WO2022033536A1

WO2022033536A1 - An integrated drivetrain assembly for an electrified vehicle and an electrified vehicle

Info

Publication number: WO2022033536A1
Application number: PCT/CN2021/112159
Authority: WO
Inventors: Yejin JIN; Kai Chen; Guoqiang Sun
Original assignee: Valeo Powertrain (shanghai) Co., Ltd.
Priority date: 2020-08-12
Filing date: 2021-08-12
Publication date: 2022-02-17
Also published as: KR20230104585A; CN114079354A; JP2023537137A; EP4196700A1

Abstract

The present disclosure relates to a drivetrain assembly for an electrified vehicle. 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 one cooling circuit with a single inlet and a single outlet. The cooling circuit is configured for being flowed through with ultra-low viscosity oil and for distributing the ultra-low viscosity oil throughout the drivetrain assembly for lubricating and cooling down all the components in the drivetrain assembly.

Description

AN INTEGRATED DRIVETRAIN ASSEMBLY FOR AN ELECTRIFIED VEHICLE AND AN ELECTRIFIED VEHICLE

FIELD OF THE INVENTION

Embodiments of the present disclosure relate generally to an integrated drivetrain assembly for an electrified vehicle and an electrified vehicle comprising the integrated drivetrain assembly.

BACKGROUND OF THE INVENTION

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, HEV, PHEV, Range extended EV, Fuel Cell 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. Specially, cooling solutions for high power electrified vehicles, e.g., for BEV whose power is larger than 200kW, contain at least two cooling circuit in the drivetrain system, e.g., one oil cooling circuit for motor/reducer and one water cooling circuit for inverter, which will require at least two hydraulic circuits with at least two pumps, however, the arrangement of each cooling circuit with different coolant for cooling different component in the drivetrain system would be more complex and the cost would be high. However, this oil cooled motor and reducer guarantees the higher performance and efficiency.

For lower power less than 100kW, it becomes hard to justify the use of both oil and water-cooling in one system due to high cost, even if the benefits are clear with the additional possibilities of downsizing the motor. Therefore, using only oil cooling for the full system may be an appealing solution if the inverter can be efficiently cooled by the oil as well which constitutes the major difficulties with a conventional design of inverter cooling.

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 OF THE INVENTION

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, an integrated drivetrain assembly for an electrified vehicle is provided. The drivetrain assembly comprises an electric motor comprising a rotor and a stator; a power inverter electrically connected to the electric motor and configured for supplying the stator with electric energy; a reducer coupled to the electric motor and configured for receiving torque provided by the rotor. The drivetrain assembly further comprises one cooling circuit with a single inlet and a single outlet, the cooling circuit is configured for being flowed through with ultra-low viscosity oil and for distributing the ultra-low viscosity oil throughout the assembly for lubricating and cooling down all the components in the drivetrain assembly.

In one embodiment, an oil pump configured for being in communication with the inlet for controlling a flow of the ultra-low viscosity oil through the cooling circuit.

In one embodiment, the oil pump is provided by the electrified vehicle side and is connected to the inlet when the integrated drivetrain assembly is installed into the electrified vehicle, or the oil pump is integrated with the drivetrain assembly.

In one embodiment, the oil pump is a volumetric pump.

In one embodiment, a heat dissipater configured for being in communication with between the outlet and the oil pump for cooling the ultra-low viscosity oil discharged from the drivetrain assembly and transferring the cooled down ultra-low viscosity oil into the drivetrain assembly.

In one embodiment, the heat dissipater is integrated with the drivetrain assembly or provided by the electrified vehicle side.

In one embodiment, the cooling circuit comprises an oil reservoir that is provided within the reducer.

In one embodiment, the cooling circuit comprises an oil distribution passage arranged inside a cooling plate configured for cooling at least one power switching device provided by the power inverter, a plurality of cooling spikes are provided within the oil distribution passage, the cooling spikes are arranged full or partially of the oil distribution passage with a high density.

