FR3028689A3 - ELECTRIC MOTOR COMPRISING A ROTOR COOLING CIRCUIT. - Google Patents

Abstract

The invention relates to an electric motor (1) comprising a rotor (2) and a stator (3) separated from one another by an air gap (4) allowing the rotation of said rotor (2), said electric motor (1). ) further comprising a heat transfer fluid circuit (5) adapted to project at least a portion of said heat transfer fluid onto said rotor (2) so as to cool said rotor (2), said circuit (5) extending into the stator (3) to project said at least a portion of said heat transfer fluid to the rotor (2) through said gap (4).

Description

TECHNICAL FIELD The invention relates to an electric motor comprising a rotor cooling circuit, for a motor vehicle. The rotor of an electric motor of a motor vehicle comprises coils of magnets or aluminum which must be kept below a critical temperature beyond which the energy efficiency decreases sharply or causes irreversible damage to the rotor for example demagnetization of permanent magnets. The cooling of the rotor is typically provided by the forced convection of air enclosed in the machine or air passing through the engine. However, such a solution is of little interest insofar as the air is a bad heat transfer agent, and insofar as it is relatively complex to make the air pass through the machine, for example because of the filtration of the air before entering the machine.

There is also known the use of an oil circulation circuit to cool a rotor. Document FR2107547, which describes the use of a hollow shaft forming the axis of rotation of the rotor, is particularly known, this hollow shaft integrates a pressurized oil circulation circuit and having a plurality of bores for spraying the oil on the rotor. However, such a solution imposes relatively large mechanical stresses and requires the use of a hollow shaft specifically designed for this purpose. Also, there is a need for an electric motor including a less complex rotor cooling circuit.

For this purpose, there is provided an electric motor comprising a rotor and a stator separated from each other by an air gap allowing the rotation of said rotor, the electric motor further comprising a circuit of a coolant, for example a circuit oil, or any other type of heat transfer fluid, in particular any type of non-conductive fluid, so that it can be put in direct contact with electrical conductors, adapted to project at least a portion of the coolant on the rotor so as to cool the rotor. The circulation circuit extends in the stator in order to be able to project the at least part of the coolant towards the rotor through the air gap. Thus the rotor can be cooled using the heat transfer fluid of the coolant circuit. This allows the rotor to be cooled by using only a heat transfer fluid circuit, and without having to provide in the rotor a heat transfer fluid supply circuit. Advantageously, without limitation, the stator being provided with an alternation of teeth and notches, the heat transfer fluid circuit is at least partially housed inside the notches. In this way, the heat transfer fluid circuit is used to cool the stator windings housed in the notches and the rotor, while projecting a portion of the fluid into the gap from the notches. Thus one can share a same fluid circuit to cool the stator and the rotor, which allows to obtain an electric motor 15 comprising a rotor not specifically designed for a particular cooling mode. Thus the electric motor is more simply cooled than in the known prior art. Advantageously and in a nonlimiting manner, the notches are interconnected by the heat transfer fluid circuit, so that the fluid passes through all the notches. In other words, the heat transfer fluid circuit passes in series through the notches of the stator. The coolant circuit in the notch can also be connected by two manifolds on each machine side. A parallel / serial combination is also possible. Advantageously, without limitation, each notch of the plurality of notches is closed by a closure wall extending between the two teeth adjacent to the notch. Thus the content of the notches, for example the coils, the coolant circuit and / or the coolant, can be isolated from the air gap. Advantageously and in a nonlimiting manner, the notch and the corresponding closure wall form part of the heat transfer fluid circuit. In other words, the heat transfer fluid passes through the notch in direct contact with the conductors installed in the notch. The heat transfer fluid flows freely in the notch.

The coolant is channeled through the closure wall so that it does not flow freely into the air gap.

