Continuously variable transmission control device and control method

A continuously variable transmission control method for a continuously variable transmission, wherein:

• the continuously variable transmission includes a primary pulley at an input side, a secondary pulley at an output side, a belt wound around the primary pulley and the secondary pulley, a secondary pressure control section for controlling a secondary pressure, a primary pressure control section for controlling a primary pressure, a line pressure control section for controlling a line pressure, and a pressure-equalizing control section for performing a pressure-equalizing control to equalize an actual oil pressure of the line pressure with an actual secondary pressure;
• the secondary pressure control section is configured to:
• set a secondary pressure command value on a basis of a required torque transmission capacity, wherein the secondary pressure command value is a command value of the secondary pressure supplied to the secondary pulley;
• and
• control the secondary pressure on a basis of the secondary pressure command value;
• the primary pressure control section is configured to:
• set a primary pressure command value on a basis of a target transmission ratio, wherein the primary pressure command value is a command value of the primary pressure supplied to the primary pulley;
• and
• control the primary pressure on a basis of the primary pressure command value;
• the line pressure control section is configured to:
• set a line pressure command value on a basis of one of the secondary pressure command value and the primary pressure command value, wherein the line pressure command value is a command value of the line pressure;
• and
• control the line pressure on a basis of the line pressure command value;
• and
• the continuously variable transmission control method comprises:
• performing the pressure-equalizing control during a period from a satisfaction of a predetermined start condition to a satisfaction of a predetermined termination condition, wherein the predetermined start condition includes being in a state of operation where the secondary pressure is higher than the primary pressure;
• performing an action during the pressure-equalizing control, wherein the action includes in sequence:
• a secondary pressure raising step of causing the secondary pressure control section to raise the secondary pressure command value by a predetermined quantity;
• a line pressure reducing step of:
• sensing the actual secondary pressure, wherein the actual secondary pressure is an actual oil pressure supplied to the secondary pulley;
• and causing the line pressure control section to reduce the line pressure command value gradually, in response to a determination based on the actual secondary pressure that the secondary pressure raising step is completed;
• and
• a line pressure control step of causing the line pressure control section to control the line pressure in a manner to conform the actual secondary pressure to the secondary pressure command value, in response to a determination based on a decrease of the actual secondary pressure that the actual oil pressure of the line pressure has become equal to the actual secondary pressure;
• and
• while the pressure-equalizing control is being performed, causing the primary pressure control section to calculate a difference between the secondary pressure command value and the actual secondary pressure by subtracting the secondary pressure command value from the actual secondary pressure, and control the primary pressure by performing a pressure-equalizing-control-condition correction control when the difference is negative, wherein the pressure-equalizing-control-condition correction control includes correcting the primary pressure command value on a basis of the difference.