ELECTRIC MACHINE WITH ROTOR COOLING

Description

[0001] The invention relates to an electrical machine with a stator and a rotor, wherein the rotor has rotor laminations mounted on a shaft, wherein the shaft comprises an oil channel, and the rotor laminations have channels parallel to the axis of the shaft and end plates at the ends, wherein the oil channel has transverse openings. State of the art

[0002] Permanent magnets containing rare earth elements are used in electric motors. If the permanent magnet gets too hot, there is a risk of demagnetization, which can cause irreparable damage to the electric motor. Therefore, cooling the electric motor is a crucial factor in hybrid vehicles, regardless of the specific installation method.

[0003] Thermal management is particularly problematic in 2.5-liter hybrid architectures. An example of such a transmission can be found in DE 10 2010 004 711 C5. Due to the special connection, higher speeds of the electric motor occur when driving at high vehicle speeds, which can easily last for minutes.

[0004] Due to the high losses that occur in the electrical machine, the temperature reaches a point where it becomes critical for the magnets.

[0005] Therefore, heat must be actively removed from the rotor laminations and the areas close to the magnet in order to be able to operate the electrical system for longer without limitations.

[0006] JP 2011 254 580 A shows an electric machine with a stator and rotor. A refrigerant flow path is provided along the rotor axis, with the coolant exiting the rotor shaft through openings and flowing through end plates to longitudinal channels in the rotor laminations.

[0007] JP 2009-118 686 A covers the features of the preamble of claim 1.

[0008] The cooling path located on the second level runs through the oil channel in the rotor shaft and a distribution port, as well as through a switching unit preloaded by a spring. If the spring keeps the distribution port open, coolant can flow into the channels of the rotor core. However, the oil flow in the two cooling paths is not parallel and always simultaneous. Rather, the two cooling paths are controlled so that either one or the other cooling oil path is active.

[0009] WO 2019 / 049 397 A1 shows a cooling system with a cooling channel that has a single supply via a connecting opening. The coolant is not spun off via a rotor shaft, but rather supplied by a pump specifically for the rotor channels. No oil is sprayed from a bore onto a shoulder due to centrifugal force.

[0010] JP 2019-30 051 A also provides for a redirection of an incoming coolant supplied by a pump. The coolant flows through a pocket-like structure, supplying a rotor channel with coolant.

[0011] JP 2018-191 363 A also provides only cooling for the rotor, with the rotor channels being supplied with coolant directly via a pump. A side plate of the rotor with grooves and openings serves for distribution.

[0012] JP 2009 118 686 A shows an electrical machine with a stator and rotor, wherein the rotor has rotor laminations mounted on a shaft, wherein the shaft comprises an oil duct, and wherein the rotor laminations have ducts parallel to the axis of the shaft and end plates at the ends of the rotor laminations, wherein the oil duct has transverse bores which are arranged on the front side of the electrical machine in axially spaced-apart planes and supply a first and a second cooling oil path, and a first plane of the planes runs within the thickness of an end plate designed as a balancing disk and a second plane outside the balancing disk in the region of winding heads of the stator, wherein the second cooling oil path runs via the oil duct and the transverse bores, wherein oil sprays out of the duct and the transverse bores.

[0013] WO 2020 / 217 075 A1 shows a balancing disc which has a cooling oil path on the front side, wherein the balancing disc is guided into the channels of the rotor core and the balancing disc has at least one circumferential shoulder in which openings or pockets to the channels in the rotor core are provided along the circumference of the shoulder, through which the oil impacting on the shoulder is guided axially to the rotor.

[0014] The object of the invention is to provide an electric machine with an improved cooling system that enables efficient cooling of the rotor while maintaining stator cooling. Description of the invention

[0015] The object is achieved with an electrical machine with stator and rotor, wherein the rotor has rotor laminations mounted on a shaft, wherein the shaft comprises an oil channel, and the rotor laminations have channels parallel to the axis of the shaft and end plates, wherein the oil channel has transverse openings which are arranged on the front side of the electrical machine in axially spaced planes.

[0016] The arrangement of the transverse openings creates axially offset oil jets that are thrown away from the shaft.

