Variable Valve Closure for Engine Gas Exchange Pressure Control
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Solution Overview
Problem
Existing methods for controlling gas exchange in internal combustion engines are sluggish due to delays in pressure changes in the intake manifold, making it difficult to precisely regulate the portions of fresh air, residual gas, and purge air, which affects fuel consumption and pollutant emissions.
Innovation Solution
A method and control device that adjust gas pressure in the gas line section by recognizing torque change requests, determining a target gas pressure value, and shifting the valve closure time relative to a fixed point in the engine cycle, using actuators like throttle valves or turbochargers to achieve the target pressure quickly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a throttle valve is used to regulate cylinder charge by adjusting intake manifold pressure, then the portions of fresh air, residual gas, and purge air can be controlled, but the response is sluggish due to delay in pressure changes in the large-volume intake manifold
Solution Approach 1:
The invention extracts the pressure regulation function from the large-volume intake manifold system and implements it locally in the cylinder using a controllable closure element. This closure element can be opened or closed independently to rapidly adjust the effective cylinder volume and control charge portions without being constrained by the slow pressure response of the entire intake manifold system.
Solution Approach 2:
The closure element is positioned and controlled in advance within the cylinder to prepare for rapid charge adjustment. By having the closure element ready within the cylinder space, the system can immediately respond to torque change requests by adjusting the closure element position, rather than waiting for pressure waves to propagate through the intake manifold.
2Loss of time
If valve train control is used to regulate cylinder charge, then response time can be improved, but precise knowledge of pressure conditions in intake manifold and exhaust port is required which is difficult to obtain
Solution Approach 1:
The closure element within the cylinder serves dual functions: it controls the charge portions and simultaneously defines the measurement volume for the pressure sensor. The pressure sensor measures pressure in the space created by the closure element position, providing direct feedback on the charge conditions without requiring separate measurements from the intake manifold or exhaust port.
3Use of energy by moving object
If the intake valve closes early as in the Miller cycle to save fuel, then fuel consumption is reduced and cylinder temperature is lowered, but the expansion volume is increased requiring precise control to maintain charge portions
Solution Approach 1:
The closure element serves multiple functions: it controls the effective cylinder volume for charge regulation, defines the measurement volume for pressure sensing, and enables rapid response to torque changes. This multi-functional component simplifies the overall control system by integrating charge control and measurement capabilities in one element within the cylinder.
Data Source
AI summary
A method for carrying out a gas exchange in a cylinder of an internal combustion engine is provided. The cylinder is connected to a gas line section via a valve. An actuator adjusts a gas pressure in the gas line section. The valve closes at a fixed point in time in a working cycle of the internal combustion engine in case of a constant torque of the internal combustion engine. The method includes the steps of recognizing a torque change request; determining a target value for the gas pressure in the gas line section in dependence on the torque change request; and determining a variable point in time for closing the valve as a result of the torque change request, wherein the variable point in time is shifted in the working cycle relative to the fixed point in time in dependence on the target value of the gas pressure.