Patent Application
20120204825
1. Technical Field of the Invention
In a spark ignited internal combustion engine, the camshaft has the singular most influence over the efficiency, performance and output of an engine than any other single component. The lift, duration, lobe separation angle and timing events of both the intake and exhaust valves (whether singular or multiple in number per cylinder; and/or multiple cylinders per engine) are vital influences over how the engine performance both in output and efficiency. This invention relates to valve actuation devices and the ability to vary the valve timing of both the intake valves and the exhaust valves independently. This independent variation of valve timing allows the valve timing events to be both advanced, both retarded, or varying degrees of each, effectively varying the lobe separation angle (LSA) of the camshaft, which provides custom camshaft tailoring for specific and varying applications and demands. This invention will allow a “valve event map” to be determined, varying the intake and exhaust valve opening & closing points, and the separation of the exhaust and intake valve centerlines in crankshaft degrees, which will directly affect performance and economy. In addition, when used in conjunction with a form of modulation (to be presented in subsequent patent filings) the amount of valve lift and duration may also be varied to better achieve desired engine efficiency, emissions and/or performance.
2. Background
Internal combustion engines provide the power for the majority of modes of transportation here in the United States. In today's time, with dwindling fossil fuel supplies and environmental concerns, the emphasis placed on creating higher quality and more efficient engines has never been higher. In recent decades, there has been much emphasis placed on improving the control and operation of the valve train of an internal combustion engine due to its influence on the efficiency, emissions, power and overall performance of the engine. The primary reason that valve train has such significant effects on engine operation is that it primarily determines the volumetric efficiency of the engine. Volumetric efficiency is effectively how well the cylinder is filled with air and fuel.
The design of a valve train determines several parameters that can affect the operation of an engine Ideally, these parameters could be modified or altered real-time during the operation of the engine to meet the ever-changing requirements of the engine. One of these parameters is valve timing. Valve timing is described as the opening and closing points of valve events as measured in crankshaft degrees. The combination of intake and exhaust valve timing is significant in the way in which an engine performs. Lobe separation angle (LSA), is described as the separation angle (in degrees of camshaft rotation) between the centerline of the intake valve event and the centerline of the exhaust valve event. This parameter has numerous effects on the operation of the engine. The following is a list of some of the effects of varying LSA:
1. Broadens power band.
2. Decreases peak torque.
3. Reduces maximum cylinder pressure.
4. Decreases the likelihood of detonation.
5. Decreases cranking compression.
6. Idle vacuum is increased.
7. Idle quality is increased.
8. Piston-to-valve clearance is increased.
9. Valve overlap is decreased.
1. Narrows power band.
2. Increases peak torque.
3. Increases maximum cylinder pressure.
4. Increases the likelihood of detonation.
5. Increases cranking compression.
6. Idle vacuum is decreased.
7. Idle quality is decreased.
8. Piston to valve clearance is decreased.
9. Valve overlap is increased.
Optimal valve overlap varies substantially with engine speed and thus being able to change this parameter as engine speed changes would be very beneficial to the overall performance of an engine.
3. Related art
Until this invention, many attempts at variable valve timing had been attempted by several different inventors, including a majority of the Original Equipment Manufacturers (OEM), such as Alfa Romeo, BMW, Fiat, Chrysler, Ford, General Motors, Honda, Hyundai, Kawasaki, Lexus, Mazda, Mitsubishi, Nissan, Porsche, Suzuki, Subaru, Toyota Volkswagen, Volvo, Yamaha and others. Such devices include Okui's and Uchida's U.S. Pat. No. 6,367,435, Otobe's U.S. Pat. No. 4,876,995, Miura's U.S. Pat. No. 6,772,731, Sugiuchi's and Kamiyama's U.S. Pat. No. 5,159,905, Rhoads' U.S. Pat. No. 4,656,976, Pruzan's U.S. Pat. No. 4,716,863 and Barnard's U.S. Pat. No. 5,857,438. These lists are not exhaustive, merely illustrative. Some of these inventions are complicated with several parts that would be costly to manufacture, difficult to incorporate into the design of an engine and would likely be unreliable. Others simply do not control the valve events as desired, merely shortening or lengthening the valve event but not changing lobe separation angle. Most of these designs change valve timing with side effects of changes in valve lift and duration. Despite the number of attempts, the need for an improved variable valve timing (VVT) device still exists.
