Exhaust Gas Sensor Heater Control for Crack Prevention
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Solution Overview
Problem
Existing heater control devices for exhaust gas sensors in internal combustion engines face challenges in activating the sensor elements promptly while preventing element cracks due to condensed water, as they often require a lower energization duty to avoid temperature exceeding the crack prevention limit, leading to insufficient heating and prolonged activation times.
Innovation Solution
A heater control device that executes a preheating control with a larger preheating promotion energization duty until the sensor element reaches a predetermined upper limit temperature, then maintains this temperature to prevent cracking, and subsequently increases energization to activate the sensor element efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the energization duty of the heater is increased to raise the temperature of the sensor element quickly, then the activation time is reduced, but the temperature may exceed the element crack prevention temperature upper limit value causing element cracks
Solution Approach 1:
The heater control device dynamically adjusts the energization duty of the heater based on the real-time temperature of the sensor element. The control portion increases the energization duty when the temperature is below the upper limit and decreases it when the temperature reaches the upper limit, creating a dynamic control system that adapts to changing temperature conditions to prevent element cracks while reducing activation time
Solution Approach 2:
The control portion continuously monitors the temperature of the sensor element and uses this feedback information to adjust the energization duty of the heater. This closed-loop feedback mechanism ensures that the temperature remains within the safe operating range while achieving rapid activation, resolving the contradiction between speed and reliability
2Device complexity
If the energization duty of the heater is set to a constant value during preheating control, then the control is simple, but the temperature of the sensor element is insufficiently raised and activation time is lengthened
Solution Approach 1:
The system transitions from static constant energization duty to dynamic variable energization duty based on temperature conditions. The control portion automatically adjusts the energization duty level according to whether the temperature is below or at the upper limit, optimizing the heating process without requiring complex external control mechanisms
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 rapid temperature increase to the upper limit and active temperatures, reducing activation time while preventing element cracks, ensuring timely and effective sensor activation.
Implementation Method 1
a heater (16) for heating a sensor element of the exhaust gas sensor
Implementation Method 2
an 'element crack' that the sensor element heated to a high temperature is cracked by local cooling (thermal strain) caused by adhesion of the condensed water
Implementation Method 3
the water vapor in the exhaust gas may be condensed in the exhaust pipe, and a condensed water may be generated
Data Source
AI summary
A preheating control for controlling an energization of a heater is executed so that a sensor element of an exhaust gas sensor is preheated within a temperature range in which no element crack caused by water occurs until a predetermined preheating period elapses after an engine starts. In performing the preheating control, first, an energization duty of the heater is set to a preheating promotion energization duty to promptly raise a temperature of the sensor element until it is determined that the temperature of the sensor element reaches a predetermined upper limit temperature. After it is determined that the temperature of the sensor element reaches the upper limit temperature, the energization duty of the heater is set so that the temperature of the sensor element is maintained at the upper limit temperature to sufficiently raise the temperature of the overall sensor element during the preheating control.