Electric machine comprising a stator stack of metal sheets with cooling oil supply

Abstract

The invention relates to an electric machine having a machine housing; an annular stator stack, which comprises a plurality of metal sheets (1), each metal sheet (1) having, on the outer circumference thereof, a plurality of holding lugs (5), each of which defines an opening (4), the metal sheets (1) being stacked one on top of the other, and the openings (4) being aligned with one another in order to define a channel; and a securing element, which passes through the channel in order to secure the stator stack to the machine housing. The electric machine is characterized in that the stator stack is formed by sub-stacks, which form, by virtue of partly reduced circumferences, grooves (6) for cooling the outer casing of the stator, wherein the sub-stacks are installed so as to be axially rotated with respect to one another.

Description

[0001] Electric machine with a stator stack made of laminations with cooling oil supply

[0002] The invention relates to an electric machine with a machine housing, an annular stator stack comprising a plurality of laminations, each lamination comprising several retaining lugs located on its outer circumference, each defining an opening, the laminations being stacked on top of each other, the openings being aligned with each other to define a channel; a fastening element passing through the channel to fasten the stator stack to the machine housing.

[0003] State of the art

[0004] Rotating electrical machines are found in many industrial and product applications. Significant torsional forces can be transmitted to a stator, which in certain applications necessitates that the stator be properly secured and mechanically connected to a wall to prevent unwanted displacement and disruptive noise, vibration, and surface roughness.

[0005] According to DE 102021 110483 A1, an electric machine can include a substantially annular stator stack containing a plurality of laminations, each lamination having a circumferentially external projecting portion that defines an opening. The laminations are stacked adjacent to one another, with a larger portion of adjacent laminations with respective openings substantially aligned with each other to define a stator stack with a circular stator mounting projection, and with a first, smaller portion of adjacent laminations with respective openings substantially aligned with each other to define a first support stack with a first support mounting lug. The first support stack is located at one end of the

[0006] 2025P00008 WOStator stacks are stacked, with the round stator mounting projection and the bracket mounting lug being offset from each other at an angle. The laminations used are stamped from a metal strip.

[0007] Such a geometry, with mounting lugs protruding from the outer circumference, consumes more material, so the actual circumference increases due to the mounting lugs.

[0008] An optimized solution with an annular stator stack comprising a multitude of laminations, each lamination having multiple retaining lugs on its outer circumference, each defining an opening, the laminations being stacked on top of each other with the openings aligned to define a circular channel; a fastening element passing through the circular channel to secure the stator stack to the machine housing, the retaining lugs on the outer circumference being made of components manufactured separately from the laminations, is from the unpublished

[0009] DE 102024 131 509 is known.

[0010] In electric machines, it is common practice to cool the stator to dissipate waste heat generated during operation. Some systems incorporate cooling tubes within the stator, which are part of a cooling system and through which a heat transfer fluid flows. The cooling system may also include a pump to circulate the heat transfer fluid and a heat exchanger.

[0011] From EP 3989400 A1, a stator with a stator lamination stack and stator windings arranged therein is known, with cooling channels arranged entirely within and surrounded by the stator lamination stack. The cooling channels, stator winding slots, and recesses are produced by punching or cutting corresponding cutouts in the individual stator laminations. When the stator laminations are stacked on top of each other, the cooling channels are formed. If the stator laminations are not twisted during stacking, axially extending

[0012] 2025P00008 WO Cooling channels. If the stator laminations are slightly twisted against each other during stacking, the cooling channels will be tilted.

[0013] There are various concepts where the outer shell of the stator is directly flooded with oil to keep the operating temperature of the stator at an optimal level.

[0014] The following formula for convective heat transfer serves as a basis for designing the heat dissipation:

[0015] Q = h A (T2-TI)

[0016] q: Rate of heat transfer in watts

[0017] h: Heat transfer coefficient in watts / m² 2 * K

[0018] A: Coolant contact area in m² 2

[0019] T2-T1 temperature difference.

[0020] The linear influence of the coolant contact area A is limited by the geometric properties of the stator shell surface.

[0021] The object of the invention is to produce a stator made of stator laminations that has an optimized coolant contact surface but is simple in design.

[0022] Description of the invention

[0023] The problem is solved with an electric machine comprising a machine housing, an annular stator stack comprising a plurality of laminations, each lamination having several retaining lugs on its outer circumference, each defining an opening, the laminations being stacked on top of each other, the openings being aligned with each other to form a channel.

[0024] 2025P00008 WOdefine, and a fastening element passing through the channel to fasten the stator stack to the machine housing, characterized in that the stator stack is formed by sub-stacks which, by means of partially reduced circumferences, form grooves for cooling the outer shell of the stator, wherein the sub-stacks are installed twisted relative to each other.

[0025] The surface area of ​​the stator's outer shell can be approximately doubled by longitudinal grooves or slots, resulting in a significant improvement in heat dissipation.

[0026] Sub-stacks contain the same number of sheets to form grooves of equal length, or sub-stacks contain different numbers of sheets to form grooves of different lengths.

[0027] The outer shell of the stator is supplied via a distribution element, which distributes the oil evenly over the outer shell of the stator.

[0028] The distribution element extends along the longitudinal axis of the stator, and the oil flows out along the distribution element by gravity.

[0029] The problem is also solved by a method in which sheets are stamped as lamellae of the stator, whereby end lamellae and middle lamellae are produced, the middle lamellae having areas on the outer circumference with reduced diameter.

[0030] The middle lamellae are brought together to form sub-stacks, and another sub-stack is connected to the sub-stack by rotating the next middle lamellae around the longitudinal axis of the stator.

