Electric drive axle and electric truck

Abstract

The present invention relates to an electric drive axle and an electric truck. The electric drive axle is used for an electric truck, and the electric drive axle is provided with a unique driving electric motor, a speed reducer assembly and a differential, wherein the speed reducer assembly is provided with a first-stage speed reduction stage, a first-gear transmission mechanism, a second-gear transmission mechanism, and a hollow shaft, which is designed as a power output shaft; the first-gear transmission mechanism comprises a first-gear driving gear and a first-gear driven gear, which mesh with each other; the second-gear transmission mechanism comprises a second-gear driving gear and a second-gear driven gear, which mesh with each other; the first-gear driven gear and the second-gear driven gear are arranged on the hollow shaft; the first-gear transmission mechanism is provided with a first-gear shifting mechanism for implementing the switching between a neutral gear and a first gear; the second-gear transmission mechanism is provided with a second-gear shifting mechanism for implementing the switching between the neutral gear and a second gear; the first-gear shifting mechanism and the second-gear shifting mechanism are both arranged on the hollow shaft; and the hollow shaft is directly connected to the differential. The electric truck is provided with the electric drive axle according to the present invention.

Description

E-axles and electric trucks

[0001] This application claims priority to Chinese patent application No. 202311594895.1 filed on November 28, 2023, and the contents of the above-mentioned Chinese patent application disclosure are hereby incorporated by reference in their entirety as a part of this application. Technical Field

[0002] The invention relates to an electric drive axle and an electric truck. Background Art

[0003] For electric axles in electric trucks, such as those used in medium- and heavy-duty electric trucks, the current market-proven solution uses a fixed-ratio reducer. This solution results in low-speed torque at low motor speeds, failing to meet the hill-climbing requirements of heavy trucks and resulting in low vehicle power. At high speeds, the motor cannot operate in its economical range due to power constraints, increasing power consumption and poor vehicle economy. This significantly reduces the truck's transport efficiency, shortens its range, and increases its operating costs. This approach, in turn, hinders market adoption.

[0004] Furthermore, in electric axles with differentials, the space available for the reducer and motor is even more limited due to the large space occupied by the differential, necessitating a more space-efficient reducer. Numerous electric axle designs for passenger cars are known in this regard, but they differ significantly from those for electric trucks in many respects. For example, electric trucks have balancing suspension and leaf springs on their chassis, which often occupy a significant amount of space. Therefore, electric axles designed for passenger cars are generally not directly adaptable for electric trucks.

[0005] As for the electric drive axles of electric trucks, especially those equipped with power take-offs, many types of reducers are known. However, many reducers are only designed in principle and often do not consider the size and efficiency of the gears in the actual reduction stage, making them difficult to implement. In addition, the transmission path and efficiency of the power take-off cannot be guaranteed.

[0006] For example, in one known design, the reducer has three forward gears, all located on a central shaft, and features a central planetary gear transmission. Furthermore, input force is transmitted to the power take-off (PTO) via a four-stage transmission. However, the three gears and the planetary gear transmission on the central shaft in this design result in an excessively large axial dimension for the reducer, making it virtually impossible to install in the electric drive axle of an electric truck. Furthermore, the PTO's power transmission efficiency is poor.

[0007] In another known design, the electric drive axle has a reducer with a fixed transmission ratio. The force input can be transmitted to the power take-off through the shift element, but the power transmission to the wheels is cut off at this time, so power cannot be taken off during driving.

[0008] In another known design, the driven gear of the primary reduction stage is mounted directly on a hollow shaft (or power output shaft), and the secondary reduction stage is formed by a central planetary gear reducer coaxially arranged with the hollow shaft. The hollow shaft is then connected to the differential via the central planetary gear reducer. However, this design has limitations in terms of the service life of the central planetary gear reducer, and it also has high process requirements and manufacturing costs.

[0009] In another known design, dual motors are provided in an electric drive axle with a differential. However, the dual motor design itself is complex in structure and requires very high precision of the transmission gears assigned to the two motors. In addition, this design has low transmission efficiency.

[0010] Therefore, there is currently no ideal solution that takes into account power, economy, and space utilization.

[0011] Summary of the Invention

[0012] Based on the above-mentioned prior art, the technical problem to be solved by the present invention is to overcome the defects of the prior art to a large extent and provide an electric drive axle with high practical use value.

