Method of connecting a conductor wire to a hook-shaped element, and rotor and/or stator for an electrical machine in which the method is used

Abstract: The invention relates to a method of electrically and mechanically connecting an electrical conductor wire (5) to a hook-shaped element (3) of an electrically conductive supporting body (1). The conductor wire, which comprises an electrically conductive core (7) and a sheath (9) of an insulating material, is introduced into the open hook-shaped element after which a radiation beam (11) is aimed at the conductor wire, for example, to ablate the insulating sheath by heating. After this the conductive core of the conductor wire is clamped in the hook-shaped element by cold deformation of the hook-shaped element.

Description: The invention relates to a method of electrically and mechanically connecting an electrical conductor wire comprising an electrically conductive core and a sheath of insulating material to a hook-shaped electrically conductive body, said method comprising introducing the wire into the hook-shaped body while the hook-shaped body is open and closing the hook-shaped body provided with the wire. The invention relates to a rotor for an electrical machine comprising a rotor winding provided with an electrical conductor wire having an electrically conductive core and a sheath of insulating material, and a commutator with an electrically conductive hook-shaped body, said wire being connected to the hook-shaped body of the commutator. A method as defined above is disclosed in EP-A 0,280,356 (herewith incorporated by reference). In accordance with the prior-art method a wire of a rotor coil is connected to a hook of a commutator segment by means of an electric current. For this purpose the wire is wrapped around the hook, after which the hook and the commutator segment are connected to electrodes. One of the electrodes is in contact with the commutator segment and another electrode is in contact with the hook, which is thus closed. An electric current is applied between the electrodes to heat the hook, the heat thus produced causing the insulation layer to be burnt off the wire and electrical contact to be established between the wire and the hook. A drawback of the prior-art method is that during connection of the wire to the hook the hook and hence the adjacent constructional parts are heated to a high temperature, so that a comparatively large surrounding area is heated. In modern equipment comprising, for example, temperature-sensitive electronic devices such a thermal load is often impermissible. Moreover, said high temperatures impose limitations on the choice of the materials for the constructional parts. Said EP-A 0,280,386 also discloses a rotor for an electrical machine comprising a rotor winding and a commutator, a conductor wire of the rotor winding being connected to a hook-shaped element of the commutator. It is an object of the invention to improve the method defined in the opening paragraph in such a manner that no heating or only local heating is necessary to connect a conductor wire to a hook-shaped element. To this end the method in accordance with the invention is characterized by the following steps: after introduction of the wire into the open hook-shaped body, ablating the insulating material of the wire in the open hook-shaped body with a radiation beam, aiming a gas stream at the wire in the open hook-shaped body during ablating to remove the ablated insulating material, and after ablation, clamping the electrically conductive core in the hook-shaped body by cold deformation of the body. Ablation is to be understood to mean removal as a result of melting, evaporation, burning or pulverising or a combination of two or more of these processes. The wavelength of the radiation used for this purpose may lie in the UV and/or IR region. When UV radiation is used the insulating material is pulverised. An advantage of the method in accordance with the invention is that if UV radiation is employed substantially no heat is produced and if IR radiation is employed the heat is administered to the conductor wire, in particular the insulating sheath thereof, directly, locally and in a well-defined manner. An effective removal of the insulating material is obtained due to the gas stream aimed at the conductor wire positioned in the open hook-shaped body during aiming of the radiation beam. An accurately defined and bounded radiation beam is obtained if a laser source is used. It is found that a TEA (= Transversely Excited Atmospheric) CO₂ laser is very suitable for the ablation of thin wires. Such a laser is capable of producing pulsating laser beams and high power densities. It is to be noted that GB-A 2,214,360 discloses the use of a laser, such as a TEA-CO₂ laser, for producing a laser beam for removing an insulation coating. The laser beam is directed to a straight piece of thin wire covered with the insulating coating and clamped in a predetermined position by a clamper mechanism. It is another object of the invention to provide the prior-art rotor with a connection between a conductor wire of the rotor winding and a hook-shaped body or element of the commutator, which connection is established by means of the method in accordance with the invention. During manufacture such a rotor is subjected to hardly any thermal load, which is beneficial for the life of the rotor. Moreover, the requirements as regards thermal sensitivity imposed on the materials of the rotor, in particular the commutator, can be less stringent, which generally leads to the choice of cheaper materials. It is another object of the invention to provide a stator for an electrical machine, which stator comprises a stator winding and a connecting member, a conductor wire of the stator winding being connected to a hook-shaped body or element of the connecting member by means of the method in accordance with the invention. It is to be noted that DE-A 23 28 698 discloses a method of connecting an armature wire to a commutator, the bare armature wire being introduced into an open hook is bent towards the segment. The armature wire is then flattened to establish metallic contact between the armature wire and the segment. It is to be noted also that US-A 4,671,848 describes a method of locally removing a dielectric coating from a wire by means of a high-energy radiation source such as a laser. Finally, it is to be noted that from DE-A 35 42 380 (herewith incorporated by reference) it is known per se to use a laser beam in a method in which a coil lead of a rotor winding and a commutator hook are welded to one another. In accordance with this known method the coil lead is introduced into a recess formed in the commutator hook, after which the lead is bent. After the commutator has been closed a pulsating or non-pulsating laser beam is aimed at the coil lead via the recess to form a weld between the coil lead and the commutator hook. The invention will now be described in more detail, by way of example, with reference to the drawing, in which: Fig. 1 is a side view of a part of a commutator segment with an open commutator hook, Fig. 2 shows a part of Fig. 1 in a sectional view taken on the line II-II, Fig. 3 is a sectional view of the part of the commutator segment of Fig. 1, the commutator hook being closed by means of a closing die, Fig. 4 shows an electric motor and a stator with various connecting members, and Fig. 5 shows one of the connecting members of the electric motor shown in Fig. 4. Figs. 1 and 2 show a part of a conductive supporting body 1 comprising a hook-shaped element 3. In the present example the supporting body is constructed as a commutator segment of a commutator of an electrical machine. For this reason the supporting body and the hook-shaped element will be referred to hereinafter as the commutator segment 1 and the commutator hook 3 respectively. In Fig. 1 the commutator hook 3, which serves for electrically and mechanically connecting an electrical conductor wire, in the present example a coil lead 5 of a rotor winding, to the commutator segment 1, is open. The commutator hook 3 and the commutator segment 1 then extend, for example, at an angle alpha of 22° to each other. When the method in accordance with the invention is carried out the coil lead 5, which has a conductive core 7 of, for example, copper and an electrically insulating plastics sheath 9, is introduced into the space bounded by the commutator segment 1 and the open commutator hook 3, after which an infrared radiation beam 11, preferably produced by a laser source 13, for example a CO₂ laser, is aimed at the coil lead. The radiation beam 11 heats the coil lead 5 locally, causing the insulating sheath 9 of, for example, polyester imide to be subjected to such physical and chemical changes, for example melting or burning, that the conductive core 7 can be brought into electrical contact with the commutator segment 1 and the commutator hook 3. This may be achieved by aiming a gas stream at the coil lead 5, as is indicated by the arrow P, and in the cold condition the commutator hook 3 is bent towards the commutator segment 1 by a closing die 14 which is moved in the direction indicated by the arrow A, yielding the situation illustrated in Fig. 2, in which the coil lead 5 is firmly clamped between the commutator segment 1 and the commutator hook 3 and the conductive core 7 is in electrical contact with the commutator segment 1 and the commutator hook 3. After the commutator hook 3 has been closed, which may be effected by means of a counter-die, the die 14 is removed by a movement in the direction indicated by the arrow B. Fig. 4 shows an a.c. motor comprising a stator 20 and a rotor 22. The laminated stator 20 is surrounded with a plastics housing 24 and comprises a stator winding 26 having coil leads 28 connected to connecting members 30. Fig. 5 shows one of the connecting members 30 to an enlarged scale. The connecting member shown in this Figure comprises a plate-shaped supporting body 31 and a hook-shaped element 33, between which one of the coil leads 28 is clamped, the coil lead 28 being connected to the connecting member 30 by means of the method in accordance with the invention. The rotor 22 of the electric motor shown in Fig. 4 comprises a rotor shaft 32 with a rotor body 34 and a commutator 36 with commutator segments 31. The rotor body 34 takes the form of a lamination assembly with radial slots 38 in which the coil sides of rotor coils, not shown, of a rotor winding are arranged. The rotor winding comprises coil leads 40, which are connected to hook-shaped elements 43 of the commutator segments 31. The commutator segments 31 and the hook-shaped elements 43 correspond to the commutator segment 1 and the commutator hook 3 shown in Fig. 3. The coil leads 40 are connected by means of the method in accordance with the invention.

