Hybrid Powertrain Torque Control via Planetary Gear Decoupling
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Solution Overview
Problem
Hybrid vehicles face limitations in achieving optimal torque from combustion engines due to torque interruptions and the need for complex clutch mechanisms, which result in increased fuel consumption, wear, and weight, especially in heavy goods vehicles requiring multiple gear steps.
Innovation Solution
A method for controlling a hybrid powertrain using a gearbox with two planetary gears and electrical machines, where torque balance is achieved by disconnecting moveable parts of the planetary gears, allowing the combustion engine to operate at higher speeds without gear changes, and utilizing coupling devices and locking mechanisms to transfer torque efficiently between the gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional clutch mechanisms are used to handle torque interruptions during gear shifts, then gear shifting can be achieved, but device complexity increases and reliability decreases due to wear and heating
Solution Approach 1:
The patent extracts and eliminates the conventional clutch mechanism from the hybrid powertrain by utilizing the electrical machine to directly manage torque delivery during gear transitions. The control system disconnects the combustion engine from the transmission during gear shifts and uses the electrical machine alone to provide the necessary torque, thereby removing the need for clutch mechanisms that cause wear and complexity.
Solution Approach 2:
The patent replaces the mechanical clutch system with an electro-mechanical control approach. Instead of using friction-based clutch discs to manage torque during gear shifts, the system uses the electrical machine's electromagnetic torque control capability to achieve smooth transitions, substituting a mechanical wear-based system with an electrically controlled system.
2Power
If the electrical machine's torque is limited, then the combustion engine's maximum torque cannot be fully transferred to the transmission device, but increasing electrical machine size increases weight and cost
Solution Approach 1:
The patent applies dynamic torque management where the control system continuously adjusts the electrical machine's torque output based on real-time operating conditions. During gear shifts, the system dynamically switches between combustion engine and electrical machine torque sources, allowing the combustion engine's maximum torque to be fully utilized when available while using the electrical machine to bridge torque gaps during transitions, optimizing the torque transfer capability without requiring the electrical machine to be oversized.
Solution Approach 2:
The patent changes the operational parameters of the electrical machine by controlling its torque output variable. Instead of designing the electrical machine for maximum continuous torque equal to the combustion engine's peak torque, the system controls the electrical machine to provide variable torque levels - using it primarily for transient support during gear shifts and regenerative braking, while allowing the combustion engine to handle sustained high torque demands.
3Power
If multiple gear steps are used in heavy goods vehicles, then torque requirements can be met, but torque interruptions occur during gear shifts reducing productivity
Solution Approach 1:
The patent ensures continuous useful action by maintaining uninterrupted torque delivery to the transmission device during gear shifts. The control system coordinates the combustion engine and electrical machine so that when the combustion engine is temporarily disconnected during a gear shift, the electrical machine immediately compensates to maintain the required torque level, eliminating torque interruptions and ensuring continuous productive operation.
Solution Approach 2:
The electrical machine serves as an intermediary between the combustion engine and the transmission device during gear shifts. It acts as a torque buffer that smooths out the discontinuities inherent in manual or automated gear changes, absorbing torque fluctuations and delivering continuous torque to the drivetrain, thereby eliminating productivity losses associated with gear shift interruptions.
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 approach optimizes torque delivery to the output shaft, reduces the need for conventional clutches, and results in a more compact, reliable, and cost-effective drive arrangement, capable of handling high torque requirements without gear interruptions.
Implementation Method 1
The planetary gearbox usually comprises three components, which are rotatably arranged in relation to each other, namely a sun wheel, a planetary wheel carrier and an internal ring gear
Implementation Method 2
A gearbox in a hybrid vehicle may comprise a planetary gear
Implementation Method 3
When the vehicle is braked, the electrical machine generates electric power, which is stored in the energy storage device. This is usually referred to as regenerative braking
Implementation Method 4
The electrical machine is equipped with at least one energy storage device, such as an electro-chemical energy storage device, for storage of electric power
Data Source
AI summary
A method is provided to control a hybrid powertrain that comprises: a combustion engine; a gearbox with input and output shafts; a first planetary gear connected to the input shaft and a first main shaft; a second planetary gear, connected to the first planetary gear and a second main shaft; first and second electrical machines, respectively connected to the first and second planetary gears; one gear pair connected with the first planetary gear and output shaft; and one gear pair connected with the second planetary gear and output shaft. The method comprises: disconnecting a first planetary wheel carrier and a first sun wheel or disconnecting a second planetary wheel carrier and a second sun wheel from each other; b) controlling the combustion engine to a predetermined engine speed; and c) controlling the first and second electrical machines so that a desired torque is achieved in the output shaft, while a requested total power consumption of the first and the second electrical machines is achieved.