Electric machine comprising an air cooling circuit

Abstract

The invention relates to an electric machine (1), in particular an axial magnetic flux electric machine, comprising: - a stator (3); - a rotor (2) that is rotatable relative to the stator about an axis of rotation (X); - a casing (13) surrounding the stator and the rotor; - an air cooling system configured to cool the stator and / or the rotor, wherein the cooling system comprises an air circuit; and - a valve (20) that is movable relative to the casing between an open position and a closed position, wherein the air circuit is in a closed loop inside the casing when the valve is in the closed position, and the air circuit is in an open loop and in communication with the exterior of the casing when the valve is in the open position.

Description

Description Title of the invention: Electrical machine comprising an air-cooling circuit. Technical field of the invention

[0001] The invention relates to an electrical machine, particularly one with axial magnetic flux, the electrical machine comprising an air-cooling circuit. The invention also relates to a method for controlling such an electrical machine. The invention further relates to a motor vehicle comprising such an electrical machine. Prior art

[0002] So-called "electric" or "hybrid" motor vehicles include an electric motor configured to drive the vehicle's drive wheels. Among the various electric motor architectures, axial flux motors are well-known. In such motors, one or more air gaps between a stator and a rotor extend perpendicularly to the rotor's axis of rotation. The rotor typically consists of a ring equipped with magnets and is fixed to a rotating shaft of the electric motor. The stator contains windings of electrical wire through which a high-power electric current can flow.

[0003] The flow of electric current through the stator's wire windings generates significant heat, which can damage certain parts of the electric motor and / or disrupt its proper operation. Therefore, it is important to cool the electric motor during operation. For this purpose, axial flux electric motors are known to incorporate a closed-loop oil cooling system. Oil is circulated by a pump and flows through oil channels within the motor housing. The oil cooling circuit is connected to a heat exchanger designed to cool the oil and thus dissipate the heat generated by the stator. However, an oil cooling system does not sufficiently cool the rotor and / or stator. Furthermore, some parts of an axial flux electric motor may be incompatible with oil contact.These parts therefore cannot be directly cooled by the oil cooling system. For example, the air gap cannot be immersed in oil because this would severely reduce the efficiency of the electric motor.

[0004] We also know of systems for cooling an electric motor using forced air. In this case, the electric motors are equipped with an electric blower powered by a vehicle battery. A greater or lesser quantity of air is blown depending on the temperature of the electric motor. Such systems are also bulky and consume valuable electrical energy. Presentation of the invention

[0005] The object of the invention is to provide an electrical machine, in particular with axial flux, remedying the above disadvantages and improving upon known electrical machines of the prior art.

[0006] More specifically, a first object of the invention is an electrical machine equipped with a compact cooling system that is simple to manufacture and allows for efficient modulation of the electrical machine's cooling according to requirements. Summary of the invention

[0007] The invention relates to an electrical machine, in particular one with axial magnetic flux, comprising: - a stator, - a rotor that rotates relative to the stator around an axis of rotation, - a casing enclosing the stator and rotor, - an air cooling system configured to cool the stator and / or the rotor, the cooling system comprising an air circuit, and - a movable valve relative to the housing between an open position and a closed position, the air circuit being in a closed loop inside the housing when the valve is in the closed position, the air circuit being in an open loop and communicating with the outside of the housing when the valve is in the open position.

[0008] The crankcase may include: - at least one first opening communicating between the inside and outside of the crankcase, said at least one first opening being blocked by the valve when it is in the closed position and said at least one first opening forming an air inlet into the crankcase when the valve is in the open position, and - at least one second opening communicating between the inside and outside of the crankcase, said at least one second opening being blocked by the valve when it is in the closed position and said at least one second opening forming an air outlet from the crankcase when the valve is in the open position.

[0009] The valve may include an air circulation channel comprising an air inlet and an air outlet, said channel forming a first part of the air circuit when the valve is in the closed position and when the valve is in the open position, the air inlet of the channel being positioned inside the housing when the valve is in the closed position, the air inlet of the channel being positioned outside the housing when the valve is in the open position, the air outlet of the channel being positioned inside the housing when the valve is in the closed position and when the valve is in the open position.

