Abstract: A backlash-free planetary transmission device includes an outer ring of an eccentric sleeve rotatably fitted with a dual outer gear. One outer gear of the dual outer gear is meshed with a fixed pin gear with small teeth number difference, and the other outer gear is meshed with a power output pin gear with small teeth number difference. Each of the fixed pin gear and power output pin gear includes a roller. Profiles of teeth of the outer gears are respectively enveloped by profiles of the fixed pin gear and power output pin gear meshed therewith. The outer gears and rollers are in rolling mesh, to avoid sliding friction between meshed gear teeth. The dual outer gear contacts with the fixed pin gear and power output pin gear, with zero transmission error and zero backlash. The transmission device has high accuracy, low noise, high transmission efficiency, and long service life.

Abstract: The present invention provides a backlash-free planetary transmission device, comprising a housing (10), a power input shaft (1) and a power output shaft (8). An eccentric sleeve (2) is securely positioned on a circumference of the power input shaft (1). A fixed pin gear (5) is set on the housing (10) that is concentric with the power input shaft (1). A power output pin gear (7) is set on the power output shaft (8) in circumferential transmission fit and concentric with the power input shaft (1). An outer ring of the eccentric sleeve (2) rotatably fits with a dual outer gear (4). An outer gear (42) of the dual outer gear (4) is meshed with the fixed pin gear (5) with small teeth difference, and the other outer gear (41) is meshed with the power output pin gear (7) with small teeth difference. The pin teeth of both the fixed pin gear (5) and the power output pin gear (7) include a roller that can rotate around its own axis.