The internal combustion engine, whose origin goes back to the end of the 19th century, has been generally used all over the world, principally in self-propelled vehicles that burn fuels such as gasoline, Diesel oil or other gaseous hydrocarbons.

Important improvements have been incorporated into the design of modem engines, such as better and more balanced metal alloys that enhance mechanical properties while reducing weight, fuel injection electronic systems, more valves per cylinder, more efficient cooling systems and even catalytic systems to help reduce polluting emissions.

Besides incomplete combustion and dissipated heat, friction accounts for much of the inefficiency associated with the modem combustion engine. Overall four- cycle engine efficiency can be as low as 22 to 28% for engines operating on gasoline, which means that losses account for 62 to 78% of the potential energy available from theoretically complete hydrocarbon combustion in the cylinders of such engines.

The working principle of a typical engine based on the spark-ignition or Otto cycle (initially proposed by Beau de Rochas and now used by the vast majority of self-propelled vehicles in the world) is illustrated in Figs. lA-1D. For each explosion, the piston travels along the cylinder four times, completing four strokes per combustion cycle. During the first, downward stroke (Fig. 1A), fuel and air are admitted to the

cylinder. The second, upward stroke (Fig. 1B) compresses the fuel-air mixture for ignition, which propels the piston downward toward the drive shaft (Fig. 1 C) in a third, power stroke. The fourth, upward stroke (Fig. 1D) exhausts the combustion gasses from the cylinder. Thus, only on one out of four strokes is useful power generated, and that power must be sufficient to propel the piston through its three other strokes in order to produce any net power available for useful work.

Four-cycle Diesel engines operate on a similar principle to that shown in Figs. lA-1D, except that ignition is achieved by compression rather than by spark.

These compression-ignition engines ingest air on the intake stroke, compress the air on the compression stroke, and then inject Diesel fuel into the compressed air.

Combustion of the Diesel fuel due to compression drives the piston downward on the power stroke, and the fourth stroke exhausts the combustion products.

Two-stroke engines operate on a similar principle, except that the combustion cycle is completed in only two strokes of the piston, with the intake and exhaust processes occurring during portions of the compression and expansion strokes.

The intake air and fuel are normally routed through the engine crankcase, where oil in the fuel mixture enhances lubrication. In theory, performing a complete combustion cycle in only two strokes can potentially double the power of a two-stroke engine over a four-stroke engine of comparable size, but as a practical matter such efficiencies are not achieved, in part because the entering fuel-oil-air mixture does not efficiently scavenge the combustion gasses of the previous cycle from the cylinder.

In order to provide a smooth output power of substantial magnitude, it is common to gang the pistons of several cylinders together such that they drive a common drive shaft with sequential power strokes. The total"displacement"of an engine, which is one indication of its power capacity, is the sum of the cylinder volumes displaced by all of its pistons during their power strokes. Increasing either the size or number of the cylinders, or the stroke length of the pistons may increase engine displacement, but this tends to require an undesirable increase in engine size.

Summary of the Invention The invention features a novel cylinder-piston arrangement that can double the number of power strokes of a given piston operating in a combustion engine. Thus, the invention enables a single four-stroke piston to develop power on two out of every four of its strokes, or a single two-stroke piston to develop power on every stroke, significantly increasing the effective cycle displacement available over a given stroke length from a cylinder of given diameter and more efficiently utilizing the volume of each cylinder.

The invention features a"reciprocating disk"that moves inside of each cylinder very much like pistons travel in the conventional engine, but divides the cylinder into two axially overlapping combustion chambers in which two separate combustion cycles take place. By"axially overlapping"we mean that the combustion chambers share some swept cylinder volume. Thus, the invention makes it possible to combust two fuel-air mixtures, with alternating sequence, within the same cylinder.

The two combustion chambers can be configured to be substantially of equal dimensions, and of dimensions similar to those of cylinders of conventional internal combustion engines, operating with common compression ratios. This can enable engines designed in accordance with the invention to produce a desired amount of

power with fewer and/or smaller cylinders than engines of conventional piston/cylinder arrangement.

By"disk"we do not mean to imply that, in the broadest aspects of the invention, the reciprocating member or piston dividing the cylinder into separate combustion chambers need be of any particular shape.

According to one aspect of the invention, an internal combustion engine has a housing defining a cylinder therein; and a piston movable along the cylinder and separating the cylinder into two combustion chambers. The combustion chambers are adapted to receive fuel, and exhaust combustion products after the fuel is combusted.

The combustion chambers are disposed at opposite ends of the movable piston, such that alternating explosions in the two combustion chambers tend to push the piston in alternating directions along the cylinder. Both combustion chambers include a common portion of cylinder volume swept by the piston as it reciprocates within the cylinder.

In some embodiments, the engine also has intake and exhaust valves associated with each combustion chamber for receiving and exhausting, respectively, the fuel and combustion products. The valves are closable to seal their respective combustion chambers. In some cases, the valves are operated by associated cam- driven linkages (driven, for example, by cams rotating with the drive shaft, with the drive shaft revolving once for every four strokes of the piston). In some engines, the valves are driven by associated electromagnetic actuators in response to signals received from an electronic controller.

In some configurations, the engine also includes a connecting rod operatively joining the movable piston to a drive shaft, such that reciprocating motion

of the piston along the cylinder, caused by explosions in the two combustion chambers, alternatingly pushes and pulls on the connecting rod to cause rotation of the drive shaft.

In some presently preferred embodiments, the piston has a disk extending across the cylinder, the disk of a length along the cylinder, which is less than the diameter of the cylinder, and a force transmission rod extending from one face of the disk through an end of the cylinder. The force transmission rod is pivotally attached to the connecting rod, and radially supported within the housing.

The piston has, in some embodiments, at least two compression rings in contact with a side wall of the cylinder and carried in respective peripheral grooves of the disk.

