Control apparatus and method for automatic transmission

A control apparatus for an automatic transmission, the control apparatus comprising:

• a stepwise variable transmission mechanism including a plurality of engagement portions having a first engagement portion and a second engagement portion, the stepwise variable transmission mechanism being arranged to attain a target shift stage by combining a disengagement or an engagement of each of the engagement portions;
• a power ON/OFF state judging section configured to judge a power ON/OFF state;
• and
• a shift control section configured to control the stepwise variable transmission mechanism to a target rotational speed by disengaging the first engagement portion and engaging the second engagement portion in accordance with a torque inputted to the stepwise variable transmission mechanism,
• the shift control section being configured to immediately engage one of the first engagement portion and the second engagement portion which has a function to suppress a variation of an input rotational speed of the stepwise variable transmission mechanism which is generated by switching of the power ON/OFF state when the power ON/OFF state is switched at a shift control of the stepwise variable transmission mechanism, and to immediately disengage the other of the first engagement portion and the second engagement portion,
• wherein the shift control section is configured to disengage the second engagement portion formerly to be engaged during shifting on an engagement side when the power ON/OFF state is switched during a torque phase which is precedent to an inertia phase at the shift control of the stepwise variable transmission mechanism, and to engage the first engagement portion formerly to be disengaged during shifting on a disengagement side to suppress, by the first engagement portion on the disengagement side, a variation of the input rotational speed of the stepwise variable transmission mechanism which is caused by switching of the power ON/OFF state.

A control apparatus for an automatic transmission, the control apparatus comprising:

• a stepwise variable transmission mechanism including a plurality of engagement portions having a first engagement portion and a second engagement portion, the stepwise variable transmission mechanism being arranged to attain a target shift stage by combining a disengagement or an engagement of each of the engagement portions;
• a power ON/OFF state judging section configured to judge a power ON/OFF state;
• and
• a shift control section configured to control the stepwise variable transmission mechanism to a target rotational speed by disengaging the first engagement portion and engaging the second engagement portion in accordance with a torque inputted to the stepwise variable transmission mechanism,
• the shift control section being configured to engage one of the first engagement portion and the second engagement portion which has a function to suppress a variation of an input rotational speed of the stepwise variable transmission mechanism which is generated by switching of the power ON/OFF state when the power ON/OFF state is switched at a shift control of the stepwise variable transmission mechanism, and to disengage the other of the first engagement portion and the second engagement portion,
• wherein the control apparatus further comprises a continuously variable transmission mechanism configured to cooperate with the stepwise variable transmission mechanism, and thereby to attain a target transmission ratio,
• wherein the continuously variable transmission mechanism starts cooperative control with the stepwise variable transmission mechanism when the power ON/OFF state is switched.

A control method for an automatic transmission, the automatic transmission including a stepwise variable transmission mechanism including a plurality of engagement portions having a first engagement portion and a second engagement portion, the stepwise variable transmission mechanism being arranged to attain a target shift stage by combining a disengagement or an engagement of each of the engagement portions, the control method comprising:

• judging a power ON/OFF state;
• controlling the stepwise variable transmission mechanism to a target rotational speed by disengaging the first engagement portion and engaging the second engagement portion in accordance with a torque inputted to the stepwise variable transmission mechanism;
• engaging one of the first engagement portion and the second engagement portion which has a function to suppress a variation of an input rotational speed of the stepwise variable transmission mechanism which is generated by switching of the power ON/OFF state when the power ON/OFF state is switched at shift control of the stepwise variable transmission mechanism;
• and
• disengaging the other of the first engagement portion and the second engagement portion;
• wherein immediate disengagement of the second engagement portion occurs on an engagement side formerly to be engaged during shifting when the power ON/OFF state is switched during an inertia phase at the shift control of the stepwise variable transmission mechanism;
• and
• wherein immediate engagement of the first engagement portion occurs on a disengagement side formerly to be disengaged during shifting to suppress, by the first engagement portion on the disengagement side, the variation of the input rotational speed of the stepwise variable transmission mechanism which is caused by switching of the power ON/OFF state.