Supercharged Engine Throttle Control Hunting Prevention
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Solution Overview
Problem
Internal combustion engines with superchargers experience throttle hunting due to sharp changes in pressure ratio terms when upstream and downstream throttle pressures become equal, leading to oscillations in throttle opening calculations.
Innovation Solution
A control device that calculates throttle opening using a throttling formula, employing a low-pass filter to reduce change speed when pressure ratio deviations are small, and adjusting the filter's time constant based on intake air quantity changes to prevent hunting and maintain precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the throttle opening is calculated using the formula of throttling with pressure ratio Pm/Pac as parameter, then the target intake air quantity can be realized with high precision, but the throttle causes hunting when the supercharging state changes because the pressure ratio term φ changes sharply when Pm/Pac is close to 1
Solution Approach 1:
The patent changes the parameter used in the throttling formula from the pressure ratio Pm/Pac to the pressure difference (Pm-Pac). This parameter transformation resolves the hunting issue because the pressure difference remains stable even when Pm and Pac are close, avoiding the sharp changes in the pressure ratio term φ that occur when Pm/Pac approaches 1.
2Use of energy by moving object
If the throttle is opened close to full throttle to prioritize fuel economy, then the supercharging pressure and intake pipe pressure are substantially equal, but the throttle hunting occurs more frequently due to small differential pressure
Solution Approach 1:
By changing the parameter from pressure ratio to pressure difference, the patent enables full throttle operation for fuel economy without hunting. The pressure difference parameter remains numerically stable even when both pressures are high and close to each other, allowing the throttle to maintain full opening position reliably.
3Speed
If the throttle opening changes rapidly to respond to supercharging pressure changes, then the response speed is improved, but the hunting oscillation is exacerbated due to the sharp change in pressure ratio term
Solution Approach 1:
The parameter change from pressure ratio to pressure difference decouples the throttle response from the numerical instability. The throttle can now respond rapidly to actual pressure changes without being affected by the mathematical singularity that occurs when using pressure ratio near unity, achieving both fast response and stability.
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
Prevents throttle hunting by smoothing throttle opening changes in regions with small pressure ratio deviations, ensuring high precision in achieving target intake air quantities while allowing sharp changes to be realized accurately.
Implementation Method 1
a low-pass filter to reduce change speed when pressure ratio deviations are small
Data Source
AI summary
An object of the present invention is to prevent hunting of a throttle in a region in which a throttle upstream pressure and a throttle downstream pressure become substantially equal to each other in an internal combustion engine with a supercharger. For this purpose, a control device for an internal combustion engine with a supercharger provided by the present invention processes a signal of a throttle opening which is calculated by using a formula of throttling when a ratio of the throttle upstream pressure and the throttle downstream pressure has a value close to 1, and controls an operation of the throttle with the throttle opening the change speed of which is lessened as a target throttle opening.