JPS6346803Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a non-contact displacement detector that utilizes a permanent magnet and a ferromagnetic magnetoresistive element that move linearly relative to each other.

A non-contact displacement detector combines a permanent magnet and a magnetic sensing element, detects the relative displacement of each other as a change in the magnetic field acting on the magnetic sensing element, and converts this into an electrical signal using a drive detection circuit. , structures that output are known. Compared to conventional displacement detectors that use sliding resistors or reed switches, these non-contact displacement detectors do not have mechanical contacts, so there is no contact wear or chattering, and they are highly reliable. It is applied to position detection devices such as pistons, and non-contact switches such as non-contact key switches and proximity switches. Furthermore,
This non-contact displacement detector not only detects distance displacement, but also converts various physical quantities such as pressure, flow rate, temperature, and strain into linear displacement and detects them with this non-contact displacement detector. It is also considered to have wide applications as a switch.

Magnetic sensing elements include semiconductor Hall elements, semiconductor magnetoresistive elements, ferromagnetic magnetoresistive elements, etc. Among these, ferromagnetic magnetoresistive elements (hereinafter abbreviated as MR elements) are sensitive to the strength and direction of the magnetic field. It is a ferromagnetic magnetoresistive thin film (hereinafter abbreviated as MR film) whose electrical resistance changes according to the electrical resistance, and a magnetic flux-responsive magnetosensitive element as the main part, which is sensitive only to the magnetic field of the component parallel to the film surface of the MR film. In addition, the sensitivity is high, the amount of change in resistance reaches a certain saturation amount, and power consumption can be reduced by increasing the resistance.

Conventionally, in non-contact displacement detectors that use a permanent magnet and a magnetic sensing element, both change linearly with each other, so a strong magnetic field is applied when the two approach each other, and becomes almost zero when they move away. In other words, it was configured to detect changes in the strength of the magnetic field. However, when using an MR element as a magneto-sensitive element, it has been found that a method of detecting the direction of the magnetic field is more suitable than a method of detecting changes in the strength of the magnetic field. In other words, in the method of changing the resistance value of the MR film by changing the strength of the magnetic field, the first
In addition, so-called Barkhausen noise occurs, causing the resistance value to change discontinuously, or hysteresis appears, which disrupts the correspondence function between the displacement amount and output that should be detected by a non-contact displacement detector, and also causes chattering. will occur. Second, when the MR film is dispersive with no magnetic anisotropy, or when the MR element has a differential or bridge configuration with multiple MR films in which the directions of current flowing through it are orthogonal, the overall resistance changes. Since the efficiency of the drive detection circuit decreases and the so-called dynamic range decreases, the signal-to-noise ratio when converted into an electrical signal by the drive detection circuit becomes lower than the value originally obtained, increasing the possibility of malfunction. Thirdly, since the MR film has high sensitivity to magnetic fields, if an external noise magnetic field is applied when the permanent magnet is moving away and the magnetic field strength is weakening, it will cause a change in resistance, so it cannot be used as a non-contact displacement detector. It has drawbacks such as easy malfunction.

