Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
2000-02-17
2002-08-06
Wright, Dirk (Department: 3681)
Machine element or mechanism
Gearing
Interchangeably locked
C074S333000
Reexamination Certificate
active
06427548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to an automatic transmission, especially for a motor vehicle.
2. Discussion of the Prior Art
Modem developments in automotive engineering have increasingly moved away from manual shift transmissions, i.e., transmissions in which a shifting force is transmitted mechanically from a gear lever to the transmission, toward automatic transmissions. In these transmissions, the shifting selected by the driver is determined in that a movement of the shift lever is detected by an associated sensor arrangement or automated program and, based on the detected shifting selection, an actuator arrangement is put into operation in the transmission for carrying out the desired shifting procedure. For this purpose, transmissions constructed for manual operation are outfitted in such a way that, e.g., a shifting shaft which is to be moved linearly and possibly rotationally for carrying out a shifting process is moved by means of these actuators which initiate required movements. Accordingly, when carrying out shifting processes, appropriate actuation of the shifting shaft deactivates a coupling device, e.g., in the form of a synchronizing mechanism, adjusting a previously engaged gear and, only after this device has been deactivated by the movement of the shifting shaft, the coupling device associated with the next gear speed to be adjusted is activated in the course of further movement of the shifting shaft. The time required for carrying out a shifting procedure in this way is relatively lengthy because a previously adjusted gear speed must first be fully disengaged and the shifting shaft must then be moved further to the next required position before a new gear speed can be engaged. Another problem consists in that the design of the actuators driving the shifting shaft must be appropriate to the actuating path to be traversed as well as to the required shifting force, so that relatively large drive units are required in order that the necessary shifting force can still be provided in the case of relatively long shifting paths.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an automatic transmission which minimizes the time required for carrying out shifting procedures in a simplified construction.
According to the invention, this object is met by an automatic transmission, especially for a motor vehicle, comprising a plurality of torque transmission paths which can be selectively activated for torque transmission, wherein the torque transmission paths have different transmission characteristics and, based on their transmission characteristics, can be ordered in a sequence of torque transmission paths. The transmission further comprises a clutch arrangement by which at least one of the torque transmission paths can be activated.
It is further provided in the transmission according to the invention that the clutch arrangement has a clutch unit which is associated with a group of torque transmission paths and by which a torque transmission path of a group of torque transmission paths may be selectively activated. A plurality of groups of torque transmission paths are provided, each group comprising only one individual torque transmission path, or a plurality of groups of torque transmission paths are provided, at least one group comprising a plurality of torque transmission paths, or a plurality of groups of torque transmission paths are provided, at least one group comprising an individual torque transmission path and at least one additional group comprising a plurality of torque transmission paths. At least one group of torque transmission paths, insofar as it comprises a plurality of torque transmission paths, comprises only torque transmission paths which do not immediately follow one another in sequence.
As a result of the construction, according to the invention, of an automatic transmission, it is ensured due to the appropriate grouping of different torque transmission paths and the allocation of the same to a respective coupling unit that independence from the predetermined sequence is maintained to a great extent. It is assumed, for instance, that the sequence in which the individual torque transmission paths can be ordered or listed with respect to their transmission characteristics is an indication of the descending speed reduction ratio. Accordingly, this results in a sequence which, in conventional transmissions, is defined by the individual gear speeds: first gear, second gear, third gear, fourth gear, and so on. Since it is now ensured in the transmission according to the invention that two torque transmission paths immediately following one another in this sequence are not serviced by the same clutch unit, it is possible, for example, when carrying out a shifting process from first gear to second gear, to disengage the clutch unit associated with the first gear and to engage the clutch unit associated with the second gear virtually simultaneously or with a slight delay in time, wherein, in this case, the first gear and the second gear are arranged in different groups and therefore are to be activated by means of different clutch units. Accordingly, it is not necessary to wait until the first gear is fully disengaged before activating or engaging the second gear. In this way, an appreciably faster shifting process can be carried out and the inconvenience resulting in the prior art from a period of interruption of tractive force can be appreciably reduced when carrying out the shifting process.
According to the present invention, different alternatives are possible with respect to the grouping of the individual torque transmission paths. Within the meaning of the present invention, the term “group” does not necessarily signify the assemblage of a plurality of torque transmission paths. For example, it is also possible that every group contains only one individual member, that is, an individual torque transmission path, or is defined thereby. Ultimately, this means that every individual torque transmission path is assigned its own clutch unit and that a plurality of torque transmission paths are not to be serviced by one individual clutch unit. Also, the individual torque transmission paths can be controlled optionally in this way for activation or deactivation of the same. It is also possible, for example, that a plurality of torque transmission paths is contained in one group, while the rest of the torque transmission paths are each positioned individually in respective groups, so that these individual torque transmission paths can again be controlled by their own clutch units and the plurality of torque transmission paths assembled in the group are to be activated or deactivated by a common clutch unit. Basically, the principles of the present invention already result in an improved transmission construction when, in the case of a plurality of groups of torque transmission paths, several of which also comprise a plurality of torque transmission paths, only one individual group is provided in which the torque transmission paths to be activated or deactivated by a clutch unit do not directly follow one another in the defined sequence.
A particularly simple construction can be achieved in that an actuator unit is associated with every clutch unit of the clutch arrangement. The independence of the individual clutch units can be further increased in this way.
For example, every clutch unit for every torque transmission path of the group of torque transmission paths associated with this clutch unit can comprise a synchronizing mechanism.
Further, a particularly simple construction can be achieved in the transmission according to the invention when the transmission has an input shaft and every torque transmission path comprises a transmission member, preferably a transmission gearwheel, which can be coupled by the clutch arrangement to the input shaft for common rotation therewith.
An overly complex construction of the individual clutch units can be avoided
Leimbach Lutz
Ratte Andreas
Voss Reiner
Wirth Thomas
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