ITBO20100584A1 - ELECTRIC MACHINE PRESENTING A STATIC ROLL WITH RIGID BARS AND ITS CONSTRUCTION METHOD - Google Patents

Description

DESCRIPTION

of the patent for Industrial Invention entitled:

â € œELECTRIC MACHINE WITH A STATORIC WINDING WITH RIGID BARS AND RELATIVE CONSTRUCTION METHODâ €

TECHNIQUE SECTOR

The present invention relates to an electric machine having a stator winding with rigid bars and to a related construction method.

ANTERIOR ART

Traditionally, the stator winding of an electric machine is made by means of filiform and flexible conductors which are initially wound in coils; subsequently, the coils are inserted into the stator slots and are then electrically connected to each other. This construction method is complex to automate, as it is very difficult to automatically insert the coils inside the stator slots as the coils do not have a stable shape and must be deformed to pass through the small axial opening of the slots.

In order to overcome the difficulties of construction of the stator winding made using filiform and flexible conductors, a stator winding made using rigid bars has been proposed. In a stator winding made by means of rigid bars, a series of rigid bars are used which are initially shaped like a `` U '' and then are inserted axially into the stator slots forming an inlet side, in which the cusps of the bars shaped like a â € œUâ €, and an exit side, in which the legs (that is the straight portions) of the bars shaped like a â € œUâ € are arranged. Once all the bars have been inserted into the stator slots, the legs on the output side are twisted (by means of an operation called â € œtwistingâ €) and then the free ends of the legs are connected together by welding to form the electrical paths of the winding. stator.

It has been proposed to differentiate the dimensions of the cusps of the U-shaped bars in such a way as to achieve, thanks to this differentiation, the electrical paths of the stator winding 8; however, differentiating the dimensions of the cusps of the `` U '' shaped bars involves a considerable complication both in the realization of the `` U '' shaped bars (having to make at least two different types of `` U '' shaped bars), and in the Insertion of the â € œUâ € -shaped bars into the stator slots (as it is necessary to manage at least two different types of â € œUâ € -shaped bars which must be inserted in precise and predetermined positions and are not in any way interchangeable).

During the construction of the stator winding, it was proposed to bring together all the U-shaped bars outside the stator magnetic core and then to insert all the U-shaped bars together with a single movement. € in the stator slots. However, in this way a high intensity thrust is exerted simultaneously on all the U-shaped bars and therefore it is possible that one or more U-shaped bars are subjected to an excessive thrust ( that is, too strong) and / or badly directed, causing damage to the external insulating enamel that covers the U-shaped bars.

DESCRIPTION OF THE INVENTION

The object of the present invention is to provide an electric machine having a stator winding with rigid bars and a relative construction method, which electric machine and construction method are easy and economical to produce.

According to the present invention, an electric machine is provided which has a stator winding with rigid bars and a related construction method according to what is claimed in the attached claims. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the attached drawings, which illustrate a non-limiting example of embodiment, in which:

Figure 1 is a cross-sectional view, schematic and with parts removed for clarity of an electric machine made in accordance with the present invention;

Figure 2 is a perspective view, schematic, and with parts removed for clarity of a stator of the electric machine of figure 1;

Figure 3 is a perspective and schematic view of a rigid bar folded into a "U" form part of a stator winding of the stator of figure 2; Figures 4-6, 9 and 11-14 are a succession of perspective views, schematic and with parts removed for clarity of the construction phases of the stator winding of the stator of Figure 2;

Figures 7 and 8 are two enlarged scale views of respective details of Figure 6;

Figure 10 is an enlarged scale view of a detail of figure 9;

Figure 15 is a schematic perspective view with parts removed for clarity of a variant of the stator of Figure 2;

Figure 16 is an enlarged scale view of a detail of figure 15; And

Figure 17 is a perspective view and on an enlarged scale of a small tile of the stator of figure 15.

PREFERRED FORMS OF IMPLEMENTATION OF THE INVENTION

In figure 1, the number 1 indicates as a whole a synchronous electric machine for motor vehicles of the reversible type (that is, it can work both as an electric motor by absorbing electrical energy and generating a mechanical torque, and as an electric generator by absorbing mechanical energy and generating electricity). The electric machine 1 comprises a shaft 2, which is rotatably mounted to rotate around a central rotation axis 3, a permanent magnet rotor 4 keyed to the shaft 2 to rotate together with the shaft 2 itself, and one stator 5 of cylindrical tubular shape arranged around the rotor 4 to enclose the rotor 4 itself inside.

