Method and system for controlling rate of change of ratio in a continuously variable transmission
AssigneeThe Regents of the University of California
InventorsAndrew A. Frank, Thomas Dreumont
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Abstract
Systems and methods for efficiently and effectively controlling the rate of change of ratio, not simply the ratio, in a CVT. By controlling the rate of change of ratio, the acceleration or deceleration of a vehicle can be controlled in an efficient manner. Furthermore, the rate of change of ratio can be controlled by controlling the clamping pressure of the pulleys and/or differential pressure between the pulleys with minimal slip by using a servo control mechanism adapted for control by a system controller based on equilibrium mapping and other control parameters.
Claims2
A method for controlling the operation of a continuously variable transmission (CVT) having hydraulically operated primary and secondary pulleys with varying effective diameters, and a drive belt coupling the primary pulley to the secondary pulley, comprising:
- providing a programmable controller;
- providing an algorithm or map associated with said controller, wherein said algorithm or map determines clamping pressure and/or differential pressure level between said pulleys in said CVT for achieving a desired rate of change in ratio in said CVT;
- providing a hydraulic servo control system adapted for control by said programmable controller and for control of clamping pressure and/or differential pressure between pulleys in said CVT;
- providing a pressure pump fluidly connected to said secondary pulley;
- wherein said pressure pump has a bypass control valve that opens at low pressures;
- and
- providing a shift pump fluidly connected to said primary pulley;
- wherein said shift pump is fluidly connected to said pressure pump.
A method for optimizing the operation of a continuously variable transmission (CVT) having hydraulically operated primary and secondary pulleys with varying effective diameters, and a drive belt coupling the primary pulley to the secondary pulley, comprising:
- controlling primary and secondary pulley pressure of the CVT to achieve a commanded clamping pressure in response to an input torque command and commanded ratio rate or shift velocity based on a mapping of empirical data relating pressure, ratio rate, and torque;
- providing a pressure pump fluidly connected to said secondary pulley;
- wherein said pressure pump has a bypass control valve that opens at low pressures;
- and
- providing a shift pump fluidly connected to said primary pulley;
- wherein said shift pump is fluidly connected to said pressure pump.
Dependencies are inferred from the claim text.