PROBLEM TO BE SOLVED: To provide means to prevent an increase in the temperature of a circuit part even when power of a heating part increases in an underwater heater in which the heating part and the circuit part are integrally formed.SOLUTION: An underwater heater includes: a heating part 1 having a ceramic core member in which a heating wire is wound around the outer periphery, and a thermocouple is inserted into the inside, a metal sheath-like outer cylinder for coating the core member, and a powder-type filler subjected to swaging processing, which is put between the sheath-like outer cylinder and the core member a circuit part 2 which includes a power supply circuit for supplying power to the heating wire, a control circuit for preventing overheating of the heating wire, a sleeve composed of metal circular pipe, whose both ends are water-tightly sealed after storing the control circuit inside, and a powder-type filler put in a space between the inner wall of the sleeve and a circuit board and a connection member 3 for connecting the sheath-like outer cylinder and the sleeve.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2018,JPO&INPIT【課題】発熱部と回路部が一体に形成されている水中ヒータにおいて、発熱部の電力が大きくなった場合にも、回路部の温度上昇を防止できる手段を提供する。【解決手段】外周に電熱線が巻回され、内部に熱電対が挿入されたセラミック製のコア部材と、前記コア部材を被覆する金属製の鞘状外筒と、前記鞘状外筒と前記コア部材との間に充填され、スウェージング加工が施された粉末状充填材と備えた発熱部1と、前記電熱線に電力を供給する電源回路と、前記電熱線の過熱を防止する制御回路と、金属製の円管からなり前記制御回路を内部に収蔵した後、その両端を水密封止されるスリーブと、前記スリーブの内壁と前記回路基板との間隙に充填された粉末状充填材とを備えた回路部2と、前記鞘状外筒と前記スリーブとを連結する連結部材3とを備えた水中ヒータの構成とする。【選択図】図1
