| 摘要 |
PURPOSE:To eliminate nonconformities in the tight corner braking phenomenon of a part-time four wheel drive vehicle and troublesome manipulation of the latter, by providing a hydraulic control circuit including a hydraulic pressure control means between the discharge port and suction port of a hydraulic port. CONSTITUTION:A four wheel drive coupling device 13 is composed of a vane pump 20 and a hydraulic control circuit 21, and a rotor 20a and a cam ring 20b are integrally rotated through the intermediary of oil under the static pressure of the oil when the discharge port of the pump 20 is blocked. Further, oil passages 26, 27 are communicated with a discharge oil passage 41 through two changeover check valves 31, 32 serving as changeover means, and a relief valve 33 serving as an oil control means is disposed in the discharge oil passage 41. In this device 13 the discharge pressure is controlled to be prevented from exceeding a predetermined value by means of a relief valve 33 and therefore, changeover between the four wheel drive and the two wheel drive is automatically made, and the four wheel drive condition having a drive force in accordance with the differential speed between the front and rear wheels may be obtained. |
