Stator of an axial-flux electric machine comprising a cooling device and electric machine provided with this stator
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- YEESMA
- Filing Date
- 2026-01-22
- Publication Date
- 2026-07-30
Smart Images
Figure EP2026051603_30072026_PF_FP_ABST
Abstract
Description
DESCRIPTION TITLE: Stator of an axial flux electrical machine comprising a cooling device and an electrical machine equipped with this stator TECHNICAL FIELD OF THE INVENTION
[0001] The technical field of the invention is that of axial flux machines, in particular the cooling of the stator of an axial flux machine.
[0002] The present invention relates to a stator of an axial flux electric machine comprising a cooling device and an electric machine equipped with this stator and in particular to the cooling of the stator of an electric machine with an external rotor bearing. TECHNOLOGICAL BACKGROUND OF THE INVENTION
[0003] It is known that axial flux machines are cooled by a fluid passing through a channel located on the external diameter of the stator. However, in an axial flux machine with an externally mounted rotor, it is difficult and complicated to incorporate cooling channels. Furthermore, for a given volume, for example in a vehicle wheel, the larger the diameter of the active part of the electric machine, the higher the torque will be; therefore, adding an external cooling system reduces the maximum torque of the electric machine.
[0004] There is also a need for an external bearing electric machine having a central shaft diameter that can be greater than 50% of the maximum diameter, in which it is therefore not possible to house a rotating shaft including a cooling system filling this hole.
[0005] Another solution is to radially pass through the ferromagnetic teeth of the stator; however, this magnetically saturates the stator teeth more quickly. Furthermore, it requires an external radial input and / or output, which in turn necessitates radial space.
[0006] Cooling systems between the ferromagnetic tooth and a winding guide around the tooth are known. However, this solution leads to a reduction in the copper content within the slots. Furthermore, cooling channels formed by the ferromagnetic part (teeth or base) of the stator can prevent the formation of a lamination stack or cause leakage problems between the laminations. This can also lead to corrosion of the ferromagnetic part.
[0007] Finally, there are needs for axial flux electric machines, where the part driven by the rotor is directly driven by the rotor's external diameter, and this driven part surrounds the stator. This is particularly the case for motorized wheels without a rotating central shaft.
[0008] There is therefore a need for an axial flux electric machine with a sealed cooling device, without increasing the external diameter size of the machine and without reducing the copper content or causing magnetic saturation. SUMMARY OF THE INVENTION
[0009] The invention offers a solution to the problems mentioned above, by allowing a cooling system for active parts without sealing and corrosion problems.
[0010] One aspect of the invention relates to a stator of an axial flux electrical machine comprising: at least one main body comprising: a first group of ferromagnetic stator teeth, distributed angularly and regularly around the X axis, each stator tooth of the first group having at least one radial axial air gap surface and one peripheral external surface, stator notches between each stator tooth of the first group, a winding wound in the stator slots, covering the outer peripheral surface of the teeth, a cylinder head that is fixed in rotation and translation with the main body or the winding, comprising: a one-piece body comprising a main base, a cooling circuit for the main body and / or the winding located in an area of the main base such that its maximum radius value with respect to the X-axis is closer to the value of the radius of the internal peripheral surface (122) than to the value of an external radius of the stator body teeth, the cooling circuit comprising: -a coolant inlet and a coolant outlet, each forming an orifice in the monobloc body, -at least one conduit comprising a first and second end connected respectively to the inlet and outlet, the conduit being delimited and formed by at least one part of the wall of the monobloc body in thermal contact with only a radial surface and / or an internal axial surface of the stator body and / or the winding.
[0011] Thanks to the invention, the cooling circuit's location does not significantly disrupt the stator's magnetic field and is not bulky in the radial external area. Furthermore, the cylinder head, comprising a single-piece body with an integrated cooling circuit, prevents leaks and avoids contact between the coolant and any active parts. Indeed, the circuit, and therefore the cooling conduit(s), is formed entirely by one or more walls of the single-piece body.
[0012] The external radius of the stator body teeth corresponds to the distance between the X axis and the peripheral external surface of each tooth.
[0013] The fact that the duct is delimited and formed by at least one part of the wall of the monobloc body allows for improved heat transfer.
[0014] A duct is defined as a volume within a cooling circuit through which the coolant can circulate. The duct may have one or more parallel channels.
[0015] Thermal contact refers to direct contact or contact via a thermal resin or adhesive.
[0016] The cooling circuit may include parallel conduits or a single conduit but includes all the conduits through which the fluid flows between the inlet and outlet of the cooling circuit to cool the active parts of the stator.
[0017] By closest value, we mean that the difference between the radius of the circuit and that of the internal peripheral surface of a tooth is less than the difference between the radius of the circuit and that of the external peripheral surface of a stator tooth.
[0018] In addition to the characteristics mentioned in the preceding paragraph, the stator, an aspect of the invention, may have one or more complementary characteristics from those in the following paragraphs, considered individually or according to all technically possible combinations.