[0010] The housing may include a well extending perpendicularly to the axis of rotation, the well comprising a second part of the air circuit, the valve being mounted to slide between its open position and its closed position inside the well.

[0011] The electrical machine may include a peripheral area around the stator and / or rotor, and the housing may include at least one window communicating between the peripheral area and the well, said at least one window being blocked by the valve when the valve is in the open position, said at least one window being clear when the valve is in the closed position.

[0012] The electric machine may comprise a first part including a first stator and a first rotor and a second part including a second stator and a second rotor, the electric machine comprising a central wall separating the first part of the electric machine from the second part of the electric machine, the well being formed in the central wall.

[0013] The electric machine can be an axial magnetic flux electric machine, the air circuit comprising a third part extending in an air gap formed between the stator and the rotor, the air being intended to circulate in the air circuit exclusively by means of the rotation of the rotor relative to the stator.

[0014] The electric machine may further include an actuator configured to move the valve between its open position and its closed position.

[0015] The invention also relates to a method for controlling an electrical machine as defined above, the control method comprising: - the operation of the electrical machine under operating conditions leading to moderate heating of the electrical machine, with the valve in the closed position, then - the detection of operating conditions of the electrical machine leading to significant heating of the electrical machine, then - the movement of the valve from its closed position to its open position.

[0016] The invention also relates to a motor vehicle, comprising an electric machine as defined above. Presentation of the figures

[0017] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which:

[0018] Fig. 1 is a first perspective and cross-sectional view of an electrical machine according to one embodiment of the invention, the electrical machine comprising a valve in the closed position.

[0019] Fig. 2 is a second perspective and cross-sectional view of the electrical machine, with the valve in the open position.

[0020] Figure 3 is a schematic view of the electrical machine connected to an electronic control unit. Detailed description

[0021] Figure 1 illustrates an axial flux electric machine 1 according to an embodiment of the invention. The electric machine 1 is capable of functioning as an electric motor to drive the drive wheels of a motor vehicle. The electric machine 1 can also be capable of functioning as an electric current generator using the kinetic energy of the vehicle. The motor vehicle can be, for example, a passenger car, a commercial vehicle, a truck, or even a bus.

[0022] The electric machine 1 comprises a rotor 2 and a stator 3. The rotor 2 is free to rotate relative to the stator 3 about an axis of rotation X. The electric machine 1 further comprises a rotating shaft 4 extending parallel to the axis of rotation X. The rotating shaft 4 is fixed to the rotor 2 and is intended to be mechanically connected to at least one drive wheel of the vehicle via a transmission system.

[0023] According to the embodiment presented, the rotor 2 comprises two parts 2A, 2B. Each portion 2A, 2B of the rotor is substantially in the shape of a disk extending perpendicularly to the axis of rotation X. Each portion 2A, 2B of the rotor includes a set of magnets fixed to a support 6A, 6B. Each support 6A, 6B is itself fixed to the rotating shaft 4, notably by means of fixing screws. Each support 6A, 6B may, for example, be star-shaped. The magnets may be housed in spaces formed between the points of the star. The magnets of each portion 2A, 2B of the rotor are held by a circumferential ring 8A, 8B, shrink-fitted around the magnets and / or the support 6A, 6B. Each ring 8A, 8B may be, for example, a cylindrical element, for example, made of a composite material. Each ring 8A, 8B is designed to counteract the centrifugal force that may be exerted on the magnets and thus helps to keep the magnets in place in their respective spaces.

[0024] The rotating shaft 4 also includes a first part 4A and a second part 4B. Each part 4A, 4B, is supported by two roller bearings. Each part 4A, 4B also includes splines for transmitting torque to the transmission system. Each part 4A, 4B also includes a flange through which it is fixed, specifically screwed, to a part 2A, 2B of the rotor, respectively.

