WO1996038732A1 - Detecteur d'acceleration - Google Patents
Detecteur d'acceleration Download PDFInfo
- Publication number
- WO1996038732A1 WO1996038732A1 PCT/JP1996/001439 JP9601439W WO9638732A1 WO 1996038732 A1 WO1996038732 A1 WO 1996038732A1 JP 9601439 W JP9601439 W JP 9601439W WO 9638732 A1 WO9638732 A1 WO 9638732A1
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- WO
- WIPO (PCT)
- Prior art keywords
- electrode
- annular
- acceleration sensor
- displacement
- substrate
- Prior art date
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/125—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by capacitive pick-up
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/18—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration in two or more dimensions
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P2015/0805—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration
- G01P2015/0822—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass
- G01P2015/084—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass
Definitions
- the present invention relates to an acceleration sensor, and more particularly to an acceleration sensor suitable for detecting acceleration based on an earthquake or a collision of a car. Background technology
- WO 91Z10118 and WO 92/17759 disclose a three-dimensional acceleration sensor using a capacitance element
- International Publication WO093Z02342 discloses a piezoelectric device.
- a three-dimensional acceleration sensor using an element is disclosed.
- the acceleration components in the respective directions in the XYZ three-dimensional coordinate system can also be independently detected.
- a single sensor can independently detect all of the coordinate axis components of the applied acceleration, so that the acceleration to be detected can be detected in a three-dimensional space. It can be specified as a vector amount. Therefore, such a three-dimensional acceleration sensor can be used to accurately detect the acceleration acting on an object moving in a three-dimensional space, a moving vehicle, a flying aircraft, etc., including its direction. It is widely available and is expected to increase its value in the future.
- acceleration sensors can also be used as seismometers and impact meters.
- city gas control valves and elevator control devices have built-in acceleration sensors that function as seismometers. If the acceleration based on the vibration of an earthquake exceeds a predetermined threshold, Control is performed to stop the gas supply and stop the operation of the elevator.
- automobiles equipped with airbags which have rapidly become widespread, are equipped with an acceleration sensor that functions as an impact meter. The function of protecting the driver by instantly inflating it works.
- the acceleration sensors currently used as such seismometers and impact meters are not the three-dimensional acceleration sensors described above, but, for example, depend on whether a steel ball jumps out of a bowl-shaped container.
- the mainstream is a mechanical sensor that determines whether an acceleration greater than the threshold has been applied.
- the acceleration sensors used as seismometers and impact meters are currently of the mainstream mechanical type. ⁇ Forces such as these are low in detection accuracy and reliability. Also, the detection results are electrically There is a problem that it is difficult to put out.
- a three-dimensional acceleration sensor using a piezoresistive element, a capacitive element, and a piezoelectric element has high detection accuracy and reliability, and is capable of electrically extracting a detection result.
- applications such as seismometers and impact meters do not always require such a three-dimensional acceleration sensor, and conversely, conventional three-dimensional acceleration sensors may be difficult to use.
- a seismometer will vibrate in the direction along the XY plane (rolling). It is sufficient if the magnitude of the vibration and the magnitude of the vibration (pitch) in the direction along the Z axis can be measured.
- the X-axis direction component ⁇ ; ⁇ , ⁇ $ ⁇ direction component o; y, and the Z-axis direction component are separately and independently detected for the acceleration in the XYZ three-dimensional coordinate system. Therefore, for example, to obtain the magnitude of the roll along the ⁇ ⁇ plane, it is necessary to calculate the sum of ⁇ X 2 and ay and then calculate the square root of this sum.
- an object of the present invention is to provide an acceleration sensor suitable for detecting, as an electric signal, the magnitude of acceleration directed in a direction included in a predetermined plane. Disclosure of the invention
- a first aspect of the present invention provides an acceleration sensor
- a displacement board disposed at a predetermined distance below the fixed board and opposed to the fixed board;
- Support means for elastically supporting the periphery of the displacement substrate with respect to the sensor housing
- annular fixed electrode formed on the lower surface of the fixed substrate and having an annular shape; an annular displacement electrode formed on the upper surface of the displacement substrate and functioning as a counter electrode to the annular fixed electrode;
- a second aspect of the present invention is directed to the acceleration sensor according to the first aspect described above.
- a central fixed electrode disposed in an inner area of the annular fixed electrode on the lower surface of the fixed substrate;
- the detection circuit uses the variation V 2 of the capacitance value of the central capacitance element formed by the central fixed electrode and the central displacement electrode to calculate the variation V 1 of the capacitance value of the annular capacitance element.
- the electric signal indicating the magnitude of the acceleration acting in a direction parallel to the main surface of the fixed substrate is output based on the corrected value.
- a third aspect of the present invention is the acceleration sensor according to the second aspect described above,
- the detection circuit further outputs an electric signal indicating the magnitude of the acceleration acting in the direction perpendicular to the main surface of the fixed substrate based on the variation V 2 of the capacitance value of the central capacitance element. It was done.
- Each of the annular fixed electrode, the annular displacement electrode, the center fixed electrode, and the center displacement electrode is almost rotationally symmetric with respect to a central axis passing through the center of gravity of the weight body and perpendicular to the main surface of the fixed substrate.
- the shape is as follows.
- the distance d1 between the pair of electrodes constituting the annular capacitance element and the capacitance at the center is such that the distance d2 between the electrodes of the pair of electrodes constituting the element is equal to, the area S1 of each electrode constituting the annular capacitance element, and the area S of each electrode constituting the central capacitance element 2 and, with respect to the variation V 1 of the capacitance value of the annular capacitance element,
- V s V I-(S 1 / S 2) V 2
- an electric signal indicating the magnitude of the acceleration acting in a direction parallel to the main surface of the fixed substrate is output.
- an electric signal indicating the magnitude of the acceleration acting in a direction parallel to the main surface of the fixed substrate is output.
- the distance d1 between the pair of electrodes constituting the annular capacitance element and the capacitance at the center The distance d2 between the electrodes of the pair of electrodes constituting the element is equal to, and the area S1 of each electrode constituting the annular capacitive element and the area S2 of each electrode constituting the central capacitive element , And are equal.
- An eighth aspect of the present invention is the acceleration sensor according to the second to fourth aspects described above,
- the detection circuit multiplies the variation V 1 of the capacitance value of the annular capacitance element by a predetermined constant K l 1 to obtain ( ⁇ 11 ⁇ ⁇ ⁇ ), and multiplies by a predetermined constant ⁇ 21.
- a circuit that obtains (K 21 ⁇ VI), a circuit that obtains (K 12 * V 2) by multiplying a variation V 2 of the capacitance value of the central capacitive element by a predetermined constant ⁇ 12, and a predetermined constant A circuit that obtains ( ⁇ 22 ⁇ V 2) by multiplying by ⁇ 22, a circuit that obtains the value V s by performing an operation of (K ll 'V l) — (K 12.V 2), and (K21 * V 1 ) — A circuit that performs an operation of (K 22 * V 2) to obtain a value V p, and
- an electric signal indicating the magnitude of the acceleration acting in a direction perpendicular to the main surface of the fixed substrate is output.
- a ninth aspect of the present invention is the acceleration sensor according to the second or third aspect described above,
- the annular fixed electrode and the annular displacement electrode have an annular shape that is non-rotationally symmetric with respect to a center axis passing through the center of gravity of the weight body and perpendicular to the main surface of the fixed substrate.
