WO2021109980A1

WO2021109980A1 - Drivetrain system for an electrified vehicle and method of cooling the drivetrain system

Info

Publication number: WO2021109980A1
Application number: PCT/CN2020/133069
Authority: WO
Inventors: Yejin JIN; Kai Chen; Guoqiang Sun
Original assignee: Valeo Powertrain (shanghai) Co., Ltd.
Priority date: 2019-12-02
Filing date: 2020-12-01
Publication date: 2021-06-10
Also published as: JP2023504664A; EP4082099A4; CN112977046A; EP4082099A1

Abstract

Provided is a drivetrain system for an electrified vehicle. The drivetrain system comprises an electric motor (2) comprising a rotor and a stator; a power inverter (3) configured for supplying the stator with electric energy; a reducer (4) configured for receiving torque provided by the rotor and comprising a transmission shaft; the electric motor (2), the power inverter (3) and the reducer (4) are integrated as a drivetrain assembly (1). The drivetrain system further comprises: a cooling circuit (5) configured for being flowed through with coolant and distributing the coolant throughout the drivetrain assembly (1); the cooling circuit (5) comprising a cooling channel (33) arranged inside the power inverter (3), the cooling channel (33) comprising a coolant retaining section (35) for retaining the coolant from the cooling circuit (5), an inlet (31) for receiving the coolant and an outlet (32) for discharging the coolant. Also provided is a method of cooling the drivetrain system for an electrified vehicle.

Description

DRIVETRAIN SYSTEM FOR AN ELECTRIFIED VEHICLE AND METHOD OF COOLING THE DRIVETRAIN SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

This disclosure claims priority to Chinese Patent Application No. 201911213242.8, filed on December 02, 2019, the entirety of which is incorporated herein by reference as a part of this disclosure.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to a drivetrain system for an electrified vehicle and a method of cooling the drivetrain system.

BACKGROUND

The trend towards designing and building fuel efficient, low emission vehicles has increased dramatically, this trend driven by concerns over the environment as well as increasing fuel costs. At the forefront of this trend has been the development of electrified vehicles, such as BEV (Battery Electric Vehicle) , HEV (Hybrid Electric Vehicle) , PHEV (Plug-in Hybrid Electric Vehicle) , Range extended EV, FCEC (Fuel Cell Electric Vehicle) etc., electrified vehicles that combine a relatively efficient combustion engine with an electric drive motor. Electrified vehicles can include components, particularly the drivetrain system, that generate heat. Excessive heat build-up can cause performance degradation or damage to the components.

Therefore, it would be desirable if any improvements on cooling design for the drivetrain system for electrified vehicles could be provided at least with simple configuration, high efficiency and low cost.

SUMMARY

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In accordance with one aspect disclosed herein, a drivetrain system for an electrified vehicle is provided. The drivetrain system comprises an electric motor comprising a rotor and a stator; a power inverter configured for supplying the stator with electric energy; a reducer configured for receiving torque provided by the rotor and comprising a transmission shaft; the electric motor, the power inverter and the reducer are integrated as a drivetrain assembly. The drivetrain system further comprises: a cooling circuit connecting with the drivetrain assembly, configured for being flowed through with coolant and distributing the coolant throughout the drivetrain assembly; the cooling circuit comprising a cooling channel arranged inside the power inverter, the cooling channel comprising a coolant retaining section for retaining the coolant from the cooling circuit, an inlet for receiving the coolant and an outlet for discharging the coolant.

In one embodiment, the drivetrain system further comprises a mechanical pumping component connecting with the cooling circuit and driven by the transmission shaft for transferring the coolant to the cooling channel.

In one embodiment, the mechanical pumping component is positioned at the same side of the electric motor, or at the other side of the reducer than the electric motor.

In one embodiment, auxiliary heat transferring elements are provided within the cooling channel. The auxiliary heat transferring elements comprises at least one spikes, extruded walls or the combination thereof.

In one embodiment, a thermal mass is provided with the electric motor, the reducer or the both, the power inverter is mechanically mounted on the electric motor or the reducer or the both so as to benefit from the thermal mass to dissipate heat into therein through the cooling channel of the inverter and the coolant retained in the coolant retaining section and the auxiliary heat transferring elements in it increasing further heat transfer to the thermal mass.

