Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
1999-04-26
2001-05-01
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S055000, C074S335000, C074S336001, C477S120000, C477S124000, C475S123000
Reexamination Certificate
active
06226584
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to a powershift transmission, and more specifically to a method and apparatus for adaptively shifting a powershift transmission.
BACKGROUND OF THE INVENTION
Powershift transmissions control gear ratio changes in accordance with a predetermined shift map which is a function of transmission output speed. In particular, each gear ratio has an associated upshift and downshift point that is preset at the factory. However, each upshift point is a compromise between an aggressive shift point that provides optimum work machine performance and a conservative shift point which prevents hunting, i.e. repetitive upshifting and downshifting. Hunting can cause poor engine performance as well as increase the wear and tear on various transmission components. As a result, if a single upshift point is used, it must be conservative to prevent the undesirable results of hunting.
Conservative shift points occur at higher speeds where it is less likely that the transmission will downshift and begin hunting. When shifting at higher speeds, the power output through the transmission can drop significantly prior to the upshift. This drop in power prior to the upshift is undesirable, especially when rapid acceleration is requested by the operator of the work machine. In fact, during rapid acceleration, a more aggressive shift point can be used with a lessor risk of hunting. Thus, upshifting at the conservative shift point has the drawback of limiting the performance of the work machine when rapid acceleration is requested by the operator.
What is needed therefore is a method and apparatus for adaptively selecting either the aggressive shift point or the conservative shift point which overcomes the above-mentioned drawbacks.
DISCLOSURE OF THE INVENTION
In accordance with a first aspect of the present invention, there is provided a control apparatus for a transmission having a first gear ratio, a second gear ratio, and an output shaft. The apparatus includes an actuator assembly which disengages the first gear ratio from the output shaft and engages the second gear ratio to the output shaft in response to an upshift signal. The apparatus further includes a memory device which stores a conservative upshift point and an aggressive upshift point. The apparatus yet further includes a controller operable to read the aggressive shift point and the conservative shift point from the memory device. The controller is further operable to determine if the transmission is operating in a conservative mode of operation or operating in an aggressive mode of operation. The controller is yet further operable to generate the upshift signal at the aggressive upshift point if the transmission is operating in the aggressive mode of operation or generate the upshift signal at the conservative upshift point if the transmission is operating in the conservative mode of operation.
In accordance with a second aspect of the present invention, there is provided a method of controlling a transmission assembly having a transmission with a first gear ratio, a second gear ratio, and an output shaft; an actuator assembly which disengages the first gear ratio from the output shaft and engages the second gear ratio to the output shaft in response to an upshift signal; a memory device; and a controller. The method includes the steps of storing a conservative upshift point and an aggressive upshift point in the memory device and reading the aggressive shift point and the conservative shift point from the memory device with the controller. The method further includes the steps of determining if the transmission is operating in a conservative mode of operation or operating in an aggressive mode of operation and generating the upshift signal at the aggressive upshift point if the transmission is operating in the aggressive mode of operation or generate the upshift signal at the conservative upshift point if the transmission is operating in the conservative mode of operation.
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Caterpillar Inc.
Cuchlinski Jr. William A.
Morrison John W.
To Tuan
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