Components for Exhaust Gas Recirculation
The most important components in exhaust gas recirculation are as follows:
1. EGR valves
EGR valves determine the amount of exhaust gas to be recirculated. In many cases, they are directly attached to the exhaust manifold or intake air system, or they are located in a heat-resistant exhaust gas pipe that connects the exhaust manifold and the intake air system. Right: Pneumatic EGR valve
2. Electric switch over valves (EUVs) and electropneumatic pressure transducers (EPWs)
Until the middle of the nineties, pneumatic EGR valves were mainly used. They are actuated by an electric switch over valve (EUV) by way of vacuum. On this simply designed system, the EGR valve has only an open-close function. Left: Electric switch over valve (EUV)
On more modern systems, actuation is carried out by way of an electropneumatic pressure transducer (EPW) which enables the EGR valve to be continuously adjusted. This consequently facilitates rapid and extremely precise adaptations to the relevant operating points. Right: Electropneumatic pressure transducer (EPW)
In recent years, there has been a continuous change from the pneumatic over electromagnetic to electromotive control of the EGR valve. These eEGR valves no longer need a vacuum or a solenoid valve for actuating purposes and enable an even faster adaptation of the operating point to the engine-related requirements.
Electric EGR valves are directly actuated by the engine control unit. Some EGR valves are equipped with potentiometers for position feedback. This position feedback enables both an opening correction and permanent monitoring. Other EGR valves are additionally provided with incorporated temperature sensors for monitoring purposes.
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