Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Pump and motor in series with planetary gearing
Patent
1997-07-18
1998-10-13
Wright, Dirk
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Pump and motor in series with planetary gearing
B60K 700, B60K 1704
Patent
active
058205063
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a drive device for working machines, in particular for tracked vehicles such as bulldozers or the like.
Multiple developments of a tumbler drive are to be regarded as known from the prior art. In said drive devices, a hydraulic motor drives a chain gear via a planetary gear. The drive device should have small dimensions, especially in axial directions, so as not to project over the width of a chain tractor, such as a crawler excavator. The planetary gear must have a sufficiently great ratio in order to obtain a low speed level on the chain gear. The drive device must be provided with a brake to firmly brake the output during still stand of the hydraulic motor. Since the drive device is used even under extreme external conditions, provision must be made for a reliable seal over a long service life. Finally, the drive device must be easy to assemble and to maintain. Considering the production costs, the number of parts of the drive device must be as small as possible.
The above mentioned requirements are not met by the known drive devices. When the hydraulic motor is designed as an axial piston machine with a helical-disc construction, for example, an axially short design can be obtained only when said axial piston machine is integrated in the hub carrier. Examples of this are found in DE-A 27 44 936, DE-A 28 31 458 and DE-A 42 35 697. As a rule, the speeds of the hydraulic motor are so high that a multi-stage planetary gear has to be used. This multi-stage condition generally increases the axial length of the drive device so that the advantage obtained with the integration of the hydraulic motor in the hub carrier hydraulic motor integrated in the hub carrier is that bearings of large dimensions must be used for supporting the hub upon the hub carrier. To this disadvantage is added another: since the hub must be sealed relative to the hub carrier, seals with equally large diameters are needed. These circumstances result in a cost increase. In addition, the service life of the seal suffers by the relatively high peripheral speeds.
Although radial piston engines have long been known to the expert (see, for example DE-A 15 28 519 and DE-A 22 55 239), until today they have not been used in combination with a brake and a planetary gear as a tumbler drive for tracked vehicles.
The problem, on which this invention is based, is to provide a drive device for use in tracked vehicles which, in particular, stands out by a design that is of moderate cost, compact, simple to assemble and reliable.
The problem, on which the invention is based, is solved by a drive device having the characteristics stated in the main claim.
Compared to the tumbler drives known already, the solution according to the invention is surprisingly an extraordinarily simple design. The slow running radial piston engine works at a speed level which does not make necessary any multi-stage planetary gear. In addition, this engine, conditioned by the system, consists of relatively few parts. It is designed compactly, in an axial direction, so that it can be directly mounted upon one side of the hub carrier. A drive shaft connects the cylinder block of the radial piston engine with the planetary gear, the output member of which is non-rotatably connected with the hub.
Advantageous developments of the drive device, according to the invention, can be understood from claims 2 to 5.
Other features essential to the invention, and the advantages resulting therefrom, are to be understood from the explanation of two embodiments that follows. In the drawings:
FIG. 1 shows, in a simplified representation, a first embodiment of a drive device, in particular for a tracked vehicle; and
FIG. 2 shows another embodiment which differs, in particular, from the arrangement of FIG. 1 by the structure of the end output.
The drive device reproduced in FIG. 1 in a longitudinal section and a simplified representation, is especially adequate for the drive of a chain gear of a tracked vehicle such as a bulldozer or the like. It is a drive device which is
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Wright Dirk
ZF Friedrichshafen AG
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