Make sure ignition is off and the engine is not started.The hydraulic movement structure moves down.This extension depends on the voltage and the amount of piezo elements. This greatly benefits fuel economy and pollution control.īy applying voltage on the piezo element, there is an extension created.

The piezo valve can open and close so fast it is possible to have a variable number of injections from one charge of fuel. With a piezo valve the timing, volume etc can be controlled more accurately. Control of timing, volume etc would be very poor. Without an electronic valve the fuel would pressurise and squirt into the combustion chamber. The piezo valve controls the release of this high pressure fuel through the injector nozzle into the combustion chamber. The camshaft follower presses the plunger at the top to pressurise the fuel in the injector. Pumped fuel enters the injector via the fuel feed collar and excess can return to the tank via the fuel return collar. More precise proportioning of the injected fuel and a greater umber of injections per cycle. The dilation and retraction movements of the piezoelectric elements are almost instantaneous. The major advantage of piezoelectric injectors is their speed of operation and the repeatability of the movement of the valve. Moreover, as with electromechanical injectors, the piezoelectric disks do not directly command the needle movements. To actuate them, an impulse of a hundred volts is applied to them and a tiny lever arm amplifies their movement. To obtain a useable degree of displacement, it requires a stack of no fewer than 400 ceramic disks to form the active element of the injector. In the first place, the dilation of a piezoelectric element is extremely low. However, for injectors of this type to be feasible, manufacturers had to circumvent a certain number of problems. This is characterised by its ability to dilate or retract when it receives a pulse of current – the piezoelectric effect. The operation of piezoelectric injectors is quite similar to that of solenoid injectors, with the difference that they have a ceramic core. Principle of operation of the common rail piezo injector 1 shows a typical common rail piezo injector. Some advanced common rail fuel systems perform as many as five injections per stroke.įig. The key is the innovative injection system: it works with rapid switch, compact piezo-inline injectors. The 3rd generation of Common Rail makes diesel engines even more clean, more economic, more powerful and more quiet. In order to lower engine noise, the engine's electronic control unit can inject a small amount of diesel just before the main injection event ('pilot' injection), thus reducing its explosiveness and vibration, as well as optimizing injection timing and quantity for variations in fuel quality, cold starting and so on. Common Rail injectors make possible fine electronic control over the fuel injection time and quantity, and the higher pressure that the common rail technology makes available provides better fuel atomization.

Solenoid and piezo injector tester