Tham khảo tài liệu 'lubrication fundamentals 2011 part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Figure Hypoid gears. These gears transmit motion between nonintersecting shafts crossing at a right angle. time the preceding teeth are still in mesh and carrying most of the load. As contact progresses the teeth roll and slide on each other. Rolling is from root to tip on the driver and from tip to root on the driven tooth. The direction of sliding at each stage of contact is as indicated by the small arrows. In view B contact has advanced to position 3-3 which is approximately the beginning of single tooth contact when one pair of teeth pick up the entire the load. It will be seen that to reach this point of engagement since the distance 0-3 on the driven gear is greater than the distance 0-3 on the driver there must have been sliding between the two surfaces. View C position 4-4 shows contact at the pitch line where there is pure rolling no sliding. It should be noted particularly that the direction of sliding reverses at the pitch line. Also sliding is always away from the pitch line on the driving teeth and always toward it on the driven teeth. View D shows contact at position 5-5 which marks the approximate end of a single-tooth contact. As shown another pair of teeth is about to make contact. In view E two pairs of teeth are in mesh but shown at position 8-8 the original pair of teeth is about to disengage. It will be seen that rolling is continuous throughout mesh. Sliding on the other hand varies from a maximum velocity in one direction at the start of mesh through zero velocity at the pitch line then again to a maximum velocity in the opposite direction at the end of mesh. This combination of sliding and rolling occurs with all meshing gear teeth regardless of type. The two factors that vary are the amount of sliding in proportion to the amount of rolling and the direction of slide relative to the lines of contact between tooth surfaces. With conventional spur and bevel gears the theoretical lines of contact run straight across the tooth faces Figure
