Electric machine
View Patent ↗A two-phase electric motor includes first and second coil groups and a magnet group. In the magnet group, N poles and S poles are disposed alternatively opposite the first and second coil groups. The first and second coil groups are disposed at positions that are out of phase with each other by an odd multiple of π/2 in electrical angles. The coils of the first and second coil groups have substantially no magnetic material cores, and the electric motor has substantially no magnetic material yoke for forming a magnetic circuit.
1. An electric machine comprising:
a coil group including a plurality of electrically interconnected coils disposed along a predetermined direction at a predetermined pitch;
a magnet group including at least one magnet, wherein N poles and S poles are disposed alternately opposite the coil group and a relative position of the magnet group with the coil group is changeable along the prescribed direction;
a magnetic sensor associated with the coil group, the magnetic sensor being configured to detect magnetic flux change due to movement of the magnet group to thereby generate a sinusoidal output signal; and
a drive signal generation circuit that executes PWM control based on the sinusoidal output signals of the magnetic sensor to thereby generate an AC drive signal to be supplied to the coil group,
wherein the drive signal generation circuit generates the AC drive signal so that polarity of each coil in the coil group are switched when center of each coil is opposite to one of centers of the magnets in the magnet group, and that magnetic flux density in the coil group reaches a maximum value at a timing when midway points between two adjacent coils in the coil group are opposite to the centers of the magnets in the magnet group,
wherein the drive signal generation circuit includes:
a PWM circuit for generating a PWM signal; and
a masking circuit for generating the signal AC drive signal by masking the PWM signal according to an output demand of the electric machine, and
wherein the masking circuit masks the PWM signal in temporal ranges that are symmetrically centered around a timing at which polarities of the AC drive signal are inverted while maintaining the PWM signals in other temporal ranges that are symmetrically centered around peaks of the AC drive signal.
2. An electric machine according to claim 1 , further comprising a case for housing the coil group and the magnet group,
wherein each of the coils in the coil group is wound around a support member formed from a substantially nonmagnetic and non-electroconductive material, and
the case is formed from a substantially nonmagnetic and non-electroconductive material.
3. An electric machine according to claim 1 , wherein structural members with exception of shafts and bearings are formed from substantially nonmagnetic and non-electroconductive material.
4. An electric machine according to claim 1 , wherein
the plurality of coils in the coil group are interconnected in such a manner that adjacent coils belonging to the coil group are always excited with mutually opposite polarities.
5. An electric machine according to claim 1 , wherein
the electric machine is a rotary motor or a rotary generator, in which the coil group and the magnet group rotate relative to each other in accordance with the predetermined direction, and
the number of coils in the coil group, and the number of magnets in the magnet group are equal to each other.
6. An electric machine according to claim 1 , wherein
the drive signal generation circuit reverses an operation direction of the coil group and the magnet group by reversing the electric current direction in the coil group.
7. An electric machine according to claim 1 , further comprising:
a regenerative circuit for regenerating electric power from the coil group.
8. An electric machine according to claim 1 , wherein
the coil group is disposed on a first cylindrical member constituting a hollow double-wall cylindrical structure,
and the magnet group is disposed on a second cylindrical member coaxial with the first cylindrical member.