US2788778A - Valve for two-cycle internal combustion engine - Google Patents

Description

April 16, 1957 E. c. KIEKHAEFER 2,788,778

VALVE FOR TWO-CYCLE INTERNAL COMBUSTION ENGINE Filed July 5, 195a INVENTORQ ELMER G. K/EKHAEFER United States Patnt VALVE FOR TWO-CYCLE INTERNAL COMBUSTION ENGINE Elmer C. Kiekhaefer, Cedarburg, Wis.

Application July 3, 1956, Serial No. 595,754

6 Claims. (Cl. 123-73) This invention relates generally to twocycle internal combustion engines and more specifically to valve induction means for such an engine.

In the operation of a two-cycle engine, the fuel mixture is admitted into each cylinder through a passage in the side of the cylinder block. Each passage communicates with a respective crank chamber and opens through ports into the respective cylinder bore. The exhaust gases are discharged through opposite ports opening from each cylinder bore into suitable exhaust means. The intake and exhaust ports of each bore are controlled by the respective piston which opens the ports at the lower end of each piston stroke and otherwise closes the ports during the compression and power stroke. The induction of a fuel-air mixture into the respective crank chambers and the precompression of the fuel mixture for transfer through the passages to the respective cylinder and to displace the exhaust gases remaining in the fired cylinder is effected within each crank chamber by the corresponding piston during the upward and downward power strokes respectively. Valve induction means such as rcy tary valves or reeds are provided through which the fuel mixture is admitted into the crank chambers.

In two-cycle internal combustion engines of the type described, a governor means for controlling the maximum rotational speed of the engine is normally provided separate and distinct from the crankcase valve induction means. Applicants invention provides a novel crankcase valve induction means which admits a fuel mixture into the crank chambers and functions as a governor to control the rotational speed of the engine.

It is therefore an object of the present invention to provide a crankcase valve induction means for admitting a fuel charge into the crank chamber and controlling the rotational speed of the engine.

Another object of the invention is the provision of a reed valve unit which will operate more efficiently to admit a greater fuel charge into the crank chamber.

It is still another object of the invention to provide valve induction means for adjustably varying the governing action of the engine and hence selectively controlling its maximum rotational speed.

Objects and advantages other than those set forth above will be apparent from the following description when read in connection with the acompanying drawing, in which:

Fig. l is a view in section of a two-cycle internal combustion engine employing crankcase precompression;

Fig. 2 is an enlarged view of the crankshaft shown in Fig. 1;

Fig. 3 is a reduced view taken along line 3-3 of Fig. 2; and

Fig. 4 is a reduced view taken along line 44 of Fig. 2.

As shown in the drawings, the invention is embodied in a two-cycle internal combustion engine 1 having a cylinder block 2 and crankcase member 3 which join in a transverse plane passing through the axis of the engine crankshaft 4. The crankshaft 4 is supported at each end in bearing assemblies 6, 7 carried by the cylinder block 2 and the crankcase member 3.

Each of two cylinder bores 8 formed by the block 2 and opening into the crankcase 3 carries a piston 9 connected by a rod 11 to a corresponding upper and lower crank throw 12 respectively of the crankshaft 4. The crank throws 12 comprise crankcheeks 13 and are spaced degrees with respect to the crankshaft axis so that the pistons reciprocate in opposite directions for alternate firing of each 180 degrees of crankshaft rotation.

The crankcase 3 is divided into separate upper and lower crank chambers 14, 16 by a bearing block 17 which comprises two complementary, semi-circular bearing members 18, 19 joined by bolts passing therethrough near the peripheries thereof, not shown. The bearing members 18, 19 form an axial bore 21 adapted to fit and receive a center journal 22 of the cranckshaft 4 for the journal support thereof. The center journal 22 is provided with an axial opening 23 extending through the crankchecks 13 to provide a passageway for the fuel mixture into the respective crank chambers 14, 16. The inner periphery of the bearing members 18, 19 further forms an annular groove 24 of U-shaped cross section surrounding the center journal 22. The center journal 22 is provided with a plurality of openings 26 connecting the passageway 23 with the groove 24. An induction manifold passage 27 is provided by the bearing block 17 having one end connected to the annular groove 24 and the other end registering with an opening 28 in the crankcase member 3. A carburetor 29 is secured to the crankcase member 3 by means of screws, not shown, and has a fuel opening 31 in register with the crankcase opening 28.

The admission of a fuel mixture through the passageway 23 into the crank chambers 14, 16 is controlled by reeds 32 comprising flexible thin spring steel members each of which has a U-shaped end 33 secured flatwise to the crankcheek 13 by means of cap screws 34 extending through elongated slots 36 formed by the reeds 32, and an elongated, rectangularly shaped opposite end 37 extending lengthwise over the passageway 23. During the upstroke of the piston 9 a reduced pressure is obtained within the respective chamber which allows the fuel mixture at atmospheric pressure within the passageway 23 to lift the reeds 32 from the crankcheek 13 to open the passageway.

For maximum service, the flexing of the reeds 32 must be restricted .to within the elastic limits of the metal and the stresses should be distributed equally throughout the length of the reed. Steel guard members 35 are provided to limit the flexing of the reeds to a safe amount.