- a tenth aspect of the present invention is the acceleration sensor according to the second to ninth aspects,
- the annular displacement electrode and the center displacement electrode are physically constituted by a single common electrode.
- the eleventh aspect of the present invention is the acceleration sensor according to the tenth aspect described above,
- the displacement substrate is made of a conductive material, and a part of the displacement substrate is used as a single common electrode.
- a twenty-second aspect of the present invention is the acceleration sensor according to the second to ninth aspects,
- the annular fixed electrode and the central fixed electrode are physically constituted by a single common electrode.
- the fixed substrate is made of a conductive material, and a part of the fixed substrate is used as a single common electrode.
- a fourteenth aspect of the present invention provides the acceleration sensor according to the first to thirteenth aspects
- a diaphragm is formed by forming a plurality of slits on a flexible substrate, and the diaphragm is used as a displacement substrate and a support means.
- the structure is such that each part of the diaphragm is physically connected,
- the peripheral part of the diaphragm is fixed to the sensor housing, and the center of the diaphragm is displaced based on the elastic deformation of the gap between the slits.
- each slit is formed so that the slit pattern substantially matches the pattern before rotation. It was done.
- FIG. 1 is a perspective view of a main part of an acceleration sensor according to a basic embodiment of the present invention.
- FIG. 2 is a side sectional view of the acceleration sensor shown in FIG.
- Figure 3 is a bottom view of the fixed substrate 1 0 of the acceleration sensor shown in FIG. 1 ⁇ Fig. 4, t 5
- FIG is a top view of the displacement substrate 2 0 of the acceleration sensor shown in FIG. 1
- FIG. 3 is a side cross-sectional view for explaining an operation when a force FX in the positive X-axis direction acts on the acceleration sensor shown in FIG.
- FIG. 6 is a top view of the displacement substrate 20 for illustrating a change in the capacitance value in the state shown in FIG.
- FIG. 7 is a graph showing a general relationship between a distance d between electrodes and a capacitance value C in a capacitance element.
- FIG. 8 is a graph showing the relationship between the acceleration ⁇ X acting on the acceleration sensor shown in FIG. 1 and the sensor output.
- FIG. 9 is a side cross-sectional view for explaining the operation when a force Fz in the Z $ direction is applied to the acceleration sensor shown in FIG.
- FIG. 10 is a circuit diagram showing an example of a detection circuit used in the acceleration sensor shown in FIG.
- FIG. 11 is a side sectional view showing a structure of a modification of the acceleration sensor shown in FIG.
- FIG. 12 is a top view of a displacement board 20 in a modified example of the acceleration sensor shown in FIG.
- FIG. 13 is a top view of a diaphragm 120 used for an acceleration sensor according to a practical embodiment of the present invention.
- FIG. 14 is a side sectional view of an acceleration sensor according to an embodiment using the diaphragm 120 shown in FIG.
- FIG. 15 is a bottom view of the displacement board 110 in the acceleration sensor shown in FIG.
- FIG. 16 is a side sectional view for explaining the operation when a force F X in the positive direction of the X-axis acts on the acceleration sensor shown in FIG.
- FIG. 17 is a side sectional view of an acceleration sensor according to another practical embodiment of the present invention.
- FIG. 18 is a top view of the displacement board 220 used in the acceleration sensor shown in FIG.
- FIG. 19 is a circuit diagram showing another example of the detection circuit used in the acceleration sensor shown in FIG.
- FIG. 20 is a diagram for explaining directivity of detection sensitivity when used as an impact sensor at the time of a vehicle collision.
- FIG. 21 is a bottom view of the fixed substrate 10 of the acceleration sensor according to the first embodiment having directivity according to the present invention.
- FIG. 22 is a bottom view of the fixed substrate 10 of the acceleration sensor according to the second embodiment having directivity according to the present invention.
- FIG. 23 is a bottom view of the fixed substrate 10 of the acceleration sensor according to the third embodiment having directivity according to the present invention.
- FIG. 24 is a bottom view of the fixed substrate 10 of the acceleration sensor according to the fourth embodiment having directivity according to the present invention.
- the fixed substrate and the displacement substrate are provided in the housing, and an annular fixed electrode is formed on the fixed substrate side, and an annular displacement electrode force is formed on the displacement substrate side. Both annular electrodes are arranged so as to face each other, and an annular capacitive element is formed.
- the periphery of the displacement substrate is elastically supported by a support means, and by applying a force, the displacement substrate can be displaced by being inclined or translated with respect to the fixed substrate.
- a weight is fixed to the displacement substrate, and when acceleration is applied to the entire sensor housing, a force based on the acceleration is applied to the weight to cause elastic deformation of the support means. As a result, the displacement substrate is displaced with respect to the fixed substrate.
- each ring electrode is formed to be substantially rotationally symmetric with respect to the central axis, the change in the capacitance value is equivalent in all directions parallel to the main surface of the fixed substrate. Therefore, even if an acceleration acts in a direction such as parallel to the main surface of the fixed substrate, the magnitude can be detected equally.
- each annular electrode is intentionally made to be non-rotationally symmetric, an acceleration sensor having a different detection sensitivity depending on a direction parallel to the main surface of the fixed substrate can be realized.
- a central fixed electrode is provided inside the annular fixed electrode, and a central displacement electrode is provided inside the annular displacement electrode.
- a central capacitive element is formed by the pair of electrodes.
- the capacitance value of the annular capacitance element is corrected based on the variation of the capacitance value of the central capacitance element, the output of only the horizontal acceleration component that does not include the vertical acceleration component can be obtained. Will be possible.
- the variation of the capacitance value of the central capacitive element is output as a vertical acceleration component, acceleration in both vertical and horizontal directions can be detected.
- Each electrode must be a physically independent electrode.
- the annular displacement electrode and the center displacement electrode are physically constituted by a single common electrode, or the annular fixed electrode and the center fixed electrode are physically constituted by a single common electrode.
- the structure can be simplified. Furthermore, if the displacement substrate or the fixed substrate is made of a conductive material, a part of these substrates can be used as a common electrode, and the structure can be further simplified.
- the structure can be simplified and the manufacturing cost can be reduced.
- the deflection of the diaphragm is improved. This makes it possible to make the directionality uniform, so that all lateral accelerations can be detected almost equally. Further, even if the slit pattern almost coincides with the pattern rotated by a predetermined angle of 0 °, it is possible to make the directionality of the diaphragm radius uniform, and almost all the lateral accelerations are reduced. Detection can be performed evenly.
- FIG. 1 shows a perspective view of a main part of an acceleration sensor according to a basic embodiment of the present invention
- FIG. 2 shows a side sectional view thereof.
- this acceleration sensor has a disk-shaped fixed substrate 10 and a disk-shaped displacement substrate 20, and supports 30 around the displacement substrate 20. Is installed. Further, a cylindrical weight 40 is fixed to the lower surface of the displacement substrate 20. All of these components are housed in a cylindrical sensor housing 50 (not shown in FIG. 1).
- FIG. 2 also shows a sensor housing 50 not shown in FIG.
- the periphery of the A- fixed substrate 10 is fitted and fixed inside the sensor housing 50.
- the circumference of the disk-shaped fixed substrate 10 is fixed to the inside of the cylindrical sensor housing 50 over the entire circumference c, while the displacement substrate 20 is It is supported inside the sensor housing 50 by the support means 30 attached around it.
- the support means 30 has a function of elastically supporting the periphery of the displacement board 20 with respect to the sensor housing 50.
