Device for electrically connecting two stators of an axial flux electric motor

Abstract

An electrical connection device (100) for electrically connecting two stators (30, 40) of an axial flux electric machine (1), comprising: - an electrically insulating base (110) comprising two parts inclined with respect to one another, namely a crossmember (111) and a foot (112), and - at least two electrical conductors (120U, 120V, 120W, 120N) which are electrically insulated from one another and are each housed partly in the crossmember (111) and partly in the foot (112), so as to protrude from the base (110) by three terminations (121U, 121V, 121W, 121N, 122U, 122V, 122W, 122N, 123U, 123V, 123W, 123N).

Description

Description Title of the invention: Device for electrically connecting two axial flux electric motor stators Technical field of the invention

[0001] The present invention relates generally to axial flux electric machines.

[0002] It relates more particularly to a device for electrically connecting two stators of an axial flux electric machine.

[0003] The invention finds a particularly advantageous application in electric or hybrid motor vehicles. State of the art

[0004] An electric machine is an electromechanical device that converts electrical energy into mechanical energy and / or vice versa. Electric or hybrid cars are equipped with such electric machines (commonly called "electric motors") which, when powered by a current source, drive the vehicle's wheels.

[0005] An electrical machine has at least one part that is fixed relative to the vehicle chassis (the stator), and at least one moving part (the rotor). The rotor moves relative to the stator due to an attraction and / or repulsion between the magnetic fields of the rotor and the stator.

[0006] In the case of an axial flux machine, the magnetic fields are mainly oriented parallel to the rotor's axis of rotation. To generate such magnetic fields, two stators are generally provided, distributed on either side of the rotor.

[0007] The rotor is generally a disc-shaped structure centered on an axis of rotation, which contains permanent magnets. Each stator usually includes a base generally in the shape of a disc centered on the axis of rotation of the rotor, and teeth that are distributed on the face of the base facing the rotor, all around the axis of rotation. Coils of electrically conductive wire are placed around the teeth and connected together.

[0008] The rotor and stators are usually housed in a casing in which a cooling liquid circulation circuit is also provided.

[0009] Such axial flux electric machines offer advantages in terms of compactness, cooling, and energy efficiency compared to traditional radial flux electric machines. However, they also pose technical challenges, particularly regarding the electrical connection of the two stators.

[0010] Cables are generally provided which run on either side of the housing to connect to the two stators. However, the design of the cable routing and their installation are complicated, given the space taken up in the engine compartment. These cables also pose problems during vehicle maintenance, and are also subject to wear, corrosion and overheating at their connections. Presentation of the invention

[0011] The objective of the invention is therefore to propose a device for electrically connecting the two stators of an axial flux electric machine, which is simple, easy to install, space-saving and reliable.

[0012] More particularly, according to the invention, an electrical connection device is proposed comprising: - an electrically insulating base comprising two parts inclined relative to each other, namely a crosspiece and a foot, and - at least two electrical conductors electrically insulated from each other, each housed partly in the crosspiece and partly in the foot, so as to protrude from the base by three terminations.

[0013] Thus, the connection device is intended to be housed partly in the casing, so that two of the terminations of its electrical conductors can be electrically connected to the two stators, on either side of the casing, and the third terminations of the electrical conductors can be connected to an electrical power cable.

[0014] This connection device thus reduces the wiring required to power the two stators. It therefore facilitates the design, assembly and maintenance of the axial flux electric machine. It also reduces potential sealing problems (the more cables there are, the more difficult sealing is to manage).

[0015] In practice, it is placed through an unoccupied space in the crankcase, so that it does not create any clutter. It also reduces the free volume inside the crankcase, and therefore restricts the volume of coolant required to fill it.

[0016] Its position through the casing, in the coolant, also has the advantage of promoting heat exchange to prevent the electrical contacts at its terminations from heating up too much. In addition, it is therefore possible to reduce the cross-section of the electrical conductors.

