GB2282489A

GB2282489A - Rotor for electrical machines with fan

Info

Publication number: GB2282489A
Application number: GB9419176A
Authority: GB
Inventors: Istvan Ragaly
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-10-02
Filing date: 1994-09-22
Publication date: 1995-04-05
Anticipated expiration: 2014-09-22
Also published as: ITMI940645V0; ES1029063Y; FR2710795A3; IT234125Y1; ES1029063U; ITMI940645U1; GB9419176D0; GB2282489B; FR2710795B3; DE9314984U1

Abstract

A claw-pole rotor for generators in motor vehicles, which exhibits a centrifugal fan (17) on the front side of the rotor (10) facing the slip rings which together with a slip-ring arrangement (14) at the end of the rotor shaft constitutes a structural unit. Resistance to centrifugal force and increased air throughput is provided by moulding, the fan blades (22) onto the outer region of a fan disc (24) on both sides in at least approximately mirror-image fashion. The fan hub (24) with an axial projection (27), bearing connecting leads (26), is connected in one piece to the carrier body (21) for the slip rings (13), the projection 27 passing under a bearing (18). Fig. 4 shows an alternative fan blade arrangement. <IMAGE>

Description

Rotor for Electrical Machines with Fan State of the Art The invention takes as starting-point a rotor for electrical machines, in particular claw-pole rotors for generators in motor vehicles according to the preamble to Claim 1.

In the case of such a claw-pole rotor for dynamos in motor vehicles which is known from FR-PS 1,452,972 the carrier body for the slip rings is already extended as far as the front side of the claw-pole rotor and designed as a hub for a centrifugal fan made of synthetic material which is moulded on there in one piece. The fan blades in this case protrude outwards from the periphery of the hub in the radial direction, whereby on the side facing the slip rings they are connected to one another in their outer region via a disc-shaped ring. In this connection the cooling air is guided along the fan hub to the fan blades and is then blown outwards in the radial direction on the front side of the claw-pole rotor. Since the stator housing does not exhibit any ventilation slots on the outer periphery, the cooling air there has to be transported between the claw-pole pieces and the base of the machine to the front, where it emerges through ventilation openings. The disc-shaped fan ring connecting the fan blades to one another in the outer region serves there simultaneously as a seal, keeping the cooling air in contact with the housing of the machine.

This solution has the disadvantage that, due to the relatively elaborate manner in which the cooling air is guided, the cooling capacity of the fan is only slight, and the disc-shaped connecting ring exerts a load on the fan blades at high rotary speeds, due to centrifugal forces which are then in operation. With the present solution a greater strength at high revolutions for the fan which is moulded onto the slip-ring arrangement of the claw-pole rotor is striven for, in order to improve the cooling of the electrical machine.

Advantages of the Invention The design of the fan according to the invention with the characterising features of Claim 1 has the advantage that, by virtue of a centrally arranged fan disc with fan blades moulded onto the outer region thereof on both sides in approximately mirror-image fashion, the centrifugal forces arising there at high rotary speeds act upon the fan disc symmetrically, so that the bending moments of the blades on the left and on the right of the fan disc cancel each other out. By comparison with known fans moulded from sheet metal, the design according to the invention has the advantage that together with the slip-ring body the fan constitutes a structural unit which can be counterbalanced before being mounted and which brings about a reduction in the magnetic leakage flux at the claw-pole rotor in comparison with sheet-metal fans made from steel plate.

Advantageous further developments of and improvements to the characteristics specified in Claim 1 result from the measures cited in the subclaims.

Drawing Two examples of embodiments of the invention are represented in the drawing and elucidated in greater detail in the following description. Figure 1 shows a cross-section through a claw-pole rotor with the object of the invention, Figure 2 shows a top view of the fan/slip-ring unit of the rotor from Figure 1, Figure 3 shows an additional example of an embodiment of a fan/slip-ring unit in the front view and Figure 4 shows a longitudinal section of this embodiment according to IV-IV from Figure 3.