- the displacement substrate 20 is formed by using a diaphragm having a slit or the like. It is preferable that the support means 30 be constituted.
- the fixed substrate 10 and the displacement substrate 20 are substantially parallel to each other at a predetermined distance from each other. Is kept.
- a force based on the acceleration acts on the center of gravity G of the weight body 40, and the support means 30 is elastically deformed by this force, and the displacement board 20 It becomes displaced with respect to the fixed substrate 10.
- this acceleration sensor is installed at a predetermined earthquake observation point, when an earthquake occurs, acceleration acts on the weight body 40 based on the vibration at the earthquake observation point, and the displacement board 2 0 will be displaced with respect to the fixed substrate 10.
- the weight body 40 must have a sufficient mass to induce elastic deformation of the support means 30 by the action of the acceleration to be detected.
- the sensitivity of the acceleration sensor can be adjusted by appropriately selecting the elastic coefficient of the support means 30 and the mass of the weight body 40.
- an XYZ three-dimensional coordinate system as shown in the lower left of FIG. 1 is defined here.
- Each of the main surfaces of the fixed substrate 10 and the displacement substrate 20 is a surface parallel to the XY plane in this coordinate system.
- a center axis W passing through the center of gravity G of the weight body 40 and parallel to the Z axis is defined.
- the fixed substrate 10, the displacement substrate 20, the weight 40, and the sensor housing 50 are all rotationally symmetric with respect to the central axis W.
- the support means 30 is also rotationally symmetric with respect to the central axis W.
- the support means 30 is formed by eight springs and is as rotationally symmetrical as possible. Close behavior is obtained.
- FIG. 3 shows a bottom view of the fixed board 10
- FIG. 4 shows a top view of the displacement board 20.
- an annular fixed electrode E 11 and a central fixed electrode E 12 are formed on the lower surface of the fixed substrate 10.
- an annular displacement electrode E 21 and a central displacement electrode E 22 are formed on the upper surface of the displacement substrate 20.
- the annular fixed electrode E 11 and the annular displacement electrode E 21 are both annular (so-called dash-shaped and donut-shaped) electrodes, and have a rotationally symmetric shape with respect to the central axis W shown in FIG. It is arranged at a position that is rotationally symmetric.
- the center fixed electrode E 12 and the center displacement electrode E 22 are both disc-shaped electrodes, and are also rotationally symmetric with respect to the center axis W shown in FIG.
- the annular fixed electrode E 11 and the annular displacement electrode E 21 have the same shape, are arranged at positions facing each other, and a capacitive element is formed by the pair of electrodes.
- the capacitive element of ::: is referred to as an annular capacitive element C1.
- the central fixed electrode E12 and the central displacement electrode E22 have the same shape, are arranged at positions facing each other, and a capacitor element is formed by the pair of electrodes.
- this capacitive element is referred to as a central capacitive element C 2.
- FIGS. 3 and 4 hatching is given to each electrode part, but this is for the purpose of making it easier to grasp the shape of the electrode, and is not hatching for showing a cross section. .
- the materials of the respective parts constituting the acceleration sensor having the structure shown in the basic embodiment have not been particularly described so far, at least the electrodes E 11, E 12, E 21 , E22 must be made of a conductive material such as a metal.
- the fixed substrate 10 and the displacement substrate 20 may be made of a conductive material or an insulating material, but when they are made of a conductive material, they are formed thereon. It is necessary to form an insulating film between the substrate and the electrode so that the two electrodes are not short-circuited. However, it is not necessary to configure the common electrode described in ⁇ 6.
- the feature of the acceleration sensor according to the present invention is that the “rolling” and “pitch” are distinguished and detected. It is possible.
- “rolling” means vibration in the direction along the XY plane in the XYZ three-dimensional coordinate system
- pitch means vibration in the direction along the Z axis. Shall be.
- it is known that “rolling” in an earthquake is vibration based on S-waves
- “pitch” is vibration based on P-waves. It is desirable to be able to detect it.
- the amplitude of “rolling” is detected based on the capacitance value of the annular capacitance element C 1 composed of the annular fixed electrode E 11 and the annular displacement electrode E 21. Is done.
- an acceleration sensor having the structure shown in Fig. 2 is installed at a predetermined earthquake observation point.
- this seismic observation point vibrated in the X-axis direction.
- Such vibrations are “rolling” vibrations based on S waves.
- the weight body 40 is swung in the X direction in the sensor housing 50. That is, the acceleration ⁇ X in the X cold direction acts on the weight body 40.
- a force of F X m ⁇ a x acts on the center of gravity G of the weight body 40 having the mass m.
- FIG. 5 shows a state of inclination of the displacement substrate 20 when a force F X acts in the positive direction of the X-axis.
- a force F X acts in the positive direction of the X-axis.
- the “rolling” vibration caused by the earthquake alternately generates acceleration in the positive X-axis direction and acceleration in the negative X-axis direction.
- the force FX and the car FX in the negative X-axis direction are applied alternately, and FIG. 5 shows the instantaneous state of such vibration.
- ⁇ is the dielectric constant of a medium (air in this embodiment) existing between the two electrodes forming the capacitive element
- S is the area of the electrode
- d is the distance between the electrodes.
- FIG. 6 is a top view of the displacement substrate 20 for showing the distribution of the change in the distance d between the electrodes.
- the dashed line drawn along the Y axis as the boundary line, the inter-electrode distance d decreases in the right half of the figure, and the inter-electrode distance d increases in the left half of the figure. Therefore, taking into account the above-described equation of the capacitance value C, the capacitance value increases in the right half of the figure, and decreases in the left half of the figure.
- the annular displacement electrode E 21 has a rotationally symmetric shape with respect to the central axis W (in this embodiment, an annular shape around the central axis W), it is natural that the annular displacement electrode E 2 1 becomes line symmetric. Therefore, even if the capacitance value increases in the right half of the figure, the capacitance value decreases in the left half of the figure, so that the change in the capacitance value of the entire annular capacitance element C1 is offset on the left and right sides, and The condition shown in Fig. 2 and the condition shown in Fig. 5
- a minute area Qa is defined in the right half of the annular displacement electrode E21, and a minute area Qb is defined in the left half.
- the minute area Qa and the minute area Qb exist at positions symmetrical with respect to the Y axis (dashed line), and have the same shape and the same area Sq.
- the capacitance values of the capacitance elements C a and C b formed by these minute regions Q a and Q b and the minute regions in the annular fixed electrode E 11 facing the small regions Q a and Q b? Think.
- (+ x) is increased by ⁇ Ca corresponding to the difference ⁇ d between the electrodes.
- the capacitance value C b (+ x) of the capacitive element C b is reduced by ⁇ C b corresponding to the difference ⁇ d between the electrodes. That is, while the capacitance value of the capacitance element C a increases by ⁇ C a, the capacitance value of the capacitance element C b increases.
- the electrode spacing of the capacitive element Cb becomes large as d0 + ⁇ d, and as a result, the capacitance value becomes Cb (+ X) reduced by ⁇ Cb.
- the change ⁇ d in the electrode interval is equal, the changes ⁇ C a and ⁇ C b in the capacitance value are not equal.
- the change in the capacitance value of the annular capacitance element C 1 constituted by the annular fixed electrode E 11 and the annular displacement electrode E 21 is the acceleration ⁇ ⁇ ⁇ acting in the X-axis direction.