[0019] According to one embodiment, the cooling circuit is the only cooling circuit for the stator to circulate a coolant in the stator.
[0020] In one embodiment, the stator includes recesses for receiving an external bearing of the electric machine to support the rotating rotor. These recesses may be grooves, collars, etc., allowing the insertion of the external bearing. An external bearing is a bearing with a diameter larger than the maximum diameter of the rotor.
[0021] In one embodiment, the stator includes an X-axis opening such that the ratio of the minimum internal diameter of the main body divided by the maximum external diameter is between 0.5 and 0.7, preferably between 0.55 and 0.65, for example 0.6. A ratio of 0.6 is the torque optimization for a given maximum external diameter. The minimum internal diameter and the maximum external diameter can each be measured, for example, between two diametrically opposed teeth.
[0022] According to one embodiment, the main body comprises a washer-shaped base from which the teeth extend axially, comprising an external radial face opposite the air gap surface of each tooth, the base comprising, on the side of the external radial face, a groove extending longitudinally in the shape of a cylinder around the axis housing the conduit formed in the one-piece body.
[0023] According to one example of this embodiment, the base includes an internal peripheral surface and the groove extends around the X axis, being closer to the internal peripheral surface than to an external diameter of the teeth of the stator body.
[0024] According to one example, the groove is located in a magnetically saturated area of the stator for a nominal machine current, as far away as possible from the X axis (having the maximum diameter of the magnetically saturated area).
[0025] According to an example of this embodiment, the one-piece body comprises a plate covering the base of the main body and includes two rounded side walls extending axially from the plate and a closing wall connecting the two rounded side walls to form the conduit, the groove in the base having a shape conforming to the side walls and the closing wall.
[0026] According to one embodiment, the one-piece cylinder head body comprises: a cylindrical tube-shaped wall, including an inlet and outlet for the cooling circuit, at least one wall extending from the cylindrical tube-shaped wall, delimiting the duct with the end of the cylindrical tube-shaped wall, a thermal layer between a part of the winding surrounded by the teeth of the first group and at least one wall delimiting the conduit.
[0027] According to an example of this embodiment, the stator is a central stator, in which: The main ferromagnetic body comprises: a second group of stator teeth regularly distributed angularly around the X-axis, each stator tooth of the second group having at least one radial axial air gap surface located opposite the radial axial air gap surface of the teeth of the first group and a second group of stator notches between each stator tooth of the second group, a second winding wound in the stator slots of the second group, covering the peripheral outer surface of the teeth of the second group, The cylinder head comprises: a second one-piece body including a ring surrounded by the teeth of the second group, located axially opposite the first one-piece body, a cooling circuit formed entirely within the second monobloc body comprising: -an inlet and an outlet forming an opening in the monobloc body for the entry and exit of a cooling fluid, -at least one conduit between the inlet and outlet, formed by at least one wall of the monobloc body, the thermal layer located between a part of the winding surrounded by the teeth of the second group and at least one wall delimiting the conduit.
[0028] According to one embodiment, the conduit has a radial section in the shape of a spiral.
[0029] According to a variant of this embodiment, the conduit has a radial cross-section in the shape of a circular arc. The inlet is at one angular end of the circular arc, and the outlet is at the opposite end. In the embodiment comprising a groove housing at least one wall forming the conduit, the groove may have a radial cross-section in the shape of a circular cylinder, as this is simpler to manufacture.
[0030] According to a variant of these two embodiments, the conduit has a radial cross-section in the shape of a circular cylinder. In this example, the inlet and outlet of the conduit can be diametrically opposed to each other, forming two channels.
[0031] According to one embodiment, the conduit has a rectangular axial cross-section (plane passing through the axis of rotation X). In this case, the main base of the cylinder head comprises a radial wall and at least two other lateral walls of the monobloc body extending axially from the radial wall, and a closing wall connecting the two lateral walls axially opposite the radial wall, together delimiting the conduit, the groove in the base of the main body having a shape conforming to the lateral walls and the closing wall of the main base.
[0032] According to a variant of this embodiment, the conduit has a curved cylindrical axial cross-section (plane passing through the axis of rotation X), for example, a semicircular tube. The main one-piece base of the cylinder head thus comprises a main wall and a curved cylindrical wall, for example, a semi-cylinder, having two ends from which they extend axially from the main wall, delimiting the conduit.
[0033] In one embodiment, the cooling circuit is located closer to an inner peripheral surface of each tooth than to an outer peripheral surface of the same tooth. In one example, the cooling circuit is located at least twice as close to an inner peripheral surface of each tooth as to an outer peripheral surface of the same tooth. In the case of the embodiment including a groove, the groove's position closer to the inner diameter than to the outer diameter reduces the impact of iron removal from the main body (to create the groove) on the stator's magnetic performance. This is because the closer the stator body area is to the inner diameter, the more magnetically saturated it becomes.Thus, a groove located in this area of the stator body does little to modify the magnetic characteristics and therefore the performance of the stator compared, for example, to a groove located between the average diameter (maximum diameter + minimum diameter / 2) which, depending on the material removed to form the groove, can generate magnetic saturation (which did not exist without the groove) and therefore a decrease in the magnetic performance of the stator.
