CVT Idle Speed Control for Belt Slip Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In vehicles equipped with continuously variable transmissions (CVTs) capable of mechanically locking the primary pulley at maximum gear ratio, the hydraulic pressure is insufficient during sudden deceleration or high oil temperature, leading to belt slip and decreased fuel efficiency due to high idle rotational speeds.
Innovation Solution
A control device that dynamically adjusts idle rotational speed and hydraulic pressure by using a secondary pulley rotational speed sensor to determine the gear ratio, implementing idle-up control only when the gear ratio is not at maximum, thereby optimizing fuel efficiency and preventing belt slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the idle rotational speed is increased to secure hydraulic pressure during sudden deceleration or high oil temperature, then the hydraulic pressure is sufficient to prevent belt slip, but the fuel efficiency deteriorates
Solution Approach 1:
The patent applies dynamics by making the idle rotational speed adjustable rather than fixed. The control device dynamically changes the idle rotational speed based on detected conditions (sudden deceleration, high oil temperature) to provide sufficient hydraulic pressure only when necessary, thereby preventing belt slip while avoiding unnecessary fuel consumption during normal operation
Solution Approach 2:
The patent changes the parameter of idle rotational speed from a constant value to a variable value that adapts to different operating conditions. By detecting conditions such as sudden deceleration or high oil temperature, the system adjusts the idle rotational speed parameter upward only when required to maintain adequate hydraulic pressure, thus resolving the contradiction between reliability and energy efficiency
2Ease of operation
If the gear ratio is not returned to maximum gear ratio before vehicle stop, then the vehicle can stop smoothly under various conditions, but the hydraulic pressure becomes insufficient causing belt slip
Solution Approach 1:
The patent applies preliminary action by detecting in advance whether the gear ratio is at maximum before vehicle stop. Based on this preliminary detection, the control device decides whether to increase idle rotational speed to secure hydraulic pressure, allowing the vehicle to stop smoothly under various conditions while preventing belt slip through proactive hydraulic pressure management
Solution Approach 2:
The patent uses feedback by detecting the gear ratio state and vehicle stop conditions, then adjusting the idle rotational speed accordingly. This closed-loop control ensures that hydraulic pressure is maintained at appropriate levels based on actual operating conditions, preventing belt slip while allowing flexible stopping behavior
3Reliability
If the idle rotational speed is always set high during vehicle stop, then the hydraulic pressure is sufficient for both primary and secondary pulleys, but the fuel efficiency deteriorates
Solution Approach 1:
The patent applies local quality by providing hydraulic pressure security only where and when needed. Instead of uniformly maintaining high idle rotational speed, the system selectively increases idle speed only when the gear ratio is not at maximum before vehicle stop, thereby securing hydraulic pressure locally at the primary pulley only when necessary, while avoiding unnecessary fuel consumption during other stopping conditions
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
Improves fuel efficiency by restricting high idle rotational speeds and ensuring adequate hydraulic pressure, while preventing belt slip and maintaining appropriate gear ratio control during vehicle stop and restart conditions.
Implementation Method 1
a hydraulic pressure actuator provided at a rear face side thereof so that the gear ratio is continuously adjusted
Implementation Method 2
the movable sheave of the primary pulley makes contact with a wall on the side of the case, which prevents further movement of the movable sheave
Data Source
AI summary
In a control device for a vehicle on which is mounted a continuously variable transmission capable of mechanically locking a primary pulley at the time of a maximum gear ratio (maximum Low), an idle rotational speed is not always set high to increase a hydraulic pressure at the time of stopping the vehicle. Instead, at the time of stopping the vehicle, when the gear ratio of the continuously variable transmission is the maximum gear ratio, normal idle rotational speed control is performed, and only when the gear ratio is not the maximum gear ratio, idle-up control is performed so that the idle rotational speed is set high, thereby the hydraulic pressure is set high. Thus, by restricting conditions in which the hydraulic pressure is set high by the idle-up control, it is possible to improve fuel efficiency while suppressing generation of a belt slip.