Method for making metal sheets obtained by joining a plurality of shaped metal elements and metal sheet obtained by said method

Abstract

Method for making a metal sheet (100) used for making up stators (200) or rotors (300) of a rotating electrical machine (400) or a laminated ferromagnetic core (500) of a static electrical machine. This method provides to prepare a plurality of shaped metal elements (1), wherein each of these shaped metal elements (1) comprises at least two sides (2, 3) having a shaped profile (4) joinable with the shaped profile of the sides (2, 3) of the adjacent shaped metal elements (1) so that these shaped metal elements (1) are configured to be fixedly coupled to each other by interference. The method then provides to arrange the plurality of shaped metal elements (1) in a jig (600) and press these shaped metal elements (1) so as to obtain an interference coupling between their sides (2, 3). Finally, the method provides to treat the metal sheet (100) obtained by means of the pressing operation with an annealing heat treatment.

Description

[0001] METHOD FOR MAKING METAL SHEETS OBTAINED BY JOINING A PLURALITY OF SHAPED METAL ELEMENTS AND METAL SHEET OBTAINED BY SAID METHOD.

[0002] DESCRIPTION

[0003] The invention relates to a method for making metal sheets obtained by joining a plurality of shaped metal elements.

[0004] The invention also relates to a metal sheet obtained by the aforesaid method. Furthermore, the invention relates to the rotor, stator or laminated ferromagnetic core made by stacking a plurality of the aforesaid metal sheets of the invention, as well as to the rotating electrical machine comprising the aforesaid stator and / or the aforesaid rotor arranged coaxially to each other and to the static electrical machine comprising said laminated ferromagnetic core.

[0005] It is well known that rotating electrical machines, used both as motors for producing motion and as generators of electrical energy, basically consist of a fixed hollow part, called the stator, inside which a cylindrical part, called the rotor, which is keyed to the rotating shaft, rotates.

[0006] It is also known that static electrical machines, in particular transformers, comprise a laminated ferromagnetic core of the columnar or shell type.

[0007] In order to make the stator and rotor of a rotating electrical machine or the laminated ferromagnetic core of a static electrical machine, particular elements made of metal material, with a thickness of a few tenths of a millimetre, called in technical jargon metal sheets L, an example of which is shown in Fig. 1 of the prior art, are stacked on top of each other.

[0008] In order to achieve stable stacking of the metal sheets L for the construction of the stator, rotor or laminated ferromagnetic core, the same metal sheets L are secured to each other by means of special connection techniques such as die-casting, nailing, welding or other equivalent processes.

[0009] It is also well known that, in most cases, these metal sheets L are made from sheets of metal material M, which are subjected to a moulding process using special pressing devices.

[0010] In particular, the most popular and widely used techniques for manufacturing metal sheets L provide a so-called step-by-step moulding.

[0011] With these techniques, indeed, metal sheets L are obtained as a single body with a shape corresponding to the shape of the stator, rotor or laminated ferromagnetic core to be obtained. However, as widely described in Italian Patent Application no. VI2008A000159, filed by the same Applicant, these techniques used to obtain the aforesaid metal sheets L disadvantageously have the inconvenience of wasting a high amount of metal material.

[0012] In fact, as it can be seen in Fig. 2 of the prior art where a step-by-step process of making a stator is shown, the angular ends E and the central part C of each square Q of the metal sheet M, on which the metal sheets L are formed, are not exploited and consequently become unused scrap material, which may be recovered by casting.

[0013] For this reason, the aforesaid Patent Application no. VI2008A000159 intends to reduce the scrap obtained during the moulding of the metal sheets L, aiming to obtain from the same portions of material, previously considered as scrap, shaped metal elements that, joined together, make it possible to obtain metal sheets that can be used to make the stator and rotor of the so-called “exciter”. The term exciter is used to refer to the excitation device, provided with a rotor and a stator, used to power the electromagnets on the main rotor of an alternator.

[0014] Specifically, the technique proposed by the aforesaid Patent Application provides to join the various shaped metal elements together by welding.

[0015] Disadvantageously, as mentioned above, the metal sheets thus obtained are only suitable for use in making the stator and / or rotor of an exciter, and not also for making the main stator and rotor of a rotating electrical machine or a laminated ferromagnetic core of a static electrical machine. This is because the welding technique used to join the various shaped metal elements results in a non-negligible loss of magnetic flux in the joining area, which can be as much as 50% compared to a metal sheet made as a single body.

