In the early stage, throttle was used to adjust the gas charge of gasoline engine. The throttle device was set on the carburetor cavity, which was connected with the accelerator pedal by lever and wire cable. Because it is usually butterfly valve, it is called throttle. After the electronic control injection system replaced the carburetor, the oil path became a system to conduct pressure injection; in terms of the intake system, the throttle, a simple but very important component under the intake throat of the carburetor, was retained, and ECU, throttle position sensor, air flow meter and other monitoring conditions were added.
Electronic throttle control system (ETC) is a new electronic control unit, DC motor, reduction gear, driving circuit, etc. in the throttle mechanism of EFI system, some auxiliary compensation devices are removed. Different from the traditional throttle control method, the throttle in the electronic throttle system is directly driven by the motor under any working condition, and the ECU can synthesize the vehicle management information and the change of engine working condition to prepare an optimal mixture composition at any time. The optimum mixture composition is determined according to the power and economy of the engine, especially the requirements of reducing emissions of harmful substances. It has good transition performance of idling, acceleration, deceleration, etc.
The electronic throttle is equivalent to replacing the traditional mechanical connection (i.e. rigid connection) with a flexible connection. In the rigid connection, the engine throttle opening is completely controlled by the throttle pedal opening, and the engine working condition depends on the driver's operation of the throttle pedal. In the flexible connection mode, the accelerator pedal is only a sensor reflecting the driver's control intention. The actual opening of the throttle is determined by its controller according to the driving condition of the vehicle at that time, the requirements of other on-board electronic control systems and the characteristics of the engine.