3028689 3 The heat transfer fluid is conveyed by the heat transfer fluid circuit to one end of the notch, for example a face joining the two adjacent teeth and perpendicular to the closure wall, and is extracted by the same coolant circuit, at another end, for example another face, opposite to the first routing face. Advantageously, in a nonlimiting manner, for at least one notch of the plurality of notches, the corresponding closure wall has at least one orifice opening into the gap to allow the projection of the at least part of the heat transfer fluid. Thus, the orifice makes it possible to control and limit the quantity of coolant projected in the air gap, in order to come into contact with the rotor, for example with an external wall of the rotor, for example an external circumferential surface or a lateral surface of the rotor. rotor, so that a heat exchange between the rotor and the coolant cooled the rotor. Advantageously and in a nonlimiting manner, the orifices have dimensions that are shaped so that the total amount of coolant projected in the gap remains small compared to the amount of fluid flowing in the coolant circuit, for example less than one to ten percent depending on the amount of thermal power to be discharged by the rotor. Thus, the coolant circuit is not unbalanced by the projection of a portion of the coolant in the air gap. In other words, the amount of coolant projected in the air gap only reduces the quality of the stator cooling in a manner that is almost negligible. Advantageously and in a nonlimiting manner, the coolant circuit may be supplied with heat transfer fluid at several locations in the stator, for example in at least two places, for example at two diametrically opposite locations of the stator. Thus, one can compensate in a relatively simple way the heat transfer fluid loss, for example to compensate for the amount of heat transfer fluid projected into the air gap. Advantageously, without limitation, the orifice of the closure wall 35 has a substantially hyperboloid shape. Thus one can limit the pressure drop. In other words, the orifice of the wall has on each face on either side of the closure wall a substantially concave cup shape, and forming an opening at the bottom of each cup. Thus, the projection of the oil through the orifice is more efficient, the hyperboloidal shape of the orifice facilitating the crossing of the closure wall by the coolant, which avoids the risk of clogging. of the orifice. Advantageously, without limitation, two notches distinct from the plurality of notches, opposite to the axis of rotation of the rotor, comprise a closure wall having at least one orifice. Thus, it increases the distribution of the oil projection around the axis of the rotor, which improves the flow of heat transfer fluid in the air gap. Advantageously, non-limitatively, all the orifices defined on the closure walls are distributed substantially uniformly along the axis of rotation of the rotor. Thus, the thermal exchanges between the rotor and the heat transfer fluid are optimized by distributing the heat transfer fluid projection over the entire length of the rotor along the axis of rotation of the rotor. Advantageously, without limitation, the motor 20 comprising a casing enclosing the stator and the rotor, the casing comprises a collector for collecting the heat transfer fluid projected on the rotor. Thus, the heat transfer fluid projected into the air gap is retained by the collector of the housing so that it does not escape into the rest of the motor vehicle.

Advantageously, without limitation, the circulation circuit comprises a pump for pumping the heat transfer fluid collected by the collector, the pump being able to reintroduce the heat transfer fluid pumped into the circuit. Thus, the heat transfer fluid circuit does not suffer any loss of heat transfer fluid, which allows a closed circuit operation of the cooling of the stator and the rotor. Advantageously, without limitation, the coolant is oil. This optimizes the heat exchange, the oil being a relatively good heat transfer agent.

The oil may be, for example, a silicone oil, a synthetic ester oil, a vegetable ester oil.

The oil is a dielectric fluid, which avoids the risk of short circuit in the electric motor. In addition, the oil has lubrication qualities, thus optimizing the lubrication of the rotor.

