Magnetic Encoder

Abstract

In this magnetic encoder (100): a magnetic scale unit (101) comprises a magnet (103) and a magnet (104) which are arranged side by side in a first direction and have mutually opposite magnetization directions, and a magnetic body (102) disposed at a gap from the magnets (103, 104) along the magnetization direction of the magnets (103, 104); a position detection unit (106) comprises a magnetic detection element (107) that is disposed at a gap from the magnets (103, 104) and from the magnetic body (102), and outputs a change in a magnetic field as an electrical signal; the magnetic body (102) has a length in the first direction that corresponds to one wavelength of a wavelength determined on the basis of resolution, and an opposing surface thereof opposing the magnets (103, 104) is a curved surface that is most convex at positions corresponding to 1 / 4 and 3 / 4 of the wavelength from an end in the first direction; and the magnets (103, 104) are respectively disposed at positions opposing the positions at which the opposing surface of the magnetic body (102) is most convex.

Description

[Technical Field]

[0001] The present disclosure relates to a magnetic encoder having a magnetic detection unit and a position detection unit that move relative to each other. [Background technology]

[0002] A magnetic encoder has a magnetic detection unit and a position detection unit that move relative to each other, and is used in rotary encoders, which are rotation detectors for controlling rotary servo motors, and linear encoders, which are position detectors for controlling linear motors.

[0003] Patent Document 1 discloses a magnetic scale unit having multiple magnetic poles. The magnetic scale unit has a magnetic pole row in which multiple magnetic poles of the same polarity are arranged at equal intervals. The interval between the magnetic poles is greater than the width of the magnetic poles in the arrangement direction, but less than twice the width of the magnetic poles in the arrangement direction. A magnetic sensor outputs changes in the magnetic field of the magnetic scale unit as an electrical signal, and position information is obtained from the voltage peak. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-227904 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, since the widths of the multiple magnets of the same polarity are all the same, there is a problem in that only the peak position of the magnetic field and discrete position information corresponding to the peak position can be obtained.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a magnetic encoder that can obtain a smooth, long-period sinusoidal signal and can acquire continuous, highly accurate position information over a wide range. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, a magnetic encoder according to the present disclosure is a magnetic encoder in which a magnetic scale unit and a position detection unit move relatively along a first direction, the magnetic scale unit including: a first magnetic field source and a second magnetic field source arranged side by side in the first direction and having magnetization directions opposite to each other; a magnetic body arranged along the magnetization directions of the first magnetic field source and the second magnetic field source at a distance from the first magnetic field source and the second magnetic field source; and a base for positioning the first magnetic field source, the second magnetic field source, and the magnetic body. The position detection unit includes a magnetic detection element arranged in a region between the first magnetic field source, the second magnetic field source, and the magnetic body at a distance from each of the first magnetic field source, the second magnetic field source, and the magnetic body, and for outputting a change in the magnetic field as an electric signal. The magnetic body has a length in a first direction corresponding to one wavelength determined based on the position detection resolution of the magnetic scale unit in the first direction, and the surfaces facing the first and second magnetic field sources are curved surfaces that are most convex in the first direction at positions corresponding to 1 / 4 and 3 / 4 of the wavelength from the end in the first direction. The first magnetic field source is disposed at a position facing the position corresponding to 1 / 4 of the wavelength of the magnetic body, and the second magnetic field source is disposed at a position facing the position corresponding to 3 / 4 of the wavelength of the magnetic body. [Effects of the Invention]

