Magnetic encoder

Abstract

In a magnetic encoder (100), a magnetic scale unit (101) has: a magnet (103) and a magnet (104) that are arranged side by side in a first direction and that have mutually opposite magnetization directions; and a magnet (102) disposed along the magnetization direction of the magnets (103, 104) at a distance from the magnets (103, 104), the position detection unit (106) having a magnetic detection element (107) disposed at a distance from each of the magnets (103, 104) and the magnet (102), the magnetic detection element (107) outputting a change in a magnetic field as an electric signal, and the magnetic detection element (107) being disposed at a distance from each of the magnets (103, 104) and the magnet (102). The length of the magnet (102) in the first direction is a length corresponding to one of the wavelengths determined on the basis of the resolution, the facing surfaces of the magnets (103, 104) are curved surfaces that are most convex at positions corresponding to 1 / 4 and 3 / 4 of the wavelength from the end of the magnet (102) in the first direction, and the magnets (103, 104) are each disposed at positions facing the most convex positions of the facing surfaces of the magnet (102).

Description

Technical Field

[0001] The present invention relates to a magnetic encoder having a relatively movable magnetic detection unit and a position detection unit. Background Art

[0002] The magnetic encoder has a relatively movable magnetic detection unit and a position detection unit. Such a magnetic encoder is used as a rotary encoder as a rotation detector for controlling a rotary servo motor and a linear encoder as a position detector for controlling a linear motor.

[0003] Patent document 1 shows a magnetic scale unit having a plurality of magnetic poles. The magnetic scale unit has a magnetic pole row in which a plurality of magnetic poles of the same polarity are arranged at equal intervals. The interval between the magnetic poles is greater than the width in the arrangement direction of the magnetic poles and less than twice the width in the arrangement direction of the magnetic poles. The magnetic sensor outputs the magnetic field change of the magnetic scale unit as an electrical signal, and obtains position information based on the peak value of the voltage.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2001-227904 Summary of the invention

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

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic encoder capable of obtaining a smooth long-period sinusoidal wave signal and acquiring continuous and high-precision position information over a wide range.

[0007] In order to solve the above problems and achieve the purpose, the magnetic encoder of the present invention is characterized in that the magnetic scale unit and the position detection unit move relatively in the first direction, and the magnetic encoder is characterized in that the magnetic scale unit has: a first magnetic field generating source and a second magnetic field generating source arranged in the first direction, and the magnetization directions are opposite to each other; a magnet arranged at a distance from the first magnetic field generating source and the second magnetic field generating source along the magnetization direction of the first magnetic field generating source and the second magnetic field generating source; and a base body for positioning the first magnetic field generating source, the second magnetic field generating source and the magnet. The position detection unit has a magnetic detection element, which is arranged at a distance from the first magnetic field generating source and the second magnetic field generating source and the magnet in an area sandwiched by the first magnetic field generating source and the second magnetic field generating source and the magnet, and outputs the change of the magnetic field as an electrical signal. The length of the magnet in the first direction is a length corresponding to one wavelength determined based on the resolution of the position detection of the magnetic scale unit in the first direction, and the surface opposite to the first magnetic field generating source and the second magnetic field generating source is a curved surface that is 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 generating source is arranged at a position opposite to the position corresponding to 1 / 4 of the wavelength of the magnet, and the second magnetic field generating source is arranged at a position opposite to the position corresponding to 3 / 4 of the wavelength of the magnet.

[0008] Effects of the Invention

[0009] According to the magnetic encoder of the present invention, there is an effect that a smooth long-period sinusoidal wave signal can be obtained, and continuous and high-precision position information can be acquired over a wide range. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a perspective view showing the magnetic encoder involved in Embodiment 1.

[0011] Figure 2 It is a front view showing the magnetic encoder involved in Embodiment 1.

[0012] Figure 3 It is a front view of the magnetic encoder involved in the comparative example of Embodiment 1.

[0013] Figure 4 This is a diagram showing the flow of magnetic flux in a magnetic encoder according to a comparative example of the first embodiment.

[0014] Figure 5 This is a diagram showing a waveform of the magnetic field intensity applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the comparative example of the first embodiment.

[0015] Figure 6This is a diagram showing the flow of magnetic flux in the magnetic encoder according to the first embodiment.

