Planetary gear transmission systems or components – Steering by driving – With condition responsive steer control
Patent
1996-05-30
1998-03-24
Marmor, Charles A.
Planetary gear transmission systems or components
Steering by driving
With condition responsive steer control
475 28, B62D 1106
Patent
active
057306770
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a cross-drive steering transmission for a tracked vehicle with planetary gear sets, brake and coupling means for engaging different ratios for cornering with different radii of curve.
The cross-drive steering transmissions have become widely used for steering tracked vehicles because of safety when driving at high speeds on streets and because of small steering losses in cross-country driving. DE-A 19 055 has disclosed a cross-drive Steering transmission having three radius ranges. Said cross-drive steering transmission is composed of a hydrostatic and a mechanical partial transmission. A neutral shaft of the steering transmission interacts with summarizing transmissions of a main transmission. Exclusively, the hydrostatic partial transmission acts in a first radius range and the mechanical partial transmission acts in a second radius range. Additionally, the mechanical partial transmission acts exclusively in a third, firm radius.
Steering transmissions for tracked vehicles have the essential disadvantage that they can become overloaded under certain driving conditions as a result of operating errors or abnormal driving resistances.
A small speed difference between a track inside and outside of the curve is absolutely required for cornering with large radii of curve. A low transmission output speed of the steering transmission needed for this is obtained by a large ratio between an input (engine speed) and an output of the steering transmission. Said large ratio, however, not only provides the desired lower output speed but also produces a very high excess torque on the output shafts of the main transmission. The above described conditions cause the essential danger of overloading said steering transmission, since excessively supplied torque is never demanded by the vehicle during its normal use. But under certain conditions, a high output torque can be favored, for example, in case of operating errors (such as turning around a vertical axis with a parking brake engaged) or abnormal driving resistances (such as a drive assembly being blocked by foreign bodies).
Since for reasons of economy no transmission can be designed for said eventually occurring torques, a danger exists that a steering transmission can be destroyed as a result of slipping clutches in the steering transmission.
SUMMARY OF THE INVENTION
This invention is based on the problem of providing a protection device for a steering transmission which reliably protects the mechanical cross-drive steering transmission in case of overloading.
The problem on which the invention is based is solved by the fact that the input speed, the output speed of the steering transmission and the ratios engaged in the steering transmission are detected and compared with predetermined operating parameters, and that when slippage is detected, the steering transmission is disengaged. The proposed solution makes possible, in case of overload, a reliable protection of the mechanical cross-drive steering transmission without affecting the mobility and driving safety of the vehicle and personnel thereof. The conditions for a disengagement are selected so that, in principle, the disengagement of the steering transmission occurs only under driving conditions that theoretically make an overload possible. In addition, the disengagement occurs only when starting or at very low speeds.
A simple solution for disengaging the steering transmission consists of interrupting a supply of pressure to the steering transmission when slippage is detected.
It is very advantageous to determine a disengagement conditions by a logical combination of different operating parameters. Said operating parameters comprise the following input signals: an engaged gear, a vehicle speed, an engaged ratio in the steering transmission and a comparison of the input and output speeds of the steering transmission.
It is advantageous to add an input signal from a braking signal to the operating parameters. By using the braking signal, it is possible in
REFERENCES:
patent: 3656371 (1972-04-01), Schaefer
patent: 4309917 (1982-01-01), Leet
patent: 4519275 (1985-05-01), Maruyama et al.
patent: 4890508 (1990-01-01), Zaunberger
patent: 5473541 (1995-12-01), Ishino et al.
Loichinger Walter
Sorg Johannes
Estremsky Sherry Lynn
Marmor Charles A.
ZF Friedrichshafen AG
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