Variable Geometry Cam Shafts For Multiple-Cylinder Internal Combustion Engines

Abstract

A method of conserving fuel in the operation of multi-cylinder internal combustion engines. The present method described here allows a portion of the cylinders of an internal combustion engine to be de-activated when less power is required, thus allowing the engine to provide full power when required, or less power with substantial fuel savings. The present method does so by altering the normal operation of intake and exhaust valves by leaving the intake valve at least partially closed, and the exhaust valve at least partially open. The present method overcomes numerous problems in the prior art, such as excess load placed on the engine caused by trapped gases, damaging thermal gradients across the engine block, and difficulty of retrofitting existing engines.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/519,637 filed 26 May 2011, the entire contents and substance of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to internal combustion engine valve cams, and particularly variable geometry valve cams that allow cylinders to be shut down during periods of low power demand.

2. Description of the Related Art

Internal combustion engines are typically designed for a specific mechanical load. In many applications, particularly transportation, internal combustion engines are required to operate at a wide range of power loadings. By way of example, and not limitation, a pick-up truck requires little power to maintain highway speed, but considerably more to accelerate from a stop, and even more if towing a trailer. Aircraft engines are similarly required to operate at a variety of power settings in the normal course of operations, such as between take-off, cruise, and landing. This presents a technical dilemma. When the engine is powerful enough to handle high power demands, it inherently has an excess of power available during periods requiring less power, and thus wastes fuel. Conversely, where the engine is built to meet only low power demand conditions efficiently and economically, it fails to handle high power demands satisfactorily. Thus, there is a need for an internal combustion engine that is capable of adjusting its power output in a way that conserves fuel, yet provides sufficient power during periods of high power demand.

Previous attempts have been made to overcome the above-described dilemma by periodically changing the number of operating cylinders as engine load conditions vary. Examples of these attempts are found in U.S. Pat. Nos. 2,250,814; 2,394,738; and 2,652,038. These patents disclose closing all the valves to selected combustion chambers in order to render them inoperative during periods of low power demand. By doing so, these cylinders trap a volume of gas that is repeatedly compressed and expanded with the movement of the piston. This repetitive compression and expansion imposes an additional load on the engine, thus reducing its overall efficiency and cancelling out a portion of the efficiency gains sought by deactivating the cylinders. Other patents such as U.S. Pat. No. 2,673,617 disclose using multiple throttle valves to accomplish the same purpose. Other patents such as U.S. Pat. Nos. 2,114,655; 1,121,114 disclose coupling and un-coupling the driveshaft to the portion of the engine to be deactivated. Though these approaches were feasible as modifications to automobile engines of the 1930's and -40's, they are impractical and inefficient to incorporate into modern internal combustion engines.

What is needed, therefore, is a method of de-activating a number of cylinders in an internal combustion engine in a way that does not impose an additional load on the engine. It would also be desirable for such a method to be capable of being retrofitted onto existing engines without needing to either disassemble or modify the engine block. Finally, it would be desirable for such a system to be capable of maintaining an appropriate operating temperature in the deactivated cylinders to prevent excessive cooling, and undesirable thermal gradients across the engine block. It is to these needs that the present invention is directed.

SUMMARY OF THE INVENTION

Embodiments of the present invention relate to altering the number of cylinders in operation in an internal combustion engine by modifying the operation of intake and exhaust valves. When a cylinder is de-activated, the normal operation of the intake and exhaust valves are interrupted. The exhaust valve is left in the open position, and the intake valve is left in the closed position. In this way, little to no volume of gas is trapped, and thus likely not repeatedly compressed. When re-activated, the intake and exhaust valves return to a normal operating cycle.

In some embodiments of the present invention, a microcontroller or similar device monitors the power loads placed on the engine, and can de-activate cylinders during periods of low power loading, and re-activate cylinders during periods of relatively higher power loading. By so doing, fuel can be conserved and appropriate levels of power made available to the rest of the machinery at all times.

In some embodiments of the present invention, the exhaust valve is at least partially closed when the piston in the cylinder nears its upper most position. In this way, the piston is prevented from colliding with the otherwise open exhaust valve.

In some embodiments of the present invention, the intake valves are left closed, and the exhaust valves left open by the inclusion of additional cams, axially adjacent to the normal operating cams. The additional intake cam is shaped such that the valve will remain closed throughout the engine cycle, and the exhaust cam, shaped such that the vale will remain open throughout the engine cycle. When the cylinder is de-activated, the intake and exhaust cam shafts are axially translated to engage the additional cams with the cylinder valves via rocker arms, push rods, or similar devices.

