JP2008145284A - Bipolar magnetic encoder and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bipolar magnetic encoder and its manufacturing method in which magnetic flux density variation draws a substantially perfect sine curve and increasing reliability of detection accuracy. <P>SOLUTION: In the bipolar magnetic encoder 1 with an outer circumferential surface part of a first semicircular part in a circular annular magnetic body 2 containing magnetic powder as a magnetized region 1a of an S pole and an outer circumferential surface part of the rest second semicircular part as a magnetized region 1b of an N pole, the magnetic powder includes anisotropic magnetic powder 4. The magnetic powder thereof is oriented in such a state that its magnetization easy axis 4a is parallel to a line 1d connecting central parts of the first and second semicircular parts and the magnetization is established by a magnetic field parallel to the magnetization easy axis acting on the circular annular magnetic body. The magnetic flux density variation of the outer circumferential surface part along the circumferential direction draws a sine curve in which a boundary part 1c between the magnetized region of the S pole and the magnetized region of the N pole corresponds to zero. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a two-pole magnetic encoder used for detecting an absolute position such as a crank angle and a camshaft angle for controlling an automobile engine, and to detecting an absolute position of other industrial machines, and a manufacturing method thereof.

    Recently, in order to control automobile engines, absolute positions of engine crank angle and camshaft angle have been detected. As a device for detecting the absolute position, a two-pole magnetic encoder in which the first semicircular portion of the annular magnetic body is magnetized to the S pole and the remaining second semicircular portion is magnetized to the N pole is used. Has been tried. That is, the two-pole magnetic encoder is mounted on the rotating side, and two (plural) magnetic sensors are arranged on the fixed side so as to face the annular two-pole magnetic encoder so as to face each other. Things. In such an absolute position detection device, the magnetic change by the above-mentioned two-pole magnetic encoder accompanying rotation on the rotation side is detected in an analog manner by two (plural) magnetic sensors, and the detected two (plural) The absolute position of the crank angle or camshaft angle is detected by processing the analog value.

Patent Documents 1 to 3 show examples of two-pole annular magnets. These two-pole annular magnets shown in these patent documents are made of an annular magnetic material made of a molded body such as a resin containing anisotropic magnetic powder in a state in which the magnetization facilitating axis is oriented in the radial direction (radial). Magnetization is performed by applying a magnetic field in one direction along the radial direction (a direction perpendicular to the axis of the annular magnet) to the body. By this magnetization, a two-pole annular magnet is formed in which the semicircular part is magnetized to the N pole and the other semicircular part is magnetized to the S pole. Such a change in the magnetic flux density along the circumferential direction of the two-pole annular magnet draws a curve having substantially zero peaks at the boundary portion between the N pole and the S pole, and peaks opposite to each other at the center portion. Patent Document 3 shows a waveform diagram along the circumferential direction of the magnetic flux density. FIG. 8 shows a similar magnetic flux density waveform diagram of an annular magnet having the outer peripheral surface magnetized by the method described later by the inventors.
Japanese Utility Model Publication No. 61-1225023 Japanese Patent Laid-Open No. 10-248216 JP 2003-115408 A

  By the way, when the annular magnet having the waveform characteristic of the magnetic flux density as shown in Patent Document 3 or FIG. 8 is used as the two-pole magnetic encoder for detecting the absolute position as described above, the waveform diagram of the above magnetic flux density. Is not a perfect sine curve, so when the magnetic change of the two-pole magnetic encoder mounted on the rotation side is detected in analog by two (plural) magnetic sensors arranged out of phase with each other, the detected value May not be stable, and an error may occur in absolute position detection. 9 and 10 schematically show the magnetizing method and magnetizing principle of the annular magnet showing the waveform characteristics of the magnetic flux density as shown in FIG. This will be described below.

