Direct current brushless electric motor

• US 4,357,563 A
• Filed: 06/30/1981
• Issued: 11/02/1982
• Est. Priority Date: 02/06/1981
• Status: Expired due to Term

• Current Assignee: Japan Servo Co., Ltd. (Nidec Corporation)
• Original Assignee: Japan Servo Co., Ltd. (Nidec Corporation)
• Inventors: Ohno, Osamu
• Primary Examiner(s): Smith, Jr., David
• Application Number:
  US06/279,176
• Time in Patent Office: 490 Days
• Field of Search: 318/254 A, 318/138, 310/68 B, 310/268, 310/269, 310/49 R, 310/67 R, 310/156, 310/68 R, 310/DIG. 3
• US Class Current: 318/400.41
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence
• CPC Class Codes: Y10S 310/03 Hall effect generators and converters

Abstract

A hollow cylindrical permanent magnet having its semicircle magnetized as N pole and the remaining semicircle magnetized as S pole forms the rotor. Two stator magnetic poles which are planted radially around the outer periphery of a cylindrical stator yoke, pole shoes which are firmly mounted on the outer peripheral side of each stator magnetic pole so as to have its outer peripheral side oppose to the inner peripheral surface of aforesaid permanent magnet, and intermediary magnetic poles which are planted radially on the outer periphery of the stator yoke so as to place each of them in between each of these pole shoes, form the stator with all of these components made of magnetic materials. Around each of the stator magnetic poles windings are wound. One magnetism detector which detects the revolutional position of the permanent magnet is mounted at the position within the gap of magnetic flux which is located in a position slightly deviated toward the pole shoe side from the center line connecting the center of the peripheral gap between the end point of the pole shoe and the end point of the intermediary magnetic pole with the center of the stator yoke. A current control circuit controls the flow of current that flows through the windings of each stator winding upon receiving the output of the above-mentioned magnetism detector.

Claims

1. The DC brushless electric motor which is characterized in being equipped with (a) the rotor consists of the permanent magnet of a hollow cylindrical shape with its semicircle magnetized as N pole while the remaining semicircle magnetized as S pole and the revolving hub which supports the aforesaid permanent magnet permitting it to revolve freely, (b) the stator consists of the stator yoke of a cylindrical shape, two stator magnetic poles which are planted radially on the outer periphery of the stator yoke as if to divide the outer periphery in two parts, the pole shoes which are mounted on the top part of each stator magnetic pole so as to have the outer peripheral surface of their top ends oppose the inner peripheral surface of the aforesaid permanent magnet across a small gap, and the intermediary magnetic poles which are planted redially on the outer periphery of the aforesaid stator yoke so as to position themselves between the above pole shoes, (c) with the aforesaid stator magnetic poles being wound around with stator windings and the length of the magnetic flux gap between the outer peripheral surface of the aforesaid intermediary magnetic poles and the inner peripheral surface of the permanent magnet being almost equal to the length of the magnetic flux between the outer peripheral surface of the aforesaid pole shoes and the inner peripheral surface of the permanent magnet, (d) one magnetism detector which is mounted at the position within the magnetic flux located at the point slightly deviated toward the pole shoe side from the center line connecting the center of the peripheral direction gap between the top end of the pole shoe and the top end of the intermediary magnetic pole, and (e) the current control circuit which drives and controls the revolution of the rotor in the designed direction by controlling the current which it allows to flow to each stator winding upon receiving the output of the above magnetism detector.