WO2023052115A1

WO2023052115A1 - Electric machine

Info

Publication number: WO2023052115A1
Application number: PCT/EP2022/075286
Authority: WO
Inventors: Martin Kuehnemund; Theresa Sophia BOETTINGER; Thomas Mueller
Original assignee: Robert Bosch Gmbh
Priority date: 2021-09-29
Filing date: 2022-09-12
Publication date: 2023-04-06
Also published as: DE102021210878A1

Abstract

The invention relates to an electric machine (10) comprising a system housing (12) and a stator housing (24), between which at least one cooling channel (28) runs for removing heat from the stator housing (24) of the electric machine (10). A cooling medium flows through the cooling channel, and the cooling medium enters the at least one cooling channel (28) at an inlet (14) and exits the cooling channel at an outlet (16). An inflow angle β (46) and an outflow angle γ (48) are selected on the basis of a spread angle α (44) between the inlet (14) and the outlet (16) of the at least one cooling channel (28), which has a variable height curve (72) when viewed in the axial direction (74), such that a total mass flow Ṁ (90) of the cooling medium is divided into a first sub-mass flow Ṁ1 (76) and a second sub-mass flow Ṁ2 (78). The invention additionally relates to the use of the electric machine (10) for driving an electrically driven passenger vehicle or a lightweight utility vehicle.

Description

title

electrical machine

technical field

The invention relates to an electrical machine with a system housing and a stator housing, between which runs at least one cooling channel for cooling the stator housing of the electrical machine and through which a cooling medium flows. This enters the at least one cooling channel at an inlet and leaves it at an exit point. Furthermore, the invention relates to the use of the electrical machine to drive an electrically powered passenger car or a light commercial vehicle.

State of the art

DE 10 2018 200365 A1 relates to a cooling unit for cooling an electrical machine with a cylindrical cooling jacket and a cooling channel formed in the cooling jacket. The cooling channel is formed on an outer surface of a cooling jacket.

DE 10 2018 008 209 A1 discloses an electrical machine with a housing and a casing concentrically enclosing the housing. An annular, essentially liquid-tightly sealed cooling jacket through which a coolant can flow is proposed. Viewed in the axial direction, this comprises coolant channels which are arranged next to one another and extend in the circumferential direction of the housing.

DE 10 2010 029 986 A1 relates to an electrical machine with a housing in which a stator and a rotor are arranged. The rotor is surrounded by the stator, wherein the housing comprises an outer shell and a spaced-apart from the stator-facing inner shell.

In electrical machines, the cooling medium flows into a cooling channel at an inlet socket and out again at an outlet socket opposite the inlet socket. In this way, the cooling water is routed around both sides of the electric machine. Interlocking ribs on an inner part of the stator housing and ribs designed to be complementary thereto on an outer part of a system housing ensure that the flow is influenced and the cooling effect is improved. The aim is to achieve the most uniform possible flow around the outer surface of the electrical machine.

Ideally, the inlet connection and the outlet connection are arranged offset from one another by 180° in order to achieve uniform cooling on both sides. However, due to limitations due to the installation space situation, customer requirements regarding the position of the outlet or due to venting measures, it is generally not possible to position the inlet and outlet connectors offset by essentially 180°. This leads to a hydraulic short circuit, which means that the cooling water flows from the inlet directly into the outlet and is no longer available for cooling the electric machine. As a result, the overall cooling capacity for the electric machine drops considerably. Furthermore, the basic contours of the system and stator housing are generally cylindrical in the axial direction - without considering cooling ribbing and cooling ribs. The height of the cooling channel is constant in the entire cooling area. Due to manufacturing tolerances that occur, however, the channel height between the stator housing and the system housing can vary greatly. This in turn leads to a high scattering of the cooling performance and is accompanied by pressure losses. If the height of the cooling channel is too low, the pressure losses and the cooling capacity increase significantly.

Presentation of the invention

According to the invention, an electrical machine is proposed with a system housing and a stator housing, between which at least one Cooling channel for cooling the stator housing of the electric machine runs and is flowed through by a cooling medium which enters the at least one cooling channel at an inlet and leaves it again at an outlet. Depending on the angle of spread a between the inlet and the outlet of the at least one cooling channel, which comprises a variable height profile when viewed in the axial direction, an inflow angle ß and an outlet angle y are selected in such a way that a total mass flow M of the cooling medium is divided into a first partial mass flow Mi and a second partial mass flow M2 is divided.

