Variable Valve Train for High Expansion Ratio Engines
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Solution Overview
Problem
Existing high expansion ratio internal combustion engines face challenges in achieving high thermal efficiency while minimizing size and weight, particularly under low-load conditions where knocking can occur, and in ensuring adequate air intake during high-load operations without increasing pumping losses.
Innovation Solution
A variable valve train system where some intake valves are phase-variable and others are phase-fixed, with controlled actuation timings and angles to optimize expansion ratios, mechanical compression ratios, and air intake quantities, including retarding valve-close timing of phase-variable valves and advancing valve-open timing of phase-fixed valves to manage effective compression ratios and throttle losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the mechanical compression ratio is increased to increase the expansion ratio, then thermal efficiency is improved, but knocking becomes inevitable
Solution Approach 1:
The patent applies dynamics by making the valve timing variable rather than fixed. The variable valve train adjusts the intake valve closing timing dynamically based on operating conditions, allowing the effective compression ratio to be modified independently of the mechanical compression ratio. This enables the engine to achieve high expansion ratios for improved thermal efficiency while preventing knocking by retarding the effective compression timing when necessary.
Solution Approach 2:
The patent changes the parameter of compression ratio by distinguishing between mechanical compression ratio (fixed by engine geometry) and effective compression ratio (variable via valve timing). By changing the effective compression ratio through variable valve timing, the system can optimize thermal efficiency at part load without causing knocking, as the effective compression ratio can be reduced independently of the mechanical compression ratio.
2Use of energy by moving object
If all intake valves are made phase-variable to optimize expansion ratio, then thermal efficiency is improved, but device complexity and weight increase
Solution Approach 1:
The patent applies segmentation by dividing the intake valves into different groups with different timing characteristics. Instead of making all valves phase-variable, the system uses a combination of phase-variable valves (first intake valves) and phase-fixed valves (second intake valves). This segmented approach allows optimization of expansion ratio through selective valve timing control while reducing the overall complexity compared to making all valves variable.
Solution Approach 2:
The patent applies local quality by assigning different functional characteristics to different valves within the same cylinder. The first intake valves are equipped with phase-variable mechanisms optimized for expansion ratio control, while the second intake valves maintain fixed timing. This local differentiation allows the system to achieve the desired thermal efficiency improvement without the complexity and weight penalty of making all valves phase-variable.
3Object-affected harmful factors
If valve-close timing is retarded to decrease effective compression ratio, then knocking is prevented, but expansion ratio cannot be maximized
Solution Approach 1:
The patent resolves this contradiction by dynamically controlling the valve timing based on operating conditions. The phase-variable intake valves can retard their closing timing to prevent knocking at part load, while the phase-fixed intake valves maintain their timing to preserve the geometric expansion ratio. This dynamic coordination allows the system to prevent knocking without sacrificing the maximum expansion ratio capability.
Solution Approach 2:
The patent segments the valve timing control function between phase-variable and phase-fixed valves. The phase-variable valves handle the knock prevention function by retarding timing when needed, while the phase-fixed valves maintain the optimal expansion geometry. This segmentation allows independent optimization of both knock prevention and expansion ratio without compromise.
4Quantity of substance
If valve-open timing is advanced to ensure adequate air intake, then air intake quantity is improved, but pumping losses increase
Solution Approach 1:
The patent applies dynamics by making the valve timing adjustable rather than fixed. The phase-variable intake valves can advance their opening timing when high air intake is required (such as at high load), while the phase-fixed valves maintain optimal timing for reduced pumping losses. This dynamic coordination allows the system to provide adequate air intake when needed without incurring excessive pumping losses during normal operation.
Data Source
AI summary
A high expansion ratio internal combustion engine includes: a variable compression ratio mechanism that varies a mechanical compression ratio of the internal combustion engine; and a variable valve train in which some valve(s) of a plurality of intake valves is phase-variable and the remaining valve(s) is phase-fixed, the variable valve train being configured such that a working angle of the phase-variable intake valve is larger than a working angle of the phase-fixed intake valve, wherein a valve-open timing of the phase-variable intake valve is retarded after a valve-open timing of the phase-fixed intake valve when the internal combustion engine is under low-load operating state.