Hybrid Engine Variable Valve Timing Fuel-Off Actuation
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Solution Overview
Problem
In hybrid vehicles, when the internal combustion engine is not completely decoupled from the driven wheels, shutting off the fuel supply during deceleration leads to spin and pumping losses, reducing fuel efficiency and energy recovery for battery recharging.
Innovation Solution
A method and system that utilize a mechanism with variable valve timing and lift to select a fuel-off actuation arrangement for the intake valves, limiting compression pulses and reducing oxygen intake into the three-way catalyst, thereby minimizing pumping losses and optimizing energy recovery during deceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine's fuel supply is shut off during vehicle deceleration, then fuel efficiency is improved, but spin and pumping losses increase and engine braking increases
Solution Approach 1:
The valve timing mechanism dynamically adjusts the intake valve actuation arrangement based on operating conditions (fuel supply state and engine speed). During deceleration with fuel supply shut off, the system selects a fuel-off actuation arrangement that limits compression pulses, thereby reducing pumping losses while maintaining the fuel efficiency benefit of shutting off the fuel supply.
2Use of energy by moving object
If the engine is permanently coupled and fuel supply is shut off during deceleration, then fuel efficiency gains are reduced, but the engine continues to operate as an air pump
Solution Approach 1:
The system changes the valve timing parameters by selecting different actuation arrangements (different cam lobes or variable valve timing positions) based on the fuel supply state. When fuel supply is shut off during deceleration, the fuel-off actuation arrangement is selected to modify the compression pulse magnitude, reducing the harmful air pumping effect while preserving fuel efficiency improvements.
3Loss of energy
If a fuel-off actuation arrangement is selected to limit compression pulses, then pumping losses are reduced, but the mechanism complexity increases
Solution Approach 1:
The variable valve timing and lift mechanism serves multiple functions: it controls valve timing during normal operation, selects fuel-off actuation arrangements during deceleration to reduce pumping losses, and manages oxygen intake into the three-way catalyst. This multi-functionality reduces the need for separate systems and minimizes overall complexity while achieving the energy loss reduction goal.
4Loss of energy
If the intake air is limited during deceleration, then energy recovery by motor-generator is maximized, but oxygen intake into three-way catalyst is reduced
Solution Approach 1:
The system performs preliminary action by selecting the fuel-off actuation arrangement before engine restart occurs. This limits the magnitude of compression pulses and controls oxygen intake into the three-way catalyst in advance, preparing the system for optimal energy recovery during deceleration while managing catalyst oxygen levels for subsequent operation.
Data Source
AI summary
A method is provided for controlling a hybrid electric vehicle that includes an internal combustion engine having a cylinder provided with an intake valve, an exhaust valve, and a piston configured to rotate the engine's crankshaft. The method includes determining whether deceleration of the vehicle is desired and also includes ceasing supply of fuel to the cylinder when such condition is satisfied. The method additionally includes selecting a fuel-off actuation arrangement for the intake valve via a mechanism configured to provide variable valve timing and lift, such that a magnitude of compression pulses in the cylinder during deceleration is limited. A system for controlling the hybrid vehicle and a vehicle employing such a system are also provided.