Rotation angle detection device

Abstract

Rotation angle detection device comprising: a rotor (1) having a projection and recess portion (12) formed by a magnetic body on an outer peripheral surface of the rotor (1); a stator (2) provided to oppose the projection and recess portion (12) and having a bias magnetic field generating portion (21) and a plurality of magnetic flux density detecting portions (22); and a magnetic body element (24) comprising a magnetic body radial outer side portion (241) provided on an outer side of the bias magnetic field generating portion (21) in a radial direction of the rotor (1), the magnetic body radial outer side portion (241) being arranged to cover the bias magnetic field generating portion (21) in the radial direction, and a pair of magnetic body circumferential direction outer side portions (242) embedding the bias magnetic field generating portion (21) in a circumferential direction of the rotor (1), wherein the projection and recess portion (12) is configured to change by an amount of X cycles over a mechanical angle of 360 degrees in the circumferential direction, where X is an integer greater than 1, wherein the plurality of magnetic flux density detecting portions (22) are opposed to the projection and recess portion (12) with a gap and are provided at an equal distance along the circumferential direction over one cycle of the projection and recess portion (12), wherein the bias magnetic field generating section (21) is provided on a radially outer side of the plurality of magnetic flux density detecting sections (22), covers the plurality of magnetic flux density detecting sections (22) in the radial direction and is formed to extend in the circumferential direction, wherein the magnetic body circumferential direction outer side portion (242) has an inner end portion in the radial direction provided on an inner side in the radial direction with respect to an inner end portion of the bias magnetic field generating portion (21) in the radial direction, and wherein a + b> 180 / X and a + b + c < 360 / X are satisfied, where "a" represents half of an angle between both end portions of the bias magnetic field generating portion (21) in the circumferential direction and a center of the rotor (1), "b" represents an angle between both end portions of a gap between the bias magnetic field generating portion (21) and the magnetic body circumferential direction outer side portion (242) in the circumferential direction and the center of the rotor (1), and "c" represents an angle between the two end portions of the magnetic body circumferential direction outer side portion (242) with respect to the center of the rotor (1).

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to a rotation angle detecting device using a change in magnetic field strength.2. Description of Related ArtHeretofore, there has been known a rotation angle detecting device including a rotor having a protrusion and recess portion formed by a magnetic body on an outer circumferential surface and a stator provided to oppose the protrusion and recess portion. The stator includes a plurality of magnetic flux density detection portions arranged in a circumferential direction of the rotor. In addition, the stator has a magnet. The magnet is provided on an outer side of the magnetic flux density detection portion in a radial direction, covers the respective magnetic flux density detection portion in the radial direction, and is formed to extend in the circumferential direction. Moreover, the stator includes a pair of magnet body members sandwiching the magnet in the circumferential direction (see, for example, Japanese Utility Model Application Laid-Open No. JP H04-94 581 U).However, when a dimension of the magnetic body elements in the circumferential direction of the rotor is small, leakage magnetic fluxes that do not flow through the magnetic body elements become larger. Consequently, variation among the amplitudes of the magnetic flux densities detected by the plurality of magnetic flux density detection portions increases. As a result, detection accuracy of the rotation angle detection device is deteriorated. When the size of the magnetic body members in the circumferential direction of the rotor is increased, there arises a problem in that the weight of the rotation angle detecting device increases.DE 10 2013 111 347 A1 describes a magnetic sensor system which is intended to provide an improved sensitivity and / or a larger working range. DE 10 2011 111 094 A1, DE 10 2016 009 005 A1, U.S. Pat. No. 2015 / 0 345 990 A1 and JP H04-94 581 U are further prior art. DE 112016 007 397 T5 and WO 2018 / 078 855 A1, which corresponds to DE 11 2016 007 401 B4, are prior art, which is to be used for the judgment of novelty under § 3(2) PatG.SUMMARY OF THE INVENTIONThe present invention has been made to solve the above-mentioned problem, and therefore, an object is to provide a rotation angle detection device capable of suppressing the weight increase and improving the detection accuracy.The present invention is defined by the appended claims.According to the rotation angle detection device of the present invention, the increase in the circumferential direction dimension of the magnetic body circumferential direction outer side portions can be suppressed, and the variation between the amplitudes of the magnetic flux densities detected by the plurality of magnetic flux density detection portions, respectively, can be reduced. As a result, the increase in weight of the rotation angle detection device can be suppressed, and the detection accuracy of the rotation angle detection device can be improved.BRIEF DESCRIPTION OF THE FIGURESFIG. 1 is a plan sectional view for illustrating a rotation angle detection device according to a first embodiment of the present invention. FIG. 2 is an enlarged view illustrating the portion A of the rotation angle detection device of FIG. 1. FIG. 3 is a block diagram for illustrating a stator of FIG. 2. FIG. 4 is a plan sectional view for illustrating a relevant portion of a rotation angle detection device according to a second embodiment of the present invention. FIG. 5 is a plan sectional view for illustrating a relevant portion of a rotation angle detection device according to a third embodiment of the present invention. FIG. 6 is a planar sectional view for illustrating a relevant portion of the rotation angle detection device when α>β and γ>0 are given. FIG. 7 is a graph for showing magnetic flux densities detected by three magnetic flux density detection sections of FIG. 6. FIG. 8 is a table for showing ratios of amplitudes of the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 6. FIG. 9 is a planar sectional view for illustrating the relevant portion of the rotation angle detection device when α<β and γ<0 are given. FIG. 10 is a graph for showing the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 9. FIG. 11 is a table for showing the relationships of the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 9. FIG. 12 is a planar sectional view for illustrating the relevant portion of the rotation angle detection device when α=β is given. FIG. 13 is a graph for showing the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 12. FIG. 14 is a table for showing the relationships of the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 12. FIG. 15 is a plan sectional view for illustrating a relevant portion of a rotation angle detection device according to a fourth embodiment of the present invention. FIG. 16 is an enlarged view for illustrating the portion B of FIG. 15. FIG. 17 is a plan sectional view for illustrating a relevant portion of a rotation angle detection device according to a fifth embodiment of the present invention. FIG. 18 is an enlarged view for illustrating the portion C of FIG. 17. FIG. 19 is an enlarged view for illustrating the portion D of FIG. 17. FIG. 20 is a plan sectional view for a relevant portion of a rotation angle detection device according to a sixth embodiment of the present invention.DESCRIPTION OF THE EMBODIMENTSFirst EmbodimentFIG. 