JP2727460B2 - Proximity switch magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention relates to a magnet used for detecting an external magnetic pole to control traveling of an automatic guided vehicle or the like, particularly a magnet provided with a Hall element or a bias magnet. The present invention relates to a structure of an external magnetic field magnet that can easily set an accurate threshold value when a magnetoelectric conversion element such as a magnetoresistive element made of a magnetic thin film is used as a sensor.

<Conventional example and problems> Conventionally, a flat plate-shaped magnet (permanent magnet) for an external magnetic field of this type is provided with a magnet axis perpendicular to the plate surface as shown in FIG. Magnetized ones are known. A plurality of the plate-like magnets (1), (2), and (3) are arranged and arranged so that the same magnetic pole surface faces the magnetoelectric conversion elements (100) and (101) as magnetic sensors. The magneto-electric conversion elements (100) and (101) are relatively arranged so as to move at a fixed distance to the magnets (1), (2) and (3) while sequentially moving along a locus traversing the magnetic field. I have. As the magnetoelectric element, a Hall element or a magnetoresistive element made of a ferromagnetic thin film to which a bias magnetic field is applied is used.

At the time of this relative position movement, the magnetoelectric conversion element (100),
In (101), a change in the magnetic field is detected, and a voltage corresponding to the direction of the magnetic flux and the magnetic field strength is output. The output voltage characteristics in this case are shown in FIG. 12, in which (a) shows the output of the magneto-electric conversion element (100) moving a distance far from the N pole surface of the magnets (1), (2) and (3). Characteristic curve, (b)
Is an output characteristic curve of the magnetoelectric conversion element (101) that moves a distance close to the N-pole surface of the magnets (1), (2), and (3).

The magneto-electric conversion element (100) is a magnet (1), (2),
When moving at an appropriate distance from (3), as shown in the output voltage curve (a), the magnetoelectric conversion element (10
When 1) crosses over the outer peripheral edge of the magnet and departs from the N-pole plate surface, it is not strongly affected by the S-pole magnetic field on the back side of the plate surface, and therefore does not exceed the threshold value (A2) of the S-pole. .

However, as can be seen from the output voltage curve (b) in the figure, the magneto-electric conversion element (101) has a magnet (1),
(2) and (3), each time the magnetoelectric conversion element (101) deviates from the N-pole plate surface across the outer peripheral edge of the magnet, it moves from the S-pole magnetic field on the back side of the plate surface. An output exceeding the threshold value (A2) of the S pole is strongly received and is output. For this reason, an erroneous determination of “approaching to the S pole face” is output from the OP amplifier in the control circuit (not shown).

FIG. 13 shows detection of a magnetic field change when the magnetoelectric conversion elements (102) and (103) are moved in a state where the magnet (2) in FIG. 11 is removed. The output voltage characteristics from (102) and (103) are as shown in (c) and (d) of FIG. Also in this case, when the magnetoelectric conversion element (102) moving at a short distance from the magnets (4) and (5) crosses over the outer peripheral edge of the magnet and deviates from the N-pole plate surface, the S-pole magnetic field on the back side of the plate surface is removed. And the output exceeds the threshold (B2) of the S pole. For this reason, an erroneous determination of “approaching to the S pole face” is output from the OP amplifier in the control circuit.

Further, FIG. 17 shows the magneto-electric conversion elements (104), (1) in a state where the magnet (2) at the intermediate position in FIG. 1 is removed, and the opposite pole face is arranged adjacent to the magneto-electric conversion element.
FIG. 16 shows the correlation between the magnets (6) and (7), and the output voltage characteristics from the elements (104) and (105) at that time are shown in (e) and (f) of FIG. Become like

In this case, when the magnetoelectric conversion element (105) moving at a short distance from the magnets (6) and (7) crosses over the outer peripheral edge of the magnet (6) and deviates from the N-pole plate surface, S Strongly influenced by the pole magnetic field, the S pole threshold (C
Output exceeding 2) is made. Therefore, O in the control circuit
The P amplifier outputs an erroneous judgment of “approaching to the S pole face”, and when approaching immediately above the outer periphery of the S pole of the magnet (7), the influence of the N pole magnetic field on the back side of the plate surface becomes strong. As a result, an output exceeding the threshold value (C1) of the N pole is made. For this reason, an erroneous determination of “approaching face to face N pole” is output from the OP amplifier in the control circuit.

<Means for Solving the Problems> Therefore, the present invention has been provided to eliminate the above-mentioned disadvantages, and has an object to provide a magnetic element made of a Hall element or a ferromagnetic thin film which is a magnetoelectric conversion element. In a proximity switch using a resistance element or the like, a magnet that can increase a selection range when setting a threshold value, that is, a proximity switch magnet that can increase a selection range of a distance between a magnet and a magnetoelectric conversion element. Is to provide.

