Advanced Gear Engineering by Veniamin Goldfarb Evgenii Trubachev & Natalya Barmina

Author:Veniamin Goldfarb, Evgenii Trubachev & Natalya Barmina
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

3.1 Some Features

Important features of the S-gears include:radii of curvature and flank pressure,

velocity circumstances and oil film thickness and

rolling and sliding ratio.

An intrinsic feature of S-gears is that their tooth flanks become concave in the dedendum flank. The concave area is short for gears with a low number of teeth and extends to the vicinity of the kinematic pole for a high number of teeth. Regardless of the number of teeth, this assures convex-concave contact in the meshing start and end areas. Therefore, the contact circumstances in this critical area are improved. One can agree that concave-convex contact and the curved path of contact imply higher reduced radii of curvature, which then imply lower Hertzian pressure [12].

Velocity circumstances in the gear tooth contact, appearing along the path of contact, decisively influence oil film thickness and depend on the tooth flank geometry. Absolute velocities, relative velocities of the teeth flanks, and the contact point movement velocity in the direction tangential to the path of contact can be distinguished with regard to the direction tangential to the teeth flanks at the contact point.

Figure 5 illustrates a situation in the vicinity of the meshing start area. The absolute velocities of the gear tooth flank and the pinion are represented by the vectors v S and v P , respectively. The relative velocities v rS and v rP act tangentially to the corresponding teeth flanks, whereas v At is the velocity of the contact point in the direction of a tangent to the path of contact. Thus, expressions for v S and v P are

Fig. 5Velocity circumstances for S-gears in the meshing start area [7]

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