Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Patent
1997-03-12
1998-08-18
Bonck, Rodney H.
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
477 46, 477 47, B60K 4114
Patent
active
057952612
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method of controlling an electronically controlled, continuously variable transmission. Here an electronic control device establishes the operating point of the continuously variable transmission on the basis of input variables.
Continuously variable transmissions have a first pair of tapered discs on an input shaft and a second pair of tapered discs on an output shaft. Each pair of tapered discs consists of a first disc, stationary in an axial direction, and a second disc, movable in an axial direction. Between the pairs of tapered discs extends a belt-drive member such as a sliding jointed band.
In an electronically controlled, continuously variable transmission disclosed in Antriebstechnik 24 (1985) No. 2, it is possible by means of a programmed selector switch to shift between a first economy operating mode and a second sport operating mode. In the first operating mode, a ratio of the continuously variable transmission is adjusted so that the operating point of an internal combustion engine, which drives the continuously variable transmission, is passed into the performance graph of the internal combustion engine through the islands of the least specific consumption. In the second mode of operation, the ratio of the continuously variable transmission is adjusted so that the internal combustion engine generates a maximum torque or a maximum performance.
DE-A-41 20 546 has disclosed a method of controlling a continuously variable transmission of a motor vehicle. In this control method, the range between consumption and performance is gradually covered by five characteristic lines. A characteristic line is selected on the basis of driving activity. The disadvantage in this solution is that in many cases it is insufficient.
BRIEF SUMMARY OF THE INVENTION
The invention is based on the problem of providing an operating strategy for a continuously variable transmission.
According to the invention, a first solution of the problem resides in establishing the operating point by a performance graph which constitutes a dependence of the speed of the first tapered-disc pair on a throttle valve position, a vehicle speed and a parameter K1.
According to the invention, a second solution of the problem resides in establishing the operating point by a performance graph which represents a dependence of a ratio iV on a throttle valve position, a vehicle speed and a parameter K1. The reduction ratio iV results from the quotients of the speeds of the first tapered-disc pair by the second tapered-disc pair.
Operating point is to be understood, according to the invention, as a standard value of the speed of the first tapered-disc pair to be reached or of the ratio iV to be reached.
In a development of both the first and the second solutions, it is proposed that as the values of the parameter K1 rise, the operating point is continuously moved to a higher speed value of the first tapered-disc pair or a greater ratio iV. As the values of the parameter K1 drop, the operating point is continuously moved to a lower speed value of the first tapered-disc pair or a smaller ratio iV. This solution offers the advantage that it is possible to adjust any operating point as desired. In a continuous curve of the parameter K1, the transition from an old operating point to a new operating point likewise occurs continuously. Thus no speed steps occur which, in turn, results in an improved driveability.
In a development of this, it is proposed that the electronic control device determines the parameter K1 from the input variables, said parameter K1 representing an operating condition and each operating condition being reproduced at a value of the parameter K1.
In another development, it is proposed that the parameter K1 be capable of assuming any discrete values between zero and two. At a parameter K1 value of zero, an optimum consumption is adjusted. At a value of one, an optimum maximum performance presettable by a driver on the basis, for example, of a driving activity, is adjusted.
REFERENCES:
patent: 4875892 (1989-10-01), Sueda
patent: 4945483 (1990-07-01), Tokoro
patent: 5007147 (1991-04-01), Imai et al.
patent: 5022285 (1991-06-01), Suzuki
patent: 5545106 (1996-08-01), Senger et al.
patent: 5600557 (1997-02-01), Ogawa
Abromeit, G. "Konzept einer elektronischen Steuerung fur ein stufenloses mechanisches Getriebe", Antriebstechnik 24 (1985) Nr. 2, pp. 49-51.
Speicher Patrick
Vorndran Ralf
Bonck Rodney H.
Estremsky Sherry Lynn
ZF Friedrichshafen AG
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