A METHOD OF MANUFACTURING A WINDING FOR THE STATOR OF A DIRECT-CURRENT ELECTRICAL MACHINE

Abstract: The invention relates to a method of manufacturing a winding for the stator of a starter motor for an internal combustion engine. The method comprises the steps of: winding a rigid conductor (1) into a conical helix (2), covering the conductor with a layer of electrically-insulating material, and then squashing the helical conductor (2) axially so as to cause the interpenetration of its turns.

Description: The present invention relates to a method of manufacturing a winding for the stator of a direct-current electrical machine, particularly a starter motor for an internal combustion engine. A known method for manufacturing a winding for DC and AC electrical machines is disclosed in DE-C-630697. The method according to the invention is characterised in that it comprises the following steps: winding at least one rigid, plastically-deformable conductor substantially into a conical helix, covering the conductors with a layer of electrically-insulating material, and then squashing the helical conductor axially so as to cause the interpenetration of its turns. Characteristics and advantages of the present 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: Figures 1, 2, 3 and 4 are perspective views showing successive stages of the method according to the present invention, and Figure 5 is a front elevational view of four windings upon completion of the operations illustrated in Figures 1 to 4. With reference to the drawings, a rigid metal strip of electrically-conductive material, for example copper, aluminium or alloys thereof, is indicated 1. The strip 1 is deformed plastically so as to form two conical helices, indicated 2 and 3 respectively, having rectangular turns. In the embodiment illustrated in the drawings, the axes A and B of the helices 2 and 3 are aligned and the cones of the two helices converge. The helices 2 and 3 are formed so that the outwardly-facing surface of the strip in each turn is substantially flush with the inwardly-facing surface of the adjacent larger turn. The helices 2 and 3 are interconnected by a portion 5 of the strip 1 which is bent to form an S-shape with a straight section 6, parallel to the common axis of the two helices. The strip 1 is bent automatically to produce the helices 2 and 3 with the use of known machines conventionally used for the manufacture of windings. Upon completion of the bending operation illustrated in Figure 1, the helices 2 and 3 are pivoted towards each other by the bending of the ends of the S-shaped connecting portion 5. As shown in Figure 2, upon completion of this operation, the axes of the helices 2 and 3 are substantially parallel. The straight section 6 of the connecting portion 5 is then bent in the sense indicated by the arrow D in Figure 3, so that the C-shaped portion 5 is brought into a plane perpendicular to the plane containing the axes A and B. With reference to Figure 5, one end 8 of the strip 1 is connected by welding to an end 8a of a second pair of windings. After this operation, the helices 2 and 3 are covered with an electrically-insulating varnish (for example, an epoxy-resin-based varnish) applied electrostatically. A stage of baking the varnish in an oven then follows. The helices 2 and 3 are then squashed axially so that the turns are made to interpenetrate, that is, to produce the two windings shown in Figure 4. Plastics clips 7 are then applied to each winding thus produced, as shown in Figure 5. The ends 9 and 9a of the four windings are connected to an electrical supply circuit after the four windings have been positioned on their respective stator poles of the electric motor. Alternatively, the four windings shown in Figure 5 may be produced from a single strip by winding successive portions of the latter into conical helices, as described above. The insulation of the strip 1 by means of varnishing is less bulky than conventional insulation produced by wrapping with paper and it is therefore possible to increase the cross-sections of the strips in a winding of a given overall size, and thus to achieve an increase in the power of the electric motor.

Claims: A method of manufacturing a winding for the stator of a direct-current electrical machine, particularly a starter motor for an internal combustion engine, characterised in that it comprises the following steps: winding at least one rigid, plastically-deformable conductor (1) substantially into a conical helix(2), covering the conductor (1) with a layer of electrically-insulating material, and then squashing the helical conductor (1) axially so as to cause the interpenetration of its turns. A method according to Claim 1, particularly for producing a pair of windings for the stator of an electrical machine from a single conductor, characterised by the following steps: winding first and second end portions of the conductor (1) into conical helices (2, 3), the portions which are wound into helices (2, 3) being joined by an intermediate connecting portion (5), covering the conductor (1) with a layer of electrically-insulating material, and then squashing the helical (2, 3) conductor (1) axially so as to cause the interpenetration of its turns. A method according to Claim 2, characterised in that the conductor (1) is wound so as to form first (2) and second (3) conical helices with respective axes (A, B) which are substantially coincident, and in that the intermediate connecting portion (5) is constituted by a substantially S-shaped section of conductor, the intermediate portion (6) of which is substantially parallel to the axis of the two helical portions (2, 3). A method according to Claim 3, characterised in that the first (2) and second (3) helical portions of the conductor (1) are pivoted towards each other from the configuration in which the axes (A, B) of the two helices are substantially aligned to a configuration in which the axes (A, B) are substantially parallel. A method according to Claim 4, characterised in that the S-shaped portion (5) connecting the helical portions (2, 3) is bent from a configuration in which it lies substantially parallel to the plane containing the axes (A, B) of the two helical portions to a configuration in which it extends perpendicular to that plane. A method according to Claim 1, particularly for producing a plurality of windings for the stator of an electrical machine from a single conductor, characterised by the following steps; winding adjacent portions of the conductor (1) substantially into conical helices (2), the portions which are wound into helices being joined by intermediate connecting portions (5), covering the conductor (1) with a layer of electrically-insulating material, and then squashing each of the helical portions (2) of the conductor (1) so as to cause the interpenetration of its turns. A method according to any one of the preceding claims, characterised in that the conical helix (2) has substantially rectangular turns. A method according to any one of the preceding claims, characterised in that the conductor (1) is constituted by a metal strip.

Inventors: POVERO, FELICE, VOZA, ANGELO
Applicants: INDUSTRIE MAGNETI MARELLI S.P.A.
Application year: 1989
Main classification: H02K15
IPC codes: H02K3, H02K15