| 摘要 |
To positively exclude oxygen from a heating spiral located within the interior of a glow plug, so that the heating spiral can use a material having a high positive temperature coefficient of resistance, an insulating bushing separates a central connecting bolt from the surrounding metal sleeve and at least one, and preferably both the bolt and the metal sleeve are formed with circumferential matching ridges and grooves into which the insulating bushing will be pressed to provide an effective seal and a long, tortuous path for any possible leakage of air past the seal, even under the extremes of operating conditions and temperature gradients to which glow plugs are exposed in use. To further exclude oxygen from the heating spiral, the filler material adjacent the sealing bushing can include material having a high affinity to oxygen, such as aluminum or magnesium, so that any oxygen molecules which might leak past the seal will be bound thereby.
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