WO2023144358A1

WO2023144358A1 - Electric powertrain system and vehicle

Info

Publication number: WO2023144358A1
Application number: PCT/EP2023/052105
Authority: WO
Inventors: Wenhui Wang; Xiaoxue Deng; Wanchao ZHAO; Zhichao CHU; Xucan CHEN; Rupeng CHEN
Original assignee: Valeo Eautomotive Germany Gmbh
Priority date: 2022-01-28
Filing date: 2023-01-29
Publication date: 2023-08-03
Also published as: CN116552219A

Abstract

The invention discloses an electric powertrain system, which comprises: an electric machine assembly, which comprises an electric machine shaft comprising a first electric machine shaft end and a second electric machine shaft end; a gearbox assembly comprising an input shaft comprising a first input shaft end and a second input shaft end, and the second electric machine shaft end being inserted into the first input shaft end to form a coupling part with the first input shaft end, so that the input shaft and the electric machine shaft can rotate together coaxially; a first bearing; a second bearing; a third bearing, comprising a first axial end facing the first bearing and a second axial end facing the second bearing; the coupling part comprises a spline coupling part and a radial centring part, and the spline coupling part is axially located between the second axial end of the third bearing and the tip of the first input shaft end.

Description

Electric powertrain system and vehicle

Description

Technical Field

The present invention relates to an electric powertrain system, which may be used in a vehicle, for example an electric vehicle or a hybrid vehicle. The present invention further relates to a vehicle comprising such an electric powertrain system.

Background Art

An electric powertrain system is the core power source in, for example, an electric or hybrid vehicle. It generally comprises an electric machine and a gearbox, and the electric machine shaft of the electric machine and the input shaft of the gearbox are coupled to each other to transmit torque and will experience highspeed rotation during operation. Thus, it should be ensured that the electric machine shaft of the electric machine and the input shaft of the gearbox are centred properly with respect to each other, to avoid vibration due to radial eccentricity, as well as the resulting noise and relatively low transmission efficiency. Axial positioning of the electric machine shaft and the input shaft should also be ensured, to further enhance the robustness of the entire electric powertrain system. Furthermore, firm coupling of the electric machine shaft to the input shaft of the gearbox and firm support of the electric machine shaft and the input shaft should also be ensured with a compact structure, to ensure that they operate in an optimal state, and thus ensure high transmission efficiency. However, a solution capable of achieving these technical effects simultaneously has not yet been proposed in the prior art.

The present invention is intended to achieve these technical effects through a simple and compact structure.

Summary of the Invention

To this end, the present invention proposes an electric powertrain system, which comprises a housing and the following components located in said housing: an electric machine assembly comprising an electric machine shaft, the electric machine shaft comprising a first electric machine shaft end and a second electric machine shaft end, a gearbox assembly, comprising an input shaft, wherein said input shaft comprises a first input shaft end and a second input shaft end, said second electric machine shaft end is inserted into said first input shaft end to form a coupling part with said first input shaft end, so that said input shaft and said electric machine shaft can rotate together coaxially, a first bearing, being supported at the first electric machine shaft end, a second bearing, being supported at the second input shaft end, a third bearing, being supported at said first input shaft end and comprising a first axial end facing said first bearing and a second axial end facing said second bearing, wherein said coupling part comprises a spline coupling part and a radial centring part, and said spline coupling part is axially located between the second axial end of said third bearing and the tip of said first input shaft end.

Thus, the electric powertrain system proposed in the present invention can achieve at least the following technical effects. The coupling part formed by the electric machine shaft of the electric machine assembly and the input shaft of the gearbox assembly comprises a spline coupling part and a radial centring part, and it is thereby possible to ensure that torque is transmitted between the electric machine shaft and the input shaft while also ensuring that the electric machine shaft and the input shaft are centred properly with respect to each other, effectively avoiding vibration and noise due to radial eccentricity between the electric machine shaft and the input shaft, and ensuring effective transmission of torque from the electric machine shaft to the input shaft of the gearbox assembly. At the same time, the use of the first bearing, second bearing and third bearing as defined above helps to achieve effective and firm support for the electric machine shaft and input shaft and thus for the electric machine assembly and gearbox assembly, in a compact structure. In particular, such a layout of the three bearings and the positioning of the coupling part relative to them and relative to the electric machine shaft and input shaft allow very firm support of the electric machine shaft and the input shaft of the gearbox assembly, further reducing vibration and noise, and also allow a micro-modification design of the teeth of gears of the gearbox assembly, ensuring that the gears are able to present their optimal state and thereby achieve optimal performance during operation, and further helping to reduce noise.

