Abstract: A two-stroke engine according to the present invention includes: a separating wall which confines a tip end portion of an ignition device; an ignition promoting chamber which is formed by means of the separating wall, is independent of a combustion chamber, and encloses the tip end portion of the ignition device; and a plurality of communicating holes which are provided in the separating wall, each of which is provided with a first opening that opens in the combustion chamber and a second opening that opens in the ignition promoting chamber, and which provide communication between the combustion chamber and the ignition promoting chamber.

Abstract: To optimize fuel supply of an engine with a carburetor during engine operation, a throttle opening degree detection sensor detecting a throttle opening degree and a control unit controlling a valve body variably controlling an opening degree of a fuel discharge part or a fuel supply passage based on a map are included. The map includes a plurality of sections divided based on the throttle opening degree and an opening degree of the valve body set for each section. The opening degree of the valve body set for each section is the opening degree of the valve body at which the engine rotation speed is highest in each section. The control unit controls an electric actuator driving the valve body to achieve the opening degree of the valve body set in a section to which the throttle opening degree detected by the throttle opening degree detection sensor belongs out of the plurality of sections.

Abstract: To optimize fuel supply of an engine with a carburetor during engine operation, a throttle opening degree detection sensor detecting a throttle opening degree and a control unit controlling a valve body variably controlling an opening degree of a fuel discharge part or a fuel supply passage based on a map are included. The map includes a plurality of sections divided based on the throttle opening degree and an opening degree of the valve body set for each section. The opening degree of the valve body set for each section is the opening degree of the valve body at which the engine rotation speed is highest in each section. The control unit controls an electric actuator driving the valve body to achieve the opening degree of the valve body set in a section to which the throttle opening degree detected by the throttle opening degree detection sensor belongs out of the plurality of sections.

Abstract: A carburetor achieves better emission characteristics while improving a combustion state by increasing a delivery ratio of a stratified scavenging engine and reducing intake resistance. No dividing wall is provided between a throttle valve 204 and a choke valve 242, and a gap 244 between the valves 204 and 242 is opened. Intake air in both of an upper region and a lower region of the choke valve 242 flows into an air-fuel mixture passage 246 in a lower region of the fully-open throttle valve 204. A main nozzle 202 is arranged so as to be inclined toward the throttle valve 204.

Abstract: To allow an intake negative pressure to directly act on a fuel outlet formed on a nozzle tube, and to guide a fuel discharged from the fuel outlet in the nozzle tube to the fuel-air mixture passage. A rotary carburetor (200) has a guide plate member (42) downstream of a fuel outlet (30) located in a through-hole (14). The guide plate member (42) has both side edges (42b) away from an inner wall surface (14a) of the through-hole (14). The through-hole (14) is divided by the guide plate member (42) into a first passage portion (44) and a second passage portion (46). The first passage portion (44) communicates through a piston groove with a scavenging passage of a cylinder. The fuel discharged from the fuel outlet (30) is guided by the guide plate member (42) to the second passage portion (46) and is supplied through the second passage portion (46) to a fuel-air mixture passage (24) of an engine intake system.

Abstract: The present invention is to prevent mixing of fresh air and an air-fuel mixture when a throttle valve is fully opened and increase a delivery ratio. A main nozzle (30) is surrounded by a tunnel-like air flow guiding member (52). The air flow guiding member (52) is opened at its front and back sides. A whole amount of fuel discharged via a main nozzle (30) is sent to a downstream side by an air flow created by the air flow guiding member (52). When a throttle valve (22) and a choke valve (24) are both in a fully-opened state, fresh air flows into an air-fuel mixture passage (12) through a gap between these valves (22, 24).

Abstract: To allow an intake negative pressure to directly act on a fuel outlet formed on a nozzle tube, and to guide a fuel discharged from the fuel outlet in the nozzle tube to the fuel-air mixture passage. A rotary carburetor (200) has a guide plate member (42) downstream of a fuel outlet (30) located in a through-hole (14). The guide plate member (42) has both side edges (42b) away from an inner wall surface (14a) of the through-hole (14). The through-hole (14) is divided by the guide plate member (42) into a first passage portion (44) and a second passage portion (46). The first passage portion (44) communicates through a piston groove with a scavenging passage of a cylinder. The fuel discharged from the fuel outlet (30) is guided by the guide plate member (42) to the second passage portion (46) and is supplied through the second passage portion (46) to a fuel-air mixture passage (24) of an engine intake system.