In some embodiments, the force transmission rod defines an interior lubrication groove in fluid communication with a peripheral surface of the disk between the two compression rings, for transmitting lubricating fluid to the cylinder wall between the compression rings.

In some cases, the piston also has a balance rod extending from the other face of the disk and radially supported within the housing. The force transmission and balance rods are preferably of similar diameters.

Some embodiments are constructed to operate a four-stroke combustion process, in which each combustion chamber provides power on one out of every four sequential strokes, the two combustion chambers together providing power on two out of every four sequential strokes.

In some other embodiments, the engine is constructed to operate a two- stroke combustion process, in which each combustion chamber provides power on one

out of every two sequential strokes, the two combustion chambers together providing power on every stroke.

Some versions of the disk have upper and lower sections, with each section having a broad surface forming an end of one of the combustion chambers, and the force transmission rod extending from one of the sections through one end of the cylinder. In some embodiments, the upper and lower sections of the disk are threaded together axially, with male threads of one section engaging cooperating female threads of the other section. Preferably, a locking element extends through the engaged threads to secure the threads against relative rotation.

In some embodiments, the housing and power transmission rod together define a pocket for receiving gasses leaked between the housing and power transmission rod at the end of the cylinder. The pocket is preferably in hydraulic communication with an intake passage of the engine, such that at least some of the leaked gasses are returned to the cylinder. In presently preferred embodiments, there are two or three such gas-receiving pockets, spaced apart axially along the power transmission rod within the housing.

In some configurations, the piston is mechanically coupled to a drive shaft through a pair of parallel connecting rods disposed on opposite sides of the cylinder.

Some versions of the engine of the invention have two cylinders, each cylinder equipped with a corresponding piston having a reciprocating disk and power transmission rod. In some cases, the power transmission rods of the two cylinders are both coupled to a drive shaft of the engine through a shared connecting rod extending from a power transmission bridge that spans the power transmission rods.

In some cases, each cylinder power transmission rod is mechanically coupled to drive an associated connecting rod to turn an associated power crank having a set of gear teeth engaging gear teeth of a drive shaft of the engine, such that reciprocal motion of the power transmission rods causes rotation of the power cranks and the drive shaft.

The cylinders of some engines are arranged about the drive shaft in two banks, with their power transmission rods extending in parallel directions.

Some versions of the engine have at least four such cylinders and associated reciprocating disks, with the cylinders are arranged about the drive shaft in four banks. In some cases, the power transmission rods of all of the cylinders extend in parallel directions. In some other cases, the cylinders have longitudinal axes that extend radially from a rotational axis of the drive shaft.

According to another aspect of the invention, a four-stroke internal combustion engine has a housing defining a cylinder; and a piston movable along the cylinder and separating the cylinder into two combustion chambers, one combustion chamber on either side of the movable piston but both combustion chambers including a common portion of cylinder volume, such that alternating explosions in the two combustion chambers tend to push the piston in alternating directions along the cylinder. The cylinder thus provides two power strokes out of every four strokes of the piston. The engine also has corresponding valves arranged for communication with each of the combustion chambers, the valves being closable to seal the combustion chambers, and a connecting rod operatively joining the movable piston to a drive shaft, such that reciprocating motion of the piston along the cylinder, caused by explosions in the two combustion chambers, causes rotation of the drive shaft.

Various embodiments of this aspect of the invention have various combinations of features as discussed above with respect to the first-recited aspect of the invention.

In some cases, the balance and force transmission rods each define interior lubrication grooves for circulating oil axially through the piston. For example, in some embodiments an oil nozzle is attached to the housing and arranged to extend into the interior lubrication groove of one of the balance and force transmission rods, to inject a flow of oil into the piston under pressure. The oil nozzle is preferably biased toward the piston by a spring, such that increasing oil pressure in the piston tends to compress the spring and reduce the extension of the nozzle. In some instances, the nozzle defines a longitudinal slot, such as a V-shaped slot, at its distal end for moderating piston oil pressure.

According to another aspect of the invention, a two-stroke internal combustion engine has a housing defining a cylinder; and a piston movable along the cylinder and separating the cylinder into first and second combustion chambers. One combustion chamber is disposed on either side of the movable piston but both combustion chambers including a common portion of cylinder volume, such that alternating explosions in the two combustion chambers tend to push the piston in alternating directions along the cylinder. The cylinder thus provides power on every stroke of the piston.

The housing further defines first and second exhaust ports, and a common intake port, in a side wall of the cylinder. The common intake port is disposed axially between the exhaust ports. The ports are arranged such that, with the piston at one end of its travel, the first exhaust port and the common intake port are both in fluid

communication with the first combustion chamber and the second exhaust port is in fluid communication with neither combustion chamber. With the piston at the other end of its travel, the second exhaust port and the common intake port are both in fluid communication with the second combustion chamber and the first exhaust port is in fluid communication with neither chamber.

In some embodiments, the piston includes a disk extending across the cylinder, and a force transmission rod extending from one face of the disk through an end of the cylinder. The force transmission rod is radially supported within the housing.

Another aspect of the invention provides a method of extracting useful power from a combustible fuel. The method includes the steps of : (a) providing an engine having a housing defining a cylinder therein, and a piston movable along the cylinder and separating the cylinder into two combustion chambers, the two combustion chambers disposed at opposite ends of the movable piston, with both combustion chambers including a common portion of cylinder volume swept by the piston as it reciprocates within the cylinder; (b) alternatingly injecting the combustible fuel and oxygen into each of the combustion chambers; (c) alternatingly compressing the fuel and oxygen in each of the combustion chambers; (d) alternatingly causing the compressed fuel and oxygen in each combustion chamber to combust and expand, thereby force the piston to move in a reciprocating motion; and

(e) alternatingly exhaust combustion products from each combustion chamber.

