Axial flux electric machine with cooling channel passing through the rotor shaft

Abstract

The present invention relates to an axial flux electric machine comprising a rotating part and a stationary part. The rotating part comprises a rotor shaft (7) with a longitudinal axis and at least one rotor fixed to the rotor shaft (7), and the stationary part comprises a housing and at least one stator. The at least one rotor and at least one stator are positioned longitudinally and successively inside the housing, separated by at least one air gap (11). Each stator comprises coils (3). Furthermore, the rotor shaft (7) comprises at least one radial cooling channel (6) leading to an orifice opposite the inner surface of the coils (3) of at least one stator, preferably of each stator, for spraying them. Figure 1 to be published

Description

Title of the invention: Axial flux electric machine with cooling channel passing through the rotor shaft. Technical field

[0001] The invention relates to the field of axial flux electrical machines.

[0002] This type of axial flux electric machine can find applications in electric or hybrid vehicles, such as cars, buses, trucks, and construction equipment. This type of machine can also be used for stationary applications, such as industrial charging machines or electric generators. Previous technique

[0003] In recent decades, the development of electrical machines has focused primarily on radial flux electrical machines.

[0004] Radial flux electric machines generally comprise a coaxial rotor and stator, one surrounding the other. Thus, the magnetic flux can pass radially from the rotor to the stator and vice versa, via a radial air gap which is defined as the radial clearance between the rotor and the stator.

[0005] On the contrary, axial flux machines are characterized by at least one rotor and at least one stator arranged successively one behind the other in the axial direction (of the rotor's axis of rotation), such that the path of the magnetic flux between the rotor and the stator is axial. In other words, the rotor and the stator face each other and are separated by an air gap of axial thickness (or axial clearance between the rotor and the stator).

[0006] The rotor of axial flux permanent magnet electric machines generally comprises permanent magnets bonded to the rotor yoke or inserted into a rotor body, and in this case, the permanent magnets are separated from the rotor body by radial arms. The stator generally comprises a ferromagnetic stator body, which may or may not have teeth. An electrical winding in the stator slots may be distributed or concentric, i.e., each winding then surrounds a tooth.

[0007] In the context of the development of high power and torque density machines for electric or hybrid traction, particularly for electric or hybrid vehicle applications, axial flux machine topology is among those with the highest potential, notably due to the significant axial space constraint. Axial flux electric machines are also of interest for stationary applications as well as for wind power applications.

[0008] In general, axial flux electrical machines allow higher power and torque densities than radial flux electrical machines.

[0009] This gain is generally achievable by increasing the number of pole pairs in the rotor, which increases the rotational frequency as well as the rotor losses (i.e., the losses in the magnets). Furthermore, the use of a toothed winding allows for a reduction in the size of the coil heads, but increases the harmonic content in the air gap, leading to increased losses in the stator iron and in the magnets.

[0010] As a result, axial flow machines tend to heat up more, and therefore controlling heating and cooling is an important issue for this type of machine.

[0011] US patent application 2020 / 274410 relates to the cooling of a rotor with magnets bonded to a rotor disk. Cooling channels are positioned in the rotor disk, behind the magnets. They are therefore located far from the stator situated between two rotors. Consequently, the cooling channels do not provide effective cooling of the stator.

[0012] The technical problem that we propose to solve consists of improving the cooling of the stator of the axial flux electric machine, while facilitating the implementation of this cooling. Summary of the invention

[0013] The invention relates to an axial flux electric machine comprising a rotating part and a stationary part, the rotating part comprising a rotor shaft with a longitudinal axis and at least one rotor fixed to the rotor shaft, the stationary part comprising a housing and at least one stator, the at least one rotor and at least one stator being positioned longitudinally successively inside the housing, separated by at least one air gap, each stator comprising coils. Furthermore, the rotor shaft comprises at least one radial cooling channel leading to an orifice opposite the internal surface of the coils of at least one stator, the cooling channel serving for the circulation of a cooling fluid.

[0014] Advantageously, the electric machine includes a sealing means between the rotor shaft and each stator to prevent the cooling fluid from entering at least one air gap, the sealing means preferably comprising a baffle, located between the rotor shaft and the stator concerned and preferably fixed or integrated into the rotor shaft or the stator concerned.

[0015] According to one configuration of the invention, the rotor shaft comprises several cooling channels opposite each stator, preferably regularly distributed over the circumference of the rotor shaft.

[0016] Preferably, the electric machine includes a means for collecting said cooling fluid positioned in the lower part of the casing, or in the upper part of the casing, in the operating condition of the electric machine.

[0017] According to a variant of the invention, the electric machine comprises scoops fixed on the fixed part, the scoops extending substantially in the longitudinal direction over substantially the entire longitudinal length of the coils of at least one stator and extending radially between the rotor shaft and the coils of at least one stator.

[0018] Advantageously, the electric machine includes a cooling fluid supply system, each cooling channel being fluidly connected to the cooling fluid supply system.

[0019] According to one aspect of the invention, the power supply system comprises a conduit through the casing and a sealed chamber formed between the casing and the rotor shaft, the sealed chamber being fluidically connected to the conduit, the inlet of each cooling channel being fluidly connected to said sealed chamber to convey the cooling fluid from said sealed chamber to each cooling channel.

