JP2964062B2 - Small position change detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to paper and sheet thickness,
The present invention relates to a minute position change detector that detects minute displacement of an object on the order of microns, such as the thickness of printing ink printed on paper or a sheet, or the vibration of the skin in response to the heartbeat.

[0002]

2. Description of the Related Art A Hall element utilizing the Hall effect of a semiconductor material such as InSb changes its output depending on the strength of a magnetic field line penetrating in the thickness direction of the Hall element material. is there. To measure a change in the position of an object using the Hall element, as shown in FIG. 9, a Hall element 301 is mounted on a substrate 300, while a magnet 303 mounted on an object 305 is mounted.
Is installed vertically downward with respect to the surface of the Hall element 301.

When the object to be measured 305 is displaced in the direction of arrow a with respect to the substrate 300, the number of lines of magnetic force passing through the Hall element 301 in the film thickness direction changes, and the Hall element 30 is displaced.
1 changes, whereby the displacement of the measured object 305 can be detected.

[0004] In this conventional example, there is an advantage that the magnet 303 can be installed directly below the Hall element 301, and the interval between the magnets 303 can be made relatively large, so that the degree of freedom in design is large.

However, this type of Hall element 301
The output voltage per magnetic field line itself is small, and since the magnetic field lines enter the Hall element 301 almost perpendicularly, the number of magnetic field lines penetrating the Hall element 301 does not change much if the magnet 303 is displaced by a small amount. Therefore, the output change is small. For this reason, even if the amplification degree of the detection circuit connected to the Hall element 301 is increased, noise is also amplified and the S / N ratio is poor.

Another method for detecting a change in the position of an object is to use a ferromagnetic magnetoresistive element. The ferromagnetic magnetoresistive element changes its resistance value according to a change in a magnetic field in a plane direction of a film of the ferromagnetic magnetoresistive element material. To measure a change in the position of an object using this ferromagnetic magnetoresistive element, as shown in FIG. 10, a magnetoresistive element 40 having a ferromagnetic magnetoresistive element pattern formed on its surface is used.
1 is mounted on the substrate 400, while the magnet 403 mounted on the device under test 405 is installed such that the lines of magnetic force enter the surface of the magnetoresistive element 401 almost horizontally.

When the object 405 is displaced in the direction of arrow b with respect to the substrate 400, the direction and strength of the magnetic field in the plane direction of the ferromagnetic resistance element pattern film of the magnetoresistance element 401 change. With this, the displacement of the measured object 405 can be detected.

This conventional example has an advantage that the sensitivity (resistance change) per unit magnetic field is large. However, since the magnet 403 must be displaced to a position other than directly below the magnetoresistive element 401, it is not only difficult to determine the position, but also the position of the magnet 403 is in the left-right direction (the direction of arrow c shown in FIG. ) Or a slight shift in the depth direction from the front of the paper greatly changes the strength and direction of the magnetic field with respect to the magnetoresistive element 401, so that the desired output cannot be obtained.

The present invention has been made in view of the above points, and has as its object to take advantage of the characteristics of a ferromagnetic magnetoresistive element, that is, the effect that the rate of change of resistance per magnetic field is large.
Provided is a minute position change amount detector capable of detecting a position change amount as a good signal with a large S / N ratio, easily setting a position of each component, and obtaining a sufficient output even if the position is slightly shifted. It is in.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a magnet attached to an object to be displaced, and a magnetoresistive element whose resistance value changes according to the direction and strength of a magnetic field generated by the magnet. When, in the above micro position change amount detector comprising a detection circuit for detecting a change in the resistance of the magnetoresistive element, at a predetermined distance from a straight line magnet connecting the substantially poles of the magnet For a straight line connecting both poles
A soft magnetic material serving as a magnetic path having a shape extending in a substantially perpendicular plane direction, and a magnetoresistive element provided on each of the left and right sides of the soft magnetic body in the plane direction . On the face of the body
Bending lines of magnetic force that are almost perpendicular to the surface of the soft magnetic material
This makes the lines of magnetic force almost parallel to the surfaces of both magnetoresistive elements, respectively.
It was configured to be incident. Further, in the present invention, a soft magnetic material serving as a second magnetic path is disposed further left and right outside of the magnetoresistive elements disposed on both left and right sides of the soft magnetic material.