[0017] In order to cool both the stator and the rotor, a first level is provided within the thickness of a cover plate of the rotor core designed as a balancing plate on the front side of the electrical machine and a second level is provided outside the balancing plate in the area of ​​the winding heads of the stator.

[0018] The axially offset oil jets pass the balancing disc on the one hand and directly into an internal structure of the balancing disc on the other.

[0019] This creates a first cooling oil path that extends along the oil channel, through the cross holes on the front and back of the electrical machine, and the escaping cooling oil is thrown onto the winding heads.

[0020] The second cooling oil path is led via the oil channel, the cross holes on the front side, the balancing disc into the channels of the rotor core.

[0021] The balancing disc is designed in such a way that the balancing disc has at least one circumferential shoulder in which openings or pockets to the channels in the rotor core are provided along the circumference of the shoulder.

[0022] The shoulder has a depth of up to half the thickness of the balancing disc.

[0023] According to the invention, several steps are radially spaced from one another with staggered depths.

[0024] A balancing disc with several steps is suitable for guiding channels with different radial distances through the rotor core according to the steps and thus optimally dissipating heat in the vicinity of the permanent magnets. Description of the characters

[0025] Figure 1 shows an electrical machine in section, Figure 2 shows the same cross-sectional view with sketched oil guide, Figures 3 and 4 show a top view of the front of the electrical machine, Figure 5 shows a longitudinal section through a rotor balancing disc, Figure 6 shows a top view of the rotor core inside the stator.

[0026] The Figures 1-5 do not correspond to the invention, since they only show a shoulder (15) on which channels (5 are arranged. The Figure 6however, corresponds to the invention since it shows several shoulders (15) with channels (5,5a) arranged thereon with different radial distances (r1,r2).

[0027] In the Figures 1 and 2 1 shows a longitudinal section of an electrical machine 1. The electrical machine consists of two main components: a rotor 2 and a stator 3. The stator 3 has winding heads 4 on both sides. The rotor 2 is constructed from rotor lamination stacks 9 that are mounted on a shaft 8. The shaft 8 is guided from a housing (not shown) on the front side V of the electrical machine 1. Channels 5 that extend along the axis A are arranged within the rotor lamination stacks 9. The number of channels 5 is adapted to the cooling problem.

[0028] The channels 5 extend, for example, along a radius r at a uniform radial distance from one another, which does not correspond to the invention, or are distributed according to the invention along the circumference of different radii r1, r2.

[0029] The rotor lamination stack 9 is provided with a cover plate on both the front side V and the back side R, which covers the rotor lamination stack.

[0030] On the front side V, the cover disc is designed as a balancing disc 7 with a structure, on the back side R an unstructured cover disc 6 is provided.

[0031] In the shaft 8 of the rotor 2 there is a cooling channel 10 which extends from the front side V to the rear side R.

[0032] The shaft 8 has transverse bores 11 in a first plane E1 and transverse bores 12 in a second plane E2 axially spaced therefrom. On the rear side R of the electrical machine 1, transverse bores 11 are provided in a single plane E3.

[0033] In the plane E1, the oil sprays from the channel 10 through the transverse holes 11 and a free space onto the winding heads 4 due to the centrifugal force. In the plane E2, oil sprays from the channel 10 and the transverse holes 12 onto the structure formed on the balancing disk 7 and is guided via the structure into the channels 5 of the rotor laminations 9.

[0034] In the Figure 2The oil flow is shown by arrows. The cooling of the winding heads 4 takes place via the transverse bores 11, both on the front side V of the electrical machine and on the rear side R. The cooling oil is thrown out of the openings 11 and hits the winding heads 4 via the path 13. Since the transport of the oil depends on the rotational speed of the shaft 8 and on the amount of oil available, the cooling of the winding head 4 on the rear side R of the electrical machine is sometimes weaker because no more oil reaches it.

[0035] The newly introduced cooling oil path 14 also adequately cools the winding heads 4 on the rear side R of the electrical machine 1. The cooling oil path 14 initially extends radially from the transverse bore 12 of the shaft 8, encounters the structure of the balancing disk 7 (described in more detail below), is deflected, and guided along the channels 5 of the rotor laminations 9. This portion of the cooling oil exits the rear side R of the electrical machine 1 and is propelled toward the winding head 4 on the rear side of the electrical machine.

