Method and apparatus for controlling a continuously variable transmission

Claim 1

A method for controlling an automotive vehicle including an engine and a continuously variable transmission which includes a hydrodynamic device having an input element drivingly connected to the engine and an output element, a drive pulley drivingly connected to the output element, a driven pulley, the V-belt running over the drive and driven pulleys, and a lock-up clutch engageable to mechanically connect the input element with the output element, the transmission being shiftable between different reduction ratios and having a shift motor which is movable to different positions for effecting shifting to different reduction ratios, the method comprising: detecting a demand for a rapid acceleration wherein a rapid down shift is needed and generating a rapid down shift need indicative signal; and disengaging the lock-up clutch in response to presence of said rapid down shift need indicative signal so as to allow the engine to increase its revolution speed during the down shift.

Claim 2

A method for controlling an automotive vehicle including an engine and a continuously variable transmission which includes a hydrodynamic device having an input element drivingly connected to the engine and an output element, a drive pulley drivingly connected to the output element, a driven pulley, the V-belt running over the drive and driven pulleys, and a lock-up clutch engageable to mechanically connect the input element with the output element, the transmission being shiftable between different reduction ratios and having a shift motor which is movable to different positions for effecting shifting to different reduction ratios, the method comprising: detecting a demand for a rapid acceleration wherein a rapid down shift is needed and generating a rapid down shift need indicative signal; and disengaging the lock-up clutch in response to presence of said rapid down shift need indicative signal so as to allow the engine to increase its revolution speed during the down shift.

Claim 7

An apparatus for controlling a continuously variable transmission of an automotive vehicle having an internal combustion engine, the transmission including a hydrodynamic device having an input element and an output element, a drive pulley, a driven pulley, a V-belt running over the drive and driven pulleys, and a lock-up clutch engageable to mechanically connect the input element to said output element, the transmission being shiftable between different reduction ratios, the apparatus comprising: means including a shift motor movable to different positions for shifting the transmission to different reduction ratios corresponding uniquely to said positions; means for detecting a demand for a rapid acceleration wherein a rapid down shift is needed and generating a rapid down shift need indicative signal; and means for disengaging the lock-up clutch in response to presence of said rapid down shift need indicative signal to allow the engine to increase its revolution speed during the down shift.

Claim 8

An apparatus for controlling a continuously variable transmission of an automotive vehicle having an internal combustion engine, the transmission including a hydrodynamic device having an input element and an output element, a drive pulley, a driven pulley, a V-belt running over the drive and driven pulleys, and a lock-up clutch engageable to mechanically connect the input element to said output element, the transmission being shiftable between different reduction ratios, the apparatus comprising: means including a shift motor movable to different positions for shifting the transmission to different reduction ratios corresponding uniquely to said positions; means for detecting a demand for a rapid acceleration wherein a rapid down shift is needed and generating a rapid down shift need indicative signal; and means for disengaging the lock-up clutch in response to presence of said rapid down shift need indicative signal to allow the engine to increase its revolution speed during the down shift.

Claim 9

An apparatus for controlling a continuously variable transmission of an automotive vehicle having an internal combustion engine, the transmission including a hydrodynamic device having an input element and an output element, a drive pulley, a driven pulley, a V-belt running over the drive and driven pulley, and a lock-up clutch engageable to mechanically connect the input element to the output element, the transmission being shiftable between reduction ratios, the apparatus comprising: means for detecting a vehicle speed of the automotive vehicle and generating a vehicle speed indicative signal; means for detecting an engine load on the internal combustion engine; means for retrieving a desired optimum reduction ratio for the detected vehicle speed and engine load and generating a desired optimum reduction ratio indicative signal; means for generating an actual reduction ratio indicative signal representing an actual reduction ratio of the continuously variable transmission; means for computing a deviation of the desired optimum reduction ratio indicative signal from the actual reduction ratio indicative signal and generating a deviation indicative signal representing said deviation; means for comparing said deviation with a predetermined value and generating a rapid down shift need indicative signal when said deviation is greater than said predetermined value; a shift motor rotatable between a plurality of rotary positions thereof; means operatively connected to said shift motor to be actuated thereby for shifting the transmission to a reduction ratio corresponding to one of the plurality of rotary positions of said shift motor assumed by said shift motor; means responsive to said vehicle speed indicative signal for engaging the lock-up clutch; and means for disengaging the lock-up clutch temporarily in response to said rapid down shift need indicative signal so as to allow the engine to increase its revolution speed during the rapid down shift.

