Axial flux electric machine

Abstract

Axial Flux Electric Machine The invention relates to an axial flux electric machine (1), comprising: - a stator (3) having a yoke (4), teeth (44) and stator windings (8) wound around the teeth (44), - a housing (2_2) housing the stator (3), the yoke (4) being fixed to a wall (20) of the housing (2_2), - a circular bus (7) to which are connected the ends (80) of the stator windings (8), the circular bus (7) being arranged between the stator windings (8) the yoke (4) having on the side of the housing (2_1, 2_2), passages (42) through it radially, electrical connections (32, 34, 36) passing through the passages (42) to connect the circular bus (7) to phase terminals (94, 96) at the periphery of the electric machine (1). (Figure 1)

Description

Title of the invention: Axial flux electric machine

[0001] The present invention relates to the fields of electrotechnics and mechanics and more specifically concerns an axial flux electric machine.

[0002] Currently, electric or hybrid electric vehicles use electric traction or propulsion motors, which are often radial flux electric machines, that is to say, the stator windings of such a machine generate a magnetic flux in a radial direction relative to an axial direction corresponding to the axis of rotation of the machine.

[0003] In order to reduce the size of such a motor used for traction or propulsion of an electric vehicle, it is envisaged that an axial flux electric machine could be used instead of a radial flux electric machine. This type of machine is indeed generally more compact, at least in one axial direction corresponding to the axis of rotation of the machine, which gives it a discoidal shape.

[0004] Such a machine therefore comprises a generally cylindrical housing containing at least one stator with stator coils, and a rotor attached to a rotating shaft passing through the middle of the housing. The stator coils are fixed within the housing between an inner cylindrical wall defining a bearing support for the rotating shaft, and an outer cylindrical wall. These stator coils are arranged angularly all around the inner cylindrical wall, opposite the magnetic poles of the rotor.

[0005] To electrically connect the stator coils to the phase terminals of the machine, intended to be connected to an inverter, the ends of a stator winding of each stator coil are first welded to a circular bus, for example a three-phase bus, arranged between the stator coils on one side and one of the internal or external cylindrical walls of the housing on the other. Then, phases of the circular bus are connected to electrical links connecting the circular bus to the phase terminals of the machine, accessible from outside the housing.

[0006] When the circular bus is arranged between the stator coils and the outer cylindrical wall, these electrical connections pass, for example, through the outer cylindrical wall of the housing. This circular bus configuration is advantageous for connecting the electrical machine to an inverter, but is radially bulky and expensive in terms of copper due to the size of the circular bus.

[0007] When the circular bus is arranged between the stator coils and the inner cylindrical wall, the electrical connections linking the circular bus to the phase terminals generally pass through a flat wall of the housing through which the rotating shaft exits. This solution adds axial bulk. Furthermore, it prevents a casing of another piece of equipment, for example a gearbox, directly against the flat wall of the casing of the electrical machine.

[0008] The present invention aims to remedy at least in part the aforementioned disadvantages by providing an axial flux electric machine and an electric or hybrid electric vehicle, which limit the radial and axial bulk of the electric machine despite the use of a circular bus arranged between stator coils of the machine and a rotating shaft attached to a rotor of the electric machine.

[0009] To this end, the invention proposes an axial flux electric machine, comprising: - a rotor, - a stator comprising a yoke, teeth projecting from the yoke in the direction of the rotor, and stator windings wound around the teeth, the yoke having a crown shape extending radially from an internal radial periphery of the yoke to an external radial periphery of the yoke, - a casing housing the stator, with the cylinder head attached to one wall of the casing, - a circular bus to which the ends of the stator windings are connected, the circular bus being arranged radially on the side of the internal radial periphery of the cylinder head, the electric machine being characterized in that the cylinder head has, on the side of the housing, passages radially through the cylinder head and extending from the internal radial periphery of the cylinder head to the external radial periphery of the cylinder head, and in that the electric machine further has electrical connections suitable for electrically connecting phase connections of the circular bus to phase terminals located in an external peripheral portion of the electric machine, the electrical connections passing at least partly through the passages radially through the cylinder head.