1 is a plan sectional view for illustrating a rotation angle detection device according to a first embodiment of the present invention. FIG. 2 is an enlarged view illustrating the portion A of the rotation angle detection device of FIG. 1 ; the rotation angle detection device according to the first embodiment includes a rotor 1 and a stator 2. The stator 2 is provided on an outer side of the rotor 1 in a radial direction of the rotor 1, and extends in a circumferential direction of the rotor 1.The rotor 1 includes a rotating shaft 11 having a cylindrical shape and a protruding and recessed portion 12 provided on an outer side of the rotating shaft 11 in the radial direction. The protrusion and recess portion 12 is disposed on an outer circumferential surface of the rotor portion 1. The protrusion and recess portion 12 is formed of a magnetic body. The protrusion and recess portion 12 is formed to change by an amount of X cycles over a mechanical angle of 360 degrees in the circumferential direction, where X is an integer equal to or greater than 1. In FIG. 1, the protrusion and recess portion 12 is illustrated for a case of X=12.The stator 2 is provided to oppose the protrusion and recess portion 12 in the radial direction. The stator 2 includes a bias magnetic field generating portion 21 and a plurality of magnetic flux density detecting portions 22. The bias magnetic field generating portion 21 is provided at an outer side of the magnetic flux density detecting portion 22 in the radial direction. Moreover, the bias magnetic field generating portion 21 overlaps the magnetic flux density detecting portions 22 in the radial direction and is formed to extend in the circumferential direction. The plurality of magnetic flux density detection portions 22 are arranged to face the protrusion and recess portion 12 with a gap. Moreover, the plurality of magnetic flux density detection portions 22 are provided at an equal interval along the circumferential direction over one cycle of the protrusion and recess portion 12. FIG. 2 is a diagram of the stator 2 in a case where the number of the magnetic flux density detection portions 22 is three.FIG. 3 is a block diagram for illustrating the stator 2 of FIG. 2, and the stator 2 further includes a rotation angle calculation processing section 23 configured to calculate a rotation angle of the rotor 1 by using a plurality of detection signals detected by the plurality of magnetic flux density detection sections 22.As illustrated in FIGS. 1 and 2, the stator 2 further includes a magnetic body member 24. The magnetic body member 24 is formed of a magnetic body. The magnetic body member 24 includes a magnetic body radially outer side portion 241 provided on an outer side of the bias magnetic field generation portion 21 in the radial direction. The magnetic body radially outer side portion 241 is disposed so as to cover the bias magnetic field generating portion 21 in the radial direction. The magnetic body radially outer side portion 241 is disposed to extend in the circumferential direction. The magnetic body radially outer side portion 241 of the magnetic body is formed so that a dimension in the radial direction is constant over an entire circumferential range. Both circumferential end portions of the magnetic body radially outer side portion 241 protrude to an outer side in the circumferential direction via both circumferential end portions of the bias magnetic field generating portion 21.Moreover, the magnetic body member 24 includes a pair of magnetic body circumferential direction outer side portions 242 sandwiching the bias magnetic field generating portion 21 in the circumferential direction. An inner end portion of the magnetic body circumferential direction outer side portion 242 is provided in the radial direction on an inner side in the radial direction with respect to an inner end portion of the bias magnetic field generating portion 21 in the radial direction. The pair of the magnetic body circumferential direction outer side portions 242 are connected to both end portions of the magnetic body radially outer side portion 241 in the circumferential direction.An outer surface of the magnetic body radially outer side portion 241 in the radial direction and outer surfaces of the magnetic body circumferential direction outer side portion 242 in the radial direction are on the same circle having a center at the center O of the rotor 1 as viewed in the axial direction of the rotor 1.A half angle between both end portions of the bias magnetic field generating portion 21 in the circumferential direction and the center O of the rotor 1 is represented by "a". An angle between both end portions of a gap between the bias magnetic field generating portion 21 and the magnetic body circumferential direction outer side portion 242 in the circumferential direction and the center O of the rotor 1 is represented by "b". An angle between both end portions of the magnetic body circumferential direction outer side portion 242 in the circumferential direction and the center O of the rotor 1 is represented by "c". In this case, the stator 2 is formed to satisfy a+b>180 / X and a+b+c<360 / X.In order to improve detection accuracy of the rotation angle detection device, the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection portions 22 must be equalized to each other. In order to satisfy the above-mentioned condition, it is necessary to arrange the magnetic body circumferential direction outer side portion at a position on an outer side at 180 / X degrees in the circumferential direction from the magnetic flux density detection portion 22 arranged on a central side in the circumferential direction to a position on an outer side at least at 360 / X degrees in a rotation angle detection device according to the related art.In the rotation angle detection device according to the first embodiment, a position of a magnetic body protruding portion outer end 243, which is an outer end portion of the magnetic body circumferential direction outer side portion 242 in the circumferential direction, is disposed on a circumferential direction inner side with respect to the position on an outer