Auto-Hold Brake Control for Stop-Start Engine Coordination
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Solution Overview
Problem
Conventional vehicles experience unnecessary engine restarts when shifting into PARK while the braking auto-hold function is active, which affects fuel economy, wear on components, and driver satisfaction.
Innovation Solution
A vehicle system with an auto-hold braking function and a controller that automatically stops and starts the engine based on gear shifts, maintaining the engine in an auto-stop condition until the gear is shifted out of PARK, and initiating auto-start when shifting from PARK to another gear, thereby coordinating engine operation with braking torque to prevent roll-back and optimize fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engine automatically restarts when shifting into PARK during auto-hold braking, then the vehicle can respond quickly to gear changes, but unnecessary engine restarts occur reducing fuel economy
Solution Approach 1:
The system dynamically adjusts engine restart behavior based on the detected gear shift direction. When shifting from DRIVE to PARK, the engine maintains auto-stop to save fuel. When shifting from PARK to DRIVE, the engine auto-starts to prepare for vehicle movement, optimizing the balance between response speed and fuel economy.
Solution Approach 2:
The control system changes the engine operation parameter (stopped vs. running) based on the gear shift condition. By detecting whether the shift is into or out of PARK, the system appropriately adjusts the engine state to either maintain auto-stop or initiate auto-start, resolving the contradiction between quick response and fuel efficiency.
2Reliability
If the engine auto-starts on every PARK shift, then the vehicle is ready for immediate movement, but component wear increases
Solution Approach 1:
The system dynamically determines engine restart necessity based on the specific gear transition. Engine auto-start is activated only when shifting from PARK to a driving gear, while engine auto-stop is maintained when shifting from DRIVE to PARK. This dynamic approach ensures vehicle readiness when needed while minimizing unnecessary component wear.
Solution Approach 2:
The system extracts and removes the unnecessary engine restart action from the PARK shift sequence. By recognizing that shifting into PARK does not require engine restart, the system eliminates harmful component wear while preserving the essential function of quick vehicle readiness when shifting out of PARK.
3Loss of energy
If the engine maintains auto-stop during gear shifts, then fuel economy improves, but vehicle responsiveness may be compromised
Solution Approach 1:
The control system changes the engine operation parameter based on the gear shift direction. Engine auto-stop is maintained during DRIVE-to-PARK shifts to maximize fuel economy, while engine auto-start is initiated during PARK-to-DRIVE shifts to ensure vehicle responsiveness. This conditional parameter change resolves the contradiction between fuel efficiency and responsiveness.
4Stability of the object's composition
If the engine auto-starts before the gear shifter reaches final position, then vehicle launch is smoother, but control complexity increases
Solution Approach 1:
The system performs preliminary engine auto-start action before the gear shifter reaches its final position during PARK-to-DRIVE transitions. This advance preparation ensures the engine is already running when the vehicle begins to move, providing smoother vehicle launch. The control system monitors shifter position and triggers auto-start in advance, managing complexity through proactive control.
Solution Approach 2:
The control system uses feedback from the gear shifter position sensor to determine when to initiate engine auto-start. By continuously monitoring the shifter's movement toward the DRIVE position, the system triggers auto-start at the optimal moment to ensure smooth vehicle launch while managing control complexity through sensor-based feedback control.
Data Source
AI summary
A vehicle includes an engine having auto-stop and auto-start conditions. The vehicle additionally includes a braking system having an auto-hold function. The auto-hold function is configured to, after braking the vehicle to a full stop, automatically apply braking torque independent of a brake pedal position. The vehicle further includes a controller configured to, in response to the engine being in the auto-stop condition, the auto-hold function automatically applying braking torque, and a gear shifter being moved out of a gear other than PARK, maintain the engine in the auto-stop condition.