The present invention is a device consisting of distinct components, modules or sections, assembled into one assembly comprising the entire invention. The components include the block, complete with bores, the lifters, fitted to the bores, the camshaft (whether a two lobe design for use with radial type blocks or a multi intake, multi exhaust lobe camshaft for use with blocks of an inline type arrangement), a mechanism for each block to rotate angularly but independently of the other to not only vary the intake and exhaust valve timing (advance and/or retard each one independently) but also to effectively vary the lobe separation angle of the camshaft, if so desired. Hybrid arrangements of each can be incorporated with (as an example) a singular intake lobe for use with a radial type of block and a multi lobe exhaust cam for use with an inline exhaust block or vice versa. Any combination of the two is possible in the present invention. The operation of the invention is that the camshaft inside the invention's block is driven directly in some manner by the engine's crankshaft, rotating at exactly one-half the speed of the crankshaft. The camshaft inside the invention rotates such that the lobe of the camshaft moves the lifters in the bores of the block by direct pressure, causing the lifters to displace hydraulic fluid, forcing movement of the intake and exhaust valves, respectively, by hydraulic force or by direct pressure of the lifters on the respective pushrods to open and close valves. Rotating these blocks with respect to the camshaft will directly change valve timing. Rotating the blocks opposite the direction of camshaft rotation will advance the timing; rotation in the same direction of camshaft rotation will retard the timing. By retarding or advancing the exhaust valves and intake valves different amounts, one can effectively change lobe separation angle of the camshaft. The system can be designed and manufactured such that individual valves can be retarded or advanced independently of the remainder. A form of modulation (to be presented in subsequent patent filings) when using hydraulic master/slave pistons for actuation may be fitted to either this invention or the hydraulic valve actuator, thereby varying the lift and duration of either the intake valves, (collectively or independently) the exhaust valves (collectively or independently) or both. The modulation device may also be fitted independently between the variable valve timing device and the hydraulic valve actuators such that that the modulation takes place at the valve actuators.
While the following description details the preferred embodiments of the present invention, it is understood that the invention is not limited in its application to the details of construction and arrangement of the parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced in a variety of ways and methods.
This explanation is necessary to allow the examiner to see how the original patent application compares with prior art and how this invention is differentiated from all others before. This patent contains a technically accurate description and is complete in nature as to the application of technology for which patent protection is sought.
This invention differs from all previous in a variety of ways. Although previous inventions have included ideas and methods of variable valve timing (VVT), none of which allow complete, infinitely variable valve timing of the intake and exhaust valve events, independent of one another, without using multiple camshafts, multiple differing camshaft lobes per cylinder and/or changing the angular position of said camshaft(s) with respect to the relationship of the crankshaft. Some designs have used multiple differing intake or exhaust camshaft lobes per cylinder that may allow the altering of valve timing by switching between lobes or “cam switching”, as it has sometimes been called. In addition, unlike many other VVT type inventions, this invention allows variable intake and exhaust valve timing independent of one another as well as independent of lift and duration.
This invention does not require employing multiple camshafts, any of which exclusively operate intake or exhaust valves such that the valve timing can be varied independently by changing the relative angular position of these camshafts as found in Okui's and Uchida's U.S. Pat. No. 6,367,435) granted Apr. 9, 2002 among others.
This invention does not employ multiple intake or exhaust camshaft lobes per cylinder such that the valves be operated by different lobes at different times, commonly referred to “cam switching”, to change valve timing as found in Otobe's U.S. Pat. No. 4,876,995 granted Oct. 31, 1989, Miura's U.S. Pat. No. 6,772,731 granted Aug. 10, 2004, as well as Sugiuchi's and Kamiyama's U.S. Pat. No. 5,159,905 among many others of similar design and concept.
This invention allows infinitely variable intake and exhaust valve timing independent of one another, as well as independent of lift and duration. The following inventions successfully vary valve timing but with a side-effect of altering valve lift and duration. Rhoads' U.S. Pat. No. 4,656,976 granted Apr. 14, 1987, Pruzan's U.S. Pat. No. 4,716,863 granted Jan. 5, 1988, and Barnard's U.S. Pat. No. 5,857,438 granted Jan. 12, 1999, among others in similar design and concept. Also, while these inventions change the valve opening timing and valve closing timing, the centerline of the valve event is not altered. The valve events are merely lengthened or shortened such that the timing of the opening and closing of the valves may be changed. That is, the lobe separation angle (LSA) of the camshaft remains the same and therefore the relation between the centerline of the intake valve and exhaust valve events remain unchanged.
In conclusion, this invention differs from all others known in that it is able to achieve independent intake and exhaust valve timing independent of one another (not simply opening and closing but the entire valve event), independent of valve lift and duration while remaining relatively simple without employing multiple camshafts and/or switching between lobes. In effect, the lobe separation angle (LSA) and installed centerline angle (ICA) of the camshaft can be altered real-time during the operation of an internal combustion engine; thus changing the centerline of the intake and exhaust valve events relative to the crankshaft angular position and substantially improving the operation of the engine.
