Patent GB-785963-A (GB)
Abstract: 785,963. Change-speed gear. DAIMLERBENZ AKT.-GES. Jan. 27, 1956 [Jan. 27, 1955], No. 2732/56. Class 80 (2). [Also in Group XXXIV] In a change-speed gear on a vehicle, wherein a hydrodynamic torque-converter 12 or coupling drives a multi-ratio planet gear in first and reverse starting ratios only, and is mechanically by-passed by a bridging clutch K1 in all other ratios, hydrodynamic braking of the vehicle by the converter in said other ratios is provided in varying degrees according to the ratio selected, by a bandbrake B1 for holding the converter turbine 18, which latter is connected to the gear through a one-way clutch 21 which overruns when the bridging clutch K1 is engaged. The hydrodynamic braking is additive to and considerably greater than the usual engine braking, which latter may, if desired, be eliminated by opening an additional clutch (not shown), which may be provided between the by-pass clutch K1 and the engine shaft 10. The converter brake B 1 may be operated by the gear selector control or by a separate control. The gear control provides two manually selected ranges, " Hill and " Normal," the former giving five ratios and reverse, the latter differing only by omission of the lowest ratio. Individual ratios in the ranges may be selected automatically as in Specification 740,985. All ratios are in geometrical progression. The gear comprises a stepped planet train U1, giving direct drive, two reduced ratios and reverse, in series with a simple directreduced train U2. " Hill " ratios are as follows. First, by brakes B3, B4, holding respectively a ring-gear 30 of the front train U1 and sun 36 of the rear U2. Drive passes through the torqueconverter and one-way clutch 21 to a small sun 26 of the front train and from the planet carrier 27 of the latter, through an intermediate shaft 31 to a ring 32 of the rear train, and issues to output 35 by the planet-carrier 34 of the rear train. Both trains reduce, the front at its lowest ratio. In all four subsequent ratios, the by-pass clutch K1 is engaged to provide mechanical drive to a large sun 24 of the front train. In second, with the brakes B3 and B4 still applied as for first, the front train now upshifts to a higher, but still reduced, ratio, and the rear is unaltered. In third, clutch K1 and brake B3 remain applied, leaving the front train unchanged, and a clutch K4 is engaged to connect the sun and ring of the rear train for solid drive. In fourth, clutch K1 and brake BK are applied, together with a clutch K2, connecting the planet-carrier 27 and small sun 26 of the front train for upshift to solid drive therein, whilst the rear train downshifts to reduced drive. In fifth, clutches K1, K2, K3 are engaged for direct solid drive in both trains. In " Normal " range, the first ratio of " Hill " range is omitted and its second mechanical ratio now becomes a first hydraulic ratio, by engaging only the brake B3 for lowest ratio of the front train, and clutch K4 for solid drive in the rear. Hydraulic reverse in both ranges is the same, by engaging a clutch K3 and a brake B2. The latter holds the front planet carrier 27, to reverse the output ring 30 of the front train, which then drives, through the clutch K3, shaft 38 and drum 37, the sun 36 of the rear train, which drives in reduced ratio, since its ring 22 is held with the connected front planet carrier 27 by the brake B2.