Patent Grant
7210435
The present application is related to U.S. patent application Ser. No. 10/838,107, entitled “Desmodromic Valve and Adjustable Cam System,” filed on May 3, 2004 by inventor Julian A. Decuir, the content of which is expressly incorporated by reference herein in its entirety.
The present application is also related to U.S. patent application Ser. No. 11/138,611, entitled “Desmodromic Valve Retrofit System with Replaceable Cam Lobes for Adjusting Duration & Hydraulic Lifters for Reliability,” filed on May 25, 2005 by inventor Julian A. Decuir, the content of which is expressly incorporated by reference herein in its entirety.
Not Applicable
1. Field of the Invention
The present invention relates to desmodromic valve and cam systems for traditionally configured internal combustion engines which utilize pushrods. In particular, the present invention relates to a valve train and cam system which eliminates the springs found in conventional valve trains by implementing a design which utilizes cam lobes having an internal follower groove in combination with hydraulic lifter follower assemblies. The present invention also relates to camshafts which have replaceable cam lobes providing various duration/lift adjustability options.
2. Background of the Invention
Most conventional internal combustion piston driven engines utilize valve trains to induct an air/fuel mixture into the cylinders and to expel the burned air/fuel mixture from the cylinders. Typically, each cylinder is assigned at least one intake poppet valve and at least one exhaust poppet valve. The valves are typically pushed down by rockers thereby opening the valve. To close the valve, that is to pull the valve back up so that it seats, most conventional valve trains utilize a spring which concentrically surrounds the valve stem. When the valve stem is pushed down by the rocker to open the valve, the spring is compressed. When the rocker lifts off from the distal tip of the valve stem, the valve then closes when the spring decompresses, thereby, pulling the valve stem up through the valve guides until the head of the valve seats in the valve seat.
The aforementioned conventionally configured valve train systems for opening and closing the valves has proven to be highly effective and reliable in the past. However, closing the valve by the force of the spring does have some disadvantages. Most notably, pushing the valves open against the force of the springs consumes engine power. The springs in an engine's valve train induce considerable tension into the valve train because they continuously force the valve mechanism against the rocker as the camshaft rotates. In other words, the valve springs are continuously pushing the valves closed. Another disadvantage is that because the cam mechanism cannot afford to have any “bounce” from the springs, the cam profile has to be somewhat gentle, i.e., it must gently push the valve. Another disadvantage is that when the motor is turned at high RPM's, the valves can “float” and hit the piston. Valve float happens when the speed of the engine is too great for the valve springs to handle. As a result, the valves will often stay open and/or “bounce” on their seats.
To overcome these disadvantages, innovative desmodromic valve trains have evolved over about the last century; however, in a very slow technological pace and in most applications with little or limited success. The term “desmodromic” arises from the two Greek words: “desmos” (controlled or linked), and “dromos” (course or track). A desmodromic system is also known as system that provides “positive valve actuation” wherein both strokes are “controlled”. In other words, desmodromic valves are those which are positively closed by a leverage system or follower, rather than relying on the more conventional springs to close the valves. Typically, a desmodromic valve operating system utilizes a camshaft that controls both the opening and closing of the valve.
Desmodromic valve trains have several advantages over conventional spring closed valves trains. A first major advantage is that in a desmodromic valve system there is almost no wasted energy in driving the valve train. In other words, the constant force that the springs exert on the valve train is removed. Another advantage is that because there is no tension and no possibility of “bounce” in the desmodromic system, the cam profiles can be as steep as the engine designer wishes them to be. This desirable aspect allows the engine to be more powerful. Thus, the manufacturer can use radical cam grinds or profiles for increasing performance. Another advantage is that when the motor is turned at high RPM's or even over-revved, the valves are still controlled, whereas when the valves are returned by springs the valves sometimes can “float” and hit the piston.
Nevertheless, even though desmodromic valve trains have the aforementioned advantages, they have had limited success in large scale commercial applications due to reliability issues, complexity of design, and valve train binding to name a few reasons. For instance, one of the major disadvantages of desmodromic valve trains is their sensitivity to change in size of the separate components of the system. In particular, the individual components (valves, cam lobes, rockers, etc.) of the valve train become enlarged at elevated temperatures because of thermal expansion of the metallic components. Also, the components of the valve train wear, thereby, decreasing the size of the components. As a cumulative result, of both cyclic expansion and contraction of the components caused by heating, and the shortening of components caused by wear, the tolerances of the valve train can change. The end results are components such as valves which do not seat properly, or unwanted binding in the valve train. Therefore, one of the major difficulties of prior art desmodromic valve train systems is the critical and accurate adjustment of various working components to ensure that the components operate together as intended without being subjected to binding, tension or excessive friction which results from the change of size in the individual components.
