| 摘要 |
PURPOSE:To prevent a braking phenomenon in time of a turning drive from occurring, by coupling an axle transmitting driving force to front wheels and another axle transmitting driving force to rear wheels both with a hydraulic pump which is driven by a rotation differential between these axles and discharges an oil quantity commensurate to this rotation differential. CONSTITUTION:In time of a normal straight drive, there is produced no rotation differential between a first axle 11 and a second axle 14 of a coupling device 13 for four-wheel drive use, therefore no hydraulic pressure is produced at a vane pump 20. When speed of rotation largely differs between front and rear wheels 9 and 16 due to various road conditions, a rotation differential is produced between the first axle 11 and the second axle 14 whereby large hydraulic pressure is produced at the vane pump 20. When it exceeds the specified pressure, a relief valve opens and discharge pressure is controlled to make it almost constant. With this hydraulic pressure, it comes into a four-wheel driving state, while brake torque in wheels at the side, where they are rather being locked, is made to grow large, preventing these wheels from locking, thus the rotation differential is made so as to be reduced. |
