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CN-122029723-A - Axial flux electric machine with direct core cooling

CN122029723ACN 122029723 ACN122029723 ACN 122029723ACN-122029723-A

Abstract

A stator (100) for an axial flux electric machine comprises-stator members (201), each stator member comprising an o-ferromagnetic core (202), an o-coil (204), a sleeve (203) placed around the core (202), a housing comprising ports adapted to be supplied with a cooling fluid, wherein for any stator member (201) the sleeve (203) comprises a first set of holes (305, 900) and a second set of holes (303, 304), each set comprising one or more holes arranged as openings in a sleeve wall (301, 302), and any hole comprised in the first set (305, 900) is in fluid communication with at least one hole comprised in the second set (303, 304), such that for any stator member (201) the cooling fluid flows at least partly via a path through the sleeve opening (305, 900, 303, 304) so as to flow along and/or through the respective core (202).

Inventors

  • Jasper Levroux
  • Peter Lai Yining
  • Mathieu Lenoy

Assignees

  • 麦格纳公司

Dates

Publication Date
20260512
Application Date
20240917
Priority Date
20231002

Claims (15)

  1. 1. A stator (100) for an axial flux electric machine, the stator (100) comprising: -a central axis, which, when mounted, corresponds in axial direction to the axis of rotation of the axial flux motor; -a plurality of stator members (201), the plurality of stator members (201) being symmetrically rotationally arranged about the central axis, wherein each of the stator members (201) comprises: a ferromagnetic core (202); -a coil (204), the coil (204) comprising a plurality of turns wound around the core (202); A sleeve (203), said sleeve (203) being placed around said core (202) between said core (202) and said coil (204), said sleeve (203) comprising walls (301, 302, 307, 309) extending in an axial direction, A housing comprising an inner space between an inner circumferential wall (206) and an outer circumferential wall (205), the stator member (201) being placed within the inner space, and one or more ports (207) adapted to supply a cooling fluid, The method is characterized in that: For any of the stator members (201), the sleeve (203) comprises a first set of holes (305, 900) and a second set of holes (303, 304), each of these sets comprising one or more holes arranged as openings in a sleeve wall (301, 302), and any of the holes comprised in the first set (305, 900) is in fluid communication with at least one hole comprised in the second set (303, 304), Such that for any of the stator members (201) the cooling fluid supplied to the inner space flows at least partly via a path through the sleeve openings (305, 900, 303, 304), thereby flowing along and/or through the respective core (202).
  2. 2. The stator (100) according to claim 1, Wherein the cooling fluid supplied to the inner space flows at least partially along and/or through the core (202) so as to be in direct contact with the respective core (202).
  3. 3. The stator (100) according to any one of the preceding claims, Wherein the cooling fluid supplied to the inner space flows at least partially along the core (202) so as to flow, for each of the stator members (201), in one or more channels (500) between the respective sleeve (203) and the core (202).
  4. 4. The stator (100) according to claim 3, Wherein any one of the channels (500) between the sleeve (203) and the core (202) is defined by: -an open space between the core surface (508) and the sleeve wall (301, 307, 309, 302) over the entire height of the sleeve (203), the height being measured according to the axial direction (105), and/or -Grooves provided in the core surface (508), and/or -A groove provided at the inner side of the sleeve wall (301, 307, 309, 302), said inner side facing the core (202).
  5. 5. The stator (100) according to any one of the preceding claims, Wherein the cooling fluid supplied to the inner space flows at least partially through the core (202) so as to flow, for each of the stator members (201), in one or more channels (807, 808, 1000, 1001) extending through the respective core (202).
  6. 6. The stator (100) of claim 5, Wherein, for each of the stator members (201), the core (202) is split at one or more locations along the height of the core (202) such that the core (202) is composed of a plurality of core portions (701, 702), two opposite core portions (701, 702) being connected to each other at respective connecting surfaces (801, 802), And wherein at least one of the channels through the core (202) is defined by a gap (807, 808) remaining between opposite connection surfaces (801, 802) in a connected state of the core portions (701, 702).
  7. 7. The stator (100) according to claim 5 or 6, Wherein for each of the stator members (201), the core (202) is composed of a plurality of core portions (701, 702) connected to each other by snap-fit connections (700), And wherein at least one of the channels through the core (202) is defined by a gap (807, 808) that remains between interlocking features of the snap fit (700) in a connected state of the opposing core portions (701, 702).
  8. 8. The stator (100) according to claim 5 to 7, Wherein at least one of the channels through the core (202) is a dedicated channel (1000, 1001) provided in a core portion of the core (202).
  9. 9. The stator (100) according to claim 8, Wherein the cross section of the dedicated channel (1000, 1001) has a rectangular shape, the aspect ratio of the rectangular cross section being such that the height is larger than the width.
  10. 10. The stator (100) according to claim 5 to 9, Wherein either one of the channels (1000, 1001) passing through the core (202) extends according to a direction perpendicular to a height direction corresponding to an axial direction (105) of the motor, And wherein for any of the channels (1000, 1001) through the core (202), the height position is such that the channel (1000, 1002) is closer to the core center than to the first core end (1002) and closer to the core center than to the second core end (1003).
  11. 11. The stator (100) according to any one of the preceding claims, Wherein for any of the stator members (201) a first set of holes (305, 900) and a second set of holes (303, 304) are positioned at opposite sides (306, 308) of the core sleeve (203), the first set (305, 900) being directed towards the outer circumferential wall (205) of the housing and the second set (303, 304) being directed towards the inner circumferential wall (206) of the housing.
  12. 12. The stator (100) according to any one of the preceding claims, Wherein, for any one of the stator members (201), each of the holes (600) comprised in the first and/or the second set defines a zigzag channel through the sleeve wall (301, 302).
  13. 13. The stator (100) according to any one of the preceding claims, Wherein for any one of the stator members (201) the core sleeve (203) comprises a first wall (301) pointing towards the outer circumferential wall (205) of the housing, a second wall (302) pointing towards the inner circumferential wall (206) of the housing and side walls (307, 309) pointing towards the adjacent stator member, the holes of the first set (305, 900) and the second set (303, 304) being provided as openings in the first wall (301) and the second wall (302), respectively, And wherein at least a portion (310, 311) of the first wall (301) has a greater thickness than each of the side walls (307, 309), and at least a portion (313, 314) of the second wall (302) has a greater thickness than each of the side walls (307, 309).
  14. 14. The stator (100) according to any one of the preceding claims, Wherein, for any of the stator members (201), at least some of the plurality of turns of the coil (204) are spaced apart, thereby establishing a fluid pathway (406, 901, 1103) through the coil (204).
  15. 15. The stator (100) according to any one of the preceding claims, Wherein the stator (100) is arranged such that for any of the stator members (201) a main fluid of cooling fluid is divided into a plurality of sub-streams comprising: A first substream (501, 502), in which a cooling fluid flows around the stator component (201) in direct contact with the side of the coil (204) facing away from the core (202), and/or a second substream (503, 504), in which a cooling fluid flows around the core sleeve (203) in direct contact with the side of the sleeve (203) facing away from the core (202), And -A third sub-flow (505, 506), wherein a cooling fluid flows via a path through the sleeve opening, thereby flowing along and/or through the core (202).

