Two-gear coaxial electric drive assembly, control method and vehicle

Abstract

The invention discloses a two-gear coaxial electric drive assembly, a control method and a vehicle, and relates to the technical field of automobile electric drive assemblies. The two-gear coaxial electric drive assembly comprises a motor unit, a differential mechanism, a first final speed reducing mechanism and a second final speed reducing mechanism. And the first final speed reduction mechanism and the second final speed reduction mechanism which bear the final speed reduction amplification torque are moved to the two sides of the outermost periphery of the system after the differential mechanism distributes power. By means of the layout, the second power transmission shaft penetrating through the interior of the motor unit only needs to transmit high-speed small torque before speed reduction. And meanwhile, two-gear speed change is realized by combining a dead axle gear arranged on one side and a gear shifting sleeve. According to the invention, a general small-size motor platform is utilized to stably output 8000Nm-level off-road large torque, the manufacturing cost is greatly reduced, and the escape power and the road energy consumption are both considered.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile electric drive assembly, in particular to a small outer diameter, two-gear coaxial electric drive assembly suitable for off-road vehicles with large output torque, a control method and a vehicle. BACKGROUND

[0002] With the rapid development of the new energy vehicle industry, the electric drive system as the core power source is constantly iterating. In the passenger vehicle field, the coaxial electric drive assembly has become a highly competitive transmission architecture due to its extremely high space utilization rate and left-right symmetrical chassis layout advantage. In a conventional coaxial single-gear electric drive assembly, the transmission path of the electric drive power is usually: motor rotor shaft, reducer (such as parallel shaft gear or planetary gear reducer), differential. In order to transmit the power after the differential is split to the far-end wheels, one of the output half shafts must be used as a transfer shaft, penetrating the hollow rotor shaft of the motor, and then connecting the vehicle half shaft.

[0003] In a conventional passenger vehicle (the total output torque is generally below 5000Nm), the above architecture works well. However, the current domestic new energy off-road vehicles and other special vehicles have put forward more stringent requirements for the electric drive assembly, and the total vehicle output escape torque generally needs to reach 8000Nm or more. Moreover, in order to consider the power performance of low-speed climbing escape and the economy of high-speed cruising on paved roads, the system needs to have a two-gear transmission function.

[0004] Since the existing architecture is "firstly performing final overall deceleration and then performing differential distribution", it means that the power output by the differential is already a "terminal large torque" after multiple stages of amplification. When the total demand torque is 8000Nm, considering that a single wheel may bear about 60% of the torque (i.e. 4800Nm) in extreme conditions, the transfer shaft penetrating the motor hole must bear the extreme torque of up to 4800Nm. According to material mechanics calculation, the transfer shaft diameter required to transmit such torque reaches 45mm or more, which in turn forces the motor hollow rotor shaft wrapped on the outside to expand to 50mm or more in diameter. Due to the physical limitations of motor magnetic circuit design and rotor wall thickness, a motor with a 50mm inner hole cannot use the 200mm-220mm stator outer diameter platform motor which is the most mature and cost-optimal technology in the current industry.

[0005] If a large-diameter platform motor is developed separately for this specific large-torque requirement, it will face technical and economic dilemmas such as high mold development cost, non-universal production line, and extremely low commercial return on investment. Therefore, how to realize two-gear large-torque coaxial output without increasing the outer diameter and inner hole platform of the mainstream motor has become a technical pain point that needs to be solved in this field. SUMMARY

[0006] In view of the inherent defects that the traditional coaxial electric drive "entire large torque penetrates the shaft" must expand the inner hole and outer diameter size of the motor, the application provides a two-gear coaxial electric drive assembly, a control method and a vehicle, aiming to solve how to greatly reduce the torque borne by the transmission shaft penetrating the motor under the premise of reusing an existing small outer diameter motor platform (for example, a 220 mm platform), so as to safely and stably output an ultra-large wheel end torque, and meanwhile, two-gear speed regulation is considered.

[0007] To solve the above technical problems, in a first aspect, the application provides the following technical solution:

[0008] A two-gear coaxial electric drive assembly comprises: a motor unit having a hollow hollow rotor shaft; a differential mechanism arranged on one side of the motor unit in the axial direction; the differential mechanism has a differential housing, a first output end for outputting a first power flow and a second output end for outputting a second power flow; a first final reduction mechanism and a second final reduction mechanism are arranged on both sides of the motor unit along the axial direction; the input end of the first final reduction mechanism is in transmission connection with the first output end of the differential mechanism; a second power transmission shaft has one end connected with the second output end of the differential mechanism and the other end axially penetrating the inside of the hollow rotor shaft and in transmission connection with the input end of the second final reduction mechanism; and a gear shifting mechanism is coaxially arranged on the hollow rotor shaft and is configured to selectively transmit the power output by the motor unit to the differential housing via a first power path having a first transmission ratio or to the differential housing via a second power path having a second transmission ratio.

