Machine element or mechanism – Gearing – Interchangeably locked
Patent
1999-09-15
2000-11-21
Wright, Dirk
Machine element or mechanism
Gearing
Interchangeably locked
701 51, F16H 6102
Patent
active
061486825
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a method for increasing the spontaneity of an electrohydraulically controlled automatic transmission in which a gear shift is carried out by a second clutch closing while a first clutch opens.
In automatic transmissions, the gear shifts can be carried out with overlapping gears, i.e. a first clutch opens and a second clutch closes. The state and pressure curve of the clutches involved in the gear shift is here determined by an electronic transmission control via electromagnetic actuators. Such a method of control or regulations is known from DE-OS 42 40 621.
In automatic transmissions, gear shifts are usually made when a desired performance presettable by a driver, e.g. an accelerator pedal value, exceeds a shift characteristic line of a characteristic field. Besides said gear shifts triggered by means of accelerator pedal, a driver also has the possibility at any moment manually to make downshifts. DE-OS 43 11 886, e.g. thus shows a device by which a driver can make gear shifts by means of a selector lever having a manual gate or switching levers on the steering wheel. In the practice, the following problem can arise when during an overtaking maneuver the driver must let pass the traffic coming in opposite direction. He will then release the accelerator pedal. If the accelerator pedal value exceeds an upshift characteristic line, as consequence of this the automatic transmission carries out an upshift. If during the upshift the driver detects that the opposite road is now free, he will again actuate the accelerator pedal. But the automatic transmission will first terminate the upshift, then follows a blocking time and only then will the automatic transmission carry out a downshift. The problem thus consists in that between the driver's required performance and the reaction thereto of the automatic transmission a corresponding long time elapses. Many drivers find this long reaction time disturbing.
To this extent, the problem to be solved by the invention is to increase the spontaneity of an automatic transmission.
SUMMARY OF THE INVENTION
As an improvement EP-OS 0 341 631, e.g., describes a method for control of an overlapping gear in which an introduced first gear shift is not completely carried out when after laps of a blocking time after the shift command for the first gear shift, a shift command for a second gear shift follows within a period of time in which the clutch to be disengaged is still torque conductive and the clutch to be engaged still transmits no torque. In case of a second gear shift command after this moment, that is, at the end of the first and during the second phase of the overlapping gear, it is that the started first gear shift is completely carried out, another blocking time is waited for and then the secondary gear shift is carried out.
The problem thus consists in that mostly a long time offset exists between the driver's wish relative to acceleration and the reaction thereto of the automatic transmission.
According to the invention, the problem is solved by the fact that during an upshift from a first to a second gear the upshift is not completely terminated and a change over to a downshift to the first gear immediately takes place when an abort criterion is detected. The abort criterion is determined from a downshift requirement presettable by the driver.
According to the invention, the solution offers the advantage that the characteristic of the automatic transmission is more closely tied to the driver's desired performance, i.e. unlike in the prior art the upshift immediately is interrupted and a change to the downshift immediately takes place. Due to the closer tie between the characteristic of the automatic transmission and the driver's desired performance, a shorter reaction time is achieved. The automatic transmission acts with more spontaneity.
In development of this, it is proposed that during the upshift from the first to the second reduction step, when the abort criterion has been met, an admissibility be additi
REFERENCES:
patent: 5754968 (1998-05-01), Hedstrom
Popp Christian
Rosi Hansjorg
Tenbrock Friedrich
Wright Dirk
ZF Friedrichshafen AG
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