JPH10177032A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic acceleration sensor that is suited for a seismometer operating at a low power consumption. SOLUTION: A piezoelectric element, which is deflected by the action of acceleration is prepared, electrodes A1-A9 are arranged on the upper surface, and a common electrode B is arranged on a lower surface. Normally, a switch 181 maintains an open state and a group of main detection elements 160 are in dormant state. Power is constantly supplied to a sub detection element 170 and an electric charge generated by the electrode A9 for monitoring is given to a terminal Tm via an amplifier 171. When the signal of the terminal Tm exceeds a threshold due to the initial vibration of an earthquake, the switch 181 is closed by a control signal and power is supplied to a group of main detection elements 160. An electric charge is generated due to the operation of each acceleration constituent in the directions of X, Y, and Z axes is given to terminals Tx, Ty, and Tx via amplifiers 161-163 and is detected by a computer 180.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor, and more particularly to a low power consumption type multidimensional acceleration sensor suitable for use in detecting vibration of an earthquake.

[0002]

2. Description of the Related Art It is indispensable to incorporate countermeasures in the event of a disaster into infrastructure equipment that is used very daily in urban life. In particular, countermeasures against earthquakes are the most important issue. For example, when an elevator operation control device detects an earthquake vibration, it is necessary to stop the car on the nearest floor and stop the operation. In addition, a gas meter with a built-in microcomputer is installed in the city gas supply system. When an earthquake vibration is detected, a function to close the gas supply valve and automatically stop gas supply has been added. ing.

Conventionally, a mechanical acceleration sensor has been used as a sensor for detecting such earthquake vibration. For example, a general seismometer built in a gas meter is a so-called "ball type seismic sensor",
A ball is accommodated in the bottom of a hemispherical cup in a freely rolling state, and a mechanical switch is provided at an edge portion of the cup. When the ball moves down the inner wall of the cup from the bottom to the rim due to the shaking of the earthquake and comes into contact with the mechanical switch,
It is designed to provide an electrical detection signal.

Although the "ball type seismic sensor" has a simple structure, it can only obtain a signal indicating the ON / OFF state of the mechanical switch, so that the amount of information indicating the detection result is scarce. I can't get it. Ordinarily, an earthquake includes a “rolling component (horizontal vibration component)” and a “pitch component (vertical vibration component)”, and the former includes a vibration wave called an S wave. Is the component of the shaking caused by the
It is a swaying component caused by an oscillating wave called a wave.
Generally, in order to predict damage caused by an earthquake, it is desirable to detect both the “rolling component” and the “pitch component” separately and independently. However, the conventionally used "ball-type seismic sensor" can detect only "rolling component" because of its structure. (Even if "pitching" occurs, the whole sensor vibrates up and down Therefore, the ball does not roll up to the edge of the cup, and the mechanical switch cannot be operated). Further, the "ball type seismic sensor" has another problem that it is difficult to reduce the size because it includes mechanical components.

In recent years, various types of electronic acceleration sensors have been proposed in place of such mechanical acceleration sensors. In particular, recently, two-dimensional or three-dimensional acceleration has been independently provided for each direction component. A multidimensional acceleration sensor capable of detecting and outputting as an electric signal has attracted attention. For example, International Publication No. W based on the Patent Cooperation Treaty
O88 / 08522 discloses a three-dimensional acceleration sensor using a piezoresistive element. With this sensor,
By forming a plurality of piezoresistive elements at specific positions on the semiconductor substrate, acceleration components in each coordinate axis direction in the XYZ three-dimensional coordinate system can be independently detected. In addition, International Publication Nos. WO91 / 10118 and WO92 / 17759 disclose a three-dimensional acceleration sensor using a capacitance element, and International Publication WO93 / 02342 discloses a piezoelectric acceleration sensor. A three-dimensional acceleration sensor using an element is disclosed. In these sensors, by forming a plurality of electrodes at specific positions, it is also possible to independently detect acceleration components in each coordinate axis direction in the XYZ three-dimensional coordinate system.

If the above-mentioned electronic multi-dimensional acceleration sensor is used as a seismometer, it is possible to detect both the "rolling component" and the "pitch component" separately. Moreover, since the detection result is output as an electric signal indicating the magnitude of each direction component, it is very suitable for controlling the operation of the elevator and controlling the gas supply using a microcomputer or the like. Further, the electronic acceleration sensor can be mass-produced by diverting the integration technology used in semiconductor circuits and the like, and is suitable for miniaturization and mass production.

[0007]

As described above, an electronic acceleration sensor can obtain a multidimensional detection value as an electric signal and is more suitable for miniaturization and mass production than a mechanical acceleration sensor. However, there is a problem in terms of power consumption. In the case of a mechanical acceleration sensor,
It is possible to adopt a structure in which power is consumed only when vibration occurs, and it is not necessary to constantly supply power. For example, the "ball-type seismic sensor" currently built into many gas meters is based on a machine mounted on the edge of the cup, where the ball is stationary at the bottom of the cup in normal times without an earthquake. The expression switch maintains the OFF state. In this state, in principle, no power consumption occurs. In other words, the vibration of the earthquake causes the ball to roll up to the edge of the cup and consume power only when the mechanical switch is turned on.

On the other hand, since the above-mentioned electronic acceleration sensor is a mechanism that normally operates as a sensor only after receiving power supply, it functions as a sensor unless power is constantly supplied. do not do. of course,
When used by attaching to general machine tools, etc.,
There is no problem even if the acceleration sensor is assumed to always supply power. However, in the case of a seismometer, it is necessary to detect the occurrence of vibration for an extremely long period of time while being installed in a vibration-free environment in normal times. For this reason, in order to use an electronic acceleration sensor that always requires power supply for a seismometer, it is essential to thoroughly reduce power consumption.

For example, according to Japanese standards, gas meters are to be replaced every 10 years.
Accelerometers used as seismometers for gas meters include:
A performance that will continue to operate without battery replacement for at least 10 years is required.

Accordingly, an object of the present invention is to provide an electronic acceleration sensor operable with low power consumption.

[0011]

[Means for Solving the Problems]

(1) The first aspect of the present invention provides a plurality of main detection elements for detecting an acceleration component in a predetermined detection axis direction, main power supply means for supplying power to these main detection elements, and individual main power supply means. Supporting means for supporting the detection elements so that the respective detection axis directions are different from each other, and supplying power from the main power supply means to each of the main detection elements, thereby providing a plurality of detection axes. In an acceleration sensor having a function of outputting acceleration components in the respective directions as independent electric signals, a sub-detection element supported by a support means so as to be able to detect a predetermined acceleration component in a detection axis direction for monitoring, A sub-power supply means for supplying power to the sub-detection element and a sensor operation for the sub-power supply means such that the acceleration component detected by the detection element is output as an electric signal. At least during a period during which the main power supply unit is not supplying power during the operation, control is performed so that power is supplied. And control means for controlling power supply only when the value is equal to or higher than the value level.

(2) The second aspect of the present invention is the above-mentioned first aspect.
In the acceleration sensor according to the aspect, a plurality of sets of sub-detecting elements are supported by supporting means such that the sub-detecting elements are arranged so that the directions of the monitoring detection axes are different from each other.

(3) The third aspect of the present invention is the above-described first aspect.
Alternatively, in the acceleration sensor according to the second aspect, a part of the plurality of main detection elements is also used as a sub-detection element, and a part of the main power supply is also used as a sub-power supply. .

(4) The fourth aspect of the present invention is the above-mentioned first aspect.
In the acceleration sensor according to the third to third aspects, the power supply by the sub power supply means is performed intermittently by using a pulse signal having a predetermined sampling cycle.

(5) The fifth aspect of the present invention is the above-mentioned first aspect.
In the acceleration sensor according to any one of the fourth to fourth aspects, one of the central portion and the peripheral portion is fixed to the sensor housing, and the supporting means is formed by a flexible substrate having a weight body formed on the other. When the origin O is defined at the center of the flexible substrate and the XYZ three-dimensional coordinate system is defined such that the main surface of the substrate is included in the XY plane, the stress or displacement of the positive portion of the X-axis of the substrate is obtained. , A second detector for detecting the stress or displacement of the negative portion of the X-axis of the substrate, and a third detector for detecting the stress or displacement of the positive portion of the Y-axis of the substrate. A first detector and a second detector for detecting a stress or a displacement of a negative portion of the substrate on the Y-axis;
And a third detector and a fourth detector constitute a main detection element having a Y-axis direction as a detection axis direction. Further, an auxiliary detector for detecting stress or displacement of an arbitrary part of the substrate is provided, and the auxiliary detector constitutes a sub-detection element.

(6) The sixth aspect of the present invention is directed to the above-mentioned fifth aspect.
In the acceleration sensor according to the aspect, a detector for detecting a stress or a displacement generated on the flexible substrate when a force in the Z-axis direction is applied to the weight body is further provided.
This constitutes a main detection element whose detection direction is the axial direction.

(7) The seventh aspect of the present invention is the above-mentioned first aspect.
In the acceleration sensor according to the sixth to sixth aspects, an electrode for detecting a charge generated in a predetermined portion of the piezoelectric element using a substrate of the piezoelectric element configured to apply a stress by the action of acceleration as a support means, Each detection element is constituted by an electronic circuit that outputs the amount of charge detected by the electrode as an electric signal.

(8) The eighth aspect of the present invention is the above-mentioned first aspect.
In the acceleration sensor according to the sixth to sixth aspects, a piezoresistive element formed at a predetermined position on the single crystal substrate using a single crystal substrate configured to apply stress by the action of acceleration as a support means, An electronic circuit for outputting a change in the resistance value of the piezoresistive element as an electric signal constitutes each detecting element.

(9) The ninth aspect of the present invention is the above-mentioned first aspect.
In the acceleration sensor according to any one of the first to sixth aspects, a flexible substrate configured to bend by an action of acceleration;
A fixed substrate arranged at a position facing the flexible substrate constitutes a support means, and a displacement electrode arranged at a predetermined position on the flexible substrate and a displacement electrode arranged at a predetermined position on the fixed substrate. Each detection element is constituted by a fixed electrode and a capacitance element, and the capacitance element and an electronic circuit for outputting a change in the capacitance value of the capacitance element as an electric signal.

(10) According to a tenth aspect of the present invention, in the acceleration sensor according to the seventh aspect described above, ON / OFF is performed based on electric charges generated in a piezoelectric element constituting a sub-detecting element.
An operating transistor is provided, and a current flowing through the transistor is extracted as an electric signal from a sub-detection element.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. FIG. 1 is a block diagram showing a basic configuration of a conventional general electronic three-dimensional acceleration sensor. This acceleration sensor has an acceleration component αx in the X-axis direction and an acceleration component α in the Y-axis direction in the XYZ three-dimensional coordinate system.
It has a function of detecting acceleration components αz in the y- and Z-axis directions separately and independently, and outputting these as electric signals. Here, the X-axis direction main detection element 11 has a function of detecting an acceleration component αx in the X-axis direction, and the Y-axis direction main detection element 12 has a function of detecting an acceleration component αy in the Y-axis direction. , The Z-axis direction main detecting element 13 has a function of detecting the acceleration component αz in the Z-axis direction. Further, the main power supply means 20 has a function of supplying power for operating these main detection elements 11 to 13. Each of the main detection elements 11 to 13 is a detection element that operates by receiving the power supply, and stops operating when the power supply is stopped. On the other hand, the support means 30 includes the main detection elements 11 to
13 is a means for supporting and fixing the respective members 13 in a specific direction. As described above, each of the main detection units 11 to 13
Have a function of detecting an acceleration component in each coordinate axis direction in the XYZ three-dimensional coordinate system, and each performs a detection process having a specific direction. The support means 30 is provided so that the detection axis directions of the individual main detection means 11 to 13 are different from each other (in this embodiment, the detection axis directions are orthogonal to each other).
To 13 are arranged in a predetermined direction and serve to support and fix.

The acceleration sensor having the configuration as shown in FIG. 1 operates because each coordinate axis direction component in the XYZ three-dimensional coordinate system of the applied acceleration can be detected as an independent electric signal. The direction and magnitude of the acceleration in the three-dimensional space can be specified. Therefore, if this acceleration sensor is used as a seismograph, not only can the "rolling component" and "pitch component" be recognized independently, but also the direction of the rocking can be specified to an accurate angle. .

However, in order to operate the acceleration sensor, the main power supply means 20 supplies the main detection means 11 to
Since it is assumed that power is supplied to the power supply 13, it is necessary to always supply power from the main power supply means 20 in order to function as a seismometer. So, for example,
When used for an application that requires operation without battery replacement for 10 years, it is necessary to cover power consumption for 10 years with the built-in battery, and a device for reducing power consumption is indispensable.

FIG. 2 is a block diagram showing a basic configuration of an electronic three-dimensional acceleration sensor according to the present invention. This acceleration sensor has a function of outputting acceleration components αx, αy, and αz in the respective axial directions in the XYZ three-dimensional coordinate system as independent electric signals, similarly to the conventional acceleration sensor shown in FIG. Here, each of the main detection elements 11 to 1
3. The main power supply means 20 and the support means 30 are the same components as the conventional acceleration sensor shown in FIG. The characteristics of this acceleration sensor are different from those of the conventional electronic acceleration sensor in that a sub-detecting element 40, a sub-power supply unit 50, a control unit 6
The point is that 0 is added.