[0025] The stator 3 also comprises two parts cooperating respectively with the two rotor parts 2A and 2B. Each stator part 2A and 2B comprises two stator rings 3A1 and 3A2, and respectively 3B1 and 3B2. The two stator rings 3A1 and 3A2 extend on either side of the rotor part 2A. The two stator rings 3B1 and 3B2 extend on either side of the rotor part 2B. In other words, the rotor part 2A is sandwiched between the two stator rings 3A1 and 3A2, and the rotor part 2B is sandwiched between the two stator rings 3B1 and 3B2. Each stator ring 3A1, 3A2, 3B1, 3B2 preferably comprises a set of electrical coils 11A1, 11A2, 11B1, 11B2, optionally each arranged around a ferromagnetic core. The coils 11A1, 11A2, 11B1, 11B2 may be bonded, in particular, to platters extending perpendicularly to the axis of rotation X.To ensure the coils are securely glued, it is best to avoid exposing the glue to excessively high temperatures. The stator rings 3A1, 3A2, 3B1, and 3B2 are spaced apart along the X-axis of rotation.

[0026] The electric machine 1 thus comprises a first air gap 12A1 defined between the first part 2A of the rotor and the first stator ring 3A1, a second air gap 12A2 defined between the first part 2A of the rotor and the second stator ring 3A2, a third air gap 12B1 defined between the second part 2B of the rotor and the third stator ring 3B1, and a fourth air gap 12B2 defined between the second part 2B of the rotor and the fourth stator ring 3B2. The air gaps 12A1, 12A2, 12B1, and 12B2 are free spaces, each extending in a plane perpendicular to the axis of rotation X. The air gaps 12A1, 12A2, 12B1, and 12B2 can have dimensions on the order of a millimeter along the axis of rotation X. The electrical machine 1 is said to be "axial flux" because a magnetic flux passing through the air gaps 12A1, 12A2, 12B1, and 12B2 extends globally parallel to the axis of rotation X.

[0027] The electric machine 1 also includes a casing 13, preferably metallic, particularly aluminum, inside which the rotor 2 and stator 3 are arranged. The casing 13 may, for example, be cast aluminum. The casing 13 forms a sealed or nearly sealed enclosure around the rotor 2 and stator 3 to protect these components. The electric machine 1 can be attached to a vehicle structure via its casing 13. The general shape of the casing 13 may be roughly cylindrical with its axis of revolution centered on the axis of rotation X.

[0028] The housing 13 includes a central wall 14, extending perpendicularly to the axis of rotation X. The central wall 14 separates the first part 2A of the rotor and the first part 3A of the stator respectively from the second part 2B of the rotor and the second part 3B of the stator.

[0029] The electric machine 1 thus comprises, overall, two parts IA and IB capable of operating independently. The central wall 14 may include, at least roughly, a plane of symmetry between the two parts IA and IB. Each part IA, IB of the electric machine can be intended to drive a drive wheel of the vehicle. According to an alternative embodiment, the electric machine 1 could be different. The electric machine 1 could, for example, comprise only the first part IA or the second part IB described previously. In this document, the terms "first" and "second" do not imply any preference relationship between the elements to which they refer.

[0030] For each part IA, 1B of the electric machine, an internal zone Z1A, Z1B can be defined, extending within the stator. The internal zone Z1A extends between part 4A of the rotating shaft 4 and the electrical coils 11A1 and 11A2. The internal zone Z1B extends between part 4B of the rotating shaft 4 and the electrical coils 11B1 and 11B2. The outer diameter of the stator 3 is at least roughly equal to the outer diameter of the rotor 2. A peripheral zone Z2A, Z2B can also be defined, extending around the periphery of each part of the stator and rotor. The peripheral zone Z2A extends between the electrical coils 11A1 and 11A2 and an external wall of the housing 13. The peripheral zone Z2B extends between the electrical coils 11B1 and 11B2 and the external wall of the housing 13. The zones Z1A, Z1B, Z2A and Z2B are free zones, i.e. filled with air, and they extend inside the housing 13.Zones Z1A and Z2A communicate with each other via air gaps 12A1 and 12A2. Zones Z1B and Z2B communicate with each other via air gaps 12B1 and 12B2.

[0031] The internal zone Z1A comprises a first part Z1A1 extending inside the first stator ring 3A1 and a second part Z1A2 extending inside the second stator ring 3A2. The two parts Z1A1 and Z1A2 communicate with each other via holes 15A provided in the support 6A. Similarly, the internal zone Z1B comprises a first part Z1B1 extending inside the third stator ring 3B1 and a second part Z1B2 extending inside the fourth stator ring 3B2. The two parts Z1B1 and Z1B2 communicate with each other via holes 15B provided in the support 6B.