The electric powertrain system proposed in the present invention may further comprise one or more of the following aspects, which may be employed alone or in combination.

In some embodiments, said radial centring part is axially arranged between said spline coupling part and the tip of said first input shaft end.

In some embodiments, said radial centring part is axially arranged between said spline coupling part and the tip of said second electric machine shaft end.

In some embodiments, said radial centring part is axially arranged on the outside of the second axial end of said third bearing.

In some embodiments, said radial centring part axially overlaps at least partially with said third bearing. This solution makes it possible to effectively support the input shaft and therefore the electric machine shaft at a position with greater rigidity, which is conducive to the robustness of the entire electric powertrain system.

In some embodiment, the third bearing comprises a first bearing inner ring and a first bearing outer ring. The first bearing inner ring may be press-fitted onto the centring part.

In some embodiments, a thickness of the centring part is defined to prevent deformation when the third bearing is press-fitted.

In some embodiments, a height of splines of the splined coupling part is defined to tolerate deformation of the centring part when the third bearing id press- fitted.

In some embodiments, the radial centring part and the spline coupling part are axially disposed adjacent to each other. Such a structure allows the corresponding centring part and the spline coupling part to be conveniently machined on the electric machine shaft and input shaft, and helps to simplify the assembling between the electric machine shaft and the input shaft, thereby reducing the design, manufacturing and assembly costs, and increasing cost effectiveness. In some embodiments, said radial centring part comprises the radial outer surface of said electric machine shaft and the radial inner surface of said input shaft that is in a clearance fit with said radial outer surface. Such a radial centring part is able to ensure proper centring, is very easy to machine, and facilitates assembly, further increasing cost effectiveness.

In some embodiments, a retaining ring is arranged on the second electric machine shaft end of said electric machine shaft and is axially between the tip of said second electric machine shaft end and said coupling part.

In some embodiments, said second electric machine shaft end is designed with a circumferential groove for holding said retaining ring, wherein said retaining ring is elastic so that in the assembly process, specifically, in the process of inserting said electric machine shaft into said input shaft, said retaining ring is radially compressed in said circumferential groove when said retaining ring moves with said electric machine shaft through said coupling part, and, after said retaining ring moves with said electric machine shaft through said coupling part, said retaining ring can be radially extended to press against the inner wall of said input shaft.

Thus, the retaining ring may be provided in a simple manner with a very compact structure, allowing an improvement in axial positioning of the electric machine shaft relative to the input shaft of the gearbox assembly.

In some embodiments, the first bearing comprises a first bearing inner ring and a first bearing outer ring, and an elastic member capable of applying an axial preload to the first bearing is provided between the first bearing outer ring and the housing. The elastic member makes it possible to ensure the axial positioning of the electric machine shaft relative to the input shaft of the gearbox assembly in a very simple and dynamic manner, thereby ensuring torque transmission efficiency and being conductive to robustness of the entire electric powertrain system.

In some embodiments, a stop ring for axially positioning the third bearing is provided on the input shaft. It is thereby possible to further secure the third bearing, and thus further secure the input shaft of the gearbox assembly.

In some embodiments, at least one of the first bearing, the second bearing and the third bearing is a deep groove ball bearing. In some embodiments, the electric powertrain system comprises a water cooling system for cooling the electric machine assembly.

In some embodiments, a lip-like sealing ring is provided between the electric machine shaft and the housing for fluidic sealing of a first part of the housing that accommodates the electric machine assembly relative to a second part of the housing that accommodates the gearbox assembly. Thus, in the case where the electric powertrain system comprises a water cooling system for cooling the electric machine assembly, oil in the gearbox assembly can be effectively prevented from flowing into the electric machine assembly, thus preventing the oil from negatively affecting components of the electric machine assembly that have poor oil resistance.

