CVT Oil Pump Contamination Control via Pressure Boost
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Solution Overview
Problem
In continuously variable transmissions, the risk of contamination causing inaccurate control of the oil pump rotation is high, especially with miniaturization, leading to inadequate oil flow control between pulleys and unstable speed ratios.
Innovation Solution
A hydraulic control system that includes an orifice to discharge excess oil and a controller to manage oil pressure, allowing for the detection of abnormal pump rotation and implementing a higher SEC pressure to clear contamination, ensuring accurate oil flow and maintaining desired speed ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the oil pump is miniaturized to reduce size and improve integration, then the device complexity is reduced, but the reliability deteriorates because contamination is more easily caught in the movable parts
Solution Approach 1:
The system performs preliminary detection of pump rotation abnormalities and proactively increases SEC pressure to clear contamination before it causes complete pump failure. The controller monitors pump rotation and, upon detecting abnormality, preemptively activates the contamination clearing mechanism by increasing SEC pressure, preventing the harmful effect from manifesting.
Solution Approach 2:
The system converts the harmful effect of contamination in the oil pump into a beneficial cleaning action. By detecting pump rotation abnormalities and responding with increased SEC pressure, the system uses the pressure differential to force oil through the pump in reverse or at high pressure, effectively clearing the contamination that caused the abnormality, thus transforming the harmful contamination into an opportunity for self-cleaning.
2Manufacturing precision
If the second oil pump rotation is controlled to adjust oil in/out to the primary pulley, then the speed ratio control precision is improved, but the reliability deteriorates when contamination is caught in the movable part
Solution Approach 1:
The controller continuously monitors the rotation of the second oil pump and detects abnormalities in real-time. When contamination is detected to be caught in the movable part through rotation abnormality detection, the system provides feedback by increasing SEC pressure to clear the contamination, thereby maintaining reliable operation and preventing loss of speed ratio control precision.
3Device complexity
If contamination is not cleared from the oil pump, then the device complexity remains simple, but the productivity deteriorates due to shift failures and speed ratio instability
Solution Approach 1:
The system enables the oil pump to self-clean by utilizing the existing SEC pressure mechanism. When contamination is detected, the controller increases SEC pressure, which forces oil through the pump and clears the contamination without requiring external cleaning equipment or complex additional mechanisms. The system serves itself by using its own hydraulic resources to eliminate the harmful contamination.
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 approach reduces the likelihood of shift failures by clearing contamination from the oil pump, maintaining stable speed ratios, and preventing unintentional shifts, thereby enhancing drivability and reducing ride quality degradation.
Implementation Method 1
an orifice to discharge excess oil
Implementation Method 2
the hydraulic circuit controls a speed ratio by adjusting the amounts of oil to be supplied to the primary pulley and the secondary pulley
Data Source
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AI summary
A method for controlling a continuously variable transmission is a control method of 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: an abnormality determination step of determining whether rotation of the oil pump is abnormal; and when it is determined that the rotation is abnormal in the abnormality determination step, a hydraulic control step of making a secondary oil pressure higher than a pressure before the determination of abnormality.