[0008] The magnetic encoder according to the present disclosure has the advantage that it is possible to obtain a smooth, long-period sinusoidal signal, and to obtain continuous, highly accurate position information over a wide range. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a magnetic encoder according to a first embodiment; [Figure 2] FIG. 1 is a front view showing a magnetic encoder according to a first embodiment; [Figure 3]FIG. 10 is a front view of a magnetic encoder according to a comparative example of the first embodiment; [Figure 4] FIG. 10 is a diagram showing a flow of magnetic flux in a magnetic encoder according to a comparative example of the first embodiment. [Figure 5] FIG. 10 is a diagram showing the waveform of the strength of the magnetic field applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the comparative example of the first embodiment. [Figure 6] FIG. 1 is a diagram showing a flow of magnetic flux in a magnetic encoder according to a first embodiment. [Figure 7] FIG. 10 is a diagram showing the waveform of the strength of the magnetic field applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the first embodiment. [Figure 8] FIG. 10 is a diagram showing the waveform of the strength of the magnetic field applied to the magnetic detection element by the magnetic scale unit when the distance between the magnetic scale and the magnetic detection element of the magnetic encoder according to the comparative example of the first embodiment varies. [Figure 9] FIG. 10 is a diagram showing the waveform of the strength of the magnetic field applied to the magnetic detection element by the magnetic scale unit when the distance between the magnetic scale and the magnetic detection element of the magnetic encoder according to the first embodiment varies; [Figure 10] FIG. 10 is a front view of a magnetic encoder according to a second embodiment; [Figure 11] FIG. 10 is a diagram showing the direction of internal magnetization of a magnet group in a magnetic encoder according to a second embodiment. [Figure 12] FIG. 10 is a diagram showing the waveform of the strength of the magnetic field applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the second embodiment. [Figure 13] FIG. 10 is a front view of a magnetic encoder according to a third embodiment; [Figure 14] FIG. 10 is a diagram showing the direction of internal magnetization of a magnet group in a magnetic encoder according to a third embodiment. [Figure 15] FIG. 10 is a perspective view showing the configuration of a magnetic encoder according to a fourth embodiment. [Figure 16] FIG. 10 is a front view showing the configuration of a magnetic encoder according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a magnetic encoder according to an embodiment will be described in detail with reference to the drawings.

[0011] Embodiment 1 FIG. 1 is a perspective view showing a magnetic encoder according to a first embodiment. FIG. 2 is a front view showing the magnetic encoder according to the first embodiment. A magnetic encoder 100 according to the first embodiment includes a magnetic scale unit 101 and a position detection unit 106 that detects a magnetic field generated by the magnetic scale unit 101. The magnetic encoder 100 according to the first embodiment is a linear encoder. The magnetic scale unit 101 includes a magnet 103 that is a first magnetic field generation source, a magnet 104 that is a second magnetic field generation source, a magnetic body 102 that is disposed at an interval from the magnets 103 and 104 in the magnetization directions of the magnets 103 and 104, and a non-magnetic base 105 that fixes the magnets 103 and 104 and the magnetic body 102. In the magnetic encoder 100 according to the first embodiment, the base 105 may be formed of resin. The position detection unit 106 has a plurality of magnetic detection elements 107 that detect the magnetic field generated from the magnetic scale unit 101, and a substrate 108 on which the magnetic detection elements 107 are attached.

[0012] 1 and 2 show the magnetic encoder 100 in a three-dimensional Cartesian coordinate system of xyz. The x direction corresponds to the movement direction of the magnetic scale unit 101, the z direction corresponds to the direction in which the magnetic scale unit 101 and the position detection unit 106 face each other, and the y direction is perpendicular to the x and z directions. In the present disclosure, in the case of a linear encoder, the x direction corresponds to the first direction.

[0013] 2, Tsm denotes the minimum length of the magnetic body 102 in the z direction, Lsm denotes the length of the magnetic body 102 in the x direction, Lm denotes the magnet width, which is the length in the x direction of each of the magnets 103 and 104, and G denotes the distance from each surface of the magnets 103 and 104 to the sensing surface of the magnetic detection element 107. Here, the length dTsm of the convex portion of the magnetic body 102 in the z direction satisfies the relationship dTsm > Lsm / 50. Furthermore, the length Lsm of the magnetic body 102 in the x direction is twice the magnet width Lm of each of the magnets 103 and 104. Note that the length Lsm of the magnetic body 102 in the x direction, which is the first direction, corresponds to one wavelength determined based on the position detection resolution of the magnetic scale unit 101 in the x direction.

[0014] The surface of magnetic body 102 facing magnets 103 and 104 is curved and convex toward magnets 103 and 104. The distance between magnetic body 102 and each of magnets 103 and 104 is greatest in the x direction at both ends and the center of magnetic body 102 in the x direction. The distance between magnetic body 102 and each of magnets 103 and 104 is smallest in the x direction at positions 1 / 4 and 3 / 4 of the length Lsm of magnetic body 102 in the x direction from the ends of magnetic body 102.

[0015] The magnetic scale unit 101 and the position detection unit 106 move relative to each other. In the first embodiment, the magnetic scale unit 101 is a mover that moves in the x direction. The position detection unit 106 is a stator that is fixed a certain distance away from the magnetic scale unit 101 in the z direction. The position detection unit 106 detects the position of the magnetic scale unit 101 from changes in the magnetic field when the magnetic scale unit 101 passes by.

