Engine Stop-Start Accumulator for Smooth Transmission Restart
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Solution Overview
Problem
Conventional automatic transmission systems experience slippage and delays during engine restarts due to dropped hydraulic fluid pressure when the engine stops, and they lack control over engine stop-start operations based on vehicle conditions, particularly during brief stops or idling while moving.
Innovation Solution
A system and method that uses engine speed, vehicle speed, transmission temperature, and engine temperature to determine whether an automatic stop should be activated, and selectively controls an accumulator to prime the transmission for smooth restarts, while inhibiting stops based on transmission state and brake pedal position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is stopped during idling or brief stops to improve fuel economy, then fuel efficiency is improved, but hydraulic fluid pressure drops causing clutches and brakes to disengage and creating slippage and delays during restart
Solution Approach 1:
The accumulator is pre-charged with hydraulic fluid under high pressure before engine stop events. When the engine stops and main pump pressure drops, the accumulator immediately discharges its stored pressure to maintain clutch and brake engagement, preventing slippage and delays during restart. This preliminary action ensures transmission reliability during fuel-saving engine stop events.
2Productivity
If the engine is automatically restarted after stopping, then vehicle operation is restored, but clutches and brakes take time to reengage fully causing slippage and delay
Solution Approach 1:
The system pre-charges the accumulator during engine operation before stop events occur. When restart is needed, the accumulator immediately provides high-pressure hydraulic fluid to the clutches and brakes, eliminating the delay that would normally occur while waiting for pump pressure to rebuild. This preliminary charging action eliminates engagement delays during engine restart.
3Reliability
If hydraulic pressure is maintained during engine stop to prevent clutch disengagement, then transmission engagement reliability is improved, but the system lacks controllability during brief stops or idling while moving
Solution Approach 1:
The system dynamically adapts accumulator usage based on vehicle conditions. The control module monitors parameters such as vehicle speed, engine speed, and transmission state to determine when to activate the accumulator during engine stop events. This dynamic adaptation provides controllability for brief stops or idling while moving, allowing the system to maintain reliability only when appropriate rather than universally.
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
Enables controlled automatic stop-start operations, reducing slippage and delays during engine restarts, and ensures controllability of the vehicle by maintaining hydraulic fluid pressure and pre-staging clutches, thereby improving fuel efficiency and eliminating torque bumps.
Implementation Method 1
an accumulator (52) in fluid communication with the pump (50). The accumulator (52) includes a piston having a seal that divides the accumulator (52) into a first chamber and a second chamber
Implementation Method 2
The accumulator (52) includes a piston having a seal that divides the accumulator (52) into a first chamber and a second chamber
Data Source
AI summary
A system and method for controlling automatic stop-start of a motor vehicle is provided. The system and method is configured to enable an automatic stop-start mode of operation based on vehicle conditions. In addition, the system and method is configured to selectively actuate an accumulator to prime the transmission for a smooth restart.