[0017] Other advantageous and non-limiting characteristics of the electrical connection device according to the invention, taken individually or in all technically possible combinations, are the following: - the crosspiece and the foot together form a T; - the foot is attached to a face of the sleeper, on a junction zone which extends away from the edge of the sleeper; - one of the terminations of each electrical conductor opens at a free end of the foot; - two of the terminations of each electrical conductor emerge from the crosspiece, preferably at a distance from the edge of the crosspiece; - one of said two terminations of each electrical conductor opens onto a face of the crosspiece located opposite the foot; - one of said two terminations of each electrical conductor opens into a through opening provided in the crosspiece; - the said two electrical conductors cross in the base.

[0018] The invention also proposes an axial flux electrical machine comprising a rotor flanked by two stators, a casing which houses said rotor and said stators, and an electrical connection device as mentioned above, the crosspiece of which is fixed on one side of the casing and the foot of which is engaged in the casing to be accessible from the other side of the casing (the casing preferably comprising a removable cover allowing this access).

[0019] Preferably, the casing delimits a first chamber housing said rotor and a second chamber which is sealed from said first chamber, in which a cooling and / or lubricating liquid circulates, and in which the foot of the base of the electrical connection device extends.

[0020] Advantageously, the casing has two openings respectively located on its two sides, one of which is at least partially closed by the electrical connection device and the other of which is closed by a cover.

[0021] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Detailed description of the invention

[0022] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0023] On the attached drawings:

[0024] [Fig.1] is a schematic perspective view of an electrical connection device according to the invention, in which the base of the device is shown in a semi-transparent manner;

[0025] [Fig.2] is a schematic perspective view of part of a casing of an electrical machine according to the invention, on which part of the electrical connection device of Fig. 1 appears;

[0026] [Fig.3] is a sectional view along plane AA of [Fig.2].

[0027] In Figures 2 and 3, a part of an electric machine 1 is partially represented. This is an axial flux electric machine, in this case a motor for propelling an electric vehicle (car, truck, bus, boat, airplane, etc.). Alternatively, this electric machine could be used in other ways (particularly in the form of an alternator for producing electrical energy).

[0028] This electrical machine 1 comprises a casing 10 which houses at least one rotor 20 mounted on a rotating shaft (not shown), and at least two stators 30, 40. In practice, the casing 10 here houses a single rotor 20 located between two stators 30, 40. But it could be provided that the casing houses several stators which would be mounted on the rotating shaft and which would each be flanked by one or two stators.

[0029] The rotor 20 comprises, for example, an annular-shaped frame which is fixed to the rotating shaft and which houses a plurality of magnetic pole elements such as permanent magnets. These magnetic pole elements are arranged side by side so as to together form a sort of ring around an axis of rotation of the rotor. They are preferably made up of small assembled permanent magnets. Since this rotor 20 is not itself the subject of the present invention, it will not be described in more detail here.

[0030] The two stators 30, 40 are preferably identical.

[0031] Each stator 30, 40 comprises a base centered on the axis of rotation of the rotor 20. As shown in section in [Fig. 3], this base comprises a support 31, 41 of annular shape and teeth 32, 42.

[0032] The support 31, 41 essentially has the shape of a thick disc centered on the axis of rotation. It delimits a circular central opening allowing in particular the passage of the rotor shaft.

[0033] The teeth 32, 42 all rise from the same face of the support 31, 41.

[0034] The stators 30, 40 are positioned opposite each other (on either side of the rotor 20), so that the faces of their supports 31, 41 from which the teeth 32, 42 rise are turned towards each other.

[0035] Each stator 30, 40 further comprises coils 35, 45 of conductive electrical wires which are positioned respectively around each of the teeth 32, 42 and which are connected in such a way that, when an appropriately controlled electric current flows through these coils, they generate a magnetic field capable of forcing the rotor 2 to rotate. These coils 35, 45 are here wound on supports attached to the teeth.

[0036] Each stator 30, 40 further comprises a cover 34, 44 provided to insulate the coils 35, 45 from the rotor 20. Each cover 34, 44 has an annular shape, with outer and inner peripheral edges which are applied in a sealed manner against the corresponding edges of the support 31, 41. Each cover 34, 44 thus delimits with the support 31, 41 which is associated with it a sealed space for the coils 35, 45, here containing a dielectric cooling liquid (hereinafter called “oil”). In this way, the coils 35, 45 can be cooled by this oil without the oil reaching the rotor 20.