- it indicates the magnitude of wrestler FX acting in the X-axis direction. Therefore, if the capacitance value of the annular capacitance element C1 is electrically extracted as a sensor output, an acceleration sensor that outputs the magnitude of the acceleration soil ⁇ X acting in the X-axis direction as an electric signal can be realized.
- Figure 8 shows It is a graph which shows the relationship between the applied acceleration and the sensor output.
- the acceleration in the X-axis direction alternates between positive and negative values, as shown in the upper graph of FIG.
- the sensor output that is, the capacitance value of the annular capacitive element C1
- the reference value R the output value when no acceleration is acting
- a conversion circuit that can output the capacitance value of the ring capacitance element C 1 as a voltage is prepared, and a detection circuit that can output the fluctuation width of the capacitance value of the ring capacitance element C 1 as a voltage is configured.
- the output voltage of this detection circuit can be used as it is as the absolute value of the acceleration soil ⁇ X acting in the X-axis direction. If the sensor output as shown in the lower part of Fig. 8 is smoothed, an average value of vibration can be obtained, and if this sensor output is integrated, the accumulated energy value of vibration can be obtained. .
- this acceleration sensor has been described so far in the case where the acceleration soil ⁇ X in the X-axis direction is applied. However, such a detection operation is performed only for the acceleration soil ⁇ X in the X vehicle direction. is not.
- the fixed substrate 1 ⁇ , the displacement substrate 2 ⁇ , the annular fixed electrode ⁇ 11, and the annular displacement electrode E21 are all rotationally symmetric with respect to the central axis W, so that Even when the acceleration soil ay acts, the absolute value of the acceleration can be detected by the exactly same detection operation.
- the acceleration sensor Is any direction of 360 ° on the XY plane Can be detected with the same sensitivity to the acceleration of the XY plane, and has no directivity on the XY plane. This is an ideal property for use as a seismometer or impact meter.
- this acceleration sensor is installed at an earthquake observation point so that the XY plane coincides with the horizontal plane, the magnitude of the roll in all directions at this earthquake observation point will be determined by the electrostatic capacitance of the ring capacitance element C1. It becomes possible to detect based on the capacitance value. Also, if this acceleration sensor is mounted on the vehicle so that the XY plane coincides with the running surface, the magnitude of any impact applied to the vehicle along the running surface can be determined by the circular capacitive element C. It becomes possible to detect based on the capacitance value of 1.
- the predetermined It is sufficient to have an acceleration sensor that can detect whether or not a roll above the threshold has occurred.
- an impact that is equal to or greater than a predetermined threshold is applied to the front, It is sufficient to have an acceleration sensor that can detect whether or not it has been applied from the back or side.
- the acceleration sensor according to the present invention sufficiently satisfies such a condition, and furthermore, its detection output can be directly obtained as the capacitance value of the annular capacitance element C1. , It is possible to detect necessary and sufficient acceleration.
- the acceleration sensor according to the above-described basic embodiment has a function of detecting not only “rolling” but also “pitch”.
- “rolling” based on S-waves and “pitching” based on P-waves are used. It is desirable that each can be detected independently.
- the amplitude of the "pitch” is detected based on the capacitance value of the central capacitive element C2 composed of the central fixed electrode E12 and the central displacement electrode E22. You.
- an acceleration sensor having the structure shown in Fig. 2 is installed at a predetermined earthquake observation point, and this earthquake observation point vibrates in the Z-axis direction.
- Such vibrations are “pitch” vibrations based on P-waves.
- the weight body 40 is swung in the Z axis direction in the sensor housing 50. That is, the acceleration ⁇ Z in the Z-axis direction acts on the weight body 40. Therefore, a force of Fzm ⁇ az acts on the center of gravity G of the weight body 40 having the mass m.
- FIG. 9 shows a state of displacement of the displacement substrate 20 when a force F is applied in the positive direction of the ⁇ axis.
- a force F is applied in the positive direction of the ⁇ axis.
- the vibration of “pitch” caused by the earthquake alternately generates the acceleration in the positive direction of the ⁇ axis and the acceleration in the negative direction of the ⁇ axis.
- the force F ⁇ and the force in the negative direction of the ⁇ axis-F are applied alternately, and Fig. 9 shows the instantaneous state of such vibration.
- the weight body 40 vibrates in the vertical direction in the figure in FIG. 9 and the distance d between the electrodes of the central capacitive element C 2 becomes smaller.
- the capacitance value of the central capacitive element C2 periodically changes as it increases or decreases. The amplitude of this change indicates the amplitude of the "pitch" vibration.
- the capacitance value of the central capacitive element C 2 formed by the central fixed electrode E 12 and the central displacement electrode E 22 is the acceleration ⁇ ⁇ ⁇ acting in the Z-fist direction. In other words, it indicates the magnitude of the wrestler F ⁇ acting in the axial direction. Therefore, the capacitance value of the central capacitance element C 2, is electrically taken out as a sensor output, acceleration ⁇ alpha zeta magnitude acting on ⁇ axially, i.e. electric signal the magnitude of the "longitudinal vibration" Acceleration sensor that outputs as If this sensor output is smoothed, an average value of the vibration can be obtained, and if this sensor output is integrated, the accumulated energy value of the vibration can be obtained.
- the structure of the acceleration sensor according to the basic embodiment of the present invention has been described in ⁇ 1, the roll detection operation in ⁇ 2, and the pitch detection operation in ⁇ 3.
- the roll detection operation is performed by the annular capacitance element C 1 composed of the annular fixed electrode ⁇ 11 and the annular displacement electrode ⁇ 21, and the center fixed electrode ⁇ 12 and the central Pitch detection operation by the central capacitive element C 2 composed of the displacement electrode ⁇ 22 Said to do the work.
- the reverse detection operation is also possible. That is, it is theoretically possible to perform the roll detection operation by the central capacitive element C2 and perform the pitch detection operation by the annular capacitive element C1.
- the opposite detection operation will be described.
- the roll detection operation can be performed by the center capacitive element C2.
- the displacement substrate 20 is inclined as shown in FIG.
- the capacitance value of the central capacitive element C 2 composed of the central fixed electrode E 12 and the central displacement electrode E 22
- the distance between the electrodes in the right half of the figure is short.
- the capacitance value decreases and the capacitance value increases, and the capacitance value decreases in the left half because the distance between the electrodes increases.
- the increase in the capacitance value is larger than the decrease, so that the capacitance value of the entire central capacitance element C 2 is shown in FIG.
- the state shown in FIG. 5 is larger than the state.
- the central capacitive element C2 has a function of detecting "rolling" vibration, like the annular capacitive element C1.
- the detection sensitivity of the central capacitive element C2 is much smaller than the detection sensitivity of the annular capacitive element C1. This is because, as can be seen from FIG. 5, the distance between the electrodes of the annular capacitive element C 1 disposed in the outer region of the displacement substrate 20, when the displacement substrate 20 is inclined based on “rolling”. As compared with the variation ⁇ d of d, the variation ⁇ d of the distance d between the electrodes of the central capacitive element C 2 disposed in the inner region of the displacement substrate 20 becomes smaller, and the overall capacitance value becomes smaller. Small change It is because it becomes.
- the sensor output obtained as the variation of the capacitance value of the central capacitive element C 2 is a signal obtained by superimposing the signal indicating the magnitude of “pitch” on the signal indicating the magnitude of “pitch”.
- the latter is much smaller than the former, and in practice, there is no problem if this sensor output is treated as a signal indicating the magnitude of “pitch”.
- the pitch detection operation can be performed by the annular capacitance element C1.