side at 360 / X degrees in the circumferential direction from the magnetic flux density detection portion 22 on the central side in the circumferential direction. Moreover, in the rotation angle detection device according to the first embodiment, a position of the magnetic body protruding portion inner end 244, which is an inner end portion of the magnetic body circumferential direction outer side portion 242 in the circumferential direction, is disposed on an outer circumferential side with respect to the position on an outer side at 180 / X degrees in the circumferential direction from the magnetic flux density detection portion 22 on the central side in the circumferential direction. Thus, an increase in the circumferential direction dimension of the magnetic body circumferential direction outer circumferential portion 242 is suppressed. As a result, an increase in the weight of the rotation angle detection device is suppressed.As the position of the magnetic body protruding portion outer end 243 approaches a center portion of the magnetic body member 24 in the circumferential direction, the amplitude of the magnetic flux density detected by the magnetic flux density detection portion 22 disposed on the center side in the circumferential direction among the three magnetic flux density detection portions 22 decreases. On the other hand, since the position of the magnetic body protruding portion inner end 244 separates from the central portion of the magnetic body member 24 in the circumferential direction, the amplitude of the magnetic flux density detected by the magnetic flux density detection portion 22 disposed on the magnetic body circumferential direction outer side portion 242 side from the three magnetic flux density detection portions 22 decreases. Consequently, variation among the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection portions 22, respectively, is reduced. As a result, the detection accuracy of the rotation angle detection device is improved.As described above, with the rotation angle detection device according to the first embodiment of the present invention, a+b>180 / X and a+b+c<360 / X are satisfied. Consequently, the increase in the circumferential direction dimension of the magnetic body circumferential direction outer side portions 242 can be suppressed, and the variation between the amplitudes of the magnetic flux density detected by the plurality of magnetic flux density detection portions 22, respectively, can be reduced. As a result, the increase in weight of the rotation angle detection device can be suppressed, and the detection accuracy of the rotation angle detection device can be improved.Second EmbodimentFIG. 4 is a plan sectional view for illustrating a relevant portion of a rotation angle detection device according to a second embodiment of the present invention. In the rotation angle detection device of the second embodiment, α=a+b-180 / X and β=360 / X-(a+b+c) are given. In this case, the stator 2 is formed so that α=β is satisfied. The other configurations are the same as in the first embodiment.In this embodiment, α represents an angle between a magnetic body protrusion portion inner end 244 aof an ideal magnetic body element in a case of non-downsizing and the magnetic body protrusion portion inner end 244 in the second embodiment and the center O of the rotor 1. β represents an angle between a magnetic body protrusion portion outer end 243 aof the ideal magnetic body element in the case of non-downsizing and the magnetic body protrusion portion outer end 243 in the second embodiment and the center O of the rotor 1, which is disposed on the central side in the circumferential direction. Moreover, in the case without downsizing, the ideal magnetic body member is a magnetic body member in which the position of the magnetic body protrusion portion outer end 243 ais located on an outer side at 360 / X degrees in the circumferential direction from the magnetic flux density detection portion 22 located on the central side in the circumferential direction.A detailed description will now be given of the ideal magnetic body element in the case without downsizing. The magnetic flux generated in the bias magnetic field generation portion 21 passes through the magnetic body radially outer side portion 241, the magnetic body circumferential direction outer side portion 242, a gap between the magnetic body circumferential direction outer side portion 242 and the rotor 1, the rotor 1, and a gap between the bias magnetic field generation portion 21 and the rotor 1, in the stated order. A magnetic resistance change amount of the magnetic body member 24 caused by the rotation of the rotor 1 is significantly smaller compared to a magnetic resistance change amount of the gap between the magnetic body circumferential direction outer side portion 242 and the rotor 1 and a magnetic resistance change amount of the gap between the bias magnetic field generating portion 21 and the rotor 1. Thus, the magnetic resistance change amount of the magnetic flux density detection portion 22 is determined by the change amount of the gap between the magnetic body circumferential direction outer side portion 242 and the rotor 1 and the change amount of the gap between the bias magnetic field generation portion 21 and the rotor 1.In the ideal magnetic body element in the case without downsizing, the position of the magnetic body protrusion portion inner end 244 ais a position forming an angle of 180 / X degrees, and the position of the magnetic body protrusion portion outer end 243 ais a position forming an angle of 360 / X degrees. Consequently, the protrusion portion of the rotor 1 always faces the magnet body circumferential direction outer side portion 242 regardless of the rotation angle of the rotor 1. As a result, the magnetic resistance of the gap between the magnetic body circumferential direction outer side portion 242 and the rotor 1 is constant regardless of the rotation angle of the rotor 1.The magnetic flux density detection portion 22 disposed on the central side in the circumferential direction of the three magnetic flux density detection portions 22 is referred to as a central side magnetic flux density detection portion. Each of the magnetic flux density detection portions 22 disposed on a side of a magnetic body circumferential direction outer side portion 242 among the three magnetic flux density detection portions 22 is referred to as a circumferential direction outer side magnetic flux density detection portion. The maximum value of a gap length between a portion of the bias magnetic field generating portion 21 in which the central side magnetic flux density detecting portion 22 is disposed and the rotor 1 at one rotation of the rotor 1 is equal to the maximum value of a gap length between a portion of the bias magnetic field generating portion 21 in which the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitt is disposed and the rotor 1 at the one rotation of the rotor 1. The minimum value of the gap length between the portion of the bias magnetic field generating portion 21 in which the central side magnetic flux