Driving shaft system structure and electric driving system

Abstract

The invention relates to a driving shafting structure and an electric driving system, the electric driving system comprises a motor and a speed reducer, the driving shafting structure comprises a rotor shaft of the motor, the rotor shaft is provided with a first end part and a second end part; the first bearing is arranged at the first end part of the rotor shaft, and the radial outer surface of the first end part is used as an inner ring of the first bearing; the second bearing is arranged at the second end part of the rotor shaft; and the output part is arranged at the first end part and is provided with a gear part. Corresponding matching structure design and assembling procedures do not need to be carried out on the input shaft of the speed reducer and the rotor shaft of the motor, and meanwhile the axial size is shortened. In addition, the size of the bearing is reduced, then the starting torque is reduced, heat generated under the high-speed and large-axial-force working conditions is reduced, wriggling and abrasion of the inner ring of the bearing are avoided, and axial limiting can be conducted without using the characteristics of a clamp spring, a shaft shoulder and the like.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and more specifically to a drive shaft structure and an electric drive system including the drive shaft structure. Background Technology

[0002] Electric vehicles are powered by batteries that supply electricity to a drive motor, which converts electrical energy into mechanical energy to propel the vehicle. Compared to vehicles driven by internal combustion engines, electric motors offer several advantages. For example, electric motors can rotate in both directions, eliminating the need for a dedicated reverse gear in the transmission system; simply reversing the motor is sufficient for reversing. Similarly, electric motors provide significant torque even at low speeds, meeting the vehicle's driving needs and eliminating the need for multi-stage transmissions to adjust torque.

[0003] In the electric drive system of an electric vehicle, a single-stage or two-stage transmission device (such as a reducer) is typically installed. Since the motor and transmission device are separate components, they need to be connected in a way that allows power transmission. The connection between the motor and transmission device directly affects the vehicle's driving performance, such as power transmission efficiency, vehicle vibration, and noise.

[0004] Regarding solutions known to the applicant—but not necessarily constituting prior art known to those skilled in the art—one approach involves supporting the reducer's input shaft with two bearings. One end of the input shaft is configured with a cavity into which one end of the rotor shaft extends. Thus, the reducer's input shaft and rotor shaft can be supported by a common bearing in this portion, or they can each be supported by separate bearings, with the rotor shaft supported by a separate bearing at its end away from the input shaft. This approach requires consideration of the connection structure design between the rotor shaft and the input shaft, increasing the complexity of the assembly process and thus increasing product manufacturing costs. It also results in a less compact spatial structure for the entire drive shaft system, hindering system weight reduction. Summary of the Invention

[0005] Therefore, the present invention proposes the following technical solution.

[0006] A drive shaft structure for an electric drive system, the electric drive system including a motor and a reducer, the drive shaft structure comprising:

[0007] The rotor shaft of the motor has a first end and a second end;

[0008] A first bearing is disposed at a first end of the rotor shaft, and the radial outer surface of the first end serves as the inner ring of the first bearing;

[0009] A second bearing is disposed at the second end of the rotor shaft;

[0010] An output section is provided at the first end and has a gear section.

[0011] According to one aspect of the invention, the rotor shaft further includes a shaft body, wherein the first end is integrally formed with the shaft body.

[0012] According to one aspect of the invention, the first bearing has an outer ring and rolling elements, and the radially outer surface of the first end is provided with an inwardly recessed inner track of the rolling elements for movement of the rolling elements.

[0013] According to one aspect of the invention, the outer rings of the first and second bearings are supported radially outward by a fixing component, and are also axially stopped on the side opposite to the rotor.

[0014] According to one aspect of the invention, the shaft body of the rotor shaft is provided with an opening at one end away from the first end, and the second end includes an inner end and an outer end, the inner end extending into the shaft body through the opening and abutting against the inner peripheral wall of the shaft body.

[0015] According to one aspect of the invention, the outer ring of the second bearing abuts against the housing of the motor on the side facing away from the rotor in the axial direction, and the inner ring of the second bearing abuts against a shoulder on the second end on the side facing the rotor in the axial direction.

[0016] According to one aspect of the invention, the gear portion is integrally formed at the first end.

[0017] According to one aspect of the invention, the outer ring of the first bearing abuts against the housing of the motor.

