Liquid Reducing Agent Tank Empty Judgment
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Solution Overview
Problem
Existing techniques for judging the emptiness of a liquid reducing agent tank in an exhaust emission control apparatus are prone to erroneous measurements due to bubble adhesion on concentration sensors, leading to inaccurate concentration readings.
Innovation Solution
The proposed apparatus includes a heating element, concentration measuring device, liquid-level measuring device, and an empty judging device that compares concentration and liquid-level measurements with predetermined thresholds to accurately determine the tank's emptiness, incorporating a counting device to finalize judgments and an informing device to alert users when the tank is empty.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a concentration sensor based on heating element temperature rise is used to measure liquid reducing agent concentration, then concentration measurement capability is provided, but measurement precision deteriorates when bubbles adhere to the sensor
Solution Approach 1:
The patent combines concentration measurement (via heating element temperature rise) and liquid level measurement into a single sensor assembly. The heating element serves dual purposes: measuring concentration through temperature rise characteristics and detecting liquid level through its position relative to the liquid surface. This merging allows simultaneous acquisition of both parameters to resolve ambiguities in empty judgment.
Solution Approach 2:
The control unit continuously monitors both concentration and liquid level measurements, and uses feedback logic to determine empty state. When liquid level is above the heating element, concentration measurement is trusted; when liquid level drops to or below the heating element, the system recognizes measurement becomes unreliable and triggers empty judgment. This feedback mechanism dynamically adjusts measurement interpretation based on liquid level conditions.
2Device complexity
If concentration measurement alone is used for empty judgment, then the judgment process is simple, but measurement precision deteriorates due to bubble adhesion causing erroneous readings
Solution Approach 1:
The patent adds a spatial dimension (liquid level measurement) to the traditional concentration-only measurement approach. By measuring the vertical position of the liquid level relative to the heating element, the system creates a new dimension of information that helps distinguish between true empty states and false readings caused by bubbles. This dimensional addition transforms a 1D concentration measurement problem into a 2D measurement space (concentration + level).
Solution Approach 2:
The liquid level measurement acts as an intermediary parameter that mediates between the concentration measurement and the empty judgment. Rather than directly using concentration alone for empty judgment, the system uses liquid level as an intermediate check: if the liquid level is above the heating element, concentration measurements are valid; if the level is at or below the heating element, the system infers empty state regardless of concentration reading. This intermediary prevents erroneous judgments from bubble-adhered sensors.
3Measurement precision
If multiple measurement parameters (concentration and liquid level) are combined for empty judgment, then empty judgment precision is improved, but device complexity increases
Solution Approach 1:
The heating element is designed to perform multiple functions: it heats the liquid for concentration measurement, serves as a temperature sensor, and acts as a reference point for liquid level measurement. The same physical component (heating element) and sensor assembly are used for both concentration and level detection, rather than requiring separate independent systems. This multi-functionality reduces overall device complexity while maintaining the benefits of dual-parameter measurement.
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
This approach ensures more precise empty judgments by combining concentration and liquid-level measurements, reducing erroneous readings and prompting timely replenishment, thus maintaining the exhaust emission control apparatus's functionality.
Implementation Method 1
a concentration measuring device that operates the heating element for a predetermined time and measures a concentration of the liquid reducing agent or the precursor thereof based on a temperature rise characteristic of the operated heating element
Data Source
AI summary
An apparatus for distinguishing a liquid reducing agent which judges empty with a higher precision than heretofore is provided. The apparatus for distinguishing a liquid reducing agent is provided with a concentration sensor and a liquid-level sensor in storage tank of liquid reducing agent, and is characterized in that empty is judged by utilizing the liquid-level based on the liquid-level sensor in addition to the concentration based on the concentration sensor (step 3 and step 5). Even if a bubble is adhering to the concentration sensor and an erroneous signal indicative of empty is output although the residual quantity of liquid reducing agent is sufficient, the liquid-level sensor does not output a signal indicative of empty. Consequently, erroneous judgment is prevented and accurate judgment can be made as compared to heretofore.