Power transmission system for electric vehicles

Abstract

The present application relates to a power transmission system for an electric vehicle, the power transmission system comprising: an electric motor for providing driving power, the electric motor comprising a rotor and a drive shaft driven by the rotor; a reduction gear for reducing and increasing torque received from the drive shaft, the reduction gear comprising an intermediate drive shaft having a hollow axial passage; and a pump assembly for delivering lubricant, the pump assembly being mechanically integrated on and driven by the intermediate drive shaft. The pump assembly comprises a plurality of fluid passages to deliver lubricant into the hollow axial passage of the intermediate drive shaft and components disposed on the intermediate drive shaft.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application generally relate to a power transmission system for an electric vehicle. BACKGROUND

[0002] The trend of designing and manufacturing fuel-efficient, low-emission vehicles has been greatly increased due to the environmental concerns and the increase of fuel cost. The forefront of this trend is the development of electric vehicles, such as Battery Electric Vehicles (BEV), Hybrid Electric Vehicles (HEV), Plug-in Hybrid Electric Vehicles (PHEV), Range extended EVs, Fuel Cell Electric Vehicles (FCEV), etc., which combine relatively high-efficient internal combustion engines and electric motors.

[0003] In electric vehicles, particularly in the power transmission system thereof, there are rotating components which need to be lubricated in order to achieve their relatively long service life. Generally, in order to achieve sufficient lubricant supply, the differential gear, which is composed of the power transmission system, includes a storage structure which can accommodate lubricant, and the lubricant can be delivered to the rotating components of the entire power transmission system through at least one rotating component constituting the differential gear to be in contact with and lubricated by the lubricant. However, the lubricant will always maintain a high liquid level in the storage structure of the differential gear, and the agitation loss and the splash loss of the differential gear will be great during the constant speed cruise phase of the vehicle. Alternatively, additional nozzles are provided around the specific rotating components to perform targeted active lubrication, however, the provision of nozzles and pipelines will generate additional costs and processes.

[0004] Therefore, there is an urgent need to provide an improvement in the lubrication design of the power transmission system for an electric vehicle with at least a simple structure, lower energy consumption or loss, and lower cost. SUMMARY

[0005] Aspects and advantages of the present application will be set forth in part in the following description, or can be obvious from the description, or can be learned through practice of the application.

[0006] In one exemplary aspect, a powertrain system for an electric vehicle is provided. The powertrain system includes an electric motor for providing driving force, the electric motor including a rotor and a drive shaft driven by the rotor; a reduction gear for reducing speed and increasing torque received from the drive shaft, the reduction gear including an intermediate drive shaft having a hollow axial passage; and a pump assembly for delivering lubricant, the pump assembly being mechanically integrated on and driven by the intermediate drive shaft. The pump assembly includes a plurality of fluid passages for delivering lubricant into the hollow axial passage of the intermediate drive shaft and onto components disposed on the intermediate drive shaft.

[0007] In some embodiments, the pump assembly further includes a pumping shaft coaxially integrated with the intermediate drive shaft and configured for actuating the pump assembly to deliver lubricant.

[0008] In some embodiments, the plurality of fluid passages includes at least one transverse passage for delivering lubricant into the hollow axial passage of the intermediate drive shaft, and at least one longitudinal passage for delivering lubricant onto components disposed on the intermediate drive shaft.

[0009] In some embodiments, the plurality of fluid passages further includes an axial passage in the pump assembly, the axial passage being in fluid communication with the hollow axial passage of the intermediate drive shaft.

[0010] In some embodiments, the axial passage is further in fluid communication with the at least one transverse passage.

[0011] In some embodiments, the powertrain system further includes a connecting member fixedly connected with the intermediate drive shaft and the pumping shaft for actuating the pumping shaft.

[0012] In some embodiments, the connecting member is a sleeve.

[0013] In some embodiments, the connecting member is a one-way clutch configured to rotate in one direction.

[0014] In some embodiments, the connecting member includes a connecting portion for preventing backflow or leakage of lubricant from the hollow axial passage of the intermediate drive shaft.

[0015] In some embodiments, the powertrain system further includes an annular gap between the pumping shaft and the intermediate drive shaft in fluid communication with the at least one longitudinal passage such that lubricant can be delivered therethrough to components disposed on the intermediate drive shaft.