In some embodiments, the electric powertrain system comprises an oil cooling system for cooling the electric machine assembly.

In some embodiments, the gearbox assembly employs a two-stage helical gear parallel-shaft arrangement, and comprises a differential. This enables a more compact overall structure.

The present invention further relates to a vehicle comprising an electric powertrain system as described above.

Brief Description of the Drawings

In order to explain the technical solution of embodiments of the present disclosure more clearly, the drawings that need to be used in the embodiments are briefly described below. It should be understood that the drawings below show only some embodiments of the present disclosure, so they should not be regarded as limiting the scope. Those skilled in the art could obtain other related drawings based on these drawings without inventive effort. In the drawings,

Fig. 1 shows a sectional drawing of an electric powertrain system according to an embodiment of the present invention;

Fig. la shows the connection between the electric machine shaft of the electric machine assembly of the electric powertrain system and the input shaft of the gearbox assembly according to the embodiment shown in Figure 1 in a partially enlarged sectional view; Fig. 2 shows a sectional view of the electric powertrain system according to another embodiment of the present invention;

Fig. 3 shows a sectional view of the electric powertrain system according to another embodiment of the present invention.

List of reference labels:

10 Electric powertrain system

100 Housing

110 First end cap

120 Second end cap

130 Separating part

200 Electric machine assembly

210 Electric machine shaft

211 First electric machine shaft end

212 Second electric machine shaft end

213 Tip of second electric machine shaft end

214 Retaining ring

215 Lip-like seal ring

216 Circumferential groove

220 Water cooling system

300 Gearbox assembly

310 Input shaft

311 First input shaft end

312 Second input shaft end

313 Tip of first input shaft end

314 Input gear

315 Intermediate first gear

316 Intermediate second gear

320 Differential

330 Intermediate shaft

400 First bearing 410 First bearing inner ring

420 First bearing outer ring

430 Bearing block

440 Elastic member

500 Second bearing

510 Second bearing inner ring

520 Second bearing outer ring

600 Third bearing

610 First axial end

620 Second axial end

630 Third bearing inner ring

640 Third bearing outer ring

S Spline coupling part

C Radial centring part

X Rotation axis

Specific Embodiments

The electric powertrain system according to embodiments of the present disclosure is described in detail below with reference to the drawings. In order to clarify the objective, technical solution and advantages of the present disclosure, the technical solutions in the embodiments of the present disclosure are described clearly and completely below in conjunction with the drawings in embodiments of the present disclosure. Obviously, the embodiments described are some, not all, of the embodiments of the present disclosure.

Thus, the detailed description below of some embodiments of the present disclosure provided in conjunction with the drawings is not intended to limit the scope of the present disclosure for which protection is claimed and merely indicates selected embodiments of the present disclosure. All other embodiments obtained by those skilled in the art based on the embodiments in the present disclosure without inventive effort are included in the scope of protection of the present disclosure.

Unless otherwise defined in the context, the singular form includes the plural form. In the entire specification, the terms "comprise", "have", and the like are used herein to specify the existence of the said features, numbers, steps, operations, elements, components, or combinations thereof, but do not exclude the existence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof.

In addition, even though the terms including ordinal numbers such as "first" and "second" can be used to describe various components, these components are not restricted by these terms, and these terms are only used to distinguish one component from other components. For example, without departing from the scope of the present disclosure, a first component may be called a second component and, similarly, a second component may be called a first component.

In the description of the present invention, it is necessary to understand that the orientation or position relationship indicated by the terms such as "up", "down", "left", "right", "inside", and "outside" is based on the orientation or position relationship shown in the attached drawings, or the orientation or position relationship of usual placement when the disclosed product is in use, or the orientation or position relationship that is commonly understood by those skilled in the art, and is only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation and must be constructed and operated in a specific orientation, so they cannot be understood as restrictions on the present disclosure.

