Machine element or mechanism – Gearing – Interchangeably locked
Patent
1998-05-22
2000-02-29
Wright, Dirk
Machine element or mechanism
Gearing
Interchangeably locked
F16H 6112
Patent
active
060295317
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a gear control system intended in particular for electrically operated transmissions of layshaft design.
BACKGROUND OF THE INVENTION
In electrically operated automatic transmissions of layshaft design having hydraulically controlled switching elements, the hydraulic system is controlled by means of electric energy. But if for any reason, such as on account of a short circuit, the gear control system no longer is supplied with electric energy, operation will no longer be possible in transmissions of the above mentioned kind having a gear control system known from the practice, and this necessarily results in that a vehicle, that is equipped with such a transmission, will be unfit to move and will break down.
It is true that from the practice reserve devices are known in planetary transmissions which, in case of electric failure, make possible a gearshift by a linking of numerous valves in the transmission, but such a reserve device is very expensive and cannot be transferred to a transmission of layshaft design.
In an electrically operated automatic transmission, a failure of electricity, for example, due to a short circuit in the bypass cables, can also result in, due to the unintentional engagement of a valve caused by the short circuit, two switching elements to work against each other whereby, the transmission becomes blocked. At the same time, it can result in instabilities in the behavior of the vehicle and create a situation critical for safety in which a vehicle, for example, can skid of the road.
From the prior art, safety devices which prevent a blocking of the transmission, as consequence of a short circuit, are known only in planetary transmissions, and such safety devices are impossible to use in transmissions of layshaft design, such as used in autobuses and delivery vans.
In addition, the reserve and safety devices, which in the practice can be used only in planetary transmissions, have the disadvantage that, without considering the situation of the vehicle in which the failure of electricity occurs, when an emergency gear is engaged which often is too low for the actual velocity of the vehicle and thus, overspeeding of the engine can occur.
SUMMARY OF THE INVENTION
Therefore, the problem on which the instant invention is based is to provide a gear control system especially intended for a transmission of layshaft design or an electrical operated transmission which, even in case of failure of the electric supply of energy, ensures a safe and transmission-protected continuation of the vehicle state while avoiding blocking of the transmission and inadmissible switch backs.
The gear control system, according to the invention, makes advantageously possible for a transmission of layshaft design, which is considerably more reasonable in cost than, for example, a planetary transmission, to operate despite failure of the electric supply of energy so that a vehicle can move, for example, at least until reaching the nearest service station.
The gear control system, according to the invention, further makes possible in a transmission of layshaft design that blocking of the transmission, due to a short circuit, be prevented whereby, the operating safety of the vehicle is improved.
The gear control system, according to the invention, in addition stands out by the fact that even when activating the reserve device an inadmissible switch back, which in normal operation is prevented by the electronic system, is not possible so that the transmission parts concerned in the switching are protected also in the condition of emergency running.
The gear control system, according to the invention, with its reserve switching device, the switch back safety device and an anti-transmission blocking switching device solves a complex problem fully dismissed by the known gear control systems and yet, has a very simple and inexpensive construction which, in addition, is also easy to operate.
Other advantages and advantageous developments of the invention result from the sub-claims and the embodi
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patent: 4981052 (1991-01-01), Giere
patent: 5222581 (1993-06-01), Paulsen
patent: 5492027 (1996-02-01), Eaton
patent: 5871074 (1999-02-01), Easton
patent: 5893292 (1999-04-01), Lanting
patent: 5934403 (1999-08-01), Moore et al.
Wright Dirk
ZF Friedrichshafen AG
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