[0020] Preferably, the electric machine has its longitudinal axis horizontal or substantially horizontal in the operating position.

[0021] According to one embodiment of the invention, the rotor includes a cooling duct radially passing through the rotor and preferably, the housing includes a machining forming a deflector to orient and direct the cooling fluid exiting the cooling duct towards the coils of at least one stator, preferably onto the external surface of the coils of at least one stator.

[0022] The invention also relates to the use of the electric machine according to one of the variants or combinations of variants described above, in an electric or hybrid vehicle, or in a stationary application, such as an industrial charging machine, an electric generator or a wind turbine. List of figures

[0023] Other features and advantages of the electric machine according to the invention will become apparent from the following description of non-limiting examples of embodiments, with reference to the figures attached and described below. [Fig 1]

[0024] Figure 1 represents a first embodiment of the electrical flux machine axial according to the invention. [Fig 2]

[0025] Figure 2 shows the path of the cooling fluid coming from the shaft of rotor of an axial flux electric machine according to the invention. [Fig 3]

[0026] Fig. 3 represents a second embodiment of the axial flux electric machine according to the invention. [Fig 4]

[0027] Figure 4 represents an example of an axial flux electric machine according to the invention where the electric machine is filled with cooling fluid. [Fig 5]

[0028] Figure 5 represents a third embodiment of the axial flux electric machine according to the invention. [Fig 6]

[0029] Fig. 6 represents a first variant of a power supply system for an axial flux electric machine according to the invention. [Fig 7]

[0030] Fig. 7 represents a second variant of a power supply system for an axial flux electric machine according to the invention. Description of the implementation methods

[0031] The terms "vertical", "horizontal", "upper", "lower" and equivalent related terms refer to the electrical machine of the invention in its operating condition.

[0032] The "longitudinal" direction is the direction of the axis of the rotor shaft and the electric machine.

[0033] The invention relates to an axial flux electric machine comprising a housing enclosing at least one rotor and at least one stator.

[0034] The housing may comprise two flanges directly connected to each other, or two flanges and an outer cylinder (also called a "sleeve"), or any similar design, with a flange positioned at each axial end of the outer cylinder. Thus, the housing forms an outer enclosure for the electrical machine. This outer enclosure protects the stator(s) and rotor(s) located within it. The outer enclosure also serves to position and secure the active parts of the electrical machine. Furthermore, this outer enclosure can be used to cool the electrical machine, either by convection with the ambient air or by circulating a heat transfer fluid within and / or around the outer enclosure (within and / or around the cylinder and / or the flanges). The housing is then considered a cold source.

[0035] Each stator comprises a stator body, teeth regularly distributed circumferentially on the stator body, the teeth being fixed to the stator body. The teeth extend axially (that is, longitudinally). The stator also includes coils wound around the teeth.

[0036] The heat transfer fluid can advantageously be a liquid, and more particularly cooling oil.

[0037] The axial flux electric machine according to the invention comprises a rotating part and a fixed part:

[0038] - the rotating part comprises a rotor shaft with a longitudinal axis and at least one rotor fixed on the rotor shaft. Thus, the rotor shaft can drive the different rotors in rotation or the rotor shaft can transmit the rotation generated by the rotors to other components.

[0039] - the fixed part includes the housing and at least one stator.

[0040] Since the machine is an axial flux electric machine, at least one rotor and at least one stator are positioned longitudinally and successively inside the housing, separated by at least one air gap. An air gap is a space (of axial length for an axial flux electric machine) separating a stator and a rotor. Thus, at least one rotor and at least one stator are arranged successively one behind the other in the axial direction (along the longitudinal axis of rotation formed by the rotor shaft), such that the path of the magnetic flux between each successive rotor and stator (i.e., those directly following one another), passing through each air gap, is axial. In other words, each successive rotor and stator faces each other and is separated by an air gap of axial thickness.

[0041] The axial flux electric machine may comprise an alternating succession of rotors and stators. In other words, each rotor is separated from the next rotor by a stator and each stator is separated from the next stator by a rotor.

[0042] The electric machine according to the invention can operate with the longitudinal axis substantially horizontal, substantially vertical or even at a non-zero inclined angle with respect to the horizontal and with respect to the vertical.

[0043] In addition, each stator includes coils for generating a magnetic field or for generating a current induced by the permanent magnets of the rotor.

[0044] In addition, the rotor shaft includes at least one radial cooling channel leading to an orifice opposite the internal surface of the coils of at least one stator (preferably of each stator), to spray its coils (of at least one stator and preferably of each stator) with a cooling fluid circulating in each cooling channel.

[0045] The cooling channel is used for circulating a cooling fluid, for example, water. Thanks to the orifice opposite the inner surface of the coils, the cooling fluid can exit through this orifice and thus sprays the coils. Indeed, when it exits the orifice, it is projected opposite the coils. As a result, the the cooling fluid is in contact, at least partially and preferably totally, with the internal surface of the coils.