On the other hand, if the MR element and the permanent magnet are placed close to each other,
An example of changing the direction of the magnetic field applied to the MR element is shown in Japanese Utility Model Application No. 51-18146, in which the direction of the magnetic field rotates within a plane perpendicular to the facing surface of the permanent magnet. Therefore, the MR film must be placed perpendicular to the facing surface of the permanent magnet, and it is difficult to apply a magnetic field of sufficient strength. That is, as is well known, the magnetic field strength rapidly decreases as the distance from the magnetic pole of the permanent magnet increases, so in order to obtain sufficient magnetic field strength, the MR film must be placed sufficiently close to the permanent magnet. However, an MR element has an MR film formed on a substrate, and the size in the direction parallel to the MR film depends on the size of the MR film itself, its surroundings, electrode parts for electrical connection to the outside, etc. As a result, they become quite large, and it is difficult to place them sufficiently close together. In addition, the above-mentioned Jitsukai 51-
FIG. 5c of Publication No. 18146 shows an example in which a permanent magnet and an MR film are arranged in parallel, and its output characteristics. However, even in this example, the direction of the magnetic field rotates within a plane perpendicular to the facing surface of the permanent magnet, and the direction of the magnetic field that the MR film is sensitive to never rotates. That is, the present inventors, etc. have a similar configuration,
As shown in Figure 5, the measurement results obtained by conducting an experiment with different configurations are different from the output characteristics shown in the above-mentioned publication, and sufficient output cannot be obtained near x = 0, and 1 of the saturation change amount /2 or less, and due to hysteresis, the correspondence between the displacement amount (that is, x) and the output breaks down, and Barkhausen noise also occurs, indicating a discontinuous change. (Here, the vertical axis indicates the value normalized by the saturated output value of the MR element). This is because the rotation of the direction of the magnetic field is not detected, and near x = 0, the direction of the magnetic field is MR.
This is because the magnetic field is perpendicular to the MR film and the state is the same as if no magnetic field was applied to the MR film at all.
In other words, its configuration simply detects changes in the strength of the magnetic field.

In this way, conventional non-contact displacement detectors are configured to detect changes in the strength of the magnetic field, and are not suitable for MR elements, or cannot apply a magnetic field of sufficient strength to MR elements, resulting in their characteristics. Because the system was not being used effectively, the reliability that could have been obtained had deteriorated.

An object of the present invention is to solve the above drawbacks and provide a highly reliable non-contact displacement detector using an MR element. That is, the present invention includes a permanent magnet, an MR element, and a drive detection circuit that are linearly displaced relative to each other, and the magnetic field acting on the MR film has an intensity greater than the intensity required for magnetization rotation of the MR film. The facing surface of the permanent magnet is maintained such that the direction of the magnetic field rotates in a plane parallel to the facing surface of the permanent magnet facing the MR element as the MR element and the permanent magnet move relative to each other. is a rectangle with sides parallel to the direction of relative displacement between the two, and is divided into two regions by a boundary line parallel to the direction of relative displacement, excluding all of each region or the vicinity of the boundary line. The two parts are made with opposite magnetic poles, and further MR
The MR film is characterized in that the film surface of the film, the facing surface of the permanent magnet, and the direction of relative displacement are all substantially parallel, and the center of the MR film is arranged facing away from the boundary line.

The present invention will be explained in detail below with reference to the drawings.

FIGS. 1a and 1b schematically show the basic configuration of the non-contact displacement detector of the present invention. This basically consists of an MR element 1, a permanent magnet 2, and a drive detection circuit 3, and when the permanent magnet 2 and MR element 1 are linearly displaced relative to each other, an electric signal is generated according to the displacement. This outputs the following. Since displacement of either the MR element 1 or the permanent magnet 2 is completely equivalent, the following description will be made assuming that the MR element 1 is displaced in the x direction.

The MR element 1 has an MR film 7 forming the main part on a substrate 6 and electrode terminals 8 for connection to the drive detection circuit 3. The resistance value of the MR element 1, that is, the resistance value R of the MR film 7 changes depending on the angle θ between the direction of the current I flowing through it and the direction of its magnetization M, and as is well known, R It can be expressed as = Ro−ΔRsSin ² θ (1). Here, Ro is the resistance value when the direction of the current I and the direction of the magnetization M become parallel, and ΔRs is the saturation value of the amount of resistance change. The MR element 1 moves along the displacement line 5 in the x direction without contacting the permanent magnet 2.
change above. By configuring the magnetic poles of the permanent magnet 2 as described later, the direction of the magnetic field component 4 (hereinafter referred to as the in-plane component magnetic field) in a plane parallel to the opposing surface facing the MR element 1 is aligned with the displacement line 5. Let it rotate along the The drive detection circuit 3
Supplying a current I to the MR element 1, that is, the MR film 7,
This circuit converts the change in the resistance value R into an electric signal corresponding to the change, performs further appropriate signal processing if necessary, and outputs the signal.

