CVT Slip Control via Dynamic Clamping Force
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Solution Overview
Problem
Conventional continuously variable transmissions (CVT) face inefficiencies due to high hydraulic power loss and limited torque capacity, resulting from excessive clamping force leading to belt wear and slip, and insufficient clamping force causing power transfer loss.
Innovation Solution
A method for controlling slip in CVT by adjusting the clamping force of primary and secondary pulleys based on control input torque, utilizing a transmission control unit to determine slip conditions and switch between predefined slip modes to minimize hydraulic power loss and optimize fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clamping force is increased to prevent slip, then power transfer reliability is improved, but hydraulic power loss increases and fuel efficiency deteriorates
Solution Approach 1:
The patent applies dynamics by making the clamping force adjustable and variable rather than fixed. The transmission control unit dynamically modifies clamping force based on real-time slip detection results and operating conditions, allowing the system to optimize the balance between preventing slip and minimizing hydraulic power loss during different driving phases.
Solution Approach 2:
The patent changes the parameter of clamping force from a constant high value to a variable value that is continuously adjusted based on slip detection. By modifying this critical parameter according to actual operating conditions and slip patterns, the system achieves both reliable power transfer and reduced energy loss.
2Loss of energy
If clamping force is decreased to reduce hydraulic power loss, then fuel efficiency is improved, but slip control capability deteriorates
Solution Approach 1:
The patent implements feedback control by continuously monitoring slip conditions through sensors and using this information to adjust clamping force. The transmission control unit receives slip detection results and modifies clamping force accordingly, creating a closed-loop system that maintains adequate slip control capability while minimizing hydraulic power loss.
Solution Approach 2:
The system dynamically adjusts clamping force based on real-time feedback from slip detection, transitioning from a static high clamping force approach to a dynamic adaptive approach that optimizes the balance between slip prevention and energy efficiency.
3Reliability
If high clamping force is applied to prevent slip, then torque capacity is improved, but belt lifetime deteriorates due to excessive tension
Solution Approach 1:
The patent changes the clamping force parameter from a consistently high value to a variable value that is adjusted based on actual slip conditions. This parameter modification reduces excessive tension on the belt during normal operation while maintaining adequate torque capacity when slip is detected, thereby extending belt lifetime.
Solution Approach 2:
The patent applies partial action by providing clamping force only when and where needed to prevent slip, rather than continuously applying excessive clamping force. This selective application of clamping force maintains torque capacity during critical moments while reducing overall belt tension and extending belt life.
4Duration of action of stationary object
If low clamping force is applied to reduce belt tension, then belt lifetime is improved, but power transfer function deteriorates due to macroscopic slip
Solution Approach 1:
The patent uses feedback control to monitor slip conditions and adjust clamping force in real-time. This feedback mechanism ensures that clamping force is increased only when slip is detected, maintaining power transfer function while avoiding excessive clamping force during normal operation, thus preserving belt lifetime.
Solution Approach 2:
The system performs self-service by automatically detecting slip conditions and adjusting clamping force without external intervention. This self-regulating mechanism ensures adequate power transfer function is maintained while minimizing unnecessary belt tension, extending belt lifetime.
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 method reduces hydraulic power loss and enhances fuel efficiency by dynamically managing clamping force, preventing slip and maintaining efficient power transfer within a safe operational range.
Implementation Method 1
the line pressure optimal mode is a mode for setting minimal line pressure necessary to control a primary pulley and a secondary pulley of the continuously variable transmission
Implementation Method 2
transmission of the CVT can be performed as a rotation radius of the belt is continuously changed by axially translating a primary pulley and a secondary pulley while providing clamping force to the pulleys
Data Source
AI summary
Disclosed herein is a method for controlling slip of a continuously variable transmission using a transmission control unit (TCU), comprising: receiving, by a transmission control unit, information related to determination of slip which occurs during vehicle's running; calculating a slip determining coefficient by the transmission control unit; determining, by the transmission control unit, whether the slip has occurred according to the slip determining information and a predefined slip determining algorithm; and selecting and switching to, by the transmission control unit, one of a plurality of preset slip modes based on the slip determining coefficient and a result obtained by determining whether the slip has occurred.