However, the heat transfer fluid can be any type of suitable fluid, in particular any type of dielectric fluid. Advantageously, without limitation, the electric motor being coupled to a mechanical speed variator comprising a lubrication circuit, the lubrication circuit is connected to the heat transfer fluid circuit of the electric motor. Thus, it is possible to have only one oil circuit for cooling the motor and for the mechanical speed variator, and the cooling of the oil is improved by dissipating the heat collected in contact with the lubrication circuit. The invention is now described with reference to the accompanying drawings, non-limiting, in which: - Figure 1 is a longitudinal sectional view of a radial flow electric motor according to a first embodiment of the invention; FIG. 2 is a detailed view of a notch of a stator of a radial flow electric motor according to the embodiment of FIG. 1; FIG. 3 is a schematic perspective view of an axial flow electric motor according to a second embodiment of the invention; FIG. 4 is a schematic view of a motor vehicle according to one embodiment of the invention. In the present description, the terms front, rear, upper, lower, refer to the front and rear directions of the vehicle. The X, Y, Z axes correspond respectively to the longitudinal axis (front to back), transverse and vertical of the vehicle. By substantially horizontal, longitudinal or vertical means a direction / plane forming an angle of not more than ± 20 °, or not more than 10 ° or not more than 5 ° with a direction / a horizontal, longitudinal or vertical.

By substantially parallel, perpendicular or right angle means a direction / angle deviating by not more than ± 20 °, or not more than 10 ° or not more than 5 ° from a parallel direction , perpendicular or a right angle. With reference to FIG. 1, an electric motor 1, here an electric motor 1 with a radial flow, comprises a rotor 2 and a stator 3.

The stator 3 has a cylindrical shape, extends along an axis of rotation 18, and comprises an outer circumferential face 3a and an inner circumferential face 3b. The rotor 2 has a cylindrical shape and comprises an outer circumferential face 2a.

The cylindrical rotor 2 extends along the same axis of rotation 18 as the stator 3, over a length substantially equal to that of the stator 3. The rotor 2 has between the axis of rotation 18 and the outer circumferential face 2 a radius less than the radius of the inner circumferential face 3b of the stator 3, so that the rotor 2 can be inserted into the inner radius of the stator 3. The stator 3 and the rotor 2 are separated by an air gap 4. Here, the air gap 4 has a substantially crown shape, extending between the outer circumferential face 2a of the rotor 2 and the inner circumferential face 3b of the stator 3.

The stator has an alternation of teeth 7 and notches 8, each notch 8 being flanked by two teeth 7. The notches opening into the air gap 4. Electrical conductors 11 are inserted partially into the notches 8 forming the stator windings 3.

The windings of the stator 3 are designed to be traversed by an electric current so as to produce an electromagnetic field capable of rotating the rotor 2. The electric motor 1 further comprises a circuit 5 of a coolant 6. Here, the circuit 5 is an oil cooling circuit 5, also called an oil circuit 5. The circuit 5 is adapted to convey a flow of oil into the stator 3. The cooling circuit 5 conveys the oil into the notches 8 of the stator 3, so as to circulate the oil in direct contact with the windings of the stator 3. Thus, a heat exchange takes place between the windings and the oil, which causes cooling of the windings, the oil 3028689 7 circulating in the circuit 5 carrying the heat and radiating along the path of the circuit 5, on colder surfaces. The notches 8 of the stator 3 are closed by a closure wall 9, here a rigid membrane of polymer material 9.

The closure wall 9 extends between the two adjacent teeth 7 of the corresponding notch 8. In other words, the closing wall 9 hermetically closes the corresponding notch 8 facing the air gap 4, so that the oil flowing in the notch 8 does not flow into the air gap 10 4 The oil cooling circuit 5 is fitted on each notch 8 so as to circulate the oil through the notch 8, right through the notch 8, here in an axial direction of the stator 4. The shutter wall 9 channels the flow of oil so that it passes right through the notch 8 in the axial direction without flowing into the air gap 4. The cooling circuit 5 conveys the flow of the oil. pressurized oil at a rate of substantially 2 cm to 2 m per second depending on the type of oil circulation in the notches.

Each closure wall 9 has an opening 10, here an orifice 10 opening into the gap 4. In other words, the orifice 10 makes it possible to create an opening between the inside of the notch 8 and the gap 4 according to the radial direction of the stator 3. The orifice 10 is here substantially shaped hyperboloid 25 revolution in particular to limit the pressure drop. However, the embodiment of the orifice 10 is not limited to this particular form, it can also be a cylindrical bore, extending in a radial direction of the stator, or an opening of any other shape adapted to the passage of the oil.