Next, the operation of this non-contact displacement detector will be explained.

The strength of the magnetic field from a permanent magnet is calculated from the square of the distance to 3
In particular, when detecting minute displacements, the distance between opposite magnetic poles must be shortened, so the magnetic field strength becomes even smaller. On the other hand, the MR element 1 has an MR film 7 as shown in the figure.
is formed on the substrate 6, and the permanent magnet 2
It is clear that arranging the MR film 7 parallel to the opposite surface allows for closer proximity than arranging the MR film 7 perpendicularly to the opposing surface. Although it is not necessarily necessary to make the MR film 7 and the facing surface of the permanent magnet 2 completely parallel in order to bring them close to each other, for the sake of simplicity, it is assumed here that they are completely parallel.

When the MR element 1 is displaced on the displacement line 5, the direction of the in-plane component magnetic field 4 acting on the MR film 7 changes as if rotating in accordance with the displacement. Magnetization M of MR film 7
It is only the magnetic field component parallel to the MR film 7 that changes the field, and the component perpendicular to it does not contribute at all. In this example, since the in-plane component magnetic field 4 is parallel to the MR film 7, the in-plane component magnetic field 4 itself contributes to a change in the magnetization M of the MR film 7. In this way, as long as the in-plane component magnetic field 4 has an intensity greater than or equal to the strength required to rotate the magnetization M of the MR film 7, the direction of the magnetization M follows the change in the direction of the in-plane component magnetic field 4. Here, the strength required for the rotation of the magnetization M of the MR film 7 is the strength necessary for the magnetization M to rotate smoothly as the magnetic field rotates, and it depends on the material, thickness, and width of the MR film 7. It is sufficient if the strength is such that the difference in resistance value when the magnetic field is applied in the current direction and when the magnetic field is applied in the direction perpendicular to the current is about 70% of the saturation change amount ΔRs, although it varies accordingly. When the MR element 1 moves on the displacement line 5, the angle θ between the direction of the magnetization M and the direction of the current I changes according to the displacement, and the resistance value R changes with a period of 180 degrees with respect to the angle θ. At this time, since the change in the direction of magnetization M of the MR film 7 also occurs due to magnetization rotation, so-called Barkhausen noise does not occur.
The resistance value R changes continuously and smoothly according to the displacement. Also, depending on the displacement of MR element 1, the angle θ becomes 0.
While the direction of current I and the direction of magnetization M change from parallel to perpendicular to 90 degrees, the resistance value R reaches at least 70% of the saturation change amount ΔRs,
Moreover, it does not depend on the presence or absence of magnetic anisotropy. In other words, even if the MR film is distributed, or if multiple MR films whose current directions are orthogonal to each other are used in a differential or bridge configuration,
Even in the case of MR elements, when simply utilizing changes in the strength of the magnetic field (in this case, when the magnetic field is weak, many magnetic domains are created within each MR element, and therefore a single magnetic domain is created by a strong external magnetic field). (The resistance change is smaller than when the shape is aligned.) It is possible to make a larger change in resistance. Furthermore, since the MR film 7 is always subjected to a magnetic field with an intensity higher than that required for magnetization rotation, the resistance value R is hardly affected even if a small noise magnetic field is applied from the outside. The non-contact displacement detector according to the present invention can detect such MR due to relative motion.
The drive detection circuit 3 detects the magnitude of change in the resistance value R of the element 1 and the number of cycles of change, converts it into a corresponding electric signal, and outputs it, so compared to conventional displacement detectors of the same type, The resistance value R of the MR element 1 is configured to change continuously and smoothly, and the amount of change can be utilized to a large extent.The dynamic range is large, so the S/N ratio is high, and it is not easily affected by noise magnetic fields, so there is no chattering. This is a non-contact displacement detector with fewer malfunctions. This is because the direction of the in-plane component magnetic field is changed so as to rotate so that the magnetization M of the MR film is smoothly rotated by a stronger magnetic field. This can be achieved by arranging the elements 1 accordingly.