[0037] The stators 30, 40 are each equipped with an interconnection ring 39, 49 (better known by the English term “busring”). Each of these interconnection rings 39, 49 is placed on the outside of the support 31, 41 and makes it possible to distribute the electric current to the different coils 35, 45.

[0038] In this regard, it can be specified here that the coils 35, 45, for example eighteen in number, are connected to one or other of three distinct electrical phases, usually denoted U, V, W, and to the neutral N (the references used below which end with one of these letters are respectively associated with elements connected to these phases and neutral).

[0039] The interconnection rings 39, 49 then each have four input terminals 39A, 49A respectively associated with the three phases U, V, W and the neutral N, and output terminals to be connected to the coils. They thus make it possible to distribute the current from the phase wires of an electrical power supply cable to the different coils 35, 45, the neutral wire of this cable allowing the current to restart.

[0040] In practice, these interconnection rings 39, 49 each have an annular shape, with the output terminals located in the central part and facing towards the inside of the casing 10, and the input terminals 39A, 49A located in the peripheral part and facing towards the opposite side.

[0041] The four input terminals 39A, 49A of each interconnection ring 39, 49 comprise means facilitating their electrical connection, here formed by threaded rods visible in [Fig.2]. Of course, as a variant, this could be, for example, a crimping pin, a tapped bore or any other ad hoc means.

[0042] These threaded rods are here distributed side by side. In other words, they extend along coplanar axes.

[0043] The casing 10 is designed to house the rotor 20 and the stators 30, 40 equipped with their interconnecting rings 39, 49. It is crossed by the rotating shaft of the rotor 20.

[0044] In the following, two main sides will be defined with respect to the casing 10, towards which the two faces of the rotor 20 are turned. An input side will thus be defined as being the side of the casing 10 through which the electric current supply to the stators 20 will be carried out, and, on the opposite side, a distal side.

[0045] The casing 10 here comprises two assembled half-shells 10A, 10B, which join, in the example illustrated, according to a joining plane substantially merged with the plane rotor 20 means.

[0046] The exact shape of this casing 10 will not be described here. Only certain aspects of this casing will be specified.

[0047] First of all, this casing 10 comprises two main walls 12A, 12B, located respectively on the inlet side and on the distal side, and a side wall 13 forming the junction between the two main walls 12A, 12B.

[0048] It further comprises an internal partition 11 which extends between the two main walls 12A, 12B and which makes it possible to delimit in the casing 10 two spaces which are sealed relative to each other, namely a main chamber 14 which houses the rotor 20 and stators 30, 40, and a secondary chamber 15.

[0049] As explained above, the coils 35, 45 of the two stators 30, 40 are housed in spaces containing oil which are sealed relative to the rotor 20. The secondary chamber 15 then makes it possible to connect these two spaces, by circulating the oil from the inlet side to the distal side of the casing 10.

[0050] The casing 10 also has two large openings, called the input opening 17 and the distal opening 16. These two openings are such that the input terminals 39A, 49A and two interconnecting rings 39, 49 are accessible from outside the casing 10 through these openings.

[0051] In practice, these two openings are located in the extension of secondary chamber 15.

[0052] The distal opening 16, located on the distal side of the casing 10, is closed by a removable cover 19, in a sealed manner. A seal, here an O-ring, is engaged in this regard in a groove which is provided in the edge of the cover 19 which is applied against the casing, all around the distal opening 16. The cover 19 is for example fixed to the casing 1 by fixing screws (not visible).

[0053] The axial flux electrical machine 1 further comprises, according to the invention, an electrical connection device 100 making it possible to connect together the input terminals 39A, 49A of the interconnection rings 39, 49 of the two stators 30, 40 and to supply them via a single electrical power supply cable (not shown).

[0054] The invention proposes in practice to take advantage of the secondary chamber 15 to engage the electrical connection device 100 there and establish the electrical connection between the two stators 30, 40.

[0055] Preferably, this electrical connection device 100 is further provided to seal the inlet opening 17 of the casing 10.

