Hybrid Powertrain Control for Independent Engine Speed
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Solution Overview
Problem
Existing hybrid powertrain systems face challenges in achieving a desired engine speed for combustion engines independently of the powertrain's rotational speed, leading to limitations in torque transfer and increased complexity due to the need for conventional clutches, which result in inefficiencies and higher costs.
Innovation Solution
A method involving a hybrid powertrain with two planetary gears, coupling devices, and electrical machines that control torque and engine speed independently, allowing for a compact, efficient, and reliable drive arrangement by disconnecting and reconnecting components to optimize power transfer without torque interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional clutch mechanism is used to disconnect the combustion engine from the transmission during shifting, then torque interruption is avoided, but the device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the conventional clutch mechanism from the hybrid powertrain by using the electrical machine to perform the disconnect function. The electrical machine can be independently controlled to stop torque transmission to the transmission during gear shifts, achieving smooth shifting without requiring a mechanical clutch device.
Solution Approach 2:
The patent replaces the mechanical clutch system with an electrical control system. The electrical machine's ability to independently control torque transmission allows it to substitute for the clutch's function of disconnecting the engine from the transmission, thereby reducing mechanical complexity while maintaining reliable gear shifting.
2Device complexity
If the electrical machine's torque is limited by the planetary gear configuration, then the combustion engine's maximum torque transfer is restricted, but the device complexity is reduced
Solution Approach 1:
The patent applies dynamics by making the electrical machine's torque contribution variable and controllable. During acceleration, the electrical machine can dynamically adjust its torque output to complement the combustion engine, allowing the system to achieve maximum torque transfer without being limited by the planetary gear's static constraints. This dynamic control enables the simpler drive arrangement to overcome its inherent torque limitations.
3Loss of energy
If the combustion engine speed is controlled independently of the powertrain rotational speed, then favorable engine operating conditions are achieved, but the control complexity increases
Solution Approach 1:
The patent uses the electrical machine as an intermediary between the combustion engine and the transmission. This intermediary can independently control torque and speed relationships, allowing the combustion engine to operate at favorable speeds while the electrical machine handles the speed differentiation. The control system leverages this intermediary function to achieve efficient engine operation without excessive complexity.
4Ease of operation
If separate devices are added to the gearbox to eliminate torque interruption, then smooth gear shifts are achieved, but the device complexity and space requirements increase
Solution Approach 1:
The patent applies multi-functionality by making the electrical machine perform multiple functions: it acts as a motor during acceleration, a generator during regenerative braking, and a torque interrupter during gear shifts. This universal component eliminates the need for separate devices to achieve smooth gear shifts, reducing gearbox complexity while maintaining ease of operation.
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 enables independent control of combustion engine speed, achieving desired torque and power consumption, reducing the need for conventional clutches, and enhancing the reliability and compactness of the powertrain system.
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
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 3
With knowledge about the number of cogs in the sun wheel and the internal ring gear, the mutual speeds of the three components may be determined during operation
Data Source
AI summary
A method is provided to control a hybrid powertrain to achieve a desired engine speed in a combustion engine, said powertrain comprising: a gearbox with input and output shafts with the combustion engine connected to the input shaft; 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 respectfully connected to the first and second planetary gears; first gear pair connected with the first main shaft; and second gear pair connected with the second main shaft. The method comprises a) ensuring that two rotatable components in the first planetary gear are connected; b) ensuring that all rotatable components in the second planetary gear are disconnected; c) ensuring that a gear is engaged in the first gear pair, d) ensuring that the second gear pair is disconnected; e) controlling the second electrical machine so that a desired torque is achieved in the output shaft; f) controlling the combustion engine to a desired engine speed; and g) controlling the first electrical machine so that a desired total power consumption for the first and the second electrical machines is achieved.