Another one of the problems with the aforementioned desmodromic valve train systems is that they have not been adapted to be installed or “retrofit” into existing modern conventional pushrod engines. That is to say, the aforementioned prior art desmodromic systems appear to utilize specialized designs which requires unique heads, valve trains and/or engine blocks. Thus, to use the aforementioned desmodromic systems, entirely new engine platforms have to be designed and built. Unfortunately, however, most manufacturers are not willing to invest the sizeable amounts of capital to build such desmodromic engines, or much less, market vehicles with engine platforms which have not been proven or which have had a past history for reliability problems.
Therefore, it would be advantageous to provide a reliable desmodromic valve and cam system that may be either integrated into a new engine design or of which may be retrofit onto an existing engine design without requiring the head or valves to be replaced. Furthermore, it would desirable to provide the aforementioned desmodromic system for a conventional pushrod engine, considering the popularity and success of the pushrod type platform. By providing a retrofit desmodromic system for pushrod engines, the cost of the upgrade could be maintained lower than that of a system which requires the entire head and valve train to be replaced. It would further be advantageous to provide a desmodromic valve and cam system which is simple and inexpensive to manufacture. Furthermore, it would be desirable to provide a desmodromic valve and cam system which would have interchangeable cam lobes such that the cam duration/lift could be adjusted. With such a feature, various cam lobes having varying profiles, durations, lift, etc. could be utilized on the same system by merely replacing the cam lobes. Such features would provide a wide array of adjustability in regards to being able to tune the engine's performance characteristics.
The present invention provides a desmodromic valve and cam system which utilizes hydraulic lifters and replaceable cam lobes that may be integrated into a new engine design or of which may be retrofit into an existing conventional pushrod engine without requiring the engine block, head or valves to be replaced or reworked. The present invention operates more efficiently than conventional valvetrains since binding tension is reduced from the valvetrain resulting in greater horsepower, better fuel economy and reduced emissions; while the incorporation of hydraulic lifters or the like makes the present invention desmodromic system more reliable. By providing a retrofit desmodromic system, the cost of installing the present invention into a vehicle is significantly reduced. Furthermore, the present invention is simple to manufacture and may be retrofit onto conventional pushrod type engines which are one of the most popular and successful automotive engines ever produced. Furthermore, the present invention's interchangeable cam lobe kits may be utilized on the same system, thereby, providing a wide array of adjustability in regards to being able to tune the engine's performance characteristics.
According to a first embodiment of the present invention, a desmodromic valve and cam system is provided which is adapted to be installed into an internal combustion pushrod engine comprising an engine block and at least one head which utilizes at least one intake and exhaust valve per cylinder. The system may include, but is not limited to a main camshaft assembly adapted to be received within a plurality of journals disposed internally within the engine block. The camshaft assembly includes a cam lobe assigned to each valve, where each cam lobe is adapted to be removably installed onto a main camshaft. Each cam lobe is defined by a pair of opposing sides, perimeter edge, mounting hole disposed through the opposing sides in a normal orientation, and follower groove formed in at least one side of the cam lobe which is representative of a desired lift and duration performance characteristic. Also, a valve connector assembly may be installed onto a distal tip of each valve. Furthermore, a rocker is provided which is defined by a valve movement end and a pushrod connecting end, wherein the valve movement end is adapted to be mechanically linked to a respective valve connector assembly such that the rocker can either push down or pull up a respective valve. The pushrod connecting end is adapted to be mechanically linked to an upper distal end of a pushrod such that the rocker can either push down or pull up a respective pushrod. Moreover, the system may include hydraulic lifter follower assembly assigned to each valve which is adapted to be received within a lifter seat disposed within the engine block, wherein each lifter assembly may have a pin or any other means disposed on a distal end thereof which is adapted to engage and track a respective follower groove on a respective cam lobe. Additionally, the system may include pushrods assigned to each valve, wherein each pushrod has an upper and lower distal end, the upper distal end being mechanically linked to the pushrod connecting end of a respective rocker and the lower distal end being mechanically linked to a respective hydraulic follower lifter.
