Electric motor equipped with a housing for circulating a cooling fluid

Abstract

The invention relates to an electric motor (30) comprising: - a rotor (10) comprising: a shaft (12) rotatably mounted about an axis (X), a lamination stack (14) mounted coaxially on the shaft, the lamination stack comprising a plurality of internal cavities, a plurality of conductive bars (16) formed inside the internal cavities of the lamination stack, and at least two shorting rings (17, 19) coupled to the conductive bars (16); - a stator (36) surrounding the rotor (10); and - at least one housing (20) arranged between the stator (36) and the rotor (10), the housing being provided with at least one internal fluid circulation channel (22) inside which a cooling fluid can circulate, the internal fluid circulation channel opening at least at one through-hole (26) formed through the housing (20) onto the at least one shorting ring (17, 19).

Description

[0001] Electric motor equipped with a cooling fluid circulation box

[0002] The present invention relates to an asynchronous squirrel cage electric motor and relates more particularly to the cooling of a rotor equipping such a motor.

[0003] Electromagnetic induction motors, and in particular squirrel cage asynchronous motors, essentially comprise a static element or stator, comprising a stator winding, and a rotating element, i.e. a rotor which is mounted inside the stator on a rotating motor shaft.

[0004] The rotor normally comprises a plurality of longitudinal bars, made from an electrically conductive material, and a stack of magnetic laminations, made for example from rolled steel, which are assembled on the rotating shaft and have a plurality of longitudinal grooves. The conductive bars of the rotor are housed in the grooves and are coupled at their ends to two short-circuit rings by making a squirrel cage configuration.

[0005] In operation, the stator winding is connected to an alternating current power source. The alternating current in the stator produces a rotating magnetic field. The rotor's conductor bars carry a current induced by the stator's magnetic field and produce their own magnetic field. The interaction of the two magnetic field sources produces torque in the rotor.

[0006] As it rotates, the rotor heats up due to the induced currents flowing through the squirrel cage. This heating is particularly high at the short-circuit rings.

[0007] Rotor heating reduces the overall efficiency of the electric motor, as well as its available electrical power.

[0008] Current solutions to this problem involve spraying a coolant, such as oil, onto the hot parts of the rotor, particularly the short-circuit rings. However, this spraying is usually done in an untargeted manner. As a result, oil often penetrates the space between the rotor and the stator, called the "air gap." The presence of oil in this area causes undesirable disruptions in the operation of the motor.

[0009] The present invention aims to propose a solution which responds to the aforementioned problems.

[0010] To this end, the present invention relates to an electric motor comprising:

[0011] - a rotor comprising:

[0012] • a shaft mounted rotatably about an axis, • a pack of sheets mounted coaxially on the shaft, said pack of sheets comprising a plurality of internal cavities,

[0013] • a plurality of conductive bars formed inside the internal cavities of the sheet metal pack,

[0014] • at least one short-circuit ring coupled to the conductive bars,

[0015] - a stator surrounding the rotor, the electric motor further comprising at least one housing fixedly connected to the stator, said at least one housing being provided with at least one internal fluid circulation channel inside which a cooling fluid can circulate, said at least one internal fluid circulation channel opening at at least one through hole formed through said at least one housing on said at least one short-circuit ring.

[0016] Thus configured, the electric motor of the invention will make it possible to better evacuate the heat generated by the rotor, due to the passage of a cooling fluid inside the motor, said fluid being brought by an internal channel circulating inside a housing fixed on the stator. Furthermore, this internal channel opening directly onto one of the short-circuit rings, the risk of a flow of the cooling fluid into the air gap of the motor is greatly reduced.

[0017] The engine of the invention may also include one or more of the following characteristics:

[0018] - said at least one housing comprises a lower part and an upper part, said lower and upper parts being connected to each other, preferably by welding, said lower part being provided with at least one hollow zone, and said upper part completely covers said at least one hollow zone, such that said at least one internal fluid circulation channel is partially formed by said at least one hollow zone and by a portion of the upper part which covers said at least one hollow zone.

[0019] - the lower and upper parts are each provided with a central opening of circular shape, said central opening having a diameter greater than or equal to that of an end portion of the rotor shaft.

