US 4,527,678 AGranted

Transmission clutch control system and method

AssigneeFord Motor Company

InventorsStanley L. Pierce, Larry T. Brown, Pramod K. Jain

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Abstract

A control system for transferring torque from a first, offgoing clutch to a second, oncoming clutch while a gear shift is being made includes speed sensors for determining the speeds of the engine shaft and the output shaft of the transmission, a gear selector position indicator, a throttle position indicator and a gear ratio sensor. Solenoid operated valves open and close a source of high pressure fluid to the clutches, whose engagement and disengagement holds the gear elements of the transmission by means of which the various speed ratios are produced. An electronic computer is supplied with the digital equivalent of the shaft speeds, the position of the gear selector and of the throttle. The engine speed-output shaft speed ratio is used as a feedback signal on the basis of which an error between its value and a commanded value is determined. An equation for determining the duty cycle is repetitively calculated and its value converted to a pulse width modulated electrical current that is applied to the solenoid windings. The equation corrects a previously calculated duty cycle with the feedback error value.

Claims12

Dependent claims

A system for transferring torque from one clutch to another clutch in an automotive automatic transmission during the process of changing from an original gear ratio to another gear ratio comprising:

first and second hydraulically actuated clutches;
a sensor which generates a signal that represents the transmission output shaft speed, NO;
a source of pressurized fluid;
an engine shaft sensor which generates a signal that represents the engine rotational speed, NE;
first and second solenoid-operated actuator valves connected to the pressurized fluid source and to the clutches for pressurizing the clutches from the source and for venting the clutches as the solenoid windings are energized and de-energized;
controller means provided with a data base that includes the values of integral gain, K.sub.i, derivative gain, K.sub.d, proportional gain, K.sub.p, commanded NE/NO ratio corresponding to the gear ratio from which a gear shift is made, and current actual NE/NO ratio, adapted to calculate, to store in memory and to recall from memory the current error, E.sub.c, and previous error, E.sub.p, each error representing the difference between the commanded NE/NO ratio and the actual NE/NO ratio, and for repetitively calculating current duty cycle values, DC.sub.c, for the first clutch solenoid from the relationship:
DC.sub.c =DC.sub.p +E.sub.c *K.sub.i +(E.sub.c -E.sub.p)*K.sub.d +K.sub.d +E.sub.c *K.sub.p
where DC.sub.p is the previous duty cycle for the first clutch solenoid;
the controller means being adapted to produce a duty cycle for the second clutch solenoid that increases its clutch pressure while the first clutch solenoid is controlled in accordance with the current duty cycle value;
and
means for converting the current duty cycle of the first clutch and the duty cycle of the second clutch to an electrical current applied to the respective solenoid windings whereby the torque capacity of the first clutch declines and that of the second clutch increases.

8 more elements

A method for controlling, with the aid of a computer having a data base whose contents are accessible to the computer, the transfer of torque from a first clutch to a second clutch in an automatic transmission having speed sensors for indicating the speed of the engine, NE, and of the transmission output shaft, NO, and first and second solenoid-operated actuator valves through which the clutches are pressurized and vented comprising:

storing in the data base integral gain, K.sub.i, derivative, gain, K.sub.d, proportional gain, K.sub.p, and commanded NE/NO ratios corresponding to the gear ratios of the transmission;
determining the error as the difference between the commanded NE/NO ratio and the current actual NE/NO ratio and storing the error value in the computer memory;
calculating at frequent intervals the current duty cycle value, DC.sub.c, for the first clutch solenoid from the relationship:
DC.sub.c =DC.sub.p +E.sub.c *K.sub.i +(E.sub.c -E.sub.p)*K.sub.d +E.sub.c *K.sub.p
wherein DC.sub.p is a duty cycle for the first clutch solenoid calculated using this equation during a previous interval, E.sub.c is the current error, and E.sub.p is an error determined during a previous interval;
producing a duty cycle for the second clutch solenoid which increases in magnitude over the period during which DC.sub.c is being periodically calculated;
converting DC.sub.c and the duty cycle for the second clutch solenoid to electrical currents that are applied to the windings of the first and second clutch solenoids, respectively;
and
pressurizing and venting the first and second clutches in accordance with the duty cycle values.

6 more elements

Dependencies are inferred from the claim text.