DE9106990U1 - Small electric motor for driving additional units in motor vehicles - Google Patents

Description

No. 24432
4.6.1991 Sa/Kc

ROBERT BOSCH GMBH, 7000 Stuttgart 10

Small electric motor for driving additional units in motor vehicles

State of the art

The invention is based on a small motor according to the type of the main claim. There is already such a small motor on the market that causes undesirable noises during operation. This is because when the motor is running, the so-called armature teeth located between the longitudinal grooves always enter or leave the field perpendicular to the field line.

Advantages of the invention

The small motor according to the invention with the characterizing features of the main claim has the advantage that the arrangement of the soft iron tube changes the field line path in such a way that the armature teeth enter or leave the field at an acute angle to the field lines, which causes a significant reduction in noise.

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The measures listed in the subclaims enable advantageous further developments and improvements of the small engine specified in the main claim.

drawing

An embodiment of the invention is shown in the drawing and explained in more detail in the following description. Figure 1 shows a schematic representation of a cross section through a small motor excited by a permanent magnet, cut in the area of its armature package, Figure 2 shows a reduced representation of a partially cut soft iron tube and Figure 3 shows a view of a motor armature belonging to the soft iron tube according to Figure 2.

Description of the embodiment

A permanent magnet-excited direct current motor 10, shown schematically in cross section in Figure 1, has a return pipe 12, on the inner wall 14 of which two segment-shaped permanent magnets 16, 18 are arranged opposite one another. A roller-shaped motor armature 20 is rotatably mounted within the return pipe 12. The motor armature is mounted in a manner known per se in bearing plates attached to the front of the return pipe 12, which are not shown in the drawing. The motor armature 20 is provided with an armature shaft 22 (Figure 3) which carries a laminated core 24. The laminated core 24 is connected to the motor shaft 22 in a rotationally fixed manner. The laminated core also has a number of longitudinal grooves 26 arranged at a distance from one another in the circumferential direction, in which the armature winding 28 of the motor armature 20 is located. So-called armature teeth 30 remain between the longitudinal grooves 26. A ferromagnetic

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magnetic tube 40 is applied, which is shown separately in Figure 2. Figure 1 shows the motor armature 20 with the tube 40 mounted. An air gap remains between the outer surface 41 of the tube 40 and the inner curved surface 43 of the permanent magnets 16, 18, which is designated 42 in Figure 1. The arrangement of the soft iron tube 40 on the laminated core 24 covers the armature teeth 30 from the magnet segments 16. This changes the field line path, which is caused and directed by the permanent magnets 16, 18, the laminated core 24 and the return ring 12, in the area of the armature teeth 30 so that they enter the magnetic field at a very acute angle and leave it again when the motor is running. This results in a significant reduction in motor noise.

The idle losses caused by the soft iron ring 40 can be kept small by the geometry of the ring, i.e. by its length, its thickness and/or the arrangement of grooves, so that these losses hardly play a role in practical operation. The soft iron ring 40 can be designed as a finished pipe section. In the embodiment shown in Figure 2, the soft iron pipe 40 is rolled from a plate-shaped sheet metal section and the two adjacent sheet metal edges 44 and 46 are interlocked with one another, as is generally known for return pipes and is disclosed in US Pat. No. 2,283,918. The finished soft iron pipe 40 can be connected to the sheet metal package 24 of the motor armature 20 in a variety of ways. For example, it is conceivable to press the pipe onto the sheet metal package 24 of the motor armature 20 in the direction of arrow 48 (Figure 2). Other fastening options are also available by welding, gluing, clamping or other deformations of the soft iron tube 40 on the outer surface 32 of the sheet stack 24. It is also conceivable to roll the plate-shaped sheet section directly onto the sheet stack 24 according to a method described in DE-OS 28 10 215 and

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to latch there. Usually, viewed in the direction of the axis of rotation of the motor armature 20, the length 50 of the soft iron tube 40 is matched to the length 52 of the laminated core 24. For the reasons mentioned above, however, it is also conceivable to make the soft iron tube 40 longer or shorter than the laminated core 24.

The above-mentioned publications are hereby expressly incorporated by reference, so that the disclosures from these publications, with regard to the features of interest here, become the disclosure of these application documents.

Claims (6)

R. 24432 4.6.1991 Sa/Kc ROBERT BOSCH GMBH, 7000 Stuttgart 10 Claims 1. Small electric motor for driving additional units in motor vehicles, with a housing part which acts as a magnetic yoke and is tubular in cross section at least over a longitudinal section, on the inner wall of which segment-shaped, field-generating permanent magnets are arranged opposite one another, which surround a roller-shaped motor armature which is rotatably mounted in the motor housing in sections in the direction of rotation at a radial distance, and the motor armature has a laminated core made up of a large number of sheet metal disks, which is provided with longitudinal grooves which are open to the roller shell, receive the armature windings and are arranged at a distance from one another in the circumferential direction, characterized in that the roller shell (32) of the laminated core (24) is surrounded by a ferromagnetic tube (40) which is connected to the laminated core in a rotationally fixed manner. 2. Small motor according to claim 1, characterized in that the soft iron tube (40) is rolled from a plate-shaped sheet metal section and that the two plate edges (44, 46) facing each other are interlocked with each other. - 2 - 24432 3. Small motor according to one of claims 1 or 2, characterized in that the finished tube (40) is pressed onto the laminated core (24). 4. Small motor according to one of claims 1 or 2, characterized in that the finished tube (40) is welded to the laminated core (24). 5. Small motor according to claim 2, characterized in that the plate-shaped sheet metal section is rolled around the sheet metal package (24) and latched. 6. Small motor according to one of claims 1 to 5, characterized in that the length of the tube (40) measured in the direction of the axis of rotation of the motor armature (20) is matched to the length of the laminated core (24).