Claim 10

An apparatus for controlling a continuously variable transmission of an automotive vehicle having an internal combustion engine, the transmission including a hydrodynamic device having an input element and an output element, a drive pulley, a driven pulley, a V-belt running over the drive and driven pulley, and a lock-up clutch engageable to mechanically connect the input element to the output element, the transmission being shiftable between reduction ratios, the apparatus comprising: means for detecting a vehicle speed of the automotive vehicle and generating a vehicle speed indicative signal; means for detecting an engine load on the internal combustion engine; means for retrieving a desired optimum reduction ratio for the detected vehicle speed and engine load and generating a desired optimum reduction ratio indicative signal; means for generating an actual reduction ratio indicative signal representing an actual reduction ratio of the continuously variable transmission; means for computing a deviation of the desired optimum reduction ratio indicative signal from the actual reduction ratio indicative signal and generating a deviation indicative signal representing said deviation; means for comparing said deviation with a predetermined value and generating a rapid down shift need indicative signal when said deviation is greater than said predetermined value; a shift motor rotatable between a plurality of rotary positions thereof; means operatively connected to said shift motor to be actuated thereby for shifting the transmission to a reduction ratio corresponding to one of the plurality of rotary positions of said shift motor assumed by said shift motor; means responsive to said vehicle speed indicative signal for engaging the lock-up clutch; and means for disengaging the lock-up clutch temporarily in response to said rapid down shift need indicative signal so as to allow the engine to increase its revolution speed during the rapid down shift.

Claim 14

A method for controlling an automotive vehicle including an engine and a continuously variable transmission which includes a torque converter having an input element drivingly connected to the engine and an output element, a drive pulley drivingly connected to the output element, a driven pulley, a V-belt running over the drive and driven pulleys, and a lock-up clutch engageable to mechanically connect the input element with the output element, the transmission being shiftable between different reduction ratios continuously, the method comprising: a first step of detecting an operating condition of the automotive vehicle and generating an operating condition indicative signal; a second step of retreiving a desired value indicative of a desired reduction ratio in response to said operating condition indicative signal and generating a desired value indicative signal; a third step of obtaining an actual value indicative of an actual reduction ratio in the continuously variable transmission and generating an actual value indicative signal; a fourth step of computing a deviation of said desired value indicative signal from said actual value indicative signal and generating a deviation indicative signal; a fifth step of comparing said deviation indicative signal with a predetermined reference; a sixth step of disengaging the lock-up clutch; and repeating a routine including said first, second, third, fourth, fifth and sixth steps when said deviation indicative signal satisfies a predetermined relationship with said predetermined reference.

Claim 15

A method for controlling an automotive vehicle including an engine and a continuously variable transmission which includes a torque converter having an input element drivingly connected to the engine and an output element, a drive pulley drivingly connected to the output element, a driven pulley, a V-belt running over the drive and driven pulleys, and a lock-up clutch engageable to mechanically connect the input element with the output element, the transmission being shiftable between different reduction ratios continuously, the method comprising: a first step of detecting an operating condition of the automotive vehicle and generating an operating condition indicative signal; a second step of retreiving a desired value indicative of a desired reduction ratio in response to said operating condition indicative signal and generating a desired value indicative signal; a third step of obtaining an actual value indicative of an actual reduction ratio in the continuously variable transmission and generating an actual value indicative signal; a fourth step of computing a deviation of said desired value indicative signal from said actual value indicative signal and generating a deviation indicative signal; a fifth step of comparing said deviation indicative signal with a predetermined reference; a sixth step of disengaging the lock-up clutch; and repeating a routine including said first, second, third, fourth, fifth and sixth steps when said deviation indicative signal satisfies a predetermined relationship with said predetermined reference.