In some cases, for each combustion chamber, the steps of injection, compression, expansion and exhaust occur during four successive strokes of the piston.

In some other cases, for each combustion chamber, the steps of injection, compression, expansion and exhaust occur during two successive strokes of the piston.

The advantages resulting from the invention can include, among others, a reduction in engine size, weight, materials, and corresponding costs. Increased engine efficiencies and reliabilities are also possible, given that an engine of a given power capacity requires, with the invention, fewer piston rings and other wear surfaces (with a corresponding reduction in friction losses). Friction reduction and dynamic and thermodynamic savings can improve overall four-stroke engine efficiency by as much as 25 percent or more over comparably powerful engines. As discussed below with respect to a presently preferred embodiment, the valves of each cylinder may be operated by energy supplied by rods extending from its reciprocating disk (through an appropriate mechanism), or by desmodromic valve linkages, or by electromagnetic means, eliminating the need for a shared camshaft. The rotating mass of the engine can be significantly lower (e. g., up to 40 percent lower) than that of engines of comparable power, with reductions both in crankshaft and flywheel mass.

In some respects, engines constructed according to the invention can require only one half of the number of cylinders of a conventional engine, so that many of the moving components can be eliminated. Alternatively, the invention may be employed to provide up to twice the effective combustion volume with the same number of cylinders. Thus, a four-cylinder engine embodying the invention can

provide some of the benefits of a conventional engine having eight cylinders. For example, because the power strokes of its eight combustion chambers can be sequenced as in an eight-cylinder engine, the output power is correspondingly smooth.

Additionally, a failure of one combustion chamber to fire is not as disruptive to power transmission as in a standard four-cylinder engine.

Other features and advantages will be apparent from the following embodiment description, and from the claims.

Brief Description of the Drawings Figs. IA-ID sequentially illustrate the four strokes of a cylinder in a conventional four-cycle, internal combustion engine.

Fig. 2 is a cross-sectional view of a cylinder of an engine constructed according to the invention.

Figs. 3A-3D sequentially illustrate four sequential strokes in a cylinder of a four-cycle, internal combustion engine constructed according to the invention.

Figs. 4A and 4B show the reciprocating disk with and without its rings installed.

Figs. 4C-4E illustrate a second reciprocating disk, with Fig. 4D being a cross-sectional view taken along line 4D-4D in Fig. 4C, and Fig. 4E being a cross- sectional view taken along line 4E-4E in Fig. 4D.

Fig. 5 is a cross-section through a cylinder head, illustrating a four-valve arrangement.

Figs. 6 and 7 are cross-sectional views of the head of a single cylinder, taken along lines corresponding to lines 6-6 and 7-7 in Fig. 5, respectively, with valves

and balance rod in place, illustrating a valve operation mechanism and rod seal arrangement.

Fig. 7A shows an engine with valves operated by electromagnetic actuators.

Fig. 8 shows a first power transmission arrangement, with the power generated by two cylinders of different banks transmitted to a crankshaft through separate connecting rods offset from the cylinder centers.

Fig. 8A illustrates opposed cylinder banks arranged on opposite sides of a common crankshaft, with power transmitted through more standard connecting rods.

Fig. 9 shows a second power transmission arrangement, with the power generated by two cylinders of different banks transmitted to a crankshaft through separate pairs of connecting rods straddling each cylinder.

Fig. 10 shows a third power transmission arrangement, with the power generated by two cylinders of the same bank transmitted to a crankshaft through a common connecting rod driven through a bridge spanning the two cylinders.

Figs. 11 A through 11 D sequentially illustrate the operation of an engine having two banks of two cylinders each, with power transmitted to the crankshaft via the arrangement of Fig. 10.

Fig. 12 illustrates a four-cylinder engine in which the output of each cylinder is coupled to a common drive shaft by one or more gears.

Fig. 13 is a cross-sectional view of the engine of Fig. 12, taken along line 13-13.

Figs. 14 and 15 illustrate arrangements of cylinders in two banks.

Figs. 16 and 17 illustrate additional arrangements of cylinders in four banks.

Figs. 18A and 18B illustrate the operation of an oil nozzle for providing pressurized oil to the reciprocating disk, with the engine operating at low speeds.

Figs. 19A and 19B illustrate the operation of the oil with the engine operating at high speeds.

Fig. 20 is an enlarged view of the distal end of the oil nozzle.

Figs. 21 and 22 illustrate alternative valve-operating mechanisms, featuring shared cam surfaces.

Figs. 23A-23D sequentially illustrate the reciprocating-disk principle in a cylinder of an engine operating on a two-stroke combustion cycle.

Detailed Embodiment Description Referring first to Fig. 2, a cylinder 10 of engine 2 is equipped with a piston in the form of a reciprocating disk 12 that is movable along the cylinder chamber 14, with a balance rod 16 and a power transmission rod 18 extending co-linearly from opposite sides of the disk along the center line of the cylinder. Disk 12 divides chamber 14 into an upper combustion chamber 14A and a lower combustion chamber 14B, in each of which a separate four-cycle combustion process takes place. As disk 12 is reciprocated along the cylinder, upper and lower combustion chambers 14A and 14B alternatingly increase and decrease in volume, such that at least a portion of the volume of cylinder chamber 14 is utilized for the combustion process in both the upper and lower combustion chambers. Disk 12 is shown at near its bottom-dead-center (BDC) position, at which lower combustion chamber 14B is at its minimum volume, and upper combustion chamber 14A is at its maximum volume. Preferably, combustion chambers 14A and 14B are of equivalent maximum and minimum

volumes and shapes, so as to balance the output power generated in each chamber. Of course, chambers 14A and 14B can be configured with different shapes and volumes, with other design parameters, such as compression ratio, timing or fuel mixture, altered to balance their output power. It is not necessary that the engine be configured so as to perfectly balance chamber output power.