[0010] Thanks to the invention, the electrical connections do not require an axial increase in the size of the electric machine, since they can be entirely integrated within the thickness of the cylinder head. The cylinder head is preferably fixed to a wall of the housing on the side opposite the teeth, which is a generally flat wall, by bonding, welding, or a key system. There is no play between the housing wall and the cylinder head because the axial position of the stator is guaranteed by the housing. Furthermore, the radial size of the machine is limited, as the circular bus is positioned between the stator windings and a passage is provided in the stator to allow passage of a rotating shaft attached to the rotor.

[0011] It should be noted that by circular bus we mean here circular connection means, comprising several conducting rings (circular conducting bars) not necessarily closed, each conducting ring being capable of conducting a phase current associated with a portion of the stator coils to which it is connected. One of the circular rings may correspond to a neutral connection of the machine electrical, not necessarily requiring access from outside the electrical machine (therefore not necessarily connected by an electrical link to a dedicated terminal in the external peripheral portion of the machine).

[0012] Furthermore, in this application, an axial orientation or direction refers to the direction of the rotating shaft attached to the rotor, that is, a direction parallel to the axis of this rotating shaft. A radial orientation or direction is orthogonal to the axial direction and intersecting the axis of the rotating shaft. An angular orientation or direction is orthogonal to both the axial and radial directions, that is, it is ortho-radial.

[0013] The axial flux electric machine according to the invention comprises, for example, a rotor and two stators, or more rotors and fewer or more stators. It has a discoidal shape, that is to say, its housing has a generally cylindrical shape that is compact in the axial direction. The bases of this generally cylindrical shape are, for example, traversed by the rotating shaft attached to the rotor. Alternatively, this rotating shaft passes through only one of these bases.

[0014] According to an optional feature of the invention, the electrical connections are covered with an electrically insulating material, at least in portions thereof, in the passages radially through the cylinder head. Such insulating protection is necessary when the crankcase wall and the cylinder head are metallic and not covered with electrically insulating material at the electrical connections. The crankcase is generally made of aluminum and the cylinder head is generally made of magnetic steel.

[0015] The electrical connections preferably connect each a distinct phase connection of the circular bus to a distinct phase terminal located in the outer peripheral portion of the electric machine, passing through separate passages radially through the yoke. Using a separate passage for each phase of the electric machine allows the electrical connections to be thick enough to conduct a significant current, while having small passages in the yoke that do not disrupt the flow of magnetic flux during the operation of the electric machine.

[0016] Preferably in the invention, the passages radially traversing the yoke each have a common ortho-radial plane of symmetry with a stator tooth, or each have an ortho-radial plane of symmetry located angularly at the level of a stator tooth, the distance between the passage and a winding slot adjacent to the tooth being greater than or equal to the thickness of the yoke. This feature makes it possible to machine the yoke at the base of the teeth in locations virtually untouched by the magnetic flux during the operation of the electric machine, and thus to avoid disturbing it.

[0017] In one embodiment of the invention, one of the phase terminals and one of the The phase connections of the circular bus intersect the ortho-radial plane of symmetry. One of the electrical links connecting said phase terminal to said phase connection follows the ortho-radial plane of symmetry. Since this electrical link does not deviate from the ortho-radial plane of symmetry, it is as short as possible, thus saving space and material while simplifying assembly.

[0018] The electrical machine is, for example, three-phase, with a first phase terminal and a first phase connection located on one side of the orthoradial plane of symmetry being connected by a first electrical connection through a radial passage in the yoke located on the first side; a second phase terminal, a second phase connection, and a second electrical connection corresponding to those that intersect or follow the orthoradial plane of symmetry; and a third phase terminal and a third phase connection located on a second side of the orthoradial plane of symmetry opposite to the first side, being connected by a third electrical connection through a radial passage in the yoke located on the second side. This configuration further optimizes the size of the electrical connections and facilitates their assembly.The first and third electrical connections, for example, are symmetrical to each other with respect to the ortho-radial plane of symmetry and have only two ortho-radial bends.

