Engines may be configured with various fuel systems used to deliver a desired amount of fuel to an engine for combustion. One type of fuel system includes a port fuel injector and a direct fuel injector for each engine cylinder. Only the port fuel injectors may be operated to improve fuel vaporization and reduce engine emissions, as well as to reduce pumping losses and fuel consumption at lower loads. Only the direct fuel injectors may be operated to improve engine performance and fuel consumption at higher loads. Additionally, both port fuel injectors and direct injectors may be operated together under some conditions to leverage advantages of both types of fuel delivery.
In engines configured with dual injection systems, that is engines enabled with both direct and port fuel injectors, pressurized fuel from the fuel tank may be supplied to both a direct injection high pressure fuel pump (HPFP) as well as a port injection fuel rail. However, a fuel pressure delivered to the port injector may need to be controlled to be different from (and lower than) a fuel pressure delivered to the direct injector. As such, if high pressure fuel is delivered via the port fuel injector, it may cause excess fuel deposition in the intake manifold and subsequent fuel loss due to vaporization.
Example attempts to address the issue of supplying fuel at different pressures to the port and direct injectors include the use of pressure regulators. One example approach is shown by Motoyama et al. in U.S. Pat. No. 5,193,508. Therein, a first fuel injector injects fuel directly into the combustion chamber while a second fuel injector injects fuel into the intake manifold of the engine. Fuel rails for each of the fuel injectors may receive high pressure fuel via a common pump. In addition, a plurality of pressure regulators may be incorporated in the fuel line for supplying the second fuel injector with fuel at a pressure lower than the pressure at which fuel is supplied to the first fuel injector.
However, the inventors herein have recognized potential issues with such systems. As one example, systems wherein port fuel injectors and direct injectors are used in tandem may have high component costs due to the need for distinct sets of components for each injector type. For example, Motoyama may use at least double the number of components including two fuel rails, two pressure regulators, two fuel line bundles, etc. In addition to increasing costs, the need for multiple components reduces packaging space availability around the already crowded engine space. Further still, the configuration makes routing of fuel lines more complicated as each fuel line has to optimized to feed an independent fuel injection system.
In one example, the issues described above may be addressed by a method for an engine comprising a common fuel distribution injector system. One example method includes directing fuel from a common high pressure fuel rail to one or more of a direct injector and a port injector, each of the direct injector and port injector coupled to a cylinder of an engine. In this way, a single pressurized fuel source and fuel feed line can be used to distribute fuel to each of a direct and a port injector.
As an example, a fuel distributing injector system in an engine may include a direct injector, a flow selection valve, and a high-to-low pressure regulator. The fuel distributing injector system may be configured to act as a direct injector as well as a low pressure fuel delivery unit for a port fuel injector. In particular, the fuel distributing injector system may be coupled to a port fuel injector, the port injector located external to the fuel distributing injector system. Fuel may be supplied at high pressure from a high pressure fuel rail to the flow selection valve of the fuel distributing injector system. The flow selection valve may then channel high pressure fuel into the housing of the direct injector. When port injection is required, fuel then be drawn from the direct injector housing, downstream of the fuel rail and upstream of an inlet of the direct injector into the port injector, via the pressure regulator. For example, the pressure regulator may be configured as a mechanical spill valve such that fuel delivered to the port injector downstream of the valve is regulated to a lower pressure than the pressure of fuel delivered to the direct injector upstream of the spill valve. In an alternate example, the flow selection valve may be an electronic valve configured to enable simultaneous fuel supply to both the direct injector (directly) and the port fuel injector (via the pressure regulator) based on engine operating conditions.
In this way, a single fuel distributing injector system may be used to deliver fuel at different pressures to each of the direct and port fuel injectors. The technical effect of using a fuel distributing system wherein higher pressure fuel is delivered into a direct injector housing and then drawn from the direct injector housing and delivered at a lower pressure to a port injector housing is that fuel may be delivered to each of the direct and port injector using a single fuel pump, a single fuel rail, a single fuel feed line, and a single pressure regulator. By reducing the number of parts required for dual fuel delivery, fuel systems costs may be reduced. In addition, the issue of overcrowding around the engine may be overcome.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.