The stator 5 comprises a magnetic core 6 which is made up of a series of laminations tightly packed together and has a centrally perforated tubular shape; the magnetic core 6 is traversed longitudinally by thirty-six stator slots 7 which are uniformly distributed along the inner side of the magnetic core 6 and house a three-phase stator winding 8 (illustrated in Figure 2). In the embodiment illustrated in the attached figures, the three-phase stator winding 8 is distributed in thirty-six stator slots 7 and the permanent magnet rotor 4 comprises six poles; consequently, the synchronous electric machine 1 has 2 slots per pole and per phase.

As shown in Figure 2, the three-phase stator winding 8 comprises a series of rigid bars 9 shaped like a â € œUâ €, each of which includes two legs 10 connected together by a cusp 11 (as better illustrated in Figure 3) ; the two legs 10 of the same bar 9 constitute two corresponding conductors of the stator winding 8. It is important to note that each bar 9 conformed to a â € œUâ € has a â € œthree-dimensionalâ € bending, that is, a bending on two perpendicular planes. The U-shaped bars 9 are inserted through the stator slots 7 defining an inlet side 12, in which the cusps 11 of the U-shaped bars 9 are arranged, and an outlet side 13, in which the legs 10 of the bars 9 are arranged in a â € œUâ € shape. In particular, in each slot there are four legs 10 (that is, four conductors of the stator winding 8) belonging to four corresponding rigid bars 9 shaped like a â € œUâ € different from each other. The ends of the legs 10 of the U-shaped bars 9 are electrically connected to each other to form the electrical paths of the stator winding 8.

According to a preferred embodiment, three annular insulating layers (not shown) of electrically insulating material (typically insulating paper - Namex ®â €).

Furthermore, the three-phase stator winding 8 includes three connection terminals 14 which form the electrical interface with the outside of the stator winding 8 and are electrically connected to an electronic power converter (not shown) which drives the 1 synchronous electric machine.

With reference to figures 4-14, the method of construction of the stator winding 8 is described below.

Initially, the rigid bars 9 are bent centrally by 180 ° to be shaped like a "U" and take the shape shown in Figure 3. This bending is preferably carried out by means of an electronically controlled machine tool which in a single operation gives each bar 9 rigid the final form. The bars 9 shaped like a â € œUâ € are all the same, that is, they all have exactly the same dimensions.

Once the bars 9 shaped like a â € œUâ € are ready (in particular in the stator winding 8 illustrated in the attached figures there are seventy-two bars 9 shaped like a â € œUâ €), each bar 9 shaped like a â € œUâ € is inserted individually (ie alone) in the corresponding two stator slots 7 (ie the two legs 10 of the bar 9 shaped like a "U" are axially inserted in the corresponding two stator slots 7). In other words, only one U-shaped bar 9 is inserted inside two non-adjacent stator slots 7 at a time. Preferably, before inserting the U-shaped bars 9 into the stator slots 7, each stator slot 7 is internally "coated" with an insulating layer (not shown) of electrically insulating material (typically insulating paper â € œNamex ®â €).

When all the seventy-two bars 9 shaped like a â € œUâ € have been inserted into the stator slots 7, the stator winding 8 appears as illustrated in figures 4 and 5. At this point and as better illustrated in Figure 6, the legs 10 of the U-shaped bars 9 which protrude into the outlet side 13 of the magnetic core 6 are twisted by means of respective double folds to assume a “Z” shape. As better illustrated in the enlargements of Figures 7 and 8, each double fold of a leg 10 comprises an internal fold 15 (i.e. closer to the magnetic core 6 of the stator 5) in one direction and an external fold 16 (i.e. further away from the magnetic core 6 of the stator 5) in an opposite direction. By way of example, for each leg 10 the internal fold 15 has an amplitude of about 60 ° in one direction and the internal fold 15 has an amplitude of about 60 ° in the opposite direction. In each stator slot 7 there are four corresponding legs 10 (belonging to four corresponding bars shaped as different â € œUâ €) which are twisted in alternately opposite directions by respective double folds. In other words, half of the legs 10 is twisted clockwise with a given width while the other half of the legs 10 is twisted counterclockwise (ie in the opposite direction) with the same width. It is important to note that all the double folds of the legs 8 have the same width (equal, in the embodiment illustrated in the attached figures, to a distance corresponding to three stator slots 7).

