Machine element or mechanism – Rotary member or shaft indexing – e.g. – tool or work turret – Preselected indexed position
Patent
1991-12-19
1992-11-03
Wright, Dirk
Machine element or mechanism
Rotary member or shaft indexing, e.g., tool or work turret
Preselected indexed position
74844, 475 78, F16H 5974
Patent
active
051598558
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a continuously variable driving unit of a motor vehicle according to the features of the preamble of claim 1.
German Patent 29 18 448 has disclosed a continuously variable power split transmission consisting of two parts. One contains a continuously variable hydrostatic and a mechanical transmission branch which are permanently connected with a coupling transmission having several shafts. The other transmission part is a selector transmission which acts upon the main output shaft. The coupling shafts alternatively drive the selector transmission. The changes of gear take place at synchronous speeds free of load and without interruption in the tractive force. The transmission acts like a continuous transmission with a large range of adjustment and allows a vehicle to operate the internal combustion engine along a curve for minimum fuel consumption, thus making possible the saving of fuel.
At the starting point, the hydrostatic branch of the transmission is adjusted to the maximum displacement and a clutch connects the coupling shaft for the first forward or reverse driving range with the main output shaft at a zero synchronous speed resulting from the sum of the opposite speeds of the output shafts of the hydrostatic branch and of the shaft of the mechanical branch of the transmission. At zero speed of the coupling shafts of the first forward and of the reverse drive range, the coupling shaft of the second forward drive range reaches a maximum speed. If the displacement is throttled, the speed of the output shaft of the hydrostatic branch and the speed of the coupling shaft of the second drive range decrease and reach synchronous speed with the increasing speed of the coupling shaft of the first drive range at maximum volume and reversed direction of displacement.
Since no starting clutch is provided, the internal combustion engine and the hydrostatic-mechanical transmission part must be jointly driven by a starter for the initial operation of the driving unit. The power needed for driving the transmission part and the internal combustion engine determines the dimensions of the starter and the electrical network of the motor vehicle.
In order to keep the total resistance of the driving unit low, the resistance of both the internal combustion engine and the transmission must be kept as low as possible.
Hydrostatic-mechanical power split transmissions have a high idle power in the presence of a large displacement in the hydrostatic branch. The displacement is determined by the angle of the swash plate of the primary unit. Therefore, the power needed for driving is dependent, among other things, on the angle of the swash plate of the primary unit.
Resistance additionally results from the drag effect in the disengaged clutches between the rotating coupling shafts and the drive shaft. Since independently of the displacement in the hydrostatic transmission branch, the sum of the speeds of all coupling shafts is more than zero, a drag resistance due to friction and viscosity stands opposed to the elements of the selector clutch such as discs. At low temperatures, the drag resistance increases since the lubricating capacity of the transmission oil is low at an elevated viscosity.
Due to the drag effect the drive shaft of the transmission can be driven and the vehicle set in motion, without control, even with quite disengaged clutches.
For reasons in the technique of measurement and adjustment, a precise permanent preservation of a speed of the coupling shafts is not ensured. Therefore, when the clutch is engaged between main output shaft and a coupling shaft which should be set to zero speed, the motor vehicle does not remain stationary with certainty but can move unintentionally.
The problem on which the invention is based consists in providing a continuous power split transmission which has a small resistance when the driving unit is first started and wherein in addition an unintended motion of the motor vehicle, when parked with a running engine or during a warm-up period, is ruled out.
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REFERENCES:
patent: 4561328 (1985-12-01), Hiramatsu
patent: 4754664 (1988-07-01), Dick
patent: 4840092 (1989-06-01), Sakaguchi et al.
patent: 4983149 (1991-01-01), Kita
patent: 5011463 (1991-04-01), Jarchow et al.
patent: 5052987 (1991-10-01), Hagin et al.
patent: 5080637 (1992-01-01), Tenberge et al.
Nikolaus Heinrich
Paton Robert
Wright Dirk
Zahnradfabrik Friedrichshafen AG
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