Speed change controller for automatic transmission

A speed change controller for outputting a speed change ratio command signal to a transmission of a vehicle for selectively applying plural speed change ratios from a largest speed change ratio to a smallest speed change ratio according to a command input by a driver, said vehicle comprising an engine being capable of exerting an engine brake on said vehicle according to a reduction operation input by the driver, said controlling comprising:

• means for detecting whether or not said vehicle is under the action of said engine brake,
• means for detecting a real speed change ratio of said transmission,
• means for determining whether or not said transmission is performing a shift-down operation,
• means for determining a shift-down limit speed change ratio based on the real speed change ratio before said shift-down operation is performed, wherein the shift-down limit speed change ratio is greater than the real speed change ratio, and
• means for permitting performance of a shift-down operation when said vehicle is under the action of the engine brake until the speed change ratio command signal corresponds to a speed change ratio equal to said shift-down limit speed change ratio.

A speed change controller for outputting a speed change ratio command signal to a transmission of a vehicle for selectively applying plural speed change ratios from a largest speed change ratio to a smallest speed change ratio according to a command input by a driver, said vehicle comprising an engine being capable of exerting an engine brake on said vehicle according to a reduction operation input by the driver, said controller comprising:

• an engine brake sensor for detecting whether or not said vehicle is under the action of said engine brake,
• a real speed change ratio detection sensor for detecting a real speed change ratio of said transmission, and
• a microprocessor programmed to:
• determine whether or not said transmission is performing a shift-down operation,
• set a shift-down limit speed change ratio to a second largest speed change ratio of said plural speed change ratios, wherein the shift-down limit speed change ratio is greater than the real speed change ratio, and
• permit performance of a shift-down operation when said vehicle is under the action of the engine brake until the speed change ratio command signal corresponds to a speed change ratio equal to said shift-down limit speed change ratio.