Patent Application
20090044773
1. Field of the Invention
This invention relates generally to covers for internal combustion engines, and more particularly to valve covers attached to a cylinder head.
2. Related Art
Valve covers for automotive and other internal combustion engine applications typically are made of die cast metal, metal stampings or molded thick-walled thermoset or thermoplastics materials. The covers typically have a perimeter flange formed with a series of spaced bolt holes that enable the cover to be bolted onto an associated cylinder head of the engine. Relatively tall gaskets are typically disposed between the flange of the cover and the cylinder head, and upon fastening the cover to the head, the gasket is compressed to form a seal. As such, the valve cover essentially floats on the head with the gasket being sandwiched therebetween. In this type of sandwiched construction, after extended use, the bolts can become relatively loose, for example, due to temperature changes, vibration, and loading, and thus, leaks can result.
The all-metal valve covers are common, but are costly and heavy. The thick-walled all-plastic valve covers can be less costly and can contribute to a reduction in weight, but often the structural and dimensional stability requirements call for such large wall thicknesses that the benefits offered by the plastics material are offset by the bulkiness of the product and space requirements taken up by the added wall thickness. The all-plastic valve covers also require added fasteners as compared to the all-metal valve covers in order to adequately clamp the seal or gasket to prevent leakage. As such, the span between adjacent bolt holes decreases and the number of fasteners increases as compared to metal valve covers, adding to the cost and weight of the valve cover assembly. Further adding to the cost of all-plastic valve covers is the incorporation of bolt isolators to avoid over tightening of the bolts.
Another known problem commonly encountered with valve covers is the generation of noise, vibration and harshness (NVH). As such, there have been continual efforts made in attempts to reduce NVH of these covers. Some known practices include forming an elastomeric bridge between a cover portion and a flange portion of the cover, however, these efforts have resulted in relatively high cost products, both in manufacture and in service. As such, in addition to solving the NVH problems, there are also continual efforts being made to reduce costs associated with the manufacture of covers and in servicing covers upon use. Often, in service, the entire cover needs to be replaced, regardless of the problem, thereby passing on relatively high costs to the end user and possibly resulting in waste. For example, in one known construction, the elastomeric bridge is constructed as one piece of material with the seal, and thus, if the seal becomes defective, it becomes necessary to replace the entire cover.
A valve cover assembly for sealed engagement with a cylinder block includes a cover portion with a peripheral lip, a rail with an upwardly extending flange and a molded-in-place elastomeric bridge molded to the lip of the cover portion and to flange of the rail. The rail has a rigid sealing surface for establishing a fluid-tight seal in direct abutment against the cylinder block. The elastomeric bridge eliminates the generation and propagation of noise and vibration within the cover assembly. A recessed channel extends upwardly from the sealing surface of the rail for receipt of a seal provided as a separate piece of material from the elastomeric bridge. A mounting flange is spaced outwardly from the recessed channel. The mounting flange is substantially solid with a bolt opening extending therethrough. The mounting flange has a hard mounting bottom surface coplanar with the sealing surface of the rail. The seal depends from the sealing surface of the rail when in an uninstalled, uncompressed state for elastic compression against the cylinder block upon the sealing surface and the hard mounting bottom surface being brought into engagement with the cylinder block, thereby establishing a reliable, fluid-tight seal between the valve cover assembly and the cylinder block.
According to another aspect of the invention, a method of constructing a valve cover assembly is provided. The method includes molding a cover portion and a rail as a single piece of material with the cover portion being attached to the rail by frangible tabs. Further, disposing the single piece of material in a mold cavity and injecting an elastomeric material into the mold cavity and molding an elastomeric bridge connecting the cover to the rail in spaced relation from one another. Further, during the injection molding process, separating the frangible tabs from connecting the cover portion to the rail.
According to a further aspect of the method of construction, a step of forming a recessed channel in the rail can be provided. Additionally, a step of disposing a seal in the channel can be provided, wherein the seal can be provided as a press-in-place seal.
According to a further aspect of the method of construction, the seal can be provided as a different material from the bridge.
According to yet a further aspect of the method of construction, the recessed channel and the seal can be formed to provide an air space within the channel upon clamping the valve cover assembly against the cylinder block.
According to a further aspect of the method of construction, a step of forming the rail having hard mounting flanges extending laterally outwardly from the recessed channel at selected areas of the periphery of the rail can be provided. The mounting flanges can be formed as solid members of the rail material, with the exception of forming bolt openings extending therethrough. As such, the mounting flanges provide a clamping force in direct abutment against the cylinder block without deforming the rail while tightening the bolts.