In one embodiment, a cover corresponding to the cooling plate is provided to enclose the oil distribution passage.

In one embodiment, the cooling spikes are arranged on the cooling plate and cover.

In one embodiment, the at least one power switching device is controlled in a mode of full wave or of DVPWM starting from a given RPM.

In one embodiment, the at least one power switching device is arranged between two cooling plates so that the power switching device could be cooled from dual sides.

In one embodiment, the oil distribution passage is configured as a loop forming along an inner circumference periphery of the cooling plate when the cooling plate forms as a circular shape.

In one embodiment, the cooling plate is in direct contact with the at least one power switching device without thermal grease so as to provide direct oil cooling.

In one embodiment, the cooling circuit is configured for transferring the ultra-low viscosity oil to the electric motor for cooling the stator and rotor and lowering down the phase current at high torque when the stator and rotor are in hot conditions.

In accordance with another aspect disclosed herein, an electrified vehicle comprising the integrated drivetrain assembly according to the above described is provided.

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 an integrated drivetrain assembly for an electrified vehicle in accordance with an exemplary aspect of the present disclosure;

FIG. 2A is a schematic view of one exemplary arrangement for the power switching device and cooling plate of the power inverter;

FIG. 2B is a schematic view of another exemplary arrangement for the power switching device and cooling plate of the power inverter;

FIG. 3 is a diagram illustrating thermal resistance comparison between indirect contact cooling with water and direct contact cooling with oil;

FIG. 4 is a schematic view of a part of power inverter in accordance with an exemplary aspect of the present disclosure, showing one exemplary oil distribution passage arranged within a cooling plate;

FIG. 5A is a schematic view of a part of the power inverter in accordance with an exemplary aspect of the present disclosure, showing one exemplary cooling plate and its cover;

FIG. 5B is a schematic view of a part of the power inverter in accordance with an exemplary aspect of the present disclosure, showing another exemplary cooling plate and its cover;

FIG. 6 is a diagram illustrating the relationship between the relative thermal resistance and the oil flow rate according to exemplary configurations of the oil distribution passage arranged; and

FIG. 7 is a schematic view of another exemplary oil distribution passage arranged within a cooling plate.

DETAILED DESCRIPTION OF THE INVENTION

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, FIG. 1 shows a drivetrain assembly 1 in accordance with one embodiment of the present disclosure. The drivetrain s assembly 1 is generally integrated with a power inverter 11 (as shown in FIG. 4) , an electric motor 12 and a reducer 13. The drivetrain assembly 1 as shown is therefore a single unit.

The electric motor 12 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 peak power supplied by the electric motor can be between 10KW and 80KW, for example, of the order of 40KW, for a nominal supply voltage of 48V to 400V, 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 25KW. In the illustrated embodiment, the electric motor 12 is a synchronous motor with permanent magnets, providing a peak power between 10KW and 80KW. The electric motor 12 can include a stator with a three-phase winding, or a combination of two three-phase windings or five-phase windings.

The reducer 13 is coupled to the electric motor 12. The reducer 13 can transform the electric motor’s high speed, low torque to low speed, high torque. The reducer 13 may comprise two or more gears, with one of the gears driven by the electric motor 12 for instance, for torque increase via speed reduction. The reducer may further comprise a transmission shaft, 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 12 and the reducer 13 are designed with high thermal capacity. The power inverter 11 is attached by the electrical wires to the electric motor 12 and mechanically to a wall of the electric motor 12 or to a wall of the reducer 13 or to both walls of the electric motor 12 and the reducer 13. The power inverter 11 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 11 can comprise at least one power switching device (17, as shown in FIG. 2A and FIG. 2B) , such as, 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 switching device 11 can be MOSFET transistors. In the case of a supply voltage corresponding to a high voltage, the power switching device 11 can be IGBTs.

Referring to FIG. 1, the electric motor 12 is contained in one housing (not shown) , and the reducer 13 is contained in another housing (not shown) . The two housings can be one-piece. The two housings can be rigidly fixed together, for example by means of screws. A sealing wall is here provided between the two housings.