The housing surrounding cylinder chamber 14 forms a cooling jacket 38 for removing heat generated in chambers 14A and 14B during operation.

Upper combustion chamber 14A is equipped with a head defining an upper intake inlet 24 and an upper exhaust outlet 26, leading to and from an upper intake valve 28 and an upper exhaust valve 30, respectively. A fuel injection device 32 in inlet 24 injects fuel into the air entering chamber 14A. Exposed to chamber 14A adjacent inlet 24 is ignition means 36 (e. g., a spark plug) that supplies the necessary spark to ignite the fuel mixture. Upper valves 28 and 30 are to open and close at proper intervals during the four-stroke combustion cycle occurring in upper chamber 14A.

The valves may be operated hydraulically, electrically, or mechanically, as required to provide valve motion and timing similar to that of a conventional four-stroke engine.

Extensions 20 and 22 are shown only to illustrate that energy from the moving rods may be employed, through appropriate mechanisms (not shown in this illustration), to operate the valves of the separate combustion chambers.

Similar to upper combustion chamber 14A, lower combustion chamber 14B is equipped with a lower intake inlet 42 and a lower exhaust outlet 44, with a lower intake valve 46 and a lower exhaust valve 48, respectively. Inlet 42 includes an injection device 50 that injects fuel to mix with air flowing along inlet 42, with the resulting fuel mixture passing into combustion chamber 14B. Adjacent the mixture

inlet, ignition means 52 (e. g., a spark plug) supplies the necessary spark to ignite the fuel. As with the valves of the upper combustion chamber, the lower intake and exhaust valves 46 and 48 open and close in accordance with proper timing to enable a four-stroke combustion cycle in lower combustion chamber 14B.

The engine shown in Fig. 2 has a lower housing 54 enclosing a crankshaft 56 that is coupled to power transmission rod 18 through a connecting rod 58 and a wrist pin 60. In this embodiment, guiding bushings 62 guide power transmission rod 18 through its upward and downward reciprocating motion, such that its motion is straight, allowing no substantial lateral displacement of the power transmission rod. In other embodiments, described below, the balance and power transmission rods are supported at the fixed ends of the cylinder by guide bushings. Thus, reciprocating disk 12 transforms energy liberated by fuel combustion into a lineal acceleration of power transmission rod 18, which motion is then transformed into a torque by means of crankshaft 56 and its conventional accessories. Thus, rods 16 and 18 have different functions, the principal function of power transmission rod 18 being to transmit force to the crankshaft, both by pushing and pulling on wrist pin 60, while the primary function of balance rod 16 is to provide equal pressure areas on both sides of the piston and to help radially support the piston. Other functions of rods 16 and 18 may include, in various embodiments, operating the various intake and exhaust valves, and cooling and lubrication of the reciprocating disk. In the embodiments shown in Fig. 2, the diameters of rods 16 and 18 are equal to balance the pressure areas on either side of the reciprocating disk. Of course, these two rods may have different diameters to produce different combustion pressure areas, or balance rod 16 may be omitted altogether, in

which case fuel mixtures in the two opposed combustion chambers may be correspondingly altered to provide equal power strokes, as desired.

In operation, cylinder 10 equipped with reciprocating disk 12 performs two complete four stroke combustion cycles in only four sequential strokes, as illustrated in Figs. 3A through 3D (viewed from right to left). During the first stroke towards BDC (Fig. 3A), upper intake valve 28 opens and allows injector 32 to feed fuel 34 to upper combustion chamber 14A, at the same time that reciprocating disk 12 travels downward and makes room inside combustion chamber 14A. When the reciprocating disk reaches BDC, upper intake valve 28 closes and lower intake valve 46 opens, enabling injector 50 to feed fuel 34 to lower combustion chamber 14B as the reciprocating disk 12 travels upward to top-dead-center (TDC, Fig. 3B), compressing the fuel mixture in upper combustion chamber 14A. When the reciprocating disk 12 reaches TDC, lower intake valve 46 closes and the upper ignition means 36 produces a spark to violently ignite the compressed fuel mixture in upper combustion chamber 14A, pushing the reciprocating disk (12) downward to BDC (Fig. 3C), providing useful power and also compressing the fuel mixture in lower combustion chamber 14B.

When reciprocating disk 12 reaches BDC, the lower ignition means 52 produces a spark that violently ignites the compressed fuel mixture in lower combustion chamber 14B, pushing the reciprocating disk upward to TDC (Fig. 3D) while upper exhaust valve 30 is open to expel the combustion gases from upper combustion chamber. At TDC, upper exhaust valve 30 closes and upper intake valve 28 opens to feed another burst of fuel from upper injector 32 into upper combustion chamber 14A to begin another four stroke cycle. As the reciprocating disk again moves downward toward

BDC (Fig. 3A), lower exhaust valve 48 is open to expel combustion gas from lower chamber 14B.

As shown in the sequence of Figs. 3A-3D, at BDC (e. g., Fig. 3C) the upper surface of disk 12 reaches an elevation lower than the elevation of the lower surface of disk 12 at TDC (e. g., Fig. 3B). In other words, the combustion chambers share a central portion of cylinder volume, such that that shared cylinder volume is involved in both combustion cycles. Another way of stating this is that the swept volume of each combustion chamber includes a common space within the cylinder.

Fig. 4A shows more detail of reciprocating disk 12, which has a cylindrical body 64 whose diameter () is larger than its height (h). On the central portion of the periphery of disk body 64 a peripheral lubrication groove 66 is provided with a plurality of orifices 72 in hydraulic communication with an internal lubrication groove 68 which runs inside of balancing rod 16 and power transmission rod 18 from the crankshaft. Lubricating oil from orifices 72 is spread by a lubrication ring 70 (Fig. 4B) along the internal wall of the cylinder as the disk travels back and forth, cooling the reciprocating disk and its rings and lubricating the cylinder wall.