[0009] By adopting the above technical solution, the application can greatly reduce the torque borne by the second power transmission shaft penetrating the motor inner hole. The reason is that the application breaks the traditional topology and moves the final amplification torque reduction mechanism to the end of the power chain after the differential mechanism is branched (on both sides of the motor). Therefore, the second power transmission shaft transmits a high-speed small torque that has not been amplified at the end, which directly allows it to be greatly reduced in diameter, thereby enabling the motor to reuse a small size inner hole and outer diameter platform, and solving the physical contradiction between large torque and small motor platform.

[0010] As a preferred scheme of the application, the first power path comprises a first reduction mechanism, and the second power path is configured to directly transmit power to the differential housing without passing through the first reduction mechanism; the first reduction mechanism is a fixed shaft gear reducer, and the fixed shaft gear reducer is arranged between the motor unit and the differential mechanism. By adopting this preferred scheme, the application can realize one-stage reduction and two-gear switching of power with extremely high transmission efficiency and compact axial size, and meet the flexible conversion of the vehicle between low speed and large torque and high speed and low energy consumption.

[0011] As a preferred scheme of the present application, the fixed-axle gear reducer comprises: an input gear coaxially and relatively rotatably sleeved outside the hollow rotor shaft; a reduction output gear fixedly connected to the differential case of the differential mechanism; and an intermediate transmission assembly meshed and transmitted with the input gear and the reduction output gear respectively, for transmitting the power of the input gear to the reduction output gear after reduction. By adopting the preferred scheme, the present application can construct a stable power bypass parallel to the main axis, with good gear transmission rigidity and strong bearing capacity.

[0012] As a preferred scheme of the present application, the intermediate transmission assembly comprises at least one double gear, which comprises coaxially and fixedly connected intermediate first and second gears; the input gear is meshed with the intermediate first gear, and the reduction output gear is meshed with the intermediate second gear. By adopting the preferred scheme, the present application can realize a great reduction ratio span through the series connection of fixed-axle gear trains in a limited radial space, further amplifying the torque basis before entering the differential.

[0013] As a preferred scheme of the present application, the shift mechanism is a shift coupling sleeve or a friction clutch assembly, which is coaxially nested outside the hollow rotor shaft and fixedly connected with the hollow rotor shaft in the circumferential direction and slidable or engaged in the axial direction; the shift coupling sleeve or the friction clutch assembly has a first engagement position, a second engagement position and a neutral position therebetween; when in the first engagement position, the shift coupling sleeve locks and connects the hollow rotor shaft with the input gear; when in the second engagement position, the shift coupling sleeve directly locks and connects the hollow rotor shaft with the differential case. By adopting the preferred scheme, the present application can realize reliable switching of power flow between the reduction path and the direct drive path by using a single mechanical actuating element (coupling sleeve), and the mechanical structure is simple and not prone to failure due to sliding friction.

[0014] As a preferred scheme of the present application, the first and second final reduction mechanisms are configured as planetary gear sets for reducing rotational speed and increasing torque. By adopting the preferred scheme, the present application can realize a high-density large-scale reduction and torque increase in the narrow coaxial space at the wheel or chassis end, and the self-balancing characteristics of the planetary gear train ensure the structural stability under extreme torque.

[0015] As a preferred scheme of the present application, the first final reduction mechanism on the same side of the differential mechanism comprises a first sun gear and a first planet carrier; the first sun gear is connected with the first output end of the differential mechanism through the first power transmission shaft as an input end, and the first planet carrier is connected with a first wheel drive shaft as an output end; the second final reduction mechanism on the other side of the motor unit comprises a second sun gear and a second planet carrier; the second sun gear is connected with the second power transmission shaft as an input end, and the second planet carrier is connected with a second wheel drive shaft as an output end; the first final reduction mechanism and the second final reduction mechanism are configured as planetary gear sets for reducing the rotation speed and increasing the torque. By adopting the preferred scheme, the physical connection mode of the final reduction is determined, the sun gear is high-speed input, and the planet carrier is low-speed and high-torque output, so that perfect conversion of dynamics is realized.

[0016] As a preferred scheme of the present application, the platform range of the outer diameter size of the stator of the motor unit is 200 mm to 220 mm. By adopting the preferred scheme, the present application can realize great cost saving on the industrial level, and completely avoids huge investment caused by re-development of non-standard large-size motors.

