Shift control method and system for an automatic transmission

A shift control method for an automatic transmission using a shift pattern including at least one vehicle-speed-relevant shift line and at least one throttle-opening-relevant shift line for specific gear-shifting depending on a vehicle speed and a throttle opening,

• wherein one reference gradient is selected from a plurality of reference gradients depending on whether a vehicle speed change and a throttle opening change for a predetermined time are a positive value or a negative value, and one shift line is selected from at least one vehicle-speed-relevant shift line and at least on throttle-opening-relevant shift line on the basis of a comparison of an operating point changing gradient and the selected reference gradient, the operating point changing gradient being calculated as a ratio of the calculated throttle opening change to the vehicle speed change,
• wherein the plurality of reference gradients comprises:
• a first reference gradient for a case when a vehicle speed change and a throttle opening change are respectively positive values;
• a second reference gradient for a case when the vehicle speed change is a positive value and the throttle opening change is a negative value;
• a third reference gradient for a case when a vehicle speed change and a throttle opening change are respectively negative values;
• and
• a fourth reference gradient for a case when the vehicle speed change is a negative value and the throttle opening change is a positive value, and
• wherein when the calculated vehicle speed change and the calculated throttle opening change are respectively positive values, the shift control is performed according to the throttle-opening-relevant shift line if the operating point changing gradient is greater than the first reference gradient and according to the vehicle-speed-relevant shift line if the operating point changing gradient is not greater than the first reference gradient,
• wherein when the calculated vehicle speed change is a positive value and the calculated throttle opening change is a negative value, the shift control is performed according to the throttle-opening-relevant shift line if the operating point changing gradient is less than the second reference gradient and according to the vehicle-speed-relevant shift line if the operating point changing gradient is not less than the second reference gradient,
• wherein when the calculated vehicle speed change and the calculated throttle opening change are respectively negative values, the shift control is performed according to the throttle-opening-relevant shift line if the operating point changing gradient is greater than the third reference gradient and according to the vehicle-speed-relevant shift line if the operating point changing gradient is not greater than the third reference gradient, and
• wherein when the calculated vehicle speed change is a negative value and the calculated throttle opening change is a positive value, the shift control is performed according to the throttle-opening-relevant shift line if the operating point changing gradient is less than the fourth reference gradient and according to the vehicle-speed-relevant shift line if the operating point changing gradient is not less than the fourth reference gradient.

A shift control system for an automatic transmission, comprising:

• at least one sensor including a vehicle speed sensor for detecting a vehicle speed and a throttle position sensor for detecting a throttle opening;
• a control unit for performing a shift control on the basis of signals from the at least one sensor;
• and
• a shift control actuator for performing a specific shift in response to the shift control of the control unit,
• wherein the control unit stores a plurality of reference gradients depending on whether a vehicle speed change and a throttle opening change for a predetermined time are a positive value or a negative value and at least one vehicle-speed-relevant shift line and at least one throttle-opening-relevant shift line for specific gear-shifting depending on a vehicle speed and a throttle opening, and
• wherein the control unit executes instructions for selecting a shift line from the at least one vehicle-speed-relevant shift line and the at least one throttle-opening-relevant shift line on the basis of a vehicle speed change and a throttle opening change for a predetermined time, and
• wherein the control unit is configured to select the shift line by:
• calculating the vehicle speed change and the throttle opening change for the predetermined time;
• selecting one reference gradient from a plurality of predetermined reference gradients, on the basis of the calculated vehicle speed change and the calculated throttle opening change;
• and
• selecting one shift line from the at least one vehicle-speed-relevant shift line and the at least one throttle-opening-relevant shift line, on the basis of a comparison of an operating point changing gradient and the selected reference gradient, the operating point changing gradient being calculated as a ratio of the calculated throttle opening change to the vehicle speed change.