Shaft assembly and vehicle power system

Abstract

The utility model provides a shaft assembly and a vehicle power system. The shaft assembly comprises a first shaft and a second shaft which are assembled together, and the second shaft is partially inserted into the first shaft. An inner spline is arranged on the inner circumferential face of the first shaft, an outer spline is arranged on the outer circumferential face of the second shaft, and the inner spline and the outer spline are matched with each other. A first spherical surface portion is formed on the inner circumferential surface of the first shaft, a second spherical surface portion is formed on the outer circumferential surface of the second shaft, the internal spline and the first spherical surface portion are arranged at an interval in the axial direction of the first shaft, and the second spherical surface portion and the external spline are arranged at an interval in the axial direction of the second shaft. Therefore, the shaft assembly can still work smoothly under the condition that the central axes of the first shaft and the second shaft are not collinear, and the condition that the first shaft and the second shaft generate unexpected bending loads is avoided, so that the problems that the shaft assembly works unstably and the service life is shortened due to the existence of the bending loads are solved.

Description

Technical Field

[0001] This application relates to assemblies with different axle configurations, and more specifically to an axle assembly and a vehicle powertrain system including the axle assembly. Background Technology

[0002] Currently, in pure electric and hybrid vehicles, the motor and transmission can be integrated to form an electric drive system. Typically, the motor includes a stator, a rotor, and a motor shaft, which is mounted to the rotor so that it can rotate relative to the stator along with the rotor. The transmission includes a gear drive mechanism, an input shaft, and an output shaft, both of which are driveably connected to the gear drive mechanism. Furthermore, in the prior art, the motor shaft and the input shaft are rigidly connected to each other via, for example, long bolts to form a shaft assembly, allowing the motor and transmission to transmit torque via this assembly. Additionally, the motor shaft is supported by bearings within the motor housing, and the input shaft is supported by bearings within the transmission housing.

[0003] However, due to manufacturing and assembly errors in the bearings and bearing housings, the central axes of the motor shaft and input shaft may not be collinear after they are installed with their respective bearings. In this case, after rigidly connecting the motor shaft and input shaft, at least one of them will be in a bent state, resulting in the motor shaft operating in a bent state. This will cause both shafts to be subjected to bending loads during operation, leading to instability and reduced lifespan; furthermore, it will cause the bearings corresponding to these two shafts to bear periodic static or dynamic loads, further reducing bearing lifespan. Utility Model Content

[0004] To overcome the shortcomings of the prior art, one object of this application is to provide a shaft assembly that can avoid unwanted bending loads from two different shafts with non-collinear central axes and transmission connections. Another object of this application is to provide a vehicle powertrain system including the above-mentioned shaft assembly.

[0005] To achieve the above objectives, the present application may adopt the following technical solutions.

[0006] This application provides a shaft assembly comprising a first shaft and a second shaft assembled together, wherein the second shaft is partially inserted into the first shaft.

[0007] The first shaft has an internal spline on its inner circumferential surface, and the second shaft has an external spline on its outer circumferential surface. The internal spline and the external spline cooperate to form a spline mechanism. The inner circumferential surface of the first shaft has a first spherical portion, and the outer circumferential surface of the second shaft has a second spherical portion. The first spherical portion is fitted onto the second spherical portion and they are shaped to fit together. The first spherical portion and the internal spline are spaced apart axially from each other on the first shaft, and the second spherical portion and the external spline are spaced apart axially from each other on the second shaft.

[0008] By utilizing the first spherical surface and the second spherical surface, the shaft assembly is able to transmit torque between the first shaft and the second shaft via the spline mechanism, even when the central axes of the two shafts are not collinear.

[0009] In an alternative embodiment, the first shaft and the second shaft are engaged only through the first spherical surface and the second spherical surface, as well as through the internal spline and the external spline.

[0010] In another alternative, the diameter of the second spherical part is smaller than the diameter of the first spherical part.

[0011] In another alternative, the first spherical surface tends to extend radially outward as it extends toward the side where the second axis is located, and the second spherical surface tends to extend radially inward as it extends toward the side where the first axis is located.

[0012] In another alternative embodiment, the axial length of the internal spline is greater than the axial length of the first spherical surface portion, and the axial length of the external spline is greater than the axial length of the second spherical surface portion.

[0013] In another alternative embodiment, the first spherical portion is located radially outside the inner spline in the radial direction of the first shaft, and the second spherical portion is located radially outside the outer spline in the radial direction of the second shaft.

