FR3144445A1 - Rotating electric machine with axial electromagnetic flux, module and associated assembly process - Google Patents

Abstract

Rotating electric machine with axial electromagnetic flux, module and associated assembly process The present invention relates to a rotating electric machine with axial electromagnetic flux (1, 1') comprising: - a stator (6) comprising a plurality of coils (11), - a first (7a) and a second (7b) rotors arranged in either side of the stator (6), - a transmission shaft (3) on which the first (7a) and the second (7b) rotors are fixed, - a bearing (5) comprising: - a central housing (5a ) configured to receive the transmission shaft (3) and two guide bearings (9a, 9b), - an intermediate housing (5b) arranged around the central housing (5a) and receiving the coils (11) of the stator (6) , - a peripheral housing (5c) arranged around the intermediate housing (5b) and receiving a device for cooling the coils (11) of the stator (6). Abstract figure: Fig. 1

Description

Rotating electrical machine with axial electromagnetic flux, associated module and assembly method

The present invention falls within the field of rotating electrical machines or axial electromagnetic flux motors, i.e. in which the electromagnetic flux circulates axially between the stator(s) and the rotor(s).

Axial flux machines are increasingly used, particularly in electric or hybrid vehicles, due to their efficiency and energy density, which make it possible to obtain a motor with reduced size and high torque.

However, this energy density also causes significant heating at the coil level. It is therefore advisable to limit this heating in order to ensure the proper functioning of the electrical machine over time.

Furthermore, the configuration of axial electromagnetic flux electrical machines involves significant mechanical constraints so that the assembly of the different elements of the machine can be complex and difficult to ensure the correct positioning of the different elements.

It is therefore necessary to find a solution to obtain a rotating electrical machine with axial electromagnetic flux that is easy to assemble and limits the heating of the coils.

For this purpose, the present invention relates to a rotating electrical machine with axial electromagnetic flux comprising:
- a stator comprising a plurality of coils,
- a first rotor and a second rotor arranged on either side of the stator,
- a transmission shaft on which the first rotor and the second rotor are fixed,
- a landing comprising:
- a central housing configured to receive the transmission shaft and at least one guide bearing, preferably two guide bearings,
- an intermediate housing arranged around the central housing and receiving the stator coils,
- a peripheral housing arranged around the intermediate housing and receiving a device for cooling the stator coils.

Such a rotating electrical machine makes it possible, in particular through the geometry of the bearing, to obtain a compact structure which is easy to assemble and allows efficient cooling of the coils.

According to another aspect of the present invention, the electric machine also comprises a generally cylindrical housing positioned at least partially around the bearing and fixed to the bearing in which the coil cooling device comprises a coil cooling channel formed by the assembly of the housing on the bearing and in which a cooling fluid is capable of circulating.

Alternatively, the cooling channel for the coils can be provided in the bearing, with the peripheral housing then forming the cooling channel. The geometry of the housing can then be different.

According to another aspect of the present invention, at least one of the bearing or the housing includes a peripheral groove configured to receive an O-ring configured to seal the cooling channel of the coils.

According to another aspect of the present invention, the housing comprises a first hydraulic connector and a second hydraulic connector fluidically connected to the cooling channel of the coils via respectively an inlet port and an outlet port of the cooling channel of the coils. The hydraulic connectors are configured to ensure the inlet and outlet of a cooling fluid in the cooling channel. The hydraulic connectors are for example connected to a cooling circuit comprising means for circulating a cooling fluid such as a pump and a heat exchanger.

According to another aspect of the present invention, the inlet port and the outlet port are disposed adjacent in a circumferential direction, and the coil cooling channel includes a first axially extending wall disposed between the inlet port and the outlet port for forcing the passage of coolant in the coil cooling channel around the entire coil assembly.

According to another aspect of the present invention, the electric machine also comprises an inverter configured to power the coils, the inverter being fixed to the housing and the housing comprising a cooling channel for the inverter formed in an axial face of the housing and extending around a central portion receiving the transmission shaft.

