Injection unit for internal combustion engines fed with gaseous fuels such as liquefied petroleum gas or methane

摘要

A gaseous fuel injection unit for internal combustion engines fed with gaseous fuel such as liquefied petroleum gas or methane, comprises at least one volumetric measuring device (7) arranged to feed during each engine cycle a determined volume related to the piston displacement, and into which there is fed and respectively discharged that quantity of gaseous fuel complying with the required mixture ratio of fuel to air drawn in by the engine during each cycle. A control unit (5) senses operating pressures along the intake pipe system (1), namely in the injection zone (19) and in the zone (18) downstream of the throttle valve (2), in order to control an expander unit (10, 11) which feeds the gaseous fuel to the volumetric measuring device (7) at a pressure equal to the sum of the absolute values of the two pressures at the aforesaid points, and to control said volumetric measuring device.