Title of Invention

AN ELECTRIC MACHINE, PARTICULARLY A DIRECT CURRENT MOTOR FOR VEHICLES

Abstract

The present invention is with regard to an electric machine, a direct current motor for vehicles in particular, with a multiple pole stator that has a ring-shaped pole casing (1) and a plurality of magnets (2) that are located at the inner surface of the pole casing (1); and a magnetic chip guard (3) that shields the magnets (2) inwards in a radial direction up to the rotor, whereby the magnetic chip guard (3) is composed of a rectangular pre-cut part, and has an overlapping area (4) that extends along the axial length of 'the magnetic chip guard (3) in the peripheral direction and has a centring ring (8) located at the ends (6, 7) respectively of the magnetic chip guard lying in the axial direction in order to centre the magnetic chip guard (3), the magnets (2) have a pole lift-off (10) and the overlapping area (4) of the magnetic chip guard (3) is located at the pole lift-off (10).

Full Text

Permanently Energised Electric Machine Prior Art The present invention is with regard to a permanently energised electric machine, particularly a direct current motor for vehicles, in accordance with the preamble of Claim 1. A direct current motor has been established in DE 1160080 A1 in which the stator pole is composed of rectangular shaped permanent magnets and pole shoes that are attached to the latter. The permanent magnets are fixed to a pole casing by means of adhesion. The operating air gap between the stator and rotor is thus restricted by the pole shoes. In the case of established direct current machines due to various reasons such as e.g., the rough operating environment of a vehicle, one can not absolutely exclude the possibility of rifts and cracks forming in the permanent magnets as a result of tension in the material, which could result in small slivers of material or pieces getting detached from the permanent magnets. When these kinds of slivers of material enter the operating air gap, the same could cause the rotor to seize or jam up. This is particularly critical when using the motor for steering effort support in vehicles. This has led to the proposal that a cylindrical magnetic chip guard be provided between the magnets of the stator and the rotor, whereby the magnetic chip guard is held at the stator with the help of two cover rings. Advantages of the Invention In contrast, the advantage of the electric machine in accordance with the invention with characteristics of Claim 1 is that it has a magnetic chip guard that is cost-effective and easy to manufacture. The magnetic chip guard is composed of a rectangular pre-cut part and exhibits an overlapping area that extends along the axial length of the chip guard. This thus results in an easy-to-manufacture magnetic chip guard that prevents chipped pieces of the magnet from reaching the operating air gap between the stator and rotor. Overlapping thereby ensures that chipped pieces can not reach the operating air gap through the two plies of the overlapping areas. Furthermore centring rings are provided in accordance with the invention and are located at both ends of the magnetic chip guard, lying in the axial direction. This enables a centring of the magnetic chip guard so that an operating air gap can be maintained that is constant along its entire length besides being as narrow as possible. Consequently, the electric machine in accordance with the invention can be used particularly in motor vehicles, for example as a support for steering effort in steering boxes or can be employed as an electric motor for brake power transmission for which high operational reliability must be guaranteed in order to prevent the vehicle from being in a condition where it can not be steered. Thereby, the overload clutch that is being used at present to prevent this kind of a situation in which a vehicle can not be steered can, in particular, be done away with. The measures listed in the other claims render beneficial developments or improvements of the electric machine in accordance with the invention feasible. Particularly favoured is the magnetic chip guard which is thereby designed in such a manner that in the assembled condition, it automatically moves outwards in a radial manner towards the magnets and thus holds its position through its own elasticity without any other assistance. The centring rings thereby serve as additional security features. In order to enable a quick and simple centring that can be automatically achieved in the case of this assembly, the centring rings respectively exhibit a tapered region. Also preferred is that the centring rings lock in the magnets between the pole casing and the magnetic chip guard to prevent any possibility of magnetic slivers escaping from this closed space. In order to provide an improved magnetic flux, the magnets primarily display pole lift-offs. It is thereby especially preferred that the overlapping areas of the magnetic chip guard be located at these pole lift-offs. It is also preferred that a terminal strip be located at the outer periphery of the magnetic chip guard in order to achieve the fastening of the magnetic chip guard by clamping the terminal strip between two contiguous magnets. Furthermore, the terminal strip prevents the magnetic chip guard from rotating. In order to enable an especially simple assembly, those