[0056] As shown in [Fig.l], this electrical connection device 100 comprises for this purpose an electrically insulating base 110, and electrical conductors 120U, 120V, 120W, 120N electrically insulated from each other.

[0057] The base is described as insulating in the sense that at room temperature (25°C), it has a resistivity greater than 1000 Ohm.m. In practice, the base 110 can be made of polymer material.

[0058] The 120U, 120V, 120W, 120N electrical conductors have a resistivity of less than 1 mOhm.m. In practice, the 120U, 120V, 120W, 120N electrical conductors can be made of metallic material, for example copper.

[0059] The base 110 is formed of two parts inclined relative to each other, one of which is intended to pass through the casing 10 from the inlet side to the distal side, and the other of which makes it possible to close the inlet opening 17 of the casing 10.

[0060] Here, these two parts are inclined at right angles to each other (this angle can be different, but it will preferably be between 80 and 100 degrees).

[0061] As shown in [Fig.l], the two parts of the base 110 are fixed to each other so as to form a T. These two parts are then called crosspiece 111 and foot 112.

[0062] The crosspiece 111 preferably has, on the side of the foot 112, a flat inner face. Here, the crosspiece 111 has a quasi-parallel piped shape. In the example illustrated in the figures, it has the shape of a square plate, with four ears at its four corners.

[0063] The foot 112 also has a quasi-parallel pipe shape here. It extends in length, from the crosspiece 111, over a distance substantially equal to the thickness of the casing between the inlet 17 and distal 16 openings.

[0064] In practice, the foot 112 is profiled, in the sense that it has a section of constant shape over its entire length. It has a width and a height less than those of the crosspiece 111. Thus, it is attached to the inner face of the crosspiece 111 by a junction zone which extends at a distance from the peripheral edge of the crosspiece 111. In this way, the inner face of the crosspiece 111 has a peripheral part which extends all around this junction zone and which is flat. This peripheral part is intended to bear against the casing 10 in order to close the inlet opening 17.

[0065] A seal 50 is preferably provided between the crosspiece 111 and the casing 10, which extends all around this inlet opening 17. This is a flat seal, for example comprising a metal core coated with a polymer sheath. Alternatively, an O-ring could have been used, in which case the casing or the crosspiece would have a groove to accommodate this seal.

[0066] Means are preferably provided for fixing the base 110 to the casing 10. Here, the crosspiece 111 has several screw holes. In the example illustrated, four holes are provided through the four ears of the crosspiece 111. Four screws 60 thus make it possible to fix this crosspiece to the casing 10 ([Fig.2]).

[0067] The 120U, 120V, 120W, 120N electrical conductors housed in this base 110 are preferably four in number (three phase and one neutral). Alternatively, the number of electrical conductors could be different (typically equal to two).

[0068] The electrical conductors 120U, 120V, 120W, 120N are here coated in the base 110 so as to protrude therefrom only by three terminations 121U, 121V, 121W, 121N, 122U, 122V, 122W, 122N, 123U, 123V, 123W, 123N. In practice, the base 110 is overmolded on these electrical conductors 120U, 120V, 120W, 120N, which are installed so as to be electrically insulated from each other.

[0069] This base also makes it possible to electrically isolate the half-shells 10A, 10B of these conductors.

[0070] Each of the electrical conductors 120U, 120V, 120W, 120N has an input termination 123U, 123V, 123W, 123N for its connection to a wire of the electrical power cable, and two output terminations 121U, 121V, 121W, 121N, 122U, 122V, 122W, 122N for its connection to the two stators 30, 40.

[0071] Here, these electrical conductors 120U, 120V, 120W, 120N are all formed by metal bars of rectangular sections. They are for example each formed of a first bar folded at a right angle, one part of which extends into the foot 112 and the other part of which extends into the crosspiece 111 of the base 110, and of a second bar welded to the first and folded so as to form the input termination.

[0072] In practice, the input terminations 123U, 123V, 123W, 123N open onto an outer face of the crosspiece 111 located opposite the foot 112. They open from this outer face orthogonally to it, and are folded at right angles on the same side, in the same plane. These terminations therefore extend side by side. They are preferably equipped with means facilitating the fixing of the wires of the electrical power cable. In the example illustrated, they are pierced to facilitate the connection of the wires of the power cable by bolts. Other fixing means could alternatively be used for this purpose.

