Machine element or mechanism – Gearing – Interchangeably locked
Patent
1995-04-26
1996-06-11
Wright, Dirk
Machine element or mechanism
Gearing
Interchangeably locked
74360, F16H 3093
Patent
active
055245005
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a multi-stage reversing gear that is changeable under load, such as specially used in construction machines like excavators. The gear has an input shaft and a changing set consisting of a countershaft, fixed gears and idler gears with clutches for connecting one of said idler gears with the input shaft or countershaft. In this manner, it is possible to change the direction of rotation of an output shaft. In addition a transmission with synchronous clutches is fitted downstream of the changing set of the reversing gear. This is preferably a transmission having four speeds.
Reversing gears that are changeable under load are distinguished by a series of advantages. For this reason such gears are used in many commercial vehicles. The changing set combined with a hydrodynamic torque converter allows for smooth driving and reversing under load. When a transmission with synchronous clutches is fitted downstream of the reversing gear that is changeable under load, the driver can engage the adequate speed to be used. For example, in an excavator the work is done in the first or second speed, while the third and fourth speeds are available for transportation.
The multiplicity of working machines demands a constantly increasing degree of adaptability of the gear. It is in particular disadvantageous that the installation space can be considerably large, which is to be specially attributed to the considerable axial length and/or width of said gear.
This invention is based on the problem of providing a multi-stage reversing gear that is changeable under load, having a transmission with synchronous clutches fitted downstream for switching at least four speeds, which is especially distinguished by a small installation space.
The problem on which the invention is based is solved by the fact that, the idler gears of the changing set permanently mesh with a fixed gear, the drive pinion, of a countershaft of the transmission. To obtain a compact construction, in relation to the axial longitudinal section of the countershaft, two other fixed gears are situated on one side of said drive pinion and two idler gears are situated on the other side. The fixed gears here have a small diameter and form the input gears for the gear ratios 1 and 2. High reducing ratios can be obtained for said speeds, since the smallest diameters to be kept of said gears are not determined by structural parts of the synchronous clutch, as is the case with the idler gears. In gear ratios 3 and 4 the input gears are formed by the idler gears. Larger diameters can be used here so that the synchronous clutch can be housed without problem from the construction point of view. Gear ratios 1 to 4 are completed by two idler gears on the output shaft and two other fixed gears on the output shaft. The idler gears of the output shaft have in turn larger diameters so that a synchronous clutch can be installed without problem. The fixed gears on the output shaft, which are component parts of the gear ratios 3 and 4, have in turn smaller diameters. It can be readily understood that a large total ratio step of the gears can be achieved in this manner.
In a preferred embodiment of the gear according to the invention, the fixed gears are made integral with the countershaft. Hereby gear teeth of very small diameters can be easily produced. It is similarly advantageous to make the fixed gears integral with the output shaft.
The gears of larger diameters are advantageously designed as idler gears. It is therefore advantageous to situate two idler gears respectively on the countershaft and the output shaft and to associate with each a synchronous clutch.
When the driving connection between the idler gears of the changing set and the fixed gears of the countershaft is at a speed reducing ratio, the pairs of gears of the third and fourth speeds can have speed increasing ratios without the output speed thereby becoming too high. At the same time, the ratio in the fourth speed can be selected so that the total ratio step of the gears (between the first and
REFERENCES:
patent: 3858455 (1975-01-01), Sisson et al.
patent: 4063464 (1977-12-01), Crabb
patent: 4640146 (1987-02-01), Bubak
patent: 5079965 (1992-01-01), Leber et al.
Leber Fritz
Rebholz Wolfgang
Wright Dirk
ZF Friedrichshafen AG
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