Patent GB-714019-A (GB)
Title: Improvements relating to change-speed gears composed of gear groups disposed in series
IPC: F16H3/66
Filed: 1952-07-11
Abstract: 714,019. Change-speed gear. DAIMLER-BENZ AKT.-GES. July 11, 1952 [July 11, 1951], No. 17613/52. Class 80 (2) In the vehicle change-speed gear of Specification 707,269 wherein planetary trains P<SP>1</SP>, P<SP>2</SP> are connected in series through a sleeve c between the driven ring gear u of the first and sun v of the second, and also connected between a reaction sun t of the first and carrier x of the second through a sleeve d and separating clutch q<SP>3</SP>, and forward and counter free-wheels, e.g. f, g are provided in addition to normal bidirectional selecting clutches and brakes q<SP>1</SP>, q<SP>3</SP>, p<SP>1</SP>, p<SP>2</SP>, to take forward and overrun torque during shifts, the free-wheels of one train are common to the other whereby two two-speed trains need only two free-wheels. The front train P<SP>1</SP>, provides direct and overdrive, the rear P<SP>2</SP>, reduced and direct, all bi-directional except during a shift. First speed is by clutching at q, the reaction sun t to the input planet-carrier r in the front train, and braking at p<SP>2</SP> the carrier x of the second, whereby the main input shaft a drives solid through the front train, and at reduced speed through the rear to its larger driven sun y and output shaft b, giving overall directlow. For second speed the front train alone is upshifted to overdrive by the brake p', giving overall overdrive-low. For third the front train is downshifted and the rear upshifted by engaging the front clutch q<SP>1</SP> to lock the front train, and the separating clutch q" to lock the rear through the front, giving overall direct-direct; whilst for fourth the front train alone is upshifted to overdrive by applying the brake p', the rear being maintained in direct by changing over from the separating clutch q' to the clutch q<SP>2</SP>, for overall overdrive-direct. During shifts both up and down, the free-wheels f, g, under control of the. separating clutch q' ensure continuance of forward drive in the ratio being superseded and of overrun drive in the ratio to which the shift is being made, thus restricting the relative freedom between input and output shafts to the corresponding gear step. The freewheel g connects a brake p 0 , which is permanently applied in all forward speeds, to the front sun t and shaft d of the separating clutch q<SP>3</SP>, and supports negative reaction; and the free-wheel f connects the same elements t, d, q' to the front carrier r and supports positive reaction. Thus with the normal selecting clutches and brakes q', q<SP>2</SP>, p', p<SP>2</SP>, all released and the separating clutch q<SP>3</SP>, (and brake p 0 ) engaged, the front and rear trains both reacting on the free-wheel g transmit forward overdrive-low (second speed), whilst on overrun both react on the free-wheel f to transmit on forward direct-direct (third speed). Sequential control effects the following forwardoverrun control during shifts. In first-speed. direct-low, the clutch q, and brake p<SP>2</SP>, are engaged and the separating clutch q<SP>3</SP>, is released. For the 1-2 upshift, requiring upshift in the front train alone, the clutch q<SP>1</SP> is first released and the front train, reacting on the free-wheel f still drives in an unchanged forward direct, the rear train being also unchanged. On overrun, the front train, now reacting on the free-wheel g transmits on forward overdrive, giving overall overdrive-direct, i.e. second speed, which is then rendered bi-directional for normal forward second-speed by engaging the brake p, thus completing the shift. The 2-3 upshift requires simultaneous downshift in the front and upshift in the rear trains, sequenced as follows. The separating clutch q' is first engaged, its clutch parts at this time being undter no load and without relative movement. Both brakes p<SP>2</SP> and p<SP>1</SP> are next released in that order, whereupon the free-wheel g reacts to give an unchanged forward second speed (overdrive-low) whilst on overrun both trains react on the free-wheel f giving overall forward direct-direct, which is next rendered bi-directional for normal third speed by engaging the single clutch q<SP>1</SP>. This 3-4 upshift requires upshift in the front train alone. The rear clutch q<SP>2</SP> is first engaged, being under no load and without relative movement, thus locking the rear train independently of the connection to the locked front train through the separating clutch q'. The separating clutch q' and front clutch q', are next released, the rear train remaining in bi-directional direct, whilst the front, reacting on the free-wheel f transmits an unchanged forward direct, and overruns in forward overdrive, reacting on the free-wheel'g, giving overall overdrive-direct, which latter is rendered bi-directional for normal fourth speed by engaging the brake p<SP>1</SP>. Downshift procedure is similar but the overrun steps are now down. The reaction brake p 0  of the free-wheel g is kept engaged for all forward speeds, but is disengaged for reverse to avoid dual-ratio lodk-up, such disengagement being either automatic or volitional, in which latter case the brake may be engaged in reverse to prevent roll-back of a vehicle on an upgrade. In a practical construction, Fig. 6, the clutches and brakes are all actuated by oil pressure supplied by a single output-driven pump through passages some, e.g. n‹, n<SP>1</SP>, of which, for the rotating clutches, pass through a central casing-web. The front clutch q<SP>1</SP> and rear-brake p<SP>2</SP>, used for first speed are engaged by springs i<SP>1</SP>, i<SP>3</SP>, and disengaged by oil pressure so that the starting speed is always available independently of oilpressure, the remaining clutches and brakes being pressure-engaged. The front clutch and brake q<SP>1</SP>, p<SP>1</SP>, actuated by a common piston m<SP>1</SP>, loaded by the spring i<SP>1</SP> which engages the clutch whilst disengaging the brake, are of the progressive multi-disc type. The rear clutches q<SP>2</SP>, q' which are always under no load and without relative movements when to be engaged, each comprise conical rings which may be split and are forced into radial engagement with the respective clutch parts by axially-moved pistons m<SP>2</SP>, m<SP>3</SP>, or they may be cone or dog clutches. The rear brake p<SP>2</SP>, also only engaged under no load and when stationary, is a double opposed cone disengaged by oil-pressure on a piston m<SP>4</SP> in opposition to the engaging spring 2<SP>3</SP>, whilst the brake p 0  is a combined cone and piston. A main clutch and separate reverse gear may be arranged in front of or behind the gear.