This invention relates to a component for a fuel injection system for use with an internal combustion engine, and particularly to a component as described and claimed in our pending UK Patent Application 8622425.

In that earlier invention, there was provided a fuel injection system component adapted to interface at one side with an engine cylinder head and at another side with an air intake manifold, the component comprising a block in which a plurality of air passages extend from said one side to said another side, the block including at least one passage for each cylinder of the engine, a plurality of fuel injector seats, and fuel feed and return passages communicating with the injector seats.

In order to provide idle air to the engine cylinders, it was proposed to provide an idle air supply duct in the block to supply idle air to the engine independently of the air supply route employed when the engine is running under load.

We have now found a more cost effective way of providing the idle air duct in the component.

According to the present invention, there is provided a fuel injection system component adapted to interface at one side with an engine cylinder head and at another side with an air intake manifold, the component comprising a block in which a plurality of main air passages extend from said one side to said another side, the block including at least one main air passage for each cylinder of the engine, a plurality of fuel injector seats, fuel feed and return passages communicating with the injector seats, and an idle air supply duct formed as an open-sided groove in an end face adapted to interface with either the

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engine cylinder head or an air intake manifold, the supply duct providing an idle air supply path from an idle air valve to each main air passage.

In one embodiment, a second open-sided groove can be formed in the same end face as the idle air supply duct, to provide ducts for conducting crankcase emissions to the main air passages. Preferably the second open-sided groove opens into the main air passages away from the fuel injector positions, to avoid any possibility of fouling the injectors.

When the component is installed, the open sides of the open-sided grooves will be closed by the cylinder head or intake manifold with which the said end face interfaces, so that the supply ducts are completed. Normally, the open sides will be closed by a gasket between the mating faces.

Preferably the grooves are in the end face which interfaces with the cylinder head.

To serve the idle air supply function, there may be two independent open-sided grooves in the end face, each serving two cylinders of a four cylinder engine, and each with its own connection to an idle air valve. Where the invention is applied to an engine having a different number of cylinders, the open-sided grooves will be appropriately configured to provide the necessary communication with the air passages in the component.

In an alternative embodiment, the idle air supply ducts may be used for carrying crankcase emissions in addition to idle air, and in this case, the grooves preferably enter the main air passages at positions spaced from the entry into those passages of the fuel injectors, so as to avoid fouling of the injector passages by foreign particles emitted from the crankcase.

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The invention will now be further described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of one end face of a fuel injection system component in accordance with the invention;

Figure 2 is a cross-section through the component of Figure 1, on the line II-II; and

Figure 3 is a perspective view of an alternative form of component in accordance with the invention.

The drawings show details of only one face of the component 10 (the face which will interface with the cylinder head) , and the reader is referred to the specification of our copending UK Patent Application 8622425 (Serial No. 2 195 394) for full details of the component.

Opening into the end face 12 are four main air passages 14 each of which provides a straight-through air connection from the intake manifold side to the cylinder head side shown. Opening into each passage 14 is an injector seat 18.

Formed in the flat end face 12 is a groove 20 which has a connection 22 for idle air and branches 23, 25, 27 and 29 leading into the respective cylinders.

A second groove 30 is also formed in the face 12, and this has a connection 32 for receiving crankcase emissions which are distributed to all four air passages 14 so that these emissions can be burnt in the engine cylinders.

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In an alternative embodiment shown in Figure 3, there are two grooves 20, each with a connection 22. The grooves extend to each of the passages 14, and because of the geometry of the arrangement shown, the pair of outermost passages 14 both experience the same idle air flow, as to the pair of innermost passages. By suitably apportioning the idle air reaching the grooves, it can be ensured that all the passges 14 receive the same volume of air.

In this embodiment, the grroveε 20 also carry the crankcase emissions, and it will be noted that their points of entry to the passages 14 are angularly offset relative to the positions of the injector seats 18.

In use, the component 10 is to be fitted against a cylinder head 24, with a gasket 26 between the joint faces. As will be apparent from Figure 2, the gasket will close the open side of the groove 20.

The grooves 20 can easily be formed in the die-casting operation used to produce the component. No machining is required as the as-cast surface will be adequate for idle air.

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