Method for welding adjacent terminals of conductor elements of an electric machine induction winding and welding station therefor

Abstract

A welding method for a winding (B) of an electric motor, the motor including a hairpin-shaped conductor element (C) positioned within a corresponding longitudinal slot (D) of a ferromagnetic core (E). The welding method includes the steps of: arranging the ferromagnetic core (E) containing the conductor element (C) in a welding area; and welding the terminals (A) of the conductor (C) to each other with a laser beam (2a) using a welding apparatus (2) to irradiate the front portion (H) of adjacent terminals (A) at time intervals suitable for melting the ends of the material constituting them, thereby generating weld droplets (L). According to the invention, the step of arranging the core (E) provides that the core is arranged such that its longitudinal axis (F) is oriented in a horizontal direction. Furthermore, the method includes the step of injecting a gas jet (3a) toward the front portion (H) of the terminals (A) in a substantially vertical and bottom-up direction.

Description

Technical Field

[0001] This invention relates to a welding method for adjacent terminals of conductor elements in an electric motor induction winding and a welding workbench thereof. Background Technology

[0002] In this specification, the term "conductor element" is understood to include all portions of conductive elements (electric conductors) that can be used to provide induction windings for motors (such as, for example, electric motors, AC generators, DC generators, and others): therefore, so-called "hairpins," "I-shaped pins," and any other type of conductive material that can be used to provide portions of the induction winding of interest also fall within this definition.

[0003] The terminals of the various parts of the conductor element must be coupled to each other (by welding) to ensure the necessary electrical continuity of the induction winding so that it can trigger the electromagnetic interactions that ensure the proper operation of the motor; thus, when a suitable current is carried, the induction winding of the stator of the motor generates a traction force on the rotor through electromagnetic induction, thereby causing the rotor to rotate.

[0004] Typically, the terminals of conductor elements are soldered while maintaining the conductor elements in a vertical orientation with their longitudinal axis facing upwards. In this way, the effect of gravity holds the molten metal blob at the top of both terminals (a small portion of the molten material may drip down the first short section of the sidewall of the terminal).

[0005] This well-established technique, used in almost all devices for welding the terminals of conductor elements that make up the inductor windings of an electric motor, has some problems because the welding step is usually performed by means of a laser welding device facing upwards from the terminals of the conductor element, with the aim of firing a laser beam downwards in a direction with a vertical component in order to melt the metal material of such terminals.

[0006] During the step of melting the metal of the terminals of a conductor element, fumes are generated. As the fumes reach high temperatures, they tend to rise relative to the surface of the terminals and therefore return towards the laser welding equipment located above the terminals, interfering with the laser beam. This can be problematic because it may reduce the efficiency of the laser beam, leading to uneven melting of the material.

[0007] Furthermore, after the metal material supplied by the laser beam melts, there is a solidification step of the weld droplets, which is usually characterized by rapid cooling. During this period, the weld droplets undergo physical instability, and therefore molten metal spatter (i.e., the "welding spatter" in jargon) may occur and may interfere with the laser beam, or in any case, damage the quality of the surfaces adjacent to those surfaces to be welded (the surfaces on which the spatter of the molten material may be deposited).

[0008] Furthermore, the presence of a large amount of welding fumes near the molten droplet during melting and cooling increases the porosity of the weld droplet, and once such a droplet has solidified, the porosity of the resulting weld joint increases. Although this effect can only be detected by microscopy, it can significantly reduce the permissible tear strength (the maximum mutual tearing force applied to two different conductor elements welded together) of the weld joint of the conductor element terminals.

[0009] The problem described, namely, the presence of welding fumes and the generation of welding spatter, sometimes reduces the net area (and net volume) of the weld joint performed between two terminals (understood as the difference between the total area or volume of the weld joint and the area or volume occupied by the pores), (in particular, what can happen in a completely unpredictable way is that the tear strength of some of the welded terminals—understood as the force required to separate the two welded terminals by their spacing from each other—is below the required standard due to such a problem). Summary of the Invention

[0010] The object of the present invention is to solve the above-mentioned problems by providing a method for welding adjacent terminals of conductor elements of induction windings of an electric motor, which ensures that high tear strength values ​​are obtained for the welded terminals.

[0011] Within this scope, the object of the present invention is to provide a method for welding adjacent terminals of conductor elements of an induction winding of an electric motor, which ensures that a substantially constant tear strength value of the welded terminals is obtained even on very large weld samples.

[0012] Another object of the present invention is to provide a method for welding adjacent terminals of conductor elements of an induction winding of an electric motor, wherein the quality of the weld joint is not affected by the presence of fumes emitted from molten metal.

[0013] Another object of the present invention is to provide a method for welding adjacent terminals of conductor elements of an induction winding of an electric motor, wherein the quality of the weld joint is not affected by the presence of welding spatter, as it may increase the porosity of the weld joint, reduce tear strength, or settle on some parts of the welding table (such as laser welding equipment), thereby reducing efficiency during subsequent terminal welding.

