Electric machine and method of manufacture

Abstract

An electric machine, in particular an electric motor for driving at least one compressor or circulator, comprising a stator (2) and a rotor (3) arranged in a housing (10), the electric machine (1) comprising a cooling device arranged around the stator (2) and comprising a circulation circuit for a cooling fluid, characterized in that the cooling device comprises a circulation duct (5) for the cooling fluid, a portion of the circulation duct being embedded in a mass (4) of high thermal conductivity material, such as a metal or a metal alloy.

Description

TECHNICAL FIELD

[0001] The present invention relates to an electric machine and to a manufacturing method thereof.

[0002] More specifically, the present invention relates to an electric machine, in particular an electric motor for driving at least one compressor or circulator, comprising a stator and a rotor arranged in a housing, the electric machine comprising a cooling device arranged around the stator, the cooling device comprising a circuit for circulating a cooling fluid. BACKGROUND

[0003] It is known to provide a device for cooling an electric motor, in particular the stator of the motor, see for example EP2680408 A1.

[0004] The known cooling device provides a circuit for circulating a cooling fluid, the circuit being housed in a housing which is sealed or hermetically sealed with respect to the external environment. The circuit is sealed with respect to the remaining internal volume of the electric machine housing by means of a weld and / or a seal.

[0005] If the seal fails, the leakage of the cooling fluid into the remaining part of the electric machine can have serious consequences. In particular, when the electric machine is a motor for driving a compressor housed in a sealed housing of the electric machine, the leaked cooling fluid can mix with the compressed circulating gas. This contamination can damage the equipment using this circulating gas.

[0006] Repairing the point of leakage requires time-consuming and costly disassembly and operations. SUMMARY

[0007] The aim of the present invention is to remedy all or part of the drawbacks of the prior art described above.

[0008] To this end, the essential characteristics of the electric machine according to the invention, which also complies in other respects with the general definition given in the preamble, are that the cooling device comprises a duct for circulating a cooling fluid, a portion of the duct being embedded in a mass of high thermal conductivity material, such as a metal or a metal alloy.

[0009] Furthermore, the embodiments of the invention can have one or more of the following characteristics:

[0010] - the mass of high thermal conductivity material is overmoulded around the fluid circulation duct,

[0011] - the mass of high thermal conductivity material is composed of aluminium or an aluminium alloy,

[0012] - the duct for circulating the cooling fluid is composed of a metal material or a metal alloy, in particular a stainless steel alloy,

[0013] - the mass of high thermal conductivity material has a cylindrical shape and the stator is housed in said mass and in contact with the cylindrical inner surface of the mass,

[0014] - the stator is housed in the mass of high thermal conductivity material by interference fit,

[0015] - the housing delimits a preferably airtight volume which houses the stator, the rotor and the cooling device, which volume is for example pressurized,

[0016] - the circulation duct is connected to an inlet and to an outlet passing through a wall of the housing,

[0017] - the housing comprises an access hatch which, in the open position, provides access to the stator, to the rotor and to the cooling device, in a longitudinal direction parallel to the rotation axis of the rotor and to the mounting direction of the assembly of the stator, rotor and cooling device in the housing,

[0018] - the circulation duct comprises preferably curved end portions connected respectively to the inlet and to the outlet, the hatch also providing, in the open position, access to the end portions of the circulation duct connected to the inlet and to the outlet, so as to allow removal of the end portions connected to the housing and extraction or introduction of the assembly of the stator, rotor and cooling device and of said end portions of the circulation duct into the housing,

[0019] - the housing is airtight,

[0020] - the part of the circulation duct embedded in the mass of high thermal conductivity material forms at least one of the following: a sawtooth, a spiral, a reciprocating section, a rectilinear segment, a curved segment.

[0021] The invention can also relate to a method for manufacturing an electric machine, in particular a motor, according to any of the above or below described characteristics, comprising a stator and a rotor arranged in a housing, and a cooling device comprising a duct for circulation of a cooling fluid, a part of which is embedded in a mass of high thermal conductivity material, such as a metal or a metal alloy, in which method the cooling device is preassembled with the stator before being introduced into the housing.