  An annular magnetic body 100 shown in FIG. 9 is obtained by kneading an anisotropic magnetic powder 101 into a rubber raw material, a resin raw material, or a sintered raw material, and molding the anisotropic magnetic powder 101 into an annular shape. The magnetization facilitating axis 101a (see FIG. 10) is oriented so as to face in the radial direction (radial). This orientation is performed by mechanical action during the kneading and molding, or by applying an orientation magnetic field during molding. In this way, the annular magnetic body 100 in which the magnetization facilitating axes 101a of the magnetic powder 101 are radially oriented is placed in the magnetic field of the magnetizing apparatus in which the magnetic field m indicated by the white arrow is formed. The outer peripheral surface portion is magnetized by allowing it to stand so as to be orthogonal to the outer periphery. FIG. 10 (a) schematically shows a two-pole annular magnet 103 obtained by such magnetization, and the two-pole annular magnet 103 is magnetized with an S pole in the upper semicircular portion of the drawing. The region 103a is composed of an N-pole magnetized region 103b in the lower semicircular portion.

  The waveform characteristics of the magnetic flux density in FIG. 8 are as shown in FIG. 10A, in which the magnetic sensor 104 is disposed so as to face the magnetized surface of the above-mentioned two-pole annular magnet 103, and the two-pole annular magnet 103 is This is obtained by detecting the magnetic change by the magnetic sensor 104 while rotating around the axis in the direction of arrow a. If the waveform of the magnetic flux density is not a perfect sinusoidal curve, analog magnetic changes are not stable when used as a magnetic encoder for absolute position detection as described above, and the reliability of detection accuracy is obtained. As a result, it has become a bottleneck in application to the above-mentioned two-pole magnetic encoder.

  When the magnetic field m is applied to the annular magnetic body 100 as indicated by the white arrow, the direction of the magnetic force A applied to each magnetic powder 101 and the direction of the magnetization facilitating axis 101a of each magnetic powder 101 are The deviation amount (angle) of the magnetic field depends on the position (angle θ) of each magnetic powder 101, and the detected magnetic flux density X in the radial direction (magnetization facilitating axis 101a direction) at each position after magnetization is the angle. A function depending on θ: X = B (θ), but this function B is not a sinusoidal curve, and therefore, the detection waveform of the magnetic flux density is not considered to be a complete sinusoidal curve.

  The present invention has been made in view of the above circumstances, and provides a two-pole magnetic encoder capable of drawing a substantially perfect sinusoidal curve of the magnetic flux density and improving the reliability of detection accuracy, and a method for manufacturing the same. It is aimed.

  In the two-pole magnetic encoder of the present invention, the outer peripheral surface portion of the first semicircular portion in the annular magnetic body containing magnetic powder is magnetized in the S pole, and the outer peripheral surface portion of the remaining second semicircular portion is N poled. The magnetic powder is made of an anisotropic magnetic powder, and these magnetic powders have an easy-magnetization axis of the first semicircular portion and the second semicircular portion in an annular magnetic body. Oriented in a state parallel to the line connecting the central portions, and the magnetization is performed by applying a magnetic field parallel to the magnetization facilitating axis to the annular magnetic body, and the magnetic flux density of the outer peripheral surface portion along the circumferential direction is increased. The change is characterized in that it draws a sinusoidal curve in which the boundary between the S-pole magnetization region and the N-pole magnetization region is zero.

  In the present invention, the annular magnetic body may be integrated with a metal reinforcing ring. The annular magnetic body may be formed of a molded or sintered body of rubber or resin containing anisotropic magnetic powder. Furthermore, the two-pole magnetic encoder of the present invention can be incorporated as a constituent member of a bearing.

  A method for manufacturing a two-pole magnetic encoder according to the present invention comprises preparing a magnetic material containing unoriented anisotropic magnetic powder, a magnetic field generator, and a molding apparatus having an annular cavity. The magnetic material is loaded into the annular cavity after being left in the hollow inner cylindrical portion of the magnetic field generator so that the axial center of the annular cavity is orthogonal to the magnetic field direction of the magnetic field generator, A magnetic field is applied to form the magnetic material into an annular shape, and the anisotropic magnetic powder is oriented and magnetized.