[0046] The cooling fluid may advantageously be a liquid, a gas, or a multiphase fluid. The cooling fluid may advantageously be a liquid, and more particularly a cooling oil. For example, the cooling fluid may be water, glycol water, or oil. In the case of direct contact between the cooling fluid and the winding, it is preferable that the cooling fluid be a dielectric fluid.

[0047] The internal surface of the coils is defined as the surface closest to the rotor shaft, and therefore approximately on the internal diameter of the coil mounting. This allows the coils to be cooled efficiently and simply by the rotation of the rotor shaft. Furthermore, the rotation of the radial cooling channels of the rotor shaft generates a suction of the cooling fluid from the inside to the outside. Thus, a pump is not required.

[0048] For example, at least one cooling channel may include an axial inlet in the rotor shaft and one or more radial channels.

[0049] The cooling fluid which arrives on the internal surface of the coils can then pass between the coils to reach the external part of the stator.

[0050] Each rotor may, for example, comprise a rotor disk made of metallic material and permanent magnets. Thus, when an electric current flows through the coils of a stator of the electric machine, an electromagnetic torque is generated and causes a rotor of the machine to rotate, thanks to the interaction between the stator field produced by the winding and the rotor field produced by the permanent magnets. Conversely, when a rotor is driven in rotation by any means of rotation (the rotor shaft, for example), the permanent magnets generate a magnetic field that creates an induced voltage in the coils of a stator. This allows the mechanical energy of the rotor's rotation to be transformed into electrical energy in the stator.Therefore, the electric machine can be used as an electric motor that transforms electricity into mechanical energy through the rotation of the rotor, or as an electric generator that transforms rotating mechanical energy into electrical energy.

[0051] The rotor disk can then serve as a support for permanent magnets and, for this purpose, it can, for example, comprise housings, preferably with a substantially trapezoidal cross-section (but other shapes can of course be considered), distributed circumferentially within the rotor disk, the permanent magnets being positioned in the housings. The rotor disk can also comprise radial arms separating said housings. Preferably, when the The housing section is trapezoidal, with the largest base of the trapezoid on the outer side of the rotor.

[0052] By radial arms, we mean rays situated between the housings which extend radially from an inner extremity to an outer extremity.

[0053] For example, the rotor disc may consist of an inner ring (or central hub) intended to be mounted on a shaft, an outer ring (or outer flange), and radial arms that connect the inner and outer rings and leave the necessary space for the insertion of permanent magnets. The spaces between the radial arms (and delimited by the inner and outer rings) thus form the housings.

[0054] Advantageously, the housings can pass axially through the rotor disk to open at both axial ends of the rotor disk. Thus, the permanent magnets can pass axially through the rotor disk from each side. This configuration is particularly advantageous when the electric machine comprises one rotor and two stators, each stator being on either side of the rotor disk. This type of machine, comprising one rotor and two stators, one stator on either side of the rotor with the permanent magnets passing completely through the rotor disk, is called a "through-hole permanent magnet electric machine".

[0055] The rotor disk may, for example, have an annular shape between a cylindrical surface of internal diameter and a cylindrical surface of external diameter. In addition, it may have an external axial thickness (i.e., the axial length of the disk, taken at its external surface) at its external cylindrical surface.

[0056] Advantageously, the electric machine may include a sealing means between the rotor shaft and each stator to prevent the cooling fluid (coming from the cooling channels) from entering at least one air gap separating each stator from the rotor(s) preceding and / or following the stator in question, preceding and following being understood along the longitudinal axis of the electric machine. By preventing the cooling fluid from entering an air gap and preferably all air gaps, the energy losses due to friction in the electric machine are limited.

[0057] Preferably, the sealing means may include a baffle. Indeed, this type of sealing means is effective for dynamic seals, such as those between the rotating rotor shaft and the stationary stator. The baffle is located between the rotor shaft and the relevant stator and may be fixed to or integrated into the rotor shaft or the relevant stator.

[0058] Preferably, the rotor shaft may include several cooling channels opposite each stator to further cool the internal surface of the coils of the stator concerned.

[0059] Preferably, the various cooling channels opposite each stator can be regularly distributed around the circumference of the rotor shaft to better homogenize stator temperatures, particularly when the longitudinal axis is horizontal. Indeed, when the longitudinal axis is horizontal, the cooling fluid tends to flow down by gravity into the lower part of the housing, which tends to increase the temperature difference between the upper and lower parts of the stator.

[0060] The terms "lower" and "upper", as well as "top" and "bottom", are understood with the electrical machine in an operating position with the horizontal longitudinal axis and relative to the vertical axis.

[0061] According to one embodiment of the invention, the electric machine may include a means for collecting the cooling fluid positioned either at the bottom or at the top of the housing. When the collection means is at the bottom of the housing, the cooling fluid flows into it by gravity. This simplifies the collection of the cooling fluid. When the collection means is at the top of the housing, the collection of the cooling fluid is only possible when the housing is immersed in the cooling fluid. This configuration is advantageous because the cooling fluid then surrounds the coils, which improves both the cooling of the machine and the uniformity of the cooling between the upper and lower parts of the stator, i.e., between the coils located at the top and those located at the bottom.Furthermore, in this submerged configuration, the cooling fluid passes between the coils and also wets the external surface of the coils, even if the suction generated by the rotation would be insufficient to allow the cooling fluid to cross radially the space between the coils.

