JP3196100B2 - Small displacement detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the micro-displacement of objects on the order of microns, such as the vibration of the skin in response to the heartbeat, the thickness of paper or sheet, and the thickness of printing ink printed on paper or sheet. The present invention relates to a small displacement detector that detects

[0002]

2. Description of the Related Art Conventionally, as a method of measuring a position change,
There is a method using a ferromagnetic magnetoresistive element. Here, the ferromagnetic magnetoresistive element changes its resistance value in accordance with 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, a magnetoresistive element 401 having a ferromagnetic magnetoresistive element pattern formed on its surface is mounted on a substrate 400 as shown in FIG. On the other hand, the magnet 403 attached to the displaceable object 405 is attached to the magnetoresistive element 401.
The magnetic field lines are installed so as to enter the surface almost horizontally.

When the displaced object 405 is displaced in the direction of the arrow b with respect to the substrate 400, the direction and strength of the magnetic field in the plane direction of the ferromagnetic element pattern film of the magnetoresistive element 401 change. Thus, the displacement of the object 405 that is displaced can be detected. The small displacement detector using the ferromagnetic magnetoresistive element has an advantage that the sensitivity (resistance change) per unit magnetic field is large.

In this conventional example, the magnet 403 is disposed at a position other than immediately below the magnetoresistive element 401 in order to optimize the sensitivity of the magnetoresistive element 401, but it is difficult to determine the position. It is.

[0006]

For this reason, the applicant of the present application attaches a soft magnetic body of a predetermined shape in addition to the magnetoresistive element and the magnet, and collects and guides the lines of magnetic force emitted from the magnet by the soft magnetic body. A method of effectively making the light incident substantially horizontally on the surface of the magnetoresistive element was considered (Japanese Patent Application No. 6-232 / 1990).
No. 361, Japanese Patent Application No. 6-340076).

[0007] Each of the above-mentioned minute displacement detectors is installed so that the line connecting the NS pole of the magnet is orthogonal to the magnetoresistive forming surface of the magnetoresistive element. Is displaced in the direction of the line connecting the NS poles.

[0008] The relative positions of the magnetoresistive element and the magnet (or the soft magnetic material when a soft magnetic material is used) are optimally determined to improve the detection sensitivity. As long as it is installed at that position, good detection sensitivity can be obtained.

However, the optimum installation position between the members has a certain range, and the minute displacement of the structure in which the magnet or the magneto-resistive element is displaced in the direction of the line connecting the NS poles of the magnet as in each of the minute displacement detectors described above. In the case of a detector, there is a problem that its range is narrow.

For example, an elastic movable film is used as an object to be displaced in order to detect a human beating, and a magnet (in some cases, a magnetoresistive element or a soft magnetic material) is attached to the movable film, and the movable film is attached to the human. When used to detect the pulse by pressing against the skin of the wrist, the amount of the movable membrane pushed up by the skin varies greatly due to the large difference in the subcutaneous fat depending on the person. In some cases, the distance between the attached magnet and the other member is too small (or too large), and may deviate from the optimal mutual detection position. Specifically, if the amount of deviation from the optimal position is at least about 0.4 mm,
Even if it tried to detect a minute displacement at that position, it could not be done.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to detect a small displacement at a displaced position even if the relative positional relationship between a magnet and a magnetoresistive element is displaced. It is another object of the present invention to provide a minute displacement detector capable of obtaining a stable output with a small displacement.

[0012]

If the displacement of the object which is displaced as described above is directly detected as the amount of change of the line of magnetic force, no detectable output can be obtained when a relative displacement occurs between the members. Instead, the inventor of the present application has once converted the displacement of the displaced object into a rotational motion of the line of magnetic force and detected the displacement of the rotational motion. That is, the minute displacement detector according to the present invention includes a body and a mounting attached to the body.
A member and one rod rotatably mounted on the mounting member
And the other for converting the rotational movement of the one rod into a swinging movement.
A rod member comprising a rod, and the one rod and the mounting member facing each other.
A magnet and a magneto-resistive element attached to a position
The other rod of the rod member is attached to the body so as to be vertically movable.
And a detection head coupled to the detection head.
The vertical displacement caused by the vibration of the displaced object
From the swinging motion of the other bar to the rotational motion of one bar
Incident on the surface of the magnetoresistive element approximately parallel
The direction of the magnetic field lines of the magnet is
It is characterized in that it changes by rotating in a horizontal direction.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1A and 1B are schematic views showing the basic operation principle of a minute displacement detector according to the present invention. FIG. 1A is a perspective view, FIG. 1B is a plan view, and FIG. It is. As shown in FIG. 1, the minute displacement detector includes a flat magnetoresistive element 10 and the magnetoresistive element 10.
And a rotating member 40 for rotating the magnet 30.

