Patent Application
20160181881
This invention relates to an electric machine and its method of assembly.
As is known, electric machines, whether motors or generators, comprise a rotor and a stator that rotates relative to the stator.
The stator can be of various types and, in particular, can be of the bar type, in which the conductors comprise a plurality of bars bent in a “U” so as to have two free ends, i.e., the ends of the branches of said bars bent in a “U”. These free ends must be electrically connected so as to close the windings and, some of them, are welded to related plates made of conductive material, typically copper, which act as electrical bridges; the remaining free ends are welded to each other in sequence.
These bridges serve to obtain the proper connections between the different phases of the windings, so as to allow the electrical connection to an external power supply.
It is obvious that the steps of assembling the electrical bridges and the ends of the conductive bars must be performed with extreme precision and care.
In current solutions of the known art, these operations are not automated, but are performed substantially by hand, the work of specialised personnel.
It is clear that these assembly operations are particularly slow and therefore costly, because they cannot be automated.
Therefore, there is a need to solve the drawbacks and limitations mentioned in reference to the prior art.
Therefore, there is a need to make the assembly of stators of electric machines faster and more economical, with particular reference to electrical bridges.
This need is met by an electric machine according to claim 1 and by an assembly method according to claim 17.
Further characteristics and advantages of this invention will be more understandable from the following description of its preferred and non-limiting examples of embodiments, wherein:
The members, or parts of members, in common between the embodiments described below will be indicated with the same reference numbers.
As mentioned above, this invention refers to the construction/assembly of parts of electric machines.
The specific type of electric machine is not relevant for the purposes of the scope of protection of this invention.
In other words, this invention refers to any electric machine that can function either as a motor or electric generator, in a known manner.
The electric machine is provided with at least one stator 8 and a rotor not shown.
For example, the stator 8 comprises a magnetic core 10, comprising a series of pack-tightened plates and has a centrally perforated shape.
The magnetic core 10 may comprise a plurality of slots 12 that house a stator winding 16.
For example, the stator winding 16 is a three-phase stator winding distributed in a plurality of slots 12 of the stator 8.
The stator winding 16 comprises a plurality of stator winding elements 20 each of which extends from a first to a second end 22,24, separate from each other. The number of stator winding elements 20 is variable as a function of the type of electric machine to be made.
For example, said stator winding elements 20 can be bar-shaped, of different section and size, bent so as to assume an overall “U”-configuration, having two branches 28 that, on the one side terminate in said first and second ends 22,24 separate from each other and, on the other, are connected in a curved portion or knee 30.
Said stator winding elements 20 are inserted into the slots 12 of the magnetic core 10.
The stator winding 16 comprises for example a plurality of connection terminals 30 that constitute the electrical interface with the outside of the stator winding 16 and are connected electrically to an electronic power converter (not shown) that drives the electric machine.
The stator 8 comprises at least one electrical bridge 32 suitable to electrically connect the separate ends 22,24 of two different stator winding elements 20.
The stator 8 comprises at least one support and attachment plate 36 made of electrically insulating material which defines at least one seat 40 suitable to house at least partially, and retain in position, the electrical bridge 32.
For example, the support and attachment plate 36 is made of electrically-insulating plastic.
The support and attachment plate 36 is a rigid element which constitutes a rigid support for the positioning and attachment of the relative electrical bridges 32 in the stator 8.
The seat 40 is provided with attachment means 44 which form at least partially a shaped coupling with the at least one electrical bridge 32, so as to mechanically lock it in position on the support and attachment plate 36.
Said seat 40 also allows the passage of the ends 22,24 of one or more stator winding elements 20 and the electrical connection between these 22,24 and the electrical bridge 32.
In addition, the seat 40 electrically isolates the electrical bridge 32 from other components of the stator 8, obviously except for the corresponding stator winding elements 20 connected to said electrical bridge.
According to an embodiment, the attachment means 44 are shaped so as to form a snap-fit shaped coupling with the electrical bridge 32.
For example, the attachment means 44 create a locking of the electrical bridge 32 by means of at least one undercut 48 in a direction perpendicular to a median extension plane M of said support and attachment plate 36.
According to an embodiment, the attachment means 44 comprise flexible tabs 52 having at least one tooth 54 that forms an undercut 48 in abutment against a portion of the electrical bridge, to secure it in position on the support and attachment plate 36.
Preferably, the attachment means 44 are in turn made of electrically insulating material, preferably said attachment means are an integral part of the plate 36 itself.
According to an embodiment, the support and attachment plate 36 comprises at least one through hole 56 which intercepts the housing seat 40 of the electric bridge 32, so as to allow the passage of one end 22,24 of the stator winding element 20 and its mechanical and electrical connection with the electrical bridge 32.
According to a possible embodiment, the electrical bridge 32 comprises at least a pair of connectors 60 defining a housing space 64 which receives the ends 22,24 of the stator winding element 20 to be connected electrically to the bridge 32 itself, wherein the connectors 60 constitute attachment elements for the ends 22,24 of the stator winding element 22.
For example, the connectors 60 form a snap-fit shaped coupling with the ends 22,24 of the stator winding element 20 and/or a support for a welding of said ends 22,24.
