Variable Displacement Engine Cylinder Deactivation Valve Control
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Solution Overview
Problem
Existing engine control systems for variable displacement engines face challenges in maintaining NOx trap catalyst temperature, especially when one bank of the engine is consecutively disabled, leading to degraded catalyst activity and increased complexity and cost due to the need for precise valve control.
Innovation Solution
The method involves selecting either the first or second cylinder group for deactivation, closing the valve between the selected group and the downstream catalyst to limit air flow, and adjusting the second valve to vary exhaust gas recirculation, thereby maintaining catalyst temperatures and improving engine efficiency and emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiple control valves are used to direct exhaust flow through alternate cylinder banks to maintain catalyst temperature, then catalyst temperature control is improved, but device complexity and component cost increase
Solution Approach 1:
The patent combines the functions of multiple control valves into a single control valve that manages exhaust flow for both cylinder banks. This single valve alternately directs exhaust from bank 1 or bank 2 to the catalyst, maintaining temperature control while reducing component count and system complexity compared to using separate valves for each bank.
Solution Approach 2:
The control valve is designed to perform multiple functions: it controls exhaust flow from both cylinder banks, manages catalyst temperature maintenance, and coordinates with the variable displacement mechanism. This multi-functional valve eliminates the need for separate dedicated valves for each cylinder bank, reducing overall system complexity.
2Reliability
If exhaust flow is reversed through alternate banks to maintain NOx trap catalyst temperature, then catalyst activity is maintained, but system complexity and control precision requirements increase
Solution Approach 1:
The system implements periodic alternation of exhaust flow between cylinder banks to maintain catalyst temperature. The control valve switches between directing exhaust from bank 1 or bank 2 to the catalyst in a periodic manner, ensuring the catalyst receives hot exhaust periodically even when one bank is deactivated, thereby maintaining catalyst activity without requiring complex continuous control.
Solution Approach 2:
The variable displacement engine system utilizes its own exhaust flow to maintain catalyst temperature. By alternately directing exhaust from the active cylinder bank through the catalyst, the system uses its inherent thermal resource (exhaust heat) to self-maintain catalyst temperature, eliminating the need for external heating systems or complex active control mechanisms.
3Device complexity
If a single valve is used to limit air flow through the catalyst during cylinder deactivation, then device complexity is reduced, but catalyst temperature maintenance capability may be compromised
Solution Approach 1:
The control valve is operated dynamically in conjunction with the variable displacement mechanism. When a cylinder bank is deactivated, the valve closes to prevent cool air from entering the catalyst through the deactivated bank's exhaust path. When the bank is active, the valve opens to allow exhaust flow through the catalyst. This dynamic operation maintains catalyst temperature despite using only a single valve.
Solution Approach 2:
The control valve is actuated in advance of catalyst temperature degradation. When the control system detects that a cylinder bank is being deactivated, it closes the valve beforehand to prevent cool air from entering the catalyst exhaust path, thereby proactively maintaining catalyst temperature and preventing temperature drop before it occurs.
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 maintains catalyst efficiency, reduces emissions, and enhances fuel economy by limiting air flow through the catalyst during deactivation conditions and coordinating engine operations.
Implementation Method 1
closing a valve coupled between the selected cylinder group and a downstream catalyst based on the selection to limit air flow through the catalyst
Implementation Method 2
adjusting the second valve to vary an amount of exhaust gas recirculated through the second cylinder group
Data Source
AI summary
Methods and systems are provided for selecting a group of cylinders for selective deactivation, in a variable displacement engine system, based at least on a regeneration state of an exhaust catalyst. The position of one or more valves and throttles may be adjusted based on the selective deactivation to reduce back-flow through the disabled cylinders while also maintaining conditions of a downstream exhaust catalyst. Pre-ignition and knock detection windows and thresholds may also be adjusted based on the deactivation to improve the efficiency of knock and pre-ignition detection.