On either side of the lubrication groove 66 are two peripheral grooves 74 to accommodate upper and lower compression rings 76A and 76B (Fig. 4B), both of which hermetically seal the upper and lower combustion chambers of the cylinder, respectively, to avoid combustion gas leakage around the disk.

Figs. 4C through 4E illustrate a second disk/rod construction. As shown in Fig. 4E, the reciprocating disk has upper and lower halves 450 and 452, respectively, each of the disk halves formed integrally (e. g., cast) with its associated rod. In this example, upper disk half 450 and balance rod 454 form a unitary structure, and lower

disk half 452 and power transmission rod 456 form another unitary structure. The disk halves are held together by cooperating threads 458, the disk halves being threaded together until their mating faces tightly engage in transverse areas 460, leaving an axial gap between the disk halves at their outer diameter of between about 0.020 and 0.025 inch. With the disk halves tightly threaded together, providing appropriate preload on threads 458, three lateral holes 462 are drilled and reamed from the outer diameter of the disk assembly across threads 458, into each of which a pin 464 (such as a spring roll pin) is pressed to inhibit loosening of threads 458. Preferably, a lip 466 is formed both at the bottom of holes 462 and at the opening of holes 462, to prevent subsequent axial movement of pins 464. As will be appreciated, this connection between disk halves does not require threads 458 to carry the substantial axial loads generated by combustion. Combustion forces in the combustion chamber formed beneath lower disk half 452 (which tend to push the reciprocating disk upward, causing tension in power transmission rod 456) will be transmitted only through the lower disk half directly into the power transmission rod. Combustion forces in the upper combustion chamber (formed above upper disk half 450, tending to force the reciprocating disk downward and place the power transmission rod in compression) are transmitted from upper disk half 450 to lower disk half 452 across areas 460 and not through threads 458.

To reduce their weight and provide for cooling, disk halves 450 and 452 are cast with inner cavities 468 that are hydraulically connected, via channels 470 and balance rod bore 472, to a pressurized oil supply. This cooling oil is also exposed to the cylinder wall (e. g., through holes 462) to lubricate the piston rings during operation.

To promote lubrication, additional holes (not shown) may be provided between cavities

468 and the outer diameter of the disk assembly between the piston rings. A small orifice 473 between balance rod bore 472 and power transmission rod bore 474 provides a return path for oil to the crankcase and is sized appropriately to maintain oil pressure in cavity 468.

As shown in Fig. 4E, each set of compression rings consists of two rings (e. g., rings 470A and 470B) sharing a common groove (e. g., groove 473). These rings are installed with their gaps 476 on opposite sides of the disk assembly to promote compression, as shown in Fig. 4D. Each set of compression rings seals a corresponding one of the combustion chambers separated by the reciprocating disk. If desired, one or more lubrication rings may be provided between the sets of compression rings. Also, as will be understood from this disclosure, the compression rings for each combustion chamber may be separated into spaced-apart grooves, as is typically the case with the compression rings of a standard four-stroke engine.

Referring now to Figs. 18A and 18B, one method of supplying lubricating and cooling oil under pressure to the reciprocating disk features a spring-loaded oil nozzle 478 arranged to feed oil into the balance rod 480 of the reciprocating disk assembly. Nozzle 478 is of such a length that, with the reciprocating disk at BDC (Fig.

18B), it extends a sufficient distance dl into the balance rod bore that a desired minimum oil pressure is maintained within the balance rod. The radial gap between the outer diameter of nozzle 478 and the inner diameter of balance rod 480 is sufficient to avoid contact, under all circumstances, between the nozzle and balance rods, but small enough to enable adequate oil pressure to be maintained, at operating oil viscosities, without requiring excessive flow rates. Oil leaving the distal end of balance rod 480, due to leakage through the gap about nozzle 478, is collected and returned to

the oil sump (not shown). The remainder of the oil from nozzle 478 is supplied to reciprocating disk assembly 482, for lubricating the cylinder wall and extracting heat from the disk assembly. The inner bore of power transmission rod 484 provides a return path to the oil sump.

It will be understood that the oil viscosity, the radial clearance between oil nozzle 478 and balance rod 480, and the amount of overlap between the nozzle and balance rod, may all be varied cooperatively to produce the desired average, maximum and minimum reciprocating disk oil pressure. For many four-stroke applications, an average oil pressure on the order of about 30-50 pounds per square inch is preferred, but the actual oil pressure requirements will depend on the characteristics of the interface between the piston rings and cylinder wall and other application-specific factors.

It should also be noted that another reciprocating disk and rod structure is illustrated in Figs. 18A and 18B, in which the disk assembly 482 consists of two halves 486 and 488 which are separately threaded onto a continuous shaft 490 which forms both the power transmission rod and the balance rod. Although this may facilitate assembly of the disk, as compared, for instance, with the structure of Figs. 4C-4E, it is only recommended for applications in which the threaded connection securing the disk halves to the shaft can be designed to carry the full axial loads generated by combustion. Disk halves 486 and 488 may be made from die cast aluminum, for example, with appropriate inserts for threads, and shaft 490 made from stainless steel.

Nozzle 478 is biased toward the cylinder, against a nozzle travel stop 492, by a compression spring 494. Spring 494 is placed under sufficient pre-load that at low engine speeds nozzle 478 remains fully extended and stationary throughout the range

of reciprocating disk motion, as shown in Figs. 18A and 18B. Referring also to Fig.

20, the distal end of nozzle 478 is provided with a V-shaped slot 496 that at low engine speeds is fully sheathed by balance rod 480. At higher engine speeds, nozzle 478 is displaced away from the cylinder by increasing oil pressures, further compressing spring 494. As a result, the overlap between nozzle 478 and balance rod decreases to a distance d2, such that notch 496 is partially exposed beyond the distal end of balance rod 480 at one end of its reciprocal motion (i. e., in the position shown in Fig. 19B).