According to a possible embodiment, the support and attachment plate 36 comprises at least one through hole 56 aligned with the housing space 64 delimited by the connectors 60, for the passage of the ends 22,24 of the stator winding element 20 to be connected mechanically and electrically to the electrical bridge 32.
According to an embodiment, said connectors 60 extend as far as an inner 68 or outer 72 radial edge of the support and attachment plate 36, in a radial direction R perpendicular and incident with a rotation axis X-X of the associable rotor, so as to be accessible respectively from an inner side, facing the rotation axis X-X, or from an outer side, opposite the inner side, and to allow the positioning of automatic attachment and/or welding devices for attaching the ends 22,24 of the stator winding 20 to the electrical bridge 32.
Preferably, each support and attachment plate 36 comprises a plurality of seats 40, each seat 40 houses a corresponding electrical bridge 32 attached to the support and attachment plate 36 by means of relative attachment means 44 and each electrical bridge 32 is electrically separate from the other bridges attached to the same support and attachment plate 36.
In addition, the stator 8 comprises a plurality, i.e., at least two support and attachment plates 36, for example one lower 36′ and one upper 36″, reciprocally superposed in an axial direction Y-Y, parallel to said rotation axis X-X, wherein between said superposed support and attachment plates 36′,36″) electrically insulating spacers 76 are present to space the support and attachment plates 36′,36″ by a distance such as to allow the housing of the respective electrical bridges 32.
For example, said spacer elements 76 comprise a protuberance 78 and a corresponding recess 80, suitable to receive said protuberance 78, arranged between an upper wall 82 of the bottom plate 36′ and a lower wall 84 of the upper plate 36″, mutually facing each other.
Preferably, the spacer elements 76 are shaped so as to block between them two support and attachment plates 36′,36″ adjacent in an axial direction Y-Y, both parallel to the axial direction Y-Y and to a plane perpendicular to the axial direction Y-Y.
Now the method of assembling an electric machine according to this invention will be described.
The steps described below can also be executed in a different order than that described without thereby departing from the scope of protection of this invention.
For example, the method comprises the steps of:
Then the step of pre-assembling the electrical bridge 32 in the respective seat 40 is carried out using the attachment means 44, so as to mechanically lock it in position on the support and attachment plate 36 and the ends 22,24 of the stator winding elements 20 are mechanically and electrically connected to the respective electrical bridge 32.
This connection may be mechanical, for example by means of interlocking attachment means and/or by welding.
Preferably, the method involves pre-assembling a plurality of electrical bridges 32, by means of respective attachment means 44, on respective support and attachment plates 36 superposed with each other.
Then the ends 22,24 of related stator winding elements 20 are mechanically and electrically connected to respective electrical bridges 32 according to a predetermined wiring diagram.
For example, the insertion of the stator winding elements in the pack of superposed support and attachment plates can take place by inserting the ends 22,24 from an input side 86 of the core 10 to bring them in correspondence with an output side 88 of the same core, along the slots 12 of the magnetic core.
On the output side 88, the ends 22,24 are inserted in correspondence of the through holes 56 of the support and attachment plates 36 so as to intercept the connectors 60 of the respective electrical bridges.
The attachment of the ends 22,24 to the connectors can be performed automatically by means of crimping machines/heads and/or welding that secure/weld the ends 22,24 to the connectors 60. This operation is facilitated by the fact that the connectors 60 and the housing spaces 64 delimited by these extend up to the respective inner and outer radial edges 68,72 of the support and attachment plates 36. In this way, the connectors 60 and the ends 22,24 are easily accessible by the automatic machines that carry out the mechanical/electric attachment.
Obviously, thanks to this invention, all the construction/assembly operations described above can be automated so as to limit as much as possible the manual intervention of the operator and to reduce the cost and time of assembly of the stators of the electrical machines.
As can be appreciated from the description, this invention allows overcoming the drawbacks presented in the prior art.
In fact, the invention described allows implementing the isolation between the different layers of the windings of the stators of electric machines using support and attachment plates made of electrically insulating material that allow simple handling and assembly by means of automatic machines.
In addition, the support and attachment plates made of insulating material according to the invention hold the electrical bridges in position through interlocking tabs that prevent any movement of the latter, which remain constrained to the respective plate by the undercut of the tabs.
In this way, one obtains automatic attachment of the electrical bridges without requiring the manual intervention of an operator.
Moreover, the support and attachment plates are made in a manner that facilitates their correct “stacking” through for example spacers placed between two support and attachment plates superposed and contiguous with each other; the mechanical connection between the pin/protuberance of one plate and the recess/seat of another superposed plate allows having a mechanical attachment between the plates that facilitates the assembly steps through the use of automatic lines.
The solution according to the invention allows the manipulation and assembly of electrical bridges using an automatic machine, thus facilitating the assembly of the machine itself, and reducing the time and cost of assembly of the stators of electric machines.
A person skilled in the art, in order to satisfy contingent and specific needs, may make numerous modifications and variations to the electric machines and assembly methods described above, all however contained within the scope of the invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102014902318553 | Dec 2014 | IT | national |
