ELECTRICAL MACHINE INCLUDING COOLING PLATES

Abstract

The invention relates to an electrical machine having a main axis of rotation (A) and comprising a rotor or stator subassembly, the subassembly comprising a stack of magnetic metal laminations (2) extending transversely to the axis, characterized in that the subassembly comprises at least one hollow plate (3) extending transversely to the axis, interposed between two magnetic metal laminations, and forming a cooling element for the magnetic metal laminations, each hollow plate comprising at least one inlet (11) for cooling fluid and one outlet (12), each hollow plate being configured to circulate cooling fluid along a predefined path, said predefined path being perpendicular to the axis between the inlet and the outlet. Figure 2

Description

Title of the invention: ELECTRIC MACHINE COMPRISING COOLING PLATES

[0001] The invention relates to an electrical machine comprising a stack of magnetic metal sheets and a cooling system. In particular, cooling members are provided in the form of plates interposed at the heart of the stack of magnetic metal sheets.

[0002] In electric or hybrid vehicles, engineers seek to increase the specific power of electric machines to be able to produce very high torque in a limited space.

[0003] It is therefore increasingly important to design a high-performance cooling system to support the integration of the traction motor, i.e. the electric machine, into the vehicle.

[0004] It should be noted that the present invention is applicable to any electric machine, even outside the context of an electric traction vehicle.

[0005] Document US2015280525 proposes circulating, inside the stator and the rotor, oil acting as a heat transfer fluid. Passages are provided in the magnetic metal sheets, which form pipes axially conducting the heat transfer fluid inside the stator and inside the rotor. In the configurations proposed in document US2015280525, it is very difficult to achieve sufficient sealing to be able to imagine circulating glycolated water. In addition, the orifices provided in the magnetic metal sheets generate undesirable inhomogeneities in the magnetic flux.

[0006] The inventors therefore sought to propose new cooling solutions for electrical machines.

[0007] To this end, the present invention proposes an electrical machine having a main axis of rotation and comprising a stator or rotor subassembly, the subassembly comprising a stack of magnetic metal sheets extending transversely to the axis, characterized in that the subassembly comprises at least one hollow plate extending transversely to the axis, interposed between two magnetic metal sheets, and forming a cooling member for the magnetic metal sheets, each hollow plate comprising at least one inlet for cooling fluid and one outlet, each hollow plate being configured to circulate cooling fluid along a predefined path, said predefined path being perpendicular to the axis between the inlet and the outlet.

[0008] Thanks to the arrangements promoted above, the cooling fluid circulates in the heart of the subassembly (stator or rotor), and the calories are taken as close as possible to the elements which heat, namely the electrical conductors and / or the permanent magnets. Each hollow plate forms an effective heat sink for cooling the magnetic metal sheets and the electrical conductors which are located in the grooves formed by the different aligned notches.

[0009] It is noted that one of the objectives of the arrangement promoted above is to be able to use glycolated water as a cooling fluid.

[0010] It is noted that the hollow plates act as spacers in the assembly consisting of the magnetic metal sheets and the hollow plates. Each hollow plate generally appears as a flat disc with a hollow in its center.

[0011] It should be noted that the following presentation will mainly illustrate a subassembly forming a machine stator. However, the principle and the characteristics are just as applicable for a subassembly forming a machine rotor.

[0012] According to one embodiment, the magnetic metal sheets have a first outside pitch diameter, and each hollow plate has a second outside pitch diameter, identical to the first outside pitch diameter.

[0013] In the case of a stator-forming subassembly, the outside primitive diameter is the general diameter of the machine, not including the fixing and clamping lugs and not including the cooling fluid supply and return pipes.

[0014] The hollow cooling plates do not protrude radially outwards from the magnetic metal sheets. The overall diameter of the machine does not change due to the presence of the hollow plates.

[0015] In the case of a rotor subassembly, the outside pitch diameter is the outside diameter of the rotor. The gap left free between the rotor and the stator (air gap) is everywhere of the same dimension, which promotes homogeneity of the air gap around the entire periphery of the machine.

[0016] According to one embodiment, each magnetic metal sheet has a first cross-section in a plane perpendicular to the axis, each hollow plate has a second cross-section, and the second cross-section has a shape substantially identical to the shape of the first cross-section.

[0017] Thanks to this correspondence of shapes, when the stacking of the subassembly is tightened, there is no singular point of force, and the metal sheets and the hollow plates lie flat on each other.