[0017] As a preferred scheme of the present application, the first final reduction mechanism and the second final reduction mechanism are both NGW type planetary reducers or NW type planetary reducers. By adopting the preferred scheme, the present application can select mature shelf reducer components according to the slight difference of the wheelbase of the chassis in actual engineering application, and improve the platform expansion capability.

[0018] As a preferred scheme of the present application, the second power transmission shaft is configured to transmit the torque not amplified by the second final reduction mechanism, and the torque borne by the second power transmission shaft is less than 1 / i of the output torque of the second final reduction mechanism, wherein i is the reduction ratio of the second final reduction mechanism; the outer diameter of the second power transmission shaft is smaller than the inner diameter of the hollow rotor shaft, and a gap is formed between the second power transmission shaft and the hollow rotor shaft.

[0019] To solve the above technical problems, in a second aspect, the present application provides the following technical scheme:

[0020] A vehicle comprising a vehicle control unit and a two-gear coaxial electric drive assembly according to any one of the first aspect.

[0021] The present application can endow the off-road vehicle with excellent all-terrain escape ability and excellent road energy consumption performance without sacrificing the chassis ground clearance and suspension arrangement space.

[0022] To solve the above technical problems, in a third aspect, the present application provides the following technical scheme:

[0023] A control method based on the two-speed coaxial electric drive assembly described in the first aspect, the method being executed by the vehicle's control unit, comprising: acquiring the vehicle's current operating condition parameters and determining a target gear based on the operating condition parameters; in response to determining that the target gear is a high-torque output first gear, controlling the shift mechanism to perform a first action, guiding the power of the motor unit to the first power path, the power being amplified and then input to the differential mechanism, which then splits the power and inputs it to the first final reduction mechanism and the second final reduction mechanism for final deceleration output; in response to determining that the target gear is a high-speed cruising second gear, controlling the shift mechanism to perform a second action, guiding the power of the motor unit to the second power path and inputting it to the differential mechanism, which then splits the power and inputs it to the first final reduction mechanism and the second final reduction mechanism for final deceleration output.

[0024] By adopting this preferred solution, the present invention can form an optimal power distribution and scheduling that matches the hardware architecture at the software and control logic level, thereby realizing adaptive and intelligent switching of vehicle power performance.

[0025] In a preferred embodiment of the present invention, the control method further includes: in response to receiving a coasting command or a towing command, controlling the shifting mechanism to perform a third action, moving it to a neutral position that engages neither the first power path nor the second power path, thereby cutting off the physical transmission between the motor unit rotor and the road surface's anti-drag torque. By adopting this preferred embodiment, the present invention can completely eliminate the risk of the high-voltage back EMF generated by the motor reversing during passive towing of the vehicle damaging the controller, and reduce mechanical resistance.

[0026] In a preferred embodiment of the present invention, during the first or second gear operation, the control unit monitors the total target output torque in real time and ensures, through a low-level torque limiting algorithm, that the peak value of the actual load torque allocated to the second power transmission shaft does not exceed a preset safety threshold. The actual load torque is calculated by comprehensively considering the total target output torque, the differential distribution coefficient, and the reduction ratio of the second final reduction mechanism. By adopting this preferred embodiment, the present invention can establish a physical protection closed loop for the internal transmission shaft of the hollow rotor at the software level, preventing torsional fracture failure under extreme operation.

[0027] In a preferred embodiment of the present invention, when the vehicle is on a road surface with extreme traction differences and the target gear is first gear, the control unit further controls the limited-slip actuator in the differential mechanism to lock, causing the first and second output terminals to rotate synchronously, so as to concentrate the torque output to the final deceleration mechanism on the side with traction. By adopting this preferred embodiment, the present invention can further extend the vehicle's extreme off-road performance in harsh environments.

[0028] Compared with the prior art, the present invention has the following outstanding advantages:

[0029] 1. Compatible with standard motor platforms and economical: This invention, through an innovative power flow architecture, places the final reduction mechanism after the differential mechanism, significantly reducing the torque carried by the power transmission shaft passing through the motor shaft. This allows for a significant reduction in the diameter of the power transmission shaft, eliminating the need to increase the inner diameter of the motor shaft. It enables the direct use of mainstream, economical small-diameter motor platforms (such as 220mm or 200mm platforms), greatly reducing development and manufacturing costs.

[0030] 2. Achieve high torque output: By arranging a high-ratio final reduction mechanism (such as a planetary reducer) on both sides of the motor, the present invention can easily achieve high torque output at the vehicle level (such as above 8000Nm), meeting the stringent power performance requirements of special vehicles such as off-road vehicles.

