US3749067A - Two-cycle internal combustion engine - Google Patents

Abstract

A two-cycle internal combustion engine comprising a cylinder having an exhaust port, an exhaust passage, a main scavenging port, a main scavenging passage, an auxiliary scavenging port and an auxiliary scavenging passage; a piston; a connecting rod; a crank shaft; a crank case and an intake reed valve mounted on said crank case for introducing therethrough fuel-air mixture into said crank case; in which the end of said auxiliary scavenging passage open at one end into said crank case is located substantially in alignment with a tangential line of circular periphery of one of crank webs of the crank shaft, which tangential line extends parallel to the axis of said cylinder from crank web portion moving toward said cylinder, and said intake reed valve is located between said open end of the auxiliary intake passage and said crank web in the proximity to said tengential line, whereby a part of the mixture having been drawn into said crank case through said intake reed valve is forcibly fed into said cylinder through said auxiliary scavenging passage and said auxiliary scavenging port under the booster effect of the rotating crank web, thus enhancing the fuel charging efficiency of the engine.

Description

( 1 July 31, 1973 United States Patent 1 Kobayashi et a1.

ABSTRACT 1 TWO-CYCLE INTERNAL COMBUSTION ENGINE A two-cycle internal combustion engine comprising a lnventors: Torao Kobayashi; Hisashi lnaga, cylinder having an exhaust port, an exhaust passage, a

' both of Tokyo, Japan main scavenging port, a main scavenging passage, an auxiliary scavenging port and an auxiliary scavenging [73] Assignee: Kioritz Corporation, Tokyo, Japan Filed: Nov. 19, 1971 passage; a piston; a connecting rod; a crank shaft; a

crank case and an intake reed valve mounted on said crank case for introducing therethrough fuel-air mixture into said crank case; in which the end of said auxiliary scavenging passage open at one end into said crank [21] App]. No.: 200,332

case is located substantially in alignment with a tangential line of circular periphery of one of crank webs of the crank shaft, which tangential line extends parallel to the axis of said cylinder from crank web portion 4 3 0A7 3 A 3 F5 /33 3 A3 73 ,0A H P P P m7 3 n 3 3 H mm 3 i 2 1 U/ 3 3A 3 1 u W A 3 w W3 m .D m m C S3 L C 3 d2 s m UhF F ned 555 moving toward said cylinder, and said intake reed valve is located between said open end of the auxiliary intake drawn into said crank case through said intake reed valve is forcibly fed into said cylinder through said auxiliary scavenging passage and said auxiliary scavenging port under the booster effect of the rotating crank web, thus enhancing the fuel charging efficiency of the eng1 References Cited UNITED STATES PATENTS 3,687,118 8/1972 Nomura............................ 1,795,551 3/1931 Geisse....... 2,822,793 2/1958 Bellwinkle et a1. 2,844,131 7/1958 Beveridge.........................

Primary ExaminerWendell E. Burns Attorney-Karl W. Flocks 3 Claims, 4 Drawing Figures PAIENIED m3 1 ma SHEET 1 BF 2 FIG PAIENIEUJUU 1 I975 SHEET 2 0f 2 FIG.3

i I TWO-CYCLE INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION Conventional piston valve type two-cycle internal combustion engines have been so constructed that an intake pipe is connected to the wall of a cylinder and the mixture is drawn into a crank case through an intake port formed in the wall of said cylinder by making use of the suction created by the reciprocal motion of a piston. However, in such a piston valve type twocycle engine, since an exhaust port, a scavenging port and an intake port must be arranged in the wall of the cylinder whose surface area is limited, the relative positions, the shapes and the sizes of these ports have been subjected to restriction. Moreover, since the intake port is opened and closed by the reciprocating piston, the opening range of the intake port has been restricted to the crank angles symmetrical with respect to the bottom dead center of the piston.

Recently, another type of internal two-cycle combustion engine has been developed and put in practical use, in which an intake pipe and an intake valve are connected to a crank case and the wall of a cylinder has -only an exhaust port and a scavenging port formed therein this type being referred as crank valve type two cycle engine hereunder. According to such type of two-cycle internal combustion engine, since only the exhaust port and the scavenging port are formed in the wall of the cylinder, the positions and shapes of these ports can be selected more freely as compared with the conventional piston valve types and hence an improved scavenging efficiency and an improved cooling effect has become obtainable. Further, the opening and closing ranges of the intake valve mounted on the crank case can be set within optional angular ranges in the crank rotation, which enables a higher charging efficiency to be obtained and the output of the engine to be increased to the extent.

This invention concerns a construction of such crank valve type two-cycle internal combustion engine.

