An experimental study of the driving of a solenoid type diesel common rail injector using microprocessors

A fuel injection system to drive a common rail injector was developed using an 8-bit microprocessor. Common rail pressure control and injector driving systems are both essential for injecting fuel at a controlled pressure. With various duty ratios of the square wave generated from the CCP (capture compare PWM) pin of a microprocessor to the common rail pressure controller, the common rail pressure can be controlled continuously. An increase of the duty ratio of the supplied PWM square wave decreases the common rail pressure. The common rail pressure is controlled at 600, 1000, and 1500 bars. Moreover, a solenoid-type common rail injector driver was developed using a microprocessor. In order to drive the common rail injector, the current in the solenoid should be controlled using what is known as a peak and hold pattern, which consists of a high current level with a short time duration (peak) in the first step and a low current level with a long time duration (hold) in the subsequent step. The CCP pin in the microprocessor was used to generate the peak and hold current pattern. The PWM square wave generated from the CCP pin has a duty ratio of 100% of the PWM square wave for the peak current, with ratios of 10%, 20%, and 30% for the hold pattern. The developed common rail pressure controller and injector driver were applied to an injection rate measurement system. The needle lift in the common rail injector was also determined by attaching an accelerometer to the nozzle holder.