To prevent the slip of a vehicle owing to the air pressure reduction after the parking, by reducing the ground pressure to a normal value when a parking brake is operated, in a vehicle furnishing a start auxiliary device of the vehicle to increase the ground pressure of a driving shaft.
To a driving shaft of rear side two shafts, a start auxiliary device 500 using air springs 505 is furnished, and the ground pressure of a driving shaft 200 is increased in the starting time and the like of the vehicle, so as to increase the traction at the starting time. A control device 800 detects the pressures of a high pressure detecting switch 872 and a low pressure detecting switch 850 according to the ON and OFF of an operation switch 872, and when the air in the air springs 505 is short, a valve 820 is opened for a short time to send the air to the air springs 505. By such a constitution, the consumption of the air can be reduced.
KANO MASAAKI