Control apparatus for automatic transmission and control method therefore

A control apparatus for an automatic transmission mounted on a vehicle having a vehicle power train comprising an engine, an automatic transmission having a torque converter, and detecting means for detecting an engine rotating speed, an engine load of said vehicle power train and a vehicle speed of the vehicle, said control apparatus controlling said vehicle power train using signals detected by said detecting means, which control apparatus comprises:

• first characteristic memory means for storing vehicle characteristics;
• first control means for obtaining a driving shaft torque before gear shift using at least signals expressing engine rotating speed, engine load detected by said detecting means and the engine output power characteristic stored in said first characteristic memory means;
• for calculating a value of a driving shaft torque after a gear shift wherein a gear position is shifted using the signals expressing said engine load and vehicle speed;
• and for outputting a gear shifting signal to said automatic transmission at a time when said driving shaft torque before gear shift becomes smaller than the calculated value of said driving shaft torque after the gear shift, plus a certain value;
• second characteristic memory means for storing an engine output power characteristic, a torque converter characteristic and a fuel consumption characteristic;
• and
• second control means for calculating a fuel consuming rate before gear shift, and a fuel consuming rate after gear shift assuming a throttle opening of said engine controlled to maintain engine torque after the gear shift which is equal to engine torque before the gear shift, based on said engine rotating speed, engine load detected by said detecting means and said engine output power characteristic, said torque converter characteristic and said fuel consumption characteristic stored in said second characteristic memory means;
• and outputting a gear shifting signal to said automatic transmission at a time when said fuel consuming rate before the gear shift becomes larger than said fuel consuming rate after the gear shift;
• said first control means and said second control means being switched depending on said running state detected by said detecting means.

A method of controlling an automatic transmission mounted on a vehicle having a vehicle power train comprising an engine, an automatic transmission having a torque converter, and detecting means for detecting an engine rotational speed, an engine load of said vehicle power train and a vehicle speed of the vehicle, said method comprising the steps of:

• storing an engine output power characteristic, torque converter characteristic and fuel consumption characteristic in a characteristic memory;
• calculating a fuel consuming rate before a gear shift, and a fuel consuming rate after the gear shift assuming a throttle opening of said engine controlled to maintain an engine torque after the gear shift which is equal to engine torque before the gear shift, based on said engine rotating speed, said engine load detected by said detecting means, said engine output power characteristic, said torque converter characteristic, and said fuel consumption characteristic stored in said second characteristic memory means;
• and
• outputting a gear shifting signal to said automatic transmission at a time when said fuel consuming rate before the gear shift becomes larger than said fuel consuming rate after the gear shift.

A method of controlling an automatic transmission mounted on a vehicle having a vehicle power train comprising an engine, an automatic transmission having a torque converter, and detecting means for detecting an engine rotational speed, an engine load of said vehicle power train and a vehicle speed of the vehicle, said method comprising the steps of:

• providing a first control method wherein a driving shaft torque before gear shift is determined using signals expressing at least engine rotating speed, engine load detected by said detecting means and the engine output power characteristic stored in a first characteristic memory means;
• a driving shaft torque after gear shift is calculated assuming that a gear position is shifted using the signals expressing said engine load and vehicle speed;
• and a gear shifting signal is output to said automatic transmission at a time when said driving shaft torque before gear shift becomes smaller than the calculated value of said driving shaft torque after the gear shift, plus a certain value;
• providing a second control method wherein a fuel consuming rate before gear shift is calculated;
• a fuel consuming rate after the gear shift is calculated assuming that a throttle opening of said engine is controlled to maintain an engine torque after the gear shift which is equal to engine torque before the gear shift based on said engine rotating speed, said engine load detected by said detecting means, said engine output power characteristic, a torque converter characteristic and a fuel consumption characteristic stored in a second characteristic memory means;
• and a gear shifting signal is output to said automatic transmission at a time when said fuel consuming rate before the gear shift becomes larger than said fuel consuming rate after the gear shift;
• and
• switching control of said automatic transmission between said first control method and said second control method, as a function of an operating state detected by said detecting means.