KR20230104585A - Integrated drivetrain assemblies for electric vehicles and electric vehicles - Google Patents

Abstract

The present disclosure relates to a drivetrain assembly for an electric vehicle. The drivetrain system includes an electric motor including a rotor and a stator, a power inverter configured to supply electrical energy to the stator, a cooling circuit having a single inlet and a single outlet, and a reducer configured to receive torque provided by the rotor. The cooling circuit is configured to flow through the extra-low viscosity oil and distribute the extra-low viscosity oil throughout the integral drivetrain assembly to lubricate and cool all components within the drivetrain assembly.

Description

Integrated drivetrain assemblies for electric vehicles and electric vehicles

Embodiments of the present disclosure relate generally to integrated drivetrain assemblies for electric vehicles and electric vehicles including integrated drivetrain assemblies.

Concerns about the environment and concerns about rising fuel costs have led to a rapid rise in the trend towards designing and building fuel-efficient, low-emission vehicles. At the forefront of this trend has been the development of electric vehicles, such as BEVs, HEVs, PHEVs, Range Extended EVs, Fuel Cells, etc., which combine a relatively efficient combustion engine with an electric drive motor. Electric vehicles may include components that generate heat, particularly drivetrain systems. Excessive heat build-up can degrade performance or damage components. In particular, a cooling solution for a high-powered electric vehicle such as a BEV with a power of 200 kW or more includes at least two cooling circuits in the drivetrain system, for example, one oil cooling circuit for a motor/reducer and one water cooling circuit for an inverter, , which requires at least two hydraulic circuits with at least two pumps, but the arrangement of each cooling circuit using a different coolant to cool different components of the drivetrain system is more complex and expensive. However, this oil-cooled motor and reducer guarantee higher performance and efficiency.

For low power, less than 100 kW, the high cost makes it difficult to justify using both oil and water cooling in one system, although the benefits are clear with the additional possibility of downscaling the motor. Therefore, using only oil cooling for the entire system can be an attractive solution if the inverter can be efficiently cooled by oil, which constitutes a major difficulty in conventional inverter cooling designs.

Therefore, it would be desirable if at least the cooling design of the drivetrain system for an electric vehicle could be improved with a simple configuration, high efficiency, and low cost.

Aspects and advantages of the present invention are partially described in the following description, may be apparent from the following description, or may be learned through practice of the present invention.

According to one aspect disclosed herein, an integrated drivetrain assembly for an electric vehicle is provided. A drivetrain assembly includes an electric motor comprising a rotor and a stator, a power inverter electrically connected to the electric motor and configured to supply electrical energy to the stator, coupled to the electric motor and configured to receive torque provided by the rotor. Including reducers. The drivetrain assembly further includes a cooling circuit having a single inlet and a single outlet, the cooling circuit allows the extra-low viscosity oil to flow and distributes the extra-low viscosity oil throughout the assembly to cool all components of the drivetrain assembly. It is configured to lubricate and cool.

In one embodiment, an oil pump is configured to communicate with the inlet to control the flow of extra low viscosity oil through the cooling circuit.

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

In one embodiment, the oil pump is a positive displacement pump.

In one embodiment, the radiator is configured to communicate between the outlet and the oil pump to cool the ultra-low viscosity oil discharged from the drivetrain assembly and to deliver the cooled ultra-low viscosity oil into the drivetrain assembly.

In one embodiment, the radiator is integrated with the drivetrain assembly or provided on the electric vehicle side.

In one embodiment, the cooling circuit includes an oil reservoir provided within the reducer.

In one embodiment, the cooling circuit includes an oil distribution passage arranged inside a cooling plate configured to cool at least one power switching device provided by a power inverter, a plurality of cooling spikes are provided in the oil distribution passage, the cooling spikes are arranged wholly or partially in the oil distribution passage at high density.

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

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

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

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

In one embodiment, the oil distribution passage consists of a loop formed along an inner circumference of the cooling plate when the cooling plate is formed in a circular shape.

