Heavy-Duty Wheel Drive Unit With Compact Multispeed Gear Train
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Solution Overview
Problem
Existing wheel drive units in heavy-duty vehicles face efficiency losses due to the electric motor being far from the wheels, leading to increased stress on gearbox components and reduced durability, while also occupying valuable space that could be used for batteries.
Innovation Solution
A compact wheel drive unit with a multispeed transmission system, featuring a 3-gears system for optimal performance and efficiency, and a planetary gear train with force balancing to reduce bearing size and weight, allowing for aluminum housings and improved lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a wide gear reduction ratio (20-50) is provided with several reduction stages to compensate for high-speed/low torque conditions, then torque demand at the wheels is met in all situations, but the gearbox requires more space and becomes more complex
Solution Approach 1:
The patent applies dynamics by making the gear ratio adjustable through a variable ratio transmission mechanism. The gearbox can change its reduction ratio dynamically based on operating conditions, allowing it to provide high torque when needed (starting, climbing) and efficient high-speed operation during cruising, eliminating the need for multiple fixed reduction stages.
Solution Approach 2:
The patent changes the parameter of gear ratio from fixed to variable. By implementing a variable ratio transmission system, the gearbox can adapt its reduction ratio to match different operational requirements, providing both the torque multiplication needed for starting and the efficiency required for cruising, thereby reducing overall system complexity.
2Speed
If high-speed gears are used to achieve high-speed conditions, then cruising performance is improved, but lubrication problems occur as oil is centrifugally ejected from gear teeth
Solution Approach 1:
The variable ratio transmission allows the gearbox to operate at lower speeds with higher torque during cruising conditions by adjusting the gear ratio dynamically. This reduces the centrifugal force on the lubricating oil, preventing oil ejection from gear teeth and maintaining proper lubrication, thereby improving reliability while still achieving high vehicle speeds.
Solution Approach 2:
By changing the operating parameters of the gears (reducing rotational speed at the gear level while maintaining vehicle speed through variable ratio), the patent eliminates the lubrication problem caused by centrifugal force. The variable ratio mechanism allows the gears to operate in an optimal speed range where lubrication is effective.
3Ease of manufacture
If the electric motor is positioned far from the wheels under the truck cab, then the transmission layout is simplified, but efficiency losses increase and space for batteries is reduced
Solution Approach 1:
The patent integrates the variable ratio transmission mechanism directly within the electric motor assembly, creating a compact nested structure. The gearbox is positioned immediately adjacent to or integrated with the motor, eliminating long transmission shafts and reducing energy losses while maintaining a simplified overall layout. This nested arrangement also frees up space in the truck cab for battery installation.
4Volume of moving object
If a compact axle assembly is designed to fit within the vehicle without interfering with suspension or braking, then space for batteries is increased, but the gearbox must be smaller and more complex to fit
Solution Approach 1:
The variable ratio transmission mechanism is designed as a compact dynamic system that provides multiple gear ratios in a reduced space. By using planetary gear sets with variable ratio capability, the patent achieves both compactness and the necessary gear multiplication, avoiding the need for multiple large fixed-ratio stages.
Solution Approach 2:
The patent employs composite structural designs in the gearbox, combining multiple functional elements (gears, bearings, housing) into integrated composite components. This allows the gearbox to be smaller and more compact while maintaining strength and durability, fitting within the constrained axle assembly space.
Data Source
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AI summary
A wheel drive unit (5) to be fitted on a chassis of a heavy-duty vehicle (2), said wheel drive unit comprising at least one wheel shaft (50, 52), configured to drive a wheel in rotation, at least one electric motor (8), capable of generating a torque, a gearbox (20) for transmitting the torque of the motor(s) to the wheel shaft(s) and a transmission system between the electric motor(s) and the gearbox, wherein the transmission system consists of a gear train; and wherein a rotation axis of the electric motor is parallel to that of the wheel shaft(s).