The present invention relates to an electric powertrain system, which for example is used in an electric vehicle or hybrid vehicle, and generally comprises an inverter (not shown), an electric machine assembly and a gearbox assembly. The inverter is connected to the electric machine assembly, and provides the necessary source of electrical energy for the electric machine assembly. The source of electrical energy is converted to mechanical energy inside the electric machine assembly, which transmits the mechanical energy to the gearbox assembly. The gearbox assembly transmits the mechanical energy to vehicle wheels for example, generally via a differential included in the gearbox assembly, to drive the wheels to move.

Specifically, as shown in Figs. 1-3, the electric powertrain system 10 proposed in the present invention comprises a housing 100. Inside the housing 100 are accommodated the electric machine assembly 200 and the gearbox assembly 300, as well as a support structure which supports the electric machine assembly 200 and the gearbox assembly 300. More specifically, the interior of the housing 100 may be divided into a first part for accommodating the electric machine assembly 200 and a second part for accommodating the gearbox assembly 300. In some embodiments, as shown in Figs 1-3, the housing 100 can be configured to include a single body shared by the electric machine assembly 200 and the gearbox assembly 300, which can reduce the number of parts, simplify the assembly process, achieve a lighter housing, and ensure space compactness. In other embodiments (not shown in the drawing), the housing can be constructed to comprise a first housing for accommodating the electric machine assembly and a second housing for accommodating the gearbox assembly, and the first housing and the second housing are manufactured separately and can be assembled together, which is conducive to achieving modular manufacturing and allows more flexible design of the electric machine assembly and the gearbox assembly.

The electric machine assembly 200 comprises an electric machine shaft 210, which is rotatable about a rotation axis X and comprises a first electric machine shaft end 211 and a second electric machine shaft end 212 axially opposite each other. The first electric machine shaft end 211 may be supported by a first bearing 400. The first bearing 400 may be positioned in a first bearing block 430 disposed on the housing 100. More specifically, the first bearing block 430 may be disposed in an end cap of the housing 100, and the end cap may be called a first end cap 110. This is conducive to overall compactness.

The gearbox assembly 300 comprises an input shaft 310. The input shaft 310 comprises a first input shaft end 311 and a second input shaft end 312 axially opposite each other. The second input shaft end 312 may be supported by a second bearing 500. The second bearing 500 is positioned in a second bearing block disposed on the housing 100. More specifically, the second bearing block may be disposed in another end cap of the housing 100. This other end cap may be called a second end cap 120 and is arranged axially opposite the first end cap 110. This is conducive to overall compactness.

As shown in Figure 1-3, in the electric powertrain system 10 proposed according to the present invention, the second electric machine shaft end 212 can be inserted into the first input shaft end 311 and form a coupling part with the first input shaft end 311 so that the input shaft 310 can coaxially rotate together with the electric machine shaft 210, thus transmitting the torque from the electric machine shaft 210 to the input shaft 310, that is, the input shaft 310 can also rotate around the rotation axis X. Besides, a third bearing 600 is also set and supported at said first input shaft end 311 and comprises a first axial end 610 facing said first bearing 400 and a second axial end 620 facing said second bearing 500. The third bearing 600 can more specifically support the first input shaft end 311 at the coupling part, thus supporting the electric machine shaft 210 and the input shaft 310 at the same time. In a more specific embodiment, the housing 100 can comprise a separating part 130 with holes for at least partially separating said first part used to accommodate the electric machine assembly 200 and said second part used to accommodate the gearbox assembly 300, wherein the holes allow the electric machine shaft 210 and the input shaft 310 to pass, and the third bearing 600 can be positioned in the third bearing block set on the separating part 130, which is conducive to overall compactness. As shown in Figs 1-3, in the case that the housing 100 is constructed to be a single main body that comprises and is shared by the electric machine assembly 200 and the gearbox assembly 300, the separating part 130 can be set to be integrated with the main body. Alternatively, the separating part 130 may also be a separate component attached to the housing 100. In addition, the coupling part can comprise a spline coupling part S and a radial centring part C, and the spline coupling part S is located axially between the second axial end 620 of the third bearing 600 and the tip 313 of the first input shaft end 311.