[0016] Thus, disadvantageously, the use of the metal sheets thus obtained for making stators and main rotors of rotating electrical machines or for making laminated ferromagnetic cores of static electrical machines would lead to a high loss of efficiency of the machines themselves, thus making the aforesaid metal sheets clearly unsuitable for this purpose.

[0017] In order to overcome these drawbacks, it was envisaged to make shaped metal elements which, when joined together, allow to obtain metal sheets with an efficiency only a few percentage points lower than that of metal sheets made as a single body. In particular, to achieve this effect, each shaped metal element has two sides having a shaped profile that can be joined with the shaped profile of the sides of the adjacent shaped metal elements so that said shaped metal elements can be fixedly coupled together by interference in order to define the aforesaid metal sheets.

[0018] In other words, this solution allows to couple the various shaped metal elements in order to obtain a metal sheet without the need for the aforesaid welding. However, even this solution is not free from drawbacks.

[0019] In particular, the interference coupling between the various shaped metal elements is not optimal, especially in the case of mechanical stresses of the metal sheet defined by these elements, and therefore there is a tendency for these shaped metal elements to decouple when the stator or rotor is being made up.

[0020] For this reason, the main object of the present invention is to define a method for making the aforesaid metal sheets that allows to define a more robust metal sheet which is less prone to breaking up.

[0021] In particular, the object of the invention is to propose a method that makes interference coupling between the shaped metal elements that make up a metal sheet more robust.

[0022] The aforementioned objects are achieved by the method of the invention having the characteristics according to the main claim.

[0023] Advantageously, this solution also allows to minimise the loss of magnetic flux in the joining area and thus to imperceptibly vary the efficiency compared to metal sheets obtained as a single body.

[0024] Further characteristics of the method of the invention are described in the dependent claims.

[0025] The metal sheet made by joining a plurality of the aforesaid shaped metal elements, the rotor, the stator and the laminated ferromagnetic core obtained by stacking a plurality of the aforesaid metal sheets are also part of the invention. Said objects and advantages will be better highlighted during the description of a preferred embodiment of the invention which is given, by way of indicative and non-limiting example, with reference to the attached drawings where:

[0026] - Fig. 1 shows a metal sheet of the prior art obtained as a single body and used to make the main stator of a rotating electrical machine;

[0027] - Fig. 2 shows the moulding technique of the prior art to obtain a metal sheet as a single body from a sheet of metal material;

[0028] - Fig. 3 shows the shaped metal element of the invention according to a first embodiment;

[0029] - Fig. 4 shows the shaped metal element of the invention according to a second embodiment;

[0030] - Fig. 5 shows a metal sheet of the invention obtained by interference coupling of a plurality of shaped metal elements of the invention;

[0031] - Fig. 6 shows the stator of the invention obtained by stacking a plurality of metal sheets of the invention;

[0032] - Fig. 7 shows the rotor of the invention obtained by stacking a plurality of metal sheets of the invention;

[0033] - Fig. 8 shows the rotating electrical machine comprising at least the stator and / or at least the rotor of the invention;

[0034] - Fig. 9 shows the laminated ferromagnetic core of the invention obtained by stacking a plurality of metal sheets of the invention;

[0035] - Fig. 10 shows a jig on which a plurality of shaped metal elements of the shaped metal element of Fig. 3 is arranged so as to define the shape of the stator to be obtained.

[0036] The method of the invention for making metal sheets obtained by joining a plurality of shaped metal elements provides the following steps.

[0037] First of all, this method provides to obtain, by the moulding technique, the aforesaid shaped metal elements 1 at the unexploited portions of a metal sheet on which, still by moulding, single-body metal sheets are made.

[0038] However, in an alternative embodiment of the method of the invention, it is not excluded that these shaped metal elements 1 are formed on a metal sheet especially used for moulding the aforesaid shaped metal elements 1.

[0039] In particular, this alternative provides to optimally define the moulding positioning of each single shaped metal element 1 so as to make the most of the entire area of the metal sheet itself.

[0040] In detail, according to the invention these shaped metal elements 1 have the following characteristics.

[0041] First of all, it can be observed that each of said shaped metal elements 1 is adapted to be connected, at two sides 2 and 3 thereof, to shaped metal elements 1 of the invention placed adjacent thereto, so as to define a metal sheet 100 adapted, subsequently, to be used to make a stator 200 or a rotor 300 of a rotating electrical machine 400 or a laminated ferromagnetic core 500 of a static electrical machine, represented respectively in Figs. 5, 6, 7, 8 and 9.

