JP7573612B2 - Powertrain system for an electric vehicle and method for cooling the powertrain system - Patents.com - Google Patents

Description

Embodiments of the present disclosure generally relate to driveline systems for electric vehicles and methods for cooling driveline systems.

There is a significant trend to design and manufacture vehicles that are fuel efficient and have low emissions. This trend is driven by environmental concerns and rising fuel costs. At the forefront of this trend is the development of electric vehicles that combine a relatively efficient internal combustion engine with an electric drive motor, such as BEVs (battery electric vehicles), HEVs (hybrid electric vehicles), PHEVs (plug-in hybrid electric vehicles), range-extended EVs, and FCECs (fuel cell electric vehicles). Electric vehicles may contain components that generate heat, particularly the driveline system. Excessive heat generation can cause components to perform poorly or to break.

It would therefore be desirable to provide improved cooling designs for drivetrain systems for electric vehicles that are at least simple in configuration, highly efficient, and low cost.

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

According to one aspect disclosed herein, a driveline system for an electric vehicle is provided. The driveline system includes an electric motor having a rotor and a stator, a power inverter configured to supply electrical energy to the stator, and a reducer having a transmission shaft configured to receive the torque provided by the rotor, the electric motor, the power inverter, and the reducer being integrated as a driveline assembly. The driveline system further includes a cooling circuit connected to the driveline assembly and configured to flow a coolant and distribute the coolant throughout the driveline assembly, the cooling circuit including a cooling channel disposed within the power inverter, the cooling channel including a coolant retention 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 drive system further comprises a mechanical pump component connected to the cooling circuit and driven by the transmission shaft to transport the coolant to the cooling channel.

In one embodiment, the mechanical pump components are located on the same side as the electric motor or on a different side of the reducer than the electric motor.

In one embodiment, an auxiliary heat transfer element is provided within the cooling channel. The auxiliary heat transfer element comprises at least one spike, an extruded wall, or a combination thereof.

In one embodiment, the thermal mass is provided with an electric motor, a gear reducer, or both, and the power inverter is mechanically attached to the electric motor, or gear reducer, or both, thereby benefiting from the thermal mass and dissipating heat therein via the cooling channels and coolant held in the coolant retaining sections and auxiliary heat transfer elements therein that further increase heat transfer to the thermal mass.

In one embodiment, cooling fins are provided on the exterior of the electric motor, the reducer, or both the electric motor and the reducer, and the power inverter benefits from the cooling fins by being mechanically attached to the electric motor, or the reducer, or both, to dissipate heat therein via the cooling channels and the coolant held in the auxiliary heat transfer elements therein that further increase heat transfer to the coolant holding sections and the cooling fins.

In one embodiment, the cooling channel is configured as a loop formed along the inner periphery of the power inverter, with the inlet and outlet located at the upper end of the cooling channel in a gravity orientation.

In an alternative embodiment, the cooling channel is configured as a serpentine-shaped channel within the power inverter housing space.

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

In an alternative embodiment, the cooling channels are configured as Z-shaped channels within the power inverter housing space.

According to another aspect disclosed herein, a method for cooling a driveline system for an electric vehicle including an integrated driveline assembly including an electric motor, a power inverter, and a speed reducer is provided. The method includes providing a cooling circuit configured to flow a coolant and distribute the coolant throughout the driveline assembly, and providing the cooling circuit with a cooling channel disposed within the power inverter and further providing a coolant retention section for retaining the coolant in the cooling channel.

In one embodiment, the method further comprises providing a mechanical pump component connected to the cooling circuit and driven by a transmission shaft of one of the drive train assemblies to transport coolant to the cooling channel.

In one embodiment, the method further comprises providing an auxiliary heat transfer element in the cooling channel to facilitate heat dissipation from the power inverter. The auxiliary heat transfer element comprises at least one spike, an extruded wall, or a combination thereof.

In one embodiment, the method further comprises providing an electric motor, a gear reducer, or both, on the thermal mass, and the power inverter benefits from the thermal mass by being mechanically attached to the electric motor, or the gear reducer, or both, to dissipate heat therein via the inverter's cooling channels and the coolant retained in the coolant retaining section and auxiliary heat transfer elements therein that further increase heat transfer to the thermal mass.

