Air-Fuel-Ratio Control Apparatus Suppressing Fluctuation Loops
Solution Overview
Problem
The existing air-fuel-ratio control apparatus for internal combustion engines experiences increased fluctuations in air-fuel ratio due to the 'transmission loop of fluctuation,' where disturbances in the downstream feedback correction value propagate and amplify, leading to unstable engine performance.
Innovation Solution
The proposed air-fuel-ratio control apparatus calculates the fuel injection quantity based on an upstream feedback correction value derived from a composite air-fuel ratio, using a control-use base fuel injection quantity that adjusts to cancel changes in the downstream feedback correction value, incorporating a delay process and low-pass filter to synchronize with sensor response delays, thereby suppressing fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the composite air-fuel ratio is calculated by summing the upstream sensor output and downstream feedback correction value, then the air-fuel ratio feedback control is achieved, but the fluctuation in air-fuel ratio increases due to repeated transmission loops
Solution Approach 1:
The patent applies preliminary action by calculating a preliminary feedback correction value based on downstream sensor output before it is used in the composite air-fuel ratio calculation. This preliminary correction is then adjusted by a gain coefficient to create a modified feedback correction value that is applied to the base fuel injection quantity. This staged approach prevents the direct transmission and amplification of fluctuations through the feedback loop, thereby stabilizing the air-fuel ratio control.
2Speed
If the downstream feedback correction value is used directly in composite air-fuel ratio calculation, then the control response is fast, but disturbances are amplified through the transmission loop
Solution Approach 1:
The patent applies parameter changes by introducing a gain coefficient that modifies the downstream feedback correction value before it is applied to the fuel injection control. This gain coefficient adjusts the magnitude of the feedback correction, allowing the system to respond quickly to disturbances while preventing excessive amplification of fluctuations. The gain coefficient acts as a scaling parameter that balances response speed with stability.
3Reliability
If the upstream feedback correction value is calculated from the composite air-fuel ratio, then the feedback control is achieved, but the fluctuation from downstream sensor propagates and amplifies
Solution Approach 1:
The patent applies the intermediary principle by introducing a modified feedback correction value as an intermediate element between the downstream sensor output and the composite air-fuel ratio calculation. This modified correction value, which incorporates the gain coefficient adjustment, acts as a mediator that prevents direct propagation of sensor fluctuations. The intermediary structure allows feedback control to function while filtering out excessive variations.
Data Source
AI summary
The air-fuel-ratio control apparatus for an internal combustion engine obtains a composite air-fuel ratio abyfs from a downstream-side correction value Vafsfb(k) based upon an output value Voxs from a downstream air-fuel-ratio sensor 67 and an output value Vabyfs from an upstream air-fuel-ratio sensor 66, and obtains an upstream-side feedback correction value DFi on the basis of the composite air-fuel ratio abyfs. A fuel injection quantity Fi is determined to a value obtained by adding the upstream-side correction value DFi to a control-use base fuel injection quantity Fbasec (=base fuel injection quantity Fbase·coefficient Ksub). The coefficient Ksub is determined on the basis of the downstream-side feedback correction value Vafsfb(k) in such a manner that the control-use base fuel injection quantity Fbasec (accordingly, the fuel injection quantity Fi) is determined such that the output value Vabyfs from the upstream air-fuel-ratio sensor 66 changes in the direction of canceling the change in the downstream-side feedback correction value Vafsfb(k).