JP2000286120A - Magnet, and method for magnetizing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet which can increase the flexibility in design for the miniaturization, simplification, etc., of a device, using the magnet by localizing magnetic poles of the magnet to one end face side only and can widen the use of the magnet itself, and a method for magnetizing the magnet. SOLUTION: A magnet is magnetized on one end face section side only by adjacently forming N and S poles on the end face section side. Alternatively, the magnet is characterized in that the density of magnetic fluxes directed toward an S pole formed adjacently to an N pole formed on one end face section side from the N pole formed on the end face section side is higher than that of magnetic fluxes directed toward an S pole, formed adjacent to an N pole formed on the other end face section side from the pole formed on the end face section side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnet and a magnetizing method.

[0002]

2. Description of the Related Art In general, in order to produce a thin and small-diameter disk-shaped magnet, a magnetizing method using an air-core coil is known as a magnetizing device. It is difficult to form an N pole and an S pole adjacent to each other.

Therefore, as shown in FIG. 7, the N and S poles of a magnetizing device 4 composed of a horseshoe-shaped yoke 2 and an energizing coil 3 face one end surface of a disk 1 as a magnetic material, A magnetizing method in which an auxiliary yoke 5 as a magnetic material is provided alongside the other end surface of the body 1 and a magnetic field H is applied from the one end surface of the disk body 1 has been attempted.

According to this magnetizing method, the magnetic moment oriented in a random direction is changed to a magnetic field H as shown in FIG.
And a disk-shaped magnet 6 is formed in which the N pole and the S pole are formed adjacent to one end face side and the N pole and the S pole are formed adjacent to the other end face side. .

[0005]

However, according to this magnetizing method, as shown in FIGS. 8 and 9, an S pole formed on one end face side from the N pole on one end face side. The magnetic flux Φ2, the magnetic flux Φ3, and the magnetic flux Φ4 are present in addition to the magnetic flux Φ1 traveling toward the, so that the absolute value of the magnetic flux density is dispersed. Because of this, the disc-shaped magnet 6
The N pole and the S pole are localized on one end face of the magnet, and a magnetic field does not exist on the other end face or the strength of the magnetic field is significantly smaller than that of the one end face. Was.
For this reason, if the magnetic poles can be localized only on one end side of the magnet, the degree of freedom in design for possible miniaturization and simplification is limited, and the use of the magnet itself is narrowly limited. For example, when the magnet is used as a detection signal output unit such as an encoder, since the magnetic poles are not localized as described above, the size of the magnet is increased in order to obtain a necessary magnetic field strength, and the relative arrangement with the sensor is also reduced. It was restricted to a certain range.

SUMMARY OF THE INVENTION An object of the present invention is to localize the magnetic pole only on one end side of the magnet, thereby increasing the degree of freedom in designing a device using the magnet for miniaturization, simplification, and the like.
It is still another object of the present invention to provide a magnet capable of expanding the use of the magnet itself and a method of magnetizing the magnet.

[0007]

In order to achieve the above object, in the magnet according to the present invention, an S pole is formed adjacent to an N pole formed on one end face side, and an S pole is formed on the one end face side. It is characterized by being magnetized only.
According to the present invention, since the N pole and the S pole are localized on one end surface of the magnet, the magnetic field is concentrated on the one end surface even if the magnet is small, thereby increasing the strength of the magnetic field. It becomes possible. As a result, it is possible to increase the degree of freedom of design for miniaturization, simplification, and the like of the device using the magnet, and to further expand the use of the magnet itself.

The magnet according to the second aspect of the present invention is arranged such that the N pole formed on the one end face side moves from the N pole to the one end face side.
The density of the magnetic flux heading toward the S pole formed adjacent to the pole is the density of the magnetic flux heading from the N pole formed at the other end surface to the S pole formed adjacent to the N pole at the other end surface. It is characterized by being larger than. According to the present invention, by making the magnetic flux density on one end surface side of the magnet higher than that on the other end surface side, it is possible to obtain the same effect of magnetic pole localization as in the first aspect of the present invention.