In one embodiment, cooling fins are provided onto an outer surface of the electric motor, the reducer, or both of the electric motor and reducer, the power inverter is mechanically mounted on the electric motor or the reducer or the both so as to benefit from the cooling fins to dissipate heat into therein through the cooling channel and the coolant retained in the coolant retaining section and the auxiliary heat transferring elements in it increasing further heat transfer to the cooling fins.

In one embodiment, the cooling channel is configured as a loop forming along an inner circumference periphery of the power inverter, the inlet and the outlet are positioned at a top end of the cooling channel in a gravitational orientation.

In an alternatively embodiment, the cooling channel is configured as a serpentine-shaped channel within an accommodating space of the power inverter.

In an alternatively embodiment, the cooling channel is configured as a spiral-shaped channel within an accommodating space of the power inverter.

In an alternatively embodiment, the cooling channel is configured as a Z-shaped channel within an accommodating space of the power inverter.

In accordance with another aspect disclosed herein, a method of cooling a drivetrain system for an electrified vehicle comprising a drivetrain assembly integrated by an electric motor, a power inverter and a reducer is provided. The method comprises: providing a cooling circuit connecting with the drivetrain assembly and configured for being flowed through with coolant so as to distribute the coolant throughout the drivetrain assembly; and providing the cooling circuit with a cooling channel arranged inside the power inverter and further providing the cooling channel with a coolant retaining section so as to retain coolant therein.

In one embodiment, the method further comprises providing a mechanical pumping component connecting with the cooling circuit and driven by one transmission shaft of the drivetrain assembly for transferring the coolant to the cooling channel.

In one embodiment, the method further comprises providing auxiliary heat transferring elements within the cooling channel so as to promote the heat disposition from the power inverter. The auxiliary heat transferring elements comprising at least one spikes, extruded walls or the combination thereof.

In one embodiment, the method further comprises providing a thermal mass with the electric motor, the reducer or the both, wherein the power inverter is mechanically mounted on the electric motor or the reducer or the both so as to benefit from the thermal mass to dissipate heat into therein through the cooling channel of the inverter and the coolant retained in the coolant retaining section and the auxiliary heat transferring elements in it increasing further heat transfer to the thermal mass.

In one embodiment, the method further comprises providing cooling fins onto the outer surface of the electric motor, the reducer, or both of the electric motor and reducer, wherein the power inverter is mechanically mounted on the electric motor or the reducer or the both so as to benefit from the cooling fins to dissipate heat into therein through the cooling channel of the inverter and the coolant retained in the coolant retaining section and the auxiliary heat transferring elements in it increasing further heat transfer to the cooling fins.

In one embodiment, the method further comprises forming the cooling channel as a loop along an inner circumference periphery of the power inverter, positioning an inlet and an outlet of the cooling channel at a top end of the cooling channel in a gravitational orientation.

In an alternatively embodiment, the method further comprises forming the cooling channel as a serpentine-shaped channel within an accommodating space of the power inverter.

In an alternatively embodiment, the method further comprises forming the cooling channel as a spiral-shaped channel within an accommodating space of the power inverter.

In an alternatively embodiment, the method further comprises forming the cooling channel as a Z-shaped channel within an accommodating space of the power inverter.

These and other features, aspects, and advantages of the present disclosure will become better understood with reference to the following detailed description. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 is a schematic view of a drivetrain system in accordance with an exemplary aspect of the present disclosure;

FIG. 2 is a schematic view of a drivetrain system in accordance with another exemplary aspect of the present disclosure;

FIG. 3 is a schematic view of a power inverter of the drivetrain system in accordance with an exemplary aspect of the present disclosure;

FIG. 4 is a schematic view of one exemplary cooling channel of the power inverter shown in FIG. 3;

FIG. 5 is a schematic view of another exemplary cooling channel of the power inverter shown in FIG. 3;

FIG. 6 is a schematic view of another exemplary cooling channel of the power inverter of the present disclosure;

FIG. 7 is a schematic view of another exemplary cooling channel of the power inverter of the present disclosure;

FIG. 8 is a schematic view of another exemplary cooling channel of the power inverter of the present disclosure;

FIG. 9 shows a thermal mass and one exemplary power inverter with the cooling channel of FIG. 8;

FIG. 10 shows cooling fins and one exemplary power inverter comprising the cooling channel of FIG. 8;

FIG. 11 shows a thermal mass and another exemplary power inverter comprising the cooling channel of FIG. 8 with spikes; and

FIG. 12 is a flow diagram of a method of cooling a drivetrain system in accordance with an exemplary aspect of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made to in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “a” , “an” and “the” are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. The terms “comprising” , “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. The terms “first” and “second” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of individual components.

Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures, FIGs 1 to 2 show a

drivetrain system

101, 102 in accordance with embodiments of the present disclosure. More particularly, for the embodiment of FIG. 1, the drivetrain system 101 comprises a drivetrain assembly 1 which is generally integrated with a power inverter 3 (as shown in FIG. 3) , an electric motor 2 and a reducer 4. The drivetrain assembly 1 as shown is therefore a single unit.

The electric motor 2 can be a synchronous motor or an asynchronous motor. When it is a synchronous motor, it may include a wound rotor or a permanent magnet rotor. The nominal power supplied by the electric motor can be between 10 KW and 60KW, for example, of the order of 15 KW, for a nominal supply voltage of 48V to 350V, or up to 800V for higher power. In the case of an electric motor adapted to a high voltage supply, the nominal power supplied by this electric motor may be 60 KW. In the illustrated embodiment, the electric motor 2 is a synchronous motor with permanent magnets, providing a nominal power between 10 KW and 60 KW. The electric motor 2 can include a stator with a three-phase winding, or a combination of two three-phase windings or five-phase windings.

The reducer 4 is coupled to the electric motor 2. The reducer 4 can transform the electric motor’s high speed, low torque to low speed, high torque. The reducer 4 may comprise two or more gears, with one of the gears driven by the electric motor 2 for instance, for torque increase via speed reduction. The reducer 4 may further comprise a transmission shaft 41, i.e., an intermediate shaft, linking a driving gear driven by one transmission shaft of the electric motor (not shown) and another gear of larger diameter coupled to a driven mechanical load (not shown, e.g., vehicle wheel shafts) .

In the illustrated embodiments, the electric motor 2 and the reducer 4 are designed with high thermal capacity. The power inverter 3 (as shown in FIG. 3) is attached by the electrical wires to the electric motor 2 and mechanically to a wall of the electric motor 2 or to a wall of the reducer 4 or to both walls of the electric motor 2 and the reducer 4. The power inverter 3 converts the direct current ( “DC” ) supplied by an electrical energy storage unit (not shown) providing with the electric energy of a nominal voltage to the alternating current ( “AC” ) used to the electric motor 2. The power inverter 3 can be, without limitation, field effect transistors ( “FETs” ) , metal oxide semiconductor field effect transistors ( “MOSFETs” ) or insulated gate bipolar transistors ( “IGBTs” ) . In the case of a nominal supply voltage of 48V, the power inverter 3 can be MOSFET transistors. In the case of a supply voltage corresponding to a high voltage, the power inverter 3 can be IGBTs.

Referring to FIGs 1 to 2, the electric motor 2 is contained in a first housing 11, and the reducer 4 is contained in a second housing 12. The first housing 11 or the second housing 12 can be one-piece or be formed by the assembly of housing sub-parts together. The first housing 11 and the second housing 12 can be rigidly fixed together, for example by means of screws. A sealing wall is here provided between the first housing 11 and the second housing 12.

Cooling fins 91, 92 are provided for the heat dissipation towards the outside of the drivetrain assembly 1. The cooling fins 91, 92 are carried by the outer surface of the first and second housing 11, 12. These cooling fins 91, 92 are for example made in one piece with the first and second housing 11, 12. These cooling fins 91, 92 allow to increase the outer surface of the first and second housing 11, 12, and thus promote the heat dissipation to the outside of the drivetrain assembly 1 via the first and second housing 11, 12. The entire outer surface of the first housing 11 and the entire outer surface of the second housing 12 may carry cooling fins 91, 92. The cooling fins 91, 92 may be arranged in rows, and a pitch, constant or not, may exist between two adjacent rows. These rows may or may not all have the same orientation. Where appropriate, the same fins may extend firstly to the first housing 11 and secondly to the second housing 12.

For the embodiment depicted, a cooling circuit 5 being flowed through with coolant is provided for distributing the coolant throughout the drivetrain assembly 1. The coolant flowing in the cooling circuit 5 can be for example oil, water, or water based coolant.