The sub-detecting element 40 is an element supported by the supporting means 30 so as to detect a preset acceleration component in the direction of the monitoring detection axis. Here, the monitor detection axis is an axis indicating a direction in which acceleration (vibration) is to be monitored, and the monitor detection axis may be set in a direction that seems to be most effective according to the application. of course,
This monitoring detection axis may be set in the same direction (specifically, the X axis, the Y axis, and the Z axis) as the detection axis of the main detection element. In practice, each of the main detection elements 11 to 13 and the sub-detection element 40 are constituted by the same kind of detection elements having the same physical structure and using the same principle, which simplifies the entire structure and reduces the manufacturing cost. It is preferable in reducing the amount.

The sub-power supply means 50 is a means for supplying power to the sub-detection element 40, and has an essential function of supplying power.
Is exactly the same as The sub-detecting element 40 receives the power supply from the sub-power supply means 50 and outputs an acceleration component in the monitoring detection axis direction, that is, a monitor acceleration component αm as an electric signal.

The control means 60 has a function of giving a power supply instruction to the main power supply means 20 and the sub power supply means 50. First, for the sub power supply means 50,
During the operation of the sensor, an instruction to supply power is always given. That is, the power switch of this acceleration sensor is set to O
When N is set, the control unit 60 gives an instruction to always supply power to the sub-power supply unit 50, and the sub-detection element 40 receives this power supply and always performs the detection operation. On the other hand, the main power supply means 20 is instructed to supply power only when the value of the monitor acceleration component αm output as an electric signal from the sub detection element 40 is equal to or higher than a predetermined threshold level. Is given. In other words, if the value of the monitor acceleration component αm does not reach the threshold level, an instruction to stop power supply is given to the main power supply means 20, and power supply to each of the main detection elements 11 to 13 is performed. Will not be performed.

After all, when the acceleration sensor of the present invention shown in FIG. 2 is used as a seismometer, by turning on the power switch, first, power is supplied from the sub power supply means 50 to the sub detection element 40. The main power supply means 2
From 0, the power supply to the main detection elements 11 to 13 is stopped. In other words, the main detection elements 11 to 13 do not operate, and only the sub-detection element 40 operates.
The sub-detecting element 40 detects the acceleration component αm in the direction of the predetermined detection axis for monitoring and outputs it as an electric signal. Since the value is equal to or smaller than the threshold value, the control means 60 still gives an instruction to supply power only to the sub power supply means 50. Thus, in the normal operation mode of the acceleration sensor, the state where only the sub-detection element 40 is functioning continues.

However, when an earthquake actually occurs, the monitor acceleration component αm output from the sub-detecting element 40 exceeds a predetermined threshold, and an initial vibration of the earthquake is detected. Then, the control means 60 gives an instruction to the main power supply means 20 to start power supply. as a result,
Power is supplied from the main power supply unit 20 to each of the main detection elements 11 to 13, and each of the main detection elements 11 to 13 starts an original detection operation. As a result, the axial components αx, αy, αz of the acceleration are detected independently and output as electric signals. Eventually, when the vibration of the earthquake stops and the monitor acceleration component αm output from the sub-detecting element 40 falls below the predetermined threshold, the control unit 60 instructs the main power supply unit 20 to stop the power supply. Is given. As a result, the power supply from the main power supply means 20 to each of the main detection elements 11 to 13 stops, and the operation of each of the main detection elements 11 to 13 stops.

As described above, in the acceleration sensor according to the present invention, each of the main detection elements 11 to 13 is normally in a dormant state, and only during the period from when the initial vibration of the earthquake is detected to when the earthquake stops. Will work. Therefore, the power consumed in normal times is only the power required for the operation of the sub-detecting element 40, and the power consumption is reduced as compared with the conventional acceleration sensor shown in FIG. Specifically, even if an element requiring the same power consumption as each of the main detection elements 11 to 13 is used as the sub detection element 40, the power consumption of the acceleration sensor shown in FIG. Is reduced to 1/3 of the normal power consumption of the acceleration sensor shown in FIG.

The threshold value for the monitor acceleration component αm may be set appropriately according to the application. If high-sensitivity measurement that can detect even minute vibrations is required, the threshold value should be set low.On the other hand, high-sensitivity measurement is unnecessary but power consumption must be reduced as much as possible. In some cases, the threshold may be set higher.

The direction of the monitor detection axis to be detected by the sub-detection element 40 may be set appropriately according to the application. When a flexible substrate is used as a support means as in an embodiment described later, and a detection element is configured by a detector that detects stress or displacement of each part of the flexible substrate,
One detector can detect accelerations on a plurality of detection axes. Therefore, it is convenient to use it for a seismometer or the like that needs to detect both the “pitch component” and the “roll component”. For example, in the XYZ three-dimensional coordinate system shown in FIG. 3, the detection axis directions of the main detection elements 11 to 13 are Dx, Dy, and Dz (that is, the X-axis direction, the Y-axis direction, and the Z-axis direction). Try. In this case, two monitor detection axes Dm11 and Dm as shown in FIG.
If a detection element capable of detecting both accelerations related to the acceleration signal 12 is used as a sub-detection element, the sub-detection element causes a “rolling component (a component in the direction of the detection axis Dm11 for monitoring)” and a “pitch component (monitoring for the monitor). Detection axis Dm12
In the direction of the direction)).

However, in this case, it is not possible to detect a "rolling component" in a direction orthogonal to both of the two monitor detection axes Dm11 and Dm12. If it is necessary to detect the swing in any direction in the three-dimensional space by using the sub-detection elements, two sets of sub-detection elements may be provided. For example, a first sub-detecting element 41 and a second sub-detecting element 42 are prepared, and as shown in FIG. 3, the first sub-detecting element 41 causes acceleration components with respect to two monitoring detection axes Dm11 and Dm12. Can be detected, and the two sub-detection elements can be arranged so that the second sub-detection element 42 can detect the acceleration components for the two monitoring detection axes Dm21 and Dm22. The directions of the detection axes for monitoring need only be such that at least three detection axes are not parallel to each other. However, in order to perform the most efficient detection, it is preferable to set the relation such that the three detection axes are orthogonal to each other. In the example shown in FIG. 3, three detection axes Dm
11, Dm12 and Dm21 are orthogonal to each other, and if such two sets of sub-detecting elements 41 and 42 are used, three directions orthogonal to each other (detection axes Dm11 and Dm shown in FIG. 3).
12, Dm21) can be monitored.

FIG. 4 shows the two sets of sub-detecting elements 41,
It is a block diagram which shows the basic structure of the acceleration sensor using 42. The difference from the acceleration sensor shown in FIG. 2 is that two sets of sub-detecting elements 41 and 42 are used instead of the sub-detecting element 40. The monitor acceleration component αm1 (the monitor detection axis Dm11 shown in FIG.
Or an acceleration direction component along Dm12) is output,
From the second sub-detecting element 42, the monitor acceleration component αm
2 (monitoring detection axis Dm21 or Dm2 shown in FIG. 3)
2) are output. Control means 6
0 gives an instruction to the main power supply means 20 to start power supply when one of the monitor acceleration components αm1 and αm2 becomes equal to or greater than a predetermined threshold value. Note that different threshold values may be set for the monitor acceleration components αm1 and αm2.

In practicing the present invention, it is also possible to use a part of the plurality of main detection elements as a sub-detection element and also use a part of the main power supply means as a sub-power supply means. FIG. 5 is a block diagram showing a basic configuration of an embodiment in which such dual use is performed. In this example, of the three main detection elements, a part of the X-axis
, And a part of the Y-axis direction main detecting element 12 is also used as a second sub-detecting element. Further, a part of the main power supply unit 25 is also used as the sub power supply unit 55.

In normal times, the control means 60 controls the sub-power supply means 55 which is a part of the main power supply
The power supply to the first sub-detection element forming part of the X-axis direction main detection element 11 and the power supply to the second sub-detection element forming part of the Y-axis direction main detection element 12 To instruct.
In this operation mode, the X-axis direction main detection element 11 and Y
The axial main detecting element 12 operates only in a part thereof, and power is not supplied to the Z-axis main detecting element 13, so that power consumption is smaller than in the original operation. . That is, the X-axis direction main detection element 11
Originally, it has a function of detecting an accurate value of the acceleration component αx in the X-axis direction, and the Y-axis direction main detection element 12 originally has a function of detecting an accurate value of the acceleration component αy in the Y-axis direction. In this normal operation mode, it is not necessary to detect such an accurate value, and it is sufficient to operate only a part of the value. Thus, in this normal operation mode,
The monitor acceleration component αm1 is output from the first sub-detection element (part of the X-axis main detection element 11), and the monitor acceleration component αm1 is output from the second sub-detection element (part of the Y-axis main detection element 12). The component αm2 will be output.

When any of the monitor acceleration components αm1 and αm2 exceeds a predetermined threshold value (either the same threshold value or different threshold values), The main power supply means 25 is instructed to supply power. As a result, power is supplied to each of the main detection elements 11 to 13 for performing an original operation, and accurate detection values αx, αy, and αz of each axial component of the acting acceleration are output. become. At this time, the monitor acceleration components αm1 and αm2 are also continuously output. When both of these values are less than the predetermined threshold, the control unit 60 instructs the main power supply unit 25 to stop the power supply. Is issued. Thereafter, only the power supply from the sub power supply means 55 is continued, and the operation mode returns to the normal operation mode.

As described above, when the main power supply means and the sub power supply means are partially used, and the main detection element and the sub detection element are partially used, the overall structure is further simplified. A specific embodiment in which such dual use is performed will be described later.

The power supply from the sub power supply means may be temporarily stopped when the power supply from the main power supply means starts. In this case, the main detection element is temporarily used as a sub-detection element, and when the signal output from the main detection element falls below a predetermined threshold, the power supply of the main power supply means is stopped, and The power supply from can be resumed.

Subsequently, an additional approach for further reducing the power consumption in normal times will be described. In this method, the main frequency component of the acceleration to be detected is
This is effective when only components below a certain frequency are included, and is very effective especially for acceleration detection based on an earthquake. In general, it is known that the maximum value of a main frequency component having a certain magnitude of amplitude among frequency components constituting an earthquake tremor is at most about 10 Hz. Therefore, in the acceleration sensor according to the present invention, when monitoring the shaking of the earthquake in the normal operation mode, it is not necessary to continuously monitor the shaking. For example, a sampling frequency of about 50 Hz may be determined with a sufficient margin for the above-mentioned maximum frequency of the earthquake shaking of 10 Hz, and monitoring may be performed periodically at this sampling frequency. In other words, when the acceleration sensor according to the present invention is used as a seismometer, it is sufficient that the sub-detection element performs the normal detection operation at a sampling frequency of 50 Hz, that is, a cycle of 20 ms.

After all, when measuring not only seismometers but also acceleration components that include only components below a certain frequency,
From the sub power supply means 50, 55, the sub detection elements 40, 41,
As shown in FIG. 6, it is sufficient for the power supply to the power supply 42 to be performed intermittently by using a pulse signal that alternately repeats a power supply state and a non-power supply state. In particular, when used as a seismograph, it is sufficient to set the cycle L of the pulse signal to about 20 ms (sampling frequency 50 Hz). Further, the pulse width W of the pulse signal may be any time that can secure a sufficient time for detecting acceleration at an instant. For example, in various embodiments described later, if the rise time of the circuit is about 1 ms, It is sufficient to set the width W to about 2 ms. If the pulse signal period L is 20 m
If s and the pulse width W are set to 2 ms, the power supply time can be reduced to 1/10 of the whole, and the power consumption can be suppressed to almost 1/10. Therefore, in the above-described acceleration sensor according to the present invention, if the power supply by the sub-power supply unit is performed intermittently using the pulse signal having the predetermined sampling cycle, the power consumption can be reduced as compared with the conventional acceleration sensor. The power can be significantly reduced.

[0042]

[Example] §1. Basic Embodiment Using Piezoelectric Element Here, a basic embodiment using a piezoelectric element as each detecting element will be described. That is, in this embodiment, a flexible substrate made of a piezoelectric element configured to apply stress by the action of acceleration is used as a support means, and an electrode for detecting electric charges generated in a predetermined portion of the piezoelectric element, Each detection element is constituted by an electronic circuit that outputs the amount of charge detected by the electrode as an electric signal.

Hereinafter, the basic structure of an embodiment of an acceleration sensor using a piezoelectric element will be described with reference to the drawings. FIG.
FIG. 8 is a perspective view of the main body of the acceleration sensor according to this embodiment as viewed obliquely from above, and FIG. 8 is a perspective view of the main body of the acceleration sensor viewed from obliquely below. This acceleration sensor main body has nine upper electrodes A1 to A9 formed on the upper surface of a disc-shaped piezoelectric element 110 and one lower electrode B formed on the lower surface. Here, for convenience of explanation, the origin O of the XYZ three-dimensional coordinate system is defined at the center position of the upper surface of the disk-shaped piezoelectric element 110, and the X axis and the Y axis are defined in directions along the upper surface of the piezoelectric element 110. , Z-axis is defined as a direction going upward and perpendicular to the upper surface. Therefore,
The upper surface of the piezoelectric element 110 is included in the XY plane. It should be noted that, here, 45
The W1 axis and W2 axis forming an angle of ° are defined as shown in FIG.