Accordingly, the present invention provides a magnet for a proximity switch which is relatively moved toward and away from a magnetoelectric conversion element in a fixed trajectory with one of the N-pole and the S-pole facing at least. A proximity switch magnet in which a sub-magnet having a smaller magnetic force than the main magnet and having the same magnetic pole orientation and an appropriate width is connected and fixed to the outer peripheral edge of the main magnet on the side where the moving trajectory of the conversion element intersects. Is achieved.

<Example> Next, the present invention will be described in more detail with reference to the example shown in Figs.

FIG. 1 shows a substantially square proximity switch magnet (M1). (7) is a substantially square plate-shaped main magnet having a thickness of 0.3 mm to 5.0 mm and a side of about 40.0 mm,
The plate surface is magnetized in the thickness direction such that one surface is an N pole and the other surface is an S pole.

(8) is a plate-shaped sub-magnet connected and fixed so as to surround the outer four sides of the main magnet (7) with a width of about 15.0 mm, and has a smaller magnetic force than the main magnet (7) and a smaller magnetic force. In addition, they are arranged so as to face the same magnetic pole as the main magnet (7) (in FIG. 1, both upper surfaces are N-poles).

When the magnetoresistive elements (106) and (107) move horizontally in the x-axis direction in the figure, the movement trajectory is determined by the outer peripheral edges (7a) and (7b) of the main magnet (7) and the sub magnet (8).
And crosses over the outer peripheral edges (8a) and (8b) of the.

The output voltage characteristics (g) and (h) of the magnetoresistive elements (106) and (107) at this time are shown in FIG. As is apparent from the output characteristic (h) of the magnetoresistive element (107) closer to the proximity switch magnet (M1), the magnetoresistive element (107) is connected to the outer peripheral edge (7a) of the main magnet (7). ) (7b) or the outer peripheral edge (8
a) The magnetic pole is not affected by the magnetic force from the S pole on the back side of the plate surface of the magnet (M1) even when it is separated from above (8b), so that it exceeds the threshold (D2) of the S pole. No output occurs. That is, only the determination of either "approaching to the N pole face" or "leaving from the N pole face" is correctly output from the OP amplifier of the control circuit (not shown), and "approaching face to the S pole face". There is no misjudgment.

Further, as described above, since neither of the magnetoresistive elements (106) and (107) output a voltage on the S pole side, the thresholds (D1) and (D2) are wide from values close to 0 (zero). The width can be set arbitrarily and there is no possibility of malfunction.

FIG. 2 shows a case in which a plurality of proximity switch magnets (M1) in FIG. 1 are arranged adjacent to each other and arranged so that the N pole surface of the main magnet (7) is flush. It is shown.

Thus, the magnetoresistive elements (106) and (107) move just above the magnets (M1), (M1) and (M1) in the row direction, that is, in the x-axis direction, and sequentially change the magnetic field of each magnet. The output voltage at the time of detection is shown in FIG. Again, in this case,
The magnetoresistive element (10
As is clear from the output characteristic curve (j) of (7), the magnetoresistive element (107) is connected to the outer peripheral edge (7a) of the main magnet (7).
(7b) or the outer magnets (8a) and (8b) of the sub-magnet (8) are hardly affected by the magnetic force from the south pole on the back side of the plate surface when they are separated from each other across the upper side. , The output exceeding the threshold value (E2) of the S pole is not generated.
That is, “N” is output from the OP amplifier of the control circuit (not shown).
Only the determination of either "approach to the pole face" or "separation from the N pole face" is correctly output, and the erroneous determination of "approach to the S pole face" does not occur.

FIG. 3 shows the outer peripheral edge (7c) of the four sides of the plurality of main magnets (7) that are adjacent to each other.
Only the sub-magnets (81) to (8) having the same thickness, magnetic force, and magnetic pole orientation as those of the sub-magnet (8) above (7d).
4) Proximity switch magnet (M
An embodiment 2) is shown.

In this case, N of the plurality of main magnets (7), (7).
Proximity switch magnet (M
2), (M2)... Are arranged adjacent to each other, and the magnetoresistive elements (106) and (107) are main magnets (7), (7).
The output voltage characteristics (k) and (l) of the magnetoresistive elements (106) and (107) at that time are shown in FIG. I have.

Also in this case, as is clear from the output characteristic curve (l) of the magnetoresistive element (107) closer to the magnet (M2), the magnetoresistive element (107) is located outside the main magnet (7). Periphery (7c) (7d) or secondary magnet (81)-
When moving away from above (84), separate the magnet (M
Since the magnetic force is hardly affected by the S pole on the back side of the plate surface in 2), no output exceeding the threshold value (F2) of the S pole is generated. In other words, only the judgment of “approaching to the N pole face” or “separation from the N pole face” is correctly output from the OP amplifier of the control circuit (not shown), and “approaching to the S pole face” There is no misjudgment.

