JPS62229079A - Magnetic detector and position detector using same - Google Patents

Abstract

PURPOSE:To let a position detector have output characteristics wherein an output shows a hysteresis in response to changes in an external magnetic field by making an external member magnetized thereby have a magnetic hysteresis. CONSTITUTION:A casing 3 shows the magnetic characteristic of hysteresis because it is made of a ferromagnetic metal. Therefore, the magnetic inductivity (coercive force) of the casing 3 in the case wherein a given value of a magnetic field strength is reached while it is increasing is different from that in the case wherein the value is reached while it is decreasing even though the external magnetic field strength does no change. Accordingly, a magnetic field Hca in the case wherein the level of the magnetic field strength is reaches while it is increasing is different from that in the case wherein the level is reaches while the strength is decreasing for each level of the magnetic field strength acting on a magnetic detector 1. Thus, the magnetic detector 1 itself has the characteristic of hysteresis.

Description

Detailed Description of the Invention [Summary] The present invention provides a magnetic detector and a position detection device using the same, in which a magnetically sensitive element is covered with a member made of ferromagnetic material, and the magnetic hysteresis characteristic of the member is used to detect the magnetic field. The output characteristic of the detector exhibits a hysteresis characteristic, and furthermore, the output characteristic of the position detecting device exhibits a hysteresis characteristic, making it suitable for detecting the position of a portion to be detected whose nature is likely to fluctuate.

[Industrial application field]

The present invention relates to a magnetic detector and a position detection device using the same.

[Conventional technology]

Conventional magnetic detectors that use a magnetoresistive element, which is a type of magnetic sensing element, have a configuration that simply uses a magnetoresistive element, and the output characteristics of the magnetoresistive element are the same as the output characteristics of a Va magnetic detector. This output characteristic is as shown by the square in FIG. 15, and has no hysteresis.

Further, the conventional position detection device has a structure in which the above-mentioned magnetic detector is movably provided inside a closed magnetic circuit structure that forms a leakage magnetic field. This output characteristic is shown in Figure 16.
It has no hysteresis and outputs the same voltage at the same position regardless of the direction in which the magnetic detector moves. This position detection device is generally used as a detection section of a control device.

[Problem that the invention seeks to solve]

Since the above position detecting device exhibits characteristics without hysteresis, when this position detecting device is applied to the liquid level detecting section of a control device ξ that keeps the liquid level in a tank constant, it is possible to This results in the following inconveniences.

When liquid is supplied into the tank by the pump, the liquid level gradually rises, and the magnetic detector also rises together with the float.
Output voltage increases. When the wave level reaches hl in Fig. 16,
The output voltage becomes vl, the pump stops, the liquid supply is cut off, and the liquid level in the tank becomes hl, which is somewhat higher than h+. Because the liquid level is undulating, the magnetic detector moves up and down with the float even after the pump has stopped. When the magnetic detector, which is moved downward by the waves, reaches t''I+, the output voltage drops by more than V, and the pump starts.The magnetic detector then moves upward by the waves, and when it exceeds hl, the pump starts. stops.

As described above, a problem arises in that the pump is frequently operated temporarily due to the influence of waves on the liquid surface.

[Means for solving problems]

The magnetic detector of the present invention includes a magnetically sensitive element that is sensitive to a magnetic field acting on the element and is packaged with an exterior member made of ferromagnetic material.

Book y! ! 1! The 11th place n detection device is composed of an elongated magnetic member arranged to face each other at a distance, and a permanent magnet placed between the elongated magnetic members at both ends of the elongated magnetic member.
It has a structure in which a magnetic circuit structure and a magnetic sensing element that is sensitive to the magnetic field acting on the structure are covered with an exterior member made of ferromagnetic material. It consists of a magnetic detector that can be moved in different directions.

[Effect]

Due to the external magnetic field, the ferromagnetic housing member itself additionally generates a magnetic field that acts on the magnetically sensitive element.

Since this exterior member has magnetic hysteresis, the output characteristics of the magnetic sensing element, ie, the output characteristics of the magnetic detector, determine the hysteresis with respect to changes in the external magnetic field.

Since the position detection device uses the magnetic detector mentioned above,
Its output characteristics also have hysteresis with respect to changes in the position of the magnetic detector. This hysteresis prevents the pump from being activated frequently.

〔Example〕

FIG. 1 is a partially cutaway perspective view showing a magnetic detector 1 according to an embodiment of the present invention. In the figure, 2 is a magnetoresistive element as a magnetic sensing element, 3G is a cylindrical case as an exterior member, and 4 is a lead terminal.

