Motor vehicles – Having four wheels driven – With differential means for driving two wheel sets at...
Patent
1990-10-25
1992-11-10
Hill, Mitchell J.
Motor vehicles
Having four wheels driven
With differential means for driving two wheel sets at...
74650, 180249, 475 84, 475 86, 475230, B60K 1735
Patent
active
051616360
DESCRIPTION:
BRIEF SUMMARY
The invention concerns an all-wheel driven field tractor having a gear change that comprises a front and a rear output shaft, wherein the front output shaft is connectable to a front-axle differential and a rear-axle differential can be driven via the rear output shaft as well as a power train including a clutch, a bevel-pinion shaft and a crown gear.
BACKGROUND OF THE INVENTION
An all-wheel driven motor vehicle of the kind mentioned above has been disclosed in German Patent 29 33 267. The gear change of this field tractor has a rear-mounted range change group with an overdrive for transportation speed in which the field tractor must generally be operated with front-wheel drive. A gear of an axle reduction situated between the output shaft and the bevel-pinion shaft is connected, when working in arable land, with the bevel-pinion shaft via a positive locked clutch. Simultaneously with the actuation of the overdrive, said positive locked clutch is released via a connecting linkage. Favorable traction values can be obtained in heavy traction works of the field tractor in arable land only with permanent all-wheel drive, the rigid connection between front and rear axles having a negative effect when the field tractor corners. The problem consists in that the front wheels, as a result of the larger radius of curve needed for maintaining traction, must rotate quicker than the rear wheels. Due to the equal axle speeds, the front wheels are pushed when cornering so that, as a consequence of the increased slip, the traction of the field tractor cannot be utilized and serious warping of the soil also appears as well as an enlarged radii of turn of the field tractor.
SUMMARY OF THE INVENTION
Therefore, the problem to be solved by the invention is to avoid the above mentioned problems and consequently to provide a mechanism which, when cornering, prevents distortions between front and rear axles when the all-wheel drive of the field tractor is permanently engaged and which can be integrated in the field tractor using constructionally simple means and requiring small space.
The above problem is solved in an all-wheel driven field tractor of the kind mentioned by the fact that the clutch is situated between the crown gear and a differential cage of the rear-axle differential and is designed as a controlled slip clutch whose slip status is regulated according to the size of the track radius to be executed with the field tractor and/or the traction needed. It is possible here to feed to a central unit certain parameters, which affect the track radius, as control volumes. The slip controlled at a given time in the power train toward the rear axle allows a reduction of speed of the rear axle so that good traction remains in the front axle during cornering. Due to the fact that when working the soil, for instance, with a plough or rotary harrow, it is necessary to turn around on the narrowest space at the end of the furrow or field where the mounted implement does not engage the soil, the change of traction need can also be used as a parameter for the slip status. If according to the invention the clutch is situated between the crown wheel and differential cage, on the one hand, it is possible to transmit a great torque as a result of the radial dimension of the clutch and, on the other hand, the accommodation of the controlled slip clutch requires absolutely no structural changes in the field tractor inasmuch as sufficient space is normally available in the rear-axle housing for its accommodation. The gear change remains unchanged.
Although DE-OS 34 27 725 has disclosed placing a controlled slipping clutch in the power train of a rear axle of a motor vehicle, what is concerned there is a front-driven automobile where the slip of the additionally activatable wheels of the rear axle must remain in a controllable firm relation to the slip of the wheels of the front axle. Besides, the controlled slip clutch is situated within the drive shaft leading to the rear axle.
DE-OS 34 34 395 has also disclosed a front-driven autom
REFERENCES:
patent: 4741407 (1988-05-01), Torii et al.
patent: 4829849 (1989-05-01), Masuda et al.
patent: 4895217 (1990-11-01), Hueckler et al.
Gazyakan Unal
Haupt Josef
Niezurawski Thomas
Hill Mitchell J.
Zahnradfabrik Friedrichshafen AG
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