Machine element or mechanism – Control lever and linkage systems – Multiple controlled elements
Patent
1995-03-31
1996-12-24
Herrmann, Allan D.
Machine element or mechanism
Control lever and linkage systems
Multiple controlled elements
F16H 6336
Patent
active
055864708
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a gear-changing device for a transmission, in particular a motor vehicle transmission. In gear-changing operations of multi-step or multi-group toothed gear systems, such as in countershaft transmissions, two gear stages of a gear group should not be simultaneously engaged. A faulty operation results in a positive blocking of the gear group and therewith a blocking of the whole transmission line of the motor vehicle or also failure of the transmission. The related effects of the vehicle and surroundings thereof on gear change operations were difficult to control and could be serious.
BACKGROUND OF THE INVENTION
A gear-changing device where the gear-changing elements (for ex., dog rings) of the toothed gear system are moved to their switching position via a slider-crank mechanism is shown and described in the applicant's prior patent application (German patent application P 41 37 145.3 filed on Nov. 12, 1991 or European patent application). The slider-crank mechanisms are here formed by oscillating cranks and a slide rod. The oscillating cranks are connected with the slide rod, via coupling mechanisms, according to the speed to be engaged or there is produced a stationary stop, of the oscillating crank, on a part that is formed in the housing.
SUMMARY OF THE INVENTION
The problem on which this invention is based is to improve the gear-changing device of the former idea, in order to prevent, with certainty, the disadvantageous consequences of a possible faulty operation.
According to the invention said problem is solved by a gear-changing device for a transmission, in particular a motor vehicle transmission, having gear-changing elements moved from a stationary rest position to their switching position by slider-crank mechanisms, such as oscillating cranks and a slide rod, in a manner such that their coupling mechanisms are biased into their stationary rest positions and a driving position is produced with the slide rod, the distance between the rest positions and the distance between the driving positions of the coupling mechanisms being different.
By virtue of the distance between the rest positions and the distance between the driving positions, of the coupling mechanisms being unequal, there is established a safety, which acts geometrically-mechanically and prevents, with certainty, a blockage of a gear group in the case of a possible faulty operation. No simultaneous engagement of several speeds is possible.
In possible embodiments of the gear-changing device, the slide rod has driving apertures, the distance between which is smaller or greater than the distance between their coupling mechanisms in their rest positions. Depending on whether the distance is smaller or greater, a negative or positive offset results. In the case of a negative offset, the regulating distance of the slide rod lengthens, since an overlapping of the switching strokes occurs. If, on the contrary, a positive offset is selected, the switching intervals between adjacent switching sets is shortened. In accordance with the type of transmission, the expert will, in a given case, find the suitable offset.
In a preferred embodiment, at least one of the driving apertures is offset in relation to the rest position of the coupling mechanism associated therewith. Said drive aperture can be offset in such a manner that, in a selecting or switching operation, the coupling mechanisms leave the driving apertures in the slide rod or mesh therein at separate times. Thus, since the switching stroke becomes reduced by the offset of at least one driving aperture, there additionally results the possibility of shortening the switching times between adjacent gear-changing sets. Alternatively, the adjusted speed of the slide rod becomes reduced in the movement from one to the adjacent gear-changing set. Thus the selection operation becomes safer, without it being necessary to prolong the switching time when changing a gear-changing set.
BRIEF DESCRIPTION OF THE DRAWING(S)
Herebelow, an embodiment of the invention is expl
REFERENCES:
patent: 5481935 (1996-01-01), Bailly et al.
Baasch Detlef
Bailly Gerhard
Gazyakan Unal
Herrmann Allan D.
ZF Friedrichshafen AB
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