CVT Pulley Pressure Control for Reverse Belt Slip Prevention
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Solution Overview
Problem
In vehicles equipped with belt-type continuously variable transmissions (CVT), the loss of hydraulic pressure balance between the primary and secondary pulleys leads to belt slippage and deteriorated traveling performance, especially when reversing uphill, as existing solutions either prevent slippage by increasing primary pulley pressure, which deviates the transmission ratio from LOW, obstructing smooth movement.
Innovation Solution
A control device and method that adjust the lateral pressure of the drive and driven pulleys by setting different correction amounts based on the vehicle's in-gear state and shift position relative to the traveling direction, using a first lateral pressure increase correction amount when not in-gear and a second, smaller amount when in-gear, to maintain the transmission ratio at LOW and prevent belt slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the hydraulic pressure of the primary pulley is increased to prevent belt slippage, then belt slippage is prevented, but the transmission ratio deviates from LOW and the vehicle cannot move smoothly
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the lateral pressure correction amount based on the vehicle's operational state (in-gear or out-of-gear). When the vehicle is in the in-gear state during reverse movement, a smaller correction amount is applied compared to when it is out-of-gear, allowing the system to adapt pressure parameters to different operational contexts and prevent belt slippage while maintaining smooth vehicle movement.
2Reliability
If the line pressure is maximized to supplement dropped hydraulic pressure, then belt slippage is prevented, but the transmission ratio cannot be maintained
Solution Approach 1:
The patent applies local quality by differentiating the pressure correction strategy based on the specific operational state. Instead of applying a uniform maximum pressure correction in all reverse movement scenarios, the system applies different correction amounts depending on whether the transmission is in the in-gear state or not. This localized approach allows precise control over when and how much pressure is applied, preventing belt slippage while maintaining transmission ratio accuracy.
3Reliability
If the lateral pressure of the primary pulley is increased during reverse movement, then belt slippage is prevented, but the traveling performance is deteriorated
Solution Approach 1:
The patent applies dynamics by making the lateral pressure correction amount variable rather than fixed. The correction amount dynamically changes based on the transmission's gear state during reverse movement. When in the in-gear state, a smaller correction is applied; when out-of-gear, a larger correction is applied. This dynamic adjustment optimizes both belt slippage prevention and traveling performance by applying pressure only when necessary.
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 effectively prevents belt slippage and maintains smooth vehicle operation by optimizing the pressure difference between the pulleys, ensuring the transmission ratio remains at LOW during restarts and reversing maneuvers, thus enhancing traveling performance without compromising belt durability.
Implementation Method 1
a first lateral pressure generation circuit, generating a lateral pressure of the drive pulley
Implementation Method 2
a second lateral pressure generation circuit, generating a lateral pressure of the driven pulley
Data Source
AI summary
Disclosed is lateral pressure control of a continuously variable transmission (CVT) with a transmission ratio changed by changing groove widths of a drive pulley and a driven pulley, a drive force from a drive source being transmitted to a wheel. A control part controlling respective lateral pressures of the drive pulley and the driven pulley is provided. The control part sets an increase correction amount of the lateral pressure of the drive pulley to a first lateral pressure increase correction amount if the CVT is not in an in-gear state or a shift position is consistent with a traveling direction of the vehicle, and, sets said amount to a second lateral pressure increase correction amount smaller than the first lateral pressure increase correction amount if the CVT is in the in-gear state and the shift position is not consistent with the traveling direction of the vehicle.