Fuel injector tappet retention mechanism

#The present invention relates generally to tappet assemblies for fuel injectors, and more particularly to a mechanism that maintains a tappet connected to the body of a fuel injector during shipping, handling and installation.

#One class of fuel injectors used in internal combustion engines, such as diesel engines, are mechanically actuated via a rocker arm assembly that moves with each rotation of an engine's cam shaft. The rocker arm moves a tappet downward, and a plunger underneath the tappet pressurizes fuel during the downward stroke. A spring retracts the plunger and tappet between injection events. The spring, which is always compressed, also maintains the tappet in contact with the rocker arm throughout the operation of the system. In most of these types of injectors, the spring pushes the tappet away from the injector body, but the rocker arm limits how far the tappet can be moved away from the injector body, and thus prevents the tappet from disconnecting from the injector body after installation.

#During assembly, shipping and handling before the injector is installed in an engine, there is often the possibility that the tappet will accidentally disconnect from the injector body. This occurs because the tappet return spring pushes the tappet away from the injector body, and there is often no means provided for holding the tappet connected to the injector body prior to installation. In some instances, it is possible to use an external clamping mechanism to hold the tappet to the injector body prior to, and during, installation in an engine. However, in many cases space constraints during installation are so severe that no room on the outside of the assembled injector is available for retaining the tappet in the injector body. In these cases, one must either include an internal retention means or accept the risk that some tappets will become disconnected from their respective injector bodies during pre-installation shipping and handling. Oftentimes internal retention means are limited or unavailable due to internal structural and space constraints. In addition, any retention means should be either removable upon installation or arranged such that the same will not interfere with normal operation of the injector after being installed in an engine.

#FIG. 1 is a side view of an engine;

#FIG. 2 is a cross sectional view taken along line 2-2 of FIG. 1 of the engine;

#FIG. 3 is an enlarged cross-sectional view of a fuel injector within the engine;

#Referring to the Figs., an internal combustion engine 10 is shown. The engine 10 includes a cylinder block 12, a cylinder head 14 attached to the block 12, and a valve cover 16 attached to the head 14. These components are of a generally conventional design.

#Referring now to FIG. 1, the block 12 includes a top mounting surface 18, a bottom mounting surface 20, a plurality of cylinder bores 22 located between the top mounting surface 18 and the bottom mounting surface 20, and, as shown in FIG. 2, a longitudinally disposed through bore 24 spaced from the centers of the plurality of cylinder bores 22 and intermediate the top and bottom mounting surfaces 18, 20. In the embodiment shown in FIG. 1, six cylinder bores 22 are equally spaced, in-line, and perpendicularly positioned with respect to the top mounting surface 18. However, the cylinder block 12 may be of any other conventional design, such as “V” or radial, and may have any number of bores 22. Referring to FIG. 2, the block 12 contains a cam shaft 26 rotatably positioned within the through bore 24 that is driven by a conventional mechanism, not shown. The camshaft 26 has a centerline axis 27 and a plurality of profile cam portions 28 thereon. A plurality of roller cam followers 30 of conventional design are in contact with the camshaft 26. Each of the roller cam followers 30 has a roller 32 and a cupped portion 34.

#Referring to FIG. 2, the cylinder head 14 includes a valve cover mounting surface 36 and a block mounting surface 38. The cylinder head 14 is attached to the block 12 by a plurality of bolts 40. In this application, a plurality of rocker arm assemblies 42 are attached to the head 14 in a conventional arrangement. As an alternative, a single rocker arm assembly 42 could be used. In the specific example shown, an individual rocker arm assembly 42 is provided for each of the cylinder bores 22. Each of the rocker arm assemblies 42 includes at least one rocker arm 46 pivotally mounted on a shaft 48 and attached to the head 14 in a conventional manner. In the specific example illustrated, three rocker arm assemblies 42 are provided for each cylinder bore 22 of a six cylinder engine. Each of the rocker arms 46 has a first end 50 including a pin 52 having a spherical head 54 thereon. Each of the rocker arms 46 has an actuation end 56. A pushrod 58 has a spherical end 60 and a cupped end 62 having a contacting surface normally in contact with the spherical head 54 of the rocker arm 46. The spherical end 60 of the pushrod 58 is in contact with the cupped portion 34 of one of the plurality of roller cam followers 30. One of the rocker arms 46 engages a fuel injector 64 in a conventional manner. A similar rocker arm 46 is used with each of a plurality of intake and exhaust valves, 66 and 68, respectfully, shown in FIG. 1.