PROBLEM TO BE SOLVED: To provide a thermal protection mechanism of an electronic endoscope having a simple mechanism.SOLUTION: The thermal protection mechanism of the electronic endoscope is provided on the end surface 12a of the distal end portion 12 of an insertion portion of the electronic endoscope and is equipped with a water feed nozzle 14, a light irradiation port 15, and a metal connecting member 17 as metal members for detecting a temperature of the distal end portion 12, an LED light source provided on the distal end portion 12, a constant voltage source which applies a certain voltage to the LED light source and makes the LED light source emit light, and a PTC thermistor 31 which is connected to the constant voltage source and has an ohmic value changing in accordance with the temperature detected by the water feed nozzle 14, the light irradiation port 15, and the metal connecting member 17. The PTC thermistor 31 detects the temperature of the distal end portion 12, and the ohmic value changes in accordance with the detected temperature. When the ohmic value of the PTC thermistor 31 suddenly increases because of abnormal heating, a current flowing to the LED light source is reduced. Consequently, the abnormal heating of the distal end portion 12 is prevented by the reduction in the light amount of the LED light source and the reduction in the amount of heat generation.COPYRIGHT: (C)2012,JPO&INPIT【課題】簡易な機構を有する電子内視鏡の熱保護機構を提供する。【解決手段】電子内視鏡の熱保護機構は、電子内視鏡の挿入部の先端部12の端面12aに設けられ、先端部12の温度を検知する金属部材として、送水ノズル14、光照射口15と金属連結部材17と、先端部12に設けられたLED光源と、LED光源に一定の電圧を印加してLED光源を発光させる定電圧源と、定電圧源に接続され、送水ノズル14、光照射口15、金属連結部材17で感知した温度に応じて抵抗値が変化するPTCサーミスタ31とを備える。PTCサーミスタ31は、先端部12の温度を感知し、感知した温度に応じて抵抗値が変化する。異常加熱によりPTCサーミスタ31の抵抗値が急上昇すると、LED光源に流れる電流が減少し、LED光源の光量が低下して発熱量が減少することにより先端部12の異常加熱が防止される。【選択図】図1
