CVT Hydraulic Pump Control for Belt Slip-Free Downshifting
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Solution Overview
Problem
Existing continuously variable transmission systems face challenges in effectively suppressing belt slip, particularly during downshifting, due to inadequate control over oil pressure and flow rates, leading to potential belt slip on the primary pulley side.
Innovation Solution
A controller is implemented to manage the shift oil pump's rotation direction and oil flow between the primary and secondary pulley hydraulic chambers, using feedback control to maintain target speed ratios and prevent oil pressure from falling below the minimum required to prevent belt slip, by calculating and limiting the current command value to ensure sufficient oil pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the flow rate of the second oil pump is controlled to achieve a target speed ratio, then the speed ratio control is improved, but the belt slip suppression is insufficient
Solution Approach 1:
The control device calculates a required oil pressure to suppress belt slip based on the relationship between engine output torque and belt clamping force, then compares this with the actual oil pressure from the second oil pump. Based on this feedback comparison, the control device adjusts the second oil pump's rotation speed to ensure the actual oil pressure meets the required level, thereby suppressing belt slip while maintaining speed ratio control
Solution Approach 2:
The control device dynamically changes the rotation speed parameter of the second oil pump based on real-time operating conditions. By calculating the required oil pressure from the belt slip suppression requirement and adjusting the pump speed accordingly, the system adapts to varying torque and speed ratio conditions to maintain optimal belt grip
2Productivity
If the second oil pump is used to adjust oil in/out from the primary oil chamber for speed ratio control, then the speed ratio adjustment is improved, but the oil pressure may fall below the minimum required to prevent belt slip
Solution Approach 1:
The control device continuously monitors the actual oil pressure generated by the second oil pump and compares it with the calculated required oil pressure for belt slip suppression. When the actual pressure is insufficient, the feedback mechanism increases the pump's rotation speed to raise the pressure to the required level, ensuring belt slip prevention is prioritized
Solution Approach 2:
The control device proactively calculates the required oil pressure based on engine torque and speed ratio conditions before belt slip occurs. By anticipating the pressure requirements and adjusting the pump speed in advance, the system prevents belt slip rather than merely responding to it
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively suppresses belt slip by maintaining optimal oil pressure and flow rates, optimizing the operation of the shift oil pump and ensuring consistent transmission performance.
Implementation Method 1
a shift oil pump configured to pump the hydraulic oil from the secondary pulley side to the primary pulley side
Implementation Method 2
controlling the rotation direction of the shift oil pump to adjust the oil in/out to/from the primary oil chamber
Data Source
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AI summary
A method for controlling a continuously variable transmission is a control method for controlling in/out of oil to/from a primary oil chamber by using an oil pump provided in an oil passage between the primary oil chamber and a secondary oil chamber. The method for controlling the continuously variable transmission includes: a current command value calculation step of calculating a current command value for the oil pump in accordance with an operating state; a current limiting step of limiting the current command value to a lower-limit current at which belt slip does not occur when an oil pressure in the primary oil chamber falls below a lower-limit oil pressure in the primary oil chamber at which the belt slip does not occur; and a pump control step of driving the oil pump by using the current command value to control a piston position of the primary oil chamber.