Abstract: There is provided a method for manufacturing a cylinder for an internal combustion engine by making use of an insert core, which makes it possible to manufacture the cylinder by a die casting method such as a high-pressure die casting method at low cost and in high accuracy.

Abstract: A cylinder for an internal combustion engine and a method for treating the inner surface of the cylinder, which enables the inner surface constituting a piston-sliding surface of the cylinder to have a high quality plated layer which is uniform in thickness and smooth in surface at low cost without necessitating grinding work such as honing work. The cylinder and the method of the present invention are characterized in that the inner surface of the cylinder is provided with a plated layer which is deposited thereon by a PR (Periodical Reverse) method employing a high-speed polarity reversal power source.

Abstract: There are provided a method and an apparatus for applying electroless plating to the cylinder of an internal combustion engine, which are capable of applying the plating exclusively to the portion where the plating is essentially required, thereby making it possible to save the plating solution and to reduce the cost for the metal plating. The plating apparatus is capable of applying electroless plating to the inner surface of the cylinder having a through-hole at the head portion thereof and is constituted by: clamping means for holding the cylinder in a predetermined posture; plating solution-introducing means for introducing a plating solution into the cylinder; and plating solution-circulating means for filling the interior of the cylinder with the plating solution introduced by the plating solution-introducing means while enabling the plating solution to pass along the axial line and through the interior of the cylinder to thereby apply the plating to the inner surface of the cylinder.

Abstract: A portable power working machine is disclosed, which is capable of effectively minimizing the clogging of the air cleaner, thereby dispensing with frequent maintenance. This portable power working machine comprises an air cleaner (30) having a base body case (32) provided with a clean air discharge port (33) for introducing the air cleaned into an intake port (25) of a carburetor (14), a filter (35) which is mounted on a filter mounting opening (32a) of base body case (32) so as to seal it, and a cleaner cover (37) which is attached onto the filter (35) so as to cover the filter (35) and to guide outside air toward the filter (35), while giving a predetermined directionality to the outside air.

Abstract: A power blower having a frame, a blower, and a loop-shaped filter member. In an embodiment of the invention, the blower is disposed apart from the frame by an air intake space and has an air intake port facing the frame, and the loop-shaped filter member is disposed around a periphery of the air intake port and is adapted to catch debris on an upstream side of the air intake port.

Abstract: A spark plug guard can be switched between a spark-plug covering position to protect a spark plug and a spark-plug opening position. An operator displaces the spark plug guard from the spark-plug covering position to the spark-plug opening position, thereby obtaining a wide working space to perform the maintenance and inspection of the spark plug efficiently. The spark plug guard has a function of fixing a predetermined part in the spark-plug covering position. Consequently, the need for a part fixing member which was conventionally required for fixing the predetermined part to the engine body is eliminated, thus contributing to a decrease in the weight of the whole internal combustion engine and to cost reduction.

Abstract: The present invention is directed to a portable brushcutter, which comprises a hollow tubular operating rod having a front end provided with a cutting bade and a rear end provided with a drive unit. An output shaft extends longitudinally within the operating rod to transmit a driving force from the drive unit to the cutting blade. Four or more bushings each having an elastic member are disposed in the operating rod while being longitudinally spaced apart from each other, to support the output shaft. A liner is provided to extend within the rod. The liner has a through-hole extending along the axis thereof to allow the output shaft to pass therethrough, and a radially outermost periphery formed as a plurality of strip-shaped faces circumferentially spaced apart from each other. The present invention can provide a portable brushcutter having excellent anti-vibration effect, high strength and sufficiently reduced weight.