[0034] Another aspect of the invention relates to a machine comprising: A stator according to the first aspect of the invention, with or without one of the features of the embodiments described above; a rotor comprising an air gap area opposite the air gap area of the stator teeth; the machine comprising an X-axis opening having a radius greater than the difference in radius between the maximum external radius of the main body of the stator and the minimum internal radius of the main body. For example, the rotor comprises an X-axis opening identical to that of the stator such that a ratio equal to a minimum internal diameter of the main body divided by the maximum external diameter is between 0.5 and 0.7, preferably between 0.55 and 0.65, for example 0.6. The minimum internal diameter therefore corresponds to the diameter of the X-axis opening (without winding).
[0035] According to one embodiment, the electrical machine comprises: two stators according to the first embodiment, with or without the various characteristics described in the examples of this embodiment, A central rotor located axially between the two stators.
[0036] According to one embodiment, the electrical machine comprises: two rotors, a central stator located axially between the two rotors, the stator being according to the second embodiment with or without the different characteristics described in the examples of this embodiment.
[0037] According to one embodiment, the machine comprises a single stator and a single rotor with teeth, each having an air gap surface axially opposite the radial air gap surface of one of the stator teeth. The rotor body and the stator body each comprise a ferromagnetic base. The teeth of the rotor and stator bodies extend from the base to the teeth of the other body, respectively.
[0038] Another aspect of the invention relates to a vehicle wheel comprising an electric machine according to the first aspect of the invention, with or without one of the features of the embodiments described above, a tire fixed to the rotor, the electric machine comprising a bearing between the stator and a rotating part of the machine fixed and rotatable with the tire, and at least a first and second arm for connecting to a vehicle chassis, the first arm comprising a circuit connected to the inlet for connection to a vehicle cooling circuit, and the second arm comprising a circuit connected to the outlet for connection to a vehicle cooling circuit. The rotating part may be an outer ring or the first or second rotor.
[0039] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES
[0040] The figures are presented for illustrative purposes only and are in no way limiting to the invention.
[0041] [Fig. 1] represents a three-dimensional view of part of an electrical machine comprising two stators according to a first embodiment.
[0042] [Fig. 2] represents a part of a main ferromagnetic body of the stator according to the first embodiment.
[0043] [Fig. 3] represents two stator cylinder heads according to the first embodiment.
[0044] [Fig. 4] represents a radial section of a stator according to the first embodiment.
[0045] [Fig. 5] represents a three-dimensional view of part of an electrical machine comprising a central stator according to a first example of a second embodiment.
[0046] [Fig. 6] represents a three-dimensional view of the central stator according to the first example of the second embodiment.
[0047] [Fig. 7] represents a radial section of a part of the stator according to the first example of the second embodiment.
[0048] [Fig. 8] schematically represents a radial section of an electrical machine including the central stator according to the first example of the second embodiment.
[0049] [Fig. 9] schematically represents a radial section of an electrical machine including the central stator according to a third example of the second embodiment.
[0050] [Fig. 10] schematically represents a radial section of an electrical machine including the central stator according to a third example of the second embodiment.
[0051] [Fig. 11] schematically represents a vehicle wheel comprising an electric machine equipped with one or two stators of one of two embodiments. DETAILED DESCRIPTION
[0052] The figures are presented for illustrative purposes only and are in no way limiting to the invention.
[0053] [Fig. 1] shows a schematic representation in a three-dimensional view of a part of an electrical machine M comprising two stators 51, S2 according to a first embodiment and a central rotor R. The central rotor R is located axially between the two stators S1, S2. The central rotor R includes radial surfaces of axial air gap on both sides.
[0054] The two stators S1 and S2 are identical and include the same references for each of their identical parts / pieces etc.
[0055] Each stator S1, S2 comprises a ferromagnetic main body 1 in the form of a washer with axis X. The two main bodies 1 are shown in perspective in Figure 2. The stator therefore includes an opening with axis X passing through the main body 1. Preferably, the opening with axis X is such that a ratio equal to a minimum internal diameter of the main body divided by the maximum external diameter is between 0.5 and 0.7, preferably between 0.55 and 0.65, for example 0.6.
[0056] In this embodiment, each main body 1 comprises a washer-shaped base 10, that is, it comprises an external peripheral surface 121 and an internal peripheral surface 122 in the shape of a circular cylinder. The main body 1 further comprises teeth 11, each comprising a base extending axially from the base 10, distributed angularly and regularly around the X-axis. Each tooth 11 comprises an axial radial air gap surface 110, an external peripheral surface 111, and an internal peripheral surface 112. Each axial radial air gap surface 110 is located opposite an axial radial air gap surface of the central rotor R. Each tooth may have a T-shape, the base of which is the vertical portion of the T, and includes a beak forming the horizontal portion of the T, comprising the axial radial air gap surface 110.