- the displacement substrate 20 is displaced as shown in FIG.
- the displacement substrate 20 is displaced downward in the diagram in FIG. 9, so that the annular capacitive element C 1 is disposed between the electrodes.
- the capacitance value of the annular capacitance element C 1 indicates the magnitude of the “pitch,” and the annular capacitance element C 1 is, like the central capacitance element C 2, “ It has the function of detecting the vibration of "pitch.”
- the sensor output obtained as a change in the capacitance value of the annular capacitive element C1 is a signal obtained by superimposing a signal indicating the magnitude of “pitch” on a signal indicating the magnitude of “rolling”.
- a signal indicating the magnitude of “pitch” is a signal obtained by superimposing a signal indicating the magnitude of “pitch” on a signal indicating the magnitude of “rolling”.
- the change caused by the "pitch” The displacement of the substrate 20 is exactly the same for both the annular capacitive element C 1 and the central capacitive element C 2, and a sufficient signal indicating the magnitude of ⁇ pitch '' can be obtained in the central capacitive element C 2.
- a signal indicating the magnitude of the "pitch” can be sufficiently obtained also in the annular capacitance element C1. Therefore, the sensor output obtained as the variation of the capacitance value of the annular capacitance element C1 is obtained by superimposing the signal indicating the magnitude of “rolling” and the signal indicating the magnitude of “pitch”. And both are non-negligible signals. Therefore, in order to treat the sensor output obtained as the variation of the capacitance value of the annular capacitive element C1 as a signal indicating the magnitude of “rolling”, the signal component indicating the magnitude of “pitch” is required. Must be subtracted.
- the roll detection operation described in S2 can actually detect the magnitude of “roll” in an environment where “pitch” does not exist, but In an environment where "sway” exists, correct detection cannot be performed.
- the pitch detection operation described in ⁇ 3 can detect the magnitude of the pitch with sufficient accuracy in practice, even in an environment where a roll exists. . Therefore, when the acceleration sensor according to the present invention is used in an environment where both “pitch” and “roll” exist, it is necessary to correct the roll detection operation described in ⁇ 2. There is. An example of the correction method is shown below.
- the center capacitance element C 2 is obtained from the sum of the component indicating the amplitude of “rolling” and the component indicating the amplitude of “pitch” detected as the variation of the capacitance value of the annular capacitance element C 1. If the correction is performed by subtracting the component indicating the amplitude of the "pitch” detected as the variation of the capacitance value of the above, only the component indicating the amplitude of the "rolling" can be obtained.
- FIG. 10 is a circuit diagram showing an example of a detection circuit having a function of performing a correction operation based on such a basic concept.
- the variable capacitance elements C1 and C2 shown at the left end are equivalent circuits showing the annular capacitance element C1 and the central capacitance element C2, respectively.
- the CZV conversion circuit 61 and the CZV conversion circuit 62 are circuits that convert the capacitance values of the annular capacitance element C1 and the central capacitance element C2 into voltage values, respectively.
- the calibration is performed so that the output voltage of the CZV conversion circuits 61 and 62 becomes 0 volt when there is no "pitch" and "roll", that is, when the acceleration is zero.
- the output voltage VI of the C / V conversion circuit 61 indicates the variation of the capacitance value of the ring capacitance element C1
- the output voltage V2 of the CZV conversion circuit 62 indicates the output voltage V2 of the center capacitance element C2. Indicates the variation of the capacitance value.
- the output voltage VI is the sum of the component indicating the amplitude of “rolling” and the component indicating the amplitude of “pitch”, whereas the output voltage V 2 is, in practice, It can be treated as a component indicating the amplitude of “pitch”.
- the voltage V 2 output from the CZV conversion circuit 62 is supplied to the
- the signal is amplified by k times and supplied to the negative input terminal of the differential amplifier 64.
- k is given assuming that the area of the annular fixed electrode E 1 1 (or the annular displacement electrode E 21) is S 1 and the area of the central fixed electrode E 12 (or the central displacement electrode E 22) is S 2.
- V s V l— k * V 2
- the following operation is performed, and the voltage Vs is output to the output terminal T1.
- the voltage (k ⁇ V 2) output from the doubling circuit 63 is output to the output terminal T 2 as the output voltage Vp through the buffer circuit 65.
- the output signal k V 2 of the doubling circuit 63 is supplied to the input terminal of the buffer circuit 65, but the output signal V 2 of the CZV conversion circuit 62 is directly supplied to the input terminal of the buffer circuit 65. May be given.
- the voltage V p output to the output terminal T 2 in this manner indicates the magnitude of “pitch” detected by the acceleration sensor, and when used as a seismometer, the magnitude of the P wave It will be shown. This is because this voltage V becomes a voltage proportional to the variation of the capacitance value of the central capacitive element C2.
- the voltage Vs output to the output terminal T1 indicates the magnitude of the "rolling” detected by the acceleration sensor, and when used as a seismometer, the magnitude of the S wave is It will be shown. Because the voltage VI is the sum of a component indicating the magnitude of “rolling” and a component indicating the magnitude of “pitch” detected by the acceleration sensor, and the voltage (k
- V 2 Three V 2) is a component indicating the magnitude of “pitch” detected by the acceleration sensor, and the voltage V s obtained as the difference between the voltage V 1 and the voltage (k ⁇ V 2) is “rolling”. This is because a voltage corresponding to only the component indicating the magnitude of “” is obtained.
- the reason why the voltage V 2 is multiplied by the electrode area ratio k is to correct the detection sensitivity due to the difference in the area. That is, as shown in FIGS. 3 and 4, the electrodes E 11 and E 21 constituting the annular capacitance element C 1 and the electrodes E 1 2 and E 22 constituting the central capacitance element C 2 Then, the areas are different from each other (in the example shown, the former> the latter). Therefore, even when the magnitude of “pitch” is detected based on the principle shown in FIG. 9, the difference between the value detected by the annular capacitive element C1 and the value detected by the central capacitive element C2 is obtained. Causes a difference according to the area ratio k.
- a capacitance element having a larger electrode area can obtain a higher detection voltage. Therefore, the difference in detection sensitivity based on the difference in the electrode area is corrected by multiplying one of the detected values by the area ratio k by the multiplier circuit 63.
- a doubler circuit 63 is provided at the subsequent stage of the CZV converter circuit 62 to perform the process of multiplying the voltage V2 by k times. It is also possible to provide a doubling circuit 63 in the subsequent stage to perform the process of multiplying the voltage VI by (l Z k).
- the detection circuit shown in Fig. 10 performs a correction process to accurately detect the magnitude of “rolling” in an environment where “pitch” and “rolling” coexist.
- the doubling circuit 63 in the detection circuit shown in FIG. 10 is not always necessary. Instead, the delay multiplying circuit 63 can be omitted by devising the configuration of the electrode. That is, the capacitance value of the capacitive element is
- the doubling circuit 63 in the detection circuit shown in FIG. 10 can be omitted.
- ⁇ C ⁇ S (1 / d) ⁇ (1-(l -A d / d))
- the detection of “pitch” can be detected.
- the sensitivity can be made equal, and the doubling circuit 63 can be omitted.
