US 5,683,326 AGranted

Toroidal continuous variable transmission

AssigneeIsuzu Motors Limited

InventorEiji Inoue

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Abstract

This toroidal continuous variable transmission detects a deviation of the spool valve from its neutral position and performs a feedback control to prevent the transmission ratio from converging on other than the target transmission ratio or the speed change sequence from being started again. Further, the toroidal continuous variable transmission performs control so that as the actual transmission ratio approaches the target transmission ratio, the transmission speed decreases in order to prevent an overshoot of the speed change control. When the difference between the actual transmission ratio and the target transmission ratio is smaller than a specified value, the output signals to the solenoid valves are controlled so that the pressure difference between the pilot pressures acting on the ends of the spool valves is proportional to the difference between the actual transmission ratio and the target transmission ratio. When the difference between the actual transmission ratio and the target transmission ratio exceeds the specified value, the target transmission speed is set according to the difference and the output signals to the solenoid valves are controlled so that the pressure difference between the pilot pressures acting on the ends of the spools is proportional to the difference between the actual transmission speed and the target transmission speed.

Claims7

Dependent claims

A toroidal continuous variable transmission comprising:

an input disk;
an output disk arranged opposite the input disk;
a pair of power rollers which continuously change and transmit the rotation of the input disk to the output disk according to changes in a tilt angle of the power rollers with respect to the input disk and the output disk;
a pair of trunnions that each rotatably support the power rollers and can be displaced in the direction of a tilt axis;
hydraulic cylinders each having two cylinder chambers to move the trunnions in the direction of the tilt axis;
a spool valve having a spool to regulate oil pressure supplied to the hydraulic cylinders, the spool valve being adapted to cut off the cylinder chambers when the spool is at a neutral position and to selectively communicate the cylinder chambers to an oil pressure source and a tank when the spool is shifted from the neutral position;
solenoid valves that control the positions of the spool;
and
a controller that outputs to the solenoid valves duties corresponding to the difference between an actual transmission ratio and a target transmission ratio;
wherein when a correction execution condition is satisfied, the controller performs a correction control on the neutral position of the spool valve by integrating with respect to time the difference between the actual transmission ratio and the target transmission ratio to calculate an integrated error, determining an amount of duty correction that corresponds to the error of the neutral position of the spool valve based on the integrated error, and correcting the duty with the amount of duty correction thus determined.

7 more elements

A toroidal continuous variable transmission comprising:

an input disk;
an output disk arranged opposite the input disk;
a pair of power rollers which continuously change and transmit the rotation of the input disk to the output disk according to changes in a tilt angle of the power rollers with respect to the input disk and the output disk;
a pair of trunnions that each rotatably support the power rollers and can be displaced in the direction of a tilt axis;
hydraulic cylinders each having two cylinder chambers to move the trunnions in the direction of the tilt axis;
a spool valve having a spool to regulate oil pressures supplied to the hydraulic cylinders, the spool valve being adapted to cut off the cylinder chambers when the spool is at a neutral position and to selectively communicate the cylinder chambers to an oil pressure source and a tank when the spool is shifted from the neutral position;
solenoid valves that control pilot pressures acting on the ends of the spool;
and
a controller that sets a target transmission speed according to the difference between an actual transmission ratio and a target transmission ratio and controls output signals to the solenoid valves in such a way that the difference between the pilot pressures acting on the ends of the spool is proportional to the difference between the actual transmission speed and the target transmission speed.

6 more elements

Dependencies are inferred from the claim text.