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System Composition and Principle of Automobile Electronic Throttle

System Composition and Principle of Automobile Electronic Throttle

The throttle direct drive idle speed control system is mainly composed of throttle position sensor, idle throttle position sensor, idle switch and actuator (idle DC motor) and a set of gear driving mechanism, which is the internal circuit diagram. Throttle position sensor and idle throttle position sensor are both composed of a double track carbon film resistance and a contact sliding on it. In addition, there is a double gear on the throttle body, which is composed of a coaxially large gear and a small gear. The pinion which is coaxial with the idle DC motor is meshed with the big gear in the double gear, and the sector gear is coaxial with the throttle and meshed with the big gear in the double gear. When the driver steps on the accelerator pedal, the idle switch is disconnected, and the engine ECU judges the running condition of the engine according to the input signal of the throttle position sensor, and controls the fuel injection and ignition. When the driver does not press the accelerator pedal, the throttle is closed under the action of return spring, and the idle switch is closed. The engine ECU receives the signal that the idle switch is closed to know that the engine is in the idle running state, and controls the action of the DC motor according to the signal of the idle throttle position sensor and the signal of the crankshaft position sensor. The speed of the electric motor is transmitted to the throttle through the pinion, double gear and sector gear to open the corresponding angle and make the idle speed reach the value.

(1) Throttle position sensor

The throttle position sensor is installed in the throttle body and is directly connected with the throttle shaft. It is a potentiometer type sensor, whose output voltage is inversely proportional to the throttle opening. The voltage signal is sent to the engine ECU. The engine ECU judges various operating conditions of the engine according to the size of the signal and the rate of change, and controls the fuel injection amount and ignition timing under various operating conditions. If the engine ECU does not receive the signal from the throttle position sensor, an alternative value will be calculated based on the engine speed and air flow signals.

(2) Idle throttle position sensor

The idle throttle position sensor is installed in the throttle body, which is also a kind of potentiometer sensor. Its output voltage is only controlled by the idle DC motor. When the engine is running at idle speed, the idle throttle position sensor converts the change of its resistance value into a voltage signal. The engine ECU determines the throttle position according to the voltage value, and adjusts the engine idle speed by micro adjusting the throttle opening. When the actual speed of the engine is lower than the standard speed, the motor shaft will open the throttle at a small angle through the gear mechanism to increase the air intake of the engine, so as to increase the engine speed and gradually approach the standard speed; when the actual speed of the engine is higher than the standard speed, the motor shaft will close the throttle at a small angle through the gear mechanism, so as to reduce the air intake of the engine and the engine The rotating speed of the motor decreases and gradually approaches to the standard rotating speed.

(3) Idle switch

The idle switch is installed in the throttle body and is directly connected with the main drive shaft of the throttle. It is a contact switch. Only when the throttle main drive mechanism is reset, the contact switch is closed, which informs the engine control module that the engine enters idle condition. The engine ECU adjusts the idle fuel supply and engine speed according to the signal and engine load; when the throttle is opened, the idle contact switch is disconnected, and the engine ECU controls the fuel injection under the transitional condition from idle to small load according to the signal. The idle switch signal can also be used as a signal for the engine control module to determine whether to carry out automatic idle control and quick deceleration oil cut-off control.

(4) Idle DC motor

Idle DC motor. When the engine is idling, or the engine load increases due to the low temperature of the engine coolant, the operation of the air conditioner, the addition of the power steering and other reasons, in order to make the engine idling stable, the idle DC motor pushes the throttle valve through a set of gear mechanism, increases its opening to increase the air intake of the engine, and increases the engine speed; on the contrary, when the engine is idling, the load is reduced, Under the action of idle DC motor, the opening of throttle valve is reduced to avoid engine overspeed, so as to ensure the stable operation of engine under idle condition.


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