  In the two-pole magnetic encoder and the method for manufacturing the same according to the present invention, the magnetization facilitating axis of the magnetic powder contained in the annular magnetic body is parallel to the line connecting the central portions of the first semicircular portion and the second semicircular portion. Since the magnetic field oriented in the state and parallel to the magnetization facilitating axis is applied to the annular magnetic body, the direction of the magnetic force applied to each magnetic powder and the magnetization facilitating axis of each magnetic powder are There is no deviation from the direction. When this is seen in the radial direction of the annular magnetic body, the radial magnetic force of each magnetized magnetic powder is expressed as an angular component with respect to the magnetic field direction. In addition, the magnetization is performed by causing a magnetic field parallel to a line connecting the central portions of the first semicircular portion and the second semicircular portion to act on the annular magnetic body, whereby the first semicircular portion becomes the S pole. Since the second semicircular portion is magnetized to the N pole, the radial component of the magnetic force of each magnetic powder depends only on its position (angle), and the magnetized annular magnetic body The change in the magnetic flux density at the outer peripheral surface portion along the circumferential direction is zero at the boundary between the S-pole magnetization region and the N-pole magnetization region, and each of the S-pole magnetization region and the N-pole magnetization region. An ideal sine curve is drawn with peaks in the center opposite to each other. Therefore, if a two-pole annular magnetic body having such a change characteristic of magnetic flux density is used in the magnetic encoder for detecting the absolute position as described above, the reliability of the detection accuracy is improved and the absolute position detecting The suitability as a two-pole magnetic encoder is increased.

  In the two-pole magnetic encoder of the present invention, if the annular magnetic body is integrated with the metal reinforcing ring, its strengthening is achieved, and there is no risk of damage during handling. This reinforcing effect is effective if it is made of a rubber or resin molded body or sintered body containing powder, and if it is made of a rubber or resin molded body, the shape retention effect is also added. If the two-pole magnetic encoder of the present invention is incorporated as a component of a bearing, the bearing function of the rotating part and the functions such as absolute position detection or rotation detection can be configured in a compact manner.

  In the method of manufacturing a two-pole magnetic encoder of the present invention, after the molding apparatus is left in the magnetic field generator, the magnetic material is filled in the annular cavity, and the magnetic material is annular while acting the magnetic field. Since the anisotropic magnetic powder is oriented and magnetized, the orientation of the anisotropic magnetic powder and the direction of the magnetic force applied to the anisotropic magnetic powder are shifted. Therefore, it is possible to efficiently manufacture a highly accurate two-pole magnetic encoder. Therefore, according to the two-pole magnetic encoder obtained by the manufacturing method of the present invention, positioning with high accuracy for making the orientation direction of the anisotropic magnetic powder coincide with the direction of the magnetic force applied to the anisotropic magnetic powder. Need not be performed.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a partially cutaway perspective view showing an embodiment of a two-pole magnetic encoder of the present invention, and FIG. 2 is a cross-sectional view of a main part showing a state in which a bearing incorporating the same two-pole magnetic encoder and an absolute position detection device are configured. FIGS. 3 and 3 are conceptual cross-sectional views showing a magnetization procedure by a magnetic field generator (magnetization pot), and FIGS. 4A and 4B are magnetization methods and magnetization methods by the magnetic field generator (magnetization pot). FIG. 5 is a diagram schematically showing the principle, FIG. 5 is a waveform diagram of magnetic flux density of the dipole magnetic encoder, FIG. 6 is a longitudinal sectional view showing another embodiment of the magnetic field generator, and FIG. 7 is a diagram of another embodiment. FIG.

  A two-pole magnetic encoder 1 shown in FIG. 1 has a first semicircular portion of an annular magnetic body 2 with a south pole magnetized region 1a and a remaining second semicircular portion with a north pole. In the region 1b, the annular magnetic body 2 is integrated with a metal reinforcing ring 3 having an L-shaped cross section composed of a cylindrical portion 3a and an inwardly saddle-shaped portion 3b so as to surround an outer peripheral portion thereof. . In the illustrated annular magnetic body 2, an anisotropic magnetic powder 4 is kneaded with an unvulcanized rubber material, filled in a mold (not shown) having a predetermined shape, and vulcanized together with a metal reinforcing ring 3. Although integrally formed is shown, the present invention is not limited to this, and may be a resin molded body or sintered body. As the anisotropic magnetic powder 4, ferrite powder, rare earth magnetic powder, or the like is desirably employed.

