GB2107130A

GB2107130A - Improvements in or relating to alternating current generators having air-cooled rectifiers

Info

Publication number: GB2107130A
Application number: GB08225382A
Authority: GB
Inventors: Manfred Frister
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1981-09-08
Filing date: 1982-09-07
Publication date: 1983-04-20
Also published as: FR2512601B1; FR2512601A1; GB2107130B

Abstract

An alternating current generator has a rectifier unit on a plate-like heat sink (40). The heat sink has a collar- like projecting edge portion which together with the housing of the generator creates an annular gap (36) for the passage of cooling air when in operation. The edge portion (32) and/or the inside wall of the housing are provided with deformations (such as 41) which promote turbulent flow of cooling air for improved heat transfer from the heat sink (40). <IMAGE>

Description

SPECIFICATION Improvements in or relating to alternating current generators having air-cooled rectifiers The present invention relates to alternating current generators, particularly three-phase generators.

German Patent Specification No. 1 6 1 3 040 describes a rectifier unit for an a.c. generator, particularly for a three-phase generator, in which a plurality of rectifiers is mounted on two plate-like heat sinks which extend transversely of the axis of the generator and have edge portions which project in a collar-like manner and deflect the cooling air outwardly towards the interior wall of the machine housing such that a high velocity is imparted to the cooling air which is guided in a substantially laminar manner in the annular gap existing between the projecting edge portions and the interior wall of the housing.

According to the present invention there is provided an alternating current generator, particularly a three-phase generator for feeding the electrical system of a motor vehicle, in which a rectifier unit comprising a plurality of rectifiers is mounted on at least one plate-like heat sink in the generator housing which when in operation has cooling air flowing therethrough in a longitudinal direction and whose end face adjacent the rectifiers incorporates a plurality of ports for the cooling air, and the heat sink extends transversely of the axis of the generator and has an edge portion which projects in a collar-like manner and by which the cooling air when in operation is guided through an annular gap formed relative to the interior wall of the housing, and deformed portions are provided on the edge portion and/or the interior wall of the housing in the region of the annular gap to increase the turbulence of the flow of cooling air when in operation.

By embodying the present invention it is possible to obtain a reduction of temperature at the heat sink by improved heat transfer to the cooling air. The deformed portions operate disturbances and/or discontinuities in the path of the flow of the cooling air and result in turbulent flow in which heat transfer is substantially better than in the case of laminarflow.

The invention will be further described by way of example with reference to the accompanying drawings in which: Figure 1 is an axial longitudinal section through a three-phase generator, equipped with rectifiers, for motor vehicles, according to one embodiment of the invention, Figures 2 and 3 are respectively an axial half section of the heat sink and the generator housing wall of Figure 1 to a larger scale and a fragmentary perspective view of the heat sink of Figure 1, Figures 4 and 5 are respectively an axial half section of the heat sink and the generator housing wall and a fragmentary perspective view of the heat sink of a second embodiment of the invention, Figures 6 and 7 are respectively an axial half section of the heat sink and the generator housing wall and a fragmentary perspective view of the heat sink of a third embodiment of the invention, Figures 8 and 9 are respectively an axial half section of the heat sink and the generator housing wall and a fragmentary perspective view of the heat sink of a fourth embodiment of the invention, and Figure 10 is an axial part section of the heat sink and the generator housing wall according to a further embodiment of the invention.

Referring to Figure 1 a three-phase generator has a generator housing 10 comprising a bearing plate 11 at the drive end and a bearing plate 12 at the slip-ring end. A holding arm and/or pivoted arm 13 are formed on the bearing plate 11 at the drive end. A stack of stator laminations 1 5 is clamped between the bearing plates 11 and 12 by through bolts 14 screwed into the bearing plate 12. The two bearing plates 11 and 12 accommodate ball bearings 1 6 and 17 for the generator shaft 1 8 which projects out of the bearing plate 11 at the drive end and which carries a claw pole armature 20 which has four pairs of poles and which carries a d.c. excitation winding 21.The excitation current is fed to the excitation winding 21 by way of slip rings 22 and 23 rotating with the shaft 1 8. The magnetic field induced by the excitation current permeates the stator 1 5 and three windings of the three-phase windings 24 which are uniformly distributed around the circumference of the stator and whose ends are respectively connected to one of three negative diodes 25 carrying the main current of the generator, one of three positive diodes 26, and one of three excitation current diodes 27. All three excitation current diodes 27 are electrically connected to the slip ring 23 by way of a carbon brush (not illustrated) and are mounted on a support plate 28 of insulating material.The positive diodes 26 are electrically interconnected and the negative diodes 25 are also electrically interconnected by conductors which are laminated on the support plate 28, the negative diodes 25 being insulated from the positive diodes 26.