[0016] In some embodiments, the annular gap is disposed laterally adjacent to a bearing supporting the intermediate drive shaft such that lubricant can be delivered to the bearing through the annular gap.

[0017] In some embodiments, the intermediate drive shaft further comprises at least one radial passage in fluid communication with the hollow axial passage for delivering lubricant to components disposed on the intermediate drive shaft.

[0018] In some embodiments, the pump assembly further comprises a chamber configured for storing lubricant delivered for the plurality of fluid passages. The at least one radial passage extends radially from the chamber for delivering lubricant stored in the chamber, and the at least one longitudinal passage extends axially from the chamber for delivering lubricant stored in the chamber.

[0019] In some embodiments, the pump assembly is a rotary gear pump.

[0020] In some embodiments, the pump assembly is configured to deliver lubricant in only a single direction when the pump assembly is driven to rotate.

[0021] In some embodiments, the powertrain further comprises a differential for distributing the reduced driving force to driven wheels; and a separable clutch disposed on the intermediate drive shaft for providing intermittent transmission of driving force between the electric motor and the differential; wherein the pump assembly is configured for delivering lubricant to provide active lubrication for the differential to minimize the level of lubricant injected into the differential.

[0022] In some embodiments, the powertrain further comprises an actuator coaxially disposed with the separable clutch for providing engagement and non-engagement forces for the separable clutch.

[0023] In some embodiments, the actuator is cooled via lubricant delivered from at least one radial passage in fluid communication with the hollow axial passage of the intermediate drive shaft.

[0024] In some embodiments, the actuator is a solenoid valve.

[0025] 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. BRIEF DESCRIPTION OF DRAWINGS

[0026] The complete and illustrative disclosure of the present application, including its best mode, directed to one of ordinary skill in the art, is set forth in the specification and drawings, wherein:

[0027] Figure 1 is a schematic diagram of a powertrain according to an exemplary embodiment of the present application.

[0028] Figure 2 yes Figure 1 A cross-sectional view of one direction of an exemplary embodiment of the power transmission system shown.

[0029] Figure 3 yes Figure 1 Another cross-sectional view of an exemplary embodiment of the power transmission system shown illustrates a transverse channel in the hollow axial channel that delivers lubricant to the intermediate drive shaft.

[0030] Figure 4 yes Figure 1 The illustrated exemplary embodiment of the power transmission system is shown in a cross-sectional view in one direction, which shows multiple radial channels on the intermediate drive shaft. Detailed Implementation

[0031] The embodiments of this application will now be described in detail with reference to the figures, including one or more examples of embodiments of this application. Each example is provided for the purpose of explaining this application and not for limiting it. In fact, those skilled in the art will appreciate that various modifications and variations can be made to this application without departing from the scope or spirit of this application. For example, a feature illustrated or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, it is intended that this application cover such modifications and variations, which are within the scope of the appended claims and their equivalents. As used in this specification, the terms “first,” “second,” etc., are used interchangeably to distinguish one component from another and are not intended to indicate the location or importance of the components. As used in this specification, unless the context clearly indicates otherwise, the terms “a,” “an,” “the,” and “the” are intended to indicate the presence of one or more elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be other elements in addition to those listed.

[0032] Referring now to the accompanying drawings, in which the same numbers throughout the drawings denote the same elements. Figures 1 to 4 An exemplary powertrain system 100 for an electric vehicle is shown. The powertrain system 100 comprises an inverter (not shown), an electric motor 1, a reducer 2, and a differential 3. Specifically, the electric motor 1 may be housed in one housing, and the reducer 2 and the differential may be housed in another housing. These two housings may be integrally formed or assembled from multiple housing components. The two housings may be fixedly connected, for example, by screws. A sealing wall may be provided between the two housings.

[0033] The electric motor 1 can be a synchronous electric motor, or an asynchronous electric motor. When the electric motor 1 is a synchronous electric motor, it can comprise a wound rotor or a permanent magnet rotor. For a nominal supply voltage of 48V to 350V, or for higher power where the supply voltage can be up to 800V, the nominal power provided by the electric motor can be between 10KW and 300KW, for example in the order of 15KW. In case the electric motor is suitable for a high voltage supply, the nominal power provided by the electric motor can be 300KW. In the illustrated embodiment, the electric motor 1 is a synchronous electric motor with permanent magnets, which provides a rated power between 10KW and 300KW. The electric motor 1 can comprise a stator with a three-phase winding, or a combination of two three-phase windings or a five-phase winding. Furthermore, the electric motor 1 can comprise a drive shaft 11, which is driven by the electric power resulting from the electromagnetic effects of the rotor and the stator comprised in the electric motor 1.

