Controller for continuously variable transmission

1. A controller for a continuously variable transmission mounted in a vehicle which has an engine and a cruise control system for maintaining a target vehicle speed, said controller comprising:

basic speed ratio setting means for setting a basic speed ratio of said continuously variable transmission based on said target vehicle speed;

adjustment speed ratio setting means for sequentially setting an adjustment speed ratio of said continuously variable transmission based on a target torque interrelated value which is a value interrelated with a target torque of said engine; and

speed ratio control means for controlling said continuously variable transmission so that an actual speed ratio of said continuously variable transmission becomes equal to a target speed ratio obtained by adding said adjustment speed ratio set by said adjustment speed ratio setting means to said basic speed ratio set by said basic speed ratio setting means;

wherein said adjustment speed ratio setting means comprises

adjustment speed ratio increasing means for progressively increasing said adjustment speed ratio according to an increase in said target torque interrelated value only when said target torque interrelated value is increased and when an operating point determined by said target torque interrelated value and adjustment speed ratio is present on a first operating area, and

adjustment speed ratio decreasing means for progressively decreasing said adjustment speed ratio according to a decrease in said target torque interrelated value only when said target torque interrelated value is decreased and when said operating point is present on a second operating area;

and wherein, when said operating point is present within a third operating area between said first operating area and said second operating area, said adjustment speed ratio setting means maintains said adjustment speed ratio that is set finally.

2. The controller according to claim 1 , wherein said adjustment speed ratio setting means sets a maximum value and a minimum value of said adjustment speed ratio.

3. The controller according to claim 2 , wherein

said adjustment speed ratio setting means includes an adjustment speed ratio map for setting said adjustment speed ratio based on said target torque interrelated value;

said first operating area is provided on an adjustment speed ratio increasing line which forms part of said adjustment speed ratio map;

said second operating area is provided on an adjustment speed ratio decreasing line which forms part of said adjustment speed ratio map;

if said target torque interrelated value is increased over said adjustment speed ratio increasing line, said adjustment speed ratio setting means sets said adjustment speed ratio along said adjustment speed ratio increasing line; and

if said target torque interrelated value is decreased under said adjustment speed ratio decreasing line, said adjustment speed ratio setting means sets said adjustment speed ratio along said adjustment speed ratio decreasing line.

4. The controller according to claim 3 , wherein said target torque interrelated value is expressed in accelerator pedal position.

5. The controller according to claim 3 , wherein said target torque interrelated value is expressed in throttle opening.

6. The controller according to claim 3 , wherein said target torque interrelated value is expressed in fuel injection quantity.

7. The controller according to claim 2 , wherein said target torque interrelated value is expressed in accelerator pedal position.

8. The controller according to claim 2 , wherein said target torque interrelated value is expressed in throttle opening.

9. The controller according to claim 2 , wherein said target torque interrelated value is expressed in fuel injection quantity.

10. The controller according to claim 1 , wherein

said adjustment speed ratio setting means includes an adjustment speed ratio map for setting said adjustment speed ratio based on said target torque interrelated value;

said first operating area is provided on an adjustment speed ratio increasing line which forms part of said adjustment speed ratio map;

said second operating area is provided on an adjustment speed ratio decreasing line which forms part of said adjustment speed ratio map;

if said target torque interrelated value is increased over said adjustment speed ratio increasing line, said adjustment speed ratio setting means sets said adjustment speed ratio along said adjustment speed ratio increasing line; and

if said target torque interrelated value is decreased under said adjustment speed ratio decreasing line, said adjustment speed ratio setting means sets said adjustment speed ratio along said adjustment speed ratio decreasing line.

11. The controller according to claim 10 , wherein said target torque interrelated value is expressed in accelerator pedal position.

12. The controller according to claim 10 , wherein said target torque interrelated value is expressed in throttle opening.

13. The controller according to claim 10 , wherein said target torque interrelated value is expressed in fuel injection quantity.

14. The controller according to claim 1 , wherein said target torque interrelated value is expressed in accelerator pedal position.

15. The controller according to claim 1 , wherein said target torque interrelated value is expressed in throttle opening.

16. The controller according to claim 1 , wherein said target torque interrelated value is expressed in fuel injection quantity.