GB2225490A

GB2225490A - An alternator with two forced ventilation fans, particularly for motor vehicles

Info

Publication number: GB2225490A
Application number: GB8925133A
Authority: GB
Inventors: Pietro Navarra; Guglielmo Baggi; Lorella Annovazzi
Original assignee: Industrie Magneti Marelli SRL; Magneti Marelli SpA
Current assignee: Industrie Magneti Marelli SRL; Marelli Europe SpA
Priority date: 1988-11-17
Filing date: 1989-11-07
Publication date: 1990-05-30
Anticipated expiration: 2009-11-07
Also published as: ES1012064Y; IT1223913B; GB8925133D0; BR8906021A; DE8913392U1; BE1003399A6; ES1012064U; IT8868025A0; SE8903845D0; NL8902781A; FR2639162A3; GB2225490B; SE8903845L; FR2639162B3

Abstract

An alternator with forced ventilation, particularly for motor vehicles, has two fan impellers, a rear impeller 30 and a front impeller 31 respectively, of which the former is arranged to generate an axial-radial flow and the latter is situated outside the front end of the alternator housing. In the region corresponding to the stator plates 24, the side wall 18 of the casing has a plurality of circumferential series of lateral apertures 22 communicating with respective axial ducts 23 through which an air flow is drawn into the casing by the front fan. <IMAGE>

Description

ALTERNATOR WITH FORCED ENTILA=ION, PARTICULARLY FOR MOTOR VEHICLES The present invention relates in general to alternators with forced ventilation, particularly for automotive applications.

In particular, the invention relates to an alternator of the t?e comprising a housing including two axially-ir.tefconnected portions, a front portion and a rear portico respectively, a rotor comprising a shaft which is swer^tEd by the housing and from which two facing pole plates with interpenetrating pole fingers extend radially a stator winding with respective plates and winding heads surrounding the rotor, and forced ventilatice weans including two fan impellers, a front impeller e a rear impeller respectively, carried by the rotor shaft.

When an alternator of this type is operating, the temperature of the rotor and the stator tend to increase, causing a corresponding increase in the resistance of the respective windings and, in particular, a consequent reduction in the excitation current, so that the alternator is less efficient.

The object of the present invention is to provide an alternator of the type defined at the beginning which has very efficient forced ventilation, in order to reduce the adverse effects resulting from heating in operation and thus improve the efficiency of the alternator.

According to the invention, this object is achieved by virtue of the following combination of characteristics: - the rear housing portion has axial end inlet apertures and radial side outlet apertures for the air flow generated by the rear fan impeller, - the front housing portion is open at its end which faces away from the rear housing portion and, in the region corresponding to the stator plates, has a plurality of circumferential series of lateral apertures communicating with respective axial ducts which are formed by internal recesses in the front housing portion and open towards the open end thereof, - the front impeller or fan is situated outside the open end of the front housing portion and is arranged to draw an air flow into the housing from the lateral apertures towards the open end of the front housing portion.

Further characteristics of the invention will become clear from the detailed description which follows with reference to the appended drawings, provided by way of non-limiting example, in which: Figure 1 is a schematic axial section of an alternator with forced ventilation according to the invention, Figure 2 is an axial section of one of the components of the alternator, and Figure 3 is an axial elevation in the direction of the arrow III of Figure 1.

With reference to the drawings, the alternator according to the invention comprises a casing 1 which contains a stator la and a rotor 2 with a shaft 3 supported coaxially for rotation in the stator la.

The casing 1 is constituted by a housing formed by a rear housing portion 4 and a front housing portion 5 which are connected together axially by means of screws 6. The rear casing portion 4 has an end wall 7 provided with axial apertures 10 and forming a central hub part 8 for rotatably supporting one end of the shaft 3 of the rotor 2 by means of a bearing 9. A side wall 11 is connected to the end wall 7 and has radial apertures 12.

The supplementary components of the alternator (a rectifier circuit 13, a voltage regulator 14, a brush-holder 15) are fixed to the outer surface of the end wall 7 and are enclosed in a protective cover 16 fixed to the wall -7 by means of the screws -6 and provided in turn with axial end apertures 17.

The front housing portion 5, shown in greater detail in Figures 2 and 3, has a side wall 18 and an open end 19 which faces away from the end wall 7 of the rear portion 4, and is formed with a central hub 20 for supporting the other end of the shaft 3 of the rotor 2 by means of a bearing 21.

