Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
2000-09-18
2001-08-21
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C477S053000, C477S040000, C477S052000, C192S003250, C192S003580, C475S127000, C475S296000
Reexamination Certificate
active
06278926
ABSTRACT:
TECHNICAL FIELD
The invention relates to multiple-ratio automatic transmissions for automotive vehicles and a control system for optimizing and maintaining shift quality.
BACKGROUND ART
Automatic transmissions for automotive vehicles of contemporary design typically include multiple-ratio gearing having torque input gear elements connected drivably to an internal combustion engine through a hydrokinetic torque converter. A driven element of the gearing is drivably connected to a differential axle assembly for vehicle traction wheels. Relative motion of the elements of the gearing is controlled by clutches and brakes that establish plural torque flow paths through the gearing, each torque flow path being associated with a discrete torque ratio.
Ratio changes during forward-drive operation of the vehicle are achieved by engaging and disengaging a friction element, which may be a friction clutch or a friction brake, in the torque flow path. Further, overrunning couplings may cooperate with the friction element during a speed ratio change. As a friction element is engaged, an overrunning coupling is released. When the friction element is disengaged, the overrunning coupling element establishes a mechanical torque flow path through associated gearing elements.
An example of a known multiple-ratio automotive transmission mechanism in an automotive vehicle powertrain may be seen by referring to U.S. Pat. Nos. 5,150,297, 5,081,886, 4,509,389, 5,303,616, 5,474,506 and 5,383,825, each of which is assigned to the assignee of the present invention.
The lowest speed ratio in a transmission of the kind disclosed in the foregoing patents includes an overrunning coupling that serves as a torque reaction brake during operation in the lowest speed ratio. A nonsynchronous upshift to the second lowest speed ratio is achieved by engaging a friction clutch, thereby establishing a nonsynchronous 1-2 upshift. Nonsynchronous ratio changes from the second ratio to the third ratio and from the third ratio to the fourth ratio also are achieved by selectively engaging friction clutches as the state of a companion overrunning coupling changes from a torque delivery mode to an overrunning mode. Such shifts commonly are referred to as nonsynchronous shifts since only a single friction element is involved in the ratio change. The other coupling, which may either be an overrunning brake or an overrunning clutch, need not be disengaged nor released in synchronism with the application or a release of the friction element because the overrunning coupling freewheels the instant the torque flow path through the overrunning coupling is interrupted during a ratio change.
Another example of a known transmission system capable of being used in an automotive vehicle driveline includes a compound planetary gear unit in combination with a simple planetary gear unit, the compound planetary gear unit having three forward-driving ratios. When the simple planetary gear unit is combined with the compound planetary gear unit, either one or two additional ratios are obtained. An example of a transmission of this type can be seen by referring to U.S. Pat. Nos. 5,758,302, 5,586,029 and 5,722,519. These patents, as in the case of the previously described prior art patents, are owned by the assignee of the present invention.
The gearing systems of the '302, '029 and '519 patents have a friction brake and a friction clutch for controlling the relative motion of the elements of the simple planetary gear unit. An overrunning coupling establishes and disestablishes a driving connection between the elements of the simple planetary gear unit. A nonsynchronous 1-2 upshift is achieved as the friction brake is applied and the companion overrunning coupling freewheels. As in the case of the transmission previously described, this 1-2 upshift is a nonsynchronous upshift.
The control systems for such contemporary transmissions are designed initially for the best possible shift quality. They are not capable, however, of accommodating unit variations in the clutch and brake actuators. Neither are they capable of accommodating system characteristic changes during the life of the transmission as the friction elements are subjected to wear.
DISCLOSURE OF INVENTION
The electronic, adaptive, transmission control system of the invention, unlike control systems of the kind described in the U.S. patents discussed in the preceding section, includes a hydraulic circuit with a hydraulic accumulator controller and an adaptive shift quality control strategy, which maintain consistent shift quality to accommodate unit-to-unit variations in the transmission system. It accommodates also changes in the dynamic characteristics of the friction elements of the transmission throughout the life of the transmission.
Shift quality is achieved by controlling the pressure on the spring side of a hydraulic accumulator for the oncoming friction element. The pressure applied to the accumulator is referred to in this description as bias pressure. It is developed by a variable-force solenoid.
The system may include two variable-force solenoids, which provide independent pressure control of both the static and the dynamic capacity of the separate friction elements. During a speed ratio change, a feedback control system is used to control ratio change rate. The shape of the gear ratio change rate profile during the shift is optimized to maintain maximum shift quality.
The transmission controller includes pressure control solenoids that are under the control of a microprocessor that receives powertrain variables at its signal input conditioning portion, including engine control signals and driver activated signals.
An appropriate ratio shift strategy is calibrated initially and is maintained in the ROM portion of the microprocessor memory. The initial powertrain characteristics then depend initially on the initial calibration.
Shift quality consistency is maintained during operation of the powertrain by adapting the commanded clutch pressure and then determining a clutch accumulator bias pressure. At the end of the shift, the adaptive clutch pressure is computed based on linearly extrapolated ratio change time, the time from the start of the shift to the start of the ratio change mode and the initial rate of pressure change. The overall algorithm thus is modified by learned powertrain variables as an adaptive strategy is developed and stored in a keep-alive memory (KAM) portion of the microprocessor.
The microprocessor is a digital micro-controller that receives input continuously from sensors and stores and executes control logic. The logic is modified during continued use of the powertrain as output signals for transmission line pressure control and for accumulator bias pressure control are developed on a real-time basis. Engine speed, turbine speed and output shaft speed are determined from appropriate sensors located in the powertrain hardware. Other inputs are throttle position, manual driver range selector lever position, brake on/off switch state, air conditioner on/off signals, and a transmission temperature signal.
The oncoming friction element pressure, during a shift, is based on control logic. The information that is learned from the input signals on a real-time basis is used to calculate pressures. Digital signals from the microprocessor control electronic driver circuits, which convert the digital signals to electrical current for variable-force solenoids. The solenoids, in turn, control the flow of oil to the friction element actuators based on the input signals. The static and dynamic pressures developed by the solenoids achieves optimum shift quality.
REFERENCES:
patent: 4509389 (1985-04-01), Vahratian et al.
patent: 5081886 (1992-01-01), Person et al.
patent: 5150297 (1992-09-01), Daubenmier et al.
patent: 5157608 (1992-10-01), Sankpal et al.
patent: 5303616 (1994-04-01), Palansky
patent: 5305663 (1994-04-01), Leonard et al.
patent: 5383825 (1995-01-01), El-Khoury et al.
patent: 5460582 (1995-10-01), Palansky et al.
patent: 5474506 (1995-12-01)
Jain Pramod K.
Kuhn Howard Cecil
Vodicka Ronald James
Cuchlinski Jr. William A.
Ford Global Technologies Inc.
McKenzie Frank G.
To Tuan C
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