Single excitation pulse brushless DC motor

• US 4,667,137 A
• Filed: 04/04/1985
• Issued: 05/19/1987
• Est. Priority Date: 04/04/1985
• Status: Expired due to Fees

• Current Assignee: Applied Motion Products, Inc. (Shanghai Moons' Electric Company Limited)
• Original Assignee: Applied Motion Products, Inc. (Shanghai Moons' Electric Company Limited)
• Inventors: Macleod, Donald J.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ro, Bentsu
• Application Number:
  US06/719,970
• Time in Patent Office: 775 Days
• Field of Search: 318/138, 318/254 A, 318/254, 318/439, 310/46, 310/68 R, 310/154, 310/156, 310/181
• US Class Current: 318/400.26
• CPC Class Codes: G11B 19/2009 Turntables, hubs and motors for disk drives; Mounting of motors in the drive means for clamping of disk to turntable G11B17/022 and subgroups
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence

Abstract

A single excitation phase pulse brushless DC motor (10) including a rotor portion (12) mounted upon a shaft subassembly (14) and rotating therewith with respect to a stator portion (16). The rotor portion (12) includes a first zone of steady state magnetization in the form of a main field magnet (24) divided into radially polarized sectors (26). The stator portion (16) includes the main stator stack (34) upon which the stator windings (38) are placed and a second zone of steady state magnetization in the form of a permanent disk magnet (46). The disk magnet (46) is divided into radially polarized sectors (48) similarly to those of the field magnet (24). A hall effect senior (40) is also provided to act as a commutator triggering element. The motor (10) is characterized in that the opposition of the first and second steady state zones of magnetization provides a steady state torque curve which urges the rotor (12) to rotate with respect to the stator (16 ) when it is in certain rotational positions. A current through the stator winding (38) overcomes the steady state torques at other positions and causes, upon properly timed activation, continuous rotation of the rotor (12). The primary usage of the motor (10) is in high speed, low cost fans and in magnetic media disk drives.

Claims

1. A single excitation phase pulse direct current electrical motor, comprising:

a rotor portion and

a stator portion;

said motor being characterized by having;

a first zone of steady state magnetization, said first zone being situated upon the rotor portion, said first zone being radially symmetrical and being divided into n, where n is an even integer, alternating opposingly polarized sectors;

a second zone of steady state magnetization situated on the stator portion opposite from at least a ring shaped portion of said first zone, said second zone also being divided into n alternating opposingly polarized sectors; and

induction means including exactly one switching element for selectively inducing a variable zone of magnetization, divided into n alternating opposingly polarized sectors, opposing at least a ring-shaped portion of said first zone, the magnetic field strength of said variable zone, when induced, being approximately twice the magnetic field strength of said second steady state zone such that alternating activation and deactivation of the induction means, depending on the relative positions of the rotor portion and the stator portion, will cause the rotor portion to continually rotate.

2. A single excitation phase pulse direct current electrical motor, comprising:

a rotor portion and a stator portion having main motor windings; and

said motor being characterized by having;

a first zone of steady state magnetization, in the form of main field magnets of the motor, said first zone being situated upon the rotor portion, said first zone being radially symmetrical and being divided into n, where n is an even integer, alternating opposingly polarized sectors;

a second zone of steady state magnetization, in the form of a permanently magnetized ring, axially offset from the main motor windings, situated on the stator portion opposite from at least a ring shaped portion of said first zone, said second zone also being divided into n alternating opposingly polarized sectors; and

;

induction means including exactly one switching element for selectively inducing a variable zone of magnetization, divided into n alternating opposingly polarized sectors, opposing at least a ring-shaped portion of said first zone, the magnetic fiedl strength of said variable zone, when induced, being greater than the magnetic field strength of said second steady state zone such that alternating activation and deactivation of the induction means, depending on the relative positions of the rotor portion and the stator portion, will cause the rotor portion to continually rotate.

