BACKGROUND OF THE INVENTION

This invention relates to injecting apparatus for injecting a fluid under pressure, e.g. fuel injecting apparatus for internal combustion engines, apparatus for injecting liquids, e.g. a catalyst into chemical reaction vessels under pressure, and other apparatus for injecting a dose of fluid.

Although the present invention is applicable to any situation where a measured dose of fluid is to be injected under pressure, it will be convenient to describe the invention with particular reference to injecting fuel into an internal combustion engine.

Fuel injectors used in internal combustion engines, including both spark ignition and compression ignition (or diesel) engines generally utilise an external pump for supplying the fuel under sufficient pressure to be injected into the engine cylinder. The timing of the injection point in the engine operating cycle is determined by externally controlling the operation of an injector valve by mechanical means. One disadvantage of providing external pumping and control is the need for the provision and servicing of such external systems.

A general problem with injectors, particularly ones supplied from an external pump, is lack of responsiveness to any faulty condition in the associated cylinder. For example, if a piston ring is broken, known injectors will continue to inject fuel charges into the cylinder. Thus fuel will be exhausted from the engine leading to air pollution by exhausted unburnt fuel.