FIG. 4 shows that, of the four sides of the main magnet (7), only one of the four sides adjacent to each other, ie, one of the main magnets (7) has the sub-magnet (7e) on the outer peripheral edge (7e) side. Secondary magnet (85) with the same configuration as 81)
The other main magnet (7) is connected to and fixed to a pair of sub-magnets (86) having the same configuration as the sub-magnet (81) on the outer peripheral edge (7f) side. Examples of (M3) and (M3) are shown.

In this case, the two proximity switch magnets (M3) and (M3) are arranged adjacent to each other with a space therebetween so that the N pole faces of the pair of main magnets (7) and (7) are flush with each other. The magnetoresistive elements (106) and (107) move just above the main magnets (7) and (7) in the row direction, that is, the x-axis direction.
The output voltage characteristics (m) and (n) at (107) are shown in FIG.

Also in this case, as is clear from the output characteristic curve (n) of the magnetoresistive element (107) closer to the magnet (M3), the magnetoresistive element (107) is located outside the main magnet (7). Periphery (7e) (7f) or secondary magnet (85)-
(86) when moving away from the magnet (M
Since the magnetic pole is hardly affected by the S pole on the back side of the plate surface in 3), no output exceeding the threshold (G2) of the S pole is generated. That is, only the judgment of “approaching to the N pole face” or “separation from the N pole face” is correctly output from the operational amplifier (not shown) of the control circuit (not shown). Will not be misjudged.

FIG. 5 shows the case where one of the proximity switch magnets (M3) (right side in FIG. 4) in FIG.
An example is shown in which the upper surface of the right magnet (M4) is disposed so as to be an S pole.

In this case, when the magnetoelectric conversion elements (106) and (107) move to detect a change in the magnetic field, the elements (106) and (10)
The output voltage characteristic from 7) is the characteristic curve (o) in FIG.
This is indicated by (p).

At this time, as is evident from the output voltage (p) of the magneto-electric conversion element (107) moving at a short distance above the magnets (M3) and (M4), this magneto-electric conversion element (107) Even if it crosses over the outer peripheral edge (7i) of (M4) and deviates from the N-pole surface, the sub-magnet (85) of the N-pole on the upper surface hardly receives the S-pole magnetic field on the back side of the plate surface.
No output will exceed the pole threshold (H2).
Therefore, only the correct output "leaving from the N pole face" is generated from the OP amplifier of the control circuit (not shown) by this movement, and the erroneous determination that "the face is approaching the S pole face" is not output. .

Next, it approaches the outer peripheral edge of the upper surface S pole of the magnet (M4).
Therefore, there is almost no reception of the N-pole magnetic field on the back side of the plate surface, and no output exceeding the threshold value (H1) of the N-pole is generated. Therefore, due to this movement, only the correct output of "approaching the S pole" is generated from the OP amplifier of the control circuit (not shown), and the erroneous determination of "approaching facing the N pole" is not output.

The present invention provides an N pole of each proximity switch magnet,
The same effect is obtained when the S pole is inverted.

<Effect> According to the magnet according to the present invention, in a proximity switch using a Hall element or a ferromagnetic thin film magnetoresistive element which is a magnetoelectric conversion element, while maintaining accurate operation, Since the selection range of the threshold value setting can be widened, the selection range of the distance between the magnet and the magnetoelectric conversion element can be widened and can be adjusted arbitrarily.

Further, since the structure is simple, it is easy to manufacture and mass-produced at low cost.

[Brief description of the drawings]

1 to 5 are perspective views showing an embodiment of a proximity switch magnet according to the present invention, and FIGS. 6 to 10 are output voltage characteristic graphs in the embodiment of FIGS. 11, 13 and 15 are perspective views showing a proximity switch magnet according to a conventional example. No. 12,
14 and 16 are output voltage characteristic graphs in the above conventional example. (7) ... main magnet, (8) ... sub magnet,
(81) to (87): sub-magnet, (106): magnetoresistive element (107): magnetoresistive element

Claims (1)

(57) [Claims] A magnet for a proximity switch which is relatively moved toward and away from a magnetoelectric conversion element with a fixed trajectory toward one of an N pole and an S pole, wherein at least the movement of the magnetoelectric conversion element A proximity switch magnet in which a sub-magnet having a smaller magnetic force than the main magnet and having the same magnetic pole orientation and an appropriate width is connected and fixed to the outer peripheral edge of the main magnet on the side where the tracks intersect.