[0018] The present invention also proposes an electric drive system, including a motor and a reducer, wherein the motor includes a rotor assembly and the aforementioned drive shaft structure.

[0019] According to one aspect of the invention, the rotor assembly includes a pressure plate and a rotor lamination assembly, the rotor assembly being axially limited by a stop and a locking ring.

[0020] This invention, on the one hand, sets the input gear of the reducer on the rotor shaft of the motor, using the rotor shaft of the motor as the input shaft of the reducer. This eliminates the need for corresponding mating structure design and assembly processes for the input shaft of the reducer and the rotor shaft of the motor, and also shortens the axial dimension. Furthermore, by simultaneously constructing the end of the rotor shaft as the inner ring of a bearing, the bearing size can be reduced, thereby lowering the starting torque and reducing heat generated under high-speed and large axial force conditions. It also avoids creep and wear of the bearing inner ring and eliminates the need for axial restraint using features such as snap rings or shaft shoulders. Attached Figure Description

[0021] The features and advantages of the present invention will become clear from the following detailed description provided with reference to the accompanying drawings. It should be understood that the following drawings are merely schematic and not necessarily drawn to scale, and therefore should not be considered as limitations on the invention, wherein:

[0022] Figure 1 A schematic diagram of a car having an electric drive system according to the present invention is shown.

[0023] Figure 2 An external schematic diagram of a drive shaft system structure according to an exemplary embodiment of the present invention is shown.

[0024] Figure 3 A schematic diagram of a drive shaft system structure supported in a housing according to an exemplary embodiment of the present invention is shown.

[0025] Figure 4 A cross-sectional view of a drive shaft system structure according to an exemplary embodiment of the present invention is shown.

[0026] Figure 5 An external schematic diagram of a drive shaft system structure according to an exemplary embodiment of the present invention is shown, wherein the bearing located on the left side is removed.

[0027] Figure 6 A schematic diagram of the drivetrain of a car having an electric drive system according to the present invention is shown. Detailed Implementation

[0028] Embodiments of the present invention are described below with reference to the accompanying drawings. In the following description, numerous specific details are set forth to enable those skilled in the art to more fully understand and implement the invention. However, it will be apparent to those skilled in the art that implementations of the invention may not include some of these specific details. Furthermore, it should be understood that the invention is not limited to the specific embodiments described. Rather, the invention can be conceived to be practiced with any combination of the features and elements described below, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments, and advantages are for illustrative purposes only and should not be construed as features or limitations of the claims unless expressly set forth in the claims.

[0029] The descriptions of orientation used in the following description, such as “upper,” “lower,” “inner,” “outer,” “radial,” and “axial,” are merely for convenience of description and are not intended to limit the technical solution of the invention unless explicitly stated otherwise. Furthermore, the terms “first,” “second,” and other similar terms used below to describe the elements of this application are only used to distinguish individual elements and are not intended to limit the nature, sequence, order, or number of these elements.

[0030] Figure 1 A schematic diagram of a car having an electric drive system according to the present invention is shown. As an example, Figure 1 The car shown has four wheels: two front wheels and two rear wheels. The two front wheels are connected by an axle, and the front wheels serve as steering wheels. Between the two front wheels, there is a drive motor M, which serves as the power source, and a transmission device T, mechanically connected to the drive motor, for transmitting the power from the drive motor to the wheels. Figure 1 The diagram also shows an arrangement where the same drive motor M and transmission T are also mounted on the rear axle, thus enabling the vehicle to function as a four-wheel drive vehicle. Of course, the drive motor M and transmission T can be mounted only on the front axle to create a front-wheel drive vehicle, or only on the rear axle to create a rear-wheel drive vehicle.

[0031] Figure 1 The diagram also shows the battery pack B and the vehicle's electronic control unit (ECU). The battery pack B is electrically connected to the drive motor M, enabling it to supply electricity to the drive motor M to propel the vehicle. When the vehicle decelerates, the drive motor M can also perform regenerative braking, converting the vehicle's kinetic energy into electrical energy to charge the battery pack B.

[0032] To enable power transmission from the motor to the wheels, this invention proposes a specific connection method between the drive motor M and the transmission device T, such as... Figure 2 and Figure 3 and Figure 6 As shown.

