Abstract: The present invention provides a diaphragm carburetor wherein heat transferred from the engine to the carburetor through the insulator is reduced to lower the temperature of the carburetor unit and reduce the occurrence of bubbles in the fuel. The carburetor of the present invention is a diaphragm carburetor in which a fuel channel that extends from a pump chamber of the carburetor to a constant-pressure fuel chamber is divided into two branches to form one branch as a main fuel channel connected to the constant-pressure fuel chamber, and the other branch as a fuel circulation channel for passing the fuel through the body side surface of the carburetor on the insulator side, or the body side surface of the insulator on the carburetor side, causing the fuel to make a circuit around the carburetor, and returning the fuel to the fuel tank.

Abstract: A carburetor having a choke valve has an open-close valve sliding reciprocatingly inside a valve hole partway along a bypass air passage. The open-close valve, pressed by urging member, slides according to a rotation angle of a choke valve shaft while a distal end side continuously contacts a side face of the shaft. A projecting part, urged by a coil spring, projects from a distal end of a body. The urging member includes a temperature-sensitive material that expands at or above a prescribed temperature. When the choke valve is closed and the ambient temperature is less than the prescribed temperature, the bypass air passage enters a closed state while the body remains in a closed-valve position; and when the ambient temperature is at or above the prescribed temperature, the urging member elongates and the body enters an open-valve position, and the bypass air passage enters an open state.

Abstract: A dust seal structure for a valve stem in a rotary throttle valve The dust seal structure has a cylindrical throttle valve with a metering needle and a throttle through-hole, and a fuel nozzle disposed on the central axis of the throttle valve that is openable into the throttle through-hole with the metering needle inserted therein. The valve stem of the throttle valve, which protrudes at one end from the shaft hole formed in the cover body of a valve hole in the carburetor body, is caused to rotate in accordance with the operation of the accelerator pedal, whereby the throttle valve moves in the direction of a central axis thereof while rotating as a whole, and controls airflow and fuel-flow rate. A dust-proof member composed of a sealing ring is fitted between the valve stem and the shaft hole formed in the cover body.

Abstract: A carburetor including a columnar throttle valve, a fuel nozzle, a metering needle inserted into the fuel nozzle and a cam mechanism caused to rotate in accordance with the throttle operation, whereby the throttle valve is moved by the cam mechanism in the direction of the valve stem while rotating to adjust the air flow rate and the fuel flow rate. The cam mechanism has a cam groove provided with a cam surface so as to gradually deepen in the direction of rotation in a designated range on the external peripheral side of the bottom surface of the throttle valve, and a support pin for supporting the throttle valve from the bottom surface, wherein the support pin being disposed between the cam surface and the bottom surface of the columnar throttle valve chamber rotatably provided with the throttle valve.

Abstract: The opening of a solenoid valve is automatically adjusted after an engine is started and before actual work is performed for an appropriate air-fuel ratio, whereby it is possible to attain a good and stable driving of the engine without any delay even for an abrupt change in load. After the engine is started, when a rotation speed enters a “fuel flow rate adjusting rotation speed range” in which a definite load is applied to the engine in a working rotation speed range of the engine in which a throttle valve is opened to a definite opening, a detected rotation speed is fed back to a target rotation speed, and the opening of the solenoid valve is controlled to adjust a fuel flow rate, so that the combustion state in the engine is optimized at the valve opening so determined.

Abstract: A speed reduction method for a hand-carried engine-driven working machine is provided in which a speed reduction of an engine can be attained reliably and safely by preventing the occurrence of lean come-down phenomenon in such a state that the engine is operating in a practical revolution speed range. An acceleration is calculated based on a change in revolution speed, and when the acceleration becomes smaller than a predetermined threshold, an ignition timing is retarded by a desired amount based on a determination that the engine is being decelerated, and further, a fuel flow rate is also increased, whereby the decelerated state of the engine is maintained without fail, so that the occurrence of lean come-down phenomenon is prevented in the process of reducing the revolution speed of the engine.