In one embodiment, the method further comprises providing cooling fins on an exterior surface of the electric motor, the reducer, or both the electric motor and the reducer, and the power inverter benefits from the cooling fins by being mechanically attached to the electric motor, or the reducer, or both, to dissipate heat therein via the cooling channels and the coolant held in the auxiliary heat transfer elements therein which further increase heat transfer to the coolant retaining sections and the cooling fins.

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

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

In an alternative embodiment, the method further comprises forming the cooling channel as a helical shaped channel within the housing space of the power inverter.

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

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

A full and enabling disclosure of the present invention, including its best mode, directed to one of ordinary skill in the art, is set forth in the specification, which refers to the accompanying drawings.

FIG. 1 is a schematic diagram of a driveline system according to an exemplary aspect of the present disclosure. FIG. 2 is a schematic diagram of a driveline system according to another exemplary aspect of the present disclosure. FIG. 3 is a schematic diagram of a power inverter of a driveline system according to an exemplary aspect of the present disclosure. FIG. 4 is a schematic diagram of one exemplary cooling channel of the power inverter shown in FIG. FIG. 5 is a schematic diagram of another exemplary cooling channel of the power inverter shown in FIG. FIG. 6 is a schematic diagram of another exemplary cooling channel of a power inverter of the present disclosure. FIG. 7 is a schematic diagram of another exemplary cooling channel of a power inverter of the present disclosure. FIG. 8 is a schematic diagram of another exemplary cooling channel of a power inverter of the present disclosure. FIG. 9 illustrates an example power inverter having the thermal mass and cooling channels of FIG. FIG. 10 illustrates an example power inverter including the cooling fins and cooling channels of FIG. FIG. 11 illustrates another example power inverter with a thermal mass and the cooling channels of FIG. 8 having spikes. FIG. 12 is a flow diagram of a method for cooling a driveline system according to an exemplary aspect of the present disclosure.

The embodiments of the present invention are described in detail. Examples of the present invention are illustrated in the accompanying drawings. In the detailed description, numerical and letter designations are used to refer to features in the drawings. Like or similar designations in the drawings and description are used to refer to like or similar parts of the present invention. As used herein, the terms "a," "an," and "the" are intended to mean that there is one or more elements, unless the context clearly dictates otherwise. The terms "comprise," "include," and "have" 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 part from another and are not intended to denote the location or importance of the individual parts.

Referring to the drawings, where like numerals refer to like elements throughout, FIGS. 1 and 2 show driveline systems 101, 102 according to embodiments of the present disclosure. More specifically, for the embodiment of FIG. 1, driveline system 101 includes driveline assembly 1. Driveline assembly 1 is generally integrated with power inverter 3 (shown in FIG. 3), electric motor 2, and speed reducer 4. Thus, the illustrated driveline assembly 1 is a single unit.

The electric motor 2 may be a synchronous motor or an asynchronous motor. If it is a synchronous motor, it may include a wound rotor or a permanent magnet motor. The nominal power provided by the electric motor may be 10KW to 60KW, for example around 15KW, or up to 800V for higher power, for a nominal supply voltage of 48V to 350V. For electric motors suitable for high voltage supplies, the nominal power provided by the electric motor may be 60KW. In the illustrated embodiment, the electric motor 2 is a synchronous motor with permanent magnets, providing a nominal power of 10KW to 60KW. The electric motor 2 may include a stator with a three-phase winding, or a combination of two three-phase or five-phase windings.

The reducer 4 is connected to the electric motor 2. The reducer 4 can convert the high speed and low torque of the electric motor into a low speed and high torque. The reducer 4 can have two or more gears. One of the gears is driven, for example, by the electric motor 2 for the purpose of increasing the torque through reduction. The reducer 4 can further have a transmission shaft 41, i.e. an intermediate shaft. The transmission shaft 41 connects a drive gear driven by one transmission shaft (not shown) of the electric motor with another gear of a larger diameter connected to a driven mechanical load (not shown, for example, the wheel shaft of a vehicle).

In the illustrated embodiment, the electric motor 2 and the reducer 4 are designed to have a high thermal capacity. The power inverter 3 (shown in FIG. 3 ) is attached by wires to the electric motor 2 and mechanically to the wall of the electric motor 2 or to the wall of the reducer 4 or to both the walls of the electric motor 2 and the reducer 4. The power inverter 3 converts a direct current ("DC") provided by an electric energy storage unit (not shown) with electrical energy at a nominal voltage into an alternating current ("AC") used by the electric motor 2. The power inverter 3 can be, but is not limited to, a field effect transistor ("FET"), a metal oxide semiconductor field effect transistor ("MOSFET") or an insulated gate bipolar transistor ("IGBT"). For a nominal supply power of 48V, the power inverter 3 can be a MOSFET transistor. For supply voltages corresponding to high voltages, the power inverter 3 can be an IGBT.

