Glow Plug Center Pole Vibration Damping via Intermediary Member
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Solution Overview
Problem
The increasing length of glow plugs in diesel engines leads to decreased natural frequency of the center pole, causing resonance issues during engine operation, which can result in electrical insulation loss, center pole breakage, and ceramic heater failure due to vibration-induced stress, especially with compact metal shells and tight clearance spaces making it difficult to effectively insert and secure vibration preventing members.
Innovation Solution
A glow plug design featuring a mechanically rigid center pole and heater integration with a vibration preventing member press-fitted between the center pole and metal shell, where the vibration preventing member is fixed on the outer surface of the center pole and has varying thickness to ensure effective vibration suppression, and is manufactured using injection molding to secure the member on a small-diameter portion with increased surface roughness for reliable positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the overall length of the glow plug is increased to achieve compact engine mounting, then the natural frequency of the center pole decreases, but this causes resonance to occur more frequently leading to center pole breakage and ceramic heater failure
Solution Approach 1:
A vibration preventing member is introduced as an intermediary component between the center pole and the metal shell. This member absorbs and dampens vibrations, preventing direct contact between the vibrating center pole and the metal shell, thereby eliminating the harmful resonance effect while maintaining the compact overall length
Solution Approach 2:
The natural frequency of the center pole is modified by changing its physical parameters - specifically reducing the outside diameter at the vibration loop portion. This parameter change shifts the natural frequency away from the engine operating frequency range, preventing resonance from occurring
2Length of stationary object
If the outside diameter of the center pole is reduced to increase clearance for vibration preventing member insertion, then the clearance space increases, but the rigidity of the center pole declines causing plastic deformation under resonance stress
Solution Approach 1:
The center pole is designed with non-uniform diameter along its length. The outside diameter is reduced only at the specific location corresponding to the vibration loop (where clearance is needed for vibration prevention), while maintaining the original diameter at other portions to preserve overall rigidity and structural strength
3Reliability
If the thickness of the vibration preventing member is increased to improve vibration suppression, then the vibration damping effect is enhanced, but the difficulty of inserting the member into the axial hole increases due to tight clearance
Solution Approach 1:
The vibration preventing member is pre-formed with a tapered shape before insertion. The smaller diameter end of the tapered member is inserted first into the axial hole, allowing the member to gradually work its way in. Once inserted, the member expands to provide sufficient thickness for effective vibration suppression
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 reduces stress on the center pole and ceramic heater, preventing breakage and maintaining vibration suppression even under resonance conditions, ensuring reliable operation and extended lifespan by securely fixing the vibration preventing member and enhancing its thickness for sufficient damping effect.
Implementation Method 1
a vibration preventing member for preventing vibration of the center pole... the vibration preventing member being disposed so as to be radially compressed between the inner peripheral surface of the axial hole and the outer peripheral surface of the center pole
Data Source
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AI summary
A glow plug including a center pole extending along an axial direction; a heater including a heating element capable of generating heat upon energization, which heater is connected to a leading end portion of the center pole so as to constitute together with the center pole an integrated heater/center pole member in a mechanically rigid state; a metal shell as defined herein; and a vibration preventing member for preventing vibration of the center pole, the vibration preventing member being fixed on an outer peripheral surface of the center pole at an axial position corresponding to a portion where an inside diameter of the axial hole of the metal shell is constant.