In the embodiment variant as shown in Fig. 1, the radial centring part C is axially arranged between the spline coupling part S and the tip 313 of the first input shaft end 311. In the embodiment variant shown in Fig. 2, the radial centring part C is axially arranged between the spline coupling part S and the tip 213 of the second electric machine shaft end 212. In the embodiment variant shown in Fig. 3, the radial centring part C is axially arranged on the outside of the second axial end 620 of said third bearing 600.

Thus, in the electric powertrain system 10 proposed in the present invention, the coupling part formed by the electric machine shaft 210 of the electric machine assembly 200 and the input shaft 310 of the gearbox assembly 300 comprises a radial centring part C, and it is thereby possible to ensure that the electric machine shaft 210 and the input shaft 310 are centred properly with respect to each other, such that they are able to rotate together about the same rotation axis X, effectively avoiding vibration and noise due to radial eccentricity between the electric machine shaft 210 and the input shaft 310, and ensuring effective transmission of torque from the electric machine shaft 210 to the input shaft 310 of the gearbox assembly 300. At the same time, the use of the first bearing 400, second bearing 500 and third bearing 600 as defined above helps to achieve effective and firm support for the electric machine shaft 210 and input shaft 310, and thus for the electric machine assembly 200 and gearbox assembly 300, in a compact structure. In particular, such a layout of the three bearings and the positioning of the coupling part relative to them and relative to the electric machine shaft 210 and input shaft 310 allow very firm support of the electric machine shaft 210 and the input shaft 310 of the gearbox assembly 300, further reducing vibration and noise. Excellent support precision is provided for the input shaft 310 of the gearbox assembly 300 in particular, thereby allowing a micro-modification design of the teeth of gears of the gearbox assembly 300, ensuring that the gears are able to present their optimal state and thereby achieve optimal performance during operation, and further helping to reduce noise.

Note that, in some embodiments, as shown in Fig. 3, said radial centring part C can axially overlap at least partially with said third bearing 600. This embodiment makes it possible to effectively support the input shaft 310 and therefore the electric machine shaft 210 at a position with greater rigidity, which is conducive to the robustness of the entire electric powertrain system 10.

In some embodiments, as shown in Figs. 1-3, the radial centring part C and the spline coupling part S are disposed axially adjacent to each other. Such a structure allows the corresponding radial centring part and spline coupling part to be conveniently machined on the electric machine shaft 210 and input shaft 310, and helps to simplify the assembling between the electric machine shaft 210 and the input shaft 310, thereby reducing the design, manufacturing and assembly costs, and increasing cost effectiveness.

In some embodiments, as shown in Figs. 1-3, the radial centring part C comprises a radial inner surface of the electric machine shaft 210, and a radial outer surface of the input shaft 310 which is in a clearance fit with the radial inner surface. Such a radial centring part C is able to ensure proper centring, is very easy to machine, and facilitates assembly, further increasing cost effectiveness. Preferably, in the embodiment variant shown in Fig. 1, the radial outward surface of the electric machine shaft 210 that forms the radial centring part C can be formed on an annular protrusion; in the embodiment variants shown in Fig. 2 and Fig. 3, the radial inner surface of the input shaft 310 that forms the radial centring part C can be formed on an annular protrusion. Thus, in both of the designs described above, the centring part C is formed of a structure that is easy to machine, reducing the design, machining and assembly costs. Of course, such designs of the radial centring part are merely exemplary and not exclusive; all common structures capable of achieving radial centring of the electric machine shaft and input shaft are included in the scope of protection of the present invention.

In addition, the electric powertrain system 10 proposed in the present invention is further provided with a series of axial positioning designs, to ensure that the electric machine shaft 210 of the electric machine assembly 200 and the input shaft 310 of the gearbox assembly 300 can be axially held in the desired position, thereby optimizing the operating performance thereof.

