Engine Exhaust Temperature Estimation for Upstream Catalyst Diagnosis
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Solution Overview
Problem
Existing control systems for internal combustion engines fail to adequately determine abnormalities in upstream cleaning devices due to temperature estimation inaccuracies, which can lead to missed opportunities for performing active air-fuel ratio control and subsequent deterioration of catalysts.
Innovation Solution
A control device with a first temperature estimating unit to accurately estimate the downstream cleaning device's temperature and a second unit to estimate the upstream cleaning device's temperature without relying on the temperature sensor, ensuring the abnormality determining process is performed when the downstream device's temperature exceeds a threshold, thereby securing opportunities for diagnosing upstream device abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temperature of the downstream cleaning device is estimated based on the temperature sensor detection value, then the filter regeneration can be appropriately controlled, but the opportunity to perform active air-fuel ratio control for upstream catalyst diagnosis cannot be satisfactorily secured
Solution Approach 1:
The patent divides the temperature estimation into two separate segments: a first temperature estimating unit that estimates downstream cleaning device temperature based on the temperature sensor detection value, and a second temperature estimating unit that estimates upstream cleaning device temperature using additional parameters. This segmentation allows each unit to specialize in its respective function, ensuring both filter regeneration control and catalyst diagnosis opportunities are preserved
Solution Approach 2:
The patent introduces an intermediary approach by using multiple estimation methods simultaneously. The first temperature estimating unit provides accurate downstream temperature for regeneration control, while the second temperature estimating unit acts as a complementary mechanism to identify when upstream catalyst diagnosis should be performed, ensuring neither function compromises the other
2Reliability
If active air-fuel ratio control is performed to diagnose upstream catalyst abnormality, then catalyst health can be monitored, but the downstream filter may overheat if temperature estimation is inaccurate
Solution Approach 1:
The patent implements a feedback mechanism where the first temperature estimating unit continuously monitors downstream cleaning device temperature based on temperature sensor data. This feedback allows the system to adjust or prohibit active air-fuel ratio control when downstream temperature is high, preventing filter overheating while still enabling catalyst diagnosis when conditions are appropriate
Solution Approach 2:
The system dynamically adjusts its operation mode based on real-time temperature conditions. When the first temperature estimating unit determines downstream temperature is within safe ranges, the second temperature estimating unit can perform active air-fuel ratio control for diagnosis. When downstream temperature exceeds thresholds, the system dynamically switches to a prohibited state, preventing overheating
Data Source
AI summary
A control device for an internal combustion engine including an upstream cleaning device and a downstream cleaning device that are provided in an exhaust gas passage and a temperature sensor that detects a temperature of exhaust gas between the upstream cleaning device and the downstream cleaning device is provided. The control device includes a first temperature estimating unit configured to estimate a temperature of the downstream cleaning device from the temperature of exhaust gas detected by the temperature sensor and a second temperature estimating unit configured to estimate a temperature of the downstream cleaning device without using the temperature of exhaust gas detected by the temperature sensor. An abnormality determining process for the upstream cleaning device is performed when at least the temperature of the downstream cleaning device estimated by the second temperature estimating unit is equal to or greater than a predetermined threshold value.