Abstract: A method for making an optimum combustion during engine operating time changes a fuel flow rate of the solenoid valve on the basis of engine rotational speed feedback control during engine idling time at low engine rotational speed and low electric power consumption. During engine idling time of an engine are carried out a rotational speed detecting process, an idle rotation adjusting process of making a rotational speed detected by the rotational speed detecting process equal to an initial value of rotational speed by controlling an ignition timing while comparing the detected rotational speed with the initial value of rotational speed as target value, and a valve opening correction process according to idle ignition timing change (I.I.T.C.) obtained by the idle rotation adjusting process. The valve opening is set to an adjusted valve opening (A.V.O.) plus a correction valve opening (C.V.O.) by the valve opening correction process.

Abstract: The present invention provides a diaphragm carburetor wherein heat transferred from the engine to the carburetor through the insulator is reduced to lower the temperature of the carburetor unit and reduce the occurrence of bubbles in the fuel. The carburetor of the present invention is a diaphragm carburetor in which a fuel channel that extends from a pump chamber of the carburetor to a constant-pressure fuel chamber is divided into two branches to form one branch as a main fuel channel connected to the constant-pressure fuel chamber, and the other branch as a fuel circulation channel for passing the fuel through the body side surface of the carburetor on the insulator side, or the body side surface of the insulator on the carburetor side, causing the fuel to make a circuit around the carburetor, and returning the fuel to the fuel tank.

Abstract: Carburetor start system comprising a primer pump bulb coupled to a valve-opening mechanism, the primer pump bulb and valve-opening mechanism being operably coupled to a throttle valve and/or a choke valve. Pushing the primer pump bulb causes the throttle valve and/or choke valve to be rotated and releasably fixed in a starting position.

Abstract: The present invention provides an internal shape of a rotor for a two-bore rotary carburetor used in a stratified scavenging engine whereby an engine for a power saw, lawn mower, or the like can be stabilized in the course of a complete change in orientation during idling. A groove pocket (10) in communication with a fuel supply-side bore (8) is formed at the aperture edge of each of the upstream end and the downstream end of a carburetor rotor valve (6) toward an accelerated rotation direction in the fuel supply-side bore (8) of the rotor valve (6). The groove pocket (10) is shaped so as to gradually rise and decrease in cross-sectional surface area toward the accelerated rotation direction along a peripheral surface of the rotor valve (6).

Abstract: A carburetor for a stratified charge two cycle engine with a choke bore, venturi, and throttle bore configuration matching an irregularly shaped choke valve. The trailing and leading edges of the choke and throttle valves, respectively, preferably overlap during wide open throttle operation to separate a single intake passage bore into an air intake passage above the choke and throttle valves and an air/fuel intake passage below the choke and throttle valves. The choke valve is preferably bent to minimize operational rotation and limit fuel spit back.

Abstract: A carburetor for a stratified scavenging two-cycle engine, in which a throttle valve and a air valve are formed in a valve element that is a single cylindrical member in which a throttle through-hole and an air through-hole are diametrically formed and which is rotatably fitted in a body, the mixture passage and the air passage being formed piercing through a body, wherein the height of the body is decreased so as to miniaturize the carburetor as a whole, and the mixture passage (6) and the air passage (9) are formed in a single cylindrical common hole (69) in which the mixture passage (6) and the air passage (9) are partitioned by a partition wall (68).

Abstract: An interlocking lever having first and second cam faces is mounted on a throttle valve stem, and a throttle valve is arbitrarily opened to perform start-up in a state in which the first cam face makes contact with the choke valve lever and the interlocking lever is stopped during low-temperature start-up with the choke valve closed. After the choke valve has been returned to the fully open position, the throttle valve alone is opened with a small degree of opening to perform low-load operation; and in the mid- and high-load region, the interlocking lever integrally turns with the throttle valve, the second cam face pushes the air valve lever, and the throttle valve and air valve are caused to open and close proportionally. Preferably, the degree of opening of the throttle valve for low load operation is adjustable.

Abstract: A carburetor for a stratified scavenging two-cycle engine, in which a throttle valve and an air valve are formed in a valve element that is a single cylinderical member in which a throttle through-hole and an air through-hole are diametrically formed and which is rotatably fitted in a body, the mixture passage and the air passage being formed piercing through a body, wherein the height of the body is decreased so as to miniaturize the carburetor as a whole, and the mixture passage (6) and the air passage (9) are formed in a single cylindrical common hole (69) in which the mixture passage (6) and the air passage (9) are partitioned by a partition wall (68).

