Page 229 - Understanding Automotive Electronics

2735 | CH 6 Page 216 Tuesday, March 10, 1998 1:10 PM

6 SENSORS AND ACTUATORS

element is typically connected to a mechanism that is correspondingly moved
by the snap action of this element. Applications of solenoids in automotive
electronics include fuel injectors and EGR valves.

Fuel Injection
A fuel injector is (in essence) a solenoid-operated valve. The valve opens
or closes to permit or block fuel flow to the engine. The valve is attached to the
movable element of the solenoid and is switched by the solenoid activation
(Figure 6.25).
In a fuel injector with no current flowing, the solenoid movable element
is held down against the stop, covering the aperture or nozzle. Fuel is thereby
blocked from flowing from the pressurized fuel chamber into the aperture.
When current flows through the solenoid coil, the movable element is switched

Figure 6.25
Schematic Drawing of
a Solenoid

216 UNDERSTANDING AUTOMOTIVE ELECTRONICS