Abstract: A two-stroke internal combustion engine (1) is provided with one pair or plural pairs of C-shaped scavenging passageways (31, 32) of a reverse flow system where scavenging inlet ports (31a) as well as scavenging outlet ports (31b, 32b) are both opened to a cylinder bore (10a), wherein a scavenging introducing passageway (40) for introducing an air-fuel mixture (K) from a crank chamber (18) into the scavenging inlet ports (31a) is provided between the cylinder bore and the piston adapted to reciprocatively move up and down in the cylinder bore (10a), and an effective opening area of the scavenging inlet ports (31a) is gradually decreased due to the piston (20) in the course of descending stroke of the piston (20).

Abstract: A recoil starter for a backpack-type power working machine which is capable of easily and smoothly performed the starting operation even when the working machine is kept on the operator's back irrespective of differences in the operator's build. This recoil starter comprises a recoil grip which is attached to a distal end portion of a recoil rope extended out of the main body of the recoil starter, wherein the recoil grip is designed such that it can be anchored to a recoil grip-supporting member to be positioned close to an operator's waist and that it can be pulled out in front of the operator from the recoil grip-supporting member. The recoil grip-supporting member is made optionally alterable in position.

Abstract: A method is provided for manufacturing a cylinder for an internal combustion engine, which makes it possible not only to manufacture the cylinder by a high-pressure die casting method at low cost and in high precision, but also to prevent relative misalignment among the scavenging port, suction port and exhaust port of the cylinder. This method is characterized by the steps of: preparing a cylinder liner made of an aluminum alloy pipe and provided with the scavenging port, and a bore-core die as well as cores for scavenging ducts both being uncollapsible and configured so as not to intrude into the scavenging ports; setting the cylinder liner in place in the bore-core die; and casting, by means of metal mold casting method, an aluminum alloy onto the outer peripheral surface of the cylinder liner to thereby mold a main body of the cylinder.

Abstract: It is the object of the present invention to provide a centrifugal blower fan capable of reducing a noise in an operating rotational speed range without degradation in blàwer performance. A centrifugal blower fan comprises a base plate, and a plurality of fan blades arranged on the base plate in a radial pattern to define a plurality of air passages between the pairs of adjacent fan blades, respectively. A portion of the base plate serving as a bottom wall of each of the air passages is formed with a plurality of through-holes.

Abstract: There is provided a portable air blowing working machine capable of obviating frequent operation for the maintenance of air cleaner and hence capable of improving working efficiency. This working machine includes an internal combustion engine having the air cleaner disposed in the air-intake system thereof, and an air blower to be rotationally driven by the engine; which is characterized in that the air cleaner is provided with a suction port for inhaling external air, with a filter member for cleaning air inhaled from the suction port to thereby permit the cleaned air to be introduced into the engine, and with a discharge port for enabling part of the air inhaled from the suction port to be discharged out of the air cleaner without permitting part of the air to pass through the filter member; and that an air flow directed to flow from the suction port to the discharge port is permitted to generate inside the air cleaner by making use of suction force of the air blower.

Abstract: There is provided a portable power working machine, which is capable of rationally and effectively preventing the generation of the icing without giving rise to early clogging of air cleaner, the malfunction of a internal combustion engine and deterioration of performance. This working machine comprises a small air-cooled internal combustion engine which is mounted inside a main housing, a cooling fan disposed on one side of the main housing; a carburetor coupled to an upper portion of an intake port of the internal combustion engine; a clean air chamber disposed on an upstream side of the carburetor; an air cleaner cover coupled to the clean air chamber; a warm air introducing passageway for introducing, through a region adjacent to the intake port, part of air which has been sucked by the cooling fan for cooling the internal combustion engine into the air cleaner cover; and a shutter for and externally opening or closing the warm air introducing passageway as desired.

Abstract: The present invention provides an air-cooled four-stroke internal combustion engine capable of achieving a high degree of cooling. The present invention is directed to an air-cooled four-stroke internal combustion engine including a crankshaft and a fan rotor rotatably driven by the crankshaft to generate cooling air for cooling the engine. The engine comprises an oil pan disposed below the crankshaft. A space formed below the oil pan extends in the axial direction of the crankshaft along the lower surface of the oil pan and allows a cooling air to pass therethrough. An upstream portion of the lower surface is inclined upward, toward the upstream, in a vertical section taken along the axis of the crankshaft to receive the cooling air therein.