[0016] The substrate 108 is strip-shaped with a surface extending parallel to the xy plane, with the x direction being its longitudinal direction. As shown in FIG. 2, the multiple magnetic detection elements 107 are arranged on the substrate 108 at equal pitches in the x direction. The pitch at which the magnetic detection elements 107 are arranged is set to be equal to or less than the wavelength of the sine wave formed by the magnetic scale unit 101, so as to prevent the occurrence of areas where position detection is not possible. The magnetic detection elements 107 are arranged in areas sandwiched between the magnets 103 and 104 and the magnetic material 102, with a gap between them and each of the magnets 103 and 104 and the magnetic material 102, and output changes in the magnetic field as an electrical signal.

[0017] FIG. 3 is a front view of a magnetic encoder according to a comparative example of the first embodiment. In the magnetic encoder 110 according to the comparative example of the first embodiment, the magnetic scale unit 111 does not include a magnetic material, and the base 115 has magnets 113 and 114 fixed thereto. The position detection unit 116 has a plurality of magnetic detection elements 117 that detect the magnetic field generated by the magnetic scale unit 111, and a substrate 118 on which the magnetic detection elements 117 are attached. The substrate 118 is strip-shaped with a surface extending parallel to the xy plane, and its longitudinal direction is the x direction. As shown in FIG. 3, the plurality of magnetic detection elements 117 of the position detection unit 116 are arranged on the substrate 118 at equal pitches in the x direction.

[0018] 4 is a diagram showing the flow of magnetic flux in a magnetic encoder according to a comparative example of embodiment 1. In magnetic encoder 110 according to the comparative example of embodiment 1, for example, most of the magnetic flux emitted from magnet 113 dissipates without returning to magnet 114, and only a small portion of the magnetic flux returns to magnet 114. For this reason, in magnetic encoder 110 according to the comparative example, the magnetic flux becomes significantly weaker with increasing distance from the surfaces of magnets 113 and 114, and as the distance G from each surface of magnet 113 and magnet 114 to the sensing surface of magnetic detection element 117 increases, the amplitude of the strength of the magnetic field applied to magnetic detection element 117 decreases.

[0019] FIG. 5 is a diagram showing the waveform of the magnetic field strength applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the comparative example of the first embodiment. The magnetization direction of magnet 113 is the +z direction, and the magnetization direction of magnet 114 is the −z direction. In FIG. 5, the vertical axis represents magnetic flux density Bz, and the horizontal axis represents the position of magnetic scale unit 111. Note that [au] on the vertical and horizontal axes represents an arbitrary unit. In FIG. 5, the solid line represents the magnetic field strength applied to magnetic detection element 117 by magnetic scale unit 111 of magnetic encoder 110 according to the comparative example of the first embodiment, and the dashed line represents the waveform of a sine wave, which is an ideal waveform. As shown in FIG. 5, in the magnetic encoder 110 according to the comparative example, the rise and fall of the magnetic flux density are steeper than in a sine wave, and the section of the magnet position where the amplitude approaches its maximum value is longer.

[0020] 6 is a diagram showing the flow of magnetic flux in the magnetic encoder according to embodiment 1. In magnetic encoder 100 according to embodiment 1, for example, magnetic flux emitted from magnet 103 flows into magnetic body 102 and flows toward magnet 104 via magnetic body 102. Therefore, a magnetic circuit is formed by magnet 103, magnetic body 102, and magnet 104, suppressing the divergence of magnetic flux, resulting in a high magnetic flux density in the region surrounded by magnets 103, 104, and magnetic body 102, and there is little variation in the magnetic flux density even when moving away from the surfaces of magnets 113 and 114.

[0021] FIG. 7 is a diagram showing the waveform of the magnetic field strength applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the first embodiment. The magnetization direction of magnet 103 is the +z direction, and the magnetization direction of magnet 104 is the −z direction. In FIG. 7, the vertical axis represents magnetic flux density Bz, and the horizontal axis represents the position of magnetic scale unit 101. Note that [au] on the vertical and horizontal axes represents an arbitrary unit. In FIG. 7, the solid line represents the magnetic field strength applied to magnetic detection element 107 by magnetic scale unit 101 of magnetic encoder 100 according to the first embodiment, and the dashed line represents an ideal sinusoidal waveform. As shown in FIG. 7, in the magnetic encoder 100 according to the first embodiment, the waveform of the magnetic field strength applied to magnetic detection element 107 by magnetic scale unit 101 is a waveform close to a sinusoidal wave.