[0022] The invention can also relate to any alternative device or method comprising any combination of the above or below described characteristics within the scope of the claims. BRIEF DESCRIPTION OF DRAWINGS

[0023] Further specific features and advantages will become apparent on reading the following description, provided with reference to the attached drawings, in which:

[0024] [ Figure 1 ] shows a schematic partial cross-sectional view illustrating an exemplary embodiment of the invention,

[0025] [ Figure 2 ] shows a schematic partial perspective view illustrating an exemplary arrangement of the circulation pipe. DETAILED DESCRIPTION

[0026] Figure 1 The electric machine 1, in particular electric motor, illustrated in the figures comprises a stator 2 and a rotor 3 arranged in a housing 10.

[0027] Preferably, the housing 10 delimits a hermetic and sealed volume containing the stator 2, the rotor 3 and the cooling device.

[0028] The stator 2 is arranged around the rotor 3 with respect to the longitudinal axis 11.

[0029] The rotor 3 drives, for example, a rotating shaft on which a compressor 9 or circulator is mounted. This means that the electric machine 1 can be in particular a motor-compressor. Of course, the electric machine can also be a motor-turbocharger (with a turbine mounted on the other end of the shaft) and / or a motor driving a plurality of compressors, for example a two-stage motor-compressor (with compressor wheels on both sides of the rotating shaft).

[0030] At least one portion of the housing 10 can have an axisymmetric (symmetric with respect to the axis 11), for example cylindrical or tubular, shape arranged around the stator 2 (around the longitudinal axis 11). The housing 10 can be constituted by metal part(s) assembled in a sealed manner, in particular by means of a seal or fastening pin.

[0031] The electric machine 1 comprises a cooling device arranged around the stator 2. This device conventionally comprises a cooling fluid circuit, in particular for a heat transfer liquid. Such a heat transfer fluid is generally a liquid intended to exchange heat directly or indirectly with a part of the electric machine, in particular the stator 2. To this end, the cooling fluid can be water or any other liquid or gas or two-phase mixture capable of transferring heat.

[0032] According to an advantageous feature, this cooling device comprises a pipe 5 for circulation of the cooling fluid, a portion of which is embedded in a mass 4 of high thermal conductivity material, such as a metal or a metal alloy.

[0033] This portion of the circulation pipe 5 embedded in the mass 4 of high thermal conductivity material can in particular be helical and / or described as zigzag. This means that the pipe forms a plurality of passages (annular, zigzag or other shape) around and / or along the stator 2.

[0034] For example, the pipe 5 is curved (preferably without welds).

[0035] As[ Figure 2As illustrated in figure 1, the duct 5 for example takes the form of helical reciprocating sections in the direction of the longitudinal axis 11. This makes it possible to homogenize the temperature of the stator 2. In this case, the fluid inlet 6 and outlet 7 can be located on the same longitudinal side of the stator 2. For example, the duct 5 is formed by two sets of helices respectively advancing in opposite directions (respectively reciprocating) in the longitudinal direction 11. The two sets of helices can be nested or alternated. This means that, between two helices or turns making the fluid travel in a first longitudinal direction, there are helices or turns making the fluid circulate in the opposite longitudinal direction.

[0036] Of course, this embodiment is in no way limiting. For example, alternatively or in combination, the duct 5 can be longitudinally curved. This means that the duct 5 can have portions (in particular rectilinear) whose directions extend in a direction parallel to the longitudinal axis 11. This means that the duct 5 forms rectilinear reciprocating sections in a direction parallel to the longitudinal direction 11. These longitudinal portions can correspond to generatrices of a cylinder whose central axis is the longitudinal axis 11. The duct then curves between two adjacent longitudinal portions. Other orientations can be provided.

[0037] Similarly, it is conceivable to provide a duct 5 of any other geometry, which surrounds the entire stator or only a portion of the stator.

[0038] Furthermore, in order to have the inlet 6 and outlet 7 on the same side of the electric machine, the return portion of the duct 5 can be achieved directly through the mass 4 of high thermal conductivity material via a tube, in particular a rectilinear tube.

[0039] Thus, the assembly comprising the mass 4 of high thermal conductivity material and the duct 5 can form a tubular barrier extending in the longitudinal direction, the two ends 6, 7 of which are located on the same longitudinal end of the mass 4.

[0040] This forms an assembly 4, 5 that can be screwed into the housing 10 (for example, the stator 2 and the rotor 3 are already mounted into the central portion of this assembly 4, 5).

[0041] This makes it easier to connect the piping to the electric machine 1.