[0031] 3. Integrated dual-mode functionality, wide applicability: This invention achieves two modes—high torque (first gear) and high speed (second gear)—through a built-in shifting mechanism and a first reduction mechanism. First gear can be used for scenarios requiring extreme torque, such as off-road driving and climbing; second gear can be used for scenarios requiring high efficiency and high speed, such as highway cruising, perfectly balancing the needs of different working conditions.

[0032] 4. Compact structure, maintaining the advantages of coaxial design: While achieving the above functions, this invention still maintains the advantages of coaxial electric drive structure, such as compactness and ease of vehicle layout, thus achieving a balance between high performance and high integration.

[0033] In summary, this invention, based on the core design concept of "torque gradation and final deceleration," cleverly moves the mechanism bearing extremely high torque from the middle of the system to the outer end, creating a low-torque operating environment for the power transmission shaft. This fundamental change in mechanical path resolves the "shaft diameter-bore diameter" contradiction that has constrained the development of coaxial electric drives, allowing an 8000Nm power system of off-road vehicle grade to be seamlessly integrated into a mature 220mm motor platform for passenger vehicles. The superimposed single-stage gear and shifting mechanism give the system two-speed adjustment capability. The overall solution not only significantly reduces R&D and material costs but also achieves a high degree of unity between power performance, economy, and compact layout. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments disclosed in this invention, the accompanying drawings of the embodiments will be briefly described below. These drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0035] Figure 1 This is a schematic diagram of the power topology connection of the two-speed coaxial electric drive assembly architecture in an embodiment of the present invention.

[0036] Figure 2 This is a simplified diagram of the power transmission path of the two-speed coaxial electric drive assembly in the first-speed (high torque traction) mode in an embodiment of the present invention.

[0037] Figure 3 This is a simplified diagram of the power transmission path of the two-speed coaxial electric drive assembly in the second-speed (high-speed) mode in an embodiment of the present invention.

[0038] In the diagram: 1. Motor unit; 2. Input gear; 3. Intermediate transmission assembly; 31. Intermediate first-stage gear; 32. Intermediate second-stage gear; 4. Reduction output gear; 5. Differential mechanism; 6. First power transmission shaft; 7. First sun gear; 8. First planetary carrier; 9. First wheel drive shaft; 10. Second power transmission shaft; 11. Second sun gear; 12. Second planetary carrier; 13. Second wheel drive shaft; C. Gear shifting mechanism. Detailed Implementation

[0039] The technical solutions (including preferred technical solutions) of the present invention will be further described in detail below with reference to the accompanying drawings and by way of listing some optional embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment provides a device for a two-speed coaxial electric drive assembly, and details the assembly structure and mechanical topological relationship of its internal components.

[0042] like Figure 1 As shown, the two-speed coaxial electric drive assembly of the present invention consists of a series of highly integrated electromechanical modules. The power source is motor unit 1. Motor unit 1 includes a stator and a rotor. To solve the common platform reuse problem in the industry, in this embodiment, the outer diameter of the stator of motor unit 1 is strictly limited to the standard platform size of 200 mm to 220 mm. The motor unit 1 has a hollow rotor shaft, and both ends of the hollow rotor shaft are stably supported inside the motor housing by high-speed ceramic ball bearings (not shown).

[0043] On the right side (first side) of the motor unit 1, a fixed-axis gear reducer (as the first reduction mechanism), a shifting mechanism C, and a differential mechanism 5 are arranged in sequence.

[0044] Specifically, the fixed-axis gear reducer comprises three main transmission gear sections. First, the input gear 2 is loosely fitted onto the outer shaft segment extending axially to the right of the hollow rotor of the motor unit 1 via a needle roller bearing. This means that when not in gear, the input gear 2 can freely rotate relative to the hollow rotor shaft without transmitting power. Second, the intermediate transmission assembly 3 is supported by a deep groove ball bearing on an offset shaft parallel to the main axis. In this embodiment, the intermediate transmission assembly 3 is a double gear, integrally forged from a large-diameter intermediate primary gear 31 and a small-diameter intermediate secondary gear 32. Third, the reduction output gear 4 is securely fixed to the outside of the differential housing of the differential mechanism 5 by bolts or welding. In terms of spatial meshing, the input gear 2 is normally meshed with the intermediate primary gear 31, while the reduction output gear 4 is normally meshed with the intermediate secondary gear 32.

[0045] To achieve power path switching, the shift mechanism C (in this example, a mechanical shift sleeve) is coaxially nested on the hollow rotor shaft between the input gear 2 and the motor rotor body. The inner ring of the shift sleeve has an internal spline that mates with the involute external spline machined on the outer surface of the hollow rotor shaft, ensuring it always rotates synchronously with the motor and can slide axially. Engaging teeth are machined on the outer side of the shift sleeve. When the shift fork drives the shift sleeve to one side to the first engagement position, its engaging teeth rigidly mesh with the engaging gear ring (dog teeth) on the side of the input gear 2; when the shift fork drives it to the opposite direction to the second engagement position, its other engaging teeth directly cross the input gear and mesh with the engaging gear ring fixed to the side of the differential housing. If it remains in the middle position, it is in neutral.