[0022] FIG. 8 is a diagram showing the waveform of the magnetic field strength applied to the magnetic detection element by the magnetic scale unit when the distance between the magnetic scale and the magnetic detection element of the magnetic encoder according to the comparative example of embodiment 1 varies. In FIG. 8, the dashed line represents an ideal sine wave waveform. In FIG. 8, of the three solid lines of different thicknesses, the medium-thickness solid line represents the magnetic field strength applied to the magnetic detection element 117 by the magnetic scale unit 111. In FIG. 8, the thick solid line represents the magnetic field strength applied to the magnetic detection element 117 by the magnetic scale unit 111 when the distance G from the surfaces of the magnets 113 and 114 to the sensing surface of the magnetic detection element 117 increases. In FIG. 8, the thin solid line represents the magnetic field strength applied to the magnetic detection element 117 by the magnetic scale unit 111 when the distance G from the surfaces of the magnets 113 and 114 to the sensing surface of the magnetic detection element 117 decreases. In magnetic encoder 110 according to the comparative example of embodiment 1, when the distance between the mover and the stator fluctuates and the distance G from the surfaces of magnets 113 and 114 to the sensing surface of magnetic detection element 117 changes, the strength of the magnetic field applied to magnetic detection element 117 differs greatly from an ideal sine wave, regardless of whether distance G increases or decreases. Furthermore, the waveform of the magnetic field strength applied to magnetic detection element 117 has a longer section at the magnet position where the wave is flattened and the amplitude approaches its maximum value than a sine wave. This makes it difficult to accurately match the strength of the magnetic field applied to magnetic detection element 117 with the magnet position, resulting in reduced position detection accuracy.

[0023] FIG. 9 is a diagram showing the waveform of the magnetic field strength applied to the magnetic detection element by the magnetic scale unit when the distance between the magnetic scale and the magnetic detection element of the magnetic encoder according to embodiment 1 varies. In FIG. 9, the dashed line indicates an ideal sine wave waveform. In FIG. 9, of the three solid lines of different thicknesses, the medium-thickness solid line indicates the magnetic field strength applied to the magnetic detection element 107 by the magnetic scale unit 101. In FIG. 9, the thick solid line indicates the magnetic field strength applied to the magnetic detection element 107 by the magnetic scale unit 101 when the distance G from the surfaces of the magnets 103 and 104 to the sensing surface of the magnetic detection element 107 increases. In FIG. 9, the thin solid line indicates the magnetic field strength applied to the magnetic detection element 107 by the magnetic scale unit 101 when the distance G from the surfaces of the magnets 103 and 104 to the sensing surface of the magnetic detection element 107 decreases. In magnetic encoder 100 according to embodiment 1, when the distance between the mover and the stator fluctuates and the distance G from the surfaces of magnets 103 and 104 to the sensing surface of magnetic detection element 107 changes, whether distance G increases or decreases, the difference between the strength of the magnetic field applied to magnetic detection element 107 and an ideal sine wave is small. Furthermore, the waveform of the strength of the magnetic field applied to magnetic detection element 107 is approximately sine wave in shape. Therefore, the strength of the magnetic field applied to magnetic detection element 107 can be accurately matched to the magnet position, thereby improving position detection accuracy.

[0024] In order to detect the absolute position of the magnetic scale unit 101, it is necessary to generate a signal with a long period, one period relative to the stroke of the magnetic scale unit 101. In the magnetic encoder 100 according to the first embodiment, the magnetic body 102 has a curved surface that is convex toward the magnets 103 and 104, and the magnetic scale unit 101 can generate a smooth sinusoidal signal with a long period by the magnets 103 and 104. Furthermore, the magnetic body 102 forms a magnetic circuit together with the magnets 103 and 104, so that the absolute position of the magnetic scale unit 101 can be detected continuously over a wide range with high accuracy.

[0025] Although the structure described here is one in which magnets 103 and 104 are spaced apart from magnetic body 102 in the y direction, magnets 103 and 104 may also be spaced apart from magnetic body 102 in the z direction.