Slot 496 functions as a variable oil orifice that helps to resist changes in oil pressure within the reciprocating disk.

Also of note in Figs. 18A and 18B is that in some cases the cylinder may be constructed for air cooling, with the cylinder formed by a cylindrical tube 520, such as of cast aluminum or iron, sandwiched between opposing valve heads 522 and 524 at either end. Tube 520 is provided with appropriate fins 526 for convective cooling.

Each combustion chamber may be configured with multiple intake and exhaust valves. For example, Fig. 5 shows a four-valve arrangement for a single combustion chamber, with two intake inlets 80A and 80B, and two exhaust outlets 82A and 82B, each equipped with a corresponding valve (not shown).

Referring to Fig. 6, one presently preferred method of operating the valves employs a pivot bar 84 pivotable about a stationary pin 86 at one end, and having a follower pin 88 at its other end. The follower pin 88 is constrained to follow a prescribed path defined by a groove 90 within a rotating cam 92, which is driven (e. g., by the crankshaft) to rotate about point 94. As the bar pivots back and forth, it opens and closes a pair of intake valves 28A and 28B, which are held against the bar by corresponding flexible steel springs 96 attached to a near edge of the bar and engaging

grooves 98 at the tips of the valve stems. Valves 28A and 28B open and close intake inlets 80A and 80B, respectively, in Fig. 5. It will be apparent that such operation will cause one intake valve (in this case, valve 28B) to open farther than the other, but the timing of both valves will be identical and will be controlled by the configuration of cam groove 90 and the controlled rotation of cam 92. As shown in Fig. 7, a similar pivot bar 84'and cam 92'operate the two exhaust valves of the combustion chamber, only one of which (30A) being shown. Additional pivot bars and cams are employed to operate the valves at the other end of the cylinder.

Cams 92 may be driven mechanically from the crankshaft, either by gears or belts, or operated independently, such as by electric motor. Alternatively, the valves may be operated by magnetic solenoids. For example, Fig. 7A illustrates an engine employing the reciprocating disk principle and having two valves per combustion chamber. Each valve is operated by an associated electromagnetic actuator 570 that positions the valve in response to signals received from a common electronic controller 572, which varies the timing of the valves in accordance with operating conditions for enhanced fuel efficiency and performance characteristics. Those of skill in the art will recognize that such controlled valve operation can also provide for engine braking, all under the automated control of a programmable processor in controller 572, or with input from the operator.

Fig. 7 also illustrates a seal bushing arrangement for sealing between balance rod 16 and the cylinder head 102. High cylinder pressure requires an efficient sliding seal between the balance and power transmission rods and their supporting structure. Upper and lower bronze rod guide bushings 104A and 104B are pressed into head 102 and provide wear surfaces for balance rod 16. The head and bushings

together define three chambers about the balance rod, which are ported to the intake inlet 24 by passages in the head to recycle leaked gasses. The two primary chambers 106 are connected to the intake inlet by passages 108 (see also Figs. 5 and 6), and the secondary chamber 110 is connected to the intake inlet by passage 112. Each of the chambers acts as a trap to collect leaked combustion gasses and recycle them through the intake inlet, which is normally at sub-atmospheric pressure. In some embodiments, axial or canted grooves are provided along the wear surface of lower rod guide bushing 104B, and in some cases along the rod head bore to secondary chamber 110, to define a controlled leak path for combustion gasses and to reduce bushing wear. It will be appreciated that combustion must not take place within the intake inlet, and so the labyrinth formed by the series of collection chambers and passages must be sufficiently circuitous that any fire propagating into the primary chambers is extinguished by combustion gasses before reaching the intake inlet. For some applications it may be necessary to make passages 108, for example, of very small diameter. High in-cylinder temperatures in some applications may require bushing 104B to be formed of a harder material than bronze. A similar seal bushing arrangement is provided at the other end of the cylinder, along the power transmission rod (not shown).

Multiple cylinders may be arranged in various configurations and coupled to a common crankshaft for transmitting power. In Fig. 8, for example, two cylinders are arranged on opposite sides of a common crankshaft 840, with their power transmission rods 118 and 218 connected to the crankshaft through offset connecting rods 830, such that the linear motion of the reciprocating disks is transformed into a rotary motion of the flywheel 800. By arranging the cylinders with their power transmission rods extending away from the crankshaft, the cylinders may be placed

closer to the crankshaft for a desirably small overall engine size. Additionally, smaller connecting rod angles provide a more efficient transfer of power from the power transmission rods to the crankshaft.

Fig. 8A illustrates a cylinder arrangement in which cylinders are disposed on opposite sides of a common crankshaft, as in Fig. 8, but with their power transmission rods 530 coupled to crankshaft 532 by short connecting rods 534 encased within a crankcase 536. The distal ends of the power transmission rods are supported against bending loads caused by connecting rod angulation by linear bushings at 538.

This arrangement can be particularly useful for packaging an engine in areas such as, for example, under the passenger seat of a vehicle, as the engine can be arranged with its cylinders extending horizontally and therefore require very little vertical space.

In another arrangement, shown in Fig. 9, the power transmission rods of two cylinders are each connected to crankshaft 840 by a pair of connecting rods 830 straddling their corresponding cylinders.

Similarly, two adjacent cylinders may drive a single connecting rod, as shown in Fig. 10. In this example, a power transmission bridge 808 that spans the two cylinders and drives the central connecting rod 830 to rotate crankshaft 840 couples the power transmission rods of the two cylinders. Such a power transmission bridge is preferably constructed with a small amount of beam flexibility, so as to provide a much-desired amount of shock absorption between the explosions in the combustion chambers and the crankshaft. With both cylinders arranged in a common bank, the crankshaft is provided with counterweights 900, as known in the art, to balance the inertia of the connecting rods, bridges and disks. The combustion timing is preferably the same in both cylinders to balance the loading across bridge 808.