[0046] After receiving external power, the differential mechanism 5 (in this example, a bevel gear differential) distributes the power proportionally (or according to the adhesion distribution) to the left and right half-shaft gears through the internal cross shaft and planetary bevel gear set, namely the first output end and the second output end of the differential mechanism 5.

[0047] The breakthrough design of this invention lies in the layout of the final power transmission and the final deceleration. The first output end of the differential mechanism 5 is directly connected to a short first power transmission shaft 6, which extends to the right and serves as the power input end, connecting to the first final deceleration mechanism located on the far right of the assembly.

[0048] More importantly, the second output end of the differential mechanism 5 is connected to a slender second power transmission shaft 10 (i.e., a transition shaft in the prior art). This second power transmission shaft 10 extends to the left in the opposite direction, penetrating laterally through the hollow rotor shaft inside the motor unit 1. To prevent rubbing during high-speed operation and ensure coaxiality, a precise safety clearance is maintained between the outer wall of the second power transmission shaft 10 and the inner hole of the hollow rotor shaft, and oil seals are provided at both ends. After penetrating the motor unit 1, the second power transmission shaft 10 reaches the leftmost side of the assembly and serves as the power input end connected to the second final reduction mechanism.

[0049] In this embodiment, both the first and second final reduction mechanisms are NW-type (single-row external meshing) planetary gear reducers. Taking the right side as an example, the first power transmission shaft 6 transmits power by inserting its external spline into the internal spline of the first sun gear 7 of the first final reduction mechanism. The first sun gear 7 drives multiple planetary gears around it. These planetary gears rotate and revolve within a gear ring fixed to the outermost end cover housing of the assembly, thereby driving the first planet carrier 8, which supports them, to rotate at low speed and with high torque. The first planet carrier 8 serves as the final output end and is connected to the first wheel drive shaft 9 (right half-shaft of the vehicle) via a rigid flange or a constant velocity universal joint. Similarly, the second power transmission shaft 10 on the left side inputs power to the second sun gear 11, and after end reduction, outputs power from the second planet carrier 12 to the second wheel drive shaft 13 (left half-shaft of the vehicle).

[0050] In the above-described device embodiment, since the amplification process of bearing the ultimate torque (i.e., through the planetary gear system) is moved to the very end of the power chain (the left and right ends of the electric drive assembly housing), the second power transmission shaft 10, which runs through the inside of the motor, is effectively "protected" before the planetary gear reducer amplification process, thus successfully avoiding the technical paradox of shaft enlargement.

[0051] It should be noted that although the first and second final reduction mechanisms in this embodiment are shown as NW type (sun gear input, planetary carrier output, fixed gear ring), this is not the only limitation. In another embodiment, the final reduction mechanism can adopt an NGW type planetary gear mechanism. For example, a double planetary gear structure can be used, in which the sun gear is the input, the large planet gear meshes with the sun gear, the small planet gear meshes with the fixed internal gear ring, and the planetary carrier is the output. Regardless of the planetary gear configuration used, as long as the structure satisfies the requirement of "the input end is connected to the power transmission shaft, the output end is connected to the wheel drive shaft, and it provides a reduction and torque increase function," it falls within the protection scope of this invention.

[0052] Example 2

[0053] This embodiment provides a vehicle, which can be a new energy off-road vehicle or a heavy-duty pickup truck requiring extremely high low-speed traction. The vehicle's chassis is equipped with the two-speed coaxial electric drive assembly described in Embodiment 1. The first wheel drive axle 9 and the second wheel drive axle 13 of the assembly are respectively connected to the right and left drive wheels of the vehicle's rear axle (or front axle). Because this invention employs a design that places the massive final reduction planetary gear set near the wheels on both sides (or at the end of the axle housing), and the centrally located motor unit 1 thereby reuses a small outer diameter platform of 200-220mm, the central volume of the entire electric drive assembly is exceptionally compact.

[0054] This advantage gives the vehicle a higher ground clearance, and the electric drive system does not interfere with the large battery pack space above the chassis or the complex suspension arm structure. In terms of overall vehicle weight, since the motor does not require excessive redundancy, the sprung mass of the vehicle is also effectively controlled, improving the vehicle's dynamic response in various extreme terrains.

[0055] Example 3

[0056] This embodiment provides a control method based on the aforementioned two-speed coaxial electric drive assembly, detailing the power flow transmission logic under different operating conditions and the coordinated operation of hardware and software.

