Engine Oil Pressure Control Using Hydraulic Accumulator
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Solution Overview
Problem
In hybrid vehicles with a 'start-stop' feature, the rapid increase in engine starting events leads to a significant decrease in oil pressure when the engine is shut off, causing issues with lubrication and component control due to the mechanical oil pump's cessation, resulting in inefficient engine restarts and potential damage from physical contact between moving surfaces.
Innovation Solution
A fluid lubrication and control system incorporating an accumulator that maintains and discharges oil pressure when the engine is running and shut off, utilizing check-valves and electronic control valves to manage oil flow and pressure, ensuring consistent lubrication and control of components like the camshaft phaser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is shut off to conserve fuel in hybrid vehicles, then fuel efficiency is improved, but oil pressure rapidly diminishes causing lubrication failure and component control issues
Solution Approach 1:
The accumulator pre-accumulates pressurized oil during engine operation before shutdown. When the engine is shut off for fuel economy, the accumulator already contains stored pressurized oil that can immediately continue lubrication and component control without waiting for pump repressurization, thus maintaining reliability during the shutdown period
Solution Approach 2:
The accumulator acts as an intermediary between the mechanical oil pump and the lubrication system components. During engine shutdown, the accumulator mediates by providing continuous pressurized oil supply to bearings, piston rings, and camshaft phaser, bridging the gap between pump cessation and restart repressurization
2Speed
If the engine is frequently restarted in hybrid vehicles, then vehicle acceleration responsiveness is improved, but oil pressure does not have sufficient time to reestablish before next shutdown
Solution Approach 1:
The accumulator continuously accumulates pressurized oil during engine operation, building up a reservoir of stored energy. During frequent restart cycles, this pre-accumulated oil provides immediate pressure support, allowing the system to withstand rapid shutdown-restart sequences without compromising oil pressure stability or lubrication reliability
3Stress or pressure
If a mechanical oil pump is used to supply pressurized oil, then oil pressure is maintained during engine operation, but oil pressure rapidly drops when the engine shuts off
Solution Approach 1:
The system uses hydraulic principles by introducing an accumulator filled with pressurized oil into the lubrication system. This hydraulic energy storage device extends the duration of oil pressure availability beyond what the mechanical pump alone can provide during shutdown, using fluid pressure storage to bridge the pressure gap
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
The system effectively maintains oil pressure during engine shutdown and rapid restarts, enhancing lubrication, reducing wear, and improving engine reliability by ensuring timely and consistent fluid pressure delivery to critical components.
Implementation Method 1
an accumulator in fluid communication with the lubrication and control system. The accumulator is configured to accumulate and retain fluid when the engine is running, and to discharge the fluid when the engine is not running
Implementation Method 2
a check-valve configured to allow filling of the accumulator with fluid when the engine is running, and retain the fluid inside the accumulator when the engine is shut-off
Data Source
AI summary
An engine having a fluid lubrication and control system is provided. The engine also includes a pump configured to maintain fluid pressure in the lubrication and control system when the engine is running. The engine additionally includes an accumulator in fluid communication with the lubrication and control system. The accumulator is configured to accumulate and retain fluid when the engine is running, and to discharge the fluid when the engine is not running in order to maintain fluid pressure in the lubrication and control system. A method for controlling oil pressure in the engine is also provided.