Note that when the magnitude of the displacement to be detected is relatively small, the angle θ between the magnetization M and the current I is 0.
If the change is made to vary from 90 degrees to 90 degrees, the amount of change and the amount of change in resistance value correspond one-to-one, so conversion into an electrical signal in the drive detection circuit can be made easier.

Furthermore, in the above explanation, it has been assumed that the MR film and the opposing surface are completely parallel for simplicity, but if the direction of the in-plane component magnetic field is rotated, they will become almost parallel to each other, that is, ± If the tilt is within 30 degrees, the magnetization of the MR film can be rotated as long as the magnetic field strength is sufficient. Therefore, even if the two cannot be arranged in parallel due to space constraints, the magnetic field strength will be reduced to some extent, but a non-contact displacement detector with fewer malfunctions can be constructed in the same way. Of course, it goes without saying that it is more effective if the MR film and the facing surfaces of the permanent magnet are made parallel, since they can be brought closest to each other.

Next, we will describe the configuration of the magnetic poles of the permanent magnets so that the direction of the in-plane component magnetic field rotates along the displacement line of the MR element. Generally, the magnetic field from the permanent magnet is in a direction perpendicular to the sides of the opposing surfaces or the boundary line between opposite magnetic poles on the opposing surfaces. Therefore, the direction of the in-plane component magnetic field can be rotated by configuring the magnetic poles so that the directions of the sides and boundary lines of the opposing surfaces change by about 90 degrees near the displacement line of the MR element, and by setting the displacement line. can be done.

Figure 2 is an embodiment of the configuration of the present invention, and a is a plan view;
b is a perspective view. Again, the direction of the in-plane component magnetic field is
It rotates 90 degrees. The direction of relative displacement between the MR element 21 and the permanent magnet 22 is defined as the x-axis direction.
The facing surface of the permanent magnet 22 facing the MR element 21 is a rectangle with one side parallel to the x-axis direction, and is divided into two areas 25 and 26 by a boundary line 27 in the x-axis direction, one of which is divided into two areas 25 and 26. The north pole is the north pole, and the other is the south pole. When the center of the MR film 28 is displaced on the displacement line 23, the directions of the side 29 of the opposing surface of the permanent magnet 22, the boundary line 27, and the side 30 of the opposing surface are changed in the vicinity of the displacement line 23. It is configured to change in 90 degree increments. With this configuration, the in-plane component magnetic field 24 becomes as shown in the figure, and at positions shifted left and right near the boundary line 27, the direction of the in-plane component magnetic field 24 rotates along the x-axis. In this way, as the MR element 21 is displaced on the displacement line 23 located at a position deviated from the boundary line 27, the direction of the in-plane component magnetic field 24 changes to point 2.
It can be rotated continuously from 3A to point 23B to make a 90 degree change. In particular, it is effective if the current direction of the MR film 28 is set at 45 degrees with respect to the x-axis direction, since the amount of resistance change can be utilized to the greatest extent. Note that the magnetic field distribution is the same even if the portion along the boundary line 27 is a non-magnetized region.