In one embodiment, the cooling plate directly contacts the at least one power switching device without thermal grease to provide direct oil cooling.

In one embodiment, the cooling circuit is configured to deliver extra low viscosity oil to the electric motor to lower the phase current and cool the stator and rotor at high torque when the stator and rotor are in a hot condition.

According to another aspect disclosed herein, an electric vehicle is provided that includes the integrated drivetrain assembly described above.

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

A complete and possible disclosure of the present invention, including the most preferred embodiments of the present invention, which is directed to one skilled in the art, is set forth in the specification with reference to the accompanying drawings.
1 is a schematic diagram of an integrated drivetrain assembly for an electric vehicle according to an exemplary aspect of the present disclosure.
2A is a schematic diagram of one exemplary arrangement for a cooling plate and a power switching device of a power inverter.
2B is a schematic diagram of another exemplary arrangement for a cooling plate and a power switching device of a power inverter.
3 is a diagram comparing thermal resistance between indirect contact cooling using water and direct contact cooling using oil.
4 is a schematic diagram of a portion of a power inverter according to an exemplary aspect of the present disclosure showing one exemplary oil distribution passage arranged within a cooling plate.
5A is a schematic diagram of a portion of a power inverter according to an exemplary aspect of the present disclosure showing one exemplary cooling plate and its cover.
5B is a schematic diagram of a portion of a power inverter according to an exemplary aspect of the present disclosure showing another exemplary cooling plate and its cover.
6 is a diagram illustrating the relationship between relative thermal resistance and oil flow rate according to an exemplary configuration of arranged oil distribution passages.
7 is a schematic diagram of another exemplary oil distribution passage arranged within a cooling plate.

Present embodiments of the present invention will now be described in detail, one or more examples of which are shown in the accompanying drawings. The detailed description uses numeric and letter designations to describe features of the drawings. In the drawings and description, the same or similar designations are used to refer to the same or similar parts of the invention. As used herein, the terms "a", "the" and irrelevant terms are intended to mean that there is more than one element, unless the context dictates otherwise. The terms “comprises,” “includes,” and “has” are intended to be inclusive and mean that there may be additional elements other than those listed. The terms "first" and "second" may be used interchangeably to distinguish one element from another and do not imply the location or importance of the individual elements.

Referring now to the drawings, like reference numbers indicate like elements throughout the drawings, and FIG. 1 shows a drivetrain assembly 1 according to one embodiment of the present disclosure. The drivetrain assembly 1 is generally integrated with a power inverter 11 (shown in FIG. 4 ), an electric motor 12 and a gear reducer 13 . Therefore, the drivetrain assembly 1 shown is a single unit.

Electric motor 12 may be a synchronous motor or an asynchronous motor. The electric motor 12 may include a wound rotor or a permanent magnet rotor if it is a synchronous motor. The peak power supplied by the electric motor may be between 10 KW and 80 KW, for example approximately 40 KW with a nominal supply voltage of 48V to 400V, or up to 800V for higher powers. In the case of an electric motor suitable for high voltage supply, the nominal power supplied by this electric motor may be 25 kW. In the illustrated embodiment, electric motor 12 is a synchronous motor with permanent magnets providing a peak power of 10 kW to 80 kW. The electric motor 12 may include a stator having a three-phase winding or a combination of two three-phase windings or five-phase windings.

Reducer 13 is coupled to electric motor 12 . The reducer 13 can convert high speed, low torque of the electric motor into low speed, high torque. Reducer 13 may include two or more gears, one of which is driven by electric motor 12, for example to increase torque via speed reduction. The reducer is a transmission shaft, i.e., a driving gear driven by one transmission shaft of an electric motor (not shown) and another of large diameter coupled to a driven mechanical load (not shown, for example, a vehicle wheel shaft). An intermediate shaft connecting gears may be further included.