[0014] Another object of the present invention is to provide a workbench for welding adjacent terminals of conductor elements of an induction winding of an electric motor, which allows for obtaining high tear strength values ​​of the welded terminals.

[0015] Another object of the present invention is to provide a workbench for welding adjacent terminals of conductor elements of an induction winding of an electric motor, which allows a substantially constant value of the tear strength of the welded terminals to be obtained even on very large samples of welding.

[0016] Another object of the present invention is to provide a workbench for welding adjacent terminals of conductor elements of an induction winding of an electric motor, which ensures that the welding quality is independent of the presence of fumes emitted by the molten metal.

[0017] Another object of the present invention is to provide a workbench for welding adjacent terminals of conductor elements of an induction winding of an electric motor, which ensures that the welding quality is independent of the presence of welding spatter emitted by molten metal.

[0018] Another object of the present invention is to provide a method and corresponding welding table for welding adjacent terminals of conductor elements of induction windings of an electric motor, which are low cost, relatively simple and easy to implement in practice, and reliable in application.

[0019] This objective and these objectives are achieved by the method of welding adjacent terminals of the conductor elements of the induction winding of an electric motor according to claim 1.

[0020] This objective and these objectives can also be achieved by means of a soldering station for the terminals of the conductor element of the induction winding of an electric motor according to claim 6. Attached Figure Description

[0021] Other features and advantages of the invention will become more apparent from the description of a preferred, but not exclusive, embodiment of the method for welding adjacent terminals of the conductor elements of the induction winding of an electric motor and the welding table for performing it, which is illustrated by way of non-limiting example in the accompanying drawings, wherein:

[0022] Figure 1 It is a schematic front view of an incomplete induction winding set inside the ferromagnetic core of a motor;

[0023] Figure 2 yes Figure 1 A schematic isometric view of the incomplete induction winding, and an illustrative block diagram of a workbench suitable for performing the method according to the invention;

[0024] Figure 3 yes Figure 2 A magnified view of detail III, as indicated in the diagram, combined with an illustrative block diagram of a portion of a workbench suitable for performing the method according to the invention;

[0025] Figure 4 It is a schematic front view of the induction winding installed inside the ferromagnetic core of the motor;

[0026] Figure 5yes Figure 4 A schematic isometric view of the induction winding;

[0027] Figure 6 yes Figure 5 A magnified view of the details of the VI marked in the middle;

[0028] Figure 7 This is an enlarged schematic isometric view of the gas jet injector of the workbench according to the present invention;

[0029] Figure 8 It is a schematic side view of a set of terminals during a welding method with terminals arranged vertically, according to the prior art;

[0030] Figure 9 It is a schematic side view of a set of terminals during a welding method with terminals arranged horizontally according to the prior art;

[0031] Figure 10 This is a schematic side view of a set of terminals during the welding method according to the present invention. Detailed Implementation

[0032] Referring to the above figures, the welding station for adjacent terminals A of the conductor element C of the inductor winding B of the motor suitable for performing the method according to the invention is generally indicated by reference numeral 1.

[0033] The welding method according to the invention is suitable for completing the winding B of an electric motor (closing the circuit, intended to provide its continuity), comprising a hairpin-shaped conductor element C (i.e., a portion of a conductor wire made of conductive material and provided with an outer coating A1 made of dielectric material, bent in a substantially hairpin shape and provided with a form suitable for engaging with corresponding ends of other conductor elements C to provide the end of the electrical winding B). Specifically, the conductor element C is positioned within a corresponding longitudinal slot D of the ferromagnetic core E of the motor winding B, stator, or rotor.

[0034] In practice, the ferromagnetic core E can be one of the stators of a rotating electric machine (as in the example given in the accompanying drawings as a non-limiting example) or one of the rotors, or one of the cores of a static electric machine (such as a power and non-power transformer and / or an autotransformer).

[0035] The ferromagnetic core E of the motor on which the component 1 of the present invention can operate includes a longitudinal axis F, which is perpendicular to the two mutually opposite heads E1 and E2 of the core E.

[0036] A particular end of the conductor element C (which at least partially protrudes from the corresponding heads E1, E2 of the ferromagnetic core E) includes a corresponding terminal A (which fully protrudes from the corresponding heads E1, E2 of the ferromagnetic core E), which will be soldered to at least one additional terminal A arranged adjacently, wherein at least one additional terminal A also fully protrudes from the same heads E1, E2 of the ferromagnetic core E.

[0037] Terminal A is arranged in groups of at least two adjacent terminals A: all terminals A belonging to the corresponding group are suitable for soldering to each other.

[0038] The welding method includes a first step in which a ferromagnetic core E, comprising the conductor element C, is arranged in the welding area, according to the configuration of the terminal A of the conductor element C facing and oriented toward the welding equipment 2. The welding area corresponds to the compartment of the welding station 1, which is better shown below and is configured to accommodate the iron core E.

[0039] Then, a second step is provided: welding terminals A together using welding equipment 2. Welding equipment 2 is of the laser type and is configured to emit a laser beam 2a oriented substantially parallel to the direction of terminal A in conductor C. In the ferromagnetic core E, terminal A is arranged such that its longitudinal axis G is parallel to the axis F of the ferromagnetic core E.