[0034] The inverter is connected to the electric motor 1 by means of electric wires. The inverter converts direct current (DC) supplied by an electric energy storage unit (not shown) provided with a nominal voltage into alternating current (AC) for the electric motor 1. The inverter 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). In case the nominal supply voltage is 48V, the inverter can be a MOSFET. In case the supply voltage corresponds to a high voltage, the power inverter can be an IGBT.

[0035] The reduction gear 2 is associated with the electric motor 1. The reduction gear 2 can convert the high speed, low torque of the electric motor into a low speed, high torque. The reduction gear 2 can comprise a plurality of reduction gears connected to the electric motor 1 and to the differential 3 and having different speeds, wherein one gear is driven by, for example, the electric motor 1, thereby increasing the torque by reduction. The reduction gear 2 can further comprise an intermediate drive shaft 21 connected to one gear driven by the drive shaft 11 and to another gear having a larger diameter and further connected to the differential 3, thereby distributing the driving force of the reduction to the driven wheels 4.

[0036] In the illustrated embodiment, the intermediate drive shaft 21 is rotatably supported in the housing by two bearings 9, which can be provided in the form of a rolling contact bearing, and each bearing is placed at an end of the intermediate drive shaft 21.

[0037] In some embodiments, the reduction gear 2 comprises at least three reduction gears, a separable clutch 6 is coaxially arranged with one of the at least three reduction gears closest to the differential or closest to the electric motor, for providing an intermittent transmission of driving force between the electric motor 1 and the differential 3. In some embodiments, one of the at least three reduction gears is fixedly connected to a part of the separable clutch.

[0038] In the illustrated embodiment, the speed reducer 2 comprises two stages of reduction gears, wherein the first stage of reduction gears comprises a first driving gear 22 connected to the electric motor 1 and a first driven gear 23 connected to the intermediate transmission shaft 21, the first driving gear 22 and the second driven gear 23 being engageable with each other. The second stage of reduction gears comprises a second driving gear 24 connected to the intermediate transmission shaft 21 and a second driven gear 25 connected to the differential 3, the second driving gear 24 and the driven gear 25 being engageable with each other.

[0039] Please continue to refer to Figure 1 A separable clutch 6 is also provided for providing intermittent transmission of driving force between the electric motor 1 and the differential 3. The separable clutch 6 is arranged on the intermediate transmission shaft 21 and fixedly connected to the second driving gear 24. In some embodiments, the separable clutch 6 can be fixedly connected to the first driven gear 23. When the separable clutch 6 is engaged, the driving force of the electric motor 1 can be transmitted to the vehicle via the speed reducer 2 and the clutch 6 to provide auxiliary driving force.

[0040] As shown, a bearing 7 is also provided to support the separable clutch 6, the second driving gear 24 rolling on the bearing 7 coaxially arranged on the intermediate transmission shaft 21. In some embodiments, if the clutch 6 is fixedly connected to the first driven gear 23, the first driven gear 23 can roll on the bearing 7.

[0041] Further, an actuator 8 is also provided to provide engagement force and non-engagement force for the separable clutch 6. Specifically, the actuator 8 is arranged on the intermediate transmission shaft 21 and mechanically connected to another part 61 of the separable clutch 6. In some embodiments, the actuator 8 can be a solenoid valve. When the vehicle needs auxiliary driving force, the actuator 8 will be activated to provide engagement force, so that the separable clutch is in the engaged state, thereby driving the intermediate transmission shaft 21 to rotate, and ultimately driving the differential 3 through the reduction gears to provide driving force to the vehicle.

[0042] As shown, a pump assembly 5 is also provided for transporting lubricant throughout the power transmission system 100, and in particular for providing active lubrication for the speed reducer 2 by pumping lubricant into a storage structure (not shown) of the differential 3 that can accommodate lubricant. The pump assembly 5 will always work, i.e. keep pumping lubricant from the differential 3, in the case that the separable clutch 6 is in the non-engaged state, so that the electric motor can be continuously lubricated and cooled.

