Inyección directa Common rail - parte 2

Fuel Injection System Overview

Fuel Delivery and Pressure Regulation

• The fuel pressure increases progressively until it opens the delivery valve, allowing fuel to flow through the high-pressure line towards the pressure regulator.

• The pressure regulator adjusts the operating pressure in the injector rail using a spring that acts on a ball valve; when fuel pressure exceeds approximately 100 bars, the valve opens to return excess flow to the tank.

• Fuel pump pressures can range from 200 to 1400 bars, largely controlled by both the regulator and control unit.

• The regulator features a magnetic core that moves within a coil connected to the control unit, which modulates current intensity to adjust fuel pressure as needed.

• If lower fuel pressure is required for engine operation, the control unit reduces pulse frequency and current intensity, decreasing magnetic field strength and thus lowering pressure.

Deactivator Functionality

• A component called the deactivator manages one of three pressure groups in the pump, reducing power consumption during low-load vehicle operation.

• The deactivator consists of a coil and an axis that moves due to magnetic field action; it interrupts command circuits when at rest, allowing fuel entry while closing during expulsion.

• Activation occurs above 1100 RPM or with medium throttle input while ensuring fuel temperature exceeds 105 degrees Celsius for optimal performance.

Lubrication and Safety Features

• The same circulating fuel cools and lubricates the pump; a lubrication valve at intake prevents potential seizing due to low priming circuit pressure.

• Under normal conditions, this valve remains retracted by fuel force but closes if priming pressure drops, maintaining lubrication during operation.

Common Rail System Components

• After examining the pump's function, attention shifts to the common rail or accumulator where temperature sensors and output lines toward injectors are located. Some models include flow limiters in these lines to stabilize fluctuations during injector openings.

Injector Mechanism

• Injectors are typically mounted on cylinder heads but differ from other diesel injection systems as they operate electrically rather than mechanically.

• Inside each injector is an electroválvula controlled by a unit that dictates injection timing; it also contains a hydraulic actuator regulating fuel exit based on internal pressures between upper and lower chambers.

• When injection is triggered by control signals, it excites an electromagnetic coil causing movement in a ball valve which allows fluid flow into return channels leading to reduced upper chamber pressure—this initiates cylinder feeding via needle lift caused by lower chamber pressures exceeding those above it.[( t =490 s)]

Conclusion of Injection Process