Patent Application
20060075979
The present invention is generally related to reciprocating internal combustion engines and, more particularly, is related to a substitute cylinder head for mounting on an internal combustion engine.
In a reciprocating internal combustion engine, the performance of the engine is a complex balance of competing and differing design characteristics. One way that an engine's performance can be enhanced is to improve the engine's ability to breathe, which requires improving the engine's ability to pass air and fuel into a cylinder and to pass exhaust gases out of the cylinder. Improving the engine's ability to pass air and fuel into a cylinder results in a greater performance improvement than improving the engine's ability to pass exhaust gases from the cylinder because it is typically more difficult to draw air and fuel into a cylinder than it is to push exhaust gases out of the cylinder.
Many conventional engines use a cylinder head that has a single inlet valve and a single exhaust valve per cylinder. Each valve is actuated by a rocker arm that is driven by the oscillatory motion of a lobe, lifter, and push-rod combination, where the push-rod oscillates up and down due to the lifter riding on the lobe of the cam shaft. When a valve is open gases flow through it. In the case of the inlet valve, these gases are air or an air/fuel mixture. In the case of the exhaust valve, these gases are exhaust gases.
There are various ways to design and control a single valve such that more gas passes by the valve when the valve is open. One design is to increase the diameter of the valve, but larger valves generally require more mass. Valves that have more mass require stiffer springs to bias the valve into its closed position than do valves that have less mass. Consequently, larger valves tend to degrade engine performance at high revolutions per minute (RPM) due to the increased mass.
Another way to increase the gas flow past an open valve is to hold the valve open longer. Typically, the length of time that a valve is open depends upon the shape of the lobe that is driving the valve. However, there are problems associated with having the valve open for a long period time. Generally, when valves are open for a long period of time, the engine does not run well at low RPMs.
Instead of using only one valve per cylinder for inlet or exhaust purposes, high performance engines typically use multiple inlet or exhaust valves per cylinder to improve the engine's performance. Generally, each of the valves is individually driven, meaning one lobe, lifter, and push-rod combination drives each rocker arm, which drives each valve. Each one of the multiple valves is usually of smaller mass than a single valve, and therefore the springs for the multiple valves may not be as stiff as the spring for a single valve. However, a disadvantage of engines that employ multiple inlet or exhaust valves per cylinder is that they generally use more parts, such as lifters, lobes and push-rods, than do engines that employ only one inlet and exhaust valve per cylinder. Consequently, the engine can be less reliable and require more maintenance because more parts can malfunction.
Fewer parts may be used in an engine having multiple inlet or exhaust valves by coupling the valves together via a bridge. In such an engine, a single lobe, lifter, and push-rod combination drives a single rocker arm which drives both valves in unison via the bridge. One problem with using coupled valves actuated via a bridge is that friction between the rocker arm and the bridge is likely to cause the bridge to wear. Furthermore, the rocker arm may apply an undesirable torque to the bridge that may prevent the valves from opening and closing properly.
Some owners of small-block Chevrolet engines or other standard original equipment manufacturer (OEM) engines would like to increase the engine's power output by adding a valve to a cylinder of the engine. However, this modification cannot be made economically at the present time, because the modification would require extensive re-working of the engine structure. Thus, a need exists for an improved cylinder head assembly that improves engine performance by increasing gas flow into or out of a cylinder. A need also exists for a replacement cylinder head assembly that can replace an OEM cylinder head assembly so as to add a valve to each cylinder, improving the existing engine's performance.
In a typical internal combustion piston engine, each valve of the engine is actuated via a single rocker arm, push-rod, lifter, and lobe. The lobe riding on the cam shaft transmits movement of the cam shaft to the lifter and push-rod, causing the rocker arm to actuate the valve. In such an engine, adding valves requires adding rocker arms, push-rods, lifters, and lobes, increasing the number of parts that could malfunction and require maintenance. Alternatively, multiple valves may be coupled to a bridge that is actuated via a single rocker arm, push-rod, lifter, and lobe combination. Such an engine uses fewer parts, but friction between the rocker arm and the bridge may wear the bridge, or the rocker arm may apply an undesirable torque to the bridge preventing the bridge from remaining properly aligned with the valve stems.
