CVT Line Pressure Control Using Oil-Temperature Compensation
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Solution Overview
Problem
Existing transmission systems are unable to sufficiently reduce excess line pressure due to the low detection accuracy of line pressure sensors.
Innovation Solution
A transmission system comprising a primary pulley, a secondary pulley, an oil pump, a hydraulic control circuit, a line pressure detection unit, and a controller that selects the higher target pulley pressure, variably sets a target differential pressure based on oil temperature, and adjusts the line pressure to a target value calculated from the total pressure of the target pulley pressure and differential pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a line pressure sensor is provided to prevent hydraulic pressure variation and reduce excess line pressure, then the line pressure can be detected and controlled, but the detection accuracy is low and the excess line pressure cannot be sufficiently reduced
Solution Approach 1:
The patent segments the line pressure control into two independent detection paths: one for detecting the line pressure itself and another for detecting the pulley pressure. By separating these detection functions, the system can accurately determine the actual pressure acting on the pulley and calculate the true differential pressure, thereby reducing excess line pressure while maintaining accurate measurement.
Solution Approach 2:
The patent introduces a pulley pressure detection unit as an intermediary component to indirectly measure the actual line pressure effect on the pulley. By detecting the pulley pressure and comparing it with the line pressure, the system can identify and compensate for detection errors, thus reducing excess line pressure caused by inaccurate sensing.
2Device complexity
If the target line pressure is set to a fixed value above the target pulley pressure, then the control is simple, but the excess line pressure increases and fuel consumption rises
Solution Approach 1:
The patent dynamically adjusts the target line pressure based on detected pulley pressure and calculated differential pressure requirements. Instead of using a fixed offset, the system continuously adapts the target line pressure to match actual operating conditions, minimizing excess pressure while maintaining simple control logic through automated feedback.
Solution Approach 2:
The patent implements a feedback mechanism where the detected pulley pressure and line pressure are continuously compared, and the target line pressure is adjusted based on the actual differential pressure needed. This closed-loop feedback reduces excess pressure by eliminating the need for conservative fixed offsets, thereby reducing fuel consumption without increasing control complexity.
3Ease of operation
If the target differential pressure is set to a fixed value, then the control is simple, but the excess line pressure cannot be sufficiently reduced due to low detection accuracy
Solution Approach 1:
The system performs self-correction by using the pulley pressure detection unit to identify actual pressure conditions and automatically adjusting the target line pressure accordingly. This self-service mechanism eliminates the need for manual calibration or fixed differential pressure settings, reducing excess line pressure while maintaining ease of operation through automated adaptation.
Solution Approach 2:
The patent changes the target line pressure parameter dynamically based on detected pulley pressure and required differential pressure. By adjusting this parameter in real-time rather than using a fixed value, the system reduces excess line pressure while keeping the control operation simple through automated parameter adaptation.
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
The system effectively reduces excess line pressure by improving detection accuracy and adjusting pressures dynamically based on oil temperature, leading to a more efficient driving torque.
Implementation Method 1
an oil pump configured to supply oil; a hydraulic control circuit configured to adjust a pressure of the oil supplied from the oil pump to a line pressure which is a source pressure of a primary pulley pressure supplied to the primary pulley and a secondary pulley pressure supplied to the secondary pulley
Implementation Method 2
a line pressure detection unit configured to detect the line pressure
Data Source
AI summary
A transmission comprising: a primary pulley; a secondary pulley; a transmission member wound around the primary pulley and the secondary pulley; an oil pump configured to supply oil; a hydraulic control circuit configured to adjust a pressure of the oil supplied from the oil pump to a line pressure which is a source pressure of a primary pulley pressure supplied to the primary pulley and a secondary pulley pressure supplied to the secondary pulley; a line pressure detection unit configured to detect the line pressure; and a controller configured to control the hydraulic control circuit, wherein the controller is configured to select, as a target pulley pressure, a higher one of a target value of the primary pulley pressure and a target value of the secondary pulley pressure, variably set, according to an oil temperature, a target differential pressure including a detection variation of the line pressure detection unit that varies according to the oil temperature, set a target line pressure which is a target value of the line pressure to a total pressure of the target pulley pressure and the target differential pressure, and control the hydraulic control circuit such that the detected line pressure is adjusted to the target line pressure.