[0019] Preferably in the invention, the passages radially through the cylinder head are radial grooves formed on a surface of the cylinder head opposite the housing wall. This embodiment facilitates the mounting of electrical connections. Furthermore, when the radial grooves each have a common ortho-radial plane of symmetry with a stator tooth, they minimize the disturbance of the magnetic flux by each being centered on the edge of a tooth base. Alternatively, the passages are in the form of radial holes in the cylinder head, i.e., at the base of the teeth.

[0020] According to an optional feature of this embodiment of the invention, the cylinder head has a radial groove for each stator tooth, the electrical connections leaving a free radial groove between them, the phase terminals being grouped on the outer periphery of the same tooth. These radial grooves save material in the cylinder head without disturbing the magnetic flux passing through it during operation. They also facilitate mounting the cylinder head on the housing wall when the cylinder head is segmented into different parts, each having a stator tooth. Indeed, the radial grooves serve, for example, to position and / or angularly fix every other segment of the cylinder head on the housing wall by sliding in keys of complementary shape, for example, keys that are integral with the housing wall.For example, radial grooves have a dovetail cross-section to facilitate proper angular and axial retention of the cylinder head segments. Other groove cross-section shapes are possible, for example... rectangular.

[0021] Furthermore, the phase terminals of the electric machine are, for example, grouped in a bomier arranged on the radial periphery of one of the teeth, which facilitates electrical connections between the electric machine and one or more inverters.

[0022] According to another optional feature of the invention, the circular bus comprises one conductive bar per phase, the conductive bars being connected to the ends of the stator windings by forks arranged angularly on these conductive bars, the entire set of conductive bars being overmolded, leaving the phase connections to the electrical links free. This feature facilitates the connection of the winding ends to the circular bus. The mechanical strength of the conductive bars to each other is ensured by the overmolding. The phase connections of the circular bus are, for example, unmolded areas allowing each electrical link to be soldered by one of its ends to one of these areas, each area being located on a separate conductive bar of the circular bus.

[0023] Preferably, the electric machine according to the invention comprises two stators and two corresponding circular buses, the electrical connections of each stator being electrically linked together in a terminal block comprising said phase terminals, in the external peripheral portion of the electric machine, located in a radial extension of the electric machine housing. The electric machine housing is, for example, made in two parts, each forming a half-housing housing one of the machine's stators. The rotor being mounted between the two stators, the two half-housings are screwed together around the circumference of the rotor at the end of the electric machine assembly. The terminal block is, for example, integrated into a radial extension of one of the half-housings, forming a housing that the other half-housing closes axially.

[0024] The invention also relates to an electric or hybrid electric vehicle comprising an electric machine according to the invention. The electric or hybrid electric vehicle according to the invention has advantages similar to those of the axial flux electric machine according to the invention.

[0025] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given by reference to the accompanying schematic drawings on the other hand, in which:

[0026] [Fig-1] represents a perspective view of an electrical machine according to the invention, in one embodiment of the invention, and in which one half of the casing is not shown in order to reveal a face of one of the stators of the electrical machine, intended to be fixed to this half of the casing,

[0027] [Fig.2] represents in axial section a part of the electrical machine of [Fig. 1],

[0028] [Fig.3] represents a stator tooth of a stator of an electrical machine according to the invention, in one embodiment of the invention, the tooth being wound and protruding from a cylinder head segment through which an electrical connection is arranged, and

[0029] [Fig.4] is an ortho-radial cross-sectional view of a cylinder head segment of a machine electric according to the invention, from which a stator tooth protrudes, in another embodiment of the invention.

[0030] According to an embodiment of the invention shown in [Fig.1], an axial flux electric machine 1 according to the invention comprises two stators 3 and a rotor 5, the rotor 5 being able to be fixed to a rotating shaft with axis of rotation X by means of a hub 54. The electric machine 1 is three-phase, but alternatively it contains more or less than three supply phases.