According to another aspect of the present invention, the electric machine comprises a first fluid connection and a second fluid connection allowing fluid communication between the cooling channel of the coils and the cooling channel of the inverter, the cooling fluid being able to flow through the cooling channel of the inverter and the cooling channel of the coils between the first hydraulic connector and the second hydraulic connector.

According to another aspect of the present invention, the housing includes a second wall extending radially between the first fluid connection and the second fluid connection to force the passage of cooling fluid in the cooling channel of the inverter around the transmission shaft.

According to another aspect of the present invention, the bearing comprises a plurality of radial walls disposed between the coils in the intermediate housing and configured to increase the thermal exchanges between the coils and the cooling fluid circulating in the cooling channel of the coils.

According to another aspect of the present invention, the coils are made by windings wound on teeth and in which the teeth are fixed on an interconnector, the assembly comprising the interconnector and the coils being positioned in the intermediate housing of the bearing.

According to another aspect of the present invention, the interconnector comprises terminals configured to receive a supply current from the coils and wherein the bearing comprises connectors configured on the one hand to come into contact with the terminals of the interconnector and on the other hand to be connected to a power inverter.

According to another aspect of the present invention, the bearing also comprises a temperature sensor and at least one rotor position sensor and connectors associated with said temperature and position sensors configured to allow the power supply and/or transmission of measurement signals from said temperature and position sensors.

According to another aspect of the present invention, the cooling fluid is water or glycolated water.

According to another aspect of the present invention, the bearing structure is made of plastic or aluminum, in particular anodized aluminum.

The present invention also relates to a module comprising an electric machine as described above and a mechanical reducer coupled in rotation to the transmission shaft.

The present invention also relates to a method of assembling a rotating electrical machine with axial electromagnetic flux as described above comprising the following steps:
- winding coils on the teeth,
- fixing the coils on the interconnector,
- positioning of the transmission shaft and bearings in the central housing of the bearing,
- positioning of the coils and the interconnector in the intermediate housing of the bearing,
- positioning of the rotors on the transmission shaft, on either side of the bearing,
- positioning and assembly of the housing on the bearing.

According to another aspect of the present invention, the assembly method also comprises the following steps:

- positioning and tightening of axial retaining collar on the transmission shaft outside the rotors,

- fixing a closing cover on the bearing on the side opposite the housing.

- assembly of connectors associated with the power supply of the coils or with temperature and/or position sensors on the bearing.

Other characteristics and advantages of the invention will appear more clearly on reading the following description, given as an illustrative and non-limiting example, and the appended drawings among which:

represents an exploded schematic view of a rotating electrical machine according to a first embodiment of the present invention;

represents a schematic perspective view of the coils and the interconnector of the rotating electrical machine of the ;

represents a schematic perspective view of the coils and the interconnector of the in assembled state;

represents a schematic perspective view of the structure of the bearing of the ;

represents a schematic perspective view of the bearing structure and coils;

represents a sectional view of the rotating electrical machine of the ;

represents a schematic perspective view of the structure of the bearing of the ;

represents a flowchart of the steps in a process for assembling a rotating electrical machine;

represents a schematic perspective view and partially in transparency of a rotating electrical machine according to a second embodiment of the present invention;

represents a schematic perspective view of the bearing of the rotating electrical machine of the ;

In these figures, identical elements have the same references.

The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference is to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments.

The present invention relates to a rotating electrical machine (or electric motor) with axial electromagnetic flux, i.e. a machine in which the stator and the rotor are arranged so as to create an electromagnetic field extending in a direction parallel to the axial direction (relative to an axis of rotation of the rotor). The present invention relates more particularly to a rotating electrical machine with electromagnetic flux comprising a stator and two rotors arranged on either side of the stator. The rotating electrical machine can be used in a motor vehicle, in particular for the propulsion of an electric or hybrid vehicle.

