Manufacturing method of magnetic encoder and manufacturing magnet for magnetic encoder

Abstract

To provide a magnetic encoder, a magnet for a magnetic encoder, and a method of manufacturing the same, which can easily manufacture a magnetic track with magnetic flux density continuously changing at low cost.SOLUTION: Magnetic encoders 51, 52, 53 include magnets 21, 31 and magnetic sensors 51b, 52b, 53b for detecting magnetic flux densities of the magnets 21, 31. The magnets 21, 31 have a string-like or endless string-like main body 11 made of an elastic material mixed with a magnetic material. The magnets 21, 31 have a plurality of magnetic poles 12 provided on the peripheral surface of the main body 11 along the axial direction of the string-like body that constitutes the main body 11. The magnetic encoders 51, 52, 53 are arranged such that the magnets 21, 31 face the magnetic sensors 51b, 52b, 53b, and the magnetic poles 12 rotate about the axis along the above-mentioned axial direction.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a magnetic encoder. Manufacturing method of magnet for magnetic encoder It relates to a manufacturing method. [Background technology]

[0002] Conventionally, linear encoders and rotary encoders have been widely used in the fields of automobiles and other industrial machinery, and magnetic encoders that do not require a power source are widely used as such encoders. Such magnetic encoders include a magnetic track whose magnetic flux density changes and a magnetic detection element that detects the magnetic flux density of the magnetic track, and detect the amount of displacement, etc., from the change in magnetic flux density caused by the relative movement between the magnetic track and the magnetic detection element.

[0003] In order to enable the position of the magnetic track to be identified from the magnetic track and the magnetic flux density detected by the magnetic detection element, various magnetic track structures in which the magnetic flux density changes continuously have been proposed (see, for example, Patent Documents 1 and 2). For example, Patent Document 1 discloses a configuration in which, in a rotary magnetic encoder, the ratio of the width of the north pole and the south pole exposed on the surface of the magnetic track facing the magnetic detection element changes continuously over one circumference of the magnetic encoder. Also, Patent Document 2 discloses a configuration in which, in a rotary magnetic encoder, a single magnetic pole exposed on the surface of the magnetic track facing the magnetic detection element is covered with a magnetic body, an opening is provided in a part of the magnetic body, and the opening width of the opening changes continuously over one circumference of the magnetic encoder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-322474 A [Patent Document 2] JP 2007-101454 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the structure disclosed in the above-mentioned Patent Document 1 requires magnetization so that the ratio of the width of the north pole to the south pole varies continuously, and a device capable of realizing this magnetization must be prepared. In addition, in order to manufacture a variety of magnetic tracks with different diameters, it is also necessary to perform magnetization according to the diameter. In addition, the structure disclosed in the above-mentioned Patent Document 2 is easy to magnetize because the magnet itself has a simple structure in which the south pole and the north pole overlap, but requires processes for covering the magnetic material and forming the opening. Therefore, neither structure is easy to manufacture, and the manufacturing costs are high.

[0006] The present invention has been made in view of the above-mentioned circumstances, and provides a magnetic encoder capable of easily manufacturing a magnetic track in which the magnetic flux density changes continuously at low cost. Manufacturing method of magnet for magnetic encoder The present invention aims to provide a method for producing the same. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention employs the following technical means. The present invention relates to a method for manufacturing a magnetic encoder including a magnet and a magnetic sensor for detecting the magnetic flux density of the magnet. The manufacturing method of the magnetic encoder according to the present invention includes the steps of vulcanization molding a string-shaped magnet body made of an elastic body mixed with a magnetic material, forming magnetic poles along the axial direction of the string-shaped body constituting the magnet body on the peripheral surface of the magnet body by magnetization with a unidirectional magnetic field, and disposing the magnet body in a position facing a magnetic sensor with the magnetic poles rotating around the axis along the axial direction. In the step of forming the magnetic poles, the magnet body arranged in a coil shape is magnetized by a magnetic field along the axis of the coil. With this configuration, the magnetic encoder can be manufactured easily and at low cost.