Next, regarding this example, the results were obtained through experiments.
The output characteristics of the MR element will be explained. The experiment was conducted using a bridge-type MR element shown in FIG. This consists of four MR film stripes 92 whose current directions are perpendicular to each other on a substrate 91 and electrode terminals 93, 9.
4, 95, 96 are formed, and the substrate 9
1 is 1.5 mm square, and the MR film stripe 92 is located within a 1 mm square. Each MR film stripe 92 is made of Ni/Fe with a thickness of 500 Å and a width of 20 μm.
Made of alloy. When a voltage is applied between electrode terminals 93 and 94 and a current flows, electrode terminals 95 and 96
The output is obtained as the potential difference Φ between. As a non-contact displacement detector, this output is further amplified by a drive detection circuit and processed electrically to produce an output, but as mentioned above, the output of the MR element determines the reliability of the non-contact displacement detector. The output of this MR element itself is shown below. First, we will briefly describe the characteristics of this MR element. The MR film stripe 92 had the above material, film thickness, and width, and the strength of the magnetic field required to rotate its magnetization was about 30 oersteds. When the magnetic field H is applied in the direction of the angle θ, the resistance value of each MR film stripe 92 changes as shown in equation (1) above, and the output of the MR element,
In other words, as is well known, the potential difference Φ is Φ(θ)=Voa/2cos2θ...(2). Here, a is the resistance change rate expressed as ΔRs/Ro using Ro and ΔRs in equation (1), and Vo is
This is the voltage applied to the MR element. Further, the angle θ is based on the current direction of one MR film stripe (hereinafter abbreviated as the reference direction). As can be seen from equation (2), in order to change the potential difference Φ the most, it is sufficient to change the direction of the magnetic field from θ = 0 degrees to θ = 90 degrees, and the potential difference changes from Voa/2 to -Voa/2. do. In addition, when there is no magnetic field H at all, the potential difference Φ
is almost zero (actually it deviates somewhat from zero randomly due to the hysteresis of the MR membrane),
Therefore, when changing the strength of the magnetic field, the potential difference Φ
The value changes at most from zero to Voa/2 or from zero to -Voa/2, and the so-called dynamic range is halved.

The permanent magnets used in the experiment were rubber magnets magnetized in the thickness direction and cut and arranged according to each configuration, and the plate thickness was 2 mm. Furthermore
The distance between the MR element and the facing surface of the permanent magnet was set to 1.5 mm.

Figure 4b shows the actually measured MR element output, showing the magnetic poles 25 and 26 of the permanent magnet and the MR element 21.
The displacement line 23 of is taken as shown in Fig. 4a, and the MR element 2
The reference direction of 1 is set at 45 degrees with the x-axis direction. Fourth
The horizontal axis in figure b is the distance in the x-axis direction, and the vertical axis is
This is the MR element output normalized to Voa/2. In this case as well, there is no hysteresis or Barkhausen noise, and it can be seen that the changes are smooth and maximum.

In this way, by configuring the magnetic poles of the permanent magnet so that the direction of the magnetic field rotates in a plane parallel to the facing surface of the permanent magnet, the MR film of the MR element is aligned parallel to the facing surface of the permanent magnet. Moreover, as the direction of the magnetic field rotates, or in other words, the magnetic field strength is uniform and a stronger rotating magnetic field can be applied, the output of the MR element is smooth without any hysteresis or Barkhausen noise. The maximum amount of change is possible, making the non-contact displacement detector extremely reliable.