density detecting portion is disposed and the rotor 1 at the one rotation of the rotor 1 is equal to the minimum value of the gap length between the portion of the bias magnetic field generating portion 21 in which the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitt is disposed and the rotor 1 at the one rotation of the rotor 1. Accordingly, the resistance change amount of the central-side magnetic flux density detection portion is equal to the magnetic resistance change amount of the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitts.The change amounts of the gap lengths between the portions of the bias magnetic field generating portions 21 in which the three magnetic flux density detecting portions 22 are arranged and the rotor 1 are equal to each other. Thus, the magnetic resistance change amounts of the three magnetic flux density detection portions 22 are equal to each other. The amplitude of the magnetic flux density detected by the magnetic flux density detection section 22 is calculated as a product of a magnetomotive force of the bias magnetic field generation section 21 and the magnetic resistance change amount of the magnetic flux density detection section. Thus, the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection portions 22 are equal to each other. Consequently, the variation between the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection portions 22 is eliminated. As a result, the detection accuracy of the rotation angle detection device is improved.Meanwhile, when the position of the magnetic body protruding portion outer end 243 is greater than 360 / X degrees and the gap length between the portion of the bias magnetic field generating portion 21 in which the central side magnetic flux density detecting portion is disposed and the rotor 1 is minimum, an area in the protruding portion of the rotor 1 facing the magnetic body circumferential direction outer side portion 242 increases. Consequently, the maximum value of the magnetic resistance of the central-side magnetic flux density detection portion decreases. As a result, the amplitude of the magnetic flux density detected by the central-side magnetic flux density detection section increases.When the position of the magnetic body protruding portion end 243 is 360 / X degrees, and the gap length between the portion of the bias magnetic field generating portion 21 in which the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitt is disposed and the rotor 1 is the maximum or the minimum, the protruding portion of the rotor 1 faces the magnetic body circumferential direction outer side portion 242. Meanwhile, when the position of the magnetic body protruding portion outer end 243 is greater than 360 / X degrees and the gap length between the portion of the bias magnetic field generating portion 21 in which the Umfangsrichtungsaußenseitenmagnetflussdichtenerfassungsabschnitt is disposed and the rotor 1 is the maximum or the minimum, the protruding portion of the rotor 1 faces the magnetic body circumferential direction outer side portion 242. Thus, even when the position of the magnet body protruding portion outer end 243 is changed from the position forming an angle of 360 / X degrees to the position forming an angle equal to or greater than 360 / X degrees, an area in the protruding portion of the rotor 1 facing the magnet body circumferential outer side portion 242 is not increased. The magnetic body circumferential direction outer side portion 242 facing the protrusion and recess portion 12 of the rotor 1 increases, and thus the maximum value and the minimum value of the magnetic resistance of the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitts increase slightly for one rotation of the rotor 1.From the above description, when the position of the magnetic body protrusion portion outer end 243 is greater than 360 / X degrees, the amplitude of the magnetic flux detected by the central side magnetic flux density detection portion is greater than the amplitudes of the magnetic flux densities detected by the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitten. Consequently, the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection sections 22 are different from each other. As a result, the detection accuracy of the rotation angle detection device is deteriorated.When the position of the magnetic body protrusion portion inner end 244 is less than 180 / X degrees, the maximum value of the magnetic resistance of the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitts decreases. Consequently, the amplitude of the magnetic flux density detected by the circumferential outer-side magnetic flux density detection portion increases. Meanwhile, a decrease in the maximum value and a decrease in the minimum value of the magnetic resistance of the central-side magnetic flux density detection portion are small. Thus, an increase in the amplitude of the magnetic flux density detected by the central-side magnetic flux density detection section is small. Thus, the amplitudes of the magnetic flux densities detected by the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitte are larger than the amplitude of the magnetic flux density detected by the central-side magnetic flux density detection portion. Consequently, the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection sections 22 are different from each other. As a result, the detection accuracy of the rotation angle detection device is deteriorated. Thus, the magnetic body member in which the position of the magnetic body protrusion portion inner end 244 ais a position forming an angle of 180 / X degrees and the position of the magnetic body protrusion portion outer end 243 ais a position forming an angle of 360 / X degrees corresponds to the ideal magnetic body member in the case without downsizing.In the rotation angle detection device according to the second embodiment, the angle of displacement toward the circumferential direction inner side from the position of the magnetic body projecting portion outer end 243 ain the ideal magnetic body element in the case of no downward shift to the position of the magnetic body projecting portion outer end 243, and the angle of displacement toward the circumferential direction outer side from the position of the magnetic body projecting portion inner end 244 ain the ideal magnetic body element in the case of no downward shift to the position of the magnetic body projecting portion inner end 244 are equal to each other. As a result, the decrease values of the amplitudes of the magnetic flux densities detected by the magnetic flux density detection portions 22 disposed on the magnetic body circumferential direction outer side portion 242 side of the three magnetic flux density detection portions 22 and the decrease value of the amplitude of the magnetic flux density detected by the magnetic flux density detection portion 22 disposed on the circumferential central side of the three magnetic flux density detection portions 22 are equal to each other.As described above, in the rotation angle detection device according to the second embodiment of the present invention, α=β is satisfied when α=a+b-180 / X and β=360 / X-(a+b+c) are given. Consequently, the variation among the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection portions 22 can be reduced. As a result, the detection accuracy of the rotation angle detection device can be improved, and the size and weight of the rotation angle detection device can be reduced.Third EmbodimentFIG. 