JP2003066063A - Vibration sensor and manufacturing method of vibration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration sensor further easy in damping adjustment and precise with a small size. SOLUTION: This vibration sensor 1 comprises magnets 3 provided within a magnetic circuit 2 fixed to a measuring body, a movable part 4 provided between the magnets 3, and a detection part 5 for detecting the electromotive force generated by a coil 9 provided on the upper surface of the movable part 4, and it measures an acceleration or the like from the electromotive force generated by the coil 9. This sensor 1 further comprises a feedback circuit 6 for carrying a current to a coil 10 provided on the lower surface of the movable part on the basis of a detection value outputted from the detection part 5. The movable part 4 comprises a silicon board 8 inserted between two glass base plates 7, and the pressure within the gap between the glass base plates 7 and the silicon board 8 is adjustable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil type vibration sensor attached to an object to be measured in order to detect the vibration of the object to be measured, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, as a coil type speed detecting device, one exemplified in FIG. 5 has been known. The speed detecting device 20 is composed of a coil 22 movably supported by a leaf spring 21 and a magnetic circuit 23 that applies a magnetic field to the coil 22. The magnetic circuit 23 is composed of a permanent magnet and a magnetic body, and is arranged so that a magnetic field can be reasonably applied to the coil 22. In addition,
The coil 22 is configured by winding a conductive wire around a coil bobbin. When vibration is applied to the coil type velocity detecting device 20 from the object to be measured, the coil 22 as a conductor moves vertically in the static magnetic field in FIG. 5 while being restrained by the leaf spring 21. As a result, an electromotive force represented by V = vBL is induced in the coil 22. Where v
Is the moving speed of the coil 22, B is the magnetic flux density of the magnetic circuit 23, and L is the coil length of the coil 22. Then, the speed of the object to be measured is detected based on the induced electromotive force V induced in the coil 22 in the process of vibrating the object to be measured.

[0003]

However, the conventional coil type velocity detecting device 20 has a problem that it is large in size.

The present invention has been made in view of the above problems, and an object thereof is to provide a smaller vibration sensor.

[0005]

In order to solve the above-mentioned problems, a vibration sensor according to a first aspect of the present invention, for example, as shown in FIG. 1, detects a vibration of an object to be measured. A vibration sensor (1) mounted on a substrate (8) elastically supported so as to be freely displaced at least in the thickness direction in accordance with the vibration of the object to be measured, and a surface of the substrate (8). A detection coil (9) that is spirally patterned and a first magnetic field generating means (3) that applies a first magnetic field to the detection coil (9). It is characterized in that the vibration of the object to be measured is detected based on the induced electromotive force generated in 9).

Here, the first magnetic field generating means is not particularly limited as long as it generates a magnetic field,
For example, it can be configured by a magnetic circuit using a permanent magnet or a coil. Further, the vibration of the object to be measured mentioned here is equivalent to the displacement, speed, acceleration, jerk of the object to be measured.

According to the first aspect of the present invention, when the object to be measured vibrates, the detection coil is displaced in the first magnetic field accordingly. As a result, V =
An induced electromotive force V represented by vBl (V: induced electromotive force, v: speed of displacement of detection coil, B: strength of first magnetic field, l: length of conductor wire forming detection coil) is generated. To do.
Since the substrate is elastically supported, the velocity (v) at which the detection coil is displaced has a value according to the displacement, velocity, acceleration, jerk or the like of the object to be measured. Therefore, the vibration of the measured object can be detected based on the induced electromotive force V. Here, since the detection coil is spirally patterned on the surface of the substrate, the space occupied by the detection coil can be minimized while ensuring a sufficient coil length. That is, according to such arrangement of the detection coils, the coil bobbin, which is conventionally required, becomes unnecessary, and the vibration sensor as a whole can be made smaller by that much.

A second aspect of the present invention is the vibration sensor according to the first aspect, wherein, for example, as shown in FIG.
The magnetic field generating means (3) is characterized in that the magnetic flux is arranged so as to be directed in the radial direction or centripetal direction of the detection coil (9).