Referring to Figures 1 and 2, the electric motor 2 is housed in a first housing 11, and the reducer 4 is housed in a second housing 12. The first housing 11 and the second housing 12 may be integral or may be formed by assembling sub-parts of the housing together. The first housing 11 and the second housing 12 may be firmly fixed to each other, for example, by screws. Here, a sealing wall is provided between the first housing 11 and the second housing 12.

The cooling fins 91, 92 are provided to dissipate heat towards the outside of the drivetrain assembly 1. The cooling fins 91, 92 are supported by the outer surfaces of the first housing 11 and the second housing 12. These cooling fins 91, 92 are, for example, made integrally with the first housing 11 and the second housing 12. These cooling fins 91, 92 can increase the outer surfaces of the first housing 11 and the second housing 12, thereby facilitating the dissipation of heat through the first housing 11 and the second housing 12 to the outside of the drivetrain assembly 1. The cooling fins 91, 92 may be supported on the entire outer surface of the first housing 11 and the entire outer surface of the second housing 12. The cooling fins 91, 92 may be arranged in rows. There may be a constant or non-constant pitch between two adjacent rows. These rows may or may not all have the same orientation. If necessary, the same fins may extend first towards the first housing 11 and then towards the second housing 12.

For the illustrated embodiment, a cooling circuit 5 through which a coolant flows is provided to distribute the coolant throughout the driveline assembly 1. The coolant flowing through the cooling circuit 5 may be, for example, oil, water, or a water-based coolant.

Further, in the illustrated embodiment, a mechanical pump component 6 is provided in the cooling circuit 5. The mechanical pump component 6 may be a gerotor pump that can promote the flow of the coolant in the cooling circuit 5. Furthermore, the mechanical pump component 6 is connected to the driveline assembly 1 and is configured to transfer the coolant to the driveline assembly, in particular to the power inverter 3, through one section 51 provided by the cooling circuit 5, and to withdraw the coolant from the driveline assembly, in particular from the reducer 4, through another section 52 provided by the cooling circuit 5. The sections 51, 52 are arranged outside the driveline assembly 1. By using the mechanical pump component 6, in particular by a gerotor pump, the coolant transferred and flowing in the section 51 towards the driveline assembly provides a large constant delivery volume and a high pressure. As shown in FIG. 1, the mechanical pump component 6 is mechanically connected to one end of the transmission shaft 41, so that the mechanical pump component 6 can be driven by mechanical power from the rotating shaft. It can be seen that the mechanical power generated by the rotating shaft can be fully utilized and no additional power source is required to drive a pump disposed in the cooling circuit to transport the coolant (e.g., using electrical power to drive an electric pump). Thus, energy can be saved, costs can be reduced, and space can be reduced by eliminating a dedicated motor.

However, it should be further understood that the exemplary system 101 described herein is merely exemplary. In some exemplary embodiments, the mechanical pump component 6 may be mechanically connected to another end of the transmission shaft 41, depending on the different conditions and needs of the assembly, to better utilize the rotational force of the shaft within the driveline assembly 1 (e.g., the exemplary system 102 shown in FIG. 2).

Referring to FIG. 3, FIG. 3 shows a power inverter 3 of a driveline system according to 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 gravity orientation are defined. In the illustrated embodiment, a cooling channel 33 is provided by a cooling circuit 5. The cooling channel 33 further includes an inlet 31 for receiving the coolant from the mechanical pump component 6 and an outlet 32 for discharging the coolant. The cooling channel 33 also includes a coolant retention section 35, so that the coolant is present in the cooling channel whether the mechanical pump component 6 is operating or not. Therefore, the cooling channel 33 can be constantly kept cool by the coolant flowing or remaining in the cooling channel 33 due to the action of gravity.

In particular, as shown in Figs. 3-5, the cooling channel 33 disposed within the radial surface of the power inverter 3 and formed along the inner periphery of the power inverter is essentially an annular loop. The inlet 31 and outlet 32 are disposed at the upper end of the cooling channel 33, 331 in the gravity orientation. The inlet 31 and outlet 32 may also be disposed in a horizontal plane or there may be a slight height difference. Furthermore, a coolant retention section 35, 351 is formed at the lower part of the cooling channel 33, 331 along the gravity orientation. Due to the high thermal weight of the reducer and/or electric motor and the coolant residue ensuring the heat transfer, the inverter can be continuously cooled even when the mechanical pump system is stopped or only operates at a very low flow rate.