  For example, as shown in FIG. 2, the above-described two-pole magnetic encoder 1 is incorporated in a bearing 5 that is mounted on a rotating part that requires absolute position detection. FIG. 2 shows a part of the bearing 5, and the bearing 5 shown in the figure is an angular ball bearing, and includes an inner ring 5a on the rotation side, an outer ring 5b on the fixed side, and a cage 5d between the inner and outer rings 5a and 5b. It is comprised by the rolling element (ball | bowl) 5c interposed in the state hold | maintained, and the sealing member (seal ring) 5e with which it mounts | wears between the edge parts of the inner-outer ring 5a, 5b. The inner ring 5a is integrally fitted with a rotation side member (not shown), and the two-pole magnetic encoder 1 is integrally fitted with a cylindrical portion 3a of the reinforcing ring 3 on the outer diameter surface of the end of the inner ring 5a. Has been. Two magnetic sensors 6 are installed so as to be opposed to each other so as to face the outer peripheral surface portion of the two-pole magnetic encoder 1, and the two magnetic sensors 6 and the two-pole magnetic encoder 1 are used to detect the absolute position of the rotary member. 7 is configured.

  FIG. 3 shows a magnetic field generator for forming an S-pole magnetized region 1a and an N-pole magnetized region 1b on the outer peripheral surface of the annular magnetic body 2, and a magnetizing procedure by the magnetic field generator. Yes. Here, as an example of a structure in which the molding device 10 is arranged in the magnetic field generator 8, an example is shown in which the magnetizing pot 8 is used as the magnetic field generator 8, and the magnetizing pot 8 in the figure is When a current in the direction of the arrow is passed through the coil 8b wound around the magnetized yoke 8a as shown in the figure, the magnet 8b is wound into the hollow space of the magnetized yoke 8a. A magnetic field M in the direction of the white arrow along the axial direction is generated in the cylindrical portion 8c. In the hollow inner cylindrical portion 8c of the magnetizing pot 8, a molding apparatus 10 having an annular cavity 10a is placed stationary. At this time, the molding apparatus 10 is placed in the hollow inner cylindrical portion 8c of the magnetizing pot 8 so that the axis of the annular cavity 10a is orthogonal to the magnetic field direction.

A manufacturing method of the two-pole magnetic encoder 1 using the magnetizing pot 8 is as follows.
First, the molding device 10 is placed in the hollow inner cylindrical portion 8c of the magnetizing pot 8 as described above, and then the metal reinforcing ring 3 is disposed at a predetermined position in the molding device 10 and is anisotropically formed in the cavity 10a. The magnetic material raw material kneaded with the magnetic powder 4 is filled. Then, the magnetic material is molded into an annular shape while passing a current through the coil 8b to generate the magnetic field M, vulcanized and molded so as to be integrated with the metal reinforcing ring 3, and the anisotropic magnetic powder 4 is oriented. At the same time, magnetize. At this time, the magnetic material is vulcanized to form the annular magnetic body 2, the outer peripheral surface portion of the upper semicircular portion of the annular magnetic body 2 is magnetized to the S pole, and the outer peripheral surface portion of the lower semicircular portion is N Magnetized on the pole.
In this way, the outer peripheral surface portion of the first semicircular portion of the annular magnetic body 2 as shown in FIG. 1 is an S-polarized magnetic region 1a, and the outer peripheral surface portion of the remaining second semicircular portion is an N-polarized magnetic region 1b. A two-pole magnetic encoder 1 is formed.