FIG. 2 shows a position detection device 5 according to an embodiment of the present invention. In the figure, reference numeral 6 denotes a closed magnetic circuit structure, which includes a pair of elongated magnetic metal plates 7°8 spaced apart and facing each other, and magnetic metal plates 7 and 7 on both ends of the long magnetic metal plates 7 and 8. It consists of permanent magnets 9° and 10 placed between two magnets. Inside the closed magnetic circuit structure 6, leakage magnetic fluxes 11a and 11b leaked from the magnetic metal plates 7.8 flow as shown by arrows. The external magnetic field due to the leakage magnetic fluxes 11a and 11b becomes zero at the top center Pc in the potato direction of the magnetic metal plate 7.8, becomes positive when it deviates from Po in the direction of arrow X1, becomes stronger in the positive direction as it deviates, and vice versa. When it deviates from Pc in the direction of arrow X2, it becomes negative, and as it deviates, it becomes stronger in the negative direction.

12 is a non-magnetic rod, and 13 is a non-magnetic guide that movably guides the rod 12. The magnetic detector 1 is fixed to one end of the rod 12 and arranged inside the closed magnetic circuit structure 6, and is arranged in the direction of the arrow X according to the movement of the rod 12.
+, moves back and forth linearly in the X2 direction. Magnetic detector 1
The axis e of the cylindrical case 3 is aligned with the magnetic metal plates 7 and 8 so that the magnetic resistance element 2 can detect the leakage magnetic fluxes 11a and 11b.
It is attached to the rod 12 in a direction perpendicular to the above. The leakage magnetic fluxes 11a and 11b enter the case 3 through openings at both ends of the case 3, and act on the magnetic resistance element 2.

The above-mentioned position detection device 5 is used, for example, as a liquid level detection section of a liquid level control device as shown in FIG. In the same figure, 2
0 is a tank, 21 is a liquid, and 22 is a float. The closed magnetic circuit structure 6 is fixed vertically, and the float 22 is attached to the lower end of the rod 12. The magnetic detector 1 detects leakage magnetic fluxes 11a and 11b (external magnetic fields) and moves in the directions of arrows X+ and X2 according to the movement of the float 22.

113, the liquid level control device operates or stops the pump according to the output from the liquid level detection device 5 to maintain the liquid level of the liquid 21 in the tank 20 at a predetermined level Lo. It is a device to control.

Further, an amplifier 14 and a comparator 15 are connected to the magnetic detector 1, as shown in FIG. magnetic detector 1,
Amplifier 14 and comparator 15 function as a switch without moving contacts. 16 is an output terminal from which a control signal is taken out.

Next, the detector 1, position detecting device 5, etc. will be explained in more detail.

In Fig. 1, the output voltage of the magnetoresistive element 2 changes in proportion to the external magnetic field, and the magnetoresistive element 2 itself does not exhibit hysteresis, as shown by the line ■ in Fig. 5, and the external magnetic field - output voltage exhibiting characteristics.

A cylindrical case 3 surrounding the magnetoresistive element 2 is made of ferromagnetic metal. For example, permalloy or silicon steel plate. Therefore, when an external magnetic field acts on the case 3, the case 3 is magnetized as shown in FIG. 6 or 7 depending on the external magnetic field, and leakage magnetic flux 17.18 is generated from the case 3 itself.

This leakage magnetic flux 17.18 acts on the magnetoresistive element 2.

As a result, when the magnetic detector 1 is located to the right of Pc in FIG. leakage magnetic flux 17 is applied. When the magnetic detector 1 is located to the left of Pc in FIG. 2, the magnetic resistance element 2 absorbs the above-mentioned leakage magnetic flux in addition to the leakage magnetic flux 11b of the closed magnetic circuit structure 6, as shown in FIG. 18.

That is, the magnetic field formed by the closed magnetic circuit structure 6 is I-1.
e x and the magnetic field formed by case 3 is )lCa, then a magnetic field 1-1rv, which is the sum of the above magnetic fields Hex and HCa, is applied to the magnetoresistive element 2 (t + r v =
He x + l-1c a ), magnetoresistive element 2
outputs a voltage corresponding to this.