In embodiments disclosed below, a coupled valve assembly may be used to actuate multiple valves using a single rocker arm, push-rod, lifter, and lobe combination. The coupled valve assembly uses a bridge that has features to minimize wear to the bridge or transverse force on the bridge. In one embodiment, the couple value assembly may be added to an original equipment manufacturer (OEM) engine to increase the number of valves in a cylinder with minimal disruption to the engine structure. In another embodiment, the coupled valve assembly may be used in conjunction with an OEM engine such that multiple valves may be actuated using a single rocker arm that will not wear or torque the bridge.
Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Referring now in more detail to the drawings, in which like numbers refer to the same parts in the several views,
Referring to
Referring to
Referring to
Referring again to
The cylinder head assembly 20 illustrated in
Engine 10 has at least one intake duct 52 and at least one exhaust duct 54 in each cylinder 16, but each cylinder 16 may have more than one of either type of duct. The exhaust duct 54 is in pneumatic communication with the exhaust manifold 18. Exhaust gases from cylinder 16 are ported through the exhaust duct 54 by the opening and closing of the valve of the single valve assembly 26. Therefore, in this embodiment, the cylinder 16 has a single exhaust valve actuated via the single valve assembly 26.
Further, in
As shown in
While the embodiment shown in
While each valve in a conventional engine requires its own rocker arm, push-rod, lifter, and lobe, the coupled valve assembly actuates multiple valves using a single rocker arm 28, push-rod 82, lifter 80, and lobe 78, which in turn cause valves 30A and 30B to remove from and return to their valve openings 56A and 56B. As the cam shaft 76 rotates such that the lobe 78 moves upward, the lifter 80 rides over the lobe 78 causing the lifter 80 to rise. The motion of the lifter 80 causes the push-rod 82 to reciprocate upwardly. The upward motion of the push-rod 82 causes the cam end 66 of the rocker arm 28 to be raised, thereby causing the bridge end 68 to be lowered. As the bridge end 68 lowers, the roller 70 travels along the upper platform 46 of the bridge 32, pushing the bridge 32 downward. Path 86, shown in
As the lifter 80 rides down the lobe 78, the springs 38A and 38B bias their valves 30A and 30B to the closed position, which closes the cylinder 16 from the duct. The springs 38A and 38B also respectively engage plates 40A and 40B to return the bridge 32 and the bridge end 68 of the rocker arm 28 to their upward positions. In this manner, the rotation of cam shaft 76 causes the rocker arm 28 to pivot about the base 64 such that the valves are removed from and returned to their openings 56A and 56B. Arc 84, shown in
As the rocker arm 28 oscillates about the base 64, the rocker arm 28, bridge 32, and valves 30A and 30B should remain in general alignment so that the valves create an effective seal between cylinder 16 and the duct. For this reason, the rocker arm 28 and bridge 32 are designed to minimize the creation and transfer of transverse force from the rocker arm 28 to the bridge 32 and from the bridge 32 to the valve stem ends 42A and 42B. Otherwise, the transverse force on the valve stem ends 42A and 42B might inhibit discs 34A and 34B from aligning with openings 56A and 56B, affecting the seal between the cylinder 16 and the duct.
The rocker arm 28 contacts the bridge 32 using a roller 70 to minimize transverse force applied to the bridge 32. As roller 70 contacts bridge 32, it travels a path 86 that is parallel to the length and bisects the width of upper platform 46, as shown in
To further minimize transverse force on the bridge 32, the rocker arm 28 and the bridge 32 are generally aligned as shown in
If the rocker arm 28 does apply a transverse force to the bridge 32, the bridge 32 and the valve stems 36A and 36B remain in general alignment, because the valve stems ends 42A and 42B are free to travel along the bridge's lower surfaces 50A and 50B. The bridge 32 contacts valve stem end 42A somewhere along the portion of the lower surface 50A at opposed end 44A having a concave radius of curvature. The radius of curvature ensures that the longitudinal center axis of valve stem 36A remains perpendicular to a plane that is tangential to the point of contact between the valve stem end 42A and the lower surface 50A. Therefore, valve stem 36A moves in the plane of motion of the rocker arm 28. Similarly, the bridge 32 contacts valve stem end 42B somewhere along the portion of lower surface 50B at opposed end 48B having a concave radius of curvature, ensuring the plane of motion of valve stem 36B is parallel to the plane of motion of rocker arm 28.
