| 摘要 |
PURPOSE:To prevent partial overheating by fixing plural number of combustion tubes by wrap casting of the combustion tubes through a diecasting method. CONSTITUTION:A main body 11 formed through aluminum alloy diecast molding possesses a burner storing chamber 13 and an exhaust manifold 14 and makes an inlet 15a and an outlet 15c of a U shape combustion tubes 15 open to both chambers 13 and 14 respectively. An inside radius R1 of a curved part 15b of the combustion tube 15 is made larger than a half of a distance L1 between center lines of an inlet 15a and an outlet 15c, and a center line of the curved part 15b is connected smoothly with a straight part of tubes with a radius R2. The inlet 15a and the outlet 15c which are fixed through wrap casting at a time of a diecasting molding are expanded, and a metal die 31 which is used for the diecast molding and is keeping a distance L1 between the inlet 15a and the outlet 15c is moved to the curved part 15b and pulled out at a space 30 of the radius R1 by moving to a direction where the combustion tubes 15 are provided in parallel with each other. |
