Cooling device for an axial magnetic flux electrical machine.

Abstract

An axial magnetic flux electric machine with two stators 10, 20 and a liquid cooling circuit in contact with the coils 13 and yokes 14. The stators consist of a frame 11a, 21 made of non-magnetic or composite material, comprising a radial portion 11ar, 21r, more or less disc-shaped, which supports stator pads 12 and two axial extensions, more or less cylindrical internally 11ai, 21i and externally 11ae, 21e, surrounding the windings 13 and yoke 14. The axial extensions are closed by covers 16, 25 and seal the sealed chambers 16a, 25a for the circulation of the cooling fluid. The cooling fluid reaches the cooling chambers via a single conduit 31, located in the highest part of the machine. This conduit discharges the coolant into a radial conduit 33 belonging to the central plate 30 separating the two stators 10,20.The coolant then flows through an axial conduit 34 in the frames 11ae, 21e, and at the end of these conduits, a recess 35 provides a passage communicating with the cooling chamber 16a, 25a. The coolant, having reached the lower part of the chambers 16a, 25a, is then discharged through a recess 35 in communication with two second axial conduits 34 in the axial extensions 11ae, 21e. The coolant then flows into a chamber 33 belonging to the central plate 30 in communication with the single discharge conduit 32. Figure for the abbreviation: Fig. 8b.

Description

Title of the invention: Cooling device for an axial magnetic flux electrical machine. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to an axial magnetic flux motor or electric generator comprising at least one discoid rotor with several permanent magnet pads and at least one flat, annular stator with several radially distributed coils in a regular manner and whose axis is oriented parallel to that of the rotor. STATE OF THE ART

[0002] Two main concepts are known: that comprising a central stator and two lateral rotors, illustrated by publication GB2482928, and conversely that comprising a central rotor arranged between two stators, illustrated by publication FR3064422. Precisely, the invention relates to the second type.

[0003] In this design, since the rotor is confined between the stators, it cannot be cooled. If excessive heating occurs, generated primarily by eddy currents, the magnets can lose their magnetic properties when the temperature exceeds a critical value. Furthermore, radiative heating of the stators can further increase the rotor temperature. The solution proposed in publication FR3110767 to mitigate this heating is the very high segmentation of the magnet blocks. The eddy currents are then drastically reduced.

[0004] In publication FR3046888, each stator is an assembly of identical pads carrying coils. A pad is a radial stack of thin, electrically insulated ferromagnetic laminations of various sizes to obtain a trapezoidal shape. The radial stacking of the laminations allows each tooth to form, at the rear, a portion of the yoke (closing the magnetic circuit) and, at the front, the isthmus facing the rotor disc. It is well known that ferromagnetic materials, which are electrically conductive, are subject to parasitic electrical currents placed in an alternating, variable magnetic field: eddy currents. This creates heat that reduces the machine's energy efficiency. The solution proposed to mitigate these energy losses in publication GB2482928 is to replace the lamination stack with a "Soft Magnetic Composites - SMC".The stator pin is made from soft iron powder, the particles of which are coated with an electrical insulator. The powder is compressed in a mold to obtain the desired shape, then undergoes heat treatment to ensure cohesion and mechanical strength.

[0005] For the construction of a stator, there are multiple ways to assemble the pads. In publication FR3046888, each portion is attached and held onto a support plate by a dovetail joint, or by insertion into a groove and welding. Each portion can also be glued directly onto this plate, which is then attached to the casing fabric, common to the water chamber.

[0006] For a machine thus constructed, the cooling means is an exchange by conduction between the coolant circulating in a chamber in each casing and the stator stud, and this through the sheet metal supporting the studs and the casing fabric.

[0007] The cooling capacity determines the maximum power of the machine. Improving cooling is possible by ensuring that the heat sources, Joule effect in the windings, and eddy currents causing iron losses are in direct contact with the coolant. PRESENTATION OF THE INVENTION

[0008] The object of this invention is to propose a cooling device which includes, by stator, a cooling fluid circulation chamber in which the latter is in direct contact with the heat sources.

