CVT Control Switching Position and Hydraulic Feedback
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Solution Overview
Problem
Existing continuously variable transmission systems face challenges in effectively controlling speed ratios and preventing belt slip, particularly during downshifts, due to limitations in hydraulic feedback and position control mechanisms.
Innovation Solution
A method for controlling oil flow and pressure in a continuously variable transmission system that includes determining downshift speed requirements, performing position feedback control when downshift speed is slower, and hydraulic feedback control when it is faster, to adjust piston position and oil pressure dynamically and prevent belt slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position feedback control is used to control piston position, then shift control precision is improved, but downshift speed becomes slower
Solution Approach 1:
The control method dynamically switches between position feedback control and hydraulic feedback control based on the current operating state and downshift speed requirements. When downshift speed is sufficient, position feedback control maintains precision; when downshift speed becomes slower than required, the system transitions to hydraulic feedback control to accelerate the downshift process.
Solution Approach 2:
The system changes the control parameter from position-based feedback to hydraulic pressure-based feedback depending on the downshift speed condition. This parameter switching allows the system to optimize between precision and speed by selecting the appropriate control mode based on real-time performance requirements.
2Speed
If hydraulic feedback control is used to increase downshift speed, then downshift speed is improved, but belt slip risk increases due to pressure fluctuations
Solution Approach 1:
The system employs dual feedback mechanisms: hydraulic feedback for rapid pressure adjustment during downshift, and position feedback for maintaining stable piston position. The controller integrates both feedback signals to balance speed and reliability, ensuring primary pulley pressure remains above the required threshold to prevent belt slip while achieving fast downshift.
Solution Approach 2:
The control system acts as an intermediary that coordinates between hydraulic feedback control and position feedback control, combining their advantages while mitigating their individual disadvantages. The controller processes both feedback signals and adjusts the second oil pump accordingly to maintain optimal performance.
3Ease of operation
If second oil pump flow rate is controlled to achieve target flow rate, then speed ratio control is simplified, but belt slip suppression capability is insufficient
Solution Approach 1:
The second oil pump is designed to perform multiple functions: it controls speed ratio by adjusting primary pulley pressure and simultaneously suppresses belt slip by maintaining pressure above the required threshold. The pump's rotation direction and flow rate are controlled based on comprehensive feedback from both position and hydraulic sensors, enabling it to handle both control objectives effectively.
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 method enables precise shift control and suppresses belt slip by ensuring the primary pulley pressure remains above the required threshold during downshifts, maintaining efficient speed ratio management and reducing the risk of belt slip.
Implementation Method 1
a first oil pump configured to pump up oil from an oil pan to generate a line pressure
Implementation Method 2
a second oil pump configured to be provided between a primary oil chamber and a secondary oil chamber to adjust the oil in/out to/from a primary oil chamber
Implementation Method 3
the hydraulic circuit can control a speed ratio by controlling the rotation direction of the second 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 includes: a determination step of determining whether a required downshift speed is faster than an allowable value; a position control step of setting a target piston position of the primary oil chamber in accordance with an operating state of a vehicle and performing a position control of a piston of the primary oil chamber based on the target piston position; a hydraulic control step of setting a target oil pressure of the primary oil chamber in accordance with the operating state and performing a hydraulic control of the primary oil chamber based on the target oil pressure; and a feedback setting control step of increasing weighting according to a position feedback control based on the target piston position in the position control step when it is determined that the downshift speed is slower than the allowable value in the determination step and of increasing weighting according to a hydraulic feedback control based on the target oil pressure in the hydraulic control step when it is determined that the downshift speed is faster than the allowable value.