doubly supported beam type It is installed. The supporting members H _{1 to} H ₄ are fixed by fixing members P _{1 to} P ₄ , respectively. On one side of the movable member MB, movable electrodes M ₁₁ , M ₂₁ , M ₂₄ , and M ₁₄ are provided so as to protrude in parallel with the substrate surface, and on the other side of the movable member MB, the movable electrodes M ₁₃ , M ₂₃ , M ₂₂ , and M ₁₂ are provided so as to protrude in parallel to the substrate surface. The projecting lengths of the movable electrodes M _{11 to} M ₁₄ and M _{21 to} M ₂₄ are equal to each other. The width of the movable electrode _M 11 _{~M 14} are equal to each other. The width of the movable electrode _M 21 _{~M 24} are equal to each other greater than the width of the movable electrode _M 11 _{~M 14.}

Movable member MB, the movable electrode _{M 11 ~M 14, M 21 ~M} 24 and the support member _H 1 to H ₄ are intended to form a integral with each other, for example, a semiconductor or a metal deposited on an insulating film covering the substrate surface after patterning the conductive layer made of, formed by removing the movable member MB, the insulating film so as to permit movement of the movable electrode _{M 11 ~M 14, M 21 ~M} 24 and the support member _H 1 to H ₄ can do. The fixing members P _{1 to} P ₄ are formed of a semiconductor or metal conductive plug formed by providing four fixing holes respectively corresponding to four fixing positions in an insulating film covering the substrate surface and filling the fixing holes. be able to.

Fixed electrodes S _{11 to} S are formed on the surface of the substrate so as to form capacitances C _{11 to} C ₁₄ that are opposed to the movable electrodes M _{11 to} M ₁₄ and have almost the same capacitance C _{11 to} C ₁₄ when the input acceleration is zero. ₁₄ , and when the input acceleration is zero, the fixed electrodes S ₂₁ to C ₂₄ are formed so as to face the movable electrodes M _{21 to} M ₂₄ and to form capacitances C _{21 to} C ₂₄ having large and substantially equal facing areas. S ₂₄ is provided. The fixed electrodes S ₁₁ , S ₁₂ , S ₂₁ , S ₂₂ are respectively movable electrodes M ₁₁ , M ₁₂ , M when the displacement direction DS of the movable member MB is determined in the forward direction parallel to the paper surface as shown in FIG. ₂₁ , M ₂₂ are arranged so that the facing areas thereof decrease and the capacitances C ₁₁ , C ₁₂ , C ₂₁ , C ₂₂ decrease, respectively, and the fixed electrodes S ₁₃ , S ₁₄ , S ₂₃ , S ₂₄ are capacitance _C 13 facing area is _{increased, C 14, C 23, C} 24 are arranged so as to increase each of the movable electrodes _{M 13, M 14, M 23} , M 24 each under similar conditions . In FIG. 4, a decrease in capacitance is indicated by an arrow pointing downward to the left, and an increase in capacitance is indicated by an arrow pointing upwards.

The fixed electrodes S _{11 to} S ₁₄ and S _{21 to} S ₂₄ may be constituted by an impurity doped region formed by selectively doping a conductivity determining impurity on the substrate surface, or on an insulating film covering the substrate surface. A semiconductor or metal conductive layer deposited on the substrate may be patterned.

From the fixed electrode _{S 11 ~S 14, S 21 ~S} 24 , respectively wiring layer _{W 11 ~W 14, W 21 ~W} 24 is derived. The wiring layers W ₁₁ and W ₁₂ are connected to the detection line Ta via connection members Q ₁₁ and Q ₁₂ , respectively. The wiring layers W ₁₃ and W ₁₄ are connected to the detection line Tb via connection members Q ₁₃ and Q ₁₄ , respectively. The wiring layers W ₂₁ and W ₂₂ are connected to the detection line Tc via connection members Q ₂₁ and Q ₂₂ , respectively. The wiring layers W ₂₃ and W ₂₄ are connected to the detection line Td via connection members Q ₂₃ and Q ₂₄ , respectively. The support member H ₁ is detected lines Te is connected.

