Gear housing for electric power steering device, manufacturing method thereof, and electric power steering device

A manufacturing method for a gear housing for an electric power steering device, the gear housing for an electric power steering device comprising:

• a front-side housing and a rear-side housing combined in a front-rear direction;
• the front-side housing comprising:
• a worm wheel housing portion housing a worm wheel inside, a worm housing portion housing a worm shaft inside, and one or more reinforcing ribs;
• the worm wheel housing portion having:
• a worm wheel cylindrical portion arranged around the worm wheel;
• and a disk shaped worm wheel bottom portion bent inward in a radial direction from a front end portion of the worm wheel cylindrical portion;
• the worm housing portion provided on a part in a circumferential direction of an outer-diameter side portion of the worm wheel housing portion;
• the reinforcing ribs provided on a front side surface of the front-side housing, extending in a direction in which an engagement reaction force acts between the worm wheel and a worm that is provided on the worm shaft, and spanning between the worm housing portion and the worm wheel bottom portion,
• a mounting stay protruding toward a front side from the worm wheel bottom portion and for supporting the front-side housing to a vehicle body, and
• at least one reinforcing rib of the reinforcing ribs being continuous with the mounting stay,
• wherein
• the manufacturing method comprises manufacturing the front-side housing by casting or injection molding of a synthetic resin using a mold having a cavity, material is allowed to flow in the cavity from a worm housing portion forming space side for forming the worm housing portion to a worm wheel housing portion forming space side for forming the worm wheel housing portion.