Cooling fins (not shown) may be provided for the heat dissipation towards the outside of the drivetrain assembly 1. The cooling fins may be carried by the outer surface of the housings. These cooling fins are for example made in one piece with the housings. These cooling fins allow to increase the outer surface of the housings, and thus promote the heat dissipation to the outside of the drivetrain assembly 1 via the housings, which gives the possibilities to integrate a standalone radiator 5. The entire outer surface of the housings may carry cooling fins. The cooling fins 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 one housing and secondly to the other housing.

For the embodiment depicted, a cooling circuit 3 being flowed through with coolant is provided for distributing the coolant throughout the drivetrain assembly 1. The coolant flowing in the cooling circuit 3 can be the oil with ultra-low viscosity. The kinetic viscosity value of this kind of ultra-low viscosity oil at 40℃ will be less than 40 and the kinetic viscosity value at 100℃ will be less than 10. By using this kind of ultra-low viscosity oil flowing throughout the drivetrain assembly via the cooling circuit 3, all components contained in the drivetrain assembly could be both lubricated and cooled down more efficiently with lower pressure drop.

The cooling circuit 3 comprises a single inlet 31 and a singlet outlet 32 which are provided onto the drivetrain assembly 1. The inlet 31 can be connected with an oil pump 4 for controlling a flow of the ultra-low viscosity oil to be provided to the cooling circuit 3 at a required flow rate, while the outlet 32 can be connected with a heat dissipater 5 for cooling down the heated oil discharged from the cooling circuit 3. Meanwhile, the heat dissipater 5 can be connected with the oil pump 4 so as to transfer the cooled down oil into the drivetrain assembly 1 via the oil pump 4. In the illustrated embodiment, the oil pump 4 and the heat dissipater 5 are positioned in the electrified vehicle side 2. When the drivetrain assembly 1 is installed into an electrified vehicle, the inlet 31 and outlet 32 will be fluidly in communication with the oil pump 4 and the heat dissipater 5, respectively, via several hoses 6 in the electrified vehicle side 2, such that the ultra-low viscosity oil can autonomously flow throughout the drivetrain assembly 1 for cooling and lubrication during operating.

In one embodiment, the heat dissipater 5 can be integrated with the drivetrain assembly 1 for receiving heated oil from the drivetrain assembly 1 and transferring the cooled oil back to drivetrain assembly.

In one embodiment, the oil pump 4 can be an electrical pump or a mechanical pump, and can be integrated with the drivetrain assembly 1, particularly mechanically integrated on the reducer 13. The oil pump 4 can be a volumetric pump to provide with a required flow rate, particularly, an accelerated flow rate. The volumetric pump is used instead of a centrifugal pump, in order to be able to apply high oil pressure for the cooling, which will increase the thermal dissipation capabilities through the heat sink withdrawing the heat from the switching device.

In one embodiment, the cooling circuit 3 can comprise an oil reservoir (not shown) provided within the reducer 13, the oil reservoir is used for keeping necessary ultra-low viscosity oil therein, which can ensure a minimum flow of the oil for cooling and lubricating inside the drivetrain assembly 1.

Referring now to FIGs 2A and 2B, the power switching device 17, such as an IGBT, can be single-side cooled by the oil flowing within an oil distribution passage arranged inside a cooling

plate

18, 181 of the power inverter 11. The power switching device 17 can be dual side cooled by the oil flowing within two cooling plates, i.e., the power switching device and the cooling plates form as a sandwich structure.

In one embodiment, the power switching device 17 is in direct contact with the oil so that the heat dissipation thermal resistance can be improved, referring now to FIG. 3, since the thermal grease and additional aluminum heat sink are removed in the direct cooling power switching device 17, i.e., IGBT module. Current market uses an indirect contact cooling method for the peak power ～60kW. The adoption of the direct contact cooling will increase in a limited way the cost, but can easily be compensated by the use of the downsized oil cooled motor for example, which makes the use of the oil cooling relevant for the inverter.

