Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Patent
1994-05-09
1995-12-12
Wright, Dirk
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
477 43, 477 47, F16H 6116
Patent
active
054745055
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to application Ser. No. 08/170,184 filed on Dec. 21, 1993 in the name of Joseph PETERSMANN et al. for METHOD OF CONTROLLING A CONTINUOUSLY VARIABLE TRANSMISSION, now pending.
The invention relates to a method according to the species of the main claim.
In conventional automatic transmission controls of motor vehicles powered by internal combustion engines, when the accelerator pedal is released, because of the reduced load signal (throttle aperture angle) at approximately the same driving speed, as a rule initiate a reduction of the gear ratio or an upshift. This is not always desirable, however, when rounding curves or when braking, since load changes of this kind under certain conditions may lead to unsafe driving states, or when the motor vehicle is being accelerated again by pressing harder on the accelerator and an increase in the gear ratio or a downshift must be forced. This effect is independent of the transmission design and occurs in both multi-step transmissions and in continuously variable transmissions.
In DE 33 41 652 C2, in the latter and in connection with automatically shifted multi-step transmissions, it is proposed to prevent this reduction of the gear ratio (upshifts) on curves by detecting the transverse acceleration of the motor vehicle. However, this can only be used to avoid shifting on curves.
EP 00 93 312 A1 teaches a method and a device for adjusting the gear ratio of a continuously variable transmission in which, to increase the engine braking effect, it is proposed to keep the gear ratio constant for a certain period of time when the accelerator is released rapidly. If a minimum speed is undershot before this time elapses, or the brake is actuated, or the throttle reaches its neutral position, maintenance of the constant state is interrupted.
In order to be able to prevent a reduction of the gear ratio even when approaching curves, in the method for controlling an automatically shifting transmission according to DE 39 22 040 A1 the rate of change in the accelerator pedal is detected and, when a certain (negative) boundary value is undershot, the signal to suppress an upshift process is derived as soon as coasting is detected. Then upshifts are suppressed until power is applied again and a fixed time interval has elapsed.
It is also provided in DE 39 22 051 A1 to make this time interval dependent upon another parameter (driving activity), which is derived from one or from a combination of several operating and/or driving parameter(s) of a motor vehicle and evaluates a driving style of a driver or a traffic situation prevailing at the moment.
On the basis of this prior art, it is the goal of the invention to provide a method for controlling an automatically operated transmission for a motor vehicle, which in particular is improved further as regards behavior ahead of curves and during braking and which can be used both for multi-step transmissions and for continuously variable transmissions.
The goal is achieved according to the invention by the characterizing features of claim 1. Additional features that characterize the invention are contained in the subclaims.
The advantages of the invention lie primarily in the fact that a method for controlling an automatically actuated continuously variable transmission for a motor vehicle is provided in which the adjustment behavior ahead of curves and during braking is further improved and which is usable both for multi-step transmissions and for continuously variable transmissions. A coast function to suppress a shifting or gear ratio changing process is initiated as soon as the accelerator pedal is released rapidly. This coast function is maintained until the application of power is detected once more and the vehicle accelerates. Then a holding time is started during which the coast function is started again as soon as the vehicle begins coasting.
During coasting, the gear ratio set when the function was initiated is maintained and the gear that was engaged when the fun
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Petersmann Joseph
Seidel Willi
Dr. Ing. h.c.F. Porsche AG
Wright Dirk
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