Injector (Common Rail)

In spite of large currents, it is not possible to operate a high-pressure injection system directly with 12 volts of rated voltage. For this, the pressure is simply too high. So one provides for an approximate pressure balance. A raised tension marks the opening or closing of the nozzle needle.

	1	High pressure inlet
	2	Return trace
	3	Magnetic valve (1. series)
	4	Compression spring (close)
	5	More pushed area: more power with stable pressure
	6	Less pushed area: less power with stable pressure

The Rail pressure just works from below onto the pressure shoulder as it does in case of the hole-type nozzle. Indeed, in this case the nozzle needle is not raised because from above the nozzle spring presses and the Rail pressure is spread on a larger surface. If this Rail pressure is drained to the runback, the pressure can assert itself from below against the spring and open the nozzle needle. Exactly this is carried out by a valve which can be operated electro magnetically or with the help of piezo crystals.

Indeed, approx. 70 (magneto valves) or 140 volts (piezo crystals) are necessary, nevertheless (except with In line injectors) for a definite opening of the valve. This tension is generated by a condenser in the control unit which is charged by self-induction (magneto valves) or discharge tension (piezo crystals) again.

The opening can be controlled in the garage test by checking the runback amounts of the single injectors. These are collected for every injector individually. A defective injector would strike by an especially large runback amount per time unit.

He became possible by the smaller design of the piezo module. Though the length of the whole injector is preserved because of the geometry in the cylinder head, the control moves around a great deal into the direction of the nozzle. The movable mass is thereby decisively reduced. 09/08