5 is a plan cross-sectional view for illustrating a relevant portion of a rotation angle detection device according to a third embodiment of the present invention. In the rotation angle detecting device of the third embodiment, α = a + b - 180 / X, β = 3 - 60 / X - (a + b + c) and y = a - 180 / X are given. In this case, the stator 2 is configured such that α>β and γ>0, or α<β and γ<0 are satisfied. The other configurations are the same as in the first embodiment.On this occasion, α represents an angle between a magnetic body protrusion portion inner end 244 aof an ideal magnetic body element in the case of no stepping down and the magnetic body protrusion portion inner end 244 in the third embodiment and the center O of the rotor 1. β represents an angle between a magnetic body protrusion portion outer end 243 aof the ideal magnetic body element in the case of no stepping down and the magnetic body protrusion portion outer end 243 in the third embodiment and the center O of the rotor 1. The ideal magnetic body element in the case of no stepping down is a magnetic body element in which the position of the magnetic body protrusion portion inner end 244 aof the magnetic body protrusion portion on an outer side at 180 / X degrees in the circumferential direction of the magnetic flux density detection portion 22, which is arranged on the central side in the circumferential direction. Moreover, in the case without downsizing, the ideal magnetic body member is a magnetic body member in which the position of the magnetic body protrusion portion outer end 243 aon an outer side is 360 / X degrees in the circumferential direction from the magnetic flux density detection portion 22 disposed on the central side in the circumferential direction.The angle of displacement to the circumferential direction inner side from the position of the magnetic body protruding portion outer end 243 ain the ideal magnetic body member in the case without being downsizing to the position of the magnetic body protruding portion end 243 is smaller than the angle of displacement to the circumferential direction outer side from the position of the magnetic body protruding portion inner end 244 ain the ideal magnetic body member in the case without being downsizing to the position of the magnetic body protruding portion inner end 244. Moreover, the dimension of the bias magnetic field generating portion 21 in the circumferential direction is larger than the dimension of the ideal bias magnetic field generating portion in the case without downsizing in the circumferential direction. As a result, the reductions in the amplitudes of the magnetic flux densities detected by the magnetic flux density detection portions 22 disposed on the magnetic body circumferential direction outer side portion 242 from the three magnetic flux density detection portions 22 are compensated by the size increase of the bias magnetic field generation portion 21.FIG. 6 is a planar sectional view for illustrating a relevant portion of the rotation angle detection device when α>β and γ>0 are given. FIG. 7 is a graph for showing the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 6. FIG. 8 is a table for showing ratios of the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 6. In FIG. 6, α=7 degrees, β=6 degrees, and γ=1 degrees. In FIGS. 6 to 8, one of the pair of Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitten is denoted by U. The central side magnetic flux density detecting section is denoted by V. The other Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitt is denoted by W. In FIG. 8, the relationships of the amplitudes of the magnetic flux densities detected by the magnetic flux density detection sections to the amplitude of the magnetic flux density detected by the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitt U are shown. As shown in FIG. 8, the amplitudes of the magnetic flux densities detected by the magnetic flux density detection section 22 are equal to each other.FIG. 9 is a planar sectional view for illustrating a relevant portion of the rotation angle detection device when α<β and γ<0 are given. FIG. 10 is a graph for showing the magnetic flux density detected by the three magnetic flux density detection sections of FIG. 9. FIG. 11 is a table for showing ratios of the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 9. In FIG. 9, α=0 degrees, β=1 degrees, and γ=-1 degrees. In FIGS. 9 to 11, one of the pair of Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitten is denoted by U. The central side magnetic flux density detecting section is denoted by V. The other Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitt is denoted by W. In FIG. 11, the relationships of the amplitudes of the magnetic flux densities detected by the magnetic flux density detection sections to the amplitude of the magnetic flux density detected by the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitt U are shown. As in FIG. 11, the amplitudes of the magnetic flux densities detected by the magnetic flux density detection sections 22 are equal to each other.FIG. 12 is a planar sectional view for illustrating a relevant portion of the rotation angle detection device when α=β is given. FIG. 13 is a graph for showing the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 12.FIG. 14 is a table for showing ratios of the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection sections of FIG. 12. In FIG. 12, α=3 degrees and β=3 degrees are given. In FIGS. 12 to 14, one of the pair of Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitten is denoted by U. The central side magnetic flux density detecting section is denoted by V. The other Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitt is denoted by W. In FIG. 14, the relationships of the amplitudes of the magnetic flux densities detected by the magnetic flux density detection sections to the amplitude of the magnetic flux density detected by the Umfangsrichtungsaußenseitenmagnetflussdichteerfassungsabschnitt U are shown. As shown in FIG. 14, the amplitudes of the magnetic flux densities detected by the magnetic flux density detection portions 22 are equal to each other.As described above, in the rotation angle detection device according to the third embodiment of the present invention, α>β and γ>0 or α<β and γ<0 are satisfied, where α=a+b-180 / X, β=360 / X-(a+b+c), and γ=a-180 / X are given. Consequently, the variation among the amplitudes of the magnetic flux densities detected by the three magnetic flux density detection portions 22 can be reduced. As a result, the detection accuracy of the rotation angle detection device can be improved, and the size and weight of the rotation angle detection device can be reduced.Moreover, the angle of displacement to the circumferential direction inner side from the position of the magnetic body projecting portion outer end 243 ain the ideal magnetic body member in the case without being down-sized to the position of the magnetic body projecting portion outer end 243 may be smaller than the angle of displacement to the circumferential direction outer side from the position of the magnetic body projecting portion inner end 244 ain the ideal magnetic body member in the case without being down-sized to the position of the magnetic body projecting portion inner end 244. As a result, a degree of freedom in the design of the magnetic body member 24 can be improved.Fourth EmbodimentFIG. 