In the operation of the engine, with the pistons 9 as shown in Fig. 1, a pressure below atmospheric is developed in the upper crank chamber 14 whereas a pressure in excess of atmospheric is developed in the lower crank chamber 16. The force developed by the pressure differential between atmospheric and upper crank chamber pressure acting upon the reed area exposed thereto lifts the reed valve 32 and causes a fuel mixture to be forced from the carburetor 29 through the opening 28, passage 27, groove 24, openings 26 and passageway 23 into the upper chank chamber 14. The greater pressure within the lower crank chamber 16 closes the reed valve 32 therein. As the reed valve 32 in the upper crank chamber 16 rotates with the crankshaft 4, a centrifugal force which I increases as the rotational speed of the engine 1 increases acts thereon tending to close the reed valve 32 and decrease the effective fuel mixture inlet area in opposition to the aforementioned force acting to lift the reed valve 32. In this manner, the reed valve 32 functions as an elfective governor for maintaining and limiting the maximum rotational speed of the engine 1. The maximum rotational speed of the engine 1 may be changed by loosening the cap screws 34 and moving the reed valve 32 radially outwardly or inwardly thereby subjecting the reed 32 to an increased or decreased centrifugal force respectively acting on the reed at any constant rotational engine speed. Subjecting the reed valve 32 to an increased or decreased centrifugal force in effect decreases or increases respectively the maximum rotational speed of the engine 1. Therefore, by permitting radial movement of the reed valve, it is possible to selectively vary within a fixed range the maximum rotational speed of the engine 1.

Although but one embodiment has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a two-cycle internal combustion engine having a crankshaft forming a crankcheek and being supported by a crankcase, a valve induction means therefore comprising: an axial fuel mixture induction passage formed by said crankshaft and extending through said crankcheek into said crankcase; and a flexible reed secured at one end to said crankcheek and having the other end disposed to control the admission of a fuel mixture through said fuel induction passage, said other end of said reed being subjected to a centrifugal force upon rotation of said crankshaft tending to close said reed to provide a governing means for said engine.

2. In a two-cycle internal combustion engine having a V crankshaft forming a crankcheek and being supported by a crankcase, a valve induction means therefore comprising: an axial fuel induction passage formed by said crankshaft and extending through said crankcheek into said crankcase; a flexible reed secured at one end to said crankcheek and having the other end disposed to control the admission of a fuel mixture through said fuel induction passage, said other end of said reed being subjected to a centrifugal force upon rotation of said crankshaft tending'to close said reed to provide a governing means for said engine; and means provided by said reed for selectively varying the maximum rotational speed of the engine.

3. In a two-cycle internal combustion engine having a crankshaft forming a crankcheek and being supported by a crankcase, a valve induction means therefore comprising: an axial'fuel mixture induction passage formed by said crankshaft and extending through said crankcheek into said crankcase; a flexible reed having an elongated slot at one end through which a screw extends to secure said reed end to said crankcheek, said reed being adjustably movable along a substantially radial line to selectively vary the maximum rotational speed of said engine; and said other end of said reed being disposed to control the admission of a fuel mixture through said fuel induction passage and further being subjected to a centrifugal force upon rotation of said crankshaft tending to close' said reed to provide a governing means for said engine.

4. in a two-cycle internal combustion engine, the combination of: a crankcase; a crankshaft carried by said crankcase and having spaced crankcheeks connected by a center journal, said crankcheeks and said center journal forming an axial passageway therethrough, said center journal having a radially extending opening connected to said passageway; a bearing member journally supporting said center journal and dividing said crankcase into individual crank chambers adapted to receive a fuel mixture for precompression, said bearing member having an annular groove surrounding said center journal in register with said opening; a fuel passage formed by said bearing member connected to said groove for the admission of a fuel mixture through said passage, said groove, said opening and said passageway to said chambers during the induction cycle'of the respective chamber; and a flexible reed secured at one end to each of said crankcheeks and having the other end disposed to control the admission of the fuel mixture through said passageway, said other end of said reed being subjected to a centrifugal force upon rotation of said crankshaft tending to close said reed to provide governing means for said engine.

5. In a two-cycle internal combustion engine, the combination of: a crankcase, a crankshaft carried by said crankcase and having spaced crankcheeks connected by a center journal, said crankcheeks and said center journal forming an axial passageway therethrough, said center journal having a radially extending opening connected to said passageway; a bearing member journ-ally supporting said center journal and dividing said crankcase into individual crank chambers adapted to receive a fuel mixture for precompression, said bearing member having an annular groove surrounding said center journal in register with said opening; a fuel passage formed by said bearing member and connected to said groove for the admission of a fuel mixture through said passage, said groove, said opening and said passageway to said chambers during the induction cycle of the respective chamher; a flexible reed secured at one end to each of said crankcheeks and having the other end disposed to control the admission of the fuel mixture through said passageway, said other end of said reed being subjected to a centrifugal force upon rotation of said crankshaft tending to close said reed to provide a governing means for said engine; and means provided by said reed for selectively varying the maximum rotational speed of the engine.

bination of: a crankcase; a crankshaft carried by said crankcase and having spaced crankcheeks connected by a center journal, said crankcheeks and said center jourbers during the induction cycle of the respective cham-' her; a flexible reed having an elongated slot at one end through which a screw extends to secure said reed end to said crankcheek, said reed being adjustably movable along a substantially radial line to selectively vary the maximum rotational speed of said engine; and saidother end of said reed being disposed to control the admission of a fuel mixture through said fuel induction passage and further being subjected to a centrifugal force uponrrotation of said crankshaft tending to close said reed to provide a governing means for said engine.

References Cited in the file of this patent UNITED STATES PATENTS 861,673 Parnell July '30, 1907 FOREIGN PATENTS 7 45,000 Sweden Nov. 15,1917

392,732 Germany Mar. 25,1924

6. in a two-cycle internal combustion engine, the com

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