Exhaust Valve Partial Closure Prevents Sticking
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Solution Overview
Problem
The valve device for controlling exhaust gas flow in internal combustion engines experiences sticking issues due to contamination, leading to operational disruptions when the actuator fails, as impurities form deposits that cause the shut-off element to adhere to the valve seat, preventing proper closure and opening.
Innovation Solution
The return spring is tensioned in the opening direction and pivots the shut-off element to a rest position before the fully closed position, with a housing-side stop preventing further pivoting by the spring, thus avoiding sticking and allowing the element to be used as a fail-safe mechanism without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shut-off element is moved into the fully closed position when the internal combustion engine is switched off, then the exhaust gas flow is completely blocked, but the shut-off element sticks to the valve seat due to contamination deposits
Solution Approach 1:
The return spring is designed to pivot the shut-off element only partially to a rest position before the fully closed position is reached. This partial action is sufficient to prevent sticking by avoiding complete contact between the shut-off element and valve seat, while still providing adequate flow control. The spring's moment arm and force are calibrated to achieve this optimal partial closure without over-closing.
Solution Approach 2:
The system changes the position parameter of the shut-off element from a binary state (fully open/fully closed) to a continuous range of positions. By adjusting the rest position of the shut-off element to a specific angular position before full closure, the patent optimizes the balance between preventing sticking and maintaining closure functionality. This parameter optimization allows the valve to operate reliably in the partial closure state.
2Reliability
If a strong return spring is used to hold the shut-off element in the open position, then sticking is prevented, but the device complexity and cost increase
Solution Approach 1:
The patent optimizes the spring constant and pre-load parameters of the return spring to achieve the minimum necessary force for preventing sticking. By carefully selecting these parameters, the spring provides sufficient restoring moment to pivot the shut-off element to the rest position without requiring excessive strength. This parameter optimization reduces the size and complexity of the spring while maintaining reliability.
Solution Approach 2:
The return spring is designed to provide just enough restoring force to achieve partial closure to the rest position, rather than requiring strong forces to maintain full open position. This partial action approach reduces the spring strength requirements compared to designs that must continuously hold the valve fully open against contamination forces.
3Reliability
If the shut-off element is kept in the open position to prevent sticking, then operational disruption is avoided, but exhaust gas flow control is reduced
Solution Approach 1:
The patent optimizes the rest position parameter to a specific angular position that balances two competing requirements: preventing sticking by avoiding full closure, and maintaining adequate flow control for exhaust gas recirculation. This optimized rest position allows sufficient valve opening area for proper exhaust gas flow while ensuring the valve does not contact the valve seat in a way that causes sticking.
Solution Approach 2:
The system maintains a copy of the valve's functional capability through the rest position design. By positioning the shut-off element at an optimal angle before full closure, the valve retains enough opening area to control exhaust gas flow effectively, copying the flow control function of a fully open valve while avoiding the sticking problem of full closure.
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 solution prevents the shut-off element from sticking to the valve seat, ensuring reliable operation by maintaining the element in a position that avoids full closure, thus preventing operational disruptions and allowing for continued functionality even when the actuator fails.
Implementation Method 1
a restoring spring (17), which can be acted upon when the shut-off element (13) is actuated in the opening direction and is tensioned in this process
Implementation Method 2
When the internal combustion engine is switched off, impurities in the exhaust gas that have cooled or have cooled down are deposited on the valve seat and on the shut-off element
Data Source
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AI summary
The device (10) has a shutoff device (13) arranged in an exhaust gas channel (12) that is pivotable between closing and opening positions by an adjusting drive (15) and a transfer device (16) in opening and closing directions. The shutoff device is pivotable during failure of drive in the closing direction by a reset spring (17) loadable in the opening direction. The shutoff device is pivotable back only during failure of the drive in a resting position between the closing and opening positions with a condition of only small opening position during pivoting movement in the closing direction.