15 is a plan sectional view for illustrating a rotation angle detection device according to a fourth embodiment of the present invention. FIG. 16 is an enlarged view for illustrating the portion B of FIG. 15 ; the magnetic body circumferential direction outer side portion 242 has a circumferentially extending surface 245 extending from an outer surface in the radial direction in the magnetic body radially outer side portion 241 to the outer side in the circumferential direction. Moreover, the magnetic body circumferential direction outer side portion 242 has a circumferential direction outer side facing surface 246 facing outward in the circumferential direction. Moreover, the magnetic body circumferential direction outer side portion 242 has a peripheral inclined surface 247 connected to a portion of the circumferential direction extending surface 245 on an outer side in the circumferential direction and a portion of the circumferential direction outer side facing surface 246 on an outer side in the radial direction. The magnetic body circumferential direction outer peripheral portion 242 has the peripheral inclined surface 247, and therefore, the size and the weight of the magnetic body circumferential direction outer side portion 242 in the fourth embodiment are reduced as compared with the magnetic body circumferential direction outer side portion 242 in the first embodiment.A radial direction dimension at an outer end portion of the magnetic body radially outer side portion 241 in the circumferential direction is represented by "d". A dimension of the circumferentially extending surface 245 in the circumferential direction is represented by "e". A dimension of the circumferential direction outer side facing surface 246 in the radial direction is represented by "f". In this case, the magnetic body member 24 is formed so that d≤e and f≤d are satisfied.The magnetic body member 24 is formed of a plurality of laminated steel sheets. The stator 2 has a pair of first 25 crimps provided in the magnetic body circumferential direction outer side portions 242. The first crimps 25 are configured to fix the plurality of steel sheets. Moreover, the stator 2 has second crimps 26 provided at a center portion of the magnetic body radially outer side portion 241 in the circumferential direction. The second crimp 26 is configured to fix the plurality of steel sheets. The other configurations are the same as those of the first embodiment, the second embodiment, or the third embodiment.When d=e, a magnetic flux density at the end portion of the magnetic body radially outer side portion 241 on the magnetic body circumferential direction outer side portion 242 side and a magnetic flux density at an end portion of the magnetic body circumferential direction outer side portion 242 on the magnetic body radially outer side portion 241 side are substantially equal to each other. In consideration of the position of the first crimp 25 provided in the magnetic body circumferential direction outer side portion 242, when d≤e is given, the magnetic flux density at the end portion of the magnetic body radially outer side portion 241 on the magnetic body circumferential direction outer side portion 242 side and the magnetic flux density at the end portion of the magnetic body circumferential direction outer side portion 242 on the magnetic body radially outer side portion 241 side are substantially equal to each other.A magnetic flux passing through the magnet body circumferential direction outer side portion 242 crosses the gap between the magnet body outer circumferential portion 242 and the protrusion and recess portion 12, and passes through the protrusion and recess portion 12 until reaching the circumferential direction outer side facing surface 246. Thus, only f≤d needs to be satisfied.As described above, with the rotation angle detection device according to the fourth embodiment of the present invention, d≤e and f≤d are satisfied. As a result, the weight and cost of the rotation angle detection device can be reduced. Moreover, the durability of the rotation angle detecting device against vibration can be increased by the weight decrease of the rotation angle detecting device. Moreover, the influence of noise from external devices such as a motor on the detection signals of the rotation angle detection device can be reduced by the decrease in the size of the magnetic body member 24. Moreover, the weight of the magnetic body member 24 can be reduced without decreasing the magnetic flux density passing through the magnetic body member 24. As a result, the weight of the magnetic body member 24 can be reduced without reducing the detection signals of the magnetic flux density detection portion. Moreover, heat transfer from external devices such as the motor can be reduced by decreasing the size of the magnetic body member 24. As a result, the temperature of the bias magnetic field generating portion 21 can be prevented from rising. Consequently, demagnetization of the bias magnetic field generation portion 21 can be suppressed. When demagnetization of the bias magnetic field generation section 21 occurs, the detection signals of the magnetic flux density detection section 22 decrease. Thus, the detection accuracy of the rotation angle detection device can be improved by suppressing demagnetization of the bias magnetic field generation section 21.Fifth EmbodimentFIG. 