[0016] Figure 7 This is a diagram showing a waveform of the magnetic field intensity applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the first embodiment.

[0017] Figure 8 This is a diagram showing a waveform of the magnetic field intensity 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.

[0018] Fig. 9 This is a diagram showing a waveform of the magnetic field intensity 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.

[0019] Fig.10 It is a front view of the magnetic encoder involved in Embodiment 2.

[0020] Fig.11 This is a diagram showing the direction of internal magnetization of a magnet group in the magnetic encoder according to the second embodiment.

[0021] Fig.12 This is a diagram showing a waveform of the magnetic field intensity applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the second embodiment.

[0022] Fig.13 It is a front view of the magnetic encoder involved in Embodiment 3.

[0023] Fig.14 This is a diagram showing the direction of internal magnetization of a magnet group in the magnetic encoder according to the third embodiment.

[0024] Fig.15 It is a perspective view showing the structure of a magnetic encoder according to a fourth embodiment.

[0025] Fig.16 It is a front view showing the structure of the magnetic encoder involved in the fourth embodiment. DETAILED DESCRIPTION

[0026] Hereinafter, the magnetic encoder according to the embodiment will be described in detail with reference to the drawings.

[0027] Implementation method 1.

[0028] Figure 1 It is a perspective view showing the magnetic encoder involved in Embodiment 1. Figure 21 is a front view showing a magnetic encoder according to Embodiment 1. The magnetic encoder 100 according to Embodiment 1 includes a magnetic scale unit 101 and a position detection unit 106 for detecting a magnetic field generated by the magnetic scale unit 101. The magnetic encoder 100 according to Embodiment 1 is a linear encoder. The magnetic scale unit 101 includes a magnet 103 as a first magnetic field generating source and a magnet 104 as a second magnetic field generating source, a magnet 102 arranged at intervals from the magnets 103 and 104 in the magnetization direction of the magnets 103 and 104, and a non-magnetic base 105 for fixing the magnets 103 and 104 and the magnets 102. In the magnetic encoder 100 according to Embodiment 1, the base 105 may be formed of a resin. The position detection unit 106 includes a plurality of magnetic detection elements 107 for detecting a magnetic field generated by the magnetic scale unit 101 and a substrate 108 for mounting the magnetic detection elements 107.

[0029] exist Figure 1 and Figure 2 , the magnetic encoder 100 is shown in a three-dimensional orthogonal coordinate system of xyz. The x direction corresponds to the moving 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 are relative, and the y direction is a direction perpendicular to the x direction and the z direction. In the present invention, in the case of a linear encoder, the x direction corresponds to the first direction.

[0030] exist Figure 2 In the figure, Tsm represents the minimum length of the magnet 102 in the z direction, Lsm represents the length of the magnet 102 in the x direction, Lm represents the length of each of the magnets 103 and 104 in the x direction, i.e., the magnet width, and G represents the distance from the surface of each of the magnets 103 and 104 to the sensing surface of the magnetic detection element 107. Here, it is assumed that the length dTsm in the z direction of the convex portion of the magnet 102 is in the relationship of dTsm>Lsm / 50. In addition, the length Lsm in the x direction of the magnet 102 is twice the magnet width Lm of each of the magnets 103 and 104. In addition, the length Lsm in the x direction of the magnet 102 as the first direction corresponds to one wavelength of the wavelength determined based on the resolution of the position detection of the magnetic scale unit 101 in the x direction.

[0031] The opposing surfaces of the magnet 102, the magnet 103 and the magnet 104 are curved surfaces convex toward the magnet 103 and the magnet 104. The intervals between the magnet 102, the magnet 103 and the magnet 104 are the largest at both ends and the center of the magnet 102 in the x direction. In addition, the intervals between the magnet 102, the magnet 103 and the magnet 104 are the smallest at positions 1 / 4 times the length Lsm of the magnet 102 in the x direction and 3 / 4 times the length Lsm from the ends of the magnet 102 in the x direction.

[0032] The magnetic scale unit 101 and the position detection unit 106 move relatively. In Embodiment 1, the magnetic scale unit 101 is a movable member that moves in the x direction. The position detection unit 106 is a fixed member that is separated from the magnetic scale unit 101 by a certain distance in the z direction and is fixed. The position detection unit 106 detects the position of the magnetic scale unit 101 based on the change in the magnetic field when the magnetic scale unit 101 passes by.