SUMMARY OF THE INVENTION The present invention consists in a crank valve type two-cycle internal combustion engine with intake reed valve and additionally provided with an auxiliary scavenging port formed in the wall of the cylinder and opened and closed at substantially the same angular range in the crank rotation as that of the main scavenging port, and an auxiliary scavenging passage extending in the wall of the cylinder and communicating said auxiliary scavenging port with the interior of the crank case, the relative geometrical positions of the open end of said auxiliary scavenging passage open into the crank case, the outer periphery of one of the crank webs of the crank shaft rotatably supported in the crank case, and the intake reed valve mounted on said crank case being such that said open end of the auxiliary scavenging passage is substantially in alignment with a tangential line from a point on the circular periphery of one of the crank webs, which point lying on that side of the crank web of the rotating crank shaft as moving toward the cylinder, and said intake reed valve is located between said open end of the auxiliary scavenging passage and said crank web in the proximity to said tangential line, a part of the mixture having been drawn into the crank case through said intake reed valve is forcibly fed into the cylinder through said auxil- 2 iary scavenging passage and said auxiliary scavenging port under the booster effect of the rotating crank web. Thus, a primary object of the invention is to increase the quantity of the mixture to be charged into the cylinder through the auxiliary scavenging passage in one cycle of the engine operation and thereby to enhance the charging efficiency of the engine as a whole and increase the output of the two-cycle internal combustion engine.

Another object of the invention is to enhance the charging efficiency of the two-cycle internal combustion engine by a simple and inexpensive construction.

Still another object of the invention is to achieve the objects set forth above and at the same time, to render the construction of particularly a multi-cylinder twocycle internal combustion engine relatively compact.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of a two-cycle internal combustion engine according to the present invention;

FIG. 2 is a plan view of the crank case of a twocylinder two-cycle internal combustion engine according to the invention as viewed from the cylinder side.

FIG. 3 is a transverse sectional view of the cylinder of the two-cycle internal combustion engine of the invention taken along the line III-III of FIG. I; and

FIG. 4 is a vertical sectional view of a reed valve particularly adapted to be used as the intake valve of the two-cycle internal combustion engine of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, reference numeral 1 designates a cylinder in which a piston 4 makes a reciprocal motion along the inner surface thereof. Reference numerals 2 and 3 designate an upper portion and a lower portion of a crank case respectively, and a crank shaft is rotatably supported within the crank case. Reference numeral 5 designates a piston pin, 6 a connecting rod, 7 a crank pin of the crank shaft and 8 a crank webs of the crank shaft. The cylinder 1 is provided with an exhaust port 14 and a main scavenging port 15, and an exhaust pipe 26 is connected with said exhaust port. Reference numeral 20 designates the mating surface of the cylinder and the crank case.

An intake reed valve 9 is mounted in a valve chamber 24 defined by the wall of the crank case (the upper portion 2 of the crank case) and an intake pipe 13 is connected with the crank case for communication with said intake reed valve 9.

An auxiliary scavenging passage 17 is formed extending through the wall of the cylinder 1, with one end thereof open in the inner surface of the cylinder as an auxiliary scavenging port 16 and the other end open into the crank case at a notch 19 formed in the crank case and open at the mating surface 20.

The two-cycle internal combustion engine of the invention is characterized especially by the relative position of the intake reed valve 9, the notch 19 formed in the crank case for communication with the auxiliary scavenging passage and serving as one end of said auxiliary scavenging passage 17, and the crank web 8.

Namely, according to the present invention, the end of the auxiliary scavenging passage open into the crank case is located substantially in alignment with a tangential line extending from a point on the circular periphery of the crank web 8 in parallel relation to the axis of the cylinder at side of the rotating crank web moving toward the cylinder, and the intake reed valve is located between said open end of the auxiliary scavenging passage and said crank web in the proximity to said tangential line.

By arranging as described above, in a portion of the mixture having been drawn into the crank case through the intake reed valve 9 there may be induced a velocity toward said end of the auxiliary scavenging passage 17 open into said crank case by the rotation of the crank web. This velocity has an effect of directing said mixture toward the cylinder. Thus, the mixture is forcibly directed into the auxiliary scavenging passage under the booster effect and fed into the combustion chamber of the cylinder through the auxiliary scavenging port 16, whereby the charging efficiency of the engine can be drastically increased and the output of the two-cycle internal combustion engine can be substantially increased. A test conducted on the actual engine revealed that the output is increased by about 10 percent.

FIG. 2 is a plan view of the crank case of the twocylinder two-cycle internal combustion engine, according to the present invention, in which the relative positions, in the circumferential direction of the cylinder, of a scavenging passage leading to the scavenging port and the auxiliary scavenging passage 17 are shown.

In FIG. 2, the line Y-Y is the median line of the two cylinders, and the pertinent portions of the crank case and the two cylinders are arranged symmetrically with respect to this line. With regard to each cylinder, notches 22 (formed at two locations circumferentially of the cylinder in the embodiment shown) communicating with the scavenging port 15 of the cylinder are symmetrically arranged with respect to the center line CC passing through the center of each cylinder and making an angle of X with respect to the median line Y-Y. The other notch 19 for communication with the auxiliary scavenging port 16 is arranged on said center line CC.

FIG. 3 shows a sectional view of one of the cylinders which is to be mounted on the crank case shown in FIG. 2, taken along the line corresponding to the line III-III of FIG. 1. The line CC in FIG. 3 of course corresponds to the line CC in FIG. 2. It will be seen from this FIGURE that the auxiliary scavenging port 16 and the exhaust port 14 are located on the line CC in diametrically opposite positions of the cylinder and the two scavenging ports 15 are arranged symmetrically with respect to said line CC.