[0057] Notches 13 are formed between each tooth 11 of each stator S1, 52.
[0058] The base 10 further comprises an external radial face 12 opposite the air gap surface 110 of each tooth 11. The base 10 includes, on the side of the external radial face 12, a groove 120 rounded around the X-axis. In this example, the groove 120 has the shape of a circle with axis X, but could have the shape of an arc of a circle or a spiral with axis X. The external radial face 12, which is also an external face of the stator body 1, thus comprises a flat radial surface 121 and the groove 120.
[0059] The bottom of groove 120 is, in this example, flat but could be rounded, or have another shape. Groove 120 also includes two surfaces in the shape of a cylinder of revolution with axis X.
[0060] The combination of the external peripheral surfaces 111 of the teeth 11 with the external peripheral surface 121 of the base 12 forms an external face of the stator body 1; the combination of the internal peripheral surfaces 112 of the teeth 11 with the internal peripheral surface 122 of the base 12 forms an external face of the stator body 1. In this example, these two external faces have the shape of a cylinder of revolution. An external face of the stator body 1 or of a stator winding 2, as explained below, can therefore be radially external or radially internal (towards the X-axis) but is not a radially internal face.
[0061] Each stator S1, S2 further comprises a winding 2 consisting of windings wound in stator slots 3, each surrounding at least one base of a corresponding tooth 11 by covering the outer peripheral surface 111 and the inner peripheral surface 112 of the corresponding tooth or of another tooth, depending on the winding type. The winding 2 thus comprises an inner bung 22 and an outer bung 21. In this example, the stator opening is delimited by the inner bung 22, the inner radial end edge of each tooth beak (opposite the axis), and the inner radial end edge of the base 12 of the stator body 1. The inner radial end edge of the base 12 is cylindrical in shape. The inner radial end edge is preferably an extension of the inner radial end edge of each tooth beak 11.According to another example, the internal radial end edge of base 12 has a minimum internal diameter smaller than that between two internal radial end edges of two diametrically opposed tooth beaks.
[0062] Each stator S1, S2 further comprises a yoke 3 not shown in Figure 1. The yokes 3 are shown in perspective in Figure 3. Each yoke 3 is mounted in this embodiment against the main body 1. The yoke 3 comprises a one-piece body 37 having a first internal radial face 31 mounted against an external face 11 of the stator body, here in this case the external radial face 12 of the base 10. The stator opening passes through the yoke 3. In this example the minimum diameter of the opening is at the yoke 3 but could be at the base 12 of the body or at the internal bung 22.
[0063] Each yoke 3 comprises a main base 38 fixed in rotation and translation to the main body 1 and the corresponding stator winding 2 S1, S2. Each main base 38 comprises: an internal radial face 31 facing the external radial face 12 of the base 10, an external radial face 32 opposite the internal radial face 31.
[0064] Each cylinder head 3 includes a cooling circuit 30 comprising a conduit 300 delimited by at least one wall of the monobloc body 37 extending from the inner radial face 31 and by a portion of the inner radial face 31 of the radial wall. The cooling circuit 30 has a maximum radius value with respect to the X-axis closer to the radius value of the inner peripheral surface 122 than to the radius value of the outer peripheral surface 121 of the base 12 and those of the teeth of the stator body 1. In other words, the portion of the cooling circuit 30 most radially close to an outer peripheral surface of the stator body 1 is closer to the inner peripheral surface 122 of the base 12 than to the outer peripheral surface of the stator body 1.
[0065] In this case, the cylinder head 3 comprises, on the side of the internal radial face 31 of the main radial base 38: a radial flat surface 310 of a radial wall of the main base 38 from which the conduit 300 is formed, as explained below, an outer ring 311 extending from the radial flat surface 310 of the radial main base 38, an inner ring 312 extending from the radial flat surface 310 of the radial main base 38 and walls delimiting the duct 300 explained later.
[0066] The radial flat surface 310 may not be flat and may only be a radial surface. Figure 4 shows an axial section (the plane includes the X-axis) of the stator S1 and the rotor R. In this figure 4, it can be seen that the outer ring 311 is centered on the outer peripheral surface 121 of the base 10 and the inner ring 312 is centered on the inner peripheral surface 122 of the base 10. The inner ring 312 and / or the outer ring 311 may be press-fitted onto the base 10 or may be fixed to the base 10 by bonding or screws (not shown). In this example, the inner and outer rings 311, 312 are monobloc with the other parts of the radial main base 38, but one or both of the rings 311, 312 could be fixed to the main base 38, in particular each at a radial end of the radial wall of the main base, for example by being tight-mounted to the radial wall, surrounding or being surrounded by the radial wall.As can be seen in this figure, the yoke 3 has an external diameter less than or equal to that of the winding 2 (outer coil) of the stator S1; this prevents it from obstructing the external volume of the electrical machine. The inner ring 312 of the yoke 3 has an internal radial end edge with a cylindrical surface. As explained above, in this example, the minimum diameter of the stator 1 opening is located at the level of the inner ring 312. In this example, the stator 1 opening has a maximum diameter located at the level of the minimum internal diameter of the stator body 1.