As a result of the aforementioned desmodromic system configuration, when the main camshaft assembly rotates, the cam lobes impart reciprocal motion to the hydraulic lifters, which impart reciprocal motion to the pushrods, which impart a rocking motion to the valve movement end of the rocker, which results in each valve being reciprocally moved upwards to a closed position or downwards to an open position as a function of each cam lobe's lift and duration. Moreover, this is all accomplished without the need to use valve springs to return the valves to a closed position. And, according to another aspect of the present invention, the hydraulic lifter follower assemblies automatically adjust valve lash for each respective valve.
According to another aspect of the present, the valve connector assembly comprises a valve connecting fitting comprising a rocker connecting end portion with a receiving slot formed therein which is adapted to slidably and rotatably receive a connecting pin from the valve movement end of the rocker; and a lower fitting portion adapted to receive a valve keeper fitting, the lower fitting portion including a hollow valve tip seat adapted to receive the distal end of the a respective valve; a valve keeper fitting adapted be fastened to the lower fitting portion; and a pair of valve keepers.
In another aspect of the present invention, the valve keeper fitting has a bore disposed there through for receiving a valve stem from each respective valve, while the keeper fitting further includes an upper portion having a frustro-conical shaped seat formed therein; and a lower portion having a flange adapted to be received by a tool; wherein each respective valve has at least one radial groove formed on the valve stem for receiving the pair valve keepers; and wherein the valve keeper fitting is adapted to be installed into the lower fitting portion of the valve connecting fitting such that the pair of valve keepers are received into the frusto-conical shaped seat and maintained by a compression fit.
Moreover, another aspect of the present invention, the valve connector assembly comprises a main valve connector body adapted to be connected to the distal tip of a respective valve, the body defined by a center axis, a lower end having a radial flange with a hole disposed there through for receiving the upper end of the valve, an upper end having a pair of opposing yokes arms projecting upwards, each arm having a pin receiving hole, and an internal cavity disposed through the body about the center axis from the upper end and terminating within the body to form a backside of the radial flange about the center axis; a first connecting pin installed into the pin receiving holes of the yoke arm; a linking member having a pair pin receiving holes, the linking member being rotatably connected to the second connecting pin via one of the pin receiving holes and further rotatably connected to the valve connector pin disposed on the valve movement end of the rocker via the other pin receiving hole. According to yet another aspect of the present invention, a coil spring may be positioned if desired between the distal tip of the valve stem and the valve connector for dampening shock imparted to the valve.
According to another aspect of the present invention, the valve connector assembly comprises a main valve connector body adapted to be connected to the distal tip of a respective valve, the body defined by a center axis, a lower end having a radial flange with a hole disposed there through for receiving the upper end of the valve, an upper end having a pair of opposing yokes arms projecting upwards, each arm having a pin receiving hole, and an internal cavity disposed through the body about the center axis from the upper end and terminating within the body to form a backside of the radial flange about the center axis; a first connecting pin installed into the pin receiving holes of the yoke arm; a linking member having a pair pin receiving holes, the linking member being rotatably connected to the second connecting pin via one of the pin receiving holes and further rotatably connected to the valve connector pin disposed on the valve movement end of the rocker via the other pin receiving hole.
According to other aspects of the present invention, the valve connector further comprises at least one first wave washer adapted to be received by the valve stem, the first wave washer being positioned adjacent the backside of the radial flange; a pair of frustro-conically shaped valve keepers adapted to be received by at least one radial groove formed on the valve stem for receiving the pair of valve keepers, the valve keepers being positioned over the at least one first wave washer; at least one second wave washer adapted to be received by the valve stem, the second wave washer being positioned over the valve keepers; and at least one locking retainer adapted to be received by the valve stem, the at least one locking retainer positioned over the at least one second wave washer.
According to another aspect of the present invention, each rocker may comprise a main body having a bored disposed there through for receiving a pair of rocker bearings and a rocker shaft which is adapted to be mounted to a mounting stud protruding from the head; a valve movement end comprising a pair of opposing arms having a receiving slot formed there between and a valve connecting pin transversely spanning across both arms, the been being adapted to be rotatably received by a respective valve connector assembly; and a pushrod connecting end which has a threaded hole which is adapted to receive a ball joint assembly.