The selected inflow geometry or the selected inflow angle ensures that a hydraulic short circuit does not occur and, in particular, that a first partial mass flow Mi and a second partial mass flow M2 flow around the stator housing of the electric machine. The two partial mass flows are advantageously divided in such a way that the larger of the two partial mass flows, namely the first partial mass flow Mi, wets the larger wetting surface on the circumference of the stator housing, while the second partial mass flow M2 flows around the smaller wetting surface of the stator housing. The solution proposed according to the invention results in uniform, homogeneous cooling of the stator housing of the electrical machine when it is being cooled.

In a further development of the electrical machine proposed according to the invention, the inflow angle β and the outflow angle γ are differential angles, based on the ideal radial alignment. In a further advantageous embodiment of the electrical machine proposed according to the invention, the first partial mass flow is

wed

¹ = — M with 360° a = spread angle,

M = total mass flow of cooling medium.

Furthermore, the electric machine proposed according to the invention is designed in terms of its cooling in such a way that the second partial mass flow

is with a = angle of spread,

M = total mass flow of cooling medium.

Due to the two differently dimensioned partial mass flows Mi and M2, the total mass flow M of the cooling medium is divided along the circumference of the stator housing in such a way that homogeneous cooling, i. H. cooling of the electrical machine that extends uniformly over the circumference of the stator housing can be achieved. Due to its longer wetting path and its dimensioning, the first partial mass flow Mi dissipates a larger part of the waste heat of the electrical machine than the remaining, second partial mass flow M2, which is not only dimensioned smaller in terms of the flow volume of the cooling medium, but also flows over a smaller wetting surface of the stator housing.

The first partial mass flow Mi advantageously heats a first wetting surface of the stator housing, which is larger than a second wetting surface of the stator housing, which is heated by the second partial mass flow M2 of the cooling medium.

In the electrical machine proposed according to the invention, the entry angle β and the exit angle γ are in the range between −90° and +90°.

In an advantageous development of the electrical machine proposed according to the invention, an opening angle of a conicity of the at least one cooling channel is <5°. By manufacturing the at least one cooling channel with the specified taper, an excessive narrowing of the cooling channel and thus a pressure loss that occurs can be avoided in a simple manner in terms of manufacturing technology.

In an advantageous development of the electrical machine, the variable height profile of the at least one cooling channel runs from a transmission side of the stator housing to an electrical machine side of the stator housing. Accordingly, the at least one cooling duct has a minimum duct height on the transmission side, while a maximum duct height is implemented on the e-machine side of the stator housing. In the electrical machine proposed according to the invention, the stator housing is advantageously cooled by the first partial mass flow Mi and the second partial mass flow M2 of the cooling medium flowing around it in a homogeneous manner, with the first partial mass flow Mi and the second partial mass flow M2 of the cooling medium being the at least one Flow through cooling channel opposite to each other.

Furthermore, the invention relates to the use of the electric machine to drive an electrically powered passenger car or to drive a light, electrically powered commercial vehicle.

Advantages of the Invention

The solution proposed according to the invention makes it possible to achieve improved homogenization of the flow around the outer surface of the electric machine by appropriate adjustment of the inflow direction and outflow direction. The homogenization of the heat dissipation is also significantly supported by the fact that the at least one cooling duct, which is formed between the inside of the system housing and the outside of the stator housing of the electrical machine, essentially has a conical basic shape. This allows a significant reduction in sensitivity to be achieved, for example due to geometric tolerances. Furthermore, by implementing the solution proposed according to the invention, the positions of inlet connectors and outlet connectors can be implemented according to customer requirements. Since no additional components are required in the solution proposed according to the invention, cost savings can be achieved. For the appropriate positioning of the exit position in the customer's desired area, no additional components, such as tubing, are required in the solution proposed according to the invention; instead, the outlet nozzle is geometrically shifted according to customer requirements.

Furthermore, improved ventilation of the at least one cooling duct can be achieved by the solution proposed according to the invention, for example by skillful selection of the outlet position, which is typically carried out at the highest point, regardless of the position of the inlet. This allows Additional measures to ensure ventilation, for example in the form of a vent valve, are avoided.