[0067] The conduit 300 is formed within the main base 38. The main base 38 comprises a first and second wall 313, 314, radially delimiting the conduit 300. The first and second walls 313, 314 each have a cylindrical ring shape about concentric X-axis and extend from the radial flat surface 310 of the radial wall. The main base 38 has a ring-shaped closing wall 315 connecting the first and second ring-shaped walls 314, 315, located opposite the radial wall. Thus, the conduit 300 is axially delimited by the closing wall 315 and a portion of the radial wall on the side of the radial flat surface 310.
[0068] In this example, the conduit 300 has an axial cross-section (plane passing through the axis of rotation X), rectangular but could have another shape such as a curved cylindrical cross-section and be delimited by a single curved wall having two ends extending from the radial flat surface 310. Here in this case the conduit 300, the closing wall 315 and the first and second walls 314, 315 are housed in the groove 120 of the base 10. Thus, the closing wall 315 is in thermal contact with only an external radial surface of the base 10 of the main body 1 forming the groove and the first and second walls 314, 315 are each in contact with an internal axial surface delimiting the groove, (by internal axial surface we mean that it is inside the base 10 main body 1 as opposed to the external axial surface forming the external periphery of the base 10). The closing wall 315 is located against the bottom of the groove 120.The conduit 300 is thus delimited by the closing wall in thermal contact with only the external radial face 12 of the base 10 (the external radial face 12 including the groove 120). The cooling circuit 30 is entirely formed by the cylinder head 3 and is monobloc. The cooling circuit 30 comprises an inlet 301 and an outlet 302, each forming an orifice opening onto the external radial face 32 of the monobloc body 37, located opposite the internal radial face 31 of the monobloc body 37. Preferably, the conduit 300 has a single, arc-shaped cooling channel, and the shorter angular portion between the end of the conduit 300 connected to the inlet 301 and the end of the conduit 300 connected to the outlet 302 is unconduited to allow the liquid to pass through the larger arc-shaped angular portion of the conduit.In another example, groove 120 has the same arc shape housing conduit 300 and thus defining its walls. In yet another example, the conduit has a ring or torus shape. In this ring or torus shape, the inlet 301 and outlet 302 will preferably be diametrically opposed, forming two cooling channels.
[0069] Of course, other examples of conduit shapes 300 are possible as long as it is housed in a groove 120 on the radial outer face of the base 10, and preferably on the radial inner side, that is, closer to an internal peripheral surface 122 of the base 10 than to its external peripheral surface 121. This allows for less reduction in the stator's magnetic characteristics and therefore its efficiency. Indeed, the closer the stator body is to the X-axis (the closer it is to the minimum diameter), the more magnetically saturated the area. The groove located in an internal area of the base 10 between the average diameter and the outer diameter of the stator body 1 therefore has less of a detrimental magnetic effect on the stator body than on an external area between the average diameter and the outer diameter of the stator body 1. In fact, adding a groove in the external area can magnetically saturate the base 12, which is not saturated without the groove.Preferably, the groove is located in a magnetically saturated area as far away as possible from the X axis (the largest possible diameter) in base 12. Having a groove with the maximum diameter in the saturated area increases the heat exchange surface with the duct 300 and therefore improves cooling.
[0070] Thus such a cylinder head 3 allows both to support the stator and to form a cooling channel 30 whose channel 300 is in thermal contact with an external face 12 of the base 10 of the stator body 1. In this case the thermal contact is made by contact between the walls 313, 314, 315 and the walls defining the groove 120 of the main body 1.
[0071] The conduit 300 can also be in thermal contact with the winding in particular for a central stator S as explained in the second embodiment.
[0072] Figure 5 shows a schematic representation in three-dimensional view of a portion of an electrical machine M' comprising two rotors R1, R2 and a central stator S, according to a first example of a second embodiment. The central stator S is located axially between the two rotors R1, R2. Unlike the first embodiment, the central stator S comprises, on either side axially, a first and a second radial air gap surface 110, 110', referenced in Figure 8, which shows an axial cross-section of the electrical machine M' at the winding level. The first radial air gap surface 110 is visible in Figure 6, which represents the central stator S in three-dimensional view.
[0073] The two rotors R1 and R2 are identical and each, in this example, comprises teeth R11, R21, each with an air gap surface R110, R210, referenced in Figure 8, opposite a corresponding radial axial air gap surface 110, 110' of the stator S1. In this example, the two rotors R1, R2 each comprise a winding R12, R22 wound in slots formed between each tooth R11, R21. Of course, each rotor R1, R2 can include permanent magnets and even be devoid of windings R12, R22.
