Control of and control method for vehicle continuously variable transmission

A control device for a vehicle continuously variable transmission comprising:

• a continuously variable transmission mechanism having a speed ratio that can be modified continuously;
• and
• a subtransmission mechanism provided in series with the continuously variable transmission mechanism, including a first gear position and a second gear position, the second gear position having a smaller speed ratio than the first gear position, as forward gear positions, and switching between the first gear position and the second gear position by engaging or disengaging a plurality of frictional engagement elements selectively,
• wherein the control device comprises:
• final speed ratio setting means for setting an overall speed ratio of the continuously variable transmission mechanism and the subtransmission mechanism reachable on the basis of an operating condition of the vehicle as a final speed ratio;
• shift control means for controlling the continuously variable transmission mechanism and the subtransmission mechanism such that the overall speed ratio aligns with the final speed ratio at a predetermined transient response;
• stagnation determining means for determining whether a stagnation period in which the overall speed ratio stops varying will occur during an upshift;
• and
• reduction control means for shortening time required to advance to an inertia phase from commencement of shifting in the subtransmission mechanism following determination that the stagnation period will occur.

A control method for a vehicle continuously variable transmission comprising:

• a continuously variable transmission mechanism having a speed ratio that can be modified continuously;
• and
• a subtransmission mechanism provided in series with the continuously variable transmission mechanism, including a first gear position and a second gear position, the second gear position having a smaller speed ratio than the first gear position, as forward gear positions, and switching between the first gear position and the second gear position by engaging or disengaging a plurality of frictional engagement elements selectively,
• wherein the control method comprises:
• setting, using a transmission controller, an overall speed ratio of the continuously variable transmission mechanism and the subtransmission mechanism reachable on the basis of an operating condition of a vehicle as a final speed ratio;
• controlling, using the transmission controller, the continuously variable transmission mechanism and the subtransmission mechanism such that the overall speed ratio aligns with the final speed ratio at a predetermined transient response;
• determining, using the transmission controller, whether a stagnation period in which the overall speed ratio stops varying will occur during an upshift;
• and
• shortening using the transmission controller, time required to advance to an inertia phase from commencement of shifting in the subtransmission mechanism after determining that the stagnation period will occur.