The solution proposed according to the invention makes it possible to achieve an optimal distribution of the total mass flow M of the cooling medium in order to achieve a uniform cooling capacity and temperature distribution over the circumference of the stator housing.

The conical basic shape of the at least one cooling channel between the inside of the system housing and the outside of the stator housing significantly reduces the influence of manufacturing tolerances, in particular their effects on the cooling capacity.

Brief description of the drawings

Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

Show it:

Figures 1.1 and 1.2 A distribution of a flow of a cooling medium in a cooling channel whose inlet and outlet are offset by 180 °,

Figure 2.1 a hydraulic short circuit,

Figure 2.2 a cooling channel between the system housing and the stator housing of an electrical machine with a constant height,

FIG. 3 shows the representation of the spread angle a proposed according to the invention between the inlet and outlet of the cooling medium and the first and second partial mass flows Mi and M ₂ that occur,

FIG. 4 shows a section through the system housing of the electric machine and its stator housing as well as between them resulting, at least one cooling channel, which is manufactured in a conicity and

FIG. 5 shows the partial volume flows Mi and M2 that are set up along the circumference of the stator housing.

FIG. 1.1 shows an electrical machine 10 in whose system housing 12 there is an inlet 14 and an outlet 16 for a cooling medium which is arranged at a 180° offset 20 relative thereto. According to Figure 1.2, this results in a uniform volume flow distribution 18 or mass flow distribution 18 through both halves of the system housing 12.

FIG. 2.1 shows the occurrence of a hydraulic short circuit 32 with a corresponding positioning of the inlet 14 and the outlet 16 of the cooling medium relative to one another. According to FIG. 2.1, only a small partial mass flow of the cooling medium gets into the at least one cooling channel 28, which extends between a ribbing 22 of the system housing 12 and a ribbing 26 of the stator housing 24.

Figure 2.2 shows a section through the system housing and the stator housing of an electrical machine, which shows that the at least one cooling channel 28, which extends between the system housing 12 and the stator housing 24, has a constant height when viewed in the axial direction.

Embodiments of the invention

In the following description of the embodiments of the invention, the same or similar elements are denoted by the same reference symbols, with a repeated description of these elements being dispensed with in individual cases. The figures represent the subject matter of the invention only schematically. FIG. 3 shows a cross section through an electrical machine 10 which includes a system housing 12 which encloses a stator housing 24 . The cooling medium is fed into the at least one cooling channel 28 via the inlet 14 . This includes a connecting piece 52. The cooling system also includes a line 54 through which the cooling medium is supplied to the inlet 14.

The representation according to Figure 3 shows that the at least one cooling duct 28 between the system housing 12 and the stator housing 24 is formed on the one hand by ribbing 22 on the inside of the system housing 12 and on the other hand by the ribbing 26 on the outside of the stator housing 24. The cooling medium supplied to the inlet 14 via the connecting piece 52 circulates through the at least one cooling channel 28 formed in this way.

As can be seen from the representation according to FIG. In the illustration according to FIG. 3, the angle of spread a 44 is in the range between 90° and 100°. The angle of spread a 44 could also be smaller or larger than shown, depending on how the inlet 14 and the outlet 16 are to be positioned, which in turn is specified by the customer. In relation to an axis of symmetry 64 as shown in FIG. 3, reference numerals 50 indicate ideal radial alignments. The inlet 14 and the outlet 16 are positioned in relation to the ideal radial alignments 50 . In relation to the inlet 14, an inflow angle β 46 is shown. This is between −90° and +90° in relation to the ideal radial alignment 50. Similarly, the outlet 16 is oriented around the outflow angle y 48 in relation to the ideal radial alignment 50, as shown in FIG. Depending on the customer's requirements, depending on the spread angle a 44 between the inlet 14 and the outlet 16, corresponding inflow angles ß 46 and outflow angles y 48 can be realized.