[0014] This application also provides a vehicle powertrain system, including the shaft assembly, motor and transmission described in any of the above technical solutions, wherein the first shaft is the input shaft of the transmission and the second shaft is the motor shaft of the motor.

[0015] In one alternative embodiment, the assembly further includes a housing, a first bearing, a second bearing, and a third bearing, wherein the first bearing and the second bearing are located between the first shaft and the housing, and the third bearing is located between the second shaft and the housing, such that the housing supports the shaft assembly via the first bearing, the second bearing, and the third bearing.

[0016] In another alternative embodiment, the first bearing and the second bearing are located at the two axial ends of the first shaft, and the third bearing is located at the end of the second shaft away from its external spline.

[0017] In another alternative embodiment, the motor includes a rotor, the second shaft is mounted on the rotor, and the third bearing and the second bearing are located on opposite sides of the rotor along its axial direction.

[0018] By adopting the above technical solution, this application provides a shaft assembly and a vehicle powertrain system including the shaft assembly. The shaft assembly includes a first shaft and a second shaft assembled together, with the second shaft partially inserted into the first shaft. On one hand, the first shaft has an internal spline on its inner circumferential surface, and the second shaft has an external spline on its outer circumferential surface. The internal and external splines cooperate to enable a transmission connection between the first and second shafts. On the other hand, the inner circumferential surface of the first shaft forms a first spherical surface, and the outer circumferential surface of the second shaft forms a second spherical surface. The internal spline and the first spherical surface are spaced apart axially from each other on the first shaft, and the second spherical surface and the external spline are also spaced apart axially from each other on the second shaft. Utilizing the first and second spherical surfaces, the shaft assembly can transmit torque between the first and second shafts via the spline mechanism even when the central axes of the first and second shafts are not collinear.

[0019] Thus, the spline mechanism formed by the internal spline of the first shaft and the external spline of the second shaft enables the first and second shafts to be connected by a spline mechanism, thereby transmitting torque between them. Furthermore, the first spherical part of the first shaft and the second spherical part of the second shaft fit together to form a spherical joint structure, allowing the first and second shafts to swing relative to each other within a predetermined range. Therefore, the shaft assembly according to this application utilizes the aforementioned spherical joint structure for support and a spline mechanism for transmission connection, instead of employing the rigid connection method of the prior art to achieve the above functions. As a result, the shaft assembly according to this application can operate smoothly even when the central axes of the first and second shafts are not collinear, while avoiding unwanted bending loads on the first and second shafts with non-collinear central axes. This eliminates the problems of unstable operation and reduced lifespan of the shaft assembly caused by such bending loads. Furthermore, by employing a scheme in which the internal spline and the first spherical surface are spaced apart axially on the first shaft, and the external spline and the second spherical surface are spaced apart axially on the second shaft, compared to a scheme where the spline may be directly mounted on the spherical surface, the machining process of the spline and the spherical surface can be simplified, and the spline design can be made longer, which is beneficial for transmitting large torques or for reducing the radial dimension of the shaft assembly.

[0020] It is understood that a small relative oscillation within a predetermined range allows for a relative positional relationship where the central axes of the first and second shafts are not aligned due to manufacturing and / or assembly errors. The magnitude of this relative oscillation should not affect the function of transmitting torque between them via the spline mechanism. However, during design and production, it is desirable that the central axes of the first and second shafts be collinear. Attached Figure Description

[0021] Figure 1A This is a cross-sectional schematic diagram showing a vehicle powertrain system according to an embodiment of the present application, wherein the cross-sectional lines are omitted.

[0022] Figure 1B It shows Figure 1A An enlarged schematic diagram of a portion of the vehicle's powertrain system.

[0023] Figure 2A It shows Figure 1A A three-dimensional schematic diagram of the first shaft of the axle assembly of the vehicle powertrain system.

[0024] Figure 2B It shows Figure 2A A cross-sectional view of the first axis in the diagram, where section lines are omitted.

[0025] Figure 3A It shows Figure 1A A three-dimensional schematic diagram of the second shaft of the axle assembly of the vehicle powertrain system.

[0026] Figure 3B It shows Figure 3A A cross-sectional view of the second axis in the diagram, where section lines are omitted.

[0027] Explanation of reference numerals in the attached figures

[0028] 1-axis assembly;

[0029] 11 First axis; A1 First axial direction; R1 First radial direction; 11t Internal spline; 11s First spherical surface;

[0030] 12 Second axis; A2 Second axial direction; R2 Second radial direction; 12t External spline; 12s Second spherical surface;

[0031] 2. Electric motor;

[0032] 21. Stator;

[0033] 22 Rotors;

[0034] 3. Transmission;

[0035] 4. Shell;

[0036] 5a First bearing; 5b Second bearing; 5c Third bearing. Detailed Implementation

[0037] Exemplary embodiments of this application are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are for teaching those skilled in the art how to implement this application only, and are not intended to exhaust all possible methods of this application, nor to limit the scope of this application.