For example, in some embodiments, as shown in Fig. la, a retaining ring 214 is arranged on the second electric machine shaft end 212 of said electric machine shaft 210 and is axially between the tip 213 of said second electric machine shaft end 212 and said coupling part. More specifically, a circumferential groove 216 for accommodating the retaining ring 214 can be set in the second electric machine shaft end 212, and the retaining ring 214 can be elastic so that, during the assembly, specifically, when the electric machine shaft 210 is inserted into the input shaft 310, the retaining ring 214 is radially compressed in the circumferential groove 216 during the movement of the retaining ring 214 with the electric machine shaft 210 through the coupling part, so as not to hinder the insertion of the electric machine shaft 210, and, after the retaining ring 214 moves through the coupling part with the electric machine shaft 210, the retaining ring 214 can be radially extended to press against the inner wall of the input shaft 310 to realize the relative axial positioning between the electric machine shaft 210 and the input shaft 310. Thus, the retaining ring 214 may be provided in a simple manner with a very compact structure, allowing an improvement in axial positioning of the electric machine shaft 210 relative to the input shaft 310 of the gearbox assembly 300.

In some embodiments, as shown in Figs. 1-3, the first bearing 400 comprises a first bearing inner ring 410 and a first bearing outer ring 420. The first bearing inner ring 410 may form an interference fit with the electric machine shaft 210, and the first bearing outer ring 420 may form a transition fit with the electric machine shaft 210, to allow a very small amount of axial displacement of the first bearing outer ring 420 relative to the electric machine shaft 210. In some embodiments, as shown in Figs. 1-3, aforesaid first bearing block 430 is arranged at the first bearing outer ring 420, for example, a steel bearing block. It should be noted that in the absence of the first bearing block 430, relative movement of the first bearing 400 and the housing 100 will cause a bearing block hole provided in the housing to steadily increase in size, thus giving rise to a centring problem. The first bearing block 430 avoids such a problem. More specifically, an elastic member 440, such as a wave spring, can also be arranged between the second bearing outer ring 420 and the housing 100 such as the first end cover 110 of housing 100, and can exert an axial preload on the first bearing 400, e.g., an axial preload towards the input shaft 310 of the gearbox assembly 300, so as to conveniently and dynamically adjust the axial positioning of the electric machine shaft 210 relative to the input shaft 310, and ensure the torque transmission efficiency, which is beneficial to the robustness of the entire electric powertrain system 10. In some embodiments, a retaining ring (not shown in the figure) for axial positioning of the third bearing 600 may also be provided on the input shaft 310 of the gearbox assembly 300. More specifically, the retaining ring can be arranged on the axial inside of the first axial end 610 of the third bearing 600, that is, the side towards the electric machine shaft 210. More specifically, the third bearing 600 can comprise the third bearing inner ring 630 and the third bearing outer ring 640, wherein the third bearing inner ring 630 forms an interference fit with the input shaft 310, the third bearing outer ring 640 forms a slight interference fit or transition fit with the input shaft 310, and the retaining ring can be pressed against the third bearing inner ring 630. Therefore, setting the retaining ring can further stabilize the third bearing 600 axially, and thus further stabilize the input shaft 310 of the gearbox assembly 300.

In some embodiments, as shown in Figs. 1-3, the second bearing 500 comprises a second bearing inner ring 510 and a second bearing outer ring 520. The second bearing inner ring 510 forms an interference fit with the input shaft 310, and the second bearing outer ring 520 may form a loose fit with the input shaft 310.

It should be noted that when the second bearing 500 and third bearing 600 are arranged as described above, the input shaft 310 may be regarded as axially immovable. This ensures that the input shaft 310 transmits torque to a downstream component such as a differential 320 effectively, and helps to make the entire electric powertrain system 10 stable and robust.

It should be noted that the first end cover can be the end cover of the first housing and the second end cover can be an integral part of the second housing in the embodiment not shown in which the housing is constructed to comprise the first housing for accommodating the electric machine assembly and the second housing for accommodating the gearbox assembly. In such an embodiment, the separating part can be another part of the second housing that is separately manufactured and assembled with the second end cover.