It can be seen from FIG. 3 that the spread angle a 44 shown here, which is between 90° and 100°, results in different mass flows in relation to the cooling medium. Cooling medium flows in via at least one cooling channel 28 via the connecting piece 52 in the area of the inlet 14 . Behind the inlet 14, ie behind the connecting piece 52, the total mass flow M (cf. position 90 in FIG. 5) is divided within the at least one cooling channel 28 into a first partial mass flow Mi 76 and a second partial mass flow M2 78. The representation according to FIG. 3 shows that the first partial mass flow Mi 76 of the cooling medium wets a first wetting surface 40 in the circumferential direction and thus cools it. In contrast, the second partial mass flow M2 78 of the cooling medium flows in the opposite direction to the flow direction of the first partial mass flow Mi 76 within the at least one cooling channel 28. The two partial mass flows of the cooling medium Mi 76 and M2 78 flow to the outlet 16 and leave the at least one cooling channel at this point correspondingly heated 28 between the system housing 12 and the stator housing 24 of the electrical machine 10.

3 shows that the larger first partial mass flow Mi 76 heats a larger first wetting surface 40 in the circumferential direction compared to the second wetting surface 42 in the circumferential direction, which is cooled by the second partial mass flow M2 78 of the cooling medium. The inflow proposed according to the invention, given by the inflow angle β 46 or the outflow angle y 48, allows a targeted, optimal distribution of the two partial mass flows Mi 76 and M2 78 in relation to the circumferential surface of the stator housing 24 of the electrical machine 10 to be cooled.

The sectional view according to FIG. 4 shows that the stator housing 24 is surrounded by the system housing 12 of the electrical machine 10 . A stator 66 of the electrical machine 10 is arranged inside the stator housing 24 . A transmission side of both the system housing 12 and the stator housing 24 is identified by item 56 while an electric machine side 58 denotes the opposite end side of both the system housing 12 and the stator housing 24 of the electric machine 10 . The system housing 12 and the stator housing 24 are designed essentially symmetrically to an axis of symmetry 64 . A bearing 60 is shown in the stator housing 24, in which the rotor, not shown here, of the electric machine 10 is mounted on the electric machine side 58. On the opposite gear side 56, the in Figure 4 not shown rotor of the electrical machine 10 mounted in a bearing 62.

FIG. 4 shows that in the solution proposed according to the invention, the at least one cooling channel 28 extends in a conicity 68 between the stator housing 24 and the system housing 12 . The conicity 68 is given by the opening angle 70, which is <5°. The sectional view according to FIG. 4 shows that, seen in the axial direction 74 , starting from the transmission side 56 to the electric machine side 58 , the at least one cooling duct 28 widens continuously. While the conical height profile 72 in the axial direction 74 on the transmission side 56 is characterized by a minimum channel height 84 , viewed in the axial direction 74 this transitions from the minimum channel height 84 to the maximum channel height 82 on the electric machine side 58 . Due to the conicity 68 of the at least one cooling channel 28 proposed according to the invention, its sensitivity to manufacturing tolerances and pressure losses can be significantly reduced. The solution proposed according to the invention results in a variable channel height 80 seen in the axial direction 74 , which increases continuously starting from the transmission side 56 in the direction of the electric machine side 58 .

The illustration according to FIG. 5 shows that a total mass flow M 90 of the cooling medium enters the at least one cooling channel 28 between the system housing 12 and the stator housing 24 through the inlet 14 . Corresponding to the spread angle a 44, an inflow angle ß 46 is set on the side of the inlet 14 in relation to the ideal radial alignment 50, and an outflow angle y 48 on the side of the outlet 16, also in relation to the ideal radial alignment 50. In the illustration according to Analogous to the representation according to FIG. 3, FIG. 5 shows a spread angle a 44 which lies between 90° and 100°.

Corresponding to the distribution of the total mass flow M 90 of the cooling medium, it is divided into the first partial mass flow Mi 76 and the second partial mass flow M2 78 . Depending on the selected spread angle a 44, inflow angle ß 46 and outflow angle y 48, the partial mass flow is Mi 76

while the smaller, second partial mass flow M2 78

amounts to

The two partial mass flows of the cooling medium Mi 76 and M2 78 each sweep over the first wetting surface 40, which is larger than the second wetting surface 42 wetted by the second partial mass flow M2 78, viewed in the circumferential direction of the stator housing 24.