Abstract: A set of split bodies for forming a synthetic-resin blower fan through a hollow-article injection molding process, wherein the blower fan integrally includes a circular base, a cover portion having an air inlet opening at the center thereof, and a plurality of blades. The set of split bodies comprise a first split body including the circular base and a plurality of blade members, and a second split body defining the inner surface of the cover portion and having an outer surface on the opposite side of the first split body. The outer surface of the second split body is formed with a plurality of reservoirs each extending radially in alignment with the corresponding blade member of the first split body to define spaces to be filled with molten synthetic resin in a state where the first and second split bodies are assembled together.

Abstract: A fuel injection device mounted on a main body of an air-fuel mixture generating device including an electromagnetic driving-type fuel injection valve for injecting, at predetermined times, fuel into an air-intake passageway of an intake system of an internal combustion engine, and a collision plate operationally coupled to the fuel injection valve adapted to be disposed in the air-intake passageway for enabling the injected fuel to collide therewith.

Abstract: An internal combustion engine capable of optimizing the amount of oil in the crank chamber with a simplified structure of lubrication system, in which a U-shaped oil reservoir is formed surrounding and adjacent to a crank chamber. At least one small hole is formed on a partition wall which separates the oil reservoir and the crank chamber from each other so that the crank chamber may always communicate with the oil reservoir through the small hole. Due to a flow resistance in the small hole, a pressure Po in the oil reservoir changes following a change of pressure Pc in the crank chamber with some delay, and where the pressure difference between the oil reservoir and the crank chamber caused by a delay in the change of the pressure Po in the oil reservoir, results in the introduction of the oil in the oil reservoir into the crank chamber. It further allows excessive oil in the crank chamber to be circulated back into the oil reservoir.

Abstract: A starter which is capable of having an operator easily perform the starting operation of a backpack-type power working machine while shouldering it, is lighter in weight and cheaper in manufacturing cost, is relatively free from trouble, and can not easily be damaged even if a portion of the starter is caught by the branch of a tree. In this starter, a recoil handle attached to one end portion of the recoil rope is placed remote from the main body of the starter by a predetermined distance and adapted to be supported by a handle-supporting member provided at a specific portion of the working machine; and an extended portion of the recoil rope which is located between the main body and the handle-supporting member is loosely sheathed by a flexible guide pipe, one end of which being fixed, and the other end being made free.

Abstract: A portable trimmer capable of applying to a throttle valve a different operation from that according to a throttle operation lever. The portable trimmer includes a brake device for braking the movement of a cutting blade that is released in conjunction with a throttle operation. The portable trimmer includes a throttle wire having a first throttle wire extending between a throttle operation lever and a swingable member, and a second wire portion extending between a swingable member and a throttle to provide a first operation transmission path for transmitting the movement of the throttle operation lever to the throttle valve. The portable trimmer further includes an additional operation lever for performing a different operation from said throttle operation, and a pulley pivotally attached to the swingable member.

Abstract: A portable power working machine (10) is disclosed, which is capable of effectively improving the performance thereof to cool the internal combustion engine (20), and also capable of preventing an air cleaner (30) of the air intake system of the internal combustion engine (20) from being clogged with dust. This portable power working machine is characteristic in that it comprises a guiding wall (28) disposed on one side of a main housing (12) and at a location rear to a cooling fan (25) and projected inward therefrom for guiding cooling air toward the cylinder (21) of the internal combustion engine (20); an intake passageway (50) formed at a location rear to the cooling fan (25) for introducing air into an air-intake system (30, 34, 35) of the internal combustion engine (20); and an air-intake port (55) for the intake passageway (50), the air-intake port (55) being positioned in the vicinity of a root portion (28a) of the rear face of the guiding wall (28).