Driveline Torque Converter Creep Control
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Solution Overview
Problem
Conventional drivelines face inefficiencies in providing consistent wheel creep torque, especially when transitioning between different operating modes, as they rely solely on an internal combustion engine or an electric machine, leading to reduced driveline efficiency and inconsistent low-speed control.
Innovation Solution
A driveline operating method that adjusts electric machine torque based on wheel creep torque, both when the torque converter is locked and unlocked, allowing for smooth transitions between different wheel torque creep modes, ensuring uniform wheel creep torque whether the engine or electric machine is the propulsion source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the torque converter is unlocked and the engine is the sole propulsion source, then wheel creep torque is provided, but driveline efficiency is reduced
Solution Approach 1:
The system dynamically switches between unlocked and locked torque converter modes based on operating conditions. The controller monitors vehicle speed, accelerator pedal position, and brake pedal position to determine when to transition between modes, optimizing the balance between providing wheel creep torque and maintaining driveline efficiency.
Solution Approach 2:
The system changes the operational parameters of the torque converter by switching between locked and unlocked states. This parameter change allows the system to provide wheel creep torque when needed (unlocked mode) while maintaining high efficiency during normal operation (locked mode).
2Loss of energy
If the torque converter is locked and the electric machine is the sole propulsion source, then driveline efficiency is improved, but consistent wheel creep torque control becomes difficult
Solution Approach 1:
The system uses a hybrid driveline configuration where both the engine and electric machine can serve as propulsion sources. The electric machine can provide wheel creep torque independently when the torque converter is locked, while the engine can take over when the torque converter is unlocked, ensuring consistent creep torque control across all operating modes.
Solution Approach 2:
The controller acts as an intermediary that coordinates between the engine, electric machine, and torque converter. It manages the transitions between different propulsion modes and ensures smooth handoff between the engine and electric machine, maintaining consistent wheel creep torque throughout the transition process.
3Adaptability or versatility
If transitions between driveline modes are made, then operational flexibility is improved, but wheel creep torque consistency may be compromised
Solution Approach 1:
The system performs preliminary actions by pre-coordinating the state changes of the torque converter, engine, and electric machine before actual mode transitions occur. The controller prepares the propulsion sources in advance to ensure they are ready to immediately provide the required wheel creep torque, preventing any disruption during mode switching.
Solution Approach 2:
The system continuously monitors wheel creep torque levels and provides feedback to the controller. This feedback mechanism allows the controller to make real-time adjustments during mode transitions to maintain consistent wheel creep torque, ensuring that the transition process does not compromise the stability of the creep torque output.
Data Source
AI summary
Systems and methods for operating a vehicle that includes an engine and an electric machine are described. In one example, electric machine torque is adjusted according to a wheel torque in a wheel torque creep mode where an engine provides torque to vehicle wheels. Operating the electric machine in this way may allow the electric machine to emulate wheel creep torque that is generated via an engine.