[0033] Figure 2 A front view of a drive shaft system structure according to an embodiment of the present invention is shown. Figure 3 It shows Figure 2 A schematic diagram of the drive shaft system structure supported in the housing. Figure 4 A cross-sectional view of a drive shaft system structure according to an exemplary embodiment of the present invention is shown. The drive shaft system structure is herein part of an electric drive system, which may include a motor, a reducer, and may also include an inverter, a differential, etc. Figure 2 and Figure 4 As shown, the drive shaft system structure according to this embodiment is located within the housing of the motor and mainly includes a rotor shaft 1 of the drive motor M, an output portion 2 of the rotor shaft 1, a first bearing 3, and a second bearing 4. The rotor shaft 1 may include a shaft body 11 and a first end portion 12 and a second end portion 13 extending axially from both ends of the shaft body 11. The shaft body 11 is used to mount a rotor assembly 5, which will be described in detail below. The output portion 2 is located axially at the end of the first end portion 12 away from the shaft body 11. The first bearing 3 is disposed at the first end portion 12, and the second bearing 4 is disposed at the second end portion 13. The outer rings of the first bearing 3 and the second bearing 4 can abut against a support structure, such as a housing. The housing may include multiple parts (e.g., a first fixing portion 6 and a second fixing portion 7), which can support the outer rings of the first bearing 3 and the second bearing 4 respectively, thereby supporting the rotor shaft 1.

[0034] like Figure 4 As shown, rotor shaft 1 has a certain length and defines an axis. In conventional designs, rotor shaft 1 is assembled with the input shaft of the transmission device, which also has a certain length and defines an axis. Therefore, when assembling the two, it is necessary to ensure that the axes of the two shafts coincide as much as possible to ensure smooth power transmission. Otherwise, if there is an angle between the axes of the two shafts, it will lead to lower power transmission efficiency and undesirable vibration and noise, which will reduce the driving experience for passengers and shorten the actual service life of the electric drive system.

[0035] To ensure that the axes of the two shafts are as aligned as possible, one solution is to insert one end of the rotor shaft into the cavity at one end of the transmission input shaft, preload the rotor shaft and transmission input shaft with a small interference fit, and ensure the shoulders of the two shafts are in contact. Then, long bolts are used to secure the rotor shaft and transmission input shaft together. However, this design requires additional long bolts for fastening and necessitates drilling a hole at one end of the transmission input shaft to support the bolt installation, making the forming and manufacturing process more complex and requiring additional assembly.

[0036] Therefore, the present invention proposes the following improvement scheme. For example... Figure 2 As shown, an output section 2 is provided at the end of the rotor shaft 1 near the reducer, which serves as the transmission device. The output section 2 has a gear section 21, which meshes with another gear to transmit power. That is, in the present invention, the input gear of the reducer is directly mounted on the rotor shaft of the motor, instead of a separate or additional reducer input shaft. Thus, unlike the known solutions, the present invention does not require connecting the rotor shaft and the reducer input shaft as in the known solutions, thereby avoiding the steps of pre-tightening the required interference fit between the reducer input shaft and the rotor shaft and securing them with long bolts.

[0037] Furthermore, as a preferred embodiment of the present invention, the gear part 21 is integrally formed with the rotor shaft 1, thereby eliminating the need for a separate gear part 21 to be connected to the rotor shaft 1 by a spline connection or other fixing method and to be provided with an axial fixing device such as a lock nut.

[0038] As a further improvement of the present invention, since the gear part 21 is integrally formed with the rotor shaft 1, in order to install the bearing supporting the rotor shaft, the inner ring of the bearing needs to be larger than the outer diameter of the gear part 21. At the same time, due to other considerations, the diameter of the rotor journal will also be larger, which will also result in a larger bearing size, which is not conducive to the high-speed design of the motor. Therefore, the present invention further proposes the following improvement.

[0039] like Figure 4 and Figure 5 As shown, a cylindrical journal is formed on the first end 12, and a radially inwardly recessed inner rolling element track 121 is formed on the journal. Thus, the portion of the first end 12 at the journal can constitute the inner ring of the first bearing 3. The first bearing 3 may include an outer ring 31, a plurality of rolling elements 32, and a cage. The outer ring 31 has an outer rolling element track disposed opposite to the inner rolling element track. The inner and outer rolling elements track 121 are adapted to a portion of the outer contour of the rolling elements 32, thereby allowing the plurality of rolling elements 32 to be disposed between the inner rolling element track 121 formed on the first end 12 and the outer rolling element track of the outer ring 31. The cage is disposed between the radially outer surface of the first end 12 and the outer ring 31, and a plurality of frames, each capable of accommodating a plurality of rolling elements 32, are arranged at equal intervals along the circumference of the first bearing 3, thereby separating the plurality of rolling elements 32 so that each rolling element 32 can roll within its corresponding frame and between the inner and outer rolling elements track. The rolling elements may be in the form of balls, thus the bearing is correspondingly, for example, a ball bearing.

