Brushless D.C. motor
AssigneeRotron Incorporated
InventorsWharton McDaniel, Fred A. Brown, Donald Thompson
Life of this patent
Estimating the term…
Abstract
A D.C. brushless motor with a permanent magnet rotor employs Hall switches to effect commutation. The rotor magnets are of a greater axial length than the stator stack and the Hall switches are mounted on a printed circuit panel within the motor frame so as to be actuated by the fringe flux from the portion of a rotor magnet extending beyond the stator stack. The pole faces of the stator stack are stepped to assure proper starting and direction of rotation. A voltage regulating circuit forming part of the commutating arrangement on the printed circuit panel enables the same circuit to be used for a range of stator energizing voltages.
Claims9
In combination, a D.C. brushless motor with stator windings and a permanent magnet rotor, semiconductor commutation circuit means for switching current to the windings of the stator in dependence on the angular position of the rotor, the permanent magnets of the rotor extending arcuately less than 180.degree. and operative to impart rotary motion to the rotor upon commutated energization of the stator winding, the commutation circuit means including at least two Hall switching means for changing output states in response to a magnetic field, said Hall switching means being arcuately displaced and connected with winding activating switching means to energize at least one of the stator windings when only one of said Hall switching means changes output state in the presence of a magnetic field of one of said rotor magnets said two Hall switching means being connected in "or" fashion to the winding activating switching means to effect energization of one winding when either Hall switching means responds to the magnetic field of the one rotor magnet, whereby one winding is energized as one of the Hall switching means enters the magnetic field of the magnet and is de-energized when the other Hall switching means leaves the magnetic field of the one magnet, and whereby the effective arc of the rotor magnet is increased for commutation purposes.
The combination of a brushless D.C. motor and a commutation circuit;
- the motor having a stator with at least one winding thereon and a rotor carrying at least one permanent magnet, the commutation circuit including input connections for supplying a D.C. voltage to the motor, switching means for alternating the application of the D.C. voltage to the at least one winding to cause continuous rotation of the rotor, a Hall switch connected between the input connections and the switching means, said Hall switch being mounted for repeated application thereto of the magnetic field of the magnet and having an output switching sharply between binary "1" and "0" in response to the movement of the magnet into and out of proximity with the Hall switch, said Hall switch being connected in controlling relation with said switching means to effect commutation of the motor under the influence of the magnet, and means connected with said switching means for reducing the rate of change that the switching means provides each alternation of the voltage applied to the winding, said means for reducing the rate providing a change in voltage across the winding more gradually than the sharp change of binary states of the Hall switch to thereby substantially diminish interference resulting from said change in voltage.
In combination, a D.C. brushless motor with at least one stator winding and a permanent magnet rotor, a semiconductor commutation circuit means for switching current in the at least one winding of the stator in dependence on the angular position of the rotor and to change the angular position of the magnetic field of the stator, the rotor carrying at least one permanent magnet having at least one pole proximate the stator extending arcuately through a first angle and operative to impart rotary motion to the rotor upon commutated energization of the stator winding, the commutation circuit including switching means having a first state for conducting current through the winding in one direction and a second state terminating conduction of current through the winding in that direction, at least two Hall effect devices for changing output states in response to a magnetic field, said Hall devices being effectively arcuately spaced apart by a second angle and each coupled in control relation with the same switching means to cause that switching means to assume one of its said states when the first of the Hall devices is effectively proximate the rotor permanent magnet pole, maintaining the switching means in said one of its said states when either or both Hall devices are effectively proximate said magnet pole and returning the switching means to the other of its said states when the second Hall device effectively leaves the influence of the pole, whereby the commutation arc of the permanent magnet is extended beyond the first angle of its arcuate extent by substantially the second angle of effective arcuate spacing of the Hall devices.
Dependencies are inferred from the claim text.