[0043] In some embodiments, the pump assembly 5 can be a mechanical pump. For the embodiment shown, the pump assembly 5 is mechanically integrated on and driven by the intermediate drive shaft 21. When the pump assembly 5 is driven to rotate in either a clockwise or counterclockwise direction, the pump assembly 5 will always supply lubricant in one direction to prevent backflow of the lubricant, thereby creating unnecessary air bubbles in the lubricant to affect the performance of the lubricant.

[0044] As shown in Figs. 1 and 2, the pump assembly 5 is disposed at an end of the intermediate drive shaft 21. The pump body of the pump assembly 5 includes a chamber 54 therein for storing lubricant. In addition, the pump body of the pump assembly 5 includes a plurality of fluid passages for receiving and delivering lubricant from the chamber 54, by which lubricant can be delivered to the hollow axial passage 211 of the intermediate drive shaft 21 and to components disposed outside of the intermediate drive shaft 21. Figure 2 Figure 3 The pump assembly 5 further includes a pumping shaft 53 coaxially integrated with the intermediate drive shaft 21. A connecting member 28 is also provided for fixedly connecting the intermediate drive shaft 21 and the pumping shaft 52, such that the pumping shaft 53 is rotationally and axially fixed to the intermediate drive shaft 21. In some embodiments, the connecting member can be a sleeve. With the connecting member 28, the pumping shaft 53 can be actuated by the intermediate drive shaft, and the pump assembly 5 is thereby actuated to supply lubricant. Due to the high pressure generated by the actuation of the pump assembly 5, the lubricant in the chamber 54 will flow to the plurality of fluid passages in the pump assembly 5. In some embodiments, if the pump assembly 5 is not configured to provide lubricant in only one direction, the connecting member 28 can be a one-way clutch that allows rotation in only one direction and prevents driving force in the opposite direction, such that the pumping shaft 53 is actuated by the connecting member 28, i.e., the one-way clutch, to operate in only the forward direction and lubricant flows in only one direction.

[0045] In the embodiment shown, the plurality of fluid passages includes an axial passage 531 within the pumping shaft 53 that is in fluid communication with the hollow axial passage 211 of the intermediate drive shaft 21. As shown in Fig. 2, the plurality of fluid passages also includes at least one lateral passage 51 that extends radially from the chamber 54 to deliver lubricant stored therein. The axial passage 531 is also in fluid communication with the at least one lateral passage 51, such that lubricant stored in the chamber 54 can be delivered via the lateral passage 51 into the axial passage 531 and, in turn, to the hollow axial passage 211 of the intermediate drive shaft 21. Such a configuration can enable lubrication of bearings located at the end of the intermediate drive shaft.

[0046] In the embodiment shown, the plurality of fluid passages includes an axial passage 531 within the pumping shaft 53 that is in fluid communication with the hollow axial passage 211 of the intermediate drive shaft 21. As shown in Fig. 2, the plurality of fluid passages also includes at least one lateral passage 51 that extends radially from the chamber 54 to deliver lubricant stored therein. The axial passage 531 is also in fluid communication with the at least one lateral passage 51, such that lubricant stored in the chamber 54 can be delivered via the lateral passage 51 into the axial passage 531 and, in turn, to the hollow axial passage 211 of the intermediate drive shaft 21. Such a configuration can enable lubrication of bearings located at the end of the intermediate drive shaft. Figure 3

[0047] ​​In some embodiments, the connecting member 28 includes a connecting portion 281 located on the radial surface between the axial channel 531 of the pumping shaft 5 and the hollow axial channel 211 of the intermediate drive shaft 21. This connecting portion 281 is designed to prevent backflow or leakage of lubricant from the hollow axial channel 211 of the intermediate shaft 21. Such a structure can also be used to actuate the pump assembly 5.

[0048] like Figure 2 As shown, the plurality of fluid channels also includes at least one longitudinal channel 53 52 extending axially from the chamber 54 to provide lubrication for components on the intermediate drive shaft. The at least one longitudinal channel 52 is in fluid communication with an annular gap 26 located between the pump shaft 53 and the intermediate drive shaft. Lubricant within the chamber 54 can be delivered to components on the intermediate drive shaft via the longitudinal channel 52 and the annular gap 26.

[0049] In the illustrated embodiment, the annular gap 26 is radially adjacent to the bearing 27 supporting the intermediate drive shaft 21, and lubricant can flow from the longitudinal channel 52 and through the annular gap 26 to the bearing 27 to lubricate it.