  According to this, the magnetic material is molded into an annular shape, and the annular magnetic body 2 is integrally molded into the metal reinforcing ring 3, and the orientation and magnetization of the magnetic powder 4 are simultaneously performed. And the direction of the magnetic force applied to the magnetic powder 4 can be produced without causing a positional shift. For example, in the conventional manufacturing method in which the magnetic field orientation is made at the same time that the annular magnetic body 2 is integrally formed on the metal reinforcing ring 3, a magnetic powder that is partially magnetized when the magnetic field is oriented, such as ferrite, is used. When it was used, it was magnetized after being demagnetized once after orientation. For rare earths, it is common to raise the temperature of the product to the Curie point (300 ° C to 400 ° C) due to its magnetic properties, and the magnetism is extinguished. However, in the case of a bonded magnet containing rubber and resin, the binder itself However, it cannot withstand that temperature, and it is difficult to demagnetize after forming the magnetic field. However, according to this manufacturing method, since the annular magnetic body 2 is molded and the magnetic powder 4 is oriented and magnetized, the magnetic powder 4 that is partially magnetized when the magnetic field is oriented is used. Even in this case, the highly accurate two-pole magnetic encoder 1 can be manufactured without demagnetization. Further, it is not necessary to perform positioning with high accuracy for making the orientation direction of the magnetic powder 4 coincide with the direction of the magnetic force applied to the magnetic powder 4.

  FIG. 4A schematically shows a two-pole magnetic encoder 1 obtained by such magnetization. The two-pole magnetic encoder 1 shown in FIG. The lower semicircular portion 1a is an N-pole magnetized region 1b. This two-pole magnetic encoder 1 is magnetized by a magnetizing pot 8 as shown in FIG. 3, and as shown in FIGS. 4 (a) and 4 (b), the magnetization facilitating axis 4a of each magnetic powder 4 is an upper semicircle. Oriented in a state parallel to the center line 1d that connects the central portions of the portion (first semicircular portion) and the lower semicircular portion (second semicircular portion), and the magnetization is parallel to the magnetization facilitating axis 4a. This is done by applying a magnetic field M to the annular magnetic body 2. The radial component MX of the magnetic force MA applied to each magnetic powder 4 by the action of the magnetic field M parallel to the magnetization facilitating axis 4a, that is, in the direction of the white arrow, is the magnetic powder with respect to the radial line perpendicular to the magnetic field M. When the angle in the radial direction of 4 is θ, theoretically, MX = MAsinθ. At this time, since there is no deviation between the direction of the magnetic force M applied to each magnetic powder 4 and the direction of the magnetization facilitating axis 4a of each magnetic powder 4, the magnetic force MA applied to each magnetic powder 4 Does not take into account the magnetization facilitating element (function depending on the angle of the magnetization facilitating axis with respect to the magnetic field direction), and the radial component MX of the magnetic force MA uses only sin θ as a variable.

  Here, as shown in FIG. 4A, the magnetic sensor 9 is disposed so as to face the magnetized surface which is the outer peripheral surface portion of the two-pole magnetic encoder 1, and the two-pole magnetic encoder 1 is moved around the axis by the arrow b. As a result of detecting the magnetic change by the magnetic sensor 9 while rotating in the direction, the waveform characteristic of the magnetic flux density in FIG. 5 was obtained. As described above, the waveform of the magnetic flux density along the circumferential direction of the magnetized surface in the two-pole magnetic encoder 1 is such that the boundary 1c between the S-pole magnetized region 1a and the N-pole magnetized region 1b is zero. A substantially complete sine curve is shown in which the central portions of the magnetized region 1a and the N-pole magnetized region 1b have peaks in opposite directions. This coincides with the fact that the radial component MX of the magnetic force MA possessed by each magnetic powder 4 by magnetization as described above has only sin θ as a variable.

  The two-pole magnetic encoder 1 obtained as described above is incorporated as, for example, a constituent member of a bearing 5 as shown in FIG. 2, mounted on the inner ring 5a on the rotation side of the absolute position detection target, and this annular 2 on the fixed side. The absolute position detector 7 can be configured by arranging the two magnetic sensors 6 so as to face the polar magnetic encoder 1 so as to be out of phase with each other. That is, in the absolute position detection device 7, the magnetic change by the two-pole magnetic encoder 1 accompanying the rotation on the rotation side is detected in an analog manner by the two magnetic sensors 6, and the detected two analog values are calculated and the like. By performing processing, the absolute position on the rotation side can be detected. In this case, since the two-pole magnetic encoder 1 draws a substantially complete sine curve as shown in FIG. 5, the analog value is stable, and therefore the reliability of the absolute position detection accuracy 7 is improved. Therefore, its usefulness is extremely large as a two-pole magnetic encoder for detecting the absolute position of a crank angle, a camshaft angle or the like for controlling an automobile engine, or for detecting the absolute position of other industrial machines.

