Secondary Air Valve Control Assembly for High Vacuum Closure
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Solution Overview
Problem
In modern engines, high vacuums in the exhaust system pose a challenge for securely closing secondary air valves, as existing control arrangements relying on spring force and operational over/underpressure sources are insufficient to ensure reliable closure against high negative pressures.
Innovation Solution
The control arrangement connects a changeover valve to a vacuum source, a pressure vessel with overpressure, and an intake pipe, where the pressure vessel is fluidly connected to a pressure source, ensuring secure closure by maintaining overpressure in the pressure vessel, even against high negative pressures, using check valves and a pop-off valve for fail-safe and pressure-limiting functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If spring force and operational over/underpressure sources are used to close the secondary air valve, then the valve can be closed under normal operating conditions, but the closing force is insufficient against high negative pressures in the exhaust system
Solution Approach 1:
The pressure vessel is pre-filled with pressurized gas (overpressure) that is ready to act on the control chamber. This preliminary anti-action counterbalances the high negative pressures in the exhaust system before they can cause unintended valve opening, providing sufficient closing force under all operating conditions including overrun.
Solution Approach 2:
The check valve establishes a preliminary connection between the pressure vessel and the control chamber, ensuring that overpressure is maintained in the control chamber before the valve needs to close. This preliminary action prepares the closing force in advance, ensuring reliable closure even when high negative pressures occur suddenly in the exhaust system.
2Ease of operation
If a changeover valve connects the control chamber to vacuum or overpressure sources, then the valve can be controlled to open or close, but unintentional opening may occur under high negative pressure conditions
Solution Approach 1:
The pressure vessel acts as an intermediary between the overpressure source and the control chamber. It buffers and stabilizes the pressure in the control chamber, preventing direct exposure to high negative pressures in the exhaust system that could cause unintended valve opening. The check valve further mediates this connection, allowing pressure equalization only in the desired direction.
3Speed
If the control chamber is connected to vacuum sources for fast closing, then closing speed is improved, but the closing force becomes insufficient against very high vacuums (approx. 150 mbar)
Solution Approach 1:
The invention merges two pressure control mechanisms: the vacuum source for fast closing and the pressure vessel for providing sufficient closing force. The control chamber receives both vacuum pressure (for speed) and overpressure from the pressure vessel (for force), combining the benefits of both approaches to achieve fast and forceful closure even against very high vacuums.
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 configuration ensures the secondary air valve remains securely closed under all operating conditions, including overrun, by providing sufficient closing force against higher negative pressures in the exhaust system, preventing unintentional opening.
Implementation Method 1
a first and a second control chamber which are fluidically separated from one another by a membrane, the membrane acting on the valve rod and a changeover valve being provided which is fluidically connected to a control chamber in such a way that the control chamber is in a negative pressure or an overpressure can be applied
Implementation Method 2
a non-return valve is provided in the fluidic connection between the pressure vessel and the suction pipe
Implementation Method 3
The support of a spring closing force by operation-dependent overpressure or underpressure sources is not sufficient in this case
Implementation Method 4
the pressure vessel can have a pressure-limiting valve, which is designed as a pop-off valve, which opens when the pressure exceeds a limit and closes again when the pressure falls below it
Data Source
Figure 1
AI summary
The arrangement (10) has a valve body (44) moved between open and closed positions by a valve rod (50). Control chambers (58, 60) are separated from each other in a fluid-sealed manner by a membrane that acts on the rod. A switching valve (14) is fluidically connected with the chambers such that the chambers are exposed to low or high pressure. The valve has three connectors connected with one of the chambers, a low pressure source and a pressure container (16), respectively. The container is fluidically connected with a pressure source such that the high pressure is obtained in the container.