The invention discloses an electric-drive mechanical
type variable-speed
power transmission system for electric vehicles, which comprises a vehicle motor (2) and a speed-changing gearbox (1), wherein the speed-changing gearbox (1) comprises a power input shaft (27), a
power output shaft (28), an intermediate shaft (29), gears (35, 36, 37, 38, 39 and 40) and an air cylinder (30), the air cylinder (30) is connected with a shifting fork through a
piston (31), the shifting fork is correspondingly connected with the gears, and the output shaft (27) of the vehicle motor (27) and the input shaft (27) of the speed-changing gearbox share the same shaft. The speed-changing gearbox is provided with a gear shifting
interlocking device formed by an ejector rod (53), positioning steel balls (51 and 52) on two sides of the ejector rod (53), and the shifting fork; and the shifting fork is provided with a positioning groove matched with the positioning steel balls. Due to the function of the gear shifting
interlocking device, the phenomena of gear disorder, gear misoperation and gear striking generated by the traditional speed-changing gearbox without a
synchronizer during speed changing can be avoided, and gear shifting is smooth and more reliable.