If we look at the magnetic properties of case 3, we find that case 3
are made of ferromagnetic metal, so lines IV and V in Figure 8
The magnetic characteristics having hysteresis shown in 51 are as follows. Therefore, even if the strength of the external magnetic field acting on Case 3 is the same, the strength of the magnetic field increases and reaches that strength, and conversely, it decreases and reaches that strength. The magnetic induction (coercive force) of case 3 is different depending on the case. For example, considering the point where the external magnetic field is zero, when the strength of the magnetic field of opposite polarity decreases and reaches zero, the degree of magnetic induction (coercive force) is HC
In contrast, when the strength of the positive magnetic field decreases and reaches zero, the magnetic induction (coercive force) becomes HO2. This also applies to points where the strength of the external magnetic field is other than zero.

Therefore, for each level of the strength of the magnetic field acting on the magnetic detector 1, when the strength of the magnetic field increases and reaches that level, and conversely, when it decreases and reaches that level, The magnetic field 1-ICa is different. As a result, the characteristic of the magnetic detector 1 itself becomes a characteristic having hysteresis as shown by lines 2 and 3 in FIG.

Since the magnetic detector 1 itself has hysteresis characteristics, the output characteristics of the position detection device fi5 (magnetic detector 1) also have the first
As shown by circles (■) and (■) in Figure 0, the characteristic has hysteresis. That is, when the magnetic detector 1 moves from the left end in FIG. 2 in the direction of arrow x1, the output voltage of the magnetic detector 1 changes as shown by the line When moving from the right end in the x2 direction of the arrow, this output voltage changes as shown by the line ■.

In this case, it is assumed that the comparison voltage of the comparator 15 is set to Vr (see FIG. 9).

As the pump is driven and the liquid 21 is supplied into the tank 20, the float 22 moves upward in FIG. 3, and the magnetic detector 1 moves in the x1 direction of the arrow in FIGS. 2 and 3. When the liquid level becomes LO and the magnetic detector 1 reaches the level 71 P +, the voltage exceeds Vr and the comparator 15 outputs a signal. As a result, a control signal shown at 25 in FIG. 11 is output from the terminal 16 (FIG. 4), and the pump is stopped.

Further, as the liquid 21 in the full tank 20 is consumed and the liquid level decreases, the magnetic detector 1 moves in the direction of arrow x2 in FIGS. 2 and 3. Even if the liquid level reaches LO and the magnetic detector 1 reaches the position P1, the output voltage of the magnetic detector 1 is Vl higher than vr, and as shown by 26 in FIG. continues and the pump is stopped). When the liquid level further decreases and position detector 1 exceeds position P2, the voltage becomes below Vr and comparator 15
The twist outlet is cut off and the pump is activated at this point.

In this way, the position of the magnetic detector 1 when the signal from the comparator 15 is output is different from the position of the magnetic detector 1 when the signal from the comparator 15 is cut off.

Next, in Figures 2, 3, and 10, the liquid is supplied and the liquid level rises, the liquid level exceeds Lo and reaches Ll, and magnetic detection occurs when the liquid level ripples in this state. v! The output of H1 will be explained.

Assume that the liquid level ripples with an amplitude W around the liquid level L1. The magnetic sensor 51 is located at positions P4 and P along with the float 22.
It moves back and forth between s. At this time, the output voltage of the magnetic detector 1 increases to v2 along the line ■ due to the first movement of the magnetic detector 1 to P4, and when the magnetic detector 1 moves to P5, it rises to v2 along the line X. When moving to P4 again, it changes as shown in line XI, and from then on,
It changes with hysteresis as shown by lines X and XI.

The magnetic detector 1 moving in the direction of the arrow x2 crosses the position P1 and reaches the position 7. Even when I P s is reached, the output voltage of the magnetic detector 1 does not fall to Vr, but remains at V3, which is slightly higher than this.
Comparator 15 continues its output state.

Therefore, even if the liquid level is rippled, so-called chittering does not occur, the magnetic detector 1 and position detection device 5 work well as a liquid level detection section, and the liquid level control device stabilizes the liquid level. can be controlled.

Further, as shown in FIG. 1, the magnetoresistive element 2 is oriented such that its sensitive axis 2a coincides with the axis of the cylindrical case 3. Furthermore, the axis of easy magnetization 3a of the case 3 made of permalloy or silicon steel plate is oriented in the same direction as the above-mentioned axis, as shown in FIGS. 6 and 7, by heat treatment or the like. That is, case 3 has anisotropy in the north direction of the axis.

As a result, the output characteristics of the magnetic detector 1 have a substantially symmetrical shape with respect to the origin O, as shown in FIG.

Note that the case 3 may have a rectangular cylindrical shape.

The material of the case 3 may be ferromagnetic resin.

Although not shown, the inside of the case 3 is filled with resin so as to surround the magnetoresistive cable 2.