[0062] The collection means may have a calibrated outlet: for example, the outlet may be an opening of predefined diameter to improve the circulation of the cooling fluid. Furthermore, this calibrated outlet may be adjustable or modulated according to the state of the electrical machine (based on its power and / or temperature, for example).

[0063] Advantageously, the electric machine may include scoops fixed to the stationary part, the scoops extending substantially in the longitudinal direction over substantially the entire longitudinal length of the coils of at least one stator (preferably of each stator) and extending radially between the rotor shaft and the Coils of at least one stator (preferably, of each stator). The scoops are therefore guide components designed to direct the flow exiting the rotor shaft opening towards the inner surface of the coils. Thanks to the scoops, a substantially identical flow can be ensured in all the coils. The scoops serve to form receptacles around the rotor shaft to distribute the cooling fluid evenly to the different stator coils.

[0064] The scoops can be fixed to the stator or the crankcase, for example to a crankcase flange.

[0065] Preferably, the electric machine may also optionally include a fixed membrane attached to at least one stator (preferably a fixed solar membrane for each stator) to electrically isolate the stator coils. The membrane (or skin) serves to prevent contact between the cooling fluid and the coils. It thus acts as a sealing system. The membrane is a thin wall (preferably less than 1 mm) and preferably flexible to easily make contact with the coils. The membrane may, in particular, be adapted to the cooling fluid and the temperature of the cooling fluid in the electric machine. It may, in particular, be made of polymer(s).

[0066] Advantageously, the electric machine may include a cooling fluid supply system, with each cooling channel being fluidly connected to the cooling fluid supply system. As a result, the supply system can directly and almost simultaneously supply all the cooling channels, thus simplifying the electric machine.

[0067] Furthermore, the collection means and the supply system can be fluidically connected by a pipe to form a closed-loop circuit for the cooling fluid. In addition, the centrifugal effects associated with the rotation of the rotor shaft provide a "pump" effect, i.e., a suction effect that generates circulation of the cooling fluid in the closed-loop circuit without the use of a pump. Of course, it is also possible to add a pump to the closed-loop circuit to better control the flow rate of the cooling fluid and thus improve its cooling.

[0068] The closed-loop circuit may also include a radiator or heat exchanger to cool the cooling fluid.

[0069] According to one embodiment of the invention, the power supply system may include a conduit, for example passing through the housing, and a sealed chamber formed between the housing and the rotor shaft. The sealed chamber may then be fluidically connected to the conduit, and the inlet of each cooling channel may be fluidly connected to the sealed chamber to convey the cooling fluid from the chamber. The sealed chamber is connected to each cooling channel. The conduit allows the introduction of the cooling fluid into the electrical machine. The sealed chamber may include dynamic sealing means (by a succession of grooves and without the use of gaskets, also called "labyrinth seals") or sealing means including gaskets (made of elastomer, for example) to ensure its seal.

[0070] As the rotor rotates, a centrifugal force is generated. This force creates a vacuum in the sealed chamber, and as a result, the cooling fluid is drawn into the cooling channels.

[0071] Advantageously, the supply system may include a means for extending the conduit (such as a tube fixed to the end of the conduit on the housing) towards the rotor shaft so that the cooling fluid enters the rotor shaft by gravity. The rotor shaft may then include an annular enclosure into which the cooling fluid exiting the extension means falls under the effect of gravity, particularly when the rotor shaft is horizontal or substantially horizontal. The annular enclosure is connected to the various inlets of the different cooling channels and can thus supply the different cooling channels with cooling fluid. This solution does not require sealing means and operates simply.

[0072] According to another embodiment of the invention, the rotor shaft may have a longitudinal bore, preferably axial, the cooling fluid being able to enter through this longitudinal bore to supply the various cooling channels. As a result, the longitudinal bore is then in fluidic connection with the various cooling channels.

[0073] According to one configuration of the invention, the electric machine can have its longitudinal axis horizontal or substantially horizontal in the operating position.

[0074] According to one embodiment of the invention, the rotor (in particular the rotor disc) may include at least one cooling duct passing radially through the rotor (the rotor disc advantageously passing through a radial arm) to circulate the cooling fluid within the rotor disc. This allows for the efficient simultaneous cooling of the rotor, particularly the permanent magnets, and the stator. Preferably, the rotor may include at least one cooling duct in each of the radial arms to provide homogeneous cooling of the rotor.

[0075] Each cooling duct can be in fluidic connection with the power supply system and / or with the cooling channels to facilitate the overall cooling system of the electrical machine with a single fluid. cooling allowing both the cooling of the stator(s) and the rotor(s).

