Fuel Injectors
Compared to a piezo fuel injector on a gasoline engine, the diesel injector operates quite differently. The concept of piezo electricity is the same, but applied in a different manner.
| Index | Explanation |
|---|---|
| 1 | Control chamber |
| 2 | Piezo element |
| 3 | High pressure supply |
| 4 | Supply duct to the nozzle |
| 5 | Actuator module |
| 6 | Coupler module |
| 7 | Relay valve |
| 8 | Nozzle needle |
On a gasoline engine, the piezo element is used to physically operate the injector pintle in an outward motion. Due to the very high pressures used in a diesel engine, the piezo element cannot be used to directly actuate the pintle. The pintle on a diesel fuel injector moves inward (away from the combustion chamber).
Instead, the piezo element is used to trigger a relay valve in the actuator module. The injector is then hydraulically "imbalanced" which causes the pintle to open via the fuel rail pressure.
The piezo-element (2) is located inside the actuator module (5). When controlled, it produces the movement necessary to open the relay valve.
Circuited between the two elements is the coupler module (6), which functions as a hydraulic compensating element, e.g. to compensate for temperature-related length expansions.
When the fuel injector is controlled, the actuator module expands. This movement is transferred to the relay valve (7) by the coupler module. When the relay valve opens, the pressure in the control chamber (1) drops and the nozzle needle opens.
The benefits of the piezo-fuel injector are that they offer a considerably faster control response, which results in greater metering accuracy. In addition, the piezo-fuel injector is smaller, lighter and has a lower power consumption.