[0011]

With the construction described above, the lines of magnetic force of the magnet are attracted to the central soft magnetic material, and most of the attracted lines of magnetic light enter the magnetoresistive elements arranged on the left and right thereof almost in parallel. That is, the lines of magnetic force can be effectively made substantially parallel to the magnetoresistive element. Moreover, since the magnetic force lines are induced to be attracted to the soft magnetic material,
Even if the position of the magnet is slightly shifted, the line of magnetic force is reliably guided to the magnetoresistive element. When a soft magnetic material serving as the second magnetic path is provided, the magnetic force lines drawn to the central soft magnetic material are
The magnetic force is forcibly guided in the direction of the left and right soft magnetic bodies, whereby a larger number of lines of magnetic force can be collected in the magnetoresistive element located therebetween.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration side view of a minute position change amount detector according to a first embodiment of the present invention. As shown in the drawing, this minute position change amount detector attaches a magnet 15 to a displaceable object 11, and also on a substrate 17 disposed at a predetermined distance from the magnet 15 and directly above the magnet 15. A soft magnetic body 19 serving as a magnetic path is mounted at a position, and magnetoresistive elements 21 and 23 are mounted on substrates 17 on both left and right sides of the soft magnetic body 19, respectively. Hereinafter, each component will be described.

The magnet 15 is a permanent magnet, and is mounted such that its NS poles are perpendicular to the object 11.

FIG. 2 is a plan view of the substrate 17. As shown in FIG. 1 and FIG. 1, the soft magnetic body 19 mounted on the substrate 17 is a rectangular flat plate, and the width L2 thereof is smaller than the width L1 of the magnet 15 as shown in FIG. Is configured. The thickness of the soft magnetic body 19 is formed to be slightly larger than the thickness of the magnetoresistive elements 21 and 23.

Next, the magneto-resistive element 21 is formed on the glass substrate 25 so that the zig-zag directions of the two zig-zag magneto-resistive element patterns 29 and 31 are orthogonal to each other. , 31 are connected in series. Then, from both ends and the midpoint of the two magnetoresistive element patterns 29, 31, terminals 33, 3 are respectively provided.
5 and 37 are taken out to constitute a half bridge circuit.

Next, the magnetoresistive element 23 is similarly formed on the glass substrate 27 so that the zigzag directions of the two zigzag magnetoresistive element patterns 39 and 41 are orthogonal to each other, and are connected in series. Further, terminals 43, 45, 47 are taken out from both ends and a middle point of the two magnetoresistive element patterns 39, 41, respectively, to constitute a half bridge circuit.

Here, the two magnetoresistive element patterns 29, 31 of the magnetoresistive element 21 and the two magnetoresistive element patterns 39, 41 of the magnetoresistive element 23 are formed not to be line-symmetric but to be point-symmetric. Have been.

Since the minute position change amount detector is constructed as described above, as shown in FIG. 1, the magnetic lines of force of the magnet 15 are attracted to the soft magnetic body 19, and most of the attracted magnetic lines of force are arranged on the left and right sides. The light enters the magnetoresistive elements 21 and 23 almost in parallel.

That is, as shown in FIG.
The lines of magnetic force can be effectively incident substantially parallel to the magnetoresistive elements 21 and 23 without displacing the magnetoresistive element 3 at a position other than immediately below the magnetoresistive element 401.

Further, since the lines of magnetic force are induced to be attracted to the soft magnetic body 19, even if the position of the magnet 15 is slightly shifted, the lines of magnetic force are surely guided to the magnetoresistive elements 21 and 23.

In particular, if the width L2 of the soft magnetic body 19 is made narrower than the width L1 of the magnet 15 as in this embodiment, the lines of magnetic force emitted from the magnet 15 and about to spread are applied to the soft magnetic body 19. Since the magnetic flux can be guided to be collected, a larger number of lines of magnetic force can be guided to the magnetoresistive elements 21 and 23, which is effective.

Here, the magnetoresistive element patterns 29, 3
The zigzag direction of 1 is orthogonal to the magnetoresistive element 21.
By making the angles of incidence of the lines of magnetic force incident almost parallel to the surface on the horizontal plane on the two magnetoresistive element patterns 29, 31 different, the two magnetoresistive element patterns 29, 31 are different.
Differentiate the value of each resistance value and the rate of change of that value,
This is because a change in the line of magnetic force is extracted as a change in the output potential from the midpoint terminal 35. The same applies to the magnetoresistive element patterns 39 and 41.

FIG. 3 is a diagram showing a signal detection circuit of the above-mentioned minute position change amount detector. As shown in the figure, one terminal 33, 43 of the two magnetoresistive elements 21, 23 is connected to the power supply voltage Vcc, and the other terminals 37, 47 are connected to ground. Then, the central terminals 35 and 45 are pulled out and connected to RC circuits 49 and 51 for taking out an AC component, and these are connected to a differential amplifier 53. 57 and 59 are bias circuits.