According to the second aspect of the present invention, since the magnetic flux of the first magnetic field applied to the detection coil is directed in the radial direction or centripetal direction of the detection coil, the direction of the magnetic flux and the displacement of the substrate. The direction (thickness direction) and the direction of the induced electromotive force generated in the spiral detection coil are substantially orthogonal to each other. Therefore, the induced electromotive force according to the displacement of the substrate can be efficiently obtained. As a result, the sensitivity or accuracy of measurement can be improved.

According to a third aspect of the invention, in the vibration sensor according to the first or second aspect, the detection coil (9) is
The braking coil (10) is provided on one surface of the substrate (8) and is spirally patterned on the other surface of the substrate (8). The second magnetic field generating means (3) for applying a second magnetic field to (10) and a current according to the magnitude of the induced electromotive force are supplied to the braking coil (10), whereby the substrate (8) Control means (12) for reducing the inertial force of (1) by the force generated by the braking coil (10) in the second magnetic field.

According to the third aspect of the present invention, the control means causes the current according to the magnitude of the induced electromotive force generated in the detection coil to flow in the braking coil. As a result, F = iBl (F: force,) is applied to the braking coil arranged in the second magnetic field.
A force (F) represented by i: magnitude of current, B: strength of second magnetic field, l: length of lead wire forming the braking coil is generated. This force reduces the inertial force of the substrate. As a result, the displacement of the substrate can be minimized regardless of the vibration intensity of the object to be measured, so that the detectable measurement band (dynamic range) can be expanded. Also, since the braking coil is spirally patterned, the coil length can be increased,
The force F generated when a current is passed through the braking coil can be efficiently obtained.

According to a fourth aspect of the invention, in the vibration sensor according to the third aspect, the second magnetic field generating means (3) is
The magnetic flux is arranged so as to be directed in the radial direction or centripetal direction of the braking coil (10).

According to the invention of claim 4, since the magnetic flux of the second magnetic field applied to the braking coil is directed in the radial direction or centripetal direction of the braking coil, the direction of the magnetic flux and the spiral shape The direction of the current passed through the braking coil and the direction of the current are substantially orthogonal to each other. Therefore, it is possible to efficiently obtain the destructive force in the direction perpendicular to these, that is, in the thickness direction of the substrate.

According to a fifth aspect of the present invention, in the vibration sensor according to the third or fourth aspect, the substrate (8) is separated by two magnetically permeable substrates (7, 7) arranged substantially in parallel therewith. The first magnetic field is applied to the detection coil (9) via one of the magnetically permeable substrates, and the braking coil (10) is provided via the other. ) Is applied with the second magnetic field.

According to the fifth aspect of the invention, the first magnetic field is applied to the detection coil via one of the two magnetically permeable substrates, and the second magnetic field is applied to the braking coil via the other. Since it is configured as described above, the arrangement structure for realizing the function of the sensor is further rationalized, and thus the vibration sensor can be further downsized.

The invention according to claim 6 is the method for manufacturing a vibration sensor according to claim 3, comprising the steps of forming the detection coil by micromachining, and forming the braking coil by micromachining. And are included.

According to the sixth aspect of the invention, since the detection coil and the braking coil are patterned in a spiral shape by micromachining, the respective coils can be made extremely small and they are constituted. The density of the conductor wire can be increased. Thereby, the vibration sensor can be further downsized.

The invention according to claim 7 is the method for manufacturing a vibration sensor according to claim 5, wherein the substrate (8) and the substrate (2) are provided.
A first step of adjusting the internal pressure to a predetermined value while maintaining airtightness between the two magnetically permeable substrates (7, 7), and then hermetically sealing the substrate using the two magnetically permeable substrates. And a second step of performing.

According to the invention described in claim 7, the damping applied to the substrate is set by setting the internal pressure of the gas surrounding the substrate to be hermetically sealed by using the two magnetically permeable substrates to a predetermined value. You will be able to adjust it freely. Therefore, it is possible to easily realize a vibration sensor that matches the frequency band of the vibration of the measured object. Therefore, for example, a large damping can be easily applied to the movable electrode plate, and when it is used as an accelerometer, it is possible to easily create a wide frequency characteristic of a flat band.

