Multi-Stage Valve System for Automatic Transmission Pressure Control
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Solution Overview
Problem
Hydraulic control units in automatic transmissions face position inaccuracies in low pressure ranges due to high valve reinforcement, leading to increased pump absorption torque and power consumption.
Innovation Solution
A valve system comprising a multi-stage system pressure valve, a pilot valve, and a control valve with a pressure-reducing valve design that adjusts pressure based on pilot pressure, achieving high resolution in low pressure ranges and low resolution in high pressure ranges without breaking the pilot pressure/system pressure characteristic curve, using a control piston to govern the differential area of the system pressure valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pilot-operated pressure relief valve is used to adjust system pressure, then the system pressure can be continuously adjusted between minimum and maximum values, but position inaccuracies occur in the low pressure range due to high valve reinforcement
Solution Approach 1:
The system divides the pressure control into two stages: a first pressure stage (0-10 bar) handled by a first pressure relief valve with low reinforcement for high precision, and a second pressure stage (10-40 bar) handled by a second pressure relief valve with high reinforcement for high pressure capability. This segmentation resolves the contradiction by assigning different valve characteristics to different pressure ranges.
Solution Approach 2:
Different parts of the pressure control system are given different properties: the first pressure relief valve has low valve reinforcement optimized for low pressure precision, while the second pressure relief valve has high valve reinforcement optimized for high pressure capability. Each component is locally optimized for its specific function.
2Power
If high valve reinforcement is used to achieve maximum system pressure, then the maximum pressure capability is improved, but position inaccuracies increase in the low pressure range
Solution Approach 1:
The pressure control function is segmented between two valves: the first pressure relief valve handles low pressure (0-10 bar) with low reinforcement for precision, while the second pressure relief valve handles high pressure (10-40 bar) with high reinforcement for power capability. This eliminates the trade-off by separating the functions.
Solution Approach 2:
The system dynamically switches between two different valve configurations depending on the pressure range. The first valve operates in the low pressure range with optimal precision characteristics, while the second valve takes over in the high pressure range with optimal power characteristics, allowing the system to adapt its characteristics to the required operating conditions.
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 solution ensures accurate pressure control in low pressure ranges while minimizing position inaccuracies and reducing pump absorption torque, allowing for efficient operation across varying pressure ranges without significant increases in power consumption.
Implementation Method 1
a control valve with a control piston downstream from the pilot valve, which governs the pressure at a differential area of the system pressure valve, depending on the pilot pressure
Data Source
AI summary
A valve system for controlling a system pressure control system, in particular a hydraulic control unit of an automatic transmission, includes a multi-stage system pressure valve, a pilot valve and a control valve with a control piston downstream from the pilot valve that governs the pressure at a differential area of the system pressure valve, depending on the pilot pressure. The pilot pressure/system pressure characteristic curve features a continuous development, and whereas, from a predefined pilot pressure, on the basis of a sudden change to the dependency of the change to the system pressure as a function of the change to the pilot pressure, the gradient of the system pressure as a function of the pilot pressure is significantly steeper than that prior to the predefined pilot pressure.