In the embodiment shown, the electric motor 12 and reducer 13 are designed with a high thermal capacity. The power inverter 11 is connected to the electric motor 12, and mechanically to the wall of the electric motor 12, or to the wall of the reducer 13, or to both walls of the electric motor 12 and the reducer 13, Attached mechanically by wires. The power inverter 11 converts direct current ("DC") supplied by an electrical energy storage device (not shown) in which electrical energy of nominal voltage is provided to alternating current ("AC") used in the electric motor 2. convert The power inverter 11 includes at least one power switching device 11, 17, such as a field effect transistor (“FET”), a metal oxide semiconductor field effect transistor (“MOSFET”) or an insulated gate bipolar transistor (“IGBT”). 2a and 2b). When the nominal supply voltage is 48V, the power switching device 11 may be a MOSFET transistor. For a supply voltage corresponding to a high voltage, the power switching device 11 may be an IGBT.

Referring to Figure 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 may be integral. The two housings can be rigidly fastened together, for example by means of screws. A sealing wall is provided here between the two housings.

Cooling fins (not shown) may be provided for heat dissipation of the drivetrain assembly 1 towards the outside. Cooling fins may be supported by the outer surface of the housing. These cooling fins are made integrally with the housing, for example. These cooling fins increase the outer surface of the housing to promote heat dissipation through the housing to the outside of the drivetrain assembly 1 , providing the possibility of integrating a stand-alone radiator 5 . The entire outer surface of the housing can hold the cooling fins. The cooling fins may be arranged in rows, and the pitch may be between two adjacent rows, with or without a constant pitch. These columns may or may not all have the same orientation. Where appropriate, the same pin may extend first into one housing and second into the other housing.

For the illustrated embodiment, a cooling circuit 3 with coolant flow is provided for distributing the coolant throughout the drivetrain assembly 1 . The coolant flowing in the cooling circuit 3 may be oil having a very low viscosity. The kinetic viscosity value of this kind of ultra-low viscosity oil at 40°C is less than 40, and the kinematic viscosity value at 100°C is less than 10. Using this kind of ultra-low viscosity oil flowing throughout the drivetrain assembly through the cooling circuit 3, all components included in the drivetrain assembly can be lubricated and cooled more efficiently with lower pressure drop.

The cooling circuit 3 comprises a single inlet 31 and a single outlet 32 provided on the drivetrain assembly 1 . The inlet 31 can be connected with the oil pump 4 to control the flow of the ultra-low viscosity oil to be supplied to the cooling circuit 3 at a required flow rate, and the outlet 32 is the heating discharged from the cooling circuit 3. It can be connected with a radiator (5) for cooling the oil. Meanwhile, the radiator 5 may be connected to the oil pump 4 to deliver cooled oil into the drivetrain assembly 1 through the oil pump 4 . In the embodiment shown, the oil pump 4 and radiator 5 are located on the electric vehicle side 2 . When the drivetrain assembly (1) is installed in an electric vehicle, the inlet (31) and the outlet (32) are connected to the oil pump (4) and the radiator (5) respectively through several hoses (6) on the electric vehicle side (2). It is in fluid communication so that extra low viscosity oil can flow autonomously throughout the drivetrain assembly 1 for cooling and lubrication during operation.

In one embodiment, the radiator 5 may be integrated with the drivetrain assembly 1 to receive heated oil from the drivetrain assembly 1 and deliver cooled oil back to the drivetrain assembly.

In one embodiment, the oil pump 4 can be an electric pump or a mechanical pump and can be integrated with the drivetrain assembly 1 , in particular mechanically integrated on the reducer 13 . The oil pump 4 may be a positive displacement pump to provide a required flow rate, in particular an accelerated flow rate. Instead of a centrifugal pump to be able to apply high oil pressure for cooling, a positive displacement pump is used, which increases the heat dissipation function through a heat sink that draws heat from the switching device.

In one embodiment, the cooling circuit 3 may include an oil reservoir (not shown) provided in the gearbox 13, which is used to retain the necessary ultra-low viscosity oil therein, which is used for the drivetrain. A minimal flow of oil for cooling and lubrication inside the assembly 1 can be ensured.