A structural feature of the piezoelectric element 110 is that an annular groove 115 is formed on the lower surface as shown in FIG. In this embodiment, the annular groove 115 has the origin O
It has a circular shape that surrounds. The lower electrode B is a single electrode layer, and is formed on the entire lower surface of the piezoelectric element 110 including the inside of the annular groove 115. On the other hand, the nine upper electrodes A1 to A9 all have a band shape along an arc centered on the origin O, as clearly shown in the top view of FIG. Alternatively, the shape and the arrangement are line-symmetric with respect to the W2 axis.

The structure of the acceleration sensor body is shown in FIG.
See more clearly. FIG. 10 is a side sectional view of the acceleration sensor main body cut along the XZ plane. The portion of the piezoelectric element 110 where the annular groove 115 is formed is thinner than other portions and has flexibility.
Here, a portion of the piezoelectric element 110 located above the annular groove 115 is referred to as a flexible portion 112, and the flexible portion 112
The central portion surrounded by is referred to as a central portion 111, and the portion located on the outer periphery of the flexible portion 112 is referred to as a peripheral portion 113. The relative position of these three parts is
This is clearly shown in the bottom view of FIG. That is, the flexible portion 112 is formed in a portion around the central portion 111 where the annular groove 115 is formed, and the peripheral portion 113 is formed around the flexible portion 112.

Here, for example, when only the central portion 111 is fixed to the sensor housing and the entire sensor housing is shaken, the peripheral portion 1
13 functions as a weight body, and a force based on acceleration acts on this weight body, and this force causes the flexible portion 11 to function.
2 will bend. Conversely, when only the peripheral portion 113 is fixed to the sensor housing and the entire sensor housing is shaken, the central portion 111 functions as a weight body. That is, a force based on the acceleration acts on the central portion 111, and this force also causes the flexible portion 112 to bend. After all, since the central portion 111 and the peripheral portion 113 are joined by the flexible portion 112 having flexibility, when acceleration is applied to one of them, a stress is generated in the flexible portion 112 and the bending is reduced. Will happen. The generation mode of the stress is as follows.
It depends on the direction and magnitude of the applied acceleration. The acceleration sensor detects the distribution of the stress to detect the direction and magnitude of the applied acceleration.

In order to detect the stress generated in the flexible portion 112, nine upper electrodes A1 to A9 are arranged above the flexible portion 112. The arrangement of the upper electrodes A1 to A9 is clearly shown in the top view of FIG. 9, but as can be seen from the side sectional view of FIG.
Both are arranged above the flexible part 112. This is for extracting electric charges generated in each part of the piezoelectric element due to the bending of the flexible part 112.

In general, a piezoelectric element causes a polarization phenomenon by the action of mechanical stress. That is, when a stress is applied in a specific direction, one side generates a positive charge and the other side generates a negative charge. In the acceleration sensor main body of this embodiment, a piezoelectric ceramic having polarization characteristics as shown in FIG. That is, as shown in FIG. 12A, when a force extending in the direction extending along the XY plane acts, a positive charge is generated on the upper electrode A side, and a negative charge is generated on the lower electrode B side. Conversely, as shown in FIG. 12B, when a force in the direction of contraction along the XY plane acts, a negative charge is applied to the upper electrode A and a positive charge is applied to the lower electrode B. , Have polarization characteristics as they occur. Here, such a polarization characteristic is referred to as a type. In the acceleration sensor of the embodiment described here, the piezoelectric element 110 has this type of polarization characteristic in any part.

Next, the operation principle of the above-described acceleration sensor will be described. This acceleration sensor is a three-dimensional acceleration sensor capable of detecting an applied acceleration for each axial component in an XYZ three-dimensional coordinate system whose origin is the center position of the upper surface of the piezoelectric element 110. In order to function as such a three-dimensional sensor, nine upper electrodes A1 to A9 having a specific arrangement are prepared. As will be described later, of the nine electrodes, the electrodes A1 to A8 function as main detection elements, and the electrode A9 functions as a monitoring electrode of the sub-detection element.

Here, first, referring to the top view of FIG. 9, let's look at the specific arrangement of the nine upper electrodes A1 to A9. First, the upper electrodes A1, A3, A7, A2
A4 and A6 are arranged along a circular annular band (hereinafter, referred to as an inner annular region), and are arranged along an outer circular annular band (hereinafter, referred to as an outer annular region) along the upper electrode A.
5, A8 and A9 are arranged. Thus, the origin O
Arranging each upper electrode along the inner and outer annular regions defined to enclose a very efficient detection is possible. In particular, the outer peripheral portion of each upper electrode arranged in the outer annular region is aligned with the outer peripheral portion of the flexible portion 112 (that is, the outer wall portion of the annular groove 115), and the upper electrode of each upper electrode arranged in the inner annular region is arranged. The inner peripheral portion is connected to the inner peripheral portion of the flexible portion 112 (ie, the annular groove 1).
(15 inner wall portions) is preferable in order to perform sensitive detection.

Now, regarding the main body of the acceleration sensor,
Consider what kind of phenomenon will occur when a force based on acceleration in a predetermined direction acts on the action point P in the central part 111 functioning as a weight body with the peripheral part 113 fixed to the sensor housing. . First, as shown in FIG.
Consider a case in which a force Fx in the X-axis direction (force based on acceleration in the X-axis direction) acts on. When such a force Fx acts, the flexible portion 112 bends, and a deformation as shown in FIG. 13 occurs. As a result, stress is generated at positions X1, X2, X3, and X4 on the upper surface of the piezoelectric element 110 along the X axis, as indicated by arrows in the figure. That is, a stress that shrinks along the X-axis direction is generated at the positions X1 and X3, and a stress that extends along the X-axis direction is generated at the positions X2 and X4.

Incidentally, this piezoelectric element 110 is the same as that shown in FIG.
As shown in the figure, since it has a type of polarization characteristic, a charge having a polarity of “−” is generated on the upper surface of the positions X1 and X3 of the piezoelectric element 110, and “+” is generated on the upper surface of the positions X2 and X4. ”Will be generated. At this time, since the lower electrode B is a single common electrode,
Even if charges having a polarity of "+" or "-" are partially generated, they are canceled out, and no charge is generated in total. In this embodiment, the lower electrode B is a single common electrode. However, if an electrically independent individual lower electrode is provided at a position opposed to each upper electrode, the lower electrode B is generated at each electrode. It is possible to process the individual charges individually.

On the other hand, a force Fy in the Y-axis direction with respect to the point of action P
Acts, the flexible portion 112 is similarly bent, and charges of the same polarity are generated on the upper surface portion at each position along the Y axis (in FIG. 13, the X axis is replaced with the Y axis,
Positions X1, X2, X3, X4 are converted to positions Y1, Y2, Y
3, Y4).

Next, a case is considered where a force Fz in the Z-axis direction (force based on acceleration in the Z-axis direction) acts. in this case,
The flexible portion 112 is deformed as shown in FIG. 14, and the portions at positions X1 and X4 corresponding to the outer annular region are contracted, so that “−” charges are generated on the upper surface portion, and the position X2 corresponding to the inner annular region is generated. , X3 are extended, so that "+" charges are generated on the upper surface.

Here, a table shown in FIG. 15 is obtained by summarizing the polarities of the electric charges generated in each upper electrode when each of the forces Fx, Fy, Fz acts. In the table, "0" indicates that the piezoelectric element partially expands but partially contracts, so that positive and negative are canceled out and no charge is generated as a whole. In particular, the upper electrodes A1 to A4
It has a shape symmetrical with respect to the X axis or the Y axis and is arranged at a position symmetrical with respect to each other. Therefore, the force Fy acts on the upper electrodes A1 and A2 that generate electric charges by the action of the force Fx. No electric charge is generated, and conversely, no electric charge is generated on the upper electrodes A3, A4, which generate electric charge by the action of the force Fy, even when the force Fx is applied. As described above, it is important to keep the electrode shape line-symmetric in order to avoid other-axis interference. The table in FIG. 15 shows the polarity when the positive force + Fx, + Fy, + Fz of each axis acts, but the negative force −Fx, −Fy, −Fx, of each axis.
When -Fz is applied, charges having polarities opposite to those in the table appear. Obtaining such a table is based on the stress distribution indicated by the arrows in FIGS.
It can be easily understood by referring to the arrangement of each upper electrode shown in FIG. The magnitude of the applied force can be detected as the amount of generated electric charge.

In order to detect the applied acceleration using the above-described acceleration sensor main body, a detection circuit as shown in FIG. 16 may be prepared. This detection circuit includes a main detection element group 130 and a sub detection element 150. The main detection element group 130 corresponds to each of the main detection elements 11 to 13 in the block diagram shown in FIG. 2, and the sub detection element 150 corresponds to the sub detection element 40 in the block diagram. Circuit components A1 to A9 and B shown on the left side of the circuit diagram shown in FIG. 16 indicate the upper electrodes A1 to A9 and the lower electrode B of the acceleration sensor main body described above. The connected Q / V conversion circuits 131 to 138 and 151 are circuits that convert the amount of charge generated in each of the upper electrodes A1 to A9 into a voltage value when the potential of the lower electrode B is set as a reference potential. For example, when a “+” charge is generated on the upper electrode, a positive voltage (relative to the reference potential) corresponding to the generated charge is output, and conversely, a “−” charge is generated on the upper electrode. When the voltage is generated, a negative voltage (relative to the reference potential) corresponding to the generated charge amount is output. Arithmetic units 141 to 143
Is a circuit for performing predetermined arithmetic processing on the voltages V1 to V8 output in this manner.
A predetermined voltage is output to each of x, Ty, Tz, and Tm. Here, the voltage value of the terminal Tx with respect to the reference potential is the detection value of the force Fx, the voltage value of the terminal Ty with respect to the reference potential is the detection value of the force Fy, and the voltage value of the terminal Tz with respect to the reference potential is the detection value of the force Fz. Become.

The fact that the voltage values obtained at the respective output terminals Tx, Ty, Tz become the detected values of the forces Fx, Fy, Fz can be understood by referring to the table of FIG. For example, when the force Fx is applied, a “+” charge is generated on the upper electrode A1, and a “−” charge is generated on the upper electrode A2. Therefore,
V1 is positive and V2 is negative. Therefore, the arithmetic unit 14
By performing the operation of V1−V2 by 1, the sum of the absolute values of the voltages V1 and V2 is obtained, and this is output to the terminal Tx as the detected value of the force Fx. Similarly,
When the force Fy acts, a charge of “+” is generated on the upper electrode A3, and a charge of “−” is generated on the upper electrode A4. Therefore, V3 is positive and V4 is negative. Therefore, the sum of the absolute values of the voltages V3 and V4 is obtained by performing the calculation of V3-V4 by the calculator 142.
This is output to the terminal Ty as a detected value of the force Fy. When the force Fz is applied, the upper electrode A
6, A7 generates a "+" charge, and the upper electrodes A5, A7
8, a "-" charge is generated. Therefore, V6, V
7 is positive, and V5 and V8 are negative voltages. Then, the operation of -V5 + V6 + V7-V8 is performed by the calculator 143, whereby the sum of the absolute values of the voltages V5 to V8 is obtained, and this is output to the terminal Tz as a detected value of the force Fz.

It should be noted that the main detecting element group 13
This means that the detected values obtained at the output terminals Tx, Ty, Tz constituting 0 do not include other axis components. For example, as shown in the table of FIG. 15, when only the force Fx acts, no charge is generated on the upper electrodes A3 and A4 for detecting the force Fy, and no detection voltage is obtained at the terminal Ty. .
At this time, electric charges are generated in the upper electrodes A5 to A8 for detecting the force Fz, respectively.
Since 5 to V8 are added to each other, they are canceled out, and no detection voltage is obtained at the terminal Tz. Similarly, when only the force Fy acts, no detection voltage can be obtained except at the terminal Ty. Similarly, when only the force Fz is applied,
No detection voltage can be obtained other than at the terminal Tz. By operating the main detection element group 130 in this manner, the three-axis XYZ components can be detected independently.

On the other hand, the sub-detecting element 150 has a very simple configuration. That is, the amount of charge generated in the upper electrode A9 is converted into a voltage value V9 by the Q / V conversion circuit 151, and the voltage value V9 is output to the terminal Tm as it is. The voltage value V9 obtained at the terminal Tm can be used as a voltage value indicating the monitor acceleration component αm. As shown in the table of FIG. 15, any charge is generated on the monitor upper electrode A9 regardless of whether a force Fx in the X-axis direction or a force Fz in the Z-axis direction is applied. . Therefore, the voltage value V obtained at the terminal Tm
Reference numeral 9 denotes a voltage value indicating the monitor acceleration component αm when the X axis and the Z axis are used as the monitoring detection axes.

