Machine element or mechanism – Elements – Gear casings
Patent
1987-07-16
1990-01-23
Diehl, Dwight G.
Machine element or mechanism
Elements
Gear casings
F16H 4704
Patent
active
048950505
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an infinitely variable hydromechanical transmission with multiple power-transmission paths for motor vehicles and having at least two gear-shift ranges in which the infinitely variable control of the transmission is affected by a hydrostatic transmission.
A transmission with multiple power-transmission paths for motor vehicles is taught by German Pat. No. 28 54 375. However, this transmission is limited to a relatively low power range or requires fairly large hydrostatic units.
The object of this invention is to create a transmission system which manages with smaller hydrostatic units, whose power-to-weight ratio and volume are reduced and which achieves a high degree of overall economy, in particular by its extensive adaptability to various vehicle-specific conditions, while allowing for an easy-to-produce design, generally low production costs, and realizability of modular methods of production.
According to this invention, this object is achieved as follows:
Owing to the type of transmission system with multiple power-transmission paths incorporating the invention versus a pure hydrostatic transmission, the efficiency is increased six to ten times, depending on the form of construction and vehicle conditions (degree of power increase corresponds to the marginal-power factor f.sub.E). This reduces substantially the power-to-weight ratio and the volume or the size of hydrostatic units, as the case may be. Technically speaking, the high speeds, e.g. in a passenger car, can only be handled, with small hydrostatic units. That means that the high power requirements of fairly large passenger cars call for systems with a correspondingly high power volume in spite of the small hydrostatic units, i.e., with a correspondingly high degree of power increase or marginal-power factor, as the case may be. In the aforementioned system taught by German Patent DE-PS No. 28 54 375, the efficiency can be increased four times compared to that of hydrostatic units, while allowing for a back-up speed acceptable for passenger cars. Consequently, compared to the invention, considerably large hydrostatic units are required.
All specific embodiments shown in FIGS. 1 through 10 are based on the same fundamental system. Using the basic modules of hydrostatic units, planetary gear train 10; 110; 210 and second planetary gear train 11; 111, it is possible to make different combinations of transmissions. All these modules are in constant mesh with each other. Depending on the range shifted, the clutches 12; 112 connect the output shaft to one of the shafts of the summation planetary gear train 10 or 100; 210, as the case may be, or to one shaft of the second planetary gear train 11; 111.
In accordance with the broader aspects of the invention, the invention provides an infinitely variable hydromechanical transmission mechanism having a power input shaft, a power output shaft and multiple path power-transmission means for transmitting power in at least two speed ranges from the input shaft to the output shaft. In particular the transmission mechanism comprises hydrostatic drive means connected to the power input shaft and including a first hydrostatic unit and a second hydrostatic unit having a hydrostatic power outlet. The mechanism also includes a four-shaft summation planetary gear train having a first shaft connected to the input shaft, a second shaft connected in constant driving relationship to the hydrostatic power outlet, a third shaft and a fourth shaft. First clutch means is provided for selectively drivingly connecting the third shaft and the output shaft and second clutch means is provided for selectably drivingly connecting the fourth shaft and the output shaft. The mechanism also includes a three shaft planetary gear train having a shaft that is connected to either the second shaft or the third shaft of the four-shaft planetary gear train.
In accordance with a more specific aspect of the invention, the summation gear train may comprise a double planetary gear train having two intermeshed planet gea
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