CN114079354A

CN114079354A - Power assembly system for electric vehicle and electric vehicle

Info

Publication number: CN114079354A
Application number: CN202010805571.8A
Authority: CN
Inventors: 陈睿进; 陈凯; 孙国强
Original assignee: Faleiao Powertrain Shanghai Co ltd
Current assignee: Valeo Powertrain Nanjing Co Ltd
Priority date: 2020-08-12
Filing date: 2020-08-12
Publication date: 2022-02-22
Also published as: KR20230104585A; EP4196700A1; JP2023537137A; WO2022033536A1

Abstract

The present application relates to a powertrain system for an electric vehicle. The powertrain system includes an electric motor including a rotor and a stator; an inverter electrically connected to the motor and providing electrical energy to the stator; a reducer connected to the motor and receiving torque of the rotor; and a cooling circuit including a single inlet and a single outlet, the cooling circuit configured to flow an ultra-low viscosity oil therethrough and distribute the ultra-low viscosity oil throughout the powertrain system to lubricate and cool all components therein.

Description

Power assembly system for electric vehicle and electric vehicle

Technical Field

Embodiments of the present application relate generally to a powertrain system for an electric vehicle and a corresponding electric vehicle.

Background

The trend of designing and manufacturing fuel-efficient, low-emission vehicles has been greatly increased, which is inevitable due to environmental concerns and increased fuel costs. The forefront of this trend is the development of Electric vehicles, such as pure Electric vehicles (BEV), Hybrid Electric Vehicles (HEV), Plug-in Hybrid Electric vehicles (PHEV), Range extended Electric Vehicles (EV), Fuel Cell Electric Vehicles (FCEV), and the like, which combine a relatively efficient internal combustion engine and an Electric motor. Electric vehicles may include components, particularly drive trains, that generate heat, and excessive heat build-up may result in reduced performance or component damage. In particular, for high-power electric vehicles, for example BEVs with a power greater than 200kW, the cooling solution involves at least two cooling circuits in the transmission system, such as at least one oil cooling circuit for the electric motor or the retarder and at least one water cooling circuit for the inverter, whereby at least two hydraulic circuits equipped with at least two hydraulic pumps are required in the transmission system, which makes the system design complicated and costly. However, the use of oil cooling for the motor and the speed reducer ensures better cooling performance and cooling efficiency.

For lower power motors, below 100kW, there can be significant benefits by reducing the motor size, while the use of both oil and water cooling throughout the system can be costly. Therefore, a solution that can use only oil for cooling the whole system would become very attractive if the inverter could also be cooled efficiently for oil. Thus, difficulties in existing inverter cooling designs are overcome, and it is highly desirable to provide improvements in cooling designs for powertrain systems of electric vehicles, at least with high efficiency, low cost, and simple structure.

Disclosure of Invention

Aspects and advantages of the present application will be set forth in part in the description which follows, or may be obvious from the description, or may be learned by practice of the application.

In one exemplary aspect, a powertrain system for an electric vehicle is provided. The powertrain system includes an electric motor including a rotor and a stator; an inverter electrically connected to the motor and providing electrical energy to the stator; a reducer connected to the motor and receiving torque of the rotor; and a cooling circuit including a single inlet and a single outlet, the cooling circuit configured to flow an ultra-low viscosity oil therethrough and distribute the ultra-low viscosity oil throughout the powertrain system to lubricate and cool all components therein.

In some embodiments, the powertrain system further includes an oil pump configured to communicate with an inlet of the cooling circuit to control a flow of the ultra-low viscosity oil through the cooling circuit.

In some embodiments, the oil pump is located on the electric vehicle side, and the oil pump is connected to the inlet of the cooling circuit when the powertrain system is installed in the electric vehicle, or the oil pump is integrated on the powertrain system.

In some embodiments, the oil pump is a positive displacement pump.

In some embodiments, the powertrain system further includes a radiator configured to be connected between the outlet of the cooling circuit and the oil pump to cool the ultra-low viscosity oil discharged by the powertrain system and to convey the cooled ultra-low viscosity oil back into the powertrain system.

In some embodiments, the heat sink is integrated on the powertrain system or on the electric vehicle side.

In some embodiments, the cooling circuit includes an oil reservoir, the oil reservoir being located in the retarder.

