Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid pump and motor in one of plural paths to or from...
Patent
1990-10-09
1992-05-19
Diehl, Dwight
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid pump and motor in one of plural paths to or from...
475 81, F16H 4704
Patent
active
051143852
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to infinitely variable hydromechanical transmission with multiple power-transmission paths and having a first hydrostatic unit with an adjustable volume and a second hydrostatic unit, preferably with a constant volume, and one or more summation gear trains for adding together the power which originally is separated at the transmission input for transmission hydraulic and along separate mechanical power-transmission paths.
German Patent Specification 31 47 447 discloses a hydromechanical transmission with multiple power-transmission paths and having a plurality of gear-shift ranges which, similarly to the transmission of the invention, has a first hydrostatic unit with an adjustable volume and a second hydrostatic unit with a constant volume in this known transmission, during start-up and with the first driving range clutch closed, the first adjustable hydrostatic unit is adjusted to its maximum operating volume and the summation planetary gear train is so designed that in this operating state the transmission power output shaft is driven at a predetermined output speed, which corresponds to the design minimum speed of the vehicle. However, this known transmission does not include either a bypass valve the high-pressure and low-pressure lines of the hydrostatic circuit to facilitate starting or a first driving range clutch which is arranged for used also as a starting clutch. This known transmission includes a separate contrifugal starting clutch which is connected between the drive motor and the input shaft of the transmission. Such starting mechanism is very expensive and it is well known that centrifugal are not capable of gradual shock free engagement as is ordinarily required in passenger cars.
The object of the present invention is therefore to provide a hydromechanical transmission with multiple power-transmission paths which, in order to broaden the gear-shift range and/or to increase the power density, has an expanded first driving range and does not require a separate starting clutch.
Compared to the prior art transmissions of this type which includes an additional starting clutch, the invention has the advantage that it is simpler and less expensive and conserves the space which would otherwise be required for the starting clutch. Moreover, in accordance with the present invention the input shaft of the transmission maybe connected directly to the drive motor.
Certain preferred specific embodiments of the invention will now be discussed hereinbelow with reference to the drawings, in which:
FIG. 1 is a schematic illustration of a hydromechanical transmission that has multiple power-transmission paths and two hydro-mechanical forward driving ranges, the first range being expanded by the transmission-ratio dimension X, and the reverse range being similarly expanded,
FIG. 2 is a speed diagram for the specific embodiment of FIG. 1,
FIG. 3 is a schematic illustration of a transmission design that has two forward driving ranges and one reverse range, the first forward driving range and the reverse range being expanded in the same way as in the embodiment of FIG. 1,
FIG. 4 is a speed diagram for the specific embodiment shown in FIG. 3,
FIG. 5 is a schematic illustration of a transmission design that has three forward ranges and one reverse range, the first forward range and the reverse range being expanded and,
FIG. 6 is a speed diagram for the specific embodiment depicted in FIG. 5.
A hydromechanical transmission system 100 with multiple power-transmission paths which embodies the concepts and principles of the invention is illustrated in FIG. 1. Transmission system 100 includes a first hydrostatic unit A with an adjustable volume and a second hydrostatic unit B which preferably has a constant volume. Transmission system 100 also includes a four-shaft summation planetary gear train 4 and a three-shaft planetary gear train 9 that is collocated therewith and preferably includes a planet gear on a carrier 20, a sun gear 21 and an internal gear 22. Transmission 100 also has thr
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