[0042] High thermal conductivity means a thermal conductivity comparable to that of a metal or metal alloy.

[0043] For example, the mass 4 of high thermal conductivity material is composed of aluminum or an aluminum alloy.

[0044] The mass 4 of high thermal conductivity material can be overmolded around the fluid circulation duct 5.

[0045] The duct 5 for circulation of the cooling fluid can be composed of a metal material or metal alloy, in particular a stainless steel alloy.

[0046] As illustrated, the mass 4 of high thermal conductivity material has for example a tubular and / or cylindrical shape, and the stator 2 (which is for example cylindrical) is housed in said mass 4 and in contact with the inner surface of this mass. This means that the mass 4 can have a cylindrical shape, through which the tube formed by the circulation duct 5 passes, which means that the volume of metal mass does not fill the entire cylinder.

[0047] For example, the outer surface of the stator 2 is cylindrical and is screwed in a longitudinal direction parallel to the rotation axis of the rotor 3 into the cylindrical tube formed by the mass 4 of high thermal conductivity material.

[0048] For example, the stator 2 can be mounted in the mass 4 of high thermal conductivity material by interference fit. This provides good thermal conductivity between the two elements to effectively cool the stator 2. If necessary, an intermediate element can also be interposed to reduce the contact thermal resistance (for example, a thermal grease or an adhesive).

[0049] The volume of the mass 4 of high thermal conductivity material can be greater than or equal to (for example 1.5 to 3 times) the volume of the duct portion it houses. Therefore, the mass 4 can have a thermal inertia that facilitates effective cooling.

[0050] The cooling device and the stator 2 can be pre-assembled, and then the rotor can be mounted in the stator, and the assembly can be mounted in the housing 10 of the electric machine 1.

[0051] For example, the housing 10 comprises an access hole cover 8 which, in the open position, provides access to the stator 2, the rotor 3 and the cooling device. Preferably, the access hole is oriented in a longitudinal direction 11 parallel to the rotation axis of the rotor 3 and to the direction in which the assembly of stator 2, rotor 3 and cooling device is mounted in the housing 10.

[0052] As illustrated, the circulation duct 5 is connected to an inlet 6 and an outlet 7 which open into the wall of the housing 10. Preferably, the inlet 6 and the outlet 7 open into the wall of the housing 10 adjacent to the cover (this means that the inlet 6 and the outlet 7 do not open into the cover, making assembly and disassembly easier).

[0053] This means that the ends of the circulation duct 5 for supplying the cooling fluid (before circulation in the mass 4) and for returning the cooling fluid (after circulation in the mass 4) can be connected to the inlet and outlet at the housing 10 (for example by welding).

[0054] As illustrated, the circulation duct 5 can comprise curved ends 15 connected respectively to the cooling fluid inlet 6 and outlet 7.

[0055] As mentioned above, said inlet 6 and outlet 7 can be located on the same longitudinal side of the stator or opposite each other.

[0056] Moreover, preferably, when the cover 8 is in the open position, access holes are also provided to the curved ends 15 of the circulation duct 5 connected to the inlet 6 and to the outlet 7. This arrangement allows the curved ends 15 connected to the casing 10 to be removed and the assembly to be extracted from the casing 10. Conversely, this arrangement allows the assembly of the stator 2 and of the rotor 3 and of the cooling device and of the curved ends 15 of the circulation duct 5 to be introduced into the casing during assembly.

[0057] The above arrangement limits the risk of leakage of the cooling fluid inside the casing 10 of the electric machine 1.

[0058] In particular, the proposed structure eliminates or limits the number of welds that are at risk. For example, if appropriate, only one or a few welds can be provided between the ends of the circulation duct 5 and the casing 10, in positions that are easily accessible for maintenance.

[0059] As indicated above, the casing 10 is preferably hermetically closed and therefore the various fluid circuits connected to the outside of the casing pass through the casing in a sealed manner so as to ensure the sealing of the various circuits. Therefore, the inlet 6 and the outlet 7 of the duct pass through the casing 10 in a sealed manner.