In particular, all the notches 8 comprise a closure wall 9, and each closure wall 9 may be pierced with an orifice 10 opening into the gap 4. A small portion of the oil flowing in the notch through the hole 10.

Here, about 0.1% to 1% of the flow rate per orifice of the oil in the notch 8 is projected into the gap 4, the remainder passing through the notch 8 and continuing the path defined by the circuit 5. The percentage 3028689 The flow rate varies according to the number of orifices, the power to be discharged from the rotor, and so on. All the notches 8 have a closure wall 9 comprising an orifice 10 opening into the gap 4, a small portion 5 of the oil flows around the axis of rotation 18 of the rotor 2, on the circumferential face of the rotor 2, which improves the flow and the evacuation of the oil from the circuit 5. In other words, the projection of oil on the rotor 2 takes place relatively regularly in rotation about the axis of rotation 18.

According to an alternative not shown, the closure walls 9 define a plurality of orifices 10, distributed on the closure wall 9 in a direction substantially parallel to the axis of rotation 18, so that the projection of the oil on the rotor 2 is moreover carried out relatively evenly in the length of the cylinder formed by the rotor 2. In other words, the opening orifices 10 are formed in the closing walls 9 so that the projection of oil from the oil circuit 5 flowing in the gap 4 is substantially regular both in rotation about the axis of rotation of the rotor 2 and along the inner faces of the closure walls 9 in a direction substantially collinear with the axis of rotation of the rotor 2. Advantageously, all of the orifices 10 of all the closure walls 9 has a substantially helical shape on the inner circumferential face of the stator. However, the invention is not limited to this particular arrangement of the orifices 10, and the arrangement of the orifices 10 can be freely decided, for example according to specific zones, for example in order to project the oil onto particularly hot areas of the rotor 5, for example on the permanent magnets of a rotor 5 with permanent magnets, or on the coil heads of the coils of a winding rotor 5. The motor 1 comprises a housing 15 enclosing the rotor 2 and the stator 3. The housing 15, isolates the rotor 2 and the stator 3 from the other mechanical elements of the motor vehicle 40. The housing 15 comprises a collector 16 for collecting the oil 35 projected on the rotor 2. By the effect of gravity, the oil projected into the gap 4 on the rotor 2 flows by the effect of the gravitational field.

The collector 16 is installed vertically above the rotor 2, so that the oil flowing in the gap 4 is collected by the collector 16. The collector 16 is here a container 16 installed in the bottom of the lower part of the casing 15.

The lower part of the casing 15 is defined according to the orientation of the casing 15 when the electric motor 1 is mounted in the motor vehicle 40. The collector 16 cooperates with a pump 17, here the pump 17 is installed in the casing 15 and comprises a suction nozzle, not shown, disposed in the manifold 16 and connected to the oil cooling circuit. The pump 17 pumps, through the nozzle, the oil collected by the collector 16 and reintroduced into the oil cooling circuit 5. Thus, the oil which has been extracted from the circuit 5 to be projected into the gap 4, is collected by the collector 16 and then reintroduced by the pump 17 into the circuit 5. In this way, the oil cooling circuit 5 does not suffer oil loss, or negligible amount, which ensures a permanent operation of the oil circuit 5.

The oil projected into the air gap 4 allows the rotor 2 to be cooled in a relatively efficient manner without it being necessary to use means for conveying the oil directly into the rotor 2, for example by means of installation of a hollow shaft connected to an oil propulsion circuit or other means known from the prior art.

The oil projected into the air gap 4 ensures, furthermore, the good lubrication of the rotor 2. The motor vehicle 40, with reference to FIG. 4, comprises a mechanical speed variator 41. The mechanical speed variator 41 comprises a lubrication circuit 42.