In some specific embodiments, at least one of the first bearing 400, the second bearing 500 and the third bearing 600 is a deep groove ball bearing. In some embodiments, the electric powertrain system 10 may also comprise a water cooling system 220 for cooling the electric machine assembly 200, wherein the water cooling system 220 may comprise a water channel for water circulation, and, in one specific embodiment, the water channel may be integrated with the first end cover 110. More specifically, especially when the housing 100 is constructed to be a single main body that comprises and is shared by the electric machine assembly 200 and the gearbox assembly 300, a lip-like seal ring 215 can be arranged between the electric machine shaft 210 and the housing 100 and used for fluidic sealing of the first part of said housing 100 that accommodates said electric machine assembly 200 relative to the second part of said housing 100 that accommodates said gearbox assembly 300. The lip-like seal ring 215 is a two-way sealing element. When the electric machine assembly 200 and the gearbox assembly 300 operate, a positive or negative pressure will be generated in the housing 100, and the lip-like seal ring 215 can withstand two-way pressure. Thus, oil in the gearbox assembly 300 can be effectively prevented from flowing into the electric machine assembly 200, thus preventing the oil from negatively affecting components of the electric machine assembly 200 that have poor oil resistance. Meanwhile, the existence of the lip-like seal ring 215 can also prevent the water in the water cooling system from flowing into the gearbox assembly 300 due to accidental leakage.

In some alternative embodiments, the electric powertrain system 10 may comprise an oil cooling system (not shown in the figure) for cooling the electric machine assembly 200. More specifically, the oil from the gearbox assembly 300 can be transported to the electric machine assembly 200 through the following two paths: The first one is that the oil is transported to the inside of the housing of the electric machine assembly through the oil pipe or the housing pipe, and an oil groove is processed in the stator so as to cool down the stator; the second one is to send the oil to the electric machine shaft 210 through the input shaft 310, an oil hole is processed in the electric machine shaft 210, the oil hole can provide oil to the stator coil for cooling the stator end and stator coil. Preferably, in this case, the electric machine shaft 210 can be set as hollow, which is conducive to overall lightweightness. Meanwhile, compared with the water cooling system, the oil cooling system does not need to have a water channel set in the housing and more specifically in the first end cover, which simplifies the design and manufacture of the housing, more specifically the first end cover. In addition, the cooling oil can also be returned from the electric machine assembly 200 to the gearbox assembly 300 through the return pipe to realize recycling for reuse. In this case, it is not necessary to set the lip-like seal ring as described above.

In some specific embodiments, the gearbox assembly 300 employs a two- stage helical gear parallel- shaft arrangement, which enables a more compact overall structure. In addition, the gearbox assembly 300 may comprise the differential 320 as mentioned above; the differential 320 may, for example, be coupled to the vehicle wheels and thus transmit torque to the wheels. More specifically, the gearbox assembly 300 may comprise an input gear 314, an intermediate first gear 315 and an intermediate second gear 316. The input gear 314 is fixedly coupled to the input shaft 310, and the input gear 314 is preferably integrally formed with the input shaft 310, which helps to achieve a more compact and more stable assembly. Alternatively, the input gear 314 may be coupled to the input shaft 310 by splines. The intermediate first gear 315 and intermediate second gear 316 are disposed on an intermediate shaft 330. The intermediate shaft 330 is arranged in parallel with the input shaft 310, and the intermediate shaft can be hollow. The intermediate first gear 315 is transmission-meshed with the input gear 314, and the intermediate second gear 316 may be fixed to the differential 320. A two-stage helical gear parallel-shaft arrangement between the input shaft 310 and the differential 320 is thereby illustratively achieved.

Demonstrative embodiments of the electric powertrain system proposed in the present invention have been described in detail above with reference to preferred embodiments. However, those skilled in the art will understand that without departing from the concept of the present invention, various modifications and alterations may be made to the specific embodiments above, and various technical features and structures proposed in the present invention may be combined in various ways, without exceeding the scope of protection of the present invention. The scope of the present disclosure is not defined by the embodiments described above but is defined by the attached claims and their equivalent scope.

