To connect a shifting hydraulic clutch with a required boosting property while having an inexpensive structure without a special boosting system, by using a hydraulically actuating negative brake.
A combine is provided with a main shifting system having three stages for forward moving and one stage for backward moving on a crawler transmission system by selectively engaging hydraulic clutches interposed to each gear system having a different transmission, and an accumulator 51 which releases braking of a brake 91 to the crawler when pressure is in existence and actuates the brake 91 to brake when the pressure is not in existence. In order to gradually release the braking of the brake 91, the hydraulic clutches are connected in series so as to supply pressure oil into the hydraulic clutched through the accumulator 51 equipped with an orifice 86. However, the orifice 86 is structured in order not to act on clutch meet.
NAKADA MASAYOSHI
HIDA SADANORI
YASUDA KAZUO
