ADJUSTABLE COMPRESSION RATIO PISTON/CYLINDER APPARATUS

RELATED APPLICATION

This application is a complete application based on a provisional application Serial No. 60/003,809 filed September 15, 1995. TECHNICAL FIELD

This invention relates to an adjustable compression ratio piston/cylinder apparatus and more particularly to such an apparatus in which the height of the piston within the cylinder is varied in response to rotational movement of the piston to vary the ratio. BACKGROUND ART

A number of patents teach the use of a variable piston height to provide variable compression to the operation of an internal combustion engine. See for example U.S. Pat No. 5,179,916 to Schonfeld, U.S. Pat. No. 5,178,103 to Simko, U.S. Pat No. 5,476,074 to Boggs et al, and U.S. Pat. No. 5,331,928 to Wood. Each of the patents referenced uses a fluid (hydraulic or lubricating) to change the height of the piston head. This procedure is highly complicated due to the need for valves and fluid control devices. This complexity leads to a less reliable system.

There is a need for an adjustable compression ratio piston cylinder arrangement which is simple and controllable, for example, via a servo system which changes the ratio in response to the desired and measured peak compression pressure. SUMMARY OF THE INVENTION

It is known in the art that a spark plug offset to one side of a piston can develop a pressure differential across the piston head which, when the piston is worn, can be evidenced by "piston slap" . In accordance with the present invention this force is employed in conjunction with a dual combustion initiation system and a shaped combustion chamber to direct the combustion wave

front in a manner so that the piston is caused to rotate and change its height relative to the head of the cylinder. The combustion initiation system may comprise a pair of spark plugs in a gasoline engine or a pair of fuel injectors in a diesel ^" engine. Each combustion initiator is offset on either side of the piston's rotational axis whereby one of the two combustion initiators can be selected to urge the piston to rotate clockwise or counterclockwise.

More specifically, the piston includes a head or top and an internal hollow cavity. The piston head preferably has radially disposed ridges and valleys and an internally threaded hollow cavity. A drive assembly block, for securing the piston to a conventional connecting rod, includes an outside head or top, a bottom, a outer cylindrical wall, an internal hollow circular cavity extending lengthwise from the bottom and proceeding to less than the top of the block and an internal hollow lateral cavity running the width of the drive assembly block. The outer wall of the drive assembly is threadably received in the threaded internal hollow cavity of the piston. A wrist pin is mounted in the lateral cavity of the drive block for receiving one end of the connecting rod, the other end thereof being connected to the engine crankshaft .

The piston is slidably received in a cylinder assembly forming part of an engine block. First and second igniters or spark plugs (gasoline engines) or first and second fuel injectors (for diesel engines) are mounted in the head of the cylinder. Preferably, the cylinder head is provided with shaped cavities which direct the combustion wave front associated with the igniters or fuel injectors along opposite sides of the piston. A pressure transducer is also mounted in the cylinder head for providing a measure of the pressure within the cylinder.

An ignition system (for gasoline engines) is connected to the igniters or a fuel injection system (for diesel engines) is connected to the fuel injectors for controlling the energy supplied to each igniter or the fuel delivered to each fuel injector.

Pressure signals from the transducer may be supplied to an electronic control system (or fuel injection system) along with signals representative of other information such as the altitude at which the engine is performing, the grade of the fuel being supplied to the engine or the power demanded from the engine. The electronic control system in response to such signals controls the electrical energy supplied to the first and second igniters or the fuel supplied to the first and second fuel injectors. The electrical energy or fuel supplied to the igniters or fuel injectors induces a clockwise or counter clockwise movement of the piston relative to the drive assembly block which in turn changes the position of the piston relative to the connecting rod. This procedure allows the piston to obtain a plurality of heights and results in a variation of the compression ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a cross-sectional view of the variable compression ratio piston/cylinder apparatus in accordance with the present invention; Figure 2 is a top perspective plan view of the piston of the apparatus of Figure 1 showing the ridges (and valleys) formed on the top thereof;

Figure 3 is a schematic diagram of the dual igniter piston arrangement of the apparatus of Figure 1 along with an electronic ignition system for receiving signals from a pressure transducer secured within the cylinder head of the apparatus and for supplying high voltage pulses to the igniters;

Figure 4 is a wave form showing the pressure within the cylinder of Figure 1 as a function of the rotation of the engine's crankshaft;

Figure 5 is a cross-sectional view of another embodiment of a piston and drive assembly block for use in the cylinder of Figure 1, illustrating the use of an alternative stop arrangement between the piston and drive block; Figure 6 is a bottom view of the cylinder head taken along lines 6-6 of Figure 1 showing the shaped cavities in the cylinder

head;

Figure 7 is a partial cross-sectional view of the apparatus taken along lines 7-7 of the Figure 6 showing the shaped cavities in the cylinder head; and Figure 8 is a schematic diagram of a dual fuel injector system and control for adjusting the piston position of a diesel engine.