According to a preferred embodiment, during the twisting of the legs 10 of the U-shaped bars 9, the legs 10 are not twisted all together, but are twisted in groups; in other words, the legs 10 of the bars 9 shaped like a â € œUâ € are divided into at least two groups which are twisted with two successive (ie non-simultaneous) operations. During the twisting of a first group of legs 10, the legs 10 of the second group that will be twisted later are temporarily translated axially along the stator slots 7 so as to reduce the length that protrudes from the stator slots 7 in the output side 13 (typically up to canceling or almost canceling the length of the legs 10 which protrudes from the stator slots 7 in the outlet side 13). In this way the legs 10 of the second group are not an obstacle to the twisting of the legs 10 of the first group, but at the same time the legs 10 of the second group engage the stator slots 7 to help keep the legs 10 of the first group still during the twisting. At the end of the twisting of the first group of legs 10, the legs 10 of the second group are axially translated in the opposite direction to return to their original position and then be twisted in their turn. In this way, the twisting of the legs 10 of the first group is simplified since this twisting takes place without the obstacle represented by the legs 10 of the second group. The twisting of the legs 10 of the second group is in any case simpler, as it occurs when the legs 10 of the first group have already been twisted and therefore have a much smaller axial dimension.

Once the twisting of the legs 10 of the U-shaped bars 9 is finished, the ends of the legs 10 of the U-shaped bars 9 are electrically connected to each other (typically by laser welding) to form the electrical paths of the stator winding 8. It should be noted that the two legs 10 whose ends are electrically connected to each other are twisted in opposite directions by respective double folds.

As previously mentioned, the bars 9 shaped like a â € œUâ € are all the same and therefore the width of the cusps 11 of the bars 9 shaped like a â € œUâ € is the same for all the bars 9 shaped like a â € œUâ €. As illustrated in figure 7, to allow the realization of the foreseen electrical paths of the stator winding 8 in the part of the stator winding 8 of each phase, the ends of at least one pair 17 of legs 10 initially not adjacent are folded one towards the ™ other until they touch each other to allow an electrical connection between the two ends. According to a preferred embodiment, the external folds 16 of each pair 17 of legs 10 have a U-shape (i.e. they have a width of about 150 °) and opposite orientations so that the corresponding ends of the legs 10 touch each other. This is made possible by the fact that the legs 10 of each pair 17 of legs 10 are twisted in opposite directions by respective double folds. As illustrated in figure 6, in the stator winding 8 illustrated in the attached figures, each phase comprises four pairs 17 of legs 10 initially not adjacent which are folded towards each other until they touch each other and then overall in the whole winding 8 stator there are twelve pairs 17 of legs 10.

As illustrated in Figure 9, in order to allow the realization of the foreseen electrical paths of the stator winding 8 in the part of the stator winding 8 of each phase, the ends of at least one pair 18 of legs 10 initially not adjacent are electrically connected to each other by means of a connecting bridge 19. As shown in Figure 9, in the stator winding 8 illustrated in the attached figures each phase comprises two pairs 18 of legs 10 and two corresponding connection bridges 19 and therefore, overall, six pairs 18 of legs are present throughout the stator winding 8 10 and six corresponding connecting bridges 19. According to a preferred embodiment, each connection bridge 19 is constituted by a flat plate which is arranged perpendicularly to the central axis 3 of rotation, is shaped like a â € œSâ €, and has two opposing seats which engage the respective ends of the legs 10 of the pair 18 of legs 10. Furthermore, according to a preferred embodiment, all the ends of the pairs 17 of legs 10 are arranged at the same first axial level and all the ends of the pairs 18 of legs 10 together with the corresponding connecting bridges 19 are arranged at the same second axial level which is arranged above the first axial level. Preferably, between the first axial level and the second axial level there is an insulating layer 20 of electrically insulating material (typically `` Namex® '' insulating paper) which separates the ends of the legs 10 of the pairs 17 of legs 10 from the ends of the 10 legs of 18 pairs of legs 10.

In other words, as previously said, all the double folds of the legs 8 have the same width equal, in the embodiment illustrated in the attached figures, at a distance corresponding to three stator slots 7. Therefore, normally the electrical connection between two adjacent ends of two legs 10 takes place between two legs 10 six stator slots 7 distant from each other (ie with a jump of six stator slots 7); however, at each complete revolution of the stator magnetic core 6 it is necessary that there be a jump of five stator slots 7 (made for the pairs 17 of legs 10 by means of the U-bending of the ends) or a jump of seven stator slots 7 (made for the pairs 18 of legs 10 by means of the connection bridges 19) in such a way as to follow the electrical paths of the stator winding.