Here, the magnetoresistive element 10 is formed by forming magnetoresistive element patterns 29, 31, 33, 35 on its upper surface. FIG. 2 is a schematic plan view showing the surface of the magnetoresistive element 10 on which the magnetoresistive element patterns 29, 31, 33, 35 are formed. As shown in the figure, four zigzag formed magnetoresistive element patterns 29, 31, 33, 3
Numeral 5 is formed on the glass substrate 37 in a point-symmetric manner so that the zigzag directions are alternately orthogonal to each other, and each of the magnetoresistive element patterns 29, 31, 33, and 35 is connected to each other by 4. Book terminals 39,4
1, 43 and 45 are drawn out.

Returning to FIG. 1, the magnet 30 is a bar-shaped permanent magnet having N and S poles at both ends.

The rotating member 40 is mounted on the magnetoresistive element 10 so that the axis of rotation is perpendicular to the surface of the magnetoresistive element 10. At the lower end of the rotating member 40, the magnet 30 is fixed so that both ends thereof protrude from the outer peripheral side surface of the rotating member 40. 10 so as to be parallel to the surface. Accordingly, when the rotating member 40 is rotated, the line connecting the two poles N and S of the magnet 30 is rotated immediately above the magnetoresistive element 10 and in a plane parallel to the surface of the magnetoresistive element 10.

The rotation member 40 is provided with a conversion mechanism (not shown) for converting the movement of a displaced object (not shown) into a rotational movement and rotating the rotation member 40.

FIG. 3 is a diagram showing a signal detection circuit of the magnetoresistive element 10. As shown in FIG. As shown in FIG.
To the power supply voltage Vcc and the terminal 45 to ground. Then, the terminals 41 and 43 are pulled out to extract an AC component.
9 and 51, which are further connected to a differential amplifier 53. Note that 57 and 59 are bias circuits.

When the magnet 30 is rotated by the rotating member 40 shown in FIG. 1, for example, the directions of the lines of magnetic force incident on the four magnetoresistive element patterns 29, 31, 33, and 35 are changed. , 31 and the resistance values r3, r4 of the magnetoresistive element patterns 33, 35 change, and their AC components are extracted by the RC circuits 49, 51, respectively. The signal is amplified by the differential amplifier 53 and output.

As shown in FIG. 2, the magnetoresistive element patterns 29, 31 and the magnetoresistive element patterns 33, 35
Are formed to be point-symmetrical because the two midpoint terminals 41 and 43
This is for inverting the output signal output from. That is,
This is because by inverting the output signals output from the terminals 41 and 43, the differential amplification of the detection circuit shown in FIG. 3 becomes effective. If the output signal is not reversed,
Since the outputs of 1, 43 have substantially the same phase signal waveform, output changes cannot be taken out.

FIG. 4 is a diagram showing output signals of the signal detection circuit shown in FIG. 3 when the rotating member 40 shown in FIG. 1 is rotated by a predetermined angle (120 ° left and right).

The output signal obtained as shown in FIG.
Draw n curves. And, for the straight line part, a part of about -70 ° to -15 ° is obtained for the minus angle part,
The rotation angle is as wide as about 55 ° (the same applies to the plus angle portion).

Therefore, if the rotating member 40 rotates within the range of the rotation angle of 55 °, the output corresponding to the displacement changes linearly, and it can be seen that the optimum output can be obtained.

FIGS. 5A and 5B show an example of a beat detector using the above-described basic principle. FIG. 5A is a plan view and FIG.
Is a schematic side sectional view.

As shown in FIG. 1, this beat detector includes a substantially circular body 50, a mounting member 51 fixed to the upper surface of the body 50, and a substantially T-shaped rotatably mounted on the mounting member 51. Rod member 53, a magnet 30 attached to the rod member 53, a magnetoresistive element 10 fixed to a position of the attachment member 51 facing the magnet 30, and attached to the center of the body 50 movably up and down. It comprises a detection head 55 and a spring member 57 mounted on the body 50. Hereinafter, each component will be described.