Claim 16

A method for controlling an automotive vehicle including an engine and a continuously variable transmission which includes a torque converter having an input element drivingly connected to the engine and an output element, a drive pulley drivingly connected to the output element, a driven pulley, a V-belt running over the drive and driven pulleys, and a lock-up clutch engageable to mechanically connect the input element with the output element, the transmision being shiftable between different reduction ratios continuously, the method comprising: a first step of detecting an operating condition of the automotive vehicle and generating an operating condition indicative signal; a second step of retrieving a desired value indicative of a desired reduction ratio in response to said operating condition indicative signal and generating a desired value indicative signal; a third step of obtaining an actual value indicative of an actual reduction ratio in the continuously variable transmission and generating an actual value indicative signal; a fourth step of computing a deviation of said desired value indicative signal from said actual value indicative signal and generating a deviation indicative signal; a fifth step of comparing said deviation indicative signal with a predetermined reference; a sixth step of increasing a timer by a predetermined timer value; a seventh step of comparing the timer with a predetermined elapse time; an eighth step of disengaging the lock-up clutch; a ninth step of setting the timer to zero; a tenth step of comparing the timer with zero; and repeating a first routine including said first, second, third, fourth, fifth, sixth, seventh and eighth steps when said deviation indicative signal satisfies a predetermined relationship with said predetermined reference and said timer is less than said predetermined elapse time; repeating a second routine including said first, second, third, fouth, fifth, sixth, seventh, ninth and eighth steps when said deviation indicative signal satisfies said predetermined relationship with said predetermined reference and said timer is not less than said predetermined elapse time; and repeating a third routine including said first, second, third, fourth, fifth, tenth, sixth, seventh steps when said timer is less than said predetermined elapse time even when said deviation indicative signal fails to satisfy said predetermined relationship with said predetermined reference.

Claim 17

A method for controlling an automotive vehicle including an engine and a continuously variable transmission which includes a torque converter having an input element drivingly connected to the engine and an output element, a drive pulley drivingly connected to the output element, a driven pulley, a V-belt running over the drive and driven pulleys, and a lock-up clutch engageable to mechanically connect the input element with the output element, the transmision being shiftable between different reduction ratios continuously, the method comprising: a first step of detecting an operating condition of the automotive vehicle and generating an operating condition indicative signal; a second step of retrieving a desired value indicative of a desired reduction ratio in response to said operating condition indicative signal and generating a desired value indicative signal; a third step of obtaining an actual value indicative of an actual reduction ratio in the continuously variable transmission and generating an actual value indicative signal; a fourth step of computing a deviation of said desired value indicative signal from said actual value indicative signal and generating a deviation indicative signal; a fifth step of comparing said deviation indicative signal with a predetermined reference; a sixth step of increasing a timer by a predetermined timer value; a seventh step of comparing the timer with a predetermined elapse time; an eighth step of disengaging the lock-up clutch; a ninth step of setting the timer to zero; a tenth step of comparing the timer with zero; and repeating a first routine including said first, second, third, fourth, fifth, sixth, seventh and eighth steps when said deviation indicative signal satisfies a predetermined relationship with said predetermined reference and said timer is less than said predetermined elapse time; repeating a second routine including said first, second, third, fouth, fifth, sixth, seventh, ninth and eighth steps when said deviation indicative signal satisfies said predetermined relationship with said predetermined reference and said timer is not less than said predetermined elapse time; and repeating a third routine including said first, second, third, fourth, fifth, tenth, sixth, seventh steps when said timer is less than said predetermined elapse time even when said deviation indicative signal fails to satisfy said predetermined relationship with said predetermined reference.