[0038] In this application, the terms "axial", "radial", and "circumferential" for each axis refer to the direction of the axis along the central axis, the direction perpendicular to the central axis, and the direction of rotation about the central axis.

[0039] The following description, in conjunction with the accompanying drawings, describes a vehicle powertrain system and its included axle assemblies according to an embodiment of this application.

[0040] like Figure 1A and Figure 1B As shown, a vehicle power system according to an embodiment of this application is an electric axle drive system, which includes an axle assembly 1, a motor 2, a transmission 3, a housing 4, a first bearing 5a, a second bearing 5b, and a third bearing 5c ​​assembled together.

[0041] In this embodiment, as Figure 1A and Figure 1B As shown, the shaft assembly 1 includes a first shaft 11 and a second shaft 12 assembled together and drivingly connected to each other, wherein the central axis of the first shaft 11 and the central axis of the second shaft 12 may be collinear or non-collinear.

[0042] like Figure 1A , Figure 1B , Figure 2A and Figure 2B As shown, the first shaft 11 is driven by the gear transmission mechanism of the transmission 3, serving as the input shaft of the transmission 3. The first shaft 11 extends linearly along the first axial direction A1 and is formed as a hollow shaft extending through the first axial direction A1. At the central portion of the first shaft 11 located between its two axial ends, the first shaft 11 is provided with an internal spline 11t on its inner circumferential surface. The internal spline 11t includes a plurality of key teeth protruding radially inward from the inner circumferential surface of the first shaft 11. Furthermore, at one axial end of the first shaft 11 ( Figure 1A , Figure 1B and Figure 2BAt the left end of the first shaft 11, a first spherical surface 11s is formed on the inner circumferential surface. The first spherical surface 11s extends continuously along the circumference of the first shaft 11, so that the outline of the first spherical surface 11s in any cross-section containing the central axis of the first shaft 11 consists of two arcs on the same circle. The first spherical surface 11s extends towards the side where the second shaft 12 is located while also extending radially outward, that is, in the above-mentioned arbitrary cross-section, each arc extends radially outward while extending towards the side where the second shaft 12 is located, and this extension trend changes monotonically. Further, the center of the sphere corresponding to the spherical surface of the first spherical surface 11s can be located on the central axis of the first shaft 11. In the first radial direction R1, the first spherical surface 11s is located radially outward of the inner spline 11t, so that the first spherical surface 11s is located radially outward than the inner spline 11t. In the first axial direction A1, the first spherical surface 11s is spaced apart from the inner spline 11t. In addition, the axial length of the internal spline 11t is greater than the axial length of the first spherical surface 11s, thus the internal spline 11t has the ability to transmit sufficient torque.

[0043] like Figure 1A , Figure 1B , Figure 3A and Figure 3BAs shown, the second shaft 12 is mounted on and driven by the rotor 22 of the motor 2, serving as the motor shaft of the motor 2. The second shaft 12 extends linearly along the second axis A2 and is partially inserted into the first shaft 11. At the portion of the second shaft 12 inserted into the first shaft 11, an external spline 12t is provided on its outer circumferential surface. The external spline 12t includes a plurality of key teeth protruding radially outward from the outer circumferential surface of the second shaft 12. The key teeth of the external spline 12t and the key teeth of the internal spline 11t are always engaged, such that the external spline 12t and the internal spline 11t cooperate to form a spline mechanism. Furthermore, spaced apart from the portion where the external spline 12t is provided, a second spherical surface 12s is formed on the outer circumferential surface of the second shaft 12. The second spherical surface 12s extends continuously along the circumference of the second shaft 12, such that the outline of the second spherical surface 12s in any cross-section containing the central axis of the second shaft 12 consists of two arcs lying on the same circle. The second spherical surface portion 12s extends towards the side where the first shaft 11 is located while also extending radially inward. In other words, in any of the aforementioned cross-sections, each arc segment extends towards the side where the first shaft 11 is located while simultaneously extending radially inward, and this extension trend changes monotonically. Furthermore, the center of the sphere corresponding to the spherical surface of the second spherical surface portion 12s can be located on the central axis of the second shaft 12. In the second radial direction R2, the second spherical surface portion 12s is located radially outward of the outer spline 12t, thus the second spherical surface portion 12s is positioned radially outward than the outer spline 12t. In the second axial direction A2, the second spherical surface portion 12s is spaced apart from the outer spline 12t. Additionally, the axial length of the outer spline 12t is greater than the axial length of the second spherical surface portion 12s, thus the spline 12t has the ability to transmit sufficient torque.

