Multi-Cylinder Engine Variable Valve Timing for Knock Reduction
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Solution Overview
Problem
Spark ignition engines with high compression ratios face issues with knocking at low and middle speed ranges, leading to reduced torque, as conventional countermeasures either lower the compression ratio or retard ignition timing, which do not effectively address the problem of maintaining high torque.
Innovation Solution
A multi-cylinder spark ignition engine with a geometric compression ratio greater than 12, featuring a variable exhaust valve timing mechanism, an ignition timing controller, and an effective compression ratio adjuster, which adjusts the compression ratio to over 10 and retards ignition timing in low and middle speed ranges, ensuring a valve overlap period for negative pressure waves from exhaust pressure pulses to reach the exhaust port, enhancing scavenging action and torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high compression ratio is used to improve thermal efficiency and fuel efficiency, then fuel efficiency is improved, but knocking occurs more easily in low and middle speed ranges
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the effective compression ratio through variable valve timing control. The intake valve closing timing is varied based on engine operating conditions (speed and load) to optimize the effective compression ratio, allowing the engine to maintain high thermal efficiency while preventing knocking by adapting the compression ratio parameter to match operating requirements
Solution Approach 2:
The patent implements dynamics by using a variable valve timing mechanism that can change the intake valve closing timing in real-time based on engine speed and load conditions. This dynamic adjustment allows the effective compression ratio to be optimized for each operating point, resolving the contradiction between maintaining high compression ratio for efficiency and avoiding knocking
2Object-affected harmful factors
If ignition timing is retarded significantly to reduce knocking, then knocking is reduced, but torque cannot be maintained at an appropriately high level
Solution Approach 1:
The patent uses parameter changes by adjusting the effective compression ratio through variable valve timing rather than relying solely on ignition timing retardation. By optimizing the effective compression ratio at each operating point, the engine can maintain higher torque levels while still managing knocking, as the compression ratio optimization addresses the root cause of knocking more effectively than ignition timing alone
3Power
If the effective compression ratio is increased to maintain high torque, then torque is improved, but knocking occurs more easily in low and middle speed ranges
Solution Approach 1:
The patent applies dynamics by using a variable valve timing mechanism that can change the intake valve closing timing in real-time based on engine speed and load conditions. This dynamic adjustment allows the effective compression ratio to be optimized for each operating point, resolving the contradiction between maintaining high compression ratio for efficiency and avoiding knocking
Solution Approach 2:
The patent uses parameter changes by dynamically adjusting the effective compression ratio through variable valve timing control. The intake valve closing timing is varied based on engine operating conditions (speed and load) to optimize the effective compression ratio, allowing the engine to maintain high thermal efficiency while preventing knocking by adapting the compression ratio parameter to match operating requirements
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 configuration increases intake volumetric efficiency, reduces ignition timing retardation, and significantly enhances torque while maintaining high compression ratios, effectively reducing knocking and improving fuel efficiency.
Implementation Method 1
negative pressure waves from the exhaust pressure pulses reach an exhaust port during the valve overlap period
Implementation Method 2
spark ignition engine with four or more cylinders into which a fuel containing at least gasoline is injected
Data Source
AI summary
An exhaust manifold has a plurality of branched exhaust passages connected to respective exhaust ports of individual cylinders; a plurality of first collector segments each of which joins the branched exhaust passages for the cylinders which are not adjacent in the exhaust order sequence; a plurality of middle exhaust passages connected to the downstream of the first collector segments, respectively; and a second collector segment that joins the middle exhaust passages. In at least low and middle speed ranges in a high load region of the engine, a valve opening time of an exhaust valve is changed according to the engine speed so that a predetermined amount of a valve overlap period is ensured and that negative pressure waves from exhaust pressure pulses reach an exhaust port during the valve overlap period in a plurality of engine speed ranges.