[0018] This shape correspondence also makes it possible to avoid possible risks of whistling at high rotation speeds, for the rotor but also at the interface between the rotor and the stator.

[0019] According to one embodiment, each hollow plate is made of non-magnetic metal material, preferably of an aluminum or copper-based alloy. Such an aluminum or copper-based material proves to be a very good thermal conductor, whereby the magnetic metal sheets are efficiently cooled by the nearest hollow plate.

[0020] Due to the non-magnetic characteristic of this material, the presence of the hollow plates does not modify the magnetic flux lines in space and in particular in the air gap between the stator and the rotor.

[0021] Alternatively, it is noted that it is not excluded, however, to use, for the hollow plates, the same material as that used for the magnetic metal sheets.

[0022] According to one embodiment, each hollow plate comprises an interior space delimited by a front wall and a rear wall, an outer rim and an inner edge. Each hollow plate forms a jacketed spacer for containing fluid. When the hollow plate is manufactured in two pieces, a sealed joint is provided at the peripheral interface between the two pieces, for example a structural weld, so as to create an interior space that is sealed with respect to the external environment. Only the inlet and the outlet allow fluid to enter and exit this interior space.

[0023] According to one embodiment, each hollow plate has an axial thickness between 2 mm and 3 mm. For example, the front wall and the rear wall each have a thickness of between 0.7 mm and 1 mm. According to the different embodiments, the gap left free between the two walls has a thickness which can be between 1 mm and 2 mm, which represents the height of the interior space provided for the circulation of the fluid.

[0024] According to one embodiment, a plurality of pins, bridges or walls are provided in the interior space of each hollow plate to direct or constrain the path of the cooling fluid in this interior space. Furthermore, these elements act as spacers or props to take up compression forces when the assembly of the subassembly is tightened.

[0025] According to one embodiment, the subassembly is a stator subassembly and the subassembly is characterized in that the inlet and the outlet are diametrically opposed, arranged outside the outside pitch diameter.

[0026] As a result, the path of the fluid inside the interior space of the hollow plate between the inlet and the outlet is the shortest, and the temperature gradient remains low.

[0027] According to one embodiment, the inlet and the outlet are adjacent, arranged outside the outside primitive diameter. The fluid circuit is then more compact, more rational and easier to integrate.

[0028] According to one embodiment, in the case of a rotor subassembly, the inlet and outlet are central, arranged inside a rotor shaft. This is an elegant solution which allows the circulation of a fluid in a rotating part by using rotating joints to connect the rotating parts to the stationary parts.

[0029] According to one embodiment, cooling fluid passage conduits are provided, comprising a supply conduit and a return conduit. These conduits are part of a closed circuit for circulating the cooling fluid, also using a circulator or a pump and a heat exchanger for removing calories.

[0030] In the case of a rotor subassembly, the supply and return conduits are coupled to the rotor shaft.

[0031] In the case of a stator subassembly, the supply and return conduits are arranged outside the original diameter. The supply and return conduits run along the body of the stator. They do not substantially increase the overall diameter of the machine.

[0032] According to one embodiment, each hollow plate comprises an annular body and teeth projecting radially in the direction towards the axis, two neighboring teeth delimiting a notch for the passage of the winding conductors. Thus the teeth protect and surround the winding conductors. The annular body ensures structural robustness for the hollow plate and acts as a notch bottom.

[0033] According to one embodiment, each hollow plate comprises lugs, interposed between lugs of the two magnetic metal sheets which frame the hollow plate. Said lugs are crossed by a bolting for fixing and axially stressing the stack. The hollow plates are thus maintained in a well-controlled position. Furthermore, the lugs present in each hollow plate allow for continuous axial stacking which promotes reliable and uniform compression.

[0034] The invention further relates to an electromotive group comprising an electric machine as described above.

[0035] The invention further relates to a vehicle comprising an electromotive group as described above.

[0036] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: [Fig.l] is a perspective view of an exemplary embodiment of the invention on an electric machine stator; [Fig.2] is analogous to [Fig.l] and shows the motor stator in sectional view and in perspective, the section plane being taken in a median plane of a hollow cooling plate; [Fig.3] illustrates in front view a portion of a section taken through a median plane of a hollow cooling plate, a portion of the hollow plate being omitted; [Fig.4] illustrates in axial sectional view a portion of a section of a hollow cooling plate and neighboring magnetic metal sheets; [Fig.5] is a schematic representation of another example of an electric machine in which both the stator and the rotor include hollow cooling spacer-shaped plates, viewed in axial section; [Fig.6] is a schematic representation of another example of an electric machine in which both the stator and the rotor include hollow cooling spacer plates, viewed in cross-section through the axis; [Fig.7] illustrates a variant of the fluid path in the case of a subassembly forming a stator; [Fig.8] is similar to [Fig.4] and illustrates in partial axial section view two variants of hollow cooling plate made of two pieces assembled together.

