Pump drive cartridge assembly

The present invention relates to direct injection internal combustion engines; more particularly, to high-pressure mechanical fuel pumps used in high-pressure direct injection fuel systems; and most particularly, to a pump drive cartridge assembly.

It has become generally known in the art of internal combustion engine design to use high-pressure mechanical fuel pumps in direct injection fuel systems. In known direct injection fuel systems, a high-pressure fuel injection pump typically disposed in the engine compartment close to the injector fuel rail is arranged to supply fuel from a pumping chamber to associated injectors located downstream of the pumping chamber.

Traditionally, high-pressure mechanical fuel pumps require a camshaft follower, such as a flat foot follower or a roller follower, operated by a dedicated camshaft lobe on a rotating jack shaft, to transmit the rotational motion and lift of the camshaft lobe to a linear motion required to drive a typical piston compression pump. A high-pressure fuel pump may generate fuel system pressure approaching 100 atmospheres or more.

These high fuel pressures generate high loads in the system and require a robust pump and pump drive design. Based on the design of the internal combustion engine and/or the pump placement, the assembly of the pump and lifter assembly becomes cumbersome and costly, especially when roller followers are used, and alignment of the roller follower and a camshaft is required.

Typically, a lifter engages a camshaft lobe via the camshaft follower end, which preferably includes a roller. Unless suitably constrained by an anti-rotation guide, a roller follower lifter may rotate axially in its bore during reciprocation, thereby undesirably misaligning its roller follower from the associated camshaft lobe.

Lifter anti-rotation guides in the prior art are often integrated in the engine block adjacent to the lifter bore. A locating feature in the guide aperture, such as a longitudinal groove or undercut, receives a mating feature in the lifter to prevent the lifter from rotating about its longitudinal axis during reciprocation. Machining of such locating features is cost and labor intensive. Other prior art lifter anti-rotation guides utilize secondary anti-rotation attachments of locator features that are attached to the engine following lifter installation and, therefore, add another step to the assembly process.

What is needed in the art is to simplify the assembly process of a high-pressure direct injection fuel system and to reduce the total number of parts of such system.

It is a principal object of the present invention to provide a cartridge assembly that integrates all pump drive components in one integral part.

It is a further object of the invention to simplify engine block machining by eliminating secondary anti-rotation attachments or locator features.

The present invention successfully addresses the shortcomings of the prior art by providing in a first aspect of the invention a cartridge pump drive assembly that includes an anti-rotation sleeve and that integrates all pump drive components in one integral part.

The anti-rotation sleeve extends from the base of a high-pressure pump, around a reciprocating plunger and spring assembly, over a push rod assembly (if one is required for driving the pump), and to a lifter body above a lifter engine bore. The inner pump shaft may be extended as needed or a simple lower cost push rod may be used to connect the pump plunger to the lifter body as needed). The anti-rotation sleeve engages an end of the lifter body but is designed to allow the lifter body to slide up and down within the anti-rotation sleeve based on the drive motion created by a camshaft lobe profile thereby transmitting the vertical reciprocating motion to the pump. The sleeve may be made out of a lightweight polymer or drawn from thin sheet steel and may be designed to minimize the reciprocating weight and to reduce engine friction. The anti-rotation sleeve may be designed to allow additional spring packaging to support the lifter body and push rod reciprocating mass.

All drive components are self-contained within the anti-rotation sleeve thereby resisting separation during shipping or assembly. A simple press/snap fit or other engagement technique may be used at the pump end and a captive ring, snap fit or other engagement technique may be used at the sliding end. If a roller lifter is used and anti-rotation is required, the sleeve can be pinned or retained to the upper pump body and undercuts can be provided on the top of the lifter body or a sliding pin device can be utilized.

By using the anti-rotation sleeve in accordance with the invention, a relatively simple single piece cartridge assembly is provided utilizing relatively low cost modifications. The pump drive cartridge assembly in accordance with the invention minimizes engine assembly steps, total number of parts, and installation time. Existing manufacturing and assembly techniques can be used to implement the anti-rotation sleeve in accordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1 is a cross-sectional view of a pump assembly, in accordance with a first embodiment of the invention;

FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1, in accordance with the first embodiment of the invention;

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