Smart Relief Valve Control for Transmission Pumping Loss Reduction
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Solution Overview
Problem
Existing hydraulic systems in transmissions face inefficiencies due to high pumping losses as they supply maximum pressure continuously, which is not utilized by all hydraulic devices, and are not adaptable to varying pressure demands across different devices like clutches and hydrostatic pumps, leading to potential over or underprediction of pressure needs.
Innovation Solution
A hydraulic system with a boost pump, relief valve, and control valves that actively adjust the boost pressure based on aggregate hydraulic pressure demands of multiple devices, using triggers to predict imminent pressure needs and reduce pressure during engine cranking to minimize torque absorption and pumping losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump displacement is selected to meet maximum flowrate demands at design pressure, then the hydraulic system can satisfy peak pressure demands of all hydraulic devices, but a relatively high amount of energy is wasted due to pumping losses as hydraulic devices do not use all the oil provided at design pressure
Solution Approach 1:
The relief valve is dynamically controlled by adjusting its opening degree based on real-time aggregate pressure demands of hydraulic devices. The controller receives pressure demand signals from multiple hydraulic devices and continuously modulates the relief valve position to maintain optimal pressure, transforming the static relief valve into a dynamic pressure regulation component that adapts to varying system conditions.
Solution Approach 2:
The system changes the pressure parameter dynamically by varying the relief valve opening degree in response to changing pressure demands. When aggregate pressure demand is low, the relief valve opens more to reduce pressure and minimize pumping losses; when demand is high, the valve closes to maintain pressure, thus adapting the pressure parameter to system needs.
2Device complexity
If a single relief valve control strategy is used for all hydraulic devices, then the system structure is simplified, but it cannot accommodate varying pressure demands of different hydraulic devices such as clutches and hydrostatic pumps
Solution Approach 1:
The single relief valve is designed to serve multiple hydraulic devices simultaneously by receiving aggregate pressure demand signals from various devices (clutches, hydrostatic pumps, etc.) and adjusting its opening degree to satisfy the combined pressure needs of all devices. This multi-functional approach allows one relief valve to replace what would traditionally require multiple device-specific relief valves.
Solution Approach 2:
The control strategy merges the pressure demand requirements of multiple hydraulic devices into a single aggregate pressure demand signal that controls one relief valve. By combining individual device pressure demands into a unified control parameter, the system achieves coordinated pressure regulation for all devices through a single control mechanism.
3Productivity
If the relief valve is proactively controlled in anticipation of shift events, then shifting performance is improved, but pumping losses occur when pressure demands are overpredicted or shifting performance suffers when underpredicted
Solution Approach 1:
The controller continuously receives feedback signals representing real-time pressure demands from hydraulic devices and adjusts the relief valve opening degree accordingly. This closed-loop feedback mechanism allows the system to respond accurately to actual pressure needs, avoiding both overprediction (which causes pumping losses) and underprediction (which degrades shifting performance).
Solution Approach 2:
The system anticipates upcoming pressure demands by monitoring triggers from hydraulic devices before they occur, allowing the relief valve to be pre-positioned to meet future pressure requirements. This preliminary action enables smooth shift events while minimizing unnecessary pressure regulation that would cause pumping losses.
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 reduces pumping losses and enhances transmission efficiency by dynamically adjusting pressure to match real-time demands of various hydraulic components, ensuring high performance and reduced energy waste.
Implementation Method 1
relief valves are positioned downstream of the pump and upstream of clutch control valves to permit fluid to be bled off the line
Implementation Method 2
a boost pump; a relief valve in fluidic communication with the boost pump and a reservoir
Implementation Method 3
a controller designed to actively adjust a position of the relief valve based on an aggregate hydraulic pressure demand of the hydraulic devices to alter a boost pressure of a hydraulic fluid supplied to the control valves
Data Source
AI summary
Methods and systems for a transmission are provided herein. In one example, a hydraulic system is provided that includes a boost pump, a relief valve in fluidic communication with the boost pump and a reservoir, and a plurality of control valves in fluidic communication with the boost pump, positioned downstream of the relief valve, and in fluidic communication with a plurality of hydraulic devices. The hydraulic system further includes a controller designed to actively adjust a position of the relief valve based on an aggregate hydraulic pressure demand of the plurality of hydraulic devices to alter a boost pressure of a hydraulic fluid supplied to the plurality of control valves.