[0032] The electric machine also includes an oil cooling system comprising an oil circuit. The oil circuit includes oil lines 18A, 18B passing close to the stator 3.

[0033] The electric machine 1 also includes an air-cooling system comprising an air circuit adapted to cool the stator and / or the rotor. The electric machine also includes a movable valve 20 relative to the housing 13 between an open position (illustrated in [Fig. 2]) and a closed position (illustrated in [Fig. 1]). As we will see in detail later, the air circuit is either a The circuit is closed-loop when the valve is in the closed position, and open-loop when the valve is in the open position. Controlling the position of valve 20 therefore allows modification of the cooling circuit for the electrical machine 1, thus modulating its cooling performance.

[0034] A "closed-loop" air circuit means that the air circuit does not communicate with the ambient air outside the electrical machine 1, i.e., outside the casing 13. The air is therefore completely recycled within the air circuit. This prevents the introduction of particles and / or moisture into the casing 13, which could damage the electrical machine. A heat exchanger cools the air in the air circuit. An "open-loop" air circuit means that the air circuit communicates with the ambient air outside the electrical machine 1, i.e., outside the casing 13. In an open loop, hot air is expelled from the casing, and in return, fresh air from the surrounding environment is drawn into the casing.An open-loop air circuit allows for more efficient cooling of the electrical machine but generates a risk of introducing particles and / or moisture inside the casing 13.

[0035] When the electric machine 1 is operating, the air in the air gaps 12A1, 12A2, 12B1, and 12B2 is drawn in a centrifugal direction by the rotation of the rotor. The rotor is designed to rotate at very high speeds, up to approximately 12,000 to 15,000 revolutions per minute, which generates a centrifugal force on the air masses in contact with it. Therefore, the rotation of the rotor 2 establishes a centrifugal airflow in the air gaps 12A1, 12A2, 12B1, and 12B2.

[0036] The air in the air circuit is circulated solely by the rotation of rotor 2, without the use of a blower or any other means of air circulation requiring an electrical power supply. It should be noted that rotor 2 does not necessarily have blades or any other surface features to more effectively move the air. Rotor 2 may, in particular, have generally smooth surfaces. Indeed, simply rotating rotor 2 at a sufficiently high speed is enough to establish airflow within the air circuit. Alternatively, such features could be integrated into the rotor; however, this would require a more complex rotor design and could also increase the overall size of the electric machine 1.

[0037] It is therefore understood that the air circuit comprises a first section in which the air flows in a centrifugal direction. This first section passes through the air gaps 12A1, 12A2, 12B1, and 12B2. The air circuit also comprises a second section in which the air flows in a centripetal direction. Between the first and second sections portion of the air circuit, the air passes through the peripheral zones Z2A and Z2B, moving at least roughly parallel to the axis of rotation X.

[0038] The housing 13 includes a radial well 21, that is, a well extending perpendicularly to the axis of rotation X. Well 21 is formed in the central wall 14 separating the two parts IA and IB of the electrical machine. Well 21 forms an air conduit between the peripheral zones Z2A and Z2B and a central zone Z3 positioned between the two parts 4A and 4B of the rotating shaft 4. Well 21 can advantageously be lined by the oil lines 18A and 18B. Well 21 can thus form a relatively cool zone of the electrical machine 21, thereby cooling the air circulating within it.

[0039] Each section of the rotating shaft 4 may include a circulation channel 22A, 22B for conveying air from the central zone Z3 to the internal zones Z1A1, Z1A2, Z2A1, Z2A2. The circulation channel 22A, 22B may include a central section, in particular a bore, extending parallel to the axis of rotation X at the center of each section of the rotating shaft 4, and radial openings 23A, 23B, connecting the central section to the internal zones Z1A1, Z1A2, Z2A1, Z2A2. The rotating shaft 4 can thus be configured to guide air from the air circuit from downstream of the well 21 to the various internal zones Z1A1, Z1A2, Z2A1, Z2A2. Alternatively or in addition, lateral openings 24A and 24B can also be provided in well 21 to convey air directly into internal zones Z1A2 and Z1B1. Well 21 can be formed in the casing 13 during a casing casting process.Alternatively, well 21 could result from a drilling of the casing 13.