In some embodiments, the cooling circuit includes an oil distribution channel disposed within a cooling plate for cooling at least one power switching device provided by the inverter, a plurality of heat sink fins disposed within the oil distribution channel, the heat sink fins being disposed in high density in all or a portion of the oil distribution channel.

In some embodiments, the powertrain system further includes a cover corresponding to the cooling plate for closing the oil distribution passage in the cooling plate.

In some embodiments, the heat fins are located on the cooling plate and cover.

In some embodiments, the at least one power switching device is controlled for full-wave mode or DVPWM mode starting at a given speed.

In some embodiments, the at least one power switching device is arranged between two of the cooling plates so that it can be cooled on both sides of the power switching device.

In some embodiments, when the cooling plate is circular, the cooling passage is configured as a ring formed along an inner peripheral edge of the inverter.

In some embodiments, the cooling plate directly contacts the at least one power switching device without a thermally conductive paste to provide direct oil cooling.

In some embodiments, the cooling circuit is configured to deliver the ultra-low viscosity oil to the motor to cool the stator and rotor and reduce phase current at high torque when the stator and rotor are in a high temperature state.

In another exemplary aspect, an electric vehicle is provided, which includes the aforementioned powertrain system.

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

Drawings

A full and enabling disclosure of the present application, 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 illustration of a powertrain system for an electric vehicle according to an exemplary embodiment of the present application.

Fig. 2A is a schematic diagram of a power switching device cooling plate according to an exemplary embodiment of the present application.

Fig. 2B is a schematic diagram of a power switching device cooling plate according to another exemplary embodiment of the present application.

Fig. 3 shows a comparison of the thermal resistances of indirect cooling with water and direct cooling with oil.

Fig. 4 is a schematic diagram of an inverter according to an exemplary embodiment of the present application, showing a preferred implementation of oil distribution channels arranged in the cooling plates.

Fig. 5A is a power switching apparatus according to an exemplary embodiment of the present application, showing a preferred implementation of a cooling plate and a cover cooperating therewith.

Fig. 5B is a power switching apparatus according to an exemplary embodiment of the present application, showing another preferred implementation of a cooling plate and a cover mated thereto.

FIG. 6 illustrates a relationship between relative thermal resistance and oil flow for an oil distribution passage according to an example.

Fig. 7 shows another preferred embodiment of the oil distribution channel arranged in the cooling plate.

Detailed Description

Reference now will be made in detail to embodiments of the present application, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the application, not limitation of the application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the scope or spirit of the application. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present application cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. As used in this specification, the terms "first," "second," and the like may be used interchangeably to distinguish one element from another and are not intended to indicate the position or importance of each element. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

Referring now to the drawings, in which like numerals indicate like elements throughout the several views, FIG. 1 illustrates a preferred embodiment of a powertrain system for an electric vehicle. The illustrated powertrain system is generally assembled from an inverter (as shown in fig. 4), a motor 12, and a reducer 13, thereby forming a single assembly.

The motor 12 may be a synchronous motor or an asynchronous motor. When the motor 12 is a synchronous motor, it may include a wound rotor or a permanent magnet rotor. For nominal supply voltages of 48V to 400V, or for higher powers which may be up to 800V, the peak power provided by the motor may be between 10KW and 80KW, for example of the order of 40 KW. In case the motor is adapted for a high voltage power supply, the nominal power provided by the motor may be 25 KW. In the embodiment shown, the electric motor 12 is a synchronous motor with permanent magnets, which provides peak power between 10KW and 80 KW. The motor 12 may include a stator having three-phase windings, or a combination of two three-phase windings or five-phase windings.

A reducer 13 is associated with the motor 12. The speed reducer can convert the high-speed and low-torque of the motor into low-speed and high-torque of the motor. The reducer 13 may include two or more reduction gears, one of which is driven by an electric motor, for example, to increase torque by reducing speed.

The reducer 13 may also drive a shaft, such as an intermediate shaft, which may be connected to a gear driven by the drive shaft of the motor and another gear having a larger diameter, thereby distributing the reduced driving force to a driven mechanical load (not shown), such as a driven wheel shaft.

