When a pair of conjugate spiral bevel gears are driven, when the bevel gear with the number of teeth Z1 ω 1 when rotating at a constant speed, the bevel gear with the number of teeth Z2 matched with it is ω 2, and ω 1 and ω 2. The relationship must be satisfied: ω 1/ ω 2 = Z2 / Z1 = transmission ratio I. As shown in Figure 2.3, the transmission of two spiral bevel gears can also be understood as the pure friction rolling of two cones without sliding, in which the cone angles of the two friction cones are respectively the pitch cone angles of the spiral bevel gears δ 1、 δ 2 equal.
For different shaft intersection angles in spiral bevel gear transmission Σ, The pitch cone angle of bevel gear has the following relationship:
(1) When Σ< At 90 °
(2) When Σ> At 90 °
(3) When Σ= At 90 °