[0009] According to a first characteristic, the stator has a carcass made of non-magnetic or composite material comprising a radial plate, supporting the stator pads and two more or less cylindrical axial extensions surrounding internally and externally the windings and the yoke.

[0010] According to a second feature, each chamber is closed at the end of the axial extensions by a ring-shaped cover.

[0011] According to other features, the coolant reaches the cooling chambers via a single conduit, located in the highest area of ​​the machine, supported by the central plate separating the two stators and communicating with a radial conduit made in the latter.

[0012] The coolant then circulates in an axial conduit internal to the outer extension of the casing of each stator.

[0013] At the end of this conduit a recess provides a passage communicating with the cooling chamber.

[0014] The coolant, arriving at the lower part of the machine, is evacuated through a recess in communication with a second axial conduit internal to the external axial extension of the casing.

[0015] The coolant then flows into a radial chamber in the central plate connected to a single drain channel. DETAILED DESCRIPTION OF THE INVENTION

[0016] These features, objectives and advantages of the present invention will become apparent from the detailed description that follows and from the accompanying drawings given by way of non-limiting examples and on which:

[0017] [Fig-1] is a first cross-sectional view of the complete machine.

[0018] [Fig.2] is a second cross-sectional view of the complete machine, showing different fastening devices.

[0019] [Fig.3] is a third cross-sectional view of the complete machine, showing the coolant supply and discharge conduits.

[0020] [Fig.4a] is a cross-sectional view of the partially assembled left stator.

[0021] [Fig.4b] is a cross-sectional view of the components of the left stator shown in exploded view, then this one completely assembled.

[0022] [Fig.5a] is a cross-sectional view of the partially assembled right stator.

[0023] [Fig.5b] is a cross-sectional view of the components of the right stator shown in exploded view, then this one fully assembled.

[0024] [Fig.6a] is a cross-sectional view of the rotor hub components shown in exploded view, and then the rotor hub fully assembled.

[0025] [Fig.6b] is a cross-sectional view of the rotor components shown in exploded view.

[0026] [Fig.6c] is a cross-sectional view of the assembled rotor.

[0027] [Fig.7a] is a sectional and exploded view of the left stator, rotor and the components necessary for their assembly.

[0028] [Fig.7b] is a cross-sectional view of the rotor assembled on the left stator.

[0029] [Fig.8a] is a cross-sectional view of the engine block in the plane of the fuel pipes and coolant drainage.

[0030] [Fig.8b] is a cross-sectional view, in the same plane, of the assembled machine with the directions of circulation of the cooling fluid.

[0031] The electric machine shown in a first section on [Fig.1] consists of a motor block arranged in a casing 70 and a closing plate 80.

[0032] The engine block consists of: • of the left stator 10 connected to the casing 70 using screws 72; • of the right stator 20; • of the central spacer plate 30 which provides a precise axial space between the two stators 10,20; • of the discoid rotor 40 carried by a bearing 45, assembled using screws 46, and carried by the left stator 10; • of the resolver 60 (device for measuring the rotational speed and angular position of the rotor) whose stator is fixed to the cover 80 by the screws 62. • Finally, the cover 80 is fixed to the casing 70 using the screws 81. The entire machine is fixed to a transmission (reducer or gearbox) using the screws 82.

[0033] The cross-section of the electrical machine shown in [Fig. 2], according to a second cross-section, shows additional fixings and in particular: • The centering pin 1 of the two elements 1a, 11b of the frame 11 of the stator 10, described below; • Screws 17 for assembling two elements 1 la,l 1b of the frame 11 of the stator 10 and of the cover 16. • 18 screws for fixing the stators 10,20 and their cover 16,25 on the central spacer 30. • The centering pin 19 of the stators 10,20 between them and on the central spacer 30. • The bolt 26,27 for fixing the cover 25 to the frame 21 of the right stator 20.