[0040] In this way, since the first end 12 of the rotor shaft 1 is directly used as the inner ring of the first bearing 3, the size of the outer ring 31 can be reduced while maintaining the same rated load capacity. Due to the reduced size of the first bearing 3, the contact linear velocity between the rolling elements 32 and the inner and outer tracks of the rolling elements also decreases, thereby reducing the starting torque of the rotor shaft 1. Furthermore, under high-speed and large axial force conditions, this improved design also reduces the risk of heat generation from friction between the rolling elements 32 and the inner and outer tracks. On the other hand, if the outer diameter of the outer ring 31 is maintained, the diameter and number of rolling elements 32 can be increased due to the reduced diameter of the inner track, thereby further improving the load capacity of the first bearing 3.

[0041] Furthermore, by directly forming the inner track 121 on the first end 12, not only can the inner ring creep and wear phenomenon caused when the bearing is directly installed on the first end 12 be avoided, but the limitations of the bearing positioning shoulder structure and the snap ring can also be eliminated.

[0042] As can be seen from the above, the solution of the present invention uses a structure that supports the gear with only two bearings and provides cantilever support, which greatly reduces the axial dimension and saves space for the all-in-one electric drive system. Preferably, the journal of the first end 12 can also be surface treated by heat treatment, such as surface heat treatment, local heat treatment, etc., to improve the surface quality of the journal, improve the wear resistance and mechanical properties of the journal, thereby improving the fatigue life of the first bearing 3.

[0043] Continue to refer to Figure 4 The first end 12 and the shaft body 11 are integrally formed into one piece, and the second end 13 is connected to the end of the shaft body 11 away from the first end 12. Figure 4 The second end 13 can be configured as a separate component from the shaft body 11 and then connected together. Specifically, the second end 13 includes an inner end 131 and an outer end 132, while the shaft body 11 has an opening. The inner end 131 extends into the shaft body 11 through the opening and abuts against the inner peripheral wall of the shaft body 11.

[0044] The outer end portion 132 has a shoulder 133 extending radially outward on its outer peripheral wall. The second bearing 4 adopts a conventional bearing structure and is fitted onto the outer end portion 132, with its inner ring abutting against the shoulder 133 and its outer ring abutting against the support portion of the housing on the other axial side of the second bearing 4.

[0045] Compared to existing technologies that require pre-tensioning components such as wave springs and snap rings, the drive shaft system structure of this invention eliminates the need for pre-tensioning components like wave springs and snap rings by using a first bearing and a second bearing for diagonal axial fixation. Specifically, see... Figure 3The outer rings of the first bearing 3 and the second bearing 4 are supported radially outward by fixing components such as the first fixing part 6 and the second fixing part 7, and are also axially stopped on their opposite side from the rotor. Figure 2 and Figure 3 For example, the outer ring of the first bearing 3 is supported radially outward by the first fixed part 6 and stopped on its left side by the first fixed part 6; the outer ring of the second bearing 4 is supported radially outward by the second fixed part 7 and stopped on its right side by the second fixed part 7. Therefore, when the entire rotor shaft is subjected to a force to the right, the second bearing 4 transmits the axial force to its supporting component, and the first bearing is not subjected to axial force; when the entire rotor shaft is subjected to a force to the left, the first bearing 3 transmits the axial force to its supporting component, and the second bearing is not subjected to axial force.

[0046] This invention also proposes an electric drive system. For example... Figure 2 and Figure 6 As shown, the electric drive system may include a motor, and at least one of a reducer, an inverter, and a differential. The motor includes a rotor assembly 5 and a drive shaft structure as described above. Figure 6 As shown, the gear section 21 on the output shaft of the motor rotor meshes with the first gear 81 of the gear transmission device 8, while the second gear, coaxial with the first gear 81, meshes with the input gear 91 of the differential transmission device 9. Thus, the differential gear system located within the differential transmission device housing 92 can rotate and transmit power to the two half-axles. As previously mentioned, the motor rotor shaft also serves as the input shaft of the reducer, thereby the gear section 21 and the gear transmission device 8 together form a reduction transmission device.

