| 摘要 |
PURPOSE:To make improvements in acceleration and braking performance ever so better, by closing an oil passage and making it come into a directly coupled four-wheel driving state at a time when a variation in discharge pressure out of a differential hydraulic pump to be driven by a revolving speed difference between a front-wheel side axle and a rear-wheel side axle. CONSTITUTION:This driving-coupling device 13 for four-wheel drive is provided with a vane pump 20 or a differential hydraulic pump producing hydraulic pressure when a relative revolving speed difference (differential rotation) occurs between a rotor 20a and a cam ring 20b, namely, both first and second axles 11 and 14. Suction and discharge ports 22a-24a and 22b-24b are interconnected with one another through oil passages 26 and 27 which are interconnected to an oil sum 30. In addition, an orifice control valve 46 and an orifice 45 are installed side by side in an oil passage 44 connecting an oil passage 41 interconnecting an interval between a vane energizing oil passage 39 and the oil passage 27 to the oil sump 30, whereby pressure inside an oil chamber 50 acting on a valve body 46a of the valve 46 is constituted so as to be adjustable by a pump discharge pressure responding member 47.
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