Encoder

Abstract

To provide an encoder contributing to improvement in detection accuracy of a sensor device, for example.SOLUTION: A base (10) including two end surfaces (10a, 10b) extending in a radial direction and an outer circumferential surface (10o) connected to the two end surfaces (10a, 10b), and a ring-shaped magnet (20) fixed to a first end surface (10b) included in the two end surfaces (10a, 10b) of the base (10); Wherein the magnet (20) is magnetized in a radial direction, the two end surfaces (10a, 10b) form reference planes (P, Q) parallel to each other, and a direction of a magnetic flux on a surface (200) of the magnet (20) facing in a radial direction is along a direction in which the reference planes (P, Q) extend.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an encoder. [Background technology]

[0002] Known sensor devices for detecting shaft rotation include those that use an encoder with a magnet and a magnetic sensor. For example, Patent Document 1 discloses a device that includes an encoder with a magnet fixed to an annular core and a magnetic sensor that faces the encoder in the axial direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-98159 Summary of the Invention [Problem to be solved by the invention]

[0004] In a sensor device including an encoder and a magnetic sensor, it is desirable to improve the detection accuracy of shaft rotation. An object of the present invention is to provide an encoder that contributes to improving the detection accuracy of a sensor device. [Means for solving the problem]

[0005] An encoder as an example of the present invention comprises a base having two end faces extending radially and an outer peripheral surface connected to the two end faces, and a ring-shaped magnet fixed to a first end face included in the two end faces of the base, wherein the magnet is magnetized radially, the two end faces form reference planes parallel to each other, and the direction of magnetic flux on the radially facing surface of the magnet is along the direction in which the reference plane extends. [Brief explanation of the drawings]

[0006] [Figure 1]1 is a perspective view of a sensor device including an encoder according to an embodiment; [Figure 2] FIG. 10 is another perspective view of the sensor device including the encoder according to the embodiment. [Figure 3] 1 is a perspective view showing a cross section along a rotation axis of a sensor device including an encoder according to an embodiment; [Figure 4] 1 is a perspective view showing the arrangement of an encoder according to an embodiment and a substrate to which a magnetic sensor is connected. [Figure 5] 1 is a diagram showing a part of a cross section along a rotation axis of a sensor device including an encoder according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0007] In describing the embodiments of the present invention, for convenience of explanation, the direction along the rotation axis X (the central axis of the shaft S) will be referred to as the axial direction. In the axial direction, the direction from the holder 101 to the base 10 (the direction of arrow a) will be referred to as one side, and the opposite direction (the direction of arrow b) will be referred to as the other side. Furthermore, the direction of arrow cd perpendicular to the rotation axis X will be referred to as the radial direction, the direction of arrow c away from the rotation axis X will be referred to as the outer side or one side in the radial direction, and the direction of arrow d approaching the rotation axis X will be referred to as the inner side or other side in the radial direction. In a given member or part, the surface on the outer side in the radial direction (the direction of arrow c) will be referred to as the outer peripheral surface, and the surface on the inner side in the radial direction (the direction of arrow d) will be referred to as the inner peripheral surface. Furthermore, the direction of rotation around the rotation axis X will be referred to as the circumferential direction.

[0008] An embodiment of the present invention will now be described with reference to the drawings (FIGS. 1 to 5). FIG. 1 is a perspective view of a sensor device 100 including an encoder 1 according to this embodiment. FIG. 2 is a perspective view of the sensor device 100 from another angle. FIG. 3 is a perspective view showing a cross section of the sensor device 100 taken along the rotation axis X. FIG. 4 is a perspective view showing the arrangement of the encoder 1 and a substrate 103 to which a magnetic sensor 103s is connected. FIG. 5 is a view showing a portion of a cross section of the sensor device 100 taken along the rotation axis X.

[0009] As shown in FIGS. 1 to 3, the sensor device 100 includes a shaft S, an encoder 1, a holder 101, a bearing 102, and a substrate 103.