In the illustrated embodiment, the motor 12 and the reducer 13 are designed to have a high heat capacity. The inverter 11 is attached to the motor 12 by electric wires, and is mechanically attached to a wall of the motor 12 or a wall of the speed reducer 13 or walls of the motor 12 and the speed reducer 13. The inverter 11 converts direct current ("DC") provided by an electrical energy storage unit (not shown) of electrical energy at nominal voltage to alternating current ("AC") for the electric motor 12. The inverter 11 may include at least one power switching device 17 (shown in fig. 2A and 2B), which may be, for example, a field effect transistor ("FET"), a metal oxide semiconductor field effect transistor ("MOSFET"), or an insulated gate bipolar transistor ("IGBT"). In case of a nominal supply voltage of 48V, the power switching device 17 may be a MOSFET transistor. In case the supply voltage corresponds to a high voltage, the power switching device 17 may be an IGBT.

Referring to fig. 1, the motor 12 is accommodated in a housing (not shown), and the reducer 13 is accommodated in another housing (not shown). The two housings may be integrally formed or assembled from a plurality of housing assemblies, and the two housings may be rigidly secured together, for example by screws, and a sealing wall may be provided between the two housings.

In some embodiments, a heat sink (not shown) may also be provided for dissipating heat towards the outside of the powertrain system 1. The heat sink is carried by the outer surface of the housing. The heat sinks may be integrally formed with the housing. The heat dissipation fins increase the area of the outer surface of the shell, thereby improving the heat dissipation effect of the power assembly system through the shell. The entire outer surface of the housing may be provided with cooling fins. The fins may be arranged in rows and there may be a constant or non-constant spacing between adjacent rows. The rows may or may not have the same orientation. Where appropriate, the same heat sink may extend first to one housing and then to the other housing.

In the embodiment shown, a coolant flow-through cooling circuit 3 is also provided for distributing coolant throughout the powertrain system 1. The coolant flowing in the cooling circuit 3 may be an oil having an ultra-low viscosity. Such ultra low viscosity oils will have a kinematic viscosity value at 40 ℃ of less than 40 and a kinematic viscosity value at 100 ℃ of less than 10. With such ultra-low viscosity oil, all components contained in the powertrain assembly can be lubricated and cooled more efficiently with a lower pressure drop by flowing it through the cooling circuit 3 to the entire powertrain system 1.

The cooling circuit 3 comprises a single inlet 31 and a single outlet 32 provided on the drive train 1. The inlet 31 may be connected to the oil pump 4 to control the flow of the ultra-low viscosity oil through the cooling circuit 3, while the outlet 32 may be connected to a radiator to cool the heated oil discharged from the cooling circuit 3. Meanwhile, the radiator 5 may be connected to the oil pump 4 so as to deliver the cooled oil into the powertrain system 1 through the oil pump 4. In the illustrated embodiment, the oil pump 4 and the radiator 5 are located on the electric vehicle side 2. When the powertrain system 1 is installed in an electric vehicle, the inlet 31 and outlet 32 will be in fluid communication with the oil pump 4 and radiator 5, respectively, through the plurality of hoses 6 in the electric vehicle side 2 so that the ultra-low viscosity oil can automatically flow through the powertrain system 1 to cool and lubricate it during operation.

In some embodiments, the radiator 5 may be integrated with the powertrain system 1 to receive heated oil from the powertrain system 1 and to transfer cooled oil back to the powertrain system.

In some embodiments, the oil pump 4 may be an electric pump or a mechanical pump, and the oil pump 4 may also be integrated with the powertrain system 1, in particular mechanically integrated on the speed reducer 13. The oil pump may be a positive displacement pump to provide the required flow rate of fluid, particularly an accelerated flow rate. In some embodiments, a positive displacement pump instead of a centrifugal pump may apply a higher oil pressure for cooling to increase the ability to dissipate heat from the switchgear absorbed by the radiator.

In some embodiments, the cooling circuit 3 may include an oil reservoir (not shown) disposed within the retarder 13 for retaining the necessary ultra-low viscosity oil, which may ensure a minimum flow of oil for lubrication and cooling inside the powertrain system 1.

Referring to fig. 2A and 2B, power switching devices 17, such as IGBTs, may be single-sided cooled by oil distribution channels in cooling

plates

18, 181 of inverter 11. The power switching device 17 may also be double-sided cooled by oil flowing through two cooling plates, i.e. the power switching device 17 and the cooling plates form a "sandwich" structure.