There represents an exploded view of such a rotating electrical machine 1. The rotating electrical machine 1 comprises a transmission shaft 3 around which are positioned a central bearing 5 comprising the stator 6, a first rotor 7a and a second rotor 7b. The first rotor 7a and the second rotor 7b are positioned axially on either side of the stator 6. The rotors 7a, 7b comprise for example a set of permanent magnets arranged on the face opposite the stator 6.

The transmission shaft 3 is for example a stepped shaft comprising several different diameters, in particular a larger central diameter D1, intermediate diameters D2 smaller than the central diameter D1 and extreme diameters D3 smaller than the intermediate diameters.

The bearing 5 comprises a central housing 5a configured to receive the transmission shaft 3 and two bearings 9a and 9b for guiding the transmission shaft 3. The bearings 9a, 9b are for example ball bearings. The bearings 9a, 9b are for example positioned around the intermediate diameters D2 of the transmission shaft 3. The bearings 9a, 9b are for example force-fitted on one side and the other of the central housing 5a of the bearing 5.

The bearing 5 also comprises an intermediate housing 5b arranged around the central housing 5a. The intermediate housing 5b is configured to receive coils 11 and an interconnector 13 forming the stator 6. The coils 11 are for example formed by windings around teeth, the different teeth being fixed on the interconnector 13 which provides the electrical connections between the different coils 11. FIGS. 2 and 3 represent an exemplary embodiment of the stator 6 comprising 16 teeth fixed on the interconnector 13 and distributed circularly. However, a different number of teeth (and therefore coils 11) can be used. The coils 11 are configured to be positioned around the central housing 5a of the bearing 5. The intermediate housing 5b can comprise radial walls 50 better visible in FIGS. 4 and 5. The radial walls 50 are arranged between the teeth of the stator 6.

The bearing 5 also comprises a peripheral housing 5c arranged around the intermediate housing 5b. The peripheral housing 5c is configured to receive a device for cooling the coils 11 of the stator 6, in this case, a part of a cooling device.

The rotating electrical machine 1 also comprises a housing 15 of generally cylindrical shape. The housing 15 also comprises a wall closing one of the ends of the cylinder. The housing 15 is configured to be positioned at least partially around the bearing 5 and to be fixed to the bearing 5. The assembly of the housing 15 on the bearing 5 makes it possible to close the peripheral housing 5c to form a cooling channel 19 for the coils 11 (better visible in the sectional view of the ) extending around the intermediate housing 5b enclosing the coils 11. The cooling channel 19 is capable of receiving a cooling fluid such as water or glycol water. The housing 15 can be fixed to the bearing 5 by screws 21 but other fixing means can also be used.

The bearing 5 and/or the housing 15 may comprise one or more peripheral grooves 17 configured to receive an O-ring 23 to ensure the sealing of the cooling channel 19 of the coils 10. The housing is welded to the bearing, in particular by welding, in particular by friction stir welding.

The housing 15 also comprises a first and a second hydraulic connectors 25a and 25b fluidically connected to the cooling channel 19 of the coils 11 via respectively an inlet orifice 27a and an outlet orifice 27b of the cooling channel of the coils 11. The first hydraulic connector 25a is configured to allow the arrival of the cooling fluid in the cooling channel 19 of the coils 11 via the inlet orifice 27a and the second hydraulic connector 25b is configured to allow the evacuation of the cooling fluid out of the cooling channel 19 of the coils 11 via the outlet orifice 27b after having circulated inside the cooling channel 19 from the first connector 25a.

The first connector 25a and second connector 25b are for example fluidically connected to a cooling circuit comprising a pump allowing the circulation of the cooling fluid in the cooling circuit and a heat exchanger allowing the cooling fluid to be cooled, for example a front radiator of a motor vehicle.

The inlet port 27a and the outlet port 27b may be positioned adjacently in a circumferential direction as shown in FIG. . In this case, the peripheral housing 5c may comprise a first wall 29 (visible on the ) extending axially and arranged between the inlet port 27a and the outlet port 27b to prevent the cooling fluid from going directly from the inlet port 27a to the outlet port 27b without having circulated in the cooling channel 19 around the coils 11.