[0013] The electric drive axle according to the present invention is used for electric trucks, especially medium-sized electric trucks or heavy-duty electric trucks. The electric drive axle has a unique drive motor, a reducer assembly and a differential. The reducer assembly has a first reduction stage, a first-gear transmission mechanism, a second-gear transmission mechanism and a hollow shaft designed as a power output shaft, wherein the first-gear transmission mechanism includes a first-gear driving gear and a first-gear driven gear that are meshed with each other, and the second-gear transmission mechanism includes a second-gear driving gear and a second-gear driven gear that are meshed with each other, and the first-gear driven gear and the second-gear driven gear are arranged on the hollow shaft, wherein the first-gear transmission mechanism has a first-gear shift mechanism for switching between neutral and first gear, and the second-gear transmission mechanism has a second-gear shift mechanism for switching between neutral and second gear, wherein the first-gear shift mechanism and the second-gear shift mechanism are both arranged on the hollow shaft, and the hollow shaft is directly connected to the differential.

[0014] Within the scope of the present invention, "direct connection of the hollow shaft to the differential" means that there is no separate reduction gear, in particular no planetary gear reduction gear, between the hollow shaft and the differential input. This makes it possible to directly avoid the various problems associated with centrally located planetary gear reduction gears.

[0015] Through the electric drive axle of the present invention, the motor can disengage power transmission when it is in neutral gear, thereby solving the energy loss caused by the passive idling of the motor when the electric truck is gliding at high speed, and avoiding the gear oil stirring loss in the reducer housing. The coaxial arrangement of the shift mechanism and the hollow shaft further avoids the gear oil stirring loss in the reducer housing, and the structure is more compact. In the known solutions of the prior art, in order to reduce the impact of the space occupied by the shift mechanism, the solution of reducing the size of the motor is adopted, but this reduces the power of the motor. From this perspective, compared with the known solutions in the prior art, the present invention reduces the space occupied by the shift mechanism while ensuring sufficient motor power.

[0016] In addition, by using the high-speed gear (second gear) and the low-speed gear (first gear), the ability of the electric truck to climb a slope at a low speed is guaranteed, and the drive motor of the electric truck can operate more in the economic zone or the high-efficiency zone when traveling at high speed. Within the scope of the present invention, the high-efficiency zone of the drive motor of the electric truck is set between 90% and 96%, and more preferably between 94% and 96%. Therefore, in the actual operation of the electric truck, better power and economy are provided, which not only adapts to a wider range of road conditions, but also reduces energy consumption, thereby reducing operating costs. In addition, the electric drive axle of the present invention can reduce the manufacturing difficulty during the product manufacturing process, and better utilize the limited space on the axle during the installation of the product, thereby reducing manufacturing and installation costs.

[0017] In one embodiment, the primary reduction stage includes a primary reduction driving gear and a primary reduction driven gear that mesh with each other. The motor shaft of the drive motor is connected to the primary reduction driving gear. The primary reduction driven gear is fixed to a first shaft, to which a first gear driving gear and a second gear driving gear are also fixed. The first gear driving gear and the second gear driving gear are arranged on either side of the primary reduction driven gear. With this design, the primary reduction driven gear, the first gear driving gear, and the second gear driving gear are integrated on the first shaft, forming a compact structure.

[0018] In one embodiment, the first-gear shift mechanism includes a first-gear hub of the first-gear driven gear, a hollow-shaft fixed hub, and a shift sleeve, and the second-gear shift mechanism includes a second-gear hub of the second-gear driven gear, a hollow-shaft fixed hub, and a shift sleeve. The shift sleeve couples the hollow-shaft fixed hub to the first-gear hub of the first-gear driven gear, and the shift sleeve couples the hollow-shaft fixed hub to the second-gear hub of the second-gear driven gear. The technical solution of the present invention realizes a shared shift sleeve on the hollow shaft, enabling a compact layout of the two shift mechanisms while providing more installation space for the motor.

