GB964798A - Improvements in and relating to drive transmissions - Google Patents

Abstract

964,798. Friction clutches; hydrodynamic transmissions; clutch combinations; clutch control; hydro-mechanical change speed gear; change-speed control. FRANCAISE DU FERODO S.A. Feb. 24, 1961 [Feb. 25, 1960; June 15, 1960], No. 6929/61. Headings F2C, F2D and F2L. An hydraulically disengaged, spring engaged, multi-disc friction clutch E, series-arranged between a fluid coupling or, as shown, an hydrodynamic torque converter C and an input shaft 11 of a motor vehicle change speed gear, comprises an hydraulic servo cylinder 21 secured to the converter turbine T, and a presser piston 22 constrained to rotate with the cylinder 21 by a Belleville spring washer 23 which constantly urges the piston 22 rightwards to grip friction discs 24, 25 respectively splined to the piston 22 and a hub 26 splined on the shaft 11. The torque converter comprises an impeller P connected to a driving shaft 10 through a housing 13 and a flexible diaphragm 12, a reactor R reacting on a fixed sleeve 16 through a oneway detent 19, and the turbine T which also is one-way detained with respect to the sleeve 16 to prevent backward movement of the vehicle when parked on a slope. In Fig. 2, oil from the engine lubrication circuit is circulated from a sump 66 by a pump 65 through a spring-loaded electromagnetic distributer valve 49a, lines 40a, 40, the torque converter through an inlet 68 and an outlet 69, around the cylinder 21 leftwards of the presser piston 22 to augment clutch engaging pressure, through radial ports 54 in the hub 26, a bore 55 in the shaft 11 and a calibrated spring-loaded one-way valve 73 adjusted to prevent converter cavitation, and back to the sump 66. When the usual gear lever L is moved during shift a switch 75 is closed to rightwardly move the valve 49a to direct oil through lines 34, 50, 51 to the cylinder space 28 rightwards of the presser piston 22 to disengage the clutch E against the Belleville washer 23. When the gear lever is released the valve 49a is returned to recirculate oil to the converter and drain the cylinder space 28 through the line 50 and a line 77 in the valve 49a. The linings of the discs 25 have radial grooves 25a so that during upshift when the discs 25 rotate slower than the turbine T the oil mass in the cylinder space 28 is braked to relatively increase the centrifugal force of the oil leftwards of the presser piston 22 and thereby shorten the period of clutch reengagement. During downshift when the discs 25 rotate faster than the turbine T, the centrifugal force in the cylinder space 28 is increased and the clutch re-engagement period is prolonged. The continuous engaging force of the Belleville washer 23 enables engine-starting by movement of the vehicle. The bearings of the concentric shafts are provided with drain pipes 79, 79a, to the sump, upstream of the seals 78, 78a. In Fig. 3 (not shown) oil return from the converter is through a non-return valve into the cylinder space 28, the radial grooves 25a in the discs 25, and the lines 55, 77. This non- return valve is preferably calibrated to prevent converter cavitation. During gear change, the space 28 is pressurized through a further non- return valve, the electromagnetic valve, and the line 55, the cylinder non-return valve closing. In Fig. 4, a further single disc friction clutch 89, hydraulically engaged, spring disengaged, is provided between the driving housing and a hollow shaft 90 coaxial with the shaft 11. The shafts 11, 90 carry gears 93, 94 respectively constantly meshing gears 95, 96 on a shaft 97. By suitable overlapping control of the two clutches, break in transmission during shift can be avoided. Engine braking may be obtained through both shafts 11, 90. A freewheel clutch may be interposed in one of the two gear trains, e.g. between the gear 95 and the shaft 97, in which case only the shaft 90 is available for engine braking and clutch E need not be disengaged. Alternatively, the shafts 11, 90 may drive two input shafts of an epicyclic train which, with the two clutches engaged, could be locked-up for split-torque direct drive.