[0010] The shaft S (rotating member) is a substantially cylindrical member extending in the axial direction. The shaft S is supported by a holder 101 via a bearing 102. The shaft S serves as an input shaft that rotates when it receives external force from an external device such as a motor (not shown), a rider or operator, or a load. In this embodiment, the shaft S is a bicycle crankshaft. In the axial direction, one end Sa and the other end Sb of the shaft S are connected to a crank arm (not shown), etc. In FIGS. 1 and 2, the one end Sa and the other end Sb of the shaft S are illustrated as parts formed in the shape of a rectangular tube (a tube with four corners in this embodiment). However, the one end Sa and the other end Sb of the shaft S may have any other shape. A gear portion Sg is formed near the center of the shaft S in the axial direction. Rotation of a motor (not shown) or the like is transmitted to the gear portion Sg via a reduction gear (not shown), etc., thereby enabling the shaft S to rotate. However, the shaft S does not necessarily have to be formed with the gear portion Sg.

[0011] 3, the bearing 102 is a ball bearing having an inner ring 102i, an outer ring 102o, and rolling elements. The bearing 102 is not limited to a ball bearing and may be various other bearings, such as a sleeve bearing. Although the bearing 102 is illustrated as having a shield in the drawings, the bearing 102 does not have to have a shield.

[0012] The inner ring 102i of the bearing 102 is bonded or press-fitted to the outer peripheral surface of the shaft S. As a result, the inner ring 102i of the bearing 102 is fixed to the shaft S and is rotatable together with the shaft S. The outer ring 102o of the bearing 102 is supported by an inner peripheral surface 110i of a holding portion 110 (described later) of the holder 101. As a result, the bearing 102 supports the shaft S rotatably relative to the holder 101.

[0013] The holder 101 includes a holding portion 110 and a fixing portion 120. The holding portion 110 is a portion that holds the bearing 102. The fixing portion 120 is connected to the radially outer side of the holding portion 110 via a connecting portion 130. The fixing portion 120 has a hole 120h that extends in the axial direction. In this embodiment, the holder 101 has a plurality of fixing portions 120 (four in this embodiment). The holder 101 is fixed to an external member (such as a housing) by fastening members (not shown) such as bolts that are inserted into the holes 120h. The holder 101 may be configured to deform slightly when stress acts on the shaft S. The holder 101 may be part of a sensor that detects stress acting on the shaft S. A strain sensor or the like may be separately fixed to the holder 101.

[0014] Next, the substrate 103 and the encoder 1 in the sensor device 100 will be described in detail mainly with reference to FIGS.

[0015] The substrate 103 is, for example, an arc-shaped, flat printed circuit board (PCB) on which circuits and electronic components (neither of which are shown) are arranged. However, the substrate 103 may have any other shape. In this embodiment, the substrate 103 is arranged so as to surround a cylinder 11 of a base 10 (described later) of the encoder 1 from the outside in the radial direction. The substrate 103 has a surface 103a facing one side in the axial direction (the direction of arrow a) and a surface 103b facing the other side in the axial direction (the direction of arrow b). The surfaces 103a and 103b are parallel to each other and extend in the radial direction. The substrate 103 is arranged on one side in the axial direction of the holder 101 (the direction of arrow a). The substrate 103 is arranged away from the holder 101 in the axial direction.

[0016] 4, circular holes 103h are formed at both ends of the arc-shaped substrate 103. The substrate 103 is fixed to the holder 101 by fastening members (not shown) such as bolts that are inserted into the holes 103h.

[0017] A magnetic sensor 103s is disposed on the surface 103b of the substrate 103. The magnetic sensor 103s is attached to the edge of the substrate 103 on the inner side in the radial direction (in the direction of arrow d). The magnetic sensor 103s is a sensor capable of detecting magnetic flux or changes in magnetic flux, and may be, for example, a Hall element, a Hall IC, or a magnetoresistive element (MR element, TMR element). The magnetic sensor 103s detects magnetic flux (or changes in magnetic flux) from a magnet 20 (described later) that rotates together with the shaft S. The substrate 103 is provided with, for example, a circuit (not shown) for amplifying the signal from the magnetic sensor 103s and communicating it with an external device (such as a control unit). This allows the sensor device 100 to measure the rotation speed or rotation angle of the shaft S, or both.

[0018] The encoder 1 includes a base 10 and a ring-shaped magnet 20. The base 10 is a non-magnetic member that surrounds the shaft S from the outside in the radial direction. The base 10 may be made of, for example, aluminum, an aluminum alloy, copper, a copper alloy, or resin. As shown in FIG. 5, the base 10 is disposed on one side of the bearing 102 in the axial direction (the direction of arrow a).

