Electric machine with cooling oil channels and method for producing a coolant flow

Abstract

Electric machine consisting of a stator and a rotor, wherein the rotor consists of a hollow shaft (1) and a rotor laminated core (2), wherein the rotor laminated core is press-fitted onto the hollow shaft (1), and wherein the hollow shaft (1) has radial shaft openings (4) at at least one axial position of the hollow shaft (1), wherein the rotor laminated core (2) comprises standard rotor laminations (7) and inlet laminations (9), and the inlet laminations (9) have radial cooling channels (6) which are connected to the radial shaft openings (4) of the hollow shaft (1).

Description

[0001] Electric machine with cooling oil lines and method for producing a coolant flow

[0002] The invention relates to an electric machine with a stator and a rotor, which is constructed from a rotor shaft with rotor laminations and has a cooling oil line inside the rotor shaft.

[0003] The invention also relates to a method for producing a coolant flow in a rotor with permanent magnets.

[0004] State of the art

[0005] DE 11 2018 003 438 T5 discloses an electric machine with a rotor that is perpendicular to the axial direction of a first inner wall surface of a magnet receiving opening in the circumferential direction. Each of the permanent magnets is housed in a magnet receiving opening, while a first gap is formed between a first outer wall surface and the first inner wall surface, and a third outer wall surface is directed radially outwards. The rotor core has a rotor core cooling opening that communicates with the first gap at a position on a radially inner side with respect to a central section of the first inner wall surface in the longitudinal direction. The rotor core has a radially outer refrigerant flow channel that communicates with a radially outer end section of the first gap.A first endplate has a connecting channel designed to extend from an inner end face of the first endplate to the rotor core cooling opening. A second endplate has an outlet channel designed to allow the radial-outer refrigerant flow channel to connect to an outer surface.

[0006] The cooling circuit runs through an inlet in the central rotor shaft and an end cap on the rotor shaft. The cooling flow is directed through the end cap of the rotor shaft.

[0007] 2024P00098WO direct contact with the permanent magnets both on their inner wall and in the outer wall of the room in one direction.

[0008] From CN 2021 102 80 145 A, a cooling structure of the internal oil circuit of a rotor in a machine casing arranged outside of a motor is disclosed, wherein end covers are arranged at two ends of the machine casing and a bearing for supporting a rotating hollow shaft is arranged between the end covers, wherein a rotor yoke section is arranged at the outer side end of the rotating hollow shaft, a radial flow channel of the rotor yoke section and an axial flow channel of the rotor yoke section are arranged within the rotor yoke section, and the radial flow channel of the rotor yoke section and the axial flow channel of the rotor yoke section each pass through the entire radial body and the entire axial body of the rotor yoke section;a permanent magnet is arranged on the rotor yoke part, one side of the hollow rotating shaft is provided with a hole, one side of the hole is provided with a bearing chamber, the outer wall of the bearing chamber is provided with an oil inlet and an oil outlet corresponding to the oil inlet is arranged at the bottom of the housing.

[0009] This means that the permanent magnets are cooled only by heat conduction to the rotor lamination.

[0010] From a cooling perspective, the rotor design follows the concept of coolant flowing axially into a hollow shaft. The coolant exits through radial holes in the shaft, located on both sides of the rotor lamination stack.

[0011] The object of the invention is to present a special rotor cooling system that does without end caps on the rotor lamination stack and provides direct cooling of the permanent magnets in their magnet pockets in the rotor laminations.

[0012] 2024P00098WO Description of the invention

[0013] The problem is solved with an electric machine consisting of a stator and a rotor, wherein the rotor consists of a hollow shaft and a rotor laminated core, wherein the rotor laminated core is pressed onto the hollow shaft, and wherein the hollow shaft has radial shaft openings at at least one axial position of the hollow shaft, wherein the rotor laminated core has standard rotor laminations as well as inlet laminations, and the inlet laminations have radial cooling channels which are connected to the radial shaft openings of the hollow shaft.

[0014] The radial cooling channels terminate at axial cooling channels that extend axially in the magnet pockets of permanent magnets to end-face outlets.

