Patent ID: 6199653
Filing Date: 2001-03-13
Classification: B60K

Abstract:
A four-wheel driven vehicle comprising front wheels, rear wheels, a rear-wheel driving system and a front-wheel driving system branching from an intermediate of said rear-wheel driving system, said front-wheel driving system including:a first transmission for driving said front wheels at a peripheral speed substantially identical with that of said rear wheels;a clutch casing supported onto a front wheel driving output shaft;a first friction clutch disposed in said clutch casing, said first friction clutch being hydraulically operable to engage for connecting said first transmission with said rear-wheel driving system and to disengage for separating said first transmission from said rear-wheel driving system;a first piston housed in said clutch casing for switching said first friction clutch, said first piston partitioning an interior space of said clutch casing into a first chamber and a second chamber along said front-wheel driving output shaft;a biasing member disposed in said first chamber for biasing said first friction clutch toward engagement with a friction plate disposed in said second chamber; anda directional control valve changeable between a first position for supplying fluid into said first chamber and a second position for supplying fluid into said second chamber, wherein when said directional control valve is put into said first position, said first piston is acted to make said first friction clutch engage by the hydraulic pressure through said first chamber in addition to the biasing force of said biasing member, and when said directional control valve is put into said second position, said first piston is acted to make said first friction clutch disengage against the biasing force of said biasing member by the hydraulic pressure through said second chamber.