The wiring layers W _{11 to} W ₁₄ and W _{21 to} W ₂₄ are made as thin as possible to reduce parasitic capacitance, and the distance between the movable parts (MB, M _{11 to} M ₁₄ , M _{21 to} M ₂₄ ) is made as large as possible. Moreover, the pattern may be formed so that the amount of overlap with the movable part is as small as possible. The wiring layers W _{11 to} W ₁₄ and W _{21 to} W ₂₄ can be configured by impurity-doped regions or patterned conductive layers in the same manner as the fixed electrodes S _{11 to} S ₁₄ and S _{21 to} S ₂₄ . The connection members Q _{11 to} Q ₁₄ and Q _{21 to} Q ₂₄ are semiconductors formed by providing eight connection holes corresponding to the eight connection positions in the insulating film covering the substrate surface and filling these connection holes, respectively. It can be formed by a metal conductive plug. Connecting member Q ₁₁ or the like, it may be formed by diverting the formation process of the fixing member, such as P _1.

As an example, after the wiring layers W _{11 to} W ₁₄ and W _{21 to} W ₂₄ are formed as impurity doped regions on the substrate surface, the first-layer wiring formation process is diverted on the insulating film covering the substrate surface to fix the fixed electrode S. _{11 to} S ₁₄ , S _{21 to} S ₂₄ are formed, and the second layer wiring formation process is diverted on the insulating film covering the fixed electrodes S _{11 to} S ₁₄ and S _{21 to} S ₂₄ , and the movable member MB and the movable member MB are movable. electrode _{M 11 ~M 14, M 21 ~M} 24, may be formed a supporting member _H 1 to H ₄ and the detection line Ta～Te. In this way, the wiring layer _{W 11 ~W 14, W 21 ~W} 24 and the movable portion _{(MB, M 11 ~M 14,} M 21 ~M 24) the spacing can be increased, the reduction of the parasitic capacitance Is possible.

An equivalent circuit of the acceleration sensor 10 of FIG. 3 is shown in FIG. FIG. 4 shows an example of an acceleration measuring device using the acceleration sensor 10 of FIG. In the measuring apparatus of FIG. 4, the input acceleration in the range of 0G to 8G shown in FIG. 2 is measured, and the curve K ₇ is used to measure a relatively small input acceleration from 0G to 4G, and 8G larger than 4G is used. the measured relatively large input acceleration to use the curve K _8. This is because, in the range R _{1 where} 0G ≦ input acceleration ≦ 4G, the curve K ₇ has a larger capacitance change rate C _U / C _D than the curve K ₈ , and highly accurate measurement is possible. This is because in the range R _{2 where} 4G <input acceleration ≦ 8G, the curve K ₇ has a non-measurable region and the curve K ₇ cannot be used, and the curve K ₈ is more suitable for measurement. In addition, in order to prevent erroneous detection due to noise contamination, the change steep region of curve K ₇ is not used in the acceleration range R ₁ , and the change steep region of curve K ₈ is not used for input acceleration exceeding 8 G. Yes (out of measurement range).

Detection lines Ta, Tb, and Te are connected to the detection circuit 12A, and detection lines Tc, Td, and Te are connected to the detection circuit 12B. As an example, the change characteristic of the capacitance according to the input acceleration in the capacitance detection unit including the capacitances C _{11 to} C ₁₄ is shown by a curve K ₇ in FIG. 2, and the capacitances C _{21 to} C _24. change characteristic of the capacitance in response to an input acceleration in the capacitance detection unit that includes a shall be represented by the curve K ₈ of FIG. Rate of change in capacitance _C U / _{C D} in FIG. 2, the use of the electrostatic capacitance _{C 11 ~C 14, C 21 ~C} 24 in FIG. _{4, (C 13 + C 14} ) / (C 11 + C 12) or This corresponds to (C ₂₃ + C ₂₄ ) / (C ₂₁ + C ₂₂ ).

In the detection circuit 12A, a voltage corresponding to a ratio (or difference) between (C ₁₃ + C ₁₄ ) and (C ₁₁ + C ₁₂ ) is detected as the acceleration signal AS ₁ using the change characteristic of the curve K ₇ . In the detection circuit 12B, the voltage corresponding to the ratio (or difference) between (C ₂₃ + C ₂₄ ) and (C ₂₁ + C ₂₂ ) is detected as the acceleration signal AS ₂ using the change characteristic of the curve K ₈ . Acceleration signal AS _1, the input acceleration is generated to increase the level as increasing from 0G. Acceleration signal AS ₂ takes the acceleration signal AS ₁ substantially the same level when the input acceleration is 4G, the input acceleration is generated to the level increases the level from the time of 4G as increasing the 4G .