[0015] The axial cooling channels are designed as single channels or as twin or multiple channels.

[0016] The radial shaft openings are arranged at two positions, each at the end of the rotor lamination stack.

[0017] First radial wave openings convey the coolant from the inlet side to an outlet on the opposite side, and the second radial wave openings convey the coolant in the opposite direction to an outlet on the side of the coolant inlet.

[0018] The flow direction through the rotor sheet stack is opposite in adjacent sectors, which are assigned to the phases of the electrical machine.

[0019] The radial shaft openings are located in a single central position.

[0020] The radial shaft openings are in contact with the radial cooling channels, and the coolant flow is distributed in two flow directions in the inlet plate.

[0021] The inlet plates are either axially end-mounted or centrally located.

[0022] 2024P00098WO Rotor lamination package installed.

[0023] The problem is also solved by a method for producing a coolant flow in a rotor with permanent magnets which are received in magnet pockets, wherein the magnet pockets form axial cooling channels, wherein coolant is introduced via an inlet on one side of a hollow shaft of the rotor and is distributed in two flow directions via radial shaft openings and radial cooling channels and axial cooling channels which are formed in inlet plates of the rotor lamination stack.

[0024] By using specially designed finned plates that form cooling channels in the rotor assembly, coolant can be directed from the shaft to the rotor finned channels to cool the magnets. This is normally done with rotor end caps, which are not required in this invention.

[0025] Description of the characters

[0026] Figure 1 shows a first embodiment of a rotor,

[0027] Figure 2a and Figure 2b each show a section through a sheet of the sheet metal stack,

[0028] Figure 3 shows a bidirectional, alternating (left to right, right to left) scheme with terminal radial channels,

[0029] Figure 4 shows a second embodiment with a central radial channel for bidirectional coolant flow,

[0030] Figure 5 shows a third embodiment.

[0031] The following section shows various possible solutions, in particular coolant routing, using the example of an eight-pole rotor with a single-V magnet configuration and a hollow rotor shaft.

[0032] Figure 1 shows an electric machine 10, of which only the rotor is shown in the figure.

[0033] Figure 2 shows the rotor 2 having a hollow shaft 1 on which a rotor sheet stack is mounted.

[0034] 2024P00098WO 2 is pressed on. The rotor sheet metal package 2 is held only by friction and has no end caps.

[0035] The hollow shaft 1 has radial shaft openings 4, with the first radial shaft openings 4a shown on the right side of the figure and the second radial shaft openings 4b shown on the left side of the figure in the example shown in Figure 1. The first and second radial shaft openings 4a and 4b are each located axially at a position in the hollow shaft corresponding to the end region 12 of the rotor lamination stack 2. The rotor lamination stack 2 consists of a plurality of laminations 7 stacked axially. In the region of the end regions 12, inlet plates 9 are installed, forming a radial cooling oil line 6. Depending on the thickness of the laminations 7, only a few inlet plates 9 are used for this purpose.

[0036] The rotor lamination stack 2 contains so-called magnet pockets 8 in which permanent magnets 3 are inserted. In this embodiment, the permanent magnets 3 extend axially over the entire length of the rotor lamination stack 2.

[0037] In direct contact with the permanent magnets 3, an axial cooling oil line 5 extends from the inlet area of ​​the radial cooling oil line 6 to the defective end of the rotor sheet metal package 2.

[0038] The arrows indicate the direction of flow of the coolant, which will be explained in more detail later.

[0039] Figures 2a and 2b each show a section through an inlet plate 9. The inner ring is the wall of the hollow shaft 1, onto which the inlet plate 9 is pressed. The annular inlet plate 9 has, by way of example, 8 sectors 11, which are assigned to the respective poles of the electric machine. Figures 2a and 2b show, by way of example, two permanent magnets 3, which are arranged at a V-shaped angle to a radial axis. The two permanent magnets are installed in magnet pockets 8, which, in the case of Figure 2a, also form a common axial cooling channel 5. The radial cooling channel 6, which

[0040] The 2024P00098WO, which is fed via the radial shaft opening 4, leads into the common axial cooling channel 5.