In order to realize the acceleration sensor according to the present invention, it is necessary to add a main power supply means 20, a sub power supply means 50, and a control means 60 to the components shown in the circuit diagram of FIG. (See block diagram in FIG. 2). Here, the main power supply unit 20 is a unit for supplying power to the eight Q / V conversion circuits 131 to 138 and the three arithmetic units 141 to 143 that constitute the main detection element group 130. The sub power supply means 50 is a means for supplying an electrode to the Q / V conversion circuit 151 constituting the sub detection element 150, and the control means 60 is a means for controlling the power supply operation of each of these power supply means. It is.

If these means are added to the circuit shown in FIG. 16, this acceleration sensor can operate as follows. First, when the power switch of the acceleration sensor is turned ON, power supply from the sub power supply means 50 to the sub detection element 150 is started. That is, the Q / V conversion circuit 151
Is supplied, and a voltage value V9 corresponding to the monitor acceleration component αm is obtained at the terminal Tm. Control means 60 gives a predetermined instruction to main power supply means 20 based on this voltage value V9. That is, only when the voltage value V9 is equal to or higher than the predetermined threshold value, the main power supply unit 20 is instructed to supply power. Therefore, power is not supplied from main power supply means 20 to main detection element group 130 unless voltage value V9 reaches the threshold value.

If the acceleration sensor having such a configuration is used as a seismometer, an electronic multidimensional seismometer with very low power consumption can be realized. That is, in the normal operation mode, the Q / V conversion circuit 15
1 is supplied to only the main detection element group 130.
The power consumption is very low because the sleep state is maintained. In particular, as described above, if a pulse signal having a predetermined sampling cycle is given to the Q / V conversion circuit 151 and the voltage value V9 is obtained at the terminal Tm for each sampling cycle, the power consumption is further reduced. Will be done. When an earthquake of a predetermined level or more occurs, the voltage value V9 obtained at the terminal Tm exceeds a predetermined threshold value due to the vibration of the earthquake. Is started. As a result, the direction and magnitude of the applied acceleration are output to the terminals Tx, Ty, and Tz independently for each of the X-axis, Y-axis, and Z-axis components. As described above, this detection result is an accurate value without interference of other axis components.
Eventually, when the vibration of the earthquake stops, the voltage value V9 obtained at the terminal Tm becomes less than the threshold value.
0 is stopped, and the operation returns to the normal operation mode in which only the sub-detecting element 150 operates.

According to the table of FIG. 15, when a force Fx in the X-axis direction and a force Fz in the Z-axis direction act on the upper electrode A9 for monitoring, a charge of a predetermined polarity is generated.
When a force Fy in the Y-axis direction acts, no charge is generated. Therefore, theoretically, when a shaking of an earthquake consisting only of the acceleration component in the Y-axis direction or a shaking of an earthquake having extremely small acceleration components in the X-axis direction and the Z-axis direction occurs, the shaking is detected by the sub-detecting element 150. It cannot be detected. In order to cope with such a problem, as described above with reference to FIGS. 3 and 4, another set of sub-detecting elements may be provided. A specific embodiment in which two sets of the sub-detecting elements are provided will be described later in §2. It is to be noted that a normal earthquake generally includes both vibration components of "pitch" and "roll", and as in the above-described embodiment, only one set of sub-detection elements is used. Even if the acceleration sensor is used, no serious problem occurs in practical use.

§2. Practical embodiment using piezoelectric element
(1) In the above §1, the basic embodiment of the acceleration sensor using the piezoelectric element according to the present invention has been described. Here, some more practical modifications will be described.

FIG. 17 is a circuit diagram showing an example of a detection circuit for realizing a more practical sensor using the acceleration sensor main body shown in FIG. The main components of this detection circuit are a main detection element group 160 and a sub detection element 170.
And the microcomputer 180. This FIG.
A1 to A9 and electrode B shown in the circuit diagram of FIG.
Correspond to the upper electrodes A1 to A9 and the lower electrode B formed on the acceleration sensor main body in FIG. The charge amplifiers 161 to 163 and 171 correspond to the Q / V conversion circuit in the circuit shown in FIG. Have. In the circuit shown in FIG. 16, a total of nine sets of Q / V conversion circuits are used, whereas in the circuit shown in FIG. 17, only a total of four sets of charge amplifiers are used. This is because the charge amplifier 161 in the main detection element group 160 also functions as the Q / V conversion circuits 131 and 132, and the charge amplifier 162 functions as the Q / V conversion circuits 133 and 1
This is because the charge amplifier 163 also has the function of the Q / V conversion circuits 135 to 138. The charge amplifier 171 in the sub-detection element 170 corresponds to the Q / V conversion circuit 151 as it is. Further, each of the arithmetic units 141 and 1 in the detection circuit shown in FIG.
42 and 143 are unnecessary in the detection circuit shown in FIG.

However, in order to use the detection circuit shown in FIG. 17 instead of the detection circuit shown in FIG. 16, it is necessary to make some design changes to the acceleration sensor main body shown in FIG. As described above, the piezoelectric element 110 used in the acceleration sensor body shown in FIG. 7 has a polarization characteristic of the type shown in FIG. When a piezoelectric element 110 having this type of polarization characteristic is used, charges having polarities as shown in the table of FIG. . Therefore, as described above, if a circuit as shown in FIG. 16 is prepared, each axial component of the applied force can be detected separately and independently. This figure 1
The reason why the arithmetic units 141 to 143 are required in the circuit 6 is to obtain a difference between signals. In other words, FIG.
6, the voltage values V2, V4, V5, V8
Means that the positive and negative polarities are inverted by the arithmetic units 141 to 143 and then added to other voltage values. Therefore, if the polarities of these voltage values V2, V4, V5, and V8 can be originally reversed, the computing unit 141
143 is unnecessary. Voltage values V2, V4, V5, V8
Of the upper electrodes A2, A4, A5,
What is necessary is just to invert the polarity of the electric charge generated in A8.

In this embodiment, the polarity reversal of the generated charges is performed by using piezoelectric elements having partially different polarization characteristics. That is, the “type polarization characteristic” which is completely opposite to the “type polarization characteristic” shown in FIG. 12 is defined, and the upper electrodes A2, A4, A
The design of only the region in which 5, A8 is formed is changed so as to obtain “type polarization characteristics”. By using the acceleration sensor body having undergone such a design change, FIG.
Of the upper electrodes A2, A4, A5 and A8 in the table shown in FIG. 19, the result is reversed (see the thick frame in FIG. 19). As a result, no subtraction is required for the voltage values V1 to V8.

The detection circuit shown in FIG. 17 is a circuit to be applied to the acceleration sensor body having undergone such a design change. When the force Fx in the positive direction of the X-axis is applied by the above-described design change, positive charges are generated in both of the upper electrodes A1 and A2. The charge amplifier 161 has a function of generating a voltage value corresponding to the sum of the positive charges generated on the two electrodes A1 and A2, and applying the voltage value to the terminal Tx of the microcomputer 180. Further, when a force Fy in the Y-axis positive direction acts due to the above design change,
Positive charges are generated in both of the upper electrodes A3 and A4. The charge amplifier 162 is connected to both electrodes A
3, a function to generate a voltage value corresponding to the sum of the positive charges generated in A4, and to apply this voltage value to the terminal Ty of the microcomputer 180. Similarly, when a force Fz in the positive direction of the Z-axis is applied due to the above design change, the upper electrode A
Positive charges will be generated in any of 5 to A8.
The charge amplifier 163 is connected to these four electrodes A5 to A8.
Has a function of generating a voltage value corresponding to the sum of the generated positive charges, and applying this voltage value to the terminal Tz of the microcomputer 180. As described above, by performing local polarization processing on the piezoelectric element, the configuration of the detection circuit can be further simplified.

The operation of the acceleration sensor using the detection circuit shown in FIG. First, set the power switch of this sensor to O
When N, power is supplied to the power supply E. The microcomputer 180, which has been supplied with power from the power supply E, supplies a control signal for maintaining the OFF state to the control switch 181 and also sets a voltage value input from the charge amplifier 171 to the terminal Tm to a predetermined threshold. The process of comparing with the value voltage is started. Since the power is always supplied from the power supply E to the power supply input terminal e of the charge amplifier 171, the charge amplifier 171 is connected to the upper electrode A9.
Always generates a voltage corresponding to the electric charge generated in the microcomputer 180, and supplies the voltage to the terminal Tm of the microcomputer 180. In a normal operation mode in which no large vibration is applied to the sensor main body, the voltage value applied to the terminal Tm is smaller than the threshold value, so that the microcomputer 180 continuously outputs a control signal to maintain the OFF state. It is given to the control switch 181. As a result, the power of the power supply E is reduced by the charge amplifiers 161 to 163 constituting the main detection element group 160.
, And the main detection element group 160 maintains the sleep state. Therefore, the terminal T of the microcomputer 180
No detected value of acceleration is obtained for x, Ty, and Tz.

As described above, in the normal operation mode, the electric power supplied from the power source E
Are consumed in the sub-detection element 170, but are not consumed in the main detection element group 160. For this reason, the power consumption in normal times is significantly reduced as compared with the case where the normal operation is performed.

On the other hand, when a large vibration is applied to the sensor main body due to the occurrence of the earthquake, the voltage value applied to the terminal Tm exceeds a predetermined threshold value. Then, the microcomputer 180 gives a control signal to be switched to the ON state to the control switch 181. Thereby, the power supply E
Then, power supply to the main detection element group 160 is started, and the charge amplifiers 161 to 163 receive power supply to the respective power input terminals e and start the original operation. As a result, at the terminals Tx, Ty, Tz of the microcomputer 180, the detected values of the X-, Y-, and Z-axis components of the actually applied acceleration are obtained. For example, if this acceleration sensor is a sensor for a gas meter, the microcomputer 1
80 determines whether or not the supply of gas should be stopped based on these detected acceleration values. Output.

Eventually, when the vibration of the earthquake stops and the voltage value applied to the terminal Tm becomes smaller than a predetermined threshold value, the microcomputer 180 supplies a control signal to be switched to the OFF state to the control switch 181. As a result, the power supply from the power supply E to the main detection element group 160 is stopped again, the main detection element group 160 enters a sleep state, and returns to the normal operation mode.

As shown in the table of FIG.
When only the force Fy in the Y-axis direction acts on the monitor upper electrode A9, no charge is generated. Therefore, Y
When the X-axis component and the Z-axis component are extremely small in comparison with the axial component, even if the entire component is relatively large, only a small amount of electric charge is generated on the monitor upper electrode A9. And the microcomputer 18
The voltage value applied to the 0 terminal Tm does not reach the threshold value. In order to avoid such a situation, it is preferable to provide a plurality of sub-detecting elements in which the directions of the monitoring detection axes are different from each other.

FIG. 18 is a top view showing an acceleration sensor main body having two sets of sub-detecting elements. This acceleration sensor main body differs from the acceleration sensor main body shown in FIG. 9 in the following two points. First, the first difference is that the piezoelectric element 110 shown in FIG. 9 has a type of polarization characteristic in all regions, but the piezoelectric element 118 shown in FIG.
The point that the regions where A2, A4, A5, and A8 are formed is subjected to a polarization treatment that exhibits a type of polarization characteristic. The reason for performing such a local polarization process is to eliminate the subtraction in the detection circuit and simplify the circuit, as described above. The second difference is that the tenth upper electrode A10 is formed on the Y axis. In this sensor, the upper electrode A9 formed on the X axis functions as a first sub-detection element, and the upper electrode A10 formed on the Y axis functions as a second sub-detection element.

FIG. 19 is a table showing the polarity of the electric charge generated in each upper electrode in the acceleration sensor main body shown in FIG. Here, the columns surrounded by thick frames indicate the electrodes formed in the region having the type of polarization characteristics, and FIG.
It can be seen from the comparison with the table shown in FIG. As shown in the table of FIG. 19, in the sensor of this embodiment, two upper electrodes A9 and A10 are prepared for monitoring, and the upper electrode A9 can detect acceleration in the X-axis and Z-axis directions. And the upper electrode A
Numeral 10 is capable of detecting accelerations in the Y-axis and Z-axis directions.
Therefore, if both electrodes A9 and A10 are used, the X axis,
Detection can be performed when any of the Y-axis and Z-axis acceleration components act.

The detection circuit shown in FIG. 20 is a circuit to be applied to the acceleration sensor main body shown in FIG. A major difference from the detection circuit shown in FIG. 17 is that a sub-detection element group 175 is provided instead of the sub-detection element 170 in the circuit shown in FIG. The charge amount generated on the monitor upper electrode A9 is converted into a voltage value by the charge amplifier 171 and given to the terminal Tm1 of the microcomputer 185. The charge amount generated on the other monitor upper electrode A10 is charged. The voltage value is converted into a voltage value by the
To the terminal Tm2. Microcomputer 18
Reference numeral 5 determines ON / OFF of a control signal supplied to the control switch 181 based on two sets of voltage values supplied to the terminals Tm1 and Tm2. Specifically, a common threshold value is set in advance, and when any one of the voltage values becomes equal to or greater than the threshold value, a control signal indicating switch ON may be given, When the sum of the two voltage values exceeds a predetermined threshold value, a control signal indicating ON may be provided. Also, separate threshold values may be set for each voltage value.