According to another aspect of the present invention, the hydraulic lifter follower assembly may comprise a generally cylindrically-shaped lifter body having a cylindrical cavity disposed therein with an opening to the cavity formed on one end thereof, the lifter body having a notched portion disposed on the other end thereof, the notched portion including a groove pin or any other equivalent means to be received by a respective follower groove from a cam lobe; a coil spring concentrically adapted to be retained internally within a cylindrical cavity; a cylindrical shaped lower ball seat adapted to be retained internally within the cylindrical cavity above the coil spring; an upper ball receiving seat sleeve adapted to be received by a respective pushrod; and a lifter cap adapted to be received by the respective pushrod, the lifter cap further adapted to be attached to the opening to the cavity formed on the end of the lifter body; wherein oil is fed through each respective pushrod into the cavity formed in the lifter body; and wherein the lifter acts as a dampener that maintains a constant, yet adjustable tension, to the rocker.
According to another aspect of the present invention, the camshaft assembly further may include a drive hub removably attached to one end of the camshaft assembly adapted to receive a timing drive sprocket; a timing gear hub removably attached to the camshaft assembly proximate the drive hub; a plurality of camshaft bushings removably attached to the camshaft assembly; and an end hub removably attached to the other end of the camshaft assembly.
According to yet still another aspect of the present invention, the mounting hole of each cam lobe has a cam lobe key receiving slot formed along a length of the mounting hole; and the main camshaft has a camshaft key receiving slot disposed in an exterior surface of the shaft for each respective cam lobe; wherein a key is installed into the cam lobe key receiving slot for each cam lobe and a respective camshaft key receiving slot is assigned to each respective cam lobe for rigidly securing the cams lobes to the main camshaft.
According to another aspect of the present invention, the desmodromic valve and adjustable cam system may further comprise a plurality of cam lobe assembly kits adapted to be installed and removed onto the main camshaft, wherein each kit provides a differing cam profile offering a unique set of lift and duration tuning characteristics for each respective kit.
According to another embodiment of the present invention, a desmodromic valve and cam system retrofit kit for a pushrod engine is provided. The kit may include, but is not limited to, a main camshaft assembly having removable cam lobes, each cam lobe having mounting hole formed there through, and follower groove formed in at least one side of the cam lobe; a valve connector assembly adapted to be installed onto a distal tip of each valve of the engine; a rocker having a valve movement end and pushrod connecting end, the valve movement end being adapted to be mechanically linked to a respective valve connector assembly such that the rocker can either push down or pull up a respective valve and the pushrod connecting end being adapted to be mechanically linked to an upper distal end of a pushrod such that the rocker can either push down or pull up a respective pushrod; a hydraulic lifter follower assembly assigned to each valve which is adapted to be received within a lifter seat disposed within the engine block, each lifter assembly having a connecting means disposed on a distal end thereof which is adapted to engage and track a respective follower groove on a respective cam lobe; and a pushrod assigned to each valve, each pushrod having an upper and lower distal end, the upper distal end adapted to mechanically linked to the pushrod connecting end and the lower distal end adapted to be mechanically linked to a respective hydraulic follower lifter. As a result of the configuration of the aforementioned kit, the conventional valve springs may be moved from the engine's valvetrain, thereby increasing horsepower, fuel efficiency while reducing emissions.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawings.
The present invention is further described in the detailed description that follows, by reference to the noted drawings by way of non-limiting examples of preferred embodiments of the present invention, in which like reference numerals represent similar parts throughout several views of the drawings, and in which:
The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.
The present invention provides a desmodromic valve and adjustable cam system for a conventional pushrod combustion engine which eliminates the use of valve springs normally used to close poppet valves. The system may be retrofit onto an existing engine design or which the features thereof may be integrally included into an entirely new engine design. For instance, the present invention may be retrofit to existing engine designs, such as those used in conventional pushrod V8's, V6's, in-line 4's, in-line 6's or the like. Moreover, the present invention may be utilized with gasoline type engines or diesel engines. The present invention may also utilize a stock engine block, a stock head and stock valves without any modifications. Also, the scope of the invention should not be limited to the exemplary embodiments disclosed in the instant specification. Rather, the exemplary embodiments of the present invention desmodromic cam and valve system should be viewed as merely a few embodiments of numerous engine systems and platforms which may utilize the fundamental concepts taught and disclosed in the instant application.
Referring now to
Still referring to
Still referring to
Still referring to
Although the invention has been described with reference to several exemplary embodiments, it is understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the invention in its aspects. Although the invention has been described with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed; rather, the invention extends to all functionally equivalent structures, methods, and such uses are within the scope of the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5347965 | Decir | Sep 1994 | A |
| 5394843 | Decir | Mar 1995 | A |
| 5732670 | Mote, Sr. | Mar 1998 | A |
| Number | Date | Country | |
|---|---|---|---|
| 20070006835 A1 | Jan 2007 | US |