[0019] In one embodiment, an electric drive axle includes a power take-off (POT), comprising a PTO gear, a gear hub for the PTO gear, a PTO output shaft, a fixed output shaft gear, and a PTO engaging sleeve. The PTO gear is capable of meshing with a second-gear driven gear. The PTO gear is supported on the PTO output shaft via a bearing, and the gear hub of the PTO gear and the fixed output shaft gear can be coupled or decoupled via the PTO sleeve. Alternatively, the PTO gear can mesh with a first-gear driven gear. In a more complex design, the PTO gear can selectively mesh with either the first-gear driven gear or the second-gear driven gear. In the present invention, when the electric truck is stationary and in neutral, the PTO engaging sleeve engages, allowing the PTO to output power via a three-stage transmission. This allows the PTO to transmit power with high efficiency. Furthermore, while the electric truck is in motion, the PTO can also output power in either first or second gear, meeting varying operating conditions. In the application of electric trucks, especially in engineering work vehicles, the electric drive axle with a power take-off is particularly important, and the combination of the power take-off and the electric drive axle of the present invention can realize a compact and efficient unit. The actual spatial layout of the power take-off is more favorable, thereby taking into account power, economy, space utilization and power take-off efficiency.

[0020] In one embodiment, the output shaft of the power take-off can be connected to a hydraulic pump, which transmits hydraulic fluid to a hydraulic motor through a hydraulic oil pipe, and the hydraulic motor can be connected to an external device.

[0021] In one embodiment, the power take-off is axially arranged between the first gear driven gear and the second gear driven gear. This design can further make the axial space of the reducer housing more compact.

[0022] In one embodiment, the electric drive axle has a first axle and a second axle and a first wheel-side reducer and a second wheel-side reducer, wherein the first axle is connected to the first wheel via the first wheel-side reducer, and the second axle is connected to the second wheel via the second wheel-side reducer. Given that the present invention eliminates the centrally arranged planetary gear reducer, the arrangement of the wheel-side reducer is very advantageous when used in conjunction with the electric drive axle of the present invention, making deceleration smoother and reducing overall costs. In a preferred embodiment, the wheel-side reducer is designed as a planetary gear reducer, but the wheel-side planetary gear reducer is smaller in size, simpler in structure, and lower in cost than the centrally arranged planetary gear reducer. More importantly, by replacing the centrally arranged planetary gear reducer with a wheel-side reducer, a compact design within the reducer housing is facilitated, thereby making the reducer housing more compact, requiring less lubricating oil within the reducer housing, and reducing the mass of the reducer assembly. It should be noted that the use of the electric drive axle and the wheel-side reducer according to the present invention should be considered as the overall design of the electric drive axle.

[0023] In one embodiment, the drive motor, reducer assembly, and differential are housed in a common reducer housing. This design allows for integrated and modular design of the electric drive axle, thereby increasing the overall service life of the reducer assembly and enabling flexible lubrication strategies, thus facilitating the coupling of other systems to the reducer housing.

[0024] In one embodiment, the motor shaft of the drive motor, the first shaft, and the hollow shaft are arranged parallel to each other. This design further facilitates the arrangement of the drive motor, transmission assembly, and differential, thereby improving compactness and facilitating smoother force transmission, thereby reducing the complexity of the design of the individual gears.

[0025] Another aspect of the present invention relates to an electric truck having the electric drive axle according to the present invention.

[0026] Overall, the electric axle and electric truck according to the present invention address the challenge of simultaneously balancing power, economy, space utilization, and power takeoff efficiency in electric drive systems. Through the various preferred embodiments of the present invention, the electric axle or electric truck according to the present invention can further reduce energy consumption and operating costs, as well as manufacturing and installation costs. This offers significant advantages over existing gasoline-powered vehicles and increases the future market penetration of electric trucks. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above features and advantages of the present invention and the manner of achieving them are described in detail below with reference to specific embodiments and the accompanying drawings, but the present invention is not limited to the features of the specific embodiments. In the accompanying drawings:

[0028] FIG1 shows a schematic diagram of an electric drive axle according to the present invention. DETAILED DESCRIPTION

[0029] To further clarify the objectives, technical solutions, and advantages of the embodiments of the present invention, the technical solutions of the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments represent only a portion of the embodiments of the present invention, and not all of them. Unless otherwise defined, the technical or scientific terms used herein should have the same ordinary meanings as those understood by persons of ordinary skill in the art to which the present invention pertains. The terms "first," "second," and similar expressions used in the present patent application specification and claims do not denote any order, quantity, or importance; they are merely used to distinguish between different components. Terms such as "include" or "comprising" mean that the element or object preceding the term encompasses the elements or objects listed following the term, and their equivalents, without excluding other elements or objects. Terms such as "inside," "outside," "upper," and "lower" are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0030] The drawings in the present invention are not drawn strictly according to the actual scale, and the specific size and quantity of each structure can be determined according to actual needs.

