Hypoid gear design method and hypoid gear

Abstract

A degree of freedom of a hypoid gear is improved. Instantaneous axis in a relative rotation of a gear axis and a pinion axis, a line of centers, intersection between the instantaneous axis and the line of centers, and an inclination angle of the instantaneous axis regarding the rotation axis of the gear are calculated based on a shaft angle, an offset, and a gear ratio of a hypoid gear. Based on these variables, base coordinate systems are determined, and the specifications are calculated using these coordinate systems. For spiral angles, pitch cone angles, and reference circle radii of the gear and pinion, one of the values for the gear and the pinion is set and a design reference point calculated. Based on the design reference point and a contact normal of the gear, specifications are calculated. The pitch cone angle of the gear or the pinion can be selected.

1 . A hypoid gear comprising a pair of gears including a first gear and a second gear, wherein
 a tip cone angle Γ f  of the second gear is set at a value in a predetermined range around an inclination angle Γ s  of an instantaneous axis S which is an axis of a relative angular velocity of the first gear and the second gear with respect to a rotational axis of the second gear, and the predetermined range is a range in which each of tooth trace contact ratios of a drive-side tooth surface and a coast-side tooth surface is greater than or equal to 2.0.   
     
     
         2 . A hypoid gear comprising a pair of gears including a first gear and a second gear, wherein
 a tip cone angle Γ f  of the second gear is set at a value in a predetermined range around an inclination angle Γ s  of an instantaneous axis S which is an axis of a relative angular velocity of the first gear and the second gear with respect to a rotational axis of the second gear.   
     
     
         3 . A hypoid gear comprising a pair of gears including a first gear and a second gear, wherein
 a tip cone angle Γ f  of the second gear is set at a value which is greater than or equal to an inclination angle Γ s  of an instantaneous axis S which is an axis of a relative angular velocity of the first gear and the second gear with respect to a rotational axis of the second gear.   
     
     
         4 . A uniform tooth depth hypoid gear comprising a pair of gears including a first gear and a second gear and in which a tooth depth is constant along a face width direction and a tooth trace shape is such that a radius of curvature of a tooth trace is not constant, wherein
 a ratio r c /D g0  between a cutter radius r c  and an outer diameter D g0  is less than or equal to 0.52, a ratio E/D g0  between an offset E and the outer diameter D g0  is greater than or equal to 0.111, and a gear ratio is greater than or equal to 2 and less than or equal to 5, and   a tip cone angle Γ f  of the second gear is set at a value which is within a range of ±5° of an inclination angle Γ s  of an instantaneous axis S which is an axis of a relative angular velocity of the first gear and the second gear with respect to a rotational axis of the second gear.   
     
     
         5 . The uniform tooth depth hypoid gear according to  claim 4 , wherein
 the tooth trace shape is an epicycloidal shape.   
     
     
         6 . An tapered tooth depth hypoid gear comprising a pair of gears including a first gear and a second gear and in which a tooth depth changes along a face width direction, wherein
 a ratio r c /D g0  between a radius of curvature r c  of a tooth trace of the second gear and an outer diameter D g0  is less than or equal to 0.52, a ratio E/D g0  between an offset E and the outer diameter D g0  is greater than or equal to 0.111, and a gear ratio is greater than or equal to 2 and less than or equal to 5, and   a tip cone angle Γ f  of the second gear is set at a value which is greater than or equal to an inclination angle Γ s , of an instantaneous axis S which is an axis of a relative angular velocity of the first gear and the second gear with respect to a rotational axis of the second gear, and less than or equal to (Γ s +5)°.