[0042] In particular, each shaped metal element 1 requires that on each side 2 and 3 a shaped profile 4 be made which can be coupled to a corresponding side 2 and 3 of the shaped metal element 1 placed adjacent to the first, so that the aforesaid shaped metal elements 1 can be coupled to each other by interference.

[0043] Preferably but not necessarily, as it can be seen in Fig. 3, the aforesaid shaped profile 4 is made for the entire length of each of the two sides 2 and 3. This last feature advantageously allows to obtain interference coupling along the entire extension of the two sides 2 and 3 of two adjacent shaped metal elements 1. As a result, in this situation, the percentage value of the magnetic flux loss in this coupling section compared to a metal sheet made as a single body is reduced by about ten percentage points.

[0044] Moreover, the preferred embodiment of the invention, as it can be observed in Fig. 3, provides that each of these sides 2 and 3 has a joinable comb-shaped profile 4.

[0045] Even more in detail, as it can be noted in Fig. 3, this joinable comb-shaped profile 4 has teeth 41 and concavities 42 substantially triangular in profile.

[0046] It is important to underline that the joinable shaped profile 4 at the first side 2 of the shaped metal element 1 is made in such a way as to be perfectly joined with the joinable shaped profile 4 made on the second side 3 of the same shaped metal element 1.

[0047] This makes it advantageously possible to manufacture shaped metal elements 1 equal to each other for each individual type of stator, rotor or laminated ferromagnetic core, greatly simplifying the design and construction step of these stator, rotor and core.

[0048] In an alternative embodiment of the invention shown in Fig. 4, the joinable shaped profile 4 made on the first side 2 of the shaped metal element 1 of the invention has a dovetail profile, while the joinable shaped profile 4 of the second side 3 is a profile complementary and joinable to the dovetail profile of the first side 2.

[0049] Also in this case, therefore, each first side 2 of each shaped metal element 1 can be coupled by interference to each second side 3 of the shaped metal element 1 placed adjacent to the first.

[0050] In further alternative embodiments of the invention, the joinable shaped profiles 4 of the aforementioned sides 2 and 3 may be of a different type than those described above, provided that they allow for the interference coupling of the shaped metal elements 1 placed adjacent to each other, advantageously avoiding their joining by welding techniques.

[0051] Thus, connection and direct contact between each pair of shaped metal elements 1 is achieved along the entire length of the joining area of the sides 2 and 3, as observed in Fig. 5.

[0052] This makes it advantageously possible to have a magnetic flux loss reduced by about ten percentage points along the joining area compared to a single-body metal sheet, while maintaining the efficiency of the stators, rotors and laminated ferromagnetic cores made from these shaped metal elements very similar to the efficiency of the stators, rotors and laminated ferromagnetic cores made from single-body metal sheets.

[0053] Furthermore, for the advantages that will be set forth during the description of the method of the invention, these shaped metal elements 1 are made from at least two different types of metal materials, i.e. they are made from two different types of metal sheets.

[0054] It is not excluded that these shaped metal elements 1 are produced from a single type of metal material or are made from more than two different types of metal materials.

[0055] In particular, these types can be distinguished from each other by the different percentage content of silicon within their alloy.

[0056] Also, according to the preferred embodiment of the invention, still for the advantages that will be set forth below, these shaped metal elements 1 are made in at least two different thicknesses.

[0057] However, it is not excluded that these shaped metal elements 1 are made with a single thickness or with more than two different thicknesses.

[0058] Returning now to the method of the invention, following the definition and then the preparation of these shaped metal elements 1 , the same method provides to arrange the shaped metal elements 1 in a jig 600 comprising a plurality of seats 601 which jointly define the shape of the stator 200, the rotor 300 or the laminated ferromagnetic core 500 to be obtained.

[0059] The example in Fig. 10 obviously shows a jig 600 for manufacturing a stator 200. According to the preferred embodiment of the invention, this arrangement in said jig 600 provides to arrange shaped metal elements 1 of a first type of metal material alternately with shaped metal elements 1 of a second type of metal material.