[0041] Figure 2b shows an alternative embodiment in which the magnetic pockets 8 separately accommodate the two permanent magnets shown and each form its own cooling channel 5a and 5b. As a result, the radial cooling channel 6 has a different path and extends in a V-shape, deviating from its radial path, as channels 6a and 6b to the respective cooling channels 5a and 5b.

[0042] In the embodiment shown in Figure 1, the coolant enters the hollow shaft 1 on one side, in this case the right side of Figure 1, and is guided radially from the inner diameter to the outer diameter of the hollow shaft 1 via the radial bores 4a and 4b in the hollow shaft 1. At this point, the coolant enters the radial cooling channels 6 in the rotor lamination stack 2 and flows radially or quasi-radially outwards to the permanent magnets 3. There, the coolant is guided along the cooling channel 5 or the two twin cooling channels 5a, 5b.

[0043] Figure 3 schematically illustrates the cooling process, where, in the example of the eight-pole motor, coolant flows through four sectors 11 in a first radial direction and four sectors 11 in a second radial direction within the rotor. The coolant inlet is always located on one side of the hollow shaft 1, while the outlets are located at four positions on each end face of the rotor lamination stack 2. The two flow directions through the rotor lamination stack 2 alternate per sector 11, so that adjacent sectors 11 are always cooled in the opposite direction.

[0044] The double arrows indicate that this is the embodiment according to Figure 2a with the axial twin cooling channels 5a and 5b.

[0045] Flow direction 13 shows a path in which, near the coolant inlet to the hollow shaft 1, the radial cooling oil line 6 transports the coolant outwards to the cooling channel 5. The coolant then flows along the

[0046] 2024P00098WO Rotor lamination stack 2 and exits at the opposite end of the rotor lamination stack 2. The second coolant path has the same inlet on the hollow shaft 1, whereby the coolant runs in the hollow shaft to the end of the rotor lamination stack 2 furthest from the inlet, where it is guided to the outside via the radial cooling oil line 6 located there and begins its return path via the axial coolant line 5. Here, the coolant exits axially near the position where it was supplied.

[0047] At both ends of the rotor lamination stack, the coolant exits the rotor lamination stack and is flung by centrifugal forces onto the winding head of the stator (not shown).

[0048] Figure 4 shows a possible variant in which the special inlet plates 9, which form the cooling channels 6, are arranged in the center of the rotor stack. The coolant flows from the radial bores 4 in the hollow shaft 1 into the radial cooling channel 6 in the rotor lamination stack 2. As soon as the coolant reaches the axial cooling channel 5, the flow splits and flows in both axial directions to the end of the rotor lamination stack 2. The coolant exits the rotor lamination stack through outlets on the end face of the rotor lamination stack 2 and is sprayed radially onto both winding heads. In this example, the coolant flows axially into the magnet pockets, where it is in direct contact with the permanent magnets 3. In this embodiment, the inlet plates 9 are arranged only in the center.Furthermore, if an embodiment according to Figure 2b is chosen, a twin channel solution can be achieved in which the two twin channels 5a and 5b can be supplied with coolant in different directions.

[0049] Figure 5 shows another alternative embodiment in which more than two positions of the radial shaft openings 4 are used, namely at three

[0050] 2024P00098WO different positions. Here, inlet plates 9 are installed both at the end in the end area 12 on the rotor plate package 2 and in the middle.

[0051] The coolant flow to the permanent magnets 3 is achieved by integrating the cooling channels 5, 6 into the rotor lamination stack 2. This enables a design without end caps and a direct approach to magnet cooling directly at the permanent magnet 3. The elimination of two rotor end caps and the associated assembly process results in a cost advantage while providing efficient cooling of the lossy magnets directly in contact with the coolant.

[0052] Within the scope of the present invention, it is possible to divide the coolant flow in the rotor lamination stack 2 via a plurality of radial shaft openings as well as axial cooling channels 5 and radial cooling channels 6 in order to direct specific portions of the coolant to different locations in the rotor itself, to the permanent magnets 3, or to the winding head of the stator. Any desired routing of the radial cooling channels 6 and axial cooling channels 5 and any type of branching is possible.