In some embodiments, since the thermal conductive paste and the additional aluminum heat sink are removed in the direct cooling of the power switching device 17, i.e., the IGBT module, the power switching device 17 may be in direct contact with the oil so that the thermal dissipation resistance may be improved, please refer to fig. 3. For peak powers of about 60kW, the existing market employs an indirect contact cooling method. The use of direct contact cooling will increase the costs to a limited extent, but can be compensated for, for example, by using a reduced size oil-cooled motor, which necessitates the use of oil cooling by the inverter.

In some embodiments, the power switching device 17 is controlled for full-wave mode or DVPWM mode starting at a given rotational speed, so that power losses from the IGBTs can be reduced, which will allow the use of oil cooling.

With this configuration, the motor 12 can be cooled by oil, and the efficiency at high torque can be greatly improved. The oil-cooled motor will be 5% more efficient than the water-cooled motor under heating conditions. The current through the IGBT can be significantly reduced, limiting the amount of heat that the heat sink and oil will dissipate.

Referring to fig. 4, an oil distribution passage is disposed inside the inverter 11. Specifically, the oil distribution passage is located in a radial plane of a housing or cooling plate 18 of the inverter 11, and is formed along an inner peripheral surface of the cooling plate 18, substantially forming an annular circuit 15. An auxiliary heat transfer element may be provided in the oil distribution channel to provide additional heat dissipation. As shown in the embodiment, the auxiliary heat transfer element may be a plurality of metal fins 16 or extruded walls (not shown) provided by the cooling plate 18, in particular by the inner radial surface of the cooling plate, the fins 16 extending in the X-direction at the radially inner surface. The secondary heat transfer element is made of a thermally conductive material, such as aluminum. In some embodiments, heat fins 16 (not shown) having a circular and/or square cross-section may cover the annular loop 15, either entirely or partially, at high density. High density of fins is a significant burden on conventional centrifugal water pump circuits due to higher pressure drop, whereas positive displacement oil pumps are almost insensitive to higher pressure drop.

Referring to fig. 6, there is shown a relation between a relative thermal resistance and a flow rate according to an exemplary configuration of the oil distribution passage 15, wherein a line "W" represents a value of the relative thermal resistance for water cooling, a line "a" represents a value of the relative thermal resistance for oil cooling, which can be performed using the oil distribution passage without or with a limited number of auxiliary heat transfer elements, and a line "C" represents a value of oil cooling using the oil distribution passage filled with the heat radiating fins 16 as shown in fig. 4. It can be seen from fig. 6 that the value of line "C" is close to the value of line "W", i.e. the water cooling, which is always approximately equal to 1 regardless of the flow rate variation, with a maximum difference of 2% between line "W" and line "C". Therefore, the same cooling effect as water can be achieved with only one oil cooling circuit, of the improved configuration (as shown in fig. 4) related to line "C" and the characteristics of the ultra-low viscosity oil.

Referring to fig. 5A and 5B, different exemplary configurations of the cooling plate 18 and the cooperating cover 19 for enclosing the oil distribution channel therein are shown. In the conventional design involving a cover, the cover 19 is a flat plate, as shown in fig. 5A, and the heat sink fins 16 are provided on the cooling plate 18, as shown in fig. 4. In the present design involving a cover, both the cover 19 and the cooling plate 18 may be provided with cooling fins 16, as shown in fig. 5B, the cooling fins provided by the cover 19 extend axially toward the cooling plate 18, and the cooling fins provided by the cooling plate extend axially toward the cover 19, so that the cooling fins from the cooling plate 18 and the cover 19 may be spaced apart from each other, narrowing the flow path gap between the cooling fins 16, which narrows the flow velocity of the fluid around the cooling fins 16, thereby further improving the cooling performance of the cooling plate 18. Even if the original water cooling circuit has a large number of fins, the oil-using double-sided fin structure can achieve a cooling level similar to that of water.