[0020] - the lower part has a central zone, of annular shape, and a peripheral zone, of annular shape, the central and peripheral zones being connected by at least one intermediate segment, oriented radially, and the upper part has a central zone, of annular shape, intended to come opposite the central zone of the lower part, and at least one radial branch intended to come opposite said at least one intermediate segment of the lower part.

[0021] - said at least one internal fluid circulation channel has a first section, extending between the at least one intermediate segment of the lower part and the at least one radial branch of the upper part, the first section opening into a second section, said second section forming an internal cavity between the central zone of the lower part and the central zone of the upper part.

[0022] - said at least one through hole is formed through the central area of ​​the lower part.

[0023] - said at least one through hole has a radial orientation.

[0024] - said at least one through hole has an axial orientation.

[0025] - the motor further comprises a two-part casing housing the stator and the rotor, said casing being provided with at least one fluid inlet channel and at least one fluid outlet channel, said at least one fluid inlet channel being in fluid communication with the at least one internal fluid circulation channel of said at least one housing and said at least one fluid outlet channel being configured to discharge the cooling fluid flowing by gravity from said at least one through-hole of said at least one housing.

[0026] - said at least one housing is provided with a plurality of through holes through which the cooling fluid circulating in the at least one internal fluid circulation channel can exit.

[0027] Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of a preferred embodiment thereof, given by way of non-limiting example, and made with reference to the appended drawings in which:

[0028] [Fig. 1] is an axial sectional view of an electric motor according to a first embodiment of the invention.

[0029] [Fig. 2] is a perspective view of the fluid circulation housing fitted to the engine of Figure 1.

[0030] [Fig. 3] is an exploded perspective view of the fluid circulation housing shown in Fig. 2.

[0031] [Fig. 4] is a perspective view of the engine of Fig. 1 with the housing and upper portion of the fluid circulation housing removed.

[0032] [Fig. 5] is an axial sectional view of an electric motor according to a second embodiment of the invention.

[0033] [Fig. 6] is a perspective view of the engine of Fig. 5 with the casing removed.

[0034] In the figures and in the rest of the description, the same references represent identical or similar elements. In addition, the different elements are not represented to scale so as to favor the clarity of the figures.

[0035] With reference to Figure 1, there is shown an electric motor according to a first embodiment of the invention. This electric motor 30 comprises in particular a two-part casing housing a rotor 10 integral in rotation with a rotor shaft 12 and an annular stator 36 which surrounds the rotor 10 coaxially with the rotor shaft 12. The casing consists in particular of a front bearing 32 and a rear bearing 34 connected to each other, for example by means of screws. The bearings 32, 34 are hollow in shape and each centrally carry a ball bearing respectively 33 and 35 for the rotational mounting of the rotor shaft 12. The rotor shaft 12 is rotatably mounted around an axis X.

[0036] Buns 37 project axially on either side of the stator lamination pack 36.

[0037] The rotor 10 comprises a body formed by a stack of laminations 14, for example, formed from a ferromagnetic material, in particular steel, the stack of laminations 14 being mounted coaxially on the rotor shaft 12. The stack of laminations 14 is formed from an axial stack of laminations which extend in a radial plane perpendicular to the axis of the rotor shaft 12. The rotor shaft 12 may for example be force-fitted inside a central opening of the stack of laminations 14 so as to connect the body of the rotor 10 to the rotor shaft 12 in rotation.

[0038] The sheet metal pack 14 comprises a plurality of internal cavities within which a plurality of longitudinal bars 16 are housed, each longitudinal bar being formed by adding a molten metal into said internal cavities. The longitudinal bars 16 are made of an electrically conductive material, such as copper or aluminum.

[0039] Each conductive bar 16 is coupled at each of its ends to a short-circuit ring, respectively a front short-circuit ring 17 and a rear short-circuit ring 19, the assembly formed by the conductive bars and the short-circuit rings forming a squirrel cage structure. The short-circuit rings 17 and 19 each have the shape of a disc extending in a radial plane perpendicular to the axis X of the rotor shaft 12. The short-circuit rings 17, 19 are also formed of an electrically conductive material, such as copper or aluminum. As mentioned previously, the conductive bars 16 and the short-circuit rings 17, 19 will thus be crossed by currents induced during the rotation of the rotor, which generates significant heating of the squirrel cage structure.