3. A single excitation phase pulse direct current electrical motor, comprising:

a rotor portion; and

a stator portion; and

said motor being characterized by having;

a first zone of steady state magnetization, in the form of main field magnets of the motor, said first zone being situated upon the rotor portion, said first zone being radially symmetrical and being divided into n, where n is an even integer, alternating opposingly polarized sectors;

a second zone of steady state magnetization, in the form of a conductive ring being wound with electrical leads carrying constant electrical current such that a steady state magnetic field is generated thereby, situated on the stator portion opposite from at least a ring shaped portion of said first zone, said second zone also being divided into n alternating opposingly polarized sectors; and

induction means including exactly one switching element for selectively inducing a variable zone of magnetization, divided into n alternating opposingly polarized sectors, opposing at least a ring-shaped portion of said first zone, the magnetic field strength of said variable zone, when induced, being greater than the magnetic field strength of said second steady state zone such that alternating activation and deactivation of the induction means, depending on the relative positions of the rotor portion and the stator portion, will cause the rotor portion to continually rotate.

4. A singled excitation phase pulse direct current electrical motor, comprising:

a rotor portion; and

a stator portion including stator poles and stator windings connected to activation circuitry; and

said motor being characterized by having;

a first zone of steady state magnetization, in the form of main field magnets of the motor, said first zone being situated upon the rotor portion, said first zone being radially symmetrical and being divided into n, where n is an even integer, alternating opposingly polarized sectors;

a second zone of steady state magnetization, in the form of a steady state conductive winding, carrying a constant DC current, wound about said stator poles such that the magnetic field generated thereby is polarized oppositely to that generated by activation of current in said stator windings, situated on the stator portion opposite from at least a ring shaped portion of said first zone, said second zone also being divided into n alternating opposingly polarized sectors; and

induction means including exactly one switching element for selectively inducing a variable zone of magnetization in said stator poles and windings, divided into n alternating opposingly polarized sectors, opposing at least a ring-shaped portion of said first zone, the magnetic field strength of said variable zone, when induced, being greater than the magnetic field strength of said second steady state zone such that alternating activation and deactivation of the induction means, depending on the relative positions of the rotor portion and the stator portion, will cause the rotor portion to continually rotate.

5. The motor of claim 4 wherein:

the magnitude of the magnetic field generated by said variable zone, when activated, is approximately double that generated by said second zone.

6. A simple brushless DC motor, comprising:

a rotor portion including a main field magnet mounted therein, said main field magnet being divided into n, where n is an even integer, alternately radially polarized pole sectors and further including a shaft assembly about which the rotor assembly is concentrically formed;

a stator portion, concentrically formed with respect to said shaft assembly, including n stator poles being separated from said rotor pole sectors by a radial air gap, each said stator pole being wound with a stator winding connected to a power source and control circuitry such that when current is delivered through said stator winding said stator poles are induced to generate radially polarized magnetic stator pole fields, the polarity of said stator pole fields being opposite in adjacent said stator poles; and

a stationary steady state zone of magnetization, situated such that the stationary zone is axially separated from said stator poles and separated by a radial air gap from said rotor pole sectors, the stationary zone being divided into n alternating radially polarized sector poles, with each of said sector poles being radially positioned to be equivalent to a corresponding one of said stator poles, the magnetic field strength generated in each of said sector poles being less than the magnetic stator pole field generated by said corresponding stator pole and the polarity thereof being opposite.

7. The motor of claim 6 wherein:

the stationary zone of steady state magnetization includes conductive pole material wound with a steady state winding through which a constant current is passed.

8. The motor of claim 6 wherein:

the magnitude ratio of said magnetic stator pole field to the field existing about the stationary zone of steady state magnetization is approximately two to one.

9. In a brushless direct current motor including a stator portion having a stator and a stator field, a rotor portion having a rotor with a main field magnet, the improvement comprising:

a steady state zone of magnetization opposing the main field magnet, the magnetic field of the steady state zone being locally opposite to and approximately one-half the magnitude of the field generated by the activation of the stator; and

control circuitry means for activating the stator field only when the position of the rotor is such that a negative torque is generated by the juxtaposition of the magnetic fields generated by the main field magnet and the steady state zone of magnetization.