[0034] The cross-section of the electric machine shown in [Fig. 3], according to a third section which we will call vertical, shows the supply and discharge pipes for the cooling fluid. The supply pipe 31, supported by the central spacer plate 30, is located in the upper part of the machine. It is bent and passes through an elastomer pad 71 arranged in a notch 70a in the housing 70. Thus, the pipe 31 makes a sealed passage through the wall of the housing 70. The pipe 32, also supported by the spacer plate 30, is located in the lower part of the machine. It collects the cooling fluid after it passes through the stators. Similarly, it passes through an elastomer pad 71 arranged in a notch 70a in the housing 70.

[0035] Figure [Fig.4a] shows in cross-section the left stator 10 partially assembled. The stator 10 comprises a frame 11 made up of two main elements linked together: • the peripheral part 1 receives the stator pads 12 on its radial part 1 lar in the shape of a crown, and has internal axial extensions 1 lai and external extensions 1 lae which create a volume for receiving the stator pads; • the central part 11b has a central hole 1 Ibl which receives the support shaft of the rotor 40.

[0036] Element 1a is made of non-magnetic material, preferably fiber-reinforced composite material. The stator pads 12 are preferably fixed by bonding in the form of a continuous bead 12a. These pads are made of soft magnetic composite powder. This material offers satisfactory performance and, above all, low energy losses due to eddy currents. The shape, obtained by molding, and the assembly of the studs make it possible to easily create the isthmus between two consecutive studs.

[0037] Element 11b is made of steel. It is attached to element lia by bonding or temporary screws and positioned by pins 1 le.

[0038] At the assembly stage shown on the right of [Fig. 4a], a machining operation is performed to obtain high geometric accuracy and facilitate the positioning of the rotor between the stators during machine assembly. This machining operation makes it possible to obtain a single face Fl for: • the docking of the Fia-marked spacer plate; • the common face of the stator pads 12 opposite the rotor and called functional indexed Flb; • the bearing face of the air gap balancing washer on which the rotor guide bearing, indexed Fie, rests; • finally the perpendicularity of the axis G (common axis with the axis of rotation of the rotor) with the face Fl is guaranteed.

[0039] Fig. 4b is a cross-sectional view of the left stator, with its components shown Left side exploded view, then fully assembled on the right. A coil 13 is attached to each stator pad, then a ring-shaped yoke 14 made of wound sheet metal, preferably glued to each pad, closes the magnetic circuit between consecutive pads. Next, a cover 16 is attached to close the sealed chamber for the cooling fluid circulation. It is fixed internally to structural element 1a by screws 17, common to the connection of elements 1a and 11b, and externally by screws 18 (added later) common to the connection of the stator to the central spacer plate. Finally, the bearing support shaft 15 and the stator centering pins 19 on the central spacer plate are attached.

[0040] Figure [Fig. 5a] shows in cross-section the partially assembled right-hand stator. includes a frame 21 comparable in shape and material to element 1 of the left stator 10. It supports the same stator pads 12 fixed, preferably, by gluing in the form of a continuous bead 12a. The frame 21 receives the stator pads 12 on its radial part 21r in the form of a crown, and has internal axial extensions 21i and external axial extensions 21e which create the volume for receiving the stator pads.

[0041] At the assembly stage shown on the right of [Fig. 5a], a machining operation is performed to obtain high geometric accuracy and facilitate the positioning of the rotor between the stators during machine assembly. This machining operation defines a unique face F2 for: • the docking of the spacer plate 30, indexed F2a; • the common face of the stator pads 12 opposite the rotor and called functional, indexed F2b.

[0042] Figure 5b is a cross-sectional view of the right-hand stator, with its components shown in exploded view on the left, and then fully assembled on the right. A coil 13 is mounted on each stator pad, and then a ring-shaped yoke 14 made of wound sheet metal, preferably bonded to each pad, closes the magnetic circuit between consecutive pads. Next, a cover 25 is fitted to close the sealed chamber for the circulation of the cooling fluid. It is fixed internally to the structural element 21 by bolts 26, 27 and externally by screws 18 (added later) which are common to the connection of the stator 20 with the central spacer plate 30.

[0043] Figure 6a is a cross-sectional view of the rotor hub 42. A ring 44, intended to support a subsequently mounted cover, is attached to the inside of the hub, followed by a grounding ring 43, designed to protect the bearing 45 from any potential parasitic current. The resolver target 62 and its press-fit retaining ring 63 are attached to the outside.