During operation of the mechanical pump component 6, such as a gerotor pump, a certain amount of coolant may be transferred from the gerotor pump to the cooling channels 33, 331 in the power converter 3. In particular, the coolant enters the cooling channels via the inlet 31, flows through the cooling channels, and exits the cooling channels via the outlet 32. Thus, heat from the power inverter 3 is dissipated by the flow of coolant. When the rotating shaft, i.e., the transmission shaft 41, to which the gerotor pump 6 is mechanically connected, is stopped, the coolant remains in the coolant retention section 35, 351 of the cooling channel 33, 331. This allows the power converter 3 to remain cool by absorbing heat itself and transferring the heat to the thermal mass.

Referring to Figures 4 and 5, these figures show different exemplary cooling channels 33, 331. Auxiliary heat transfer elements are provided in the cooling channels 33, 331. This provides additional heat dissipation to the high heat capacity components, i.e., the reducer and the electric motor, even when, for example, the gerotor pump is operating at low speed or at rest. As illustrated in the embodiment, the auxiliary heat transfer elements can be a number of metal spikes 34 as shown in Figure 5, or an extruded wall 341 as shown in Figure 6, or a combination of spikes 34 and extruded wall 341. The auxiliary heat transfer elements are made of a thermal material, such as aluminum.

Referring 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 in the center of the shape and an outlet 322 is provided at the outer edge of the shape. A coolant retention section 352 is formed between the inlet 312 and the outlet 322.

Referring 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 the bottom of the shape and an outlet 323 is provided at the top of the shape. A coolant retention section 353 is formed between the inlet 313 and the outlet 323.

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

However, it should be understood that the exemplary cooling channels 33, 331, 332, 333, 334 described herein are merely exemplary. In addition to these shapes shown, other shapes of cooling channels should be included that can maintain the coolant and have minimal air inside, even when the coolant pump has a very low flow rate.

9 and 10, the power inverter 3 housing the cooling channel, such as the exemplary cooling channel 334 shown in FIG. 8, may contact a large thermal mass, such as the electric motor 2, or the reducer 4, or both the electric motor 12 and the reducer 4. Alternatively, the exemplary cooling channel 334 may contact cooling fins 91, 92 disposed on the outer surface of the electric motor 2, or the reducer 4, or both the electric motor 2 and the reducer 4. With this configuration, the coolant remaining in the cooling channel 334 can ensure heat transfer from the power inverter 3. Furthermore, heat from the power inverter 3 can be further dissipated by the large thermal mass or the cooling fins.

Referring to FIG. 11, for additional heat dissipation to a larger thermal mass or cooling fin (as shown), multiple auxiliary cooling elements such as spikes 34 are provided in a cooling channel such as the exemplary Z-shaped cooling channel 334. The distance d between the spikes and the surface of the cooling channel facing the thermal mass or cooling fin should be minimized. This will increase the heat dissipation area and provide a higher heat transfer effect.

Referring to FIG. 12, a flow diagram of an example method 200 for cooling a driveline system according to an example aspect of the present disclosure is shown. For example, the example method 200 may be used to cool the example driveline systems 101, 102 described above with reference to FIGS. 1 and 2.

An exemplary method 200 includes providing 201 a cooling circuit connected to a driveline assembly, the cooling circuit configured to flow a coolant therethrough to distribute the coolant throughout the driveline assembly. The driveline assembly is integrated with an electric motor, a power inverter, and a reduction gear.

The exemplary method 200 further includes step 202 of providing a cooling circuit with cooling channels disposed within the power inverter and further providing a coolant retention section in the cooling channel to maintain heat dissipation to a thermal mass, such as a motor and/or gearbox, or cooling fins provided by an exterior surface of the motor and/or gearbox, to facilitate removal of heat from the power inverter.

The exemplary method 200 then includes step 203 of providing at least one spike, extruded wall, or combination thereof within the cooling channel to facilitate heat dissipation from the power inverter.

