Spark-Ignition Direct Injection Engine Control for Knock Suppression
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Solution Overview
Problem
High compression ratio spark-ignition engines experience knocking and pre-ignition issues at low engine speeds and high loads, limiting torque production due to conventional countermeasures that suppress knocking but do not adequately secure torque.
Innovation Solution
The method involves setting an effective compression ratio of 10:1 or above, retarding ignition timing, and implementing a divided injection fuel mode within specific engine speed ranges to cool the cylinder gas and advance ignition timing, thereby improving anti-knock performance and increasing torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the compression ratio is increased to improve fuel consumption, then heat efficiency is improved, but knocking and pre-ignition occur more easily at low speed and high load
Solution Approach 1:
The fuel injection is divided into multiple stages: a first injection during the intake stroke and a second injection during the compression stroke. This segmentation allows different portions of fuel to be injected at different times, with the second injection providing cooling effect during compression to suppress knocking while maintaining the high compression ratio for efficiency
Solution Approach 2:
The injection timing is changed from conventional single-stage intake stroke injection to two-stage injection with the second stage occurring during the compression stroke. This parameter change in injection timing enables the fuel to cool the cylinder gas during compression, allowing high compression ratio operation without excessive knocking
2Object-affected harmful factors
If ignition timing is greatly retarded to suppress knocking, then knocking is suppressed, but sufficient torque cannot be secured
Solution Approach 1:
The fuel injection during the compression stroke, which initially might seem to delay combustion, actually cools the cylinder gas and suppresses knocking. This cooling effect allows the ignition timing to be advanced beyond what would be possible without injection, thereby recovering and even increasing torque output
3Object-affected harmful factors
If divided injections are performed with final injection in the earlier-half stage of compression stroke, then anti-knock performance is improved by cooling cylinder gas, but torque may be reduced in higher engine speed ranges
Solution Approach 1:
The injection timing is made dynamic and adaptive based on engine operating conditions. At low engine speeds where knocking is more severe, the final injection is performed in the earlier-half stage of compression stroke for maximum cooling effect. At higher engine speeds where knocking is less severe, the injection timing is adjusted to maintain torque while still providing knock suppression
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
This approach effectively suppresses knocking while enhancing torque production by cooling the cylinder gas and advancing ignition timing, particularly in low-speed, high-load conditions, without compromising anti-knock performance.
Implementation Method 1
performing, within the first engine speed range of the particular operating range, the final injection of the divided injections in the earlier-half stage of the compression stroke... improves, within a range where the engine speed is relatively low within the particular operating range where knocking easily occurs, an anti-knock performance by cooling a gas inside a cylinder
Data Source
AI summary
A method for controlling an engine includes, when the engine is operating within a particular range with comparatively low engine speed and high load, setting an effective compression ratio of 10:1 or above, retarding ignition timing by a predetermined amount and retarding the ignition timing within a first, relatively low engine speed range more than within a second, higher engine speed range, setting an injection mode of an injection valve to divided injections performed at least twice in a period from an intake stroke to an earlier-half stage of a compression stroke, performing, within the first engine speed range, a final injection in the earlier-half stage of the compression stroke, and performing, within the second engine speed range, the final injection in a late stage of the intake stroke and at least one injection other than the final injection in a middle stage of the intake stroke.