Dual-Circuit Transmission Pump Control for Stable Hydraulic Pressure
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Solution Overview
Problem
Existing hydraulic systems in motor vehicle transmissions face inefficiencies in energy balance and gear change execution due to frequent switching between single-circuit and dual-circuit operating states, leading to unstable system pressure and potential interruption of power flow.
Innovation Solution
A control method and device that stabilize system pressure by controlling the rotational speed of the electric machine to prevent frequent switching between single-circuit and dual-circuit operations, optimizing the distribution of primary and secondary flows based on predefined threshold values to maintain stable operating states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the hydraulic system switches between single-circuit and dual-circuit operating states to meet varying flow demands, then the system can adapt to different operating conditions, but frequent switching causes unstable system pressure and potential interruption of power flow
Solution Approach 1:
The control device determines in advance whether a required primary flow increase exceeds a threshold value before switching operating states. This preliminary assessment prevents unnecessary switching and stabilizes system pressure by ensuring transitions only occur when genuinely needed.
Solution Approach 2:
The system dynamically adjusts the electric machine's rotational speed to meet primary flow demands without necessarily switching between single-circuit and dual-circuit operating states. This dynamic speed adjustment provides adaptability while maintaining operating state stability.
2Quantity of substance
If the hydraulic pump delivers excess hydraulic fluid to the primary circuit to meet increasing flow demands, then the primary circuit receives sufficient fluid, but energy is wasted delivering fluid that cannot be utilized
Solution Approach 1:
The control device continuously monitors the actual primary flow and compares it with the target primary flow. Based on this feedback, it determines whether to increase the electric machine's rotational speed or switch to dual-circuit operation, ensuring hydraulic fluid is delivered only when needed and minimizing energy waste.
Solution Approach 2:
The system changes operational parameters by adjusting the electric machine's rotational speed to precisely match the required primary flow demand. This parameter adjustment ensures optimal fluid delivery without excessive energy consumption.
3Productivity
If the system uses a dual-circuit pump driven by both internal combustion engine and electric machine, then the system can provide sufficient hydraulic flow under all conditions, but the device complexity increases
Solution Approach 1:
The control device autonomously manages the dual-circuit pump system by monitoring flow demands and automatically adjusting the electric machine's rotational speed or switching operating states. This self-service control simplifies the overall system architecture while maintaining high productivity.
Solution Approach 2:
The electric machine serves multiple functions: it can drive the dual-circuit pump in dual-circuit mode, provide additional drive power in single-circuit mode, or be adjusted to meet varying flow demands. This multi-functionality reduces the need for separate dedicated components.
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
Stabilizes system pressure, reduces manufacturing tolerances and wear effects, and enhances energy efficiency by minimizing unnecessary transitions between operating states, ensuring consistent hydraulic fluid supply for shift elements.
Implementation Method 1
a dual-circuit pump (14) having a primary flow (16) and a secondary flow (18)
Implementation Method 2
a system pressure valve (32)... Only once this has taken place can an excess amount of oil or an excess volumetric flow of oil be delivered into the secondary circuit (30) of the hydraulic system via the system pressure valve (32)
Implementation Method 3
The dual-circuit pump is coupled to an internal combustion engine and an electric machine via a superposition gear unit in order to drive the dual-circuit pump by superimposing the rotational speeds of the internal combustion engine and the electric machine
Data Source
AI summary
A method for operating a motor vehicle having a transmission including a hydraulic system with a dual-circuit pump includes driving the dual-circuit pump by both an internal combustion engine and an electric machine via a superposition gear unit that superimposes a rotational speed of the internal combustion engine and a rotational speed of the electric machine. The method further includes determining whether a subset is less than a subset threshold value when a target value of a required primary flow increases in a dual-circuit operating state to a value higher than a current primary flow actual value, with the subset being a difference between the target value and the current primary flow actual value. Additionally, the method includes increasing the second rotational speed of the electric machine when the subset is less than the subset threshold value.