In the detection circuit of FIG. 20, power is supplied to the sub-detection element group 175 by the pulse signal Ep output from the terminal Tp of the microcomputer 185. This pulse signal Ep is a signal having a predetermined sampling frequency as shown in FIG.
The operation of the sub-detecting element group 175 is performed intermittently. Therefore, the terminal T of the microcomputer 185
Although voltage values are given to m1 and Tm2 at a predetermined sampling period, as described above, if the sampling period is set shorter than the period of the shaking of the earthquake, it can be used as a seismograph. No hindrance occurs. In the detection circuit shown in FIG. 20, the two charge amplifiers 171 and 172 operate in the normal operation mode. However, since the operation is intermittent by the pulse signal Ep, the detection circuit shown in FIG. Power consumption is lower than in circuits. Other operations of the detection circuit of FIG. 20 are the same as those of the detection circuit of FIG. 17 described above.

In the detection circuit of FIG. 17 or FIG. 20, the control switch 181 is turned on / off by a control signal from the terminal Tc of the microcomputer, and the power supply from the power supply E to the main detection element group 160 is controlled. However, this control signal may be supplied as it is to the power supply input terminal e of each of the charge amplifiers 161 to 163 as a power supply signal.

FIG. 21 is a top view showing another acceleration sensor main body having two sets of sub-detecting elements. This acceleration sensor main body is provided with a monitor upper electrode A11 instead of the monitor upper electrode A9 in the acceleration sensor main body shown in FIG. Although the monitor upper electrodes A9 and A10 shown in FIG. 18 were both formed in the outer annular region, the monitor upper electrode A1 shown in FIG.
0 is formed in the outer annular region, and A11 is formed in the inner annular region. FIG. 22 is a table showing the polarity of electric charges generated in each upper electrode in the acceleration sensor main body shown in FIG. Again, the columns surrounded by thick frames show the electrodes formed in the region having the type of polarization characteristics. Looking at the columns of the upper electrodes A10 and A11 for monitoring, it is also possible to detect accelerations in all directions of the X-axis, the Y-axis, and the Z-axis by these two sets of upper electrodes A10 and A11.

In the embodiment shown in FIG. 18, since the upper electrode A9 is arranged on the X axis and the upper electrode A10 is arranged on the Y axis, the two arrangement axes are orthogonal. However, FIG.
In one embodiment, the upper electrode A10 is arranged on the Y axis,
Since the upper electrode A11 is arranged on the W1 axis, the two arrangement axes are not in an orthogonal relationship. When two sets of sub-detecting elements are provided, they need not necessarily be arranged on axes that are orthogonal to each other. Further, in the embodiment of FIG. 18, two sets of sub-detecting elements (upper electrodes A9 and A10) are both arranged in the outer annular area. However, as shown in FIG. The other can be arranged in the inner annular area, or both can be arranged in the inner annular area.

§3. Practical embodiment using piezoelectric element
(2) Here, an embodiment in which a part of the main detection element is also used as the sub detection element will be described. FIG. 23 is a top view showing an acceleration sensor main body that also serves such an element. Only eight upper electrodes A1 to A8 are formed on the acceleration sensor main body, and the monitor upper electrodes A9 to A11 described in the above embodiments are not formed. On the other hand, the piezoelectric element 118 has been
As in the piezoelectric element 118 shown in FIG.
5, a region where A8 is formed has a type of polarization characteristic, and the other regions are subjected to a polarization process having a type of polarization characteristic.

As described above, the upper electrodes A1 and A2 are used for detecting the acceleration component in the X-axis direction.
A4 is used for detecting an acceleration component in the Y-axis direction, and the upper electrodes A5 to A8 are used for detecting an acceleration component in the Z-axis direction.
Therefore, these eight upper electrodes A1 to A8 are all electrodes constituting the main detection element. However,
In the embodiment described here, of these eight electrodes, the upper electrodes A2 and A4 are also used as electrodes (monitoring electrodes) constituting the sub-detection element. Upper electrodes A2 and A
Assuming that the electrode 4 also serves as a monitoring electrode, the polarity of the electric charge generated in each upper electrode of the acceleration sensor main body is represented as shown in the table of FIG. Here, the column surrounded by a thick frame shows the electrodes formed in the region having the type of polarization characteristics. As can be seen from this table, when the upper electrodes A2 and A4 are used as monitoring electrodes, the X-axis and
It is possible to detect acceleration in all directions of the Y axis and the Z axis.

FIG. 25 is a circuit diagram showing a detection circuit to be applied to the acceleration sensor main body shown in FIG. The main detection element group 190 includes an upper electrode A1 formed on the sensor main body.
To A8 and lower electrode B, and five sets of charge amplifiers 19
1 to 195 and three sets of arithmetic units 196 to 198. Each of the charge amplifiers 191 to 194 has a function of converting the amount of electric charge generated in the upper electrodes A1 to A4 into a voltage value. It has a function to convert. The arithmetic units 196 and 197 are formed of adders, and the arithmetic unit 198 is formed of a simple amplifier circuit. Each of the charge amplifiers 191 to 195 and each of the arithmetic units 196 to 198 operate by receiving power supply to the power input terminal e. The power supply to each power input terminal e is
The control is performed from the power supply E via the control switches 182 and 183. Further, with respect to the charge amplifiers 192 and 194, power is also supplied to the power input terminal e in the form of a pulse signal Ep supplied from the terminal Tp of the microcomputer 188.

First, when the power switch of this sensor is turned on, power is supplied to the power source E. The microcomputer 188, which has been supplied with power from the power supply E, supplies a control signal to maintain the OFF state to the control switches 182 and 183, and outputs a pulse signal Ep having a predetermined sampling cycle from the terminal Tp. To start processing. This pulse signal Ep is output from two charge amplifiers 192 and 192 out of the five charge amplifiers 191 to 195.
194 is supplied only to the power input terminal e. As described above, in this embodiment, the upper electrodes A2 and A4 also function as constituent elements of the sub-detection elements, and the two sets of charge amplifiers 192 and 194 also function as sub-detection elements. As a result, in the normal operation mode in which no large vibration is applied to the sensor body, the power input terminals e of the two sets of charge amplifiers 192 and 194 which also serve as sub-detection elements among the elements in the main detection element group 190 are connected. Only the power is supplied (pulse signal Ep), and the voltage value corresponding to the amount of charge generated in the upper electrode A2 is calculated by the microcomputer 188.
And a voltage value corresponding to the amount of electric charge generated in the upper electrode A4.
88 terminal Tm2.

The microcomputer 188 has a terminal Tm
A process of comparing the voltage value input to 1 and the voltage value input to the terminal Tm2 with a predetermined threshold voltage is performed. In the normal operation mode in which no large vibration is applied to the sensor main body, these voltage values are smaller than the threshold value. 183
Give to. As a result, the power of the power supply E is
90, charge amplifiers 191, 193, 195
The main detection element group 190 is not supplied to the arithmetic units 196 to 198, and the charge amplifier 1 constituting the sub detection element group.
Except for 92 and 194, they remain dormant. Therefore, the terminals Tx, Ty, T of the microcomputer 188
No detected acceleration value is obtained for z.

As described above, in the normal operation mode, the power supplied from the power supply E is supplied to the microcomputer 188.
Is only consumed by the microcomputer 188
Although a certain amount of power is consumed to generate the pulse signal Ep, the power consumption in normal times is significantly reduced as compared with the case where a normal operation is performed.

On the other hand, when a large vibration is applied to the sensor body due to the occurrence of an earthquake, the voltage value applied to the terminal Tm1 or Tm2 exceeds a predetermined threshold value. Then, the microcomputer 188 gives a control signal to be switched to the ON state to the control switches 182 and 183. As a result, power supply from the power supply E to the main detection element group 190 starts, and the charge amplifiers 191 to 195 and the calculators 196 to 198 receive power supply to the respective power supply input terminals e and start their original operations. At this time, the microcomputer 188 stops outputting the pulse signal Ep from the terminal Tp (the output may be continued as long as there is no problem in the circuit). As a result of the main detection element group 190 starting its original operation, the terminals Tx, Ty, and Tz of the microcomputer 188 have X
The detected values of the components in the axis, Y-axis, and Z-axis directions are obtained. For example, if the acceleration sensor is a sensor for a gas meter, the microcomputer 188 determines whether or not to stop the gas supply based on the detected acceleration values, and determines that the supply needs to be stopped. In this case, a shutoff signal is output from the terminal Toff to the gas supply valve.

Eventually, the vibration of the earthquake stops and the terminal Tm1
Alternatively, when the voltage value applied to Tm2 becomes smaller than a predetermined threshold value, the microcomputer
The control signal to be switched to the FF state is supplied to the control switch 18.
2,183. Thus, the power supply from the power supply E to the main detection element group 190 stops again. On the other hand, the microcomputer 188 starts supplying the pulse signal Ep from the terminal Tp. In this way, the main detection element group 190 enters the sleep state except for the charge amplifiers 192 and 194 which also serve as the sub detection element groups, and returns to the normal operation mode.

§4. Embodiment using a piezoresistive element FIG. 26 is a top view of an embodiment in which an acceleration sensor main body that can be used in the present invention is constructed using a piezoresistive element. FIG. FIG. 3 is a side cross-sectional view taken along the X axis. The semiconductor substrate 210 is a silicon single crystal substrate. For convenience of description, an origin O of an XYZ three-dimensional coordinate system is defined at the center of the upper surface of the semiconductor substrate 210, and the X axis and the Y axis , Z axis are defined. Therefore, the upper surface of the semiconductor substrate 210 is a surface included in the XY plane. Also, as shown in the figure, the W1 axis and the W2 axis that form an angle of 45 ° with the X axis and the Y axis are defined.

The structural features of the semiconductor substrate 210 are shown in FIG.
As shown by a broken line in FIG. 6, an annular groove 215 is formed on the lower surface. In this embodiment, the annular groove 21
Reference numeral 5 denotes a circle surrounding the origin O. As shown in the side sectional view of FIG. 27, the portion of the semiconductor substrate 210 where the annular groove 215 is formed is thinner than the other portions, and has flexibility. Here, a portion of the semiconductor substrate 210 located above the annular groove 215 is referred to as a flexible portion 212, a central portion surrounded by the flexible portion 212 is referred to as a central portion 211, and A portion located on the outer periphery is referred to as a peripheral portion 213.

Such a mechanical structure is exactly the same as the above-described acceleration sensor main body using the piezoelectric element. Therefore, also in this semiconductor substrate 210, when only the central portion 211 is fixed to the sensor housing and the entire sensor housing is shaken, the peripheral portion 213 functions as a weight, and the weight has an acceleration. Is applied, and this force causes the flexible portion 212 to bend. Conversely, when only the peripheral portion 213 is fixed to the sensor housing and the entire sensor housing is shaken, the central portion 211 functions as a weight body. That is, a force based on the acceleration acts on the central portion 211, and the force also acts on the flexible portion 21.
2 will bend.

In this embodiment, the stress generated in each part due to such bending is detected as a change in the resistance value of the piezoresistive element. Therefore, as shown in FIG. 26, a total of 14 resistance elements
At a predetermined position on the upper surface of the. That is, four resistance elements Rx1 to Rx4 are formed on the X axis, four resistance elements Ry1 to Ry4 are formed on the Y axis, and four resistance elements Rz1 to Rz4 are formed on the W2 axis. ing. In addition to these 12 resistance elements, a monitoring resistance element Rm
1, Rm2 are formed at the positions shown in the figure. Resistance element R
x1 to Rx4 are main detection elements for detecting an acceleration component in the X-axis direction, and resistance elements Ry1 to Ry4 are main detection elements for detecting an acceleration component in the Y-axis direction.
The resistance elements Rz1 to Rz4 are main detection elements for detecting an acceleration component in the Z-axis direction. On the other hand, the monitoring resistance elements Rm1 and Rm2 are sub-detection elements, and when used as a seismometer, perform a function of detecting an initial vibration of an earthquake.

The positions of the resistance elements Rm1 and Rm2 for monitoring may be arbitrarily determined. However, the two sets of sub-detection elements can efficiently detect all the X-axis, Y-axis and Z-axis acceleration components. To do so, two orthogonal to each other
It is preferable to arrange each monitoring resistance element along the axis. In the illustrated embodiment, the resistance element Rm
1 is arranged along the W1 axis, the resistance element Rm2 is arranged substantially along the W2 axis, and the two arrangement axes are in an orthogonal relationship.

FIG. 28 is a circuit diagram showing a detection circuit applied to the acceleration sensor main body shown in FIG. In this detection circuit, an upper part of the microcomputer 230 constitutes a main detection element group, and a lower part thereof constitutes a sub detection element group. The bridge circuit Brx is configured by four sets of resistance elements Rx1 to Rx4 shown in FIG.
The bridge circuit Bry includes four sets of resistance elements Ry1 to Ry4 shown in FIG.
rz is the four resistance elements Rz1 to Rz1 shown in FIG.
Rz4. A predetermined power supply voltage is supplied to the upper end point of each bridge circuit from the terminal Te of the microcomputer 230, and the lower end point of each bridge circuit is grounded. Individual bridge circuits Brx, Bry, Brz
The voltage difference between the left and right end points of the
22, 223, and the amplified voltage value is
The signals are supplied to terminals Tx, Ty, and Tz of the microcomputer 230. Further, each of the amplifier circuits 221, 222, 22
3 is connected to the microcomputer 230
Is supplied from the terminal Te.