[0008] On the other hand, another aspect of the present invention is a method for manufacturing a magnet for a magnetic encoder that constitutes a magnetic track of the magnetic encoder. The manufacturing method of a magnet for a magnetic encoder of the present invention includes the steps of vulcanization molding a string-shaped or endless string-shaped main body made of an elastic body mixed with a magnetic material, and forming magnetic poles along the axial direction of the string-shaped body constituting the main body on the peripheral surface of the main body by magnetization using a unidirectional magnetic field, and is characterized in that in the step of forming the magnetic poles, the main body is magnetized in a state where a north pole is provided on one half and a south pole is provided on the other half, with a portion twisted around the axis of the string-shaped body constituting the main body, and after magnetization, the twist of the string-shaped body is released and the magnetic poles are arranged in a state where they rotate around the axis along the axial direction of the main body. With this configuration, the magnet for the magnetic encoder can be manufactured easily and at low cost. Effect of the Invention

[0017] According to the present invention, it is possible to easily manufacture, at low cost, a magnetic track in which the magnetic flux density changes continuously. [Brief description of the drawings]

[0018] [Figure 1]1A is a side view showing an example of a string-shaped magnet constituting a magnet for a magnetic encoder according to one embodiment of the present invention; FIG. 1B is a cross-sectional view showing the magnetic pole arrangement of the string-shaped magnet; and FIG. 1C is a side view showing the magnetic pole arrangement of the string-shaped magnet. [Diagram 2] FIG. 1A is a side view showing an example of a magnet for a linear magnetic encoder according to one embodiment of the present invention; FIG. 1B is a plan view showing an example of a magnet for a rotary magnetic encoder according to one embodiment of the present invention; and FIG. 1C is a diagram showing the distribution of magnetic flux density of a magnet for a magnetic encoder according to one embodiment of the present invention. [Diagram 3] 1A is a side view showing another example of a magnet for a linear magnetic encoder according to one embodiment of the present invention; FIG. 1B is a plan view showing another example of a magnet for a rotary magnetic encoder according to one embodiment of the present invention; and FIG. 1C is a diagram showing the distribution of magnetic flux density of a magnet for a magnetic encoder according to one embodiment of the present invention. [Figure 4] 1A is a plan view showing a schematic diagram of another example of a magnet for a rotary magnetic encoder according to one embodiment of the present invention, and FIG. 1B is a plan view showing a schematic diagram of another example of a magnet for a rotary magnetic encoder according to one embodiment of the present invention. [Diagram 5] FIG. 1A is a perspective view showing a schematic example of a linear magnetic encoder according to an embodiment of the present invention; FIG. 1B is a perspective view showing a schematic example of a rotary magnetic encoder according to an embodiment of the present invention; and FIG. 1C is a perspective view showing a schematic example of another rotary magnetic encoder according to an embodiment of the present invention. [Figure 6] FIG. 2 is a flow diagram showing an example of a manufacturing procedure for a magnet for a magnetic encoder according to an embodiment of the present invention. [Figure 7] 1A and 1B are diagrams showing a schematic diagram of the state at the time of magnetization in the manufacturing procedure of a string-shaped magnet for a magnetic encoder according to one embodiment of the present invention. [Figure 8] 1A and 1B are diagrams illustrating a schematic state during magnetization in a manufacturing procedure for an annular magnet for a magnetic encoder according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings. First, a magnet for a magnetic encoder according to the present invention will be described. Fig. 1(a) to Fig. 1(c) are diagrams showing an example of a string-shaped magnet constituting a magnet for a magnetic encoder according to one embodiment of the present invention. Fig. 1(a) is a side view, and Fig. 1(b) is a cross-sectional view. Fig. 1(c) is a side view showing a schematic arrangement of magnetic poles of the string-shaped magnet.

[0020] As shown in Figures 1(a) and 1(b), the magnet 10 for a magnetic encoder according to this embodiment is composed of a string-like body with a circular cross section. The main body 11, which is the string-like body, is composed of an elastic body mixed with a magnetic material. The material of the elastic body is not particularly limited, but for example, rubber such as nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, ethylene acrylic rubber, fluororubber, etc., or a thermoplastic elastomer can be used. In addition, for example, ferrite, rare earth, etc. can be used as the magnetic material, but is not particularly limited.

