Fluid system and method for supplying an electric machine and a transmission with a cooling fluid

Abstract

The invention relates to a fluid system (4) of an electric axle, which comprises an electric machine (2) and a transmission (3), with a fluid sump (5) from which both the electric machine (2) and the transmission (3) are supplied with a cooling fluid for cooling and / or lubricating purposes, wherein the electric machine (2) comprises a stator base body with stator slots which serve to partially accommodate a coil, wherein the stator slots additionally represent fluid channels which run from a first axial end to a second axial end of the stator base body. In order to improve the E-axis with regard to cooling and / or lubrication, the second axial end of the stator base body is fluidly connected to the gearbox (3) via a fluid return.

Description

[0001] The invention relates to a fluid system of an electric axle comprising an electric machine and a transmission, having a fluid sump from which both the electric machine and the transmission are supplied with a cooling fluid for cooling and / or lubrication. The electric machine comprises a stator base body with stator slots that serve to partially accommodate a coil, the stator slots additionally representing fluid channels that run from a first axial end to a second axial end of the stator base body. The invention further relates to a method for supplying an electric machine and a transmission with a cooling fluid in a fluid system as described above.

[0002] During active operation, electrical machines generate power losses and thus heat input. When cooling via natural convection is no longer sufficient, active cooling is required. This type of cooling can be achieved using a moving fluid, which in the case of an internal rotor, for example, is guided through a cooling jacket around the stator. New cooling methods focus on direct cooling in the stator to dissipate heat from the iron and conductor. Direct cooling, for example within the stator slot or at the winding overhang, therefore makes it possible to dissipate heat precisely where it is generated. This can lower the general temperature level in electrical machines and ensure a more homogeneous temperature distribution. This enables, for example, the use of cheaper and lighter materials.

[0003] Prior art is known from DE 10 2021 120 773 A1, in which an active component of an electrical machine is disclosed, comprising a cooling channel which, at least in sections, has a substantially axial extension which has a substantially constant cross-sectional area, wherein a reducing element protruding into the extension, which is designed to reduce the cross-sectional area in such a way that turbulences of the cooling fluid arise when a cooling fluid flows through it.

[0004] The object of the invention is to improve an electric axle comprising an electric machine and a transmission with regard to cooling and / or lubrication.

[0005] The object is achieved in a fluid system of an electric axle, which comprises an electric machine and a transmission, with a fluid sump from which both the electric machine and the transmission are supplied with a cooling fluid for cooling and / or lubricating, wherein the electric machine comprises a stator base body with stator slots that serve to partially accommodate a coil, wherein the stator slots additionally represent fluid channels that run from a first axial end to a second axial end of the stator base body, in that the second axial end of the stator base body is fluidly connected to the transmission via a fluid return line. The coil preferably comprises a winding head at both of its axial ends. The term axial refers to a rotor of the electric machine that is arranged in the stator of the electric machine so that it can rotate about an axis of rotation. Axial means in the direction of or parallel to this axis of rotation.The stator slots advantageously perform a dual function. Firstly, the stator slots serve to at least partially accommodate the coil. Furthermore, the stator slots serve to represent fluid channels through which the cooling fluid is specifically directed to cool the electric machine. The stator base body advantageously comprises a plurality of stator laminations. By using the existing stator slots as fluid channels, the manufacture of the stator base body with improved cooling is considerably simplified. The cooling fluid is preferably a hydraulic medium, such as oil. The cooling fluid serves both for cooling and for lubrication in the fluid system. The cooling fluid is sucked in from a fluid sump, for example, with the help of a pump. A heat exchanger is advantageously arranged between the fluid inlet and an outlet of the pump, with the help of which the fluid is cooled during operation.An electric axle is an electrically driven axle of a motor vehicle that includes at least one electric drive motor. In the fluid system described, the electric motor is first supplied with cooling fluid. This allows for optimal cooling of the electric motor. Only the cooling fluid exiting the electric motor is fed to the transmission via the fluid return line. The resulting series connection allows both the electric motor and the transmission to be adequately supplied with cooling fluid.

[0006] A preferred embodiment of the fluid system is characterized in that the fluid return comprises at least one return channel that runs through the stator base body. The associated increased manufacturing effort can be justified by the fact that no additional installation space is required for the fluid return.

[0007] Another preferred embodiment of the fluid system is characterized in that the fluid return runs axially through the stator base body. This simply ensures that the fluid is guided through the stator base body via the shortest possible path.

[0008] Another preferred embodiment of the fluid system is characterized in that the fluid return is arranged radially outside the stator slots in the stator base body. This has proven advantageous with regard to the stability and function of the stator base body.

[0009] Another preferred embodiment of the fluid system is characterized in that the fluid return comprises at least one return line that runs outside the stator slots. The return line runs, for example, along a stator back. The separate return line provides the advantage that the stator does not have to be modified to accommodate the fluid return.

[0010] A further preferred embodiment of the fluid system is characterized in that an annular chamber at the first axial end of the stator base body is surrounded by a capsule having a recess for fluid return. Thus, fluid return can be advantageously implemented without requiring additional installation space at the first axial end of the stator base body.