[0036] The permanent magnets not shown in the drawing are embedded in the rotor laminations 9 and are located close to the channels 5. The heat of the permanent magnets is dissipated by the cooling oil in the channels 5. The Figures 3 and 4 show a view of the front V of the electrical machine 1. A section through the Figure 3 The balancing disc 7 shown can be seen in Figure 5.

[0037] In the exemplary embodiment, the balancing disc 7 has a shoulder 15 in which the thickness D of the balancing disc is almost halved. This creates an edge approximately half the thickness of the balancing disc. The depth of the shoulder 15 is adapted to the specific design of the balancing disc and the cooling channels 5.

[0038] The balancing disc 7 also has axial recesses in the form of pockets 16 through which the oil impacting on the shoulder 15 is guided axially to the rotor 2 and then through the channels 5.

[0039] For optimized cooling of the electric machine, part of the oil quantity is collected by the balancing disc 7 and directed axially through the rotor 2. The remaining oil sprays through transverse openings 11 onto the winding heads and cools the stator.

[0040] Figure 6 shows the inventive solution, which is not limited to one type of channel.

[0041] The figure shows winding heads 4 arranged around the rotor cores 9. Permanent magnets 20 are installed in a typical arrangement within the rotor cores 9. One set of permanent magnets 20 is located along the outer circumference of the rotor cores 9, while additional permanent magnets are arranged in a V, alternating inward and outward. This creates installation spaces 21 and 22 in the interstices between two permanent magnets 20. Channels 5 are distributed along a circumference of the first radius r1 in the installation space 21. Additionally, channels 5a are provided along a circumference with radius r2, which in this example have a smaller inner diameter than channels 5.

[0042] A further advantageous arrangement uses channels arranged in the installation space 22 adjacent to three permanent magnets 20.

[0043] In order to ensure that all channels 5, 5a can be supplied with oil, the balancing disc is adapted accordingly according to the invention by means of further shoulders 15 and pockets 16 along the circumferences of the radii r1 and r2 etc.

Claims

1. Electric machine (1) with a stator (3) and rotor (2), wherein the rotor (2) has rotor laminated cores (9) mounted on a shaft (8), wherein the shaft (8) comprises an oil channel (10), and wherein the rotor laminated cores (9) have channels (5) parallel to the axis (A) of the shaft (8) and terminating discs (6, 7) at the ends of the rotor laminated cores (9), wherein the oil channel (10) has transverse bores (11, 12) which are arranged on a front side (V) of the electric machine (1) in axially spaced-apart planes (E1, E2) and which provide a supply to a first and a second cooling-oil path, and a first plane (E2) of the planes (E1, E2) extends within the thickness (D) of a terminating disc designed as a balancing disc (7) and a second plane (E1) extends outside the balancing disc (7) in the region of winding heads (4) of the stator (3), characterized in that the second cooling-oil path is routed into the channels (5) of the rotor laminated core (9) via the oil channel (10) and the transverse bores (12) on the front side (V), wherein oil sprays out of the channel (10) and the transverse bores (12), and via the balancing disc (7), and the balancing disc (7) has at least one encircling shoulder (15) in which provision is made along the circumference of the shoulder of apertures or pockets (16) to the channels (5) in the rotor laminated core, which direct the oil impinging on the shoulder (15) axially to the rotor (2), wherein provision is made of multiple shoulders (15) spaced apart radially from one another with staggered depths, and channels (5, 5a) with different radial spacings (r1, r2), corresponding to the shoulders (15), lead through the rotor laminated core (9).

2. Electric machine (1) according to Claim 1, characterized in that a first cooling-oil path extends along the oil channel (10) and through the transverse bores (11) of the front side (V) and of a rear side (R) of the electric machine, and the exiting cooling oil is centrifuged onto the winding heads (4).

3. Electric machine (1) according to Claim 1, characterized in that the shoulder (15) has a depth of up to half the thickness (D) of the balancing disc (7).