The selector 14 selects and outputs the acceleration signal AS ₁ as the input A if the selection signal SB is 0, and selects and outputs the selection output SO ₂ of the selector 18 as the input B if the selection signal SB is 1. Is. The comparator 16 compares the acceleration signal AS ₁ with the reference voltage V _R1 and supplies the comparison output CO ₁ as the selection signal SB to the selector 14. If AS ₁ ≦ V _R1 , CO ₁ = 0 is set. _{If 1} > _VR1 , CO ₁ = 1 is supplied to the selector 14 respectively.

As the reference voltage V _R1 of the comparator 16, a voltage corresponding to the capacitance change rate C _U / C _D when the input acceleration is 4 G in the curve K ₇ in FIG. 2 is given as the detection upper limit value. As a result, the selector 14 outputs an acceleration signal AS ₁ corresponding to the input acceleration as a selection output SO _{1 in} the range R ₁ of 0G ≦ input acceleration ≦ 4G shown in FIG.

The selector 18, in which selection signal SB selects and outputs the acceleration signal AS ₂ as 0 if the input A, and outputs selection signals SB selects the range signal ASx representing the outside 1 if the measurement range is there. The comparator 20 compares the acceleration signal AS ₂ with the reference voltage V _R2 and supplies the comparison output CO ₂ to the selector 18 as the selection signal SB. If AS ₂ ≦ V _R2 , CO ₂ = 0 is set. _{If 2} > _VR2 , CO ₂ = 1 is supplied to the selector 18 respectively.

As the reference voltage _VR2 of the comparator 20, a voltage corresponding to the capacitance change rate C _U / C _D when the input acceleration is 8 G in the curve K ₈ in FIG. 2 is given as the detection upper limit value. As a result, the selector 18, the acceleration signal AS ₂ in response to an input acceleration in the range _{R 2} 4G <input acceleration ≦ 8G shown in FIG. 2 is sent as the selection output SO _2. In this case, the selector 14, since the state of selecting the selected output SO ₂ as an input B in response to the comparison output CO ₁ from the comparator 16, the selector 14, the acceleration signal AS ₂ as the selected output SO ₁ Sent out.

Level of the acceleration signal AS ₂ exceeds the reference voltage _{V R2} and _(becomes AS _{2> V R2),} the comparison output CO ₂ becomes 1 from the comparator 20, the selector 18, range signal ASx selection output SO ₂ is sent out. In this case, the selector 14 and is in a state to select the input B, and the selector 14 is out of range signal ASx is sent as the selection output SO _1. An acceleration display (not shown) can display the acceleration based on the acceleration signals AS ₁ and AS ₂ and can also indicate that the measurement range is out of the range based on the out-of-range signal ASx.

According to the acceleration measuring apparatus of FIG. 4 described above, acceleration can be measured with high accuracy in a wide range R ₁ , R ₂ of 0G ≦ input acceleration ≦ 8G. Further, since the acceleration detection is performed by excluding the region where the change is steep in the curves K ₇ and K ₈ in FIG. 2, it is possible to prevent erroneous detection due to noise mixing. In the example of FIG. 4, two curves K ₇ and K ₈ are used among the curves K _{1 to} K ₈ shown in FIG. 2, but it is needless to say that three or more curves may be used.

FIG. 5 shows the relationship between the input acceleration and the capacitance change rate C _U / C _D when the electrode overlap amount is set to various values in another capacitive acceleration sensor according to the present invention. is there.