[0031] The rotation of the sub-stacks always aligns the retaining lugs.

[0032] 2025P00008 WO Description of the figures

[0033] Figure 1 shows a stator lamination with mounting lugs as end lamellae in a top view, Figure 2 shows a stator in a perspective view,

[0034] Figure 3 shows top and bottom views of a stator,

[0035] Figure 4 shows lamellae from the section planes BB and CC,

[0036] Figure 5 shows an oil flow to the stator,

[0037] Figures 6 to 8 show an alternative embodiment.

[0038] The sheets 1 are essentially ring-shaped and have an inner radius and an outer radius 1a. Figure 1 shows an end lamella 11 whose outer diameter 1a is constant around the circumference. The sheets 1 contain a plurality of teeth 2 extending radially from the inside to the outside. The material is low-carbon, high-silicon steel with structural and magnetic properties optimized for use in an electric machine. The sheets 1 are manufactured by a stamping press capable of processing rolled steel sheet material.

[0039] Each retaining lug 5 has a circular opening 4 which serves as a fastening element for receiving a retaining bolt or screw when mounting the sheets.

[0040] To increase the surface area of ​​the shell, ribs are used, as shown in Figure 2, which extend in the circumferential direction, the ribs being formed by stacks of sheets 1.

[0041] Figure 3 shows a central end lamella 11, i.e. a sheet metal that closes off the stator stack 20 at the end.

[0042] The end lamella 11 is surrounded by sections, with a longitudinal section on the right side containing further sections AA, BB, and CC. Section AA is the end lamella 11, while the other sections are shown in Figure 4. Section BB is shown on the left side. The

[0043] 2025P00008 WOOuter diameter 1a, which in this embodiment has a reduced diameter 1b in three positions.

[0044] The reduced diameter 1b is created directly during the stamping of the sheets. This results in a step 1c, which lies on the outer circumference between two retaining lugs 5.

[0045] The number of identical, stacked central lamellae12 forms the desired channel width or web width.

[0046] Only a single punching tool is required for the center lamellae, since a channel is formed by pivoting a lamella 120° around the X-axis, the longitudinal axis of the stator stack 20. To ensure that all lamellae can be attached, only the retaining lugs 5 need to be aligned with each other.

[0047] To achieve efficient cooling, a direct channel 14 is used to supply oil to the stator stack 20. The stator stack 20 is then geodesically supplied with oil from above. It is also possible to spray the oil onto the shell surface under pressure.

[0048] Channel 14 leads into a distribution element 16, which distributes the oil 15 evenly over the stator shell surface. The oil spreads through the slots 6 and thus over the entire shell of the stator stack 20. The distribution element 16 can be a simple tube with inlet and outlet openings.

[0049] In the embodiment shown in Figure 5, the entire axial length L of the stator stack 20 is regularly divided into a sequence of slots 6. By staggering the laminations in a first position relative to the longitudinal axis, a slot of length 11 is formed, and by stacking the laminations in a second position rotated axially relative to the first position, a slot of length 12 is formed.

[0050] The anisotropic magnetic properties of rolled steel used in sheet metal production are balanced by the number of smaller sub-stacks 21, which enable a rotating reorientation of these sub-stacks 21.

[0051] 2025P00008 WOIn Figures 6, 7 and 8, another solution is shown that does without an end lamella.

[0052] The stator stack 20 can be completed with a sub-stack 21, so that it is not necessary to use another tool for the stamping process, since then all sheets of the stator stack are manufactured identically.

[0053] 2025P00008 WO

Claims

8 Claims 1. Electric machine with a machine housing, an annular stator stack (20) comprising a plurality of laminations (1), each lamination (1) having several retaining lugs (5) on its outer circumference, each defining an opening (4), the laminations (1) being stacked on top of each other, the openings (4) being aligned with each other to define a channel for a fastening element, characterized in that the stator stack (20) is formed by sub-stacks (21) which form grooves (6) for cooling the outer shell of the stator through partially reduced diameters (1b), the sub-stacks (21) being installed axially rotated relative to each other.

2. Electric machine according to claim 1, characterized in that partial stacks (21) contain the same number of sheets (1) to form grooves (11, I2) of equal length.

3. Electric machine according to claim 1 or 2, characterized in that partial stacks (21) contain different numbers of sheets (1) to form grooves of different lengths (11, 12).

4. Electric machine according to one of the preceding claims, characterized in that the supply of the outer shell of the stator is carried out via a distribution element (16) which distributes the oil (15) evenly over the outer shell of the stator.

5. Electric machine according to claim 4, characterized in that the distribution element (16) extends along the longitudinal axis of the stator and the oil (15) escapes or is sprayed along the distribution element (16) by gravity. 2025P00008 WO9 6. Method for manufacturing the stator shell of an electric machine according to one of the preceding claims, wherein sheets (1) are stamped as lamellae of the stator having areas on the outer diameter (1a) with reduced diameter (1b).

7. Method for manufacturing the stator stack (20) of an electric machine according to claim 6, wherein sheets (1) are stamped as lamellae of the stator stack (20) wherein end lamellae (11) and middle lamellae (12) are manufactured, wherein the middle lamellae (12) have areas on the outer circumference (1a) with reduced circumference (1b).

8. Method according to claim 7, wherein central lamellae (12) or all lamellae are joined together to form partial stacks and a further partial stack (21) is connected on the partial stacks (21) by rotating the next central lamellae (12) about the longitudinal axis of the stator.

9. Method according to claim 7, wherein the rotation of the partial stacks (21) always brings the retaining lugs (5) into alignment. 2025P00008 WO

Images