According to a third aspect of the present invention, in the magnet according to the first or second aspect, the magnet is formed by magnetizing a molded disk by mixing magnetic powder with a molding resin. It is a plastic-based magnet. Thereby, a magnet having a desired shape can be easily manufactured by injection molding, and at the same time, the magnet is lightweight and hard to be broken, so that the handleability is improved.

According to a fourth aspect of the present invention, in the magnet according to the third aspect, a gate mark generated when the plastic-based magnet is injection-molded is used as a front and back identification mark of the magnet. It is characterized by the following. In the magnet, since the magnetic pole is localized on one end surface side, it is necessary to distinguish between the front and back sides.According to the present invention, the gate mark which is inevitable by the injection molding method is `` back '', that is, Since the magnetic pole is used as a mark indicating the other end surface side opposite to the localized one end surface side, the front and back can be distinguished without bothering the addition of a new distinction mark.

Next, the magnetizing method according to a fifth aspect of the present invention is characterized in that the N pole formed on the one end face side moves from the N pole to the one end face side.
The density of the magnetic flux directed to the S pole formed adjacent to the pole is higher than the density of the magnetic flux directed from the N pole formed on the other end face side to the S pole formed adjacent to the N pole on the other end face side. In order to form a large magnet, the magnetic field is applied to the magnetic body with the N and S poles of the magnetizing device facing only one end surface side of the magnetic body before magnetizing. .

According to a sixth aspect of the present invention, in the magnetizing method according to the fifth aspect, an auxiliary material comprising a magnetic material for forming an N pole and an S pole on the other end surface of the magnetic material. It is characterized in that no yoke is provided.
According to a seventh aspect of the present invention, in the magnetizing method according to the fifth aspect, the magnetic body is a small-diameter disk.

According to the fifth to seventh aspects of the present invention, an N pole and an S pole are localized on one end surface of the magnet, and a magnet capable of increasing the strength of a magnetic field can be easily manufactured. can do.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnet, a magnetizing method and a rotation detecting device using the magnet according to the present invention will be described below. FIG. 1 is a schematic diagram for explaining the magnetization state of the magnet of the present invention, FIG. 2 is an explanatory diagram for explaining the magnetization of the magnet using the magnetization method of the present invention, and FIG.
FIG. 4 is an explanatory view of a magnetic pole formed on the magnet, FIG. 4 is a view showing an example of a rotation detecting device using the magnet according to the present invention, and FIG. 5 is a diagram showing the principle of rotation detection by the rotation detecting device using the magnet according to the present invention. Schematic diagram for explaining, FIG. 6
FIG. 3 is a diagram showing an analog electric signal generated based on rotation of a magnet.

In FIG. 2, reference numeral 10 denotes a small-diameter disk as a magnetic material. The disk body 10 is formed by mixing a magnetic powder with a plastic molding resin at a predetermined ratio and by injection molding. In the embodiment of the present invention, the mixing ratio of (magnetic powder) :( plastics molding resin material) is 8: 2, and the mixing ratio can be appropriately changed according to use. In addition, as a material of the magnetic powder, for example, a neodymium alloy, a samarium-cobalt alloy, or the like is used.

As shown in FIG. 2, the N pole and the S pole of a magnetizing device 13 comprising a horseshoe-shaped yoke 11 and an energizing coil 12 face one end face of the disc body 10, and the other end face of the disc body 10 is provided. The magnetic field H does not have an auxiliary yoke made of a magnetic material for forming an N pole and an S pole on the other end surface side.
Is applied only from one end surface side of the disk body 10.