The center plane CC is at an angle a to a line perpendicular to the crank axis. This angle a is about 30 in the case that the notch 19 (see FIG. 2) communicated with the auxiliary scavenging port 16 is located on the tangential line extending from a point on the circular periphery of one of the crank webs 8 in parallel relation to the central axis of the cylinder. By inclining the line CC with respect to the median line Y-Y as described above and locating the auxiliary scavenging port 16 and the exhaust port 14 on said line CC in diametrically opposite positions of the cylinder, it is possible to locate the main scavenging ports 15 in positions symmetrical with respect to the center line CC as shown in FIGS. 2 and 3, and hence to make the dimensions of the crank case and the cylinder in the direction of crank shaft relatively small as compared with the case of selecting said line CC in a direction perpendi cular to the axis of the crank or in parallel to the median line Y(.

Namely, by arranging the crank web and the notch 19 to communicate with the auxiliary scavenging port 17 as in the present invention, the charging efficiency can be increased and simultaneously the dimensions of the crank case-cylinder assembly, when it is a multicylinder engine, can be made compact.

In FIG. 4 there is shown the structure of a reed valve which is particularly adapted for use as the intake valve of the two-cycle internal combustion engine according to the invention. As seen, a reed 10 and stop 11 for regulating the degree of opening of said reed are connected to a support 9 having a substantially triangular portion projecting toward the downstream of the passage. The reed valve of such construction may be mounted in an intake valve inserting opening 21 formed on the crank case wall as shown in FIG. 2.

We claim:

1. A two-cycle internal combustion engine comprising at least one cylinder each having an exhaust port, main scavenging ports, main scavenging passages, an auxiliary scavenging port and an auxiliary scavenging passage; a piston; a connecting rod; a crank shaft; a crank case and an intake reed valve mounted on said crank case; in which the end of said auxiliary scavenging passage open into said crank case is located substantially in alignment with a tangential line extending from a point on a circular periphery of one crank web of the crank shaft in parallel relation to the axis of said cylinder at the side of the crank web moving toward said cylinder, and said intake reed valve is located between said end of the auxiliary scavenging passage open into said crank case and said crank web in the proximity to said tangential line, whereby part of the mixture having been drawn into said crank case through said intake reed valve is forcibly fed into said cylinder through said auxiliary scavenging passage and said auxiliary scavenging port under the booster effected by the rotation of said crank web.

2. A two-cycle internal combustion engine according to claim 1, in which a notch formed on a surface of the crank case mating with the cylinder and serving as one end of said auxiliary scavenging passage and said exhaust port are located in diametrically opposite positions of the cylinder, and a plane including the center of said notch and said exhaust port is inclined at an angle of about 30 to a plane perpendicular to the crank axis of the engine.

3. A two-cycle internal combustion engine according to claim 2 comprising a plurality of cylinders, the positional arrangement in one cylinder of those inclusive of the exhaust port, a pair of the main scavenging passages, the auxiliary scavenging passage, the notch serving as one end of said auxiliary scavenging open into the crank case, and a pair of notches formed on the mating surface of the crank case in symmetrical relation with each other with respect to the center line of the cylinder and serving as the open ends of said main scavenging passages is substantially in symmetrical relation with that of the next cylinder with respect to the median line between said two cylinders.

t t t i U

Claims (3)

1. A two-cycle internal combustion engine comprising at least one cylinder each having an exhaust port, main scavenging ports, main scavenging passages, an auxiliary scavenging port and an auxiliary scavenging passage; a piston; a connecting rod; a crank shaft; a crank case and an intake reed valve mounted on said crank case; in which the end of said auxiliary scavenging passage open into said crank case is located substantially in alignment with a tangential line extending from a point on a circular periphery of one crank web of the crank shaft in parallel relation to the axis of said cylinder at the side of the crank web moving toward said cylinder, and said intake reed valve is located between said end of the auxiliary scavenging passage open into said crank case and said crank web in the proximity to said tangential line, whereby part of the mixture having been drawn into said crank case through said intake reed valve is forcibly fed into said cylinder through said auxiliary scavenging passage and said auxiliary scavenging port under the booster effected by the rotation of said crank web.

2. A two-cycle internal combustion engine according to claim 1, in which a notch formed on a surface of the crank case mating with the cylinder and serving as one end of said auxiliary scavenging passage and said exhaust port are located in diametrically opposite positions of the cylinder, and a plane including the center of said notch and said exhaust port is inclined at an angle of about 30* to a plane perpendicular to the crank axis of the engine.

3. A two-cycle internal combustion engine according to claim 2 comprising a plurality of cylinders, the positional arrangement in one cylinder of those inclusive of the exhaust port, a pair of the main scavenging passages, the auxiliary scavenging passage, the notch serving as one end of said auxiliary scavenging open into the crank case, and a pair of notches formed on the mating surface of the crank case in symmetrical relation with each other with respect to the center line of the cylinder and serving as the open ends of said main scavenging passages is substantially in symmetrical relation with that of the next cylinder with respect to the median line between said two cylinders.

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