Electric machine with cooling circuit

Abstract

The present invention relates to a cooling system for an electrical machine comprising at least one stator (32) disposed in a stator housing (33), the assembly being disposed in a second housing (34), and formed between the two housings (33, 34), at least one contact surface between the stator (32) and the stator housing (33) being configured to control the distribution of the contact pressure between the stator (32) and the housing (33) over the entire length (L) of the stator housing (33). Figure for the abstract: Fig. 1.

Description

Title of the invention: Electric machine with cooling circuit

[0001] The present invention relates to the cooling of a powertrain, and more particularly of the electric machine of an electric powertrain of a motor vehicle.

[0002] To limit the temperature of the stator, and indirectly of the reduction gear of the powertrain, a cooling circuit is formed around the stator, between the stator housing of the machine and the wall of the powertrain housing.

[0003] Usually, heat transfer between the stator and the stator housing occurs through radial clamping. The stator housing is heated and expands, the stator is inserted, and once cooled, radial clamping is achieved. A drawback of this system is that the stator housing is asymmetrical, and therefore stiffer on one side than the other.

[0004] This results in an uneven contact pressure distribution. Since heat transfer occurs via contact, the thermal contact resistance is not uniform along the cylinder, and therefore cooling is not uniform around the stator. Furthermore, manufacturing tolerances can cause contact losses, particularly at the ends of the stator housing. Consequently, the pressure is not optimized along the entire length of the housing, which, in addition to cooling problems, leads to poor stator centering and / or noise issues.

[0005] The present invention therefore aims to overcome one or more of the drawbacks of prior art devices by proposing an improved cooling system that optimizes cooling while maintaining effective centering and limiting noise.

[0006] For this purpose, the present invention proposes a cooling system for an electrical machine comprising at least one stator disposed in a stator housing, the assembly being disposed in a second housing, and formed between the two housings, at least one contact surface between the stator and the stator housing being configured to control the distribution of the contact pressure between the stator and the housing over the entire length of the stator housing.

[0007] This allows for optimized radial clamping and thus also optimized cooling.

[0008] According to one embodiment of the invention, the stator housing is configured so as to distribute the pressure over the entire length of the stator housing.

[0009] According to one embodiment of the invention, the housing has a diameter which decreases continuously along its length, from a first end of the housing to a second end of the housing.

[0010] According to one embodiment of the invention, the wall thickness of the stator housing is modified so as to decrease regularly in a straight line along the length of the housing.

[0011] According to one embodiment of the invention, the wall thickness of the stator housing is modified so as to decrease in a non-rectilinear manner over the length of the housing.

[0012] According to one embodiment of the invention, the wall thickness of the stator housing is modified so as to decrease curvilinearly over the length of the housing.

[0013] According to one embodiment of the invention, the wall thickness of the stator housing is modified so as to decrease in a concave curvilinear manner over the length of the housing.

[0014] According to one embodiment of the invention, the wall thickness of the stator housing is modified so as to decrease in a curvilinear convex manner over the length of the housing.

[0015] According to one embodiment of the invention, the surface of the stator is adapted to allow optimized cooling, and for example, the outer diameter of the stator is modified to obtain a cone shape.

[0016] Such a cone shape allows the management of the pressure loss generated by the length of the housing.

[0017] The invention also relates to an electrical machine, in particular a powertrain, comprising a cooling system according to the invention.

[0018] Other objects, features and advantages of the invention will be better understood and will become more apparent upon reading the description given below, with reference to the accompanying figures, given by way of example and in which:

[0019] - [Fig. 1] is a cross-sectional view of a powertrain according to the invention,

[0020] - [Fig. 2] is a schematic representation of a cross-sectional view of a part of the stator housing according to an embodiment of the invention,

[0021] - [Fig. 3] is a schematic representation of a cross-sectional view of a part of the stator housing according to another embodiment of the invention,

[0022] - [Fig. 4] is a schematic representation of a cross-sectional view of a part of the stator housing according to another embodiment of the invention.

[0023] Fig. 1 schematically illustrates an electric powertrain 1 for a motorized vehicle according to the invention, comprising a reversible electric machine 30 including a stator 32, a rotor 31 mobile in rotation around a machine axis X, an electric current inverter supplying the electric machine and a speed reducer 40 kinematically linked to the rotor of the electric machine. The output shaft of the speed reducer drives one or more drive wheels of the motor vehicle, in this case a motor vehicle.

[0024] The speed reducer 40 housed inside the transmission casing includes transmission shafts to which gears are rotationally attached, enabling a speed reduction ratio to be achieved between the rotor of the electric machine and the output shaft of the speed reducer.

[0025] According to one embodiment of the invention, the stator 32 is arranged in a stator housing 33. The assembly is arranged in a housing 34 of the powertrain 1, this housing 34 forming a second housing 34.

[0026] The space between the two housings 33, 34 forms the conduit 35 of the cooling circuit in which, according to one embodiment, a cooling fluid circulates.

[0027] According to one embodiment of the invention, the fluid is a coolant or air.

[0028] According to one embodiment of the invention, the stator 32 housing 33 is asymmetrical. More precisely, it is not formed by a perfect cylinder, and the thickness of its wall varies along its entire circumference. Heat transfer between the stator and its housing 33 is thus achieved by radial clamping of the housing 3 onto the stator 32. The housing 33 is heated and expands, the stator is inserted, and once the housing 33 has cooled, the radial clamping is performed.

