Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-05-07
2001-08-07
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
Reexamination Certificate
active
06269796
ABSTRACT:
The present invention relates to an apparatus for conveying high pressure fluid, in particular for conveying an actuating fluid to hydraulically-actuated, electronically-controlled, injectors in an internal combustion engine, and to an engine including said apparatus.
Hydraulically-actuated, electronically controlled injection (HEUI) systems utilise a high pressure pump to convey an actuating fluid, preferably oil ‘borrowed’ from the engine's lubrication system, to a fluid rail (manifold) where it is stored in readiness for actuating the engine injectors under electronic control.
Each injector typically includes an intensifier piston having an upper portion of larger diameter than a lower portion and hence the pressure of the actuating fluid on the upper portion intensifies the pressure of fuel enclosed below the lower portion during an injection event. An electronically-operated valve controls the pressure of the actuating fluid in the fluid rail up to approximately 230 bar and the pressure of the fuel in the injector is correspondingly intensified up to approximately 1500 bar, depending upon the required engine operation characteristics.
Prior HEUI systems have required a fluid rail to be situated remotely from the injectors of the engine, the fluid rail being connected to each injector by a pipe or other form of conduit. Reasons for this include the need for access to injector clamping means. However, disassociation of the rail and the injector has the disadvantages that an undesirable pressure drop may be experienced between these components, there may arise a number of potential leak-points and the engine envelope size may be compromised.
Examples of prior art relating to the above mentioned disadvantages may be seen in
FIG. 1
included herewith and in U.S. Pat. No. 5,499,612. In both of these systems a fluid rail in mounted on the cylinder head at a point distant from the injector location. This necessitates the use of a relatively long fluid transfer conduit (the rail branch passage
26
in US 5,499,612 or the jumper block in
FIG. 1
) to transfer high pressure fluid from the manifold to the injector. This gives rise to the potential problems of leakage, pressure drop and the like set out above.
It is an object of the present invention to provide an actuating fluid feed apparatus between the fluid rail and the injectors in a HEUI system in which the fluid rail is closely adjacent to the injectors to minimise pressure drop.
It is a further object to provide an actuating fluid feed apparatus in which the number of leak-paths is minimised.
It is a yet further object to provide an actuating fluid feed apparatus of a compactness which will minimise engine envelope size.
It is a yet further object to provide an actuating fluid feed apparatus which enables injector removal for servicing with minimal disturbance to the remainder of the high pressure fluid feed system.
According to one aspect of the invention an apparatus for conveying high pressure actuating fluid to a hydraulically actuated electronically controlled injector in an internal combustion engine, comprising a fluid rail defining an actuating fluid reservoir and having an outlet port connectable to communicate actuating fluid to an actuating fluid inlet of an injector and fluid rail support means adapted to be mountable on an engine and so configured that when so mounted in use the fluid rail is located above the actuating fluid inlet of the injector.
In this configuration the fluid rail is lifted above the injector and can be located closely adjacent to the injector thus reducing pressure drop associated with the prior art arrangements where the rail is fixed to the cylinder head some distance from the injector. This also opens up a number of possibilities for clamp and injector design which will permit easy removal of the injector for servicing with minimal disturbance to the high pressure fluid feet system itself.
Engines of this type may incorporate a rocker box which sits on the cylinder head of the engine. Alternatively, the rocker box may be defined by walls integral with, and extending upwardly from, the cylinder head. Preferably the apparatus for conveying high pressure actuation fluid further comprises a rocker box engagable with or formed by walls extending upwardly from the upper surface of a cylinder head of an engine and comprising integral fluid rail support means.
The fluid rail support means are conveniently in the form of a plurality of pedestals.
Preferably the fluid rail has a plurality of fluid outlet ports. This allows a single fluid rail to communicate actuating fluid to a plurality of injectors the number of fluid outlet ports corresponding in numbers to the injectors to be fed with actuation fluid by that fluid rail.
It has already been mentioned that engine lubricating oil is the preferred fluid for actuating the injectors. If the engine fuel were to be used for activation, a secure means would need to be provided for transfer of the fuel from the intensifier back to the tank. Further, the temperature increase within the fuel, brought about by the intensification event, could be detrimental to engine operation when the fuel was subsequently injected into the engine.
When using lubricating oil for activation, the oil is dispensed from the injector following the actuation event and may be returned to the engine sump for cooling by normal engine oil cooling means and subsequently re-used. Conveniently, oil drain means are provided to return the oil to the engine sump. If the injector is situated within an enclosed volume of the engine, it is possible to use the engine's conventional existing oil drain means to return the oil.
In accordance with a second aspect of the invention a hydraulically actuated fuel injection system for an internal combustion engine comprises an injector, an apparatus as above described for conveying actuating fluid to the injector, clamping means for clamping the injector in place comprising a clamp having a first end adapted to engage the body of the injector, clamp support means adapted to locate the clamp in position on an engine and clamp force applying means to engage the clamp so as to apply a clamping load to the injector body.
To ensure that sufficient space is provided in the engine to locate the fluid rail closely adjacent to the injectors the clamp support means are preferably located distant from the first end and more preferably substantially at the second end of the clamp. The clamp force applying means are adapted to engage the clamp at a location distant from the first end and more preferably substantially at the second end of the clamp. The fluid rail support means are preferably so configured that in use fitted to an engine the fluid rail is located above the clamp arm between the injector and the clamp force applying means.
The clamp and fluid rail are adapted to engage together in a point of rolling contact to provide a fulcrum point through which the clamping load is transferred from the force applying means through the first end of the clamp to the injector body. Preferably the fulcrum point is located between the first end and the clamp force applying means. Preferably the fulcrum comprises a curved upper surface portion on the clamp adapted to engage a planar lower surface on the fluid rail.
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Hickman Alan J.
Miller Carl S.
Perkins Engines Company Limited
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