Speed change control device for belt type continuously variable transmission

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 an engine is input and a secondary pulley connected to an output side of a drive system of a vehicle, and a rotation speed of the engine is varied continuously and output, the method comprising:

• controlling a speed ratio in accordance with a first speed change line when a throttle opening is substantially fully open and a vehicle accelerates during running, and controlling the speed ratio in accordance with a second speed change line, in which an upper limit value of a primary pulley rotation speed is set higher than an upper limit value of the primary pulley rotation speed on the first speed change line, when the throttle opening is substantially fully open and the vehicle starts from standstill;
• counting a number of times the primary pulley rotation speed exceeds a first predetermined rotation speed, which is higher than the upper limit value of the primary pulley rotation speed on the first speed change line, when the throttle opening is substantially fully open and the vehicle starts from standstill;
• and
• controlling the speed ratio in accordance with the first speed change line instead of the second speed change line, even when the throttle opening is substantially fully open and the vehicle starts from standstill, after a counted value exceeds an assurance frequency number, which is a number at which a strength of the belt can be assured.

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 an engine is input and a secondary pulley connected to an output side of a drive system of a vehicle, and a rotation speed of the engine is varied continuously and output, the device comprising:

• speed change control means for controlling a speed ratio in accordance with a first speed change line when a throttle opening is substantially fully open and a vehicle accelerates during running, and controlling the speed ratio in accordance with a second speed change line, in which an upper limit value of a primary pulley rotation speed is set higher than an upper limit value of the primary pulley rotation speed on the first speed change line, when the throttle opening is substantially fully open and the vehicle starts from standstill;
• and
• counting means for counting a number of times the primary pulley rotation speed exceeds a first predetermined rotation speed, which is higher than the upper limit value of the primary pulley rotation speed on the first speed change line, when the throttle opening is substantially fully open and the vehicle starts from standstill,
• wherein the speed change control means controls the speed ratio in accordance with the first speed change line instead of the second speed change line, even when the throttle opening is substantially fully open and the vehicle starts from standstill, after a value counted by the counting means exceeds an assurance frequency number, which is a number at which a strength of the belt can be assured.