[0033] The substrate 108 is in the shape of a strip having a surface extending parallel to the xy plane, and the x direction is the length direction. Figure 2 As shown in FIG. 1 , the magnetic detection elements 107 are arranged on the substrate 108 at equal intervals in the x direction. The interval at which the magnetic detection elements 107 are arranged is set to be less than or equal to the wavelength of the sine wave formed by the magnetic scale unit 101 so as not to generate an area where position detection cannot be performed. The magnetic detection elements 107 are arranged in an area sandwiched by the magnets 103 and 104 and the magnet 102, separated from the magnets 103 and 104 and the magnet 102, and output changes in the magnetic field as electrical signals.

[0034] Figure 3 1 is a front view of a magnetic encoder according to a comparative example of Embodiment 1. In the magnetic encoder 110 according to the comparative example of Embodiment 1, the magnetic scale unit 111 does not have a magnet, and the magnets 113 and 114 are fixed to the base 115. The position detection unit 116 has a plurality of magnetic detection elements 117 for detecting the magnetic field generated by the magnetic scale unit 111 and a substrate 118 for mounting the magnetic detection elements 117. The substrate 118 is in the shape of a strip having a surface extending parallel to the xy plane, and the x direction is the length direction. The plurality of magnetic detection elements 117 of the position detection unit 116 are as shown in FIG. Figure 3 As shown, they are arranged on the substrate 118 at equal intervals in the x direction.

[0035] Figure 41 is a diagram showing the flow of magnetic flux in the magnetic encoder according to the comparative example of the first embodiment. In the magnetic encoder 110 according to the comparative example of the first embodiment, for example, most of the magnetic flux emitted from the magnet 113 does not return to the magnet 114 but is dispersed, and only a very small part of the magnetic flux returns to the magnet 114. Therefore, in the magnetic encoder 110 according to the comparative example, if the distance from the surface of the magnet 113 and the magnet 114 is large, the magnetic flux becomes significantly weaker, and if the distance G from the surface of each of the magnet 113 and the magnet 114 to the sensing surface of the magnetic detection element 117 becomes large, the amplitude of the magnetic field strength applied to the magnetic detection element 117 becomes small.

[0036] Figure 5 1 is a diagram showing a waveform of the magnetic field strength applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder involved in the comparative example of Embodiment 1. The magnetization direction of the magnet 113 is the +z direction, and the magnetization direction of the magnet 114 is the -z direction. Figure 5 In FIG. 1 , the vertical axis shows the magnetic flux density Bz, and the horizontal axis shows the position of the magnetic scale unit 111. In addition, [au] on the vertical axis and the horizontal axis is an arbitrary unit. Figure 5 In FIG. 1 , the solid line indicates the intensity of the magnetic field applied to the magnetic detection element 117 by the magnetic scale unit 111 of the magnetic encoder 110 according to the comparative example of the first embodiment, and the dotted line indicates the waveform of a sine wave as an ideal waveform. Figure 5 As shown, in the magnetic encoder 110 according to the comparative example, the rise and fall of the magnetic flux density become more rapid compared with the sine wave, and the interval of the magnet position where the amplitude is close to the maximum value becomes longer.

[0037] Figure 6 1 is a diagram showing the flow of magnetic flux in the magnetic encoder according to Embodiment 1. In the magnetic encoder 100 according to Embodiment 1, for example, the magnetic flux emitted from the magnet 103 flows into the magnet 102 and flows toward the magnet 104 side via the magnet 102. Therefore, the divergence of the magnetic flux is suppressed by forming a magnetic circuit by the magnets 103, 102, and 104, and the magnetic flux density becomes high in the area surrounded by the magnets 103, 104, and the change of the magnetic flux density is small even if it is far from the surface of the magnets 113 and 114.

[0038] Figure 7 1 is a diagram showing a waveform of the magnetic field strength applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to Embodiment 1. The magnetization direction of the magnet 103 is the +z direction, and the magnetization direction of the magnet 104 is the -z direction. Figure 7 In FIG. 1 , the vertical axis shows the magnetic flux density Bz, and the horizontal axis shows the position of the magnetic scale unit 101. In addition, [au] on the vertical axis and the horizontal axis is an arbitrary unit. Figure 7In FIG. 1 , the solid line indicates the intensity of the magnetic field applied to the magnetic detection element 107 by the magnetic scale unit 101 of the magnetic encoder 100 according to the comparative example of the first embodiment, and the dotted line indicates the waveform of a sine wave as an ideal waveform. Figure 7 As shown, in the magnetic encoder 100 according to the first embodiment, the waveform of the magnetic field intensity applied to the magnetic detection element 107 by the magnetic scale unit 101 is a waveform close to a sine wave.

