Hybrid Vehicle Fuel Cutting Control Using Mode-Dependent Margin Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hybrid vehicles face challenges in determining optimal fuel cutting times during mode changes, which affects fuel efficiency and drivability, as existing systems rely on engine torque comparisons with friction torque without considering varying driving modes.
Innovation Solution
A method and system that use a control unit to determine margin torque based on engine torque influence, comparing engine torque with the sum of friction torque and margin torque to decide when to cut fuel injection, allowing for adaptive fuel cutting times based on driving modes, with motor/generators generating charging torque during coasting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fuel injection is cut based on simple engine torque comparison with friction torque, then fuel consumption is reduced, but drivability deteriorates due to inadequate torque margin in certain driving modes
Solution Approach 1:
The system dynamically adjusts the fuel cutting determination criterion based on the current driving mode. In power saving modes (EV mode, hybrid mode), the control unit uses a higher torque threshold (engine torque ≤ friction torque + margin torque) to enable earlier fuel cutting, while in engine modes it uses a lower threshold (engine torque ≤ friction torque) to maintain drivability. This dynamic adaptation resolves the contradiction by optimizing fuel savings without compromising drivability in different operating conditions.
Solution Approach 2:
The invention changes the parameter used for fuel cutting determination based on driving mode. Instead of using a fixed torque threshold, the system introduces a mode-dependent margin torque parameter. When in power saving modes, the threshold becomes friction torque plus margin torque, allowing earlier fuel cutting. When in engine modes, it reverts to friction torque only. This parameter change enables the system to achieve both fuel efficiency and drivability across different operating conditions.
2Loss of energy
If fuel injection is cut earlier to enhance fuel efficiency, then fuel consumption is reduced, but engine stability deteriorates due to insufficient torque reserve
Solution Approach 1:
The system dynamically adjusts the fuel cutting threshold based on driving mode to balance fuel efficiency and engine stability. In power saving modes where engine stability is less critical, the system allows earlier fuel cutting (engine torque ≤ friction torque + margin torque). In engine modes where stability is paramount, it delays fuel cutting until engine torque ≤ friction torque. This dynamic approach enables fuel efficiency improvements while maintaining engine stability when required.
Solution Approach 2:
The invention applies different fuel cutting criteria to different driving modes, treating each mode with the appropriate level of conservatism. Power saving modes receive a more aggressive fuel cutting strategy (higher threshold) to maximize fuel efficiency, while engine modes receive a conservative strategy (lower threshold) to ensure stability. This local quality approach allows the system to optimize fuel efficiency in appropriate contexts without compromising engine stability when needed.
3Device complexity
If a fixed fuel cutting criterion is used across all driving modes, then system complexity is reduced, but fuel efficiency deteriorates due to inability to optimize for specific modes
Solution Approach 1:
The control unit dynamically selects the appropriate fuel cutting criterion based on the current driving mode detected by the mode determination unit. This dynamic selection allows the system to optimize fuel efficiency for each specific mode (EV mode, hybrid mode, engine mode) without requiring a completely separate control system for each mode. The dynamic approach achieves high fuel efficiency while maintaining relatively simple system architecture through centralized mode-based decision making.
Solution Approach 2:
The control unit serves multiple functions: it determines the current driving mode, compares engine torque against the appropriate threshold based on that mode, and controls fuel injection accordingly. This multi-functionality allows a single control system to handle both mode recognition and optimized fuel cutting decisions, achieving high fuel efficiency across different modes without requiring separate specialized systems for each function.
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
Enhances fuel efficiency by varying fuel cutting times according to driving modes, reducing fuel consumption and maintaining drivability by accurately determining when to stop or maintain fuel injection based on torque comparisons.
Implementation Method 1
the second motor/generator 52 generates charging torque corresponding to the coasting torque when the fuel injection is cut
Implementation Method 2
an engine generating torque by combusting fuel
Data Source
AI summary
Disclosed is a method and a system for cutting fuel for a hybrid vehicle. More specifically, a control unit in the vehicle is configured to determine margin torque according to each driving mode, determine whether a current vehicle driving condition is a coasting driving condition, compare a engine torque and a sum of friction torque and the margin torque to determine whether the engine torque is greater than the sum of the friction torque and the margin torque and cut fuel injection to the engine when the engine torque is equal to or less than the sum of the friction torque and the margin torque.