Analytical Method to Determine Press-fit Tolerance between Torque Carrying Members 2012-01-1996
This paper deals with an analytical method to calculate the press-fit tolerance and fits between gears and shaft for automotive applications. The relative interferences increase sharply in the small diameter range, therefore one must be especially careful when designing small diameter joints. The strength of press-fit depends on the amount of relative interference; extreme interference leads to excessive contact stresses between the gear and shaft eventually leading to failure. Too little interference leads to slippage of gear on the shaft.
In the press fit connection a shaft's spline rolling operation and gear internal broaching is eliminated. It is more economical than a conventional spline connection. Press fit connections are used in various transmission between a shaft and a gear. They are used in 6 speed transmission to 9-speed transmission for (German based Vehicle Manufacturer) heavy and light commercial vehicle company. In India 5-speed transmission to 9-speed transmission for heavy and light commercial vehicle companies, also uses press fit connections.
The strength of the press fit joint is directly proportional to the coefficient of the friction between the mating parts. The strength depends upon the pressure at the contacting surface, surface micro irregularities and material properties. Adequate surface finish of the mating component is an essential condition for the strength of the pressed connection. For connections undergoing heating during the operation, the influence of the temperature upon the fit must be considered.
Therefore it is challenge to design an optimum press fit joint; a fine balance need to be determined while calculating interferences for the press-fit connection.