CVT Clamping Pressure Sensor for Belt Slipping Control
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Solution Overview
Problem
Conventional power transmission devices with belt type continuously variable transmission mechanisms face issues with belt slipping during coast traveling, leading to reduced durability and compromised responsiveness due to inaccuracies in engine revolution calculations and hardware variations, especially when vehicle speed decreases.
Innovation Solution
A control device for a power transmission device that includes an oil pump, hydraulic control system, clamping pressure sensor, and engagement element control part, which disengages the hydraulic engagement element when the detected clamping pressure falls below a threshold after engine stop, eliminating the need for engine revolution calculations and addressing hardware variations, thus preventing belt slipping and ensuring responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the predetermined number of revolutions is set to a high value to suppress belt slipping, then belt durability is improved, but clutch engagement responsiveness deteriorates
Solution Approach 1:
The patent replaces the mechanical monitoring method (using engine revolution count) with a direct sensing method (using a sensor to detect clutch engagement state). This substitution eliminates the need to set a high threshold value for engine revolutions, allowing the clutch to be disengaged at the appropriate moment without causing belt slipping, while maintaining fast responsiveness to acceleration requests.
Solution Approach 2:
The patent introduces feedback by using a sensor to directly detect the clutch engagement state and feed this information back to the control unit. This real-time feedback enables precise control of clutch disengagement timing, ensuring that the clutch is disengaged exactly when needed to prevent belt slipping, without requiring conservative high threshold values that would delay responsiveness.
2Speed
If the predetermined number of revolutions is set to a low value to improve clutch engagement responsiveness, then acceleration responsiveness is improved, but belt slipping increases
Solution Approach 1:
The patent replaces the indirect mechanical monitoring method with direct sensor detection of clutch engagement state. This allows the system to respond quickly to acceleration requests by disengaging the clutch promptly, while simultaneously preventing belt slipping by accurately detecting when the clutch is fully disengaged, eliminating the need to choose between low threshold values and high threshold values.
Solution Approach 2:
The real-time feedback from the clutch engagement state sensor enables the control unit to make precise decisions about clutch disengagement. The system can respond quickly to acceleration requests while continuously monitoring the actual engagement state to ensure belt slipping is prevented, achieving both fast responsiveness and reliable belt protection simultaneously.
3Device complexity
If engine revolution calculation is used to determine clutch disengagement timing, then device complexity is reduced, but measurement precision deteriorates due to hardware variations
Solution Approach 1:
The patent substitutes the calculation-based control method with a sensor-based direct detection method. The sensor directly detects the clutch engagement state, providing accurate measurement without relying on engine revolution calculations that are affected by hardware variations. This approach maintains simple device architecture while achieving high measurement precision.
Solution Approach 2:
The clutch engagement detection system serves itself by using a sensor that directly measures the engagement state without requiring external calculation or inference from engine revolutions. The sensor provides self-contained, accurate detection that is independent of hardware variations in the engine or transmission components.
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 solution effectively suppresses belt slipping and maintains responsiveness by accurately determining sufficient clamping pressure and disengaging the hydraulic engagement element at appropriate times, enhancing the durability and performance of the power transmission device.
Implementation Method 1
a hydraulic control device that regulates pressure of oil from the oil pump
Implementation Method 2
a clamping pressure sensor that detects clamping pressure of the belt applied by the first or second hydraulic cylinder
Data Source
AI summary
A power transmission device mounted on a vehicle in which operation of an engine is stopped when vehicle speed has been reduced to a predetermined vehicle speed. The device includes an oil pump driven by the engine; a hydraulic control device regulating pressure from the oil pump; a continuously variable transmission mechanism in which groove widths of a primary pulley and a secondary pulley are set by hydraulic pressure from the hydraulic control device; a hydraulic engagement element engaged by hydraulic pressure from the hydraulic control device to couple the continuously variable transmission mechanism to the engine; a clamping pressure sensor that detects clamping pressure of a belt of the continuously variable transmission mechanism; and a control device disengaging the hydraulic engagement element when the detected clamping pressure of the belt reaches less than or equal to a threshold value after operation of the engine is stopped.