Patent ID: 7389847

Claim:
A hydraulic four-wheel driving articulated vehicle comprising: a first frame, on which first wheels and a first hydraulic motor driving the first wheels are mounted; a second frame, on which second wheels and a second hydraulic motor driving the second wheels are mounted, wherein the first and second frames are connected to each other so as to be relatively rotatable centering on a vertical axis by a steering operation; a hydraulic pump; a hydraulic circuit fluidly connecting the first and second hydraulic motors in series to the hydraulic pump, the hydraulic circuit including a first passage interposed between the hydraulic pump and the first hydraulic motor, a second passage interposed between the hydraulic pump and the second hydraulic motor, and a third passage interposed between the first and second hydraulic motors, wherein, when the vehicle is stationary and the first and second frames are relatively rotated by the steering operation, the first wheels rotate according to the rotation of the first frame relative to the second frame so as to cause a first flow of oil from the first passage to the third passage through the first hydraulic motor, and the second wheels rotate according to the rotation of the second frame relative to the first frame so as to cause a second flow of oil from the second passage to the third passage through the second hydraulic motor opposite to the first flow of oil, thereby excessively accumulating oil in the third passage because of the opposite first and second flows of oil; and pressure control means connected to the third passage so as to automatically release the excessively accumulated oil from the third passage when the vehicle is stationary and the first and second frames are relatively rotated by the steering operation so as to excessively accumulate oil in the third passage.