- the embodiment whose side sectional view is shown in FIG. 11 is an example of an acceleration sensor having an electrode structure satisfying the above expression. That is, between the area S 1 of the electrodes E 11 and E 21 constituting the annular capacitance element C 1 and the area S 2 of the electrodes E 21 and E 22 constituting the central capacitance element C 2, Although there is a relationship of S 1> S 2, the distance d 1 between the electrodes E 11 and E 21 constituting the annular capacitive element C 1 and the respective electrodes E 21, E constituting the central capacitive element C 2 The relationship of d 1> d 2 is also established between the electrode distances d 2 and 22 of the 22 electrodes so that the detection sensitivity of the ⁇ pitch '' of both capacitor elements C 1 and C 2 is equal. So o
- annular displacement electrode E 23 and a center displacement electrode E 24 having the same area are formed on the upper surface of the displacement substrate 20, and a corresponding counter electrode is also formed on the lower surface of the fixed substrate 10.
- the annular capacitive element C1 and the central capacitive element C2 have the same electrode-to-electrode distance and electrode area, and the detection sensitivity for "pitch" becomes equal.
- the diameter of the center displacement electrode E 24 is too large, the component of “rolling” included in the variation of the capacitance value of the center capacitance element C 2 is too large. It should be noted that the information may not be ignored.
- an annular fixed electrode E 11 and a central fixed electrode E 12 which are physically independent from each other are formed on the lower surface of the fixed substrate 10.
- an annular displacement electrode E 21 and a central displacement electrode E 22 which are physically independent were formed on the upper surface of the displacement substrate 20. That is, a total of four physically independent electrode layers are formed. However, it is not always necessary to form four electrode layers in this way.
- variable capacitances C 1 and C 2 shown at the left end of the figure are the ones corresponding to the annular capacitance element C 1 and the central capacitance element C 2, respectively. Are grounded. Therefore, when detecting acceleration based on the principle described above, the fixed substrate Either the two electrodes E 11 and E 12 formed on the 10 side or the two electrodes E 21 and E 22 formed on the displacement substrate 20 side are physical It may be a single common electrode. In this case, if the common electrode side is grounded, the detection circuit shown in FIG. 10 can be configured.
- a disk-shaped common electrode having the same diameter as the outer diameter of the annular fixed electrode E 11 If one electrode is prepared, this one common electrode can perform the same function as the two electrodes E 11 and E 12.
- a disk-shaped common electrode having the same diameter as the outer diameter of the annular displacement electrode E 21 is used. If one electrode is prepared, this one common electrode can perform the same function as the two electrodes E 21 and E 22.
- the structure of the entire acceleration sensor can be further simplified.
- a part of the fixed substrate 10 or the displacement substrate 20 is connected to the common electrode. May be used.
- a substrate made of a conductive material such as a metal
- a part of the fixed substrate 10 facing the annular displacement electrode E 21 is formed.
- a part of the fixed substrate 10 facing the center displacement electrode E22 functions as the annular fixed electrode E11, and functions as the center fixed electrode E12.
- the annular displacement electrode E 21 and the center can be used. There is no need to form the partial displacement electrode E22. If one displacement substrate 20 made of such a conductive material is opposed to the fixed substrate 10 shown in FIG. 3, a part of the displacement substrate 2 It functions as the displacement electrode E 21. A part of the displacement substrate 20 facing the center fixed electrode E 12 functions as the center displacement electrode E 22. In fact, the embodiments described below in ⁇ 7 and ⁇ 8 are of this type.
- the operation and the modification of the acceleration sensor according to the basic embodiment described in ⁇ 1 have been described.
- the surrounding displacement of the substrate 2 0 consists of eight springs, however, such a structure for realizing a practical acceleration sensor suitable for mass production So it's not always optimal.
- a diaphragm is formed by forming a plurality of slits on a flexible substrate and the diaphragm is used as the displacement substrate 20 and the support means 30 will be described.
- a diaphragm 120 as shown in a plan view in FIG. 13 is prepared.
- the diaphragm 120 is formed by forming a large number of slits 122 on a disk-shaped flexible substrate 121 (a thin metal plate in this embodiment).
- This large number of slits can be divided into two groups.
- the slits belonging to the first group are arc-shaped slits 122 a and 122 b formed along a circumferential ring line surrounding the center point 0, and the second group includes slits.
- the slits belonging to them are straight slits 122c and 122d formed along the outward radiation from the center point 0.
- the slits 122a and 122b and the slits 122c and 122d belonging to the second group are connected to each other at or near their ends.
- the arc-shaped slits include the outer arc-shaped slits 122 a and the inner arc-shaped slits arranged along a double concentric circle surrounding the center point 0.
- the linear slit is composed of two slits 122c and 122d arranged in parallel.
- Such a diaphragm 120 fulfills both functions of the displacement substrate 20 and the support means 30 in the present invention. Since the diaphragm 120 is made of a conductive material (metal plate), the diaphragm 12 ⁇ also serves as the annular displacement electrode E 21 and the center displacement electrode E 22. It also has a function as a common electrode.
- the fixed substrate 110 is a disk-shaped substrate made of an insulative rigid body.
- a fixed electrode E111 and a central fixed electrode E112 are formed.
- FIG. 15 is a bottom view of the fixed substrate 110, in which the shapes of the annular fixed electrode E111 and the central fixed electrode E112 are clearly shown.
- the diaphragm 120 is arranged at a predetermined distance below the fixed substrate 110, and a weight body 140 is fixed to the lower surface thereof.
- the periphery of the fixed substrate 110 and the periphery of the diaphragm 120 are both fitted and supported inside the cylindrical sensor housing 150.
- the fixed substrate 110 and the diaphragm 120 are kept parallel, and an annular capacitive element C1 and a central capacitive element C2 are formed. That is, a portion of the diaphragm 120 facing the ring-shaped fixed electrode E 111 functions as a ring-shaped displacement electrode, and the two electrodes form a ring-shaped capacitive element C 1. Of 0, the portion facing the central fixed electrode E112 functions as a central displacement electrode, and these electrodes form the central capacitive element C2.
- the operation of the acceleration sensor is exactly the same as the operation of the sensor according to the basic embodiment described above.
- the diaphragm 120 is bent as shown in FIG. A change occurs in the capacitance value of the capacitive element C2, and “rolling” and “pitching” can be detected using this change. That is, in the diaphragm 120, the portion surrounded by the inner arc-shaped slit 122b is the function as the displacement substrate 20 in the acceleration sensor described in S1 and the annular displacement electrode E2. 1 and the center part, the function as the displacement electrode E 22, and the outer part thereof functions as the support means 30.
- the deformed state of the diaphragm 120 is drawn in a simplified manner, but it is actually located between the slit 122a and the slit 122b shown in FIG.
- the beam portion and the beam portion located between the slit 122c and the slit 122d take a considerably complicated deformation state.
- the detection operation of the acceleration sensor according to the present invention has a very simple structure.
- a displacement suitable for a vehicle can be achieved, and a sufficient displacement can be achieved by the action of a relatively small acceleration. Therefore, an inexpensive and highly sensitive acceleration sensor can be realized.
- the structure of the diaphragm 120 is completely rotationally symmetric with respect to the center point 0. Is preferred. However, they cannot be completely rotationally symmetric as long as they form a physical slit 122. Therefore, in this embodiment, when the flexible substrate 121 is rotated by 90 ° in a plane including its main surface, the slit turns almost coincide with the pattern before rotation. Each slit 122 is formed.
- the displacement state when “rolling” in the direction of 45 ° acts on the X axis is, strictly speaking, the displacement state when “rolling” in the X axis direction acts. It will be slightly different. However, in practice, since the arc-shaped slits 122a and 122b are formed, any direction of 360 ° around the center point 0 There is no hindrance assuming that almost uniform displacement can be obtained, and "rolling" in any direction can be detected with almost uniform sensitivity.