[0019] As shown in FIGS. 4 and 5, the base 10 is disposed inside the substrate 103 in the radial direction. The base 10 and the substrate 103 are spaced apart in the radial direction. In other words, the base 10 and the substrate 103 face each other across a gap in the radial direction. The axial position of the base 10 overlaps with the axial position of the substrate 103. Here, the axial position refers to the x-coordinate when the rotation axis X is defined as the x-axis. In other words, when the rotation axis X is defined as the x-axis, the x-coordinate range occupied by the substrate 103 overlaps with the x-coordinate range occupied by the base 10.

[0020] 5, in this embodiment, the base 10 and the shaft S are spaced apart in the radial direction. As will be described later, the base 10 is fixed to the inner ring 102i of the bearing 102, and rotates together with the shaft S via the inner ring 102i of the bearing 102. However, in some cases, the base 10 and the shaft S may be in contact with each other in the radial direction, and the base 10 may be fixed to the outer circumferential surface of the shaft S.

[0021] As shown in FIG. 5 , the base 10 has a tube 11 and a flange portion 12. The tube 11 is a cylindrical portion extending in the axial direction. The flange portion 12 is a portion extending radially outward from the end of the tube 11 on one side in the axial direction (in the direction of arrow a). The base 10 does not necessarily have to have the flange portion 12. The tube 11 has an expanded diameter portion 13 and a protruding portion 14. The expanded diameter portion 13 is a portion of the tube 11 whose diameter expands radially outward and is located on one side in the axial direction of the tube 11 (in the direction of arrow a). The expanded diameter portion 13 extends from the end of the tube 11 on one side in the axial direction (in the direction of arrow a) to a portion closer to the other side (in the direction of arrow b) than the center of the tube 11 in the axial direction. The protruding portion 14 is a cylindrical portion extending from the end of the tube 11 on the other side in the axial direction (in the direction of arrow b) further toward the other side in the axial direction (in the direction of arrow b), and has a smaller outer diameter than the rest of the tube 11. The base 10 does not necessarily have to have the protrusion 14 .

[0022] 5, the base 10 has two end faces 10a, 10b extending radially and an outer peripheral surface 10o connected to the end faces 10a, 10b. The end face 10a is an end face of the base 10 facing one side in the axial direction (the direction of arrow a), and the end face 10b is an end face of the expanded diameter portion 13 of the base 10 facing the other side in the axial direction (the direction of arrow b). The two end faces 10a, 10b form reference planes P and Q that are parallel to each other.

[0023] In this embodiment, the parallelism between the two end faces 10a, 10b is 0.01 mm or less. The parallelism between the two end faces 10a, 10b may be 0.008 mm or less, or may be 0.005 mm or less. In this specification, "parallelism" is defined in JIS B 0621:1984. The parallelism between the two end faces 10a, 10b can be expressed by the size of the area occupied by the end face 10b in a direction perpendicular to a reference plane P including the end face 10a, which is set as a datum plane. The evaluation of the parallelism excludes the recess G, which will be described later. The parallelism can be measured by performing eight-point measurements using a micrometer (standard outside micrometer (digital)) manufactured by Mitutoyo Corporation or a linear height gauge (ID-H0560) manufactured by Mitutoyo Corporation.

[0024] In this embodiment, the cylindricity of the inner peripheral surface 11i of the cylinder 11 is 0.1 mm or less. The cylindricity of the inner peripheral surface 11i of the cylinder 11 may be 0.08 mm or less, 0.06 mm or less, 0.04 mm or less, or 0.02 mm or less. In this specification, "cylindricity" is as defined in JIS B 0621:1984. The cylindricity can be evaluated using a three-dimensional measuring device, for example, a roundness measuring device such as the RONDCOM 43C manufactured by Tokyo Seimitsu Co., Ltd.

[0025] The inner peripheral surface 11i of the cylinder 11 is coaxial with the rotation axis X. In this embodiment, the coaxiality of the inner peripheral surface 11i of the cylinder 11 with respect to the rotation axis X is 0.1 mm or less. The coaxiality of the inner peripheral surface 11i of the cylinder 11 with respect to the rotation axis X may be 0.08 mm or less, 0.06 mm or less, 0.04 mm or less, or 0.02 mm or less. In this specification, "coaxiality" is defined in JIS B 0621:1984. The coaxiality can be evaluated using a three-dimensional measuring device, for example, a roundness measuring device RONDCOM 43C manufactured by Tokyo Seimitsu Co., Ltd.