Here, the manufacturing method of the two-pole magnetic encoder of the present invention is not limited to the method of simultaneously molding and magnetizing the magnetic powder 4 as described above, and performing molding and orientation of the magnetic powder 4, Magnetization may be performed after demolding.
FIG. 6 is a longitudinal sectional view showing another embodiment of the magnetic field generator. In the embodiment shown here, the molding apparatus 10 is not arranged in the magnetic field generator 8 as shown in FIG. 3, but a non-magnetic type member and a magnetic type member are formed integrally in the molding apparatus 10 itself to form a magnetic field. A generation mechanism is provided. The same parts as those described above are denoted by the same reference numerals, and description thereof is omitted. The magnetic field generator 8 is a pressure / vulcanization molding apparatus, but does not exclude an injection molding apparatus.

The magnetic field generator 8 includes an upper mold 11 and a lower mold 12, and the lower mold 12 a in which the cavity 10 a is formed of the upper mold 11 and the lower mold 12 is configured by a nonmagnetic member in order to generate the magnetic field M. The lower mold 12b on which the magnetic field generating coil 8b is arranged is formed of a magnetic member made of carbon steel or the like. In addition, the heating device of the molding device 10, the driving means of the coil 8b, and the like are provided in the periphery, but the illustration is omitted.
At this time, the molding apparatus 10 configured as the magnetic field generator 8 is configured such that the axis of the annular cavity 10a is orthogonal to the magnetic field direction.

A manufacturing method of the two-pole magnetic encoder 1 by the magnetic field generator 8 is as follows.
First, the metal reinforcing ring 3 is disposed at a predetermined position in the cavity 10a, and a magnetic material mixed with the anisotropic magnetic powder 4 in advance is filled in the cavity 10a. Then, the coil 8b is heated while generating a magnetic field M by passing an electric current, pressure-molded, and vulcanized magnetic field molding is performed. At this time, the magnetic material is vulcanized to form an annular magnetic material 2, and the anisotropic magnetic powder 4 kneaded and mixed in the magnetic material is subjected to a magnetic field effect during the vulcanization process to facilitate its magnetization. The shaft 4a is oriented in a state parallel to the line connecting the central portions of the first semicircular portion and the second semicircular portion, and is fixed in the vulcanized rubber layer in this state along with vulcanization.

  After completion of the magnetic field molding, the mold is removed to obtain an annular vulcanized rubber molded body, and the outer peripheral surface portion of the first semicircular portion of the annular magnetic body 2 is an S-polarized magnetic region by a known magnetizing device. 1a, the two-pole magnetic encoder 1 in which the outer peripheral surface portion of the remaining second semicircular portion becomes the N-pole magnetized region 1b is formed.

  FIG. 7 shows another embodiment. An annular magnetic body 2 constituting the two-pole magnetic encoder 1 in the figure is integrally formed with an L-shaped metal reinforcing ring 3 having a cylindrical portion 3a and an outward flange portion 3c so as to surround an outer peripheral portion thereof. In the same manner as described above, a semicircular S-pole and N-pole magnetized region is formed on the outer peripheral surface portion. The two-pole magnetic encoder 1 has a cylindrical portion 3a so that the outward flange portion 3c is on the seal member 5e side, and is integrally fitted on the outer diameter surface of the inner ring 5a of the bearing 5. Two IC chip (sensitive element) type magnetic sensors 6a are installed so as to be opposed to the outer peripheral surface portion of the two-pole magnetic encoder 1, and the two magnetic sensors 6a, the two-pole magnetic encoder 1, Thus, the absolute position detecting device 7 of the rotation side member is configured. Also in this example, the absolute position detection with high accuracy similar to the above can be performed. Since other configurations are the same as described above, common portions are denoted by the same reference numerals, and descriptions thereof are omitted.

