CVT Hydraulic Pressure Controller for Belt Slip Prevention
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Solution Overview
Problem
Conventional belt-type continuously variable transmission systems experience variations in speed ratio during braking, leading to uncomfortable driving experiences due to uneven hydraulic pressure distribution between pulleys, causing imbalance in thrust ratios and resulting in unintended acceleration and deceleration feelings for the driver.
Innovation Solution
A vehicle with a belt-type continuously variable transmission system that includes a hydraulic pressure controller to incrementally increase the belt sandwiching force by both the primary and secondary pulleys before a braking force request, using a first correction amount to establish a balanced force distribution, thereby reducing the difference in hydraulic pressures and minimizing speed ratio changes during braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the primary hydraulic pressure and secondary hydraulic pressure are increased to quicken the response time, then the belt sandwiching force increases faster, but the difference in rising trends between primary and secondary hydraulic pressure breaks the balance of thrust ratios, causing speed ratio variation
Solution Approach 1:
The system performs preliminary action by increasing the belt sandwiching force in advance before the braking force request occurs. The control device predicts the braking request based on accelerator pedal state changes and proactively adjusts hydraulic pressures, allowing the system to be prepared before the actual braking event, thus reducing the magnitude of pressure changes needed at the critical moment
Solution Approach 2:
The control system dynamically adjusts the hydraulic pressure increase strategy based on the predicted braking state. When braking is anticipated, the system modifies the pressure increase rate and magnitude to maintain thrust ratio balance, transitioning from a static pressure control approach to a dynamic, condition-based control approach that adapts to predicted operational changes
2Reliability
If the secondary hydraulic pressure is increased by a large amount to prevent belt slip, then the belt sandwiching force is sufficient, but the variation width of speed ratio increases, making the uncomfortable feeling more remarkable
Solution Approach 1:
By increasing the belt sandwiching force in advance before braking occurs, the system reduces the magnitude of pressure increase needed at the moment of braking request. This preliminary action ensures that smaller, more controlled pressure adjustments are sufficient to prevent belt slip, thereby minimizing speed ratio variation and reducing uncomfortable sensations for the driver
Solution Approach 2:
The control device changes the timing parameter of hydraulic pressure adjustment, shifting from increasing pressure only when braking is detected to increasing pressure in advance when braking is predicted. This parameter change in timing allows for more gradual and controlled pressure increases, reducing abrupt speed ratio changes and improving driver comfort
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 prevents the uncomfortable feeling for the driver by reducing the variation in speed ratio and maintaining a stable belt sandwiching force, ensuring smoother vehicle behavior during braking by controlling the hydraulic pressure increments before the braking force request is made.
Implementation Method 1
a belt-type continuously variable transmission configured by bridging a belt across a set of pulleys increases a sandwiching force by the respective pulleys to prevent a belt slip against a torque input from a driving wheel side during a deceleration
Implementation Method 2
a hydraulic pressure controller that changes hydraulic pressures supplied to the primary pulley and the secondary pulley to control a belt sandwiching force
Data Source
AI summary
A hydraulic pressure controller includes belt sandwiching force increasing means. The belt sandwiching force increasing means increases a belt sandwiching force by a primary pulley and a secondary pulley on the basis of a braking force request from a driver, up to a predetermined value to prevent a belt from slipping due to a braking force. The belt sandwiching force increasing means increases the belt sandwiching force in a range of less than the predetermined value before the braking force request occurs.