Glow Plug Load Sensing Sleeve With Elastic Link
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Solution Overview
Problem
Existing glow plug technologies face challenges in integrating a load sensor to measure cylinder pressure effectively, as they must withstand high pressure variations while minimizing stress on the sensor and maintaining reliability, and must avoid exposure to extreme temperatures and atmospheric conditions, with prior solutions failing to find a suitable compromise between mechanical and thermal reliability.
Innovation Solution
A glow plug design featuring a tubular load sensing sleeve with elastically deformable mechanical links between the heating rod and the plug body, allowing for axial translation and compression, which optimizes sensitivity and precision while reducing stress on the sensor and maintaining thermal isolation, using elastically deformable elements made of high-strength materials like stainless steel to manage differential thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the heating rod is rigidly mounted in the plug body to ensure structural stability, then the structural stability is improved, but the sensitivity of cylinder pressure measurement deteriorates
Solution Approach 1:
The mounting structure is divided into separate functional elements: a rigid support structure for thermal isolation, an elastic mounting element for pressure-sensitive movement, and a load sensor for measurement. This segmentation allows each component to perform its specific function without compromising the others.
Solution Approach 2:
An elastic mounting element acts as an intermediary between the rigid plug body and the heating rod, allowing the heating rod to move in response to pressure changes while maintaining structural support and thermal isolation through the rigid components.
2Measurement precision
If the heating rod is allowed to move axially with high flexibility to improve pressure measurement sensitivity, then the measurement sensitivity is improved, but the ability to resist cylinder pressure variations deteriorates
Solution Approach 1:
The system separates the function of resisting pressure (handled by the rigid plug body and heating rod structure) from the function of detecting pressure (handled by the controlled axial movement through the elastic mounting element and load sensor).
Solution Approach 2:
The elastic mounting element's stiffness parameter is optimized to allow sufficient axial movement for sensitive pressure detection while maintaining enough rigidity to resist the full range of cylinder pressure variations.
3Ease of operation
If the load sensor is exposed to the combustion chamber atmosphere to directly measure pressure, then the measurement directness is improved, but the reliability of the sensor deteriorates due to high temperatures
Solution Approach 1:
The heating rod serves as an intermediary that transmits pressure information from the combustion chamber to the load sensor, which remains in the protected proximal zone. The load sensor measures the axial movement of the heating rod rather than directly exposing itself to harsh conditions.
Solution Approach 2:
The load sensor is extracted from the high-temperature combustion chamber environment and placed in the protected proximal zone, while still being able to measure pressure through the axial movement of the heating rod.
4Strength
If the elastic impermeability membrane is made thin to reduce stress on the sensor, then the stress on the sensor is reduced, but the thermal protection capability deteriorates
Solution Approach 1:
The thermal management function is separated from the pressure sensing function. The elastic impermeability membrane handles pressure transmission, while a dedicated thermal management system (including the rigid plug body structure and positioning of components in the proximal zone) handles thermal protection.
Solution Approach 2:
The rigid plug body acts as a thermal barrier intermediary between the heating rod in the combustion chamber and the load sensor in the proximal zone, protecting the sensor from high temperatures without requiring the impermeability membrane to provide thermal protection.
5Temperature
If the elastic impermeability membrane is made thick to improve thermal protection, then the thermal protection capability is improved, but the stress on the membrane and sensor deteriorates
Solution Approach 1:
The functions of thermal protection and pressure transmission are separated into different components: the rigid plug body structure provides thermal protection, while the thin elastic impermeability membrane provides pressure transmission with minimal stress.
6Volume of stationary object
If the available space in the plug body is maximized for sensor housing, then the sensor integration is improved, but the thermal isolation capability deteriorates
Solution Approach 1:
The plug body structure provides localized thermal isolation where needed (between the heating rod and the proximal zone), while maximizing available space in the proximal zone for sensor housing and other 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
The design enables precise measurement of cylinder pressure across a wide range with minimal interference, maintaining sensor reliability and avoiding exposure to extreme temperatures, while ensuring mechanical and thermal stability, allowing for finer engine control and extended sensor lifespan.
Implementation Method 1
a mechanical link between said second axial extremity of the load sensing sleeve and the plug body, said mechanical link being elastically deformable against axial translation movements of the heating rod relative to the plug body
Implementation Method 2
using elastically deformable elements made of high-strength materials like stainless steel to manage differential thermal expansion
Implementation Method 3
a tubular load sensing sleeve having: a first axial extremity, which is connected to the heating rod so as to be driven in axial translation by the movements of the latter
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention concerns a glow plug comprising a heating rod (11), a plug body (13) having a receiving housing (14) of the heating rod, a mounting device (48) for mounting the heating rod, permitting axial translation movements of the heating rod relative to the plug body and ensuring impermeability between the heating rod and the plug body, and a load sensing sleeve (17). An elastically deformable element (18) is interposed between the load sensing sleeve and the plug body.