| 摘要 |
A system for a four-wheel drive vehicle for automatically changing a power transmission of the engine of the vehicle from two-wheel drive system to four-wheel drive system in accordance with road surface condition and driving condition. The transmission system is provided for transmitting a power from the engine to two main driving wheels, and a clutch is provided for transmitting the power of the engine to drive two other wheels. Speed sensors are provided for producing output signals dependent on speeds of the four wheels, respectively. A steering-angle sensor is provided for producing an output signal dependent on the steering-angle. Computation circuits are provided to compute an actual slip rate from the output signals of the speed sensors and to compute a theoretical slip rate from the output of the steering-angle sensor. A comparing circuit compares the actual slip rate and the theoretical slip rate with each other and produces an output signal for a set time when the difference between both slip rates exceeds a predetermined level. The output signal operates the clutch for the engagement thereof for establishing the four-wheel drive system. |