[0026] The base 10 is disposed on one side of the bearing 102 in the axial direction (in the direction of arrow a). An end of the base 10 on the other side in the axial direction (in the direction of arrow b) is fixed to an inner ring 102i of the bearing 102. As a result, the base 10 rotates together with the shaft S and the inner ring 102i of the bearing 102. As shown in FIG. 5 , a groove 102g extending in the axial direction is formed in the inner ring 102i of the bearing 102. In this embodiment, the groove 102g is formed as a recess that runs around the rotation axis X at an end of the inner ring 102i on one side in the axial direction (in the direction of arrow a) and on the inner side in the radial direction (in the direction of arrow d). The protrusion 14 of the base 10 engages with the groove 102g formed in the inner ring 102i of the bearing 102. However, the end of the inner ring 102i of the bearing 102 on one side in the axial direction (in the direction of arrow a) may be flat or may have a protrusion. In either case, the base 10 may be fixed to the inner ring 102i of the bearing 102 via an adhesive, or by press-fitting or fitting.

[0027] The dimension of the base 10 in the axial direction is larger than the dimension of the substrate 103. In this embodiment, the distance between the reference planes P and Q in the axial direction is larger than the dimension of the substrate 103 in the axial direction and is more than twice the dimension of the substrate 103 in the axial direction. In this embodiment, the substrate 103 is disposed between the reference planes P and Q. In this embodiment, the substrate 103 is disposed at a position of the reference planes P and Q that is closer to the reference plane Q.

[0028] Hereinafter, for convenience, the end face 10b of the base 10 will be referred to as the "first end face 10b." Of the two end faces of the base 10, the first end face 10b is the face that faces closer to the bearing 102. The first end face 10b and the bearing 102 are separated from each other in the axial direction. A ring-shaped magnet 20 is fixed to the first end face 10b of the base 10. The magnet 20 faces the bearing 102 in the axial direction. The magnet 20 contacts the cylinder 11 of the base 10 in the radial direction.

[0029] The magnet 20 is magnetized in the radial direction. The direction of magnetic flux on the radial surface of the magnet 20 (the outer peripheral surface 20o shown in FIG. 5) is aligned with the direction in which the reference planes P and Q extend. That is, the angle that the direction of magnetic flux on the outer peripheral surface 20o of the magnet 20 forms with the axial direction is, for example, 80° to 100°, or may be 85° to 95°, 88° to 92°, 89° to 91°, or even strictly 90° (radial direction). Here, the direction of magnetic flux on the outer peripheral surface 20o of the magnet 20 does not need to be aligned with the direction in which the reference planes P and Q extend throughout the entire circumferential direction. It is sufficient that the direction of magnetic flux on the outer peripheral surface 20o of the magnet 20 is aligned with the direction in which the reference planes P and Q extend at the magnetic pole (north or south pole) portion of the magnet 20. The number of poles of the magnet 20 is not particularly limited, and may be two, four, six, eight or more.

[0030] The cylindricity of the outer peripheral surface 20o of the magnet 20 may be 0.1 mm or less. The cylindricity of the outer peripheral surface 20o of the magnet 20 may be 0.08 mm or less, 0.06 mm or less, 0.04 mm or less, or 0.02 mm or less. The outer peripheral surface 20o of the magnet 20 is coaxial with the rotation axis X. The coaxiality of the outer peripheral surface 20o of the magnet 20 based on the rotation axis X may be 0.1 mm or less. The coaxiality of the inner peripheral surface 11i of the cylinder 11 based on the rotation axis X may be 0.08 mm or less, 0.06 mm or less, 0.04 mm or less, or 0.02 mm or less.

[0031] The magnet 20 is fixed to the first end surface 10b of the base 10 by adhesive 30. Therefore, the magnet 20 and the first end surface 10b of the base 10 face each other via the adhesive 30. A recess G formed in the magnet 20 or the base 10 is interposed between the magnet 20 and the base 10 in the axial direction. As shown in FIG. 5 , in this embodiment, the recess G is a groove formed in the radially inner end of the first end surface 10b of the base 10. By interposing the recess G between the magnet 20 and the base 10, a portion of the adhesive 30 is accommodated in the recess G, preventing the magnet 20 from peeling off or shifting.

