Glow Plug Coil Deformation Prevention via Segmented Insulator
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Solution Overview
Problem
Conventional glow plug manufacturing methods result in coil deformation and inconsistent temperature rising characteristics due to the softness of the coil and variations in winding pitch, leading to potential short-circuits and reduced durability.
Innovation Solution
A method involving a rod-like insulator with a thin portion at the front end, allowing it to reach the taper-shaped reduced diameter portion of the coil, ensuring consistent deformation and preventing early disconnection during the swaging process, while maintaining appropriate clearances between the sheath tube and coil to prevent short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rod-like insulator with large diameter is inserted in the coil to reduce clearance and prevent coil bending, then the coil deformation is reduced, but the insulator cannot reach the front end of the taper-shaped reduced diameter portion of the coil, resulting in low density insulating powder filling and local coil deformation during swaging
Solution Approach 1:
The insulator is segmented into two distinct portions: a front end portion with a first diameter designed to reach the front end of the taper-shaped reduced diameter portion of the coil, and a rear end portion with a second diameter for maintaining appropriate clearance. This segmentation allows each portion to fulfill its specific functional requirement independently.
Solution Approach 2:
Different portions of the insulator are given different diameters to satisfy different local requirements: the front end portion has a larger diameter to reach the coil's reduced diameter portion and provide support, while the rear end portion has a smaller diameter to maintain proper clearance and allow insulating powder filling. This local differentiation resolves the contradiction between preventing coil deformation and achieving precise insulator positioning.
2Ease of manufacture
If the coil is subjected to swaging step without adequate support, then the sheath tube is properly formed, but the soft coil becomes bent or eccentric, causing inconsistent winding pitch and potential short-circuits
Solution Approach 1:
The insulator is inserted into the coil before the swaging step to provide preliminary support and maintain the coil's shape. This preliminary action prevents the soft coil from bending or becoming eccentric during the subsequent swaging process, ensuring consistent winding pitch and preventing short-circuits while allowing the sheath tube to be properly formed.
3Quantity of substance
If insulating powder is filled only in the vicinity of the front end portion of the coil where the insulator does not reach, then the front end coil is inadequately protected, causing local deformation and inconsistent thickness during swaging
Solution Approach 1:
The insulator's segmented structure with different diameters enables it to reach the front end of the coil's reduced diameter portion while maintaining proper clearance at the rear. This allows insulating powder to be adequately filled throughout the entire coil length, including the front end portion, ensuring uniform protection and preventing local deformation during swaging.
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 method effectively prevents coil deformation and eccentricity, enhances durability, and reduces variations in temperature rising characteristics, ensuring reliable operation and improved manufacturing yield.
Implementation Method 1
a coil made of a resistance wire, disposed along the axis of the sheath tube and joined to a front end of the sheath tube
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
The present invention provides a glow plug capable of preventing a deformation or eccentricity of the coil, improving a durability of the coil and preventing a variation in temperature rising characteristic. Also, the present invention provides a method for manufacturing the glow plug. A sheath heater 3 of the glow plug includes a metal sheath tube 7 having a closed front end, a heating coil 9 or the like joined to a front end of the tube and accommodated in the sheath tube 7, a rod-like insulator 11 inserted in the heating coil 9 or the like, and insulating powders filled in gaps between the sheath tube 7, a rod-like insulator 11 and the heating coil 9. A front end taper portion 11a having a smaller outer diameter than a outer diameter of a general portion of the insulator 11 is formed on the front end side of the insulator 11. Prior to a swaging step, the insulator 11 is inserted in the heating coil 9 or the like, and the front end taper portion 11a is disposed inside of a taper-shaped reduced diameter portion 9a of the heating coil 9. Thus, influence of the swaging step on the taper-shaped reduced diameter portion 9a can be reduced.