Appeal No. 2006-1094
Application No. 09/976,788
impeller. The converter thus contributes to smooth torque transfer from the engine
to the traction wheels (col. 1, ll. 19-25).
Cowan’s controller reduces slip error using a calculation that takes into
account the desired slip less a computed actual slip. The slip error is determined to
be the difference between a desired slip and the measured slip. The difference in
the present error and the error that occurred during a previous background control
loop of the controller is determined and that value is used with a corresponding
value of the present control loop to get a rate of change in the error. A duty cycle
is then computed as a result of that computation so that the bypass clutch control
valve, which is sensitive to changes in duty cycle, will produce a controlled decay
of slip with respect to time. See col. 3, ll. 5-40. The converter slip is measured
using engine RPM and torque converter output shaft speed sensors and that value
is subtracted from the desired slip to obtain the slip error (col. 3, ll. 60-63). The
desired slip depends on information from the throttle position sensor, an engine
speed sensor, a gear shift selector sensor, oil temperature sensor and transition
input shaft speed sensor such that the bypass clutch capacity is adjusted to a value
that is necessary to achieve the desired slip at any given torque. Torque transients
caused by engine operating variables, transmission ratio shifting or throttle
movements are then absorbed by momentary periods of increased slip as the
bypass clutch solenoid output signal is adjusted during each background control
loop of the processor in accordance with the new torque conditions (col. 3, l. 67, to
col. 4, l. 11).
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Last modified: November 3, 2007