US3059624A

US3059624A - Two-stroke internal combustion engines

Info

Publication number: US3059624A
Authority: US
Publication date: 1962-10-23
Anticipated expiration: 1979-10-23

Description

Oct. 23, 1962 P. TORRE TWO-STROKE INTERNAL COMBUSTION ENGINES 3 Sheets-Sheet 1 Filed June 8, 1961 a 7 .Hllll Fr ///v f/V////////V// 12:8.

Oct. 23, 1962 P. L. ,TORRE 3,059,624

-TWO-STROKE INTERNAL COMBUSTION ENGINES Filed June a, '19s; 3 Sheets-Sheet 2 c n1|- FLQ- 2 Oct. 23, 1962 P. TORRE 3,059,624

TWO-STROKE INTERNAL COMBUSTION ENGINES Filed June 8, 1961 3 Sheets-Sheet 3 Fig. 3

United States Patent 3,059,624 TWO-STROKE INTERNAL COMBUSTION ENGINES Pier Luigi Torre, Milan, Italy, assignor of one-half to Innocenti Soc. Gen. per PIndustria Metallurgica e Meccanica, Milan, Italy Filed June 8, 1961, Ser. No. 115,761 Claims priority, application Italy June 15, 1960 4 Claims. (Cl. 123-59) This invention relates to two-stroke internal combustion engines of the character wherein fuel mixture is drawn from a carburetor to the crankcase of the engine through a non-return valve on compression stroke and is compressed in the crankcase and ultimately transferred to the cylinder during expansion stroke.

In bi-cylindrical engines of the character mentioned above a partition is provided in the crankcase accommodating an intermediate bearing for the crankshaft and sub-dividing the crankcase into two pre-compression chambers associated with the respective cylinders, each of the two pre-compression chambers connecting with the carburetor through its own non-return valve and through a common induction passage extending from the valves to the carburetor.

Serious difliculties have been encountered in practice in the attempt of reducing the pressure drop across the valves as far as possible thereby to improve the filling factor of the engine. Reed-valves have been employed to this end, having low inertia and ofiering relatively large ports for the flow of fuel mixture.

-It is an object of this invention to still more increase the overall area of the ports thereby to substantially increase filling the pre-compression chambers hence efficiency of the engine.

Another object of the invention consists in providing a non-return valve unit for the cylinder or each cylinder of the engine which is easily assemblable and exchangeable when necessary.

Further objects and characteristic features of the invention will result from the following description wherein reference is made to the accompanying drawing, in which:

FIG. 1 is a vertical sectional view of a two-cylinder twostroke engine embodying the invention;

FIG. 2 is a vertical sectional view of a one-cylinder engine, and

FIG. 3 is a cross sectional view on line IHIH of FIG. 2.

Referring to FIGURE 1, the engine shown comprises an engine block A having a crankcase B fluid-tight bolted thereto and a pair of cylinders C in in-line arrangement, one only of the cylinders being therefore visible on the drawing. =A crankshaft extends perpendicularly to the plane of the figure including a pair of crankpins D associated with the respective cylinders C and an intermediate bearing journal D the crankpins D being operatively connected by means of connecting rods E with pistons F reciprocable in the respective cylinders.

The intermediate journal D is rotatably supported by a plain bearing M mounted in a transverse partition L which is cast-formed both in the engine block A and crankcase B. In this manner each of the cylinders has an underlying pre-compression chamber associated therewith. A section of the partition which is adjacent the bottom B of the crankcase in enlarged to thereby enclose a pair of co-axial outwardly opening

cylindrical seatings

3, 3, the common axis of which extends transversely of the crankshaft axis beneath the bearing M.

Two independent valve bodies 21 are inserted into respective seats 3. The valve bodies each comprise a prismatic flat-face middle portion 21 and two

cylindrical end flanges

22, 23. A sealing ring 11 is provided on each inward flange 22.

The seats 3 connect with respective pre-compression chambers and comprise each a middle cylindrical portion 3a as obtained from casting and two machined cylindrical end portions 3b, 36, which are larger and smaller in diameter, respectively, than the middle portion 3a. The portion 3c of the seat 3 receives in a fluid-tight relation the flange 22 with its sealing ring .11.

The flange 23 is received by the portion 3b of the respective seat 3 and is formed with an outer bead 23a to thereby act as a cover sealed by a flat annular seal 24.

An inwardly flaring recess 5 is formed within each of the valve bodies and opens on the inward flange 22 to connect with an induction conduit 6 leading to a carburetor, the conduit 6 being formed in the crankcase from the bottom of the latter towards bearing M.

Transverse apertures 7 extend from the recess 5 perpendicular to the flat opposite faces of the prismatic portion 21 of the valve body. The apertures are controlled by reeds 8 in a manner known in the art, providing nonreturn valves between the conduit 6 and respective pre compression chambers in the crankcase which open during the compression stroke of the respective piston to allow flow of fresh mixture from the carburetor to said precompression chamber.

It will be seen that the

seats

3, 3 leave therebetween a solid portion. 25 in the crankcase supporting the bearing M to thereby reinforce this region of the crankcase against thrusts applied thereon by the crankshaft.