[0032] In the radial direction, the magnet 20 faces the magnetic sensor 103s arranged on the substrate 103. The axial position of the magnet 20 overlaps with the axial position of the magnetic sensor 103s. Here, the axial position refers to the x-coordinate when the rotation axis X is the x-axis. In other words, when the rotation axis X is the x-axis, the x-coordinate range occupied by the magnetic sensor 103s overlaps with the x-coordinate range occupied by the magnet 20. When the rotation axis X is the x-axis, half or more of the x-coordinate range occupied by the magnetic sensor 103s may overlap with the x-coordinate range occupied by the magnet 20, two-thirds or more of the x-coordinate range occupied by the magnetic sensor 103s may overlap with the x-coordinate range occupied by the magnet 20, three-quarters or more of the x-coordinate range occupied by the magnetic sensor 103s may overlap with the x-coordinate range occupied by the magnet 20, or four-fifths or more of the x-coordinate range occupied by the magnetic sensor 103s may overlap with the x-coordinate range occupied by the magnet 20.

[0033] The distance between the magnet 20 and the magnetic sensor 103s in the radial direction is not particularly limited as long as it is within a range in which the magnetic sensor 103s can detect the magnetic flux (or change in magnetic flux) from the magnet 20.

[0034] The dimension of magnet 20 in the axial direction is smaller than the dimension of base 10. Here, the dimension of magnet 20 in the axial direction can be determined by setting eight measurement points in the circumferential direction of magnet 20 and dividing the sum of the axial dimensions of each measurement point by 8 (average value). The dimension of magnet 20 in the axial direction may be smaller than 1 / 2 the dimension of base 10, or smaller than 1 / 4 or 1 / 8 of the dimension of base 10. In this embodiment, the dimension of magnet 20 in the axial direction is 0.5 mm or less.

[0035] The magnet 20 may contain magnetic particles and a cured thermosetting resin. Thermosetting resins include, for example, phenolic resin, epoxy resin, unsaturated polyester resin, and polyimide, and can be selected according to the application. From the viewpoint of moldability, epoxy resin is preferably used. The magnetic particles may be, for example, rare earth magnetic powder. Specifically, isotropic Nd (neodymium)-Fe (iron)-B (boron) magnetic powder or isotropic Sm (samarium)-Fe (iron)-N (nitrogen) magnetic powder may be used. Examples of isotropic Nd-Fe-B magnetic powder include MQP-14-12 (product name), MQP-8-5 (product name), MQP-10-8.5HD (product name), MQP-11-8 (product name), and MQP12-8HD (product name) manufactured by Magnequench. Examples of isotropic Sm-Fe-N based magnet powder include SP-14 (product number) and SP-14L (product number) manufactured by Daido Electronics Co., Ltd.

[0036] The magnet 20 may contain Nd—Fe—B-based magnet powder produced by a rapid cooling method. Such magnet powder is specifically obtained by the following method. First, an Nd—Fe—B-based alloy is melted by high-frequency induction heating under reduced pressure or in an argon atmosphere. Next, the molten alloy is sprayed onto a rotating copper roll and rapidly cooled (rapidly cooled) to produce ribbon-shaped thin strips. These thin strips are then broken into pieces, for example, several millimeters to several tens of millimeters in size, and pulverized using a grinder or the like to obtain powder. This pulverized powder is classified using a sieve with a specified mesh and then heat-treated to obtain rare earth magnet powder. The obtained rare earth magnet powder is magnetically isotropic because the easy axes of magnetization of the crystal grains are not aligned in a single direction.

[0037] The particle size of the magnetic particles is, for example, 45 μm or more and 75 μm or less. The particle size of the magnetic particles can be adjusted, for example, by classification using a sieve with a specified mesh. By keeping the particle size of the magnetic particles within an appropriate range, it is possible to suppress a decrease in the squareness of the demagnetization curve of the magnetic particles themselves and oxidation degradation, while also suppressing adverse effects on the flatness, waveform, and magnetic characteristics of each magnetic pole of the magnet 20.

[0038] Magnet 20 may contain magnetic particles in an amount of, for example, 70% to 80% by volume, and cured resin in an amount of 20% to 30% by volume, where the total of the magnetic particles and cured resin is 100% by volume. If the content ratios of the magnetic particles and cured resin are within an appropriate range, this is advantageous from the viewpoints of making it easier to improve the flatness of magnet 20, making it less likely for the magnetic particles to fall off, increasing the electrical resistivity of the material itself, which reduces loss during high-speed rotation, and improving rust resistance.

