Exhaust gas recirculation positioner, basic function

P14.20-2437-79

Overview

This document contains information on:

 General

 Location

 Function

General

The exhaust gas recirculation positioners for high pressure and low pressure control the exhaust flows, which are led into the intake air system of the engine to reduce the nitrogen oxide (NOx) emissions. The exhaust gas recirculation positioners are integrated in the coolant circuit of the engine to protect against thermal overload.

Location

The low pressure exhaust gas recirculation actuator is located on the combustion engine together with the exhaust gas recirculation cooler downstream of the exhaust gas turbocharger.

The high pressure exhaust gas recirculation actuator is located on the combustion engine together with the exhaust gas recirculation cooler upstream of the exhaust gas turbocharger.

Function

The exhaust gas recirculation positioners comprise exhaust gas recirculation actuators in the form of flap valves and electric actuator motors. When opening the flap valves, the exhaust flows are routed back into the intake air system as necessary. For each exhaust gas recirculation positioner, an exhaust gas recirculation cooler integrated in the coolant circuit cools down the exhaust on this route.

The exhaust gas recirculation positioners for high pressure and low pressure control the opening of the exhaust gas recirculation actuators using an electric actuator motor as necessary.

When they are not being operated, a spring in the respective exhaust gas recirculation actuator rotating magnet holds the exhaust gas recirculation actuators closed.

For the purpose of regulation and diagnosis of the exhaust gas recirculation, the Hall sensors of the exhaust gas recirculation actuator transmit the position of the rotating magnet and the opening cross-section of the exhaust gas recirculation actuators to the combustion engine control unit.

As a result of the individual actuation of the actuator motors via the combustion engine control unit, the exhaust gas recirculation actuator changes the flow cross-section of the respective duct, through which the recirculated exhaust gas flows.