Exhaust Purification Catalyst Hydrocarbon Slippage Detection
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Solution Overview
Problem
Current internal combustion engine exhaust purification systems cannot detect the amount of hydrocarbon slippage through the NOx storage catalyst efficiently, leading to wasteful consumption of hydrocarbons.
Innovation Solution
An exhaust purification system with a hydrocarbon feed valve, upstream and downstream air-fuel ratio sensors, and an exhaust purification catalyst that uses precious metal catalysts and a basic exhaust gas flow surface to react NOx with reformed hydrocarbons, allowing for detection of hydrocarbon slippage by varying the hydrocarbon concentration within specific amplitude and period ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fuel addition valve feeds more than the necessary amount of hydrocarbons to ensure NOx release, then the NOx release function is improved, but the amount of hydrocarbons that slip through the catalyst increases causing wasteful consumption
Solution Approach 1:
The patent implements a feedback control system using downstream air-fuel ratio sensors to detect hydrocarbon slippage and feed this information back to the control unit. The control unit adjusts the fuel addition valve operation based on this feedback to optimize hydrocarbon feeding amount, ensuring sufficient NOx release while minimizing wasteful consumption through continuous monitoring and adjustment.
Solution Approach 2:
The patent replaces direct mechanical measurement of hydrocarbon slippage with an electrical sensing system. Air-fuel ratio sensors convert chemical composition information into electrical signals that can be processed by the control unit, enabling precise detection and control of hydrocarbon feeding without complex mechanical measurement devices.
2Loss of substance
If the fuel addition valve feeds less than the necessary amount of hydrocarbons, then hydrocarbon consumption is reduced, but the NOx release function deteriorates
Solution Approach 1:
The feedback control system continuously monitors the air-fuel ratio downstream of the catalyst and adjusts the fuel addition valve to maintain optimal hydrocarbon feeding levels. This ensures the minimum necessary hydrocarbons are supplied for effective NOx release while avoiding excessive consumption, dynamically balancing consumption and performance.
Solution Approach 2:
The system dynamically changes the hydrocarbon feeding parameters (amount, timing, duration) based on real-time operating conditions detected by the air-fuel ratio sensors. The control unit adjusts these parameters to optimize the balance between NOx release effectiveness and hydrocarbon consumption efficiency under varying engine operating conditions.
3Measurement precision
If air-fuel ratio sensors are installed both upstream and downstream of the hydrocarbon feed valve, then hydrocarbon slippage detection capability is improved, but the system complexity increases
Solution Approach 1:
The patent uses the air-fuel ratio downstream of the catalyst as an intermediary indicator to indirectly measure hydrocarbon slippage. Instead of directly measuring hydrocarbon concentration, the system measures the resulting air-fuel ratio change, which serves as a reliable proxy that simplifies the measurement approach while maintaining detection accuracy.
Solution Approach 2:
The downstream air-fuel ratio sensor serves multiple functions: it detects hydrocarbon slippage, monitors catalyst performance, and provides feedback for fuel injection optimization. This multi-functionality reduces the need for separate dedicated sensors for each measurement task, thereby reducing overall system complexity while maintaining measurement precision.
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
Enables the detection of hydrocarbon slippage through output signals from air-fuel ratio sensors, optimizing hydrocarbon injection to reduce wasteful consumption and enhance NOx purification.
Implementation Method 1
an exhaust purification catalyst for reacting NOx contained in exhaust gas and reformed hydrocarbons is arranged in the engine exhaust passage downstream of the hydrocarbon feed valve
Implementation Method 2
an upstream side air-fuel ratio sensor for detecting an air-fuel ratio of exhaust gas is arranged in the engine exhaust passage upstream of the hydrocarbon feed valve, a downstream side air-fuel ratio sensor for detecting the air-fuel ratio of the exhaust gas is arranged in the engine exhaust passage downstream of the exhaust purification catalyst
Data Source
AI summary
In an internal combustion engine, an upstream side air-fuel ratio sensor (23), hydrocarbon feed valve (15), exhaust purification catalyst (13), and the downstream side air-fuel ratio sensor (24) are arranged in an engine exhaust passage in that order from the upstream side. If hydrocarbons are fed from the hydrocarbon feed valve (15), the air-fuel ratio which is detected by the downstream side air-fuel ratio sensor (24) changes to the rich side from the reference air-fuel ratio which is detected when hydrocarbons are not fed from the hydrocarbon feed valve (15). The amount of hydrocarbons which are fed from the hydrocarbon feed valve (15) and which slip through the exhaust purification catalyst (13) is detected from the air-fuel ratio difference between the air-fuel ratio detected by the upstream side air-fuel ratio sensor (23) and the reference air-fuel ratio detected by the downstream side air-fuel ratio sensor (24).