The exemplary method 200 further includes forming the cooling channel as a loop around the inner periphery of the power inverter, with the cooling channel inlet and outlet located at the top end of the cooling channel in a gravity orientation, or forming the cooling channel as a serpentine-shaped channel, a spiral-shaped channel, or a Z-shaped channel within the containment space of the power inverter. The shape of the cooling channel and the location of the cooling channel inlet and outlet assist in forming a coolant retention section within the cooling channel.

Furthermore, the exemplary method 200 includes step 205 of providing a mechanical pump component connected to the cooling circuit, the mechanical pump component being driven by a transmission shaft of one of the driveline assemblies. The transmission shaft may be a rotating shaft driving an electric motor or a reducer.

The written description uses examples to disclose embodiments of the disclosure, including the best mode, and to enable any person skilled in the art to practice the embodiments of the disclosure, including making and using any device or system 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 that do not differ substantially from the literal language of the claims.

Claims (10)

A drive train system for an electric vehicle, comprising:
an electric motor comprising a rotor and a stator;
a power inverter configured to supply electrical energy to the stator;
a reducer having a transmission shaft configured to receive the torque provided by the rotor;
the electric motor, the power inverter and the speed reducer are integrated as a driveline assembly;
the driveline system further comprising a cooling circuit configured to flow a coolant and distribute the coolant throughout the driveline assembly, the cooling channel disposed within the power inverter, the cooling channel including a coolant retention section for retaining the coolant from the cooling circuit, an inlet for receiving the coolant, and an outlet for discharging the coolant ;
the cooling channel is configured as a loop formed along an inner periphery of the power inverter;
The inlet and the outlet are disposed at an upper end of the cooling channel in a gravity orientation . The drive train system of claim 1 further comprising a mechanical pump component connected to the cooling circuit, the mechanical pump component being driven by the transmission shaft to transport the coolant to the cooling channel. an auxiliary heat transfer element is provided within the cooling channel;
The driveline system of claim 1 or 2, wherein the auxiliary heat transfer element comprises at least one spike, an extruded wall, or a combination thereof. a thermal mass is provided with the electric motor, the reducer, or both;
4. The driveline system of claim 3, wherein the power inverter benefits from the thermal mass by being mechanically attached to the electric motor, or the speed reducer, or both, to dissipate heat therein via the cooling channels and the coolant retained in the coolant retaining section and the auxiliary heat transfer elements therein which further increase heat transfer to the thermal mass. cooling fins are provided on an outer surface of the electric motor, the reducer, or both the electric motor and the reducer;
4. The driveline system of claim 3, wherein the power inverter benefits from the cooling fins by being mechanically attached to the electric motor, or the speed reducer, or both, to dissipate heat therein via the cooling channels and the coolant retained in the coolant retaining section and the auxiliary heat transfer elements therein which further increase heat transfer to the cooling fins. 1. A method for cooling a driveline system for an electric vehicle having an integrated driveline assembly with an electric motor, a power inverter, and a speed reducer, comprising:
providing a cooling circuit configured to flow a coolant and distribute said coolant throughout said driveline assembly;
providing a cooling channel in the cooling circuit disposed within the power inverter and further providing a coolant retention section for retaining a coolant in the cooling channel;
forming the cooling channel as a loop around an inner periphery of the power inverter;
and positioning the inlet and outlet of the cooling channel at a top end of the cooling channel in a gravity orientation . 7. The method of claim 6, further comprising the step of providing a mechanical pump component connected to the cooling circuit, the mechanical pump component being driven by a transmission shaft of one of the driveline assemblies to pump the coolant to the cooling channel . providing an auxiliary heat transfer element within the cooling channel to facilitate heat dissipation from the power inverter;
The method of claim 6 or 7 , wherein the auxiliary heat transfer element comprises at least one spike, an extruded wall, or a combination thereof. providing the electric motor, the speed reducer, or both, on a thermal mass;
9. The method of claim 8, wherein the power inverter benefits from the thermal mass by being mechanically attached to the electric motor, or the speed reducer, or both, to dissipate heat therein via the cooling channels of the power inverter and the coolant retained in the coolant retaining section and the auxiliary heat transfer elements therein that further increase heat transfer to the thermal mass. providing cooling fins on an outer surface of the electric motor, the reducer, or both the electric motor and the reducer;
9. The method of claim 8, wherein the power inverter benefits from the cooling fins by being mechanically attached to the electric motor, or the speed reducer, or both, to dissipate heat therein via the cooling channels of the power inverter and the coolant retained in the auxiliary heat transfer elements therein that further increase heat transfer to the coolant retaining section and the cooling fins.

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