[0037] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the description, certain elements are not necessarily shown to scale. This applies in particular to the thickness of the hollow plates and the magnetic sheets, the thicknesses of which have been exaggerated in order to facilitate understanding of the description.

[0038] We are interested here in an electric or hybrid motor vehicle, namely a vehicle equipped with an electric powertrain.

[0039] In practice, the electric or hybrid vehicle comprises an electromotive group. The electromotive group comprises an electric machine, used as a motor or an alternator depending on the driving circumstances, and a transmission usually equipped with a speed reducer.

[0040] Generally in the context of the present invention, it is considered that the electrical machine 1 comprises two sub-assemblies: a first static sub-assembly called stator 1ST and a second rotating sub-assembly called rotor 1ROT.

[0041] A general diagram of an electrical machine stator is now described with reference to [Fig. 1]. The first part of the presentation below focuses on the description of a stator in which the hollow cooling plates are installed.

[0042] The electrical machine 1 has a main axis of rotation A.

[0043] In this document, reference is made to a cylindrical type spatial reference based on the main axis A. A so-called axial direction is parallel or coincident with the main axis A. The adverb axially characterizes an axial direction.

[0044] A so-called radial direction noted R is defined by a direction perpendicular to the axis A and which intersects the axis A. The adverb radially characterizes an axial direction, qualified as "internal" if it is directed towards the axis and qualified as "external" if it is directed away from the axis. A so-called tangential direction is defined by a direction perpendicular to the axis and perpendicular to the local radial direction at the point of interest.

[0045] The rotor 1ROT is mounted on a shaft 6. The shaft 6 is mounted on bearings via roller bearings (not shown) as known per se.

[0046] The electrical machine 1 is here a radial flux machine. The main magnetic field lines in the air gap are directed radially.

[0047] The stator 1ST is arranged around the rotor. The stator 1ST is mounted in a stationary manner, i.e. it does not rotate around the axis A (note that the motor as a whole moves when it is mounted in a vehicle).

[0048] As visible in figures 1, 2 and 5, the stator subassembly 1ST comprises a stack of magnetic metal sheets 2.

[0049] Each magnetic metal sheet 2 is obtained by cutting a blank of metallic material into the desired shape. The thickness E1 of the blank and of the metal sheet resulting from the cutting is for example in practice between 0.3 mm and 0.8 mm. Each magnetic metal sheet 2 can be coated with an electrically insulating varnish. The varnish prevents the passage of current between sheets and greatly reduces eddy current losses.

[0050] Each magnetic metal sheet is made of mild silicon steel, preferably grain oriented.

[0051] Each magnetic metal sheet comprises an annular outer portion 20 and teeth 21 extending in the direction of the axis A. Depending on the architecture and the power of the machine, the number of magnetic metal sheets can range from 25 to 200, without these numbers being limiting.

[0052] The free end of the teeth comprises in the example illustrated a flattened or flared shape 22 which makes it possible to retain the conductive wires once they are mounted in the groove formed by the interval between the different aligned teeth.

[0053] Protruding ears 28 are provided to receive fixing and tightening screws 29 of the subassembly (note: only one fixing screw is shown in [Fig.l]). In the embodiment shown, each magnetic metal sheet comprises three ears 28 regularly distributed around the circumference at 120° from each other. A hole is provided in each ear to allow a bolt or a fixing and tightening screw 29 to pass through, along the axis A3 (see [Fig.l]).

[0054] The stator subassembly has an external primitive diameter noted DI (radius RI) excluding ears and an internal diameter noted D2 (radius R2).

[0055] The outer radius of the rotor R3 corresponds to the radius R2 reduced by the dimension of the air gap EF.

[0056] The annular outer portion 20 of the magnetic metal sheets 2 has as its diameter the first exterior primitive diameter Dl, and the same is true for the hollow plates, the annular body 30 of which also has as its diameter the first exterior primitive diameter DL

[0057] Advantageously according to the present invention, one or more hollow plates 3 are provided. Each hollow plate 3 extends transversely to the axis A.

