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Gearshift quality now simulated
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01/02/2007
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There is hardly a road test report that does not make reference to manual gearshift quality with terms like ‘firm’, ‘notchy’ or ‘sloppy’ used to describe feel.
It’s a complex business. Gears are difficult or easy to engage and the feedback through the lever is felt more or less strongly depending on specific force curves in the gear shift unit. The perceived force is produced mainly by a shift detent rolling over a multidimensional contour. The geometry of the contour can be freely selected within certain limits (lift, curvature). The gearshift lever is guided precisely by the shift gate, which enables it to be moved within the shift pattern at any time. This results in the driver feeling varying degrees of resistance when changing gear.
Gearshift optimisation on the basis of a ‘qualitative force curve’ is no easy task. Specialists find it difficult to estimate exactly what effect modifications to shifting force and shift travel will have on the gearshift feeling. Extensive prototyping is often the only way forward.
To help the process, engineers working at Schaeffler KG for the INA brand have developed the INA shift force simulator, which could significantly reduce the time required for optimising shift quality along with the prototyping requirement.
Once the customer has selected a number of potential force curves, the shift force simulator is programmed with these and the shift gate data. The simulator is designed like a proper vehicle with seat, pedals, mock-up steering wheel and gearshift knob so the user can test almost any desired and calculated force curve directly and realistically.
The software, linked to a CAD program, uses the selected force curves first to calculate the appropriate
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Author
Roger Bishop
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