17 is a plan sectional view for illustrating a relevant portion of a rotation angle detection device according to a fifth embodiment of the present invention. FIG. 18 is an enlarged view for illustrating the portion C of FIG. 17, FIG. 19 is an enlarged view for illustrating the portion D of FIG. 17, and the magnetic body radially outer side portion 241 includes magnetic body narrow portions 248 and magnetic body wide portions 249 at outer sides of the magnetic body narrow portions 248 in the circumferential direction. The magnetic body narrow portion 248 is provided at a portion between the center portion and the outer end portion of the magnetic body radially outer side portion 241 in the circumferential direction. A recessed portion 250 extending in the circumferential direction is provided on an outer surface of the magnetic body narrow portion 248 in the radial direction. A dimension of the magnetic body width portion 249 in the radial direction is larger than a dimension of the magnetic body narrow portion 248 in the radial direction.A dimension of the magnetic body wide portion 249 in the radial direction is represented by "g". A dimension of the magnetic body narrow portion 248 in the radial direction is represented by "h". A half of a circumferential dimension of the bias magnetic field generating portion 21 is represented by "i". A dimension of a portion opposed to the magnetic body narrow portion 248 of the bias magnetic field generating portion 21 in the circumferential direction is represented by "j". In this case, the stator 2 is formed so that g≥h×(i / j) is satisfied. The dimension "g" of the magnetic body width portion 249 in the radial direction is the same as the dimension "d" in the radial direction at the outer end portion of the magnetic body radially outer side portion 241 in the circumferential direction. The other configurations are the same as in the fourth embodiment.A dimension of the magnetic body radial outer portion 241 in the radial direction needs to have a length proportional to a length of the bias magnetic field generating portion 21 in the circumferential direction in order to prevent magnetic saturation of the magnetic body member 24. A magnetic flux density in the bias magnetic field generating section 21 is denoted by B. A magnetic flux density in the magnetic body element 24 given when the magnetic saturation occurs is denoted by B s. In this case, h in a case without the magnetic saturation is calculated by a relationship of B×j≤B s×h. The magnetic flux density B can be derived from a product of a permeability and a magnetomotive force of the bias magnetic field generating portion 21. The permeability used here is a permeability given when the gap length between the magnetic body member 24 and the rotor 1 is the minimum. The "g" given when the magnetic body element 24 is not magnetically saturated is calculated from "h", "i", and "j".The magnetic flux generated in the bias magnetic field generating portion 21 is referred to as a product of the magnetic flux density B in the bias magnetic field generating portion 21 and a region of a surface facing an outer side of the bias magnetic field generating portion 21 in the radial direction. A magnetic flux coupled to the magnetic body radially outer side portion 241 is referred to as a product of a magnetic flux density B' in the magnetic body radially outer side portion 241 and a region of a surface facing the circumferential direction in the magnetic body radially outer side portion.On this occasion, it is assumed that an axial dimension of the bias magnetic field generation portion 21 and an axial dimension of the magnetic body radially outer side portion 241 are equal to each other. In this case, the magnetic flux in the bias magnetic field generation portion 21 and the magnetic flux coupled to the magnetic body radially outer side portion 241 are equal to each other, and thus B×j=B'xh is true. When the magnetic flux density in the magnetic body element 24 at the magnetic saturation is indicated as B S the magnetic flux density B' in the magnetic body radially outer side portion 241 of the magnetic body must be B' ≤ B S in order to prevent the occurrence of the magnetic saturation in the magnetic body radially outer portion 241. Thus, the dimension "h" of the magnetic body narrow portion 248 in the radial direction given when the magnetic body member 24 is not magnetically saturated is calculated by the relationship B×j≤B S×h.The magnetic flux generated in the bias magnetic field generating portion 21 is indicated as the product of the magnetic flux density B in the bias magnetic field generating portion 21 and the area (or surface) of the surface facing an outer side of the bias magnetic field generating portion 21 in the radial direction. Thus, the magnetic flux coupled to the magnetic body wide portion 249 is greater than the magnetic flux coupled to the magnetic body narrow portion 248. The magnetic flux density B' in the magnetic body narrow portion 248 satisfies B'=(B×j) / h. Moreover, a magnetic flux density B" in the magnetic body wide portion 249 satisfies B"=(B×i) / g. The magnetic flux density B" in the magnetic body wide portion 249 must be smaller than the magnetic flux density B' in the magnetic body narrow portion 248. Thus, B" ≤ B'. Thus, the dimension "g" of the magnetic body width portion 249 in the radial direction is calculated by a relationship g≥h×(i / j).As described above, with the rotation angle detection device according to the fifth embodiment of the present invention, g≥h×(i / j) is satisfied. As a result, the weight and cost of the rotation angle detection device can be reduced. Moreover, the durability of the rotation angle detecting device against vibration can be increased by the weight decrease of the rotation angle detecting device. Further, the influence of noise from external devices such as the motor on the detection signals of the rotation angle detection device can be reduced by the decrease in the size of the magnetic body member 24. Moreover, the weight of the magnetic body member 24 can be reduced without decreasing the magnetic flux density passing through the magnetic body member 24. As a result, the weight of the magnetic body member 24 can be reduced without decreasing the detection signals of the magnetic flux density detection portions.Sixth EmbodimentFIG. 20 is a plan sectional view for illustrating a relevant portion of a rotation angle detection device according to a sixth embodiment of the present invention. The magnetic body member 24 is formed of a plurality of laminated steel sheets. The stator 2 has the first crimps 25 provided in the magnet body outer circumferential portion 242 in the circumferential direction, and is configured to fix the plurality of steel sheets. Moreover, the stator 2 further includes the second crimp 26 provided at the circumferential direction center portion of the magnetic body radially outer side portion 241 and configured to fix the plurality of steel sheets. A plurality of recessed portions 250 extending in the circumferential direction are provided on the outer surface of the magnetic body radial outer portion 241 in the radial direction. The second crimp 26 is disposed in a portion where the recessed portion 250 is not formed in the magnetic body radial outer portion 241. The other configurations are the same as in the fifth embodiment.As described above, in the rotation angle detection device of the sixth embodiment according to the present invention, the stator 2 includes the first crimps 25 provided in the magnet body circumferential direction outer side portion 242 and configured to fix the plurality of steel sheets. As a result, without affecting the detection accuracy of the rotation angle detecting device, the plurality of laminated steel sheets can be fixed.Moreover, the stator 2 includes the second crimp 26 provided at the circumferential direction center portion of the magnetic body radially outer side portion 241 and configured to fix the plurality of steel sheets. As a result, without affecting the detection accuracy of the rotation angle detecting device, the plurality of laminated steel sheets can be fixed.