[0073] One of the output terminations 122U, 122V, 122W, 122N of each electrical conductor, the one located in the crosspiece 111, opens into a through opening 113 provided in this crosspiece 111. This through opening 113 therefore opens onto the inner and outer faces of this crosspiece 111. It has an oblong-shaped edge. The output terminations 122U, 122V, 122W, 122N emerge from the crosspiece 111 of the base 110 via one of the elongated sides of the edge of this through opening 113 so as to extend side by side.

[0074] These output terminations 122U, 122V, 122W, 122N are preferably equipped with means facilitating their connection to the input terminals 39A of one of the stators 30. In the example illustrated, they are drilled to allow them to engage on the threaded rods of these input terminals 39A. Nuts are then provided to screw onto these threaded rods and thus lock these output terminations 122U, 122V, 122W, 122N. Other means could alternatively be used for this purpose.

[0075] It will be noted here that these output terminations 122U, 122V, 122W, 122N and the input terminations 123U, 123V, 123W, 123N all open at a distance from the peripheral edge of the crosspiece 111, so that they do not generate any bulk.

[0076] As shown in [Fig.3], the other output terminations 121U, 121V, 121W, 12 IN of each electrical conductor 120U, 120V, 120W, 120N open at a free end of the foot 112.

[0077] Here again, these output terminations 121U, 121V, 121W, 121N are preferably equipped with means facilitating their connection to the input terminals 49A of the other of the stators 40. In the example illustrated, they are in the form of threaded rods located side by side, at a distance from the threaded rods of the input terminals 49A. They are then intended to be connected to the latter via separate interconnection bars 70. Other means could alternatively be used for this purpose.

[0078] Here, the two stators 30, 40 used are identical, but positioned opposite each other. The neutral among the input terminals 39A, 49A of one of the interconnecting rings 39, 49 is therefore not located opposite the neutral of the other of the interconnecting rings. In other words, the two input terminals 39A, 49A to be connected to the neutral are located diagonally to each other.

[0079] Therefore, it is provided that one of the electrical conductors 120N, here the neutral, crosses at least one of the other electrical conductors in the base 110. In the example illustrated, taking into account the configuration of the input terminals of the stators 30, 40, this electrical conductor 120N crosses the three other electrical conductors 120U, 120V, 120W, preferably within the foot 112 of the base 110. The foot 112 then has a thickness allowing this crossing. The three other electrical conductors 120U, 120V, 120W, which extend in parallel, then each comprise at least one section inclined relative to the longitudinal axis of the foot 112.

[0080] For the assembly of this electrical connection device 100 on the casing 10 of the axial flux electric machine 1, it is planned to proceed as follows.

[0081] The seal 50 is first installed on the casing 10, around the inlet opening 17, then the electrical connection device 100 is attached to the casing 10, by engaging its foot 112 in the secondary chamber 15 and sliding it parallel to the axis of rotation of the rotor 20. When the crosspiece 111 comes to bear against the seal 50, the threaded rods of the input terminals 39A of the interconnection ring 39 naturally engage through the holes provided in the output terminations 122U, 122V, 122W, 122N.

[0082] At this stage, the base 110 is screwed onto the casing 10 by the four screws 60, so as to sandwich the sealing gasket 50. Nuts are then screwed onto the threaded rods of the input terminals 39 A to ensure a good electrical connection of the output terminations 122U, 122V, 122W, 122N.

[0083] Then, a plug (not shown) is inserted into the through opening 113 of the crosspiece 111 of the base 110 to close it tightly.

[0084] On the opposite side of the housing 10, the output terminations 121U, 121V, 121W, 121N are accessible through the distal opening 16. They can then be respectively connected to the input terminals 49A of the interconnection ring 49, here by straight interconnection bars 70.

[0085] Nuts are then screwed onto the threaded rods of these 49A input terminals and those of the 122U, 122V, 122W, 122N output terminals, to ensure a good electrical connection of the 70 interconnection bars.