[0044] like Figure 1A and Figure 1B As shown, with the vehicle powertrain assembled, the second shaft 12 is inserted into the first shaft 1. On one hand, the first spherical portion 11s fits onto the second spherical portion 12s, and their shapes are matched, so that the first spherical portion 11s is in a state of enclosing the second spherical portion 12s. On the other hand, the spherical diameter of the second spherical portion 12s is smaller than the spherical diameter of the first spherical portion 11s. Therefore, during the assembly of the first shaft 11 and the second shaft 12, the shape matching between the first spherical portion 11s and the second spherical portion 12s, as well as the gap caused by the difference in spherical diameters, help to achieve a slight relative oscillation between the first shaft 11 and the second shaft 12 even when their central axes are not collinear. This allows adjustment of the relative positional relationship between the first shaft 11 and the second shaft 12.

[0045] It is understood that in the shaft assembly 1 including the first shaft 11 and the second shaft 12, the first shaft 11 and the second shaft 12 are engaged only through the engagement of the first spherical part 11s and the second spherical part 12s, and the mating of the inner spline 11t and the outer spline 12t. That is, apart from the torque transmission through the mating of the inner spline 11t and the outer spline 12t, the first shaft 11 and the second shaft 12 are supported only by the contact between the first spherical part 11s and the second spherical part 12s; other parts of the two shafts do not need to contact each other. Thus, by utilizing the spherical mating of the first spherical part 11s and the second spherical part 12s and the gap between the spherical surfaces, the first shaft 11 and the second shaft 12 can swing relative to each other within a predetermined range even when their central axes are not collinear. This allows the shaft assembly 1 to smoothly transmit torque between the first shaft 11 and the second shaft 12 via the spline mechanism even when their central axes are not collinear, and the first shaft 11 and the second shaft 12 are not subjected to additional bending loads.

[0046] In this embodiment, as Figure 1A As shown, the motor 2 includes a stator 21 and a rotor 22. The stator 21 is fixed relative to the housing 4. The rotor 22 is located radially inside the stator 21, and there is an air gap between the rotor 22 and the stator 21, allowing the rotor 22 to rotate relative to the stator 21. The rotor 22 can be directly fixed to the second shaft 12 or fixed to it through a rotor bracket, thereby enabling a transmission connection between the rotor 22 and the second shaft 12.

[0047] In this embodiment, as Figure 1A and Figure 1B As shown, the transmission 3 includes a gear transmission mechanism, which can change torque through, for example, a planetary gear set. Figure 2A and Figure 2B As shown, the first shaft 11 is provided with an external spline on its outer circumferential surface, and the first shaft 11 can be connected to the gear transmission mechanism via the external spline.

[0048] In this embodiment, as Figure 1A and Figure 1B As shown, the housing 4 can be made of a hard material such as metal. Specifically, the housing 4 can be constructed by assembling separately manufactured parts together, and the aforementioned parts and the housing 4 formed by them can have different external shapes and specific structures depending on different application scenarios. In the assembled state, the housing 4 has a hollow structure to form an installation space for accommodating and installing the motor 2 and the transmission 3.

[0049] In this embodiment, as Figure 1A and Figure 1BAs shown, the first bearing 5a, the second bearing 5b, and the third bearing 5c ​​can be ball bearings. The first bearing 5a and the second bearing 5b are located between the first shaft 11 and the housing 4. The outer rings of these two bearings are fixed to the housing 4, and the inner rings are fixed to the first shaft 11. The first bearing 5a and the second bearing 5b are located at the two axial ends of the first shaft 11, thus the first shaft 11 is stably supported by the housing 4 via the first bearing 5a and the second bearing 5b. The third bearing 5c ​​is located between the second shaft 12 and the housing 4. The outer ring of the third bearing 5c ​​is fixed to the housing 4, and the inner ring is fixed to the second shaft 12. The third bearing 5c ​​and the second bearing 5b are located on opposite sides of the rotor 22. The third bearing 5c ​​is located on the non-driving end side of the second shaft 12 (specifically, the end of the second shaft 12 furthest from the external spline 12t). Thus, the housing 4 stably supports the shaft assembly 1 via the first bearing 5a, the second bearing 5b, and the third bearing 5c.