[0040] The housing 13 includes a first opening 25 communicating between the inside and outside of the housing 13. The valve 20 is slidably mounted in the first opening 25. The first opening 25 is blocked by the valve when it is in the closed position, and it is unobstructed (i.e., free to allow air to pass through) when the valve is in the open position. The first opening 25 is formed in a cylindrical wall 26 of the housing 13. The cylindrical wall 26 extends generally parallel to the axis of rotation X, around the axis of rotation X. In particular, the first opening 25 is positioned directly above the well 21. The first opening 25 forms an air inlet into the air circuit when the valve is in the open position.

[0041] The housing 13 also includes at least one second opening 27 communicating between the inside and outside of the housing 13. This at least one second opening 27 is separate from the first opening 25. This at least one second opening 27 is positioned next to the first opening 25. This at least one second opening 27 is formed in the cylindrical wall 26 of the housing 13. Similar to the first opening 25, this at least one second opening 27 is closed. by the valve when it is in the closed position, and it is clear when the valve is in the open position. The at least one second opening 27 preferably comprises an opening 27A communicating between the peripheral zone Z2A and the outside of the housing 13, and an opening 27B communicating between the peripheral zone Z2B and the outside of the housing 13. The at least one second opening 27 forms an air outlet for the air circuit when the valve is in the open position.

[0042] The valve 20 is roughly T-shaped. The valve 20 includes, in particular, an airflow channel 28 and a cover 29 extending perpendicularly to the channel 28. The cover 29 is configured to close the openings 25 and 27 when the valve is in the closed position. The channel 28 extends completely into the well 21 when the valve is closed and at least partially out of the well 21 when the valve is open. The channel 28 may have a cylindrical shape complementary to the shape of the well 21 so as to slide inside the well 21. The well 21 thus forms a means of guiding the valve 20 in translation between its open and closed positions. The channel 28 forms a first part of the airflow circuit both when the valve is closed and when the valve is open. Channel 28 includes an air inlet 30 and an air outlet 31.The air inlet 30 is positioned inside the housing 13 when the valve is in the closed position, and outside the housing 13 when the valve is in the open position. The air outlet 31 is positioned inside the housing. 13, and in particular in well 21, when the valve is in the closed position and when the valve is in the open position.

[0043] Well 21 includes a second part of the air circuit, downstream of channel 28. Advantageously, the portion of well 21 in which the valve 20 slides may have an enlarged diameter. The portion of well 21 downstream of the enlarged portion may have a diameter substantially equal to the diameter of channel 28. Thus, when the valve 20 is in the closed position, the cross-sectional area of ​​airflow in channel 28 and in the downstream portion of the well is substantially constant.

[0044] The casing 13 also includes at least one window communicating between the peripheral zone Z2A, Z2B and the shaft 21. In particular, the casing includes a first window 32A communicating between the peripheral zone Z2A and the shaft 21, and a second window 32B communicating between the peripheral zone Z2B and the shaft 21. The windows 32A and 32B are through-holes formed in the central wall 14. The two windows can be positioned opposite each other. They can extend parallel to the axis of rotation X. Windows 32A, 32B are blocked by the valve 20, specifically by a tubular sleeve 33 of the channel 28 when the valve is in the open position. Windows 32A, 32B are unobstructed when the valve 20 is in the closed position. This is achieved, in particular, by positioning the inlet air 30 of channel 28 opposite windows 32A, 32B when the damper is in the closed position. In particular, the air inlet 30 comprises a first air inlet 30A suitable for positioning opposite window 32A and a second air inlet 30B suitable for positioning opposite window 32B.

[0045] It is therefore understood that well 21 guides an airflow from the peripheral areas Z2A, Z2B to the internal area Z3 when the valve is in the closed position, and that well 21 guides an airflow from the outside of the housing to the internal area Z3 when the valve is in the open position.

