Abstract: An air-leading type, stratified scavenging two-stroke engine. The engine including a cylinder member and a crankcase joined therewith has an intake passage, an exhaust passage, first and second scavenging passages, a communicating portion and an air passage. The intake passage, the exhaust passage and the air passage are formed in the cylinder member. The first and the second scavenging passages each has a cylinder member-side passage and a crankcase-side passage. The cylinder member-side passages of both of the first and the second scavenging passages communicate with each other via the communicating portion. The air passage is connected to the cylinder member-side passage of the first scavenging passage. In the engine, air for pre-scavenging is introduced from the air passage through a check valve into the cylinder member-side passage of the first scavenging passage, and a part of the introduced air flows into the second scavenging passage through the communicating portion.

Abstract: A stratified scavenging two-stroke engine includes: an intake passage that connects an intake opening through an outer surface of a cylinder member with an intake port opening to the inside of a cylinder, and supplies gaseous mixture of fuel and air; an exhaust passage that connects an exhaust outlet opening through the outer surface of the cylinder member with an exhaust port opening to the inside of the cylinder, and discharges combustion gas; a scavenging passage; and an air passage that connects an air inlet opening through the outer surface of the cylinder member with the scavenging passage and supplies pre-scavenging air into the scavenging passage. The intake and the air inlet are arranged at positions opposite from the exhaust port across the axis of the cylinder, and arranged side by side in a substantially circumferential direction of the cylinder or a direction substantially perpendicular to the axis of the cylinder.

Abstract: The present invention relates to a portable work machine including an engine placed in an internal space of an engine case, an ignition coil for igniting the engine provided closer to the engine, and a high voltage cord routed to connect the ignition coil to an ignition plug of the engine. The portable work machine includes a passage portion for housing and guiding the high voltage cord on a route from an area in which the ignition coil is placed to an area in which the ignition plug is placed, in which the passage portion is arranged on an upper face side of the engine case.

Abstract: There is provided a two-stroke engine configured to effectively prevent blow-by of the scavenging air from the discharge port and to be able to improve the engine output while abating pollution. The two-stroke engine includes a cylinder having an exhaust port and a scavenging port, and a piston, wherein: the piston has a top surface; a piston concave portion is provided in the top surface in the discharge direction; an entire surface of the piston concave portion is formed in an approximately spherical shape; and a slope of the piston concave portion extending from an outer circumferential edge of the piston concave portion in the discharge direction to a deepest portion is steeper than a slope of the piston concave portion extending from an outer circumferential edge of the piston concave portion in the anti-discharge direction to the deepest portion.

Abstract: There is provided a two-stroke engine configured to effectively prevent blow-by of the scavenging air from the discharge port and to be able to improve the engine output while abating pollution. The two-stroke engine includes a cylinder having an exhaust port and a scavenging port, and a piston, wherein: the piston has a top surface; a piston concave portion is provided in the top surface in the discharge direction; an entire surface of the piston concave portion is formed in an approximately spherical shape; and a slope of the piston concave portion extending from an outer circumferential edge of the piston concave portion in the discharge direction to a deepest portion is steeper than a slope of the piston concave portion extending from an outer circumferential edge of the piston concave portion in the anti-discharge direction to the deepest portion.

Abstract: A stratified scavenging two-stroke engine includes: an intake passage that connects an intake opening through an outer surface of a cylinder member with an intake port opening to the inside of a cylinder, and supplies gaseous mixture of fuel and air; an exhaust passage that connects an exhaust outlet opening through the outer surface of the cylinder member with an exhaust port opening to the inside of the cylinder, and discharges combustion gas; a scavenging passage; and an air passage that connects an air inlet opening through the outer surface of the cylinder member with the scavenging passage and supplies pre-scavenging air into the scavenging passage. The intake and the air inlet are arranged at positions opposite from the exhaust port across the axis of the cylinder, and arranged side by side in a substantially circumferential direction of the cylinder or a direction substantially perpendicular to the axis of the cylinder.

Abstract: An air-leading type, stratified scavenging two-stroke engine. The engine including a cylinder member and a crankcase joined therewith has an intake passage, an exhaust passage, first and second scavenging passages, a communicating portion and an air passage. The intake passage, the exhaust passage and the air passage are formed in the cylinder member. The first and the second scavenging passages each has a cylinder member-side passage and a crankcase-side passage. The cylinder member-side passages of both of the first and the second scavenging passages communicate with each other via the communicating portion. The air passage is connected to the cylinder member-side passage of the first scavenging passage. In the engine, air for pre-scavenging is introduced from the air passage through a check valve into the cylinder member-side passage of the first scavenging passage, and a part of the introduced air flows into the second scavenging passage through the communicating portion.