- the slit In order to secure such non-directionality in the direction of the “rolling” sensitivity, when the flexible substrate 121 is rotated by 0 ° in a plane including its main surface, the slit is not moved.
- a technique such as laser processing or etching, it is possible to form a slit having a width of about 100 ⁇ m. Can be further improved.
- FIG. 17 is a side sectional view showing still another embodiment of the practical embodiment of the present invention.
- This acceleration sensor includes a fixed substrate 210 made of glass, a displacement substrate 220 made of silicon, a pedestal 230 made of glass, a weight body 240 also made of glass, and a bottom plate made of silicon. And a substrate 250.
- the displacement substrate 222 is surrounded by a fixed part 221 provided around, a flexible part 222 provided inside the fixed part 222, and the flexible part 222. Acting part 2 2 3 and 3 parts are constituted.
- a groove 222 having a ring shape is dug in the lower surface of the displacement substrate 220, and the portion where the groove 222 is formed has a small thickness.
- the flexible portion 222 is a portion corresponding to a region where the groove 222 is formed, and has flexibility because of its small thickness.
- a large number of slits 225 are formed in the flexible portion 222.
- FIG. 18 is a top view of the displacement substrate 220, and a perspective view of the slit 222 is shown in FIG. -Is clearly shown.
- the pattern of the slit 225 shown in FIG. 18 has the same pattern as the pattern of the slit 122 shown in FIG. That is, a slit belonging to the first group formed along the annular line surrounding the center point 0 and a slit belonging to the second group formed along the radiation going outward from the center point 0.
- the slit belonging to the first group and the slit belonging to the second group are connected to each other at or near the end.
- each slit 220 is rotated so that the slit pattern substantially matches the pattern before rotation. 5 are formed.
- the flexible portion 222 is a portion having a reduced thickness due to the formation of the groove 224, and the holding force is also a portion where the slit 225 is formed as shown in FIG. Therefore, it has sufficient flexibility.
- the action portion 223 is a portion whose periphery is supported by the flexible portion 222, and is also a portion to which the force applied to the weight body 240 is transmitted. Therefore, when the acceleration acts on the weight body 240, the force generated due to the acceleration is transmitted to the acting portion 223, and the flexible portion 222 is elastically deformed.
- a shallow groove is dug in a region corresponding to the flexible portion 222 and the acting portion 222, and a slight gap is formed between the displacement substrate 222 and the lower surface of the fixed substrate 210. Space is formed.
- an annular fixed electrode E211 and a central fixed electrode E212 are formed, and a displacement opposed to these electrodes with a space therebetween.
- a part of the upper surface of the substrate 220 functions as an annular displacement electrode and a central displacement electrode, respectively, and the annular capacitive element C1 and the central capacitive element C2 are formed.
- the action section 223 and the flexible section 222 function as the displacement board 20 of the acceleration sensor described in ⁇ 1. 22 and the fixed portion 2 2 1 force This functions as the support means 30 of the acceleration sensor described in ⁇ 1.
- the weight body 240 of this acceleration sensor is surrounded by a pedestal 230, and the bottom plate 250 is disposed on the lower surface.
- excessive displacement of the weight body 240 is suppressed by contact with the inner surface of the pedestal 230 or the upper surface of the bottom plate substrate 250.
- the weight body 240 can be displaced excessively by the action of excessive acceleration, and as a result, excessive stress can be applied to the flexible portion 222, thereby preventing damage. .
- the embodiment shown in FIG. 17 is an acceleration sensor which is very suitable for mass production.
- Each substrate is made of glass or silicon, and the manufacturing process can be performed using existing semiconductor manufacturing technology and micromachining technology.
- the pedestal 230 and the weight body 240 can be originally formed by cutting a single substrate.
- the electrodes formed on the lower surface of the fixed substrate 210 can be formed by, for example, a process of evaporating a metal such as aluminum, and the bonding between the substrates must be performed using a technique such as anodic bonding. Is possible.
- the detection circuit as shown in FIG. 10 can be formed as a semiconductor circuit in the displacement substrate 220 or the bottom plate substrate 250 made of silicon, even the detection circuit is included in one chip. It is also possible to realize a built-in acceleration sensor. ⁇ 9. Stricter amendments
- a voltage Vs indicating "rolling” can be obtained at the output terminal T1 and a voltage VP indicating "pitch” can be obtained at the output terminal T2. become. Then, as described in ⁇ 5, if a specific electrode configuration is adopted, the doubler 63 can be omitted.
- the circuit shown in FIG. 10 is based on the premise that the voltage V 2 corresponding to the variation of the capacitance of the central capacitive element C 2 consists only of the component showing the amplitude of “pitch”. This is a detection circuit that holds.
- both the variation V 1 of the capacitance of the annular capacitance element C 1 and the variation V 2 of the capacitance of the central capacitance element C 2 have a component indicating the amplitude of “rolling”. It is the sum of the component indicating the amplitude of "pitch”. However, at the voltage V 2 that indicates the variation of the capacitance of the central capacitive element C 2, the component indicating the amplitude of “rolling” is much smaller than the component indicating the amplitude of “pitch”.
- the circuit shown in FIG. 19 may be used instead of the circuit shown in FIG.
- the variable capacitance elements C 1 and C 2 shown at the left end of the figure are similar to the circuit shown in FIG. 6 is an equivalent circuit showing C2.
- the CZV conversion circuits 61 and 62 are also circuits for converting each capacitance value to a voltage value.
- both the voltages VI and V2 are composed of the sum of the component indicating the amplitude of "rolling" and the component indicating the amplitude of "pitch".
- the purpose of this detection circuit is Performing some kind of calculation on VI and V2 to obtain voltages Vs and Vp, and outputting these to output terminals Tl and ⁇ 2.
- such calculation is performed by the quadruple circuits 71 to 74 and the differential amplifiers 75 and 76. Hereinafter, this calculation will be described.
- V l Ml l »V s + M 12Vp
- V 2 M21Vs + M22Vp
- M1, M12, M21, and M22 are predetermined proportional constants.
- V l Ml l »V s + M 12 Vp
- V 2 M22Vp
- V 1 M 1 1 Vs + (M 1 2 / M2 2)-V 2
- V ⁇ V 2 / M22
- V l M l l »V s + M 12 Vp
- V 2 M2 1 «V s + M2 2 ⁇ V p
- V 1 and V 2 are values obtained as measured values, and Mil, M 12, M 21, and M 22 are proportional constants having predetermined values. Therefore, there are only two unknowns, V s and V p. Therefore, solving these two simultaneous equations gives unknown solutions. In order to perform this by an operation using an analog circuit, specifically, the following may be performed. Now, if the above two simultaneous equations are expressed by determinants,
- K 11, K 12, K 21, and K 22 are elements of an inverse matrix with respect to a matrix having M 11, M 12, M 21, and M 22 as elements. Therefore, the inverse matrix is obtained by calculation, and the values of the elements K 11, K 12, K 21, and K 22 are obtained. Then, doubling circuits 71 to 74 having these values K11, K12, K21, and K22 as doubling constants are prepared, and as shown in Fig. 19, these doubling circuits 7 :! -74 and differential amplifiers 75 and 76,
- Vs K1 1V1-K12V2
- V p -K 21-V I + K 22V 2
- the analog operation circuit shown in FIG. For example, the voltage V s obtained at the output terminal T 1 indicates the exact amplitude value of “rolling”, and the voltage V p obtained at the output terminal T 2 indicates the exact amplitude value of “pitch”. become.
