Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
1999-11-18
2001-10-09
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S146000, C475S128000
Reexamination Certificate
active
06299565
ABSTRACT:
TECHNICAL FIELD
The invention relates to a control strategy for controlling engagement of a forward drive clutch or a reverse drive clutch in a vehicle driveline that does not include a hydrokinetic torque converter.
BACKGROUND ART
In conventional multiple-ratio transmissions, a hydrokinetic torque converter typically is included in the driveline. It is located between the crankshaft of an internal combustion engine and the multiple-ratio gearing that establishes torque flow paths to the vehicle traction wheels. Attempts have been made to eliminate the torque converter from the driveline in order to eliminate the inherent hydrokinetic efficiency losses at the converter. Elimination of the torque converter also reduces the rotary mass of the torque transfer elements at the input side of the multiple-ratio gearing. A transmission of this kind may be seen by referring to copending U.S. patent application Ser. No. 09/353,289, filed Jul. 15, 1999. This application is assigned to the assignee of the present invention.
A gearing arrangement that is capable of being used with the control strategy of the present invention is shown in U.S. Pat. No. 4,938,097. The strategy of the present invention complements the control strategy shown, for example, in U.S. Pat. No. 5,389,046. The complete hydraulic circuit and electronic control strategy for a transmission of the kind shown in the '097 patent is disclosed in the '046 patent. The '097 patent and the '046 patent, as well as application Ser. No. 09/353,289, are incorporated herein by reference.
DISCLOSURE OF INVENTION
The invention may be used in the control of a forward drive clutch and a reverse drive clutch for a multiple-ratio transmission of the kind disclosed in copending application Ser. No. 09/353,289. It may be used also with a lay shaft manual transmission, where a forward drive clutch and a reverse drive clutch selectively deliver torque to a forward drive torque input gear and to a reverse drive torque input gear. Further, it may be used in a continuously variable transmission having driving and driven sheaves with an endless belt.
Although the invention has been disclosed herein with a transmission having forward and reverse clutches, it may be used also with an auto-clutch, or stand-along clutch, between the engine and the transmission gearing.
The invention comprises control logic that consists of multiple operating modes. These modes include a fill mode during which the clutch is filled with activating fluid, a stroke mode in which the clutch is stroked to a position at which incipient torque transfer will occur, a creep mode during which a minimal torque transfer across the clutch is achieved as the engine throttle is at a zero setting, a drive-away mode during which the engine is operating at an advanced throttle and the clutch is fully engaged, a soft-lock mode which accommodates torque transfer through a slipping clutch, a hard-lock mode during which the clutch is fully engaged, a shift mode wherein the control valve system effects ratio changes in response to changing operating variables for the driveline, a tip-out mode during which torque transfer is controlled as the vehicle operator relaxes the engine throttle quickly, and a tip-in mode during which the engine throttle is advanced rapidly.
The control strategy establishes the conditions that must be met to achieve entry or exit from any of the operating modes for the control system. The driveline variables that establish conditions for entry into or exit from any of the modes are tested during each control loop of the microprocessor. If the exit conditions for any given mode are satisfied, the control logic for the mode that is entered from the existing mode is executed. If the exit conditions are not met for any given mode, the control routine will remain with that current mode and the control logic for that mode will continue to be executed.
The control logic of the invention makes it possible to achieve a rapid and smooth engagement of a friction clutch during vehicle launch in forward drive and reverse drive. It is also possible to achieve a vehicle creep mode, assuming the necessary entry conditions for that mode are detected by the processor whenever the transmission range selector is not in the neutral or park positions and the vehicle brakes are not applied.
The strategy will make it possible to achieve maximum acceleration with maximum engine torque for any given engine speed and for any given engine throttle position. The acceleration is obtained with maximum smoothness during the launch period.
The strategy of the invention will permit transient damping of the clutch by allowing the clutch to slip with a controlled degree of slip during the so-called tip-in and tip-out control states as the engine throttle is rapidly advanced or retarded.
Maximum vehicle acceleration is achieved by controlling the engine speed so that the engine operates at its maximum torque value for any given engine throttle position.
REFERENCES:
patent: 4928227 (1990-05-01), Burba et al.
patent: 4938097 (1990-07-01), Pierce
patent: 5389046 (1995-02-01), Timte et al.
patent: 5577584 (1996-11-01), Ortmann
patent: 6110068 (2000-08-01), Kraska
Jain Pramod Kumar
Jiang Hong
Sankpal Balaram G.
Estremsky Sherry
Ford Global Technologies Inc.
Lewis Tisha D.
McKenzie Frank G.
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