Description of the Exemplary Embodiments In Figure 1 a claw-pole rotor of a three-phase generator for motor vehicles is designated as 10. Its excitation winding 11 is connected via connecting lines 12 to two slip rings 13 of a slip-ring arrangement 14 attached to the stub shaft 15 on the slip-ring side of a rotor shaft 16. In this connection a ball bearing 31 is arranged on the rotor shaft 16 between the slip-ring arrangement 14 and a centrifugal fan 17 on the slip-ring side. The fan 17 is located directly upstream of the front side of the right-hand claw-pole disc 18. Upstream of the front side of the left-hand pole disc 19 there is arranged a drive-side centrifugal fan 20. The fan 17 on the slip-ring side is manufactured in one piece with the carrier body 13 for the slip rings 14 which is made of synthetic material.

In connection with Figure 2 it can be seen that the fan blades 22 of the centrifugal fan 17 are moulded onto the outer region of a fan disc 23 on both sides in mirror-image fashion. The fan disc 23 is moulded externally onto a fan hub 24 attached to the rotor shaft 16, whereby two connecting pieces 25 located opposite one another jut out radially on said fan hub in order in each case to be able to connect there a connecting line 12 of the excitation winding 11. The connecting pieces 25 form the ends of two connecting leads 26, the other end of each of which is welded onto one of the slip rings 13, that are embedded in the fan hub 24, in an axial projection of the hub designed as a bridge 27 and also in the carrier body 21 for the slip rings 13. Commutator shell 21, bridge 27, fan hub 24, fan disc 23 and fan blades 22 are manufactured in one piece from synthetic material, whereby the axial bridges 27 with the connecting leads 26 embedded therein are guided through under the rear bearing 18 of the rotor shaft 16. From Figure 2 it can be seen that the fan disc 23 is provided between its hub 24 and the fan blades 22 with several apertures 28 distributed evenly over the periphery, by means of which an air current indicated by arrows in Figure 1 passes through to the rear region of the fan blades 22 and dissipates from the front side of the claw-pole rotor 10 the heat generated in said claw-pole rotor towards the outside.

In one of the apertures 28 one connecting piece 25 for the connection of the excitation winding 11 is arranged in freely accessible manner.

Figures 3 and 4 show an additional example of an embodiment of a fan/slip-ring structural unit for a claw-pole rotor according to Figure 1, whereby like components are provided with identical reference numbers. The essential difference in relation to the first embodiment consists in that, instead of the apertures 38, viewed in the direction of rotation of the rotor 10 the external region of the fan disc 23 now exhibits a recess 30 in front of each fan blade 22 which extends from the top 22a to the base 22b of each of the fan blades 22. Through these recesses 30 a part of the air current - as indicated by arrows in Figure 4 - reaches the claw-pole rotor 10 and another part of the air current, which takes up the heat of a semiconductor rectifier unit arranged in front of the fan and not represented, is led away to the outside by the fan 17 through suitable slots in the housing of the generator, which is not represented.

Claims

1. Rotor for electrical machines, in particular claw-pole rotors for generators in motor vehicles, with a slip-ring arrangement at one end of the rotor shaft, whereby the slip rings of said rotor shaft are connected to the ends of a rotor winding and to a fan on the front side of the rotor facing the slip rings which is manufactured from synthetic material in one piece with the carrier body for the slip rings, characterised in that the fan blades (22) are moulded onto the outer region of a fan disc (23) on both sides in at least approximately mirror-image fashion and in that the fan hub (24) with an axial projection (27) bearing connecting leads (26) protrudes through under a bearing (18) of the rotor shaft (16), said projection being connected in one piece to the carrier body (21) for the slip rings (13).

2. Rotor according to Claim 1, characterised in that the rotor disc (23) is provided between its hub (24) and the fan blades (22) with apertures (28) for the passage of air to the rear region of the fan blades.

3. Rotor according to Claim 2, characterised in that in at least one of the apertures (28) one connection (25) of the rotor winding (11) is connected to the connecting lead (26) of one of the slip rings (13).

4. Rotor according to Claim 1, characterised in that in the direction of rotation of the rotor (16) in front of each fan blade (22) the outer region of the fan disc (23) exhibits a recess (30) which extends from the top (22a) to the base (22b) of each of the fan blades.

5. Either of the rotors substantially as herein described with reference to the accompanying drawings.