[0031] The electrical machine 1, generally discoid in shape, comprises a first housing 2_1 (referenced in [Fig. 2]) and a second housing 2_2, each containing one of the stators 3 of the electrical machine. The two housings 2_1 and 2_2 are screwed together to form a complete housing or enclosure for the electrical machine 1, closing around the rotor 5 mounted between the stators 3. The housings 2_1 and 2_2 each have an outer cylindrical wall with screw holes for securing the housings 2_1 and 2_2 together, and a generally flat wall 20 (visible in [Fig. 2]) with a central hole for the rotating shaft. The flat walls 20 of the housings 2_1 and 2_2 each have a bearing support bordering this central hole, in which a bearing is mounted for the rotating shaft.

[0032] The stators 3 in each of the housings 2_1 and 2_2 are almost structurally identical, being symmetrical to each other with respect to a main extension plane of the rotor, and therefore include many identical components, referenced identically in the figures.

[0033] In particular, each stator 3 comprises a yoke 4, made for example of magnetic steel, with stator teeth 44 (one of which is visible [Fig.2]) projecting axially from the yoke 4, in the direction of the rotor 5. The stator teeth 44 are attached to the yoke 4 or are formed at the same time as the yoke 5, the latter being able to be a yoke formed from an assembly of magnetic sheets glued together, or from an assembly of segments of magnetic steel, each segment comprising for example a stator tooth 44 attached or formed from the material with the segment, or the yoke 4 is formed as a single block with the stator teeth 44. When the stator teeth 44 are attached to the yoke 4, the latter is possibly formed from a wound magnetic sheet.

[0034] It is understood here that the breech 4 is a base surmounted by the stator teeth 44, therefore forming the bases of these, and intended to allow the magnetic flux to loop back inside the cylinder head 4 during the operation of the electrical machine 1.

[0035] The cylinder head 4 takes the overall form of a ring extending radially from an internal radial periphery 46 of the cylinder head 4 to an external radial periphery 48 of the cylinder head 4. The face 41 of the cylinder head 4 shown [Fig.1], extending in an ortho-radial plane, is fixed to the flat wall 20 of the housing 2_1, 2_2.

[0036] In this embodiment of the invention, the cylinder head 4 is segmented along the various stator teeth 44, and has, under the base of each stator tooth, on the face 41, a radial groove 42 extending from the inner radial periphery 46 of the cylinder head 4 to an outer radial periphery 48 of the cylinder head 4. These radial grooves 42 are used when fixing the cylinder head to the flat wall 20, in particular for positioning the segments of the cylinder head 4. The corresponding positioning and / or fixing system uses, for example, a system of keys with a cross-section complementary to that of the cross-sections of the radial grooves 42. Once positioned, the segments are, for example, screwed to the flat wall 20.

[0037] Stator windings 8 are wound around the stator teeth 44. To facilitate the mounting of these stator windings 8 on the stator teeth 44, an insulating winding support 82, shown [Fig.2], on which a stator winding 8 is pre-wound, is fitted onto each stator tooth 44.

[0038] The ends 80 of the stator windings 8 are connected to a circular bus 7, formed of four conductive bars 71, 73, 75, and 77, and located radially within the limits of the inner radial periphery 46 of the yoke 4, i.e., the circular bus 7 is closer to the rotating shaft than this inner radial periphery 46 of the yoke 4. These conductive bars are circular, forming rings nested radially within one another. Alternatively, these rings are not closed or are arranged differently.

[0039] In this embodiment of the invention, each conductive bar 71, 73, 75, and 77 has forks 78 angularly distributed on these bars, each fork allowing one end of one of the stator windings 8 to be welded to it, thus electrically connecting the end of the stator winding 8 to one of the conductive bars 71, 73, 75, and 77. The forks are metallic and, for example, made from material or welded to the conductive bars 71, 73, 75, and 77. The material used for the forks and the conductive bars is preferably copper, but other conductive materials are of course usable.

[0040] The conductor bar 71 corresponds for example to a neutral connection of the electrical machine 1, and the conductor bars 73, 75, and 77 carry the electrical phases of the electrical machine 1.

