CVT Bypass Valve Timing for Low-Torque Ratio Changes
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Solution Overview
Problem
Existing vehicle transmission systems, particularly those using Continuously Variable Transmissions (CVTs), face challenges in managing torque variations caused by internal combustion engines, leading to issues such as slip, damage, and reduced efficiency due to varying ratios of normal to tractive forces.
Innovation Solution
A method involving a continuously variable transmission system with a servo motor-controlled pump and a bypass valve that adjusts pressure along the flow path between the pump output and engine intake manifold, allowing controlled pressure release during ratio changes to minimize shift torque and maintain efficient engine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the CVT ratio is changed rapidly to improve responsiveness, then the shift speed increases, but the torque variations cause slip and damage to the CVT components
Solution Approach 1:
The bypass valve is opened before the CVT ratio change begins, preemptively reducing the load on the CVT. This preliminary action allows the ratio change to occur with minimal torque variation, preventing slip and damage while maintaining rapid shift capability.
Solution Approach 2:
The bypass valve acts as an intermediary mechanism between the engine and CVT. By providing an alternative path for fluid flow, it mediates the torque transmission, reducing peak torques during ratio changes and protecting the CVT components from damage.
2Ease of operation
If the bypass valve is opened to reduce pressure during ratio change, then the shift torque is reduced and shifting becomes smoother, but the engine boost pressure may be compromised
Solution Approach 1:
The bypass valve is opened periodically or temporarily only during the ratio change event, then closed to restore full boost pressure. This periodic action allows smooth shifting during the brief opening period while maintaining optimal engine performance during normal operation.
Solution Approach 2:
The bypass valve is opened in advance of the ratio change to reduce pressure buildup, then closed after the ratio change completes. This timing strategy ensures smooth shifting while minimizing the duration of reduced boost pressure, thereby maintaining overall engine performance.
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 enables rapid and efficient shifting of the CVT under low loading conditions, reducing wear and tear while maintaining engine boost pressure, thereby improving fuel efficiency and extending the service life of transmission components.
Implementation Method 1
opening the valve to decrease the pressure caused by the pump at a point along a flow path between the pump output and the engine intake manifold to change a shift torque exerted on the continuous variable transmission during the ratio change
Implementation Method 2
changing the control ratio of the continuous variable transmission causes the pump to increase pressure at a point along a flow path between the pump output and the engine intake manifold
Data Source
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AI summary
A method of controlling a pump (43), including operating an engine (23) having an engine intake (49) coupled to a pump output (51) of a pump, and a transmission (41 )coupled to the engine and to the pump, and operating a valve (58) between a pump input of the pump and the engine intake, such that the valve can be opened during a ratio change of the transmission.