[0040] To mitigate this heating, the solution of the invention consists of spraying a cooling fluid, such as oil for example, onto the short-circuit rings so that the cooling fluid absorbs part of the heat released by the short-circuit rings. This cooling fluid can circulate inside the motor via two fluid circulation boxes 20 fixedly connected to the stator 36, as illustrated in FIG. 1. A first box 20 is arranged between the front bearing 32 and the rotor 10 and partially surrounds the front short-circuit ring 17. A second box 20 is arranged between the rear bearing 34 and the rotor 10 and partially surrounds the rear short-circuit ring 19.The cooling fluid may in particular be supplied from outside the electric motor via a first fluid inlet pipe 38a arranged at the outer periphery of the front bearing 32 and crossed by a first fluid inlet channel 24a. This first fluid inlet channel 24a opens, inside the casing, onto an internal fluid circulation channel 22 formed inside the first housing 20. Similarly, the cooling fluid may be supplied from outside the electric motor via a second fluid inlet pipe 38b arranged at the outer periphery of the front bearing 32 and crossed by a second fluid inlet channel 24b. This second fluid inlet channel 24b opens, inside the casing, onto an internal fluid circulation channel 22 formed inside the second housing 20.Each of the housings 20 is advantageously provided with one or more through holes 26 opening onto the short-circuit ring 17 or 19 which it partially surrounds, said through hole(s) 26 being in fluid communication with the internal channel 22. Thus, the cooling fluid circulating in the internal channel 22 can escape from the housing 20 from said through hole(s) 26 and fall by gravity or be projected under pressure onto said short-circuit ring 17 or 19. Once in contact with this short-circuit ring 17 or 19, it will absorb part of the heat released by the latter and, subsequently, it will flow by gravity into the lower part of the casing. It can then be evacuated outside the casing by means of a first outlet opening 25a and a second outlet opening 25b formed in the front bearing 32.

[0041] Referring to Figures 2 to 4, a possible embodiment of the housing 20 is shown. In this embodiment, the housing 20 is formed of a lower part 21 and an upper part 23, said lower and upper parts 21, 23 being connected to each other, preferably by welding. These lower and upper parts 21, 23 are each provided with a central opening 215, 235 of circular shape. These central openings 215, 235 have a diameter greater than or equal to that of an end 123 or 124 of the shaft 12 of the rotor 10.

[0042] The lower part 21 of the housing 20 has a central ring 211 and a peripheral ring 212, said rings 211, 212 being connected by three intermediate segments 213a, 213b, 213c, oriented radially and spaced at 120° from each other. The peripheral ring 212 may be fixed, by any conceivable means, to a peripheral wall of the stator 36. In addition, the peripheral ring 212 is provided with tabs 214 projecting from the lower edge of said peripheral ring 212 and intended to engage in corresponding hollow shapes of the stator 36, as shown in FIG. 3. These tabs 214 serve as an anti-rotation device for this peripheral ring. The central ring 211 is provided with a recessed area 216 comprising an annularly deformed inner section 216a and a series of three outer sections 216b forming annular portions extending radially outward from the inner section 216a.Each of the outer sections 216b is disposed between two adjacent intermediate segments 213a-213c of the housing 20 such that the outer sections 216b are spaced 120° apart from each other.

[0043] When the housing 20 is in its final assembled state, as illustrated in FIG. 2, the central ring 211 is covered by a central area 231 of the upper part 23. This central area 231 comprises an inner section 231a of annular shape and a series of three outer sections 231b forming annular portions extending radially outwards from the inner section 231a. The internal section 231a is arranged opposite the internal section 216a of the hollow zone 216 and the external sections 231b are arranged opposite the external sections 216b of the hollow zone 216, so that an internal cavity 222 is formed inside the housing 20. This internal cavity 222 is delimited, on the one hand, by the walls of the lower part 21 which surround the hollow zone 216 and, on the other hand, by the lower wall of the upper part 23.

[0044] Furthermore, one of the intermediate segments of the lower part 21 of the housing

[0045] 20 (the one bearing the reference 213a in Figure 3) is provided with two parallel ribs 218i, 218j oriented axially, which form a radially oriented hollow zone 219. This hollow zone 219 communicates with the hollow zone 216.