[0029] In the context of the invention, to allow for optimized radial clamping and thus optimized cooling, at least one contact surface between the stator 32 and the stator housing 33 is configured to control the distribution of contact pressure between the stator 32 and the housing 33 over the entire length L of the stator housing 33. The length of the housing 33 is defined along the longitudinal X-axis of the electrical machine and therefore of the stator 32. The length L is thus parallel to the X-axis.

[0030] According to one embodiment of the invention, the housing 33 of the stator 32 is machined so as to distribute the pressure, represented by the arrows F, F' and F” in the figures, for optimized cooling over the entire length L of the housing 33 of the stator.

[0031] According to one embodiment of the invention, the housing has a diameter that decreases continuously along its length L, from a first end 311 of the housing 33 to a second end 312 of the housing 33, thus maintaining the clamping force over the distance. Contact between the stator and the housing is therefore maintained along the entire length L of the stator housing 33, thereby optimizing cooling.

[0032] According to one embodiment of the invention, the diameter is modified by changing the wall thickness P of the stator housing 33. That is to say, the wall thickness P decreases regularly in a straight line, at the face 36 oriented towards the stator housing 33, along the length L of the housing 33 from a first end 311 of the housing 33 towards a second end 312 of the housing 33. The reduction in thickness allows the housing to be flexible and therefore deformable as illustrated [Fig.2]. Thus, before insertion, the second end of the housing 33 is flexed (before insertion is shown in dotted lines in the figures) inwards, then straightens R as the stator 32 is inserted to perfectly fit the contour of the stator and allow for optimized cooling.

[0033] According to an embodiment of the invention, the wall thickness P decreases in a non-rectilinear manner, at the level of the face 36 oriented towards the stator housing 33, over the length L of the housing 33 from a first end 311 of the housing 33 to a second end 312 of the housing 33 [Fig.3] and [Fig.4].

[0034] According to an embodiment of the invention, the thickness of the wall P decreases curvilinearly, at the level of the face 36 oriented towards the stator housing 33, over the length L of the housing 33 from a first end 311 of the housing 33 to a second end 312 of the housing 33 [Fig.3] and [Fig.4].

[0035] According to an embodiment of the invention, the thickness of the wall P decreases in a concave curvilinear manner (hollow) 361, at the level of the face 36 oriented towards the stator housing 33, over the length L of the housing 33 from a first end 311 of the housing 33 to a second end 312 of the housing 33[Fig.4].

[0036] According to an embodiment of the invention, the wall thickness P decreases in a curvilinear convex (bump) 362, at the level of the face 36 oriented towards the stator housing 33, over the length L of the housing 33 from a first end 311 of the housing 33 to a second end 312 of the housing 33 [Fig.3].

[0037] According to one embodiment of the invention, the face 36 oriented towards the stator housing 33 is the one in contact with the housing 33.

[0038] According to another embodiment of the invention, it is the surface of the stator 32 that is in contact with the stator housing 33 that is adapted to allow for optimized cooling. For example, the outer diameter of the stator 32 is modified to obtain a conical shape.

[0039] Such a cone shape allows the management of the pressure loss generated by the length L of the housing 33.

[0040] The scope of the present invention is not limited to the details given above and allows for embodiments in many other specific forms without departing from the field of application of the invention. Therefore, the present embodiments should be considered by way of illustration and may be modified without, however, departing from the scope defined by the claims.

Claims

Demands

1. Cooling system for an electrical machine comprising at least one stator (32) disposed in a stator housing (33), the assembly being disposed in a second housing (34), and formed between the two housings (33, 34), characterized in that at least one contact surface between the stator (32) and the stator housing (33) is configured to control the distribution of the contact pressure between the stator (32) and the housing (33) over the entire length (L) of the stator housing (33).

2. Cooling system according to claim 1, wherein the housing (33) of the stator (32) is configured to distribute the pressure over the entire length (L) of the housing (33) of the stator.

3. Cooling system according to claim 1 or 2, wherein the housing (33) has a diameter which decreases continuously over its length (L), from a first end (311) of the housing (33) to a second end (312) of the housing (33).

4. Cooling system according to any one of claims 1 to 3, wherein the wall thickness (P) of the stator (32) housing is modified so as to decrease regularly in a straight line over the length (L) of the housing (33).

5. Cooling system according to any one of claims 1 to 3, wherein the wall thickness (P) of the stator (32) housing is modified so as to decrease non-rectilinearly over the length (L) of the housing (33).

6. Cooling system according to any one of claims 1 to 3, wherein the wall thickness (P) of the stator (32) housing is modified so as to decrease curvilinearly over the length (L) of the housing (33).

7. Cooling system according to any one of claims 1 to 3, wherein the wall thickness (P) of the stator (32) housing is modified so as to decrease in a concave curvilinear manner over the length (L) of the housing (33).

8. Cooling system according to any one of claims 1 to 3, wherein the wall thickness (P) of the housing (33) of the stator (32) is modified so as to decrease in a curvilinear convex manner over the length (L) of the housing (33).

9. Cooling system according to claim 1, the surface of the stator (32) is adapted to allow optimized cooling, and for example, the outer diameter of the stator (32) is modified to obtain a cone shape.

10. Electric machine, in particular powertrain, comprising a cooling system according to any one of claims 1 to 9.

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