[0021] The magnet 10 for magnetic encoder comprises a plurality of magnetic poles 12 arranged on the circumferential surface of the main body 11 along the axial direction of the string-like body (indicated by an arrow in FIG. 1(a)). In this embodiment, as shown in FIG. 1(b) and FIG. 1(c), a pair of magnetic poles (two magnetic poles) consisting of an N pole 12a and an S pole 12b are arranged along the axial direction of the string-like body. Although not particularly limited, here, an N pole is provided on one half of the circumferential surface of the main body 11, and an S pole is provided on the other half. That is, in a cross section of the main body 11, the arc portion on the upper half of the figure is the N pole 12a, and the arc portion on the lower half of the figure is the S pole 12b.

[0022] When the above-mentioned magnet 10 for a magnetic encoder is used as a magnetic track of a magnetic encoder, the magnet 10 for a magnetic encoder is positioned in the magnetic encoder opposite a magnetic sensor that detects the magnetic flux density of the magnet 10 for a magnetic encoder, with the magnetic pole 12 rotating around the axis along the axial direction of the above-mentioned string-like body.

[0023] Fig. 2(a) is a side view showing a schematic diagram of an example of a magnet for a linear magnetic encoder according to an embodiment of the present invention. As shown in Fig. 2(a), the magnet for a linear magnetic encoder 21 has a configuration in which a magnet for a magnetic encoder 10 of a desired length is arranged linearly with one end rotated 180 degrees around the axis of a string-like body relative to the other end. As a result, each magnetic pole 12 (N pole 12a, S pole 12b) is arranged on the circumferential surface of the linear main body 11 in a state of rotating around the axis along the axial direction of the string-like body.

[0024] Also, Fig. 2(b) is a plan view showing a schematic example of a magnet for a rotary magnetic encoder according to an embodiment of the present invention. As shown in Fig. 2(b), the magnet for a rotary magnetic encoder 31 has a configuration in which both ends of the magnet for a magnetic encoder 10 of a desired length are joined in a state in which one end is rotated 180 degrees around the axis of a string-like body, thereby arranging the magnet in a ring shape (endless string shape) (a configuration in which both ends of the magnet for a linear magnetic encoder 21 in Fig. 2(a) are joined to each other). As a result, each magnetic pole 12 (N pole 12a, S pole 12b) is arranged on the circumferential surface of the ring-shaped main body 11 in a state of rotating around the axis along the axial direction of the string-like body.

[0025] Fig. 2(c) is a diagram showing a schematic distribution of magnetic flux density of a magnetic field formed by a magnetic track composed of the magnet 21 for linear magnetic encoder shown in Fig. 2(a) and the magnet 31 for rotary magnetic encoder shown in Fig. 2(b). The diagram shown in Fig. 2(c) corresponds to the magnetic flux density detected by the magnetic sensor when the magnetic sensor is placed facing the string-like body constituting the magnet 21 for linear magnetic encoder in Fig. 2(a) at the top in the figure (see Fig. 5(a)). Also, the diagram shown in Fig. 2(c) corresponds to the magnetic flux density detected by the magnetic sensor when the magnetic sensor is placed facing the string-like body constituting the magnet 31 for rotary magnetic encoder in Fig. 2(b) at the front in the figure (see Fig. 5(c)).

[0026] Also, the horizontal axis in FIG. 2(c) corresponds to the position on the magnetic track (position on the magnet). That is, in the case of the magnet 21 for the linear magnetic encoder, the distribution of magnetic flux density from the left end to the right end of the horizontal axis corresponds to the distribution of magnetic flux density from the left end to the right end of the magnet 21 for the linear magnetic encoder in FIG. 2(a). Also, in the case of the magnet 31 for the rotary magnetic encoder, the distribution of magnetic flux density from the left end to the right end of the horizontal axis corresponds to the distribution of magnetic flux density from the end of the magnet 10 for the magnetic encoder arranged on the left side of the joints of both ends of the magnet 31 for the rotary magnetic encoder to the other end in a counterclockwise direction in FIG. 2(b). In the case of the magnet 31 for the rotary magnetic encoder, the N pole and the S pole are adjacent to each other at the joints of both ends, so strictly speaking the magnitude of the magnetic flux density is reduced due to mutual interference, but in FIG. 2(c) the influence of the interference is omitted because the explanation is based on the principle. In addition, the vertical axis in FIG. 2(c) corresponds to the magnetic flux density with the N pole in the positive direction.