In the acceleration sensor having the characteristics shown in FIG. 5, the displacement amount of the electrode when the input acceleration is 1 G is set to 0.5 [μm], and the electrode displacement amount d is linear with respect to the input acceleration. Change. Assuming that the electrode overlap amount L is L ₁ , L ₂ , L ₃ ... L _n from the smaller electrode width, L _n is L _n = L _n−1 +1 (where L ₀ = 0) [μm] Represented. The change rate of capacitance C _U / C _D = (L + d) / (L−d) when n = 1 to 5 in the range of input acceleration 0 to 8G is shown by curves J _{1 to} J in FIG. ₅ . The curves J ₁ , J ₂ , J ₃ , J ₄ , J ₅ are L ₁ = 1 [μm], L ₂ = 2 [μm], L ₃ = 3 [μm], L ₄ = 4 [μm], L _The capacitance change rate (L + d) / (L−d) is shown when ₅ = 5 [μm].

The capacitance change rate (L + d) / (Ld) increases rapidly as the electrode displacement amount d approaches the electrode width, as shown by the broken line in FIG. Therefore, an upper limit value for the electrode displacement amount d for each curve moves to the curve J ₂ when it exceeds the upper limit of the curve J _1, moves to the curve J ₃ When exceeding the upper limit of the curve J ₂ ... and change the curve to measure the acceleration. Upper limit _{d n} electrode displacement amount d _is, d _{n = d n-1} +1 is set as _{(although, L 0 = 0) [μm} ]. That is, a displacement such as d ₁ = 0.9 [μm], d ₂ = 1.9 [μm], d ₃ = 2.9 [μm]... Corresponding to J ₁ , J ₂ , J ₃ . It becomes the amount upper limit. Threshold _{T n} of electrostatic capacitance change rate _C U / _{C D} at this _time, since expressed as _{T n = (L n + d} n) / (L n -d n) = T n-1 +20, electrode it is possible to set a threshold T _n for overlap amount L _n and the displacement amount upper limit value d _n. FIG. 5 shows threshold values T ₁ = 19, T ₂ = 39, T ₃ = 59, and T ₄ = 79 in relation to the curves J ₁ , J ₂ , J ₃ , and J ₄ , respectively. Table 1 below collectively shows the relationship among L _n , d _n , and T _n .

  FIG. 6 shows an example of an acceleration measuring apparatus using an acceleration sensor having the characteristics shown in FIG. 5. In the apparatus of this example, the measurement process is controlled by a small computer.

The acceleration sensor 10A is configured in the same manner as the acceleration sensor 10 described above with reference to FIGS. 1 to 4, but n capacitors each corresponding to the curves J _{1 to} J _n (eg, n = 5) in FIG. The sensor 10 is different from the sensor 10 in that it includes a detection unit. The detection circuits DT _{1 to} DT _n make the voltages corresponding to the capacitance change rates C _U / C _D from the capacitance detection units corresponding to the curves J _{1 to} J _n in the sensor 10A in the same way as the detection circuits such as the above-described 12A. And detected as an acceleration signal. The detection circuit _DT 1 to DT _n, curve _J 1 through J _n corresponding detection line was derived from the capacitance detection unit of _TL 1 _{~TL n} are connected. Each of the detection lines TL _{1 to} TL _n includes three detection lines corresponding to the detection lines Ta, Tb, and Te in FIG. 4 and is shown as a single line for convenience.

From the detection circuit _DT 1 to DT _n, each acceleration signal _a 1 ~a _n in analog form is sent. Each acceleration signals _a 1 ~a _n is supplied to the A / D (analog / digital) converter _AD 1 to AD _n is converted into acceleration data _A 1 to A _n of the digital form. Acceleration data _A 1 to A _n represents an acceleration value corresponding to the acceleration signal _a 1 ~a _n respectively.

Connected to the bus 30 are a CPU (Central Processing Unit) 32, a ROM (Read Only Memory) 34, a RAM (Random Access Memory) 36, a utilization device 38, A / D conversion circuits AD _{1 to} AD _n, etc. Has been.

The CPU 32 executes a measurement process according to a program stored in the ROM 34. The measurement process will be described later with reference to FIG. In addition to the program, the ROM 34 stores reference data AT _{1 to} AT _n . The reference data AT _{1 to} AT _n represent reference acceleration values (detection upper limit values) respectively corresponding to threshold values T _{1 to} T _n of the capacitance change rate C _U / C _D.