The body 50 is formed by forming a non-magnetic material such as aluminum or synthetic resin into a cylindrical shape, and has substantially circular concave portions 59 and 61 on its upper and lower surfaces, respectively. In the center of the body 50, a through hole 63 that penetrates the detection head 55 is provided.

The mounting member 51 is formed by forming a non-magnetic material into an E-shape, and its three parallel plate portions 65, 67,
Circular holes 69, 71 are formed in two plate portions 65, 67 of 69.
Is provided.

Further, the magnetoresistive element 10 shown in FIG. 1 is adhered to another plate portion 69.

Next, the rod member 53 includes two circular rods 73,
75 are connected in a T-shape. One rod 73 is rotatably inserted into the two circular holes 69 and 71 of the mounting member 51. The magnet 30 is attached to one end of the rod 73.

The magnet 30 is arranged close to the magnetoresistive element 10 so that the line connecting the N and S poles is parallel to the magnetoresistive surface of the magnetoresistive element 10. Therefore, part of the lines of magnetic force emitted from the magnet 30 pass substantially parallel to the magnetoresistance forming surface of the magnetoresistance element 10.

Next, the detection head 55 is formed by forming a non-magnetic material into a rod shape, and has an insertion hole 77 at its upper end for inserting the rod 75 of the rod member 53 with a predetermined play.
At its lower end, a disk-shaped head 79 is provided.

The spring member 57 is formed of a rod-shaped spring material.
One end thereof is fixed to the recess 59 of the body 50 by the fixing screw 83.
Is fixed inside. At this time, the vicinity of the distal end of the spring member 57 elastically contacts the rod 75 that has penetrated the insertion hole 77 so as to repel the rod 75 downward. Due to this repulsion, the rod 75 reliably contacts the bottom surface of the insertion hole 77.

Next, the operation of the beat detector will be described. That is, first, the lower surface of the heartbeat detector is mounted on the chest (or on the wrist) near the human heart, and the head part 79 is in close contact with the skin, and the signal detector circuit shown in FIG. The output of the magnetoresistive element 10 is measured.

The head portion 79 of the detection head 55 moves up and down with the vibration of the skin. This vertical displacement is converted into the swinging motion of the bar 75 of the bar member 53,
5 is converted into a rotational movement of the rod 73. That is, the detection head 55 and the rod member 53 constitute a conversion mechanism that converts a linear motion into a rotary motion.

At this time, since the rod 75 is always repelled downward by the spring member 57 and is in contact with the lower surface of the insertion hole 77, the rod 75 is moved up and down by the detecting head 55.
Will follow without any play.

The rotation of the rod 73 causes the magnet 30 to rotate.
Also rotates, whereby each of the magnetoresistive element patterns 29, 31, 33, and 35 provided on the magnetoresistive element 10 (FIG. 2).
) Changes, the resistance of each of the magnetoresistive element patterns 29, 31, 33, 35 changes accordingly, and the output waveform changes.

At this time, if the linear portion shown in FIG. 4 is used as the output, the vertical movement of the detection head 55 can be faithfully reproduced in the output waveform.

The skin vibration accompanying the heartbeat was ± 5 μm.
m, but the detection head 5
When 5 is displaced by ± 5 μm, the rotation angle of the rod 73, that is, the magnet 30, is about ± 0.08 ° when the distance from the central axis of the rod 73 to the central axis of the detection head 55 is 7 mm.
From FIG. 4, the output is 169.3 in total amplitude.
mV / 90 °, or 1.881mV / 1 ° per degree,
The output change of about ± 0.15 mV is obtained from the swing of ± 0.08 °. Therefore, the detection of the minute vibration is sufficiently possible.

FIG. 6A is a diagram showing an output waveform measured by the above method. FIG. 6B is a diagram showing a result of measuring a current waveform caused by contraction of the heart using an electrocardiogram.

When comparing the waveforms shown in FIGS. 6 (a) and 6 (b), it can be seen that the waveforms are very similar and accurate waveforms are obtained.

