Control system for continuously variable automatic transmission

A control system for a continuously variable automatic transmission for an automotive vehicle, comprising:

• means for detecting a throttle opening;
• and
• a controller that executes a change-speed control in a normal mode in which a desired transmission input speed is determined based on operating conditions of the vehicle and a desired transmission ratio is determined based on the desired transmission input speed when the throttle opening is less than or equal to a first predetermined throttle opening, and that executes the change-speed control in a first linear mode in which the desired transmission ratio is fixed to a predetermined first value preprogrammed to be suitable for a predetermined first acceleration requirement when the throttle opening is greater than a second predetermined throttle opening and less than or equal to a third predetermined throttle opening and a time rate of increase in the throttle opening is less than or equal to a predetermined time rate of increase, and that executes the change-speed control in a second linear mode in which the desired transmission ratio is fixed to a predetermined second value preprogrammed to be suitable for a predetermined second acceleration requirement higher than the predetermined first acceleration requirement when the throttle opening is greater than the second predetermined throttle opening and less than or equal to the third predetermined throttle opening and the time rate of increase in the throttle opening is greater than the predetermined time rate of increase, and that executes the change-speed control in a third linear mode in which the desired transmission ratio is fixed to a predetermined third value preprogrammed to be suitable for a predetermined third acceleration requirement higher than the predetermined second acceleration requirement when the throttle opening is greater than a fourth predetermined throttle opening, the fourth predetermined throttle opening being greater than the third predetermined throttle opening, the fourth predetermined throttle opening being greater than the third predetermined throttle opening being greater than the second predetermined throttle opening being greater than the first predetermined throttle opening;
• each of the predetermined first, second, and third values being set based on the desired transmission ratio used in the normal mode prior to switching to either of the first, second, and third linear modes.

A method for controlling a continuously variable automatic transmission for an automotive vehicle, the method comprising:

• detecting a throttle opening;
• determining, based on the throttle opening and a time rate of increase in the throttle opening, whether a running mode is a normal mode, a first linear mode, a second linear mode, or a third linear mode;
• executing a change-speed control in the normal mode in which a desired transmission input speed is determined based on operating conditions of the vehicle and a desired transmission ratio is determined based on the desired transmission input speed when the throttle opening is less than or equal to a first predetermined throttle opening;
• executing the change-speed control in the first linear mode in which the desired transmission ratio is fixed to a predetermined first value preprogrammed to be suitable for a predetermined first acceleration requirement when the throttle opening is greater than a second predetermined throttle opening and less than or equal to a third predetermined throttle opening and the time rate of increase in the throttle opening is less than or equal to a predetermined time rate of increase;
• executing the change-speed control in the second linear mode in which the desired transmission ratio is fixed to a predetermined second value preprogrammed to be suitable for a predetermined second acceleration requirement higher than the predetermined first acceleration requirement when the throttle opening is greater than the second predetermined throttle opening and less than or equal to the third predetermined throttle opening and the time rate of increase in the-throttle opening is greater than the predetermined time rate of increase;
• executing the change-speed control in the third linear mode in which the desired transmission ratio is fixed to a predetermined third value preprogrammed to be suitable for a predetermined third acceleration requirement higher than the predetermined second acceleration requirement when the throttle opening is greater than a fourth predetermined throttle opening, the fourth predetermined throttle opening being greater than the third predetermined throttle opening, the fourth predetermined throttle opening being greater than the third predetermined throttle opening being greater than the second predetermined throttle opening being greater than the first predetermined throttle opening;
• and
• setting each of the predetermined first, second, and third values based on the desired transmission ratio used in the normal mode prior to switching to either of the first, second, and third linear modes.