Other configurations for the inlet 27a and outlet 27b ports and for the first wall 29 can be envisaged.

The bearing 5 also comprises a first electrical connector 31 electrically connected to terminals 33 of the interconnector 13. The electrical connector 31 is configured to receive a supply current for the coils 11 coming for example from a current inverter.

The bearing 5 may also comprise sensors (not shown) such as a temperature sensor and at least one rotor position sensor 7a, 7b and a connector 35 associated with said temperature and position sensors. The connector 35 is configured to allow the power supply and/or transmission of the measurement signals of said temperature and position sensors.

The rotating electrical machine 1 may also comprise a first collar 37a and a second collar 37b for axial retention 37a, 37b arranged on the transmission shaft 3 outside the first and second rotors 7a and 7b to axially maintain the rotors 7a, 7b in position.

The rotating electrical machine 1 may also comprise a closing cover 39 arranged on the side opposite the housing 15. The closing cover 39 is fixed to the bearing 5, for example via fixing screws 41 (other fixing means may also be used). The closing cover 39 has for example a central opening 43 to allow the transmission shaft 3 to pass through. Alternatively, a central opening may be provided in the housing 15 to allow the transmission shaft 3 to protrude.

According to a variant embodiment not shown of the rotating electrical machine 1 presented previously, the cooling channel 19 of the coils 11 is arranged in the bearing 5, the peripheral housing 5c is then a closed housing. The hydraulic connectors 25a, 25b are then positioned on the bearing 5 and the housing 15 can be a simple closing cover similar to the closing cover 39. The rotating electrical machine 1 can also be similar to the variant embodiment presented previously.

The structure of bearing 5 is for example made of aluminum, in particular anodized aluminum, or of a plastic material.

The coils 11 may be partially or completely embedded in a resin, for example epoxy having a high thermal conduction coefficient, for example greater than 3W/m K. The epoxy has good adhesion to the stator and its support and to the housing, which makes it possible to improve the mechanical properties of the electric machine.

The present invention also relates to a method of assembling a rotating electrical machine with axial electromagnetic flux as described above. represents a flowchart of the different stages of the assembly process.

The first step 101 concerns the winding of winding wires around teeth to form the coils 11. The coils 11 thus formed are for example 16 in number but a different number of coils 11 is also conceivable.

The second step 102 concerns the fixing of the coils 11 obtained in step 101 on an interconnector 13. The fixing is for example carried out by snapping the teeth onto the interconnector 13. Alternatively, the teeth can be arranged on the interconnector 13 and held axially by their positioning between a bottom of the intermediate housing 5b and the interconnector 13.

The third step 103 concerns the positioning of the transmission shaft 3 and the guide bearings 9a, 9b in the central housing 5a of the bearing 5, the guide bearings 9a, 9b being positioned between the bearing 5 and the transmission shaft 3, on one side and the other of the bearing 5. The guide bearings 9a, 9b are for example force-fitted into the central housing 5a.

The fourth step 104 concerns the positioning of the assembly comprising the coils 11 and the interconnector 13 in the intermediate housing 5b of the bearing 5. The assembly is for example force-fitted into the intermediate housing 5b.

The fifth step 105 concerns the positioning of the rotors 7a, 7b on the transmission shaft 3, on either side of the bearing 5. The rotors 7a, 7b are for example force-fitted around the transmission shaft 3.

The sixth step 107 concerns the positioning and assembly of the housing 15 on the bearing 5. The assembly is for example carried out by an axial translation of the housing 15 towards the bearing 5. The housing 15 is then fixed to the bearing 5, for example by screws 21.

The assembly process may also include the following steps:

- a step 106 of positioning and tightening the retaining collars 37a and 37b on the transmission shaft outside the rotors 7a, 7b,

- a step 108 of fixing a closing cover 39 on the bearing 5 on the side opposite the housing 15,

- a step 109 of assembling electrical connectors 31 associated with the power supply of the coils 11 on the bearing 5 and of assembling connectors 35 associated with temperature and/or position sensors on the bearing 5.