Two banks of cylinders, each configured as shown in Fig. 10, may be coupled to a common crankshaft, as shown in Fig. 11 A, to form a four-cylinder, eight- combustion chamber engine 1000. Cylinders 100 and 300 form a left cylinder bank, and cylinders 200 and 400 form a right cylinder bank. Each of the cylinders forms two combustion chambers separated by a reciprocating disk, as described above, and each has a separate power transmission rod. Power transmission rods 118 and 318 of cylinders 100 and 300, respectively, are operatively joined to a common power transmission bridge 808A that transmits motive force to crankshaft 840 through a central connecting rod 830. Similarly, power transmission rods 218 and 418 of cylinders 200 and 400, respectively, drive connecting rod 850 through bridge 808B. In the arrangement shown, cylinders 100 and 300 always operate to transmit power simultaneously to their bridge 808A, and cylinders 200 and 400 fire together to drive their bridge 808B.

The sequential firing of the cylinders of engine 1000 is illustrated in Figs.

11A through 11 D. The illustrated sequence begins with explosions in the lower combustion chambers 114A and 314A of cylinders 100 and 300, respectively, that force their shared power transmission bridge 808A toward crankshaft 840 (Fig. 11 A) and compress the fuel mixtures in the upper combustion chambers 114B and 314B of the same cylinders. Although the terms"upper"and"lower"are used with respect to the combustion chambers, this is not meant to imply any orientation of the cylinders.

Indeed, in many instances the cylinders may be arranged in horizontal banks, each cylinder thus having left and right combustion chambers. Throughout this sequence, "BDC"will refer to the position shown in Fig. 11A, with the reciprocating disks at the end of their cylinders closest the crankshaft. While the combustion gasses are

expanding in combustion chambers 114A and 314A, expanded combustion gasses are being expelled from lower combustion chambers 214A and 414A of cylinders 200 and 400, respectively, and fuel mixtures are being drawn into upper combustion chambers 214B and 414B of those cylinders.

With the reciprocating disks at BDC, the compressed fuel mixtures in the upper combustion chambers 114B and 314B of cylinders 100 and 300, respectively, are ignited to drive the reciprocating disks toward TDC (Fig. 11B), compressing fuel mixtures in upper combustion chambers 214B and 414B of cylinders 200 and 400, respectively, drawing fuel into the lower combustion chambers of cylinders 200 and 400, and expelling combustion gasses from the lower combustion chambers of cylinders 100 and 300. With these two power strokes, flywheel 800 has completed one full revolution.

With the reciprocating disks at approximately TDC (Fig. 11B), the compressed fuel mixtures in combustion chambers 214B and 414B are ignited to drive their reciprocating disks inward to BDC (Fig. 11 C), again imparting a useful burst of energy to crankshaft 840, this time through connecting rod 850. During this third stroke, fuel mixtures are compressed in combustion chambers 214A and 414A, combusted gasses are expelled from chambers 114B and 314B, and fresh fuel mixtures are drawn into chambers 114A and 314A.

To drive the last of the four strokes of the complete cycle, the compressed fuel mixtures in combustion chambers 214A and 414A is ignited, pushing the reciprocating disks of cylinders 200 and 400 to TDC (Fig. 11D), exhausting combustion gasses from chambers 214B and 414B, compressing fuel mixtures in chambers 114A and 314A, drawing fresh fuel mixtures into chambers 114B and 314B,

and transmitting useful energy to crankshaft through connecting rod 850. Thus, on each of the four strokes of the cycle, the fuel mixtures of two combustion chambers are ignited to provide useful power, the same number of ignitions occurring on one stroke of an eight-cylinder engine.

Table 1 shows the states of each of the combustion chambers of engine 1000 during the above-described four-stroke cycle.

Table 1 Oylinder300Oylinder200Oylinder400Oylinder100 LowerUpperLowerUpperLowerUpperLowerStrokeUpper PowerCompressionPowerIntakeExhaustIntakeExhaustFirstCompress ion ExhaustPowerExhaustCompressionIntakeCompressionIntakeSecondP ower IntakeExhaustIntakePowerCompressionPowerCompressionThirdExha ust Fourth Intake CompressionExhaustPowerExhaustPowerIntake Due to its dimensional and modular characteristics engine 1000, which is practically half the size of a conventional engine, front traction can be used for heavy vehicles. It is possible to install modules or cylinder blocks separated from the crankshaft block, at the designer's convenience.

Referring now to Figs. 12 and 13, engine 2000 has four cylinders equipped with reciprocating disks, as described above, arranged in a common plane. The power transmission rod 2002 of each cylinder is rigidly attached to a cross-bar 2004 pivotally connected at each end to the slender ends of connecting rods 2006. The opposite, large ends of connecting rods 2006 are pinned between corresponding pairs of drive gears 2008 at offset pivot points 2010 to form drive cranks, such that rectilinear reciprocation of the disks in the cylinders produces a unidirectional rotational of drive gears 2008.

Drive gears engage mating driven gears 2012 of a central drive shaft 2014, with a drive

ratio of 2: 1, such that every two rotations of a drive gear 2008 produces a single revolution of a driven gear 2012.

Thus, four driven gears 2012 receive power from sixteen drive gears, with the drive shaft 2014 and driven gears 2012 together rotating substantially as a rigid body. Spur, helical or herringbone gear profiles may be employed, as appropriate to the application.

As in above-described embodiments, the use of advantageously long connecting rods reduces overall connecting rod angulation, with a corresponding improvement in power transmission efficiency. Additionally, lower transverse connecting rod loads enables the use of light rod materials and slender rod profiles. A presently preferred rod shape is one that has a bulbous larger end, as shown, and a more slender distal end.