[0046] When the electric machine 1 operates with the valve 20 in the closed position, an electric current flows through the stator's electric coils 11A1, 11A2, 11B1, and 11B2, causing them to heat up. The rotor magnets are also likely to heat up. The air in contact with the stator and rotor also heats up. As the rotor 2 rotates around its axis of rotation X, a centrifugal airflow is generated at the air gaps 12A1, 12A2, 12B1, and 12B2. The air heated by the stator and rotor reaches the peripheral zones Z2A and Z2B and then enters the channel 28 through the air inlets 30A and 30B. The air then flows through the well 21 in a centripetal direction. Inside well 21, the air cools down, notably due to the cooling of the walls of well 21 by the oil lines 18A, 18B.Next, the airflow exits well 21 in the central zone Z3, from which it returns to the internal zones Z1A1, Z1A2, Z2A1, Z2A2 via the radial openings 23A, 23B formed in the rotating shafts 4A, 4B and / or via the lateral openings 24A, 24B. The air thus reaches the internal zones Z1A1, Z1A2, Z2A1, Z2A2 again and begins a new cycle in the air circuit. The airflow in the air circuit is represented by arrows E1 in [Fig. 1].

[0047] When the electric machine 1 operates with the valve 20 in the open position, an electric current also flows through the stator's electric coils 11A1, 11A2, 11B1, and 11B2, causing them to heat up. The rotor magnets are also likely to heat up. The air in contact with the stator and rotor heats up. As the rotor 2 rotates around the axis of rotation X, a centrifugal airflow is generated at the air gaps 12A1, 12A2, 12B1, and 12B2. The air heated by the stator and rotor enters the peripheral zones Z2A and Z2B. Air is prevented from entering the channel 28 because the tubular casing 33 blocks the windows 32A and 32B. On the other hand, openings 27A, 27B are clear, which allows the airflow to exit from the housing 13. The evacuation of hot air through openings 27A, 27B creates an air intake at the air inlets 30A, 30B.Fresh air from outside the crankcase thus rushes into well 21 and reaches the central zone Z3 from which it returns to the internal zones Z1A1, Z1A2, Z2A1, Z2A2 by way of the radial openings 23A in the rotating shafts 4A, 4B and / or by way of through the lateral openings 24A, 24B. The air thus reaches the internal zones Z1A1, Z1A2, Z2A1, Z2A2 where it is centrifuged by the rotation of the rotor. The airflow in the air circuit is represented by arrows F2 in [Fig.2].

[0048] In relation to [Fig. 3], the electric machine 1 also includes an actuator 40 configured to move the valve 20 between its open and closed positions. The actuator 40 may, for example, include an auxiliary electric motor 41 and a transmission mechanism 42 configured to act on the valve 20. Alternatively, other forms of actuators may be considered, for example, a hydraulic actuator. The actuator 40 may be controlled by an electronic control unit 43 or, alternatively, by a control means such as a lever directly operated by a vehicle user. In the latter case, the control means may be mechanically connected, for example, by a cable, to the valve 20.

[0049] Assuming that the valve 20 is intended to be controlled by an electronic control unit 43, the latter advantageously comprises a detection means 44, a memory 45 containing software, and a microprocessor 46 capable of executing the software. The electronic control unit 43 is then electrically connected to the actuator 20, in particular to the electric motor 4L. The detection means 44 can be configured to detect a temperature of the electric machine 1, and / or a torque request from a vehicle user, and / or a rotational speed of the rotating shaft 4. These different quantities can be calculated or estimated directly by the detection means 44 or received by the detection means 44, for example via a vehicle data bus. The software can be configured to compare the quantity detected, calculated, or received by the detection means 44 with a predefined threshold.Next, if this value is greater than or equal to the first predefined threshold, the electronic control unit issues a suitable command to move the valve from its closed position to its open position. Similarly, the software can be configured to compare this value with a second predefined threshold. Then, if this value is less than or equal to the predefined threshold, the electronic control unit issues a suitable command to move the valve from its open position to its closed position.

[0050] This allows the valve 20 to be controlled so that it is in the open position under the operating conditions of the electrical machine 1 that could lead to significant heating of the stator and / or rotor. Thus, under these specific operating conditions, the stator and rotor are effectively cooled and do not reach a critical temperature that could damage them. Conversely, the valve 20 is kept in the closed position under the conditions of The operation of the electric machine 1 leads to moderate heating of the stator and / or rotor. This prevents particles from entering the electric machine.

