GB2184895A

GB2184895A - Retaining bearing guard plate relative to electric motor rotor

Info

Publication number: GB2184895A
Application number: GB08630715A
Authority: GB
Inventors: Claus Schaffer; Gerhard Welle; Oskar Zimmer
Original assignee: Berger & Co Gerhard GmbH
Current assignee: Berger & Co Gerhard GmbH
Priority date: 1985-12-23
Filing date: 1986-12-23
Publication date: 1987-07-01
Anticipated expiration: 2006-12-23
Also published as: FR2594608A1; GB2184895B; FR2594608B1; DE3545886A1; DE3545886C2; GB8630715D0; CH672700A5

Abstract

A rotor for an electric motor with a spindle (3) journalled in bearings has a non circular guard plate (5) mounted between the bearings (4) and the rotor. This guard plate (5) is positively connected (Fig. 3) to the rotor in the direction of rotation in order to prevent relative movements between the disc and the rotor and is also secured to the rotor (Fig. 2,3) in order that the rotor can be prefabricated together with the guard plates (5) as a complete unit. <IMAGE>

Description

SPECIFICATION Rotor for an electric motor The invention relates to a rotor for an electric motor, particularly a permanent magnet rotor, preferably for synchronous or stepping motors, having a spindle mounted in bearings with a guard plate provided between the bearings and the rotor.

Rotors of this kind are known. During rotation, there should be no direct contact between the core of the rotor and the bearings, in order to prevent any abrasion in this region.

For this reason, a guard plate is incorporated between the rotor and the bearings in rotors journalled both at one end and at both ends.

These guard plates may cause noise during movement relative to the rotor and particularly during assembly and in the case of permanent magnet rotors during magnetisation having regard to, the guard plates involves considerable extra work. On account of the guard plates and possibly also a compression spring in the region of the rotor, further processing with automated equipment is virtually impossible.

The aim of the invention is therefore to provide a rotor of the kind mentioned hereinbefore which simplifies handling during final assembly or during any magnetisation required to such an extent that automated machinery can be used. Moreover, the quietness of the motor should be improved.

The solution to this problem consists essentially in the fact that the guard plate is positively coupled to the rotor in the direction of rotation and is secured in position on the rotor. As a result, this guard plate (or, in the case of a rotor journalled at both ends, both guard plates) can be connected to the rotor beforehand so that the assembly can subsequently be handled as much as necessary without having to give any thought to the guard plates to be provided between the rotor and the bearings. Moreover, relative movements between the plates and the rotor are avoided and consequently noise is prevented.

It is convenient if the guard plate is noncircular and is a positive circumferential fit in a similarly outlined recess in the end face of the rotor.

Preferably the outline of the guard plate is a circle interrupted by at least one, preferably three, flattened portions.

It is particularly advantageous, particularly during assembly or during any magnetisation, if the guard plate is positively connected to the rotor in the axial direction leading away from the rotor. This ensures that the guard plate cannot be iost from its operational position during assembly or other handling of the rotor.

Thus in a preferred construction a recess for the guard plate is of a depth greater than the thickness of the guard plate and on the edge of the recess there is at least one deformation, preferably a plurality of deformations distributed around the circumference, which project over the outside of the guard plate and are preferably formed after the guard plate has been inserted in the recess.

Other preferred features of the invention will be apparent from the following description, by way of example, of a preferred embodiment thereof with reference to the accompanying drawings wherein: Figure 1 shows a fully assembled electric motor with a rotor according to the invention, Figure 2 shows a longitudinal section through the rotor with the spindle and guard plates provided at both ends and positively secured, whilst a compression spring is also provided at one end, and Figure 3 shows an end face of the rotor as shown in Fig. 2 with a guard plate having a non-circular outline.

An electric motor, has a rotor which, particularly in the case of a synchronous or stepping motor, could be a permanent magnet rotor.

In the embodiment shown, the rotor has a spindle 3 journalled in bearings at both ends, whilst according to Fig. 1 there is a guard plate 5 provided between the bearing 4 (for example a sintered bearing) and the rotor.

Figs. 2 and 3 in particular show that the guard plates 5 are shaped so as to be positively coupled to the rotor in the direction of rotation and are secured in position on the rotor in a manner which will be described hereinafter.

Fig. 3 in particular shows that the guard plate 5 is non-circular and positively fits with its circumference into a similarly outlined recess 6 in the end face of the rotor. The guard plates 5 are also positively connected to the rotor 5 in the axial direction leading away from the rotor, as will be explained hereinafter.

According to Fig. 3, the outline of the guard plate 5 is a circle interrupted by at least one flattened portion, in this embodiment three flattened portions 7. This helps the rotational symmetry of the motor on the one hand but also makes it possible to fit the guard plates 5 positively in similarly outlined recesses 6.

The flattened areas 7 of the circumference are connected by arc portions 8.

Figs 1 and 2 show that the recesses 6 of the rotor in which the guard plates 5 are positively retained are deeper than the thickness of the guard plates 5 warrant. Consequently, there is a certain degree of protrusion relative to the guard plates at the end faces of the rotor, but the bearings 4 project up to the plates.

The above mentioned protrusion of the recesses 6 is connected with the positive securing of the guard plates 5 in the axial direction.