[0039] Figure 8 This is a diagram showing a waveform of the magnetic field intensity 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 changes. Figure 8 In the figure, the dotted line represents the waveform of an ideal sine wave. Figure 8 In FIG. 1 , the solid line with a medium thickness among the three solid lines with different thicknesses represents the intensity of the magnetic field applied to the magnetic detection element 117 by the magnetic scale unit 111. Figure 8 In FIG. 1 , the thick solid line indicates the intensity of the magnetic field applied to the magnetic detection element 117 by the magnetic scale unit 111 when the distance G from the respective surfaces of the magnet 113 and the magnet 114 to the sensing surface of the magnetic detection element 117 increases. Figure 8 In FIG. 1 , the thin solid line indicates the intensity of the magnetic field applied to the magnetic detection element 117 by the magnetic scale unit 111 when the distance G from the respective surfaces of the magnets 113 and 114 to the sensing surface of the magnetic detection element 117 is reduced. In the magnetic encoder 110 according to the comparative example of Embodiment 1, when the distance between the movable part and the fixed part changes and the distance G from the respective surfaces of the magnets 113 and 114 to the sensing surface of the magnetic detection element 117 changes, even if the distance G increases or decreases, the difference between the intensity of the magnetic field applied to the magnetic detection element 117 and the sine wave as an ideal waveform is large. In addition, the waveform of the magnetic field intensity applied to the magnetic detection element 117 is flattened compared to the sine wave, and the interval of the magnet position where the amplitude is close to the maximum value becomes longer. Therefore, it is difficult to accurately correspond the intensity of the magnetic field applied to the magnetic detection element 117 and the magnet position, and the position detection accuracy is reduced.

[0040] Fig. 9 This is a diagram showing a waveform of the magnetic field intensity 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 changes. Fig. 9 In the figure, the dotted line represents the waveform of an ideal sine wave. Fig. 9 In FIG. 1 , the solid line with a medium thickness among the three solid lines with different thicknesses represents the intensity of the magnetic field applied to the magnetic detection element 107 by the magnetic scale unit 101. Fig. 9 In FIG. 1 , the thick solid line indicates the intensity of the magnetic field applied to the magnetic detection element 107 by the magnetic scale unit 101 when the distance G from the surface of each of the magnets 103 and 104 to the sensing surface of the magnetic detection element 107 increases. Fig. 9 In the figure, the thin solid line indicates the intensity of the magnetic field applied to the magnetic detection element 107 by the magnetic scale unit 101 when the distance G from the respective surfaces of the magnets 103 and 104 to the sensing surface of the magnetic detection element 107 becomes smaller. In the magnetic encoder 100 according to the first embodiment, when the distance between the movable part and the fixed part changes and the distance G from the respective surfaces of the magnets 103 and 104 to the sensing surface of the magnetic detection element 107 changes, even if the distance G increases or decreases, the difference between the intensity of the magnetic field applied to the magnetic detection element 107 and the sine wave as an ideal waveform is small. In addition, the waveform of the magnetic field intensity applied to the magnetic detection element 107 is in the shape of a substantially sine wave. Therefore, the intensity of the magnetic field applied to the magnetic detection element 107 can be accurately matched to the magnet position, and the position detection accuracy can be improved.

[0041] In order to detect the absolute position of the magnetic scale unit 101, it is necessary to generate a signal with a long period of one cycle relative to the stroke of the magnetic scale unit 101. The magnetic encoder 100 involved in the first embodiment has a curved surface of the magnet 102 convex to the magnets 103 and 104, and the magnetic scale unit 101 can generate a smooth sine wave signal with a long period of one cycle through the magnets 103 and 104. In addition, the magnets 103 and 104 form a magnetic circuit with the magnet 102, so the absolute position of the magnetic scale unit 101 can be detected continuously and with high accuracy over a wide range.