In one embodiment, the power switching device 17 is controlled in a mode of full wave or of DVPWM starting from a given RPM so that the power loss from the IGBT could be reduced, which will allow to use the oil cooling.

With such configuration, the electric motor 12 is cooled down by the oil, improving in a significant way the efficiency at high torque. The oil cooled motor can be 5%more efficient in the heated condition than the water cooled motor. The current flowing through the IGBT can be significantly reduced limiting the heat to be dissipated by the cooling plate and oil.

Referring now to FIG. 4, an oil distribution passage is arranged inside the power inverter 11. Specially, the oil distribution passage is positioned within a radial surface of a case or cooling plate 18 of the power inverter 11, and is formed along an inner circumference periphery of the cooling plate 18, basically, to be an annular loop 15. Auxiliary heat transferring elements are provided within the oil distribution passage so as to provide with additional heat dissipation. As illustrated in the embodiment, the auxiliary heat transferring elements can be several metallic spikes 16, or extruded walls (not shown) provided by the cooling plate 18, particularly by an inner radial surface of the cooling plate, the spikes 16 extend from the inner radial surface along an X direction. The auxiliary heat transferring elements are made of thermal material, for example aluminum. In one embodiment, the metallic spikes 16 with a transverse cross section of circular shape and/or of square shape (not shown) can be full or partially of the loop 15 with a high density. High density spikes is an important burden for a conventional centrifugal water pump circuit due to higher pressure drop, whereas the volumetric oil pump is almost not sensitive to the higher pressure drop.

Referring now to FIG. 6 which shows the relationship between the Relative Thermal Resistance and the Flow Rate according to exemplary configurations of the oil distribution passage 15, wherein line “W” indicates the value of the relative thermal resistance for water cooling, line “A” indicates the value for oil cooling using the oil distribution passage without or with limited number of auxiliary heat transferring elements, and line “C” indicates the value for oil cooling using the oil distribution passage full of metallic spikes 16 as shown in FIG. 4. It could be seen from the diagram, the value of line “C” close to that of line “W” , i.e., water cooling, which is always equal to 1 regardless of the change of Flow Rate, there will be only max 2%difference between “W” and “C” . Therefore, the improved configuration relating to line “C” (as shown in FIG. 4) and the oil properties of ultra-low viscosity may realize the same cooling effect as by the water with only one oil cooling circuit.

Referring now to FIGs 5A and 5B, showing different exemplary configurations of the cooling plate 18 and 19 a corresponding cover using for enclosing the oil distribution passage therein. In a conventional design concerning the cover, the cover 19 can be a flat plate, as shown in FIG. 5A, while the spikes 16 are provided onto the cooling plate 18 as shown in FIG. 4. In the present design concerning the cover, the cover 19 and the cooling plate 18 can both provide with the spikes 16, as shown in FIG. 5B, the spikes provided by the cover 19 axially extend towards the cooling plate 18 while the spikes provided by the cooling plate axially extend towards the cover 19 so that the spikes from the cooling plate 18 and the cover 19 are spaced so that the flow passage gap between the spikes 16 can be narrowed which will increase the flow velocity around the spikes 16, increasing further the cooling performance of the cooling plate 18. Even if the original water cooling circuit was with high number of the spikes, this double sided spike distribution will allow reaching similar level of cooling as water using oil.

Referring now to FIG. 7, showing another exemplary configuration of the cooling plate. In the illustrated embodiment, the cooling plate 181 is configured as a rectangular shape and is full of spikes 16 with different shapes and different arrangements. Specifically, several spikes 16 with a transverse cross section of circular shape or of square shape (not shown) are full of a cooling side of the cooling plate 181, among which forms the oil distribution passage. With the supply of the oil pump, oil flows through the distribution passage from one side of the cooling plate 181 to the opposite side. The oil pump provides with an accelerated flow rate for increasing the oil flow F speed so as to increase the heat dissipation.