As illustrated in Figure 11, the three ends of respective legs 10 which constitute a star-center of the stator winding 8 are electrically connected to each other by means of a connection bridge 21, which consists of a flat plate which is arranged perpendicularly to the central axis 3 of rotation and is provided with three seats which engage the respective ends of the legs 10. As shown in figure 11, two star connections are provided in the stator winding 8 illustrated in the attached figures. in turn connected to each other in parallel (as will be better described later). The two connecting bridges 21 are arranged at a third axial level which is arranged above the second axial level of the connecting bridges 19. Preferably, between the second axial level and the third axial level an insulating layer 22 of electrically insulating material is interposed (typically insulating paper â € œNamex®â €) which separates the two connecting bridges 21 from the six connecting bridges 19.

According to what is illustrated in figures 12-14, each connection terminal 14 is electrically connected to the two ends of two legs 10 which constitute respective terminals of a star connection of the stator winding 8; in this way, each connection terminal 14 forms part of the parallel connection of the two star connections of the stator winding 8. Preferably, each connection clamp 14 consists of a transverse flat plate which is arranged perpendicularly to the central axis 3 of rotation, connects the two ends of the two corresponding legs 10 together and has two seats which engage the ends of the legs. 10 itself, and by an axial flat plate which rises perpendicularly from the transverse plate, is arranged parallel to the central axis 3 of rotation, and is used for the external connection of the synchronous electrical machine 1. Preferably, the three transverse plates of the three connecting clamps 14 are arranged (stacked) one on top of the other in respective fourth axial levels arranged above the third axial level. Preferably, three respective insulating layers 23 of electrically insulating material (typically `` Namex® '' insulating paper) are arranged below the transverse plates of the three connection terminals 14, which separate the first connection terminal 14 from the underlying two bridges 21 of connection and separate the three connection terminals 14 from each other.

In the embodiment illustrated in Figure 15, a plurality of small tiles 24 is also provided, each of which is made of molded plastic material (therefore of electrically insulating material), resting on a base surface of the magnetic core 6 in correspondence of the outlet side 13, it is arranged between two successive stator slots 7, and has a shape that reproduces the curvature of the internal folds 15 of the double folds of the legs 10 of the bars 9 shaped like a `` U '' in such a way that the legs 10 themselves rest on the tile 24.

As illustrated in Figure 17, each small tile 24 comprises an external wall 25 which is arranged outside the stator winding 8 and has a larger dimension than the space present between two successive stator slots 7. Furthermore, each small tile 24 comprises an internal element 26 which is end-connected to the external wall 25, extends perpendicularly to the external wall 25, and has a rounded shape and a half-moon cross section. The upper surface 27 of the internal element 26 reproduces the curvature of the internal folds 15 of the double folds of the legs 10 of the bars 9 shaped like a "U". To follow the outline of the stator slots 7, the internal element 26 of each small tile 24 has a trapezoidal shape in plan which tapers towards the center of the stator 5.

Preferably, each small tile 24 is arranged between each pair of successive stator slots 7 before twisting the legs 10 of the U-shaped bars 9 which protrude into the outlet side 13 of the magnetic core 6; subsequently, the legs 10 of the U-shaped bars 9 which protrude into the outlet side 13 of the magnetic core 6 are twisted against the small tiles 24 (that is, leaning against the upper surfaces 27 of the small tiles 24).

The electric machine 1 described above has numerous advantages.

In the first place, the electric machine 1 described above is simple and inexpensive to manufacture, since all the bars 9 shaped like a `` U '' have the same shape and the same dimensions (in this way both the realization of the bars are greatly simplified 9 conformed to â € œUâ €, and the insertion of the bars 9 conformed to â € œUâ € in the slot 7 of the stator since all the bars 9 conformed to â € œUâ € are identical and therefore equivalent). In order to be able to realize the electrical paths of the stator winding 8, the particular folds of the ends of the pairs 17 of legs 10 and the bridges 19 connecting the ends of the pairs 18 of legs 10 are used; in this way, the electrical paths of the stator winding 8 are created in a simple, fast, easily automatable way even in the presence of "U" -shaped bars 9 that are all the same.

