P07.03-A004-79
Example illustration of 6-cylinder spark-ignition engine |
1.1 | Cylinder 1 fuel injector | 1.4 | Cylinder 4 fuel injector | |
1.2 | Cylinder 2 fuel injector | 1.5 | Cylinder 5 fuel injector | |
1.3 | Cylinder 3 fuel injector | 1.6 | Cylinder 6 fuel injector |
P07.03-A008-79
Example illustration of 4-cylinder diesel engine |
1.1 | Cylinder 1 fuel injector | 1.3 | Cylinder 3 fuel injector | |
1.2 | Cylinder 2 fuel injector | 1.4 | Cylinder 4 fuel injector |
Overview
This document contains information on:
General
Location
Function
General
The fuel injectors spray the fuel under high pressure into the respective cylinder.
The respective injected fuel quantity depends on the actuation duration of the relevant fuel injector.
The injection quantity is determined by additional factors:
Opening and closing speed of nozzle needle
Needle lift height
Nozzle geometry
Fuel distributor pressure
Location
The individual fuel injectors are located at the respective cylinder in the cylinder head.
Function
Spark-ignition engine
The fuel injectors switch very rapidly and can also inject the smallest fuel quantities.
Due to the high fuel pressure of approx. 130 to 250 bar, the outward opening nozzle produces a stable hollow-cone jet under all operating conditions, this is a basic requirement for an interruption-free stratified charge operation. The combustion engine control unit generates the control voltage of 140 to 210 V for the fuel injectors and actuates the fuel injectors with a ground signal. The stroke of the nozzle needle is, in this connection, approx. 35 μm. The piezo actuator module represents a capacitative load for the combustion engine control unit. When opening, a current of approx. 8 A flows for a few milliseconds. The combustion engine control unit reverses the polarity for opening and closing. The short switching times of the piezo injectors facilitate a multiple injection with short breaks during a combustion cycle.
Connected in parallel to the piezo actuator module is a 220 kΩ discharge resistor. This value is measurable at the electrical connections for the fuel injectors.
Diesel engine
This is shortened by the discharging of the piezo actuator in the fuel injector. With a coupler module (travel-stroke amplifier), the movement is transferred to the nozzle needle of the nozzle module. The nozzle needle lifts of the nozzle module and exposes the injection holes of the nozzle module. The injection occurs until the piezoceramics are recharged by the combustion engine control unit. The piezo actuator expands due to the charging. The nozzle needle closes the injection holes of the nozzle module. In the event of "Circuit 61 OFF" and missing actuation of circuit 30 g of the combustion engine control unit, the nozzle needle is pressed through a spring in the seat so that the injection holes of the nozzle module remain closed.