The negative diodes 25 are pressed into or soldered onto a plate-like heat sink 30 in an electrically conductive manner, the positive diodes 26 also being secured to, although insuiated from, the heat sink 30. The plate-like heat sink 30 extends transversely of the axis 31 of the generator and has an edge portion 32 which is bent towards the stator windings 24. Cooling air 33 entering the bearing plate 12 at the slip ring end through cooling air ports 34 is deflected towards the interior wall of the generator housing 10, and flows at a high velocity through the annular gap remaining between the edge 32 of the heat sink 30 and the interior wall.In order to improve the transfer of heat to the cooling air 33, deformations are provided on the edge 32 and/or on the interior wall 35 of the housing in the region of the annular gap 36 remaining between the interior wall 35 of the housing and the edge 32 of the heat sink 30, and these deformations increase the turbulence of the flow of cooling air.

Examples of such deformations are illustrated in detail to a larger scale in Figures 2 to 10 of the drawings.

Referring to Figures 2 and 3, the plate-like heat sink 40 into or onto which the three negative diodes 25 are pressed or soldered in an electrically conductive manner, has an edge portion 32 with a plurality of pressed-out circular or angular projections 41 at which the cooling air 33 is deflected to form a large number of vortices 43, the heat sink 40 and thereby is better able to take away heat in the annular gap 36.

In the embodiment of Figures 4 and 5, the outwardly directed deformations 42 are of scalelike configuration, and a narrow window 44 is formed in the region of the air inlet port 34 and has an inwardly pressed tongue 45 which also guides cooling air along the inside of the edge portion 32 of the heat sink 40.

In the embodiment of Figures 6 and 7, the edge portion 32 of the heat sink 40 is provided with a surface by stretching and folding to form a large number of corrugations 46, as will be clearly seen.

from the perspective illustration of Figure 7. Here also, individual windows 44 are provided in the region of transition to the edge 32.

In the embodiment of Figures 8 and 9, the heat sink 40 has outwardly directed, stamped-out tongues 47 which are variously distributed around the circumference and over the height of the edge region 32 and, as a result of their differing distances from the interior wall of the housing 10, give rise to differing flow velocities and improve the transfer of heat in the same manner as in the embodiments described previously.

Finally, Figure 10 shows a different embodiment in which vortex-producing steps 48 are incorporated in the interior wall of the bearing plate 12 at the slipping end and merge into one another with sharp turbulence edges 49 in the direction of flow.

A particularly effective arrangement is provided by combining the vortex steps 48 (illustrated in.

Figure 10) on the bearing plate 12 with the stamped-out portions 41, 42 and 47 of Figures 2 and 3, 4 and 5, 8 and 9, or with the enlarged edge surface 32 of Figures 6 and 7.

Claims

1. An alternating current generator, particularly a three-phase generator for feeding the electrical system of a motor vehicle, in which a rectifier unit comprising a plurality of rectifiers is mounted on at least one plate-like heat sink in the generator housing which when in operation has a cooling air flowing therethrough in a longitudinal direction and whose end face adjacent the rectifiers incorporates a plurality of ports for the cooling air, and the heat sink extends transversely of the axis of the generator and has an edge portion which projects in a collar-like manner and by which the cooling air when in operation is guided through an annular gap formed relative to the interior wall of the housing, and deformed portions are provided on the edge portion and/or the interior wall of the housing in the region of the annular gap to increase the turbulence of the flow of cooling air when in operation.

2. A generator as claimed in claim 1, in which a plurality of pressed-out, circular or angular projections is provided in the bent-over edge portion of the heat sink in the region of the annular gap between the interior wall of the housing and the edge portion of the heat sink.

3. A generator as claimed in claim 1, in which outwardly directed, scale-shaped stamped-out portions are provided in the bent-6ver edge portion of the heat sink.

4. A generator as claimed in claim 1, in which corrugations produced by stretchirig and/or foiding are provided on the outer surface of the edge portion of the heat sink.

5. A generator as claimed in claim 1, in which the heat sink incorporates outwardly directed, stamped-out tongues variously distributed around the periphery and over the height of the edge portion thereof.

6. A generator as claimed in any of claims 1 to 5, in which the heat sink has a plurality of openings provided in the vicinity of the region of transition from that surface of the heat sink which extends transversely of the axis of the generator to the bent-over edge portion, whereby when in operation the'cooling air is guided along the inside of the edge of the heat sink.

7. A generator as claimed in any of claims 1 to 6, in which at least one vortex-producing step is provided on the interior wall of the generator housing.

8. A generator as claimed in claim 7 in which several steps disposed one behind another are provided in the direction of flow of the cooling air and merge into one another by way of sharply stepped edges.

9. An alternating current generator, constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in Figure 1, and in Figures 2 and 3 or Figures 4 and 5 or in Figures 6 and 7 or in Figures 8 and 9 of the accompanying drawings.

1 0. An alternating current generator as claimed in claim 9, including the feature constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illutrated in Figure 10 of the accompanying drawings.