[0039] The magnet 20 may have a porosity of 5% by volume or less. When the porosity is within an appropriate range, it becomes easier to improve the flatness of the magnet 20 and also to reduce the thickness of the magnet 20. The porosity can be controlled, for example, by adjusting the content ratio of the magnetic particles and the cured resin.

[0040] The encoder 1 according to this embodiment may be manufactured, for example, by molding a composition containing magnetic particles and a thermosetting resin into a ring shape, thermally curing it to form a cured body (thermosetting body), and then adhesively fixing it to the first end face 10b of the base 10, and then magnetizing it.

[0041] Alternatively, the encoder 1 according to this embodiment may be manufactured by molding a composition containing magnetic particles and a thermosetting resin into a ring shape, placing this on the first end surface 10b of the base 10 before thermally curing it, and fixing it to the base 10 using the thermosetting resin in the composition as an adhesive, followed by appropriate thermal curing and magnetization. Although the above-described method is preferable, the encoder 1 according to this embodiment may also be manufactured by other methods.

[0042] The encoder 1 according to this embodiment and the sensor device 100 including the encoder 1 have the above-described configuration. The inner ring 102i of the bearing 102 is fixed to the shaft S, the base 10 is fixed to the inner ring 102i of the bearing 102, and the magnet 20 is fixed to the base 10. Therefore, when the shaft S rotates due to an external force, the magnet 20 rotates together with the shaft S.

[0043] When the magnet 20 rotates, the magnetic flux detected by the magnetic sensor 103s changes. The signal output from the magnetic sensor 103s is transmitted to a control unit or the like via a circuit or the like provided on the substrate 103. In this way, the sensor device 100 can measure the number of rotations or the rotation angle of the shaft S, or both.

[0044] In the encoder 1 according to this embodiment, a radially magnetized magnet 20 is fixed to a first end face 10b included in two end faces 10a, 10b of a base 10 that form parallel reference planes P, Q. If the magnetic pole direction of the magnet 20 is misaligned, periodic noise occurs in the magnetic flux detected by the magnetic sensor 103s, which may reduce the detection accuracy of the sensor device 100. By magnetizing the magnet 20 after it is fixed to the base 10, the influence of assembly accuracy during fixation is reduced, and misalignment of the magnetization direction can be easily suppressed. In this regard, the configuration of the encoder 1 according to this embodiment improves positioning accuracy during magnetization of the magnet 20, making it even less likely that the magnetic pole direction will be misaligned, which makes it easier to improve the detection accuracy of the sensor device 100.

[0045] In the encoder 1 according to this embodiment, the parallelism between the two end faces 10a, 10b is 0.01 mm or less. Therefore, according to the encoder 1 according to this embodiment, the magnet 20 fixed to the base 10 can be positioned with high precision when magnetizing the magnet.

[0046] In the encoder 1 according to this embodiment, the cylindricity of the inner peripheral surface of the cylinder of the base 10 is 0.1 mm or less. Therefore, in the encoder 1 according to this embodiment, the coaxiality of the magnet 20 fixed to the base 10 with respect to the rotation axis X is likely to be high, which is advantageous from the viewpoint of the detection accuracy of the sensor device 100.

[0047] In the encoder 1 according to this embodiment, the base 10 is made of a non-magnetic material. As a result, even if the magnet 20 is magnetized after being fixed to the base 10, the base 10 is not magnetized, and is less likely to have an adverse effect on the magnetic flux detected by the magnetic sensor 103s. In other words, since the base 10 is made of a non-magnetic material, it is easy to employ a method of magnetizing the magnet 20 after it is fixed to the base 10. Furthermore, since the base 10 is made of a non-magnetic material, it is possible to prevent the base 10 from acting as a yoke to form a magnetic circuit, and it is possible to ensure sufficient magnetic flux directed toward the magnetic sensor 103s.

[0048] In the encoder 1 according to this embodiment, the magnet 20 is disposed so as to face the magnetic sensor 103s in the radial direction, and therefore the axial dimension of the sensor device 100 can be easily reduced.

