Automatic transmission for vehicle

An automatic transmission for a vehicle, comprising:

• a rotation shaft rotating by a driving force of the vehicle;
• a slider portion provided on the rotation shaft and provided to slide along an axial direction of the rotation shaft;
• a first connecting member having a first end portion hinged to the rotation shaft and a second end portion rising or falling by a centrifugal force as the rotation shaft rotates;
• a second connecting member having a first end portion hinged to the first connecting member and a second end portion connected to a slider portion to vertically slide the slider portion as the first connecting member rises or falls;
• a diaphragm elastic member coupled to the slider portion and deformed to a first side or a second side in an axial direction of the rotation shaft depending on a position of the slider portion;
• a shift fork connected to the slider portion or the diaphragm elastic member and engaging a synchronizer with a shift stage gear depending on a position of the slider portion;
• an elastic regulator controlling an elastic force of the diaphragm elastic member;
• and
• a controller configured to control the elastic regulator depending on a vehicle speed to regulate an elastic force of the diaphragm elastic member.