Patent ID: 8490284
Filing Date: 2013-07-23
Classification: F04C,F16H,Y10T

Abstract:
1. A method for forming a tooth profile of a gear, comprising (a) acquiring a standard rack according to a gear module of a desired gear, wherein said standard rack includes a plurality of basic tooth shapes each having a lateral, an addendum and a dedendum; (b) establishing a Cartesian coordinate system (Xr, Yr) halt Xr axis and a Yr axis perpendicular to the Xr axis, wherein a origin of the Cartesian coordinate system is set at the center of a tooth width of the basic tooth shape, the desired gear having a amended basic tooth shape which can be described with a cubic curve, and the cubic curve being divided into an upper partial curve (xr1, yr1) above the Xr axis and a lower partial curve (xr2, yr2) below the Xr axis, which are respectively expressed by Equation (1) and Equation (2): wherein Sw is tooth width of the basic tooth shape, and h is total tooth depth of the desired gear; (c) defining the cubic curve contacts tangentially with each basic tooth shape of the standard rack at three tangent points including a midpoint (0, h/2) of the dedendum, a midpoint (Sw/2, 0) of the lateral and a midpoint (Sw, −h/2) of the addendum, wherein the three tangent points can be used to express the coefficients of Equations (1) and (2) as Equations (3) and (4): wherein α is pressure angle of the standard rack; (d) substituting the tooth width Sw, the total tooth depth h, and the pressure angle α into Equations (3) and (4) to obtain the coefficients a1, a2, b1, b2 and substituting the coefficients a1, a2, b1, b2 into Equations (1) and (2) to obtain the amended basic tooth shape; and (e) reproducing said amended basic tooth shape acquired in said step (d) to obtain an amended rack, and using said amended rack to generate a tooth profile of said desired gear.