CVT Control Device for Hydraulic Pressure Stabilization
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Solution Overview
Problem
In continuously variable transmissions, oil vibration caused by increased belt clamping force during low line pressure conditions leads to vehicle behavior variations and unnatural driver feedback, especially when the brake switch is activated, due to insufficient hydraulic pressure regulation.
Innovation Solution
A control device with a line pressure generating means, a pilot valve to regulate pilot pressure, and a control means to increase line pressure above a predetermined threshold when it falls below this level, stabilizing hydraulic pressure and preventing oil vibration by ensuring consistent pilot pressure supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the belt clamping force is increased when the brake switch is activated, then belt slippage is prevented, but oil vibration is generated causing vehicle behavior variation
Solution Approach 1:
The system performs preliminary action by increasing line pressure before the brake switch is activated. The control unit monitors brake switch signals and pre-increases line pressure through the line pressure increase means, ensuring that when the brake switch activates and belt clamping force increases, the pilot pressure remains stable above the first predetermined pressure, preventing oil vibration while maintaining reliable belt slippage prevention
Solution Approach 2:
The system applies beforehand cushioning by maintaining line pressure above the first predetermined pressure in advance. The pilot valve and line pressure increase means work together to ensure pilot pressure is already stabilized before brake activation occurs, cushioning against the potential oil vibration that would otherwise be generated when belt clamping force increases during braking
2Use of energy by moving object
If the line pressure is maintained at a low value, then fuel economy is improved, but oil vibration occurs when the brake switch is activated
Solution Approach 1:
The system applies dynamics by making line pressure adjustable rather than fixed. The control unit dynamically switches between low line pressure mode (for fuel economy) and high line pressure mode (for preventing oil vibration during braking). The line pressure increase means enables rapid transition between pressure levels based on brake switch activation, allowing the system to optimize fuel economy during normal operation while preventing oil vibration when needed
Solution Approach 2:
The system changes the line pressure parameter dynamically. During normal operation, line pressure is maintained at a low value for fuel economy. When the brake switch is activated, the control unit changes the line pressure parameter to a high value above the first predetermined pressure, preventing oil vibration. This parameter change is achieved through the line pressure increase means and pilot valve mechanism
3Force
If the line pressure is increased when it is lower than the pilot pressure, then belt clamping force is improved, but mutual increase of hydraulic pressure variation occurs
Solution Approach 1:
The system performs preliminary action by increasing line pressure before the brake switch is activated. The control unit monitors brake switch signals and pre-increases line pressure through the line pressure increase means, ensuring that when the brake switch activates and belt clamping force increases, the pilot pressure remains stable above the first predetermined pressure, preventing oil vibration while maintaining reliable belt slippage prevention
Solution Approach 2:
The pilot valve acts as an intermediary between the line pressure increase means and the belt clamping force control. When line pressure is increased, the pilot valve regulates the pilot pressure to remain stable above the first predetermined pressure, mediating the pressure change to prevent mutual increase of hydraulic pressure variation while still allowing the belt clamping force to increase for preventing belt slippage
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 solution effectively suppresses vehicle behavior variations and unnatural driver feedback by maintaining stable hydraulic pressure, preventing oil vibration and belt slippage, even during brake activation, by ensuring the line pressure exceeds the predetermined threshold, thus stabilizing the engagement state and improving fuel economy.
Implementation Method 1
a pilot valve configured to supply a pilot pressure regulated so as not to exceed a first predetermined pressure when the line pressure exceeds the first predetermined pressure
Implementation Method 2
a belt slippage may be generated... by increasing a belt clamping force of the continuously variable transmission
Implementation Method 3
an oil vibration may be generated due to the increase of the belt clamping force
Data Source
AI summary
A control device for a continuously variable transmission includes: a line pressure generating-section configured to generate a line pressure; a pilot valve configured to supply a pilot pressure regulated so as not to exceed a first predetermined pressure when the line pressure exceeds the first predetermined pressure; a control section configured to generate the clamping forces by controlling the pilot pressure; a line pressure increase section configured to increase the line pressure to be greater than the first predetermined pressure when the control to increase the line pressure is performed when the line pressure is lower than the first predetermined pressure.