Each of the amplifier circuits 221, 222, and 223
It has a function of detecting an equilibrium state between left and right end points of each bridge circuit Brx, Bry, Brz. When no acceleration is applied to the acceleration sensor main body shown in FIG. 26, adjustment is performed so as to maintain an equilibrium state between the left and right end points of each bridge circuit Brx, Bry, Brz. When the acceleration acts, the balance of the predetermined bridge circuit corresponding to the directional component of the acceleration is lost, and the applied acceleration is detected by the predetermined amplifier circuit.
Specifically, the X-axis direction component of the acceleration applied by the amplifier circuit 221 is detected, the Y-axis direction component is detected by the amplifier circuit 222, and the Z-axis component is detected by the amplifier circuit 223.
An axial component will be detected.

The principle of such detection is almost the same as that of the above-described acceleration sensor using a piezoelectric element. That is, when the peripheral portion 213 of the semiconductor substrate 210 is fixed to the sensor housing, and the central portion 211 functions as a weight, and acceleration in each coordinate axis direction acts on the weight, the acceleration applied is considered. Depending on the orientation, the semiconductor substrate 210
As shown by arrows in FIG. 13 or FIG. 14, a stress in the extending direction or the contracting direction is generated in each part. On the other hand, each piezoresistive element formed on the semiconductor substrate 210 has a property that the resistance value increases or decreases due to mechanical deformation that expands or contracts. Therefore, FIG.
If a bridge circuit is formed as shown in FIG.
The acceleration components in the axis and Z-axis directions can be detected independently of each other while eliminating the interference of other axis components. Terminals Tx, Ty, and Tz of the microcomputer 230 provide the acceleration component in each axis direction. Is given.

On the other hand, a current path from the terminal Tp1 to the terminal Tm1 through the monitor resistor Rm1 is provided below the microcomputer 230 (sub-detection element group).
A current path from the terminal Tp2 to the terminal Tm2 through the monitoring resistance element Rm2 is formed, and the monitoring currents im1 and im2 are supplied to these current paths.
In this embodiment, as the monitor currents im1 and im2,
A pulsed current intermittently supplied at a predetermined sampling cycle is used.

The operation of the acceleration sensor using the circuit shown in FIG. 28 is as follows. First, when the power switch of the acceleration sensor is turned on, supply of the monitoring currents im1 and im2 from the terminals Tp1 and Tp2 is started, and a current path passing through the monitoring resistance elements Rm1 and Rm2 is formed. At this time, since power is not supplied from the terminal Te, each of the bridge circuits Brx, Bry, Brz and each of the amplifier circuits 221, 222, and 223 do not operate and are in a sleep state. In the normal operation mode without large vibration, the monitoring resistance elements Rm1 and Rm2 show standard resistance values. The microcomputer 230 has a terminal Tm
1, Tm2 (or terminal Tm1,
By monitoring the voltage value of Tm2), the resistance values of the monitoring resistance elements Rm1 and Rm2 can be detected. Then, as long as the difference between the detected resistance value and the standard resistance value does not reach the predetermined threshold value, the normal operation mode is maintained as it is. That is, the power supply from the terminal Te remains stopped.

After all, in the normal operation mode, only the sub-detection element shown below the microcomputer 230 is operating, and the main detection element shown above is in a sleep state. In addition, since the monitoring currents im1 and im2 supplied to the sub-detection element are supplied intermittently at a cycle required for sampling, the power consumption in the normal operation mode is extremely low.

On the other hand, when an earthquake of a predetermined level or more occurs, the vibration of this earthquake causes the semiconductor substrate 210 to bend, resulting in a large change in the resistance value of the monitoring resistance element Rm1 or Rm2. When the change in the resistance value becomes equal to or greater than a predetermined threshold value, the microcomputer 230 starts power supply from the terminal Te. As a result, each of the bridge circuits Brx, Bry, Brz and each of the amplifier circuits 221, 222, 223 start a normal operation, and the direction and magnitude of the applied acceleration are applied to the terminals Tx, Ty, Tz on the X axis. It is output independently for each of the Y-axis and Z-axis components. The microcomputer 230, for example, based on these detection values,
It is determined whether the supply of gas should be stopped or not, and if necessary, a process of giving a shut-off signal from the terminal Toff to the gas supply valve is executed.

When the vibration of the earthquake subsides, the resistance value of the monitoring resistance element Rm1 or Rm2 returns to the original standard value.
Is stopped, and the operation mode returns to the normal operation mode.

§5. Embodiment Using Capacitive Element (1) Subsequently, an embodiment in which a capacitive element is used to constitute an acceleration sensor body that can be used in the present invention will be described. Now, FIG.
As shown in FIG. 9, a flexible substrate 310 having flexibility and an insulating surface is prepared, and seven electrodes E1 are provided on the upper surface thereof.
To E7. On the other hand, a fixed substrate 320 as shown in FIG. 30 is prepared, and an electrode E0 is formed. Then, the peripheral portions of both substrates are fixed to the sensor housing so that the electrode forming surfaces of both substrates face each other. FIG. 31 is a side sectional view of the sensor main body configured as described above. In this example, the flexible substrate 310 shown in FIG.
3 is arranged so that the formation surface of the
The fixed substrate 320 shown in FIG. 0 is disposed so that the surface on which the electrode E0 is formed faces downward, and a cylindrical weight 330 is attached to the lower surface of the flexible substrate 310. The flexible substrate 310 and the fixed substrate 320 are arranged so as to be parallel to each other with a predetermined space therebetween, and the peripheral portions of both substrates are fixed to the sensor housing 340.

As shown, the fixed substrate 320 is relatively thick and has rigidity that does not cause bending, whereas the flexible substrate 310 is relatively thin and flexible. Electrodes are formed at predetermined positions on opposing surfaces of both substrates.
Now, the origin O is defined on the upper surface of the flexible substrate 310, and the X, Y, and Z axes are defined in the illustrated directions, thereby defining the XYZ three-dimensional coordinate system. Both the flexible substrate 310 and the fixed substrate 320 are arranged in parallel to the XY plane.

As shown in FIG. 29, on the flexible substrate 310, electrodes E1 and E2 are formed on the X axis, electrodes E3 and E4 are formed on the Y axis, and a circular electrode E5 is formed at the center. Are formed. Here, the electrodes E1 and E2 have shapes and arrangements that are symmetric with respect to the X axis, and the electrodes E3 and E2
E4 has a shape and an arrangement symmetrical with respect to the Y axis. In addition, W1 axis and W2 axis which form 45 ° with respect to the X axis and the Y axis are defined, and the electrodes E6 and E6 are formed.
E7 is arranged on the W1 axis and the W2 axis, respectively.
On the other hand, the electrode E0 shown in FIG.
31. When the two substrates are opposed to each other as shown in FIG. 31, the seven electrodes E1 to E7 on the flexible substrate 310 side are fixed to the fixed substrate 320, respectively. This opposes a part of the side electrode E0, and a capacitance element is formed by the pair of opposing electrodes. Here, a capacitive element formed by the seven electrodes E1 to E7 and the opposing portions of the electrode E0 is
These will be referred to as capacitance elements C1 to C7, respectively.

Now, with respect to this acceleration sensor main body,
Consider a case in which acceleration in the X-axis direction acts. in this case,
The force Fx in the X-axis direction is applied to the center of gravity P of the weight body 330, and the flexible substrate 310 bends as shown in FIG. Each part of the flexible substrate 310 is displaced by this bending. For example, a portion where the electrode E1 is formed causes a displacement in a direction approaching the electrode E0, and a portion where the electrode E2 is formed causes a displacement in a direction away from the electrode E0. Similarly, when acceleration in the Y-axis direction acts, the weight body 330
A force Fy in the Y-axis direction is applied to the center of gravity P, and the portion where the electrode E3 is formed is displaced in the direction approaching the electrode E0, and the portion where the electrode E4 is formed is the electrode E0. Displacement in the direction away from the object. Furthermore,
When acceleration in the Z-axis direction acts on this acceleration sensor body, a force Fz in the Z-axis direction is applied to the center of gravity P of the weight body 330, and the flexible substrate 310 As shown in FIG. Due to this bending, all the electrodes on the flexible substrate 310 are displaced in a direction approaching the electrode E0.

The principle of the acceleration sensor according to this embodiment is as follows.
Thus, the applied acceleration is detected based on the displacement of each portion of the flexible substrate 310. For detecting the displacement, a change in the capacitance value of the capacitance element can be used. That is, the capacitance value of the capacitor formed by the pair of electrodes changes depending on the electrode interval. The capacitance value decreases as the electrode interval increases, and the capacitance value increases as the electrode interval decreases. Therefore, by measuring the capacitance value of each capacitance element, the electrode interval can be measured, and the displacement state of each part of the flexible substrate 310 can be recognized.

The seven electrodes E1 to E shown in FIG.
Of the electrodes 7, the electrodes E1 and E2 are used for detecting acceleration in the X-axis direction, the electrodes E3 and E4 are used for detecting acceleration in the Y-axis direction, and the electrode E5 is used for detecting acceleration in the Z-axis direction.
These five electrodes are electrodes constituting the main detection element. On the other hand, the electrodes E6 and E7 are monitoring electrodes, and constitute electrodes of the sub-detection element.

By observing the displacement state of FIG. 32, it can be understood that acceleration in the X-axis direction can be detected by changing the capacitance values of the capacitance elements C1 and C2. When a force Fx is applied to the weight body 330 based on the acceleration in the X-axis direction, the electrode E1-
The distance between E0 decreases and the distance between electrodes E2-E0 increases. Therefore, the capacitance value of the capacitance element C1 increases, and the capacitance value of the capacitance element C2 decreases. As a result, the difference between the capacitance values of the two capacitance elements C1 and C2 indicates the value of the applied acceleration in the X-axis direction. Similarly, the difference between the capacitance values of the two capacitance elements C3 and C4 indicates the value of the applied acceleration in the Y-axis direction. Moreover, the electrodes E1 to E4
Is symmetrical about the X or Y axis,
The detected values of other axis components do not cause interference. For example, when acceleration in the X-axis direction acts, the electrodes E3-E0
Although the distance between them and the distance between the electrodes E4 and E0 partially increase or decrease, they do not change as a whole, so that there is no change in the difference between the capacitance values of the two capacitance elements C3 and C4.

When a force Fz is applied to the weight body 330 based on the acceleration in the Z-axis direction, as shown in FIG. 33, the distance between the electrodes E5 and E0 decreases, and the The capacitance value increases. Therefore, the value of the acceleration in the Z-axis direction exerted by the change in the capacitance value of the capacitance element C5 is shown.

On the other hand, the portion where the monitoring electrodes E6 and E7 are formed is displaced even when any of the acceleration components of the X axis, the Y axis and the Z axis is applied. Therefore,
If the change in the capacitance value of the capacitance elements C6 and C7 is monitored, detection is possible even when any of the X-axis, Y-axis, and Z-axis acceleration components act. Note that two sets of monitoring electrodes are provided because only one set cannot detect acceleration in only the W1 axis direction or acceleration in only the W2 axis direction.

FIG. 34 is a circuit diagram showing an example of a detection circuit applied to the acceleration sensor body shown in FIG. The main components of this detection circuit are a main detection element group 3
50, a sub-detection element group 360, and a microcomputer 370. The electrodes E1 to E7 shown in the circuit diagram of FIG. 34 are the respective electrodes shown in FIG.
The electrode E0 is the electrode shown in FIG. As described above, the capacitance elements C1 to C7 are formed by the facing electrodes. The main detection element group 350 includes five sets of C / V
Conversion circuits 351 to 355 and three sets of operation units 356 to 358
Is provided. 5 sets of C / V conversion circuits 351 to 35
Reference numeral 5 has a function of converting capacitance values of the capacitance elements C1 to C5 into voltage values.

The arithmetic unit 356 obtains a voltage corresponding to the difference between the output voltage of the C / V conversion circuit 351 and the output voltage of the C / V conversion circuit 352, and uses this as the detected acceleration value in the X-axis direction. To the terminal Tx. As described above, the difference between the capacitance value of the capacitance element C1 and the capacitance value of the capacitance element C2 indicates the acceleration component in the X-axis direction. Similarly, the calculator 357 obtains a voltage corresponding to the difference between the output voltage of the C / V conversion circuit 353 and the output voltage of the C / V conversion circuit 354, and uses this as the detected acceleration value in the Y-axis direction. Terminal T
It has the function of giving y. As described above, the difference between the capacitance value of the capacitance element C3 and the capacitance value of the capacitance element C4 indicates the acceleration component in the Y-axis direction. The arithmetic unit 358 functions as a mere amplifier, and has a function of applying a voltage corresponding to the output of the C / V conversion circuit 355 to the terminal Tz of the microcomputer 370 as a detected acceleration value in the Z-axis direction. As described above, the change in the capacitance value of the capacitance element C5 indicates the acceleration component in the Z-axis direction.