The lubricating circuit 42 is connected to the oil cooling circuit 5 so that the oil flowing in the lubrication circuit 42 is shared with the oil circuit 5. Thus, the same amount of oil can be used to lubricating the mechanical elements of the mechanical speed variator 41 and cooling the stator 35 3 and the rotor 2 of the electric motor 1. Advantageously, the joint use of the oil for the lubrication circuit 42 and for the cooling of the rotor 2 and the stator 30 improves the cooling of the oil which naturally radiates on the walls of the cooling circuit and the lubrication circuit 42 in which the oil moves. In other words, increasing the length of the circuit 5, by adding a lubrication circuit 42, improves the cooling of the oil, by increasing the area over which the oil radiates heat. According to a second embodiment, with reference to FIG. 3, the electric motor 1 is a motor 1 with axial flow, the rotor 2 being a rotor with permanent magnets 2. The rotor 2 and the stator 3 are aligned along the axis of rotation 18 of the rotor 2. The rotor 2 and the stator 3 are separated by an air gap 4 extending between a lateral face 2c of the rotor 2 and a lateral face 3c of the stator 3.

The gap distance 4 separating the stator 3 from the rotor 2 is deliberately exaggerated in FIG. 4 for better understanding. In this embodiment, the notches 8 open into the air gap through the lateral face 3c of the stator 3 opposite the gap 4.

The oil projected through the openings 10 of the closing walls 9 of the notches 8, is directed towards the side wall of the rotor 2 facing the air gap 4. Thus, it is possible to obtain a compact axial flow motor 1 comprising a rotor 2 effectively cooled by spraying the oil of the cooling circuit 5 of the stator 3 into the gap 4. 25

Claims (10)

REVENDICATIONS1. Electric motor (1) comprising a rotor (2) and a stator (3) separated from each other by an air gap (4) allowing the rotation of said rotor (2), said electric motor (1) further comprising a circuit (5) for a heat transfer fluid, adapted to project at least a portion of said heat transfer fluid onto said rotor (2) so as to cool said rotor (2), characterized in that said circuit (5) extends in the stator (3) to be able to project said at least a portion of said heat transfer fluid to the rotor (2) through said gap (4). 2. Electric motor (1) according to claim 1, characterized in that said stator (3) being provided with an alternation of teeth (7) and notches (8), said circuit (5) of said heat transfer fluid is at least partially housed inside said notches (8). 3. Electric motor (1) according to claim 2, characterized in that each notch (8) of the plurality of notches (8) is closed by a closure wall (9) extending between the two teeth ( 7) adjacent to said notch (8). 4. Electric motor (1) according to claim 3, characterized in that for at least one notch (8) of the plurality of notches (8), said corresponding closure wall (9) has at least one orifice ( 10) opening into said gap (4) to allow the projection of said at least a portion of the coolant in said air gap (4). 5. Electric motor (1) according to claim 4, characterized in that said orifice (10) of said closure wall (9) has a substantially hyperboloid shape. 6. Electric motor (1) according to any one of claims 2 to 5, characterized in that two notches (8) separate from said plurality of notches (8), opposite to an axis of rotation (18) of said rotor (2), comprise a closure wall (9) having at least one orifice (10). 3028689 12 7. Electric motor (1) according to claim 6, characterized in that all the orifices (10) defined on the closing walls (9) are distributed substantially uniformly along the axis of rotation. (18) of the rotor (2). 8. Electric motor (1) according to any one of claims 1 to 7 characterized in that said coolant is oil. 10 9. Motor vehicle (40) comprising an electric motor (1) according to any one of claims 1 to 8. 10. Motor vehicle (40) according to claim 9, characterized in that said electric motor (1) being coupled to a mechanical speed variator (41) comprising a lubrication circuit (42), said lubrication circuit (42). ) is connected to said circuit (5) of said coolant of said electric motor (1).