ends of the magnetic chip guard that are located axially are to preferably curve slightly outwards in a radial manner. Also favoured is that the overlapping areas of the magnetic chip guard be designed in such a manner that a gradation directed towards the outside in a radial manner is formed at the overlapping area. The overlapping can thereby be developed in such a manner that the magnetic chip guard exhibits a constant inner diameter so that the air gap between the stator and rotor remains constant. In order to guarantee prevention of unintended loosening, it is preferable that the overlapping area of the magnetic chip guard be linked in a captive manner. This can be implemented, for example, through sticking or welding or through a snap-fit of the overlapping areas or through other similar means. The tapered regions of the centring rings is to be preferably designed as a cone or an area that curves outward or as an area that curves inwards or in the form of steps in the tapered region. Drawing The invention is described in greater detail below with the help of an exemplary embodiment illustrated in the drawings. Figure 1 illustrates a schematic perspective view of a magnetic chip guard in accordance with a first exemplary embodiment of the present invention Figure 2 illustrates a schematic sectional view of the magnetic chip guard shown in Figure 1 Figure 3 illustrates a schematic sectional view of a magnetic chip guard in accordance with the second exemplary embodiment of the present invention and Figures 4-7 illustrate schematic sectional views of various exemplary embodiments of the centring rings in accordance with the invention Description of the Exemplary Embodiments Figures 1 and 2 display a magnetic chip guard 3 in accordance with a first exemplary embodiment of the present invention. As can be observed in Figure 1, the magnetic chip guard 3 is essentially cylindrical in shape and has a terminal strip 5 at its outer periphery. The magnetic chip guard 3 is composed of a rectangular pre-cut part and displays an overlapping area 4 that is designed to overlap and cover respectively in the peripheral direction of the magnetic chip guard 3 and runs along the entire axial length of the magnetic chip guard 3. The overlapping area 4 thereby exhibits a pre-determined overlapping-height H in order to achieve the abutting of the two impact side ends of the magnetic chip guard along a certain peripheral length. The terminal strip 5 of the magnetic chip guard 3 is located between two permanent magnets 2, 2 in the assembled condition shown in Figure 2. The terminal strip 5, in section, is essentially V-shaped and clamps between the two magnets in order to hold the magnetic chip guard in position. The terminal strip 5 thereby serves as a lock against rotation, preventing the rotation of the magnetic chip guard. The overlapping area 4 of the magnetic chip guard 3 can, thereby, be located at a pole lift-off 10 of the permanent magnet 2 along which the thickness of the permanent magnets 2 reduces continually until it reaches a predetermined value A (compare Figure 2). The overlapping area 4 is thus located outside the diameter of the magnetic chip guard in a radial manner and a constant inner diameter can be actualised at the magnetic chip guard 3. This ensures that the air gap between the stator and the rotor which is not illustrated, of the electric machine remains constant or can, when compared with prior art, be reduced in a performance-enhancing manner respectively. The cylindrical shaped magnetic chip guard 3 is centred by means of two centring rings 8 that are located at the ends 6, 7 of the magnetic chip guard 3 respectively that lie in an axial direction (compare with Figure 1). The centring rings 8 display a tapered region 9 which centres the magnetic chip guard from the inside during assembly. It is, thereby, also possible that the magnetic chip guard could be easily expanded in order to execute an additional holding function by means of the centring rings 8. This expansion should, however, only occur to the extent that there is constant cover in the overlapping area 4 in order to safely prevent possible splintered magnetic chips from reaching the air gap between the stator and rotor. It is also observed that the magnetic chip guard 3 is designed in such a manner that it automatically starts an expansion force when in the assembled state, that is directed axially outward allowing it to sit close to the magnets 2. The magnetic chip guard in accordance with the invention can thus ensure that no splinters reach the air gap between the stator and rotor where it could, in an extreme case result in blocking the electric machine. The magnetic chip guard in accordance with the invention is thereby built in a very simple manner and can be manufactured cost-effectively as well as be assembled easily. Figure 3 displays the magnetic chip guard in accordance with the second exemplary embodiment of the present invention. In contrast to the first exemplary embodiment, the second exemplary embodiment has a step-like region 11 at the overlapping area 4 so that the inner part of the overlapping area can lie directly at the break of the step-like region 11. A constant inner diameter of the magnetic chip guard 3 is thereby achieved so that the small offset at the overlapping area in the first exemplary embodiment can be eliminated. The