The firing sequence of the cylinders of engine 2000 will also be selected to provide the desired power stroke pattern. For very smooth power transmission, the eight combustion chambers are each timed to fire in drive shaft intervals of 45 degrees, such that no two combustion chambers fire together. In another preferred embodiment, the power strokes of the four cylinders are sequenced to fire in a clockwise pattern, as viewed in Fig. 12, with two combustion chambers firing together every 90 degrees of drive shaft rotation, producing a firing sequence of 4/1-1/2-2/3-3/4. Other useful firing patterns feature opposite cylinders firing together, such that substantially no transverse bending loads are applied to the drive shaft. Many other firing sequences are possible, as will be understood by combustion engine designers.

Referring to Figs. 14 and 15, various two-cylinder arrangements result in tight cylinder nesting about the drive shaft, producing a small overall engine size. Each

cylinder may represent an entire in-line bank of cylinders. In Fig. 14, the cylinders lie in a common plane and have parallel power transmission rods, but lie on opposite sides of the drive shaft. The drive gears 2008 engage the driven gears 2012 on opposite sides, such that the two cylinders can be fired simultaneously to balance gear separation loads. In Fig. 15, the two cylinders are arranged on a common side of the drive shaft, in parallel fashion to form a single cylinder bank.

Figs. 16 and 17 depict additional arrangements of four cylinders or four cylinder banks. In Fig. 16, the four cylinders are arranged in a cross pattern, and in Fig.

17 the four cylinders are arranged in a tangential array. In either case, the drive gears 2008 engaging the driven gears 2012 at 90-degree intervals, such that opposing cylinders may be fired simultaneously to balance gear separation loads. The arrangement of Fig. 17 provides a particularly compact engine if the cylinders are to be built into a common housing intended to enclose the gearing.

Referring now to Figs. 21 and 22, in some embodiments a common cam surface rotating with the central drive shaft or crankshaft drives the desmodromic valves. For example, Fig. 21 shows a central drive shaft 550 that is driven by drive gears 552 associated with the engine cylinders, as described above with respect to Fig.

14. Drive shaft 550 defines a cam track 554 in which the inner ends 556 of push rods 558 travel. Rigid push rods 558 are pinned, at their outer ends 560, to the reciprocating ends of their associated valve pivot bars 84. It will be understood that"push"rods 558 both push and pull on their respective valve pivot bars to force the engine valves to open and close in desired intervals, as determined by the shape of cam track 554. Fig.

22 illustrates the same principle as applied to an engine with adjacent cylinder banks.

It will be understood that these figures are for illustration only, with the overall size of

cam track 554 enlarged to show the concept. In practice, the cam track is selected for proper valve displacement.

The above-described embodiments have all featured cylinders of engines operating on a four-stroke Otto or Diesel cycle. Figs. 23A through 23D sequentially illustrate the reciprocating disk principle as applied to a cylinder configured for a two- stroke combustion cycle. A cylinder 600 of a two-stroke engine is equipped with a reciprocating disk 602 and associated balance and power transmission rods 604 and 606, similar in function to those of the four-stroke embodiments described above.

Beginning with Fig. 23A, as disk 602 begins its upward travel from BDC, both the intake port 608 and the upper exhaust port 610 are open to the upper combustion chamber 612. A flow of fuel and air rushing into chamber 612 from port 608 scavenges the combustion products from the previous combustion process from the chamber through port 610. The shape of the ends of piston 602 is appropriately selected to enhance this scavenging process, as known in the art. Meanwhile, lower exhaust port 614 is isolated between upper and lower piston rings 616A and 616B.

Once piston 602 has moved upward enough that upper ring 616A has moved beyond upper exhaust port 610 (Fig. 23B), further upward motion of the piston compresses the fuel and air in chamber 612. At or near TDC (Fig. 23C), a spark from spark plug 618 ignites the fuel mixture in chamber 612, forcing piston 602 downward to perform useful work. The expansion of gas within chamber 612 continues to perform useful work until upper piston ring 616A passes upper exhaust port 610, allowing the combustion products to begin to exhaust. Further downward motion also exposes the common intake port 608 (Fig. 23A), completing the combustion cycle in only two strokes of the piston.

Meanwhile, during the same two strokes of piston 602, another complete combustion process occurs in lower combustion chamber 620, with ignition provided by spark plug 622 near BDC (Fig. 23A). Power from both combustion cycles is transmitted through power transmission rod 606 to a drive shaft (not shown), as in the four-stroke embodiments.

The upper surface of piston 602 at BDC is shown in dashed outline in Fig.

23C (TDC), to illustrate that the upper and lower combustion chambers share a portion of the cylinder volume extending over length Ls. This sharing of cylinder volume means that, in effect, when calculating the displacement volume of the cylinder the shared portion is counted twice. In some cases, therefore, the effective displacement volume of cylinder 600 actually exceeds the overall volume of the cylinder.

Although described above with reference to primarily one, two and four- cylinder engines, it should be understood that the above description is only an illustration of the principle of the invention and should not be interpreted as limiting.

Other configurations of 6,8,10,12,14,16 or more cylinders, arranged in-line or in two or more banks, are also possible, with expected results. Similarly, the dimensions and elements of the engine may be modified in accordance with the specific requirements of any given situation.

It will be understood that the engines described above will operate with conventional fuels and lubricants, and can be configured for use with diesel oil, hydrogen, gasoline or alcohol, for example, with appropriate adaptations. All rotational joints may readily be equipped with rolling element bearings, if desired.

Although the invention has been described with particular reference to preferred embodiments, and to engines for self-propelled vehicles, the reciprocating disk mechanism can be applied in engines employed for a vast number of diverse functions.

What is claimed is: