AGMA 93FTM4-1993 pdf download.Stress Analysis of Spiral Bevel Gears A Novel Approach to Tooth Modelling.
4. DETERMINATION oF CONTACT LINES ON THE TOOTH SURFACE
In a spur gear pair, for any position of contact, the contact line is parallel to the land of the tooth and in th, case of a straight bevel gear pair, it runs along the generator of the respective front cone making a constant angl. with the axis of the gear from the toe to the heel side. It may be noted that in the case of a helical or spiral bevel gear pair, the line of contact runs across the surface of the tooth obliquely. In a helical gear pair, the contact line is inclined by base helix angle 0b with the pitch line as described in Fiq.lO, where G1G2 is the length of action. It is described in reference(8] that the contact lin, of a spiral bevel gear pair is also inclined by base spiral angle b to the pitch line. Sinc, the angle of inclination has been described only in the rectangular plane (2x F), it is very difficult to apply this theory to suit the present problem using PEN model. Hence an alternate method has been proposed to generate the coordinates of the contact lines which exactly fall on the surface of the tooth.
In th. case of spur gears, for a particular position of gear rotation ejs the line of contact will pass through the point with radius Rj and will be parallel to the axis or land of the gear. For each position of the tooth, Rj can be calculated and hence the corresponding contact point can also be determined.
In the case of h•lical gears (11), each section along the face width is out of phase relative to the previous section. Or in other words, each section of the helical gear tooth can be considered as a spur gear section rotated by a definite angle as shown in Fig. 11. The contact radii
at different section. can be determined and th. corresponding coordinates of these contact points on the tooth surface can be calculated using the same procedure described for spur gear tooth.AGMA 93FTM4 pdf download.