CVT Hydraulic Pressure Release Paths for Smooth Neutral Switching
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Solution Overview
Problem
Continuous variable transmission (CVT) systems face issues with sudden torque discharge when switching to neutral stage due to rapid hydraulic pressure release, causing vehicle impacts, and slow release leading to unintended movement, which is exacerbated by changes in oil viscosity with temperature.
Innovation Solution
A CVT hydraulic pressure control device featuring a pressure regulation valve and switch valve with different oil discharge paths, controlled by a controller based on oil temperature, to regulate hydraulic pressure release speed, using a solenoid valve and return spring to manage pilot pressure and flow resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic pressure is discharged quickly from the friction element when switching to neutral stage, then the vehicle can be prevented from unnecessary movement, but sudden torque discharge causes impact such as bump to the vehicle
Solution Approach 1:
The patent applies dynamics by making the oil discharge path variable rather than fixed. The switch valve dynamically changes the discharge path based on operating conditions (engagement state and oil temperature), allowing the system to adapt between fast discharge (to prevent movement) and controlled discharge (to reduce impact), thereby resolving the contradiction between preventing unnecessary movement and avoiding vehicle impact
Solution Approach 2:
The patent changes the parameter of oil discharge flow rate by switching between different discharge paths. The first discharge path provides higher flow rate while the second path provides lower flow rate. This parameter change allows the system to prevent unnecessary vehicle movement when needed while avoiding impact in other conditions, resolving the technical contradiction
2Device complexity
If the oil discharge path is fixed, then the device structure is simple, but the hydraulic pressure release speed cannot be adjusted according to oil temperature changes
Solution Approach 1:
The patent transforms the fixed discharge path into a dynamic, switchable system. The switch valve enables the system to select between first and second discharge paths based on oil temperature and engagement state, providing adaptability without excessive complexity. This resolves the contradiction by introducing minimal complexity (one switch valve) to achieve temperature adaptation
Solution Approach 2:
The switch valve serves multiple functions: it selects discharge paths based on temperature, coordinates with the pressure regulation valve, and adapts the system to different operating conditions. This multi-functionality allows a single component to provide temperature adaptation while maintaining relatively simple overall structure, resolving the contradiction between device complexity and adaptability
3Adaptability or versatility
If a switch valve with multiple discharge paths is added to control hydraulic pressure release speed, then adaptability to oil temperature is improved, but the device complexity increases
Solution Approach 1:
The patent merges the switch valve with the existing pressure regulation valve system. The switch valve works in coordination with the pressure regulation valve, combining their functions to achieve temperature-adaptive pressure control. This merging approach provides temperature adaptability while avoiding the need for completely separate control systems, thereby limiting the increase in device complexity
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
Prevents unnecessary vehicle movement and impact by ensuring hydraulic pressure is released at an appropriate speed, regardless of oil viscosity changes, through controlled oil discharge paths and flow resistance adjustments, maintaining smooth transitions between movement states.
Implementation Method 1
a pressure regulation valve regulating an operation pressure of oil supplied to a friction element of a forward-rearward device
Implementation Method 2
a switch valve configured to respectively switch oil discharge paths through which the oil supplied to the friction element is discharged, by a pilot pressure from the pressure regulation valve and an elastic force of a return spring
Data Source
AI summary
A continuous variable transmission (CVT) hydraulic pressure control device includes: a pressure regulation valve regulating an operation pressure of oil supplied to a friction element of a forward-rearward device; and a switch valve to respectively switch oil discharge paths through which the oil supplied to the friction element is discharged, respectively by a pilot pressure from the pressure regulation valve and an elastic force of a return spring. In particular, the oil discharge paths switched by the switch valve have oil flow resistances different from each other.