The RAM 36 includes a storage area used as a register or the like during measurement processing by the CPU 32. As the register related to the practice of the invention, the register _RS 1 to RS _n respectively corresponding to the A / D converter _AD 1 to AD _n are provided. The registers RS _{1 to} RS _n receive acceleration data from the A / D conversion circuits AD _{1 to} AD _n , respectively.

The utilization device 38 uses the acceleration data of the registers RS _{1 to} RS _n , and not only the presence / absence of acceleration, but also a device having a wide range of acceleration to be measured, or the impact of a collision from a small acceleration, etc. Devices that are required to accurately measure a wide range of accelerations up to very large accelerations, such as electronic devices such as displays, electronic game terminals and mobile phones, or automobile airbag drive devices. Become.

FIG. 7 shows an example of the measurement process. This process is started in response to power-on or the like. In step 50, initial setting processing is performed, and for example, all of the registers RS _{1 to} RS _n are set to 0.

Next, at step 52, it takes in the acceleration data _A 1 to A _n from the A / D converter _AD 1 to AD _n, respectively set (stored) in the register _RS 1 to RS _n to. In step 54, it is determined whether the following reference acceleration value acceleration value indicating the acceleration data A ₁ in the register RS ₁ instructs the reference data AT _1. As a result of the determination is sent to the acceleration data A ₁ in the register RS ₁ in step 56 if affirmative (Y) to the utilization device 38. This is the case of using the curve J ₁ in FIG.

When the decision result in the step 54 is the end of the process or step 56 when there was a negative (N), the acceleration value for indicating the acceleration data A ₂ of the register RS ₂ are designated by the reference data AT ₁ in step 58 It determines whether the following reference acceleration value from the reference acceleration value and instructs the reference data aT ₂ large. As a result of the determination is sent to the acceleration data T ₂ of the register RS ₂ in step 60 if affirmative (Y) to the utilization device 38. This is the case of using the curve J ₂ in FIG.

When the decision result in the step 58 that have been processed or step 60 when the A was negative (N), the acceleration value for indicating the acceleration data A ₃ in the register RS ₃ instructs the reference data AT ₂ in step 62 determines whether the following reference acceleration value indicating the and reference data aT ₃ in greater than the reference acceleration value. As a result of the determination is sent to the acceleration data A ₃ of register RS ₃ in step 64 if affirmative (Y) to the utilization device 38. This is the case of using the curve J ₃ in FIG.

Thereafter, it performs a process corresponding to step 62 and 64 for curve J ₄ in the same manner as described above for the curve J _3. Then, when n = 5, at step 66, or less than the reference acceleration value acceleration value indicating the acceleration data for instructing the and reference data AT ₅ in greater than the reference acceleration value for indicating the reference data AT ₄ registers RS ₅ judge. As a result of the determination is sent to the acceleration data A ₅ of the register RS ₅ in step 68 if affirmative (Y) to the utilization device 38. This is a case where the curve J5 of FIG. ₅ is used.

  When the determination result of step 66 is negative (N) or when the processing of step 68 is completed, it is determined in step 70 whether there is an instruction to end such as power off. If the determination result is negative (N), the process returns to step 52, and the processing after step 52 is repeated in the same manner as described above. When the determination result in step 70 is affirmative (Y), the processing ends.

According to the measurement process described above, acceleration can be measured with high accuracy using the curves J _{1 to} J ₅ in a wide range of 0G ≦ input acceleration ≦ 8G. Further, since the acceleration detection is performed for the curves J _{1 to} J ₅ excluding the region where the change is steep, erroneous detection due to noise mixing can be prevented. In the above description, n = 5, but it is needless to say that n may be 6 or more.

It is a top view which shows electrode arrangement | positioning of the capacity | capacitance detection part used for the capacitive acceleration sensor which concerns on this invention. 2 is a graph showing the relationship between input acceleration and capacitance change rate C _U / C _D when the electrode overlap amount L is set to various values in the acceleration sensor of FIG. 1. It is a top view which shows the electrostatic capacitance type acceleration sensor which concerns on one Embodiment of this invention. It is a circuit diagram which shows an example of the acceleration measuring apparatus using the acceleration sensor of FIG. It is a graph which shows the relationship between the input acceleration when the electrode overlap amount L is set to various values in another acceleration sensor according to the present invention, and the capacitance change rate C _U / C _D. It is a circuit diagram which shows an example of the acceleration measuring apparatus using the acceleration sensor which has the characteristic of FIG. It is a flowchart which shows the measurement process in the apparatus of FIG.

Explanation of symbols

10, 10A: acceleration _{sensor, 12A, 12B, DT 1 ~DR} n: detection circuit, 30: Bus, 32: CPU, 34: ROM , 36: RAM, 38: utilization _{device, M 1 ~M 4, M 11} ~ _{M 14,} M 21 _{~M 24:} movable _{electrodes, S 1 ~S 4, S 11} ~S 14, S 21 ~S 24: fixed _{electrode, C 0, C D, C} U, C 11 ~C 14, C 21 -C _24: capacitance, Ta~Te: detection _{line, AD 1 ~AD n: A /} D conversion circuit.

Claims (7)

A plurality of first and second movable electrodes and first and second fixed electrodes, respectively, provided on the substrate surface such that the facing area is changed by relative movement in parallel with the substrate surface according to input acceleration. With a capacity detector
The first and second movable electrodes of the plurality of capacitance detection units are configured by a movable member formed integrally,
When the input acceleration is zero, the opposing areas of the first and second movable electrodes and the first and second fixed electrodes are different for each capacitance detection unit. The first movable electrode and the second movable electrode have the same amount of electrode displacement corresponding to each other, the opposing area of the first movable electrode and the first fixed electrode, the second movable electrode, and the second movable electrode. The area facing the two fixed electrodes has a relationship in which when one decreases in accordance with the input acceleration, the other increases.
An acceleration signal corresponding to a ratio between a capacitance between the first movable electrode and the first fixed electrode and a capacitance between the second movable electrode and the second fixed electrode; A capacitance-type acceleration sensor configured to be obtained for each capacitance detection unit. A plurality of first and second movable electrodes and first and second fixed electrodes, respectively, provided on the substrate surface such that the facing area is changed by relative movement in parallel with the substrate surface according to input acceleration. With a capacity detector
In each capacitance detection unit, the first and second movable electrodes are integrally formed,
When the input acceleration is zero, the opposing areas of the first and second movable electrodes and the first and second fixed electrodes are different for each capacitance detection unit. The first movable electrode and the second movable electrode have the same amount of electrode displacement corresponding to each other, the opposing area of the first movable electrode and the first fixed electrode, the second movable electrode, and the second movable electrode. The area facing the two fixed electrodes has a relationship in which when one decreases in accordance with the input acceleration, the other increases.
An acceleration signal corresponding to a ratio between a capacitance between the first movable electrode and the first fixed electrode and a capacitance between the second movable electrode and the second fixed electrode; A capacitance-type acceleration sensor configured to be obtained for each capacitance detection unit. Among the plurality of capacitance detection units, the input acceleration that is relatively small in the capacitance detection unit having a relatively small facing area between the first and second movable electrodes and the first and second fixed electrodes. In response to the acceleration signal, the capacitance detecting unit having a relatively large facing area between the first and second movable electrodes and the first and second fixed electrodes is relatively large. The capacitive acceleration sensor according to claim 1 or 2 , wherein the acceleration signal is detected according to input acceleration. The first and second movable electrodes have a weight action;
The capacitive acceleration sensor according to any one of claims 1 to 3 . First and second movable electrodes and first and second fixed electrodes, respectively, provided on the substrate surface such that the facing area is changed by relative movement in parallel with the substrate surface according to input acceleration. The first and second capacitance detectors, wherein the first and second movable electrodes of the first and second capacitance detectors are constituted by a movable member formed integrally, and the first capacitance detector In the second capacitance detection unit, the opposed area between the first and second movable electrodes and the first and second fixed electrodes when the input acceleration is zero is set larger than the first capacitance detection unit. In each of the first and second capacitance detection units, the first movable electrode and the first fixed electrode have the same amount of electrode displacement between the first movable electrode and the second movable electrode according to the input acceleration. An area facing the electrode and the second movable electrode; Serial The opposing area between the second fixed electrode and the electrostatic capacitance type acceleration sensor having a relationship other increases when one decreases in response to the input acceleration,
A capacitance between the first movable electrode and the first fixed electrode and a capacitance between the second movable electrode and the second fixed electrode in the first capacitance detector; First detection means for detecting an acceleration signal corresponding to the ratio as first acceleration information;
A capacitance between the first movable electrode and the first fixed electrode and a capacitance between the second movable electrode and the second fixed electrode in the second capacitance detector; Second detection means for detecting an acceleration signal corresponding to the ratio of the second acceleration information as second acceleration information;
Determining means for determining whether the first acceleration information exceeds a predetermined detection upper limit for the first capacity detector;
Output means for transmitting the first acceleration information if the determination result by the determination means is negative, and for transmitting the second acceleration information if the determination result by the determination means is affirmative. Acceleration measuring device. First and second movable electrodes and first and second fixed electrodes, respectively, provided on the substrate surface such that the facing area is changed by relative movement in parallel with the substrate surface according to input acceleration. The first and second capacitance detectors, wherein the first and second movable electrodes of the first and second capacitance detectors are constituted by a movable member formed integrally, and the first capacitance detector In the second capacitance detection unit, the opposed area between the first and second movable electrodes and the first and second fixed electrodes when the input acceleration is zero is set larger than the first capacitance detection unit. In each of the first and second capacitance detection units, the first movable electrode and the first fixed electrode have the same amount of electrode displacement between the first movable electrode and the second movable electrode according to the input acceleration. An area facing the electrode and the second movable electrode; The area facing the second fixed electrode is a capacitance-type acceleration sensor having a relationship in which one increases when the other decreases in accordance with the input acceleration, and the first capacitance detection unit includes the first acceleration sensor. An acceleration signal corresponding to the ratio between the capacitance between the movable electrode and the first fixed electrode and the capacitance between the second movable electrode and the second fixed electrode is used as the first acceleration. A first detection means for detecting information; a capacitance between the first movable electrode and the first fixed electrode in the second capacitance detection unit; the second movable electrode; and the second An acceleration measurement method using second detection means for detecting an acceleration signal corresponding to a ratio of capacitance to a fixed electrode as second acceleration information,
Taking in the first and second acceleration information from the first and second detection means, respectively;
A determination step for determining whether the first acceleration information captured in the capture step exceeds a predetermined detection upper limit value for the first capacity detection unit;
If the determination result in this determination step is negative, the first acceleration information acquired in the acquisition step is transmitted, and if the determination result in the determination step is positive, the acquisition step And an output step of sending the captured second acceleration information. First and second movable electrodes and first and second fixed electrodes, respectively, provided on the substrate surface such that the facing area is changed by relative movement in parallel with the substrate surface according to input acceleration. The first and second capacitance detectors, wherein the first and second movable electrodes of the first and second capacitance detectors are constituted by a movable member formed integrally, and the first capacitance detector In the second capacitance detection unit, the opposed area between the first and second movable electrodes and the first and second fixed electrodes when the input acceleration is zero is set larger than the first capacitance detection unit. In each of the first and second capacitance detection units, the first movable electrode and the first fixed electrode have the same amount of electrode displacement between the first movable electrode and the second movable electrode according to the input acceleration. An area facing the electrode and the second movable electrode; The area facing the second fixed electrode is a capacitance-type acceleration sensor having a relationship in which one increases when the other decreases in accordance with the input acceleration, and the first capacitance detection unit includes the first acceleration sensor. An acceleration signal corresponding to the ratio between the capacitance between the movable electrode and the first fixed electrode and the capacitance between the second movable electrode and the second fixed electrode is used as the first acceleration. A first detection means for detecting information; a capacitance between the first movable electrode and the first fixed electrode in the second capacitance detection unit; the second movable electrode; and the second A program used in an acceleration measuring apparatus comprising a second detection means for detecting an acceleration signal corresponding to a ratio of the capacitance to the fixed electrode as second acceleration information, and a computer, The computer,
Capture means for capturing the first and second acceleration information from the first and second detection means, respectively;
A determination unit for determining whether the first acceleration information captured by the capture unit exceeds a predetermined detection upper limit for the first capacity detection unit;
If the determination result by the determination means is negative, the first acceleration information acquired by the acquisition means is transmitted, and if the determination result by the determination means is affirmative, the acquisition means A program that functions as output means for sending out the second acceleration information that has been taken in.

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