Electronic choke control

Abstract

Abstract An electrical heating means for the bimetallic thermostatic spring controlling a carburetor automatic choke valve is in series with a negative temperature coefficient thermistor which senses engine temperature to open the choke valve in a more efficient manner and improve engine performance during warm-up. A temperature responsive switch is in series with the heater, negative temperature coefficient thermistor and a battery and senses engine block temperature to maintain current flowing in the heater after the engine is shut off and until the entire engine cools down, to provide better warm-engine restarts and reduce pollution. BACKGROUND OF THE INVENTION This invention is in the field of automatic choke valves for internal combustion engines and particularly to electrically controlled chokes. It is conventional in internal combustion engines to provide a carburetor having a choke valve therein controlled by a thermostatic spring whereby the choke valve is held closed when the engine is cold. As the engine warms up, heat is directed to the thermostatic spring causing the same to expand and to open the choke valve until, at normal operating temperatures, the choke valve is substantially fully open. Many ambient conditions affect the operation of such metallic springs and they do not normally open the choke valve at a sufficiently high rate to hold emissions and air pollution to a minimum during engine starts and warm-up. Furthermore, after shutting an engine off, the thermostatic spring is normally subject to ambient air temperatures and normally close the choke valve before the engine block is sufficiently cool. Thus, when such a warm engine is restarted, the choke valve is often closed and this results in excessive fuel being fed to the carburetor with the attendant difficulty in starting, excessive emission of polluting materials and often causes "flooding" of the carburetor. Previous attempts have been made to overcome the above-mentioned difficulties, such as by directing warm air or warm engine coolant to the vicinity of the thermostatic spring to thus hold the choke valve open for a longer period of time after engine shut-off. However, such prior devices were capable of holding the choke valve open for only a relatively few minutes after engine shut-off, particularly at fairly low surrounding air temperatures. They were not capable of holding the choke valve open long enough to facilitate easy warm-engine start-ups after the elapse of a few minutes. SUMMARY OF THE INVENTION It is a principal object of the present invention to provide means for holding a choke valve open, by electrical means, after engine shut-off until the engine block temperature has been lowered sufficiently to require closed-choke starting conditions. The invention contemplates means for directing battery current through a resistance heater adjacent the thermostatic spring and an engine block temperature-sensing device to terminate operation of the heater only when engine block temperature has reached a predetermined low value.

Inventors

• 👤 Peter S. DePetris

Bibliographic Details