[0042] Furthermore, although the structure in which the magnets 103 and 104 are arranged with a gap between them and the magnet 102 in the y direction has been described here, the magnets 103 and 104 may be arranged with a gap between them and the magnet 102 in the z direction.

[0043] Implementation method 2.

[0044] Fig.101 is a front view of a magnetic encoder according to Embodiment 2. In the magnetic encoder 200 according to Embodiment 2, there is a magnet group 123 as a first magnetic field generating source and a magnet group 124 as a second magnetic field generating source. The magnet group 123 and the magnet group 124 are each formed by a plurality of magnets 10. The magnet group 123 and the magnet group 124 are each fixed to the magnet 202 via a base 205. The opposing surfaces of the magnet 202 and the magnet group 123 and the magnet group 124 are curved surfaces convex toward the magnet group 123 and the magnet group 124. The interval between the magnet 202 and the magnet group 123 and the magnet group 124 is the largest at both ends and the center of the magnet 202 in the x direction. The intervals between magnet 202 and magnet groups 123 and 124 are smallest at positions 1 / 4 times and 3 / 4 times the length Lsm of magnet 202 in the x direction from the ends of magnet 202 in the x direction.

[0045] Fig.11 1 is a diagram showing the direction of internal magnetization of a magnet group in a magnetic encoder according to Embodiment 2. The magnetic encoder 200 according to Embodiment 2 uses a magnet width modulation method that varies the length of the magnet 10 in the x direction as a first direction, that is, the magnet width Lm. Fig.11 The arrows in the magnet group 123 and the arrows in the magnet group 124 shown indicate the directions of the internal magnetization after magnetization. The tip of each arrow indicates the N pole, and the base end indicates the S pole. Therefore, all the magnets 10 constituting the magnet group 123 have an N pole on the side opposite to the position detection unit 206. All the magnets 10 constituting the magnet group 124 have an S pole on the side opposite to the position detection unit 206. Hereinafter, the direction of the internal magnetization of each magnet 10 will be referred to as the magnetization direction. As described above, all the magnets 10 constituting the magnet group 123 are magnetized in the same magnetization direction, and all the magnets 10 constituting the magnet group 124 are magnetized in the magnetization direction opposite to the magnetization direction of the magnets 10 constituting the magnet group 123.

[0046] The number of magnets 10 constituting the magnet group 123 and the number of magnets 10 constituting the magnet group 124 are the same number, which is greater than or equal to 3. In each of the magnet group 123 and the magnet group 124, the intervals between the magnets 10 are constant. The magnet width Lm increases and decreases in the x direction according to a sin function which is a sine wave function. That is, in each of the magnet group 123 and the magnet group 124, the magnet width Lm becomes larger from the end toward the center in the x direction. In other words, in each of the magnet group 123 and the magnet group 124, after the magnet width Lm increases step by step from one end toward the center in the x direction, it decreases step by step from the center toward the other end in the x direction. On the other hand, the interval Ld between the magnets 10 is constant.

[0047] like Fig.10 As shown, the number of magnets 10 constituting the magnet group 123 is 7. The number of magnets 10 constituting the magnet group 124 is also 7. The position of the magnet 10 disposed at the position farthest from the magnet group 124 among the magnets 10 constituting the magnet group 123, after being separated by a distance a in the -x direction from the end portion thereof, corresponds to 0 degrees of the sin function. In addition, the position of the magnet 10 disposed at the position farthest from the magnet group 123 among the magnets 10 constituting the magnet group 124, after being separated by a distance a in the +x direction from the end portion thereof, corresponds to 360 degrees of the sin function. In addition, the position of the magnet 10 among the magnets 10 constituting the magnet group 123, which is set at the position closest to the magnet group 124, separated by a distance a in the +x direction from the end thereof in the +x direction, and the position of the magnet 10 among the magnets 10 constituting the magnet group 124, which is set at the position closest to the magnet group 123, which is separated by a distance a in the -x direction from the end thereof in the -x direction, correspond to 180 degrees of the sin function.

[0048] The distance a is set so that the middle position between the end of the magnet 10 in the -x direction arranged at the position farthest from the magnet group 124 among the magnets 10 constituting the magnet group 123 and the end of the magnet 10 in the +x direction arranged at the position closest to the magnet group 124 corresponds to 90 degrees of the sin function, and the middle position between the end of the magnet 10 in the +x direction arranged at the position farthest from the magnet group 123 among the magnets 10 constituting the magnet group 124 and the end of the magnet 10 in the -x direction arranged at the position closest to the magnet group 123 corresponds to 270 degrees of the sin function.

