The structure and principle of EGR valves have undergone continuous evolution. Early EGR valves used a purely mechanical structure, controlling the flow of exhaust gas through physical laws. These mechanical EGR valves included conventional and positive/backpressure types. Their working principle was similar to a drum-shaped structure, with an internal spring and diaphragm. They utilized the vacuum in the intake manifold to overcome spring resistance, opening the valve to guide exhaust gas backflow. However, due to the limited precision of mechanical control, modern mid-to-high-end vehicles tend to use electromagnetic EGR valves.
Electromagnetic EGR valves control the opening and closing of the valve through a solenoid, rather than relying on the vacuum in the intake manifold. The engine control unit (ECU) calculates whether to open the valve and control the exhaust gas flow based on real-time data such as intake air volume, intake and exhaust manifold pressure, throttle position, coolant temperature, and engine speed. Precise control of the solenoid valve via electrical signals achieves a more efficient exhaust gas recirculation process.
In summary, the EGR system, as an effective means of reducing nitrogen oxide emissions from automobiles, achieves its environmental goals by introducing a portion of exhaust gas for secondary combustion. As a key component for controlling the amount of exhaust gas mixed in, the EGR valve plays an increasingly important role in modern vehicles. Most modern vehicles use electromagnetic EGR valves that are directly controlled by the engine computer to achieve a more precise and efficient exhaust gas recirculation process.
