Automatic choking mechanism for internal combustion engines
An air/fuel mixing apparatus configured for use with an internal combustion engine including a carburetor including a body defining a passageway therethrough and a choke valve positioned in the passageway, a solenoid, and a thermal switch configured to energize or de-energize the solenoid. The solenoid is configured to move the choke valve between the choke open position and the choke closed position, wherein the solenoid includes a rotary shaft coupled to a choke lever, and a thermostatic element coupled to the rotary shaft. The thermostatic element expands and constricts based on a temperature of the engine and restricts the movement of the choke valve between the choke closed position and a partially-open position when the solenoid is not energized.
1. An air/fuel mixing apparatus configured for use with an internal combustion engine comprising:
a carburetor comprising:
a body defining a passageway therethrough; and
a choke valve positioned in the passageway, wherein the choke valve is rotatable about a first vertical axis in response to movement of a choke lever, and wherein the choke valve is rotatable between a choke open position and a choke closed position;
a solenoid configured to move the choke valve between the choke open position and the choke closed position, wherein the solenoid comprises:
a rotary shaft coupled to the choke lever;
a thermostatic element fixedly attached at a fixed end to the rotary shaft, wherein the thermostatic element expands and constricts based on a temperature of the engine, wherein the thermostatic element restricts the movement of the choke valve between the choke closed position and a partially-open position when the solenoid is not energized; and
a thermal switch coupled to the solenoid configured to open below a predetermined temperature and close above the predetermined temperature, wherein the thermal switch is configured to de-energize the solenoid when open and energize the solenoid when closed thereby moving the choke valve to the choke open position.
2. The air/fuel mixing apparatus of claim 1 , wherein the carburetor further comprises a throttle valve positioned in the passageway downstream of fuel injection into the carburetor and coupled to a throttle lever, wherein the throttle valve is rotatable about a second vertical axis in response to movement of the throttle lever, and wherein the throttle valve is rotatable between a throttle open position and a throttle closed position.
3. The air/fuel mixing apparatus of claim 2 , further comprising a governor including a governor arm coupled to the throttle lever, wherein the governor arm moves the throttle lever between the throttle open position and the throttle closed position based on a load of the engine.
4. The air/fuel mixing apparatus of claim 1 , wherein the thermostatic element expands when the temperature of the engine increases and constricts when the temperature of the engine decreases.
5. The air/fuel mixing apparatus of claim 1 , wherein the thermostatic element further comprises a first tab on a first end of the thermostatic element and a second tab on a second end of the thermostatic element, wherein the first tab moves in relation to an expansion and a constriction of the thermostatic element, and wherein the second tab is attached to the rotary shaft of the solenoid and does not move in relation to the expansion and the constriction of the thermostatic element.
6. The air/fuel mixing apparatus of claim 5 , further comprising a cover coupled to the solenoid and configured to house the thermostatic element, wherein a restriction surface is formed on an inside of the cover.
7. The air/fuel mixing apparatus of claim 6 , wherein the first tab is movable between a first position and a second position, wherein when in the second position the first tab contacts the restriction surface.
8. The air/fuel mixing apparatus of claim 6 , further comprising a travel regulator attached to the rotary shaft, wherein the travel regulator restricts the amount of rotation that the thermostatic element imparts on the rotary shaft coupled to the choke valve when the first tab of the thermostatic element contacts the travel regulator.
9. The air/fuel mixing apparatus of claim 6 , wherein when the solenoid is not energized and the thermostatic element is fully expanded, the first tab of the thermostatic element contacts the restriction surface and the choke valve is in the partially open position.
10. The air/fuel mixing apparatus of claim 9 , wherein when the solenoid is not energized and the thermostatic element is fully constricted, the first tab of the thermostatic element is not in contact with the restriction surface and the choke valve is in the choke closed position.
11. The air/fuel mixing apparatus of claim 8 , wherein at a first engine temperature for a cold start condition, the thermal switch is open and the first tab is not in contact with the restriction surface and the travel regulator is not in contact with the first tab.
12. The air/fuel mixing apparatus of claim 11 , wherein at a second engine temperature for a warm start condition, the thermal switch is open and the first tab is in contact with the restriction surface and the travel regulator is in contact with the first tab.
13. The air/fuel mixing apparatus of claim 12 , wherein at a third engine temperature for a running condition, the thermal switch is closed and the solenoid is energized, wherein the solenoid opens the choke valve to the choke open position.
14. The air/fuel mixing apparatus of claim 1 , wherein the thermostatic element is a coil wound around the rotary shaft of the solenoid.