Needle motion sensor

A needle movement sensor ( NBF ), needle movement sensor ( NBS ) or needle lift sensor is an electromagnetic sensor in a fuel injector . It generates an electrical pulse when the nozzle needle moves to clear the injection port. Immediately afterwards, the injection of the diesel fuel begins .

The sensor consists of a current-carrying coil in which the magnetic flux density changes when the upper end of the needle is immersed . This induces a voltage that is fed via the engine control or directly to the engine control unit.

Needle motion sensors are required for purely hydraulically opening injection nozzles in conjunction with distributor or in-line pumps to regulate the start of injection. Mechanical injection systems without electronic control do not require an injection signal. In the case of pump-nozzle systems , a needle movement sensor is no longer necessary because the start of injection can be recognized by a change in the current curve of the solenoid valve . With common rail injectors, the time lag between the electronic control of the injector and opening of the needle is so small that it is no longer necessary either.