[0027] When the linear magnetic encoder magnet 21 and the magnetic sensor are arranged in the above-mentioned positional relationship, if the relative positional relationship between the linear magnetic encoder magnet 21 and the magnetic sensor changes, the magnetic sensor detects different magnitudes of magnetic flux density according to the relative positional relationship, as shown in Fig. 2(c). Therefore, the relative positional relationship between the linear magnetic encoder magnet 21 and the magnetic sensor can be identified based on the magnetic flux density detected by the magnetic sensor.

[0028] Similarly, when the rotary magnetic encoder magnet 31 and the magnetic sensor are arranged in the above-mentioned positional relationship, the magnetic sensor detects different magnitudes of magnetic flux density depending on the relative positional relationship between the rotary magnetic encoder magnet 31 and the magnetic sensor. Therefore, the relative positional relationship between the rotary magnetic encoder magnet 31 and the magnetic sensor can be identified based on the magnetic flux density detected by the magnetic sensor.

[0029] Note that Figure 2(c) shows an example in which the amount of rotation of magnetic pole 12 around the axis is uniform throughout the axial direction of the string-like body; however, even if the amount of rotation of magnetic pole 12 around the axis is non-uniform throughout the axial direction of the string-like body, the magnetic sensor detects different magnitudes of magnetic flux density depending on the relative positional relationship between the magnet for the magnetic encoder and the magnetic sensor, making it possible to identify the relative positional relationship between the magnet for the magnetic encoder and the magnetic sensor.

[0030] As described above, according to the magnet for magnetic encoder of this embodiment, since the multiple magnetic poles provided along the axial direction of the string-like body are arranged in a state in which the magnetic poles rotate around the axis along the axial direction, a magnetic track in which the magnetic flux density changes continuously can be easily formed. Therefore, a magnetic encoder can be easily realized at low cost. In addition, as shown in FIG. 2(b), in the configuration in which both ends of the string-like body are connected to form an endless string-like main body 11, a mold is not required to realize the annular main body 11 of the desired diameter, and it is possible to manufacture a magnetic encoder and a magnet for a magnetic encoder at low cost and in a short delivery time. Such a manufacturing method that does not require a mold is particularly suitable for a magnetic encoder for detecting the position and rotation status of a large detection target such as an industrial machine, a windmill, or a rotating table of heavy equipment such as a crane or a shovel car.

[0031] Hereinafter, another example of using the magnet 10 for a magnetic encoder as a magnetic track of a magnetic encoder will be described. Fig. 3(a) is a side view showing a schematic diagram of another example of a magnet for a linear magnetic encoder according to an embodiment of the present invention. As shown in Fig. 3(a), the magnet 22 for a linear magnetic encoder has a configuration in which the magnet 10 for a magnetic encoder of a desired length is linearly arranged with one end rotated 360 degrees around the axis of the string-like body relative to the other end. As a result, each magnetic pole 12 (N pole 12a, S pole 12b) is arranged on the circumferential surface of the linear main body 11 in a state of rotating around the axis along the axial direction of the string-like body.

[0032] Also, Fig. 3(b) is a plan view showing a schematic example of a magnet for a rotary magnetic encoder according to an embodiment of the present invention. As shown in Fig. 3(b), the magnet for a rotary magnetic encoder 32 has a configuration in which both ends of the magnet for a magnetic encoder 10 of a desired length are joined in a state in which one end is rotated 360 degrees around the axis of a string-like body relative to one end, and arranged in a ring shape (a configuration in which both ends of the magnet for a linear magnetic encoder 22 in Fig. 3(a) are joined to each other). As a result, each magnetic pole 12 (N pole 12a, S pole 12b) is arranged on the circumferential surface of the ring-shaped main body 11 in a state of rotating around the axis along the axial direction of the string-like body.