[0057] The vehicle's control system consists of a network of VCU (Vehicle Controller Unit) and MCU (Motor Controller Unit). The control method includes the following steps:

[0058] The control unit first acquires the vehicle's current operating parameters in real time through onboard sensors. These parameters include, but are not limited to: accelerator pedal opening, vehicle speed sensor data, slope information fed back by the IMU (Inertial Measurement Unit), and tire slip ratio fed back by the wheel speed sensors. The control unit has an embedded shift strategy map, which calculates and determines the target gear based on these parameters.

[0059] Scenario A: First Gear (High Torque Escape Mode) Control Logic

[0060] like Figure 2 As shown. When the sensor detects that the vehicle is climbing a steep slope, stuck in mud, or starting under heavy load, the control unit determines that the target gear is first gear. The control unit sends an electrical signal to the shift actuator motor (actuator), and the actuator drives the shift fork to slide the shift mechanism C (shift engagement sleeve) to the left (first action) until its internal spline is synchronized with the motor rotor, and the external engagement teeth are fully engaged and locked with the input gear 2.

[0061] In this high-torque mode, the power generated by motor unit 1 is forced into the "first power path": the rotational power of the hollow rotor shaft is transmitted to the input gear 2 via the shift sleeve C; the input gear 2 drives the intermediate first-stage gear 31, and the power is transmitted to the intermediate second-stage gear 32 coaxial with the double gear, which in turn drives the reduction output gear 4. In this stage, the high-speed, low-torque motor power is reduced in speed and increased in torque for the first time through the gear pair.

[0062] The amplified power is diverted through the differential mechanism 5. The first power flow on the right side passes through the short shaft 6 and directly enters the first sun gear 7 of the right planetary reducer. After being reduced at the end of the planetary gear set, the first planetary carrier 8 outputs maximum torque to the right half-shaft 9. The second power flow on the left side enters the slender second power transmission shaft 10. The second power transmission shaft 10, with its small diameter (e.g., 20mm), stably transmits this relatively small (without end-stage amplification) torque, passing through the motor's inner bore to reach the second sun gear 11 of the left planetary reducer. Similarly, after end-stage reduction, the second planetary carrier 12 outputs a large off-road torque to the left half-shaft 13.

[0063] Scenario B: Second-gear (high-speed cruise mode) control logic

[0064] like Figure 3 As shown. When the vehicle enters the paved road, the vehicle speed increases and the torque demand decreases, the control unit determines that the target gear is second gear. After completing the speed synchronization operation, the actuator drives the shift mechanism C to slide to the right (second action), disengaging the input gear 2 and locking its engagement teeth directly with the differential housing of the differential mechanism 5.

[0065] In this high-speed mode, power enters the "second power path": the power from motor unit 1 bypasses the fixed-axis gear set containing the input gear and intermediate transmission components (the fixed-axis gear set is either idle or running freely at this time, with no gear meshing power transmission loss), and inputs the speed unchanged to the differential mechanism 5 (in an alternative embodiment, it can also be transmitted through an intermediate gear or chain with a transmission ratio of 1:1 or similar). The subsequent splitting and end-stage planetary deceleration process is exactly the same as in first gear. Because the first-stage deceleration is eliminated, the wheel-end speed of the entire vehicle is greatly increased, achieving high-speed, low-energy-consumption cruising.

[0066] Scenario C: Neutral protection logic

[0067] When the vehicle needs to be towed, or when the driver shifts into neutral (N) to coast, the control unit drives the shift mechanism C to the neutral position (third action). At this time, the hollow rotor shaft of motor unit 1 is completely decoupled from subsequent mechanics. The kinetic energy of the road wheels dragging the planetary gear set and differential in the opposite direction will not be transmitted back to the motor rotor, completely eliminating the risk of high-voltage back electromotive force generated in the stator coils due to the passive high-speed rotation of the permanent magnet damaging the MCU inverter.

[0068] Example 4

[0069] To rigorously demonstrate the physical and mathematical basis for solving the bottleneck of existing technology through the "end-stage deceleration" architecture, this embodiment specifically provides an independent demonstration and explanation of the mathematical model of system torque transmission and core shaft diameter parameters.

[0070] Under extreme off-road conditions, the final target total output torque of the two-speed coaxial electric drive assembly in the vehicle design is set to T. total = 8000 Nm.

[0071] Considering that the two ends of the axle may be on surfaces with asymmetrical friction (e.g., one side on hard rock, the other on mud), the bevel gears inside the differential mechanism, under the intervention of the extreme anti-slip system, will bias the torque transfer towards the side with traction. The deviation coefficient for the extreme differential mechanism to distribute power to one output end is set to μ = 0.6.

[0072] The maximum output torque T that a single wheel (including the half-shaft and the final reduction output end) needs to withstand is... out For: T out = T total × μ = 8000 × 0.6 = 4800 Nm.

[0073] In a conventional single-speed coaxial electric drive (without end-stage lateral reduction) architecture, this enormous torque of 4800 Nm is entirely borne by the adapter shaft passing through the motor's inner bore. Upon verification, its shaft diameter needs to reach 45 mm, and the motor's inner diameter needs to be increased to 50 mm.

[0074] In the topology of this invention, the first and second final reduction mechanisms are arranged downstream (i.e., at the left and right ends) of the through-shaft power flow. This embodiment selects the reduction ratio i of the NW planetary gear reducer. planets = 8.

[0075] Based on the law of conservation of mechanical transmission (ignoring efficiency loss), the actual torque T carried by the second power transmission shaft 10 passing through the inner hole of the motor is... in The calculation constraint formula is as follows:

[0076]

[0077] Substituting the physical parameters of the example, we can obtain: T in = 4800 / 8 = 600 Nm.

[0078] Based on the rigorous theoretical formula derivation above, we can intuitively compare the significant advantages of our invention's architecture over existing technologies in terms of core physical dimensions using the table below:

[0079]

[0080] The underlying software of the control system is based on the aforementioned T in The real-time calculation results of the formula are monitored in a closed loop. Once the calculated through-shaft torque approaches the material yield limit, the current output of motor unit 1 is actively reduced to limit the peak, thus forming a dual hardware and software protection.

[0081] Example 5

[0082] Based on the pioneering concept of "double final deceleration at the side end to reduce through-shaft torque" in this invention, those skilled in the art can make multi-dimensional engineering derivatives and substitutions to further improve the high-order performance of the system.

[0083] For example, in the selection of the shifting mechanism, although Embodiment 1 preferably uses a simple and low-cost mechanical dog-tooth shifting engagement sleeve, in a luxury off-road vehicle platform that pursues extremely high NVH (smoothness and quietness), the shifting mechanism C can be equivalently replaced by an electro-hydraulic controlled multi-plate wet dual-clutch module. One clutch controls the engagement of the first reduction gear set, and the other controls the direct engagement of the differential housing. This equivalent replacement scheme can complete seamless slip-shifting between first and second gear without interrupting power output.

[0084] In other words, regarding the selection of the shifting mechanism, although Embodiment 1 describes the dog-tooth shift engagement sleeve in detail, in application scenarios that pursue extremely high NVH and shifting smoothness, the shifting mechanism C is replaced by a friction clutch assembly. Specifically, this assembly may include a first clutch and a second clutch (i.e., a dual-clutch module). The driving end of the first clutch is connected to the hollow rotor shaft, and the driven end is connected to the input gear 2, for connecting the first power path; the driving end of the second clutch is connected to the hollow rotor shaft, and the driven end is connected to the differential housing, for connecting the second power path. By controlling the slippage and alternating engagement of the two clutches, seamless switching between first and second gears can be completed without interrupting power output. At this time, the aforementioned "second engagement position" corresponds to the locked state of the second clutch.

[0085] For example, the housing of the differential mechanism 5 is not limited to a conventional open bevel gear system. To cope with the extreme condition of one wheel being completely suspended and slipping (where the distribution coefficient deviation is extremely large), the differential mechanism 5 can be reasonably expanded to integrate an electromagnetically or hydraulically driven limited-slip actuator (such as an LSD multi-plate clutch differential lock). When the target gear is first gear and wheel slippage is detected, the control unit drives the differential lock to lock completely. This combination further enhances the system's ultimate traction capability in complex off-road environments, and the use of all these variant components benefits from the innovative end-deceleration anti-overload architecture of this invention, and should rightfully be included within the scope of protection of this application.

[0086] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, combinations, substitutions, improvements, etc., made under the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A two-speed coaxial electric drive assembly, characterized in that, include: The motor unit has a hollow rotor shaft; A differential mechanism is arranged on one side of the motor unit's axial direction; The differential mechanism has a differential housing, a first output terminal for outputting a first power flow, and a second output terminal for outputting a second power flow. The first final reduction mechanism and the second final reduction mechanism are respectively arranged on both sides of the motor unit along its axial direction; the input end of the first final reduction mechanism is connected to the first output end of the differential mechanism. The second power transmission shaft has one end connected to the second output end of the differential mechanism, and the other end axially passes through the interior of the hollow rotor shaft and is connected to the input end of the second final reduction mechanism. as well as The shifting mechanism is coaxially arranged on the hollow rotor shaft and configured to selectively transmit the power output by the motor unit to the differential housing via a first power path having a first transmission ratio, or via a second power path having a second transmission ratio.

2. The two-speed coaxial electric drive assembly according to claim 1, characterized in that, The first power path includes a first reduction mechanism, and the second power path is configured to bypass the first reduction mechanism and transmit power directly to the differential housing; The first reduction mechanism is a fixed-axis gear reducer, which is disposed between the motor unit and the differential mechanism; The fixed-axis gear reducer includes: An input gear is coaxially and rotatably fitted around the outside of the hollow rotor shaft; A reduction output gear is fixedly connected to the differential housing of the differential mechanism; and An intermediate transmission assembly meshes with the input gear and the reduction output gear respectively, and is used to reduce the power of the input gear and transmit it to the reduction output gear.

3. The two-speed coaxial electric drive assembly according to claim 2, characterized in that, The intermediate transmission assembly includes at least one double gear, which includes an intermediate first-stage gear and an intermediate second-stage gear that are coaxially fixed together. The input gear meshes with the intermediate first-stage gear, and the reduction output gear meshes with the intermediate second-stage gear.

4. The two-speed coaxial electric drive assembly according to claim 2 or 3, characterized in that, The shifting mechanism is a shifting engagement sleeve or a friction clutch assembly. The shifting engagement sleeve or friction clutch assembly is coaxially nested outside the hollow rotor shaft and is circumferentially fixed to the hollow rotor shaft and can slide or engage axially. The shift sleeve has a first engagement position, a second engagement position, and a neutral position between the two. When in the first engagement position, the shift engagement sleeve locks the hollow rotor shaft to the input gear. When in the second engagement position, the shift engagement sleeve directly or indirectly locks the hollow rotor shaft to the differential housing.

5. The two-speed coaxial electric drive assembly according to claim 1, characterized in that, The first and second final reduction mechanisms are configured as planetary gear sets that reduce rotational speed and increase torque; The first final reduction mechanism located on the same side as the differential mechanism includes a first sun gear and a first planet carrier; the first sun gear is connected to the first output end of the differential mechanism via a first power transmission shaft, and the first planet carrier is connected to a first wheel drive shaft as the output end. The second final reduction mechanism located on the other side of the motor unit includes a second sun gear and a second planetary carrier; the second sun gear is connected to the second power transmission shaft as an input end, and the second planetary carrier is connected to a second wheel drive shaft as an output end.

6. A vehicle, characterized in that, It includes a vehicle control unit and a two-speed coaxial electric drive assembly as described in any one of claims 1 to 5.

7. A control method based on a two-speed coaxial electric drive assembly as described in any one of claims 1 to 5, characterized in that, This method is executed by the vehicle's control unit and includes: Obtain the vehicle's current operating condition parameters and determine the target gear based on the operating condition parameters; In response to determining that the target gear is a high torque output gear, the shifting mechanism is controlled to perform a first action, guiding the power of the motor unit to the first power path. After the power is reduced and amplified, it is input to the differential mechanism, and after being split by the differential mechanism, it is input to the first final reduction mechanism and the second final reduction mechanism respectively for end reduction output. In response to determining that the target gear is second gear for high-speed cruising, the shifting mechanism is controlled to perform a second action, guiding the power of the motor unit to the second power path and inputting it into the differential mechanism. After being split by the differential mechanism, the power is input to the first final reduction mechanism and the second final reduction mechanism respectively for end-stage deceleration output.

8. The control method according to claim 7, characterized in that, The control method further includes: In response to receiving a coasting command or a trailer command, the shifting mechanism is controlled to perform a third action, moving it to a neutral position that does not engage the first power path or the second power path, thereby cutting off the physical transmission of the motor unit rotor to the road surface anti-drag torque.

9. The control method according to claim 7, characterized in that, During the operation of the first or second gear, the control unit monitors the total target output torque in real time and ensures, through the underlying torque limiting algorithm, that the peak value of the actual load torque allocated to the second power transmission shaft does not exceed a preset safety threshold. The actual load torque is calculated by comprehensively considering the total target output torque, the differential distribution coefficient, and the reduction ratio of the second final reduction mechanism.

10. The control method according to claim 9, characterized in that, The actual load torque of the second power transmission shaft satisfies the formula: Among them, T in T represents the actual load torque of the second power transmission shaft. total The final target output total torque of the two coaxial electric drive assemblies is given by μ, where μ is the limit deviation coefficient for the differential mechanism to distribute power to one output end, and i is the final target output total torque at both ends. planets The reduction ratio of the second final reduction mechanism; the vehicle control unit is based on the calculated T in The output current of the motor unit is limited by a closed loop.

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