Claims

1. Electric powertrain system, comprising a housing (100) and, located within the housing (100): an electric machine assembly (200) comprising an electric machine shaft

(210), the electric machine shaft (210) comprising a first electric machine shaft end

(211) and a second electric machine shaft end (212), a gearbox assembly (300), comprising an input shaft (310), wherein said input shaft (310) comprises a first input shaft end (311) and a second input shaft end (312), said second electric machine shaft end (212) is inserted into said first input shaft end (311) to form a coupling part with said first input shaft end (311), so that said input shaft (310) and said electric machine shaft (210) can rotate together coaxially, a first bearing (400), being supported at the first electric machine shaft end (211), a second bearing (500), being supported at the second input shaft end (312), a third bearing (600), being supported at said first input shaft end (311) and the third bearing (600) comprising a first axial end (610) facing said first bearing (400) and a second axial end (620) facing said second bearing (500), wherein: the coupling part comprises a spline coupling part (S) and a radial centring part (C), said spline coupling part (S) is axially located between the second axial end (620) of said third bearing (600) and the tip (313) of said first input shaft end (311).

2. Electric powertrain system according to Claim 1, wherein said radial centring part (C) is axially arranged between said spline coupling part (S) and the tip (313) of said first input shaft end (311).

3. Electric powertrain system according to Claim 1, wherein said radial centring part (C) is axially arranged between said spline coupling part (S) and the tip (213) of said second electric machine shaft end (212).

4. Electric powertrain system according to Claim 3, wherein said radial centring part (C) is axially arranged on the outside of the second axial end (620) of said third bearing (600).

5. Electric powertrain system according to Claim 3, wherein said radial centring part (C) axially overlaps at least partially with said third bearing (600).

6. Electric powertrain system according to any one of Claims 1 to 5, characterized in that said radial centring part (C) and said spline coupling part (S) are axially arranged adjacent to each other.

7. Electric powertrain system according to any one of Claims 1 to 5, wherein said radial centring part (C) comprises a radial outer surface of said electric machine shaft (210) and a radial inner surface of said input shaft (310) that is in a clearance fit with said radial outer surface.

8. Electric powertrain system according to any one of Claims 1 to 5, wherein a retaining ring (214) is arranged on the second electric machine shaft end (212) of said electric machine shaft (210) and is axially between the tip (213) of said second electric machine shaft end (212) and said coupling part.

9. Electric powertrain system according to Claim 8, wherein said second electric machine shaft end (212) is designed with a circumferential groove (216) for holding said retaining ring (214), wherein said retaining ring (214) is elastic so that, in a process of inserting said electric machine shaft (210) into said input shaft (310), said retaining ring (214) is radially compressed in said circumferential groove (216) when said retaining ring (214) moves with said electric machine shaft (210) through said coupling part, and, after said retaining ring (214) moves with said electric machine shaft (210) through said coupling part, said retaining ring (214) can be radially extended to press against an inner wall of said input shaft (310).

10. Electric powertrain system according to any one of Claims 1 to 5, wherein the first bearing (400) comprises a first bearing inner ring and a first bearing outer ring, and an elastic member capable of applying an axial preload to the first bearing (400) is provided between the first bearing outer ring and the housing (100).

11. Electric powertrain system according to any one of Claims 1 to 5, wherein said input shaft (310) is provided with a retaining ring for axial positioning of said third bearing (600).

12. Electric powertrain system according to any one of Claims 1 to 5, wherein at least one of the first bearing (400), the second bearing (500) and the third bearing (600) is a deep groove ball bearing.

13. Electric powertrain system according to any one of Claims 1 to 5, wherein the electric powertrain system (10) comprises a water cooling system for cooling the electric machine assembly (200).

14. Electric powertrain system according to Claim 13, wherein a lip-like seal ring (215) is arranged between said electric machine shaft (210) and said housing (100) and is used for fluidic sealing of the first part of said housing (100) that accommodates said electric machine assembly (200) relative to the second part of said housing (100) that accommodates the gearbox assembly (300).

15. Electric powertrain system according to any one of Claims 1 to 5, wherein the gearbox assembly (300) employs a two-stage helical gear parallel-shaft arrangement, and comprises a differential (320).