CVT Switching Valve Control for Pump Load Reduction
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Solution Overview
Problem
Existing vehicle transmission systems face limitations in efficiently controlling the rate of change of gear ratios in continuously variable transmissions (CVTs), leading to suboptimal fuel efficiency and increased load on the engine due to the mechanical operation of transmission fluid pumps.
Innovation Solution
A control system that includes a target module to determine the target ratio between the input and output shafts of a CVT, a switching valve control module to manage the switching valve's position based on the rate of change of the target ratio, and modules to control pulley actuators, allowing for selective actuation of the switching valve to optimize fluid flow and pressure distribution, thereby reducing the load on the engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transmission fluid pump operates continuously at high capacity, then the transmission can achieve faster gear ratio changes, but the engine load and fuel consumption increase
Solution Approach 1:
The patent applies dynamics by making the transmission fluid pump's operational capacity variable rather than fixed. The pump's flow capacity is dynamically adjusted based on real-time transmission operating conditions, including the rate of change of gear ratios, vehicle speed, and engine load. This allows the system to optimize between providing sufficient fluid flow for rapid gear ratio changes and minimizing pump load to reduce fuel consumption.
Solution Approach 2:
The patent changes the operational parameters of the transmission fluid pump based on transmission state. The control system monitors parameters such as current gear ratio, target gear ratio, vehicle speed, and engine load, then adjusts the pump's flow capacity accordingly. This parameter adjustment enables the pump to operate at optimal capacity for each operating condition, preventing excessive fuel consumption during steady-state operation while maintaining capability for rapid gear ratio changes when needed.
2Ease of operation
If the switching valve remains in the open position, then transmission fluid flows freely to the pressure regulator valve, but the pump operates at higher load and fuel efficiency decreases
Solution Approach 1:
The control system performs preliminary assessment of transmission operating conditions before determining the switching valve position. By evaluating the rate of change of gear ratios, vehicle speed, and engine load in advance, the system determines whether full fluid flow capacity is needed or if reduced flow suffices. This preliminary action allows the switching valve to be positioned optimally before pump operation, preventing unnecessary energy loss while ensuring fluid availability is maintained when required.
Solution Approach 2:
The patent applies partial action by using the switching valve to restrict transmission fluid flow to only the necessary amount for current operating conditions. Rather than maintaining full flow capacity through the switching valve at all times, the system allows partial flow when gear ratio changes are slow or vehicle speed is low, reducing pump load and energy loss. The valve can be opened fully when rapid gear ratio changes are needed, providing excessive flow capacity only when necessary.
3Loss of energy
If the switching valve switches frequently between open and closed positions, then the system can optimize fuel efficiency, but mechanical wear and reliability decrease
Solution Approach 1:
The control system implements periodic evaluation of transmission operating conditions to determine optimal switching valve positions. Rather than continuous switching, the system periodically assesses parameters such as gear ratio change rate, vehicle speed, and engine load, and only switches the valve when conditions warrant a change. This periodic action reduces the frequency of switching operations, thereby minimizing mechanical wear on the switching valve while still maintaining fuel efficiency through optimized pump operation.
Solution Approach 2:
The system employs feedback control to monitor the state of the transmission and adjust the switching valve position accordingly. The control system continuously receives feedback about operating conditions and makes switching decisions based on this feedback, switching the valve only when the feedback indicates a change in operational requirements. This feedback-based approach prevents unnecessary switching that would occur without proper monitoring, thereby extending switching valve durability while maintaining optimal fuel efficiency.
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
The system enhances fuel efficiency by optimizing the operation of the transmission fluid pump, reducing engine load, and enabling faster changes in gear ratios within the limitations of pressure and output constraints.
Implementation Method 1
The switching valve also directs transmission fluid back to the transmission fluid pump when the switching valve is in the closed position
Implementation Method 2
The transmission fluid pump further pumps transmission fluid to the pressure regulator valve through a second flow path
Implementation Method 3
a pressure regulator valve of the CVT
Data Source
AI summary
A target module determines a target ratio between a speed of an input shaft and a speed of an output shaft of a continuously variable transmission (CVT) based on an accelerator pedal position. A maximum rate of change (ROC) module determines a maximum ROC of the target ratio. A switching valve control module, based on a comparison of the maximum ROC and a ROC of the target ratio, selectively actuates a switching valve of the CVT one of (i) from a closed position to an open position and (ii) from the open position to the closed position. The switching valve prevents transmission fluid flow through a flow path between a transmission fluid pump and a pressure regulator valve of the CVT when the switching valve is in the closed position. The switching valve allows transmission fluid flow through the flow path when the switching valve is in the open position.