Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
1999-10-29
2001-07-03
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S121000
Reexamination Certificate
active
06254511
ABSTRACT:
TECHNICAL FIELD
0
F THE INVENTION
The present invention generally relates to a transmission, and more specifically to a method and apparatus for adaptively controlling clutches based on engine load.
BACKGROUND OF THE INVENTION
Powershift transmissions are used in a variety of work machines where it is desirable to shift gears without interrupting the torque flow through the transmission. To this end, powershift transmissions generally have a clutch overlap period whereby both an off-going and an on-coming clutch are engaged at the same time. If this overlap period is too short, then there will be a torque interruption to an output shaft prior to the engagement of the on-coming clutch. If the overlap period is too long, then the shift will appear to be slow and the transmission will be exposed stresses which can potentially reduce the life of various transmission components.
In addition, a single overlap period may not be desirable for all load conditions. In particular, under high load conditions, it is desirable to increase the overlap period to effectively complete the gear shift. On the other hand, under light load conditions, it is desirable to decrease the overlap period to effectively complete the shift. Moreover, the rate in which the on-coming clutch is engaged may also be varied to improve the shift. Under high load conditions, it is desirable to increase the rate at which the on-coming clutch is engaged whereas under low load conditions, it is desirable to decrease the rate which the on-coming clutch is engaged.
Another problem may arise during double clutch shifts where a pair of on-coming clutches are engaged to accomplish a gear shift. During double clutch shifts, the inertia of a first clutch may be greater than the inertia of a second clutch. It may be desirable to engage the first clutch earlier than the second clutch to compensate for the change in relative inertia of the clutches. Similarly, under different load conditions, it may be desirable to engage the first clutch later than the second clutch to compensate for the change in relative inertia of the clutches.
What is needed therefore is a method and apparatus for adaptively engaging clutches based on engine load which overcomes the above-mentioned drawbacks.
DISCLOSURE OF THE INVENTION
In accordance with a first embodiment of the present invention, there is provided a drive line assembly for a work machine. The drive line assembly includes an engine driving an engine output shaft and an engine speed sensor which generates engine speed signals indicative of a speed of the engine output shaft. The drive line assembly further includes a fuel injector operable to regulate fuel flow to the engine and a transmission driven by the engine output shaft and having a first on-coming clutch. The drive line assembly yet further includes a controller operable to determine the engine speed from the engine speed signals and determine the fuel flow through the fuel injector. The controller is further operable to determine an engine load based on the fuel flow and a predetermined maximum fuel flow for the engine at the engine speed and control engagement of the first on-coming clutch based on the engine load.
In accordance with a second embodiment of the present invention, there is provided a method for controlling a drive line assembly. The drive line assembly includes an engine driving an engine output shaft, an engine speed sensor which generates engine speed signals indicative of a speed of the engine output shaft, a fuel injector operable to regulate fuel flow to the engine, a transmission driven by the engine output shaft and having a first on-coming clutch, and a controller. The method includes the steps of determining engine speed with the controller based on the engine speed signals and determining the fuel flow with the controller. The method further includes the steps of calculating an engine load with the controller based on fuel flow and a predetermined maximum fuel flow for the engine at the engine speed and adaptively controlling the engagement of the first on-coming clutch based on the engine load with the controller.
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Esterby James D.
Lorentz Timothy A.
Ryan Jeffrey T.
Vernagus Kevin A.
Caterpillar Inc.
Estremsky Sherry
Lewis Tisha D.
Morrison John W.
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