Controller for continuously variable transmission and control method thereof

1. A controller for controlling a continuously variable transmission including a variator with a primary pulley at an input side for changing a groove width by a hydraulic pressure, a secondary pulley at an output side for changing a groove width by a hydraulic pressure and a power transmission member mounted between the primary pulley and the secondary pulley, and a torque converter arranged between a drive source and the variator, comprising:

a rotational speed detecting unit configured to detect the rotational speed of a rotor located closer to drive wheels than the torque converter;

a rotational speed change amount calculating unit configured to calculate a change amount in the rotational speed per unit time;

a limit setting unit configured to set a higher absolute value of a limiter for the change amount as a rotational speed difference between an input shaft and an output shaft of the torque converter increases;

a final change amount setting unit configured to set the smaller one of the absolute value of the change amount and that of the limiter as a final change amount; and

a hydraulic control unit configured to control a hydraulic pressure to be supplied to the variator based on the final change amount.

2. The controller according to claim 1 further comprising an input torque calculating unit configured to calculate an input torque to be input to the variator based on the final change amount, wherein:

the hydraulic control unit is configured to control the hydraulic pressure to be supplied to the variator based on the input torque.

3. The controller according to claim 1 , wherein:

the rotational speed detecting unit is configured to detect the rotational speed based on a pulse signal given by the rotation of the rotor; and

the limit setting unit is configured to increase the absolute value of the limiter as the rotational speed of the rotor increases.

4. The controller according to claim 1 , wherein the final change amount setting unit is configured to set the change amount as the final change amount if the change amount is negative.

5. A control method for controlling a continuously variable transmission including a variator with a primary pulley at an input side for changing a groove width by a hydraulic pressure, a secondary pulley at an output side for changing a groove width by a hydraulic pressure and a power transmission member mounted between the primary pulley and the secondary pulley, and a torque converter arranged between a drive source and the variator, comprising:

detecting by a controller, the rotational speed of a rotor located closer to drive wheels than the torque converter;

calculating by the controller, a change amount in the rotational speed per unit time;

setting by the controller, a higher absolute value of a limiter for the change amount as a rotational speed difference between an input shaft and an output shaft of the torque converter increases;

setting by the controller, the smaller one of the absolute value of the change amount and that of the limiter as a final change amount; and

controlling by the controller, a hydraulic pressure to be supplied to the variator based on the final change amount.

6. The control method according to claim 5 , further comprising calculating by the controller, an input torque to be input to the variator based on the final change amount, wherein:

the hydraulic pressure to be supplied to the variator is controlled by the controller based on the input torque.

7. The control method according to claim 5 , wherein:

the rotational speed is detected by the controller based on a pulse signal given by the rotation of the rotor; and

the absolute value of the limiter is increased by the controller as the rotational speed of the rotor increases.

8. The control method according to claim 5 , wherein the change amount is set by the controller as the final change amount if the change amount is negative.

9. A controller for controlling a continuously variable transmission including a variator with a primary pulley at an input side for changing a groove width by a hydraulic pressure, a secondary pulley at an output side for changing a groove width by a hydraulic pressure and a power transmission member mounted between the primary pulley and the secondary pulley, and a torque converter arranged between a drive source and the variator, comprising:

rotational speed detecting means for detecting the rotational speed of a rotor located closer to drive wheels than the torque converter;

rotational speed change amount calculating means for calculating a change amount in the rotational speed per unit time;

limit setting means for setting a higher absolute value of a limiter for the change amount as a rotational speed difference between an input shaft and an output shaft of the torque converter increases;

final change amount setting means for setting the smaller one of the absolute value of the change amount and that of the limiter as a final change amount; and

hydraulic control means for controlling a hydraulic pressure to be supplied to the variator based on the final change amount.

10. The controller according to claim 9 , further comprising input torque calculating means for calculating an input torque to be input to the variator based on the final change amount, wherein:

the hydraulic control means controls the hydraulic pressure to be supplied to the variator based on the input torque.

11. The controller according to claim 9 , wherein:

the rotational speed detecting means detects the rotational speed based on a pulse signal given by the rotation of the rotor; and

the limit setting means increases the absolute value of the limiter as the rotational speed of the rotor increases.

12. The controller according to claim 9 , wherein the final change amount setting means sets the change amount as the final change amount if the change amount is negative.