According to an eighth aspect of the present invention, in the method of manufacturing a vibration sensor according to the seventh aspect, the substrate (8) is made of silicon, and the two magnetically permeable substrates (7, 7) are both made of glass. In the second step, the silicon substrate (8) and the glass substrates (7, 7) are anodically bonded.

According to the eighth aspect of the invention, the silicon substrate and the two glass substrates are anodically bonded. Therefore, the internal pressure surrounding the silicon substrate can be easily adjusted by adjusting the pressure during the anodic bonding. It becomes possible to set it to a predetermined value.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram schematically showing a configuration of a vibration sensor according to an embodiment. As shown in the figure, the main part of the vibration sensor 1 is covered with a magnetic circuit 2.

The magnetic circuit 2 comprises magnets 3 and 3. The magnets 3 are arranged so as to be opposed to each other. One magnet 3 (the magnet 3 arranged above in FIG. 1) constitutes a first magnetic field generating means, and the other magnet 3 (the magnet 3 arranged below in FIG. 1)
The second magnetic field generating means is constituted by. A plate-like movable portion (substrate) 4 arranged in the center between the magnets 3 and 3 and a glass substrate (transparent member) sandwiching the movable portion 4 from both sides with a gap (gap) secured. Magnetic substrates) 7 and 7 are arranged. The movable portion 4 is composed of the silicon substrate 8, and
The gap between the glass substrate 7 and the glass substrate 7 is formed by etching the silicon substrate 8.
By adjusting the etching depth, the gap distance can be easily adjusted.

The silicon substrate 8 is arranged between the two parallel glass substrates 7 and 7 in parallel with the glass substrates 7 and 7. A top view and a bottom view of the silicon substrate 8 are shown in FIGS. 3 (a) and 3 (b), respectively. As shown in the figure, the spiral detection coil 9 as shown in FIG. 3A is provided on one surface (upper surface) of the silicon substrate 8, and the other surface (lower surface) is provided with a drawing coil. A spiral feedback coil (braking coil) 10 as shown in FIG. 3 (b) is provided. Each of the coils 9 and 10 is formed by spirally patterning with high density by micromachining.

The magnets 3 and 3 described above are arranged so that the same poles face each other as shown in FIG. 2 (a) or 2 (b). When the N poles are arranged so as to face each other as shown in FIG. 2A, the magnetic flux of the magnet 7 arranged in the upper portion is directed in the radiation direction of the detection coil 9 and the magnet 7 arranged in the lower portion is The magnetic flux also goes in the radial direction of the braking coil 10. On the other hand, when the S poles are arranged so as to face each other as shown in FIG. 2B, the magnetic flux of the magnet 7 arranged in the upper portion is directed in the centripetal direction of the detection coil 9, and
Similarly, the magnetic flux of the magnet 7 arranged in the lower portion is also the braking coil 1
Head toward 0 centripetal direction.

Further, as shown in FIGS. 3 (a) and 3 (b), spring portions 11, 11, ... Are provided tangentially at appropriate positions on the periphery of the silicon substrate 8 which is circular in plan view. As a result, it is possible to prevent the silicon substrate 8 from resonating due to the shape itself. The spring portion 11 is made of silicon and is integrally formed with the silicon substrate 8 by etching. The silicon substrate 8 is elastically supported by the spring portion 11. Thereby, the silicon substrate 8 is freely displaced in the thickness direction (vertical direction in FIG. 1) or its posture is freely displaced due to the vibration of the measured object. The silicon substrate 8 and the two glass substrates 7, 7 are joined at their side edges by anodic bonding, and between the silicon substrate 8 and the glass substrate 7,
The air is sealed. The pressure of the sealed air can be easily adjusted to any pressure by adjusting the pressure when performing anodic bonding.

