(19)
(11) EP 2 208 930 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
24.01.2018 Bulletin 2018/04

(43) Date of publication A2:
21.07.2010 Bulletin 2010/29

(21) Application number: 10250011.3

(22) Date of filing: 06.01.2010
(51) International Patent Classification (IPC): 
F23Q 7/00(2006.01)
(84) Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR
Designated Extension States:
AL BA RS

(30) Priority: 15.01.2009 JP 2009006912

(71) Applicant: NGK Spark Plug Co., Ltd.
Nagoya-shi, Aichi-ken 467-8525 (JP)

(72) Inventors:
  • Hiraishi, Masanori
    Nayoya Aichi 485-8525 (JP)
  • Kato, Hiroshi
    Nayoya Aichi 485-8525 (JP)
  • Ando, Minoru
    Nayoya Aichi 485-8525 (JP)

(74) Representative: J A Kemp 
14 South Square Gray's Inn
London WC1R 5JJ
London WC1R 5JJ (GB)

   


(54) Manufacturing method of heater tube of glow plug and glow plug


(57) [Objective] An object is to maintain at a predetermined amount the projection length of a projecting mouth portion projecting frontward from a tapered-off portion at the front end of a heater tube, to thereby prevent occurrence of welding failure, which would otherwise occur when a front end of a heat generation coil disposed within the heater tube is welded to the projecting mouth portion.
[Means for Solution]
The diameter D21 of a straight hole portion 123 of a forming hole 121 of a die 101 used in each of press steps including the final press step is made greater than the outer diameter of a heater tube finished product. A blank material 20 to undergo forming is pressed, with a support member 151 disposed on the front end side of the forming hole 121, whereby the projection length L1 of a projecting mouth portion 35 is maintained at a predetermined projection length. When the blank material 20 is excessively long, its outer diameter increases. Therefore, the blank material 20 is then passed through an ironing hole so as to adjust the outer diameter of the straight tube portion 21 of the heater tube in-process product to a predetermined dimension. When the overall length is greater than a maximum allowable dimension, a rear-end unnecessary portion of the straight tube portion 21 is cut for adjustment. Desired dimensions can be imparted to the projecting mouth portion, etc.







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