- both the ring capacitance element C1 and the center capacitance element C2 are provided.
- the ring capacitance element It is sufficient to form only the element C1.
- collisions between cars or between a car and a building usually produce only a "shock” shock component, and a "pitch” shock.
- the components are negligible. In such a use environment, there is no need to correct for the "pitch” component, so it is sufficient to form only the annular capacitive element C1.
- each electrode is completely rotationally symmetric with respect to the central axis W, but may not be completely rotationally symmetric in practical use.
- the ring electrode in order to make the “rolling” detection as omni-directional as possible, it is preferable to make the ring electrode as rotationally symmetrical as possible, so that the “rolling” detection value does not interfere with the “rolling” detection value as much as possible.
- the center electrode in order to achieve this, it is preferable that the center electrode be as rotationally symmetrical as possible.
- the detection sensitivity to “rolling” acceleration it is desirable to have directivity in the detection sensitivity to “rolling” acceleration.
- the impact acceleration received by the driver's seat generally tends to be larger in a side collision than in a frontal collision.
- the full scale of the impact acceleration due to a frontal collision is about 50 G
- the full scale of the impact acceleration due to a side collision is about 200 G. It is considered necessary.
- the shape of the pair of annular electrodes may be non-rotationally symmetric with respect to the center axis W.
- an annular fixed electrode E 11 is provided on a fixed substrate 10. Both the line and the outer contour are complete circles. In other words, it is completely rotationally symmetric about the central axis W.
- the annular displacement electrode E21 facing the annular fixed electrode E11 is also completely rotationally symmetric as shown in FIG.
- the outer contour is a perfect circle, but the inner contour is an ellipse with the major axis in the Y-axis direction.
- the detection sensitivity in the X-axis direction is higher than the detection sensitivity in the Y-axis direction. Therefore, if this acceleration sensor is mounted on a car with the X axis facing forward, as shown in Fig. 20, the full scale of the impact acceleration due to a side collision is greater than the full scale of the impact acceleration due to a frontal collision. Can be set to increase.
- FIG. 22 shows an embodiment in which another non-rotationally symmetric annular fixed electrode E 41 is formed on a fixed substrate 10.
- the inner contour line is a perfect circle, but the outer contour line is an ellipse having a major axis in the X-axis direction.
- the width is wider than the electrode width at the portion that intersects the Y axis. Therefore, if an annular displacement electrode (not shown) of the same shape is formed on the displacement substrate 20 so as to face the same, the directivity of the X-axis detection sensitivity is higher than that of the Y-axis detection sensitivity.
- An acceleration sensor having
- FIG. 23 is a view showing an embodiment in which another non-rotationally symmetric annular fixed electrode E 51 is formed on a fixed substrate 10.
- the annular fixed electrode E51 has an elliptic shape having a major axis in the X-axis direction, both inward and outward contours. For this reason, although the width of the electrode is slightly different in each part, there is no great difference. Regarding the distribution of the force and the formation position of the electrodes, there is a considerable difference between the portion intersecting the X axis and the portion intersecting the Y axis. That is, X The part that intersects with the axis is distributed far away from the center, while the part that intersects with the Y axis is distributed relatively close to the center.
- annular displacement electrode (not shown) having the same shape is formed on the displacement substrate 20 so as to face the displacement substrate 20, even if the same magnitude of acceleration acts.
- the change in the distance between the electrodes when acting in the X-axis direction is greater than the change in the distance between the electrodes when acting in the Y-axis direction.
- the detection sensitivity in the X-axis direction is greater than the detection sensitivity in the Y-axis direction. Get higher.
- FIG. 24 is a diagram showing an embodiment in which a rectangular annular fixed electrode E61 and a central fixed electrode E62 are formed on a fixed substrate 10.
- the annular fixed electrode E61 has a square inner contour, but the outer contour is a rectangle elongated in the X-axis direction, and the central fixed electrode E62 has a square shape.
- the electrode width at the portion crossing the X axis is wider than the electrode width at the portion crossing the Y axis, and the portion crossing the X axis is considerably separated from the center. While it is distributed at positions, the part that intersects with the Y axis is distributed relatively close to the center.
- an annular displacement electrode (not shown) having the same shape is formed on the displacement substrate 20 so as to face the same, the detection sensitivity in the X-axis direction is also higher than the detection sensitivity in the Y-axis direction.
- An acceleration sensor having directivity can be realized. As described above, according to the acceleration sensor according to the present invention, since the acceleration acting on the basis of the change in the capacitance value of the annular capacitance element is detected, the acceleration in the direction included in the predetermined plane is detected. The magnitude can be detected efficiently as an electric signal. Industrial availability
- the acceleration sensor according to the present invention since the acceleration acting on the basis of the change in the capacitance value of the annular capacitance element is detected, the magnitude of the acceleration in a direction included in a predetermined plane is detected. Can be efficiently detected as an electric signal. Further, since the acceleration acting on the basis of the change in the capacitance value of the central capacitance element is detected, the magnitude of the acceleration directed in a direction perpendicular to the one plane may be detected as an electric signal. it can. As described above, the acceleration sensor according to the present invention can separately detect acceleration in a direction included in a predetermined plane and acceleration in a direction perpendicular to the plane. It is very useful if it is used for earthquake vibration detection and car collision detection.
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- Micromachines (AREA)
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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EP96919985A EP0773444A4 (en) | 1995-05-31 | 1996-05-29 | ACCELERATION GAUGE |
US08/776,172 US5856620A (en) | 1995-05-31 | 1996-05-29 | Acceleration sensor |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
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JP15710595 | 1995-05-31 | ||
JP7/157105 | 1995-05-31 | ||
JP8044120A JPH0949856A (ja) | 1995-05-31 | 1996-02-06 | 加速度センサ |
JP8/44120 | 1996-02-06 |
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WO1996038732A1 true WO1996038732A1 (fr) | 1996-12-05 |
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PCT/JP1996/001439 WO1996038732A1 (fr) | 1995-05-31 | 1996-05-29 | Detecteur d'acceleration |
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US (1) | US5856620A (ja) |
EP (1) | EP0773444A4 (ja) |
JP (1) | JPH0949856A (ja) |
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CN112781715A (zh) * | 2020-12-25 | 2021-05-11 | 深圳供电局有限公司 | 电缆振动监测装置和系统 |
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US5295386A (en) | 1989-12-28 | 1994-03-22 | Kazuhiro Okada | Apparatus for detecting acceleration and method for testing this apparatus |
US6864677B1 (en) * | 1993-12-15 | 2005-03-08 | Kazuhiro Okada | Method of testing a sensor |
US5421213A (en) * | 1990-10-12 | 1995-06-06 | Okada; Kazuhiro | Multi-dimensional force detector |
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- 1996-05-29 WO PCT/JP1996/001439 patent/WO1996038732A1/ja not_active Application Discontinuation
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CN112781715B (zh) * | 2020-12-25 | 2023-12-08 | 深圳供电局有限公司 | 电缆振动监测装置和系统 |
Also Published As
Publication number | Publication date |
---|---|
EP0773444A4 (en) | 1998-09-09 |
EP0773444A1 (en) | 1997-05-14 |
US5856620A (en) | 1999-01-05 |
JPH0949856A (ja) | 1997-02-18 |
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