[0031] FIG1 shows an electric drive axle 1 according to a specific embodiment of the present invention. The electric drive axle has only one drive motor M, a reducer assembly (including various reduction stages), and a differential 13. The reducer assembly includes a primary reduction stage, a first-gear transmission mechanism, a second-gear transmission mechanism, and a hollow shaft 12 designed as a power output shaft. The primary reduction stage includes a primary reduction driving gear 2 and a primary reduction driven gear 3. In addition, the first-gear transmission mechanism includes a first-gear driving gear 5 and a first-gear driven gear 7 that mesh with each other, and the second-gear transmission mechanism includes a second-gear driving gear 6 and a second-gear driven gear 8 that mesh with each other.

[0032] The motor shaft of the drive motor M is directly coupled to the first-speed reduction driving gear 2, which meshes with the first-speed reduction driven gear 3. The first-speed reduction driven gear 3 is fixed to the first shaft 4, to which the first-speed driving gear 5 and the second-speed driving gear 6 are also fixed. The first-speed driving gear 5 and the second-speed driving gear 6 are arranged on both sides of the first-speed reduction driven gear 3. The first-speed driving gear 5 meshes with the first-speed driven gear 7, and the second-speed driving gear 6 meshes with the second-speed driven gear 8. The first-speed driven gear 7 is rotatably supported on the hollow shaft 12 via a bearing, and the second-speed driven gear 8 is also rotatably supported on the hollow shaft 12 via a bearing. A hollow shaft fixing gear hub 24 is provided between the first-speed driven gear 7 and the second-speed driven gear 8, which is fixed to the hollow shaft. In addition, a shift sleeve 9 is provided on the hollow shaft fixed gear hub, wherein the shift sleeve 9 is capable of coupling the hollow shaft fixed gear hub to the first gear hub 10 of the first gear driven gear, and the shift sleeve 9 is capable of coupling the hollow shaft fixed gear hub to the second gear hub 11 of the second gear driven gear. In addition, the hollow shaft 12 is drivingly connected to the differential 13, and the differential 13 is further connected to the first axle 14 and the second axle 15 for transmitting torque. The first axle 14 is connected to the first wheel reducer 16, and the first wheel reducer is connected to the first wheel 18. In addition, the second axle 15 is connected to the second wheel reducer 17, and the second wheel reducer is connected to the second wheel 19.

[0033] According to this embodiment, the second-gear driven gear 8 also meshes with the power take-off gear 20, which is supported on the power take-off output shaft 23 via a bearing. The gear hub of the power take-off gear and the output shaft fixed gear 21 can be coupled or disengaged via the power take-off gear sleeve 22. Therefore, when the electric truck is stationary and in neutral, the power take-off outputs power through a three-stage transmission. When the electric truck is in motion and in second gear, the power take-off can also output power. In addition, unlike the schematic diagram shown in Figure 1, the power take-off can be arranged on the left side of the second-gear driven gear, thereby making the layout more compact.

[0034] Furthermore, the schematic diagram of this embodiment does not show the complete reducer housing. However, in the actual layout, the drive motor, reducer assembly, and differential are arranged in a common reducer housing, and lubricating oil is provided in the reducer housing. Therefore, the actual structure can achieve a very compact layout and keep the axial dimension of the reducer housing very small, thereby achieving very high utilization of the limited space of the electric drive axle.

[0035] Furthermore, in this embodiment, the shift sleeve 9 can be engaged in neutral, first gear, and second gear, namely, in the position shown in the figure, a leftward shift position, and a rightward shift position. In one embodiment, first gear is set as a low speed gear, second gear is set as a high speed gear, and the hollow shaft is set as a power output shaft. In this embodiment, both the first gear driven gear and the second gear driven gear are rotatably (non-torsionally fixed) arranged on the hollow shaft, thereby preventing gear churning losses in the reducer housing during neutral gear operation.