Claims

1. An electric machine comprising a stator (2) and a rotor (3) arranged in a housing (10), the electric machine (1) comprising a cooling device arranged around the stator (2) and comprising a circuit for circulating a cooling fluid, the cooling device comprising a duct (5) for circulating the cooling fluid, a portion of the duct being embedded in a mass (4) of a high thermal conductivity material comparable to that of a metal, the mass (4) of high thermal conductivity material being overmoulded around the fluid circulation duct (5), the housing (10) delimiting a volume containing the stator (2), the rotor (3) and the cooling device, and the circulation duct (5) being connected to an inlet (6) and an outlet (7) opening onto a wall of the housing (10), the inlet (6) and the outlet (7) of the circulation duct (5) opening at the same longitudinal end of the mass (4) of high thermal conductivity material, the longitudinal direction of the mass (4) of high thermal conductivity material being parallel to the axis of rotation of the rotor in the assembled position, and the housing (10) comprising an access hatch (8) which, in the open position, provides an access to the stator (2), the rotor (3) and the cooling device along a longitudinal direction (11) parallel to the axis of rotation of the rotor (3) and to the mounting direction of the assembly of the stator (2), rotor (3) and cooling device in the housing (10), and the inlet (6) and the outlet (7) of the duct (5) opening onto a wall of the housing (10) independent of the access hatch (8).

2. The electrodynamic machine of claim 1, wherein, The electric machine is an electric motor for driving at least one compressor or circulator.

3. The electrodynamic machine of claim 1, wherein, The volume containing the stator (2), the rotor (3) and the cooling device, delimited by the housing (10), is airtight.

4. The electrodynamic machine of claim 1, wherein, The mass (4) of high thermal conductivity material is composed of aluminium.

5. The electrodynamic machine of claim 1, wherein, The duct (5) for circulating the cooling fluid is composed of a metal material.

6. The electrodynamic machine of claim 5, wherein, The metal material is a metal alloy.

7. The electrodynamic machine of claim 6, wherein, The metal alloy is a stainless steel alloy.

8. The electrodynamic machine of claim 4, wherein, The duct (5) for circulating the cooling fluid is composed of a metal material.

9. The electrodynamic machine of claim 8, wherein, The metal material is a metal alloy.

10. The electrodynamic machine of claim 1, wherein, The mass (4) of high thermal conductivity material has a cylindrical shape and the stator (2) is contained in said mass (4) and in contact with the cylindrical inner surface of the mass.

11. The electrodynamic machine of claim 4, wherein, The mass (4) of high thermal conductivity material has a cylindrical shape and the stator (2) is contained in said mass (4) and in contact with the cylindrical inner surface of the mass.

12. The electrodynamic machine of claim 5, wherein, The mass (4) of high thermal conductivity material has a cylindrical shape and the stator (2) is contained in said mass (4) and in contact with the cylindrical inner surface of the mass.

13. The electrodynamic machine of claim 1, wherein, The stator (2) is contained in the mass (4) of high thermal conductivity material by interference fit.

14. The electrodynamic machine of claim 4, wherein, The stator (2) is contained in the mass (4) of high thermal conductivity material by interference fit.

15. The electrodynamic machine of claim 5, wherein, The stator (2) is contained in the mass (4) of high thermal conductivity material by interference fit.

16. The electrodynamic machine of claim 10, wherein, The stator (2) is contained in the mass (4) of high thermal conductivity material by interference fit.

17. An electric machine comprising a stator (2) and a rotor (3) arranged in a housing (10), the electric machine (1) comprising a cooling device arranged around the stator (2) and comprising a circuit for circulation of a cooling fluid, the cooling device comprising a duct (5) for circulation of the cooling fluid, a portion of the duct being embedded in a mass (4) of a material of high thermal conductivity comparable to that of a metal alloy, the mass (4) of high thermal conductivity material being overmoulded around the fluid circulation duct (5), the housing (10) delimiting a volume containing the stator (2), the rotor (3) and the cooling device, and the circulation duct (5) being connected to an inlet (6) and an outlet (7) opening onto a wall of the housing (10), the inlet (6) and the outlet (7) of the circulation duct (5) opening at the same longitudinal end of the mass (4) of high thermal conductivity material, the longitudinal direction of the mass (4) of high thermal conductivity material being parallel to the axis of rotation of the rotor in the assembled position, and the housing (10) comprising an access cover (8) which, in the open position, provides an access to the stator (2), the rotor (3) and the cooling device along a longitudinal direction (11) parallel to the axis of rotation of the rotor (3) and to the direction of mounting of the assembly of stator (2), rotor (3) and cooling device in the housing (10), and the inlet (6) and the outlet (7) of the duct (5) opening onto a wall of the housing (10) independent of the access cover (8).