[0076] Preferably, the housing may include a machined feature (or several machined features) forming a deflector to orient and direct the cooling fluid exiting the cooling duct towards the coils of at least one stator (preferably each stator), preferably onto the external surface of the coils of at least one stator (of each stator). These machined features in the housing allow the flow of cooling fluid exiting the cooling ducts to be guided towards a stator, in particular towards the stator coils. By using machined features, additional parts are not required to guide the flow exiting the rotor towards the stator coils. Therefore, this solution is simple and low-cost. Furthermore, the rotation of the rotor and the machined features ensure that very little cooling fluid enters the air gap separating the rotor and the stator.

[0077] Advantageously, each machining can be located at a predetermined position so as to improve the guidance of the cooling fluid towards the coils.

[0078] Preferably, when the electric machine has a horizontal longitudinal axis, these machining operations can be located on the upper part of the housing, with the electric machine in the operating position: in this configuration, the machining operations of the housing are then only on a maximum of one half of the housing.

[0079] According to one embodiment of the invention, each machining operation can thus include at least one concave bowl facilitating the guidance of the flow towards the coils. If the outlet of the cooling duct serves to cool two stators, one on each side of the rotor, each machining operation can then include two concave bowls placed side by side so as to separate the flow rate exiting the rotor into two, preferably into two substantially equal flows, to cool the stators on either side of the rotor.

[0080] These machining operations also allow the cooling fluid to flow into the upper part of the stator, spraying the external surface of the coils. Thus, the cooling fluid can then pass, within the stator, from the inside to the outside via the cooling channels of the rotor shaft and from the outside to the inside via the machining operations in the upper part of the housing.

[0081] The invention also relates to the use of the electric machine according to one of the variants or combinations of variants described above in an electric or hybrid vehicle, a wind turbine, or in a stationary application, such as an industrial charging machine or an electric generator. An "electric" vehicle is a vehicle that includes an electric machine and does not include an internal combustion engine. A "hybrid" vehicle includes an electric machine and an internal combustion engine (gasoline or diesel, for example). An application Stationary refers to an application where the electrical machine is not in a means of transport. It is stationary relative to a terrestrial reference point. An industrial load machine is a machine used in industry, and an electric generator is a machine capable of supplying electricity to a machine, system, or plant. A wind turbine can be stationary when it is on land or installed on the seabed. A floating offshore wind turbine may not be completely stationary in the sense that it can undergo movements around an average position.

[0082] Fig. 1 illustrates, schematically and not in a limiting manner, a first embodiment of an axial flux electric machine according to the invention.

[0083] The axial flux electric machine comprises a rotating part and a stationary part.

[0084] The rotating part comprises a rotor shaft 7 and a rotor comprising a rotor disk 4.

[0085] The static (or fixed) part includes a housing (not shown) and a stator comprising a stator body 2 and coils 3.

[0086] The rotor and stator are arranged successively along the longitudinal axis of the rotor shaft 7, thus forming an axial flux electric machine with an air gap 11 whose thickness (distance between the rotor and the coils 3) is in the direction of the longitudinal axis (i.e. the axis of the rotor shaft 7).

[0087] The rotor shaft 7 includes a central supply channel 1 for supplying cooling fluid to the electric machine.

[0088] The central supply channel 1 is fluidly connected to the radial cooling channel 6 located in the rotor shaft 7. The radial outlet of the radial cooling channel 6 is opposite the internal surface of the coils 3 to spray them and thus facilitate their cooling.

[0089] To prevent the cooling fluid exiting the radial cooling channel 6 from entering the air gap 11, a sealing means, corresponding here to a baffle 5, is installed between the rotor shaft 7 and the stator. This baffle 5 prevents the cooling fluid from accessing the air gap 11.

[0090] The electrical machine may also optionally include a fixed membrane attached to the stator to isolate the stator coils.

[0091] Fig. 2 illustrates, schematically and not in a limiting manner, a portion of an axial flux electric machine according to the invention.

[0092] The axial flux electric machine comprises a rotating part and a stationary part.

[0093] The rotating part comprises a rotor shaft 7 and a rotor (not shown).

[0094] The static (or fixed) part comprises a housing (not shown) and a stator comprising a stator body 2 and coils 3.

[0095] The rotor and stator are arranged successively along the longitudinal axis of the rotor shaft 7, thus forming an axial flux electric machine with an air gap whose thickness is in the direction of the longitudinal axis.

[0096] The rotor shaft 7 here includes several radial cooling channels 6 arriving opposite the coils 3 to spray them and thus cool them.

[0097] As the rotor shaft 7 is rotating around its longitudinal axis, the various radial cooling channels 6 allow the spraying of all the coils 3.

[0098] The arrows illustrate the path of the cooling fluid arriving through the radial cooling channels 6 to reach an area located between the outer surface of the rotor shaft 7 and the inner surface of the coils 3. Then the cooling fluid passes between the coils 3 radially to reach an area located between the outer surface of the coils 3 and the outer casing (not shown).

[0099] Fig. 3 illustrates, schematically and not in a limiting manner, a second embodiment of an axial flux electric machine according to the invention.

[0100] Diagram a) represents a cross-sectional view in a longitudinal plane of the axial flux electrical machine, while diagram b) represents a cross-sectional view in a plane orthogonal to the longitudinal axis of the electrical machine.