Then, for example, the magnet 15 shown in FIG.
When the number and direction of the lines of magnetic force incident on 3 change by a small amount,
The resistance value r of the magnetic resistor patterns 29 and 31
1, r2 and the resistance values r3, r4 of the magnetoresistive element patterns 39, 41 are changed, and the AC components are extracted by the RC circuits 49, 51, respectively. It is amplified and output.

In the embodiment shown in FIGS. 1 and 2, the magnetoresistive elements 21 and
One of the reasons for disposing the magnet 23 is that the magnet 15 is not always displaced in a direction perpendicular to the surface of the substrate 17 on which the magnetoresistive elements 21 and 23 are attached. That is, when the magnet 15 makes an irregular displacement, as shown in FIG.
There is a case where a magnetic field is hardly applied to one magnetoresistive element 21. Therefore, in the present invention, the soft magnetic material 1
9, the magnetoresistive elements 21 and 23 are arranged on both sides so that at least one of the magnetoresistive elements 23 can reliably detect a change in the magnetic field.

Further, as shown in FIG.
Magnetoresistive element patterns 29 and 31 and the magnetoresistive element 2
3 are formed point-symmetrically with the magnetoresistive element patterns 39 and 41 because the midpoint terminals 35 and
This is for inverting the output signal output from 45. That is, by inverting the output signals output from the midpoint terminals 35 and 45, the differential amplification of the detection circuit shown in FIG. 3 becomes effective. If you do not reverse the output signal,
Since the outputs of the midpoint terminals 35 and 45 have substantially the same phase signal waveforms, no change in the output can be obtained.

Next, FIG. 4 is a schematic side view of the configuration of a minute position change amount detector according to a second embodiment of the present invention. FIG.
Is a plan view of the substrate 17. In this embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

This embodiment differs from the first embodiment in that the left and right outer sides of the magnetoresistive elements 21 and 23 disposed on the left and right sides of the soft magnetic body 19 disposed directly above the magnet 15, respectively. A soft magnetic body 61 serving as a second magnetic path,
63 is provided.

With this configuration, the magnetic lines of force attracted to the central soft magnetic body 19 can be transferred to the soft magnetic bodies 61 and 63.
This is forcibly guided in the direction, so that a larger number of lines of magnetic force are collected in the magnetoresistive elements 21 and 23 located therebetween. With this configuration, higher detection sensitivity can be realized as compared with the first embodiment.

In this embodiment, the thickness of the central soft magnetic body 19 is larger than the thickness of the left and right soft magnetic bodies 61 and 63. This is because the lines of magnetic force of the magnet 15 are strongly attracted to the central soft magnetic body 19 so that the lines of magnetic force are not directly attracted to the left and right soft magnetic bodies 61 and 63.

Next, FIG. 6 is a schematic side view showing a paper thickness detector constituted by using the minute position change amount detector according to the second embodiment. As shown in the drawing, this paper thickness detector has a support base 67 fixed in a substantially U-shaped frame 65, an arm 69 pivotally supported on the upper end thereof, and a detection end is detected at the tip of the arm 69. The head 71 is attached. A roller 73 is attached to a lower end of the detection head 71, and a magnet 15 is attached to an upper end thereof.

The soft magnetic body 19, the magnetoresistive elements 21 and 23, and the soft magnetic bodies 61 and 63 according to the second embodiment are mounted just above the magnet 15 at the upper end of the frame 65.

When a paper 75 of, for example, 100 μm is inserted under the roller 73, the detection head 71 is pushed up, and the magnet 15 mounted on the detection head 71 is displaced by a very small amount.
The magnetic field around the magnetoresistive elements 21 and 23 changes, and the paper thickness is detected from the change in the resistance value.

Roller 73 attached to detection head 71
Is for making the paper 75 move smoothly.
For example, when the insertion speed of the paper 75 is low, a contact needle type head that does not use the roller 73 may be used.

In the same manner as the paper thickness detector, the thickness (about 10 μm) of the ink printed on paper or sheet can be detected.

Next, FIG. 7 is a schematic sectional side view showing a heart beat detector constituted by using the minute position change amount detector according to the second embodiment. As shown in the figure, this beat detector has a movable film 79 attached to the lower surface of a substantially cylindrical body 77, a magnet 15 is attached to the center of the movable film 79, and a support provided on the inner peripheral surface of the body 77. The substrate 17 is mounted on the portion 81, and the soft magnetic body 19 and the magnetoresistive elements 21 and 21 according to the second embodiment are provided at the center of the substrate 17 and directly above the magnet 15.
3 and soft magnetic bodies 61 and 63 are attached.