[0041] To ensure the mechanical stability of the circular bus 7, and in particular the conductive bars to each other, it is partially overmolded. The corresponding overmolding 70 is visible [Fig. 2]. In particular, on this [Fig. 2], an axial extension of the conductive bar 77 towards the wall 20 of the housing, located at an angle, is not overmolded to allow its connection by welding to an electrical link 34. This axial extension thus forms a phase connection 74.

[0042] The circular bus 7 has an opening in its center suitable for allowing the rotating shaft of the machine to pass through. As can be seen [Fig.2], the rotor hub 54 has a radial gap between the stator windings 8, so as to leave an axial air gap on the order of one millimeter between the rotor 5 and the stator 3.

[0043] The rotor 5 is formed of magnet poles 58 distributed angularly around the rotating shaft, these magnet poles 58 being inserted between branches of a composite body fixed centrally to the hub 54, a collar 52 clamping the magnet poles 58 at the periphery of the rotor 5 to counter the centrifugal forces on these magnet poles 58 during the operation of the electric machine 1.

[0044] Returning to [Fig. 1], the cylindrical wall of the second housing 2_2 has a radial extension housing a terminal block in an external peripheral portion 9 of the electrical machine 1. The terminal block has three phase terminals 92, 94, 96 corresponding to the supply phases of the electrical machine 1, and allowing these three phase terminals 92, 94, 96 to be electrically connected to one or more inverters. The phase terminals 92, 94, 96 each take the form, for example, of an eyelet connector for the passage of a fixing screw.

[0045] The terminal block is located radially on the outer periphery of one of the stator teeth 44, in particular it extends angularly only over a limited portion of the electrical machine 1, the outer peripheral portion 9 not radially covering more than two stator teeth 44.

[0046] For each of the power supply phases of the electric machine 1, an electrical connection 32, 34, or 36 electrically links one of the phase terminals 92, 94, 96 respectively to a respective phase connection 72, 74, 76 of the circular bus 7. These phase connections 72, 74, 76 each correspond, for example, to a location on a conductive bar of the circular bus 7, allowing the corresponding electrical connection 32, 34, 36 to be soldered to that location. Of course, other types of connections are possible, for example, by screw connection.

[0047] The electrical connections 32, 34, or 36 here take the form of copper conductive bars covered, except at their ends, with an electrically insulating material. Alternatively, these conductive bars are each formed of conductive strands or a conductive wire of round cross-section, made of copper or a different metallic material.

[0048] According to the invention, the conductive links 32, 34, and 36 pass at least partially in passages radially through the cylinder head 4, that is to say, in this embodiment of the invention, in the radial grooves 42.

[0049] The conductive links 32, 34, and 36 thus have little or no additional axial bulk, the face 41 of the cylinder head 4 coming into contact with the flat wall 20 of the housing when it is fixed there.

[0050] Preferably, after this fixing, they leave no play between on the one hand the flat wall 20 of the housing 2_1, 2_2 and on the other hand the flat surface of the face 41 on which the radial grooves 42 are cut. In this latter case, the conductive links 32, 34, and 36 cannot protrude slightly axially from the radial grooves 42.

[0051] In figures 3 and 4, an axial overhang of the conductive links, relative to the flat surface of the face 41 on which the radial grooves 42 are cut, is permitted by the presence of ribs 43 protruding on the face 41 of the cylinder head 42, these ribs 43 being in contact with the flat wall 20 of the housing 2_1, 2_2 when the electrical machine 1 is assembled.

[0052] In this embodiment of the invention, the radial grooves 42 have a dovetail-shaped cross-section, but other cross-sections are of course conceivable.

[0053] Furthermore, the radial grooves 42 each intersect an ortho-radial plane of symmetry of a stator tooth 44, that is, a plane passing through the X-axis of the rotating shaft and dividing the stator tooth 44 into two equal parts. The intersection of this ortho-radial plane of symmetry with the corresponding radial groove 42 is centered in the radial groove 42.

[0054] Figure 3 illustrates such an ortho-radial plane of symmetry P passing through a stator tooth 44, in one embodiment of the invention. In Figure 3, the elements identical to those in Figures 1 and 2 are referenced in the same way. In particular, the stator tooth 44 is provided with a stator winding 8 pre-wound on a winding support 82.

