Multi-Speed Transmission Torque Control
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Solution Overview
Problem
Conventional hybrid transmissions require large, expensive electric motor/generators for four-quadrant operation, leading to complex and costly designs, and experience significant torque reduction during gear shifting.
Innovation Solution
The electric machine is connected to a power split device and controlled to reduce torque to zero on either sub-transmission input shaft by adjusting torque levels, allowing for torque fill capacity and heat dissipation, enabling a compact, low-cost design without friction clutches or synchronizers, and utilizing negative shaft power operation to minimize power electronics and battery capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional hybrid transmissions use large electric motor/generators for four-quadrant operation, then high positive and negative shaft power is achieved, but the design becomes complex and expensive
Solution Approach 1:
The patent divides the power transmission system into two separate sub-transmissions (first and second sub-transmissions) with different gear ratios, each handling specific torque ranges. This segmentation allows the electric machine to operate in optimized modes for each sub-transmission rather than requiring full four-quadrant operation capability, reducing design complexity while maintaining power capability.
Solution Approach 2:
The control system dynamically switches between first and second sub-transmissions based on operating conditions, and the electric machine operates in different modes (motor mode, generator mode, coasting mode) depending on the current sub-transmission state. This dynamic operation allows the system to achieve high shaft power when needed while avoiding the complexity of designing for constant four-quadrant operation.
2Power
If conventional hybrid transmissions use large electric motor/generators, then sufficient power capacity is provided, but the cost increases
Solution Approach 1:
By segmenting the power transmission into two sub-transmissions with different gear ratios, the electric machine can be sized for specific operating ranges rather than requiring oversized capacity for all conditions. The first sub-transmission handles high-torque low-speed operations while the second handles lower-torque high-speed operations, allowing cost-optimized electric machine sizing.
Solution Approach 2:
The system changes operating parameters by switching between sub-transmissions with different gear ratios. This allows the electric machine to operate in its most efficient power range across different vehicle speeds and loads, reducing the need for oversized, expensive components while maintaining sufficient power capacity.
3Ease of operation
If torque is reduced to zero during gear shifting, then shifting smoothness is improved, but torque loss occurs
Solution Approach 1:
The electric machine acts as an intermediary during gear shifting operations. When shifting between gears in a sub-transmission, the electric machine provides compensating torque to maintain overall torque output while one gear disengages and another engages. This mediator function allows smooth shifting without significant torque loss by making up the difference during the transition period.
Solution Approach 2:
During gear shifting, the system temporarily discards mechanical torque transmission through the shifting gears, but the electric machine recovers or compensates for this torque loss by providing electrical torque. This allows the system to maintain power output during the brief period when mechanical torque transmission is interrupted by the shifting process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces torque loss during shifting, achieves high heat dissipation efficiency, and allows for a smaller, lighter electric machine and power electronics, with heat dissipation exceeding 50% and power capacity several times smaller than conventional systems, enabling precise launch control and eliminating the need for master clutches or torque converters.
Implementation Method 1
the internal heat generation capacity of the electric machine exceeds the power capacity of the power line in said control system
Data Source
AI summary
The invention relates to a multi-speed transmission, comprising a power split device, an input shaft of the transmission being connected or connectable to prime mover, an output shaft, two shiftable sub-transmissions, each providing a plurality of different gear ratios, and at least one rotating electric machine, connected to said power split device, wherein the two sub-transmissions can be connected alternatively to the output shaft, and a control system, connecting said electric machine with an electric battery and auxiliary electrical consumers. The electric machine is connected to the power split device in a way to reduce torque value down to zero on either an input shaft of the first sub-transmission or on an input shaft of the second sub-transmission by applying different shaft torque levels, and the internal heat generation capacity of the electric machine exceeds the power capacity of the control system power line.