engleski

Calculation of Stresses in HCR Gears with Regard to Quality Grade

High transverse contact ratio (HCR) gears are increasingly frequent in use in automotive industry because of their increased load-carrying capacity compared to low contact ratio gears, although they are very sensitive to manufacturing errors. The standard calculation procedure of load distribution on tooth pairs in simultaneous contacts doesn't take into account the influence of the pitch errors. In this paper the expressions for calculation of load distribution on spur involute HCR gears' teeth with pitch errors are established. The force distribution factors are introduced for this calculation. They are defined on the basis of equality of elastic deformation of the tooth pairs in simultaneous contact. The values of load shares calculated by using these expressions significantly differ from the values of load shares calculated by common expressions. The calculation of stresses is based on the load distribution on mating teeth. The analysis of tooth root and contact stresses is made for HCR gears with pitch errors. The choice of quality grade has the major influence on load distribution on mating teeth, and consequently on stresses. The stresses increase with higher values of pitch errors. If the pitch error is big (small quality grade), it is possible that in theoretically triple contact only two tooth pairs or even one tooth pair are in real contact, or in theoretically double contact only one tooth pair is in real contact. This effect has major influence on tooth root and contact stresses, that can be significantly increased. The existence of the contact between two teeth can be controlled by the values of load shares, calculated by using presented expressions. The use of presented expressions enables better estimation of appropriate gear quality grade. They provide more accurate calculation of load capacity of the HCR gears.

High contact ratio gear; Pitch error; Stress

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