Machine element or mechanism – Gearing – Plural power paths to and/or from gearing
Patent
1986-02-28
1988-05-17
Braun, Leslie A.
Machine element or mechanism
Gearing
Plural power paths to and/or from gearing
74740, 74761, 74763, 74767, F16H 5710
Patent
active
047442670
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a transmission system, especially for automobile vehicles, comprising an input gearbox and a main gearbox disposed between an input shaft and an output shaft and interconnected by an intermediate shaft, the input gearbox having a free neutral setting in which the intermediate shaft is decoupled from the input shaft and freely rotatable and a sequence of forward gear ratios in which the intermediate shaft is coupled to the input shaft with a variable forward gear ratio, input gearbox control means by means of which the input gearbox is selectively placed in its free neutral setting or in a forward gear with a ratio selected from said sequence of ratios, the main gearbox comprising a double planet gear with four elements including a first element coupled to the intermediate shaft, a second element, a clutch by which the second element is selectively coupled to the input shaft or disengaged, a third element coupled to the output shaft, a fourth element, and a brake by which the fourth element is selectively immobilized or released, said main gearbox having three forward running ranges respectively referred to as slow, intermediate and fast, such that: in the slow range the second element is released and the fourth element is immobilized, in the intermediate range the second element is coupled to the input shaft and the fourth element is immobilized, and in the fast range the second element is coupled to the input shaft and the fourth element is released, so that the transmission system has three forward running operating modes: a slow mode in which the input gearbox is in a forward gear and the main gearbox in the slow range, an intermediate mode in which the input gearbox is in its free neutral setting and the main gearbox is in the intermediate range, and a fast mode in which the input gearbox is in a forward gear and the main gearbox is in the fast range, a change of gear ratio within the sequence of forward gear ratios of the input gearbox varying the transmission system slow mode ratio in the same sense and the transmission system fast mode ratio in the opposite sense.
A transmission system of this type is described in U.S. Pat. No. 3,505,905 (LEPELLETIER) and is of considerable benefit for all sorts of automobile vehicle and more particularly for heavy goods vehicles, to the remarkable extent that it makes it possible to achieve at the same time: a distribution of the gear ratios with a good progression procuring both excellent conditions of insertion into traffic and economical fuel consumption by virtue of close together higher gear ratios; and simple control conditions to the extent that, in order to change from any ratio to an adjacent ratio, or even to skip a ratio, it is only necessary to operate at most two of the transmission control devices, such as clutches or brakes, and this with a range of values of torque and speed in forward running which is remarkably extended, frequently between 10 and 13, for example.
In U.S. Pat. No. 3,505,905 (LEPELLETIER) there is provision for giving the transmission system a multiple ratio reverse running condition by providing the main gearbox with a special control device adapted to provide it with a reverse running range.
There is no doubt that an arrangement of this kind has the advantage of giving the transmssion system a multiple ratio reverse running range in the form of a sequence of ratios exactly proportional to the corresponding ratios in forward running.
However, experience has shown that a multiplicity of ratios of this kind given in reverse running generally has advantages only in certain special applications, and that in everyday applications the ratios thus obtained are generally too high by 20 to 40%. It is then necessary to commensurately shorten the final drive ratio to maintain the maximum hill-climbing capacity or tractive power of the vehicle in reverse running.
One is then obliged to use only part of the remarkably extended range of torque and speed values achieved in forward running, whereas it is essential
REFERENCES:
patent: 3313183 (1967-04-01), Bailey et al.
patent: 3410157 (1968-11-01), Livezey
patent: 3812739 (1974-05-01), Mori et al.
patent: 3853023 (1974-12-01), Mori et al.
patent: 3971267 (1976-07-01), Murakami et al.
patent: 4223571 (1980-09-01), Quemerais et al.
Braun Leslie A.
Brown Charles A.
Brown Charles E.
Diehl Dwight G.
Valeo
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