[0047] See Figure 2 and Figure 4 The rotor shaft 1 is located at one end near the first end 12. Figure 2 and Figure 4 The left end shown has a stop portion 113 extending radially outward. The rotor assembly 5 may include two spaced-apart pressure plates 51 and a rotor lamination assembly 52 disposed between the two pressure plates 51. The pressure plates 51 and the rotor lamination assembly 52 can be sleeved on the shaft body 11. One pressure plate 51 ( Figure 2 and Figure 4 The pressure plate on the left side (shown) abuts against the stop portion 113, and the locking ring 53 abuts against another pressure plate 51 (shown). Figure 2 and Figure 4 (The pressure plate on the right side shown) thereby axially fixes the rotor lamination assembly 52.

[0048] The electric drive system of this invention can be applied to various types of electric vehicles. For example, it can be applied to pure electric vehicles powered solely by batteries, or to hybrid vehicles equipped with other types of power sources besides the motor, such as fossil fuel engines, hydrogen engines, etc.

[0049] The structure of the present invention has been described in detail above. Those skilled in the art will understand that many of the details described are merely exemplary and not restrictive. That is, it is sufficient to achieve the corresponding function, and it is not necessary to adopt the specific shapes, structures, and other features described above.

[0050] The above illustrative embodiments have clearly and completely described the present invention. Those skilled in the art should understand that various other embodiments can be conceived through modifications to the disclosed technical solutions without departing from the spirit and scope of the present invention. These embodiments should be understood to fall within the scope of the present invention as defined by the claims and any equivalent technical solutions.

Claims

1. A drive shaft train structure for an electric drive system, the electric drive system comprising an electric machine and a speed reducer, the drive shaft train structure comprising: a rotor shaft of the electric machine, the rotor shaft having a first end portion (12) and a second end portion (13); characterized in that the drive shaft train structure further comprises: a first bearing (3) provided at the first end portion of the rotor shaft, and a radially outer surface of the first end portion serving as an inner ring of the first bearing; a second bearing (4) provided at the second end portion of the rotor shaft; an output portion (2) provided at the first end portion and having a gear portion (21).

2. The drive shafting arrangement for an electric drive system of claim 1, wherein, the rotor shaft further comprises a shaft body (11), the first end portion (12) being integrally formed with the shaft body (11).

3. The drive shafting arrangement for an electric drive system of claim 2, wherein, the first bearing (3) has an outer ring (31) and rolling elements (32), the radially outer surface of the first end portion being provided with an inwardly recessed rolling element inner track (121) for movement of the rolling elements.

4. The drive shafting arrangement for an electric drive system according to any one of claims 1 to 3, characterized in that, The outer rings of the first and second bearings are supported on one hand radially outwardly by a fixing member and on the other hand axially on their side facing away from the rotor.

5. The drive shafting arrangement for an electric drive system of claim 4, wherein, The shaft body of the rotor shaft is provided at an end remote from the first end portion with an opening, the second end portion comprises an inner end portion and an outer end portion, the inner end portion extending into the shaft body via the opening and abutting against an inner circumferential wall of the shaft body.

6. The drive shafting arrangement for an electric drive system of claim 4, wherein, The outer ring of the second bearing abuts against a housing of the electric machine on its side axially facing away from the rotor, the inner ring of the second bearing abuts against a shoulder (133) on the second end portion on its side axially facing towards the rotor.

7. The drive shafting arrangement for an electric drive system according to any one of claims 1 to 3, characterized in that, The gear portion is integrally formed with the first end portion.

8. The drive shafting arrangement for an electric drive system according to any one of claims 1 to 3, characterized in that, The outer ring of the first bearing abuts against a housing of the electric machine.

9. An electric drive system comprising an electric machine and a reduction gear, characterized in that The electric machine comprises a rotor assembly (5) and a drive shaft train structure according to any one of claims 1 to 8.

10. The electric drive system of claim 9, wherein, The rotor assembly comprises a pressure plate (51) and a rotor lamination stack (52), the rotor assembly being axially limited by a stopper (113) and a lock ring (53).

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