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.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates preferred embodiments of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
Referring to
Lifter body 134 includes a push rod seat 146 that receives push rod 142. Push rod 142 extends between lifter body 134 and plunger 136 to transmit the linear vertical reciprocating motion of lifter body 134 to plunger 136 of pump 110. While push rod 142 is shown to have parallel axial extending walls, it may be possible to use a tapered push rod that includes a larger diameter inserted in lifter body 134 and that includes a smaller diameter at the pump side. It may also be possible to utilize a push rod 142 that is crowned at the end where it contacts plunger 136.
Lifter body 134 has a generally cylindrical elongated shape. Lifter body 134 has roller follower 144 attached at one end and receives push rod 142 through an open opposite end. The open end of lifter body 134 is received by and slidably attached to sleeve 132. Lifter body 134 may include openings 135 as oil passages that enable oil drainage and adequate lubrication of the roller follower 144/camshaft lobe 120 interface. Shown in
Anti-rotation sleeve 132 has a generally cylindrical elongated shape and extends longitudinally along a central axis 140 from a first end 148 to a second end 152. First end 148 is designed to be received by base 112 of pump 110. Sleeve 132 may be attached to base 112 of pump 110 by a typical engagement technique; for example, by a simple press/snap fit or crimp fit mechanism. If roller follower 144 is used as shown in
Anti-rotation sleeve 132 may be formed from a relatively light weight polymer material or steel and may be designed with several holes 154 as oil passages incorporated that allow splash lubrication into and out of pump drive cartridge assembly 130 to minimize the reciprocating weight of assembly 130 while enabling adequate lubrication of the interfaces of pump assembly 100. The axial length of sleeve 132 can be adjusted to various engine mounting requirements.
All pump drive components, such as plunger 136 and spring 138 assembly, push rod 142, lifter body 134, and camshaft follower, for example, a roller follower 144 as shown in
Referring to
Referring to
Sliding pin feature 160 may include a projection 162, such as a pin, formed to extend from the inner diameter of sleeve 132 and a groove 164 formed in the outer diameter of lifter body 134 receiving the projection 162. Projection 162 and groove 164 are dimensioned such that projection 162 is able to slide axially up and down within groove 164 based on the drive motion created by the profile of camshaft lobe 120 shown in
Referring now to
Lifter body 234 has a generally cylindrical elongated shape. Lifter body 234 has roller follower 244 attached at one end and receives plunger 236 through an opposite open end. The open end of lifter body 234 is received by and slidably attached to sleeve 232. Lifter body 234 may include openings 235 that enable oil drainage. A c-clip 266 or other attachment feature attaches lifter body 234 to plunger 236. The attachment feature can be used to transmit the vertical reciprocating motion of lifter body 234 to pump 210. Shown in
Anti-rotation sleeve 232 may be designed similar to anti-rotation sleeve 132 shown in
The axial length of anti-rotation sleeves 132 and 232 shown in
By providing an anti-rotation sleeve, such as sleeves 132 and 232 shown in
While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.