[0033] Fig. 3(c) is a diagram showing a schematic distribution of magnetic flux density of a magnetic field formed by a magnetic track composed of the magnet 22 for linear magnetic encoder shown in Fig. 3(a) and the magnet 32 ​​for rotary magnetic encoder shown in Fig. 3(b). As with Fig. 2(c), the diagram shown in Fig. 3(c) corresponds to the magnetic flux density detected by the magnetic sensor in the magnet 22 for linear magnetic encoder when the magnetic sensor is placed facing the string-like body constituting the magnet 22 for linear magnetic encoder at the top of the figure. Also, in the magnet 32 ​​for rotary magnetic encoder shown in Fig. 3(b), it corresponds to the magnetic flux density detected by the magnetic sensor in the magnet 32 ​​for rotary magnetic encoder when the magnetic sensor is placed facing the string-like body constituting the magnet 32 ​​for rotary magnetic encoder at the front side of the figure.

[0034] The horizontal axis in Fig. 3(c) corresponds to the position on the magnetic track, as in Fig. 2(c). That is, in the case of the magnet 22 for a linear magnetic encoder, the distribution of magnetic flux density from the left end to the right end of the horizontal axis corresponds to the distribution of magnetic flux density from the left end to the right end of the magnet 22 for a linear magnetic encoder in Fig. 3(a). In the case of the magnet 32 ​​for a rotary magnetic encoder, the distribution of magnetic flux density from the left end to the right end of the horizontal axis corresponds to the distribution of magnetic flux density from the end of the magnet 10 for a magnetic encoder arranged on the left side of the joint between both ends of the magnet 32 ​​for a rotary magnetic encoder to the other end in a counterclockwise direction in Fig. 3(b). The vertical axis in Fig. 3(c) corresponds to the magnetic flux density with the N pole in the positive direction.

[0035] When the magnet 22 for the linear magnetic encoder and the magnetic sensor are arranged in the above-mentioned positional relationship, as shown in FIG. 3(c), the magnetic flux density detected by the magnetic sensor changes depending on the relative positional relationship between the magnet 22 for the linear magnetic encoder and the magnetic sensor. Unlike the example of FIG. 2(c), in the example of FIG. 3(c), there are two relative positional relationships where the magnetic flux density is the same, but the displacement amount (differential coefficient) is different, so that, for example, the relative positional relationship between the magnet 22 for the linear magnetic encoder and the magnetic sensor can be specified based on the magnetic flux density detected by the magnetic sensor and the magnetic flux density detected by the magnetic sensor immediately before that. Similarly, when the magnet 32 ​​for the rotary magnetic encoder and the magnetic sensor are arranged in the above-mentioned positional relationship, for example, the relative positional relationship between the magnet 32 ​​for the rotary magnetic encoder and the magnetic sensor can be specified based on the magnetic flux density detected by the magnetic sensor and the magnetic flux density detected by the magnetic sensor immediately before that.

[0036] Incidentally, when forming an annular magnet for a rotary magnetic encoder by joining both ends of main body 11 made of a string-like body as shown in Figures 2(b) and 3(b), if the end faces that form the joints are formed of surfaces perpendicular to the axial direction of the string-like body, it is not easy to join both ends while rotating main body 11 at a desired angle, such as 180 degrees or 360 degrees, around the axis of the string-like body. To facilitate joining both ends while rotated at such a desired angle and to facilitate the manufacture of an annular magnet with little variation in the twisted state, it is preferable that main body 11 is provided with an angle adjustment structure at both ends according to the rotation angle.

[0037] 4(a) and 4(b) are plan views showing examples of a magnet for a rotary magnetic encoder having the angle adjustment structure. FIG. 4(a) shows an example of a magnet for a rotary magnetic encoder 33 having an inclined surface 41 inclined with respect to the axis of the main body 11 at both ends of the main body 11 as an angle adjustment structure. The inclined surface 41 is formed, for example, of a plane intersecting the axis of the main body 11 at an angle of 45 degrees. In the example of FIG. 4(a), inclined surfaces 41 are provided at both ends of the main body 11, and are arranged such that the tip 41a of the inclined surface 41 is at the same position around the axis of the string-like body in a cross-sectional view. Therefore, by joining both ends of the main body 11 with the inclined surfaces 41 provided at both ends of the main body 11 overlapping each other, it is possible to easily and reliably realize joining in a state in which one end is rotated 180 degrees around the axis of the string-like body relative to the other end, similar to the magnet for a rotary magnetic encoder 31 shown in FIG. 2(b).

