US3375383A

US3375383A - Magnetic drive device

Info

Publication number: US3375383A
Application number: US429872A
Authority: US
Inventors: Kenneth W Philbrick
Original assignee: TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1965-02-02
Filing date: 1965-02-02
Publication date: 1968-03-26
Anticipated expiration: 1985-03-26
Also published as: GB1125405A

Description

March 26, 1968 K. w. PHHLBRICZK MAGNETIC DRIVE DEVI GE Filed Feb. 2, 1965 I INVENTOR. KENNETH W. PHILBRICK BY nite ate 3,375,383 Patented Mar. 26, 1968 3,375,383 MAGNETIC DRIVE DEVICE Kenneth W. Philbriclr, Dayton, Ohio, assignor, by mesne assignments, to TRW Inc., Cleveland, Ohio, a corporation of Ohio Filed Feb. 2, 1965, Ser. No. 429,872 6 Claims. (Cl. 310-103) ABSTRACT OF THE DISCLOSURE A magnetic drive device including a central core member of magnetic material which has slots in its outer surface and windings disposed therein. A magnetic yoke ring is placed on the outside of the core member and has a series of serrations on its exterior surface. The core is placed within a housing member which has a serrated ring of magnetic material on its inner suriace, with the serrations of the ring and housing opposed to one another. The number of serrations on the yoke ring and housing are disimil ar, so that when a rotating electromagnetic field is created in the yoke ring, the resulting flux Will cause relative motion between the ring and the housing.

This invention is directed towards a magnetic drive device, and is more particularly concerned with an electromagnetically driven speed changer.

Drive devices of the type with which this invention is concerned have been constructed in which an Alnico magnet has been rotatably mounted within a ring of electromagnetic material, having on its outer surface a series of serrations. These serrations are arranged opposed to another series of serrations mounted within a housing member. In such a device a motor or other external drive means is arranged to rotate the magnet, usually through some geared arrangement, and the rotating magnet will then create a rotating field within the inner set of serrations so as to then cause the outer member to rotate. A gear reduction is obtained by making the outer set of serrations of a lesser number than the inner set of serrations. In such a device it is obvious that the cost thereof is relatively greater than the customary motor/gearbox combination, and also the device is unduly complicated in requiring an additional motive power device for rotating the magnet.

It is therefore one object of the invention to provide a magnetic drive device capable of effecting speed reduction which is economical to manufacture and requires a minimum number of parts. A further object of the invention is to provide a magnetic drive device which does not employ external motive power or external drives. A still further object of the invention is to provide a compact electromagnetically actuated drive device having a minimum number of parts.

These and other objects of the invention will become more readily apparent upon a reading of the description following hereinafter and upon a consideration of the drawings, in which:

FIGURE 1 represents a cross-sectional View taken longitudinally through a device constructed in accordance with the teachings of the invention,

FIGURE 2 represents a cross-sectional view through the device of the invention, taken along lines 22 of FIGURE 1, and

FIGURE 3 represents an enlarged representation of the relationship of the serrations on the driving and driven members of the device of the invention.

The device of the invention employs preferably an AC stator member made of a laminated material and provided with a winding through which alternating current is caused to flow. Thus, a rotating magnetic field is created within the laminations which serves as the primary driver to move the device of the invention. The

employment of a rotating field permits the arrangement of the parts in a smaller size device and further permits 5 the absence of a rotor. Additionally, no mechanical coupling need be provided between a motor shaft and gearbox input. As indicated in the drawings, a lesser number of parts need be employed, since there are omitted additional bearings for the motor and gearbox which normally would be employed. As more clearly indicated in FIG- URE 1, the magnetic drive device 1 comprises an outer housing member 28 which is aflixed to an output shaft 2. The outer housing member 28 is provided with a bore 26 which terminates in a shoulder 32. Pressed into this bore 26 and against the shoulder 32 are a series of laminations 34 which have formed on the inner periphery thereof a series of serrations or teeth 36. A stator or non-rotating member 8 is formed by first assembling a series of l aminations 14 between a pair of

spider members

10 and 12. The 'lamin-ation's 14 are provided with a series of slots 16 into which is disposed a winding 18. The

spider members

10 and 12 accommodate

bearings

4 and 6, respectively, to permit the mounting of the output shaft 2. The stator assembly 8 has pressed on the outside diameter thereof a series of laminations 22 which are formed on their outer surface with a series of teeth 24 extending entirely around the outer circumference thereof. As shown in FIGURE 2 (wherein only a small number of the teeth is indicated), the number of teeth 24 is greater in number than the number of teeth 36. The winding 18 may be immediately extended so that its leads are mounted to a terminal board 20 afiixed to the spider member 12 for a ready connection to a source of electrical power.

The device can be operated on AC or DC current. In the event that an AC winding is employed, then an outof-phase relationship would be established in the current supply to the winding as is normally done in AC motors in order to create a rotating field on the periphery of the magnetic core member 14. Alternately, a series of coils can be provided in the slots 16 which are properly pulsed with DC current in a sequential manner by any wellknown means (not shown) for providing a pulsed input. In any event, a traveling wave is created in the yoke ring 22 and in the teeth 24 thereof.

Assuming that a 4-pole stator 8 is provided, then as indicated in FIGURE 2, the poles would be spaced equidistantly around the circumference of the yoke ring 22. Upon excitation of the winding 18, a series of poles of opposite polarity would be created in the annular member 34 in the area of its serrations 36.

