Transmission ratio control system for a continuously variable transmission

Claim 2

A control system for a continuously variable transmission for transmitting power of an engine mounted on a motor vehicle, the engine having a throttle valve, the transmission comprising a drive pulley having a hydraulically shiftable drive disc and a hydraulic cylinder for operating the drive disc, a driven pulley having a hydraulically shiftable driven disc and a hydraulic cylinder for operating the driven disc, a belt engaged with both of said pulleys, the control system comprising a first hydraulic circuit having a pump for supplying oil to both of the hydraulic cylinders, a transmission ratio control valve for controlling the oil supplied to the cylinder of the drive pulley to change a transmission ratio of the transmission to a desired transmission ratio, the system comprising: transmission ratio control means for operating the transmission ratio control valve; a drive pulley speed sensor for producing a drive pulley speed signal; a driven pulley speed sensor for producing a driven pulley speed signal; a throttle position sensor for sensing an opening degree of the throttle valve and for producing a throttle opening degree signal; first calculator means responsive to the drive pulley speed signal and the driven pulley speed signal for producing an actual transmission ratio signal; means responsive to the throttle opening degree signal and to the actual transmission ratio signal for producing a desired transmission ratio signal; second calculator means responsive to the desired transmission ratio signal and to the actual transmission ratio signal for producing a transmission ratio changing speed signal; third calculator means responsive to the throttle opening degree signal for producing a throttle opening degree changing speed signal; coefficient setting means responsive to the driven pulley speed signal as a vehicle speed signal and to the throttle opening degree changing speed signal for producing a correcting coefficient, wherein the correcting coefficient represents an increasing function of the throttle opening degree changing speed signal and a decreasing function of the driven pulley speed signal as said vehicle speed signal in a low vehicle speed range lower than a predetermined vehicle speed; said second calculator means comprising correcting means for correcting the transmission ratio changing speed signal with the correcting coefficient so as to provide a higher transmission ratio changing speed in a low vehicle speed range; and driving means responsive to the transmission ratio changing speed signal corrected by the correcting means for operating the tranmission ratio control means, for controlling the transmission ratio.

Claim 3

The system according to claim 1, wherein the correcting coefficient is a decreasing function of the throttle opening degree changing speed signal and a decreasing function of the driven pulley speed signal in a high vehicle speed range higher than said predetermined vehicle speed.

Claim 4

A control system for a continuously variable transmission for transmitting power of an engine mounted on a motor vehicle, the engine having a throttle valve, the transmission comprising a drive pulley having a hydraulically shiftable drive disc and a hydraulic cylinder for operating the drive disc, a driven pulley having a hydraulically shiftable driven disc and a hydraulic cylinder for operating the driven disc, a belt engaged with both of said pulleys, the control system comprising a first hydraulic circuit having a pump for supplying oil to both of the hydraulic cylinders, a transmission ratio control valve for controlling the oil supplied to the cylinder of the drive pulley to change a transmission ratio of the transmission to a desired transmission ratio, the system comprising: transmission ratio control means for operating the transmission ratio control valve; a drive pulley speed sensor for producing a drive pulley speed signal; a driven pulley speed sensor for producing a driven pulley speed signal; a throttle position sensor for sensing an opening degree of the throttle valve and for producing a throttle opening degree signal; first calculator means responsive to the drive pulley speed signal and the driven pulley speed signal for producing an actual transmission ratio signal; means responsive to the throttle opening degree signal and to the actual transmission ratio signal for producing a desired transmission ratio signal; second calculator means responsive to the desired transmission ratio signal and to the actual transmission ratio signal for producing a transmission ratio changing speed signal; third calculator means responsive to the throttle opening degree signal for producing a throttle opening degree changing speed signal; coefficient setting means responsive to the driven pulley speed signal as a vehicle speed signal and to the throttle opening degree changing speed signal for producing a correcting coefficient, wherein the correcting coefficient represents a decreasing function of the throttle opening degree changing speed signal and a decreasing function of the driven pulley speed signal as said vehicle speed signal in a high vehicle speed range higher than a predetermined vehicle speed; said second calculator means comprising correcting means for correcting the transmission ratio changing speed signal with the correcting coefficient so as to provide a higher transmission ratio changing speed in a low vehicle speed range; and driving means responsive to the transmission ratio changing speed signal corrected by the correcting means for operating the transmission ratio control means, for controlling the transmission ratio.

Claim 5

A control system for a continuously variable transmission for transmitting power of an engine mounted on a motor vehicle, the engine having a throttle valve, the transmission comprising a drive pulley having a hydraulically shiftable drive disc and a hydraulic cylinder for operating the drive disc, a driven pulley having a hydraulically shiftable driven disc and a hydraulic cylinder for operating the driven disc, a belt engaged with both of said pulleys, the control system comprising a first hydraulic circuit having a pump for supplying oil to both of the hydraulic cylinders, a transmission ratio control valve for controlling the oil supplied to the cylinder of the drive pulley to change a transmission ratio of the transmission to a desired transmission ratio, the system comprising: transmission ratio control means for operating the transmission ratio control valve; a drive pulley speed sensor for producing a drive pulley speed signal; a driven pulley speed sensor for producing a driven pulley speed signal; a throttle position sensor for sensing an opening degree of the throttle valve and for producing a throttle opening degree signal; first calculator means responsive to the drive pulley speed signal and the driven pulley speed signal for producing an actual transmission ratio signal; means responsive to the throttle opening degree signal and to the actual transmission ratio signal for producing a desired transmission ratio signal; second calculator means responsive to the desired transmission ratio signal and to the actual transmission ratio signal for producing a transmission ratio changing speed signal; third calculator means responsive to the throttle opening degree signal for producing a throttle opening degree changing speed signal; coefficient setting means responsive to the driven pulley speed signal as a vehicle speed signal and to the throttle opening degree changing speed signal for producing a correcting coefficient, wherein the correcting coefficient represents a decreasing function of the throttle opening degree changing speed signal and a decreasing function of the driven pulley speed signal as said vehicle speed signal in a high vehicle speed range higher than a predetermined vehicle speed; said second calculator means comprising correcting means for correcting the transmission ratio changing speed signal with the correcting coefficient so as to provide a higher transmission ratio changing speed in a low vehicle speed range; and driving means responsive to the transmission ratio changing speed signal corrected by the correcting means for operating the transmission ratio control means, for controlling the transmission ratio.

Claim 6

The system according to claim 3, wherein the correcting coefficient is an increasing function of the throttle opening degree changing sped signal and a decreasing function of the driven pulley speed signal in a low vehicle speed range lower than said predetermined vehicle speed.