Patent GB-707269-A (GB)
Title: Improvements relating to change-speed gear comprising gear groups disposed in series
IPC: F16H3/66
Filed: 1952-02-12
Abstract: 707,269. Change-speed gear. DAIMLER-BENZ AKT.-GES. Feb. 12. 1952 [Feb. 12, 1951], No. 3715/52. Class 80 (2) A change-speed gear for a motor-vehicle comprises two series-arranged planetary units in each of which forward and counter freewheels, e.g. f<SP>1</SP> f<SP>3</SP>, are provided in addition to the normally operative bi-directional friction clutches q', q<SP>2</SP> and brakes p<SP>1</SP>, p<SP>2</SP> for selecting direct and geared drives, whereby the free relative movement between the input and output shafts of either one train, whilst both its clutch and brake are temporarily disengaged during a shift, is limited to the gap between its direct and geared ratios and there is thus no interruption of power on either forward drive or overrun, all as described for a single train in Specification 706,208; and in addition the two gear units are themselves connected by forward and counter free-wheels f<SP>2</SP>, f<SP>4</SP>, whereby during shifts involving simultaneous changes in both gear-units other speeds (lower on forward drive, higher on overrun) become temporarily effective so that all shifts occur without interruption of drive. The first unit comprises single planets carried by the input shaft a, an output ring u and reaction sun t, which last-named is held by a friction disc brake p<SP>1</SP> for bi-directional overdrive, or cone-clutched at q<SP>1</SP> to the output ring u for direct solid drive. Between the input shaft a and an intermediate shaft c which connects the output ring u to the following unit is a permanently effective forward-drive one-way roller clutch f<SP>3</SP>. The reaction sun t is also connected to the fixed casing by a reversely binding freewheel f<SP>1</SP> and cone' brake p" (which last named is disengaged only for reverse and neutral) so.that with both the selector clutch and brake q<SP>1</SP>, p' disengaged during a shift in the front unit the input shaft a will, on forward drive, drive the intermediate shaft c directly through the free-wheel f<SP>3</SP>, and will itself, on overrun. be driven by the shaft c at a reduced speed, i.e. forward overdrive. The second train comprises input and output suns v, y secured respectively to the intermediate shaft c and final output shaft b, and meshing stepped planets on a reaction carrier x, which is frictionally braked at p<SP>2</SP> for reduced drive and clutched at q<SP>2</SP> to the output shaft for direct-drive. The planet-carrier x is also connected to the intermediate shaft c through a friction clutch q<SP>6</SP>, engaged together with the brake p<SP>0</SP> in forward speeds only, and a reversely acting one-way clutch f<SP>4</SP>, and is additionally connected back through a friction clutch q<SP>3</SP>, an outer sleeve d and a forwardly driving one-way clutch f<SP>2</SP>, to the reaction t of the front unit. The action of the various clutches and brakes, starting from rest, is as follows. First speed is with clutch q<SP>1</SP> and brake p<SP>2</SP> engaged, giving direct in the front unit P, and reduced in the rear P<SP>2</SP> or overall direct-low. As soon as the vehicle moves forward the clutches p‹, q‹ are automatically engaged by hydraulic pressure provided by an output-driven pump, and remain engaged for all forward speeds, For - second speed, overall overdrive-low, the front unit alone is upshifted by changing from clutch q' to brake p', during which shift interval the free wheels f<SP>3</SP>, f<SP>1</SP> respectively maintain forward drive torque in direct or overrun in overdrive as above described. In preparation for the upshift to third speed, the clutch q<SP>3</SP> is also engaged simultaneously with the brake p<SP>1</SP> for second, both its coupled elements d, x being relatively at rest at that time, this clutch q<SP>3</SP> then remaining engaged for both the higher speeds. For upshift to third, overall direct-direct, both units have to be changed, the brakes p<SP>1</SP>, p<SP>2</SP> being released and clutches q', q<SP>2</SP> engaged, during which drive is maintained as follows. Disengagement of the brake p<SP>2</SP> is arranged to take precedence, the front unit meanwhile remaining on bi-directional overdrive. In the rear unit, forward drive causes backward reaction on the planet-carrier x, which is prevented by the one-way clutch f<SP>2</SP> and brake p', whereby the rear unit continues to drive in low, giving a forward overall overdrive-low as still in second speed. At this time, an overrun forward movement of the planetcarrier x relatively to the intermediate shaft c is prevented by the one-way clutch f<SP>4</SP>, so that the output shaft b drives the intermediate shaft c in direct drive, giving an overall equivalent forward ratio of overdrive. direct, which is the next higher speed (fourth). The front brake p<SP>1</SP> is next released and the front clutch q<SP>1</SP>engaged, downshifting the front unit to direct drive, followed by engagement of the rear . clutch q, upshifting the rear unit to direct drive, giving overall direct-direct. third speed. The 3-4  upshift to fourth speed, overall overdrive-direct, is by changing the front unit alone and hence is the same as the 1-2 upshift. Downshifts are similar, the sequence being the reversed. A forward-reverse gear may be arranged before or behind the gear. The clutches and brakes may be operated mechanically, hydraulically, pneumatically or electrically, but as shown are hydraulic. The clutch q, has double opposed cones engaged by a spring i<SP>1</SP> and disengaged by fluid-pressure acting at k<SP>2</SP> whilst the simiLar, but oppositely coned clutch q<SP>2</SP> is disengaged by a spring i<SP>2</SP> and engaged by a fluid-pressure at k<SP>3</SP>. Springs i<SP>3</SP> engage the disc brake p<SP>2</SP> and fluidpressure at k<SP>4</SP> disengages it. No springs are provided for the disc brake p<SP>1</SP> and the single cone clutches p<SP>0</SP>, q<SP>0</SP>, q<SP>3</SP>, since these are not engaged whilst there is, relative movement between their parts.