GB926767A - Improvements in or relating to drive-transmissions - Google Patents

Abstract

926,767. Motor vehicle driving gear. INTERNATIONAL HARVESTER CO. Nov.27, 1959, No. 40402/59. Class 79 (2) [Also in Group XXIV]. In a series arrangement of a reversing gear and a following countershaft change speed gear 14, between a driving engine shaft 16 and an output shaft 50 having a final drive bevel gear 67, in a tractor, forward speeds are obtained by engagement of a multi-disc friction clutch 13 between a shaft 20, connected to the turbine 18 of an hydrodynamic torque converter having an engine connected impeller 17 and reactors 19 reacting to the casing through one-way roller detents 23, and an input shaft 24 of the change-speed gear, and reverse speeds are obtained by engagement of a multi-disc friction clutch 12 connecting the shafts 20, 24 through a reversing train comprising gears 40, 41 (idler), 43 and 45 on a hollow countershaft 44, and 46, which train preferably provides reverse speeds higher (e.g. 62%) than forward speeds. For push-starting and engine-braking the engine may be driven from the output shaft 50 through the changespeed gear 14, the shaft 24, gears 46, 45, countershaft 44, a one-way roller clutch 72, a shaft 70, a gear 69 and a gear 68 connected to the engine shaft 16 through the impeller 17, the shaft 70, which also extends through a hollow countershaft 63 of the change-speed gear, serving as a power take-off shaft from the engine to an auxiliary drive belt pulley 71. A multi-disc friction brake 73 actuated by a release pedal 82 for the clutches 12, 13 is provided to arrest the countershaft 44 to prevent vehicle creep due to oil drag in the disengaged clutches 12, 13 which are preferably of the wet type. The change-speed gear 14 provides five forward speeds and one reverse and comprises axially sliding gears for first to fourth speeds, a direct drive dog clutch 52, 49, and conventional reversing gears on a further countershaft 65. The clutches 12, 13 are engaged by fluid pressure and disengaged by springs 31, 38 respectively. The fluid control system comprises an engine driven gear pump 92 supplying fluid, via a conventional pressure regulator 96, through a line 98 to a hand or foot operated selector valve 99 and through a line 97 to the torque converter from whence the fluid may be supplied to the vehicle lubrication system through an oil cooler 150 and a lubrication regulator valve 152. The selector valve 99 comprises a piston 103 movable to three positions viz. " R " (reverse) connecting the line 98 to a line 109, " F " (forward) connecting the line 98 to a line 108, and "N " (neutral) blocking the line 98. The selector valve is followed in series by a clutch release valve 87, the piston 86 of which is normally leftwardly moved against a spring to open, and, when the pedal 82 is depressed, is rightwardly moved by the said spring to close, lines 109, 108 to reverse and forward clutch feed lines 147 and 129. The valves 99 and 87 have exhaust ports for pressure and hence clutch release. In the line 147 between the clutch release valve and the reverse clutch 12 there is provided a reverse inhibitor valve 91 arranged to block the feed and exhaust the line 147 thereby preventing reverse clutch engagement when the change-speed gear is conditioned for particular gear ratios, e.g. as shown, direct drive, in which the spring returned piston 90 of the valve 91 is responsible to the position of the gear element comprising the direct drive dog clutch member 52. The clutch release valve piston 86 is leftwardly moved by a return spring 83 of the pedal 82 acting through the pedal 82, a link 84c, a lever 84 and an adjustable screw. In addition to releasing the piston 86 for valve spring urged, rightward, clutch disengaging movement, depression of the pedal 82 applies the brake 73 through a brake pressure limiting spring and a rod 78c having a lost motion connection with a brake actuating fork 78, which connection ensures clutch release a short time before brake 73 application. In operation, with the engine and the torque converter-turbine rotating : for drive, the pedal 82 is first depressed, the selector valve 99 is moved to " F ", and finally the pedal 82 is released for engagement of clutch 13, the appropriate speed in the change-speed gear 14 being selectively engaged before pedal release. To reverse the tractor without change in the gear 14 the selector valve is merely moved to " R " thereby disengaging the clutch 13 and engaging clutch 12. To reverse the tractor and effect a change in the gear 14 the pedal 82 is first depressed, the appropriate speed in the change-speed gear 14 is selectively engaged, the selector valve 99 is moved to " R " and finally the pedal 82 is released for engagement of the clutch 12. The pedal 82 may be used as an emergency release when interruption of fluid pressure more rapid than with selector valve actuation is necessary.