Marine Transmission Pressure Valve Venting for Stable Switching Time
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Solution Overview
Problem
Hydraulic control devices in ship gears experience temperature-dependent viscosity changes in pressure media, leading to extended switching times and mechanical loads due to pressure losses, which conventional solutions only partially mitigate.
Innovation Solution
A hydraulic control device with a pressure tax valve featuring a control piston and modulation piston, where a ventilation line with a second throttle is connected to the pressure space, allowing for coordinated throttle dimensions to minimize temperature-related volume changes, ensuring consistent pressure modulation and reduced temperature dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If mechanical pressure modulation is used with conventional throttles, then pressure control is achieved, but switching time increases significantly at low temperatures due to viscosity changes
Solution Approach 1:
The single throttle is segmented into two parallel throttles with different flow characteristics. The first throttle has a larger cross-section optimized for low-temperature operation, while the second throttle has a smaller cross-section optimized for high-temperature operation. This segmentation allows the system to maintain consistent pressure modulation performance across the entire temperature range by providing multiple flow paths with complementary characteristics.
Solution Approach 2:
The system dynamically adapts to temperature changes by providing two throttles with different flow characteristics. At low temperatures, the higher viscosity favors flow through the first throttle with larger cross-section, while at high temperatures, the lower viscosity allows effective flow through the second throttle with smaller cross-section. This dynamic adaptation eliminates the need for active control mechanisms.
2Temperature
If throttle cross-sections are optimized for high temperatures, then pressure modulation works at high temperatures, but switching time becomes unacceptably long at low temperatures
Solution Approach 1:
Instead of using a single throttle optimized for high temperatures, the system segments the flow control into two parallel throttles. The first throttle is designed with a larger cross-section to compensate for high viscosity at low temperatures, ensuring fast switching. The second throttle maintains the original high-temperature optimization. Both throttles work in parallel, with the first throttle becoming dominant at low temperatures and the second throttle becoming more significant at high temperatures.
3Speed
If throttle cross-sections are optimized for low temperatures, then switching time is fast at low temperatures, but pressure modulation fails at high temperatures due to excessive flow
Solution Approach 1:
The flow control is segmented into two parallel throttles with complementary characteristics. The first throttle has a larger cross-section optimized for low-temperature fast switching, while the second throttle has a smaller cross-section optimized for high-temperature pressure modulation. At high temperatures, the first throttle would provide excessive flow, but the second throttle limits the flow to appropriate levels, ensuring proper pressure modulation performance across all temperature conditions.
4Device complexity
If a single throttle is used, then device complexity is low, but temperature compensation is insufficient
Solution Approach 1:
The single throttle is segmented into two parallel throttles with different cross-sections. This segmentation provides inherent temperature compensation without requiring complex control systems. The first throttle with larger cross-section compensates for viscosity increases at low temperatures, while the second throttle with smaller cross-section maintains control at high temperatures. The parallel configuration is simple to implement and maintains low device complexity while dramatically improving temperature compensation.
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 solution achieves nearly constant switching times across temperatures, reducing the influence of viscosity changes and mechanical loads, allowing for quick and consistent operation of hydraulically operated switching couplings.
Implementation Method 1
The first throttle represents the sum of the flow resistances of lines and, optionally, an orifice and a filter screen
Implementation Method 2
A vent line with at least one further restrictor is connected to the pressure chamber. A second volume flow Q2 can be drawn from the pressure chamber via the further restrictor
Implementation Method 3
The control piston and the modulation piston are pushed apart by at least one spring. Preferably, for example, two compression springs can be arranged between the two pistons and push them apart
Implementation Method 4
The pressure chamber can be filled with a first volume flow Q1 of a pressure medium through a first throttle
Data Source
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AI summary
The invention relates to a hydraulic control device (20) comprising a pressure control valve (1), wherein the pressure control valve (1) has a control piston (3) and a modulating piston (4) which can be displaced relative to one another. The control piston (3) and the modulating piston (4) are pushed apart from one another by at least one spring (7). A pressure chamber (8) is arranged on one end face of the modulating piston (4) such that filling said pressure chamber causes the modulating piston (4) to be displaced in the direction of the control piston (3). The pressure chamber (8) can be filled by a first throttle (9) at a first volumetric flow rate Q of a pressure medium. A ventilation line (21) having at least one additional throttle (22) is connected to the pressure chamber (8). A second volumetric flow rate Q2 can be discharged from the pressure chamber (8) via said ventilation line (21). The invention also relates to a marine transmission (1) comprising such a hydraulic control device (20).