Rotary internal combustion engine

Details Rotary internal combustion engine Rotary internal combustion engine

2002-01-14

2003-04-01

Denion, Thomas (Department: 3748)

Internal-combustion engines

Rotary

With transfer means intermediate single compression volume...

C123S236000, C123S209000, C123S228000, C418S122000, C418S150000

Reexamination Certificate

active

06539913

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to an internal combustion engine and, more specifically, to a rotary internal combustion engine having a rotor that is directly coupled to a drive shaft without eccentric gearing.
BACKGROUND OF THE INVENTION
A conventional internal combustion reciprocating engine converts reciprocating motion of a piston within a cylinder into rotating motion via a crankshaft having offset sections coupled to a connecting rod mechanism. While long the standard for internal combustion engines, a four-stroke, or four-cycle, internal combustion reciprocating engine creates power by causing a metal piston to move up and down twice per combustion cycle in a cylinder bore, thereby varying the instantaneous size of the combustion chamber, to achieve one power stroke. This often vertical or inclined motion is changed to a rotational flywheel motion by connecting the piston to an eccentric portion of the crankshaft with a connecting rod. Inertial forces at the top and bottom of each stroke of the reciprocating piston invariably cause vibration and high internal stresses on the engine components. These vibrations and stresses increase with increasing crankshaft angular velocity measured in revolutions per minute (rpm). Only about 50 to 60 percent of total combustion gas pressure exerted on the piston is converted into useable output torque of the crankshaft due primarily to the characteristics of the crank/connecting rod mechanism. In a conventional reciprocating engine essentially all of the pressure generated by the combustion is useful in pushing the piston to do work. However, much of the energy lost in a conventional reciprocating engine is caused by the redirection of a linear motion of the piston into a rotary motion of the crankshaft.
Due to a valve overlap period in which both the intake valve and the exhaust valve are open even after exhaust is expelled, a small amount of combustion gas remains in the combustion chamber and, therefore, it is difficult to both improve on the combustibility of the mixture and to decrease the amount of unburned gas. Meanwhile, the structure of the crank mechanism and valve operating mechanism, that is: the camshaft, intake valves and exhaust valves; is quite complex and requires precise adjustment. It is therefore difficult to decrease vibration and noise caused by the reciprocating motion of the piston. It is also difficult to revise the size of the four-cycle reciprocating engine without decreasing the output horsepower of the engine.
An alternative embodiment of the internal combustion engine that has enjoyed significant development is the rotary engine. The rotary engines of interest are not to be confused with the rotary aircraft engines of the early 20th Century. These rotary aircraft engines comprise a crankshaft fixed to the aircraft structure and a plurality of cylinders radially positioned about the crankshaft such that the crankshaft remains fixedly coupled to the vehicle, in this instance an aircraft, while the engine block, cylinders and pistons, rotate about the crankshaft. The propeller is fixedly coupled to the engine block and rotates with the engine block assembly. By contrast, the rotary engine used in automotive applications employs an engine block fixed to the vehicle and an internally rotating “piston” that causes a drive shaft to rotate relative to the vehicle.
Accordingly, until present, various kinds of rotary-piston type internal combustion engines, also know as rotary piston engines, have been proposed. More specifically, rotary piston engines can be classified as either: (a) direct-rotation type rotary piston engines having a rotor rotating coaxially with the output shaft or, (b) planetary-rotation type rotary piston engines having a rotor geared to and rotating eccentrically about the output shaft. As the structure of classical approaches to the former, i.e., direct-rotation engines, has generally been believed to be more complex than that of the latter, i.e., planetary-rotation engines, the former has generally not been put into practical use. However, the Wankel rotary piston engine, an example of the planetary-rotation engine has seen considerable development and has been put to practical use since the 1930's.
In the Wankel rotary engine, an arciform deltoid rotor is held within a rotor holding bore which has an inner surface cross section that is similar to a peritrochoidal curve. The conformance to a peritrochoidal profile is driven by the requirement that all three bearing points of the Wankel rotor remain in constant contact with the inner surface of the engine. The rotor is rotated in a planetary motion through the engaging of a rotor gear on the rotor with a gear on an output shaft. The location of the arciform deltoid rotor within the rotor holding bore creates three chambers therein. Depending on the planetary motion of the rotor, while the chambers outside of the rotor vary their capacities, four strokes of intake (suction), compression, combustion (expansion) and exhaust are performed. Because of the peritrochoidal chamber, the Wankel has an exhaust cavity immediately following the ignition point that rapidly enlarges. This causes a significant portion of the gas pressure to be lost as expansion within the enlarging cavity, and not converting the expansion pressure into useable torque. It is also notable that in the Wankel engine, the combustion gas pressure is exerted on both: (a) a pressure-receiving rotor surface facing, but just rotationally beyond, the point of combustion, and (b) a trailing portion of the rotor surface facing, but that is rotationally before the point of combustion. This pressure on the trailing portion of the rotor surface effectively attempts to drive the rotor in reverse, thereby reducing the engine efficiency. Therefore, it is generally accepted that only about 60 to 70 percent of the combustion gas pressure received by the rotor can be converted into output torque. Significantly, the architecture of the Wankel engine, i.e., a peritrochoidal section, makes it difficult to improve the combustibility in the combustion stroke and to decrease the exhaust quantity of unburned gases.
Until present, various types of direct-rotation rotary engines have been proposed.
FIGS. 12-17
show highly schematic, well-known, direct-rotation rotary engines
300
A-
300
F.
FIG. 18
shows a direct-rotation rotary engine
300
G put into practical use by Malorie Co. This engine
300
G has a housing
300
, a rotor
301
, a suction port
302
, an ignition plug
303
, an exhaust port
304
and a scavenging port
305
with the rotor
301
rotating clockwise. An engine
300
H shown in
FIG. 18
is provided with a housing
310
, a suction port
311
, an exhaust port
312
, a rotor holding bore
313
, a rotor
314
coaxial with the bore
313
, cycloid tooth portions
315
,
316
formed on the rotor
314
, a first small cylindrical driven rotor
317
, a second small cylindrical driven rotor
318
, a combustion subchamber
323
and an exhaust chamber
324
. A prototype of this engine
300
H made in about 1945 was reported to have high output horse power performance notwithstanding its small and light structure. However, the engine was not put into practical use after its development.
Next, descriptions will be given concerning technical problems of the above prior art. In the various direct-rotation engines
300
A-
300
F shown in
FIGS. 12-17
, the axial center of the rotor is eccentric to the axial center of the rotor holding bore, and presumably some portion of the combustion gases will generate an intrinsically reverse-driving torque. Thus, it is difficult to improve the efficiency in converting the combustion gas pressure into output torque. For an engine having plural cylinders, a straight output shaft cannot be applied, and moreover, the structure of the output shaft becomes complicated and engine vibrations will occur due to this eccentric structure.
Other problems include: (a) difficulty in providing adequate durability of gas sealing

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