18. The electrodynamic machine of claim 17, wherein, The electric machine is an electric motor for driving at least one compressor or circulator.

19. The electrodynamic machine of claim 17, wherein, The volume containing the stator (2), the rotor (3) and the cooling device, delimited by the housing (10), is airtight.

20. The electrodynamic machine of claim 17, wherein, The mass (4) of high thermal conductivity material is composed of an aluminium alloy.

21. The electrodynamic machine of claim 17, wherein, The duct (5) for circulation of the cooling fluid is composed of a metal material.

22. The electrodynamic machine of claim 21, wherein, The metal material is a metal alloy.

23. The electrodynamic machine of claim 22, wherein, The metal alloy is a stainless steel alloy.

24. The electrodynamic machine of claim 20, wherein, The duct (5) for circulation of the cooling fluid is composed of a metal material.

25. The electrodynamic machine of claim 24, wherein, The metal material is a metal alloy.

26. The electrodynamic machine of claim 17, wherein, The mass (4) of high thermal conductivity material has a cylindrical shape and the stator (2) is contained in said mass (4) and in contact with the cylindrical inner surface of the mass.

27. The electrodynamic machine of claim 20, wherein, The mass (4) of high thermal conductivity material has a cylindrical shape and the stator (2) is contained in said mass (4) and in contact with the cylindrical inner surface of the mass.

28. The electrodynamic machine of claim 21, wherein, The mass (4) of high thermal conductivity material has a cylindrical shape and the stator (2) is contained in said mass (4) and in contact with the cylindrical inner surface of the mass.

29. The electrodynamic machine of claim 17, wherein, The stator (2) is contained in the mass (4) of high thermal conductivity material by interference fit.

30. The electrodynamic machine of claim 20, wherein, The stator (2) is contained in the mass (4) of high thermal conductivity material by interference fit.

31. The electrodynamic machine of claim 21, wherein, The stator (2) is contained in the mass (4) of high thermal conductivity material by interference fit.

32. The electrodynamic machine of claim 26, wherein, The stator (2) is contained in the mass (4) of high thermal conductivity material by interference fit.

33. The electrodynamic machine of any one of claims 1 to 32, wherein, The circulation duct (5) comprises end portions connected to the inlet (6) and to the outlet (7), respectively, the cover (8) in the open position also providing access holes to the end portions of the circulation duct (5) connected to the inlet (6) and to the outlet (7) so as to allow removal of the end portions connected to the casing (10) and extraction or introduction of the assembly of stator (2), rotor (3) and cooling device and of said end portions of the circulation duct (5) into the casing (10).

34. The electrodynamic machine of claim 33, wherein, The end portion is curved.

35. The electrodynamic machine of any one of claims 1 to 32, wherein, The casing (10) is hermetically closed.

36. The electrodynamic machine of claim 33, wherein, The casing (10) is hermetically closed.

37. The electrodynamic machine of any one of claims 1 to 32, wherein, A portion of the circulation duct (5) embedded in the mass (4) of high thermal conductivity material forms at least one of the following: a sawtooth portion, a spiral portion, a reciprocating section, a rectilinear segment, a curved segment.

38. The electrodynamic machine of claim 33, wherein, A portion of the circulation duct (5) embedded in the mass (4) of high thermal conductivity material forms at least one of the following: a sawtooth portion, a spiral portion, a reciprocating section, a rectilinear segment, a curved segment.

39. The electrodynamic machine of claim 35, wherein, A portion of the circulation duct (5) embedded in the mass (4) of high thermal conductivity material forms at least one of the following: a sawtooth portion, a spiral portion, a reciprocating section, a rectilinear segment, a curved segment.

40. A method for manufacturing an electric machine according to any one of claims 1 to 39, comprising a stator (2) and a rotor (3) arranged in a housing (10), and a cooling device comprising a duct (5) for circulating the cooling fluid, a portion of which is embedded in a mass (4) of high thermal conductivity material, wherein, The cooling device is pre-assembled with the stator (2) and is then introduced into the casing (10).

41. The method of claim 40, wherein, The electric machine is a motor.

42. The method of claim 40, wherein, The high thermal conductivity material is a metal.

43. The method of claim 40, wherein, The high thermal conductivity material is a metal alloy.

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