[0046] When the housing 20 is in its final assembled state, as illustrated in FIG. 2, the intermediate segment 213a is partially covered by a radial branch 232 of the upper part 23 which extends radially from the central zone 231. This radial branch 232 is arranged opposite the hollow zone 219, so that an internal cavity 221 is formed inside the housing 20, said internal cavity 221 communicating with the internal cavity 222. This internal cavity 221 is delimited, on the one hand, by the walls of the lower part

[0047] 21 which surround the hollow area 219 and, on the other hand, by the lower wall of the upper part 23.

[0048] Thus, as shown in Figure 2, when the upper part 23 is fixed on the lower part 21, an internal channel 22 is formed inside the housing 20, said internal channel 22 having a first section, corresponding to the aforementioned internal cavity 221, and a second section, corresponding to the aforementioned internal cavity 222. The first section 221 communicates fluidically with one of the fluid inlet channels 24a, 24b formed through one of the fluid inlet pipes 38a, 38b. Thus, a cooling fluid, supplied from said fluid inlet channel 24a or 24b, will be able to circulate inside the housing 20 through the internal channel 22. During its passage in the housing 20, this cooling fluid will be in contact with the external peripheral wall of the central ring 211.This external peripheral wall is provided with a series of through holes 26 opening, on one side, onto one of the external sections 216b of the hollow zone 216, as illustrated in FIG. 3, and, on the other side, onto one of the short-circuit rings 17, 19, as shown in FIG. 4. Thus, the cooling fluid can exit the housing 20 and come into contact with this short-circuit ring 17 or 19, and, subsequently, flow by gravity into the lower part of the casing.

[0049] It is advantageous for the outer peripheral wall of the central ring 211 to be arranged at a small distance in the radial direction from the short-circuit ring 17 or 19 so as to avoid excessive dispersion of the cooling fluid inside the casing which could cause the cooling fluid to penetrate into the air gap separating the stator from the rotor. This distance will preferably be between 0.5 mm and 10 mm.

[0050] Furthermore, it is advantageous for the outer peripheral wall of the central ring 211 to be axially aligned with the short-circuit ring 17 or 19 so as to properly direct the cooling fluid onto the inner peripheral surface of this short-circuit ring 17 or 19. For this purpose, the central ring 211 is axially offset towards the inside of the top zone of an end portion 213e of each of the intermediate segments 213a-213c, which, when the housing 20 is mounted in the motor 30, surrounds the coil ends 37 of the stator 36, as illustrated in FIG. 4.

[0051] In the configuration shown, the through holes 26 have a radial orientation.

[0052] It is however conceivable, in other configurations (not shown) of the invention, to provide for forming one or more through holes in the external peripheral wall of the central ring 211 such that it(they) has(have) an axial orientation and is arranged directly above one of the short-circuit rings 17, 19. The cooling fluid would flow from this(these) through hole(s) mainly under the effect of gravity.

[0053] The shape, size, distribution and number of through holes 26 may depend on several parameters, such as the dimensions of the engine, the cooling fluid used, or the material constituting the short-circuit rings.

[0054] Referring to Figures 5 and 6, there is shown an electric motor according to a second embodiment of the invention.

[0055] This second embodiment differs from the first embodiment described previously by the fact that only one fluid inlet channel 24 is provided in the casing. This fluid inlet channel 24 is formed through a fluid inlet pipe 38 arranged at the outer periphery of the front bearing 32. This fluid inlet channel 24 opens onto an opening 361 opening at the outer periphery of the stator 36, said opening 361 being in fluid communication with an axial channel 362 formed inside the stator 36. This axial channel 362 opens at a first opening 363a formed on the lateral face of the stator 36 which faces a first housing 20, partially surrounding the front short-circuit ring 17, and at a second opening 363b formed on the lateral face of the stator 36 which faces a second housing 20, partially surrounding the rear short-circuit ring 19.

[0056] The first and second housings 20 have substantially the same structure as that of the housing shown in Figures 2 and 3, except that the internal fluid circulation channel 22 of said housings 20 has, in addition to the first and second sections 221, 222, a third section 220, oriented axially, said third section 220 communicating fluidically with the first section 221 and opening onto the opening 363a in the case of the first housing 20 and onto the opening 363b in the case of the second housing 20. Thus, a cooling fluid, supplied from said fluid inlet channel 24, will first circulate in the axial channel 362, then inside the first and second housings 20 through the internal channel 22 formed in each of said housings 20.

