Variable Valve Timing for Rapid Catalyst Heating
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Solution Overview
Problem
Existing internal combustion engines face challenges in promoting early temperature rise of post-treatment devices and efficiently feeding exhaust gases with a high percentage of unburned fuel components, leading to issues like fuel dilution, reduced engine durability, and incomplete thermal decomposition of fuel components.
Innovation Solution
The engine employs a variable valve mechanism to adjust the exhaust valve opening timing during the afterburning period, allowing high-temperature and high-pressure exhaust gases to be fed to the post-treatment device, and an additional fuel injection or injection valve to introduce unburned fuel components, ensuring efficient thermal decomposition and catalyst activation without requiring significant additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If post injection is performed immediately after main injection to raise exhaust gas temperature, then the exhaust gas temperature increases and catalyst activation is promoted, but fuel adheres to the cylinder liner and dilutes the oil, deteriorating engine durability
Solution Approach 1:
The harmful action of post-injection is extracted and separated from the useful action of temperature rise. Instead of injecting fuel into the cylinder, the patent extracts unburned fuel components from the exhaust gas and introduces them directly into the exhaust passage, achieving catalyst activation without fuel dilution
Solution Approach 2:
The exhaust gas itself serves as an intermediary carrier to transport unburned fuel components from the cylinder to the exhaust passage. This mediator enables the fuel to reach the catalyst without contacting the cylinder liner, thus preventing oil dilution while maintaining thermal decomposition effectiveness
2Reliability
If post injection is performed in a low-temperature and low-pressure state to prevent fuel dilution, then fuel dilution is avoided, but thermal decomposition of fuel does not proceed efficiently and decomposition to HC components favorable for the catalyst is insufficient
Solution Approach 1:
The exhaust gas is heated to high temperature and maintained at high pressure before the fuel injection action occurs. By preliminarily creating the high-temperature environment in the exhaust passage, the subsequent introduction of unburned fuel components immediately undergoes efficient thermal decomposition, converting them into HC components favorable for the catalyst
Solution Approach 2:
The high-temperature exhaust gas acts as a thermal intermediary that transfers heat to the unburned fuel components introduced into the exhaust passage. This intermediary enables thermal decomposition to proceed efficiently at the higher temperature environment of the exhaust passage rather than in the lower temperature cylinder
3Productivity
If exhaust valve timing is fixed at normal combustion timing, then the engine operates efficiently under normal conditions, but the post-treatment device cannot be rapidly heated and catalyst activation is delayed
Solution Approach 1:
The exhaust valve timing is changed from a fixed static setting to a dynamic variable setting. The valve timing is dynamically adjusted based on operating conditions, opening later in the expansion stroke when high-temperature exhaust gases are present, enabling rapid heating of the post-treatment device while maintaining normal operation under other conditions
Solution Approach 2:
The valve opening timing parameter is changed from a fixed value to a variable value that can be adjusted based on thermal management needs. By changing this temporal parameter, the system achieves rapid catalyst activation without requiring additional heating components or significant mechanical modifications
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 enables rapid temperature rise of post-treatment devices, stabilizes catalyst performance, reduces noble metal consumption, and prevents fuel dilution, thereby enhancing engine durability and reducing manufacturing costs.
Implementation Method 1
opening the exhaust valve that is opened in an exhaust stroke at the time of normal combustion within a range of an afterburning period, and feeding to the post-treatment device an exhaust gas whose temperature and pressure have become high by means of combustion of fuel injected into a cylinder
Implementation Method 2
there is also a problem that thermal decomposition of feed fuel does not proceed, either, and that decomposition to an HC component favorable for the catalyst does not proceed
Data Source
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Figure 3(a)~4
AI summary
Provided is an internal combustion engine provided with: a post-treatment device that treats an exhaust gas; and a variable valve mechanism that can freely vary valve opening timing of an exhaust valve, and a control method for the internal combustion engine. The internal combustion engine is provided with: a unit configured to raise a temperature of a part or all of the post-treatment device 20 to not less than a preset temperature by an variable valve timing mechanism 11 opening an exhaust valve 6a that is opened in an exhaust stroke at the time of normal combustion within a range of an afterburning period AB, and by the variable valve timing mechanism 11 feeding to the post-treatment device 20 an exhaust gas Ga whose temperature and pressure have become high by means of combustion of fuel injected into a cylinder 1, when an exhaust gas Ga is treated by a post-treatment device 20, or when the post-treatment device 20 is regenerated; and after that, a unit configured to add an unburned fuel component to the exhaust gas Ga by at least either an additional injection of an injector 5 in the cylinder 1 or an injection of an HC addition nozzle 31 provided at an exhaust port 8a in accordance with valve opening timing of the exhaust valve 6a by the unit configured to perform temperature rise.