Self-starting brushless D.C. motor

Claim 2

A self-starting brushless d.c. motor comprising a stator, a rotor and a commutating device, characterized in that the stator is of a two-phase type and that the commutating device comprises a detection device having only one detector for distinguishing towards which of the two stator phases the rotor is mainly directed, a presettable energizing circuit for the commutated energization of the stator phases, and a presetting circuit adapted to be controlled by the detection device for, at least when the rotor is stationary, setting the energizing circuit to one of the two states which correspond to energization of the stator phase other than that towards which the rotor is mainly directed.

Claim 3

A self-starting brushless d.c. motor as claimed in claim 1, characterized in that the presettable energizing circuit is preset to a switching sequence corresponding to a desired direction of rotation of the rotor and can be switched in accordance with a cyclic permutation, under command of commutation signals, regardless of the actual direction of rotation of the rotor.

Claim 4

A self-starting brushless d.c. motor as claimed in claim 2, characterized in that the presettable energizing circuit comprises a control input and means adapted to preset the switching sequence to either one of the two possible directions as a function of a signal on said control input in order to render the direction of rotation of the motor reversible.

Claim 5

A self-starting brushless d.c. motor as claimed in claim 1, comprising p pole pairs, characterized in that the detection device comprises a permanent-magnetic member having 2p pole pairs, said member being rotatable in synchronism with the rotor, and the detector comprises a magneto-sensitive Hall element.

Claim 6

A self-starting brushless d.c. motor as claimed in claim 4, characterized in that the presetting circuit comprises a polarity detector for detecting the polarity of the magnetic field sensed by the magneto-sensitive element and a gate circuit for comparing the detected polarity with the state of the energizing circuit.

Claim 7

A self-starting brushless d.c. motor as claimed in claim 2, comprising p pole pairs, characterized in that the detection device comprises a permanent-magnetic member having 2p pole pairs, said member being rotatable in synchronism with the rotor, the detector comprises a magneto-sensitive Hall element, and a commutating-signal generator for generating commutating signals for the energizing circuit in synchronism with magnetic-field polarity changes detected by the detector.

Claim 8

A self-starting brushless d.c. motor as claimed in claim 6, characterized in that the presetting circuit comprises a polarity detector for detecting the polarity of the magnetic field sensed by the magneto-sensitive element and a first gate circuit for comparing the detected polarity with the state of the energizing circuit.

Claim 9

A self-starting brushless d.c. motor as claimed in claim 7, characterized in that the presetting circuit is adapted to supply additional commutating signals to the energizing circuit.

Claim 10

A self-starting brushless d.c. motor as claimed in claim 6, further comprising means for detecting the application of a supply voltage, wherein the presetting circuit comprises a polarity detector for detecting the polarity of magnetic field sensed by the magneto-sensitive element, and a first gate circuit for comparing the detected polarity with the state of the energizing circuit and, after detection of the application of a supply voltage, setting the energizing circuit to a state which is in conformity with the detected polarity.

Claim 11

A self-starting brushless d.c. motor as claimed in claim 2, further comprising a second gate circuit for suppressing the next commutating signal under command of the presetting circuit.

Claim 12

A self-starting brushless d.c. motor as claimed in claim 6, characterized in that the commutating signal generator comprises a polarity detector for detecting the polarity of the magnetic field sensed by the magneto-sensitive element and a gate circuit for comparing the detected polarity with the state of the energizing circuit and generating a commutating signal each time that said state does not correspond to the detected polarity.

Claim 13

A self-starting brushless d.c. motor as claimed in claim 2, characterized in that the energizing circuit comprises a shift register.

Claim 14

A self-starting brushless d.c. motor as claimed in claim 12, characterized in that the shift register has an adjustable shifting direction.

Claim 15

A self-starting brushless d.c. motor as claimed in claim 1, characterized by a rotor having a cylindrical permanent magnet which is magnetized to have substantially 2p poles, a stator having two-phase windings, arranged coaxially with the rotor inside the cylindrical permanent magnet, a wiring support secured to the stator, to which support the stator windings are connected, and a substrate arranged on said wiring support, on which substrate at least a magneto-sensitive element is arranged in such a way that said element is disposed within magnetic range of a magnetic field of the end face of the cylindrical permanent magnet which faces said support, the permanent magnet being provided with a 4p-pole magnetization at the location of said end face.

Claim 16

A self-starting brushless d.c. motor as claimed in claim 2, characterized by a rotor having a cylindrical permanent magnet which is magnetized to have substantially 2 p poles, a stator having two-phase windings, arranged coaxially with the rotor inside the cylindrical permanent magnet, a wiring support secured to the stator, to which support the stator windings are connected, and a substrate arranged on said wiring support, on which substrate at least a magneto-sensitive element is arranged in such a way that said element is disposed within magnetic range of a magnetic field of an end face of said cylindrical permanent magnet which faces said support, said permanent magnet being provided with a 4p-pole magnetization at said end face.

Claim 17

A self-starting brushless d.c. motor as claimed in claim 6, characterized in that the energizing circuit comprises a shift register.

Claim 18

A self-starting brushless d.c. motor as claimed in claim 16, characterized in that the shift register has an adjustable shifting direction.

Claim 19

A self-starting brushless DC motor as claimed in claim 1 wherein, the detection device comprises a magnetic member rotatable in synchronism with the rotor and having at least first and second pole pairs each comprising a north (N) and a south (S) pole, the one detector comprises a magneto-sensitive element responsive to said N and S poles to produce first and second signals corresponding to said N and S poles, respectively, wherein the energizing circuit has at least first and second states in which it supplies current to first and second phase windings of the stator, respectively, and wherein the presetting circuit includes a polarity detector for deriving signals indicative of the polarity (N or S) of said signals of the magneto-sensitive element, and a logic circuit responsive to said polarity signals and to signals indicative of the state of the energizing circuit to derive further signals for changing the state of the energizing circuit to produce rotation of the motor.