[0101] The axial flux electric machine comprises a rotating part and a static part.

[0102] The rotating part includes a rotor shaft 7 and a rotor comprising a rotor disc 4.

[0103] The static (or fixed) part includes a housing 18 and a stator comprising a stator body 2 and coils 3.

[0104] The rotor and the stator are arranged successively along the longitudinal axis of the rotor shaft 7, thus forming an axial flux electric machine with an air gap 11 whose thickness (distance between the rotor and the stator) is in the direction of the longitudinal axis.

[0105] The rotor shaft 7 includes a central supply channel 1 for supplying cooling fluid to the electric machine.

[0106] The central supply channel 1 is fluidly connected to the radial cooling channel 6 located in the rotor shaft 7 and to the cooling channels 10 in the rotor disc 4. The radial outlet of the radial cooling channel 6 is opposite the internal surface of the coils 3 to spray them and thus facilitate their cooling.

[0107] The passage of the cooling fluid through the cooling channels 10 of the rotor disc 4 allows the permanent magnets (not shown) of the rotor to be cooled.

[0108] The radial outlets of the cooling ducts 10 meet opposite machining operations in the housing 18, these machining operations forming deflectors to guide the cooling fluid, in particular to guide it towards the stator coils 3. These here the machining takes the form of two concave bowls 28 but a single concave bowl in the direction of the stator coils 3 could also be used or another shape than a concave bowl.

[0109] To prevent the cooling fluid exiting the radial cooling channel 6 from entering the air gap 11, a sealing means, corresponding here to a baffle 5, is installed between the rotor shaft 7 and the stator. This baffle 5 prevents the cooling fluid from accessing the air gap 11.

[0110] The arrows in diagram b) illustrate the flow path of the cooling fluid when the electric machine has its longitudinal axis horizontal. In the upper part, the cooling fluid exiting the machining, such as the concave bowls 28, flows over the outer part of the coils (see the arrows in the upper part between the coils 3 and the housing 18). In addition, the cooling fluid arriving through the cooling channels 6 enters the annular space between the outer surface of the rotor shaft 7 and the inner surface of the coils 3, passes radially between the coils 3 to reach the area between the outer surface of the coils 3 and the housing 18. The cooling fluid then flows over the outer part of the coils located between the coils 3 and the housing 18. The cooling fluid exits at the lower part through the collection means 8.The flow of the cooling fluid through the electrical machine from the concave bowls 28 is essentially by gravity.

[0111] The electrical machine may also optionally include a fixed membrane attached to the stator to isolate the stator coils.

[0112] Fig. 4 illustrates, schematically and not in a limiting way, another example of an axial flux electric machine.

[0113] The axial flux electric machine comprises a rotating part and a stationary part.

[0114] The rotating part comprises a rotor shaft 7 and a rotor comprising a rotor disk.

[0115] The static (or fixed) part includes a housing 18 and a stator comprising a stator body 2 and coils 3.

[0116] The rotor and stator are arranged successively along the longitudinal axis of the rotor shaft 7, thus forming an axial flux electric machine with an air gap whose thickness is in the direction of the longitudinal axis.

[0117] The rotor shaft 7 includes a central feed channel for supplying cooling fluid to the electric machine.

[0118] The central supply channel is fluidly connected to the radial cooling channels 6 located in the rotor shaft 7. The radial outlet of each radial cooling channel 6 is opposite the internal surface of the coils 3 to spray them and thus facilitate their cooling.

[0119] Unlike the embodiment in diagram b) of [Fig. 3], the electric machine here includes a means 8 for collecting the cooling fluid in the upper part of the housing, when the electric machine has its longitudinal axis horizontal. As a result, the stator of the electric machine is completely immersed in the cooling fluid during operation.

[0120] Figure 5 illustrates, schematically and not in a limiting manner, a third embodiment of an axial flux electric machine according to the invention.

[0121] Diagram a) represents a cross-sectional view in a longitudinal plane of the axial flux electrical machine, whereas diagram b) represents a cross-sectional view in a plane orthogonal to the longitudinal axis of the electrical machine.

[0122] The axial flux electric machine comprises a rotating part and a stationary part.

[0123] The rotating part comprises a rotor shaft 7 and a rotor comprising a rotor disk 4.

[0124] The static (or fixed) part includes a housing 18 and a stator comprising a stator body 2 and coils 3.

[0125] The rotor and the stator are arranged successively along the longitudinal axis of the rotor shaft 7, thus forming an axial flux electric machine with an air gap 11 whose thickness (distance between the rotor and the stator) is in the direction of the longitudinal axis.

[0126] The rotor shaft 7 includes a central supply channel 1 for supplying cooling fluid to the electric machine.

[0127] The central feed channel 1 is fluidly connected to the radial cooling channels 6 located in the rotor shaft 7 (and could be fluidly connected to cooling channels not shown in the rotor disk 4, such as the cooling channels 10 of [Fig. 3]). The radial outlet of each radial cooling channel 6 is opposite the inner surface of the coils 3 to spray them and thus facilitate their cooling.

