GB1326537A - Vehicle transmissions - Google Patents

Abstract

1326537 Four wheel drives HARRY FERGUSON RESEARCH Ltd 21 Oct 1970 [22 Oct 1969] 51665/69 Heading B7H In a vehicle transmission one member 18 of a drive transfer 17 is connected to its associated final drive 10 by way of an overrunning clutch 19 whereof the member 18 is overrun by its drive input 14 when the road wheels rotate at the same peripheral speed. Drive will be transmitted to the front wheels 12 either if the rear wheels 13 tend to spin or if the front wheels 12 tend to lock only when the vehicle travels in a given direction. The system is made reversible by a four-wheel drive transmission incorporating a controlled interaxle or centre differential gear 22, Fig. 2. Clockwise rotation of the shafts 15A, 15B, and 14 correspond to forward drive. Clutch 27 permits only clockwise overun of the sun gear 25 and clutch 19 permits only anticlockwise overrun of the shaft 14. Releasable coulping means 2i establishes a direct coupling between sprocket 18 and shaft 14 only during clockwise rotation, i.e. foreward drive. Thus controlled four-wheel-drive is obtained both in forward and reverse drive. The coupling means 28, Fig. 10, is constituted by a hexagonal opening 33 formed in the sprocket 18 into which extends pins 34 through mating radial holes in the shaft 14. Movement of the plunger 36 to the left against the spring 37 allows pins 34 to adopt a retracted position from their normally retained radially extended position, and allows the sprocket 18 to rotate freely with respect to the shaft 14. Springs (not shown) preferably bias the pins 34 towards their retracted position. Anticlockwise rotation of shaft 14 is transmitted to plate 41 through flange 38 and friction plates 39, 40 and plates 41, 42 are thrust apart by means of opposed ramped grooves (44), Fig. 13 (not shown) containing actuating balls 45. Brake 43 permits only clockwise rotation of plate 42 and plate 41 is axially shiftable. Thus plunger 36 is thrust leftwards. Limit pins (46) engaging slots (not shown) in plate 41 serve to limit anticlockwise rotation of the latter to prevent disarrangement of the balls 45. The plunger 36 may alternatively be actuate by a screw thread, a face cam, or by hydraulic pressure fluid being operated simultaneously with reverse gear. The interleaved friction plates 39, 40 may be replaced by a cone clutch or a single face plate clutch.