[0049] The position detection unit 206 is similar to the position detection unit 106 of the magnetic encoder 100 according to the first embodiment, and includes 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.

[0050] The magnetic scale unit 201 and the position detection unit 206 move relatively. In Embodiment 2, the magnetic scale unit 201 is a movable member that moves in the x direction. The position detection unit 206 is a fixed member that is separated from the magnetic scale unit 201 by a certain distance in the z direction and is fixed. The position detection unit 206 detects the position of the magnetic scale unit 201 based on the change in the magnetic field when the magnetic scale unit 201 passes by.

[0051] The substrate 208 is in the shape of a strip having a surface extending parallel to the xy plane, and the x direction is the length direction. Fig.10As shown, the magnetic detection elements 207 are arranged at equal intervals in the x direction on the substrate 208. The magnetic detection elements 207 are arranged at a pitch smaller than or equal to the wavelength of the sine wave formed by the magnetic scale unit 201 so as to avoid a region where position detection is not possible.

[0052] Fig.12 1 is a diagram showing a waveform of the magnetic field strength applied to the magnetic detection element by the magnetic scale unit of the magnetic encoder according to the second embodiment. Fig.12 In FIG. 1 , the vertical axis shows the magnetic flux density Bz, and the horizontal axis shows the position of the magnetic scale unit 201. In addition, [au] on the vertical axis and the horizontal axis is an arbitrary unit. Fig.12 In FIG. 1 , the solid line indicates the intensity 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 dotted line indicates the waveform of an ideal sine wave. Fig.12 As shown, in the magnetic encoder 200 according to the second embodiment, the waveform of the magnetic field strength applied to the magnetic detection element 207 by the magnetic scale unit 201 is a waveform close to a sine wave. Figure 7 Compared with the waveform of the magnetic field strength applied to the magnetic detection element 107 by the magnetic scale unit 101 of the magnetic encoder 100 involved in the first embodiment shown, the waveform of the magnetic field strength applied to the magnetic detection element 207 by the magnetic scale unit 201 of the magnetic encoder 200 involved in the second embodiment becomes a waveform closer to a sine wave.

[0053] Regarding the magnetic encoder 200 involved in embodiment 2, the waveform of the magnetic field strength 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 strength applied to the magnetic detection element 107 by the magnetic scale unit 101 of the magnetic encoder 100 involved in embodiment 1. Therefore, compared with the magnetic encoder 100 involved in embodiment 1, the position detection accuracy can be further improved.

[0054] In the second embodiment, the change of the magnet width causes the change of the sine wave magnetic field, but the magnet width may be set to be the same, and the magnetic force of each magnet 10 may be changed to cause the change of the sine wave magnetic field. As a method of changing the magnetic force, there are the following methods, that is, changing the thickness of the magnet 10 in stages, changing the distance from the magnetic detection element 207 in stages, changing the magnetization rate of the magnet 10 in stages, or changing the magnetic material of the magnet 10 in stages.

[0055] Implementation method 3.

[0056] Fig.13: is a front view of a magnetic encoder according to Embodiment 3. In the magnetic encoder 300 according to Embodiment 3, there is a magnet group 133 as a first magnetic field generating source and a magnet group 134 as a second magnetic field generating source. The magnet group 133 and the magnet group 134 are each formed by a plurality of magnets 10. The magnet group 133 and the magnet group 134 are each fixed to the magnet 302 via a base 305. The opposing surfaces of the magnet 302 and the magnet group 133 and the magnet group 134 are curved surfaces convex toward the magnet group 133 and the magnet group 134. The interval between the magnet 302 and the magnet group 133 and the magnet group 134 is the largest at both ends and the center of the magnet 302 in the x direction. The intervals between magnet 302 and magnet groups 133 and 134 are smallest at positions 1 / 4 times and 3 / 4 times the length Lsm of magnet 302 in the x direction from the ends of magnet 302 in the x direction.