[0074] The stator S comprises a main body 1, which includes a first group of ferromagnetic stator teeth 11 and a second group of ferromagnetic stator teeth 11', referenced in Figure 8. The teeth 11, 11', of the first and second groups each have a corresponding air gap area 110, 110'. In this example, the air gap area 110, 110' of each tooth is larger than that of a tooth R11, R21 of the rotor R1, R2, but could be the same size. The stator S includes a second winding 2' wound around the teeth 11' of the second group. In this example, the stator S lacks a base 10 but could have a central one. The teeth 11, 11' of the first and second group and the first and second winding 2 are held in this example by resin but could also be held together by a fret or an external bearing 7 as shown in figure 8.In this case, the electric machine S includes a rotating ring 8 surrounding the bearing 7, and connecting the first rotor R1 to the second rotor R2. The rotating ring 8 is therefore fixed in rotation with the first rotor R1 and the second rotor R2 and is free in rotation relative to the stator S via the external bearing 7 (here represented by a ball bearing but could be a roller bearing or other type of bearing etc).
[0075] In this example, the central stator block 3' differs in that it optionally includes a second monobloc body 37'. The first and second monobloc bodies 37, 37' are identical. Like the first monobloc block configuration, the first and second monobloc bodies 37, 37' comprise a radial wall with an external radial face 32, but differ from the first embodiment in that the internal radial face 31 does not have a conduit or an external ring, but only a flat surface like that of the external radial face 32. This radial wall protects the corresponding rotor R1, R2 without being in contact with it. Of course, the block 3' could be omitted.
[0076] Furthermore, the main base 38' of the first and second monoblock bodies 37, 37' is ring-shaped and therefore comprises a hollow cylindrical tube-shaped wall extending axially along the X-axis from the radial wall of the first and second blocks towards the stator S. The main base 38' of the first and second monoblock bodies 37, 37' is surrounded by the first and second rotors R1, R2 respectively, as well as by the first and second tooth groups 11, 11' respectively, and the first and second windings 2, 2' respectively. As in the first embodiment, the main base 38' is rotationally and translationally fixed to the main body 1, but here by means of the winding 2 and a thermal layer 4, for example, of thermal resin. In this second embodiment, the main base 38' of each cylinder head 3' is traversed by the stator opening and includes an internal cylindrical surface delimiting together the stator opening 1.
[0077] The cylinder head 3' comprises, within the first monobloc body 37, a cooling circuit 30 including a conduit 300 comprising at least one channel, here two channels each shaped like a half-ring. The base 38' comprises a cylindrical tube-shaped wall and an external peripheral wall 313' and an internal peripheral wall 314', each extending from the cylindrical tube-shaped wall of the main base 38. The main base 38 further comprises an axial end wall 315' opposite the axial end of the cylindrical tube-shaped wall, together axially delimiting the conduit 300. The external peripheral wall 313' and the internal peripheral wall 314' radially delimit the conduit 300.
[0078] In this example, the conduit 300 is ring-shaped. Specifically, in this configuration, the two monobloc bodies 37, 37' each include a cooling circuit 30, 30' and therefore a conduit 300, 300', each cooling the corresponding winding 2, 2' of the stator S. Of course, the yoke could consist of a single monobloc body 37 including a conduit 300 for cooling both windings 2, 2', as shown in Figure 9, which depicts an axial cross-section of a machine in which the stator is, according to a second example of this second embodiment explained later, a second example. However, having two cooling circuits 30, 30', each cooling a winding 2, 2', improves the uniformity of cooling for the two windings 2, 2'.
[0079] The stator S includes a thermal layer 4 (resin) between the outer peripheral wall 313' of each monobloc body 37, 37' defining the conduit 300 of each cooling circuit 30, 30', and the corresponding first or second winding 2, 2'. Thus, the conduit 300 delimited by the outer peripheral wall 313' of the monobloc body 37, 37' is in thermal contact with only an axial internal surface of the winding 22.
[0080] This allows for thermal contact between the conduit 300 and the external face of each winding 2, 2', in this case an internal peripheral surface formed by the internal bun 22.
[0081] In addition, the conduit 300 of each cooling circuit 30, 30', includes a first axial channel 307 extending into the main wall 38, connecting the two channels to the inlet 301. Each conduit 300 includes a second axial channel 308 located diametrically opposite the first axial channel 307 connecting the two channels to an outlet 302.
[0082] The stator S' according to the second example is identical to the first example of the second embodiment except that the main base 38" of the yoke is shaped like a ring extending axially to pass through the two rotors (surrounded by the two rotors) and that the central stator S' comprises only one cooling circuit 30" including, in this case, only one conduit 300" cooling the two stator windings 2, 2'. Optionally, the yoke S" shown includes a first and second radial wall 32', 32" fixed to the axial ends of the main base 38" but could include only one or neither, as in the third example of stator S" described subsequently in relation to Figure 10. Furthermore, according to another example not shown, the main base 38" is a single piece with the first or second radial wall 32', 32".
[0083] In this example, the 300” conduit extends axially at least along the entire length of the main body 1, i.e., from an axial end radial surface 110 of a tooth 11 of a first group of teeth to the axial end radial surface 110' of a tooth 11' of a second group of teeth.
