Planetary gear transmission systems or components – Nonplanetary variable speed or direction transmission... – Nonplanetary transmission is belt or chain gearing
Patent
1995-09-14
1997-07-01
Marmor, Charles A.
Planetary gear transmission systems or components
Nonplanetary variable speed or direction transmission...
Nonplanetary transmission is belt or chain gearing
74665P, F16H 3702
Patent
active
056431317
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a continuously variable transmission having a driving and a driven shaft, first and second intermediate shafts, first and second driving means for connecting the driving shaft with the first or second intermediate shaft. Third and fourth driving means are complementarily provided which connect the first or second intermediate shaft with the driven shaft. The power of the transmission flows through a variometer which interconnects the first and second intermediate shafts.
BACKGROUND OF THE INVENTION
A continuously variable transmission, of the above explained construction, has also been disclosed under the designation CVT with i.sup.2 arrangement (Multi-pass Continuously Variable Transmission). With it the ratio range (that is, the range of adjustment as a proportion of the maximum to minimum ratio) of a mechanical variometer can be raised to the second power.
In EP-A-O 210 053 a CVT with i.sup.2 arrangement has been disclosed. The peculiarity of said arrangement is to be seen in that the variometer is asymmetrically designed so that the maximum step-down ratio can be equal to or smaller than the maximum reduction ratio.
In comparison with a stepped selector transmission, continuous transmissions in general suffer the disadvantage of a poorer transmission efficiency.
SUMMARY OF THE INVENTION
The problem on which this invention is based is to provide a continuous transmission of the above mentioned kind which stands out by a wide ratio range of the whole transmission together with a good efficiency of the whole transmission and a high load capacity.
The problem on which the invention is based is solved by the fact that the input power of the transmission is transmitted to the driven shaft through a transmission branch with constant ratio and through the continuous transmission branch.
By means of the proposed power distribution, the input power of the transmission is distributed in several branches. The power flows via at least one transmission branch with constant ratio and via a continuous transmission branch with a variable ratio. It is of particular advantage that the variometer works according to the i.sup.2 concept. Due to the power distribution, the proportion of power transmitted via the continuous transmission branch is reduced. Thereby it is possible to improve the transmission efficiency of the whole transmission. This is based on the fact that the efficiency of the variometer enters only proportionately in the efficiency of the whole transmission. It is to be borne in mind here that the power distribution leads to a clear reduction of the power proportion of the variator and thus to the improvement of the efficiency of the whole transmission that is sought only when a wide ratio range is available, that is, the continuous transmission branch is designed with an i.sup.2 arrangement. The wide adjustment range makes an additional torque converter unnecessary; this is an additional advantage that makes itself felt especially in a favorable fuel consumption with good mileage, especially good acceleration values. Besides, the noise level is considerably improved. Because of the low starting torque of the variometer, it is possible to use a variometer of relatively small design from which results, at low cost, a smaller installation space together with favorable efficiency. The transmission proposed according to the invention can be preferably used in private cars and light commercial vehicles.
A continuously variable transmission, where a power distribution can be obtained by simple means, is advantageously characterized by the fact that the driving shaft drives a transfer differential which has two output shafts of which one is connected with the driven shaft. In this manner, at least one transmission branch is provided with a constant ratio. It is obviously possible to provide several output shafts so that the practical embodiment of several constant transmission branches is possible.
This is of special advantage when the transfer differential is formed by a planetary tra
REFERENCES:
patent: 4885955 (1989-12-01), Kraus
patent: 5121936 (1992-06-01), Cowan
Herter Hartmut
Kuhn Walter
Estremsky Sherry Lynn
Marmor Charles A.
ZF Friedrichshafen AG
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