[0057] Fig.14 It is a figure which shows the internal magnetization direction of the magnet group in the magnetic encoder which concerns on Embodiment 3. In the magnetic encoder 300 which concerns on Embodiment 3, the magnet interval modulation method which changes the interval between the magnets 10 is used. Fig.14 The arrows in the magnet group 133 and the arrows in the magnet group 134 shown in the figure indicate the direction of the internal magnetization after magnetization. The tip of each arrow indicates the N pole, and the base end indicates the S pole. Therefore, all the magnets 10 constituting the magnet group 133 have an N pole on the side opposite to the position detection unit 306. All the magnets 10 constituting the magnet group 134 have an S pole on the side opposite to the position detection unit 306. Hereinafter, the direction of the internal magnetization of each magnet 10 will be referred to as the magnetization direction. As described above, all the magnets 10 constituting the magnet group 133 are magnetized in the same magnetization direction, and all the magnets 10 constituting the magnet group 134 are magnetized in the magnetization direction opposite to the magnetization direction of the magnets 10 constituting the magnet group 133.

[0058] The position detection unit 306 includes 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 mounted.

[0059] The number of magnets 10 constituting the magnet group 133 and the number of magnets 10 constituting the magnet group 134 are the same number, which is greater than or equal to 3. In each of the magnet group 133 and the magnet group 134, the magnet width Lm is constant. The intervals between the magnets 10 increase and decrease according to the sin function, which is a sine wave function. That is, in each of the magnet group 123 and the magnet group 124, the interval Ld between the magnets 10 in the x direction becomes smaller as it moves from the end toward the center. In other words, in each of the magnet group 133 and the magnet group 134, the interval Ld between the magnets 10 decreases step by step from one end in the x direction toward the center, and then increases step by step from the center toward the other end in the x direction.

[0060] like Fig.13 As shown, the number of magnets 10 constituting the magnet group 133 is 9. The number of magnets 10 constituting the magnet group 134 is also 9. The position of the magnet 10 constituting the magnet group 133, which is disposed at a position farthest from the magnet group 134, separated by a distance a from the end in the -x direction in the -x direction corresponds to 0 degrees of the sin function. In addition, the position of the magnet 10 constituting the magnet group 134, which is disposed at a position farthest from the magnet group 133, separated by a distance a from the end in the +x direction in the +x direction corresponds to 360 degrees of the sin function. In addition, the position of the magnet 10 disposed at the position closest to the magnet group 134 among the magnets 10 constituting the magnet group 133, which is separated by a distance a in the +x direction from the end thereof, and the position of the magnet 10 disposed at the position closest to the magnet group 133 among the magnets 10 constituting the magnet group 134, which is separated by a distance a in the -x direction from the end thereof, correspond to 180 degrees of the sin function.

[0061] The distance a is set so that the middle position between the end of the magnet 10 in the -x direction arranged at the position farthest from the magnet group 134 and the end of the magnet 10 in the +x direction arranged at the position closest to the magnet group 134 among the magnets 10 constituting the magnet group 133 corresponds to 90 degrees of the sin function, and the middle position between the end of the magnet 10 in the +x direction arranged at the position farthest from the magnet group 133 and the end of the magnet 10 in the -x direction arranged at the position closest to the magnet group 133 among the magnets 10 constituting the magnet group 134 corresponds to 270 degrees of the sin function.

[0062] 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 becomes a waveform closer to a sine wave when compared with 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 with the magnetic encoder 100 according to the first embodiment.

[0063] Implementation method 4.

[0064] Fig.15 It is a perspective view showing the structure of a magnetic encoder according to a fourth embodiment. Fig.16 : is a front view showing a magnetic encoder involved in Embodiment 4. The magnetic encoder 400 involved in Embodiment 4 is a rotary encoder. The magnetic encoder 400 involved in Embodiment 4 has an annular magnetic scale unit 401 and a position detection unit 406 that detects a magnetic field generated from the magnetic scale unit 401. In Embodiment 4, the magnetic scale unit 401 is a movable part, and the position detection unit 406 is a fixed part.

[0065] The magnetic scale unit 401 has a magnet 403 as a first magnetic field generating source and a magnet 404 as a second magnetic field generating source, a magnet 402 arranged at intervals from the magnets 403 and 404 in the magnetization direction of the magnets 403 and 404, and a non-magnetic base 405 for fixing the magnets 402, 403 and 404. The opposing surfaces of the magnet 402 and the magnets 403 and 404 are curved surfaces convex to the magnets 403 and 404. The base 405 is cylindrical. The magnetic scale unit 401 is set on a rotating shaft not shown in the figure and rotates. In the present invention, in the case of a rotary encoder, the rotation direction of the magnetic scale unit 401, i.e., the circumferential direction, corresponds to the first direction.