[0044] Figure 6b is a cross-sectional and exploded view of the other rotor components. We have the rotor disc 41 composed of 3 elements: • a load-bearing structure 41,a in the shape of a “sun” because it is composed of a central cylindrical part, from which several radial branches extend. This structure can be made of non-magnetic material or a fiber-reinforced resin composite; • of several sectors of magnets 41,b each of which can be monobloc or segmented. They are glued to the "sun" structure 41a; • of a “ring” 41,c also called a fret to counter the centrifugation of the magnets. The disc 41 and the hub 42 are centered on the outer ring of a double-row angular contact ball bearing 45 with diameters 41al and 42a, respectively. The outer ring of the bearing has a cylindrical flange 45a. The cylindrical flange 45a, rotor disc 41, and hub 42 are secured by screws 46. The motion and power developed by the machine are transmitted through the splines 42b of the hub 42. The complete assembled rotor is shown in [Fig. 6c].

[0045] [Fig. 7a] shows a cross-sectional and exploded view of the left stator 10 and the rotor 40, as well as the components necessary for their assembly. Before installing the rotor, the shim 47 is first slid into place to balance the air gap thicknesses. The procedure for determining the shim value is not detailed here.Next, the rotor 40 is slid onto the shaft 15, then the thrust washer 48 of the screw 49 secures the stator and the rotor and preloads the bearing 45. Finally, the cover 44b is placed on its support 44a. The assembled rotor and left stator assembly is shown in [Fig. 7b].

[0046] Figure 8a shows a cross-section of the motor block. The assembled left stator 10 and rotor 40 are joined to the intermediate plate 30 and the right stator 20. The coolant supply and discharge conduits 31 and 32 are attached to the intermediate plate 30. These conduits connect to radial conduits 33, which are sealed by caps 36. O-rings 37 ensure a seal between the plate 30 and the housings 11a and 21. The radial conduits 33 open into axial conduits 34, which supply the stator chambers 16a and 25a via ports 35 at the ends of the axial extensions 11a and 21e. The emptying of chambers 16a and 25a is carried out in a similar manner to the supply via the communication openings 35, then the axial conduits 34, the radial conduits 33 and finally the pipe 32.

[0047] Fig. 8b shows a cross-section of the fully assembled machine on which the fluid circulation from the supply 50 to the outlet 51 is shown.

Claims

Demands

1. An axial magnetic flux electric machine characterized in that the stators (10,20) have a frame (lla,21) made of non-magnetic or composite material comprising a radial part (l lar,21r) more or less in the shape of a disc, which support stator pads (12) and two axial extensions more or less cylindrical internally (l1a,2 li) and externally (llae,21e) surrounding the windings (13) and the yoke (14).

2. An axial magnetic flux electric machine, according to claim 1 characterized in that the two chambers (16a,25a) are closed at the end of the axial extensions by covers (16,25).

3. An axial magnetic flux electric machine according to claims 1 or 2, characterized in that the coolant reaches the cooling chambers via a single conduit (31) located in the highest area of ​​the machine. The conduit discharges the coolant into a radial conduit (33) belonging to the central plate (30) separating the two stators (10, 20).

4. An axial magnetic flux electric machine according to claim 3 characterized in that the coolant then circulates in an axial conduit (34) in the axial extensions (llae,21e) of the frames (lia,21).

5. An axial magnetic flux electric machine according to claim 4 characterized in that at the end of the conduits (34), a recess (35) gives a passage communicating with the cooling chamber (16a,25a).

6. An axial magnetic flux electric machine according to claim 5 characterized in that the coolant, having reached the lower part of the chambers (16a,25a), is evacuated through a recess (35) in communication with second axial conduits (34) in the axial extensions (llae,21e) of the frames (lia,21).

7. Axial magnetic flux electric machine according to claim 6 characterized in that the coolant then flows into a chamber (33) of the central plate (30) in communication with the single discharge conduit (32).

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