On the other hand, in conventional devices configured to detect changes in magnetic field strength, the output changes only from almost zero to Voa/2, or from almost zero to -Voa/2, so it is not dynamic. The range had been halved, and the output was unstable due to hysteresis in areas where the magnetic field weakened, near zero, and was susceptible to the effects of external noise magnetic fields. Also, as mentioned earlier,
Publication No. 18146 shows an example in which the direction of the magnetic field applied to the MR film is changed, but unlike the one of the present invention, the direction of the magnetic field rotates in a plane perpendicular to the opposing surface, so the MR film must be placed perpendicular to the opposing surface. However, as is clear from Figure 3 of this application, even if the MR film itself is small, the substrate of the MR element is quite large, and although it is omitted in this figure, it is generally It will be larger because it will be placed in a package cage or molded. Therefore, the magnetic field strength may vary greatly between parts of the MR film, or a magnetic field of sufficient strength may not be applied, which tends to cause a reduction in output and a reduction in the S/N ratio. I had no choice but to use it. Furthermore, the same reference publication shows an example in which the MR film is arranged parallel to the opposing surface of the permanent magnet and the output at that time, but the inventors conducted experiments with a similar configuration and arrangement ( This is different from Figure 5b). The experiments conducted by the present inventors used the MR element shown in Figure 3 as the MR element 98, which is equivalent to the MR element in the cited publication, and the permanent magnet 99 and both The layout is exactly the same. The MR element output in Fig. 5b is different from the MR element output (Fig. 4) according to the configuration implementing the present invention,
It only changes from Voa/2 to -Voa/4, and the dynamic range has been reduced to about 3/4. Furthermore, Barkhausen noise and hysteresis appear near x=0, resulting in unstable output. This shows that the configuration of FIG. 5a does not detect rotation in the direction of the magnetic field.
In other words, in this case as well, the direction of the magnetic field changes within a plane perpendicular to the facing surface of the permanent magnet, and on the other hand, what the MR film is sensitive to is only the in-plane component; This is because the magnetic field component perpendicular to the film surface has no effect, so this arrangement simply detects changes in the strength of the magnetic field (in other words, the vicinity of x = 0 corresponds to a weak state). be.

As is clear from the above, in conventional devices, the MR element must either detect changes in the strength of the magnetic field or be placed perpendicular to the facing surface of the permanent magnet, making it impossible to obtain a uniform and sufficiently strong magnetic field. In contrast,
In the non-contact displacement detector implementing this patent, by appropriately configuring the magnetic poles of the permanent magnet, it is possible to ensure that the direction of a uniform and sufficiently strong magnetic field rotates smoothly with respect to the MR element. , we were able to obtain a smoother and larger MR output without hysteresis or Barkhausen noise, and we were able to make the non-contact displacement detector more reliable and less likely to malfunction. In addition, the MR element used for the actual measurement was
The MR membrane has a bridge structure,
Needless to say, it is exactly the same whether it is made up of a single MR film or if it has a differential configuration with two MR films whose current directions are perpendicular to each other.

Next, a more specific example of the non-contact displacement detector of the present invention will be described.

FIG. 6 shows a sectional view of a non-contact key switch, which is an example of a non-contact switch using the non-contact displacement detector according to the present invention. This non-contact key switch outputs an electrical signal indicating whether a key is pressed or not, and is essentially a non-contact displacement detector that detects and outputs the displacement of a key. This consists of a key 83 that moves up and down, a spring 84 pushing it up, a permanent magnet 82 fixed to the key 83, an MR element 81, and a drive detection circuit 8.
5, electrode pins 86, and a housing 87 that holds these and serves as an outer frame. Permanent magnet 82
is a combination of two rectangular plate-shaped ferrite magnets magnetized in the thickness direction, and is similar to the configuration example shown in FIG. The MR element 81 is the substrate 8
8 with an MR film 89 formed on the permanent magnet 8.
2, and the direction of the current flowing through it is the direction of displacement, that is, the up and down direction in which the key moves.
Make it 45 degrees. Furthermore, the size of the permanent magnet 82 and the position of the MR element 81 are such that when the key 83 is not pressed (indicated by a solid line), the MR film 89 is in the second position.
The position corresponds to point 23A in the figure, and when the key 83 is pressed (indicated by a two-dot chain line), point 23B
Set it to a position corresponding to . The drive detection circuit 85 is a circuit for supplying current to the MR element 81, that is, the MR film 89, detecting a change in its resistance value, and outputting it as an electric signal.
is used to connect to this and connect it to an external power supply or signal output line.

