Increased automatic gear box spontaneity

Details Increased automatic gear box spontaneity Increased automatic gear box spontaneity

1999-10-04

2001-02-13

Estremsky, Sherry (Department: 3681)

Interrelated power delivery controls, including engine control

Transmission control

Transmission controlled by engine

C477S154000

Reexamination Certificate

active

06186923

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a method for increasing the spontaneity in an automatic transmission in which the gear shifts are carried out as overlapping gear shifts. The overlapping gear shift comprises three phases. During the first phase the curve of a transmission input rotational speed is determined by the pressure curve of the first clutch, during the second phase the second clutch takes over the load from the first clutch and during the third phase the second clutch becomes completely closed.
In automatic transmissions, the gear shifts can be carried out as overlapping gear shifts, i.e. while a first clutch opens a second clutch closes. The pressure curve of the clutches involved in the gear shift is determined via electromagnetic actuators of an electronic transmission control. Such a control and regulation method has been disclosed, e.g. in DE-OS 42 40 621.
Gear shifts of the automatic transmission are usually initiated when a desired performance presettable by a driver, such as throttle valve position, exceeds an upshift or downshift characteristic line of a shift characteristic field. Together with the gear shifts triggered by means of accelerator pedal, a driver has the possibility at any desired moment of triggering manual gear shifts. For example, DE-OS 43 11 886 shows a device by which a driver can trigger gear shifts by means of a selector lever having a manual gate or switching levers on the steering wheel.
The following problem can now arise: during an overtaking operation the driver detects that he must give way to traffic coming from the opposite direction. As a reaction to this, he will interrupt the overtaking operation by releasing the accelerator pedal. Hereby an upshift can be triggered. During the upshift. if the driver now detects that the opposite lane is free, he will then again initiate the overtaking operation. For this purpose, the driver will either actuate the accelerator pedal or initiate a downshift via the selector lever. But according to the prior art, the automatic transmission will first completely carry out the upshift, followed by a blocking time and only then is a downshift begun. The problem thus consists in that a long time offset exists between the driver's wish relative to the acceleration and the reaction thereto of the automatic transmission.
SUMMARY OF THE INVENTION
The invention is based on the problem of improving the spontaneity of an automatic transmission.
According to the invention, the problem is solved during an upshift from a first to a second gear ratio by the upshift not being completely terminated and returning to the first gear ratio when an abort criterion is detected. An abort criterion exists when, prior to the start of the third phase of the overlapping gear shift, a request for a downshift presettable by a driver is detected. The solution, according to the invention, offers the advantage that for the above described practice, the rigid cycle of upshift, blocking time and subsequent downshift is interrupted. Unnecessary gear shifts, such as an upshift from the fourth to the fifth gear followed by a downshift from the fifth to the fourth gear, are eliminated. The characteristic of the automatic transmission is more closely tied to the driver's desired performance, i.e. the automatic transmission acts more spontaneously.
In a development of this, it is proposed that during the second phase the abort criterion be confirmed only when a time step activated with the start of the second phase still has not exceeded a limit value.
In one other development of the invention, it is proposed that during the second phase the abort criterion be confirmed only when the actual transmission input rotational speed value still has not fallen below the synchronous rotational speed of the first gear ratio. Both developments offer the advantage that an abort of the upshift be allowed only in a stage during which the driver still perceives no reaction of the automatic transmission. In other words: an abort of the upshift is no longer allowed when a reaction a driver can perceive, such as change of the vehicle acceleration occurs.
In one other development of the invention, it is proposed that during a change over from coast to traction or viceversa during the gear shift, the abort criterion be confirmed only after lapse of a time step. This develop contributes to comfort when shifting.


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