An automatic choke apparatus (54) for use in an internal combustion engine (10). The choke apparatus (54) includes a choke valve (18) automatically operable in response to the speed of the engine, a thermally conductive assembly that conducts heat from exhaust gases produced by the engine (10), a thermally responsive member (118) in thermal communication with the thermally conductive assembly (66), and a mechanism (62) that moves in response to the thermally responsive member (118) to cause the choke valve (18) to remain in at least a partially open position during engine starting when the thermally responsive (118) member senses a temperature above a predetermined temperature. The thermally conductive assembly at least partially surrounds the path of the exhaust gases.

Automatic choke for an engine

A constant force actuator transforms applied heat to an applied force on an output device. Strips of shape memory alloy are coiled into spirals and trained to have this configuration as a static state. The shape memory alloy springs are attached to the output device to apply a directional force. When one of the springs is heated, the modulus of elasticity within the spring material changes. This change in modulus increases the force which the spring exerts in returning to its static state, which in turn increases the force applied to the output device, upsetting the balance of forces and resulting in a rotation.

Constant force spring actuator

During operation of an internal combustion engine at low temperatures, the carburetor choke is closed to the extent necessary to provide the fuel which will maintain the mean effective pressure of combustion equal to the mean effective pressure occurring during operation at normal temperatures. The torque produced during low temperature engine operation is thus maintained equal to the torque produced during operation at normal temperatures.

Engine control method

An engine starting system for an internal combustion engine The starting system includes a starter switch electrically connected between a battery and a starter motor for the engine, and a choke valve disposed in an air intake of an air/fuel-mixing device for the engine The choke valve moves in response to a solenoid actuator The solenoid actuator is electrically connected to the starter motor and a temperature switch When starting the engine below a threshold temperature, the starter switch and temperature switch close such that the battery powers the starter motor and solenoid actuator The energized solenoid actuator moves the choke valve to a closed position to enrich the air/fuel mixture Above a certain threshold temperature, the temperature switch interrupts the power to the solenoid actuator

Electromechanical choke system for an internal combustion engine

A rotary solenoid having an output shaft that is indirectly coupled to the rotor or armature of the solenoid, for rotation independently of or coupled to the solenoid. In one application of the solenoid the shaft is rotated through a limited range by a bimetallic torsional element, which is overridden by operation of the solenoid to increase the range of rotation. The range of travel can be limited by a disc having a slotted peripheral flange between the solenoid rotor and the output shaft. The armature has an integral hub and spaced poles with the pole pieces being rotatably positionable within the space between the hub and poles. Structure of the unit is very simple and all parts are readily accessible for adjustment and servicing.

Rotary solenoid with indirectly coupled output shaft

An automatic choke for an internal combustion engine includes a rotary solenoid which is energized when the engine is cranked by the starter motor. During starting, the solenoid rotates a choke valve to its starting position in which choking is applied, and a bimetallic temperature responsive spring coupling the solenoid to the choke valve adjusts the amount of choking in response to the ambient temperature. A stop element limits the range over which the bimetallic spring adjusts the position of the choke valve.

Alvin P. Fenton

Papers

Automatic choke assembly for small engines