WORM WHEEL AND ELECTRIC POWER STEERING DEVICE

摘要

Worm wheel construction that is able to sufficiently increase the strength of the connecting portion between a hub 11a and a gear portion 12a, and to maintain sufficient durability even when applied to an electric power steering apparatus that applies a large auxiliary torque, is achieved. A synthetic resin gear portion 12a is molded and formed in the end portion on the outer-diameter side of a metal hub 11a. A first annular concave portion 15 is provided on one surface side in the axial direction of the hub 11a, and a second annular concave portion 22 is provided on the other surface side in the axial direction thereof. Part of the synthetic resin of the gear portion 12a is fed into the portions near the outer diameter of the first annular concave portion 15 and the second annular concave portion 22 to form a first restraining portion 18 and a second restraining portion 23. These restraining portions 18, 23 tightly hold the end portion on the outer-diameter side of the hub 11a, and improve the strength and rigidity of the connecting portion between the hub 11a and the gear portion 12a.