Gaseous fuel rail depressurization during inactive injector conditions

Abstract

The invention refers to gaseous fuel rail depressurization during inactive injector conditions. Methods and systems are provided for depressurizing a fuel pressure regulator during engine cold start and varying fuel injection pressure after cold start in a gaseous-fueled vehicle. A mechanical pressure regulator may be modified to include valves which may be controlled to depressurize a reference chamber of the regulator when gaseous fuel injection is inactive (e.g., before and during cold start), and to regulate the pressure of gaseous fuel to varying pressures based on electronic pressure feedback and engine operating conditions when gaseous fuel injection is active. In one example, the pressure in the reference chamber of a pressure regulator may be varied by controlling valves to flow gaseous fuel into the reference chamber, and then controlling the valves to exhaust the gaseous fuel from the reference chamber, for example to a fuel vapor storage canister.

Description

technical field [0001] The present application relates to variable injection pressure regulation for gaseous fueled vehicles including depressurization of the gaseous fuel rail during conditions in which fuel injectors are deactivated. Background technique [0002] Alternative fuels have been developed to mitigate the rising price of traditional fuels and to reduce exhaust emissions. For example, natural gas has been considered an attractive alternative fuel. For automotive applications, natural gas can be compressed and stored as a gas at high pressure in cylinders. A pressure regulator may then be used to supply compressed natural gas (CNG) to the engine combustion chamber at a lower pressure. The pressure regulator may provide the gaseous fuel to the engine at a fixed, constant pressure, or it may be a variable pressure regulator capable of providing the gaseous fuel to the engine at varying pressures. [0003] However, one unresolved problem with pressure regulators f...

AI Technical Summary

Problems solved by technology

Undesirably high fuel rail pressure during cold start can negatively affect fuel economy and engine performance

In addition to cold start conditions, overpressure may also be a problem during other engine operating conditions where fuel injectors are deactivated and therefore cannot be used to vent excess fuel pressure from the pressure regulator

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