The detecting section 5 is electrically connected to the detecting coil 9 so that the induced electromotive force generated by the detecting coil 9 can be detected. Further, the feedback circuit 6 is electrically connected to the feedback coil 10, and the feedback circuit 6 and the feedback coil 10 constitute a feedback control unit (control means) 12. The feedback control unit 12 supplies a current required for returning the movable unit 4 to the original position to the feedback coil 10 by the feedback circuit 6 according to the induced electromotive force detected by the detection unit 5.

Next, a method of measuring dynamic characteristics using the vibration sensor of this embodiment will be described. First, the above-mentioned vibration sensor 1 is attached to a measured object (not shown). When, for example, an acceleration is applied to the object to be measured and the object to be measured moves, the movable part 4 (silicon substrate 8) also moves accordingly, whereby the movable part 4 is moved.
The detection coil 9 on the (silicon substrate 8) also moves vertically between the glass substrates 7, 7. When the detection coil 9 moves, V = vBl (V: output voltage, because the detection coil 9 is in the magnetic field generated by the magnet 3 arranged above).
v: velocity, B: magnetic field strength, l: conducting wire length) to generate an induced electromotive force. The induced electromotive force is detected by the detection unit 5, and the acceleration of the measured object is obtained from the detected value.

Further, when the detection electromotive force is detected by the detection unit 5, the feedback circuit 6 supplies a current to the feedback coil 10. Feedback coil 10
When a current is applied to the feedback coil 10, the feedback coil 10 is in the magnetic field of the magnet 3 arranged below, so that F = iBl (F:
Force, i current, B: magnetic field strength, l: conductor length). Therefore, the movable part 4 is returned to its original position by passing an electric current so that the feedback coil 10 moves in a direction opposite to the direction in which the movable part 4 (silicon substrate 8) moves due to the acceleration of the object to be measured. Is able to. At this time, the direction of the current passed through the feedback coil 10 is determined by the direction in which the movable portion 4 (silicon substrate 8) moves. The amount of current flowing through the feedback coil 10 is determined by the amount of movement of the silicon substrate 8 (movable part 4), the strength of the magnet 3, and the length of the feedback coil 10. Acceleration can also be obtained by measuring the amount of current passed through by an ammeter (not shown).

In the vibration sensor 1 thus constructed, the movable portion 4 can be arbitrarily damped by adjusting the pressure at the time of anodic bonding between the glass substrates 7, 7 and the silicon substrate 8. Further, when etching the silicon substrate 8, the gap interval can be adjusted by adjusting the depth thereof. If the gap distance is narrowed and the pressure in the gap is increased, damping tends to occur due to the squeeze film phenomenon. If the damping force is increased to increase the braking force, the vibration sensor can be used as an accelerometer with a wide band, and damping is applied at the boundary (critical damping) between a place that moves largely without braking force and a place that becomes difficult to move due to braking force. When adjusted, it can be a jerk or speedometer. As shown in FIG. 4, the jerk, the accelerometer, and the speedometer have a jerk at a position lower than the natural frequency f ₀ of the detection coil 9, and an accelerometer and a natural frequency near the natural frequency f _0. f ₀
It is designed to be a speedometer at higher places. It should be noted that the measurement of jerk or velocity by the jerk and the speedometer is the same as the case of measuring the above-mentioned acceleration.

As described above, the vibration sensor 1 of the present embodiment
According to this, since the detection coil 9 is spirally patterned on the surface of the silicon substrate 8, the space occupied by the detection coil 9 can be minimized while ensuring a sufficient coil length. it can. That is, according to the arrangement of the detection coil 9 as described above, the coil bobbin which is conventionally required is not necessary, and the vibration sensor 1 as a whole can be made smaller by that amount. In addition, the feedback circuit 6 is provided, and a current is passed through the feedback coil 10 provided on the lower surface of the silicon substrate 8 (movable portion 4) based on the detection value output from the detection unit 5, so that the feedback coil 10 is provided. A force is applied, and the moved movable portion 4 (silicon substrate 8) can be returned to its original position. As a result, the displacement of the movable portion 4 can be suppressed to a minimum regardless of the strength of vibration of the object to be measured, so that the dynamic range can be widened. Further, the restoring force (the force for returning the movable portion 4 to the original position) by the feedback coil 10 is generated even when the movable portion 4 is largely moved due to the impact or the like applied to the vibration sensor 1. Can be increased. Furthermore, the feedback coil 1
Since the acceleration (jerk, velocity) can be measured also from the amount of current flowing to zero, the dynamic characteristics can be measured with high accuracy without being affected by unevenness in manufacturing when the vibration sensor 1 is manufactured.