Referring now to FIGS. 2A and 2B , a power switching device 17 such as an IGBT may be cooled in one side by oil flowing in oil distribution passages arranged inside the cooling plates 18 , 181 of the power inverter 11 . there is. The power switching device 17 can be cooled on both sides by oil flowing in two cooling plates, that is, the power switching device and the cooling plate are formed in 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, referring now to FIG. It can be improved because the heat sink has been removed. Currently on the market, indirect contact cooling is used for peak powers of ~60 kW. Adopting direct contact cooling has a limited increase in cost, but can easily be compensated for by using miniaturized oil-cooled motors using, for example, inverter-related oil cooling.

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

With this configuration, the electric motor 12 is cooled by oil, significantly improving efficiency at high torque. Oil-cooled motors can be 5% more efficient in heated conditions than water-cooled motors. The current flowing through the IGBT can be greatly reduced by limiting the heat dissipated by the cooling plate and oil.

Referring now to FIG. 1 , an oil distribution passage is arranged inside the power inverter 11 . In particular, the oil distribution passage is located in the case of the power inverter 11 or in the radial plane of the cooling plate 18, and is formed along the inner circumference of the cooling plate 18 to be basically an annular loop 15. . An auxiliary heat transfer element is provided within the oil distribution passage to provide additional heat dissipation. As shown in the embodiment, the auxiliary heat transfer element may be a plurality of metal spikes 16, or an extruded wall (not shown) provided by the cooling plate 18, in particular the inner radial face of the cooling plate; Spike 16 extends from the inner radial face along the X direction. The auxiliary heat transfer element is made of a thermal material, for example aluminum. In one embodiment, metal spikes 16 having circular and/or square (not shown) cross-sections may be wholly or partially dense loops 15 . High density spikes are a significant burden on conventional centrifugal water pump circuits due to their higher pressure drop, whereas volumetric oil pumps are largely insensitive to higher pressure drops.

Referring now to FIG. 6 showing the relationship between the relative thermal resistance and the flow rate according to an exemplary configuration of the oil distribution passage 15, the line "W" represents the value of the relative thermal resistance to water cooling, and the line "A" " represents the value for oil cooling using oil distribution passages with or without a limited number of auxiliary heat transfer elements, and line "C" represents an oil distribution passage filled with metal spikes 16, as shown in FIG. Indicates the value for the oil cooling used. It can be seen from the figure that the value of line "C" is close to that of line "W", i.e., the value of water cooling always equal to 1 regardless of the change in flow rate, and there is only a maximum difference of 2% between "W" and "C". Able to know. Therefore, the improved configuration (see Fig. 4) related to the line "C" and the oil characteristics of ultra-low viscosity can realize the same cooling effect as that by water with only one oil cooling circuit.

Referring now to FIGS. 5A and 5B , different exemplary configurations of cooling plates 18 and 19 are shown, with corresponding covers used to seal the oil distribution passages therein. In conventional designs for covers, cover 19 may be flat as shown in FIG. 5A while spikes 16 are provided on cooling plates 18 as shown in FIG. 4 . In the present design for the cover, both the cover 19 and the cooling plate 18 may be provided with spikes 16 as shown in FIG. ), while the spikes provided by the cooling plate extend axially towards the cover 19, so that the spikes from the cooling plate 18 and the cover 19 are spaced apart, thus The passage interval between the spikes 16 can be narrowed, so that the flow velocity around the spikes 16 increases, further increasing the cooling performance of the cooling plate 18 . Even though the original water cooling circuit has a large number of spikes, this two-sided spike distribution allows the use of oil to reach a level of cooling similar to that of water.