In addition to the objects and advantages set out in the preamble the above described arrangement aifords the further following advantages:

(a) Base in assembly of the valve bodies with their seals, for the axial pressure required for assembling the valve bodies into their seats acts only at the end of the necessary axial displacement to engage the

cylindrical flanges

22, 23 of the valve bodies in the

machined sections

3b, 3c of the seats. Wear on the sealing ring 11 during assembly is thereby insignificant.

(b) The machined surfaces 3b, 30 on the seat are of limited area and require thus a limited work only.

(0) Each valve body feeds its own cylinder.

According to the modification shown in FIGURES 2 and 3 which refer to a one-cylinder engine and in which similar references are used to denote parts similar to those shown on FIG. 1, the non-return valve unit comprises a

single valve body

21, 22, 23 of the previously described type, arranged in a seat formed transversely beneath one of the journal bearings M for the engine shaft (FIG. 3).

In use in connection with one-cylinder engines the further following main advantages are obtained.

(1) The valve body is angularly so positioned in its seating 3 that the intake passages controlled by the reeds 8 open in the direction towards the overflow conduit, so that the mixture flowing to the precompression chamber does not undergo any sharp change in direction to enter the conduit. I

(2) The sense of rotation of the engine shaft is advantageously selected so that on rotation its cranks generate at the valve region an underpressure which furthers the mixture admission to the precompression chamber.

(3) The arrangement of the valve is such that during suction of the fresh mixture before the latter enters the overflow conduit it directly impinges upon the crank pin and big end of the connecting rod, thereby improving lubrication and cooling of the said components.

(4) The solid portion 25 provides a curved baffle (FIG. 2) for the mixture flow entering the recess 5, in the valve body, thereby avoiding whirling.

What I claim is:

1. A two-stroke internal combustion engine comprising an engine block having a cylinder therein, a crankcase having a bottom wall, the said engine block and crankcase jointly enclosing a pre-compression chamber, a crankshaft rotatable in the chamber, a journal bearing for the crankshaft jointly supported by the engine block and crankcase, a cylindrical axially elongated seating formed in the crankcase on an axis which is transverse to the longitudinal axis of the crankshaft and is located between the said journal bearing and bottom wall of the crank case, the said seating including an outwardly opening first cylindrical end section, a cylindrical inner end section of a diameter smaller than that of the said first cylindrical end section and an intermediate cylindrical section of a diameter the value of which is intermediate the values of the diameters of the two end sections, the said intermediate cylindrical section opening into the pre-compression chamber, a non-return reed-valve unit axially inserted into the seating, the said valve unit including a valve body comprising a pair of end flanges engaging with respective cylindrical end sections of the .seating and a flattened intermediate section substantially co-extensive axially with the intermediate section of the seating, a cavity extending into the intermediate section of the valve body through axially inner flange of the body, reed-controlled apertures in the saidsintermediate section of the body providing an intake-connection between the cavity and the intermediate section of the seating, and an intakepassage through the bottom wall of the crankcase connecting with the said cavity in the valve body.

2. In the internal combustion engine as claimed in claim 1, a circumferential bead on that flange on the body which engages in the outwardly opening first cylindrical end section of the seating, and a sealing ring axially compressed between the said bead and the crankcase.

3. A two-stroke internal combustion engine comprising an engine block having a pair of in-line cylinders therein, a crankcase having a bottom wall, the said engine block and crankcase jointly enclosing a chamber, a crankshaft rotatable in the chamber including a pair of cranks and an intermediate journal, a transverse partition in the said chamber extending between the pair of cranks subdividing the chamber into a pair of pre-compression chambers associated with the respective cylinders, a pair of cylindrioal axially aligned seatings formed in the partition on an axis which is transverse to the longitudinal axis of the crankshaft and is located between the said intermediate journal and bottom wall of the crankcase, each of the said seatings including an outwardly opening first cylindrical end section, a cylindrical inner end section of a diameter smaller than that of the first cylindrical end section and an intermediate cylindrical section of a diameter the value of which is intermediate the values of the diameters of the two end sections, the intermediate cylindrical section in each seating opennig into its respective pre-compression chamber, a pair of non-return reedvalve units axially inserted into respective seatings each of which includes a valve body comprising a pair of end flanges engaging with respective cylindrical end sections in the respective seating and a flattened intermediate section substantially co-extensive axially with the intermediate section of the seating, a cavity extending into the intermediate section of the body through axially inner flange of the body, reed-controlled apertures in the said intermediate section of the body providing an intake-connection between the cavity and the intermediate section of the seating, and an intake-passage through the bottom wall of the crankcase connecting with the cavities in the two valve bodies.

4. In the internal combustion engine as claimed in claim 3, a circumferential bead on that flange of each valve body which engages in the outwardly opening first cylindrical end section of the seating, and a sealing ring axially compressed between the said bead and the crankcase.

References Cited in the file of this patent UNITED STATES PATENTS 2,973,752 Torre Mar. 7, 1961