Still in the illustrated embodiment, a mechanical pumping component 6 is provided within the cooling circuit 5. The mechanical pumping component 6 can be a gerotor pump which can promote a coolant flowing within the cooling circuit 5. Further, the mechanical pumping component 6 is in connection with the drivetrain assembly 1 and configured for transferring the coolant into the drivetrain assembly, particularly into the power inverter 3, via one section 51 provided by the cooling circuit 5, and recovering the coolant from the drivetrain assembly, particularly from the reducer 4 via another section 52 provided by the cooling circuit 5. The

sections

51, 52 are arranged outside of the drivetrain assembly 1. By use of the mechanical pumping component 6, specially by a gerotor pump, the transferred coolant flowing within the section 51 towards to the drivetrain assembly carries an increased and constant delivery volume and a high pressure. As shown in FIG. 1, the mechanical pumping component 6 is mechanically connected with one end of the transmission shaft 41 so that the mechanical pumping component 6 may be driven by the mechanical power from a rotary shaft. It can be understood that the mechanical power generated by the rotary shaft may be fully utilized and there is no need of an additional power source for driving a pump (e.g., using electric power for driving an electrical pump) positioned in the cooling circuit for transferring the coolant, which will cause less energy, less cost and smaller space by removing a dedicated motor.

Moreover, it should be appreciated, however, that the exemplary system 101 described herein is by way of example only. In some exemplary embodiments, the mechanical pumping component 6 can be mechanically connected with another end of the transmission shaft 41 (e.g., the exemplary system 102 as shown in FIG. 2) , depending on different assembly conditions and needs, so as to well used the rotation power of the shafts inside the drivetrain assembly 1.

Referring now to FIG. 3, FIG. 3 shows a power inverter 3 of the drivetrain system in accordance with one embodiment of the present disclosure. As shown in FIG. 3, a longitudinal orientation L corresponding to the axis of the power inverter 3, a transverse orientation T and a vertical orientation V corresponding to the gravitational orientation are provided. In the illustrated embodiment, a cooling channel 33 is provided by the cooling circuit 5. Further, the cooling channel 33 comprises an inlet 31 for receiving the coolant from the mechanical pumping component 6 and an outlet 32 for discharging the coolant. Moreover, the cooling channel 33 comprises a coolant retaining section 35 so that there would be coolant within the cooling channel whether the mechanical pumping component 6 is working or not. Accordingly, the cooling channel 33 can be always kept cooling by means of the coolant flowed or remained within the cooling channel 33 by the gravitational effect.

Specially, the cooling channel 33, as shown in FIGs 3 to 5, positioned within the radial surface of the power inverter 3 and formed along an inner circumference periphery of the power inverter is basically an annular loop. The inlet and

outlet

31, 32 are positioned at a top end provided with the cooling

channel

33, 331 in a gravitational orientation. The inlet and

outlet

31, 32 can be further arranged in a horizontal plane, or there can be slight height difference. Moreover,

coolant retaining section

35, 351 is formed in a lower portion of the cooling

channel

33, 331 along the gravitational orientation. Thanks to the high thermal weight of the reducer and/or the electric motor, and the remaining the coolant ensuring the heat transfer, the inverter can continue to be cooled down even if the mechanical pumping system is at stop or is working at very low flow.

During the operation of the mechanical pumping component 6, such as a gerotor pump, a constant volume of coolant will be transferred from the gerotor pump to the cooling

channel

33, 331 in the power converter 3. Particularly, the coolant enters the cooling channel via the inlet 31, flows through the cooling channel and exits the cooling channel via the outlet 32. The heat from the power inverter 3 is therefore dissipated by the flowing of the coolant. Once the rotary shaft, i.e., the transmission shaft 41 with which the gerotor pump 6 is mechanically in connection, is in a stop state, there will be coolant remains in the

coolant retaining section

35, 351 of the cooling

channel

33, 331 so that the power converter 3 can be kept cooling by the remained coolant by absorbing heat in itself and transferring the heat to the thermal mass.

Referring now to FIGs 4 and 5, these figures show different

exemplary cooling channels

33, 331. Auxiliary heat transferring elements are provided within the cooling

channel

33, 331 so as to provide additional heat dissipation to the high thermal capacity components, i.e., the reducer and the electrical motor, for example in the circumstances that the gerotor pump operates in a low speed or a rest state. As illustrated in the embodiments, the auxiliary heat transferring elements can be several metallic spikes 34 as shown in FIG. 5, or extruded walls 341 as shown in FIG. 6, or the combination of spikes 34 and extruded walls 341. The auxiliary heat transferring elements are made of thermal material, for example aluminum.

