The role of one-way clutch in automatic transmission

Since 1982, one-way clutches in automatic transmissions have become more and more popular, especially in mid- to high-end models. The main function is to solve the problem of slipping and friction caused by insufficient oil pressure due to the low oil pump speed when the vehicle is started, and to solve the problem of shifting shock caused by the mismatch of the speed. While the torque converter can play an important role in eliminating shift shock, the one-way clutch is the most effective method for eliminating shift shock, especially downshifting.

One-way clutches are mainly divided into roller type and wedge type. Among them, the roller type can be divided into flat type, logarithmic spiral type, and eccentric cylindrical surface type according to the different wedge angles of the outer ring. Because the balls can rotate freely between the inner and outer rings, the wear is small and uniform, and the short-term overload and roller slip are not effective. It will damage the clutch. After the torque is reduced, the clutch can still work normally. It is suitable for combination under any speed difference. Low disadvantage; wedge-type one-way clutch, due to the large radius of curvature of the contact surface, the large number of wedges, the instant bonding is good, and it can carry a large torque. Under the same raceway diameter, the bearing capacity is usually the roller type 5- 10 times, but the wedge block and the free raceway are static friction during the overrunning process, which will reduce the clutch life under high-speed overrunning conditions; in recent years, the new type of wedge block type overrunning clutch has been introduced. When the speed is higher than the set value during operation , Due to the centrifugal force, the separation of the eccentric wedge from the inner and outer rings increases the reliability of the work, but this one-way clutch has not been widely used in engineering.