Please note that the order of the steps may be different from the order presented on the flowchart of the .

Such an assembly method makes it possible to obtain a rotating electrical machine with axial electromagnetic flux 1 in a simple manner with a reduced number of steps and not requiring a specific machine to correctly position the different elements in relation to each other.

Thus, in operation, the power supply to the coils 11 makes it possible to create an electromagnetic field causing the rotation of the rotors 7a, 7b and therefore of the transmission shaft 3. In addition, the circulation of a cooling fluid through the cooling channel 19 via the hydraulic connectors 25a, 25b makes it possible to limit the heating of the coils 11. The radial walls 50 of the bearing 5 make it possible in particular to maximize the heat exchanges between the coils 11 and the cooling fluid circulating in the cooling channel 19 of the coils 11.

According to another embodiment shown in the , the rotating electrical machine 1' also comprises a current inverter 51 integrated in the housing 15'. The current inverter 51 comprises, for example, a printed circuit board (PCB) made in the form of a disk that extends radially around the transmission shaft 3 and is positioned in a dedicated housing of the housing 15'. The current inverter 51 is used for powering the coils 11. The housing 15' also comprises an electrical connector 52 for powering the current inverter 51.

In addition, in order to limit the heating of the current inverter 51, the rotating electrical machine 1′ may also comprise a cooling channel 53 for the current inverter 51. The cooling channel 53 for the current inverter 51 is for example arranged in an axial face of the housing 15′ and extends around a central part receiving the transmission shaft 3. The cooling channel 53 for the current inverter 51 is thus placed adjacent to and axially facing the current inverter 51.

In addition, the housing 15' comprises a first fluid connection 55a connecting a first hydraulic connector 25a' to the inlet of the cooling channel 53 of the inverter 51 and a second fluid connection 55b connecting the outlet of the cooling channel 53 of the inverter 51 and the inlet orifice 27a of the cooling channel 19 of the coils 11. The cooling fluid is thus able to travel through the cooling channel 53 of the inverter 51 then the cooling channel 19 of the coils 11 between the first hydraulic connector 25a' and a second hydraulic connector 25b' in fluid communication with the outlet orifice 27b of the cooling channel 19 of the coils 11. The cooling channel 53 of the inverter 51 is therefore in fluid communication with the cooling channel 19 of the coils 11. The circulation of the cooling fluid in the cooling channel 53 of the inverter 51 from the first hydraulic connector 25a' to the outlet orifice 27b of the cooling channel 19 of the coils 11. hydraulic connector 25a' then in the cooling channel 19 of the coils 11 up to the second hydraulic connector 25b' is shown diagrammatically by the arrowed line of the .

The cooling channel 53 of the inverter 51 comprises, for example, a second wall 54 arranged between the first fluid connection 55a and the second fluid connection 55b and extending radially (or even axially if necessary) to prevent the cooling fluid from passing directly from the first fluid connection 55a to the second fluid connection 55b without passing through the cooling channel 53 of the inverter 51 around the transmission shaft 3.

The rotating electrical machine 1’ may also be similar to the previous embodiment shown in Figures 1 to 7.

In addition, the assembly process steps presented in the flow chart of the can also be applied to this second embodiment presented in Figures 9 and 10.

The present invention also relates to a module comprising a rotating electrical machine 1, 1' according to one of the embodiments presented above and a mechanical reducer coupled in rotation to the transmission shaft 3 of the rotating electrical machine 1, 1'. The mechanical reducer can be coupled to the transmission shaft 3 at its end protruding from the closing cover 39 via the opening 43. The mechanical reducer makes it possible to adapt the rotation speed and the torque provided by the transmission shaft 3 according to the application used for the module.

Thus, the use of a bearing 5 configured to receive the transmission shaft 3 in a central housing 5a, the coils 11 in an intermediate housing 5b and the cooling device 19 of the coils 11 in a peripheral housing 5c makes it possible to obtain a compact rotating electrical machine 1, 1’, easy to assemble while ensuring effective cooling of the coils 11.