[0011] A further preferred embodiment of the fluid system is characterized in that the fluid return originates from an annular chamber at the second axial end of the stator base body. The annular chamber at the second axial end of the stator base body is advantageously enclosed by a capsule with a substantially U-shaped cross-section. A second winding head of the stator coil is advantageously arranged in this capsule. A first winding head is advantageously arranged in the annular chamber at the first axial end of the stator base body. The cooling fluid escaping from the stator slots collects in the annular chamber at the second axial end of the stator base body. From there, the cooling fluid reaches the gearbox via the fluid return.

[0012] A further preferred embodiment of the fluid system is characterized in that the fluid return runs above the stator slots relative to the line of action of the earth's gravity. In this area, the fluid return is arranged axially overlapping with the electric machine. There, the fluid return is advantageously located at the highest point of the fluid system. The fluid sump is located at the lowest point of the fluid system. The cooling fluid flows from the fluid return into the fluid sump via the gearbox due to gravity.

[0013] In a method for supplying an electric machine and a transmission with a cooling fluid in a previously described fluid system, the above-mentioned object is achieved alternatively or additionally by supplying the transmission with cooling fluid via the fluid return line in series after the electric machine. This accepts the perceived disadvantage of an undersupply of the transmission. Considerations and investigations conducted within the scope of the present invention have shown that the cooling of the electric machine can be effectively improved by the claimed fluid system without excessively impairing the supply to the transmission.

[0014] The invention further relates to a stator base body, an electric axle, an electric motor, a transmission, and / or a capsule for a fluid system described above. These parts are sold separately.

[0015] The invention may also relate to an electric axle with such a fluid system.

[0016] Further advantages, features, and details of the invention will become apparent from the following description, in which various embodiments are described in detail with reference to the drawings. They show: Fig. 1 a schematic representation of a fluid system for supplying an electric axle with a cooling fluid; Fig. 2 a perspective sectional view through an electric axle with an electric machine and a transmission, which are connected via a fluid system as shown in Fig. 1 is shown, supplied with cooling fluid; Fig. 3 a section through a stator base body of the electrical machine from Fig. 2 according to an embodiment with a return channel of a fluid return, which runs through the stator base body; Fig. 4 a perspective view of a capsule of the electric machine from Fig. 2 with a recess for passing through a return line of the fluid return; Fig. 5 a perspective view of a stator of the electric machine with the capsule of Fig. 4 and the gearbox of the electric axle Fig. 2; and Fig. 6 a similar representation as in Fig. 5 with a fluid return, which comprises a separate return line along a stator back of the stator, in a perspective and partially sectioned view.

[0017] In the Fig. Figure 2 shows an electric axle 1 with an electric motor 2 and a transmission 3, both in perspective and in longitudinal section. The electric motor 2 and the transmission 3 are supplied with a cooling fluid from a fluid sump 5 via a fluid system 4. The cooling fluid serves, on the one hand, to cool the electric motor 2. Furthermore, the cooling fluid serves to lubricate the transmission 3.

[0018] The cooling fluid is drawn from the fluid sump 5 by a pump 6. The cooling fluid is cooled in a heat exchanger 7 downstream of the pump 6. With the aid of the pump 6, the cooling fluid cooled in the heat exchanger 7 is conveyed into an annular chamber 8 provided at a first axial end 9 of a stator base body 10.

[0019] The stator base body 10 is part of a stator 11 of the electric machine 2. The electric machine 2 further comprises a rotor 12 which is arranged within the stator 11 so as to be rotatable about an axis of rotation.

[0020] The stator base body 10 comprises stator slots 13, which serve to partially accommodate a coil 14. The coil 14 has a winding head 15 at the first axial end 9 of the stator base body 10, which is arranged in the annular chamber 8. At a second axial end 17 of the stator base body 10, the coil 14 has a winding head 16.

[0021] The stator base body 10 is formed from a plurality of stator laminations. The stator base body 10 comprises a plurality of stator slots 13 that are evenly distributed over a circumference of the stator base body 10. The stator slots 13 serve, on the one hand, to partially accommodate the coil 14. Furthermore, the stator slots 13 serve to form fluid channels 18, 19. The stator slot 13 advantageously represents a fluid channel 18, 19 that extends axially through the stator base body 10.

[0022] The annular chamber 8 at the first axial end 9 of the stator base body 10 is enclosed by a capsule 20. The capsule 20 has a substantially U-shaped cross-section with a base 21 from which two legs 22, 23 are angled. An arrow in Fig. 2 the earth's gravity 24 is indicated.

[0023] The fluid sump 5 is located at the very bottom of the fluid system 4, relative to a line of action of the earth's gravity 24. The pump 6 with the heat exchanger 7 is located between the fluid sump 5 and the electric machine 2, relative to the line of action of the earth's gravity 24.