[0060] This has the advantage of being able to make metal sheets 100 by appropriately choosing the number of shaped metal elements 1 of a first type of metal material and the number of shaped metal elements 1 of a different type of metal material, so as to obtain metal sheets with electromagnetic characteristics with values variable between the electromagnetic characteristics of metal sheets composed of shaped metal elements 1 made up only by the aforesaid first type of metal material and the electromagnetic characteristics of metal sheets made up of shaped metal elements 1 made only by said second type of metal material.

[0061] In other words, the fact of being able to make up the metal sheets 100 by suitably choosing shaped metal elements 1 made from different types of metal materials makes it possible to vary the electromagnetic characteristics of a metal sheet 100, thus formed, along a linear scale between two limit values defined by the same two types of metal materials used.

[0062] Furthermore, still according to the preferred embodiment of the invention, this arrangement in said jig 600 provides to arrange shaped metal elements 1 with a first thickness alternating with shaped metal elements 1 with a second thickness other than said first thickness.

[0063] This additional characteristic advantageously allows, when metal sheets 100 are stacked on top of each other to form the stator 200 or the rotor 300 or the laminated ferromagnetic core 500, to define a plurality of gaps between a metal sheet 100 and another metal sheet 100 that make it possible to optimise cooling of the same stator 200 and / or rotor 300 or laminated ferromagnetic core 500 during the operation of the electrical machine.

[0064] Returning to the method of the invention, following said arrangement, it provides to fixedly couple, by pressing, the aforesaid shaped metal elements 1 previously arranged in the relative seats 601 of the jig 600, such that each side 2 or 3 with a joinable shaped profile 4 of each shaped metal element 1 couples by interference with the side 2 or 3 of the shaped metal element 1 placed adjacent thereto.

[0065] In this way, the shaped metal elements 1 are fixedly constrained to each other, resulting in a metal sheet that will later be used to make a stator 200 or a rotor 300 or a laminated ferromagnetic core 500.

[0066] According to the method of the invention, after the composition of a metal sheet 100, the latter undergoes an annealing heat treatment.

[0067] This advantageously and surprisingly makes it possible to reinforce and strengthen the joining portion between two shaped metal elements 1 where interference coupling is defined, as this treatment makes the metal material softer, more homogenous and less rigid, especially at the coupling line between two adjacent shaped metal elements 1.

[0068] In other words, through annealing the microstructure of the material is altered, especially at the joining portions of two shaped metal elements 1 , causing changes in its properties such as flexibility and hardness, and consequently strengthening the connection of the aforesaid two shaped metal elements 1.

[0069] In addition, a further advantage obtained by the implementation of the aforesaid annealing heat treatment consists in an improvement also in the electromagnetic characteristics of the metal material of the shaped metal elements 1 , especially at the aforesaid joining portions of the various shaped metal elements 1.

[0070] In fact, while the pressing operation is carried out on the various adjacent shaped metal elements 1 , for their interference coupling, at these joining portions, the metal material undergoes work-hardening, which in turn causes a deterioration of the electromagnetic characteristics of the material itself.

[0071] In contrast, by performing this heat treatment, the initial conditions of the metal material are re-established, especially on these joining portions, thus advantageously obtaining a minimal reduction in magnetic flux loss in these portions and thus obtaining an imperceptible change in efficiency compared to metal sheets obtained as a single body.

[0072] As mentioned above, the metal sheet 100, shown in Fig. 5, for making stators 200 or rotors 300 of a rotating electrical machine 400 and for making laminated ferromagnetic cores 500 of a static electrical machine, obtained by joining by interference a plurality of the shaped metal elements 1 at the aforesaid sides 2 and 3 with joinable shaped profile 4 is also part of the invention.

[0073] The stator 200 and rotor 300 of a rotating electrical machine 400 and the laminated ferromagnetic core 500 of a static electrical machine, shown respectively in Figs. 6, 7 and 9, are also part of the invention, which are obtained by stacking together a plurality of metal sheets which, in turn, are made by joining together by interference a plurality of shaped metal elements 1 of the invention.

[0074] In particular, according to the preferred embodiment of the invention, the stacking of the various metal sheets 100 on top of each other is performed by staggering the various joining portions of two consecutive metal sheets 100. This aspect makes it advantageously possible to mechanically compensate for any thickening at the aforesaid joining portions, thus achieving a more homogeneous stacking of the aforesaid metal sheets.

[0075] In addition, this staggering of the joining portions of the various adjacent metal sheets 100 also enables the electromagnetic behaviour of the stator, rotor or laminated ferromagnetic core obtained by stacking the aforesaid metal sheets of the invention to be improved and homogenised.