With the configuration as described above, only one liquid circuit for both cooling and lubrication for the drivetrain assembly is achieved. Further, oil with ultra-low viscosity is used for the liquid to obtain the same inverter cooling effect for as by the water-cooling while minimizing the pressure drop created by high density spikes in the cooling channels, cooling down especially the switching device i.e., IGBT. This IGBT’s cooling performance can even be improved for the more power demanding application, by using the direct contact cooling device, reducing the thermal resistance path to the oil. Meanwhile, such active lubrication can be realized by using of the oil and the motor can efficiently cooled down from its inside rotor, which improves the efficiency of respectively the reducer and the motor, then less current can be consumed by the inverter to produce the same mechanical torque, reducing the heat generation on one side, and on the other side, the size of battery for providing electrical power can be reduced. Moreover, thanks for the only one liquid circuit, equipment for the water-cooling, such as water tank, hoses, pump, etc., could be removed and the overall size of the drivetrain assembly can be reduced.

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

An integrated drivetrain assembly for an electrified vehicle, comprising:

an electric motor comprising a rotor and a stator;

a power inverter electrically connected to the electric motor and configured for supplying the stator with electric energy;

a reducer coupled to the electric motor and configured for receiving torque provided by the rotor; and

one cooling circuit with a single inlet and a single outlet, the cooling circuit configured for being flowed through with ultra-low viscosity oil and for distributing the ultra-low viscosity oil throughout the integrated drivetrain assembly for lubricating and cooling down all the components in it.
The drivetrain assembly of claim 1, further comprises:

an oil pump configured for being in communication with the inlet for controlling a flow of the ultra-low viscosity oil through the cooling circuit.
The drivetrain assembly of claim 2, wherein

the oil pump is provided by the electrified vehicle side and is connected to the inlet when the integrated drivetrain assembly is installed into the electrified vehicle, or the oil pump is integrated with the drivetrain assembly;

the oil pump is a volumetric pump.
The drivetrain assembly of claim 2, further comprises:

a heat dissipater configured for being in communication with between the outlet and the oil pump for cooling the ultra-low viscosity oil discharged from the drivetrain assembly and transferring the cooled down ultra-low viscosity oil into the drivetrain assembly.
The drivetrain assembly of claim 4, wherein

the heat dissipater is integrated with the drivetrain assembly or provided by the electrified vehicle side.
The drivetrain assembly of claim 1, wherein

the cooling circuit comprises an oil reservoir that is provided within the reducer.
The drivetrain assembly of claim 1, wherein

the cooling circuit comprises an oil distribution passage arranged inside a cooling plate configured for cooling at least one power switching device provided by the power inverter, a plurality of cooling spikes are provided within the oil distribution passage, the cooling spikes are arranged full or partially of the oil distribution passage with a high density.
The drivetrain assembly of claim 7, wherein

a cover corresponding to the cooling plate is provided to enclose the oil distribution passage.
The drivetrain assembly of claim 8, wherein

the cooling spikes are provided onto the cooling plate and the cover.
The drivetrain assembly of claim 7, wherein

the at least one power switching device is controlled in a mode of full wave or of DVPWM starting from a given RPM.
The drivetrain assembly of claim 7, wherein

the at least one power switching device is arranged between two cooling plates so that the power switching device could be cooled from dual sides.
The drivetrain assembly of claim 7, wherein

the oil distribution passage is configured as a loop forming along an inner circumference periphery of the cooling plate when the cooling plate forms as a circular shape.
The drivetrain assembly of claim 7, wherein

the cooling plate is in direct contact with the at least one power switching device without thermal grease so as to provide direct oil cooling.
The drivetrain assembly of claim 1, wherein

the cooling circuit is configured for transferring the ultra-low viscosity oil to the electric motor for cooling the stator and rotor and lowering down the phase current at high torque when the stator and rotor are in hot conditions.
An electrified vehicle, comprising the integrated drivetrain assembly according to any one of claims 1 to 14.