[0050] like Figure 4 As shown, the intermediate drive shaft 21 also includes at least one circumferentially distributed radial channel 212, 213, 214, which are in fluid communication with the hollow axial channel 211 for conveying lubricant to components on the intermediate drive shaft. In this way, lubricant can flow from the interior of the intermediate drive shaft 21 to the drive gear 24, driven gear 2, actuator 8, bearing 7, and other components requiring lubrication. In the illustrated embodiment, the actuator 8 may be a solenoid valve, which can be cooled using the lubricant specifically flowing from the radial channels 212, 213.

[0051] This specification uses examples to disclose this application, including preferred embodiments, and also enables those skilled in the art to practice this application, including making and using any apparatus or system and performing any incorporated methods. The patentable scope of this application is defined by the claims and may include other embodiments conceived by those skilled in the art. Such other embodiments are deemed to be within the scope of the claims if they include structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A power transmission system for an electric vehicle, comprising: An electric motor for providing driving force, the electric motor including a rotor and a drive shaft driving the rotor; A speed reducer for reducing and increasing the torque received from the drive shaft, the speed reducer including an intermediate drive shaft having a hollow axial channel; as well as A pump assembly for delivering lubricant is mechanically integrated into and driven by the intermediate drive shaft. The pump assembly includes multiple fluid channels for delivering lubricant to a hollow axial channel of the intermediate drive shaft and components disposed on the intermediate drive shaft. The multiple fluid channels include: at least one transverse channel for delivering lubricant to the hollow axial channel of the intermediate drive shaft; and at least one longitudinal channel for delivering lubricant to the components disposed on the intermediate drive shaft. The pump assembly includes a pumping shaft coaxially integrated with the intermediate drive shaft and configured to actuate the pump assembly to deliver lubricant. The feature is that it further includes an annular gap located between the pumping shaft and the intermediate drive shaft, in fluid communication with the at least one longitudinal channel so that lubricant can be delivered therethrough to a component disposed on the intermediate drive shaft, and The annular gap is arranged laterally adjacent to the bearing supporting the intermediate drive shaft, so that lubricant can be delivered to the bearing through the annular gap.

2. The power transmission system according to claim 1, characterized in that, The plurality of fluid channels also include: An axial channel located in the pump assembly, the axial channel being in fluid communication with the hollow axial channel of the intermediate drive shaft.

3. The power transmission system according to claim 2, characterized in that, The axial channel is also in fluid communication with the at least one transverse channel.

4. The power transmission system according to claim 1, further comprising: A connecting member is fixedly connected to the intermediate drive shaft and the pumping shaft, and is used to actuate the pumping shaft.

5. The power transmission system according to claim 4, characterized in that, The connecting member is a sleeve, or a one-way clutch configured to rotate in one direction.

6. The power transmission system according to claim 4, characterized in that, The connecting member includes a connecting portion for preventing lubricant from flowing back or leaking from the hollow axial channel of the intermediate drive shaft.

7. The power transmission system according to claim 1, characterized in that, The intermediate drive shaft also includes at least one radial channel, which is in fluid communication with the hollow axial channel for delivering lubricant to a component disposed on the intermediate drive shaft.

8. The power transmission system according to claim 1, characterized in that, The pump assembly further includes a chamber configured to store lubricant for delivery to the plurality of fluid channels, the at least one lateral channel extending radially from the chamber for delivering the lubricant stored in the chamber, and the at least one longitudinal channel extending axially from the chamber for delivering the lubricant stored in the chamber.

9. The power transmission system according to claim 1, characterized in that, The pump assembly is a rotary gear pump and is configured to deliver lubricant in only one direction when the pump assembly is driven to rotate.

10. The power transmission system according to claim 1, further comprising: A differential is used to distribute decelerating driving force to the driven wheels; as well as A separable clutch, located on the intermediate drive shaft, is used to provide an intermittent transmission of driving force between the electric motor and the differential; The pump assembly is configured to deliver lubricant to provide active lubrication to the gearbox, thereby minimizing the level of lubricant injected into the differential.

11. The power transmission system according to claim 10, further comprising: An actuator, coaxially arranged with the separable clutch, is used to provide the separable clutch with engagement and disengagement forces. The actuator is cooled via lubricant supplied from at least one radial channel in fluid communication with a hollow axial channel of the intermediate drive shaft.

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