[0086] The cover 19 is then attached to the casing 10 to seal the opening 16.

[0087] Finally, the input terminals 123U, 123V, 123W, 123N can be connected to the wires of the power supply cable. The secondary chamber 15 can be filled with oil.

[0088] Note that a protective and sealing cover can also be used to protect these 123U, 123V, 123W, 123N input terminations.

[0089] During operation of the axial flux electrical machine 1, the electrical conductors will naturally heat up. The position of the electrical connection device 100 within the secondary chamber 15, immersed in oil, will limit this heating. Also, the electrical conductors may have been sized taking into account the low heating that they will have to undergo, to the benefit of the cost price of the electrical connection device 100.

[0090] The present invention is in no way limited to the embodiment described and shown, but those skilled in the art will be able to provide any variation in accordance with the invention.

[0091] Typically, the base could have a different shape. For example, its foot could be cylindrical in revolution, its crosspiece could have the shape of a thick disc...

[0092] The terminations could also be oriented and / or located differently. For example, they could protrude on either side of the crosspiece (upwards and downwards in the figures).

[0093] It would also be possible to provide for the conductors to all run in parallel in the base of the plinth. In this case, interconnection bars could be used, not straight ones, as shown in the figures, but of different shapes so that the interconnection bar corresponding to the neutral crosses the other interconnection bars.

Claims

Claims

1. Electrical connection device (100) for the electrical connection of two stators (30, 40) of an axial flux electrical machine (1), comprising: - an electrically insulating base (110) comprising two parts inclined relative to each other, namely a crosspiece (111) and a foot (112), and - at least two electrical conductors (120U, 120V, 120W, 120N) electrically insulated from each other, which are each housed partly in the crosspiece (111) and partly in the foot (112), so as to project from the base (110) by three terminations (121U, 121V, 121W, 121N, 122U, 122V, 122W, 122N, 123U, 123V, 123W, 123N).

2. An electrical connection device (100) according to claim 1, wherein the crosspiece (111) and the foot (112) together form a T.

3. Electrical connection device (100) according to claim 1 or 2, in which the foot (112) is attached to a face of the crosspiece (111), on a junction zone which extends at a distance from the edge of the crosspiece (111).

4. Electrical connection device (100) according to one of claims 1 to 3, in which one of the terminations (121U, 121V, 121W, 121N) of each electrical conductor (120U, 120V, 120W, 120N) opens at a free end of the foot (112).

5. Electrical connection device (100) according to one of claims 1 to 4, wherein two of the terminations (122U, 122V, 122W, 122N, 123U, 123V, 123W, 123N) of each electrical conductor (120U, 120V, 120W, 120N) emerge from the crosspiece (111), preferably at a distance from the edge of the crosspiece (111).

6. Electrical connection device (100) according to one of claims 1 to 5, wherein one of said two terminations (122U, 122V, 122W, 122N, 123U, 123V, 123W, 123N) of each electrical conductor (120U, 120V, 120W, 120N) opens onto a face of the crosspiece (111) located opposite the foot (112) and / or within a through opening (113) provided in the crosspiece (111).

7. Electrical connection device (100) according to one of claims 1 to 6, wherein said two electrical conductors (120U, 120V, 120W, 120N) cross in the base (110).

8. Axial flux electric machine (1) comprising a rotor (20) flanked by two stators (30, 40), a casing (10) which houses said rotor (20) and said stators (30, 40), and an electrical connection device (100) according to one of claims 1 to 7, the crosspiece (111) of which is fixed on one side of the casing (10) and the foot (112) of which is engaged in the casing (110) to be accessible from the other side of the casing (110).

9. Axial flux electric machine (1) according to claim 8, in which the casing (10) delimits a first chamber (14) housing said rotor (20) and a second chamber (15) which is sealed from said first chamber (114), in which a cooling and / or lubricating liquid circulates, and in which the foot (112) of the base (110) of the electrical connection device (100) extends.

10. An axial flux electric machine (1) according to claim 8 or 9, wherein the casing (10) has two openings (11, 12) respectively located in its two sides, one of which is at least partially closed by the electrical connection device (100) and the other of which is closed by a cover (19).

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