The five sets of C / V conversion circuits 351 to 355 are also 3
Each set of arithmetic units 356 to 358 operates by receiving power supply from terminal Te of microcomputer 370 to each power input terminal e. Therefore, the terminal Te
If power is not supplied from the main detection element group 350, the main detection element group 350 stops its original function and enters a sleep state.

On the other hand, two sets of C
/ V conversion circuits 361 and 362 are provided. C / V
The conversion circuit 361 has a function of converting the capacitance value of the monitor capacitance element C6 into a voltage value and providing the voltage value to the terminal Tm1 of the microcomputer 370. The C / V conversion circuit 362
It has a function of converting the capacitance value of the monitoring capacitance element C7 into a voltage value and giving it to the terminal Tm2 of the microcomputer 370. A power input terminal e of the C / V conversion circuits 361 and 362 is connected to a terminal T of the microcomputer 370.
p supplies a pulse signal Ep, and this pulse signal Ep
The C / V conversion circuits 361 and 362 operate intermittently with the power of As described above, intermittently operating the sub-detection element using the pulse signal Ep is very effective for reducing power consumption. In addition, if the pulse signal Ep having a predetermined sampling cycle according to the use environment of the acceleration sensor is used, no trouble occurs even in the case of intermittent operation.

The operation of the acceleration sensor using the detection circuit shown in FIG. First, set the power switch of this sensor to O
When N, power is supplied to the power supply E. The microcomputer 370 that has received the power supply from the power supply E starts supplying the pulse signal Ep from the terminal Tp, and supplies power to the sub-detection element group 360. At this point, the terminal T
e, power is not supplied from the main detection element group 35.
0 maintains a dormant state. C / V conversion circuits 361 and 36
Reference numeral 2 denotes a voltage value corresponding to the capacitance value of each of the capacitance elements C6 and C7,
Give to 2. In a normal operation mode in which no large vibration is applied to the sensor body, the voltage value applied to the terminals Tm1 and Tm2 maintains a predetermined reference value. The microcomputer 370 operates as long as the difference between the voltage value applied to the terminals Tm1 and Tm2 and a predetermined reference value is smaller than a predetermined threshold value.
No power is supplied from the terminal Te. For this reason, the main detection element group 350 continues to be in the sleep state continuously, and the normal operation mode is maintained.

As described above, in the normal operation mode, the power supplied from the power supply E is supplied to the microcomputer 370.
And the C / V conversion circuits 361 and 362
, But is not consumed in the main detection element group 350. For this reason, the power consumption in normal times is significantly reduced as compared with the case where the normal operation is performed.

On the other hand, when a large vibration is applied to the sensor body due to the occurrence of the earthquake, the difference between the voltage value applied to the terminal Tm1 or Tm2 and the reference value exceeds a predetermined threshold value. Then, the microcomputer 370
The power supply from the terminal Te is started, and the main detection element group 350
Is operated normally. As a result, the microcomputer 3
At the terminals Tx, Ty, and Tz of 70, the detected values of the X-, Y-, and Z-axis components of the actually applied acceleration are obtained. For example, if the acceleration sensor is a sensor for a gas meter, the microcomputer 370 determines whether or not to stop the gas supply based on the detected acceleration values, and determines that the supply needs to be stopped. In this case, a shutoff signal is output from the terminal Toff to the gas supply valve.

Eventually, the vibration of the earthquake stops and the terminal Tm1
When the voltage value applied to Tm2 and Tm2 returns to a value close to the reference value, microcomputer 370 stops the power supply from terminal Te, and sets main detection element group 350 to the sleep state again. Thus, the operation mode returns to the normal operation mode.

§6. Embodiment Using a Capacitance Element (2) Here, an embodiment will be described in which a part of the main detection element is also used as a sub-detection element in the embodiment described in §5. FIG. 35 is a top view showing an electrode configuration on the flexible substrate 310 when such an element is shared. As can be seen from comparison with the electrode configuration shown in FIG. 29, the flexible substrate 310 shown in FIG. 35 is not provided with the monitoring electrodes E6 and E7. As described above, the electrodes E1 and E2 are used for detecting the acceleration component in the X-axis direction, and the electrodes E3 and E4 are used for detecting the acceleration component in the Y-axis direction.
The electrode A5 is used for detecting an acceleration component in the axial direction, and the electrode A5 is used for detecting an acceleration component in the Z-axis direction. Therefore, these five electrodes E1 to E5 are all electrodes constituting the main detection element. However, in the embodiment described here, of these five electrodes, the electrodes E2 and E4 are also used as electrodes (monitoring electrodes) constituting the sub-detection element.

FIG. 36 shows the flexible substrate 310 shown in FIG.
FIG. 4 is a circuit diagram showing a detection circuit to be applied to a sensor main body using the sensor. The main detection element group 359 includes electrodes E0 to E5 formed in the sensor main body and five sets of C / V conversion circuits 351.
To 355 and three sets of arithmetic units 356 to 358. This configuration is almost the same as the configuration of the main detection element group 350 in the circuit shown in FIG. However, FIG.
C / V conversion circuits 352a and 354a in the circuit shown in FIG.
Has a function of receiving both the power from the terminal Te of the microcomputer 375 and the power (pulse signal Ep) from the terminal Tp.

First, when the power switch of this sensor is turned on, power is supplied to the power source E. The microcomputer 375 that has been supplied with power from the power supply E outputs
, A process of outputting a pulse signal Ep having a predetermined sampling period from is started. This pulse signal Ep is output from two sets of C / V conversion circuits among the five sets of C / V conversion circuits 351-355.
It is supplied only to the power input terminal e of the conversion circuits 352a and 354a. As already mentioned, in this embodiment,
The electrodes E2 and E4 also function as constituent elements of the sub-detection element, and the two sets of C / V conversion circuits 352a and 354a also function as sub-detection elements. On the other hand, the microcomputer 375 does not supply power from the terminal Te at this time. Therefore, the C / V conversion circuit 35
The power is not supplied to 1, 353, 355 and the computing units 356 to 358.

After all, in the normal operation mode in which no large vibration is applied to the sensor body, the power supply of the two sets of C / V conversion circuits 352a and 354a also serving as the sub-detection elements among the elements in the main detection element group 359. Power is supplied only to the input terminal e (pulse signal Ep), a voltage value corresponding to the capacitance value of the capacitance element C2 is given to the terminal Tm1 of the microcomputer 375, and the capacitance value of the capacitance element C4 Is applied to the terminal Tm2 of the microcomputer 375.

The microcomputer 375 has a terminal Tm
A voltage difference between a voltage value input to 1 and a voltage value input to the terminal Tm2 and a predetermined reference value is determined, and it is determined whether the voltage difference is equal to or greater than a predetermined threshold value. In the normal operation mode in which no large vibration is applied to the sensor main body, the voltage difference is smaller than the threshold value, so that the microcomputer 375 continues to perform the two sets of C / V conversion circuits 3
Power is supplied only to 52a and 354a. As a result, the main detection element group 359 maintains a sleep state except for the two sets of C / V conversion circuits 352a and 354a that constitute the sub detection element group. Therefore, no detected value of acceleration is obtained at the terminals Tx, Ty, and Tz of the microcomputer 375.

As described above, in the normal operation mode, the power supplied from the power supply E is supplied to the microcomputer 375.
Is only consumed by the microcomputer 375
Although a certain amount of power is consumed to generate the pulse signal Ep, the power consumption in normal times is significantly reduced as compared with the case where a normal operation is performed.

On the other hand, when a large vibration is applied to the sensor body due to the occurrence of an earthquake, the voltage value applied to the terminal Tm1 or Tm2 fluctuates, and the voltage difference from the reference value exceeds a predetermined threshold. Then, the microcomputer 375 starts power supply from the terminal Te.
Thus, the entire main detection element group 359 starts the original operation. At this time, the microcomputer 375 stops the output of the pulse signal Ep from the terminal Tp (the output may be continued if the operation of the circuit is not hindered). As a result of the main detection element group 359 starting the original operation, the terminals Tx, Ty, T
For z, the detected values of the X-axis, Y-axis, and Z-axis components of the actually applied acceleration are obtained. For example, if the acceleration sensor is a sensor for a gas meter, the microcomputer 375 determines whether to stop the gas supply based on the detected acceleration values, and determines that the supply needs to be stopped. In this case, a shutoff signal is output from the terminal Toff to the gas supply valve.

Eventually, the vibration of the earthquake stops and the terminal Tm1
Alternatively, when the voltage value applied to Tm2 returns to a value close to the predetermined reference value, the microcomputer 375 stops supplying power from the terminal Te and starts supplying the pulse signal Ep from the terminal Tp. In this way, the main detection element group 359, except for the two sets of C / V conversion circuits 352a and 354a also serving as the sub-detection element group, enters the sleep state and returns to the normal operation mode.

§7. To further reduce power consumption
Circuit Configuration Finally, some measures to further reduce the power consumption during normal times will be described. This contrivance is applied to the embodiment using the piezoelectric element described in §1 to §3. FIG.
7, FIGS. 20 and 25 show a detection circuit according to a practical embodiment using a piezoelectric element. In these detection circuits,
The generated charge amount of the piezoelectric element functioning as a sub-detection element is converted to a predetermined voltage value using a charge amplifier,
A signal was transmitted to the microcomputer. At this time, if the power supply to the charge amplifier is intermittently performed using a pulse signal having a predetermined sampling period, the power consumption in normal times can be reduced as described above. However, in order to drive the charge amplifier, it is essential to supply power intermittently, and power consumption is inevitable.

Here, a detection circuit capable of further reducing power consumption and theoretically suppressing power consumption in normal times to zero is disclosed. FIG. 37 is a circuit diagram showing a detection circuit that extracts a signal from a sub-detection element and transmits the signal to a microcomputer using a MOS transistor instead of a charge amplifier.
Here, the piezoelectric element 410 is a piezoelectric element that functions as a sub-detection element, and is sandwiched between the upper electrode A and the lower electrode B. The lower electrode B is grounded, and the upper electrode A is P
It is connected to the gate electrodes of the type MOS transistor TR1 and the N type MOS transistor TR2. In addition, each M
One of the source and drain electrodes of the OS transistors TR1 and TR2 is grounded, and the other is a microcomputer 42
0 terminals Tm1 and Tm2. A predetermined voltage with respect to the ground potential is applied to the terminals Tm1 and Tm2 of the microcomputer 420, and when each MOS transistor is turned on, monitor currents im1 and im2 flow from the terminals Tm1 and Tm2, respectively. .

In a normal state, that is, in a state where no acceleration is applied, no charge is generated in the piezoelectric element 410.
Therefore, in normal times, each MOS transistor TR1,
The potential of the gate electrode of TR2 becomes zero (ground level),
Both transistors are turned off. Therefore, the monitor currents im1 and im2 do not flow, and the power consumption as the sub-detection element becomes zero. However, when acceleration acts due to the occurrence of an earthquake, a predetermined charge is generated on the upper electrode A, and the MOS transistor is turned on. That is,
When a positive charge is generated in the upper electrode A, a positive voltage is applied to the gate electrode of each transistor, the N-type MOS transistor TR2 is turned on, and the monitor current im2 is observed. Conversely, when a negative charge is generated on the upper electrode A, a negative voltage is applied to the gate electrode of each transistor, and the P-type MOS transistor TR1 turns on.
The monitor current im1 will be observed. The microcomputer 420 monitors the monitor currents im1 and im2 flowing through the terminals Tm1 and Tm2, and starts supplying power to a main detection element (not shown) when the current value exceeds a predetermined threshold value. do it.

Since the shaking of the earthquake is a reciprocating vibration in the vertical and horizontal directions, the direction of the acceleration is periodically reversed. Therefore, the polarity of the charge generated in the upper electrode A is also periodically inverted. Therefore, in the circuit diagram shown in FIG. 37, an example is shown in which a pair of MOS transistors TR1 and TR2 are provided. However, if it is used as a general acceleration sensor for detecting reciprocal vibration such as an earthquake, the P-type MOS transistor TR1 Alternatively, it is sufficient to provide only one of the N-type MOS transistor TR2.

FIG. 38 shows an example in which an npn-type bipolar transistor is used instead of a MOS transistor. The upper electrode A is grounded via a resistance element R and a capacitance element C, and is connected to a bipolar transistor TR3.
Are connected to the base electrode. The emitter electrode of the bipolar transistor TR3 is grounded, and the collector electrode is connected to the terminal Tm of the microcomputer 430. The terminal Tm of the microcomputer 430 includes
When a predetermined voltage is applied to the ground potential and the transistor TR3 is turned on, a monitor current im flows.

In normal times, that is, when no acceleration is applied, no charge is generated in the piezoelectric element 410.
Therefore, in normal times, the potential of the base electrode of the transistor TR3 becomes zero (ground level), and the npn-type transistor is turned off. Therefore, the monitor current im
Does not flow, and the power consumption as the sub-detection element becomes zero. However, when acceleration acts due to an earthquake,
As described above, positive and negative charges are periodically generated in the upper electrode A. When a positive voltage is applied to the base electrode, the transistor TR3 is turned on, and the monitor current im is observed. Microcomputer 4
The monitoring unit 30 monitors the monitor current im flowing through the terminal Tm, and starts supplying power to a main detection element (not shown) when the current value exceeds a predetermined threshold value.

