Engine EGR Control to Prevent Low-Temperature Passage Freezing
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Solution Overview
Problem
Existing engine systems face challenges in maintaining sufficient exhaust performance when outside air temperatures are low, particularly when the catalyst apparatus temperature is low, due to potential freezing of water in the EGR passage, leading to insufficient return of exhaust gas and increased NOx discharge.
Innovation Solution
An engine system with an adjustment apparatus and EGR valve control mechanism that sets a lower upper limit value for engine output or torque based on outside air temperature, prohibiting EGR valve opening when temperatures are low, and utilizing high-pressure EGR passage to return exhaust gas, thereby preventing freezing and reducing NOx discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the intake air amount is decreased to reduce harmful substance discharge, then the exhaust performance is improved, but the engine output is reduced
Solution Approach 1:
The control apparatus dynamically adjusts the upper limit value of engine output based on outside air temperature and catalyst apparatus temperature. When outside air temperature is low, a lower upper limit value is set to prevent freezing in the EGR passage while maintaining acceptable exhaust performance. This parameter adaptation resolves the contradiction by optimizing the balance between harmful substance discharge and engine output under varying temperature conditions.
2Object-generated harmful factors
If the EGR valve is opened to return exhaust gas to the intake passage, then the exhaust performance is improved, but water freezing occurs in the EGR passage when outside air temperature is low
Solution Approach 1:
The control apparatus acts as an intermediary by monitoring outside air temperature and catalyst apparatus temperature, and dynamically adjusting the upper limit value of engine output and EGR valve operation. This intermediary control prevents water freezing in the EGR passage by setting appropriate operational limits based on temperature conditions, while still maintaining exhaust performance when conditions permit.
Solution Approach 2:
The control apparatus takes preliminary anti-action by setting a lower upper limit value before freezing can occur. When outside air temperature is detected to be low, the system proactively restricts engine output and EGR valve operation to prevent water freezing in the EGR passage, thereby avoiding the harmful effect before it occurs.
3Reliability
If the upper limit value of engine output is set low to prevent freezing, then the reliability is improved, but the engine output is excessively reduced
Solution Approach 1:
The control apparatus implements dynamic adjustment of the upper limit value based on real-time temperature conditions. When outside air temperature is low, a lower upper limit value is set to prevent freezing. When outside air temperature is high, a higher upper limit value is set to maintain engine output. This dynamic adaptation resolves the contradiction by making the system flexible rather than fixed, optimizing both reliability and power under different operating conditions.
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 system maintains proper exhaust performance by preventing water freezing in the EGR passage and reducing NOx discharge, even at low temperatures, ensuring efficient engine operation.
Implementation Method 1
an exhaust gas purification apparatus which is disposed in the exhaust passage and purifies exhaust gas
Implementation Method 2
an EGR passage which connects the exhaust passage on a downstream side relative to the exhaust gas purification apparatus with the intake passage and returns EGR gas as a part of exhaust gas to the intake passage
Implementation Method 3
when the outside air temperature is low, water in the exhaust gas might be frozen in the EGR passage
Data Source
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AI summary
An adjustment apparatus (9) which adjusts an engine output or engine torque and an EGR passage (51) which connects an exhaust passage (40) on a downstream side relative to exhaust gas purification apparatuses (42 and 43) with an intake passage (30) and returns EGR gas as a part of exhaust gas to the intake passage are provided, restriction control is carried out which is for controlling the adjustment apparatus such that an upper limit value of the engine output or the engine torque is set lower than a maximum value and the engine output or the engine torque has a value equal to or lower than the upper limit value in a case where a purification apparatus temperature is lower than a predetermined reference temperature, and the upper limit value is set to a lower value when the outside air temperature is low than a value when that is high.