[0084] In this example, the 30” cooling circuit is further different in that it includes an outlet 302” opening radially towards the X-axis and therefore includes an outlet channel extending radially between the outlet 302” and the cooling duct 300”. Of course, the outlet could open axially either on the same axial side as in the first example or on the opposite axial side from the inlet 301' as in the third stator example S” explained below. Naturally, the inlet 301' could also open radially.
[0085] The stator S” according to the third example is identical to the second example of the second embodiment except that the cylinder head comprises only the main base 38” and the cooling circuit 30” comprises an outlet 302” opening axially opposite the inlet 301’. In this example, the cooling circuit 30” therefore comprises an axial channel 308’, extending from the ring-shaped conduit 300” to the outlet 302” opening at the axial end of the main base 38”.
[0086] In the examples of the second embodiment, the conduits 300, 300', and 300" are disc-shaped and form two channels, each shaped like a half-ring, but could have a radial cross-section in the shape of a circular arc, as in the example of the first embodiment. In this case, the inlet and outlet are not necessarily diametrically opposed as in the examples shown.
[0087] In this example, the electric machine M comprises a first and second bearing, 7' and 7". The first bearing, 7', is mounted between a first axial end of the main base, 38", and the first rotor, R1, and the second bearing, 7", is mounted between a second axial end (opposite the first axial end) of the main base, 38", and the second rotor, R2. This allows for smaller diameter bearings, resulting in less friction and therefore less mechanical wear.
[0088] In the various examples, the machine's bearings can be ball bearings, roller bearings, oiled bushings, etc.
[0089] In the various examples of the different embodiments, the cylinder head is a single piece.
[0090] In the various examples of the different embodiments of the machine, the opening of the X-axis stator and the opening of the X-axis rotor include a maximum diameter having a value between 50% and 65%, preferably between 55% and 60%, of the maximum diameter of the stator body.
[0091] In the various examples of this second embodiment, the inlets and outlets are shown diametrically opposite but can be angularly distributed as in the example of the first embodiment, that is, by forming a conduit 300 in the shape of a circular arc greater than 180°, for example, 330°, i.e., an angle of 30° between the inlet and outlet. In this case, the conduit 300 can either cool only a section of the winding 2, 2', or have a helical shape to cool the windings 2, 2' at 360°.
[0092] In the various examples, each cooling circuit includes only one outlet and one inlet, but may have several.
[0093] In the various examples of the different embodiments, the main body 1 is made of ferromagnetic material; it can be made from spirally wound sheet metal or can be made from soft magnetic composites, in particular sintered or machined.
[0094] In the various examples of the different embodiments, the cylinder head can be metallic, for example made of aluminium or ferromagnetic (for example made of iron or an alloy containing iron).
[0095] Figure 11 shows an example of a wheel of a vehicle, for example a two-wheeler, comprising a tire W fixed to the rotor R, R1, R2 of an example of an electric machine M, M' of one of the two embodiments. The electric machine M, M' comprises an external bearing 7 surrounding the stator S, S1, S2 and surrounded by a rotating ring 8 fixed in rotation with the tire W. The wheel includes an opening corresponding to the opening of the machine M, M' (i.e., having a maximum diameter between 50% and 65% of the stator body). The wheel further comprises at least a first and second support arm B1, B2 for rigidly connecting the stator S1, S2 to a vehicle chassis in translation and rotation.The first arm B1 comprises a circuit B10, shown in dashed lines, having one end connected to the inlet 301 of the cooling circuit 30, also shown in dashed lines, and a second end opposite the first, intended to be connected to a vehicle cooling circuit. The second arm B2 comprises a circuit B20, shown in dashed lines, having one end connected to the outlet 302 of the cooling circuit 30 and a second end opposite the first, intended to be connected to a vehicle cooling circuit. The vehicle may have other arms on the other side, connected either to another cylinder head in the case of an electrical machine comprising two stators S1, S2 as in an example of the first embodiment, or to the radial wall of the cylinder head according to an example of the second embodiment.
[0096] In the case of a radially opening outlet and / or inlet of the cooling circuit 30 (see, for example, outlet 302” of the second example of the second embodiment), the support arm(s) may have an L-shape comprising: a main base extending in a plane perpendicular to the X-axis, allowing it to be fixed to the radial wall of the cylinder head, and including a channel for the circulation of the coolant and a tube (which may have a cylindrical or rectangular or other cross-section) extending axially along the cylinder head in the opening, from one end of the base to the radially opening inlet or outlet.
[0097] In the various embodiments, the rotor may include a winding and / or permanent magnets.
[0098] Unless otherwise specified, the same element appearing on different figures has a unique reference.
