Control apparatus for continuously-variable transmission of vehicle

1. A control apparatus for an automatic transmission of a vehicle, the control apparatus comprising:

a primary pulley including a movable pulley, the primary pulley being connected with an input;

a secondary pulley including a movable pulley, the secondary pulley being connected with an output;

a belt wound around the primary pulley and the secondary pulley;

a shift control valve configured to regulate a hydraulic pressure acting on the movable pulley of the primary pulley;

a step motor configured to be moved to a position in accordance with a target pulley ratio between the primary pulley and the secondary pulley;

a servo link connected to the step motor, the movable pulley of the primary pulley, and the shift control valve, and arranged to move the movable pulley of the primary pulley through the shift control valve in accordance with the position of the step motor;

an actual pulley ratio sensing section configured to sense an actual pulley ratio between the primary pulley and the secondary pulley; and

a control section configured to control the step motor in accordance with the target pulley ratio and the actual pulley ratio sensed by the actual pulley ratio sensing section, the control section including:

a target pulley ratio setting section configured to set the target pulley ratio;

a normal control section configured to perform a normal control to actuate the step motor at a first speed by using a feedback control including an integral control in accordance with the target pulley ratio and the actual pulley ratio;

a high speed control section configured to perform a high speed control to actuate the step motor at a second speed higher than the first speed by an open loop control based on the target pulley ratio;

a judgment section configured to judge whether there is a high speed operation request to perform a shift operation at a high speed; and

a switch section configured to select the normal control performed by the normal control section at a normal condition, and to switch to the high speed control performed by the high speed control section when a switch start condition is satisfied, the switch start condition including a first condition that the judgment section judges there is the high speed operation request.

2. The control apparatus as claimed in claim 1 , wherein the judgment section judges that there is the high speed operation request when a deviation between the target pulley ratio set by the target pulley ratio setting section and the actual pulley ratio sensed by the actual pulley ratio sensing section is equal to or greater than a first predetermined value.

3. The control apparatus as claimed in claim 1 , wherein the switch start condition includes a second condition that a vehicle speed is equal to or greater than a predetermined vehicle speed.

4. The control apparatus as claimed in claim 1 , wherein the switch start condition includes a third condition that a load of an engine connected with the primary pulley is equal to or greater than a predetermined load.

5. The control apparatus as claimed in claim 3 , wherein the switch start condition includes a third condition that a load of an engine connected with the primary pulley is equal to or greater than a predetermined load.

6. The control apparatus as claimed in claim 2 , wherein the switching section switches from the high speed control performed by the high speed control section to the normal control performed by the normal control section when the deviation between the target pulley ratio set by the target pulley ratio setting section, and the actual pulley ratio sensed by the actual pulley ratio sensing section becomes equal to or smaller than a second predetermined value.

7. The control apparatus as claimed in claim 1 , wherein the normal control section includes a compensator configured to compensate a response delay of the step motor, and to have a time constant set in accordance with the first speed.

8. The control apparatus as claimed in claim 1 , wherein the control apparatus further comprises a secondary pressure regulating valve configured to control an engagement pressure between the belt and each of the primary pulley and the secondary pulley and the belt by regulating a secondary hydraulic pressure acting on the movable pulley of the secondary pulley; and the control section is configured to increase the secondary hydraulic pressure through the secondary pressure regulating valve when a secondary pressure increase start condition is satisfied, the secondary pressure increase start condition including the first condition that the judgment section judges that there is the high speed operation request.

9. A control method for an automatic transmission of a vehicle including: a primary pulley including a movable pulley, the primary pulley being connected with an input, a secondary pulley including a movable pulley, the secondary pulley being connected with an output, a belt wound around the primary pulley and the secondary pulley, a shift control valve configured to regulate a hydraulic pressure acting on the movable pulley of the primary pulley, a step motor configured to be moved to a position in accordance with a target pulley ratio between the primary pulley and the secondary pulley, a servo link connected to the step motor, the movable pulley of the primary pulley, and the shift control valve, and arranged to move the movable pulley of the primary pulley through the shift control valve in accordance with the position of the step motor, and an actual pulley ratio sensing section configured to sense an actual pulley ratio between the primary pulley and the secondary pulley, the control method comprising:

controlling the step motor in accordance with the target pulley ratio and the actual pulley ratio sensed by the actual pulley ratio sensing section;

setting the target pulley ratio;

performing a normal control to actuate the step motor at a first speed by using a feedback control including an integral control in accordance with the target pulley ratio and the actual pulley ratio;

performing a high speed control to actuate the step motor at a second speed higher than the first speed by an open loop control based on the target pulley ratio;

judging whether there is a high speed operation request to perform a shift operation at a high speed; and

selecting the normal control performed by the normal control section at a normal condition, and to switch to the high speed control performed by the high speed control section when a switch start condition is satisfied, the switch start condition including a first condition that the judgment section judges there is the high speed operation request.