[0053] Furthermore, the invention can be combined with any magnet configuration, e.g., single-V, double-V, spoke, split-V, etc. It is also possible to apply this cooling approach to inclined and non-inclined rotor designs.

[0054] To manufacture a rotor according to the invention and to implement different designs, the stamping system and the stamping tool must be able to stamp a certain number of special rotor laminations whose design as inlet laminations 9 differs from the standard rotor laminations 7.

[0055] All possible design options for representing cooling in the rotor sheet stack can be produced by stamping.

[0056] 2024P00098WO The fluid flow through the rotor affects the circulation losses and thus the efficiency, which is compensated for by an intelligent coolant flow control.

[0057] In all embodiments, it is essential to prevent large quantities of coolant from penetrating the air gap between the rotor and stator. The rotor as a whole must therefore be liquid-tight.

[0058] 2024P00098WQ Reference numeral list

[0059] 1 hollow shaft

[0060] 2 Rotor lamination package

[0061] 3 permanent magnets

[0062] 4 Radial shaft opening

[0063] 4a, 4b first and second radial shaft opening

[0064] 5 Axial cooling line

[0065] 5a, 5b axial twin cooling line

[0066] 6 radial cooling lines

[0067] 7 sheets

[0068] 8 magnetic pockets

[0069] 9 inlet plates

[0070] 10 Electric Machine

[0071] 11 Sector of the magnetic poles

[0072] 12 End range

[0073] 13 first flow direction

[0074] 14 second flow direction

[0075] 2024P00098WO

Claims

Claims 1. Electric machine comprising a stator and a rotor, wherein the rotor consists of a hollow shaft (1) and a rotor lamination stack (2), wherein the rotor lamination stack is pressed onto the hollow shaft (1), and wherein the hollow shaft (1) has radial shaft openings (4) at at least one axial position of the hollow shaft (1), characterized in that the rotor lamination stack (2) comprises standard rotor laminations (7) and inlet laminations (9), and the inlet laminations (9) have radial cooling channels (6) which are connected to the radial shaft openings (4) of the hollow shaft (1).

2. Electric machine according to claim 1, characterized in that the radial cooling channels (6) terminate at axial cooling channels (5) which extend axially in the magnet pockets (8) of permanent magnets (3) to end face outlets.

3. Electric machine according to claim 1 or 2, characterized in that the axial cooling channels (5) are designed as single or as twin channels (5a, 5b) or multiple channels.

4. Electric machine according to one of the preceding claims, characterized in that the radial shaft openings (4) are arranged as first shaft openings (4a) and as second shaft openings (4b) at two positions at the end region (12) on the rotor sheet metal package (2).

5. Electric machine according to claim 4 characterized in that first radial shaft openings (4a) convey the coolant from the inlet side to an outlet on the opposite side and the second radial shaft openings (4b) convey the coolant in the opposite direction to an outlet on the side of the coolant inlet. 2024P00098WO 6. Electric machine according to claim 5, characterized in that the flow direction (13, 14) through the rotor sheet stack (2) is opposite in adjacent sectors (11) which are assigned to the phases of the electric machine.

7. Electric machine according to one of claims 1-3, characterized in that the radial shaft openings (4) are located at a single central position.

8. Electric machine according to claim 7, characterized in that the radial shaft openings (4) are in contact with the radial cooling channels (6) and the coolant flow is distributed in two flow directions (13, 14) in the inlet plate (9).

9. Electric machine according to one of claims 1-3, characterized in that the inlet plates (9) are installed both axially at the ends and centrally in the rotor plate package (2).

10. Method for producing a coolant flow in a rotor with permanent magnets (3) which are received in magnet pockets (8), wherein the magnet pockets (3) form axial cooling channels (5), wherein coolant is introduced via an inlet on one side of a hollow shaft (1) of the rotor and is distributed in two flow directions (13, 14) via radial shaft openings (4) and radial cooling channels (6) and axial cooling channels (5) which are formed in inlet plates (9) of the rotor sheet stack (2). 2024P00098WO

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