[0128] To prevent the cooling fluid exiting each radial cooling channel 6 from entering the air gap 11, a sealing means, corresponding here to a baffle 5, is installed between the rotor shaft 7 and the stator. This baffle 5 prevents the cooling fluid from accessing the air gap 11.

[0129] The electric machine here comprises scoops 9 fixed to the stationary part (in particular to the stator or the housing 18). The scoops 9 extend substantially along the entire longitudinal length of the coils 3 in the longitudinal direction, for example from the baffle 5 to the opposite longitudinal end of the coils 3, and they extend radially between the rotor shaft 7 and the coils 3. The arrow on the rotor shaft in diagram b) indicates the direction of rotation of the rotor shaft 7 (clockwise in this case, but also obviously the rotor shaft 7 could rotate in the opposite direction without going outside the scope of the invention).

[0130] As shown, the scoops 9 are oriented, i.e., curved, so as to follow the direction given to the cooling fluid exiting the radial cooling channels 6 by the rotation of the rotor shaft 7 in the indicated direction. This curvature makes it easier to guide the cooling fluid towards the area between two consecutive coils, thus limiting disturbances in the flow of the cooling fluid.

[0131] Alternatively or additionally, the scoops (or at least part of them) could be completely radial (in which case they would not have curved shapes). Thus, they would essentially serve as barriers to force the cooling fluid to flow towards each coil. This solution would achieve the same efficiency regardless of the direction of rotation of the rotor shaft.

[0132] Preferably, and as illustrated, the electric machine may include the same number of scoops opposite a stator as the stator has coils (but it could include fewer scoops than the stator has coils). For example, if the stator has eighteen coils, the electric machine may include eighteen scoops opposite this stator. The scoops 9 may be evenly distributed around the rotor shaft 7 so as to better distribute the cooling fluid towards the stator, and each scoop 9 may, in particular, be positioned at a separate coil 3.

[0133] The electrical machine may also optionally include a fixed membrane attached to the stator to isolate the stator coils.

[0134] Fig. 6 illustrates, schematically and not in a limiting manner, a first variant of a cooling fluid supply system for an axial flow electric machine according to the invention.

[0135] The electric machine includes a housing 18 (the housing 18 is only partially shown) and a rotor shaft 7.

[0136] The casing 18 includes a conduit 24 passing through the casing 18 so as to allow the supply of cooling fluid to the electric machine.

[0137] The housing 18 is connected to the rotor shaft 7 by a bearing 19 so as to allow the rotation of the rotor shaft 7 in the housing 18 which is fixed.

[0138] The housing 18 extends to the rotor shaft 7 and sealing means 22 and 23 (dynamic sealing joints for example) are positioned between the housing 18 and the rotor shaft 7 so as to form a sealed chamber 21.

[0139] The conduit 24 opens into the sealed chamber 21 to supply this sealed chamber 21 with cooling fluid. In addition, the inlet of the radial cooling channels 6 enters the sealed chamber 21. In other words, the conduit 24, the sealed chamber 21 and the radial cooling channels 6 are fluidly connected to each other.

[0140] The rotation of the rotor shaft 7 drives the cooling fluid contained in the sealed chamber 21 into the radial cooling channels 6 of the rotor shaft 7.

[0141] The bold black arrows represent the coolant supply. The cooling fluid arrives through the conduit 24, passes through the casing 18 to reach the sealed chamber 21, then joins the radial cooling channels 6 and thus sprays the internal surface of the coils 3 which are opposite the radial cooling channels 6. This solution could also supply the rotor cooling channels.

[0142] Figure 7 illustrates, schematically and without limitation, a second variant of a cooling fluid supply system for an axial flux electric machine according to the invention.

[0143] The electric machine comprises a housing 18 (the housing 18 is only partially shown), a rotor shaft 7 (also partially shown) and a rotor disc 20.

[0144] As shown, the rotor shaft 7 and the rotor disc 20 are one piece but they could be made in two separate pieces and assembled by any means allowing them to be fixed to each other, by welding or screwing for example.

[0145] The figure shown illustrates two variants that can be used independently or in combination. In one case, the cooling fluid enters through the central shaft via conduit 24b. In the other case, the cooling fluid enters through the housing flange via conduit 24a. The electric machine can, of course, combine these two variants.

[0146] The housing 18 includes a conduit 24a passing through the housing 18 and / or a conduit 24b passing through the rotor shaft 7 so as to allow the supply of cooling fluid to the electric machine. In other words, the supply of cooling fluid to the electric machine can be made either through conduit 24a, or through conduit 24b, or both through conduit 24a and conduit 24b.

[0147] The housing 18 is connected to the rotor shaft 7 by a bearing 19 so as to allow the rotation of the rotor shaft 7 in the housing 18 which is fixed.

[0148] In this embodiment, the feeding system does not require sealing means between the housing 18 and the rotor disc 20.

[0149] In the case where the cooling fluid is supplied by the conduit 24b, the cooling fluid arrives in the rotor disc 20 by gravity in the collection area 28 of the rotor disc 20.

