Conventional induction cookers have generally utilized methods for indirectly detecting a temperature of a bottom of a pan, by bringing a thermosensor such as a thermistor into contact with a top plate on which the pan is placed. Further, as a detection method with more excellent responsivity, there has been utilized a method for detecting intensity of infrared rays outputted from a bottom of a pan, using an infrared ray sensor. When an infrared ray sensor is used, there are cases where the temperature cannot be accurately detected, as follows.
For example, when the infrared ray sensor is contaminated, it is impossible to accurately detect the temperature. Therefore, there has been contrived a method for determining the contamination of an infrared ray sensor, using a contamination detection section formed from a combination of an infrared-ray TED and a photo transistor, based on a reduction of an amount of light reflected by the surface layer of the top plate due to absorption of infrared rays by the contamination of the infrared ray sensor. Further, there has been a method for detecting the contamination of an infrared-ray receiving portion and correcting an actual temperature of radiation from an object to be heated, by using a temperature detected by the infrared ray sensor and a temperature detected by a thermosensor which is thermally contacted with the object to be heated (refer to Patent document 1, for example).
For example, when there is a failure in the infrared ray sensor, it is impossible to accurately detect the temperature. Therefore, there has been a method which determines that there is an abnormality and stops heating or reducing the heating power, if a value of an output of an infrared ray sensor exceeds a predetermined range. Further, there has been contrived a method which provides a thermosensor such as a thermistor for detecting the temperature of an infrared-ray sensor or a peripheral temperature around the infrared ray sensor and determines that there is an abnormality if the temperature from the thermosensor exceeds a predetermined range (refer to Patent document 2, for example).    Patent document 1: JP-A-2004-241218    Patent document 2: JP-A-2005-216585
USPTO Backgrounds
USPTO Backgrounds