GB714715A - Improvements in or relating to power transmissions embodying hydraulic torque converters - Google Patents

Abstract

714,715. Clutches; variable-speed and reversing gearing. AKTIEBOLAGET LJUNGSTROMS ANGTURBIN. Dec 18, 1951, No. 29570/51. Class 80 (2) In a motor vehicle with parallel drives from an input shaft 860 through (a) a friction clutch 856 and (b) a friction clutch 828 and a hydraulic torque converter 832 in series, the two clutches are so automatically controlled that when either is engaged the.other is disengaged, and means are provided whereby the driver can cause both clutches to be engaged together so as to allow combined engine and hydraulic braking. The impeller 810 of the converter, which is of stationary-casing type with fixed guide blades 838, is connected to clutch 828 through sleeve 814 and the turbine wheel 830 is rigid with sleeve 840 and gear 842, carrying a one-way clutch 936. Clutch 856 is connected through shaft 850 to gear 878. A reversing gear, controlled by a lever 938, precedes the output shaft 868. The clutches 856, 828 are engaged through pistons 880, 882 by pressure fluid supplied from the converter through passages 894 in the clutch casing 864 secured to shaft 860 under the control of piston valves 898 actuated through an arm 900 by the rod 902 of a fluid servomotor 904, the converter being supplied by a pump 916 geared to the clutch casing 864. Automatic control is effected by a valve 932, including a spindle and two superposed sleeves, responsive both to the speed of shaft 868 and to the speed ratio between the shafts 860, 868. In addition, a valve 912 is operated by the brake pedal 914 and a valve 908, normally spring-held in mid-position, is operated by the accelerator 970 in the two extreme positions of the latter. The valve 908 is also operated during movement of the lever 938 until the gear, forward or reverse, is properly engaged. The arrangement is such that, below a first predetermined speed of shaft 868, both clutches are disengaged, giving neutral. Between that first predetermined speed and a second predetermined speed, the converter clutch 828 is engaged. Between that second speed and a third speed, the clutch 828 is disengaged and the direct clutch 856 is engaged when the speed ratio exceeds a minimum value. Above that third speed, clutch 856 is engaged and clutch 828 disengaged irrespective of the speed ratio. Above the second speed, clutch 856 may be engaged and clutch 828 disengaged, irrespective of speed ratio, by releasing the accelerator 970,' while by fully depressing the latter clutch 828 may be engaged and clutch 856 disengaged irrespective of speed ratio. If the accelerator 'is released and the brake pedal 914 depressed, above the second speed, both clutches are engaged. During movement of lever 938, both clutches are disengaged until the gear change is completed. Spring- loaded pistons 928 cause the direct clutch 856 to be engaged when the engine is stationary, these pistons being pressed back, however, by the pressure in the passages 894 when the pump 916 is operating. A fluid-operated valve may actuate a switch to close the throttle or interrupt the ignition during a change from converter to direct drive. Specification 697,088 is referred to.