[0058] The hollow plates 3 form cooling members for the magnetic metal sheets and the electrical conductors.

[0059] Each hollow plate comprises an annular body 30 and teeth 31 projecting radially towards the axis. Two neighboring teeth delimit a notch 16 for housing electrical winding wires marked 7.

[0060] The free end 32 of each tooth 31 is slightly set back from the free end of the teeth 22 of the magnetic metal sheets.

[0061] Each hollow plate 3 comprises ears 27 with holes, of a shape similar or identical to the ears already described for the magnetic sheets.

[0062] As visible in [Fig.4], each hollow plate 3 comprises an interior space V2 delimited by a front wall 41 and a rear wall 42, an outer rim 43 and an inner edge 44. It should be noted that here the qualifiers front and rear are purely conventional; it could be the other way around.

[0063] The outer rim 43 is circular while the inner edge 44 follows the profile of the teeth.

[0064] Each hollow plate comprises an inlet 11 for admitting cooling fluid and an outlet 12 for letting fluid out.

[0065] The inlet 11 is a passage which allows a fluid supply pipe 51 to communicate fluidically with the interior space V2 of the hollow plate 3. The outlet 12 is a passage which allows the interior space V2 of the hollow plate to communicate fluidically with a fluid return pipe 52.

[0066] The fluid supply pipe 51 extends along the axis A1 parallel to A, and the fluid return line 52 extends along the axis A2 parallel to A.

[0067] According to the example illustrated, the inlet 11 and the outlet 12 are diametrically opposite. According to an alternative which will be described later, the inlet 11 and the outlet 12 are on the same side, more precisely the inlet 11 and the outlet 12 are adjacent.

[0068] Several inputs and several outputs may be provided on the periphery of the body of the stator 1ST.

[0069] Each hollow plate 3 is configured to circulate cooling fluid along a predefined path PF.

[0070] The predefined path PF is perpendicular to the axis A between the entrance and the exit.

[0071] A closed circuit for circulating the cooling fluid is provided, using for example elsewhere a circulator or a pump and a heat exchanger for evacuating calories (not shown in the figures).

[0072] The cross-section of the magnetic metal sheets 2 is substantially identical to the cross-section of each hollow plate 3, so that the metal sheets and the hollow plates lie flat on each other and can be subjected to axial pressure generated by the assembly.

[0073] Each hollow plate 3 has an axial thickness E2 between 2 mm and 3 mm. For example, the front wall 41 and the rear wall 42 may each have a thickness of between 0.7 mm and 1 mm. Depending on the different embodiments, the gap left free between the two walls has a thickness which may be between 1 mm and 2 mm. This gap is sufficient for efficient circulation of heat transfer fluid.

[0074] Advantageously, a plurality of pins 35, and / or bridges and / or walls 36 are provided in the interior space V2 of each hollow plate to orient, direct and constrain the path of the cooling fluid in this interior space V2. The pins 35, bridges or walls 36 also act as spacers or props to take up part of the tightening forces when the subassembly is assembled.

[0075] Each hollow plate 3 forms a jacketed spacer for containing fluid. When the hollow plate is manufactured in two pieces, a sealed joint 47 is provided at the peripheral interface between the two pieces, for example a structural weld.

[0076] Each hollow plate 3 is made of non-magnetic metal material, preferably an aluminum or copper-based alloy. Aluminum or copper have good thermal conductivity.

[0077] In [Fig.5], the path of the PF3 fluid is illustrated for a subassembly forming a stator and a subassembly forming a rotor.

[0078] Concerning the path of the fluid for the rotor, the fluid arrives via a rotating joint 67 positioned opposite a nozzle 63; an axial channel 61 is provided fluidically coupled to the nozzle 63 as well as to another nozzle 65 positioned opposite the internal volume V2 formed in the hollow cooling plate 3.

[0079] The fluid leaves via a nozzle 66 connected to another axial channel 62 fluidly coupled to the nozzle 64 which is positioned opposite a rotating joint 68.

[0080] Concerning the path of the fluid PF for the stator, the fluid arrives via the pipe 51, enters the interior volume of each hollow plate via the aforementioned inlet 11, circulates in the interior space V2, leaves via the outlet 12 and joins the return pipe 52.