[0026] Embodiment 2 10 is a front view of a magnetic encoder according to embodiment 2. Magnetic encoder 200 according to embodiment 2 includes magnet group 123, which is a first magnetic field generation source, and magnet group 124, which is a second magnetic field generation source. Each of magnet group 123 and magnet group 124 is formed of a plurality of magnets 10. Each of magnet group 123 and magnet group 124 and magnetic body 202 are fixed by base 205. The surface of magnetic body 202 facing magnet group 123 and magnet group 124 is curved and convex toward magnet group 123 and magnet group 124. The distance between magnetic body 202 and each of magnet group 123 and magnet group 124 is greatest at both ends and the center of magnetic body 202 in the x direction. In addition, the distance between the magnetic body 202 and each of the magnet groups 123 and 124 is smallest in the x direction at a position 1 / 4 of the x-direction length Lsm of the magnetic body 202 and at a position 3 / 4 of Lsm from the end of the magnetic body 202.

[0027] FIG. 11 is a diagram showing the direction of internal magnetization of the magnet group in the magnetic encoder according to the second embodiment. The magnetic encoder 200 according to the second embodiment uses a magnet width modulation method that changes the magnet width Lm, which is the length of the magnet 10 in the x-direction, which is a first direction. The arrows in the magnet group 123 and the magnet group 124 shown in FIG. 11 indicate the direction of internal magnetization after magnetization. The tip of each arrow indicates a north pole, and the base end indicates a south pole. Therefore, all of the magnets 10 constituting the magnet group 123 have a north pole on the side facing the position detection unit 206. All of the magnets 10 constituting the magnet group 124 have a south pole on the side facing the position detection unit 206. Hereinafter, the direction of internal magnetization of each magnet 10 will be simply referred to as the magnetization direction. As such, all of the magnets 10 constituting the magnet group 123 are magnetized in the same magnetization direction, and all of the magnets 10 constituting the magnet group 124 are magnetized in the magnetization direction opposite to that of the magnets 10 constituting the magnet group 123.

[0028] The number of magnets 10 constituting magnet group 123 and the number of magnets 10 constituting magnet group 124 are the same, three or more. In each of magnet group 123 and magnet group 124, the distance between the magnets 10 is constant. The magnet width Lm increases and decreases in accordance with a sine function, which is a sine wave function, in the x direction. That is, in each of magnet group 123 and magnet group 124, the magnet width Lm increases from the end to the center in the x direction. In other words, in each of magnet group 123 and magnet group 124, the magnet width Lm increases stepwise from one end to the center in the x direction, and then decreases stepwise from the center to the other end in the x direction. Meanwhile, the distance Ld between the magnets 10 is constant.

[0029] As shown in FIG. 10 , the number of magnets 10 constituting magnet group 123 is seven. The number of magnets 10 constituting magnet group 124 is also seven. A position a distance a in the −x direction from the −x-direction end of the magnet 10 constituting magnet group 123 that is installed at a position farthest from magnet group 124 corresponds to 0 degrees of the sine function. Furthermore, a position a distance a in the +x direction from the +x-direction end of the magnet 10 constituting magnet group 124 that is installed at a position farthest from magnet group 123 corresponds to 360 degrees of the sine function. Furthermore, a position a distance a in the +x direction from the +x-direction end of the magnet 10 constituting magnet group 123 that is installed at a position closest to magnet group 124, and a position a distance a in the −x direction from the −x-direction end of the magnet 10 constituting magnet group 124 that is installed at a position closest to magnet group 123, correspond to 180 degrees of the sine function.

[0030] Distance a is set so that the midpoint between the -x-direction end of the magnet 10 that is located farthest from magnet group 124 among the magnets 10 that make up magnet group 123 and the +x-direction end of the magnet 10 that is located closest to magnet group 124 corresponds to 90 degrees of the sine function, and the midpoint between the +x-direction end of the magnet 10 that is located farthest from magnet group 123 among the magnets 10 that make up magnet group 124 and the -x-direction end of the magnet 10 that is located closest to magnet group 123 corresponds to 270 degrees of the sine function.

[0031] The position detection unit 206 is similar to the position detection unit 106 of the magnetic encoder 100 according to embodiment 1, and has a plurality of magnetic detection elements 207 that detect the magnetic field generated from the magnetic scale unit 201, and a substrate 208 on which the magnetic detection elements 207 are mounted.

[0032] The magnetic scale unit 201 and the position detection unit 206 move relative to each other. In the second embodiment, the magnetic scale unit 201 is a mover that moves in the x direction. The position detection unit 206 is a stator that is fixed a certain distance away from the magnetic scale unit 201 in the z direction. The position detection unit 206 detects the position of the magnetic scale unit 201 from changes in the magnetic field when the magnetic scale unit 201 passes by.

