Particle Sensor Protection Phase Voltage Control
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Solution Overview
Problem
Existing particle sensors for detecting particle concentration in exhaust gases, particularly in diesel combustion engines, face cross-sensitivities and contamination issues that lead to decreased sensitivity over time due to substances like hydrocarbons, water, and ash, affecting the accuracy of measurements.
Innovation Solution
Implementing a procedure with a protection phase that includes reducing the operating voltage and applying a temperature gradient to prevent substance accumulation on the sensor's measuring route, using a control program to manage the particle sensor's operation and minimize contamination, ensuring constant sensitivity over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the particle sensor operates continuously in measuring phase, then particle concentration detection is maintained, but contamination accumulates on the measuring route causing sensitivity to decrease over time
Solution Approach 1:
The patent implements periodic switching between measuring phase and protection phase. During protection phase, the operating voltage is reduced or switched off, and heating is activated to prevent contamination accumulation. This periodic action maintains sensor sensitivity by regularly clearing contaminants while still allowing particle detection during measuring phase.
Solution Approach 2:
The patent changes operational parameters (voltage and temperature) based on the phase. During protection phase, voltage is reduced/switched off and temperature is increased through heating. During measuring phase, voltage is restored to rated level and heating is reduced or switched off. These parameter changes enable the sensor to maintain sensitivity by preventing contamination during protection phase while enabling detection during measuring phase.
2Reliability
If heating is applied during protection phase to prevent contamination, then substance accumulation is reduced, but thermal shock damage may occur if dew point conditions are not met
Solution Approach 1:
The patent uses dew point detection as feedback to control heating activation. The control unit determines whether current conditions indicate dew point risk and only activates heating during protection phase when such risk is absent. This feedback mechanism prevents thermal shock damage by avoiding heating when condensation conditions exist, while still enabling contamination prevention when safe to do so.
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
The solution maintains high measuring accuracy for particle sensors by reducing contamination and preventing substance accumulation, thereby maintaining sensitivity over a long period and avoiding thermal shock damage.
Implementation Method 1
it is provided that a relation between the measuring route during the protection phase, whereby the temperature is set to a value that lies above the exhaust gas temperature... a temperature gradient starting from the surface of the measuring route to the exhaust gas is built, which causes a thermophoretic effect
Implementation Method 2
The particles that are at least slightly electrically conductive bridge the gap between the two electrodes, so that the impedance of the sensor route of the particle sensor changes
Data Source
AI summary
A procedure for operating a collecting particle sensor, which is provided with measuring phases, during which particles that are contained in an off-gas stream accumulate on a measuring route, and a device for implementing this procedure are submitted. Protection phases are provided, during which at least one measure for diminishing the accumulation of particles on the measuring route is adopted. The measure according to this invention prevents a decrease of the sensitivity of the particle sensor over a long period of time.