[0076] Likewise, in the event that each metal sheet 100 is obtained from the composition of shaped metal elements 1 of different metal materials, the invention could provide to stack the various metal sheets to form the stator, rotor or laminated ferromagnetic core, so as to overlap shaped metallic elements 1 of different metal materials belonging to two adjacent metal sheets 100.

[0077] Furthermore, the rotating electrical machine 400 of Fig. 8, comprising at least the stator 200 or at least the rotor 300 arranged coaxially with each other, and the static electrical machine, not shown in the figures, comprising the aforesaid ferromagnetic core 500, are also part of the invention.

[0078] On the basis of the foregoing, therefore, it is clear that the method of the invention for making metal sheets achieves all the intended purposes.

[0079] In particular, the invention achieves the object of defining a method for making the aforesaid metal sheets that allows to define a stronger metal sheet that is less prone to breaking up.

[0080] More in detail, the invention achieves the object of defining a method that allows to make the interference coupling between the shaped metal elements, making up a metal sheet, more robust and stable.

Claims

CLAIMS1 ) Method for making a metal sheet (100) used for making up stators (200) or rotors (300) of a rotating electrical machine (400) or a laminated ferromagnetic core (500) of a static electrical machine, characterised in that it provides the following steps:- preparing a plurality of shaped metal elements (1 ), wherein each of said shaped metal elements (1 ) comprises at least two sides (2, 3) having a shaped profile (4) joinable with the shaped profile of the sides (2, 3) of the adjacent shaped metal elements (1 ) so that said shaped metal elements (1 ) are configured to be fixedly coupled to each other by interference;- arranging said plurality of shaped metal elements (1 ) in a jig (600) reproducing the shape of said stator (200) or of said rotor (300) or of the laminated ferromagnetic core (500);- pressing said shaped metal elements (1 ) arranged in said jig (600) so as to obtain an interference coupling between the sides (2, 3) of said adjacent shaped metal elements (1 );- treating the metal sheet (100) obtained by said pressing operation with an annealing heat treatment.2) Method according to claim 1 , characterised in that said plurality of shaped metal elements (1 ) used for making up a metal sheet (100) is made from at least two different types of metal materials.3) Method according to claim 2, characterised in that at least two different types of metal materials differ from each other in the percentage content of silicon within their alloy.4) Method according to any one of claims 2 or 3, characterised in that, during said step of arranging said plurality of shaped metal elements (1 ) in said jig (600), shaped metal elements (1 ) of a first type of metal material are arranged in said jig (600) alternately with shaped metal elements (1 ) of a second type of metal material.5) Method according to any one of the preceding claims, characterised in that said plurality of shaped metal elements (1 ) used for making up a metal sheet (100) is made of at least two different thicknesses.6) Method according to claim 5, characterised in that, during said step of arranging said plurality of shaped metal elements (1 ) in said jig (600), shaped metal elements (1 ) with a first thickness are arranged in said jig (600) alternatelywith shaped metal elements (1 ) with a second thickness.7) Stator (200) of a rotating electrical machine (400) of the type comprising a plurality of metal sheets (100) stacked on top of each other, characterised in that said metal sheets (100) are obtained by the method according to any one of claims 1 to 6.8) Rotor (300) of a rotating electrical machine (400) of the type comprising a plurality of metal sheets (100) stacked on top of each other, characterised in that said metal sheets (100) are obtained by the method according to any one of claims 1 to 6.9) Rotating electrical machine (400) of the type comprising a stator and a rotor arranged coaxially with each other, characterised in that said stator (200) is of the type according to claim 7.10) Rotating electrical machine (400) of the type comprising a stator and a rotor arranged coaxially with each other, characterised in that said rotor (300) is of the type according to claim 8.11 ) Laminated ferromagnetic core (500) of a static electrical machine of the type comprising a plurality of metal sheets (100) stacked on top of each other, characterised in that said metal sheets (100) are obtained by the method according to any one of claims 1 to 6.12) Stator (200), rotor (300) and laminated ferromagnetic core (500) according to claims 7, 8 and 11 , characterised in that said metal sheets (100) are stacked with each other so that the joining portions of each of said metal sheets (100) are offset with respect to the joining portions of the adjacent metal sheets (100).13) Static electrical machine of the type comprising a laminated ferromagnetic core (500), characterised in that said laminated ferromagnetic core (500) is of the type according to claim 11 .

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