Hybrid Transmission Shift Logic for Smooth Engine Cranking
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Solution Overview
Problem
In hybrid vehicles, the transition from electric to internal combustion engine can result in insufficient torque, leading to uncomfortable jerks due to the electric motor's limited capability to provide both drive and drag torque, especially at higher rotational speeds.
Innovation Solution
A method that involves an electronic computing device to provide a drag torque at the electric traction machine, allowing it to crank over the internal combustion engine, and adapt the characteristic diagram for the automatic transmission to ensure smooth shifting and optimal power distribution, eliminating the need for a starter device and minimizing jolts during acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electric motor provides maximum drive torque for vehicle acceleration, then the vehicle acceleration performance is improved, but the electric motor cannot provide sufficient drag torque for cranking over the internal combustion engine
Solution Approach 1:
The system performs preliminary action by cranking over the internal combustion engine before full power acceleration is needed. The electric motor first provides drag torque to start the engine, then the engine takes over power delivery, allowing the electric motor to operate at optimal speeds for acceleration without being burdened by engine cranking during high-power demands.
Solution Approach 2:
The automatic transmission serves as an intermediary between the electric motor and the wheels. By introducing transmission gears with different ratios, the system can multiply the electric motor's torque at low speeds for engine cranking, while allowing higher speeds for acceleration, thus resolving the contradiction between providing sufficient drag torque and maintaining acceleration capability.
2Reliability
If the electric motor applies drag torque for engine cranking in addition to vehicle drive torque, then the internal combustion engine can be started, but the available drive torque drops and causes vehicle acceleration collapse with uncomfortable jerk
Solution Approach 1:
The system dynamically adjusts the torque distribution between the electric motor and the internal combustion engine based on real-time operating conditions. The control system continuously monitors engine speed, vehicle speed, and torque requirements, dynamically switching between electric-only mode, hybrid mode, and engine-dominant mode to maintain smooth acceleration while ensuring reliable engine starting when needed.
Solution Approach 2:
The system changes operating parameters by adjusting the electric motor's rotational speed and torque output based on the engine cranking phase. During engine start, the motor operates at high torque/low speed; once the engine is running, the motor transitions to high speed/variable torque mode, smoothing the acceleration profile and eliminating jerks caused by fixed torque constraints.
3Measurement precision
If the characteristic diagram is adapted by reducing each curve by the drag torque to be provided, then the shifting logic can define accurate shift points, but the maximum available electrical power output for driving is reduced
Solution Approach 1:
The system applies partial action by reserving only the minimum necessary drag torque for engine cranking purposes, rather than allocating excessive torque reserves. This allows the characteristic diagram to be accurately adapted for precise shift point determination while maximizing the remaining power available for vehicle acceleration and normal driving operations.
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 enables gentle engine cranking and smooth transmission shifting, optimizing acceleration profiles and ensuring maximum performance by adapting to varying power outputs from the battery and drag torque requirements, thereby preventing gear hunting and achieving neutral traction force shifting.
Implementation Method 1
an electric traction machine (16) is provided, in particular an electric motor, which is configured to provide a traction power output for the hybrid vehicle and to crank over the internal combustion engine
Data Source
AI summary
A method for operating an automatic transmission of a hybrid vehicle which has an electric traction machine and an internal combustion engine. A drag torque is provided at the electric traction machine. On the basis of a maximally available electric power for driving the electric traction machine, a characteristic map having respective curves for respective gears of the automatic transmission of the hybrid vehicle is created. The characteristic map is adjusted according to the drag torque to be provided by each curve being reduced by the drag torque to be provided. A shifting logic is specified in which respective shifting points for shifting the automatic transmission are defined at intersections of the curves of adjacent gears of the adjusted characteristic map, wherein the automatic transmission is shifted on the basis of the shifting logic in the respective shifting points.