The glass substrates 7 and 7 and the silicon substrate 8 are anodically bonded to each other so that the movable portion 4 is hermetically sealed, and the internal pressure can be adjusted by adjusting the pressure at the time of bonding, thereby facilitating damping. Therefore, the vibration sensor 1 can be used not only as a wide band accelerometer but also as a jerk or a speedometer. Also,
By disposing the movable portion 4 between the magnets 3 and 3, the arrangement structure of these is rationalized, so that the size of the vibration sensor 1 can be reduced.

By forming the movable portion 4 by micromachining, the movable portion 4 of the vibration sensor 1 can be minimized and a plurality of movable portions 4 can be collectively formed. Therefore, a large number of movable parts 4 having a constant quality can be produced, and the cost can be reduced. Also, the silicon substrate 8
When the feedback coil 10 is formed on the coil 10, the coil 10 is spirally patterned, so that the coil length can be increased.
Since the force acting on can be increased, the silicon substrate 8 (movable part 4) can be easily returned to its original position. In addition, the gap distance can be precisely adjusted by adjusting the etching depth.

Although the movable portion is circular in the above embodiments, the invention is not limited to this.
For example, it may be a quadrangle or the like. Further, in the present embodiment, the description has been given using the vibration sensor including the feedback control unit, but the coil formed in the movable unit is
A vibration sensor may be provided (only the detection coil), and the feedback sensor may not be provided. The shape and the like of the magnetic circuit 2 are arbitrary, and it is needless to say that the specific detailed structure and the like can be appropriately changed.

[0035]

According to the present invention, since the coil for detection is formed by spirally patterning on the surface of the substrate, the coil bobbin is unnecessary, and a smaller vibration sensor is provided accordingly. Further, according to the present invention, a movable portion that moves in association with the movement of the measured object is provided in the magnetic field portion, and the detection coil is provided in the movable portion, so that the movable portion moves together with the movement of the measured object. The detection coil moves, and the detection coil is V
= VB1 (V: output voltage, v: speed, B: magnetic field strength,
l: length of conducting wire). Therefore, by detecting this electromotive force by the detection unit,
It is possible to measure velocity, acceleration, and jerk based on the change in position of the measured object.

Further, according to the present invention, since the electromotive force detected by the detection unit is included in the feedback control unit for returning the position of the movable unit to the original position, the dynamic range can be expanded and the band can be extended. Become. In addition, this restoring force (a force that returns the position of the movable portion to the original position) makes the vibration sensor stronger against impacts and the like, so that the usable range can be expanded.

Further, according to the present invention, the feedback control section is provided with the feedback coil formed in the movable section, and a current is caused to flow through the feedback coil in accordance with the electromotive force detected by the detection section. F = iBl on the conductor forming the feedback coil in
A force that can be expressed by (F: force, i: current, B: strength of magnetic field, l: length of conducting wire) acts. Therefore, since the feedback coil moves by this force F and returns the movable part to the original position, even if a shock or the like is applied to the vibration sensor, the movable part returns to the original position and the vibration sensor receives the shock. Become stronger. Further, since the dynamic characteristics can be measured not only from the electromotive force generated by the detection coil but also by measuring the current flowing in the feedback coil, accurate measurement can be performed. Also, by spirally patterning the feedback coil, the coil length can be increased and the force acting on the feedback coil can be increased, so that the movable part can be easily returned to its original position. You can

Further, according to the present invention, the movable portion is formed of the silicon substrate movable in the glass substrate direction, and the coils are formed on both surfaces of the silicon substrate. The coil of the part (silicon substrate) moves. As a result, one of the detection coils generates an electromotive force, and the jerk, acceleration, or velocity can be measured from this electromotive force. Further, by feeding a current to the other feedback coil, it is possible to perform feedback control for returning the moving movable part to the original position.