DESCRIPTION QF THE PREFERRED EHgopiMENT

Referring now to the drawings and particularly to Figures 1, 2, 6 and 7, the variable compression piston/cylinder apparatus of the present invention includes a cylinder 10 formed as part of an internal combustion engine block. The number of cylinders (and pistons) will depend upon the engine specifications, e.g., 4, 6, 8, etc., cylinders. A cylinder head 12, suitably secured to the engine block, closes the top of the cylinder and defines a piston chamber. A conventional head gasket 13 extends between the head and block. A piston 14 is slidably received within the interior wall 15 of the cylinder 10 in a conventional manner.

The piston 14 includes conventional rings 16, a top or head 17, an outer cylindrical wall 18 and an internal cylindrical cavity 20. The piston cavity 20 is provided with interior threads 22 for threadably receiving a cylindrical drive assembly block 24.

The drive block 24 is provided with external threads 26, as illustrated, for mating with the interior threads 22 of the piston. The drive block further includes a top or an outside head 28, a bottom 30, an internal cavity extending longitudinally of the block and a cylindrical lateral bore 32 which receives a wrist pin 34. A connecting rod 36 is rotatably mounted at one end to the center of the wrist pin 34 and at the other end to a conventional crank shaft (not shown) . The connecting rod and wrist pin are provided with suitable lubrication passageways 38 for supplying lubricating oil to the threads 22 and 26.

Radially extending ridges 40 (and intervening valleys) are formed on the top or outside head 17 of the piston 14 for reacting with the combustion gases within the combustion chamber

45 to rotate the piston relative to the drive assembly block 24 in a clockwise or counterclockwise direction as will be more fully explained.

A pair of spaced combustion initiators 42 and 44 extend through the cylinder head 12 and into combustion chamber 45 for initiating the combustion of the gases with the chamber. See Figures 1, 3, and 6. The combustion initiators 42 and 44 are illustrated to be in the form of fuel igniters or spark plugs; however, it should be noted that the combustion initiators will take the form of fuel injectors in diesel engines.

A pressure transducer 46 also extends through the cylinder head and into the combustion chamber 45 for providing a signal on line 48 which is representative of the pressure within the chamber. The cylinder head defines a combustion gas directional cavity 50 associated with each of the igniters 42 and 44. The cavities 50, which are symmetrical, extend from the associated igniters 42 and 44 around a portion of the periphery of the top of the piston and on opposite sides thereof as is illustrated more particularly in Figures 6 and 7.

The depth of each cavity decreases from it's proximal end 50a adjacent the igniter 42 or 44 to it's distal end 50b at the opposite end of the combustion chamber.

A stop pin 52 secured to the bottom of the drive block 24 cooperates with a radially extending arm 54 secured to the inner wall of the piston 14 to limit the upward movement of the piston relative to the drive block. The lower movement of the piston relative to the drive block is limited by the engagement of the top of the drive block with the underside of the piston head. it should be noted that the conventional intake and exhaust values are not relevant to the invention and therefore are not shown in Figure 1.

In operation when the energy resulting from the combustion of gases associated with one igniter is greater that the energy resulting from the combustion associated with the other igniter the combustion wave fronts within the cavities 50 will exert a

differential force on the ridges 40 causing the piston 14 to rotate in one direction or the other on the drive block 24. This action will change the height of the piston and the volume of the combustion chamber 45. As a result the engine compression ratio will change. For example, if only the spark plug 42 is firing or is firing at a higher energy level than the spark plug 44, the combustion wave fronts will exert a net clockwise torque on the top of the piston (looking down from the top) thereby decreasing the volume of the compression chamber and increasing the engine compression ratio. The reverse will occur if only the spark plug 44 is firing or is firing at a higher energy level than the spark plug 42. By controlling the electrical energy supplied to the spark plugs 42 and 44, the piston can be rotated between it's upper and lower limits and to any point in between, thereby dynamically controlling the piston height and the engine compression ratio. It should be noted that the use of ridges located on top of the piston 14 may not be necessary. A piston head with a level surface may provide sufficient interaction with the pressure wave resulting from the expanding combustion gases to cause the piston to rotate.

