Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
2002-02-20
2003-12-30
Black, Thomas G. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S057000, C701S062000, C477S086000, C477S174000
Reexamination Certificate
active
06671602
ABSTRACT:
FIELD OF THE INVENTION
A method for manually stipulating the ratio of a continuously variable transmission (hereinafter, “CVT”).
BACKGROUND OF THE INVENTION
The operational strategy of a CVT is first normally to allow comfortable driving and second to achieve a favorable consumption of fuel. As for good drivability, essential criteria lie in a proper relation between the speed of rotation (hereinafter, “RPM”) of the motor and the speed, in the motor dynamics, and in meeting such vehicle performance as is desired by a driver. Additionally, consideration must be given to adaption to the circumstances of travel, i.e., to city or mountain driving. Also, reliable downshifting into the highest ratio (LOW) upon stopping must be considered. Further, intervention by the driver during shifting must be easily carried out. For a satisfactory fuel consumption, what is to be striven for, is an extended period of operation in the most efficient zone of the characteristic curve of the motor, as well as a lowering of the RPM of the motor during a period when travel conditions are constant. Since the named criteria for operational strategy of a CVT are, in part, self contradictory, a compromise is normally struck.
In order to combine the advantages of a continuous change of the transmission ratio, with known gear change behavior and the motor acoustics of an automatic staged gear change transmission associated therewith, U.S Pat. No. 4,836,056 proposes to automatically switch the operational strategy of the CVT over to a control, which is based on a shifting-characteristic curve. This switchover is effected automatically, dependent upon a threshold signal representing the motor load. The achieved gear change behavior of the CVT can, in this case, be likened to an automated gear change with a very soft torque converter in which a converter bypass clutch is always open up to a particular throttle flap threshold. The RPM behavior of the motor can be regarded negatively by the driver, described as producing a “seat of the pants” effect or “rubber band effect”.
In order to bring the operational behavior of the CVT to automatically coincide better with the desires of the driver and the influences of the travel conditions, adaptive driving strategies have become known.
For instance, DE-OS 43 12 415 proposes to adjust the ratio by means of more than one type of characteristic curve of the motor map. In doing this, the operational point direction is carried out in an area between a characteristic curve of optimal fuel consumption and a characteristic curve of optimal motor loading. The operational points, between these limiting lines, lie on so-called dynamic characteristic curves, the position of which is dependent on the magnitude of the speed of change of the load demand. The choice of the shift-characteristics and the current dynamic characteristic curve, along which the operational point is directed, is done automatically.
DE-PS 41 20 546 describes an operational strategy for a CVT wherein there is a control characteristic curve according to which the continuous ratio selfadjusts in relation to the position of the throttle valve flap and the RPM of the motor. The said control line, however, represents the driving style, that is, the driving activity of the driver. The data for this “style” characteristic curve, however, is automatically selected from a multiplicity of control characteristic curves previously stored in the memory of the transmission control. The evaluation of the driver's style, that is the driving activity, is a complex function and the cost in time and money in ifs application is correspondingly great.
In DE-OS 196 00 915, the applicant describes a procedure for the guidance of an operating point, in an operational mode in which the actual preselected position of the operational point, is in a state of being continually newly determined within a predetermined zone of driving with an upper and a lower limit activated by the function of an actual, essentially drive-dependent, unfiltered input signal. Based on this, the location of the operational point in the transmission variogram is continually being computed anew and predominately defined by the activities of the driver in this case.
In all procedures for automatic operational point guidance, the disadvantage is that, in spite of the applications of great efforts, not all the desires of the driver can be fulfilled, in particular, a desire to be able to make a manual intervention during shifting.
To offset this particular disadvantage, DE-PS 41 20 540 proposes that along with a first operational mode of automatic driving strategy, a second is to be created in which the driver, by means of manual intervention, can simulate the operational behavior of a multistage transmission. For this situation, a number of set, constant ratios, i.e. shift movements, for example, are input and stored in a characteristic map. If the driver gives a manual shift command to the transmission, then the choice of the constant transmission ratio is generated from the said characteristic map relative to a driving activity. Upon the transition from the first operational mode into the second manual operational mode, by means of a selection-apparatus which is manipulated by the driver, a transition function controls the jump of the actual transmission ratio, which is running at the moment of change of operational mode, onto the next successive, constant, predetermined ratio. In order to better represent the desires of the driver during the manual type of shifting operation, DE-PS 41 20 540 proposes further to select the gear change jump out of groups of predetermined constant ratios, which simulate different characteristics of shifting, for example, a fuel consumption optimized, an economic ratio and a load optimizing, sport characteristic.
In the case of the simulation of a stage transmission with constant ratios as a manual operational strategy for a CVT, the disadvantage lies especially in the diminishing of drivability in the functional area of the operational map. In this way, the motor can be throttled down in the lower speed zone by a ratio which is so low that the motor stalls which, for a normal automatic driver, would present surprising behavior for the vehicle. Also, the available power for start would be surprisingly low if the driver had negligently forgotten to shift down through all gears upon stopping. Because of the customary spread advantage of the continuous transmission, during a start-up situation, the driver must change the gears very quickly, in the lower speed areas, in order to achieve an optimum acceleration. As a solution for this problem, DE-PS 41 20 540 proposes a forced high shifting or a forced up-shifting in fixed, predetermined gear changes, this being triggered when threshold speeds are reached.
EP 0 697 548 A1 describes a driving strategy for a CVT, in which, for a second operational mode, discrete, manually preselective, vectors are provided, which all intersect at a virtual zero-point. This virtual zero-point lies outside of the variogram of the CVT in the negative vehicle speed area and the positive motor RPM area. This, then, makes it impossible in all manual, preset vectors to achieve the start-up ratio LOW and the maximum vehicle speed.
SUMMARY OF THE INVENTION
Thus, the invention has the purpose of creating a method for stipulating the ratio of a CVT with a first, automatic operational mode and a second, manual operational mode in which the driver has direct intervention in the choice of ratio and wherein there will be an improvement in the operational behavior in the manual operational mode.
The purpose of the invention is achieved in that the driver, in the manual operational mode of the CVT, can manually predetermine, by means of a shift or selector apparatus, the RPM of the motor which is dependent upon a non-staged, vehicle velocity.
In accord with the invention, it is proposed, to so simulate the manually selectable curve of the RPM of the motor as an optional curve profile within the adjustability area of
Speicher Patrick
Vorndran Ralf
Welte Anton
Black Thomas G.
Davis & Bujold PLLC
Donnelly Arthur D.
ZF Batavia L.L.C.
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