Automobile speed transmission pneumatic gear shift device

The utility model provides a pneumatic gear shift device of a speed changer of an automobile. A sealing volume is formed between a casing and an end cover, and a piston ring fixedly connected with the left end of a gear selecting shifting fork shaft divides the sealing volume into the right and the left parts. When the compressed air is introduced into a left cavity or a right cavity, the pressure of the left cavity or the right cavity is increased to push the piston ring to do the axial movement and consequently the gear selecting shifting fork shaft and a gear selecting shifting fork are driven to do the corresponding axial movement. The right end of the gear selecting shifting fork shaft is fixedly connected with an induction ring, and sensors are arranged on the proper positions of a back cover and the casing. When the gear selecting shifting fork shaft drives the induction ring together to axially move a certain distance, the sensors send out impulse induction signals towards a control device, the supply of the compressed air is caused to be stopped through the control device and consequently the automatic gear shift of the speed changer is realized. The utility model has the advantages of simple structure, low cost and convenient operation, use and maintenance.