Referring now to FIGURE 3, it is seen that if at a given instant the tooth or serration 24a contains the center of a magnetic field created by the winding 18 in the yoke ring 22, then it will attract the serration or tooth 36a in the annular member 34 and the center lines of these teeth or serrations will be lined up. At this time, the tooth 24b and the tooth 3611 are not in alignment and as shown in FIGURE 3, the center lines of these teeth are separated 'by a distance d. When the traveling or rotating magnetic field within the yoke ring 22 moves so that the center of such field passes from the tooth 24a to the tooth 24b, then the opposite pole centered within the tooth 3611 will tend to align itself with the tooth 24b and the member 34 will be caused to move to the left, as viewed in FIGURE 3, a distance of d. In this manner, as the traveling magnetic field moves from tooth to tooth through the member 22, the member 34 will be caused to move an incremental distance to the left so that a smooth rotational output will be attained at the output shaft 2.

I have found that the most desirable arrangement is that wherein the difference in the number of

teeth

24 and 36 for a speed reducer will be equal to the number of magnetic poles created in the stator 8 or some multiple thereof. Thus, for example, in the species indicated in FIGURE 2 where the four-pole device is depicted, there must be a minimum of four teeth difference between the number of teeth 24 and the number of teeth 36. It is to be noted that in the 4-pole device there will be four teeth on the yoke ring 22 lined up with four teeth on the ring member 34 at all times, and the situation depicted in FIG- URE 3 will occur in four places around the periphery of the yoke ring 22. If the electromagnetic field created in the yoke ring 22 is made strong enough, then there will be no backlash in the device and the device will provide a smooth and positive drive. The speed at which the output shaft 2 will rotate is a function of the speed of the rotating field reduced by a ratio of the difference in the number of teeth between 24 and 36, divided into the smaller number of teeth. In the example shown in FIG- URE 2, the reduction ratio would be the number of teeth 36 divided by the differences in the number of teeth 36 land the number of teeth 24.

As indicated above, the Winding 18 can take many forms and it could be wound for a 3-phase, Z-phase, or a single phase AC; or a commutating device can be provided, and a DC winding employed. Additionally, the number of slots employed in the magnetic core member 14 is not critical.

Although the device shown is arranged so that the outer member 34 is caused to rotate and the inner memher 8 is fixed, the reverse arrangement could be employed wherein theinner member 8 is caused to rotate and the outer member would be fixed. Also it is possible that both members could be mounted for rotation, so that two output shafts would be provided. In any of these arrangements it is necessary only that one of the

members

22 and 34 be caused to rotate relative to the other member.

I have above-described a magnetic drive device in which there has been eliminated a high-speed rotor and electric motor which would normally be employed to provide a rotating magnetic field in the yoke ring 22. And, the device can be thus employed to provide high torque, but slow speed output. Therefore, a longer life can be obtained with fewer number of parts. Although one specific embodiment of the device has been shown in the drawing, it is considered to be obvious that many modifications of the device can be made, some of which have been indicated above, while still coming within the spirit and scope of the invention as set forth in the appended claims.

What I claim is:

1. A magnetic drive device comprising, in combination:

a core member of magnetic material having slots therein;

an electrical winding disposed within said slots;

a yoke ring of magnetic material having a series of serrations on an exterior surface thereof, one other surface thereof being fixed relative to said electrical winding, a housing member having a ring of magnetic material affixed thereto, said ring having a series of serrations on an exterior surface thereof arranged in opposition to the serrations on the said yoke ring; at least one of said housing and core members being mounted for rotation relative to the other member; the number of serrations on said yoke ring and housing ring being dissimilar;

and means for creating a rotating electromagnetic field in said yoke ring in the area of said serrations, whereby the flux created by said field causes relative motion between said yoke ring and said housing ring at a predetermined speed.

2. The magnetic drive device of claim 1 wherein said winding is an AC winding and said last-named means includes means for monitoring an out-of-phase relationship with said winding.

3. The magnetic drive device of claim 1 wherein said winding comprises a plurality of coils and said lastnamed means includes means for sequentially pulsing said coils.

4. A magnetic drive device comprising, in combination:

a core member of magnetic material having slots therein;

an electric winding disposed within said slots;

a yoke ring of magnetic material having a series of serrations on an exterior surface thereof, one other surface thereof being fixed relative to said electrical winding, said yoke ring being mounted upon said core member, a housing member having a ring of magnetic material affxed thereto, said ring having a series of serrations on an exterior surface thereof arranged in opposition to the serrations on the said yoke ring;

an output shaft, said housing member being fixedly mounted upon said output shaft to rotate therewith, the number of serrations on said yoke ring and housing being dissimilar; and means for creating a rotatin'g electromagnetic field in said yoke ring in the area of said serrations, whereby the flux created by said field causes relative motion between said yoke ring and said housing ring at \a predetermined speed.

5. The magnetic drive device of claim 4 wherein said winding is an AC winding and said last-named means includes means for monitoring an out-of-phase relationship with said winding.

6. The magnetic drive device of claim 4 wherein said winding comprises a plurality of coils and said last-named means includes means for sequentially pulsing said coils.

References Cited UNITED STATES PATENTS ROBERT K. SCHAEFER, Primary Examiner. H. O. JONES, Assistant Examiner.