When the key 83 is not pressed, the MR film 89 is at a position corresponding to point 23A in FIG. The angle with the current direction is 0 degrees and the resistance value is Ro. key 83
As the permanent magnet 82 is pushed in, the relative position between the permanent magnet 82 fixed thereto and the MR element 81 changes, and the MR film 89 reaches a position corresponding to point 23B in FIG. At point 23B, the direction of the in-plane component magnetic field and
Since it is perpendicular to the current direction of the MR film 89, the angle between the magnetization direction of the MR film 89 and the current direction is approximately 90
degree, and the resistance value becomes Ro−ΔRs. While the key 83 is being pushed in, the direction of the in-plane component magnetic field 84 changes continuously and smoothly as if rotating, so the resistance value of the MR film 89 also changes continuously and smoothly from Ro to Ro−ΔRs. To go. This change in resistance value is detected by the drive detection circuit 86, and if the resistance value is greater than or equal to Ro−1/2ΔRs, an electrical signal indicating that the key 83 is not pressed is output, and Ro−1/2
If it is less than ΔRs, it operates as a non-contact key switch by outputting an electric signal indicating that the key 83 is not pressed. At this time, the resistance value of the MR film 89 changes continuously and smoothly without Barkhausen noise or hysteresis, so the drive detection circuit 89
No chattering occurred in the output of 6, and the MR membrane 8
Even if 9 has magnetic field anisotropy, it is possible to change the resistance up to the saturation displacement amount, so it has a wide so-called dynamic range, and since the magnetic field is always applied with a strength greater than the strength required for magnetization rotation, external noise magnetic fields can be avoided. The signal-to-noise ratio is high because it is less susceptible to the effects of
In this way, it has become a highly reliable non-contact key switch that is unlikely to malfunction.

Note that the MR film and the facing surface of the permanent magnet facing it are completely parallel, but this is better for MR.
This is because it is effective when a more uniform and stronger magnetic field is applied to the film, and as long as the in-plane component magnetic field is applied with an intensity greater than the strength required for magnetization rotation, it is not necessary that they be completely parallel.

This non-contact key switch is just one application example of the non-contact displacement detector of the present invention, and if the keys of this embodiment are not pressed by hand, they will be displaced according to temperature and pressure. It can be used as a temperature-sensitive switch or a pressure-sensitive switch. For example, if the part corresponding to the key in this embodiment is made to make one reciprocation for each unit flow rate of gas such as propane, city gas, or liquid such as water, it can be used as a flowmeter by counting the number of times. can. Furthermore, since the above-mentioned embodiment is applied as a non-contact switch, the output electrical signal only digitally indicates two states: whether it is pressed or not. , it is easy to create a meter that measures the flow rate, temperature, pressure, etc. of water, etc. by detecting the amount of displacement, converting it directly into an electrical signal that represents the magnitude, and outputting it. Can be configured.

Ferrite, rare earth magnets, etc. can be used as materials for the permanent magnet, and magnetic poles suitable for implementing the present invention can be constructed by magnetizing them into a predetermined shape or by combining already magnetized materials. I can do it. MR elements are made by depositing an MR film of iron, nickel, cobalt, etc., or alloys mainly composed of these elements, on a sufficiently smooth insulating substrate such as silicon, glass, or ceramic, which has an insulating film formed on its surface.
It is formed by thin film forming techniques such as sputtering and plating, or by resist processing and etching techniques. Typical shapes of MR membranes are:
Stripes with a film thickness of 200 to 1000 Å and a width of several μm to 100 μm, or stripes folded multiple times, or multiple such stripes arranged so that their directions form an angle between 0 and 90 degrees. Their specific values, length, etc. are determined according to the size of the permanent magnet used, the required resistance value, etc. Note that the drive detection circuit was formed on the same substrate as the MR film using IC fabrication technology.
In the case of MR elements, silicon is used as the substrate.
The drive detection circuit is the part that supplies current to the MR element.
It has a part that detects the resistance change of the MR element and a part that processes this appropriately and outputs an electric signal corresponding to the magnitude of the relative displacement between the permanent magnet and the MR element. The simplest example is an analog signal output that outputs a voltage or current proportional to the resistance value of the MR element. It consists of an amplifier that detects and amplifies changes in current. Another example is the non-contact key switch shown in Figure 6, in which the relative displacement between a permanent magnet and an MR element is digitally output with a certain point as a boundary, and an analog signal representing the resistance change of the MR film is generated in advance. The drive detection circuit includes a comparison circuit that compares it with a set value. Furthermore, in the case of the above-mentioned analog signal output, it is also possible to perform analog-to-digital conversion and output it as a pulse train such as a binary code or BCD code, and in this case, a well-known analog-to-digital conversion circuit is included. Further, in the case of a flowmeter configured to perform one reciprocating relative displacement for each unit flow rate of gas or liquid, the drive detection circuit includes a counting circuit that counts these circuits.