Claims

A rotation angle detection device comprising: a rotor (1) having a protrusion and recess portion (12) formed by a magnetic body on an outer circumferential surface of the rotor (1); a stator (2) provided to oppose the protrusion and recess portion (12) and having a bias magnetic field generation portion (21) and a plurality of magnetic flux density detection portions (22); and a magnetic body member (24) having a magnetic body radially outer side portion (241) provided on an outer side of the bias magnetic field generation portion (21) in a radial direction of the rotor (1), the magnetic body radially outer side portion (241) being disposed so as to cover the bias magnetic field generation portion (21) in the radial direction, and a pair of magnetic body circumferential direction outer side portions (242), which embeds the bias magnetic field generating portion (21) in a circumferential direction of the rotor (1), the protrusion and recess portion (12) being formed to change by an amount of X cycles over a mechanical angle of 360 degrees in the circumferential direction, where X is an integer greater than 1, the plurality of magnetic flux density detecting portions (22) opposing the protrusion and recess portion (12) with a gap and being provided at an equal interval along the circumferential direction over a cycle of the protrusion and recess portion (12), the bias magnetic field generating portion (21) being provided on a radially outer side of the plurality of magnetic flux density detecting portions (22), covering the plurality of magnetic flux density detecting portions (22) in the radial direction, and being formed to extend in the circumferential direction, wherein the magnetic body circumferential direction outer side portion (242) has a radial direction inner end portion provided on an inner side in the radial direction with respect to an inner end portion of the bias magnetic field generating portion (21) in the radial direction, and wherein a+b> 180 / X and a+b+c<360 / X are satisfied, wherein "a" represents half of an angle between both end portions of the bias magnetic field generating portion (21) in the circumferential direction and a center of the rotor (1), "b" represents an angle between both end portions of a gap between the bias magnetic field generating portion (21) and the magnetic body circumferential direction outer side portion (242) in the circumferential direction and the center of the rotor (1), and "c" represents an angle between the both end portions of the magnetic body circumferential direction outer side portion ( 242) with respect to the center of the rotor ( 1).The rotation angle detection device according to claim 1, wherein α > β and γ > 0 or α < β and γ < 0 are satisfied, wherein α = a + b - 180 / X, β = 360 / X - (a + b + c), and γ = a - 180 / X are given.The rotation angle detection device according to claim 1, wherein α = β is satisfied, wherein α = a + b - 180 / X and β = 360 / X - (a + b + c) are given.The rotation angle detection device according to any one of claims 1 to 3, wherein the magnetic body circumferential direction outer side portion (242) comprises: a circumferential direction extending surface (245) extending in the circumferential direction from a radially outer surface of the magnetic body radially outer side portion (241); and a circumferential direction outer side facing surface (246) facing outward in the circumferential direction, and wherein d ≤ e and f ≤ d are satisfied, where "d" represents a dimension of the magnetic body radially outer side portion (241) in the radial direction at a circumferential outer end portion of the magnetic body radially outer side portion (241), "e" represents a dimension of the circumferential direction extending surface (245) in the circumferential direction, and "f" represents a dimension of the circumferential direction outer side facing surface ( 246) in the radial direction.The rotation angle detection device according to any one of claims 1 to 4, wherein the magnetic body radially outer side portion (241) includes a magnetic body narrow portion (248) and a magnetic body wide portion (249) disposed on a circumferentially outer side of the magnetic body narrow portion (248), the magnetic body narrow portion (248) being provided in a portion between a center portion and an outer end portion of the magnetic body radially outer side portion (241) in the circumferential direction, a recessed portion (250) extending in the circumferential direction being provided on a radially outer surface of the magnetic body narrow portion (248), the magnetic body wide portion (249) having a dimension in the radial direction larger than a dimension of the magnetic body narrow portion (248) in the radial direction, and wherein g ≥ h × (i / j) is satisfied, where "g" represents the dimension of the magnetic body wide portion (249) in the radial direction, "h" represents the dimension of the magnetic body narrow portion (248) in the radial direction, "i" represents a half of a dimension of the bias magnetic field generating portion (21) in the circumferential direction, and "j" represents a dimension of a portion opposing the magnetic body narrow portion (248) of the bias magnetic field generating portion (21) in the circumferential direction.The rotation angle detection device according to any one of claims 1 to 5, wherein the magnetic body member (24) is formed of a plurality of laminated steel sheets, and wherein the stator (2) further includes a first crimp (25) provided in the magnetic body circumferential direction outer side portion (242) and configured to fix the plurality of steel sheets.The rotation angle detection device according to any one of claims 1 to 6, wherein the magnetic body member (24) is formed of a plurality of laminated steel sheets, and wherein the stator (2) further includes a second crimp (26) provided at a center portion of the magnetic body radially outer side portion (241) in the circumferential direction and configured to fix the plurality of steel sheets.

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