Patent ID: 9659695
Date: 2017-05-23
CPC Classifications: G01R,H01F

Claim:
1. A dipole ring magnetic field generator comprising: a cylindrical yoke in which at least four magnet insertion holes are circularly provided in a circumferential direction between an inner circumference and an outer circumference of the cylindrical yoke, each direction of depth of the magnet insertion holes being parallel to a central axis of the cylindrical yoke; and at least four permanent magnet units inserted in the at least four magnet insertion holes, the dipole ring magnetic field generator being adapted to generate a substantially unidirectional magnetic field in a radial direction of the cylindrical yoke in an internal space of the cylindrical yoke, wherein, in the case where the central axis is defined as a Z-axis, an axis perpendicular to the Z-axis and parallel to the unidirectional magnetic field in a section perpendicular to the central axis is defined as an X-axis, and an axis perpendicular to the Z-axis and the X-axis is defined as a Y-axis, the at least four permanent magnet units are arranged such that shapes thereof in the section are line-symmetric with respect to the X-axis as an axis of symmetry and line-symmetric with respect to the Y-axis as an axis of symmetry, each of the at least four permanent magnet units comprises one or more permanent magnet pieces, each of the pieces being shaped in a rectangle in the section, the one or more permanent magnet pieces have the same magnetization direction for each permanent magnet unit, the magnetization direction being parallel or perpendicular to sides of the rectangle, and are arranged such that the magnetization direction of each of the at least four permanent magnet units in the section is line-symmetric with respect to the X-axis as the axis of symmetry, the at least four permanent magnet units comprise first, second, third and fourth permanent magnet units, and in the case where a positive direction of the X-axis, which is the same direction as the unidirectional magnetic field, is defined as 0° and 360°, and in a counterclockwise manner from the positive direction of the X-axis, a positive direction of the Y-axis is defined as 90°, a negative direction of the X-axis is defined as 180°, and a negative direction of the Y-axis is defined as 270° in the section, (i) the first permanent magnet unit is disposed within ranges of 0° to 20° and 340° to 360°, the second permanent magnet unit is disposed within a range of 70° to 110°, the third permanent magnet unit is disposed within a range of 160° to 200°, and the fourth permanent magnet unit is disposed within a range of 250° to 290°, (ii) the one or more permanent magnet pieces comprised by each of the first and third permanent magnet units are five or more permanent magnet pieces linearly arranged in parallel to the Y-axis, the one or more permanent magnet pieces comprised by each of the second and fourth permanent magnet units are five or more permanent magnet pieces linearly arranged in parallel to the X-axis, and each of the one or more permanent magnet pieces comprised by each of the first to fourth permanent magnet units has sides of the rectangle being parallel or perpendicular to the X-axis, (iii) the magnetization directions of the five or more permanent magnet pieces comprised by each of the first and third permanent magnet units are all the same as the magnetization direction of the unidirectional magnetic field, and the magnetization directions of the five or more permanent magnet pieces comprised by each of the second and fourth permanent magnet units are all opposite from the magnetization direction of the unidirectional magnetic field, and (iv) each of the first to fourth permanent magnet units has a structure in which, with respect to the five or more permanent magnet pieces comprised by each of the permanent magnet units, permanent magnet pieces on both ends are more protruding toward the internal space than remaining permanent magnet pieces.