[0055] In this embodiment of the invention, the electrical connection 34 is partly inserted into the radial groove 42 arranged in the face 41 of the cylinder head 4 opposite the flat wall 20 of the housing.

[0056] This electrical connection 34 includes an electrically insulating overmolding surrounding its conductive part except at its ends. This insulating overmolding extends angularly beyond the groove 42, into the axial gap existing between the face 41 of the cylinder head 4 and the flat wall 20 of the housing 2_1, 2_2. This angular extension of the overmolding is assembled at the same time as the electrical connection 34 on the cylinder head 4, the electrical connections 32, 34, and 36 being first assembled on the cylinder head 4 and welded to the circular busbar 7 before assembly of the whole on the housing 2_1, 2_2.

[0057] One end of the electrical connection 34, intended to be fixed to the terminal of phase 94, takes the form of an eyelet suitable for receiving a fixing screw, while the other end of the electrical link 34 is curved so as to offer a sufficient welding surface with the corresponding conductive bar of the circular bus 7.

[0058] In another visible embodiment [Fig.4], in which the elements identical to those of figures 1, 2 and 3 are referenced in the same way, the tooth 44 has fins 45 extending angularly on either side of the tooth 44, with the axial end of the latter facing the rotor 5.

[0059] On this [Fig.4], flow lines F crossing the cylinder head 4 are shown in black lines. It can be seen that the radial groove 42 is not or very little crossed by the flow lines F, due to its central position at the base of the tooth 44.

[0060] In an alternative embodiment of the invention, the radial grooves 42 do not intersect the ortho-radial plane of symmetry P, this condition being difficult to achieve when the stator is made by winding a sheet of metal (the so-called "slinky" method). In this case, the radial grooves 42 are nevertheless equidistant from each other in the angular direction, although this condition is not necessary to achieve the invention. Each groove 42 is viable provided that the shortest distance dl (referenced in [Fig. 4]) between the groove and the adjacent winding slot is substantially equal to or greater than the thickness d2 of the yoke.

[0061] Returning to [Fig. 1], the electrical connection 34 links the phase connection 74 to the phase terminal 94 without angular deviation, these three elements being centered on the ortho-radial plane of symmetry P of the same stator tooth 44.

[0062] On one side of this ortho-radial symmetry plane P, the electrical link 36 connects the phase connection 76 to the phase terminal 96 by passing through a radial groove 42 located in a stator tooth 44 spaced one other stator tooth 44 from the stator tooth 44 through which the electrical link 34 passes.

[0063] Symmetrically, on a second side of the ortho-radial symmetry plane P, distinct from the first side mentioned above, the electrical link 32 connects the phase connection 72 to the phase terminal 92 by passing through a radial groove 42 located in a stator tooth 44 spaced one other stator tooth 44 from the stator tooth 44 through which the electrical link 34 passes.

[0064] Leaving at least one out of every two radial grooves 42 free of any electrical connection in the angular direction allows these free radial grooves 42 to be used for the correct positioning of the cylinder head segments 4 on the flat wall 20 of the housing. This also ensures the feasibility of the routing of the electrical connections 32, 34, 36 in terms of radii of curvature.

[0065] The phase connections 72 and 76 are located in the extension of the radial grooves 42 receiving the electrical connections 32 and 36, the latter therefore not exhibiting any angular deviation between the phase connections 72, 76 and the radial periphery external 48 of the cylinder head 4. The electrical connections 32 and 36, on the other hand, beyond the external radial periphery 48 of the cylinder head 4, have several bends to reach the respective phase terminals 92 and 96.

[0066] As shown [Fig.2], the electrical connections 32, 34 and 36 of each stator 3 join in pairs at their electrically connected ends to the phase terminals 92, 94, and 96. Thus the electric machine 1 has a single terminal per phase for the two stators 3, accessible via a cover 24 on the radial extension of the cylindrical wall of the housing 2_2.