Furthermore, by inserting the U-shaped bars 9 individually (i.e. one at a time) in the corresponding two stator slots 7, it is possible to reduce the stresses to which the U-shaped bars 9 are subjected during the insertion thus avoiding possible damage to the external insulating enamel that covers the bars 9 shaped like a â € œUâ € themselves. This result is obtained thanks to the fact that each bar 9 conformed to `` U '' is pushed individually and therefore it is possible both to precisely calibrate the maximum thrust force that can be exerted on each bar 9 conformed to `` U '', and to apply small corrections to the thrust direction to take into account the specificities of each bar 9 conformed to â € œUâ €. On the other hand, when all the U-shaped bars 9 are inserted together in the stator slots 7, the thrust is exerted simultaneously on all the U-shaped bars 9 and therefore it is possible that one or more bars 9 to â € œUâ € â € œsuckerâ € are subjected to an excessive thrust (that is too strong) and / or badly directed which causes damage to the external insulating enamel that covers the bars 9 shaped like a â € œUâ € themselves.

Finally, the presence of the small tiles 24 improves the quality of the internal folds 15 of the double folds of the legs 10, since at each internal fold 15 the leg 10 is folded against a respective small tile 24 which accompanies and guides the deformation of the leg 10 thanks to the conformation of its upper surface 27. No less important, the presence of the small tiles 24 prevents the legs 10 from accidentally touching the magnetic core 6 of the stator against which it is easy to damage the external insulating enamel which covers the legs 10. 9 bars conformed to â € œUâ €.

Claims (6)

R I V E N D I C A Z I O N I 1) Electric machine (1) comprising: a stator (5) comprising a magnetic core (6) traversed longitudinally by a plurality of stator slots (7); and a stator winding (8) comprising a series of rigid bars (9), which are shaped like a â € œUâ € and are inserted through the stator slots (7) defining an input side (12), in which the cusps (11) of the bars (9) shaped like a â € œUâ €, and a side (13) of exit, in which the legs (10) of the bars (9) shaped like a â € œUâ € are arranged; in which the legs (10) of the bars (9) shaped like a â € œUâ € that protrude in the output side (13) of the magnetic core (6) are twisted by respective double folds, each of which includes an internal fold (15) in one direction and an outer fold (16) in an opposite direction; and in which the ends of the legs (10) of the bars (9) shaped like a â € œUâ € are electrically connected to each other to form the electrical paths of the stator winding (8); the electric machine (1) is characterized by the fact that it comprises a plurality of small tiles (24), each of which rests on a base surface of the magnetic core (6) at the output side (13), is placed between two successive stator slots (7), and has a shape that reproduces the curvature of the internal folds (15) of the double folds of the legs (10) of the bars (9) shaped like a â € œUâ € so that the legs (10) themselves rest on the small tile (24). 2) Electric machine (1) according to claim 1, in which each pan (24) comprises: an external wall (25) which is arranged outside the stator winding (8) and has a larger size than the space between two successive stator slots (7); and an internal element (26) which is end-connected to the external wall (25), extends perpendicularly to the external wall (25), and has a rounded shape and a half-moon cross section. 3) Electric machine (1) according to claim 2, in which the internal element (26) of each small tile (24) has a trapezoidal shape in plan which tapers towards the center of the stator (5). 4) Electric machine (1) according to claim 1, 2 or 3, in which the tiles (24) are made of electrically insulating plastic material. 5) Method of construction of an electric machine (1), which includes: a stator (5) comprising a magnetic core (6) traversed longitudinally by a plurality of stator slots (7); and a stator winding (8) having a number of phases and comprising a series of rigid bars (9), which are U-shaped and are inserted through the stator slots (7) defining an input side (12) , in which the cusps (11) of the bars (9) shaped like a â € œUâ € are arranged, and a side (13) of exit, in which the legs (10) of the bars (9) are arranged in the shape of a â € œUâ €; the construction method includes the steps of: twisting the legs (10) of the bars (9) shaped like a â € œUâ € which come out on the exit side (13) of the magnetic core (6) by means of respective double folds, each of which includes an internal fold (15) in one direction and an external fold (16) in an opposite direction; and electrically connect the ends of the legs (10) of the U-shaped bars (9) to each other to form the electrical paths of the stator winding (8); the construction method is characterized by the fact of including the further step of arranging between each pair of successive stator slots (7) a corresponding tile (24), which rests on a base surface of the core (6 ) magnetic at the outlet side (13), and has a shape that reproduces the curvature of the internal folds (15) of the double folds of the legs (10) of the bars (9) shaped like a â € œUâ € so that the legs (10) themselves rest on the tile (24). 6) Method of construction according to claim 5 and comprising the further steps of: place the tiles (24) between the stator slots (7) before twisting the legs (10) of the bars (9) shaped like a â € œUâ € which protrude in the output side (13) of the magnetic core (6); And twist the legs (10) of the bars (9) shaped like a â € œUâ € which protrude in the exit side (13) of the magnetic core (6) against the tiles (24).