Motor with motor parts which are movable relative to one another

Details Motor with motor parts which are movable relative to one another Motor with motor parts which are movable relative to one another

1997-07-21

1999-06-15

Ramirez, Nestor

Electrical generator or motor structure

Dynamoelectric

Rotary

310156, 310157, 310187, 310 51, 310269, H02K 700

Patent

active

059125152

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to a motor having motor parts which are movable relative to one another, of which the first motor part forms a multi-pole excitation field in an air gap by means of a permanent magnet with 2p magnet poles and of which the second motor part is a yoke having a number T of pole teeth which project towards the air gap and which carry exciter coils and are spaced by pole gaps.
Such motors are known as rotary motors, for example, from DE 28 23 208 C2 and from DE 31 22 049 C2. In such motors a detent torque is produced as a result of the interaction between the magnetized poles of the permanent magnet and the pole teeth of the yoke. This detent torque is usually undesirable because it may give rise to unwanted oscillations. The order of the fundamental frequency of the torque follows from the least common multiple of the number of magnet poles 2p and the number of teeth T and should be as large as possible because the amplitude of this undesirable torque decreases as the order increases. Accordingly, there are motors having large detent torques and motors having small detent torques on account of the number of magnet poles 2p of the permanent magnet and the number of pole teeth T. A motor having a pole-pair number 2p=2 and a tooth number T=3 will have a detent torque with a fundamental frequency of the order 6. The amplitude of the detent torque is consequently comparatively high. DE 28 23 208 C2 describes how such detent torques can be reduced by indentations in the pole teeth.
However, there are also motors which on account of their magnet pole number 2p and tooth number T already have a small detent torque without such additional measures. For example, the detent torque of a motor having a magnet pole number 2p=8 and a tooth number T=9 has a fundamental frequency of the order 72. Therefore, the amplitude of the detent torque of such a motor is very low. However, a problem associated with such a motor is that it is not symmetrical, i.e. the magnetic field in the air gap is not symmetrical. As a result, radial forces are exerted on the rotating motor part of the motor. For example, if a magnet pole of such a motor directly faces a pole tooth across the air gap, the magnet pole which is 180.degree. shifted in the circumferential direction faces a pole gap, as a result of which the radial forces between the two motor parts no longer cancel one another.


SUMMARY OF THE INVENTION

It is an object of the invention to construct a motor of the type defined in the opening paragraph so as to reduce or eliminate radial forces produced as a result of asymmetrical magnet fields in the air gap.
According to the invention this object is achieved in that, in the case of motors in which the number 2p of magnet poles and the number T of pole teeth do not have a common submultiple greater than 1, the pole teeth each have an auxiliary slot in their centers at the side facing the air gap.
Radial forces always occur if the magnetic field in the air gap has no symmetry. The magnetic field in the air gap is asymmetrical if, viewed in the circumferential direction, the magnetic field recurs periodically only after 360.degree.. This is the case if the number of magnet poles and the number of pole teeth do not have a common submultiple greater than 1 because the periodicity is exactly 360.degree. divided by the greatest common divisor.
Practical examples of motors of this type include motors having three pole teeth and two magnet poles, three pole teeth and four magnet poles and nine pole teeth and eight magnet poles.
Since the number of magnet poles 2p is always even radial forces can occur only in the case of an odd number T of pole teeth in the above arrangements. If each tooth is provided with an auxiliary slot in its center at the side facing the air gap, this will cause the number of openings of the yoke directed towards the air gap to be doubled, i.e. T pole gaps and T auxiliary slots. This results in symmetrization of the magnetic field in the air gap. If a magnet pole faces a

REFERENCES:
patent: 564703 (1896-07-01), Lamme
patent: 4280072 (1981-07-01), Gotou et al.
patent: 4874975 (1989-10-01), Hertich
patent: 4900963 (1990-02-01), Amano et al.
patent: 4998032 (1991-03-01), Burgbacher
patent: 5382853 (1995-01-01), Von Der Heide et al.

Affiliated with

Also associated with

Rating

Motor with motor parts which are movable relative to one another does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Motor with motor parts which are movable relative to one another, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motor with motor parts which are movable relative to one another will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-404443