Abstract: A four-cycle engine wherein a fuel-air-oil mixture is compressed in a crank case chamber and directed therefrom along a pathway to a combustion chamber. The pathway contains actuating mechanism for actuating the fuel intake valve leading to the combustion chamber. The pathway is restricted in volume as permitted by the actuating mechanism, preferable to a range of two to four times the piston displacement.

Abstract: A four-cycle engine fueled by a mixture of fuel and lubricant and including valve actuation mechanism contained in the path of the fuel flow. A component of the mechanism including a rotating gear having a gear shaft journalled between wall portions of the engine whereat the wall portions define in part the flow path of the fuel. Through holes provided in the walls to direct fuel-lubricant to the shaft ends journalled in the wall portions for lubrication of the said shaft ends.

Abstract: A small engine for outdoor power equipment wherein fuel is pumped to the engine's combustion chamber by a reciprocating piston. A desired rate of reciprocation is determined with the engine under load, e.g., with a grass trimmer cutting grass. Avoidance of undesired engine racing is accomplished by restricting airflow to the carburetor which prevents significant increased reciprocation over that desired when cutting. A choke mechanism is provided with a pair of end portions, one of which closes air to the carburetor for starting and the other provides a spaced barrier for inhibiting blow-back. The one end portion includes an inset that seats in the opening through which air enters the carburetor for providing rigidity and to insure closing.

Abstract: A four-cycle engine wherein a fuel-air-oil mixture is compressed in a crank case chamber and directed therefrom along a pathway to a combustion chamber. The pathway contains actuating mechanism for actuating the fuel intake valve leading to the combustion chamber. The pathway is restricted in volume as permitted by the actuating mechanism, preferable to a range of two to four times the piston displacement.

Abstract: A four-cycle engine fueled by a mixture of fuel and lubricant and including valve actuation mechanism contained in the path of the fuel flow. A component of the mechanism including a rotating gear having a gear shaft journalled between wall portions of the engine whereat the wall portions define in part the flow path of the fuel. Through holes provided in the walls to direct fuel-lubricant to the shaft ends journalled in the wall portions for lubrication of said shaft ends.

Abstract: A small engine for outdoor power equipment wherein fuel is pumped to the engine's combustion chamber by a reciprocating piston. A desired rate of reciprocation is determined with the engine under load, e.g., with a grass trimmer cutting grass. Avoidance of undesired engine racing is accomplished by restricting airflow to the carburetor which prevents significant increased reciprocation over that desired when cutting. A choke mechanism is provided with a pair of end portions, one of which closes air to the carburetor for starting and the other provides a spaced barrier for inhibiting blow-back. The one end portion includes an inset that seats in the opening through which air enters the carburetor for providing rigidity and to insure closing.

Abstract: A four-cycle engine in which a mixed gas of a fuel and air containing a lubricating oil is transferred from a carburetor to a cylinder or a crank chamber, the gas is pushed out in the stage of descending the piston to the passage on the reverse side, transferred into a rocker arm chamber including an intake valve at the top of the cylinder via a passage including a valve gear mechanism, and it is directed to the cylinder in the intake stage, whereby the engine is lubricated by the lubricating oil. The engine has no oil pan and can be run at any inclination angle (360.degree.). Also disclosed is that it is also possible for the four-cycle engine to provide a diverged second passage extending to the crank room, to provide a lead valve on a portion of the second the passage, to provide a diverged third passage extending to the lower end of the crank chamber, to provide a lead valve or rotary valve, and to provide a fourth and/or fifth passage(s) to circulate the mixed gas.

Abstract: A four-cycle engine has a base plate provided on a side of the engine and having an opening communicated with a carburetor. A choke plate is pivotally mounted on the base plate, and a choke lever is pivotally mounted on the base plate. A transmitting means is provided for transmitting the opposite rotation of the choke lever to the choke plate so as to rotate the choke plate.

Abstract: A cam gear is mounted on a camshaft, and an intake cam and an exhaust cam are formed on the cam gear for operating an intake valve and an exhaust valve of a hand starting four-cycle engine. A decompression device is rotatably mounted in the cam gear. A decompression cam of the decompression device is exposed from the exhaust cam. The decompression device has a weight, and a spring is provided for urging the weight to the cam shaft. Elastic force of the spring is set so that the weight is urged toward the camshaft in hand starting operation of the engine and moved apart from the camshaft by centrifugal force, thereby projecting the decompression cam in the compression stroke of the engine as to open the corresponding valve.