Referring 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 cooling fins 16 having different shapes and different arrangements. Specifically, the cooling side of the cooling plate 181 is filled with a plurality of heat radiation fins 16 having a circular or square cross section, in which oil distribution channels are formed. When the oil pump supplies oil, the oil F flows from one side of the cooling plate 181 to the other side of the oil distribution passage. The oil pump provides an accelerated flow to increase the fluidity of the oil F, thereby increasing heat dissipation.

By the construction as described above, it is achieved that only one fluid circuit is used for cooling and lubrication of the powertrain system. Furthermore, the use of oil with ultra-low viscosity for the fluid circuit makes it possible to obtain the same cooling effect as water cooling, while minimizing the pressure drop generated by the high-density fins in the cooling channels, in particular cooling the switching devices in the inverter, such as IGBTs. By using a direct contact cooling device, reducing the thermal resistance path to the oil, the cooling performance of the IGBT can be improved even for more power demanding applications. At the same time, active lubrication can be achieved by using oil, and the motor can be effectively cooled starting from its internal rotor, which increases the rate of the reducer and the motor, respectively, and in addition, the inverter can consume less current to produce the same mechanical torque, so that, on the one hand, heating can be reduced and, on the other hand, the size of the battery for providing electrical energy can be reduced. Furthermore, since there is only one liquid circuit, it is not necessary to use water cooling equipment such as a water tank, a hose, a pump, and the like, which can reduce the overall size of the powertrain system.

This written description uses examples to disclose the application, including the best mode, and also to enable any person skilled in the art to practice the application, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the application is defined by the claims, and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they include 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

1. A powertrain system for an electric vehicle, comprising:

an electric motor including a rotor and a stator;

an inverter electrically connected to the motor and providing the stator with electric power;

a speed reducer connected to the motor and receiving a torque of the rotor; and

a cooling circuit including a single inlet and a single outlet, the cooling circuit configured to flow an ultra-low viscosity oil therethrough and distribute the ultra-low viscosity oil throughout the powertrain system to lubricate and cool all components therein.

2. The powertrain system of claim 1, further comprising:

an oil pump configured to communicate with an inlet of the cooling circuit to control a flow rate of the ultra-low viscosity oil flowing through the cooling circuit.

3. The powertrain system of claim 2, wherein:

the oil pump is located on the electric vehicle side, and is connected to an inlet of the cooling circuit when the powertrain system is installed in the electric vehicle, or

The oil pump is integrated on the power assembly system;

the oil pump is a positive displacement pump.

4. The powertrain system of claim 2, further comprising:

a radiator configured to be connected between an outlet of the cooling circuit and the oil pump to cool the ultra-low viscosity oil discharged by the powertrain system and to deliver the cooled ultra-low viscosity oil back into the powertrain system.

5. The powertrain system of claim 4, wherein:

the radiator is integrated on the power assembly system or positioned on the side of the electric vehicle.

6. The powertrain system of claim 1, wherein:

the cooling circuit includes an oil reservoir located in the speed reducer.

7. The powertrain system of claim 1, wherein:

the cooling circuit includes an oil distribution channel disposed within a cooling plate for cooling at least one power switching device provided by the inverter, a plurality of heat dissipation fins disposed within the oil distribution channel, the heat dissipation fins being disposed in a high density in all or a portion of the oil distribution channel.

8. The powertrain system of claim 7, further comprising:

a cover corresponding to the cooling plate to close the oil distribution passage inside the cooling plate.

9. The powertrain system of claim 8, wherein:

the heat dissipating fins are located on the cooling plate and the cover.

10. The powertrain system of claim 7, wherein:

the at least one power switching device is controlled to start in full-wave mode or DVPWM mode at a given speed.

11. The powertrain system of claim 7, wherein:

the at least one power switching device is arranged between two of the cooling plates so that it can be cooled on both sides of the power switching device.

12. The powertrain system of claim 7, wherein:

when the cooling plate is circular, the cooling passage is configured as a ring formed along an inner peripheral edge of the inverter.

13. The powertrain system of claim 7, wherein:

the cooling plate directly contacts the at least one power switching device without a thermally conductive paste to provide direct oil cooling.

14. The powertrain system of claim 1, wherein:

the cooling circuit is configured to deliver the ultra-low viscosity oil to the motor to cool the stator and rotor and reduce phase current at high torque when the stator and rotor are in a high temperature state.

15. An electric vehicle comprising the powertrain of any of claims 1-14.