# US 2014/0197823 A1 · Motor unit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0197823 A1 - Document ID: US20140197823A1 - Status: Published application - Kind: A1 - Application number: 14/154,184 - Filed: 2014-01-14 - Published: 2014-07-17 - Earliest claimed: 2013-01-15 - Assignees: Kabushiki Kaisha Yaskawa Denki - Applicants: Kabushiki Kaisha Yaskawa Denki - Inventors: Shiro YOSHIDOMI; Ikuma MUROKITA; Yasushi YOSHIDA; Jiro MURAOKA; Shoji OYAMA - Web page: https://patentgrep.com/patent/US20140197823A1 ## CPC - G01B 7/30: for measuring angles or tapers; for testing the alignment of axes - G01P 3/487: delivered by rotating magnets - H02K 11/225: Detecting coils - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G}) - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## Abstract A rotation detector of a motor according to an embodiment includes a first support and a second support, a pair of magnetic field forming units, at least one magnetic field detector, and a first magnetic member and a second magnetic member. The first magnetic member and the second magnetic member are each made of a magnetic material, cover longitudinal-direction both ends of the magnetic field detector facing the first support, respectively, and face each other with a gap interposed therebetween at a longitudinal-direction mid-portion of the magnetic field detector in the longitudinal direction. A dimension of each of the magnetic field forming units in a tangential direction of a circumference is larger than a dimension of the corresponding magnetic field forming unit in a radial direction and is larger than the distance of the gap. ## Claims ### Claim 1 A motor unit comprising: a motor configured to rotate a shaft about an axial line; and a rotation detector configured to detect rotation of the shaft, wherein the rotation detector comprises: a first support and a second support that are provided in a manner separated from each other in a direction of the axial line, one of which is rotated along with rotation of the shaft using the axial line as a rotational axis; a pair of magnetic field forming units that is provided on the first support in a manner facing the second support at different positions along a circumference about the axial line and having different polarities; at least one magnetic field detector that is formed by winding a coil around a magnetic element whose magnetized direction changes in a longitudinal direction and provided on the second support such that a longitudinal-direction side of the magnetic element faces the first support; and a first magnetic member and a second magnetic member that are each made of a magnetic material, that cover longitudinal-direction both ends of the magnetic field detector facing the first support, respectively, and that face each other with a gap interposed therebetween at a longitudinal-direction mid-portion of the magnetic field detector, and a dimension of each of the magnetic field forming units in a tangential direction of the circumference is larger than a dimension of the corresponding magnetic field forming unit in a radial direction and is larger than the distance of the gap. ### Claim 2 (depends on 1) The motor unit according to claim 1, wherein the pair of magnetic field forming units is arranged in a manner facing an overlapping point serving as an intersection point at which longitudinal-direction both ends of the magnetic element overlap with the circumference, and the dimension of each of the magnetic field forming units in the tangential direction of the circumference is equal to or larger than a length twice as long as a distance from center of the corresponding magnetic field forming unit in the tangential direction of the circumference to a position corresponding to one end of the first magnetic member in a circumferential direction when the center of the corresponding magnetic field forming unit coincides with the overlapping point at one end of the magnetic field detector in the longitudinal direction and equal to or smaller than the length of a chord subtending an arc corresponding to one-half of the whole circumference of the first support. ### Claim 3 (depends on 1) The motor unit according to claim 1, wherein each of the magnetic field forming units is formed such that the dimension thereof in the radial direction is smaller at both ends in the tangential direction of the circumference than at the center thereof. ### Claim 4 (depends on 1) The motor unit according to claim 1, wherein each of the magnetic field forming units is formed such that a clearance between the corresponding magnetic field forming units and the second support is larger at both ends in the tangential direction of the circumference than at the center thereof. ### Claim 5 (depends on 1) The motor unit according to claim 1, wherein each of the magnetic field forming units is bonded magnets and formed so as to have lower magnetic force at both ends in the tangential direction of the circumference than at the center thereof. ### Claim 6 (depends on 1) The motor unit according to claim 1, wherein the first support is provided with at least two pairs of the magnetic field forming units arranged in a manner surrounding the whole circumference of the axial line at regular intervals such that the polarities thereof alternate in the circumferential direction, the second support is provided with at least three of the magnetic field detectors arranged in a manner surrounding the whole circumference of the axial line at regular intervals in the circumferential direction, each of the magnetic field detectors is provided with the first magnetic member and the second magnetic member, each of pairs of the first magnetic members and of the respective second magnetic members arranged adjacent to each other in the circumferential direction among first magnetic members and second magnetic members are positioned close to each other, forming a continuous arrangement of the first magnetic members and the second magnetic members, and the continuous arrangement covers an outer circumferential side of a portion of the second support facing the first support over nearly the whole circumference with the magnetic field detector interposed between the continuous arrangement and the second support. ### Claim 7 (depends on 1) The motor unit according to claim 1, further comprising: a storage unit configured to store therein a detection result of the magnetic field detector; and a rotation number detector configured to detect number of rotations of the shaft based on information stored in the storage unit, wherein the storage unit is arranged near the magnetic field detector. ### Claim 8 (depends on 1) The motor unit according to claim 1, further comprising: a rotational position detection sensor configured to optically detect a rotational position of the shaft, wherein the rotational position detection sensor comprises: a reflective pattern formed on the first support or the second support that rotates along with the shaft; and an optical sensor that irradiates the reflective pattern with light and receives light reflected by the reflective pattern. ### Claim 9 (depends on 8) The motor unit according to claim 8, wherein the reflective pattern is formed on a surface of the first support opposite to a surface on which the pair of magnetic field forming units is arranged or a surface of the second support opposite to a surface on which the magnetic field detector is arranged. ### Claim 10 (depends on 8) The motor unit according to claim 8, wherein the first support is arranged at a position closer to the motor than the second support and rotates along with rotation of the shaft, and the reflective pattern is formed on a surface of the first support facing the motor. ### Claim 11 (depends on 9) The motor unit according to claim 9, wherein the first support is arranged at a position closer to the motor than the second support and rotates along with rotation of the shaft, and the reflective pattern is formed on a surface of the first support facing the motor. ### Claim 12 A motor unit comprising: a motor that rotates a shaft about an axial line; and a rotation detector that detects rotation of the shaft, wherein the rotation detector comprises: a pair of magnetic field forming units that are provided at different positions along a circumference about the axial line and having different polarities; means for detecting a magnetic field, which is formed by each of the magnetic field forming units, by reversal of a magnetized direction of a magnetic element whose magnetized direction changes in a longitudinal direction, the means facing the pair of magnetic field forming units; means for forming a magnetic path via a gap by inducing the magnetic field, the magnetic path being provided between both ends of the magnetic element in the longitudinal direction and the pair of magnetic field forming units; and means for rotating the magnetic field with respect to the means for detecting the magnetic field and the means for forming the magnetic path using the axial line as a rotational axis, and the dimension of each of the magnetic field forming units in a tangential direction of the circumference is larger than the dimension of corresponding magnetic field forming unit in a radial direction and is larger than the distance of the gap.