Referring now to FIG. 6, another exemplary cooling channel 332 is shown. The cooling channel 332 is designed as a spiral shape. An inlet 312 is provided at the central of the shape and an outlet 322 is provided at the outer edge of the shape. A coolant retaining section 352 is formed between the inlet 312 and outlet 322.

Referring now to FIG. 7, another exemplary cooling channel 333 is shown. The cooling channel 333 is designed as a serpentine shape. An inlet 313 is provided at a bottom section of the shape and an outlet 323 is provided at a top section of the shape. A coolant retaining section 353 is formed between the inlet 313 and outlet 323.

Referring now to FIG. 8, another exemplary cooling channel 334 is shown. The cooling channel 334 is designed as a Z shape in a radial plane. Both an inlet 314 and an outlet 324 are provided at a top section of the shape. A coolant retaining section 354 is formed at a bottom section of the shape.

It should be appreciated, however, that the

exemplary cooling channels

33, 331, 332, 333, 334 described herein is by way of example only. Rather than these shapes as illustrated herein, other shapes of cooling channel that are possible to keep coolant therein so as to have minimum air inside when the coolant pump has very low flow rate should be included.

Referring now to FIGs 9 and 10, the power inverter 3 containing the cooling channel, for example, the exemplary cooling channel 334 as shown in FIG. 8, can be in contact with a big thermal mass, such as the electric motor 2, or the reducer 4, or both of the electric motor 2 and the reducer 4. Alternatively, the exemplary cooling channel 334 can be in contact with the cooling fins 91, 92 arranged onto the outer surface of the electric motor 2, or the reducer 4, or both of the electric motor 2 and the reducer 4. With the configuration, the remaining coolant in the cooling channel 334 can ensure the heat transferring from the power inverter 3, further, the heat from the power inverter 3 can be further dissipated by the big thermal mass or the cooling fins.

Referring now to FIG. 11, several auxiliary cooling elements, such as spikes 34, are provided with the cooling channel like the exemplary Z-shaped cooling channel 334 for additional heat dissipation to the big thermal mass (as shown) or to the cooling fins. The distance d between the spikes and surface of the cooling channel towards to the thermal mass or the cooling fins shall be minimized, so that there would be increased heat dissipation area and higher heat conducting efficiency.

Referring now to FIG. 12, a flow diagram is provided of an exemplary method 200 of cooling a drivetrain system in accordance with an exemplary aspect of the present disclosure. For example, the exemplary method 200 may be used to cool the

exemplary drivetrain system

101, 102 described above with reference to FIGs 1 through 2.

The exemplary method 200 includes step 201 of providing a cooling circuit connecting with the drivetrain assembly and configured for being flowed through with coolant so as to distribute the coolant throughout the drivetrain assembly. The drivetrain assembly is integrated with an electric motor, a power inverter and a reducer.

The exemplary method 200 additionally includes step 202 of providing the cooling circuit with a cooling channel arranged inside the power inverter and further providing the cooling channel with a coolant retaining section allowing to maintain heat dissipation to the thermal mass like motor and/or reducer, or to the cooling fins provided by the outer surface of motor and/or reducer, so as to remove heat from the power inverter.

Subsequently, the exemplary method 200 includes step 203 of providing at least one spikes, extruded walls or the combination thereof within the cooling channel so as to promote the heat dissipation from the power inverter.

Moreover, the exemplary method 200 includes step 204 of forming the cooling channel as a loop along an inner circumference periphery of the power inverter, and positioning an inlet and an outlet of the cooling channel at a top end of the cooling channel in a gravitational orientation; or forming the cooling channel as a serpentine-shaped channel, a spiral-shaped channel or a Z-shaped channel within an accommodating space of the power inverter. The shapes of the cooling channel and the positons of the inlet and outlet of the cooling channel help to form the coolant retaining section within the cooling channel.

Furthermore, the exemplary method 200 includes step 205 of providing a mechanical pumping component connecting with the cooling circuit and driven by one transmission shaft of the drivetrain assembly. The transmission shaft can be a rotary shaft driving the electric motor or the reducer.