[0033] The substrate 208 is strip-shaped with a surface extending parallel to the xy plane, with the x direction being the longitudinal direction. As shown in Fig. 10, the multiple magnetic detection elements 207 are arranged on the substrate 208 at equal pitches in the x direction. The pitch at which the magnetic detection elements 207 are arranged is set to be equal to or less than the wavelength of the sine wave formed by the magnetic scale unit 201, so as to prevent the occurrence of areas where position detection is not possible.

[0034] FIG. 12 is a diagram showing the waveform of the strength of the magnetic field applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the second embodiment. In FIG. 12, the vertical axis represents magnetic flux density Bz, and the horizontal axis represents the position of the magnetic scale unit 201. Note that [au] on the vertical and horizontal axes represents an arbitrary unit. In FIG. 12, the solid line represents the strength of the magnetic field applied to the magnetic detection element 207 by the magnetic scale unit 201 of the magnetic encoder 200 according to the second embodiment, and the dashed line represents an ideal sinusoidal waveform. As shown in FIG. 12, in the magnetic encoder 200 according to the second embodiment, the waveform of the strength of the magnetic field applied to the magnetic detection element 207 by the magnetic scale unit 201 is a waveform close to a sinusoidal wave. Compared to the waveform of the magnetic field intensity applied to the magnetic detection element 107 by the magnetic scale unit 101 of the magnetic encoder 100 of embodiment 1 shown in Figure 7, the waveform of the magnetic field intensity applied to the magnetic detection element 207 by the magnetic scale unit 201 of the magnetic encoder 200 of embodiment 2 is closer to a sine wave.

[0035] In the magnetic encoder 200 of embodiment 2, the waveform of the magnetic field intensity applied to the magnetic detection element 207 by the magnetic scale unit 201 is closer to a sine wave than the waveform of the magnetic field intensity applied to the magnetic detection element 107 by the magnetic scale unit 101 of the magnetic encoder 100 of embodiment 1, and therefore the position detection accuracy can be further improved compared to the magnetic encoder 100 of embodiment 1.

[0036] In the second embodiment, the magnet width is changed to generate a sinusoidal change in the magnetic field, but the magnet width may be kept constant and a sinusoidal change in the magnetic field may be generated by changing the magnetic force of each magnet 10. Methods for changing the magnetic force include gradually changing the thickness of magnet 10, gradually changing the distance from magnetic detection element 207, gradually changing the magnetization rate of magnet 10, or gradually changing the magnetic material of magnet 10.

[0037] Embodiment 3 13 is a front view of a magnetic encoder according to embodiment 3. The magnetic encoder 300 according to embodiment 3 includes a magnet group 133 serving as a first magnetic field generation source and a magnet group 134 serving as a second magnetic field generation source. Each of the magnet group 133 and the magnet group 134 is formed of a plurality of magnets 10. Each of the magnet group 133 and the magnet group 134 and the magnetic body 302 are fixed by a base 305. The surface of the magnetic body 302 facing the magnet group 133 and the magnet group 134 is a curved surface that is convex toward the magnet group 133 and the magnet group 134. The distance between the magnetic body 302 and each of the magnet group 133 and the magnet group 134 is greatest at both ends and the center of the magnetic body 302 in the x direction. In addition, the distance between the magnetic body 302 and each of the magnet groups 133 and 134 is smallest in the x direction at a position 1 / 4 of the x-direction length Lsm of the magnetic body 302 and at a position 3 / 4 of Lsm from the end of the magnetic body 302.

[0038] FIG. 14 is a diagram showing the direction of internal magnetization of the magnet group in the magnetic encoder according to the third embodiment. The magnetic encoder 300 according to the third embodiment uses a magnet spacing modulation method in which the spacing between the magnets 10 is changed. The arrows in the magnet group 133 and the magnet group 134 shown in FIG. 14 indicate the direction of internal magnetization after magnetization. The tip of each arrow indicates a north pole, and the base end indicates a south pole. Therefore, all of the magnets 10 constituting the magnet group 133 have a north pole on the side facing the position detection unit 306. All of the magnets 10 constituting the magnet group 134 have a south pole on the side facing the position detection unit 306. Hereinafter, the direction of internal magnetization of each magnet 10 will be simply referred to as the magnetization direction. As such, all of the magnets 10 constituting the magnet group 133 are magnetized in the same magnetization direction, and all of the magnets 10 constituting the magnet group 134 are magnetized in the magnetization direction opposite to that of the magnets 10 constituting the magnet group 133.