[0040] The second step of welding involves welding terminals A to each other using a laser beam 2a emitted by device 2, wherein the laser beam 2a is directed to irradiate the front side H of adjacent terminals A in the group: the emission of beam 2a is sustained for an appropriate time interval to melt the end of the material constituting terminal A (the end near the front side H), thereby causing the formation of weld droplets L (droplets of molten material).

[0041] According to the invention, the first step of arranging the core E is advantageously configured to arrange the core E such that its longitudinal axis F is oriented in the horizontal direction.

[0042] To provide clear identification for the terms "horizontal" and "vertical" as used in this specification, the vertical direction is to be understood as parallel to the Earth's gravitational field; more precisely, the vertical direction should be the direction of gravitational acceleration a. g The direction. Therefore, it is located perpendicular to the vertical direction (and thus with respect to gravitational acceleration a). g The direction on a plane that is orthogonal to the direction of the plane is identified as the horizontal direction.

[0043] The method according to the invention also conveniently includes the step of injecting a gas jet 3a in a substantially vertical direction and upward toward the front side H of terminal A via a specific injector 3, which is better described below. This step of injecting the gas jet 3a is performed so as to at least partially overlap with the welding step.

[0044] This means that, preferably, the step of jetting the gas jet 3a is intended to begin before the device 2 emits the laser beam 2a, and is only interrupted after the emission of the laser beam 2a is interrupted in order to continue the entire duration of the laser emission.

[0045] The emission of the synchronous laser beam 2a and the ejection of the gas jet 3a are not excluded, or in some cases, depending on the specific application, the start of the ejection of the gas jet 3a may be advanced and / or delayed relative to the start or end of the emission of the laser beam 2a.

[0046] It should be noted that, in the steps following the placement of the iron core E in the welding area and preceding the welding step, the method according to the invention may advantageously also include a step of aligning adjacently arranged terminals A to each other in order to ensure a stable mutual welding position. Such adjacently arranged terminals A belong to the same group of terminals A to be welded together, therefore preliminary alignment will enhance the welding quality.

[0047] During this initial step of aligning the terminals A with each other, preferably, the alignment operation of each group of terminals A to be welded can be performed along at least one of the directions of the Cartesian coordinate system (shown in the figures and identified by the Cartesian three-axis coordinates of X, Y and Z) and / or according to at least one rotation angle (shown in the figures and identified by the angles α, β and γ) relative to the corresponding X, Y, Z axes of the Cartesian system.

[0048] Referring to the Cartesian coordinate system shown in the attached figure, to explicitly define the geometry of the construction example shown in the figure, the X and Z axes are located in the horizontal plane, while the Y axis has a vertical direction (i.e., corresponding to the gravitational acceleration a). g (direction). Clearly, such a geometric configuration refers to one possible embodiment and is not a limitation on any other variation, wherein the axes of the Cartesian coordinate system do not require the Y-axis to be aligned with the gravitational acceleration a. g Orientation arrangement.

[0049] The initial alignment step ensures that terminals A in the same group are perfectly juxtaposed and overlapped. Considering the need to stack them vertically (so that each terminal A is above or below another terminal A), and to match the base surface of the first terminal A with the top surface of the other terminal A (and so for any other terminals A forming the group of interest), it is also suitable to provide an additional orientation step, by which terminals A can be arranged each time so that they are correctly oriented relative to the reference system and the laser welding apparatus 2 (or relative to the laser beam 2a). It should be noted that the orientations of the laser welding apparatus 2 and the laser beam 2a are fixed; therefore, the only way to correctly arrange terminals A relative to the orientation of the laser beam 2a is to spatially orient the terminals A according to the specific requirements of mutual overlap in the vertical direction. However, it is not excluded that terminals A can be arranged side-by-side (their side surfaces match), although this is a less important embodiment in the application.

[0050] Referring to an embodiment of the invention, during the step of arranging the core E, the core E is arranged such that its axis F is substantially horizontal.

[0051] The basic horizontality of axis F can be identified as the geometric condition of the axis, whereby it is arranged horizontally or tilted at a small angle relative to the horizontal direction (e.g., tilted ±15° relative to the horizontal direction, or preferably tilted ±10° relative to the horizontal direction).

[0052] With the axis F of the iron core E arranged completely horizontally, the gas jet 3a toward terminal A has a substantially vertical direction, with an upward direction, i.e., in accordance with the gravitational acceleration a. g The directions are opposite.

[0053] Similar to the basic horizontal description of axis F, the orientation of the gas jet 3a in the vertical direction can also have tilt tolerances. If the axis F of the core E is tilted relative to the horizontal state (as shown above at a small angle), the gas jet 3a can also be tilted at a low angle relative to the vertical state (e.g., ±15° relative to the vertical direction, or preferably ±10° relative to the vertical direction), or it can be completely vertical, depending on the specific requirements of the application and the objectives to be achieved by means of the gas jet 3a.