overlapping area 4 is located at the pole lift-off 10 of the magnets 2 where the thickness of the magnets is reduced continually till it reaches A (compare with Figure 2), in order to have sufficient place in the outward radial direction. Since this exemplary embodiment corresponds to the first exemplary embodiment in all other respects, the description provided for the latter can be referred to. Figures 4 to 7 illustrate various design possibilities for the centring rings 8. The tapered region 9 in the embodiment displayed in Figure 4 is designed as a cone. Furthermore, a recess 12 is designed at the cylinder ring 8 in which the magnetic chip guard 3, or more precisely, the axial side end of the magnetic chip guard, is located in its final assembled position. A light clamping in the recess 12 can thereby be provided in order to ensure that secure contact is established between the magnetic chip guard 3 and the centring rings 8. In the exemplary embodiment illustrated in Figure 5, the tapered region is built likewise in a conical manner. The end 6 of the magnetic chip guard, however, has an area that is designed outwards in a radial manner in order to enable simple assembling. The exemplary embodiment in accordance with Figure 6 illustrates a tapered region 9 that is designed curving inwards while that in Figure 7 is of a tapered region 9 that is designed as a region curving outwards. Another advantage of the invention is that apart from the centring by means of the centring rings 8, existing manufacturing tolerances could also possibly be balanced out. Furthermore, the centring rings 8 can completely seal off the space in which the magnets 2 are located thus excluding any possibility of magnetic chips flying outwards. Over and above this, the overlapping area 4 also presents the possibility of balancing out temperature changes that could occur during operation since the magnetic chip guard 3 can open up to a certain extent through the overlapping area 4 in the direction of the periphery without compromising its protective function. A constant air gap can nevertheless be maintained between the stator and rotor. 1. Electric machine, particularly a direct current motor for vehicles, with a multiple pole stator that has a ring-shaped pole casing (1) and several magnets (2) that are located at the inner surface of the pole casing (1) and a magnetic chip guard (3) that shields the magnets (2) inwards in a radial direction up to the rotor, characterised in that the magnetic chip guard (3) is composed of a rectangular pre-cut part and exhibits an overlapping area (4) that extends along the axial length of the magnetic chip guard (3) in the peripheral direction and has a centring ring (8) located at the ends (6, 7) respectively of the magnetic chip guard (3) lying in the axial direction in order to centre the magnetic chip guard (3). 2. Electric machine according to Claim 1 characterised in that the magnetic chip guard (3) automatically exercises a preload force on the magnets (2) that is directed outwards in a radial manner when in the assembled condition. 3. Electric machine according to one of the previous claims characterised in that the centring rings (8) exhibit a tapered region (9) respectively. 4. Electric machine according to one of the previous claims characterised in that the centring rings (8) seal in the magnets (2) between the pole casing (1) and the magnetic chip guard (3). 5. Electric machine according to one of the previous claims characterised in that the magnets (2) have a pole lift-off (10) and the overlapping area (4) of the magnetic chip guard (3) is located at the pole lift-off (10). 6. Electric machine according to one of the previous claims characterised in that a terminal strip (5) is located at the outer periphery of the magnetic chip guard (3) and is located between two magnets (2) when in the assembled condition. 7. Electric machine according to one of the previous claims characterised in that the axial side ends (6, 7) of the magnetic chip guard (3) are curved slightly outwards in a radial direction. 8. Electric machine according to one of the previous claims characterised in that the magnetic chip guard (3) has a step-like region (11) at the overlapping area (4) so that the magnetic chip guard (3) exhibits a constant inner diameter when in the assembled state. 9. Electric machine according to one of the previous claims characterised in that the magnetic chip guard (3) is connected at the overlapping area (4) in such a manner that it cannot be detached. 10. Electric machine according to one of the previous claims characterised in that the tapered region (9) of the centring rings (8) is designed as a cone or as an area that curves outwards or as an area that curves inwards or as a graduated, tapered area.

Documents:

1674-chenp-2005 abstract-duplicate.jpg

1674-chenp-2005 abstract-duplicate.pdf

1674-chenp-2005 claims-duplicate.pdf

1674-chenp-2005 description (complete)-duplicate.pdf

1674-chenp-2005 drawings-duplicate.pdf

1674-chenp-2005-abstract.pdf

1674-chenp-2005-claims.pdf

1674-chenp-2005-correspondnece-others.pdf

1674-chenp-2005-correspondnece-po.pdf

1674-chenp-2005-description(complete).pdf

1674-chenp-2005-drawings.pdf

1674-chenp-2005-form 1.pdf

1674-chenp-2005-form 18.pdf

1674-chenp-2005-form 3.pdf

1674-chenp-2005-form 5.pdf

1674-chenp-2005-pct.pdf

abs-1674-chenp-2005.jpg