[0039] The position detection unit 306 has a plurality of magnetic detection elements 307 that detect the magnetic field generated from the magnetic scale unit 301, and a substrate 308 on which the magnetic detection elements 307 are attached.

[0040] The number of magnets 10 constituting magnet group 133 and the number of magnets 10 constituting magnet group 134 are the same, three or more. In each of magnet group 133 and magnet group 134, magnet width Lm is constant. The spacing between magnets 10 increases and decreases according to a sine function, which is a sine wave function. That is, in each of magnet group 123 and magnet group 124, spacing Ld between magnets 10 decreases in the x direction from the end to the center. In other words, in each of magnet group 133 and magnet group 134, spacing Ld between magnets 10 decreases in stages from one end to the center in the x direction, and then increases in stages from the center to the other end in the x direction.

[0041] As shown in FIG. 13 , the number of magnets 10 constituting magnet group 133 is nine. The number of magnets 10 constituting magnet group 134 is also nine. A position a distance a in the −x direction from the −x-direction end of the magnet 10 constituting magnet group 133 that is placed farthest from magnet group 134 corresponds to 0 degrees of the sine function. Furthermore, a position a distance a in the +x direction from the +x-direction end of the magnet 10 constituting magnet group 134 that is placed farthest from magnet group 133 corresponds to 360 degrees of the sine function. Furthermore, a position a distance a in the +x direction from the +x-direction end of the magnet 10 constituting magnet group 133 that is placed closest to magnet group 134, and a position a distance a in the −x direction from the −x-direction end of the magnet 10 constituting magnet group 134 that is placed closest to magnet group 133, correspond to 180 degrees of the sine function.

[0042] Distance a is set so that the midpoint between the -x-direction end of the magnet 10 that is located farthest from magnet group 134 among the magnets 10 that make up magnet group 133 and the +x-direction end of the magnet 10 that is located closest to magnet group 134 corresponds to 90 degrees of the sine function, and the midpoint between the +x-direction end of the magnet 10 that is located farthest from magnet group 133 among the magnets 10 that make up magnet group 134 and the -x-direction end of the magnet 10 that is located closest to magnet group 133 corresponds to 270 degrees of the sine function.

[0043] In the magnetic encoder 300 according to the third embodiment, similarly to the magnetic encoder 200 according to the second embodiment, the waveform of the magnetic field intensity applied to the magnetic detection element 307 by the magnetic scale unit 301 is closer to a sine wave than the waveform of the magnetic field intensity applied to the magnetic detection element 107 by the magnetic scale unit 101 of the magnetic encoder 100 according to the first embodiment. Therefore, the magnetic encoder 300 according to the third embodiment can further improve the position detection accuracy compared to the magnetic encoder 100 according to the first embodiment.

[0044] Embodiment 4 Fig. 15 is a perspective view showing the configuration of a magnetic encoder according to embodiment 4. Fig. 16 is a front view showing a magnetic encoder according to embodiment 4. A magnetic encoder 400 according to embodiment 4 is a rotary encoder. The magnetic encoder 400 according to embodiment 4 includes a ring-shaped magnetic scale unit 401 and a position detection unit 406 that detects the magnetic field generated from the magnetic scale unit 401. In embodiment 4, the magnetic scale unit 401 is a mover, and the position detection unit 406 is a stator.

[0045] The magnetic scale unit 401 includes a magnet 403 serving as a first magnetic field generating source, a magnet 404 serving as a second magnetic field generating source, a magnetic body 402 disposed at a distance from the magnets 403 and 404 in the magnetization directions of the magnets 403 and 404, and a non-magnetic base 405 to which the magnetic body 402, the magnets 403 and 404 are fixed. The surface of the magnetic body 402 facing the magnets 403 and 404 is curved and convex toward the magnets 403 and 404. The base 405 is cylindrical. The magnetic scale unit 401 is mounted on a rotating shaft (not shown) and rotates. In the case of a rotary encoder in the present disclosure, the circumferential direction, which is the direction of rotation of the magnetic scale unit 401, corresponds to the first direction.

[0046] The position detection unit 406 includes a ring-shaped substrate 408 and a magnetic detection element 407 mounted on the substrate 408. The magnetic detection element 407 detects the magnetic field generated by the magnetic scale unit 401. The magnetic detection element 407 is fixed on the substrate 408 at a fixed distance in the z direction from the magnetic scale unit 401. The position detection unit 406 detects the position of the magnetic scale unit 401 based on changes in the magnetic field when the magnetic scale unit 401 rotates. Note that the substrate 408 is not shown in FIG. 15 .