The side wall 18 has a plurality of circumferential series of lateral apertures 22 communicating with a circumferential series of axial ducts 23 constituted by recesses formed in the side wall 18. As can clearly be seen in Figure 2 and 3, each axial duct 23 has a cross section (conveniently triangular or quadrangular) which is tapered towards the axis A of the alternator and has an open base. The ducts 23 are closed at their ends facing the rear housing portion 4 by the rear end 11a of the side wall 1 thereof, but are open at their opposite ends, that is, towards the open end 19 of the front housing portion 5.

The lateral apertures 22 may be oriented radially or, more conveniently, may be arranged in angular groups with parallel axes. This arrangement facilitates the production of the rear housing portion 5, since it enables it to be removed more easily from the die if it is produced by moulding.

The pack of stator plates is indicated 24 and its outer circumferential surface is situated in correspondence with the ducts 23 and therefore faces the lateral apertures 22.

The stator winding heads which project at oppsite ends -from the pack of plates 24 are indicated 25 and 26, and the excitation winding of the rotor 2 is indicated 27.

The latter has a generally known configuration and will not therefore be described in detail. For the purposes of the present invention, it is sufficient to say that it comprises two facing pole plates 28 keyed to the shaft 3 and having respective, bent, axial pole fingers 29 with interpenetrating ends 40.

Two fan impellers, a rear impeller 30 and a front impeller 31 respectively, are carried by the shaft 3 of the rotor 2 and are arranged to achieve the forced ventilation of the rotor and the stator when the alternator is operating.

The fan impeller 30 is situated in the rear housing portion 4, in the region defined by the rear stator winding head 25, whilst the front fan impeller 31 is arranged immediately outside the open end 19 of the front housing portion 5. The internal rear fan 30 is of the mixed type with "specialised" blades, that is, with alternating forms for generating axial and radial ventilation flows respectively.

In operation, the conformations and arrangements of the fans 30 and 31, together with those of the housing 1 described above, enable a considerably better cooling efficiency to be achieved than is the case with conventional alternators: more particularly, the fans generate two substantially separate air flows within the stator housing 1. The fan 30 draws in air from the outside through the radial apertures 17 in the cover 16 and the apertures 10 in the rear housing portion 4, distributing it axially through the pole fingers 29, 30 and the excitation winding 7 of the rotor 2 and radially through the rear stator winding head 25. The air flow generated by the rear fan 30 emerges from the housing 1 through the radial apertures 12 in the rear housing portion 4.

The front fan 31, however, draws air from outside through the lateral apertures 22, generating an axial flow through the ducts 23 which passes over the pack of plates 24 and the front winding head 26. The air drawn in the by fan 31 is then expelled through the open end 19 of the front housing portion 5. The external position of the fan 31 allows it to have an external diameter equal to that of the housing 1, which enables it to achieve an extremely efficient ventilation flow.

Claims

1. An alternator with forced ventilation, particularly for motor vehicles, comprising a housing including two axially-interconnected portions, a front portion and a rear portion respectively, a rotor comprising a shaft which is supported by the housing and from which two facing pole plates with interpenetrating pole fingers extend radially, a stator winding with respective plates and winding heads surrounding the rotor, and forced ventilation means including two fan impellers, a front impeller and a rear impeller respectively, carried by the rotor shaft, characterised in that:: - the rear fan impeller is situated in the rear housing portion and is arranged to generate an axial-radial flow from the outside to the inside of the housing, towards the rotor and towards the stator winding heads respectively, - the rear housing portion is provided with axial end inlet apertures and radial side outlet apertures for the air flow generated by the rear fan impeller - the front housing portion is open at its end which faces away from the rear housing portion and, in the region corresponding to the stator plates, has a plurality of circumferential series of lateral apertures communicating with respective axial ducts which are formed by internal recesses in the front housing portion and open towards the open end thereof, - the front fan impeller is situated outside the open end of the front housing portion and is arranged to draw an air flow into the housing from the lateral apertures towards the open end of the front housing portion

2. An alternator according to Claim 1, characterised in that the lateral apertures are arranged in angular groups with parallel axes.

3. An alternator according to Claim 1 or Claim 2, characterised in that the axial ducts have crosssections which converge towards the axis (A) of the housing

4. An alternator with forced ventilation substantially as hereinbefore described with reference to the accompanying drawings.