[0038] FIG. 4(b) illustrates a rotary magnetic encoder magnet 34 having step portions 42 at both ends of the main body 11 as an angle adjustment structure. The step portions 42 can be formed, for example, by semi-cylinders 42b having flat surfaces 42a along the axial direction of the string-like body. In the example of FIG. 4(b), step portions 42 are provided at both ends of the main body 11, with the semi-cylinders 42b arranged at the same position around the axis of the string-like body in a cross-sectional view. Therefore, by joining both ends of the main body 11 with the flat surfaces 42a of the semi-cylinders 42b provided at both ends of the main body 11 overlapping each other, it is possible to easily and reliably achieve joining in a state in which one end is rotated 180 degrees around the axis of the string-like body relative to the other end, similar to the magnet 31 for rotary magnetic encoder shown in FIG. 2(b).

[0039] Here, a magnetic encoder using the magnetic encoder magnet described above will be described. FIG. 5(a) is a perspective view showing a schematic diagram of an example of a linear magnetic encoder according to an embodiment of the present invention. The linear magnetic encoder 51 shown in FIG. 5(a) includes the above-mentioned linear magnetic encoder magnet 21 arranged in a straight line as a magnetic track on a substrate 51a, and a magnetic sensor 51b arranged facing the string-like body constituting the main body 11 of the linear magnetic encoder magnet 21. For example, by arranging the linear magnetic encoder magnet 21 on a linear body and arranging the magnetic sensor 51b on a fixed body, the relative positional relationship between the linear body and the fixed body can be detected.

[0040] 5(b) is a perspective view showing a schematic example of a rotary magnetic encoder according to an embodiment of the present invention. The rotary magnetic encoder 52 shown in FIG. 5(b) includes the above-mentioned magnet 31 for rotary magnetic encoder arranged in the circumferential direction as a magnetic track on the peripheral surface of a cylinder 52a that rotates around its axis, and a magnetic sensor 52b arranged facing the string-like body that constitutes the main body 11 of the magnet 31 for rotary magnetic encoder. With this configuration, it is possible to detect the rotation angle of the cylinder 52a that rotates around its axis.

[0041] Fig. 5(c) is a perspective view showing a schematic diagram of another example of a rotary magnetic encoder according to an embodiment of the present invention. The rotary magnetic encoder 53 shown in Fig. 5(c) includes the above-mentioned magnet 31 for a rotary magnetic encoder arranged in the circumferential direction as a magnetic track on a disk 53a that rotates around an axis, and a magnetic sensor 53b arranged facing the string-like body that constitutes the main body 11 of the magnet 31 for a rotary magnetic encoder. With this configuration, it is possible to detect the rotation angle of the disk 53a that rotates around the axis.

[0042] In the magnetic encoder of the present embodiment, the magnetic track can be easily configured as described above, so that the magnetic encoder can be easily realized at low cost. Also, in the magnetic encoder that employs a magnet for a magnetic encoder in which both ends of a string are connected to form an endless string-like main body 11, a mold is not required to realize the annular main body 11 with the desired diameter, so that it can be manufactured at low cost and in a short delivery time.

[0043] Next, the manufacturing procedure for the magnet for magnetic encoder will be explained. Fig. 6 is a flow diagram showing one example of the manufacturing procedure for the magnet for magnetic encoder according to one embodiment of the present invention. As shown in Fig. 6, in the manufacturing procedure for the string-shaped magnet for magnetic encoder of this embodiment, first, a raw material in which an elastic material is mixed with a magnetic material is extruded through a nozzle corresponding to the above-mentioned cross-sectional shape to form it into a string shape (Fig. 6, step S1). This type of forming method is well known, so a detailed description will be omitted here.