[0050] It should be understood that the above embodiments are merely exemplary and are not intended to limit this application. Those skilled in the art can make various modifications and changes to the above embodiments under the teachings of this application without departing from the scope of this application. The technical solutions of this application are further described below.

[0051] i. The vehicle powertrain system of this application can be applied to pure electric vehicles or hybrid vehicles, and the internal components of the transmission may include various other transmission mechanisms in addition to gear transmission mechanisms.

[0052] ii. It is understood that the shaft assembly 1 according to this application can operate smoothly even when the central axes of the first shaft 11 and the second shaft 12 are not collinear, while avoiding unwanted bending loads on the first shaft 11 and the second shaft 12 when their central axes are not collinear. This not only eliminates the additional bending load on the shaft assembly 1 itself, but also eliminates the additional radial load on the bearings supporting the shaft assembly 1, improving the lifespan of the shaft assembly 1 and the bearings, and reducing noise. Of course, it is still desirable for the central axes of the first shaft 11 and the second shaft 12 to be collinear during design and production.

[0053] iii. It is understood that, in shaft assembly 1, the first shaft 11 and the second shaft 12 can be independently positioned by the bearings supporting them. Furthermore, the second shaft 12 is also supported by the first shaft 11 via the engagement of the first spherical part 11s and the second spherical part 12s. This approach reduces the machining accuracy requirements for the bearings and bearing housings, and also reduces the assembly accuracy requirements between the shafts. In addition, in the above approach, the connection structure between the shafts is simple and easy to manufacture; no additional parts are needed for assembly, nor are additional assembly steps required. All these factors contribute to reducing the corresponding costs.

[0054] iv. It is understood that in a variant of the vehicle powertrain of this application, the first axle 11 may be supported by only one bearing, and the second axle 12 may be supported by two bearings.

Claims

1. A shaft assembly, characterized in that, It includes a first shaft and a second shaft assembled together, with the second shaft partially inserted into the first shaft. The first shaft has an internal spline on its inner circumferential surface, and the second shaft has an external spline on its outer circumferential surface. The internal spline and the external spline cooperate to form a spline mechanism. The inner circumferential surface of the first shaft has a first spherical portion, and the outer circumferential surface of the second shaft has a second spherical portion. The first spherical portion is fitted onto the second spherical portion and they are shaped to fit together. The first spherical portion and the internal spline are spaced apart axially from each other on the first shaft, and the second spherical portion and the external spline are spaced apart axially from each other on the second shaft. By utilizing the first spherical surface and the second spherical surface, the shaft assembly is able to transmit torque between the first shaft and the second shaft via the spline mechanism, even when the central axes of the two shafts are not collinear.

2. The shaft assembly according to claim 1, characterized in that, The first shaft and the second shaft are engaged only through the first spherical surface and the second spherical surface, as well as through the internal spline and the external spline.

3. The shaft assembly according to claim 1, characterized in that, The diameter of the second spherical part is smaller than the diameter of the first spherical part.

4. The shaft assembly according to claim 1, characterized in that, The first spherical surface tends to extend more radially outward as it extends towards the side where the second axis is located, and... The second spherical surface tends to extend more towards the side where the first axis is located, while also tending to extend more towards the radially inward side.

5. The shaft assembly according to any one of claims 1 to 4, characterized in that, The axial length of the internal spline is greater than the axial length of the first spherical surface, and The axial length of the external spline is greater than the axial length of the second spherical surface.

6. The shaft assembly according to any one of claims 1 to 4, characterized in that, In the radial direction of the first shaft, the first spherical part is located radially outside the internal spline, and In the radial direction of the second shaft, the second spherical part is located radially outside the external spline.

7. A vehicle powertrain system, characterized in that, The invention includes a shaft assembly, a motor, and a transmission as described in any one of claims 1 to 6, wherein the first shaft is the input shaft of the transmission, and the second shaft is the motor shaft of the motor.

8. The vehicle power system according to claim 7, characterized in that, It also includes a housing, a first bearing, a second bearing, and a third bearing. The first bearing and the second bearing are located between the first shaft and the housing, and the third bearing is located between the second shaft and the housing, such that the housing supports the shaft assembly via the first bearing, the second bearing and the third bearing.

9. The vehicle power system according to claim 8, characterized in that, The first bearing and the second bearing are located at the two ends of the first shaft along its axial direction, and the third bearing is located at the end of the second shaft away from its external spline.

10. The vehicle power system according to claim 9, characterized in that, The motor includes a rotor, the second shaft is mounted on the rotor, and the third bearing and the second bearing are located on opposite sides of the rotor along its axial direction.

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