ENGINE MANAGEMENT SYSTEM

ENGINE MANAGEMENT SYSTEM

Engine management system is, now-a-days, used in many of the modern cars such as Benz, Mitsuibisi, and Toyota etc.This system uses many electronic control system involving micro controllers.The generalized block diagram of this system is shown in fig

The objective of the system being to ensure that the engine is operated at its optimum settings.

The system consists of many sensors for observing vehicle speed, engine temperature, oil and fuel pressure, airflow etc. These sensors are supplying input signals to the micro controller after suitable signal conditioning and providing output signals via drivers to actuate corresponding actuators. 

A single cylinder engine consists of some of these elements in relation to an engine is shown in fig.The engine sensor is an inductive type s It consists of a coil and sensor wheel.The inductance of the coil changes as the teeth of the sensor wheel pass it and so results in an oscillating voltage.

 

The engine temperature sensor is generally thermocouple which is made of bimetallic strip or a thermistor.The resistance of the thermistor changes with change in engine temperature this results in voltage variation.Hot wire anemometer is used as a sensor for measuring mass airflow rate.The basic principle is that the heated wire will be cooled as air passes over it.The amount of cooling is depending on the mass rate of flow.

The oil and pressure sensors are diaphragm type sensors. According to the pressure variation, the diaphragm may contract or expand and activates strain gauges which produces voltage variation in the circuit.

The oxygen sensor is usually a close end tube which is made of ZirConium oxide with porous platinum electrode on the inner and outer Surfaces.The sensor becomes permeable to oxygen ions at about 300°C.This results in generation of voltage between the electrodes.The various drivers such as fuel injector drivers, ignition coil drivers. solenoid drivers are used to actuate actuation according to the signal by various sensors.

Analog signals given by sensors are converted into digital signal by using analog to digital converters (ADC) and sent it to micro controllers.The various output digital signals are converted into analog signals by DAC(i.e., Digital to Analog Converter) and shown in various recorders or meters.