[0044] Next, the molded string-like body 71 is arranged in a coil shape as shown in FIG. 7(a) (FIG. 6, step S2). Although not particularly limited, in this embodiment, the extrusion-molded string-like body 71 is arranged in a coil shape by wrapping the string-like body 71 around a cylindrical iron core 72. Next, the coil-shaped string-like body 71 is vulcanized under high temperature and high pressure (FIG. 6, step S3). This fixes the string-like shape of the string-like body 71. Then, a magnetization process is performed to complete the string-like magnet (FIG. 6, step S4).

[0045] The magnetization in the above-mentioned magnetization process can be performed, for example, by applying a unidirectional magnetic field along the axis of the coil (axis of the iron core 72) when the string-like body 71 is arranged in a coil shape as shown in FIG. 7(a). This method can realize a magnet 10 for a magnetic encoder in which an N pole is provided on one half of the circumferential surface of the main body 11 and an S pole is provided on the other half, as shown in FIG. 1(b) and FIG. 1(c). When manufacturing a magnetic encoder using such a magnet 10 for a magnetic encoder, the magnet 10 for a magnetic encoder cut to an arbitrary length is arranged in a position facing a magnetic sensor with the magnetic pole 12 rotating around the axis along the axial direction of the main body 11. In this case, the magnet 10 for a magnetic encoder is deformed (i.e., twisted) to a state in which the magnetic pole 12 rotates around the axis of the string-like body when arranged in a position facing the magnetic sensor.

[0046] Furthermore, the magnetization in the above-mentioned magnetization process can also be performed by a unidirectional magnetic field in a state in which the vulcanization-molded cord-like body 71 has a portion twisted around the axis of the cord-like body 71, that is, in a state in which the cord-like body 71 is rotated around the axis of the cord-like body 71, as shown in Fig. 7(b), for example. Note that in Fig. 7(b), in order to show the twisted state, a line that would be a straight line along the axial direction of the cord-like body on the circumferential surface of the main body 11 in an untwisted state is shown by a dashed line in the figure.

[0047] In this magnetization method, when the twist of the string-like body 71 is released after the magnetization process, a magnet for a magnetic encoder is formed in which the magnetic poles 12 are arranged in a state of rotating about the axis along the axial direction of the main body 11, as shown in Fig. 2(a). In this case, by arranging the magnet for a magnetic encoder in a position facing the magnetic sensor without twisting it, the magnetic poles 12 are arranged in a state of rotating about the axis along the axial direction of the main body 11.

[0048] According to the above-described configuration, for example, as illustrated in Figs. 2(a), 2(b), 3(a), and 3(b), a magnet is fixed in a state where the magnetic pole 12 formed on one side of the string-like body constituting the main body 11 is twisted around the axis of the main body 11, or as illustrated in Figs. 7(b) and 8(b), the string-like body constituting the main body 11 is magnetized by a unidirectional magnetic field in a state where it is twisted around the axis, and the magnet is fixed in a state where it is released after magnetization, thereby realizing a magnetic encoder or a magnet for a magnetic encoder. Therefore, a magnetic encoder or a magnet for a magnetic encoder can be easily manufactured at low cost. In addition, in the configuration where both ends of the string-like body are connected to form an endless string-like magnet body, a mold for realizing a ring-shaped magnet body of a desired diameter is not required, and it is possible to manufacture a magnetic encoder or a magnet for a magnetic encoder at low cost and in a short delivery time.

[0049] In the above-described embodiment, a particularly preferred embodiment is a ring-shaped magnet realized by joining both ends of a string-shaped magnet, but a ring-shaped magnet may be realized by molding the main body into a seamless string-like shape using a mold and vulcanizing it. In this case, as shown in FIG. 8(a), the above-described magnetization process can be performed by a unidirectional magnetic field (magnetic field perpendicular to the paper surface in the drawing) along the central axis of the ring-shaped body 81 in a state in which the string-shaped body constituting the ring-shaped body 81 is not twisted around its axis. When the magnetic encoder magnet 80 thus formed is used, the magnetic encoder magnet 80 is deformed (i.e., twisted) so that the magnetic poles rotate around the axis of the string-shaped body when it is placed in a position facing the magnetic sensor.

