Electric motor having frequency generator

An electric motor comprising:

• a yoke made of a magnetic material;
• a rotary shaft rotatably carried by said yoke;
• a disk-shaped multipolar magnet connected to said rotary shaft and sectioned to have a plurality of magnetic poles;
• a pair of driving coils mounted on said yoke and having a plurality of driving portions interlinking with magnetic flux of said magnet, one of said pair of driving coils being supplied with a first a.c. driving current and producing at the driving portions thereof a driving magnetic field interlinking with the magnetic flux of said magnet for driving said magnet, the other of said pair of driving coils being supplied with a second a.c. driving current, the phase of which is 90.degree. different from that of the first a.c. driving current, and producing at the driving portions thereof a driving magnetic field interlinking with the magnetic flux of said magnet for driving said magnet;
• a speed detecting coil disposed in the magnetic field of said magnet having series-connected generating wire elements, the number of said generating wire elements being 2n + 1 for each of said magnetic poles, where n is a positive integer, whereby a signal having a frequency corresponding to a revolution speed of said magnet is obtained in said speed detecting coil;
• and
• a frequency generator constituted by said speed detecting coil and said magnetic poles and producing a signal having a frequency corresponding to a rotational speed of said motor.

An electric motor having a frequency generator capable of producing a signal having a frequency corresponding to the revolution speed of said motor comprising:

• a yoke made of a magnetic material;
• a rotary shaft rotatably carried by said yoke;
• a disk-shaped multipolar magnet connected to said rotary shaft, said magnet being sectioned to have a plurality of magnetic poles;
• first and second star-shaped driving coils angularly displaced with respect to one another on said yoke and each having a plurality of driving portions interlinking with the magnetic flux of said magnet,
• said first driving coil being supplied with a driving a.c. current of sine wave and producing at the driving portions thereof a driving magnetic field interlinking with the magnetic flux of said magnet for driving said magnet,
• said second driving coil being supplied with a driving a.c. current of cosine wave and producing at the driving portions thereof a driving magnetic field interlinking with the magnetic flux of said magnet for driving said magnet;
• a speed detecting coil non-rotatably disposed within the magnetic field of said magnet and having series-connected generating wire elements, the number of said generating wire elements being 2n + 1 for each of said magnetic poles, where n is a positive integer, whereby a signal having a frequency corresponding to the rotational speed of said magnet is obtained in said speed detecting coil;
• and
• means for controlling said driving currents in accordance with the signal having a frequency corresponding to the rotational speed of said magnet and obtained from said speed detecting coil.

An electric motor having a frequency generator comprising:

• a yoke made of a magnetic material;
• a rotary shaft rotatably carried by said yoke;
• a disk-shaped multipolar magnet connected to said rotary shaft, said magnet being sectioned to have a plurality of magnetic poles, said magnetic poles being magnetized so that adjacent ones of said poles have different polarities;
• a first driving coil mounted on said yoke and supplied with a driving a.c. current of sine wave to produce a driving magnetic field interlinking with the magnetic flux of said magnet for driving said magnet;
• a second driving coil displaced at an angle of 22.5.degree. and arranged concentrically with respect to said first driving coil, said second driving coil being supplied with a driving a.c. current of cosine wave to produce a driving magnetic field interlinking with the magnetic flux of said magnet for driving said magnet;
• and
• a speed detecting coil disposed within the magnetic field of said magnet, said speed detecting coil having series-connected generating wire elements, the number of said generating wire elements being 2n + 1 for each of said magnetic poles, where n is a positive integer, whereby a speed detecting signal having a frequency corresponding to the rotational speed of said magnet is obtained in said speed detecting coil.

An electric motor having a frequency generator comprising:

• a first yoke made of a magnetic material;
• a bearing secured to said first yoke;
• a rotary shaft rotatably supported by said bearing;
• a second yoke secured to said rotary shaft and spaced from and oppositely to said first yoke;
• a disk-shaped multipolar magnet secured to said second yoke and spaced from said first yoke, said magnet being adapted to rotate with the rotation of said rotary shaft and said second yoke;
• eight magnetic poles formed by radially dividing said magnet into eight sections, adjacent ones of the sections being magnetized to have different polarities;
• an insulating plate disposed between said first yoke and said magnet and secured to said first yoke;
• first and second driving coils each provided with a plurality of driving portions and superimposed on said insulating plate so that the driving portions thereof form an angle of 22.5.degree. therebetween, said first driving coil being supplied with an a.c. driving current of sine wave and producing at the driving portions thereof a first driving magnetic field interlinking with the magnetic flux of said magnet for driving said magnet, and said second driving coil being supplied with an a.c. driving current of cosine wave and producing at the driving portions thereof a second driving magnetic field interlinking with the magnetic flux of said magnet for driving said magnet in the same direction as that driven by said first driving magnetic field;
• and
• a speed detecting coil opposite to said magnet and mounted on said insulating plate, said speed detecting coil having 2n + 1 series-connected generating wire elements for each of said magnetic poles and which radially extend from the center of said rotary shaft, where n is a positive integer, whereby a signal having a frequency corresponding to the rotational speed of said magnet is obtained in said speed detecting coil.