Elevator traction machine

The utility model provides an elevator traction machine, which comprises a permanent magnet synchronous motor, traction wheels and a speed reduction gear box, wherein the speed reduction gear box is an involute few-tooth difference speed reduction planetary gear box and has an outer gear output structure in an NN type few-tooth difference planetary transmission structure; a planetary gear in the speed reduction gear box has a duplex coaxial gear ring structure; and the axial distance a between the effective acting tooth width midlines of an outer gear and an inner gear is equal to 0 or small than or equal to 1/4 of the effective acting tooth width of the inner gear. Compared with the prior art, the utility model has the advantages that the elevator traction machine is compact in structure, stable in operation and high in overload capacity; the transmission efficiency reaches over 90 percent; and a soft tooth surface can be adopted in an engaged gear pair, so that the elevator traction machine is easy to machi