Claims
22 DEMANDS
1. Stator (S1, S2, S, S', S") of an axial flux electric machine (M, M') comprising: o at least one principal body (1) comprising:
1. a first group of ferromagnetic stator teeth (11), distributed angularly in a regular manner around the X axis, each stator tooth (11) of the first group having at least one radial axial air gap surface (110) and a peripheral external surface (111), 2. stator notches (13) between each stator tooth (11) of the first group, o a winding (2) wound in the stator slots (13), covering the peripheral external surface (111) of the teeth (11), o a yoke (3, 3') fixed in rotation and translation with the main body (1) and the winding (2), comprising:
1. a one-piece body (37) comprising a main base (38), 2. a cooling circuit (30) for the main body (1) and / or the winding (2) located in an area of the main base (38), such that it has a maximum radius value with respect to the X-axis, being closer to the radius value of the internal peripheral surface (122) than to the value of an external radius of the stator body teeth (1), the cooling circuit (30) comprising: a. a coolant inlet (301) and a coolant outlet (302) each forming an orifice of the monobloc body (37), b. at least one conduit (300) comprising a first and second end connected respectively to the inlet (301) and the outlet (302), the conduit (300) being delimited and formed by at least one part of the wall of the monobloc body (37) in thermal contact with only a radial external surface and / or an axial internal surface of the main body (1) and / or of the winding (22).
2. Stator (S1, S2) according to the preceding claim, wherein the main body (1) comprises a washer-shaped base (10), from which the teeth (11) extend axially, comprising an external radial face (12) opposite the air gap surface (110) of each tooth (11), the base (10) comprising, on the side of the external radial face (12), a groove (120) extending longitudinally in the form of a cylinder around the axis housing the conduit (300) formed in the one-piece body (37).
3. Stator (S1, S2) according to the preceding claim, wherein the base (10) comprises an internal peripheral surface (122) and in that the groove (120) extends around the X axis being closer to the internal peripheral surface (122) than to an external diameter of the teeth of the stator body (1).
4. Stator (S1, S2) according to claim 2 or 3, wherein the main base (38) of the cylinder head (3) comprises a plate-shaped radial wall covering the base (10) of the main body (1) and comprises two ring-shaped side walls (313, 314), each extending axially from the radial wall and a closing wall (315) connecting the two side walls axially opposite the radial wall, together delimiting the conduit (300), the groove (120) of the base of the main body (10) having a shape conforming to the side walls (313, 314) and the closing wall (315) of the main base (38).
5. Stator (S, S', S”) according to claim 1 wherein: the main base (38', 38”, 38'”) of the breechblock (3') comprises: o a cylindrical tube-shaped wall, including an inlet orifice (301, 301'), and outlet of the cooling circuit (302, 302', 302"), o at least one wall (313', 314', 315') extending from the cylindrical tube-shaped wall, delimiting the conduit (300, 300', 300") with the end of the cylindrical tube-shaped wall, o a thermal layer (4) between a portion of the winding (2) surrounded by the teeth (12) of the first group and at least one wall (313', 314', 315') delimiting the conduit.
6. Stator (S, S', S”) according to the preceding claim, wherein: - the stator (S, S', S”) is a central stator, - the main ferromagnetic body (1) comprises: o a second group of stator teeth (11') regularly distributed angularly around the X axis, each stator tooth (11') of the second group having at least one radial axial air gap surface (110') located opposite the radial axial air gap surface (110) of the teeth (11') of the first group and o a second group of stator notches between each stator tooth (11') of the second group, - a second winding (2') wound in the stator slots of the second group, covering the peripheral outer surface of the teeth (11') of the second group, - the cylinder head (3') comprising: a second monobloc body (37') comprising a ring surrounded by the teeth (11') of the second group, located axially opposite the first monobloc body (37), a cooling circuit (30') formed entirely within the second monobloc body (37') comprising:
1. an inlet and an outlet forming an orifice in the second monobloc body (37') for the entry and exit of a cooling fluid, 25 2. at least one conduit (300') between the inlet and outlet, formed by at least one wall of the monobloc body (37'), o the thermal layer (4) located between a part of the winding (2') surrounded by the teeth (11') of the second group and at least one wall delimiting the conduit (300').
7. Stator according to any one of the preceding claims, wherein the conduit has a spiral-shaped radial section.
8. Stator (S1, S2,) according to any one of claims 1 to 6, wherein the conduit (300) has a radial cross-section in the shape of a circular arc.
9. Electric machine (M, M') comprising a stator (S1, S2, S, S', S”) according to any one of the preceding claims and a rotor (R, R1, R2) comprising an air gap surface (R110, R210) opposite the air gap surface (110, 110') of the teeth (11) of the stator (S1, S2, S), the machine comprising an X-axis opening comprising a radius of a value greater than the difference in radius between the maximum external radius of the main body (1) of the stator and the minimum internal radius of the main body (1) of the stator.
10. Vehicle wheel comprising an electric machine (M, M') according to the preceding claim, comprising a tire (W) integral with the rotor (R, R1, R2), the electric machine (M, M') comprising a bearing (7, 7', 7") between the stator (S, S1, S2) and a rotating part of the machine integrally rotating with the tire (W) and at least a first and second arm (B1, B2) intended to connect to a vehicle chassis, the first arm (B1) comprising a circuit (B10) connected to the inlet (301) for connection to a vehicle cooling circuit and the second arm (B2) comprising a circuit (B20) connected to the outlet (302) for connection to a vehicle cooling circuit.