Speed change control device for belt type continuously variable transmission and control method thereof

1. A speed change control device for a continuously variable transmission in which a belt is wrapped around a primary pulley into which an output of a drive source is input and a secondary pulley which is connected to an output side of a drive system of a vehicle, and which changes a rotation speed of the drive source continuously and outputs the rotation speed by altering a groove width of the primary pulley and the secondary pulley, the device comprising:

a speed change oil pressure control unit which controls an oil pressure for determining a speed ratio of the continuously variable transmission;

a motor which drives a valve of the speed change oil pressure control unit; and

a controller, wherein

the controller detects a rotation speed of the primary pulley or the secondary pulley, and limits a driving speed of the motor based on a temperature of a working oil of the speed change oil pressure control unit and one or more of the speed ratio of the continuously variable transmission and the detected rotation speed, and

the driving speed of the motor is limited to a lower speed as the temperature of the working oil falls outside of a predetermined temperature range, as the speed ratio shifts toward a low side, and as the detected rotation speed decreases.

2. The speed change control device as defined in claim 1 , further comprising an engine as the drive source,

wherein the controller prohibits limitation of the driving speed when a throttle opening of the engine is smaller than a predetermined low opening.

3. A speed change control method for a continuously variable transmission in which a belt is wrapped around a primary pulley into which an output of a drive source is input and a secondary pulley which is connected to an output side of a drive system of a vehicle, which changes a rotation speed of the drive source continuously and outputs the rotation speed by altering a groove width of the primary pulley and the secondary pulley, and which includes a speed change oil pressure control unit which controls an oil pressure for determining a speed ratio of the continuously variable transmission and a motor which drives a valve of the speed change oil pressure control unit, the method comprising:

detecting a rotation speed of the primary pulley or the secondary pulley; and

limiting a driving speed of the motor based on a temperature of a working oil of the speed change oil pressure control unit and one or more of the speed ratio of the continuously variable transmission and the detected rotation speed, wherein the driving speed of the motor is limited to a lower speed as the temperature of the working oil falls outside of a predetermined temperature range, as the speed ratio shifts toward a low side, and as the detected rotation speed decreases.

4. The speed change control method as defined in claim 3 , wherein an engine is the drive source,

wherein the limiting a driving speed of the motor prohibits limitation of the driving speed when a throttle opening of the engine is smaller than a predetermined low opening.

5. A speed change control device for a continuously variable transmission in which a belt is wrapped around a primary pulley into which an output of a drive source is input and a secondary pulley which is connected to an output side of a drive system of a vehicle, and which changes a rotation speed of the drive source continuously and outputs the rotation speed by altering a groove width of the primary pulley and the secondary pulley, the device comprising:

pulley rotation speed detecting means for detecting a rotation speed of the primary pulley or the secondary pulley;

a speed change oil pressure control unit which controls an oil pressure for determining a speed ratio of the continuously variable transmission;

a motor which drives a valve of the speed change oil pressure control unit; and

driving speed limiting means for limiting a driving speed of the motor based on a temperature of a working oil of the speed change oil pressure control unit and one or more of the speed ratio of the continuously variable transmission and the detected rotation speed,

wherein the driving speed of the motor is limited to a lower speed as the temperature of the working oil falls outside of a predetermined temperature range, as the speed ratio shifts toward a low side, and as the detected rotation speed decreases.

6. The speed change control device as defined in claim 5 , further comprising an engine as the drive source,

wherein the driving speed limiting means prohibits limitation of the driving speed when a throttle opening of the engine is smaller than a predetermined low opening.

7. The speed change control device as defined in claim 1 , wherein the controller limits the driving speed of the motor based on the temperature of the working oil of the speed change oil pressure control unit, the speed ratio of the continuously variable transmission, and the detected rotation speed.

8. The speed control method as defined in claim 3 , wherein limiting the driving speed limits the driving speed of the motor based on the temperature of the working oil of the speed change oil pressure control unit, the speed ratio of the continuously variable transmission, and the detected rotation speed.

9. The speed change control device as defined in claim 5 , wherein the driving speed limiting means limits the driving speed of the motor based on the temperature of the working oil of the speed change oil pressure control unit, the speed ratio of the continuously variable transmission, and the detected rotation speed.

10. The speed change control device as defined in claim 1 , wherein a highest temperature in the predetermined temperature range is lower than a temperature at which a required oil pressure cannot be secured and a lowest temperature in the predetermined temperature range is higher than a temperature at which the motor falls out of step.

11. The speed control method as defined in claim 3 , wherein a highest temperature in the predetermined temperature range is lower than a temperature at which a required oil pressure cannot be secured and a lowest temperature in the predetermined temperature range is higher than a temperature at which the motor falls out of step.

12. The speed change control device as defined in claim 5 , wherein a highest temperature in the predetermined temperature range is lower than a temperature at which a required oil pressure cannot be secured and a lowest temperature in the predetermined temperature range is higher than a temperature at which the motor falls out of step.