Abstract: There is disclosed a combustion-state detecting circuit of a combustion apparatus installed in a combustion chamber, including: a flame detector that has a heat-emitting device for emitting heat on application of an alternating current signal, and produces a potential difference between the current applied to the heat-emitting device and flame-electric current produced by ignition occurring within the combustion chamber; a rectifier that changes the alternating current signal provided by the flame detector into a direct current signal; an inversion amplifier that inverts the direct current signal produced by the rectifier with respect to a reference signal and increases the magnitude of the inverted signal; and a flame discriminator that compares the output signal of the inversion amplifier with a flame discriminating reference signal to determine if ignition occurs.

Abstract: There is disclosed a combustion control circuit of a combustion apparatus with a driving signal generator, an exhaust fan controller and a gas valve controller, including: a combustion state detector for detecting the state of combustion occurring within a combustion chamber according to an output signal of a flame sensor installed in the combustion chamber, and for producing a signal corresponding to the state of combustion; a reference signal generator for producing a reference signal in response to each output signal of a temperature sensor and a flow sensor; a comparator for comparing the output signal of the combustion state detector with the output signal of the reference signal generator, and for outputting a signal corresponding to a difference therebetween; and an adder for adding the output signal of the comparator to the output signal of the driving signal-generator, and for respectively applying an output to each one of the exhaust fan controller and the gas valve controller.

Abstract: A novel exhaust gas recirculation (EGR) control system comprises an EGR valve having an inlet control port connected through a normally closed solenoid-actuated valve to venturi vacuum tap of the caburetor. The solenoid-actuated valve is controllably energized via an electrical control circuit which monitors a number of engine operational characteristics. In the preferred embodiment, these monitored characteristics include: the amount of throttle blade opening; the magnitude of intake manifold vacuum; the relative durations of idle and non-idle operation during a immediately past time period; and the engine temperature. Individual electrical control signals are derived for each of the monitored characteristics and the value of each signal indicates whether the correspondingoperating characteristic is commanding the solenoid-actuated valve to be energized.

Abstract: The method comprises introducing a mixture of uncured epoxy resin and curing agent in a coolant passage adjacent an exhaust passage and curing the resin into a solid insulating layer against the walls of the coolant passage.