In some embodiments of the present invention, the amount of fuel delivered to the de-activated cylinders is reduced. Particularly in fuel-injected-type engines, this prevents fuel from being wasted or damaging the engine, but the same concept applies to other types of engines, such as carbureted engines.

In some embodiments of the present invention, the device is capable of being retrofitted on existing modern internal combustion engines without modifying or disassembling the engine block. Because many embodiments of the present invention only affect the operation of the intake and exhaust valves, the modifications can be done at the cylinder heads.

These and other objects, features and advantages of the present invention will become more apparent upon reading the following specification in conjunction with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE FIGURES

The various embodiments 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 various embodiments of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 show details of the geometrically modified intake valve cam lobe and the normal cam lobe.

FIG. 1b shows a front view of the assembly with the cam shaft attached to the geometrically modified valve cam lobe and the normal lobe.

FIG. 1c shows a side view of the shaft geometrically modified valve cam lobe and the normal valve cam lobe;

FIG. 2 shows perspective details of exhaust valve normal cam lobe and geometrically modified cam lobe and the camshaft.

FIG. 2b is a frontal view of the normal exhaust cam lobe and the geometrically modified exhaust cam lobe attached to valve cam shaft.

FIG. 2c shows a side view of the exhaust valve cam lobe assembly with normal cam lobe followed by geometrically modified cam lobe.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Although preferred embodiments of the invention are explained in detail, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the invention is limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiments, specific terminology will be resorted to for the sake of clarity.

It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.

Also, in describing the preferred embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value.

By “comprising” or “comprising” or “including” is meant that at least the named compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

It is also to be understood that the mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.

A preferred embodiment of the present invention can comprise a variable geometry intake cam shaft, a variable geometry exhaust shaft, and a control mechanism for adjusting the cam geometry. Embodiments of the present invention enable one or more cylinders to be de-activated by altering the normal operation of intake and exhaust valves. The intake valves are left at least partially closed and the exhaust valves left at least partially open while the cylinder is de-activated. This allows the engine to conserve fuel while maintaining the operating temperature of the de-activated cylinders by drawing hot exhaust gases from the exhaust manifold into the cylinder.

In a preferred embodiment of the invention, the de-activation and re-activation of cylinders is performed by a moveable cam shaft (for single-overhead cam shaft engines) or shafts (for dual-overhead cam shaft engines) connected to the intake and exhaust valves. Each cam used for normal operation has a second cam immediately adjacent to it along the cam shaft axis. For example, FIG. 1 shows an intake valve cam arrangement with an ordinary cam for normal operation 12 and a second cam which leaves the intake valve closed no matter the angular position of the cam shaft 11. Similarly, FIG. 2 shows an exhaust valve cam arrangement with an ordinary cam for normal operation 14, and a second cam which leaves the exhaust valve open no matter the angular position of the cam shaft 15. These cam shafts can be connected to a mechanical system that allows the cam shaft to be translated axially to de-activate or re-activate a cylinder. Such axial translation can be accomplished by electric motors, other electromechanical actuators, hydraulically, pneumatically, or any other practical means that would be obvious to one of ordinary skill in the art.

In addition to manipulation of the functioning of the intake and exhaust valves, example embodiments in fuel-injected-type engines may require means for decreasing fuel flow to deactivated cylinders while the cylinder. In example embodiments in carbureted engines, if necessary, decreasing fuel flow to de-activated cylinders may be accomplished by various means well-known in the art, such as separately controlled throttle-bodies, separate carburetors, and other similar methods. Alternatively, example embodiments in carbureted engines may not affect fuel flow at all, and instead rely on the intake manifold to redirect fuel to the activated cylinders.

In some embodiments of the present invention, if an exhaust valve is left open in a de-activated cylinder, the piston will collide with the exhaust valve when it is in the uppermost position. For this reason, in some embodiments, the exhaust valve will at least partially when the piston approaches the top of the cylinder to prevent such collisions.

In some embodiments of the present invention, a controller de-activates cylinders during periods of low power demand, to conserve fuel. Alternatively, during periods of relatively higher power demand, one or more de-activated cylinders can be re-activated by the controller to provide additional power. In an example embodiment a computerized electronic control unit can monitor engine parameters such as: manifold pressure, engine temperature, engine torque, transmission position, or any other parameter essential to the proper and safe operation of the modification. Based on these engine parameters, the controller can activate the mechanism in a preprogrammed way to improve fuel efficiency or power availability.

