Machine element or mechanism – Gearing – Interchangeably locked
Patent
1997-04-30
1998-08-04
Wright, Dirk
Machine element or mechanism
Gearing
Interchangeably locked
F16H 3093
Patent
active
057877564
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a multispeed powershift reversing gear having one output shaft, countershafts and gearwheels which form a drive gear set and, mounted upon the countershafts, clutches with idler gears optionally non-rotatably connectable with one of the countershafts for a change of speed and direction, and a driven gear chain having at least one fixed gear.
In construction machinery in use today, gears, which can be basically divided in two groups, are used. It is characteristic that a hydrostatic drive unit is front-mounted on the powershift gear for one group. In said gear, the speed and torque of the front-mounted group are adapted by hydraulic or electro-hydraulic controls.
The prevailing number of used gears belongs to the other group of the powershift gear with a front-mounted hydrodynamic torque converter. By means of said drive unit, it is possible to obtain a continuous and automatic torque increase, as the working resistance of the motor vehicle such as a construction machine increases. It is possible here to generate gear input torques which substantially correspond to triple the value of the engine torque. This is important because unlike the case of passenger vehicles, the work is carried out with a gear or converter. In a wheel loader, for example, the bucket is pushed into the earth to be carried. The filling is broken up and lifted. To load, the vehicle is reversed, the bucket is further lifted and unloaded. The torque conversion is a great advantage precisely at low speeds and great speed differences between the input and the output.
The converter can be complemented by a converter ridge clutch. By means of said clutch, it is possible to obtain within the gears, at high speeds, considerable savings in consumption.
The flow of energy in the individual gears is produced by a combination of hydraulically shiftable clutches. Said clutches must, among other things, be shiftable for reversal under load and, therefore, consume much energy. The design of the housing or the arrangement of the shafts of the gear must be adapted to a specific use. Typical uses for a reversing gear are in dumps, loaders, excavators, and lift trucks, but also in vehicles operated on the road such as motor cranes. A specific center distance between the input and output shafts of the gear is required, depending on the type of vehicle. Long center distances are to be used, for example, when the bending angle of universal joint shafts must be kept small. In this case, the reversing gear assumes an additional function as a distributor gear.
In motor cranes, the reversing gear has only one output shaft. A smaller center distance is required due to space conditions.
Most cases need at least one power takeoff driven in accordance with engine speed, for example, the hydraulic system of the working machine. In addition to the power takeoff, a lubricant pump and a shift pump are also provided, which are likewise operated according to engine speed.
The tasks to be performed by a reversing gear are varied, being determined by the design of the vehicle.
DE-A 11 29 838 has disclosed a reversing gear which stands out by a small axial length. Upon one input shaft is a fixed gear which is in constant meshing contact with fixed gears upon a reversing shaft and a countershaft. All idler gears are on one side of the gear and constantly mesh with each other. Between each idler and fixed gear is situated one friction clutch. In this reversing gear already known, the structural design of the friction clutches, in particular the arrangement of the disc sets, the support of the idler gears upon the countershafts and also the indirect support of the countershaft on the side of the idler gears, is in itself relatively expensive.
DE-A 25 35 700 has disclosed a reversing gear where the friction clutches are designed as double clutches. In this gear, it is possible to obtain a relatively high number of speeds, but a larger space in an axial direction is needed, since up to four gearwheels and one double clutch have to be placed on one count
REFERENCES:
patent: 4464947 (1984-08-01), Windsor-smith et al.
patent: 5249475 (1993-10-01), McAskill
patent: 5524500 (1996-06-01), Rebholz et al.
patent: 5592853 (1997-01-01), Rebholz et al.
Leber Fritz
Rebholz Wolfgang
Wright Dirk
ZF Friedrichshafen AB
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