As shown schematically in FIG. 1 (a), the magnetic moment of the magnetic powder of the disk 10 is oriented in a random direction before magnetization, and the magnetic body 10 When H is added to the disk body 10, the magnetic moment of the magnetic powder on one end face side is more oriented along the direction of the magnetic field H as shown schematically in FIG. As a result, the number of magnetic moments arranged along the direction of the magnetic field H decreases, whereby the number (density) of magnetic fluxes Φ5 from the N pole to the S pole on one end face side increases from the N pole to the S pole on the other end face side. The disc-shaped magnet 14 is formed which is larger in number than the number (density) of the magnetic flux Φ6 heading toward. The magnetizing device 13 makes it possible to produce a disk-shaped magnet 14 having almost no magnetic flux Φ6 and only the magnetic flux Φ5. The magnetic poles N and S formed on the disk-shaped magnet 14 have a half-moon shape as shown in FIG. In addition, this disk-shaped magnet 1
4 can also be formed by sintering a magnetic material without using a plastic molding resin, but it is desirable to use a plastic magnet in terms of resistance to cracking and handling.

The disc-shaped magnet 14 is used, for example, in a rotation detecting device for detecting the rotation of a rotating body. FIG. 4 shows an example of the rotation detecting device. In FIG. 4, reference numeral 15 denotes a housing constituting a part of a steering angle sensor for detecting a rotation angle of a steering wheel (not shown) of an automobile, and reference numeral 16 denotes a housing. Reference numeral 17 denotes a circuit board fixed to the housing 15, and reference numeral 17 denotes a driven gear (rotary body) meshed with an annular drive gear 16A that is driven to rotate with the rotation of the steering wheel. The housing 15 has a circular bearing recess 18 formed therein. The driven gear 17 has a circular fitting shaft portion 19 formed on the bottom side thereof so as to be rotatably fitted into the circular bearing recess 18. Driven gear 1
7, a holding hole 20 is formed at the center, and the disc-shaped magnet 14 is fixed to the holding hole 20.

The circuit board 16 is provided with a magnetoresistive element 21 which faces the disc-shaped magnet 14 and is located on the rotation center O1 of the driven gear 17, and reference numeral 21a denotes a terminal of the magnetoresistive element. A predetermined voltage is applied to the element 21. The driven gear 17 is formed with an annular contact portion 22 that slidably contacts the circuit board 16 so as to surround the magnetoresistive element 21. This driven gear 17
While the circular fitting shaft portion 19 is supported by the circular bearing recess 18 and the annular contact portion 22 is slidably contacted with the circuit board 16, it is rotated about the rotation center O <b> 1.

The magnetic resistance element 21 has a magnetic flux Φ passing therethrough.
5 (magnetic flux density), the magnetic resistance changes.
As shown in (a), the magnetic flux Φ crossing the magnetoresistive element 21
With reference to the case where the magnetic flux of the disk-shaped magnet 14 is oriented in the direction in which the density of 5 is 0, when the disk-shaped magnet 14 rotates in the direction of the arrow and the number of magnetic fluxes Φ5 crossing the magnetoresistive element 21 increases, the When the resistance increases and the disc-shaped magnet 14 is positioned in a direction substantially 90 degrees as shown in FIG. 5B with respect to the position shown in FIG.
1 is the largest. The disk-shaped magnet 14 continues to rotate, and the position shown in FIG.
When it is positioned in the 180-degree direction as shown in (c), the magnetoresistance of the magnetoresistive element 21 becomes minimum again. Therefore, according to this rotation detecting device, the magnetoresistive element 21 causes the AC analog electric signal AC having two positive peaks due to the change in the direction of the magnetic flux Φ5 during one rotation of the disc-shaped magnet 14.
(See FIG. 6). In FIG. 6, the output of the AC analog electric signal AC when the direction of the magnetic flux of the disc-shaped magnet 14 is oriented at 45 degrees with respect to the position shown in FIG. .

As a result, the rotation of the rotating body 17 can be detected on the center of rotation, and the accuracy of rotation detection can be improved. That is, when rotation is detected at the periphery of the rotating body 17, an error due to the rotational runout of the rotating body 17 is mixed unless the bearing is manufactured with high precision. Can be detected while avoiding an error due to rotational runout or the like, without manufacturing the device with high precision.