Because valve stem ends 42A and 42B have freedom to travel along the lower surfaces 50A and 50B of bridge 32, transverse force on the bridge or any other disturbance in the system may cause bridge 32 to slip off of valve stem ends 42A and 42B. For this reason, retaining walls 48A and 48B create cavities 96A and 96B that enclose valve stem ends 42A and 42B. Bridge 32 is therefore retained on the valve stem ends 42A and 42B.
The roller 70 also minimizes friction between the rocker arm 28 and the bridge 32. Therefore, the bridge 32 is less likely to require replacement due to wear.
As is mentioned above, it is often desirable to increase the power output of an engine by increasing the number of inlet valves in cylinders of the engine. However, such a modification often requires extensive re-working of the engine. For example, a cylinder head having one inlet valve and one exhaust valve per cylinder may have a push-rod, lifter, and lobe for each valve. Adding inlet valves may require engine modification because additional lobes, lifters, and push-rods must be added to the engine to actuate the new valves. However, the cylinder head assembly 20 may be used to replace the cylinder head of the engine, adding valves to the engine without modifying it.
The cylinder head assembly 20 may be built to conform to any engine architecture, so that the cylinder head assembly 20 may be connected to the engine after the cylinder head of the engine is removed. However, the cylinder head assembly 20 also contains at least one coupled valve assembly 24 that allows two valves to be actuated via a single rocker arm, push-rod, lifter, and lobe combination. By removing the engine's cylinder head of the engine and replacing it with the cylinder head assembly 20 containing at least one coupled valve assembly 24, additional valves may be added to the engine that are actuated via the engine's parts. When the additional valves are inlet valves, the power output of the engine will likely increase as a result of increased flow into the cylinder.
In one embodiment, the replacement cylinder head assembly 20 is adapted to fit onto a “small block” Chevrolet engine, which is a V8-engine with 16 valves. The horsepower of the engine may be increased by removing the OEM cylinder head and replacing it with the replacement cylinder head assembly 20 that contains coupled valves inlet valves 30A and 30B driven by a single lobe 78 on the cam shaft 76. Consequently, inlet valves may be added without increasing the number of lobes, lifters, and push-rods over the number used in the OEM engine.
In many embodiments, the cam, lobes, lifters, and push-rods of the engine may be used with the cylinder head assembly 20. In some embodiments, the push-rod 82 of the engine 10 may be replaced with a replacement push-rod of a different length to compensate for the change in height between the cylinder head 22 and the rocker arm 28. In embodiments where the push-rod 82 is replaced, the replacement push-rod will engage the lifter 80 in substantially the same manner as the replaced push rod, but the replacement push-rod itself will be slightly longer in length. Note, however, that replacing the push-rod 82 does not affect the two-to-one relationship between the valves 30A and 30B and the push-rod 82.
In other embodiments, the cylinder head assembly 20 may be implemented originally on an engine. Using at least one coupled valve assembly 24 enables an engine manufacturer to produce an engine 10 having the performance characteristics associated with multiple inlet and/or exhaust valves without an independent driving mechanism for each valve. Thus, the manufacturer may reduce the number of lobes, lifters and push-rods using a coupled valve assembly 24.
Those skilled in the art will recognize that in alternative embodiments the rocker arm 28 may be driven by an overhead cam where the cam shaft 76 is above the cylinder head 22 instead of beneath it.
It should be emphasized that the above-described embodiments, particularly any preferred embodiments, are merely possible examples of implementations set forth for a clear understanding of the present disclosure. Variations and modifications may be made to the above-described embodiments without departing from the spirit and principles of the disclosure. All such modifications and variations are intended to be included within the scope of this disclosure and to be protected by the following claims.
This application claims the benefit of co-pending provisional U.S. Patent Application 60/616,721, filed Oct. 7, 2004.
| Number | Date | Country | |
|---|---|---|---|
| 60616721 | Oct 2004 | US |
