Patent ID: 8319469

Claim:
A brushless electric machine, comprising: a first drive member having Q permanent magnets where Q is an integer; a second drive member having a first face, a second face, and a plurality of electromagnetic coils, and capable of movement relative to the first drive member, the first drive member being separated from and opposite to the first face of the second drive member; a third drive member having a fixed relative positional relationship with the first drive member, the third drive member being separated from and opposite to the second face of the second drive member; a magnetic sensor, disposed on the second drive member, for detecting relative position of the first and second drive members; and a control circuit for controlling operation of the brushless electric machine, based on an output signal of the magnetic sensor; wherein the third drive member has at locations facing the permanent magnets of the first drive member a plurality of magnetic field strengthening members for strengthening the magnetic field at the location of the second drive member in conjunction with the permanent magnets; wherein the plurality of electromagnetic coils have two coil groups for two phases including a first coil group and a second coil group, each coil group including N electromagnetic coils, where N is an integer equal to or greater than 1; the first coil group is disposed on the first face of the second drive member but not on the second face, the second coil group is disposed on the second face of the second drive member but not on the first face, the first coil group and the second coil group are disposed with a phase difference of π/2 between each other, the control circuit drives the two coil groups with a phase difference of π/2 such that the two coil groups simultaneously generate a driving force; and the number Q of permanent magnets is equal to the number N of electromagnetic coils of each coil group.