At least the core 9 of the rotor located di rectly on the spindle 3 may conveniently consist of plastics or an aluminium alloy and the recess 6 for receiving the guard plate 5 is provided in the plastics or in the aluminium alloy. At the edge of the recess 6 there is at least one deformation, or in the embodiment shown three deformations 10 distributed around the periphery, which engage over the outside of the guard plate 5 and are conveniently formed after the guard plate 4 has been inserted. The deformations 10 in the core 9 of the rotor may project over the outer end of the guard plate 5, preferably at the arc portions 8, as shown in Fig. 3.

In a particularly preferred and important embodiment of the invention, the core 9 of the rotor has within it, near an end face, an integrally formed tube 11 with a recess for the insertion of a compression spring 12, the tube 11 being shorter than the compression spring 12 itself. At an axial spacing from the end space of the tube 11, also within the core 9 of the rotor, the guard plate 5 is simultaneously mounted as the outer abutment for the compression spring 12. Thus, in this case, the guard plate 5 has a double function, on the one hand holding the compression spring 12 which prevents axial play and on the other hand performing its guarding function with the associated bearing 4.

The core 9 of the rotor 2 projects radially beyond the magnetisable sleeve 13 at the end face of the rotor and, in relation to its external diameter, is enlarged in the form of a flange 14 in this projecting area, although the flange 14 does not project beyond the diameter of the sleeve in this instance. The core 9 of the rotor has annular recesses 15 extending into its interior from both end faces, these recesses 1 5 being reinforced by ribs 16 in the embodiment shown. The guard plate 5 which is not supported by the compression spring 12 abuts on both edges of the annular recess 15 in order to achieve a good supporting effect.

It should also be mentioned that the rotor may also be integrally formed from plasticsfilled magnetic material. In this case, components 9 and 13 would be a single component.

Fig. 2 in particular shows that the entire rotor is a very simple component as a whole, althiough it has guard plates 5 at both ends and a compression spring 12 inside it. Since the guard plates are positively connected, there are, in particular, no relative movements between these guard plates 5 and the rotor itself or the core 9 of the rotor, which means that there is no noise caused by relative movement and no abrasion of the rotor. This also applies to the compression spring 12 and its mounting, which cannot perform any movement relative to the rotor or its core. Thus, the design of the rotor according to the invention not only makes it easier to handle but also avoids undesirable noise.

It will thus be appreciated that the present invention provides a rotor in which the guard plates and any springs provided are prevented from falling out, so that the rotor can be prepared as a complete unit, thus making further handling considerably easier. More particularly, automatic handling equipment can be used, and in the case of a rotor requiring magnetisation, this may be done by means of a robot.

Furthermore, individual parts may be kept to a minimum.

Claims

1. A rotor for an electric motor, particularly a permanent magnet rotor, preferably for a synchronous or stepping motor, said rotor including a spindle to be journalled in a motor bearing adjacent to one end of the rotor, a guard plate being provided for the bearing, the guard plate being positively coupled to the rotor in the direction of rotation and being secured in position on the rotor.

2. A rotor as claimed in claim 1 wherein the guard plate is positively connected to the rotor in the axial direction leading away from the rotor.

3. A rotor as claimed in claim 1 or 2 wherein a recess is provided in the end of the rotor to receive the guard plate.

4. A rotor as claimed in claim 3 wherein the guard plate is non-circular and its periphery fits positively into a the recess in the end face of the rotor which is similarly outlined.

5. A rotor as claimed in claim 4, wherein the outline of the guard plate is a circle interrupted by at least one flattened portion, preferably three flattened portions.

6. A rotor as claimed in claim 4 wherein flattened areas of the periphery of the guard plate are connected by arc portions.

7. A rotor as claimed in any of claims 3 to 6 wherein the guard plate is positively retained in the recess of the rotor, the depth of this recess being greater than the thickness of the guard plate.

8. A rotor as claimed in claim 7 wherein on the edge of the recess there is at least one deformation, preferably a plurality of deformations distributed around the circumference, which project over the outside of the guard plate and are preferably formed after the guard plate has been inserted in the recess.

8. A rotor as claimed in claim 8 wherein the deformations project over the outer edge of the guard plate, preferably over an arc portion of the guard plate.

10. A rotor as claimed in any of the preceding claims wherein the rotor core comprises within it, near an end face, an integrally formed tube or the like with a recess for the insertion of a compression spring, this recess being shorter than the compression spring, the guard plate being also provided within the ro tor core as an outer abutment for the compression spring, at an axial spacing from the end face of the tube which is provided in and terminates inside the rotor core.

11. A rotor as claimed in any preceding claim wherein the core of the rotor projects beyond a magnetisable sleeve of the rotor at the end face of the rotor and is constructed as a flange with respect to its external diameter in the projecting region.

12. A rotor as claimed in any preceding claim wherein the rotor core has annular recesses projecting into its interior from both end faces, these annular recesses being reinforced by ribs and a further guard plate at the other end of the rotor, said further guard plate abuting on both edges of the annular recess at that end of the rotor.

13. A rotor as claimed in any of the preceding claims, wherein the rotor body is integrally formed from magnetic material filled with plastics.

14. A rotor as claimed in any of claims 1 to 12 wherein at least a core of the rotor located directly on the spindle consists of plastics, an aluminium alloy or similar material.

15. A rotor for an electric motor substantially as herein described with reference to Figs. 2 and 3 of the accompanying drawings.

16. An electric motor substantially as herein described with reference to Figs. 1 to 3 of the accompanying drawings.