In some embodiments of the present invention, the method can be performed by a system retrofitted on an existing internal combustion engine without modifying or disassembling the engine block. The system operates primarily by manipulating the intake and exhaust valves, thus modifications need only be made at the cylinder heads. In a preferred embodiment, an existing internal combustion engine can be retrofitted with a variable-geometry cam shaft comprising cams similar to those in FIGS. 1 and 2, comprising two adjacent cams. Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention.

While several possible embodiments are disclosed above, embodiments of the present invention are not so limited. For instance, the valve opening and closing could be controlled via pneumatic, hydraulic, or other means. Additionally, the cam shaft itself could be stopped completely with the intake valve closed, and the exhaust valve fully or partially open. Another possible embodiment would utilize means for disconnecting the rocker arm, push rod, or similar assembly from the cam shaft, leaving the intake valve at least partially closed, and the exhaust valve at least partially open.

The specific configurations, choice of materials, and the size and shape of various elements can be varied according to particular design specifications or constraints requiring a device, system, or method constructed according to the principles of the invention. Such changes are intended to be embraced within the scope of the invention. The presently disclosed embodiments, therefore, are considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.

Claims

1. A method for de-activating and re-activating at least a portion of the cylinders in an internal combustion engine comprising a plurality of cylinders, each having intake and exhaust valves, each cylinder having a normal operating cycle wherein the valves open and close at various times during the cycle:

de-activating at least a portion of the cylinders by maintaining the exhaust valves at least partially open, and the intake valves at least partially closed; and

re-activating that portion of the cylinders by returning the intake and exhaust valves to the normal operating cycle.

2. The method of claim 1, further comprising responding to a reduced power demand placed on the engine by activating or de-activating a cylinder.

3. The method of claim 1, wherein de-activating a cylinder includes at least partially closing the exhaust valve when the piston nears its uppermost position.

4. The cylinder receiving an amount of fuel, the method of claim 1, comprising reducing the amount of fuel delivered to the de-activated cylinder.

5. An apparatus for de-activating and re-activating cylinders of an internal combustion engine, each cylinder having intake and exhaust valves, comprising:

an intake valve assembly in communication with intake valves on a plurality of cylinders, having a normal operating mode allowing normal operation of the intake valves of the plurality of cylinders, and a de-activated mode at least partially closing the intake valves of the plurality of cylinders throughout the combustion cycle;

an exhaust valve assembly in communication with exhaust valves of a plurality of cylinders, having a normal operating mode allowing normal operation of the exhaust valves of the plurality of cylinders, and a de-activated mode at least partially opening the exhaust valve throughout the combustion cycle; and

a controlling assembly for the control of the intake and exhaust valve assemblies.

6. The apparatus of claim 5, wherein the intake and exhaust valve assemblies are adjustable cams in communication with the intake and exhaust valves.

7. The apparatus of claim 5, wherein the controlling assembly is able to place the intake and exhaust valve assemblies in the de-activated mode during periods of low power loading on the engine, and able to place the intake and exhaust valve assemblies in the normal operating mode during periods of relatively higher power loading on the engine.

8. The apparatus of claim 6, wherein the intake adjustable cams comprise two cams connected axially, one allowing normal operation, the other leaving the valve at least partially closed, and wherein the exhaust adjustable cams comprise two cams connected axially, one allowing for normal operation, the other leaving the valve at least partially open, and where the controlling assembly is capable of axially translating the cam shaft.

9. The apparatus of claim 7, wherein the controlling device includes an electronic microcontroller device.

10. The apparatus of claim 8, wherein the controlling assembly for axially translating the cam shaft is electromechanical.

11. The apparatus of claim 8, wherein the controlling assembly for axially translating the cam shaft is hydraulic.

12. The apparatus of claim 8, wherein the controlling assembly for axially translating the cam shaft is pneumatic.

13. The apparatus of claim 8, wherein the adjustable cams and valve controller device can be retrofitted on internal combustion engines.

14. The apparatus of claim 8, wherein the exhaust cam leaving the exhaust valve open at least partially closes the valve when the cylinder piston is near its uppermost position.

15. The apparatus of claim 13, wherein the retrofit can be accomplished without disassembling or modifying the engine block.