US 4,514,811 AGranted

Forward drive release system for automatic transmission

AssigneeFord Motor Company

InventorsJohn A. Daubenmier, Elias T. Boueri

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Abstract

A control system for reducing the torque applied to an automotive engine when the vehicle is idling and the transmission is set for operation in an acceptable drive range includes sensors to determine the manual gear selector position, output shaft speed, engine speed, turbine speed, and the throttle valve position. A solenoid operated valve opens and closes a source of high pressure fluid to a clutch whose engagement is required to transmit torque through the transmission from the engine to the drive wheels. An electronic computer is supplied with the digital equivalent of the shaft speeds, the position of the gear selector and of the throttle. An equation for determining the duty cycle of the solenoid valve coils is repetitively calculated through the use of a computer program algorithm. The equation corrects a previously calculated duty cycle with feedback error and terms that are proportional to the magnitude of the present error and the magnitude of the previous error.

Claims9

Dependent claims

A control system for controlling the magnitude of torque transmitted through a clutch of an automatic transmission comprising:

a throttle sensor which generates a signal that represents the throttle opening of a throttle controlled engine;
an engine speed sensor which detects a value that represents the engine rotational speed, NE;
a gear ratio sensor which generates a signal that represents disposition of the gear selector in a forward drive position;
a shaft speed sensor which generates a signal that represents the speed of the vehicle;
a torque converter having an impeller drivably connected to the engine crankshaft and a turbine driven from the impeller;
a turbine speed sensor which generates a value that represents the turbine speed, NT;
a solenoid operated valve that opens and closes communication between a source of pressurized fluid and the clutch and between atmosphere and the clutch, thereby pressurizing and venting the clutch as the solenoid windings are energized and deenergized;
computing means for repetitively computing the duty cycle of the solenoid provided the gear ratio selector is disposed and in an acceptable forward drive position, the throttle setting is equal to or less than a predetermined setting and the vehicle speed is equal to or less than a predetermined speed, having a data base that includes the values of the proportional gain, KP, the derivative gain, KD, and the desired absolute difference between engine speed and turbine speed, L, adapted to repetitively calculate current instantaneous speed difference values .vertline.NE-NT.vertline..sub.c, to store in memory and recall from memory previously calculated instantaneous speed difference values .vertline.NE-NT.vertline..sub.p and previously calculated duty cycle values, DC.sub.p, and to repetitively calculate the current duty cycle, DC.sub.c, from the relationship
DC.sub.c =DC.sub.p -KP(.vertline.NE-NT.vertline..sub.c -L)-KD(.vertline.NE-NT.vertline..sub.c -.vertline.NE-NT.vertline..sub.p);
and
means for converting the binary value of the current duty cycle to an analog current that energizes the solenoid.

8 more elements

A method for controlling with the aid of a digital computer the magnitude of torque transmitted between a throttle engine and an output shaft through a clutch of an automatic transmission having a torque converter turbine and a solenoid valve that operates to engage and disengage the clutch comprising:

providing said computer with a data base that includes at least
a predetermined engine throttle angle,
predetermined transmission gear selector positions,
a predetermined vehicle speed,
the proportional gain, KP,
the derivative gain, KD, and
a desired absolute difference between the engine speed and turbine speed, L;
continually determining and providing the computer with the current throttle opening of the engine, the current speeds of the engine, turbine and vehicle, the current setting of the gear selector and the speeds of the engine and turbine that were determined during a previous computing period;
executing the following steps provided the gear selector is set at one of the predetermined gear selector positions and the throttle angle is equal to or less than the predetermined throttle angle and the vehicle speed is equal to or less than the predetermined vehicle speed;
repetively calculating in the computer at frequent periodic intervals the equation:
DC.sub.c =DC.sub.p -KP(.vertline.NE-NT.vertline..sub.c -L)-KD(.vertline.NE-NT.vertline..sub.c -.vertline.NE-NT.vertline..sub.p)
where
DC.sub.c and DC.sub.p are the current duty cycle and previous duty cycle calculated during a previous computing period;
converting the calculated current duty cycle to a voltage pulse wave;
and
energizing the solenoid valve by applying the voltage pulse wave to the windings of the solenoid.

13 more elements

A method for controlling the magnitude of torque transmitted from a throttle controlled engine through a clutch of an automatic transmission having a torque converter turbine and a gear selector:

executing the following steps provided the gear selector is set at a predetermined gear selector position, the throttle angle, is equal to or less than a predetermined throttle angle and the vehicle speed is equal to or less than a predetermined vehicle speed;
communicating a source of pressurized fluid to the clutch cylinder through a solenoid operated valve when the valve is open and communicating the clutch cylinder to atmosphere when the valve is closed, whereby the clutch is engaged and disengaged as the solenoid is energized and deenergized;
repetitively calculating at frequent periodic intervals while the method is enabled to equation
DC.sub.c =DC.sub.p -KP(.vertline.NE-NT.vertline..sub.c -L)-KD(.vertline.NE-NT.vertline..sub.c -.vertline.NE-NT.vertline..sub.p);
wherein
DC.sub.c is the current duty cycle, DC.sub.p is previous duty cycle calculated during a previous computing period, KP and KD are the proportional gain and differential gain of the control system, respectively, .vertline.NE-NT.vertline..sub.c and .vertline.NE-NT.vertline..sub.p are the absolute current difference between engine speed, NE, and turbine speed, NT, and said speed difference during a previous computing period, respectively, and L is the desired absolute difference between engine speed and turbine speed;
converting the calculated current duty cycle to voltage pulse wave of constant amplitude;
and
energizing and deenergizing the solenoid by applying the voltage wave to the windings of the solenoid.

6 more elements

Dependencies are inferred from the claim text.