Abstract: An engine-driven working machine includes a controller, which varies a control value of a solenoid valve so as to decrease or increase an opening degree of the solenoid valve when a rotating speed of an engine is within a predetermined high rotating speed range and the rotating speed of the engine is lower or higher than a predetermined rotating speed, respectively. When the control value of the solenoid valve is varied so as to decrease the opening degree of the solenoid valve and corresponds to a predetermined opening degree larger than a fully-closed state, the control value is set to a limitation value.

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: An engine-driven working machine includes a controller, which varies a control value of a solenoid valve so as to decrease or increase an opening degree of the solenoid valve when a rotating speed of an engine is within a predetermined high rotating speed range and the rotating speed of the engine is lower or higher than a predetermined rotating speed, respectively. In case the controller determines that the engine-driven working machine gets started saw cutting, the controller stops varying the control value of the solenoid valve when the rotating speed of the engine is within the predetermined high rotating speed range and lower than the target rotating speed.

Abstract: The certainty of supplying air to a scavenging channel through a piston groove is improved. In a cylinder wall 2, a gas venting port 10 is formed below and adjacent to a scavenging port 6a. The gas venting port 10 is independent from the scavenging port 6a, and is opened/closed by a piston as each of an air port 4a and the scavenging port 6a is. Upon a piston groove 8 being brought into communication with the gas venting port 10 as a result of the piston moving up (FIG. 1(II)), blown-back gas in a piston groove 8 can move to a crankcase through the gas venting port 10. Along with this, air can enter the piston groove 8 from the air port 4a.

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: An engine-driven working machine includes a controller, which varies a control value of a solenoid valve so as to decrease or increase an opening degree of the solenoid valve when a rotating speed of an engine is within a predetermined high rotating speed range and the rotating speed of the engine is lower or higher than a predetermined rotating speed, respectively. In case the controller determines that the engine-driven working machine gets started saw cutting, the controller stops varying the control value of the solenoid valve when the rotating speed of the engine is within the predetermined high rotating speed range and lower than the target rotating speed.

Abstract: An engine-driven working machine includes a controller, which varies a control value of a solenoid valve so as to decrease or increase an opening degree of the solenoid valve when a rotating speed of an engine is within a predetermined high rotating speed range and the rotating speed of the engine is lower or higher than a predetermined rotating speed, respectively. When the control value of the solenoid valve is varied so as to decrease the opening degree of the solenoid valve and corresponds to a predetermined opening degree larger than a fully-closed state, the control value is set to a limitation value.

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: The certainty of supplying air to a scavenging channel through a piston groove is improved. In a cylinder wall 2, a gas venting port 10 is formed below and adjacent to a scavenging port 6a. The gas venting port 10 is independent from the scavenging port 6a, and is opened/closed by a piston as each of an air port 4a and the scavenging port 6a is. Upon a piston groove 8 being brought into communication with the gas venting port 10 as a result of the piston moving up (FIG. 1(II)), blown-back gas in a piston groove 8 can move to a crankcase through the gas venting port 10. Along with this, air can enter the piston groove 8 from the air port 4a.

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: It is intended to effectively prevent blow-by with no need for large changes in typical structures of two-cycle internal combustion engines. A main scavenging passage (24) for supplying air-fuel mixture from a crankcase to a combustion chamber for scavenging purposes has a branch scavenging passage (26) that extends upward aslant toward an intake port (14). The main scavenging passage (24) communicates with a first scavenging port (20) located nearer to an exhaust port (16). The branch scavenging passage (26) communicates with a second scavenging port (22). A mean cross-sectional area of the branch scavenging passage (26) is smaller than that of the main scavenging passage (24). Cross-sectional area of a portion (24b) next to an inlet port (24a) of the main scavenging passage (24) opening to the crankcase is smaller than the sum of cross-sectional areas of the first and second scavenging ports (20, 22).

Abstract: It is intended to effectively prevent blow-by with no need for large changes in typical structures of two-cycle internal combustion engines. A main scavenging passage (24) for supplying air-fuel mixture from a crankcase to a combustion chamber for scavenging purposes has a branch scavenging passage (26) that extends upward aslant toward an intake port (14). The main scavenging passage (24) communicates with a first scavenging port (20) located nearer to an exhaust port (16). The branch scavenging passage (26) communicates with a second scavenging port (22). A mean cross-sectional area of the branch scavenging passage (26) is smaller than that of the main scavenging passage (24). Cross-sectional area of a portion (24b) next to an inlet port (24a) of the main scavenging passage (24) opening to the crankcase is smaller than the sum of cross-sectional areas of the first and second scavenging ports (20, 22).

Abstract: The engine can improve a leading air suction efficiency, has a simple structure and a low cost. Accordingly, in a stratified scavenging two-stroke cycle engine provided with an exhaust port (22) and a scavenging port (21) which are connected to a cylinder chamber (10), a leading air suction port (24) not connected to the cylinder chamber and a crank chamber (11), an air-fuel mixture suction port (23) connected to the crank chamber, a scavenging flow passage (20) connecting between the scavenging port and the crank chamber, and a piston groove (25) connecting between the leading air suction port and the scavenging port and not connecting between the air-fuel mixture suction port and the scavenging port at a time of a suction stroke, and disposed in an outer peripheral portion of the piston (4), the leading air suction port is positioned at an opposite side to the air-fuel mixture suction port with respect to an axis of the cylinder (3).