The solution proposed according to the invention makes it possible to achieve an even distribution of the flow of cooling water over both sides in the circumferential direction along the stator housing 24, regardless of the position of the inlet 14 and the outlet 16 and of the geometric tolerance position between the system housing 12 and the stator housing 24. This ensures that the stator housing 24 is heated evenly in order to bring about an optimal cooling effect. The solution proposed according to the invention makes it possible to dispense with the installation of additional components. Following the solution proposed according to the invention, a homogeneous temperature field is established, which is achieved by the two partial mass flows Mi 76 and M2 78, which flow in opposite directions to one another. In order to establish the desired ratio between the first partial mass flow Mi 76 and the second partial mass flow M2 78, the inflow angle β 46 and the outflow angle y 48 are specifically selected. Typical inflow angles β 46 and outflow angles γ 48 can be in the range of -90° and +90°, depending on the position of the inlet 14 and the outlet 16 .

The solution proposed according to the invention also takes into account geometric tolerances in relation to the mass flow distribution and thus to the cooling capacity. In the solution proposed according to the invention, the basic shape of the at least one cooling channel 28, which runs between the inside of the system housing 12 and the outside of the stator housing 24, is not cylindrical but conical. In this way, the cooling medium, in particular when the at least one cooling channel 28 is relatively small, can escape into the areas in which the conicity 68 means that the channel height is greater. Typical opening angles 70 in relation to the conicity 68 are in the range of <5° and can be different, for example Manufacturing technologies and processing of the system housing 12 and the stator housing 24 can be achieved.

The invention is not limited to the exemplary embodiments described here and the aspects highlighted therein. Rather, within the through the

Claims specified range, a variety of modifications possible, which are within the scope of professional action.

Claims

Expectations

1. Electrical machine (10) with a system housing (12) and a stator housing (24), between which runs at least one cooling duct (28) for cooling the stator housing (24) of the electrical machine (10) and through which a cooling medium flows, which enters the at least one cooling channel (28) at an inlet (14) and leaves it again at an outlet (16), characterized in that depending on the angle of spread a (44) between the inlet (14) and the outlet (16) of the cooling channel (28), which has a variable height profile (72) viewed in the axial direction (74), an inflow angle ß (46) and an outflow angle y (48) are selected in such a way that a total mass flow M (90) of the cooling medium flows into a first Partial mass flow Mi (76) and a second partial mass flow M2 (78) is divided.

2. Electrical machine (10) according to claim 1, characterized in that the inflow angle β (46) and the outflow angle γ (48) are differential angles, based on the ideal radial alignment (50).

3. Electrical machine (10) according to claims 1 and 2, characterized in that the first partial mass flow Mi (76)

Mi ¹ = — 360° M is ⁰ t with a = spread angle (44), M = total volume flow (90) cooling medium

4. Electrical machine (10) according to claims 1 and 2, characterized in that the second partial mass flow M2 (78)

is with a = angle of spread (46),

M = total volume flow (90) cooling medium Electrical machine (10) according to Claims 1 to 4, characterized in that the first partial mass flow Mi (76) heats a first wetting surface (40) of the stator housing (24), which is larger than a second wetting surface (42) of the stator housing (24), which is cooled by the second partial mass flow M2 (78). Electrical machine (10) according to Claims 1 to 5, characterized in that the entrance angle β (46) and the exit angle γ (48) are in the range between -90° and +90°. Electrical machine (10) according to Claims 1 to 6, characterized in that an opening angle (70) of a conicity (68) of the at least one cooling duct (28) is <5°. Electrical machine (10) according to Claims 1 to 7, characterized in that the variable height profile (72) of the at least one cooling duct (28), starting from a transmission side (56) to an electric machine side (58) of the stator housing (24) runs. Electrical machine (10) according to Claims 1 to 8, characterized in that there is a minimum channel height (84) on the transmission side (56) and a maximum channel height (82) on the electric machine side (58). Electrical machine (10) according to Claims 1 to 9, characterized in that the cooling of the stator housing (24) is homogenized by the first partial mass flow Mi (76) and the second partial mass flow M ₂ (78) of the cooling medium flowing around it. Electrical machine (10) according to Claims 1 to 10, characterized in that the first partial mass flow Mi (76) and the second partial mass flow M ₂ (78) of the cooling medium flow through the at least one cooling channel (28) in opposite directions to one another. - 15 - Use of the electrical machine (10) according to any one of claims 1 to 11 for driving an electrically powered passenger car or a light commercial vehicle.