Exhaust Throttle Valve Sealing for Actuator Heat Isolation
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Solution Overview
Problem
Motor-driven throttle valves for exhaust ducts face challenges in thermal screening of electric actuators due to high exhaust gas temperatures and sealing issues to prevent gas leaks, which existing technologies have not adequately addressed.
Innovation Solution
The design incorporates thermally insulating ceramic materials and specific sealing mechanisms to protect the electric actuator from high temperatures and minimize gas leaks, using refractory materials like ceramic for seals and insulating discs, along with spring-assisted shaft support to manage thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the electric actuator is positioned close to the exhaust duct for compact design, then device complexity is reduced, but the actuator is exposed to high temperatures exceeding its operational limit
Solution Approach 1:
The support bearing is divided into two separate components: a first support bearing arranged inside the exhaust duct and a second support bearing arranged outside the exhaust duct. This segmentation allows the electric actuator to be positioned outside the high-temperature zone while maintaining functional connectivity through the shaft that passes through the exhaust duct wall.
Solution Approach 2:
The exhaust duct wall acts as an intermediary barrier between the high-temperature exhaust gases and the electric actuator. The shaft penetrates this barrier to transmit rotational motion, while the dual bearing arrangement ensures the actuator remains in the cooler external environment.
2Ease of operation
If a through opening is created in the exhaust duct for shaft connection, then the actuator can be connected externally, but exhaust gas leaks occur through the opening
Solution Approach 1:
A flexible sealing element is inserted into the through opening of the exhaust duct to prevent exhaust gas leaks. This sealing element accommodates thermal expansion and contraction of the duct while maintaining the seal, allowing the shaft to pass through without creating leakage paths.
3Ease of manufacture
If rubber gaskets are used for sealing the through opening, then sealing is simplified, but the gaskets cannot withstand high exhaust gas temperatures
Solution Approach 1:
The sealing solution employs a composite approach combining a flexible sealing element (providing sealing functionality) with a heat-resistant coating or material selection (providing thermal resistance). This allows the sealing element to withstand the high temperatures of exhaust gases while maintaining its sealing effectiveness.
4Strength
If metal parts are used for support bearings, then structural strength is improved, but thermal expansion causes sealing issues at the through opening
Solution Approach 1:
The design explicitly accounts for thermal expansion of metal parts by providing clearance and adjustment mechanisms in the support bearing arrangement. The first and second support bearings are positioned to accommodate dimensional changes of the shaft and exhaust duct during temperature transitions, preventing binding and maintaining sealing effectiveness.
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 effectively preserves the integrity of the electric actuator, reduces gas leaks, and maintains operational efficiency while being cost-effective and easy to manufacture.
Implementation Method 1
The sealing element is made of a ceramic material which is thermally insulating
Implementation Method 2
a spring mechanism to maintain the shaft's position and reduce friction
Implementation Method 3
it is necessary to take into account the thermal expansion of the metal parts caused by the great temperature differences (in the range of hundreds of Celsius degrees) that occur between the cold engine condition and the hot engine condition
Data Source
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AI summary
A motor-driven throttle valve (1) for an exhaust duct and having: a tubular duct (2), which is designed so that exhaust gases can flow through it; a throttle shutter (3), which is arranged inside the tubular duct (2) and is mounted so as to rotate around a rotation axis (4); a first shaft (5), which is mounted so as to rotate around the rotation axis (4) and supports the throttle shutter (3); an electric actuator (6), which is provided with a second shaft (52) and is designed to rotate the shaft (5) around the rotation axis (4); a support bearing (9), which supports the shaft (5) in a through manner and is arranged on the outside of the tubular duct (2); and a spring (11), which applies to the shaft (5) an elastic force, which axially pushes the shaft (5) and, at the same time, is configured to transmit a rotary motion around the rotation axis (4) from the second shaft (52) of the electric actuator (6) to the first shaft (5) supporting the throttle shutter (3).