Abstract: A portable engine-driven working machine has an engine unit and a cover enclosing the engine unit. The engine unit includes a cylinder block, an electronically controlled carburetor, a controller connected to the carburetor and a diagnostic connector connected to the controller. The cover has a cylinder cover partially defining a first chamber containing the cylinder block and partially defining a passage for air which cools the cylinder block, and a removable connector cover partially defining a second chamber containing the diagnostic connector.

Abstract: A carburetor achieves better emission characteristics while improving a combustion state by increasing a delivery ratio of a stratified scavenging engine and reducing intake resistance. No dividing wall is provided between a throttle valve 204 and a choke valve 242, and a gap 244 between the valves 204 and 242 is opened. Intake air in both of an upper region and a lower region of the choke valve 242 flows into an air-fuel mixture passage 246 in a lower region of the fully-open throttle valve 204. A main nozzle 202 is arranged so as to be inclined toward the throttle valve 204.

Abstract: The present invention is to prevent mixing of fresh air and an air-fuel mixture when a throttle valve is fully opened and increase a delivery ratio. A main nozzle (30) is surrounded by a tunnel-like air flow guiding member (52). The air flow guiding member (52) is opened at its front and back sides. A whole amount of fuel discharged via a main nozzle (30) is sent to a downstream side by an air flow created by the air flow guiding member (52). When a throttle valve (22) and a choke valve (24) are both in a fully-opened state, fresh air flows into an air-fuel mixture passage (12) through a gap between these valves (22, 24).

Abstract: The scavenging passage includes a wall surface that defines an orientation direction of a main scavenging gas flow spouting from the scavenging port to the cylinder chamber. In a boundary portion between the scavenging port and the scavenging passage, a wall surface located on an opposite side of the exhaust port is composed of an inclined surface inclined in a direction further away from the exhaust port than a wall surface of a deep portion of the scavenging passage. The scavenging port includes a rear wall surface located in a portion on the opposite side of the exhaust port. The rear wall surface continues to the inclined surface to extend in the direction away from the exhaust port and generates an incidental scavenging gas flow incidental to the main scavenging gas flow and higher in speed than the main scavenging gas flow.

Abstract: A main nozzle (38) of a carburetor (10) communicates with a metering chamber (26) through a first fuel feeding passage (44) originally included in the carburetor and a first additional fuel feeding passage (46). The first additional fuel feeding passage (46) includes a flow rate adjusting valve (48). The flow rate adjusting valve (48) is driven by a solenoid actuator (50). The solenoid actuator (50) is controlled on the basis of engine speed.

Abstract: The scavenging passage includes a wall surface that defines an orientation direction of a main scavenging gas flow spouting from the scavenging port to the cylinder chamber. In a boundary portion between the scavenging port and the scavenging passage, a wall surface located on an opposite side of the exhaust port is composed of an inclined surface inclined in a direction further away from the exhaust port than a wall surface of a deep portion of the scavenging passage. The scavenging port includes a rear wall surface located in a portion on the opposite side of the exhaust port. The rear wall surface continues to the inclined surface to extend in the direction away from the exhaust port and generates an incidental scavenging gas flow incidental to the main scavenging gas flow and higher in speed than the main scavenging gas flow.

Abstract: A reverse scavenged two-stroke internal combustion engine is capable of effectively suppressing the short-circuiting of fresh charge (unburnt air-fuel mixture), while at the same time being capable of further improving scavenging efficiency, combustion efficiency, etc. The horizontal sectional shape of at least one pair of scavenging passages is closer to a triangle than a parallelogram along substantially the entire lengths of the at least one pair of scavenging passages, where a cylinder outer circumferential side of the horizontal sectional shape is narrowest and a cylinder bore wall surface side of the horizontal sectional shape is wide. Further, horizontal scavenging angles, which are angles of intersection formed between lines extended towards an intake port from guide wall surfaces that define the scavenging passages, are acute.