[0051] Advantageously, the software thresholds are determined so that the valve 20 is in the closed position for most of the vehicle's operating time, and when the vehicle is not in use. The valve 20 is in the open position only under severe operating conditions, which limits the risk of particles entering the well 21. Advantageously, the valve 20 and / or the housing 13 can be fitted with a filter, for example a screen, to prevent particles from entering the well 21.

[0052] Thanks to the invention, the rotor and stator temperatures can be lowered by a few degrees under severe operating conditions. The electric machine 1 thus operates at a lower temperature and is therefore more reliable. The invention is particularly simple to implement because it requires no pump or air blower to circulate air within the air circuit. The valve is a simple and lightweight component, for example, made of plastic and / or molded. The valve can be integrated directly into a recess formed in the housing. Therefore, integrating the valve 20 into the electric machine is also straightforward.

Claims

Demands

1. An electrical machine (1), in particular with axial magnetic flux, comprising: - a stator (3), - a rotor (2) that rotates relative to the stator around an axis of rotation (X), - a housing (13) enclosing the stator and rotor, - an air cooling system configured to cool the stator and / or the rotor, the cooling system comprising an air circuit, and - a movable valve (20) relative to the housing between an open position and a closed position, the air circuit being in a closed loop inside the housing when the valve is in the closed position, the air circuit being in an open loop and communicating with the outside of the housing when the valve is in the open position.

2. An electrical machine (1) according to the preceding claim, characterized in that the housing (13) comprises: - at least one first opening (25) communicating between the inside and outside of the crankcase, said at least one first opening being blocked by the valve (20) when it is in the closed position and said at least one first opening forming an air inlet into the crankcase when the valve is in the open position, and - at least one second opening (27) communicating between the inside and outside of the crankcase, said at least one second opening being blocked by the valve (20) when it is in the closed position and said at least one second opening forming an air outlet from the crankcase when the valve is in the open position.

3. An electrical machine (1) according to any one of the preceding claims, characterized in that the valve (20) comprises an air circulation channel (28) including an air inlet (30) and an air outlet (31), said channel forming a first part of the air circuit when the valve is in the closed position and when the valve is in the open position, the air inlet of the channel being positioned inside the housing when the valve is in the closed position, the air inlet of the channel being positioned outside the housing when the valve is in the open position, the air outlet of the channel being positioned inside of the housing when the valve is in the closed position and when the valve is in the open position.

4. Electric machine (1) according to any one of the preceding claims, characterized in that the casing (13) comprises a well (21) extending perpendicularly to the axis of rotation (X), the well comprising a second part of the air circuit, the valve being mounted sliding between its open position and its closed position inside the well.

5. Electric machine (1) according to the preceding claim, characterized in that it comprises a peripheral zone (Z2A, Z2B) around the stator (3) and / or the rotor (2), and in that the housing (3) comprises at least one window (32A, 32B) communicating between the peripheral zone and the well (21), said at least one window being blocked by the valve (20) when the valve is in the open position, said at least one window being clear when the valve (20) is in the closed position.

6. Electric machine (1) according to any one of claims 4 or 5, characterized in that it comprises a first part (IA) comprising a first stator (3A) and a first rotor (2A) and a second part comprising a second stator (3B) and a second rotor (2B), the electric machine comprising a central wall (14) separating the first part of the electric machine from the second part of the electric machine, the well (21) being formed in the central wall (14).

7. Electric machine (1) according to any one of the preceding claims, the electric machine being an axial magnetic flux electric machine, the air circuit comprising a third part extending in an air gap (12A1, 12A2, 12B1, 12B2) formed between the stator (3) and the rotor (2), the air being intended to circulate in the air circuit exclusively by means of the rotation of the rotor relative to the stator.

8. Electric machine (1) according to any one of the preceding claims, characterized in that it further comprises an actuator (40) configured to move the valve between its open position and its closed position.

9. A method for controlling an electrical machine (1) according to any one of the preceding claims, characterized in that it comprises: - operating the electrical machine under conditions of use leading to moderate heating of the electrical machine, with the valve (20) in the closed position, then - the detection of operating conditions of the electrical machine leading to significant heating of the electrical machine, then - the movement of the valve from its closed position to its open position.

10. Motor vehicle, comprising an electric machine (1) according to any one of claims 1 to 8.

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