Hydraulic Variator Control Arrangement for CVT Traction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing hydraulic control systems for continuously variable transmission devices struggle to rapidly adjust the traction coefficient in response to changing reaction forces, leading to potential roller slip and inefficiencies due to reliance on continuous fluid flow and low bandwidth pulse width modulated valves.
Innovation Solution
A hydraulic control arrangement with a traction control valve that selectively connects or disconnects working chambers to reaction or traction pressures, allowing for discrete adjustment of the traction coefficient by altering the ratio of traction pressure to reaction pressure, thereby maintaining a consistent relationship between reaction force and traction load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If continuous fluid flow is used to adjust traction load, then smooth control is achieved, but response speed to torque spikes is insufficient
Solution Approach 1:
The patent employs a pulse-width modulated (PWM) valve that switches fluid flow in periodic pulses rather than continuous flow. This allows rapid adjustment of traction load in discrete steps, achieving both high response speed to torque spikes and reliable prevention of roller slip through controlled periodic action.
Solution Approach 2:
The control system dynamically adjusts the duty cycle of the PWM valve based on real-time detection of torque spikes and reaction force changes. This dynamic adjustment enables the system to respond rapidly to varying operating conditions while maintaining optimal traction load, resolving the contradiction between response speed and reliability.
2Speed
If pulse width modulated valve is used for control, then bandwidth is increased, but adjustment precision is reduced
Solution Approach 1:
The patent changes the control parameter from continuous pressure adjustment to discrete pulse width modulation. By varying the duty cycle of PWM signals, the system achieves precise control of average fluid pressure delivered to the traction load actuator, maintaining adjustment precision while enabling high bandwidth response through rapid switching.
Solution Approach 2:
The control system incorporates feedback from reaction force sensors and torque spike detection to continuously adjust PWM duty cycle. This closed-loop feedback ensures precise control of the traction coefficient despite the discrete nature of PWM actuation, resolving the contradiction between bandwidth and precision.
3Reliability
If traction load is rapidly increased to prevent slip, then reliability is improved, but energy losses increase
Solution Approach 1:
The system dynamically adjusts traction load to match actual operating conditions rather than maintaining constant high load. The PWM valve modulates fluid pressure in real-time based on detected torque spikes and reaction force, providing minimum necessary traction load to prevent slip while minimizing energy losses from excessive loading.
Solution Approach 2:
The control system changes the physical state of fluid pressure delivery from continuous to pulsed, allowing precise temporal control of traction load application. This enables the system to apply high traction load only when and where needed to prevent slip, rather than continuously, thereby reducing overall energy losses while maintaining reliability.
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 enables rapid and accurate adjustment of traction load in sympathy with reaction force changes, reducing roller slip and maintaining optimal efficiency by providing a higher bandwidth for responding to torque spikes and varying traction coefficients.
Implementation Method 1
a hydraulic traction loading actuator arranged to apply a traction load urging the roller and races into engagement to provide traction therebetween
Implementation Method 2
at least one hydraulic roller actuator arranged to apply a reaction force to the roller
Implementation Method 3
for applying fluid to the traction loading actuator at a traction pressure which is related to the reaction pressure, thereby maintaining a relationship between reaction force and traction load
Data Source
AI summary
In a continuously-variable-ratio-device of the type having races between which drive is transferred by rollers which are movable in accordance with changes of variator ratio, it is necessary to apply a traction load urging the rollers and races into engagement. Each rollers is also subject to a transverse reaction force by a hydraulic reaction roller actuator receiving a controlled reaction pressure. It is desirable to create a relationship between traction and reaction force, and also to provide for adjustment of this relationship. In the present invention this is achieved hydraulically. A traction pressure related to the reaction pressure is applied to an actuator which creates the traction load. The hydraulics also include a working chamber, which is selectively connectable to and disconnectable from either (or both) of (i) the reaction pressure and (ii) the traction pressure, the traction force being dependent upon pressure in the working chamber.