Description

Axial flux electric machine with direct core cooling Technical Field The present invention relates generally to the field of axial flux motors. In particular, a stator for an axial flux motor is proposed, which allows an improved cooling efficiency while ensuring a sufficient electrical insulation between the core and the respective coils. Background An axial flux motor is a type of motor in which the flux is generated in an axial direction, which is the direction of the axis of rotation. Typically, an axial flux motor includes a disk-shaped or ring-shaped rotor and a stator, both of which have a central axis corresponding to the rotational axis of the motor, the stator and rotor being axially spaced apart by a narrow air gap. The rotor comprises magnetic material (typically permanent magnets) that generates an axial magnetic flux. The stator includes a plurality of coils in which current can flow. Typically, each of the stator coils is wound around a core made of ferromagnetic material to direct and concentrate magnetic flux. During operation of the motor, the rotor is driven by a magnetic field generated by the stator current, whereas in the generator state, a current is induced in the stator coils due to the rotation of the rotor. Different topologies for axial flux machines (e.g. comprising one rotor disc and one stator disc, one rotor disc and two stator discs or two rotor discs positioned on both sides of a stator disc) are known. The axial flux motor may be of the toroidal type with a stator yoke or may be of the yoked type without a stator yoke. The stator design of axial flux machines presents some technical challenges, in particular with respect to the cooling of the stator elements. In fact, during operation of the axial flux motor, both the coil and the core are heated, which heat needs to be expelled for efficiency and durability reasons. In particular, high core temperatures may adversely affect the adhesive bonding the stack of cores, thereby applying the maximum core temperature allowed. Cooling of the stator may be accomplished in a variety of ways. For example, in high performance axial flux machines, the stator may be liquid cooled, wherein a cooling liquid is circulated within the hollow stator housing, thereby immersing the coils directly in the cooling liquid. For example, in WO2010/092400, the stator element is enclosed in a stator housing consisting of two half-shells. The stator housing is provided with ports allowing cooling fluid to be pumped into the spaces between the stator elements in order to cool them. A specific barrier or stop may be provided in the housing to direct the cooling fluid according to a specific flow pattern. Such a liquid cooled stator enables an optimal cooling of the coil due to the close interaction of the cooling fluid with the coil. However, taking into account the shielding position of the core, it is more challenging to extract heat from the core. Typically, the temperatures reached in the core form the actual thermal bottleneck of the motor, thereby limiting the power of the motor for a given motor size. The extraction of heat from the core may be hindered even more by the presence of an electrically insulating layer between the respective coil and the core. Such an insulating layer is placed to prevent that current can flow between the winding and the core (and thus a voltage difference between the coil and the core). Particularly when high operating voltages are applied, high demands are made on the isolation of the coil from the core physically, even small gaps or breaks in the insulating material between the coil and the core can allow the formation of an arc, thus creating a short circuit. In solutions known in the art, the insulating layer is made of an electrically insulating sheet (for example a Nomex paper sheet) wound around the core. Such an insulating sheet may be used, for example, in combination with a liquid cooled stator as disclosed in WO 2010/092400. In this solution, the core is typically impregnated with resin, so that the gap between the Nomex paper sheet and the corresponding core is also filled with resin. The filled gap results in an increase in thermal resistance, thereby adversely affecting the amount of heat that can be extracted from the core by the cooling liquid. In other solutions known in the art, the insulating layer between the core and the coil is provided as a rigid part, for example molded from an electrically insulating material (e.g. plastic). CN212969228U proposes a solution in which an insulating chamfer component is arranged on the outside of the ferromagnetic core body, at least in the vicinity of the side corners of the core body, so that the windings wound on the ferromagnetic core are spaced apart from the core. In US20150229177A1, an insulating molding consisting of a rigid sleeve and two side covers is used to separate the core from the respective coil. The article mentions that the bushing, for example