Abstract: There is provided a reverse scavenged two-stroke internal combustion engine that is capable of effectively suppressing the short-circuiting of fresh charge (unburnt air-fuel mixture), while at the same time being capable of further improving scavenging efficiency, combustion efficiency, etc. The horizontal sectional shape of at least one pair of scavenging passages (31, 31 and 32, 32) is closer to a triangle than a parallelogram along substantially the entire lengths of the at least one pair of scavenging passages, where a cylinder outer circumferential side of the horizontal sectional shape is narrowest and a cylinder bore wall surface (10a) side of the horizontal sectional shape is wide. Further, horizontal scavenging angles (?, ?), which are angles of intersection formed between lines (Ea, Ea and Eb, Eb) extended towards an intake port (33) from guide wall surfaces (31c, 31c and 32c, 32c) that define the scavenging passages (31, 31 and 32, 32), are acute.

Abstract: In a two-stroke internal combustion engine (1) using an internal cooling piston (2), the piston (2) has in-piston scavenging passages (19) defined therein by partition walls (18), and lower-end inlets (20) of the in-piston scavenging passages (19) are opened downward and narrowed in opening area by piston pin bosses (16). In-cylinder scavenging passages (14), which are opened and closed as the piston (2) moves, are supplied with an air-fuel mixture from the narrowed lower-end inlets (20) through the in-piston scavenging passages (19). Thereby, a fresh air-fuel mixture is increased in flow rate when flowing from the in-cylinder scavenging passages (14) to the combustion chamber (10), and the scavenging efficiency of the engine is improved.

Abstract: A two-stroke internal combustion engine (1) includes one pair or two pairs of scavenging passageways (31, 32) of reverse flow system where scavenging outlet ports (31b, 32b) are opened to the cylinder bore (10a); the internal combustion engine being characterized in that an external air inlet port (42, 44, 46) for introducing external air into a combustion actuating chamber (15) formed over a piston (20) is formed at a portion of the cylinder (10) which is located closer to an exhaust port than a scavenging outlet port (31b, 32b) from which an air-fuel mixture (M) is introduced into the combustion actuating chamber (15) in a descending stroke of piston, and/or the external air inlet port (42, 44, 46) is formed at a portion of the cylinder (10) which enables the external air to be introduced into the combustion actuating chamber (15) prior to introduction of the air-fuel mixture (M).

Abstract: A two-stroke internal combustion engine (1) includes one pair or two pairs of scavenging passageways (31, 32) of reverse flow system where scavenging outlet ports (31b, 32b) are opened to the cylinder bore (10a); the internal combustion engine being characterized in that an external air inlet port (42, 44, 46) for introducing external air into a combustion actuating chamber (15) formed over a piston (20) is formed at a portion of the cylinder (10) which is located closer to an exhaust port than a scavenging outlet port (31b, 32b) from which an air-fuel mixture (M) is introduced into the combustion actuating chamber (15) in a descending stroke of piston, and/or the external air inlet port (42, 44, 46) is formed at a portion of the cylinder (10) which enables the external air to be introduced into the combustion actuating chamber (15) prior to introduction of the air-fuel mixture (M).

Abstract: In a two-stroke internal combustion engine (1) using an internal cooling piston (2), the piston (2) has in-piston scavenging passages (19) defined therein by partition walls (18), and lower-end inlets (20) of the in-piston scavenging passages (19) are opened downward and narrowed in opening area by piston pin bosses (16). In-cylinder scavenging passages (14), which are opened and closed as the piston (2) moves, are supplied with an air-fuel mixture from the narrowed lower-end inlets (20) through the in-piston scavenging passages (19). Thereby, a fresh air-fuel mixture is increased in flow rate when flowing from the in-cylinder scavenging passages (14) to the combustion chamber (10), and the scavenging efficiency of the engine is improved.

Abstract: A catalyst-installed muffler includes an expansion chamber (25), and a gas-permeable exhaust gas-purifying catalyst (30), wherein exhaust gas blown out of the exhaust port (10) of an internal combustion engine is introduced into the expansion chamber (25) through the catalyst (30). The catalyst (30) may be cylindrical in configuration. An outer circumferential cross-sectional configuration of the catalyst (30) is made identical with an inner circumferential cross-sectional configuration of the outer end portion (10a) of the exhaust port (10), so that one end portion (exhaust gas introducing side 30a) of the catalyst (30) is enabled to fit in an outer end portion (10a) of the exhaust port (10). According to this muffler, it is made possible to utilize the purifying capacity of the catalyst to a maximum extent.