In the embodiment of the present invention,
Gate marks 23 (see FIG. 4) generated when the disk body 10 is injection-molded with a plastics base are used as front and back identification marks when the disk body 10 is assembled to the rotating body 17. The gate mark 23, which is unavoidable in the injection molding method, is used as a "back", i.e., a mark indicating the other end face side opposite to the one end face side where the magnetic pole is localized. It is possible to distinguish between the front and back sides without adding a new one.

The embodiments of the present invention have been described above, but the present invention is not limited to these embodiments.
Various modifications are possible without departing from the spirit of the invention.

[0024]

According to the magnet of the present invention, the N pole and the S pole are localized on one end surface of the magnet.
Even if the magnet is small, the magnetic field concentrates substantially on one end surface side, and the strength of the magnetic field can be increased. As a result, it is possible to increase the degree of freedom of design for miniaturization, simplification, and the like of the device using the magnet, and to further expand the use of the magnet itself. Further, according to the magnetizing method of the present invention, it is possible to easily manufacture the magnet having the single-sided magnetized localization.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic diagrams for explaining the state of magnetization of a magnet of the present invention, wherein FIG. 1A shows a state of a magnetic moment before magnetization, and FIG. 1B shows a state of a magnetic moment after magnetization. Show.

FIG. 2 is an explanatory diagram for explaining the magnetization of a magnet using the magnetization method of the present invention.

FIG. 3 is an explanatory diagram of magnetic poles formed on a magnet.

FIG. 4 is a diagram showing an example of a rotation detecting device using a magnet according to the present invention.

5A and 5B are schematic diagrams for explaining a principle of detecting rotation of a rotating body by a rotation detecting device according to the present invention, wherein FIG. 5A shows the direction of a magnetic flux at which the magnetoresistance of a magnetoresistive element is minimized;
(B) shows a state in which the direction of the magnetic flux changes by 90 degrees with respect to the direction of the magnetic flux shown in (a), and (c) shows a state in which the direction of the magnetic flux changes by 180 degrees with respect to the direction of the magnetic flux shown in (a). Indicates the status.

FIG. 6 is a diagram showing an analog electric signal generated based on rotation of a magnet.

FIG. 7 is an explanatory diagram of a magnetizing method using an auxiliary yoke.

8 is a diagram schematically showing a magnetized state of a magnet obtained by the magnetizing method shown in FIG.

FIG. 9 is a schematic diagram for explaining the state of distribution of a magnetic field when the magnet shown in FIG. 8 is viewed from one end face side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Small disk 13 Magnetizer 14 Disk magnet 15 Housing (of steering angle sensor) 16 Circuit board 17 Follower gear 20 Holding hole 21 Magnetic resistance element 22 Annular contact part 23 Gate mark Φ5, Φ6 Magnetic flux

Claims (7)

[Claims] 1. A magnet, wherein an S pole is formed adjacent to an N pole formed on one end face side, and magnetized only on the one end face side. 2. The density of magnetic flux from an N pole formed on one end face side to an S pole formed adjacent to the N pole on one end face side is different from that of an N pole formed on the other end face side. A magnet, wherein the density of the magnetic flux directed to the S pole formed on the end face side adjacent to the N pole is higher. 3. A plastic-based magnet according to claim 1 or 2, wherein the molded resin is mixed with a magnetic powder to magnetize a molded disk. 4. The magnet according to claim 3, wherein a gate mark generated when the plastic-based magnet is injection-molded is used as a front / back identification mark of the magnet. 5. The density of magnetic flux from an N pole formed on one end face side to an S pole formed adjacent to the N pole on one end face side is changed from an N pole formed on the other end face side to the other end face. In order to form a magnet having a density higher than the magnetic flux toward the S pole formed adjacent to the N pole on the side of the magnet, the N pole and the S pole of the magnetizing device are connected to one end surface of the magnetic body before magnetization. A magnetizing method comprising applying a magnetic field to the magnetic body so as to face only the side. 6. The magnetizing method according to claim 5, wherein an auxiliary yoke made of a magnetic material for forming an N pole and an S pole is not provided on the other end surface of the magnetic material. 7. The magnetizing method according to claim 5, wherein the magnetic body is a small-diameter disk.