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

With the configuration described above, only one liquid circuit is achieved for both cooling and lubrication of the drivetrain assembly. In addition, ultra-low viscosity oil is used in the liquid to achieve the same inverter cooling effect as water cooling, while minimizing the pressure drop caused by high-density spikes in the cooling channel to cool the switching device, i.e., the IGBT. The cooling performance of this IGBT can even be improved for applications requiring more power by using a direct contact cooling device, reducing the thermal resistance path for the oil. On the other hand, this active lubrication can be realized by using oil, and the motor can be efficiently cooled in the inner rotor, so the efficiency of the reducer and motor are improved respectively, and the current consumed by the inverter is reduced, so that the same mechanical torque can be obtained. Thus, heat generation on one side and the other side can be reduced, and the size of a battery providing power can be reduced. Additionally, thanks to the single liquid circuit, water cooling equipment such as water tanks, hoses and pumps can be eliminated and the overall size of the drivetrain assembly reduced.

The written description uses examples to disclose embodiments of the present disclosure, including the most preferred modes, and also to those skilled in the art to make and use any device or system and perform any incorporated methods. make it possible to carry out The patentable scope of the embodiments described herein is defined by the claims and may include other examples that occur to one 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 include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (15)

In the integrated drivetrain assembly for electric vehicles,
an electric motor comprising a rotor and a stator;
a power inverter electrically connected to the electric motor and configured to supply electrical energy to the stator;
a speed reducer coupled to the electric motor and configured to receive torque provided by the rotor;
one cooling circuit with a single inlet and a single outlet;
wherein the cooling circuit is configured to cause the extra-low viscosity oil to flow and distribute the extra-low viscosity oil throughout the integrated drivetrain assembly to lubricate and cool all components of the integrated drivetrain assembly.
Integrated drivetrain assembly. According to claim 1,
and an oil pump configured to communicate with the inlet to control the flow of ultra-low viscosity oil through the cooling circuit.
Integrated drivetrain assembly. According to claim 2,
the oil pump is provided by the electric vehicle and is connected to the inlet when the integrated drivetrain assembly is installed into the electric vehicle, or the oil pump is integrated with the drivetrain assembly;
The oil pump is a positive displacement pump
Integrated drivetrain assembly. According to claim 2,
Further comprising a radiator configured to communicate between the outlet and the oil pump to cool the ultra-low viscosity oil discharged from the drivetrain assembly and transfer the cooled ultra-low viscosity oil into the drivetrain assembly.
Integrated drivetrain assembly. According to claim 4,
The radiator is integrated with the drivetrain assembly or provided by the electric vehicle side.
Integrated drivetrain assembly. According to claim 1,
The cooling circuit includes an oil reservoir provided in the reducer.
Integrated drivetrain assembly. According to claim 1,
The cooling circuit includes an oil distribution passage arranged inside a cooling plate configured to cool at least one power switching device provided by the power inverter, a plurality of cooling spikes are provided in the oil distribution passage, the cooling spikes comprising: Arranged wholly or partially in the oil distribution passage at a high density
Integrated drivetrain assembly. According to claim 7,
A cover corresponding to the cooling plate is provided to seal the oil distribution passage.
Integrated drivetrain assembly. According to claim 8,
The cooling spike is provided on the cooling plate and the cover
Integrated drivetrain assembly. According to claim 7,
wherein the at least one power switching device is controlled in a propagation mode or DVPWM mode starting from a given RPM
Integrated drivetrain assembly. According to claim 7,
The at least one power switching device is arranged between two cooling plates, so that the power switching device can be cooled from both sides.
Integrated drivetrain assembly. According to claim 7,
The oil distribution passage is composed of a loop formed along the inner circumference of the cooling plate when the cooling plate is formed in a circular shape.
Integrated drivetrain assembly. According to claim 7,
The cooling plate is in direct contact with the at least one power switching device without thermal grease to provide direct oil cooling.
Integrated drivetrain assembly. According to claim 1,
wherein the cooling circuit is configured to deliver the extra low viscosity oil to the electric motor to lower the phase current at high torque and cool the stator and rotor when the stator and the rotor are in a hot state.
Integrated drivetrain assembly. comprising an integrated drivetrain assembly according to any one of claims 1 to 14;
electric car.

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