[0024] Fig. 2 shows the fluid system 4 of the Fig. 2 shown E-Axis 1 alone in the form of a fluid circuit diagram. The fluid circuit diagram in Fig. Figure 1 illustrates that first the groove-cooled electric machine 2 and only then the gearbox 3 are supplied with cooling fluid from the fluid sump 5. After the gearbox 3, the cooling fluid flows into the fluid sump 5. I

[0025] n Fig. 2, arrows illustrate how the cooling fluid from the fluid sump 5 is distributed within the fluid system 4 in the smallest possible space and with minimal manufacturing effort. The entire volume flow from the fluid sump 5 can be used in series for the electric machine 2 and the transmission 3. This improves the cooling of the electric machine 2.

[0026] In addition, you can see Fig. 2, the stator 11 of the electrical machine 2 is encapsulated by the stator base body 10 at its two axial ends 9 and 17. A capsule 59 at the second axial end 17 of the stator base body 10 is designed in the same way or similarly to the capsule 20 at the first axial end 9 of the stator base body 10. The capsule 59 comprises an annular chamber 58 in which the winding head 16 is arranged.

[0027] The cooling fluid is pumped from the fluid sump 5 by means of the pump 6 via the heat exchanger 7 into the annular chamber 8 at the first axial end 9 of the stator base body 10. From the annular chamber 8, the cooling fluid flows through the fluid channels 18, 19 formed by the stator slots 13 into the annular chamber 58 enclosed by the capsule 59 and containing the winding head 16.

[0028] Thanks to the encapsulation on both sides with the two capsules 20 and 59 at the axial ends of the stator base body 10, the electric machine 2 can be kept dry outside of the cooling system. This ideally prevents drag torques caused, for example, by cooling fluid in an air gap.

[0029] From the annular chamber 58 at the second axial end 17 of the stator base body 10, the cooling fluid is fed to the gearbox 3 via a fluid return line 50. From there, the cooling fluid returns to the fluid sump 5.

[0030] In Fig. 3 shows that the fluid return 50 comprises a return channel 52 that is directly incorporated into the stator base body 10. The stator base body 10 comprises, for example, a plurality of stator laminations, each of which has a through-hole for forming the return channel 52 in the stator base body 10.

[0031] In Fig. 5 shows that the fluid return 50 comprises a return line 53, which is guided from the return channel 52 in the stator base body 10 through a recess 55 in the capsule 20. In Fig. 4, the capsule 20 with the recess 55 for the return line 53 is shown in perspective.

[0032] In Fig.6 shows that the fluid return 50 can also include a return line 62, which extends separately from the stator base body 10 and from the annular chamber 58 past a stator back through the recess 55 of the capsule 20 to the transmission 3. The separate return line 62 is formed from a suitably stable material. List of reference symbols 1 electric axle 2 electric machine 3 gearboxes 4 Fluid system 5 Fluid sump 6 Pump 7 heat exchangers 8 annular chamber 9 axial end 10 stator base body 11 Stator 12 Rotor 13 stator slots 14 coil 15 winding head 16 winding head 17 axial end 18 Fluid channel 19 Fluid channel 20 capsules 21 Base 22 legs 23 legs 24 Earth's gravity 50 Fluid return 52 return channel 53 Return line 55 indentation 58 annular chamber 59 capsules 62 Return line QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 120 773 A1

[0003]

Claims

[1] Fluid system (4) of an electric axle (1) comprising an electric machine (2) and a transmission (3), with a fluid sump (5) from which both the electric machine (2) and the transmission (3) are supplied with a cooling fluid for cooling and / or lubricating purposes, wherein the electric machine (2) comprises a stator base body (10) with stator slots (13) which serve to partially accommodate a coil (14), wherein the stator slots (13) additionally represent fluid channels (18, 19) which run from a first axial end (9) to a second axial end (17) of the stator base body (10), characterized by that the second axial end (17) of the stator base body (10) is fluidly connected to the gear (3) via a fluid return (50). [2] Fluid system (4) according to claim 1, characterized by that the fluid return (50) comprises at least one return channel (52) which runs through the stator base body. [3] Fluid system (4) according to claim 2, characterized bythat the fluid return (50) runs in the axial direction through the stator base body (10). [4] Fluid system (4) according to one of the preceding claims, characterized by that the fluid return (50) is arranged radially outside the stator slots (13) in the stator base body (10). [5] Fluid system (4) according to one of the preceding claims, characterized by that the fluid return (50) comprises at least one return line (62) which runs outside the stator slots (13). [6] Fluid system (4) according to claim 5, characterized by that an annular chamber (8) at the first axial end (9) of the stator base body (10) is surrounded by a capsule (20) which has a recess (55) for the fluid return (50). [7] Fluid system (4) according to one of the preceding claims, characterized by that the fluid return (50) originates from an annular chamber (58) at the second axial end (17) of the stator base body (10). [8] Fluid system (4) according to one of the preceding claims, characterized by that the fluid return (50), relative to a line of action of the earth's gravity (24), runs above the stator slots (13). [9] Method for supplying an electric machine (2) and a transmission (3) with a cooling fluid in a fluid system (4) according to one of the preceding claims, characterized by that the transmission (3) is supplied with cooling fluid via the fluid return (50) in series after the electric machine (2). [10] Stator base body (10), electric axle (1), electric machine (2), transmission (3) and / or capsule (20) for a fluid system (4) according to one of claims 1 to 8.

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