Claims (11)

Axial electromagnetic flux rotating electric machine (1, 1') comprising:
- a stator (6) comprising a plurality of coils (11),
- a first rotor (7a) and a second rotor (7b) arranged on either side of the stator (6),
- a transmission shaft (3) on which the first rotor (7a) and the second rotor (7b) are fixed,
- a bearing (5) comprising:
- a central housing (5a) configured to receive the transmission shaft (3) and at least one guide bearing (9a, 9b), preferably two guide bearings,
- an intermediate housing (5b) arranged around the central housing (5a) and receiving the coils (11) of the stator (6),
- a peripheral housing (5c) arranged around the intermediate housing (5b) and receiving a cooling device (19) for the coils (11) of the stator (6). Electric machine (1, 1') according to claim 1 also comprising a housing (15, 15') of generally cylindrical shape positioned at least partially around the bearing (5) and fixed to the bearing in which the cooling device (19) of the coils (11) comprises a cooling channel (19) of the coils (11) formed by the assembly of the housing (15, 15') on the bearing (5) and in which a cooling fluid is capable of circulating. Electric machine (1, 1') according to claim 2 wherein the housing (15, 15') comprises a first hydraulic connector (25a) and a second hydraulic connector (25b) fluidically connected to the cooling channel (19) of the coils (11) via respectively an inlet port (27a) and an outlet port (27b) of the cooling channel (19) of the coils (11). Electrical machine (1, 1') according to claim 3 wherein the inlet orifice (27a) and the outlet orifice (27b) are arranged adjacently in a circumferential direction and wherein the cooling channel (19) of the coils (11) comprises a first wall (29) extending axially arranged between the inlet orifice (27a) and the outlet orifice (27b). Electric machine (1') according to one of claims 2 to 4 also comprising an inverter (51), the inverter (51) being fixed on the housing (15') and in which the housing (15') comprises a cooling channel (53) of the inverter (51) formed in an axial face of the housing (15') and extending around a central part receiving the transmission shaft (3). Electric machine (1') according to the preceding claim comprising a first fluid connection (55a) and a second fluid connection (55b) allowing fluid communication between the cooling channel (19) of the coils (11) and the cooling channel (53) of the inverter (51), the cooling fluid being able to flow through the cooling channel (53) of the inverter (51) and the cooling channel (19) of the coils (11) between the first (25a') and the second (25b') hydraulic connectors. Electric machine (1') according to the preceding claim in which the housing (15') comprises a second wall (54) extending radially between the first fluid connection (55a) and the second fluid connection (55b). Electric machine (1, 1') according to one of the preceding claims in which the bearing (15, 15') comprises a plurality of radial walls (50) arranged between the coils (11) in the intermediate housing (5b). Electric machine (1, 1') according to one of the preceding claims, in which the coils (11) are produced by windings wound on teeth and in which the teeth are fixed on an interconnector (13), the assembly comprising the interconnector (13) and the coils (11) being positioned in the intermediate housing (5b) of the bearing (5). Module comprising an electric machine (1, 1') according to one of the preceding claims and a mechanical reducer coupled in rotation to the transmission shaft (3). Method of assembling a rotating electrical machine with axial electromagnetic flux (1, 1') according to claim 9 taken alone or in combination with one of claims 2 to 8 comprising the following steps:
- winding (101) of coils (11) on the teeth,
- fixing (102) of the coils (11) on the interconnector (13),
- positioning (103) of the transmission shaft (3) and the bearings (9a, 9b) in the central housing (5a) of the bearing (5),
- positioning (104) of the coils (11) and the interconnector (13) in the intermediate housing (5b) of the bearing (5),
- positioning (105) of the rotors (7a, 7b) on the transmission shaft (3), on either side of the bearing (5),
- positioning and assembly (107) of the housing (15, 15') on the bearing (5).