Claims: A method of electrically and mechanically connecting an electrical conductor wire (5) comprising an electrically conductive core (7) and a sheath (9) of insulating material to a hook-shaped electrically conductive body (3), said method comprising introducing the wire into the hook-shaped body while the hook-shaped body is open and closing the hook-shaped body provided with the wire, characterized by the following steps: after introduction of the wire (5) into the open hook-shaped body (3), ablating the insulating material of the wire in the open hook-shaped body with a radiation beam (11), aiming a gas stream at the wire in the open hook-shaped body during ablating to remove the ablated insulating material, and after ablation, clamping the electrically conductive core (7) in the hook-shaped body by cold deformation of the body. A method as claimed in Claim 1, characterized in that a laser source (13) is used for the generation of the radiation beam. A method as claimed in Claim 2, characterized in that the laser source (13) is a TEA-CO₂ laser. A rotor (22) for an electrical machine comprising a rotor winding provided with an electrical conductor wire (5, 40) having an electrically conductive core (7) and a sheath (9) of insulating material, and a commutator (36) with an electrically conductive hook-shaped body (3, 43), said wire being connected to the hook-shaped body of the commutator by the method as claimed in Claim 1, 2 or 3. A stator (20) for an electrical machine comprising a stator winding (26) provided with an electrical conductor wire (5, 28) having an electrically conductor core (7) and a sheath (9) of insulating material, and a connecting member (30) with an electrically conductive hook-shaped body (3, 33), said wire being connected to the hook-shaped body of the connecting member by the method as claimed in Claim 1, 2 or 3.

Inventors: ENGELFRIET ADRIANUS RICHARD CH, SCHILDBACH KLAUS BENNO, VISSER REINKE ADOLF, ENGELFRIET, ADRIANUS RICHARD CHRISTOFOOR, SCHILDBACH, KLAUS BENNO, VISSER, REINKE ADOLF
Applicants: PHILIPS ELECTRONICS NV, PHILIPS ELECTRONICS N.V.
Application year: 1990
Main classification: H01R39
IPC codes: H01R43, H01R4, H02K3, H01R39, H02K23