Patent Application
20060021217
The present invention relates to the assembly of internal combustion engines including, but not limited to, a tool for use in aligning rocker arms during engine assembly.
Rocker arms are often employed in internal combustion engines. Rocker arms control the opening and closing of combustion chamber intake and outlet valves, and are typically driven by push rods. The rocker arms are typically mounted on a rocker arm carrier, an engine sub-assembly that attaches to the cylinder head or cylinder block. The rocker arms and other engine components, such as an oil rail, are installed on the rocker arm carrier before the carrier is bolted to the cylinder block. Rocker arms may be installed, for example, on ball bearing fulcrums that allow movement of the rocker arm in multiple directions. Proper engine assembly requires alignment of the rocker arms and push rods.
Because rocker arms move, rocker arms may become misaligned relative to the push rods during engine assembly. A misalignment, if not found, may cause an engine to run poorly or not run at all. For an assembled engine, discovery and repair of a misaligned rocker arm requires substantial engine disassembly and reassembly. Such a repair is time consuming and costly.
Accordingly, there is a need to prevent misalignment of rocker arms relative to push rods during engine assembly.
A tool includes a base having a base extension and at least one alignment member attached to the base and having an end. The end is capable of receiving a rocker arm and limiting movement of the rocker arm during engine assembly.
The following describes an apparatus for and method of aligning rocker arms with push rods during the assembly of an internal combustion engine. An alignment tool includes a plurality of alignment members that engage and constrain rocker arms while permitting desired movement to allowable positions that facilitate installation of the rocker arms in alignment with the push rods during engine assembly.
The alignment tool 100 is shown in
The base 105 includes a plurality of projections 107 that extend outward from a side of the base 105. A lower surface of the projections 107, in addition to other elements from the base 105, form a support surface 109 that rests on the carrier during engine assembly. The number, shape, and orientation of the projections 107 may by set based on the position of bolts or other engine components in the vicinity of the tool 100 when installed on the engine. One or more ribs 111 may be advantageously utilized to add rigidity and/or stiffness to a base extension 113 of the alignment tool 100 and to provide a mechanical load path from the base extension 113 into the projections 107. The ribs 111 may be disposed on one or both sides of the base extension 113. The base extension 113 may advantageously have an opening 115 and/or a grip 117 to facilitate holding the tool 100 during installation and removal. The base extension 113 may be handheld.
A bottom view of alignment members 101 of the alignment tool 100 is shown in
A bottom view of rocker arms engaged with the alignment members of the alignment tool is shown in
The general shape of the rocker arms shown is planar with a receptacle 501 or 503 on each end. One receptacle 501 engages a push rod while the other receptacle 503 engages a valve stem. The slot 103 in the end of the alignment member 101 may advantageously complement the shape of the corresponding rocker arm 401 or 403. For example, the inner surfaces 201, 203, and 205 of the slot 103 form a shape that engages the end of rocker arm 401 or 403. The rocker arm may alternatively be formed to receive push rods without receptacles.
The geometry of the various aspects of the tool 100 may vary depending on the spacing and component clearances of the engine and/or its associated rocker arm carrier. The tool may be formed of injection-molded plastic. Other materials and formation processes may be utilized to form the tool, which may be a single integral tool or may be comprised of multiple components assembled together.
A rocker arm carrier 601 with the alignment tool 100 installed during engine assembly is shown in
One finger 207 may advantageously be longer than the other finger 209 of the alignment member 101. The longer finger 207 is advantageously found on the side of the rocker arm 401 or 403 opposite the fulcrum plate 605 such that the longer finger 207 and the fulcrum plate 605 together restrain rocker arm movement from each side of the rocker arm 401 or 403.
In addition, the shape and physical location of other engine components, such as the rocker arm carrier 601 and fulcrum plate 605, as well as the rocker arm shape, location, and orientation, may provide some limit to rocker arm movement. The rocker arm alignment tool 100 provides additional limits on rocker arm movement. For example, upward and sideways movement of the rocker arms 401 and 403 is limited when the tool 100 is installed. The tool 100 constrains rocker arm movement within desired limits to facilitate alignment with the push rods during engine assembly without rigidly constraining rocker arms to unmovable positions.
During engine assembly, the tool 100 is installed such that at least part of the support surface 109 rests on the rocker arm carrier 601, cylinder head, or other engine component. The weight of the tool 100 may be utilized to hold the tool 100 in place on the rocker arm carrier 601, cylinder head, and so forth. Other engine components, such as the oil rail 607, may assist in positioning and/or holding the tool in place. Clips, detents, dowels, and/or other devices may be used to position and/or retain the tool 100 with respect to the rocker arm carrier 601, cylinder head, or other component as needed and/or desired. When the tool 100 is installed, the alignment members 101 limit movement of the rocker arms 401 and 403.
A flowchart illustrating a method of utilizing the alignment tool to align rocker arms during assembly of an internal combustion engine is shown in
At step 703, the push rods 611 are engaged with the receptacles 501, or other engagable feature, of the rocker arms 401 and 403. The push rods 611 extend from the crankcase or engine block (not shown) below the rocker arm carrier 601. Valve stems 609 of either intake or exhaust valves engage the other receptacles 503 of the rocker arms 401 and 403. The valve stems 609 may be engaged with the rocker arms 401 and 403 before the push rods 611 are engaged with the rocker arms 401 and 403 or at the same time the push rods 611 are engaged.
At step 705, the tool 100 is removed from the engine assembly by disengaging the tool from the rocker arms 401 and 403, leaving the push rods 611 engaged and aligned with the rocker arms 401 and 403. Advantageously, the tool 100 is removed after the rocker arm carrier 601 is secured to the crankcase. The tool 100 may be reused during the assembly of another engine.
Although the present invention is illustrated by the example of a rocker arm alignment tool for use during the assembly of a diesel engine, the present invention may be applied to: diesel engines, gasoline engines, or other types of engines; engines having one or more rocker arms; engines having any number of cylinders; various engine types, such as in-line, V type, and so forth; engines having different cylinder firing orders; turbocharged and non-turbocharged engines; and engines of any size. One or more tools may be utilized to assemble a single engine.
The present invention provides a number of advantages. The tool facilitates rocker arm alignment with push rods during engine assembly, thereby reducing the likelihood of misaligned push rods that result in poor or non-existent engine function and require time-consuming and expensive engine repair. The tool may be used to align rocker arms in a rocker arm carrier that is delivered with rocker arms that are misaligned. The tool advantageously eliminates the need for labor-intensive manual visual inspections that are increasingly more difficult to perform on more compact engine designs. Automated visual inspections may not be practical given compact engine designs and the potential inability to provide automated inspection in today's complicated assembly processes. The tool may be fabricated from inexpensive materials. The tool is reusable.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