Referring now to Figure 3, there is illustrated a simplified capacitive discharge electronic ignition system for controlling the energy input to the spark plugs or igniters 42 and 44 when used in conjunction with a four cylinder engine. A pair of conventional distributors 52 and 54 are rotated by a shaft 56 coupled to the engine's cam shaft (not shown) . The shaft 56 carries a reference magnet 58, for example, which generates a reference signal in a pick off coil 60 when the distributors are positioned to supply energy to the igniters 42 and 4 . The reference signal from the coil 60 is supplied to a microprocessor 62 which in turn controls the spark supplied to one or both igniters as will be more fully explained.

A conventional vehicle battery 65 supplies current, for example, at 12 volts to a high voltage generator 64. The generator delivers high voltage d.c. to NPN control transistors 66 and 68 which in turn charge capacitors 70 and 72,

respectively. Transistors 74 and 76 control the amount of charge on capacitors 70 and 72 as determined by the microprocessor 62.

The microprocessor also triggers SCR' s 82 and 84 which discharge the respective capacitors into the primary windings of ignition coils 86 and 88 which in turn supply the high voltage ignition pulses to the respective igniters 42 and 44 via the distributors . The microprocessor receives a combustion chamber pressure signal from the pressure transducer 46 via an A/D converter 78 and additional signals representing conditions external or internal to the engine via sensors or controls (not shown) on line 80. The microprocessor determines the current compression ratio of the cylinder from the pressure transducer and compares that ratio with the desired compression ratio as determined by the signals on line 80 to arrive at an error signal. The microprocessor reduces the error signal by controlling the charge on the capacitors and/or firing one of the igniters to cause the piston to rotate until the compression ratio has reached the desired value. At that time equal amounts of energy can be supplied to the spark plugs to maintain the piston's rotary position.

The closed loop feedback corrective cycle described above should occur in less than one second, and will occur independently and essentially simultaneously for each cylinder. The compression ratio control system disclosed herein will permit several valuable operating features not previously available.

It should be noted that a separate pressure transducer may not necessary for each cylinder, although more precise control can be effected when each cylinder is equipped with a pressure transducer. The response time of the piston to an error signal will depend on the type and pitch of the threads, the number of turns the piston must make in traversing between the upper and lower stops, the percentage of the cylinder differential pressure that can be converted to torque, the lubrication efficiency, and especially, the number of ignition events per second.

For a car at cruising speed with the engine turning over at

2400 rpm, each cylinder experiences 20 explosions per second with each explosion tending to urge the piston to the desired position; this will provide ample energy to correct piston position in 500ms or less. The faster the engine is running, the faster the correction.

A major feature of this invention is the capability of providing the vehicle operator with a selector switch on the dashboard, permitting him or her to bias engine operation for maximum economy, maximum power, minimum emissions, or even the octane rating of the fuel used. The microprocessor can store in memory the optimum ratio for each operating condition and when selected the engine can revert to that ratio as "normal"; thus, the driver could personalize the performance of his car.

Referring now to Figure 4, there is shown a wave form diagram for a typical combustion chamber pressure wave (plotted along the ordinate) as a function of the crankshaft angle (plotted along the abscissa) . The compression chamber pressure rises during the compression stroke until the pressure reaches a maximum value 90 at the occurrence of ignition. The pressure continues to rise until the peak detonation pressure is reached at 92.

Referring now to Figure 8, there is illustrated an arrangement for varying the compression ratio of a diesel engine. The piston and cylinder arrangement of Figure 8 is the same as the arrangement shown in Figures 1, 2, 6 and 7, except that fuel injectors 100 and 102 replace the igniters 42 and 44. A throttle control valve (responsive to the throttle) and injector mechanism 106 (triggered by the camshaft) set the mass flow of fuel per second to the engine. The output fuel from the injector 106 is fed to a differential valve 104 which, in response to an output from the microprocessor 60, apportions the fuel between the two injectors. An unequal flow of fuel to the two injectors will cause the piston to rotate, as explained previously, and change the compression ratio. The present invention offers an additional valuable feature for diesel operation: as diesel engines are normally difficult to

start, the engine can be programmed for a delay of about 500ms when a shutdown signal is received to allow adjusting the compression ratio for optimum restarting.

Furthermore, the adaptability of the apparatus to various fuels around the world, by compression ratio adjustment, would be of special interest to the military.

Various modifications and additions to the unique adjustable compression ratio piston/cylinder apparatus described above will occur to those skilled in the art without involving any departure from the spirit and scope of my invention as set forth in the appended claims .