[0054] The gas jet 3a produces a series of positive effects on weld quality, which will be described in detail below.

[0055] First, the gas jet 3a (characterized by having a gravitational acceleration a) gThe orientation (generally vertical, opposite to the direction of the molten droplet L) ensures support for the molten droplet L in a manner known in the art as a "fluidized bed" or "gas buffer," otherwise the molten droplet L would be affected by its own weight (due to gravitational acceleration a). g They are pulled downwards by gravity.

[0056] These aspects Figure 8 , 9 As shown in 10. In particular, Figure 8 The welding steps of a conventional method are shown, wherein terminal A is arranged vertically, and the molten droplet L is supported by terminal A below it. Furthermore, Figure 9 The welding steps of a conventional method are shown, wherein terminal A is arranged horizontally, and molten droplets L are attracted downwards under gravity (with gravitational acceleration a). g The orientation and direction of the weld (resulting in deformation) cause the weld joint to deform, leading to a poor weld joint R. Similarly, Figure 10 The welding steps according to the method of the present invention are shown, wherein the molten droplet L is supported by a gas jet 3a to resist gravity (with gravitational acceleration a). g (orientation and direction). By calibrating the intensity of the gas jet 3a, the molten droplet L can be supported, preventing it from deforming or moving downwards relative to the terminal A of the assembly being welded.

[0057] Furthermore, during the welding process, gaseous fumes M can be generated. In the prior art, these fumes M remain close to the molten droplets L, interfering with the laser beam 2a and potentially reducing its effectiveness. In addition, the fumes M may increase the porosity of the weld joint, impairing its mechanical properties (or reducing them in any case), particularly its mechanical strength.

[0058] With the presence of the gas jet 3a, the flue gas M moves rapidly away from the molten droplets L, thereby ensuring that the laser beam 2a is not disturbed by it.

[0059] During the welding process, particularly during the cooling and solidification phases following material melting (i.e., during the transition of the molten material from a liquid to a solid state), the release of particles N of molten (or even solid) material from the molten droplets L can also occur, which is commonly referred to as weld spatter in industrial technical terms. Clearly, spatter N can deposit anywhere, even close to the terminals A of the group being welded, thereby impairing the quality of the entire performed method and potentially also the quality of the induction winding B. In particular, spatter N from the molten droplets L can lead to an increase in the porosity of the weld joint, reducing tear strength (weld quality), and may settle on the components of the welding station 1, damaging them or reducing their effectiveness, thus negatively impacting subsequent welding operations performed on the terminals A of other groups.

[0060] For this reason, it is preferable to reduce spatter N that may deposit on portions of winding B and / or terminal A: the gas jet 3a facilitates the removal of spatter N from terminals A and winding B, thereby improving the soldering quality of terminal A of the group and potentially improving the quality of the entire induction winding B.

[0061] Finally, it should be noted that the gas jet 3a removes heat from the molten droplet L: the cooling ratio of the molten droplet L (and its solidification) is improved (and more uniform) in the absence of the gas jet 3a.

[0062] Experimental verification shows that improved cooling and removal of fumes M and spatter N allow for stronger (high tear strength) and more stable welds, ensuring a weld joint R with a set of weld terminals A of a regular and generally symmetrical shape. In fact, the gas jet 3a blows away spatter N in the lateral direction relative to the welding mask, increasing its lifespan because it is not subject to undesirable adhesion of welding spatter N. This results in higher yields, reduced downtime in plant equipment implementing this method due to preventative / planned maintenance operations, and reduced downtime in plant equipment implementing this method and associated "non-conforming products" due to corrective maintenance operations triggered by excessive spatter N deposited on the welding mask.

[0063] Furthermore, during the welding operation, a plasma corona is generated around the molten droplet L: such a plasma corona draws energy from the laser beam 2a, and thus degrades the quality of the weld joint and / or requires more time to complete the weld joint. The gas jet 3a ensures that the plasma corona is cleared (or otherwise displaced relative to the laser beam 2a): this ensures that the maximum possible energy supplied by the laser beam 2a is delivered to the terminal A for localized melting of its ends and its welding.

[0064] Advantageously, the method according to the invention also includes the step of oriented ferromagnetic core E, which allows ideal alignment of the groups of terminals A to be welded on each other with respect to the vertical direction of the gas jet 3a.

[0065] Referring to an embodiment of the invention, the method according to the invention may more specifically include the step of rotating the ferromagnetic core E about its longitudinal axis F so that each time the group of terminals A to be welded on each other is aligned with each other in the vertical direction of the gas jet 3a.

[0066] The method according to the invention may include the step of: at the end of the welding step performed on the previous set of terminals A, realigning a new set of terminals A in the group to be welded in the corresponding groove D of the ferromagnetic core E to each other with the laser welding device 2 (and the injector 3 of the gas jet 3a).

[0067] The movement of the ferromagnetic core E is used to allow the alignment of a new set of terminals A with the device 2 and the injector 3, aiming to bring the new set of terminals A (not yet welded) into the correct position for welding based on the correct alignment relative to the gas jet 3a. This operation is less important if the terminals A, which have a vertical longitudinal axis, are welded by means of a laser beam 2a that is also arranged in a vertical direction: in fact, in this case, the molten droplet L is not suspended in the air and subjected to a gravitational field as would occur in the case of welding along the horizontal direction of the laser beam 2a, but is supported by the terminals A, which are arranged below the molten droplet L in this case.

[0068] In this way, by means of rotating the iron core E, the welding device 2 (more precisely, the direction in which it emits the laser beam 2a) and the jet 3 (more precisely, the direction in which it delivers the gas jet 3a) can be aligned with a new set of terminals A to allow them to be welded.

[0069] It should be noted that the method according to the invention can also effectively include an additional preventative step of removing the coating A1 made of dielectric material from each conductor element C at its terminal A: the coating A1 needs to be removed to ensure that the welding quality is optimal, because when irradiated by the laser beam 2a, the dielectric material may produce gaseous emissions (fumes) or solid residues, which may degrade the welding quality of the terminal A of the assembly to be welded.

[0070] Preferably, the gas jet 3a can conveniently be a dry air stream, i.e., air with a water vapor content of less than 1%, and preferably pre-filtered.

[0071] The minimum content of water vapor and suspended particles in the airflow constituting the gas jet 3a ensures that the airflow does not interfere with the propagation of the laser beam 2a in the desired direction, thereby avoiding undesirable phenomena such as refraction, scattering, and absorption of the laser beam 2a due to the high presence of vapor. The gas jet 3a must therefore allow the laser beam 2a to be transmitted substantially completely as it passes through it.

[0072] The absence of humidity in the gas jet 3a is extremely advantageous, as the presence of vapor will have many negative effects on the molten droplets L, leading to increased porosity in the weld joint and deterioration of its mechanical properties (i.e., tear strength).

[0073] Advantageously, the gas jet 3a can be provided by using a gas of the type used as a "protective gas" (i.e., inert or semi-inert, such as nitrogen, carbon dioxide, helium, argon, etc.).

[0074] Preferably, the gas jet 3a is advantageously injected through a plurality of nozzles connected to a compressed air supply line: the specified compressed air supply line may be associated with a compressed air circuit of a known type.

[0075] The gas jet 3a can be effectively injected at pressures ranging from 100 kPa to 2 MPa (i.e., between 1 bar and 20 bar), preferably between 300 kPa and 1 MPa (i.e., between 3 bar and 10 bar), and even more preferably between 500 kPa and 600 kPa (i.e., between 5 bar and 6 bar).

[0076] An experimentally validated, unquestionable embodiment provides for injecting a gas jet 3a at a pressure of 570 kPa (corresponding to 5.7 bar); in this experimental validation, eight separate nozzles consisting of orifices of approximately 1 mm in diameter are used, which are arranged on the common generatrix of a cylindrical tube of approximately 8 mm in diameter.

[0077] In the method according to the invention, which provides horizontal welding (i.e., performed on terminals A having their respective axes G arranged in a substantially horizontal direction, and performed by means of a laser beam 2a that also has a substantially horizontal direction), it is crucial that the terminals A of the group to be welded are ideally oriented to each other and to be oriented relative to the injector 3 (in particular, the direction of its gas jet 3a).

[0078] Therefore, the rotation of the ferromagnetic core E is set around its axis F, so that its heads E1 and E2 remain on their respective fixed planes.

[0079] Preferably, the orientation step is provided to prepare the core E such that a vertical overlap is created in the group of adjacent terminals A (i.e., each terminal is above the other), and their respective axes G are substantially horizontal; this is necessary to ensure the desired weld quality. Achieving vertical overlap of adjacent terminals A in the group to be welded by rotating the core about its axis F is extremely advantageous because it ensures the uniformity of the weld joint R due to the gravitational acceleration a. g Its function is to place one terminal A on top of the other to help ensure that each weld joint R has a substantially constant tear strength.

[0080] As shown above, the mutual realignment step can be conveniently performed by means of a specific displacement of the ferromagnetic core E. In particular, an embodiment that allows for effective realignment can be achieved by means of rotation of the ferromagnetic core E about the corresponding (symmetrical) longitudinal axis F.

[0081] The scope of protection of this invention also extends to the welding table 1 for the winding B of an electric motor having a hairpin-type conductor element C.

[0082] In this workbench 1, the conductor element C is placed in the corresponding slot D of the ferromagnetic core E.

[0083] The ferromagnetic core E should include a longitudinal axis F perpendicular to two opposing heads E1 and E2 of the core E.

[0084] The corresponding ends of the conductor element C include corresponding terminals A, which protrude from at least one of the two heads E1 and E2 of the ferromagnetic core E in order to be welded together.

[0085] Terminal A is arranged in groups of at least two adjacent terminals A for welding to each other.

[0086] Advantageously, the workbench 1 according to the invention includes a support 4 for locking the ferromagnetic core E: in Figure 2 In this illustration, support 4 is shown only as an example, consisting of a pair of retaining elements (represented by corresponding graphic symbols used in physics and mechanics) that allow the core E to be rigidly locked and, if necessary, to rotate about its own axis F. Clearly, the graphic representation refers to one possible way of providing support 4, which could actually be provided according to entirely different geometries and structures, while still falling within the scope of this invention.

[0087] Furthermore, the workbench 1 includes at least one welding device 2 configured to emit a laser beam 2a directed in a direction substantially parallel to the longitudinal axis G of the terminals A to be welded. Referring to an embodiment of the invention, by way of non-limiting example, it is specified that the direction of the longitudinal axis G of the terminal A and the direction of the axis F of the core E may be parallel.

[0088] The laser beam 2a is sized to locally melt the ends (near the front side H) of the material that makes up the terminal A of the group, thereby enabling them to be welded together.

[0089] As previously stated, the support 4 used to lock the core E must ensure a movable lock so as to allow extraction of the core in which all the welds required for the completion of the inductor winding B have been performed. The support 4 is configured to arrange the core E such that its longitudinal axis F is substantially horizontal.

[0090] Furthermore, the workbench 1 according to the invention also includes a gas injector 3, which is configured and oriented to spray a gas jet 3a toward terminal A in a substantially vertical orientation at its front end H and in an upward direction.

[0091] Furthermore, it is advantageously provided that the workbench 1 may include an alignment mask, not shown in the drawings, but still conforming to the teachings of international patent applications WO2023083714 and WO2023088802 under the same applicant.

[0092] The mask allows alignment operations to be performed during translation and / or rotation of terminals A in at least one corresponding group.

[0093] In particular, the mask is advantageously configured to provide alignment of each set of terminals A to be soldered along at least one of the directions of the Cartesian coordinate system (shown in the figures and identified by the Cartesian three coordinate axes X, Y and Z) and / or according to at least one rotation angle (shown in the figures and identified by the three rotation angles α, β and γ) relative to the corresponding axes X, Y, Z of the Cartesian system.

[0094] The initial alignment step ensures that terminals A in the same group are perfectly juxtaposed and overlapped. Preferably, they overlap vertically such that each terminal A is above or below another terminal A, such that the base surface of the first terminal A is in contact with the top surface of the other terminal A or any other terminal A forming the group of interest. However, it is not excluded that terminals A can be arranged side by side with their side surfaces in contact horizontally, although this is a less important embodiment in the application.

[0095] The locking support 4 is configured for the indexing rotation of the core E about its own longitudinal axis F so as to orient a new set of terminals A to be welded together each time, wherein one terminal A is arranged vertically above another terminal A in the same set (i.e., vertically stacked, such that the base of one terminal A is juxtaposed with the top of the other terminal A in the set, as shown above).

[0096] Gas injector 3 can be configured to inject compressed air: in this case, injector 3 can be connected to a device for supplying compressed air (which is of a known type and is generally independent of workbench 1, supplying only compressed air relative to workbench 1). As an alternative to compressed air, inert gases (protective gases), such as nitrogen, CO2, helium, argon, etc., are provided for the use of cylinders.

[0097] Furthermore, it should be noted that the gas injector 3 may include a plurality of adjacent nozzles configured and sized to produce a compressed gas jet 3a that is wider than the width S of a set of adjacent terminals A to be welded together.

[0098] The compressed gas injector 3 can be composed of a tube 4 with a plurality of holes 5, which are distributed generally along the direction of its side surface and along a portion longer than the width S of a set of adjacent terminals A to be welded together.

[0099] According to the specification, in the workbench 1 according to the invention, the iron core E can be arranged such that its longitudinal axis F corresponds substantially horizontally to the configuration of the axis G of the terminal A of the conductor element C housed in the corresponding slot D of the iron core E, with a tolerance of about ±15° relative to the horizontality, preferably ±10° relative to the horizontality.

[0100] In this configuration, the compressed gas injectors 3 are arranged at their front end H, along a direction approximately perpendicular to the longitudinal axis F of the iron core E, with a tolerance of approximately ±15° relative to the orthogonal direction, preferably ±10° relative to the orthogonal direction, and in an upward direction, i.e., substantially in line with the gravitational acceleration a. g The direction is opposite, and the gas jet 3a is sprayed toward terminal A.

[0101] According to an embodiment of the present invention, there may be at least two holes 5 on the tube 4, preferably at least four, or even more preferably at least six.

[0102] Figure 7 The preferred embodiment shown by way of non-limiting example provides the use of a tube 4 having eight holes 5, the eight holes 5 being laterally adjacent and arranged along a generatrix of the side surface of the tube 4.

[0103] Each hole 5 constitutes a jet nozzle and has a diameter between 0.05 mm and 10 mm, preferably between 0.5 mm and 3 mm, or even more preferably close to 1 mm.

[0104] All embodiments shown to date have been found to be applicable to different hairpin sizes (which include varying amounts of molten droplets L depending on the width of terminal A, to be supported by a specific gas jet 3a). Other different embodiments within the inventive concept of the invention may be readily adopted for other different application requirements.

[0105] Furthermore, the support member 4 may usefully include a support device for locking the iron core E, which is configured to arrange the iron core E completely horizontally with its longitudinal axis, wherein the axis G of the terminal A is correspondingly arranged completely horizontally.

[0106] In this case, at least one welding device 2 is configured to emit a laser beam 2a having a direction substantially parallel to the longitudinal axis G of the terminal A to be welded, i.e., a horizontal direction.

[0107] Furthermore, in this case, the gas injector 3 is configured to inject a gas jet 3a in a direction perpendicular to the axis G of the terminal A to be welded, so the gas jet 3a is substantially vertical and has a gravitational acceleration a. g The opposite direction.

[0108] This leads to the consequences listed below:

[0109] - The gas jet 3a ensures at least partial support of the molten droplet L in the end region of the terminal A of the assembly subjected to the incident laser beam 2a.

[0110] - Gas jet 3a removes any liquid exudates such as splashes N and gaseous exudates such as flue gas M originating from molten droplets L;

[0111] When the laser beam 2a incident on terminal A stops emitting, during the cooling / solidification step of the weld joint R, the gas jet 3a optimizes / regulates the forced convection heat transfer of the molten droplets L, thus increasing the tear strength and stability of the weld joint.

[0112] In particular, it has been verified that terminals A welded together in a workbench 1 according to the invention and / or by applying the method according to the invention have a tear strength of approximately 400 N, which is higher than the tear strength achievable by conventional welding methods with terminals A in the vertical direction and laser beam 2a (which has a value of approximately 260 N).

[0113] Tear strength can be measured according to the standard given in UNI EN ISO 4136 ("Destructive testing of welded metal materials - transverse tensile test").

[0114] Advantageously, the present invention solves the above-mentioned problems by providing a welding method for adjacent terminals A of conductor element C of induction winding B of an electric motor, ensuring a high tear strength value for the welded terminals A.

[0115] Conveniently, the method according to the invention ensures that even on very large weld samples, the tear strength of the weld terminal A is obtained at a substantially constant value (in particular, always higher than the average value obtainable with welded joints performed using the background technique based on terminals A arranged in the vertical direction).

[0116] The method according to the invention ensures that the quality of the welded joint is not affected by the presence of fumes M emitted from the molten metal.

[0117] The method according to the invention ensures higher productivity in welding equipment for motor windings by reducing spatter N deposited on the device 2 or on the alignment mask used for welding.

[0118] The method according to the invention ensures that the weld quality is not affected by the presence of spatter N emitted from the molten metal. In particular, since the uncontrolled implosion of spatter N during rapid cooling during solidification can increase the porosity of the weld joint R (reduced tear strength), eliminating and / or reducing spatter N contributes to increased mechanical strength at the layer of the weld joint R. Furthermore, the gas jet 3a also results in a reduction of spatter N that may deposit on the welding mask, because the spatter N is propelled at a right angle to the direction of terminal A and subjected to gravitational acceleration a when outside the effective range of the gas jet 3a. g The effect of gravitational acceleration a gMoving spatter N away from the area where welding is performed (station 1) promotes greater cleanliness. Furthermore, reduced spatter N leads to lower maintenance requirements for welding station 1 and increased productivity: the welding mask is actually less affected by spatter N deposition. This reduces the need for planned / preventative maintenance operations and also reduces the cost of spare parts required to replace components damaged by the accumulation of spatter N.

[0119] The welding station 1 for the terminal A of the conductor element C of the inductor winding B of the motor according to the present invention allows for obtaining a high tear strength value for the welded terminal A.

[0120] According to the workbench 1 of the invention, even on very large welding samples, a substantially constant value of tear strength of the welded terminal A is allowed to be obtained (in particular, always higher than the average value that can be obtained by welding joints performed using the background technology based on terminals A arranged in the vertical direction).

[0121] The workbench 1 according to the present invention ensures that the welding quality is independent of the presence of fumes M emitted by the molten metal.

[0122] The workbench 1 according to the invention ensures that the welding quality is independent of the presence of spatter N emitted by molten metal.

[0123] The welding method and welding station 1 according to the invention are relatively simple to provide in practice and low in cost: these characteristics make the welding method and welding station according to the invention innovative and reliable in application.

[0124] Therefore, the conceived invention allows for many modifications and variations, all of which are within the scope of the inventive concept; all details may also be replaced by other technically equivalent elements.

[0125] In the illustrated embodiments, the various characteristics given for a particular example may actually be interchanged with other different characteristics present in other embodiments.

[0126] In practice, the materials and dimensions used can be any materials according to the requirements and conditions of the field.

[0127] The disclosure of Italian patent application No. 102023000025227, which claims priority to this application, is incorporated herein by reference.

[0128] If any technical feature mentioned in a claim is followed by a reference numeral, such reference numerals are included solely to enhance the comprehensibility of the claim, and therefore do not limit the interpretation of each element illustrated by these reference numerals.

Claims

1. A welding method for welding a hairpin-type conductor element (C) inserted into a corresponding longitudinal slot (D) of a ferromagnetic core (E), wherein... - The ferromagnetic core (E) includes a longitudinal axis (F) perpendicular to two opposite ends (E1, E2) of the core (E); - Each end portion of the conductor element (C) includes a corresponding terminal (A) protruding from one of the two heads (E1, E2) of the ferromagnetic core (E); - The terminals (A) are arranged adjacent to each other in groups of terminals (A) of at least two different conductor elements (C); The welding method includes the following steps: -The ferromagnetic core (E) on which the conductor element (C) is disposed is arranged in the welding area according to the configuration in which the terminal (A) of the conductor element (C) faces the welding equipment (2) and is oriented toward the welding equipment (2); - The terminals (A) are welded together by means of a laser beam (2a) using the welding equipment (2), the laser beam (2a) being directed to irradiate the front (H) of the adjacent group of terminals (A) for a time interval, the time interval being suitable for generating droplets (L) of molten material on the end portions. The method is characterized in that the arrangement step provides positioning the iron core (E) so that its longitudinal axis (F) is in the horizontal direction. The method further includes the step of injecting a gas jet (3a) toward a droplet (L) of molten material in a substantially vertical and bottom-up direction, and is configured to maintain the droplet (L) to prevent it from being affected by gravity (a). g The pressure is separated from the adjacent group of terminals (A), and the steps of the jet gas (3a) are performed at least partially overlapping with the welding steps.

2. The welding method according to the preceding claims, characterized in that, After the arrangement step and before the welding step, the method further includes a step of aligning the terminals (A) of adjacent arrangements of the group with each other to ensure a stable mutual welding position. The alignment step includes mutual alignment operations of translating and / or rotating the terminals (A) of each group to be welded according to at least one of the directions of the Cartesian coordinate system and / or according to at least one rotation angle relative to the corresponding axis of the Cartesian system.

3. The welding method according to one or more of the preceding claims, characterized in that, The gas jet (3a) is delivered through multiple nozzles connected to a supply pipe of compressed air.

4. The welding method according to one or more of the preceding claims, characterized in that, It includes the step of realigning the ferromagnetic core (E) and the welding equipment (2) to each other so that each arrangement will have a new set of terminals (A) that will be welded to the welding equipment (2).

5. The welding method according to the preceding claims, characterized in that, The mutual realignment step is performed by rotating the ferromagnetic core (E) about its longitudinal axis (F).

6. A welding table for welding hairpin-type conductor elements (C), wherein... - The conductor element (C) is positioned within the corresponding slot (D) of the ferromagnetic core (E); - The ferromagnetic core (E) includes a longitudinal axis (F) perpendicular to two opposite ends (E1, E2) of the core (E); - Each end portion of the conductor element (C) includes a corresponding terminal (A) protruding from one of the two heads (E1, E2) of the ferromagnetic core (E); - The terminals (A) are arranged adjacent to each other, with at least two terminals (A) of different conductor elements (C) as a group; The welding table (1) includes: - Support member (4), used to fix the ferromagnetic core (E) on which the conductor element (C) is provided; - At least one laser welding device (2) configured to emit a laser beam (2a) pointing substantially parallel to the direction of the longitudinal axis (G) of the terminal (A) to be welded, the laser beam (2a) being sized to generate droplets (L) of molten material on the end portions, thereby enabling them to be welded together; The workbench (1) is characterized in that the fixed support (4) is of a movable type and is configured to arrange the iron core (E) substantially horizontally with respect to its longitudinal axis (F). Furthermore, the workbench (1) also includes a gas ejector (3), which is configured and oriented in a substantially vertical and bottom-up direction to eject a gas jet (3a) toward the molten droplet (L) of molten material generated on the terminal (A). The size of the gas jet (3a) is determined to have a pressure suitable for supporting the molten droplet (L) to prevent it from being affected by gravity (a). g ( ) and separated from the adjacent group of terminals (A).

7. The welding workbench according to the preceding claims, characterized in that, It includes an alignment mask for the translation and / or rotation of at least one corresponding group of terminals (A), the mask being configured to achieve mutual alignment of the terminals (A) of each group to be soldered according to at least one of the directions of the Cartesian coordinate system and / or according to at least one rotation angle relative to the corresponding axis of the Cartesian system.

8. The welding table according to at least one of claims 6 and 7, characterized in that, The fixed support (4) is configured to allow the core portion (E) to rotate about its own longitudinal axis (F) so that each arrangement will weld a new set of adjacent terminals (A) to each other, with one terminal (A) being arranged on top of the other terminal (A) in the vertical direction.

9. The welding table according to at least one of claims 6, 7 and 8, characterized in that, The gas injector (3) is configured to supply compressed air and can be connected to a compressed air supply device.

10. The welding table according to at least one of claims 6 to 9, characterized in that, The gas injector (3) includes a plurality of adjacent nozzles (5) configured and sized to produce a gas jet (3a) with a width greater than the width of the group of adjacent terminals (A) to be welded together, such that the molten droplet (L) can be properly supported by the gas flow (3a).

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