[0150] In the case where the cooling fluid is supplied via the conduit 24a, the conduit is extended by means of the extension 25 (which may be a partially shrink-fitted tube) to the casing or welded to the casing). The extension means terminates in the collection zone 28 of the rotor disc 20 so as to supply the cooling fluid into the collection zone 28, by gravity.

[0151] Once in the collection zone 28, the cooling fluid can supply the cooling channels 10. The rotation of the rotor disc 20 allows the different cooling channels 10 to be supplied one after the other.

[0152] The collection zone 28 thus forms an annular enclosure of the rotor disc 20 connected to the different inlets of the different cooling ducts 10.

[0153] In this embodiment, the inlets of the cooling ducts 10, in connection with the supply system, are substantially radial, arriving in the collection zone 28.

[0154] The bold black arrows represent the coolant supply. The coolant arrives via conduit 24a and / or conduit 24b.

[0155] If it arrives via conduit 24a, it passes through casing 18. Upon exiting conduit 24a, it is conveyed by extension means 25 to arrive in collection zone 28.

[0156] If it exits the conduit 24b, it arrives directly in the collection zone 28. From this collection zone 28 which forms an annular enclosure, it then joins the cooling conduits 10 of the rotor disc 20. Examples

[0157] A solution of the invention was compared, by simulation, to a prior art solution in which the stator is cooled solely by air convection within the housing. The housing itself is cooled by water cooling. In other words, in this prior art solution, no cooling duct is installed in the rotor and no cooling channel opening opposite the coils is used.

[0158] Several hypotheses were considered for the solution to the invention: - (a): It is assumed that the internal surface of the coils is in contact with the cooling fluid exiting the rotor shaft ports; - (b): It is assumed that the internal and external surfaces of the coils are made of contact with the cooling fluid exiting the rotor shaft ports; - (c): It is assumed that all surfaces of the coils are in contact with the cooling fluid exiting the rotor shaft ports, i.e. the internal and external surfaces as well as the surfaces connecting the internal and external surfaces which separate two consecutive coils circumferentially.

[0159] According to these assumptions, for the operating point of the electric machine, the temperature of the coils is reduced by 44°C for case (a), by 65°C for case (b) and by 72°C for case (c) and the temperature of the stator body is reduced by 40°C for case (a), by 54°C for case (b) and by 59°C for case (c), all other things being equal, which demonstrates the cooling efficiency of the solution of the invention.

Claims

Demands

1. An axial flux electric machine comprising a rotating part and a stationary part, the rotating part comprising a rotor shaft (7) with a longitudinal axis and at least one rotor fixed on the rotor shaft (7), the stationary part comprising a housing (18) and at least one stator, the at least one rotor and at least one stator being positioned longitudinally successively inside the housing (18) and separated by at least one air gap (11), each stator comprising coils (3), characterized in that the rotor shaft (7) comprises at least one radial cooling channel (6) leading to an orifice opposite the internal surface of the coils (3) of at least one stator, the cooling channel serving for the circulation of a cooling fluid and in that the electric machine comprises a sealing means between the rotor shaft (7) and each stator to prevent the cooling fluid from entering the at least one air gap (11),the sealing means preferably comprising a baffle (5), located between the rotor shaft (7) and the stator concerned and preferably fixed or integrated into the rotor shaft (7) or the stator concerned.

2. An electric machine according to any one of the preceding claims, wherein the rotor shaft (7) comprises several cooling channels (6) opposite each stator, preferably regularly distributed around the circumference of the rotor shaft (7).

3. Electric machine according to any one of the preceding claims, wherein the electric machine includes a means for collecting said cooling fluid positioned in the lower part of the casing (18), or in the upper part of the casing (18), in the operating condition of the electric machine.

4. An electric machine according to any one of the preceding claims, wherein the electric machine comprises scoops (9) fixed on the fixed part, the scoops (9) extending substantially in the longitudinal direction over substantially the entire longitudinal length of the coils (3) of at least one stator and extending radially between the rotor shaft (7) and the coils (3) of at least one stator.

5. An electrical machine according to any one of the preceding claims, wherein the electrical machine comprises a cooling fluid supply system, each cooling channel (6) being fluidly connected to the cooling fluid supply system.

6. Electric machine according to claim 6, wherein the power supply system comprises a conduit (24) through the housing (18) and a sealed chamber (21) formed between the housing (18) and the rotor shaft (7), the sealed chamber (21) being fluidly connected to the conduit (24), the inlet of each cooling channel (6) being fluidly connected to said sealed chamber (21) to convey the cooling fluid from said sealed chamber (21) to each cooling channel (6).

7. An electric machine according to any one of the preceding claims, wherein the electric machine has its longitudinal axis horizontal or substantially horizontal in the operating position.

8. An electric machine according to any one of the preceding claims, wherein the rotor includes a cooling duct (10) passing radially through the rotor and preferably, the housing (18) includes a machined deflector for orienting and directing the cooling fluid exiting the cooling duct (10) in the direction of the coils (3) of at least one stator, preferably on the external surface of the coils (3) of at least one stator.

9. Use of the electric machine according to any one of the preceding claims in an electric or hybrid vehicle, or in a stationary application, such as an industrial charging machine, an electric generator or a wind turbine.

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