[0047] The magnet width modulation method shown in the second embodiment or the magnet interval modulation method shown in the third embodiment may be applied to the magnetic encoder 400 of the fourth embodiment.

[0048] In the magnetic encoder 400 according to the fourth embodiment, the magnetic body 402 forms a magnetic circuit together with the magnet 403 and the magnet 404, and therefore the absolute position of the magnetic scale unit 401 can be detected with high accuracy.

[0049] The configurations shown in the above embodiments are merely examples of the content, and may be combined with other known technologies, or parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0050] 10,103,104,113,114,403,404 Magnets, 100,110,200,300,400 Magnetic encoders, 101,111,201,301,401 Magnetic scale units, 102,202,302,402 Magnetic materials, 105,115,205,305,405 Bases, 106,116,206,306,406 Position detection units, 107,117,207,307,407 Magnetic detection elements, 108,118,208,308,408 Substrates, 123,124,133,134 Magnet groups.

Claims

1. A magnetic encoder in which a magnetic scale unit and a position detection unit move relatively along a first direction, The magnetic scale unit comprises: a first magnetic field source and a second magnetic field source arranged side by side in the first direction and having magnetization directions opposite to each other; a magnetic body arranged at a distance from the first magnetic field generation source and the second magnetic field generation source along the magnetization directions of the first magnetic field generation source and the second magnetic field generation source; a base for positioning the first magnetic field source, the second magnetic field source, and the magnetic body; The position detection unit a magnetic detection element disposed in a region sandwiched between the first magnetic field generation source, the second magnetic field generation source, and the magnetic body at a distance from the first magnetic field generation source, the second magnetic field generation source, and the magnetic body, and configured to output a change in the magnetic field as an electric signal; the magnetic body has a length in the first direction corresponding to one wavelength determined based on the position detection resolution of the magnetic scale unit in the first direction, and the surface facing the first magnetic field generation source and the second magnetic field generation source is a curved surface that is most convex in the first direction at positions corresponding to ¼ and ¾ of the wavelength from the end in the first direction, a magnetic encoder characterized in that the first magnetic field generating source is arranged at a position opposite a position of the magnetic material corresponding to 1 / 4 of the wavelength, and the second magnetic field generating source is arranged at a position opposite a position of the magnetic material corresponding to 3 / 4 of the wavelength.

2. each of the first magnetic field generation source and the second magnetic field generation source is a magnet group formed of a plurality of magnets having the same magnetization direction; the magnets of the first magnetic field source are spaced apart in the first direction; The magnets of the first magnetic field generation source are all magnetized in the same magnetization direction, the magnets of the second magnetic field source are spaced apart in the first direction; All of the magnets of the second magnetic field generation source are magnetized in a magnetization direction opposite to that of the magnets of the first magnetic field generation source, 2. The magnetic encoder according to claim 1, wherein the magnet width of the first magnetic field generating source and the magnet width of the second magnetic field generating source change stepwise along the first direction.

3. each of the first magnetic field generation source and the second magnetic field generation source is a magnet group formed of a plurality of magnets having the same magnetization direction; the magnets of the first magnetic field source are spaced apart in the first direction; The magnets of the first magnetic field generation source are all magnetized in the same magnetization direction, the magnets of the second magnetic field source are spaced apart in the first direction; All of the magnets of the second magnetic field generation source are magnetized in a magnetization direction opposite to that of the magnets of the first magnetic field generation source, 2. The magnetic encoder according to claim 1, wherein the intervals between the magnets of the first magnetic field generating source and the intervals between the magnets of the second magnetic field generating source change stepwise along the first direction.

4. the position detection unit is disposed on a stator, and the magnetic scale unit is disposed on a mover; 2. The magnetic encoder according to claim 1, wherein a plurality of the magnetic detection elements are arranged along the first direction.

5. The position detection unit is disposed on a stator, and the magnetic scale unit is disposed on a mover, 3. The magnetic encoder according to claim 2, wherein a plurality of the magnetic detection elements are arranged along the first direction.

6. The position detection unit is disposed on a stator, and the magnetic scale unit is disposed on a mover, 4. The magnetic encoder according to claim 3, wherein a plurality of the magnetic detection elements are arranged along the first direction.

7. 7. The magnetic encoder according to claim 1, wherein the magnetic encoder is a linear encoder.

8. 7. The magnetic encoder according to claim 1, wherein the magnetic encoder is a rotary encoder.

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