Combustion – Timer – programmer – retarder or condition responsive control – Of diverse feed or feed rate in starting – e.g. – enriching...
Patent
1984-12-18
1986-08-19
Dority, Jr., Carroll B.
Combustion
Timer, programmer, retarder or condition responsive control
Of diverse feed or feed rate in starting, e.g., enriching...
431 28, 431 76, 431 37, 431208, F23H 500
Patent
active
046067191
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention improves safety measures in a combustion apparatus by the employment of an oxygen concentration cell type sensor for detecting incomplete combustion in a combustor such as a petroleum or gas fan heater, stove or the like.
BACKGROUND ART
A sensor of an oxygen concentration cell type such as a zirconia sensor is generally known as a sensor for detecting incomplete combustion and is put into practical use in a combustor using gas as fuel. The zirconia sensor has certain characteristics wherein electromotive force suddenly changes at an air fuel ratio (hereinafter referred to as M value) M.ltoreq.1 as shown in FIG. 1 in a high temperature atmosphere, and the inner resistance reduces due to the temperature increase as shown in FIG. 2. Accordingly, it is used also as a sensor, with the use of the temperature characteristics, for detecting an accidental fire as well as the ignition of a fire. FIG. 3 shows one example of the detecting circuit. In the drawing, 1 is a zirconia sensor, which is made equivalent to the electromotive force e.sub.i and the inner resistance Ri. Resistor 2 is connected to a DC power supply 3 and in series with the zirconia sensor 1 and forms a voltage divider with the sensor device. At a and b are detection output terminals, respectively.
Before combustion, the inner resistance Ri becomes several hundred megohms, which is sufficiently larger than the series resistance 2, and the output electric potential becomes almost equal to the current power supply 3.
When the burner is operative, the inner resistance Ri lowers through the increase in temperature and becomes a value sufficiently smaller than the series resistance 2. The divided voltage potential through the series resistance 2 and the inner resistance Ri, therefore, drops as shown with a solid line A in FIG. 4 to an extremely small value. Accordingly, the detection of the drop in voltage can indicate that the burner has ignited. However, the conventional construction is uneconomical in power consumption as the voltage is normally applied directly to the sensor and the power supply circuit is required to impress the stabilized voltage to the sensor to positively detect the ignition because of a large dispersion of the inner resistance of the sensor so that a power-supply stabilizing circuit is required, thus resulting in complicated construction and higher cost.
As a method of solving such a problem, it is considered that voltage application to the sensor should stop and only the electromotive force e.sub.i of the sensor itself should be outputted. However, in this case, there is a problem wherein the output of the sensor will not suddenly change if the burner is ignited and the ignition detection becomes difficult to perform. Namely, although the sensor is heated with the combustion heat, when the burner is ignited, to start to generate the electromotive force of the oxygen concentration difference portion, the electromotive force change is slight, because the combustion is performed (the broken line A' range of FIG. 4) in the normal air fuel ratio zone (hereinafter referred to as a normal M value). Accordingly, there is no change in the sensor output, which makes it difficult to distinguish between the presence and the absence of the ignition.
A first object of the present invention is to ignite the burner, in a condition where the voltage application is not performed upon the sensor, in a range, i.e., a low air fuel ratio (hereinafter referred to as a low M value) smaller than 1 in the air fuel thereby to remove the above-described problems, that is, to ensure the ignition detection and to improve economy and cost.
Also, although carbon monoxide is produced in the case of the low M value ignition, a second object of the present invention is to reduce the production amount of the carbon monoxide as much as possible by the movement of the burner combustion to the normal M value simultaneously with the ignition detection.
Also, it is not desirable that much of the carbon monoxide which is harmfu
REFERENCES:
patent: 4362499 (1982-12-01), Nethery
patent: 4439138 (1984-03-01), Craig et al.
Imajima Mitsuhiro
Mori Keiichi
Uchida Kuniaki
Yamamoto Katsuhiko
Dority Jr. Carroll B.
Matsushita Electric - Industrial Co., Ltd.
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