[0049] Although the encoder of the present invention has been described above with reference to preferred embodiments, the encoder of the present invention is not limited to the configuration of the above embodiments. For example, the size, arrangement, orientation, and material of each member or component in the above embodiments may be changed as desired as long as the configuration of the present invention is maintained.

[0050] In some cases, the parallelism of the two end faces of the base may exceed 0.01 mm. The magnet may be spaced apart from the cylinder of the base in the radial direction. The cylindricity of the inner peripheral surface of the cylinder of the base may exceed 0.1 mm. The coaxiality of the inner peripheral surface of the cylinder of the base with respect to the rotation axis may exceed 0.1 mm. The encoder may be disposed on the other side of the bearing in the axial direction (in the direction of arrow b). The cylindricity of the outer peripheral surface of the magnet may exceed 0.1 mm. The coaxiality of the outer peripheral surface of the magnet with respect to the rotation axis may exceed 0.1 mm.

[0051] In some cases, the magnetic sensor does not have to be disposed on the substrate. For example, the magnetic sensor may be disposed on a holder that holds the bearing. Also, for example, the magnetic sensor may be disposed on a housing that houses the sensor device. Furthermore, for example, the magnetic sensor may be disposed on the outer ring of the bearing.

[0052] In some cases, the magnet may be fixed to the encoder base by fitting, press-fitting, engagement, etc., without using an adhesive. The magnet may be adhered to the encoder base in part using a component (such as resin) contained in the magnet. There may not be a recess between the magnet and the encoder base in the axial direction. The magnet may be a normal permanent magnet that does not contain resin. The magnet may have a dimension larger than the encoder base in the axial direction. The magnet may have a dimension greater than 0.5 mm or equal to or greater than 1 mm in the axial direction. The magnet may be fixed to one of the two end faces of the base that faces away from the bearing (the second end face).

[0053] The encoder of the present invention does not have to be used with a shaft. That is, in the above-described embodiment and all of its modified examples, "shaft" may be replaced with "rotating member." The encoder of the present invention does not have to have a base fixed to a bearing. In that case, the encoder of the present invention may have a base fixed directly to a rotating member and rotate together with the rotating member. The encoder of the present invention does not have to be used with a bearing and a holder. The encoder of the present invention is not limited to use in bicycles. For example, the encoder of the present invention may be used with a rotating member in vehicles other than bicycles, general-purpose machines, industrial machines, etc.

[0054] In addition, those skilled in the art can appropriately modify the encoder disclosed in this specification and change the shapes, dimensions, and combinations of various components in accordance with conventionally known knowledge. If such modifications still include the components of the present invention, the modified embodiment naturally falls within the scope of the present invention. [Explanation of symbols]

[0055] 1...encoder, 10...base, 10a...end face, 10b...end face (first end face), 10o...outer surface, 11...cylinder, 20...magnet, 20o...radially facing surface, 30...adhesive, 100...sensor device, 101...holder, 102...bearing, 102i...inner ring, 102o...outer ring, 103...substrate, 103s...magnetic sensor, P, Q...reference surface, G...recess, S...rotating member (shaft).

Claims

1. a base having two radially extending end faces and an outer circumferential surface connected to the two end faces; a ring-shaped magnet fixed to a first end surface included in the two end surfaces of the base, The magnet is magnetized in the radial direction, The two end surfaces form parallel reference surfaces, An encoder, wherein the direction of magnetic flux in the radially facing surface of the magnet is along the direction in which the reference surface extends.

2. 2. The encoder according to claim 1, wherein the parallelism of the two end faces is 0.01 mm or less.

3. the base comprises an axially extending tube; The magnet is in contact with the cylinder in the radial direction, 3. The encoder according to claim 1, wherein the inner peripheral surface of the cylinder has a cylindricity of 0.1 mm or less.

4. The encoder according to claim 1 , wherein the magnet and the first end surface of the base face each other via an adhesive.

5. a recess formed in the magnet or the base is interposed between the magnet and the base, The encoder of claim 4 , wherein the adhesive is contained in the recess.

6. 3. The encoder according to claim 1, wherein the base is made of a non-magnetic material.

7. The encoder according to claim 1 or 2, wherein the magnet faces the magnetic sensor in the radial direction.

8. The encoder according to claim 1 or 2, wherein the magnet has a smaller dimension than the base in the axial direction.

9. 3. The encoder according to claim 1, wherein the magnet has an axial dimension of 0.5 mm or less.

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