Further, instead of the elongated magnetic metal plate 7.8 of the position detection device 5, an elongated magnetic resin plate may be used.

FIG. 12 shows a modification of the magnetic detector. This magnetic detector 30 has a structure in which ferromagnetic plates 31 and 32 are provided to sandwich the magnetoresistive element 2 from both sides. Ferromagnetic plate 31.
32 functions similarly to the case 3 above, and the magnetic detector 3
0 has substantially the same characteristics as the characteristics shown in FIG.

FIG. 13 shows another example of use of the position detection device.

The magnetic detector 1 is attached to the float 35 itself as shown in FIG.
1 and fixed in a vertical position. 36 is a flexible wire for extracting signals.

〔Effect of the invention〕

According to the detector of the present invention, since the exterior member that is magnetized by an external magnetic field has magnetic hysteresis, the output can have an output characteristic that has hysteresis with respect to changes in the external magnetic field.

According to the position detection device of the present invention, since the above magnetic detector is used as the magnetic detector, the output can have an output characteristic having hysteresis with respect to a change in the position of the magnetic detector, that is, the same output can be 10 can be made to differ depending on the direction of movement of the magnetic detector, which prevents the occurrence of so-called chattering when detecting the position of the detected part, which is accompanied by vibrational positional changes, for example, of a float on the liquid surface. It can be done without.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a magnetic detector according to an embodiment of the present invention, FIG. 2 is a partially cutaway perspective view of a position detection device according to an embodiment of the present invention, and FIG. Figure 2 is a diagram showing an example of the use of the δ detector, Figure 4 is a block diagram of a circuit that extracts the output of the magnetic detector as a control signal, Figure 5 is a characteristic diagram of the magnetoresistive element, Figures 6 and 7 are diagrams showing the state in which the lower magnetic field acts on the magnetoresistive element, Figure 8 is a magnetic characteristic diagram of the cylindrical case, Figure 9 is a characteristic diagram of the magnetic detector itself, and Figure 10 Figure 11 is a diagram showing the characteristics of the position detection device, Figure 11 is a diagram showing the control signal taken out from the output terminal in Figure 4, Figure 12 is a perspective view showing a modification of the magnetic detector, and Figure 13 is a diagram showing the position of the magnetic detector. Figure 14 is a plan view of a float, Figure 15 is a characteristic diagram of a conventional magnetic detector, and Figure 16 is a characteristic diagram of a conventional position detection device. , 1.30 is a magnetic detector, 2 is a magnetoresistive element, 2a is a sensitive axis, 3 is a case, 3a is an axis of easy magnetization, 5.5A is a position detection device, 6 is an open magnetic circuit structure, 7.8 is a IB long magnetic metal plate, 89.10 is a permanent magnet, 11a, 11b, 17.18 is a leakage magnetic flux, 15 is a comparator, 16 is an output terminal, 20 is a tank, 21 is a liquid, 22.35 is a float, 31. 32 is a ferromagnetic plate. Figure 4: Magnetic resistance 1,000 general forces Figure 5 External 81 Hayabusa force v Magnetic resistance Yonago 1 Tekto sound P Shikikai Kai force

Claims (6)

[Claims] (1) A magnetically sensitive element (2) that is sensitive to the magnetic field that acts on it.
) is packaged with an exterior member (3, 31, 32) made of ferromagnetic material. (2) The magnetic detector according to claim 1, wherein the exterior member is a case (3) having a cylindrical shape surrounding the magnetically sensitive element (2). (3) The magnetic detector according to claim 1, wherein the exterior member is a pair of plates (31, 32) arranged to sandwich the magnetically sensitive element (2) from both sides. . (4) The exterior member is a sensitive axis (2a) of the magnetically sensitive element.
The magnetic detector according to claim 1, having anisotropy in the same direction as . (5) The magnetic detector according to claim 1, wherein the exterior member is made of ferromagnetic resin. (6) Elongated magnetic members (7, 8) arranged to face each other at a distance
and permanent magnets (9, 10) sandwiched between the elongated magnetic members (7, 8) at both ends of the elongated magnetic members (7, 8).
), and a magnetic sensing element (2) that is sensitive to the magnetic field that acts on the closed magnetic circuit structure (6), and a magnetic sensing element (2) that is sensitive to the magnetic field acting on the closed magnetic circuit structure (6), which is covered with a ferromagnetic exterior member (3, 31, 32). and a magnetic detector (1, 30) movable in the longitudinal direction of the elongated magnetic member (7, 8) inside the closed magnetic circuit structure (6).