By the way, the distance from the center axis of the bar 73 of the heartbeat detector shown in FIG. 5 to the center axis of the detection head 55 was 7 mm, and the detection head 55 was moved 2 mm vertically from its standard position. Assuming that the measurement is performed with the position as the center, the measurement is performed on the position where the rod 73 changes by the rotation angle θ ≒ ± 15.9 ° from tan θ = (2/7).

However, even if the magnet 30 at the time of measurement is shifted from the standard position by a rotation angle of ± 15.9 °, if the standard position is set at the center of the linear region of the output shown in FIG. Since the area is about 55 ° (± 27.5 °), it still falls within the linear area, so that the vertical movement of the detection head 55 can be converted into an accurate output waveform using the straight line.

That is, according to the present invention, when the heartbeat detector is pressed against human skin, the position of the detection head 55 is
Even if it is displaced by about 2 to 3 mm in the vertical direction due to the elasticity of the human skin or the swelling due to the amount of subcutaneous fat, an accurate output waveform of the heartbeat that can be sufficiently detected at that position can be obtained.

Although one embodiment of the present invention has been described in detail, the present invention is not limited to this embodiment, and for example, the following modifications are possible. In the above embodiment, an example in which the present invention is applied to a heartbeat detector has been described. However, the present invention is not limited to this, and may be applied to any part that needs to detect a minute displacement. it can. That is, for example, it can be used as a paper thickness detector for detecting the thickness of paper, or as an ink thickness detector for detecting the thickness (about 10 μm) of ink printed on paper or a sheet.

Although the magnet and the magnetoresistive element are used in the micro-displacement detector, a soft magnetic material having a predetermined shape for collecting the lines of magnetic force of the magnet and injecting the lines parallel to the magnetoresistive surface of the magnetoresistive element. You may attach your body.

The conversion mechanism for converting the motion of the displaced object into the rotary motion is not limited to the mechanism disclosed in the above embodiment, but may have other various structures. Further, the conversion mechanism is mounted on the magnet side in the above embodiment, but may be mounted on the magnetoresistive element side.

[0047]

As described above in detail, according to the present invention, an excellent effect that a stable and detectable output signal can be obtained even if the relative positions of the magnets and the magnetoresistive elements are largely shifted. Having.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the basic operation principle of a minute displacement detector according to the present invention, wherein FIG. 1 (a) is a perspective view, FIG. 1 (b) is a plan view, and FIG. FIG.

FIG. 2 shows a magnetoresistive element pattern 2 of the magnetoresistive element 10.
It is a schematic plan view which shows the surface in which 9, 31, 33, and 35 were formed.

FIG. 3 is a diagram showing a signal detection circuit of the magnetoresistive element 10;

FIG. 4 when the rotating member 40 shown in FIG. 1 is rotated.
FIG. 5 is a diagram showing an output signal of the signal detection circuit shown in FIG.

5A and 5B are diagrams showing a beat detector according to an embodiment of the present invention, wherein FIG. 5A is a plan view and FIG. 5B is a schematic side sectional view.

6A is a diagram showing an output waveform of the heartbeat detector shown in FIG. 5, and FIG. 6B is a diagram showing a current waveform generated by contraction of the heart using an electrocardiogram.

FIG. 7 is a diagram showing a conventional example using a ferromagnetic magnetoresistive element 401.

[Explanation of symbols]

 10 Magnetoresistive element 30 Magnet

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-298815 (JP, A) JP-A-2-35003 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 7/00-7/34 102 G01D 5/00-5/252 G01D 5/39-5/62 G01L 7/00-23/32 A61B 5/00-5/03 H01L 43/00-43/14

Claims (1)

(57) [Claims] 1. A body and a mounting member attached to the body.
And one of the rods rotatably mounted on the mounting member and the front
The other rod that converts the rotational movement of one rod into a rocking movement
A rod member, and the one rod and the mounting member are opposed to each other.
Magnet and magnetoresistive element attached to the
It is attached to the other rod of the rod member so as to be movable up and down.
A detection head that is connected to the head in a vertical direction accompanying vibration of an object that is displaced by the detection head.
Displacement of one rod from the swinging movement of the other rod of the rod member
Converted to rotational motion and formed on the magnetoresistive surface of the magnetoresistive element
The direction of the lines of magnetic force of the magnets incident substantially parallel is
Characterized by relative rotation and change in the plane
Micro displacement detector.