These and other aspects, features and advantages of the invention will become more readily appreciated when considered in connection with the following detailed description of presently preferred embodiments and best mode, appended claims and accompanying drawings, in which:
Referring in more detail to the drawings,
The cover portion 12 may be dome-shaped, and represented here, by way of example and without limitation, as being elongated to provide a generally trough-shaped structure. The cover portion 12 is preferably constructed from a moldable plastics material, including thermoplastics and thermosets. The cover portion 12 extends longitudinally between opposite ends 18 and laterally between opposite sides 20 that terminate at a free peripheral edge 22. In one presently preferred construction, the edge 22 extends laterally outwardly from the ends 18 and sides 20 to form an outwardly extending lip 24. The lip 24 may be peripherally continuous in shape, or otherwise constructed having recesses or through openings 26 (
The rail 14, as represented in
The rail 14 has a lower sealing surface 42 depending from the peripheral flange 34 for establishing a hard mounted seal in direct engagement with a mounting surface 43 on the cylinder block 11. The sealing surface 42 is shown here as being formed at free ends of a pair of peripherally extending inner and outer legs 44, 45 spaced from one another by a generally U-shaped, recessed channel 46. The channel 46 extends upwardly into the flange 34 and is sized to receive a seal 48 therein, such that when the laterally spaced sealing surfaces 42 are brought into mating engagement with the cylinder block 11, the seal 48, as shown in
The rail 14 has mounting flanges 50 extending laterally outwardly from the outer leg 45 at selected areas of the periphery of the rail 14. The mounting flanges 50 are preferably formed as solid, monolithic members of the rail material conjointly with the rail 14, with the exception of bolt openings 52 extending therethrough. As such, the mounting flanges 50 are able to provide suitable clamping force against the cylinder block 11 without concern of deforming the rail 14 while tightening the bolts (not shown). If desired, metallic compression inserts 54 can be disposed in the bolt openings 52 to further assure preventing deformation of the rail 14 during tightening. The bolt openings 52 extend through the thickness of the mounting flanges 50 in laterally spaced, outward relation to the channel 46, such that the openings 52 do not extend through the channel 46, and thus, are spaced away from and prevented from contacting the seal 48, thereby not affecting the sealing performance of the seal 48. In addition, the mounting flanges 50 have hard, rigid bottom mounting surfaces 56 that are brought into direct engagement with the cylinder head 11 upon tightening the bolts. As such, the mounting surfaces 56 are generally coplanar with the sealing surface 42 provided by the legs 44, 45. Accordingly, the seal 48 is assured of being compressed to the desired limit without being over or under compressed upon the bolts being tightened to a specified torque to bring the mounting surfaces 56 into clamped engagement with the cylinder head 11. Because the mounting flanges 50 are solid members, larger bolt spans (distance between adjacent bolts) are possible and thus the cover assembly 10 can be mounted with fewer fasteners than that required for traditional all-plastic covers. The cover assembly 10 also has improved dimensional stability and resistance to creep as compared to an all plastic cover of equivalent application. Further, given the abutment of the hard mounting surfaces 56 in direct contact with the hard cylinder block surface 43, the bolts fastening the valve cover assembly 10 to the cylinder block 11 are less prone to becoming loose than applications having a soft gasket layer therebetween.
The NVH bridge 16 is molded-in-place to connect the lip 24 of the cover portion 12 to the flange 34 of the rail 14. The bridge 16 maintains the cover portion 12 in spaced relation to the rail 14 to prevent the generation and/or transmission of vibration and noise. Wherein the rail 14 and the cover portion 12 are constructed as separate components from one another, the rail 14 and cover portion 12 are disposed individually into a mold cavity (not shown) of an injection mold machine. The manufacturing process continues by injecting elastomeric material, such as rubber, by way of example and with limitation, into the mold cavity to form the bridge 16, thereby coupling the cover portion 12 to the rail 14. Depending on the construction of the lip 24 and flange 34, as shown in
In
In
In addition, during the molding process, a seal 248 can be molded within a channel 246 using the same elastomeric material as the bridge 216, or a different elastomeric material, as desired. The seal 248, although molded, can still remain separate and detached from the bridge 216. Otherwise, rather than molding the seal 248 in place, the seal 248 could be provided as a preformed seal and located within the channel 246 after molding the bridge 216. Although the channel 246 is represented here as being formed by a single outer leg 245, it could be molded having a pair of laterally spaced legs, as described above.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/946,436, filed Jun. 27, 2007, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60946436 | Jun 2007 | US |