Abstract: The carburetor prevents an air-fuel mixture from becoming excessively lean and prevents a fuel pressure from becoming unstable, thereby making it possible to stably supply a fuel to an engine, in a diaphragm-type carburetor with a pressure regulator. A diaphragm-type carburetor includes a fuel pump using a pulsation pressure generated in a crank chamber of an engine or an intake pipe as a driving force, and a metering chamber having a diaphragm and a lever mechanism and provided with fuel at a desired constant pressure. The diaphragm-type carburetor includes a bubble discharge path connecting the metering chamber to other predetermined discharge portions and with a check valve in each of an inlet side and an outlet side.

Abstract: A flow rate control mechanism is provided to a low-speed fuel system that is independent from the main fuel system of a carburetor. The mechanism causes the valve element to move in a linear fashion by means of a cam coupled to the throttle stem. The mechanism increases the effective cross-sectional area of the low-speed fuel channel as the throttle valve opens from the idle position to the maximum degree of opening until the point in time at which the main fuel begins to flow, and thereafter causes the low-speed fuel flow rate to decrease and become zero in the high-output region. The transition from low-speed fuel to main fuel is made smooth, ensuring higher output and a stable fuel flow rate in the high-output region.

Abstract: The accelerator apparatus prevents air from remaining within a pump chamber and discharged fuel vapor from causing a pumping effect so as to a destabilize engine operation and increase of an exhaust gas content of harmful material, in an accelerator apparatus in which an accelerated fuel passage draws and discharges fuel to the pump chamber of an accelerator pump, which is connected to a main fuel passage. The pump chamber of the accelerator pump is mechanically coupled with a throttle valve and is connected to a fixed fuel chamber storing a fuel delivered to an intake passage at a fixed pressure by the accelerated fuel passage. Air remaining within the pump chamber and a fuel vapor generated within the pump chamber are discharged to the fixed fuel chamber, and fuel extruded from the pump chamber due to a pumping effect of the remaining air and the fuel vapor enters into the fixed fuel chamber, thereby preventing the alteration of a rate of the fuel flowing through a main fuel passage.

Abstract: An accelerated fuel passage of an accelerator pump operatively connected with a throttle shaft having a throttle valve. The accelerated fuel passage is connected to an upstream side of a needle orifice, which orifice is coupled to a main nozzle. Consequently, the fuel is discharged by the accelerator pump into an area before the needle orifice. By the addition of a one-way check valve system in a fuel pick up at a metering chamber for a fuel circuit, the fuel driven by the accelerator pump piston is discharged to a venturi tube of an intake passage through the main nozzle. A self pumping effect caused by an engine pulsation is dampened or eliminated by the needle orifice. Further, a check valve is provided within a fuel pick up at a metering chamber for a fuel circuit, whereby the fuel driven by the accelerator pump piston is discharged to a venturi tube through a main nozzle without returning to the fixed fuel chamber.

Abstract: An accelerated fuel passage of an accelerator pump operatively connected with a throttle shaft having a throttle valve. The accelerated fuel passage is connected to an upstream side of a needle orifice, which orifice is coupled to a main nozzle. Consequently, the fuel is discharged by the accelerator pump into an area before the needle orifice. By the addition of a one-way check valve system in a fuel pick up at a metering chamber for a fuel circuit, the fuel driven by the accelerator pump piston is discharged to a venturi tube of an intake passage through the main nozzle. A self pumping effect caused by an engine pulsation is dampened or eliminated by the needle orifice. Further, a check valve is provided within a fuel pick up at a metering chamber for a fuel circuit, whereby the fuel driven by the accelerator pump piston is discharged to a venturi tube through a main nozzle without returning to the fixed fuel chamber.

Abstract: A carburetor start pump circuit, for starting an engine has an auxiliary fuel pump mounted on a relatively standard carburetor body, a start pulse passage extending through the carburetor body to the auxiliary fuel pump, and a fuel circuit having an intake side which extends from a metering chamber of the carburetor body to the auxiliary fuel pump and a discharge side which is interconnected to the intake side and extends from the auxiliary fuel pump to a throttle bore in the air intake of the carburetor body. To prevent the engine from stalling, a restriction jet is placed within the start pulse passage to prevent the auxiliary fuel pump from discharging fuel into the throttling bore when the engine transmits pulses at high frequencies.