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
1996-08-13
1998-06-16
Ta, Khoi Q.
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 82, 747301, 60490, F16H 4704
Patent
active
057661073
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to continuous hydrostatic power division transmissions, and in particular to a hydrostatic transmission part of such a transmission.
2. Description of Related Technology
Continuous hydrostatic power division transmissions, abbreviated herein as CHP, make it possible to change speed without interruption of tensile force, with synchronous rpm, and without load. The principle and the structure of continuous hydrostatic power division transmissions are known, for example, from the following publications:
1) DE 28 10 086; and
2) DE 29 045 72 C2.
Such transmissions include hydrostatic and mechanical transmission portions which are coupled to each other in such a way that the power to be transmitted is transmitted to certain parts in the individual driving regions hydraulically and/or mechanically. The power division makes it possible to improve efficiency in comparison to a purely mechanical or a purely hydrostatic transmission. Both hydrostatic units can be driven as a pump and as a motor.
The transmissions that have thus far been realized in the art which are based on conventional solutions for use in passenger cars and heavy vehicles, have significantly larger dimensions and a correspondingly increased weight, and are less cost-effective in comparison to automatic torque converter transmissions.
Based on favorable characteristics, for example, a high start-up torque, better insensitivity of the system, a larger control range in variable displacement motors, significantly higher efficiency, as well as the possibility of higher limiting rpm and speed increasing ratios, the two hydrounits are designed as slanted axis units which can be operated as a pump and as a motor. However, the large dimensions and high noise level that generally characterize hydrostatic transmissions may be problematic.
Furthermore, integration of a slanted-axis hydrostat into a CHP transmission concept has not been possible so far in such a way that optimum arrangement of the other components could be achieved with a tolerable manufacturing cost. In general, in the conventional solutions, the hydrostatic units are flanged outside of the transmission housing of the mechanical transmission part, i.e., all parts that carry high pressure are disposed outside the transmission housing. Optimization of the constructional size of the hydrostat has not been possible since back gear transmissions have been limited by the distance between the axles and the shaft diameter. Also, the start-up pulling force was the essential design criterion for the hydrounits to be used. The realization of a marketable transmission regarding the size of the structure and its cost has thus so far had limited possibilities.
In a device disclosed in DE 36 24 989 C2 wherein two hydrounits are used as premounted units with a connecting or control block, the transmission design is very compact.
The hydrostats are disposed in the inner casing of the planetary gear and the control heads of the hydrostats are disposed against each other at such an angle that their ends almost touch and extend tangentially to the envelope toward the top and bottom. As a result, the space required by the structure is minimized. Disadvantages of such an arrangement consist above all in increased manufacturing costs for the control block and realization of energy coupling of the hydrounits based on the angled orientation of the control heads, and thus in providing a flange designed for this; furthermore, it is not possible to reduce the size of the hydrounits.
SUMMARY OF THE INVENTION
It is an object of the invention to overcome one or more of the problems described above. It is also an object of the invention to further develop a CHP unit of the type described in the background section herein in such a way that a transmission can be produced which is marketable from the point of view of size and cost. It is also an object of the invention that the dimensions and the weight of the transmission can be reduced using comm
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International Search Report, International Application No. PCT/EP/94/04184.
J.M. Voith & GmbH
Kwon Peter T.
Ta Khoi Q.
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