[0067] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the features of different embodiments can be combined to carry out the invention, provided that these embodiments are not incompatible with each other.

Claims

Demands

1. An axial flux electric machine (1) comprising: - a rotor (5), - a stator (3) having a yoke (4), teeth (44) projecting from the yoke (4) towards the rotor (5), and stator windings (8) wound around the teeth (44), the yoke (4) having a crown shape extending radially from an internal radial periphery (46) of the yoke (4) to an external radial periphery (48) of the yoke (4), - a housing (2_1, 2_2) accommodating the stator (3), the yoke (4) being fixed to a wall (20) of the housing (2_1, 2_2), - a circular bus (7) to which are connected the ends (80) of the stator windings (8), the circular bus (7) being arranged radially on the side of the internal radial periphery (46) of the yoke (4), the electric machine (1) being characterized in that the cylinder head (4) has on the side of the casing (2_1, 2_2),passages (42) radially traversing the cylinder head (4) and extending from the inner radial periphery (46) of the cylinder head (4) to the outer radial periphery (48) of the cylinder head (4), and in that the electrical machine (1) further comprises electrical connections (32, 34, 36) capable of electrically connecting phase connections (72, 74, 76) of the circular bus (7) to phase terminals (94, 96) located in an outer peripheral portion (9) of the electrical machine (1), the electrical connections (32, 34, 36) passing at least partly through the passages (42) radially traversing the cylinder head (4).

2. An axial flux electric machine (1) according to claim 1, wherein the electrical connections (32, 34, 36) are covered with an electrically insulating material at least on portions thereof in the passages (42) radially through the cylinder head (4).

3. An axial flux electric machine (1) according to claim 1 or 2, wherein the electrical links (32, 34, 36) each connect a separate phase connection (72, 74, 76) of the circular bus (7) to a separate phase terminal (92, 94, 96) located in the outer peripheral portion (9) of the electric machine (1), via separate passages (42) radially through the yoke (4).

4. An axial flux electric machine (1) according to any one of claims 1 to 3, wherein the radially traversing passages (42) each have a common orthoradial plane of symmetry with a tooth (44) of the stator (3) or each have an orthoradial plane of symmetry located angularly at the level of a tooth (44) of the stator (3), the distance between the passage (42) and a winding notch adjacent to the tooth (44) being greater than or equal to a thickness of the yoke (4).

5. An axial flux electric machine (1) according to claims 3 and 4, wherein one of the phase terminals (94) and one of the phase connections (74) of the circular bus (7) intersect the orthoradial plane of symmetry (P), one of the electrical links (34) connecting said phase terminal (94) to said phase connection (74) along the orthoradial plane of symmetry (P).

6. An axial flux electric machine (1) according to any one of claims 1 to 5, wherein the passages (42) radially through the cylinder head (4) are radial grooves formed on a surface of the cylinder head (4) opposite the wall (20) of the housing (2_1, 2_2).

7. An axial flux electric machine (1) according to claims 4 to 6, wherein the yoke (4) has a radial groove (42) per tooth (44) of the stator, the electrical connections (32, 34, 36) leaving a radial groove (42) free between them, the phase terminals (92, 94, 96) being grouped at an external periphery of the same tooth (44).

8. An axial flux electric machine (1) according to any one of claims 1 to 7, wherein the circular bus (7) comprises a conductive bar per phase, the conductive bars being connected to the ends (80) of the stator windings (8) by forks (78) arranged angularly on these conductive bars, the entire set of conductive bars being overmolded leaving the phase connections (72, 74, 76) connected to the electrical links (32, 34, 36) free.

9. An axial flux electric machine (1) according to any one of claims 1 to 8, comprising two stators (3) and two corresponding circular buses (7), the electrical connections (32, 34, 36) of each stator (3) being electrically connected together in a terminal block comprising said phase terminals (92, 94, 96), in the external peripheral portion (9) of the electric machine (1), located in a radial extension of the casing (2_1, 2_2) of the electric machine (1).

10. Electric or hybrid electric vehicle, comprising an electric machine (1) according to any one of claims 1 to 9.

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