Air/fuel ratio detector

DETAILED DESCRIPTION Accordingly, an object of the present invention is to provide an A/F ratio detector that is capable of producing an A/F ratio detection signal in the form of a unidirectional, unambiguous electrical quantity whether the burner device is operating in the fuel-lean region, at the theoretical A/F ratio, or in the fuel-rich region.
Such a detection signal may be used directly for performing A/F ratio control, which can then be done precisely and quite easily over the entire A/F range.
The above-stated object of the present invention can be achieved by an A/F ratio detector comprising: (1) a sensor unit composed of two elements, each consisting of an oxygen ion-conductive solid electrolyte having a porous electrode formed on both surfaces and which are disposed facing a diffusion compartment which receives a limited inflow of exhaust gas, and (2) A/F ratio signal detecting means that operates one of the two elements as an oxygen-concentration-difference-actuated electrochemical cell and the other as an oxygen pump and which controls the voltage produced by the electrochemical cell or the current flowing into the oxygen pump so as to produce an A/F ratio signal indicative of the concentration of oxygen in the exhaust gas.
The detector is characterized in that the sensor unit is provided with an air compartment so that at least the electrochemical cell contacts the atmosphere at the electrode disposed opposite to the side facing the diffusion compartment.
The detector is further characterized in that constant current supply means for supplying a predetermined amount of current to the electrochemical cell is provided in the A/F ratio signal detecting means so that oxygen is pumped at a predetermined rate from the atmosphere into said diffusion compartment by said electrochemical cell.