Further, according to the present invention, since the movable portion is formed by micromachining, the movable portion can be minimized, and a plurality of movable portions can be collectively formed. Therefore, it is possible to produce a large number of movable parts having a constant quality and keep the cost low. Furthermore, by adjusting the etching depth of the silicon substrate, the gap distance can be adjusted precisely.

Further, according to the present invention, the movable portion and the capacitor portion are completely sealed by anodic bonding the glass substrate and the silicon substrate. Further, by adjusting the pressure in the gap between the glass substrate and the silicon substrate, damping can be easily applied and the pressure can be adjusted freely. Therefore, large damping can be applied easily, and it can be used as an accelerometer.
It can also be used as a jerk or speedometer.

[Brief description of drawings]

FIG. 1 is a schematic side view of a vibration sensor as an example to which the present invention is applied.

FIG. 2 is a schematic side view of a magnet portion showing an arrangement pattern of magnets of the vibration sensor in FIG.

FIG. 3 is a diagram showing a surface of a silicon substrate, which is (a).
Is a top view of the silicon substrate, and (b) is a bottom view of the silicon substrate.

FIG. 4 is a graph showing a measurement target according to a band of the vibration sensor in FIG.

FIG. 5 is a schematic cross-sectional view showing a speed detection device as an example of a conventional technique.

[Explanation of symbols]

1 Vibration sensor 2 magnetic circuit 3 magnets (first magnetic field generating means) 3 magnets (second magnetic field generating means) 4 moving parts 5 Detector 7 Glass substrate (magnetically permeable substrate) 8 Silicon substrate (substrate) 9 Detection coil 10 Braking coil 12 Feedback control unit (control means)

Claims (8)

[Claims] 1. A vibration sensor attached to an object to be measured for detecting the vibration of the object to be measured, the sensor being elastic so as to be freely displaced at least in a thickness direction with the vibration of the object to be measured. A substrate supported, a coil for detection spirally patterned on the surface of the substrate, and a first magnetic field generating means for applying a first magnetic field to the coil for detection, A vibration sensor configured to detect vibration of the object to be measured based on an induced electromotive force generated in a coil. 2. The vibration sensor according to claim 1, wherein the first magnetic field generating means is arranged such that the magnetic flux is directed in a radiation direction or a centripetal direction of the detection coil. 3. The detecting coil is provided on one surface of the substrate, and the braking coil spirally patterned is provided on the other surface of the substrate. A second magnetic field generating means for applying a second magnetic field to the coil, and an electric current corresponding to the magnitude of the induced electromotive force are supplied to the braking coil, whereby the inertial force of the substrate is reduced to the braking coil. 3. The vibration sensor according to claim 1 or 2, further comprising: a control unit that performs control to reduce the force with a force generated in the second magnetic field. 4. The vibration sensor according to claim 3, wherein the second magnetic field generating means is arranged such that the magnetic flux is directed in a radial direction or a centripetal direction of the braking coil. 5. The substrate is arranged in parallel with the substrate 2.
It is sandwiched by two magnetically permeable substrates from both sides in a state where a gap is secured, the first magnetic field is applied to the detection coil through one of the magnetically permeable substrates, and the braking is performed through the other. The vibration sensor according to claim 3 or 4, wherein the second magnetic field is applied to the coil for use. 6. The method for manufacturing a vibration sensor according to claim 3, further comprising: a step of forming the detection coil by micromachining; and a step of forming the braking coil by micromachining. And a method of manufacturing a vibration sensor. 7. The method for manufacturing a vibration sensor according to claim 5, further comprising a first step of adjusting the internal pressure to a predetermined value while maintaining airtightness between the substrate and the two magnetically permeable substrates. Then, a second step of hermetically sealing the substrate using the two magnetically permeable substrates is included. 8. The substrate is made of silicon, and the two magnetically permeable substrates are both made of glass. In the second step, the silicon substrate and each glass substrate are anodically bonded. The method for manufacturing a vibration sensor according to claim 7.