Brushless electric machine

1. A brushless electric machine, comprising:

a first drive member having a plurality of permanent magnets;

a second drive member having a plurality of electromagnetic coils, and capable of movement relative to the first drive member;

a third drive member disposed to an opposite side from the first drive member with the second drive member therebetween, and having a fixed relative positional relationship with the first 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, and

wherein the magnetic field strengthening members are ferromagnetic bodies excluding permanent magnets.

2. The brushless electric machine according to claim 1 , wherein

each permanent magnet has a projecting portion which projects towards the second drive member.

3. The brushless electric machine according to claim 1 , wherein

the plurality of electromagnetic coils have M coil groups for M phases, each coil group including N electromagnetic coils, where M is an integer equal to 2 or greater and N is an integer equal to 1 or greater; and

the control circuit drives the M coils groups such that the M coils groups simultaneously generate driving force.

4. The brushless electric machine according to claim 1 , wherein

the magnetic sensor outputs an output signal exhibiting analog change depending on relative position of the first and second drive members.

5. The brushless electric machine according to claim 4 , wherein

the control circuit includes a PWM control circuit for generating a drive signal which simulates the analog change of the output signal of the magnetic sensor, through execution of PWM control utilizing the analog change of the output signal of the magnetic sensor.

6. The brushless electric machine according to claim 1 , wherein

the control circuit includes a regeneration circuit for regenerating power from the magnetic coils.

7. An apparatus, comprising:

a brushless machine according to claim 1 ; and

a driven member driven by the brushless machine.

8. A moving body comprising a brushless machine according to claim 1 .

9. A brushless electric machine, comprising:

a first drive member having a plurality of permanent magnets;

a second drive member having a plurality of electromagnetic coils, and capable of movement relative to the first drive member, the plurality of electromagnetic coils including first-phase coils and second-phase coils;

a third drive member disposed to an opposite side from the first drive member with the second drive member therebetween, and having a fixed relative positional relationship with the first 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, and

wherein the magnetic field strengthening members are ferromagnetic bodies excluding permanent magnets, and

wherein the second drive member further includes a support member having a first surface facing the first drive member and a second surface facing the third drive member, the first-phase coils being fixed on the first surface, and the second-phase coils being fixed on the second surface.

10. A brushless electric machine, comprising:

a first drive member having a plurality of permanent magnets;

a second drive member having a plurality of electromagnetic coils, and capable of movement relative to the first drive member, the plurality of electromagnetic coils including first-phase coils, second-phase coils and third-phase coils;

a third drive member disposed to an opposite side from the first drive member with the second drive member therebetween, and having a fixed relative positional relationship with the first 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, and

wherein the second drive member further includes first and second support members, the first-phase coils being fixed on a surface of the first support member facing the first drive member, the second-phase coils being fixed between the first and second support members, and the third-phase coils being fixed on a surface of the second support member facing the third drive member.

11. The brushless electric machine according to claim 10 ,

wherein the magnetic field strengthening members are ferromagnetic bodies excluding permanent magnets.