This invention relates to a DC motor with brushes, having a rotor comprising an axle and packets of soft-iron lamellas perpendicular to the axle and constituting poles, coils of conducting wire are provided on the poles, and the wire terminals are attached to a collector, the rotor is within a cylindrical housing with permanent magnets fastened on its in¬ ner surface.

Hungarian patent HU 193 867 disclosed an electric motor with external rotor assembly excited by permanent magnet, in which the rotor forming the outer housing as well has an inner surface on which perma¬ nent magnets are fastened, and these magnets are used at the same time to control the motor. Manufacturing the electric motor according to this patent is sophisticated and requires considerable costs. German patent DE 3 807 377 disclosed an enhanced electric motor which comprises magnets in both its rotor and its stator, used to¬ gether with electromagnets. The combination of magnets and electro¬ magnets is intended to produce enhanced torque.

German patent DE 3 636 376 had as its object to provide a loss- free electric motor. Attaining this aim seemed to be unrealistic. In this embodiment the inventors tried to overcome the troubles with a rotary magnet assembly in which the turning of the permanent magnets to the left and to the right takes place by electromagnets excited through a left run- braking ring and a right run-braking ring.

The object of the presented invention is to provide an electric motor of enhanced efficiency which can be manufactured easily by con¬ ventional means and constructed of conventional components.

The invention is based on an observation that by attaching distinct layers of magnets to each other, for example by adhesive, one can ob¬ tain greater torque, which can further be enhanced when the magnets are combined to ferrite-magnets and steel-magnets, and even further enhance when the steel-magnets are shared into further segments.

The DC motor according to the invention applied with brushes, has a rotor comprising an axle and packets of soft-iron lamellas perpen¬ dicular to the axle and constituting poles, coils of conducting wire are provided on the poles, and the wire terminals are attached to a collector. The rotor is within a cylindrical housing with permanent magnets fas¬ tened on its inner surface. The permanent magnets are arranged in at least two layers, where a first layer of a single piece and a second layer of several segments extending parallel to the longitudinal direction of the axle are arranged. The length of the segments are equal to that of the first layer taken in the longitudinal direction of the axle, and the width of the segments are of uniform 1/n share of the ring constituted by the segments, where n is identical to the number of poles if that number is even, or is greater by one than the number of poles if that number is odd. The number of the segments is two less than the number of poles in the case of ten or less poles, or four less than the number of poles in the case of more than ten poles. The segments are arranged in two groups in axial symmetry where the width of the first layer is defined by

the central angle of the segments attached to each other and to the first layer. The first layer is attached to the inner surface of the housing by adhesive.

Preferably the first layer is made of ferrite-magnet, and the seg- ments of the second layer are made of steel-magnet.

In a preferred embodiment a third layer of a single piece is pro¬ vided between the rotor and the segments of the second layer, which has a length equal to those of the two groups, has a width defined by the central angle of the segments, made of ferrite-magnet, and attached to the second layer by adhesive.

Advantageously, the poles of the layers in each group are of the same sequence in direction perpendicular to the axle.

Working aspects of the motor according to the invention will be apparent from the description based on the following drawings. Figure 1 shows a cross-section of a motor with a rotor of 12 poles and having groups of magnets in two layers,

Figure 2 shows a cross-section of a motor with a rotor of 8 poles having groups of magnets in two layers,

Figure 3 shows a cross-section of a motor with a rotor of 12 poles having groups of magnets in three layers,

Figure 4 shows a cross-section of a motor with a rotor of 11 poles and having groups of magnets in two layers,

Figure 5 shows a cross-section of a motor with a rotor of 7 poles and having groups of magnets in two layers.

The structure of the motors illustrated in the Figures are very similar. Conventional elements, such as rotor 4 and housing 2 of motors well-known from the art are kept in unchanged form, i.e. rotor 4 is con¬ structed of packets of soft-iron lamellas stowed by their plane surface and these packets are mounted perpendicularly to an axle 1. The soft- iron lamellas of the rotor 4 constitute poles 3, onto which coils of con¬ ducting wire are provided. In a conventional manner, the wire terminals are attached to a collector. Voltage is applied to the collector through carbon brushes. Housing 2 is made of steel with the axle 1 built on bearings in its centre. The difference between the shown motors and the prior art motors lies in the construction and arrangement of the magnets.

The permanent magnets have been attached by an adhesive or glue to the inner surface of the housing 2, in the height of the soft-iron lamellas of the rotor 4, at least in two layers. The first layer 5 is made of a single piece while the second layer 6 is constructed of several seg¬ ments 7. The length of the segments 7 are equal to that of the first layer 5 taken in the longitudinal direction of the axle 1 , and the width of the segments 7 are of uniform 1/n share of the ring constituted by the seg¬ ments 7, where n is identical to the number of poles 3. The number of the segments 7 is two less than the number of poles 3 in the case of ten or less poles 3 (as shown in Figure 2 for 8 poles 3), or four less than the number of poles 3 in the case of more than ten poles 3, as shown in Fig¬ ure 1 for 12 poles 3. If the number of poles 3 is odd, the ring constituted by the segments 7 should be split into n shares in such a way that n should be greater by one than the number of poles 3, and then a plurality

of segments 7 of length of arch likewise obtained are to be arranged where the plurality of the segments 7 is two less than the number of

poles 3 in the case of ten or less poles 3, or four less than the number of

poles 3 in the case of more than ten poles 3, as it has been illustrated in Figures 4 and 5.

It is also apparent from the drawings that magnet segments 7

have been placed fully adjacent to each other in two groups in axial

symmetry, where the width of the first layer 5 is defined by the central

angle ∞ of jointed segments 7 of a group, attached preferably by adhe-

sive to each other and to the first layer 5. The first layer 5 is also fixed to

the inner surface of the housing 2 by adhesive or glue. The first layer 5 is made of ferrite-magnet, while the segments 7 of the second layer 6 are made of steel-magnet. The polarity of the magnets are identified con¬ ventionally by S and N in the Figures.

Figure 3 shows an embodiment in which a third layer 8 of a single piece is provided between the rotor 4 and the segments 7 of the second layer 6, which has a length equal to those of the groups, and has a width

defined by the central angle o of the segments 7, made of barium-ferr ite-

magnet, and attached to the second layer 6 by adhesive.

In all embodiments the poles of the first layers 5, second layers 6 and third layers 8 in each constituted group are of the same sequence in direction perpendicular to the axle 1 .

To serve the purpose of adhesive or glue, any synthetic adhesive material can be applied, deposited in about 0.1 mm thickness between the surfaces to be attached.

This motor operates similar to the known motors, but yields higher efficiency. This is due partly to the steel-magnet material of the seg¬ ments 7, and partly to the considerable magnetic field enhancement between the adjacent glued segments 7. The function of barium-ferrite- magnets constituting the first layers 5 and optionally the third layer 8, beyond strengthening the magnetic field, is to prevent demagnetisation of segments 7 in the second layer 6 by draining off eddy currents, which would otherwise demagnetise the steel-magnets. In conclusion the en¬ hanced efficiency is due to the steel-magnet and to its arrangement, and the appropriate effect of the steel-magnet in ensured by the barium- ferrite-magnets. A real motor according to the embodiment in Figure 1 has a working voltage range of 6-80 V, while the load current is 0.01-1 A, and at the peak values the speed is 60,000 rpm.

The main advantages of the DC motor according to the invention lies in the higher efficiency than can be produced by the known type motors and in the ability to work within a very wide voltage range. The rotation speed is actually limited only by the quality of the mechanical components.