As described above, if the circuit shown in FIG. 37 or FIG. 38 is used for signal detection of the sub-detection element, it is possible to suppress the power consumption in normal times to zero, and further reduce the power consumption of the whole sensor. It becomes possible.

For example, in the case of the detection circuit shown in FIG.
The above-described transistor circuit may be applied instead of the charge amplifier 171. In the case of the detection circuit illustrated in FIG. 20, the above-described transistor circuit may be used instead of the charge amplifiers 171 and 172. Further, in the case of the detection circuit shown in FIG. 25, the upper electrodes A2 and A4 may be connected to the above-described transistor circuit, and the monitor current flowing through this transistor circuit may be monitored by the microcomputer 188.

[0135]

As described above, according to the acceleration sensor according to the present invention, in the normal operation mode, power is supplied only to the monitoring sub-detecting element, and this sub-detecting element supplies an acceleration of a predetermined level or more. Since power is supplied to the main detection element that performs actual acceleration detection only when the acceleration is detected, an electronic acceleration sensor operable with low power consumption can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a conventional general electronic three-dimensional acceleration sensor.

FIG. 2 is a block diagram showing a basic configuration of an electronic three-dimensional acceleration sensor according to the present invention.

FIG. 3 is a conceptual diagram showing a detection axis direction by each main detection element and each sub detection element in an XYZ three-dimensional coordinate system.

FIG. 4 is a block diagram showing a basic configuration of an acceleration sensor using two sets of sub-detecting elements.

FIG. 5 is a block diagram showing a basic configuration of an embodiment in which a part of a plurality of main detection elements is also used as a sub-detection element and a part of a main power supply is also used as a sub-power supply.

FIG. 6 is a waveform diagram showing that the power supply from the sub power supply unit to the sub detection element is performed intermittently by using a pulse signal that alternately repeats a power supply state and a non-power supply state.

FIG. 7 is a perspective view of a main body of an acceleration sensor according to a basic embodiment using a piezoelectric element, as viewed obliquely from above.

FIG. 8 is a perspective view of the sensor main body shown in FIG. 7 as viewed obliquely from below.

FIG. 9 is a top view of the sensor body shown in FIG. 7;

FIG. 10 is a side sectional view of the sensor main body shown in FIG. 7 cut along an XZ plane.

FIG. 11 is a bottom view of the sensor main body shown in FIG. 7;

FIG. 12 is a side sectional view showing an example of polarization characteristics of a piezoelectric element.

FIG. 13 shows a force Fx applied to the sensor body shown in FIG. 7 in the X-axis direction.
FIG. 9 is a side cross-sectional view showing a bent state when (force based on acceleration in the X-axis direction) acts.

14 shows a force Fz in the Z-axis direction applied to the sensor main body shown in FIG. 7;
It is a side sectional view showing the state of bending when (force based on acceleration in the direction of the Z-axis) acts.

FIG. 15 is a table showing polarities of electric charges generated in each upper electrode when each of forces Fx, Fy, and Fz acts on the sensor main body having the electrode arrangement shown in FIG. 9;

FIG. 16 is a circuit diagram showing a detection circuit for performing acceleration detection using the sensor main body having the electrode arrangement shown in FIG.

17 is a circuit diagram showing a detection circuit for performing more practical acceleration detection using the sensor main body having the electrode arrangement shown in FIG.

FIG. 18 is a top view showing an acceleration sensor main body having two sets of sub-detecting elements.

FIG. 19 is a table showing the polarities of electric charges generated in each upper electrode when each of the forces Fx, Fy, Fz acts on the sensor main body having the electrode arrangement shown in FIG. 18;

20 is a circuit diagram showing a detection circuit for performing acceleration detection using the sensor main body having the electrode arrangement shown in FIG.

FIG. 21 is a top view showing another acceleration sensor main body having two sets of sub-detecting elements.

FIG. 22 is a table showing polarities of electric charges generated in each upper electrode when each of the forces Fx, Fy, Fz acts on the sensor main body having the electrode arrangement shown in FIG. 21;

FIG. 23 is a top view showing an acceleration sensor main unit using a piezoelectric element that partially serves as a main detection element and a sub detection element.

FIG. 24 is a table showing the polarities of electric charges generated in each upper electrode when each of the forces Fx, Fy, Fz acts on the sensor main body having the electrode arrangement shown in FIG. 23;

FIG. 25 is a circuit diagram showing a detection circuit to be applied to the acceleration sensor body shown in FIG.

FIG. 26 is a top view showing a main body of an acceleration sensor according to an embodiment using a piezoresistive element.

FIG. 27 is a side sectional view of the sensor main body shown in FIG. 26 cut along an XZ plane.

FIG. 28 is a circuit diagram showing a detection circuit to be applied to the acceleration sensor main body shown in FIG. 26;

FIG. 29 is a top view of a flexible substrate 310 constituting a main body of an acceleration sensor according to an embodiment using a capacitive element.

FIG. 30 is a bottom view of a fixed substrate 320 constituting a main body of the acceleration sensor according to the embodiment using the capacitive element.

FIG. 31 is a side sectional view of a main body of an acceleration sensor according to an embodiment using a capacitance element.

32 shows a force F in the X-axis direction applied to the sensor main body shown in FIG. 31.
It is a sectional side view which shows the bending state when x (force based on the acceleration of the X-axis direction) acts.

33 shows a force F in the Z-axis direction applied to the sensor main body shown in FIG. 31.
It is a side sectional view showing the state of bending when z (force based on acceleration in the Z-axis direction) acts.

FIG. 34 is a circuit diagram showing a detection circuit to be applied to the acceleration sensor main body shown in FIG. 31.

FIG. 35 is a top view showing an electrode arrangement of an acceleration sensor using a capacitance element that partially serves as a detection element and a sub detection element.

FIG. 36 is a circuit diagram showing a detection circuit to be applied to the acceleration sensor body shown in FIG. 35;

FIG. 37 is a circuit diagram showing a detection circuit that extracts a signal from a sub-detection element using a MOS transistor.

FIG. 38 is a circuit diagram showing a detection circuit that extracts a signal from a sub-detection element using a bipolar transistor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... X-axis direction main detection element 12 ... Y-axis direction main detection element 13 ... Z-axis direction main detection element 20, 25 ... main power supply means 30 ... support means 40 ... sub-detection element 41 ... 1st sub-detection element 42 .. Second sub-detecting elements 50, 55 sub-power supply means 60 control means 110 piezoelectric element 111 central part 112 flexible part 113 peripheral part 115 annular groove 118 local polarization processing is performed. Piezoelectric element 130 ... main detection element group 131-138 ... Q / V conversion circuit 141-143 ... calculator 150 ... sub-detection element 151 ... Q / V conversion circuit 160 ... main detection element group 161-163 ... charge amplifier 170 ... Sub-detection elements 171,172 Charge amplifier 175 Sub-detection element group 180,185,188 Microcomputer 181,182,183 Control switch 190 Main detection Output element group 191 to 195 Charge amplifier 196 to 198 Arithmetic unit 210 Single crystal semiconductor substrate 211 Central part 212 Flexible part 213 Peripheral part 215 Annular groove 221 to 223 Amplifier circuit 230 Microcomputer 310 Flexible substrate 320 Fixed substrate 330 Weight body 340 Sensor housing 350 Main detection element group 351-355, 352a, 354a C / V conversion circuit 356-358 Computing device 359 Main detection element group 360 ... Sub-detection element group 361, 362 C / V conversion circuit 370, 375 microcomputer 410 piezoelectric element 420, 430 microcomputer A, A1 to A11 upper electrode B lower electrode Brx, Bry, Brz bridge circuit C, C1 to C7 ... Capacitance elements Dm11, Dm12, Dm21, Dm22 ... Detection axis direction for monitor Dx, Dy, Dz: Detection axis direction of acceleration E: Power supply E0, E1 to E7: Electrode Ep: Pulse signal e: Power supply input terminal Fx: Force acting in the X-axis direction Fz: In the Z-axis direction Acting forces im, im1, im2: monitor current L: sampling period P: center of gravity R: resistive elements Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4: piezoresistive elements Rm1, Rm2: monitor piezoresistive elements Tc: control signal output terminal Te: power supply terminal Tm, Tm1, Tm2: terminal from which a detected value of a monitor acceleration component is obtained Toff: cutoff signal output terminal Tp, Tp1, Tp2: pulse signal supply terminal TR1: P-type MOS transistor TR2: N-type MOS transistor TR3: Bipolar transistor Tx, Ty, Tz: X-axis, Y-axis, and Z-axis components of acceleration Terminal at which a detected value of minute is obtained W: Pulse width of pulse signal W1, W2: Positioning axis X1, X2, X3, X4: Position on X axis αx: X-axis component of acceleration αy: Y-axis component of acceleration αz: Z-axis component of acceleration αm, αm1, αm2: Monitor acceleration component

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G01V 1/18 G01V 1/18

Claims (10)

[Claims] 1. A plurality of main detecting elements for detecting an acceleration component in a predetermined detection axis direction, main power supply means for supplying electric power to these main detecting elements, and detecting the plurality of main detecting elements respectively. Supporting means for supporting the axial direction different from each other, by supplying power from the main power supply means to each of the main detecting elements, a plurality of acceleration components in the detection axis direction In the acceleration sensor having the function of outputting as independent electric signals, a sub-detection element supported by the support means so as to be able to detect a predetermined acceleration component in the detection axis direction for monitoring, and the sub-detection element A sub-power supply unit that supplies power to the sub-detection element, such that the detected acceleration component is output as an electric signal. In a period during which the sensor is operating, at least during a period when the main power supply unit is not supplying power, control is performed to supply power, and the output of the sub-detection element is output to the main power supply unit. Control means for performing control so as to supply power only when the electric signal is equal to or higher than a predetermined threshold level. 2. The acceleration sensor according to claim 1, wherein a plurality of sets of the sub-detecting elements are supported by supporting means such that the respective monitoring detection axis directions are different from each other. Acceleration sensor. 3. The acceleration sensor according to claim 1, wherein a part of the plurality of main detection elements is also used as a sub-detection element, and a part of the main power supply is also used as a sub-power supply. An acceleration sensor characterized in that: 4. The acceleration sensor according to claim 1, wherein the power supply by the sub-power supply unit is performed intermittently by using a pulse signal having a predetermined sampling cycle. Acceleration sensor. 5. The acceleration sensor according to claim 1, wherein one of a central portion and a peripheral portion is fixed to a sensor housing, and a weight is formed on the other. The origin is defined at the center of the flexible substrate, and the main surface of the substrate is X.
A first detector for detecting a stress or a displacement of a positive portion of the X-axis of the substrate when the XYZ three-dimensional coordinate system is defined so as to be included in the Y plane; and a negative portion of the X-axis of the substrate. A second detector for detecting the stress or displacement of the substrate, and a third detector for detecting the stress or displacement of the positive portion of the substrate on the Y axis.
And a fourth detector for detecting a stress or a displacement of a negative portion of the substrate on the Y-axis. The X-axis direction is determined by the first detector and the second detector. Forming a main detection element having a detection axis direction, wherein the third detector and the fourth detector constitute a main detection element having a Y-axis direction as a detection axis direction; An acceleration sensor comprising an auxiliary detector for detecting a partial stress or displacement, and a sub-detection element constituted by the auxiliary detector. 6. The acceleration sensor according to claim 5, further comprising a detector for detecting a stress or displacement generated on the flexible substrate when a force in the Z-axis direction is applied to the weight body. An acceleration sensor comprising a main detection element having a detection axis direction in the Z-axis direction. 7. The acceleration sensor according to claim 1, wherein a substrate of a piezoelectric element configured to apply a stress by the action of acceleration is used as a supporting means, and the acceleration is generated at a predetermined portion of the piezoelectric element. An acceleration sensor comprising: an electrode for detecting an electric charge to be generated; and an electronic circuit for outputting the amount of electric charge detected by the electrode as an electric signal. 8. The acceleration sensor according to claim 1, wherein a single crystal substrate configured to apply a stress by the action of acceleration is used as a support means, and is provided at a predetermined position on the single crystal substrate. An acceleration sensor, wherein each detection element is constituted by the formed piezoresistive element and an electronic circuit that outputs a change in the resistance value of the piezoresistive element as an electric signal. 9. The acceleration sensor according to claim 1, wherein the flexible substrate is configured to be bent by the action of acceleration, and is disposed at a position facing the flexible substrate. A fixed substrate, comprising a supporting means, a displacement electrode disposed at a predetermined position on the flexible substrate,
A fixed electrode arranged at a predetermined position on the fixed substrate forms a capacitive element, and the capacitive element and an electronic circuit that outputs a change in the capacitance value of the capacitive element as an electrical signal, An acceleration sensor characterized by comprising. 10. The acceleration sensor according to claim 7, further comprising: a transistor that performs an ON / OFF operation based on a charge generated in a piezoelectric element that constitutes a sub-detection element, and supplies a current flowing through the transistor from the sub-detection element. An acceleration sensor, which is extracted as an electric signal.