Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
1999-09-15
2001-01-23
Estremsky, Sherry (Department: 3682)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S121000, C477S154000
Reexamination Certificate
active
06176811
ABSTRACT:
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 while a first clutch opens and a second clutch closes.
In automatic transmissions, the gear shifts can be carried out as overlapping gear shifts while a first clutch opens and a second clutch closes. The pressure curve of the clutches taking part in the gear shift is determined via electromagnetic actuators by an electronic transmission control. Such control and regulation method is known, for ex., from DE-OS 42 40 621.
Gear shifts of the automatic transmission are usually triggered when a desired performance presettable by the driver, e.g. throttle valve position, an upshift or downshift characteristic line of a shift characteristic field, is exceeded. In addition to said gear shifts triggered by means of the accelerator pedal, the driver also has the possibility at any desired time to trigger manual gear shift. DE-OS 43 11 886, e.g. thus 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. In the practice, the problem arises, particularly in downshift with a subsequent upshift, that a sharp divergence appears between the driver's desired performance and corresponding acceleration capacity in relation to the adjusted gear of the automatic transmission. A typical example of this is when a driver intends to overtake another vehicle. At the start of the overtaking operation he will actuate the accelerator pedal so that the automatic transmission carries out a downshift. If the driver notices that he must interrupt the overtaking operation in view of the traffic coming from the opposite direction, he will release the accelerator pedal. The automatic transmission will first carry out a complete downshift, a retention time then elapses and only then does the upshift take place. This time lapse between the driver's desired performance and reaction thereto of the automatic transmission will be felt as disagreeable by a driver.
The problem on which the invention is based now consists in improving the spontaneity of an automatic transmission.
SUMMARY OF THE INVENTION
According to the invention, the problem is solved by the fact that during a downshift from a first to a second gear, the downshift is not completely terminated and a change to an upshift to the first gear takes place when an abort criterion is detected. The abort criterion is met with the detection of a demand for an upshift presettable by a driver.
The solution, according to the invention, offers the advantage that for the case from the practice described above, the actual characteristic of the transmission is closely linked to the driver's desired performance. The downshift is not fully carried out but is immediately interrupted after the driver signalizes this by his behavior. Compared to the prior art the automatic transmission thus acts more spontaneously.
In one development of the invention is proposed that during the downshift from the first to the second gear, when the abort criterion has been met, an admissibility be additionally tested. The admissibility is met when the actual transmission input rotational speed value is within a rotational speed range. The rotational speed range is here defined by a first and a second limit value wherein the first limit value constitutes a function of the synchronous rotational speed value of the first gear and the second limit value, a function of the synchronous rotational speed value of the second gear. In one other development is proposed that, in addition, it be tested whether the curve of the gradient of the transmission input rotational speed is within a preset rotational speed channel.
These two developments of the invention offer the advantage of it being additionally tested whether the curve of the gear shift is stable. Intermediate states critical to safety are thus detected in good time.
In another development, it is proposed that, upon issuance of the shift command for the first clutch, a time stage be started. The time stage extends up to a maximum time, a reduction time being coordinated with each value of the time stage. In development of this, it is proposed that a rapid filling time of the first clutch now is engaged in the upshift be changed depending on the reduction time. The development takes into account the circumstance that in a quick sequence of a downshift with subsequent upshift, the first clutch to be disengaged or is again engaged in the upshift is still partly filled. It is thus achieved by the variable rapid filling time that the first clutch only partly emptied comfortably close in the upshift without jolt.
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patent: 43 11 886 A1 (1995-10-01), None
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patent: 0 341 631 B1 (1989-11-01), None
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Popp Christian
Rosi Hansjorg
Tenbrock Friedrich
Davis and Bujold
Estremsky Sherry
ZF Friedrichshafen AG
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