This written description uses examples to disclose the embodiments of the present disclosure, including the best mode, and also to enable any person skilled in the art to practice embodiments of the present disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the embodiments described herein is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

A drivetrain system for an electrified vehicle, comprising:

an electric motor comprising a rotor and a stator;

a power inverter configured for supplying the stator with electric energy;

a reducer configured for receiving torque provided by the rotor and comprising a transmission shaft;

the electric motor, the power inverter and the reducer are integrated as a drivetrain assembly;

the drivetrain system further comprising:

a cooling circuit configured for being flowed through with coolant and distributing the coolant throughout the drivetrain assembly, the cooling circuit comprising a cooling channel arranged inside the power inverter, the cooling channel comprising a coolant retaining section for retaining the coolant from the cooling circuit, an inlet for receiving the coolant and an outlet for discharging the coolant.
The drivetrain system of claim 1, further comprising a mechanical pumping component connecting with the cooling circuit and driven by the transmission shaft for transferring the coolant to the cooling channel.
The drivetrain system of claim 1 or 2, wherein auxiliary heat transferring elements are provided within the cooling channel, the auxiliary heat transferring elements comprising at least one spikes, extruded walls or the combination thereof.
The drivetrain system of claim 3, wherein a thermal mass is provided with the electric motor, the reducer or the both, the power inverter is mechanically mounted on the electric motor or the reducer or the both so as to benefit from the thermal mass to dissipate heat into therein through the cooling channel and the coolant retained in the coolant retaining section and the auxiliary heat transferring elements in it increasing further heat transfer to the thermal mass.
The drivetrain system of claim 3, wherein cooling fins are provided onto an outer surface of the electric motor, the reducer, or both of the electric motor and reducer, the power inverter is mechanically mounted on the electric motor or the reducer or the both so as to benefit from the cooling fins to dissipate heat into therein through the cooling channel and the coolant retained in the coolant retaining section and the auxiliary heat transferring elements in it increasing further heat transfer to the cooling fins.
The drivetrain system of claim 1, wherein the cooling channel is configured as a loop forming along an inner circumference periphery of the power inverter, the inlet and the outlet are positioned at a top end of the cooling channel in a gravitational orientation.
The drivetrain system of claim 1, wherein the cooling channel is configured as a spiral-shaped channel, a serpentine-shaped channel, or a Z shaped channel within an accommodating space of the power inverter.
A method of cooling a drivetrain system for an electrified vehicle comprising a drivetrain assembly integrated by an electric motor, a power inverter and a reducer, the method comprising:

providing a cooling circuit configured for being flowed through with coolant so as to distribute the coolant throughout the drivetrain assembly; and providing the cooling circuit with a cooling channel arranged inside the power inverter and further providing the cooling channel with a coolant retaining section so as to retain coolant therein.
The method of claim 8, further comprising:

providing a mechanical pumping component connecting with the cooling circuit and driven by one transmission shaft of the drivetrain assembly for transferring the coolant to the cooling channel.
The method of claim 8 or 9, further comprising:

providing auxiliary heat transferring elements within the cooling channel so as to promote the heat disposition from the power inverter, the auxiliary heat transferring elements comprising at least one spikes, extruded walls or the combination thereof.
The method of claim 10, further comprising:

providing a thermal mass with the electric motor, the reducer or the both, wherein the power inverter is mechanically mounted on the electric motor or the reducer or the both so as to benefit from the thermal mass to dissipate heat into therein through the cooling channel of the inverter and the coolant retained in the coolant retaining section and the auxiliary heat transferring elements in it increasing further heat transfer to the thermal mass.
The method of claim 10, further comprising:

providing cooling fins onto the outer surface of the electric motor, the reducer, or both of the electric motor and reducer, wherein the power inverter is mechanically mounted on the electric motor or the reducer or the both so as to benefit from the cooling fins to dissipate heat into therein through the cooling channel of the inverter and the coolant retained in the coolant retaining section and the auxiliary heat transferring elements in it increasing further heat transfer to the cooling fins.
The method of claim 8, further comprising:

forming the cooling channel as a loop along an inner circumference periphery of the power inverter; and

positioning an inlet and an outlet of the cooling channel at a top end of the cooling channel in a gravitational orientation.
The method of claim 8, further comprising:

forming the cooling channel as a serpentine-shaped channel, a spiral-shaped channel or a Z-shaped channel within an accommodating space of the power inverter.