  In the embodiment described above, the annular magnetic body 2 is integrated with the metal reinforcing ring 3. However, as described above, the S-polarized region 1a and the N-polarized region 1b are formed on the outer peripheral surface portion thereof. It is also possible to make the annular magnetic body 2 formed with the magnetic encoder 1 alone. Also, the shape of the magnetic encoder 1 is not limited to that shown in the figure, and it goes without saying that other shapes can be adopted depending on the portion to be applied. Further, FIG. 2 shows an example in which the two-pole magnetic encoder 1 of the present invention is incorporated as a constituent member of a bearing whose inner ring is on the rotating side, but the outer ring is mounted on a rotating side bearing or a rotating member other than the bearing. It is also possible to constitute an absolute position detection device by incorporating it. Furthermore, the two-pole magnetic encoder of the present invention can be used not only for absolute position detection on the rotation side, but also for rotation detection devices such as the rotation speed and rotation speed.

It is a partial notch perspective view which shows one Embodiment of the 2 pole magnetic encoder of this invention. It is sectional drawing of the principal part which shows the state with which some bearings and the absolute position detection apparatus in which the same 2 pole magnetic encoder was incorporated were comprised. It is a conceptual sectional view showing how to magnetize with a magnetizing pot. (A) is a figure which shows typically the magnetization method by the same magnetization pot, (b) is a figure which shows the principle of the magnetization typically. It is a wave form diagram which shows the result of having measured the change of the magnetic flux density of the same dipole magnetic encoder. It is a longitudinal cross-sectional view which shows another embodiment of a magnetic field generator. It is a figure similar to FIG. 2 of other embodiment. It is a wave form diagram which shows the result of having measured the change of the magnetic flux density of the conventional 2 pole magnetic encoder. It is a schematic diagram which shows the point which magnetizes and forms the same 2 pole magnetic encoder. (A) is a figure which shows the same point typically, (b) is a figure which shows the principle of the magnetization typically.

Explanation of symbols

1 2-pole magnetic encoder 1a S pole magnetization region (first semicircle)
1b N pole magnetization region (second semicircle)
1c boundary 1d center line (line)
2 Annular magnetic body 3 Metal reinforcing ring 4 Anisotropic magnetic powder 4a Magnetization facilitating axis 8 Magnetic field generator (magnetization pot)
8a Magnetized yoke 8b Coil 8c Hollow inner cylinder part 10 Molding device 10a Cavity M Magnetic field

Claims (5)

This is a two-pole magnetic encoder in which an outer peripheral surface portion of a first semicircular portion is an S-polarized magnetic region and an outer peripheral surface portion of the remaining second semicircular portion is an N-polarized magnetic region in an annular magnetic body containing magnetic powder. And
The magnetic powder is made of anisotropic magnetic powder, and these magnetic powders have an easy axis of magnetization in an annular magnetic body parallel to a line connecting the central portions of the first semicircular part and the second semicircular part. The magnetization is performed by applying a magnetic field parallel to the magnetization facilitating axis to the annular magnetic body, and the change in the magnetic flux density at the outer peripheral surface along the circumferential direction is the magnetization of the S pole. A two-pole magnetic encoder characterized by drawing a sinusoidal curve with zero at the boundary between the magnetic field and the N-pole magnetized region. The two-pole magnetic encoder according to claim 1,
A two-pole magnetic encoder, wherein the annular magnetic body is integrated with a metal reinforcing ring. The two-pole magnetic encoder according to claim 1 or 2,
The two-pole magnetic encoder, wherein the annular magnetic body is made of a molded or sintered body of rubber or resin containing anisotropic magnetic powder. The two-pole magnetic encoder according to any one of claims 1 to 3,
A two-pole magnetic encoder, which is incorporated as a component of a bearing.   A magnetic material containing unoriented anisotropic magnetic powder, a magnetic field generator, and a molding device having an annular cavity are prepared, and the axial center of the annular cavity is used to generate the magnetic field. The magnetic material is placed in the magnetic field generator so as to be orthogonal to the magnetic field direction of the device, and then the magnetic material is loaded into an annular cavity and the magnetic field is applied to form the magnetic material in an annular shape. A method of manufacturing a two-pole magnetic encoder, characterized by performing orientation and magnetization of an isotropic magnetic powder.

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