When the movable membrane 79 is brought into contact with the skin near the heart, the movable membrane 79 and the magnet 15 vibrate in response to the heartbeat, and the magnetoresistive elements 21 and
The magnetic field around 23 changes and the change is detected. The pulse can be detected even in a place where an artery such as a wrist is near the skin. FIG. 8 is a waveform diagram of a beat detected by the beat detector.

FIG. 12 is a plan view of a substrate 17 according to still another embodiment of the present invention. As shown in the figure,
The magnetoresistive elements 2 are provided on both left and right sides of the soft magnetic body 19 in the X-axis direction.
In addition to the arrangement of the magnetoresistive elements 1 and 23, the magnetoresistive elements 83 and 85 may be arranged on both left and right sides in the Y-axis direction. With this configuration, even if the magnet 15 is tilted in any direction of the X and Y axes, any one of the magnetoresistive elements 21, 23, 83, and 85 can reliably detect displacement.

[0039]

As described in detail above, the minute position change amount detector according to the present invention has the following excellent effects. Since the characteristic of the ferromagnetic magnetoresistive element that the rate of change of resistance per magnetic field is large is used, the amount of position change is S /
The N ratio is large and can be detected as a good signal.

Since the soft magnetic material serving as a magnetic path is provided on a straight line connecting substantially both poles of the magnet, it is sufficient to simply dispose the magnet substantially immediately below or directly above the soft magnetic material. Arrangement can be simplified, the position of each component can be easily set, and sufficient output can be obtained even if the position is slightly displaced. This makes it easy to design and manufacture various devices using this minute position change amount detector. .

Since the change in the strength of the magnetic field can be detected, the displacement of the magnet corresponds to the output signal, the output waveform can be used, and the electrocardiogram waveform analysis and printed figure analysis can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration side view of a minute position change amount detector according to a first embodiment of the present invention.

FIG. 2 is a plan view of a substrate 17 of the first embodiment.

FIG. 3 is a diagram illustrating a signal detection circuit of a minute position change amount detector.

FIG. 4 is a schematic configuration side view of a minute position change amount detector according to a second embodiment of the present invention.

FIG. 5 is a plan view of a substrate 17 according to a second embodiment.

FIG. 6 is a schematic side view showing a paper thickness detector configured using the minute position change amount detector according to the second embodiment.

FIG. 7 is a schematic side sectional view showing a heart beat detector configured using the minute position change amount detector according to the second embodiment.

FIG. 8 is a waveform diagram of a beat detected by a beat detector.

FIG. 9 is a diagram illustrating a method of detecting a change in the position of an object using the Hall element 301.

FIG. 10 is a diagram illustrating a method of detecting a change in the position of an object using the ferromagnetic magnetoresistive element 401.

FIG. 11 is a diagram showing a case where the magnet 15 has been irregularly displaced.

FIG. 12 is a plan view of a substrate 17 according to another embodiment.

[Description of Signs] 11 Object to be displaced 15 Magnet 17 Substrate 19, 61, 63 Soft magnetic material 21, 23, 83, 85 Magnetoresistance element 25, 27 Glass substrate 29, 31, 39, 41 Magnetoresistance element pattern 33, 35 , 37, 43, 45, 47 terminals

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Sadao Miyamoto 335 Karijuku, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Teikoku Communication Industry Co., Ltd. (56) References JP-A-5-7030 (JP, A)

Claims (3)

(57) [Claims] A magnet attached to a displaced object;
A minute position change amount detector comprising: a magnetoresistive element whose resistance changes according to the direction and strength of a magnetic field generated by the magnet; and a detection circuit that detects a change in the resistance of the magnetoresistive element. On a straight line connecting the two poles of the magnet and at a position separated from the magnet by a predetermined distance , substantially perpendicular to the straight line connecting the two poles
Disposed a soft magnetic material as a conductive path of a shape spreading in a planar direction, disposed respectively magnetoresistive element on the left and right sides of the face direction of the soft magnetic material, the surface of the soft magnetic body from said magnet Almost perpendicular to
By bending the magnetic field lines incident on the
Lines of magnetic force are incident on the surfaces of both magnetoresistive elements almost in parallel.
Small position change amount detector, wherein the caulking. 2. A soft magnetic body serving as a second magnetic path is further provided on the left and right outer sides of the magnetoresistive elements provided on both left and right sides of the soft magnetic body. The minute position change amount detector described. Wherein and the left and right magnetic resistance element is connected to and in series are formed on the substrate as the zigzag directions of the two magnetoresistive elements pattern formed zigzag orthogonal, further left of the magnetic Between the resistive elements, the two magnetoresistive element patterns are arranged so as to be point symmetrical, and the middle point of each of the two magnetoresistive element patterns of the left and right magnetoresistive elements is taken out as an output terminal. The minute position change amount detector according to claim 1 or 2, wherein: