Working Machine CVT Gearbox for Electric Machine Speed Control
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Solution Overview
Problem
Existing working machines, such as wheel loaders, face inefficiencies in using electric machines due to limitations in transmission systems, leading to suboptimal performance and increased fuel consumption, especially when operating heavy loads in off-road environments.
Innovation Solution
A working machine equipped with a continuously variable transmission (CVT) gearbox that allows the electric machine to operate within an optimal speed range independently of the output shaft, enabling parallel hybridization with the internal combustion engine, and incorporating a power split mechanism between a variator unit and a planetary gear wheel unit to improve efficiency and reduce energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional transmission system with fixed gear ratios is used, then the structure is simple, but the electric machine cannot operate at optimal speed across varying load conditions
Solution Approach 1:
The patent employs a continuously variable transmission (CVT) that dynamically adjusts gear ratios in real-time based on operating conditions, allowing the electric machine to maintain optimal rotational speed across varying load requirements. This dynamic adjustment mechanism resolves the contradiction by enabling continuous optimization of electric machine efficiency while adapting to changing operational demands.
Solution Approach 2:
The transmission system continuously varies the gear ratio parameter to optimize electric machine operation. By changing the gear ratio parameter dynamically rather than using fixed discrete ratios, the system maintains the electric machine within its optimal efficiency range across different operating conditions, thereby improving energy utilization without requiring complex additional components.
2Adaptability or versatility
If the electric machine is directly connected to the gearbox, then the structure is simple, but the electric machine cannot operate independently of the output shaft speed
Solution Approach 1:
The CVT provides dynamic decoupling between the electric machine and the output shaft through continuous gear ratio variation. This allows the electric machine to operate at its optimal speed independently of the output shaft speed requirements, enabling versatile operation modes including motor mode, generator mode, and coasting mode without being constrained by fixed gear ratios.
Solution Approach 2:
The transmission system is designed to accommodate multiple operating modes of the electric machine (motor, generator, coasting) through its continuous variable capability. This multi-functional design allows the electric machine to serve different purposes depending on operational needs while maintaining optimal performance through the CVT's adaptive gear ratio adjustment.
3Loss of energy
If a torque converter is used to enable smooth transmission, then the operation is smooth, but energy losses increase significantly
Solution Approach 1:
The patent replaces the torque converter's fluid coupling mechanism with a mechanically-based CVT system that achieves smooth power transmission through varying gear ratios. This substitution eliminates the significant energy losses inherent in torque converter fluid dynamics while maintaining smooth operation characteristics through precise mechanical control of the variable transmission mechanism.
Solution Approach 2:
The invention extracts and removes the torque converter component from the transmission system, replacing its function with a CVT that achieves smooth transmission without the energy-intensive fluid coupling mechanism. This extraction eliminates the source of energy losses while preserving the desired smooth operational characteristics through alternative mechanical means.
4Use of energy by moving object
If the gearbox uses fixed gear ratios, then the structure is simple, but the electric machine cannot be driven at optimal speed independently of output shaft requirements
Solution Approach 1:
The gearbox is transformed from a static fixed-ratio structure to a dynamic CVT system that continuously adjusts gear ratios. This dynamic capability enables the electric machine to operate at optimal speed across varying load conditions by actively adjusting the transmission ratio in real-time, resolving the contradiction between structural simplicity and operational optimization.
Solution Approach 2:
The gearbox implements continuous variation of the gear ratio parameter rather than fixed discrete ratios. This parameter change capability allows the electric machine to maintain optimal operating conditions across different output shaft speed requirements, improving energy efficiency while the CVT mechanism manages the increased structural complexity through integrated design.
Data Source
AI summary
A working machine includes a prime mover for supplying torque to the driving wheels of the working machine, and a transmission line arranged between the prime mover and the driving wheels for transmitting torque from the prime mover to the driving wheels. The transmission line includes a gearbox arranged between the prime mover and the wheels, and the working machine further includes at least one hydraulic machine in a hydraulic system for moving an implement arranged on the working machine and/or steering the working machine, and an electric machine for driving or braking the driving wheels and/or for driving or braking the at least one hydraulic machine. The electric machine is arranged in parallel with the prime mover with respect to the transmission line and is mechanically connected to the transmission line between the prime mover and the gearbox. The gearbox is a continuously variable transmission having a variator unit, and the gearbox has an operation mode where the rotation speed of the output shaft of the gearbox is zero or close to zero independently of the rotation speed of the input shaft of the gearbox at the same time as torque can be transmitted from the input shaft to the output shaft.