[0036] Those skilled in the art should understand that the above-mentioned specific embodiments are merely examples and not limitations, and that various modifications, combinations, partial combinations and replacements may be made to the embodiments of the present invention according to design requirements and other factors. As long as they are within the scope of the attached claims or their equivalents, they fall within the scope of rights to be protected by the present invention.

Claims

1. An electric drive axle, which is used for an electric truck, and has a unique drive motor, a reducer assembly and a differential, characterized in that: The reducer assembly comprises a primary reduction stage, a first-gear transmission mechanism, a second-gear transmission mechanism and a hollow shaft designed as a power output shaft, wherein the first-gear transmission mechanism comprises a first-gear driving gear and a first-gear driven gear meshing with each other, the second-gear transmission mechanism comprises a second-gear driving gear and a second-gear driven gear meshing with each other, and wherein the first-gear driven gear and the second-gear driven gear are arranged on the hollow shaft, wherein the first-gear transmission mechanism has a first-gear shift mechanism for switching between neutral and first gear, and the second-gear transmission mechanism has a second-gear shift mechanism for switching between neutral and second gear, and wherein the first-gear shift mechanism and the second-gear shift mechanism are both arranged on the hollow shaft, and wherein the hollow shaft is directly connected to the differential.

2. The electric drive axle according to claim 1, characterized in that: The primary reduction stage includes a primary reduction driving gear and a primary reduction driven gear that mesh with each other, the motor shaft of the drive motor is connected to the primary reduction driving gear, and wherein the primary reduction driven gear is fixed on the first shaft, and a first gear driving gear and a second gear driving gear are also fixed on the first shaft, and wherein the first gear driving gear and the second gear driving gear are arranged on both sides of the primary reduction driven gear.

3. The electric drive axle according to claim 2, characterized in that: The first gear shift mechanism includes a first gear hub of the first gear driven gear, a hollow shaft fixed hub and a shift sleeve, and the second gear shift mechanism includes a second gear hub of the second gear driven gear, a hollow shaft fixed hub and a shift sleeve, wherein the shift sleeve can couple the hollow shaft fixed hub with the first gear hub of the first gear driven gear, and the shift sleeve can couple the hollow shaft fixed hub with the second gear hub of the second gear driven gear.

4. The electric drive axle according to claim 2, characterized in that: The electric drive axle has a power take-off, wherein the power take-off includes a power take-off gear, a gear hub of the power take-off gear, a power take-off output shaft, an output shaft fixed gear and a power take-off engaging gear sleeve, wherein the power take-off gear can mesh with the second gear passive gear, the power take-off gear is supported on the power take-off output shaft through a bearing, and the gear hub of the power take-off gear and the output shaft fixed gear can be coupled or disengaged through the power take-off gear sleeve.

5. The electric drive axle according to claim 2, characterized in that: The electric drive axle has a power take-off, wherein the power take-off includes a power take-off gear, a gear hub of the power take-off gear, a power take-off output shaft, an output shaft fixed gear and a power take-off engaging gear sleeve, wherein the power take-off gear can mesh with a first gear passive gear, the power take-off gear is supported on the power take-off output shaft through a bearing, and the gear hub of the power take-off gear and the output shaft fixed gear can be coupled or disengaged through the power take-off gear sleeve.

6. The electric drive bridge according to claim 4 or 5, characterized in that: The power take-off is arranged axially between the first-gear driven gear and the second-gear driven gear.

7. The electric drive axle according to claim 1, characterized in that: The electric drive axle has a first axle and a second axle and a first wheel-side reducer and a second wheel-side reducer, wherein the first axle is connected to the first wheel through the first wheel-side reducer, and the second axle is connected to the second wheel through the second wheel-side reducer.

8. The electric drive axle according to claim 1, characterized in that: The drive motor, the reduction gear assembly and the differential are arranged in a common reduction gear housing.

9. The electric drive axle according to claim 1, characterized in that: The motor shaft of the drive motor, the first shaft and the hollow shaft are arranged parallel to each other.

10. An electric truck, characterized in that: The electric truck has the electric drive axle according to any one of claims 1 to 9.

Images