Machine element or mechanism – Rotary member or shaft indexing – e.g. – tool or work turret – Preselected indexed position
Patent
1986-05-23
1988-05-10
Braun, Leslie
Machine element or mechanism
Rotary member or shaft indexing, e.g., tool or work turret
Preselected indexed position
74856, B60K 4104
Patent
active
047427337
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a control system for the automatic shift of a step change gear transmission.
Presently known step change gear transmissions for motor vehicles are shifted automatically in dependence on speed, preferably during speed reduction through gearing, and on load conditions as well as the various positions of the fuel controlling gas pedal, such as idling and partial load or full load (kick-down).
It is also known that certain gear ratios of a transmission may be excluded from the shift sequence under selective driver control, for example, under downhill driving conditions. Besides the standard selector control positions for forward travel D, neutral position N and reverse travel R, such selector controls have additional control positions I, II and III, whereby automatic shift of the gearing is correspondingly limited to the first gear ratio, the second ratio or the third gear ratio, as described for example in the brochure, "ZF Automatic Gearings HP 500, Description, Operation and Maintenance F 1/12 ZFF 792006". Such a system offers to the driver the ability to automatically operate a step change gear transmission with relatively fewer gear steps.
In the case of certain multigear-automatic transmissions, not only higher but also lower gear ratios are excluded from the automatic gear shift operation by corresponding displacement of two selector levers to idling and partial travel load positions, respectively. Furthermore, in certain automatic step change gear transmissions, the shift points are changed by means of a preselection control so as to provide more economical performance.
All of such prior art control systems, especially automatic shift controls for multi-speed step change gears, are unable to readily adapt the drive train from the engine to the performance characteristics of the engine so as to achieve favorable fuel economy. In the case of the usual automatic gear control system having relatively few speed ratios, the duration of drive at each speed ratio is prolonged because of the relatively high reduction gear ratios and the wide gear ratio differences between steps thereby reducing the frequency of shift. A different problem arises, however, in the case of multi-speed, automatic gear transmissions with narrow differences between gear ratio steps, as is required for fuel saving operation.
Therefore, it is an object of the present invention to provide an automatic gear shift control system which takes into consideration the small gear ratio differences between shift points of a multi-speed, automatic gear transmission without excessive shifting frequency as a result of the relatively large number of gear ratios involved.
SUMMARY OF THE INVENTION
In contrast to prior art automatic shift types of step change gear transmissions, the system of the present invention effects an automatic shift operation through the entire drive ratio range with less than all of the available gear ratios by the selection of shift patterns so that the automatic shift sequence through the entire shift range between the high and low gear ratio limits occur with jumps or skips in the available gear ratios. It is thereby possible to shift between gear ratios of the entire shift range for different travel loading conditions in a manner heretofore available only during full load operation and high demand travel conditions, excluding for example, hard braking or idle travel conditions wherein less than all of the gear ratios are selected to accommodate such latter travel conditions. The selection of gear ratios in dependence on correspondingly different travel loading conditions automatically changed under different shifting patterns results in a considerable decrease in frequency of shifting without limiting the optimum adaptation of the transmission to the corresponding state of travel and to the performance characteristics of the engine most favorable to economical fuel consumption.
In a particularly simple manner, it will be possible in accordance with the present invent
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ZF Automatic Gearings HP 500, Description, Operation and Maintenance F 1/12 ZFF 792006, p. 6.
Braun Leslie
Novais David
Zahnradfabrik Friedrichshafen AG.
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