Servo-Valve Leakage Reduction via Segmented Pilot Chambers
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Solution Overview
Problem
Existing pressure control servo valves used in hydraulic vehicle brakes, such as aircraft brakes, suffer from high leakage rates, leading to insufficient starting force and oscillations in operating pressure, especially at low temperatures or with impurities in the hydraulic fluid, which can result in difficult starts and unstable braking performance.
Innovation Solution
A pressure regulating servo valve design that includes an auxiliary pilot chamber connected to the supply port via a second restrictor and a nozzle, providing a priming pressure to ensure effective spool movement, while maintaining a low leakage rate by connecting the control chamber to the user port via a first restrictor and a nozzle, and using a vane to modulate the flow rate through the nozzle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the control chamber is connected to the supply port, then sufficient priming pressure is available for effective spool movement, but the leakage rate through the nozzle increases
Solution Approach 1:
The invention divides the pressure control system into two separate control chambers: a first control chamber connected to the supply port for generating priming pressure, and a second control chamber connected to the user port for controlling leakage flow. This segmentation allows each chamber to serve its specific function independently, resolving the contradiction between needing high priming pressure and minimizing leakage.
2Loss of substance
If the control chamber is connected to the user port, then the leakage rate through the nozzle is reduced, but the priming pressure may be insufficient to move the spool under certain conditions
Solution Approach 1:
The invention creates two distinct control chambers with different pressure sources: the first chamber connected to the high-pressure supply port provides sufficient priming force, while the second chamber connected to the lower-pressure user port controls leakage. This segmentation resolves the contradiction by assigning different functions to different chambers rather than using a single chamber for both purposes.
3Device complexity
If a single control chamber is used, then the device structure is simpler, but the valve may exhibit response difficulties and oscillations under certain operating conditions
Solution Approach 1:
The invention divides the control system into two chambers with different pressure sources and functions. The first chamber provides stable priming pressure from the supply port, while the second chamber controls leakage based on user port pressure. This segmentation improves response dynamics and eliminates oscillations without significantly complicating the overall valve structure.
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 design ensures sufficient priming pressure for effective starting and braking performance, even under low operating conditions, with a slight increase in leakage rate, while minimizing leakage through the nozzle by using a lower user port pressure, thus enhancing response dynamics and stability.
Implementation Method 1
a first restrictor (9) connecting the control chamber (8) to the user port (U) and a second restrictor (17) connecting the auxiliary pilot chamber (16) to the supply port (P)
Implementation Method 2
connected to a nozzle (10) opening into a cavity (11) connected to the return port (R)
Implementation Method 3
a vane (20) being movably mounted in a controlled manner in the cavity (11) facing the nozzle (10) to regulate a flow rate leaking through the nozzle (10)
Implementation Method 4
therefore a pilot pressure in the pilot chamber (8) acting on the control spool (2) to move the latter in a first direction
Data Source
Figure 1
AI summary
The invention relates to a pressure regulating servovalve comprising a body (1) having a working port (U), a supply port (P), and a return port (R), and a spool (2) movably mounted and adjustable within the body. The spool, together with the body, defines a pilot chamber (8) connected to the working port. According to the invention, the spool and the body further define a priming chamber (16) connected to the supply port via a second restrictor (17) and connected to the nozzle via a third restrictor (19), and in which a priming pressure (Pa) exists, acting on the spool in the first direction.