[0050] Also, the magnetization of the endless string-like main body can be performed by a unidirectional magnetic field in a state where the string-like body constituting the annular body 81 is twisted around its axis as shown in Fig. 8(b), i.e., rotated around its axis, as in Fig. 7(b). Note that in Fig. 8(b), in order to show the twisted state as in Fig. 7(b), lines along the axial direction of the string-like body constituting the annular body 81 on the circumferential surface of the annular body 81 in an untwisted state (lines concentric with the annular body 81 in Fig. 8(b)) are shown by dashed lines in the figure.

[0051] In this magnetization method, when the twist of the annular body 81 is released after the magnetization process, a magnet for a magnetic encoder is formed, in which the magnetic poles rotate about the axis along the axial direction of the string-like body constituting the annular body 81, similar to the example shown in Fig. 3(b). In this case, by arranging the magnet for a magnetic encoder in a position facing the magnetic sensor without twisting it, the magnet is arranged in a state in which the magnetic poles rotate about the axis along the axial direction of the string-like body constituting the annular body 81.

[0052] As described above, according to the present invention, it is possible to provide a magnetic encoder, a magnet for a magnetic encoder, and a manufacturing method thereof, which are capable of easily manufacturing a magnetic track in which the magnetic flux density changes continuously at low cost.

[0053] The above-mentioned embodiment does not limit the technical scope of the present invention, and various modifications and applications are possible within the scope of the present invention, other than those already described. For example, in the above-mentioned embodiment, as a particularly preferred embodiment, a case has been described in which the cross section perpendicular to the axial direction of the main body of the magnet for magnetic encoder is a circle whose outer shape does not change when the main body is twisted, but it is not essential that the cross-sectional shape is a circle, and it is possible to adopt any other shape such as an ellipse or a polygon. In addition, the above-mentioned angle alignment structure can also adopt any other structure other than the inclined surface or the step portion. Furthermore, the magnetization method in the above-mentioned magnetization process is an example, and does not exclude the use of other magnetization methods such as magnetization using multiple types of magnetic fields. [Explanation of symbols]

[0054] 10, 80 Magnets for magnetic encoders 11 Main body (magnet body) 12 magnetic poles 21, 22 Magnets for linear magnetic encoders 31, 32, 33, 34 Magnets for rotary magnetic encoders 41 Slope 42 Step 51, 52, 53 Magnetic Encoder 51b, 52b, 53b Magnetic sensors 71 Cord 81 Ring-shaped body (magnet body)

Claims

1. A method for manufacturing a magnetic encoder including a magnet and a magnetic sensor for detecting a magnetic flux density of the magnet, comprising the steps of: A step of vulcanization molding a string-shaped magnet body made of an elastic body mixed with a magnetic material; forming magnetic poles along the axial direction of the string-like body constituting the magnet body on the peripheral surface of the magnet body by magnetization using a unidirectional magnetic field; disposing the magnet body at a position facing the magnetic sensor with the magnetic poles rotating about an axis along the axial direction; having A method for manufacturing a magnetic encoder, wherein in the step of forming the magnetic poles, the magnet body arranged in a coil shape is magnetized by a magnetic field along an axis of the coil.

2. A method for manufacturing a magnet for a magnetic encoder that constitutes a magnetic track of the magnetic encoder, comprising the steps of: A step of vulcanizing and molding a string-shaped or endless string-shaped main body made of an elastic body mixed with a magnetic material; forming a magnetic pole along an axial direction of the string-like body constituting the main body on a peripheral surface of the main body by magnetizing the main body with a unidirectional magnetic field; having A manufacturing method for a magnet for a magnetic encoder, characterized in that in the step of forming the magnetic poles, the main body is magnetized in a state where a north pole is provided on one half and a south pole is provided on the other half, with a portion twisted around the axis of a string-like body that constitutes the main body, and after magnetization, the twist of the string-like body is released and the magnetic poles are arranged in a state where they rotate around the axis along the axial direction of the main body.

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