As explained above, according to the present invention, the resistance change of the MR film is continuous and smooth, and a large amount of resistance change can be obtained regardless of the presence or absence of magnetic anisotropy. Therefore, it is possible to provide a more reliable non-contact displacement detector that is less susceptible to the effects of noise magnetic fields and is free from chattering and malfunctions.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the basic configuration of the non-contact displacement detector of the present invention, in which a is a plan view, b is a perspective view, and
The figures show an embodiment of the present invention, in which a is a plan view, b is a perspective view, Fig. 3 is a plan view showing the MR element used in the experiment, and Fig. 4 is a diagram showing an example of actually measured MR element output. where a is the specific configuration diagram, b is the output curve, and the fifth
The figure shows the actual measured MR element output for a configuration that does not detect rotation in the direction of the magnetic field, where a is a specific configuration diagram, b is an output curve, and Figure 6 is a non-contact displacement detector of the present invention. FIG. 2 is a sectional view showing an example in which the switch is applied as a non-contact key switch. In the figure, 1, 21, 81, 98 are MR elements, 22, 82, 99 are permanent magnets, 3, 85 are drive detection circuits, 5, 23, 100 are displacement lines, 6, 8
8, 91 are MR element substrates, 8, 93, 94, 9
5 and 96 are electrode terminals, 23A and 23B are points on the displacement line, 4 and 24 are in-plane component magnetic fields, 25 and 26 are regions on the opposing surfaces of the permanent magnets, and 27 are boundaries of the regions on the opposing surfaces of the permanent magnets. Lines 29, 30 are one side of the opposing surface of the permanent magnet, 7, 28, 89, 92 are MR films, 8
3 is a key, 84 is a spring, 86 is an electrode pin,
87 represents a housing, and 97 represents a reference direction of the MR element.

Claims (1)

[Claims for Utility Model Registration] 1. A device comprising a permanent magnet and a ferromagnetic magnetoresistive element that are linearly displaced relative to each other, and a drive detection circuit that outputs the relative displacement as an electrical signal. In the contact displacement detector, while maintaining the strength of the magnetic field acting on the ferromagnetic magnetoresistive thin film of the ferromagnetic magnetoresistive element by the permanent magnet to be greater than the intensity required for magnetization rotation of the ferromagnetic magnetoresistive thin film. , and the opposing surfaces of the permanent magnets are arranged so that the direction of the magnetic field rotates in a plane parallel to the opposing surface of the permanent magnet facing the ferromagnetic magnetoresistive thin film. A rectangular shape with sides parallel to the direction of relative displacement, divided into two regions by a boundary line parallel to the direction of relative displacement, and excluding the entirety of each region or the vicinity of the boundary line. are mutually opposite magnetic poles, and further, the film surface of the ferromagnetic magnetoresistive thin film, the facing surface of the permanent magnet, and the direction of the relative displacement are all substantially parallel, and the center of the ferromagnetic magnetoresistive thin film is the boundary line. A non-contact displacement detector characterized in that it is placed facing away from the. 2. The device according to claim 1 of the utility model registration claim, in which the ferromagnetic magnetoresistive element is arranged so that the direction of the current flowing through the ferromagnetic magnetoresistive thin film and the direction of relative displacement are approximately 45 degrees. Contact displacement detector.