[0057] The cooling fluid will be able to exit the housings 20 at the level of the one or more through holes 26 formed in the lower part 21 of the housings 20 and come into contact with the short-circuit ring 17 or 19. Subsequently, it will flow by gravity into the lower part of the casing, and will exit the casing at the level of the outlet channels 25a and 25b.

[0058] The invention is obviously not limited to the embodiment as described above. In particular, the invention may include certain modifications compared to this embodiment, provided that these modifications are covered by the set of claims provided below.

[0059] In other embodiments of the invention, it will thus be possible to envisage providing only a single housing 20, partially surrounding the front short-circuit ring 17 or the rear short-circuit ring 19. The cooling fluid circulating through this single housing 20 will therefore only cool one of the short-circuit rings 17, 19 of the rotor 10.

Claims

CLAIMS 1. Electric motor (30) comprising: - a rotor (10) comprising: • a shaft (12) mounted to rotate around an axis (X), • a pack of sheets (14) mounted coaxially on the shaft (12), said pack of sheets (14) comprising a plurality of internal cavities, • a plurality of conductive bars (16) formed inside the internal cavities of the sheet metal pack (14), • at least one short-circuit ring (17, 19) coupled to the conductive bars (16), - a stator (36) surrounding the rotor (10), characterized in that it further comprises at least one housing (20) fixedly connected to the stator (36), said at least one housing (20) being provided with at least one internal fluid circulation channel (22) inside which a cooling fluid can circulate, said at least one internal fluid circulation channel (22) opening at at least one through hole (26) formed through said at least one housing (20) on said at least one short-circuit ring (17, 19).

2. Electric motor (30) according to claim 1, characterized in that said at least one housing (20) comprises a lower part (21) and an upper part (23), said lower and upper parts (21, 23) being connected to each other, preferably by welding, said lower part (21) being provided with at least one hollow zone (216, 219), and in that said upper part (23) completely covers said at least one hollow zone (216, 219), such that said at least one internal fluid circulation channel (22) is partially formed by said at least one hollow zone (216, 219) and by a portion (231, 232) of the upper part (23) which covers said at least one hollow zone (216, 219).

3. Electric motor (30) according to claim 2, characterized in that the lower and upper parts (21, 23) are each provided with a central opening (215, 235) of circular shape, said central opening (215, 235) having a diameter greater than or equal to that of an end portion (123, 124) of the shaft (12) of the rotor (10).

4. Electric motor (30) according to claim 2 or 3, characterized in that the lower part (21) has a central zone (211), of annular shape, and a peripheral zone (212), of annular shape, the central and peripheral zones (211, 212) being connected by at least one intermediate segment (213a), oriented radially, and in that the upper part (23) has a central zone (231), of annular shape, intended to come opposite screws of the central zone (211) of the lower part (21), and at least one radial branch (232) intended to come opposite said at least one intermediate segment (213a) of the lower part (21).

5. Electric motor (30) according to claim 4, characterized in that said at least one internal fluid circulation channel (22) has a first section (221), extending between the at least one intermediate segment (213a) of the lower part (21) and the at least one radial branch (232) of the upper part (23), the first section (221) opening inside a second section (222), said second section (222) forming an internal cavity between the central zone (211) of the lower part (21) and the central zone (231) of the upper part (23).

6. Electric motor (30) according to claim 4 or 5, characterized in that said at least one through hole (26) is formed through the central area (211) of the lower part (21).

7. Electric motor (30) according to one of the preceding claims, characterized in that said at least one through hole (26) has a radial orientation.

8. Electric motor (30) according to one of claims 1 to 6, characterized in that said at least one through hole (26) has an axial orientation.

9. Electric motor (30) according to one of the preceding claims, characterized in that it further comprises a two-part casing (32, 34) housing the stator (36) and the rotor (10), said casing being provided with at least one fluid inlet channel (24, 24a, 24b) and at least one fluid outlet channel (25a, 25b), said at least one fluid inlet channel (24, 24a, 24b) being in fluid communication with the at least one internal fluid circulation channel (22) of said at least one housing (20) and said at least one fluid outlet channel (25a, 25b) being configured to discharge the cooling fluid flowing by gravity from said at least one through-hole (26) of said at least one housing (20).

10. Electric motor (30) according to one of the preceding claims, characterized in that said at least one housing (20) is provided with a plurality of through holes (26) through which the cooling fluid circulating in the at least one internal fluid circulation channel (22) can exit.

Images