Hybrid Creep Torque Control via Engine Idle Speed Minimization
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Solution Overview
Problem
Hybrid electric vehicles face challenges in managing creep behavior efficiently, particularly when an engine pull-up is requested while the electric motor is providing creep torque, as it can result in lower than expected driver torque and inefficient fuel economy due to the need for engine idle speed management.
Innovation Solution
A method that coordinates engine and electric motor torque in three modes based on the electric motor's ability to provide wheel creep torque, including decoupling the engine from the transmission when the motor can provide all torque, mechanically coupling when the motor cannot, and optimizing engine idle speed based on impeller speeds and operating conditions to maintain fuel economy and torque accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine idle speed is minimized to improve fuel economy, then fuel economy is improved, but the creep torque becomes lower than driver-expected
Solution Approach 1:
The patent combines the output of the electric motor with the torque converter to provide creep torque. The electric motor and torque converter work together in a merged system where the electric motor can compensate for the reduced torque output when the engine operates at minimized idle speed, ensuring both fuel economy and adequate creep torque are achieved
Solution Approach 2:
The system dynamically adjusts the engine idle speed parameter based on operating conditions. When fuel economy is prioritized, the engine idle speed is minimized, and the electric motor parameter is adjusted to compensate for the reduced torque output, maintaining the required creep torque level
2Use of energy by moving object
If the engine is decoupled from the transmission to allow lower idle speed, then fuel economy is improved, but the ability to provide adequate creep torque is reduced
Solution Approach 1:
The electric motor serves as an intermediary component that bridges the gap between the decoupled engine and the transmission. When the engine is decoupled and operating at low idle speed, the electric motor mediates by providing the additional torque needed to maintain adequate creep torque output to the transmission and wheels
3Adaptability or versatility
If the engine is started in response to a pull-up request while the motor provides creep torque, then the engine can support additional loads, but the creep torque may become insufficient
Solution Approach 1:
The system dynamically transitions between different operating modes based on load requirements. When the engine is started in response to a pull-up request, the control system dynamically adjusts the torque contribution from both the electric motor and the engine-torque converter system to maintain adequate creep torque while supporting additional loads
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 allows for improved fuel economy by minimizing engine idle speed and maintaining desired creep torque, while ensuring efficient torque distribution between the engine and electric motor, thus enhancing the overall performance and efficiency of the hybrid electric vehicle.
Implementation Method 1
the torque converter may transmit enough torque to result in vehicle motion unless such motion is resisted by wheel brakes
Data Source
AI summary
Methods and systems are provided for controlling a distribution between engine and motor torques for a hybrid electric vehicle operating in a creep mode of operation in response to an engine start request. In one example, responsive to a request to start an engine while a vehicle is being propelled at a predetermined wheel creep torque via an electric motor positioned downstream of a transmission and a torque converter, coordinating an electric motor torque and an engine torque in one of a first mode, second mode, or a third mode depending on whether the electric motor can continue to provide the predetermined wheel creep torque. In this way, engine idle speed may be minimized depending on vehicle operating conditions, which may improve fuel economy.