Coolant Sensor Diagnosis After Auxiliary Heater Cold Starts
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Solution Overview
Problem
The existing methods for diagnosing coolant temperature sensors in vehicles with auxiliary heaters independent of engine operation often result in false positives during cold starts, as the auxiliary heater's previous operation is not signaled, leading to misdiagnosis of sensor malfunctions.
Innovation Solution
A method involving the activation of a coolant pump to connect the auxiliary heater circuit with the coolant temperature sensor circuit, recording temperature gradients over time, and evaluating these gradients using threshold values to determine if the auxiliary heater was active before engine start, thereby distinguishing between sensor malfunctions and auxiliary heater operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coolant temperature sensor diagnosis is performed during cold start by comparing temperature readings with ambient temperature, then sensor functionality can be checked, but false positives occur when auxiliary heater was previously active
Solution Approach 1:
The system performs preliminary detection of auxiliary heater operation status before conducting coolant temperature sensor diagnosis during cold start. By checking whether the auxiliary heater was active prior to engine startup and storing this information, the system prevents false diagnosis results that would otherwise occur when comparing coolant temperature with ambient temperature.
Solution Approach 2:
The system uses feedback from the auxiliary heater control unit to inform the diagnosis system about the heater's operational status. This feedback mechanism allows the diagnosis system to adjust its evaluation criteria based on whether the auxiliary heater was recently active, thereby avoiding misdiagnosis of the coolant temperature sensor.
2Adaptability or versatility
If auxiliary heater is connected to coolant system for heating vehicle interior independent of engine operation, then vehicle can be heated before engine start, but coolant temperature sensor diagnosis becomes unreliable
Solution Approach 1:
Before performing coolant temperature sensor diagnosis, the system preliminarily determines whether the auxiliary heater was active by checking operational status information stored in the auxiliary heater control unit. This preliminary action ensures that the subsequent diagnosis is performed with accurate context about heater operation.
Solution Approach 2:
The system introduces an intermediary check - querying the auxiliary heater control unit for operational status - that mediates between the auxiliary heater function and the coolant temperature sensor diagnosis. This intermediary step provides the necessary information to correctly interpret temperature readings during diagnosis.
3Measurement precision
If coolant pump is activated to flush coolant through auxiliary heater circuit, then temperature readings can be accurately recorded, but energy consumption increases during cold start
Solution Approach 1:
The coolant pump is activated periodically for a predetermined time period during cold start to flush coolant through the auxiliary heater circuit and bring the system to a standardized thermal state. This periodic activation ensures accurate temperature readings are obtained from the coolant temperature sensor without requiring continuous pump operation.
Solution Approach 2:
The system changes the operational parameters of the coolant pump - activating it for a specific predetermined duration during cold start - to achieve accurate temperature measurements. This parameter change allows the system to obtain reliable data while minimizing unnecessary energy consumption compared to continuous pump operation.
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 allows for accurate detection of auxiliary heater operation before engine start, preventing false diagnostics and ensuring reliable coolant temperature sensor functionality checks.
Implementation Method 1
Ashby et al. (2010) found that fluid flow through porous media can be described by Darcy's law, which states that the flow rate is proportional to the pressure gradient and the permeability of the medium
Implementation Method 2
Heat transfer occurs through conduction, convection, and radiation. Conduction is the transfer of heat through a material without the material itself moving, occurring at the molecular level through direct contact between molecules
Implementation Method 3
Joule heating, also known as resistive heating, is the process by which electrical energy is converted to thermal energy when electric current passes through a conductor with electrical resistance. The heat generated is proportional to the square of the current, the resistance, and the time
Data Source
AI summary
A method and apparatus for detecting the operation of an engine-independent auxiliary heater in a cooling system with multiple coolant circuits in a vehicle system with an auxiliary heater. On or after activating the vehicle system for a cold start, a shut-off valve is opened between a first coolant circuit with the auxiliary heater and a second coolant circuit with the coolant temperature sensor. A coolant pump is activated so that coolant from the first coolant circuit flushes around the coolant temperature sensor. A time course of a temperature reading from the coolant temperature sensor is performed for a predetermined period of time from the time the vehicle system is activated. A gradient of the temperature reading curve is determined. The gradient of the temperature reading curve is evaluated using a threshold value comparison to determine whether the auxiliary heater was activated before the cold start.