[0081] A tubular connection is provided for connecting a portion of the pipe 51 to the next, and a plug 13 is provided, which obstructs the pipe for the last hollow plate connected.

[0082] The same applies on the outlet side with a tubular connection allowing a portion of the pipe 52 to be fitted to the next and a plug 14 is provided, which obstructs the pipe for the last hollow plate connected.

[0083] In [Fig.6], regarding the path of the fluid in the rotor, it is noted that the walls 36 are in the form of an arc centered on the axis A. This defines a labyrinth path PF3 which makes it possible to cover the entire surface of the rotor. The concentric arc-shaped walls make it possible to prevent all the liquid from ending up on the outside under the effect of centrifugal forces.

[0084] In embodiments, glycolated water is used as the heat transfer fluid. Glycolated water is a very inexpensive medium and possible leakage does not pose any problem.

[0085] Of course, other fluids such as oil or even a two-phase refrigerant can be used as heat transfer fluid.

[0086] The path of the fluid is generally perpendicular to the main axis, in particular in the case of laminar flow, and generally without taking into account local turbulence induced by turbulent flow.

[0087] As illustrated in [Fig.7], the inlet 11 and the outlet 12 can be arranged on the same side, that is to say that the inlet 11 and the outlet 12 are adjacent. The path of the fluid denoted PF4 makes a complete turn in the interior space V2. A separating partition 18 is provided which forms a radial barrier and forces the fluid to learn the path of the complete turn, without going directly from the inlet 11 to the outlet 12.

[0088] As illustrated in [Fig.8], each hollow plate 3 can be manufactured in two pieces. According to the example shown on the left, a first piece 3A comprises the front wall 41 and the edges as well as the studs 35. The second piece 3B is a very simple flat cover.

[0089] According to the example shown on the right, two identical parts marked 3C are used, one being turned over so that it is in plane symmetry with the first. In both cases, the first part is welded to the second part with a continuous peripheral joint 47 which ensures a very good quality seal.

[0090] The number of hollow plates can be adapted to the cooling requirement, taking into account the axial length of the machine and / or the specific thermal power to be evacuated.

[0091] Concerning the dimensioning, for an electric or hybrid vehicle traction motor the diameter DI can typically be between 20 cm and 30 cm although these dimensions are not limiting within the meaning of the present invention.

Claims

Claims

1. Electrical machine (1) having a main axis of rotation (A) and comprising a rotor or stator subassembly, the subassembly comprising a stack of magnetic metal sheets (2) extending transversely to the axis, characterized in that the subassembly comprises at least one hollow plate (3) extending transversely to the axis, interposed between two magnetic metal sheets, and forming a cooling member for the magnetic metal sheets, each hollow plate comprising at least one inlet (11) for cooling fluid and one outlet (12), each hollow plate being configured to circulate cooling fluid along a predefined path (PF), said predefined path being perpendicular to the axis between the inlet and the outlet.

2. Electrical machine according to claim 1, characterized in that the magnetic metal sheets have a first outside pitch diameter (Dl), and each hollow plate has a second outside pitch diameter, identical to the first outside pitch diameter (Dl).

3. Electrical machine according to any one of claims 1 to 2, characterized in that each hollow plate is made of non-magnetic metallic material, preferably of an alloy based on aluminum or copper.

4. Electrical machine according to any one of claims 1 to 3, characterized in that each hollow plate comprises an interior space (V2) delimited by a front wall (41) and a rear wall (42), an outer rim (43) and an inner edge (44).

5. An electrical machine (1) according to any one of claims 1 to 4, wherein the subassembly is a stator subassembly (1ST), and the subassembly is characterized in that the input and output are diametrically opposed, arranged outside the outside pitch diameter (Dl).

6. Electrical machine (1) according to any one of claims 1 to 5, axial conduits (51, 52) for the passage of cooling fluid are provided, comprising a supply conduit and a return conduit.

7. Electrical machine (1) according to any one of claims 1 to 6, characterized in that each hollow plate comprises an annular body (20) and teeth (21) projecting radially in the direction towards the axis, two neighboring teeth delimiting a notch (16) for the passage of the winding conductors.

8. Electrical machine (1) according to any one of claims 1 to 7, characterized in that each hollow plate (3) comprises ears (27), interposed between ears (28) of the two magnetic metal sheets which frame the hollow plate.

9. An electromotive group comprising an electric machine according to any one of claims 1 to 8.

10. Electric motor vehicle comprising an electromotive group according to claim 9.

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