Coolant Sensor Diagnosis via Auxiliary Heater Temperature Gradient
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Solution Overview
Problem
Existing methods for diagnosing coolant temperature sensors in vehicles with auxiliary heaters fail to distinguish between sensor malfunctions and the influence of pre-activation of the auxiliary heater, leading to false positives during cold starts.
Innovation Solution
A method and device that detect the operation of an engine-independent auxiliary heater before engine start by monitoring the temperature gradient and integration value of the coolant temperature sensor, allowing for a threshold comparison to determine if the auxiliary heater was activated prior to the cold start.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the coolant temperature sensor remains in the engine coolant circuit during cold start, then the sensor can measure engine coolant temperature, but the sensor cannot accurately detect auxiliary heater operation status and may provide incorrect temperature readings
Solution Approach 1:
The coolant circuit is divided into two separate circuits: a first coolant circuit containing the auxiliary heater and a second coolant circuit containing the coolant temperature sensor. This segmentation allows the sensor to measure auxiliary heater coolant temperature independently from engine coolant temperature, enabling accurate detection of auxiliary heater operation status without interference from engine coolant temperature variations.
Solution Approach 2:
A shut-off valve is introduced as an intermediary component to control the connection between the first coolant circuit (auxiliary heater) and the second coolant circuit (temperature sensor). By opening or closing this valve, the system can selectively isolate the sensor from engine coolant while allowing it to measure auxiliary heater coolant temperature, thus mediating between the two different temperature measurement requirements.
2Reliability
If the coolant temperature sensor is isolated from the engine coolant circuit to diagnose auxiliary heater operation, then the auxiliary heater status can be accurately detected, but the sensor cannot measure engine coolant temperature
Solution Approach 1:
The shut-off valve provides dynamic control over the coolant circuit configuration. It can be switched between closed position (isolating the sensor from engine coolant to measure auxiliary heater temperature) and open position (connecting the sensor to engine coolant for engine temperature measurement). This dynamic switching capability allows the single sensor to serve both measurement purposes at different times without compromising either function.
3Measurement precision
If the coolant pump operates continuously to ensure coolant flow for temperature measurement, then temperature data can be continuously acquired, but energy consumption increases
Solution Approach 1:
The coolant pump operates periodically rather than continuously. It is activated only when temperature measurement is required (such as during auxiliary heater diagnostics or engine cold start monitoring) and remains inactive otherwise. This periodic operation significantly reduces energy consumption while still providing continuous temperature monitoring capability when needed, as the system can acquire temperature data at appropriate intervals without requiring constant 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
Enhances the accuracy of coolant temperature sensor diagnostics by differentiating between sensor errors and auxiliary heater operation, ensuring reliable sensor functionality assessment.
Implementation Method 1
activation of a coolant pump (8), so that coolant from the first coolant circuit (K1) flows around the coolant temperature sensor (12)
Implementation Method 2
an auxiliary heater (6)... comprising a first coolant circuit (K1) with the auxiliary heater (6)
Implementation Method 3
Acquiring (S3) a time course of a temperature measurement from the coolant temperature sensor (12)
Data Source
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AI summary
Method and device for detecting the operation of an engine-independent auxiliary heater and for diagnosing a coolant temperature sensor of a motor vehicle. The invention relates to a method for detecting the operation of an engine-independent auxiliary heater in a cooling system (2) with several coolant circuits (K1, K2, K3) in a vehicle system with an auxiliary heater (6), comprising the following steps: - Upon or after activation of the vehicle system for a cold start, opening (S2) of a shut-off valve (9) between a first coolant circuit (K1) with the auxiliary heater (6) and a second coolant circuit (K2) with the coolant temperature sensor (12) and activation of a coolant pump (8), so that coolant from the first coolant circuit (K1) flows around the coolant temperature sensor (12);- Acquiring (S3) a time course of a temperature reading from the coolant temperature sensor (12) for a predetermined time period from the time the vehicle system is activated; - Determining (S4) a gradient of the temperature reading; - Evaluating (S5, S6) the gradient of the temperature reading using a threshold comparison to determine whether the auxiliary heater (6) was activated before the cold start.