[0066] The position detection unit 406 has an annular substrate 408 and a magnetic detection element 407 provided 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 separated from the magnetic scale unit 401 by a certain distance in the z direction and fixed on the substrate 408. The position detection unit 406 detects the position of the magnetic scale unit 401 based on the change in the magnetic field when the magnetic scale unit 401 rotates. Fig.15 In the figure, the substrate 408 is omitted.

[0067] Furthermore, the magnet width modulation method described in the second embodiment or the magnet interval modulation method described in the third embodiment may be applied to the magnetic encoder 400 of the fourth embodiment.

[0068] In the magnetic encoder 400 according to the fourth embodiment, since the magnets 403 and 404 form a magnetic circuit with the magnet 402 , the absolute position of the magnetic scale unit 401 can be detected with high accuracy.

[0069] The configurations shown in the above embodiments are merely examples of the contents, and may be combined with other known technologies. Part of the configurations may be omitted or changed without departing from the spirit and scope of the invention.

[0070] Description of the label

[0071] 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 magnets, 105, 115, 205, 305, 405 substrates, 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, wherein a magnetic scale unit and a position detection unit move relative to each other in a first direction, The magnetic encoder is characterized by: The magnetic scale unit has: A first magnetic field generating source and a second magnetic field generating source are arranged in the first direction and have magnetization directions opposite to each other; a magnet disposed at a distance from the first magnetic field generating source and the second magnetic field generating source along the magnetization directions of the first magnetic field generating source and the second magnetic field generating source; as well as a substrate for positioning the first magnetic field generating source, the second magnetic field generating source and the magnet, The position detection unit includes a magnetic detection element, which is arranged in an area sandwiched by the first magnetic field generating source, the second magnetic field generating source and the magnet, and is spaced apart from the first magnetic field generating source, the second magnetic field generating source and the magnet, and outputs a change in the magnetic field as an electrical signal. The length of the magnet in the first direction is a length corresponding to one wavelength determined based on the resolution of position detection of the magnetic scale unit in the first direction, and the surface facing the first magnetic field generating source and the second magnetic field generating source is a curved surface that is 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 generating source is arranged at a position opposite to a position corresponding to 1 / 4 of the wavelength of the magnet, and the second magnetic field generating source is arranged at a position opposite to a position corresponding to 3 / 4 of the wavelength of the magnet.

2. The magnetic encoder according to claim 1, characterized in that: The first magnetic field generating source and the second magnetic field generating source are each a magnet group formed by a plurality of magnets having magnetization directions in the same direction. The magnets of the first magnetic field generating source are arranged at intervals in the first direction. All the magnets of the first magnetic field generating source are magnetized in the same magnetization direction. The magnets of the second magnetic field generating source are arranged at intervals in the first direction. All the magnets of the second magnetic field generating source are magnetized in a magnetization direction opposite to that of the magnets of the first magnetic field generating source. The magnet widths of the magnet of the first magnetic field generating source and the magnet of the second magnetic field generating source change stepwise along the first direction.

3. The magnetic encoder according to claim 1, characterized in that: The first magnetic field generating source and the second magnetic field generating source are each a magnet group formed by a plurality of magnets having magnetization directions in the same direction. The magnets of the first magnetic field generating source are arranged at intervals in the first direction. All the magnets of the first magnetic field generating source are magnetized in the same magnetization direction. The magnets of the second magnetic field generating source are arranged at intervals in the first direction. All the magnets of the second magnetic field generating source are magnetized in a magnetization direction opposite to that of the magnets of the first magnetic field generating source. The interval between the magnets of the first magnetic field generating source and the interval between the magnets of the second magnetic field generating source change stepwise along the first direction.

4. The magnetic encoder according to any one of claims 1 to 3, characterized in that: The position detection unit is arranged on the fixed part, and the magnetic scale unit is arranged on the movable part. A plurality of the magnetic detection elements are provided along the first direction.

5. The magnetic encoder according to any one of claims 1 to 4, characterized in that: The magnetic encoder is a linear encoder.

6. The magnetic encoder according to any one of claims 1 to 4, characterized in that: The magnetic encoder is a rotary encoder.

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