Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
1999-10-27
2001-09-25
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S061000, C701S064000, C477S046000, C477S068000, C477S091000
Reexamination Certificate
active
06295497
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to continuously variable transmission, and more specifically to a method and apparatus for adaptively shifting ranges in a continuously variable transmission. In particular, the initiation of an engagement of a clutch is varied based on rate of change of transmission ratio or travel speed.
BACKGROUND OF THE INVENTION
Many work machines, particularly earth working machines, use a continuously variable transmission to drive traction wheels or tracks of the work machine. Typically, a hydrostatic drive, consisting of a hydraulic pump and a hydraulic motor, provides a continuously variable speed output to the wheels or tracks of the work machine. In particular, the speed output can be continuously varied by controlling the displacements of either the hydraulic pump or the hydraulic motor which comprise the hydrostatic drive system.
In order to operate over a wide range of operating conditions, the output of the continuously variable hydrostatic transmission is transmitted through a mechanical transmission. The mechanical transmission has a number of discrete transmission ranges corresponding to different operating speeds of the work machine. The combination of the continuously variable transmission and the mechanical transmission allows a continuously variable transmission to operate over a wider range of speeds than is possible using the continuously variable transmission alone.
One drawback to having a number of transmission ranges is that power may not be smoothly transmitted through the transmission during a transmission range shift from one transmission range to another. Typically, an oncoming clutch takes a time to fill the volume of the clutch before actual engagement. Therefore, the acceleration of the work machine must be stopped to wait for the oncoming clutch to be filled and ramped up to pressure. This does not allow a constant and smooth acceleration through the shift. In particular, if a shift is performed before the desired transmission ratio, a shock may be transmitted through the transmission. On the other hand, if the shift is performed after the desired transmission ratio, the shift will appear slow. In either case, the operator has the perception that the transmission ratio is not being smoothly varied.
One of the advantages of the continuously variable transmission is that the continuous variability of the transmission ratio provides the operator with perception that the work machine is operating smoothly. If the shift from one transmission range to another is not performed at the desired transmission ratio, the perception of smooth operation is lost as the operator feels either the shock or the slow shift.
What is needed therefore is a method and apparatus for adaptively shifting ranges in a transmission which overcomes the above-mentioned drawbacks.
DISCLOSURE OF THE INVENTION
In accordance with a first embodiment of the present invention, there is provided a continuously variable transmission. The transmission includes a transmission input speed sensor which generates speed signals indicative of an input speed to the transmission and a transmission output speed sensor which generates speed signals indicative of an output speed of the transmission. The transmission further includes a controller operable to receive the transmission input speed signals and the transmission output speed signals and determine a transmission ratio based on the transmission input speed signal and the transmission output speed signal. The controller is further operable to calculate a rate of change of the transmission ratio and initiate a transmission range shift based on the transmission ratio, the rate, and the predetermined shift completion ratio such that the transmission range shift is completed when the transmission is at the predetermined shift completion ratio.
In accordance with a second embodiment of the present invention, there is provided a work machine having a transmission. The work machine includes a transmission output speed sensor which generates transmission speed signals indicative of an output speed of the transmission. The work machine further includes a controller operable to receive the transmission output speed signal and determine a travel speed of the work machine. The controller is further operable to calculate a rate of change of the travel speed and initiate engagement of a clutch based on the travel speed, the rate, and a predetermined shift completion speed such that the clutch is fully engaged when the work machine is operating at the predetermined shift completion speed.
In accordance with a third embodiment of the present invention, there is provided a method for controlling a continuously variable transmission. The transmission includes a transmission input speed sensor, a transmission output speed sensor, and a controller. The method includes the steps of generating transmission input speed signals indicative of an input speed to the transmission with the transmission input speed sensor and generating transmission output speed signals indicative of an output speed of the transmission with the transmission output speed sensor. The method further includes the steps of receiving the transmission input speed signal and the transmission output speed signals and determining a transmission ratio with the controller and calculating a rate of change of the transmission ratio. The method yet further includes the step of initiating a transmission range shift based on the transmission ratio, the rate, and a predetermined shift completion ratio such that the transmission range shift is completed when the transmission is at the predetermined shift completion ratio.
REFERENCES:
patent: 4531431 (1985-07-01), Dreher et al.
patent: 5054599 (1991-10-01), Marcott
patent: 5105922 (1992-04-01), Yant
patent: 5199313 (1993-04-01), Muller
patent: 5270930 (1993-12-01), Ito et al.
patent: 5301783 (1994-04-01), Malloy
patent: 5337871 (1994-08-01), Testerman
patent: 5343994 (1994-09-01), Kyrtsos
patent: 5467854 (1995-11-01), Creger et al.
patent: 5505100 (1996-04-01), Mitchell et al.
patent: 5551930 (1996-09-01), Creger et al.
patent: 5573473 (1996-11-01), Asayama et al.
patent: 5580332 (1996-12-01), Mitchell et al.
patent: 5586953 (1996-12-01), Abo
patent: 5682315 (1997-10-01), Coutant et al.
patent: 5790968 (1998-08-01), Kashiwabara et al.
Arthur Gertrude
Caterpillar Inc.
Cuchlinski Jr. William A.
Morrison John W.
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