Automatic transmission auto neutral clutch controls with intermittent slip and a method of control

A power transmission and control in a vehicle comprising:

• a vehicle brake mechanism an engine fuel control for establishing an engine idle condition;
• an input shaft;
• an output shaft;
• a planetary gear arrangement disposed between said input shaft and said output shaft comprising a plurality of fluid operated torque transmitting devices, planetary gear means controlled by selective engagement of said torque transmitting devices at predetermined torque capacities to establish a plurality of drive ratios between the input and output shafts including a plurality of forward ratios, a reverse ratio and neutral condition;
• ratio control means for determining the drive ratio established;
• sensor means for determining the speed of said input shaft and the speed of said output shaft;
• first means for reducing said torque capacity of one of said torque transmitting devices to a first predetermined idle minimum capacity when said output shaft and said input shaft have a zero speed, said vehicle brake mechanism is activated, one of said drive ratios controlled in part by said one torque transmitting device is established and said input speed is increased from zero to a first speed value;
• second means for increasing said torque capacity at a controlled rate until said input speed decreases from said first speed value and a first predetermined idle maximum capacity is achieved;
• third means for increasing said predetermined idle minimum capacity;
• and
• said first means being effective to reduce said torque capacity from said first predetermined idle maximum capacity to said increased predetermined idle minimum capacity.

A method of controlling power transmission in a neutral condition during engine idle, said transmission including;

• a vehicle brake mechanism, an engine fuel control for establishing an engine idle condition, an engine shaft, an input shaft, an output shaft, a planetary gear arrangement disposed between said input shaft and said output shaft comprising a plurality of fluid operated torque transmitting devices, planetary gear means controlled by selective engagement of said torque transmitting devices at predetermined torque capacities to establish a plurality of drive ratios between the input and output shafts including a plurality of forward ratios, a reverse ratio and neutral condition, ratio control means for determining the drive ratio established, and sensor means for determining the speed of said engine shaft, input shaft and the speed of said output shaft;
• said method comprising:
• a) determining the speed of said engine shaft, said input shaft and said output shaft;
• b) determining the drive ratio selected;
• c) determining the slip between the engine shaft and the input shaft;
• d) determine the operating state of the vehicle brakes;
• e) reducing said torque capacity of one of said torque transmitting devices to a first predetermined minimum capacity when said output shaft and said input shaft have a zero speed, said vehicle brake mechanism is activated, one of said drive ratios controlled in part by said one torque transmitting device is established and said input speed is increased from zero to a first speed value and the slip is less than a predetermined value;
• f) repeat steps a) through d);
• g) increasing said torque capacity at a controlled rate until said input speed decreases from said first speed value and a first predetermined idle maximum capacity is achieved;
• h) repeat step e);
• i) increasing said predetermined idle minimum capacity, and reducing said torque capacity from said first predetermined idle maximum capacity to said increased predetermined idle minimum capacity.