Method for manufacturing turbo fan

A method for manufacturing a turbo fan unit to be used in a blower device, wherein the turbo fan unit comprises:

• multiple fan blades arranged around a fan center line;
• a shroud ring connected to one side of each of the multiple fan blades in an axial direction of the fan center line and forming an air suction port through which air is sucked;
• an other-side side plate connected to the other side of each of the multiple fan blades in the axial direction of the fan center line;
• and
• an air-flow guide portion located at a position inside of the other-side side plate in a fan radial direction for guiding an air flow sucked from the air suction port in a direction from an inside to an outside of the fan radial direction,
• wherein the air-flow guide portion has an air guide surface, which is formed in the air-flow guide portion to face the air suction port and which guides the air flow sucked from the air suction port,
• wherein the other-side side plate has a plate-side guide surface, which faces blade passages respectively formed between neighboring fan blades of the multiple fan blades, and which guides an air flow passing through the blade passages,
• wherein the method for manufacturing the turbo fan unit comprises;
• a preparing step for preparing the multiple fan blades and the other-side side plate;
• and
• a connecting step for connecting each of the multiple fan blades to the other-side side plate by a welding process,
• wherein, in the preparing step, an integrally molded component is prepared, in which the multiple fan blades, the shroud ring and the air-flow guide portion are integrally molded to one another, while the other-side side plate is prepared as a separate member from the integrally molded component,
• wherein, in the preparing step, one of the multiple fan blades and the other-side side plate is prepared, which has;
• a connecting-surface forming portion having a connecting surface, which is connected to the other one of the multiple fan blades and the other-side side plate, and
• a welding projection protruded from the connecting surface;
• wherein, in the connecting step, the welding projection is melted down and the connecting surface is connected to an opposing surface, which is a surface of the other one of the multiple fan blades and the other-side side plate and which is opposing to the connecting surface, and
• wherein an inner peripheral end of the plate-side guide surface in the fan radial direction is located at a position closer to the other side of the axial direction than an outer peripheral end of the air guide surface in the fan radial direction, when the multiple fan blades are connected to the other-side side plate.