| 摘要 |
PURPOSE:To solve problems on any drawback to be produced in a driving system due to a speed differential between both front and rear wheels and troublesomeness in driving operation, by installing an auxiliary oil passage, having an oil flow control device, in position between oil passages at both discharge port and suction port sides of a hydraulic pump. CONSTITUTION:A driving-coupling device 13 for four-wheel driving consists of a vane pump 20 and a hydraulic control circuit 21, while the pump 20 discharges an oil quantity in proportion to its revolutions. Auxiliary oil passages 39 and 40 having orifices 37 and 38 serving as an oil flow control device are installed in position between suction and discharge ports 22, 25 and 23, 24 of the pump 20, making them achieve an adjusting function for hydraulic control over a relief valve 33. When a speed differential between a first axle for front wheels and a second axle for rear wheels is too much, discharge pressure in the pump 2-goes high and thereby comes more than oil flow resistance in the orifice, oil flows in these auxiliary oil passages 39 and 40 even though it does not reach to the setting control pressure of the valve 33 so that torque is transmitted to the second axle, thus a hydraulic control function in the valve 33 is adjusted. |
