Method for the production of a glow plug

Abstract

Methods for producing a glow plug having a housing, a ceramic glow pin and a protective tube from which a section of the glow pin projects which is thinner than a thicker section arranged in the protective tube. The thinner section leads to a glow tip. The glow pin is inserted into the protective tube and the protective tube is inserted into the housing. A securing element is placed onto the first end of the glow pin. The internal diameter of the securing element is smaller than the maximum diameter of the glow pin. The securing element is fastened on the protective tube. Alternatively, the protective tube is heated locally at a section of the protective tube surrounding the thinner section, and there the interior width of the protective tube is reduced to a value smaller than the diameter of the thicker section of the glow pin.

Claims

1. A method for manufacturing a glow plug having a housing, a ceramic glow pin and a protective tube from which a section of the glow pin projects, said section leading to a glow tip and being thinner than a thicker section arranged in the protective tube, the method comprising: inserting the glow pin into the protective tube and inserting the protective tube into the housing; placing a securing element onto the first end of the glow pin and into an increased internal diameter section of the protective tube, the internal diameter of the securing element being smaller than the maximum diameter of the glow pin; and fastening the securing element onto the protective tube.

2. The method according to claim 1, wherein the glow pin has a diameter that increases in a step and wherein the internal diameter of the securing element is between the diameter of the glow pin in front of the step and the diameter of the glow pin behind the step.

3. The method according to claim 1, wherein the securing element is fastened to the protective tube by an interference fit.

4. The method according to claim 1, wherein the protective tube is fastened to the housing by an interference fit.

5. The method according to claim 1, wherein the securing element is a ring or a sleeve.

6. The method according to claim 1, wherein the securing element is arranged entirely outside the housing.

7. The method according to claim 1, wherein the glow pin has a narrowing section at its end facing away from the glow tip, and in that the glow pin is pressed into a protective tube which narrows at its end arranged in the housing and surrounds there a portion of the narrowing section of the glow pin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 shows a glow plug in a partially sectional view;

(3) FIG. 2 shows a detail view to FIG. 1;

(4) FIG. 3 shows a detail view to FIG. 2;

(5) FIG. 4 shows a detail view according to FIG. 2 of a further embodiment;

(6) FIG. 5 shows a detail view to FIG. 4;

(7) FIG. 6 shows a detail view according to FIG. 2 of a further embodiment;

(8) FIG. 7 shows a detail view to FIG. 6;

(9) FIG. 8 shows a detail view according to FIG. 2 of a further embodiment; and

(10) FIG. 9 shows a detail view according to FIG. 2 of a further embodiment.

DESCRIPTION

(11) The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

(12) In FIG. 1 an embodiment is shown schematically in a view partially in section. The glow plug has a metallic housing 1, which can have an external thread 2 and a hexagon 3. In the housing 1, an inner conductor 4 is arranged, which is connected to the rear end, remote from the combustion chamber, of a ceramic glow pin 5. The glow pin 5 is surrounded by a protective tube 6, from which it projects by its two ends, and has at its front end a glow tip 7. At its rear end, the glow pin 5 has a narrowing section, which can be partially surrounded by the protective tube 6.

(13) The ceramic glow pin 5 can have, for example, an inner conductor 8, an outer conductor 9 and an insulator layer 10 lying therebetween. Such a glow pin 5 can be connected to the inner conductor 4, by the rear end of the glow pin 5 being placed in the inner conductor 4.

(14) Between its two ends, the glow pin has a cylindrical section, which may form the largest part of the length of the glow pin 5, but may also be shorter. Between the cylindrical section and the glow tip 7, the diameter of the glow pin 5 decreases inside the protective tube 6, for example in a stepped manner or in a conical section. The cylindrical section is therefore thicker than a section projecting out from the front end of the protective tube 6. This decrease in diameter enables a securing of the glow pin 5, so that the latter can not fall out from the protective tube 6 even in the case of a breakage of the glow pin.

(15) FIG. 2 shows a detail view of the front end of the protective tube 6 on the combustion chamber side, in which a cylindrical section 5a of the glow pin is arranged. Adjoining this section 5a is a thinner, preferably likewise cylindrical, section 5b of the glow pin. Between the two sections 5a, 5b there is a step or a transition section, which may be conical, for example. FIG. 3 shows an enlarged detail view to FIG. 2. In FIG. 3, the front end of the protective tube 6 and a securing element 11 fastened thereon are illustrated. The securing element 11 has a smaller internal diameter than the protective tube 6. The internal diameter of the securing element 11 is smaller than the maximum diameter of the glow pin 5, i.e., smaller than the diameter of the cylindrical section 5a.

(16) In an end section, the protective tube 6 has an increased internal diameter, and thus forms a mount for the securing element 11. In this end section, the protective tube 6 can have a reduced wall thickness. In the embodiment of FIGS. 2 and 3, the securing element 11 is a ring. This ring can be arranged entirely inside the protective tube 6 or can project out from the protective tube 6.

(17) In FIG. 4 and the associated detail view of FIG. 5, a modified embodiment is illustrated, which differs from the example of FIGS. 2 and 3 only in the configuration of the securing element 11. The securing element 11 of FIGS. 4 and 5 projects from the protective tube 6 and has an increased external diameter outside the protective tube 6. The securing element 11 sits with a first section on the protective tube 6 and with a second, thinner section in the protective tube 6.

(18) The securing element 11 can be fastened to the protective tube 6 by press joining, for example can be pressed into the protective tube after the glow pin 5 has been inserted into the protective tube 6. The protective tube 6 can be fastened to the housing 1 by press fitting. Both pressing-in processes can be carried out in one working step.

(19) FIG. 6 shows a detail view of an embodiment of a glow plug without a securing element. In FIG. 6, the front end of the protective tube 6 is illustrated together with the thicker section 5a and the thinner section 5b of the glow pin. In this example embodiment, a securing of the glow pin in the protective tube 6 was achieved in that the protective tube 6 is heated locally at least one site 12 which lies between the glow tip 7 and the thicker section 5a arranged in the protective tube 6, and the interior width of the protective tube 6 is reduced there to a value which is smaller than the diameter of the thicker section 5a of the glow pin. The protective tube 6 was heated locally at several sites 12 and pressed in there, so that radially inwardly directed protuberances, for example three protuberances, are produced. These sites 12 lie in a section of the protective tube 6 which surrounds the thinner section 5b of the glow pin.

(20) FIG. 7 shows a detail view to FIG. 6, in which one of the deformed sites 12 of the protective tube 6 is illustrated. The protective tube 6 can be fused at the sites 12, for example by a laser beam. The sites 12 can be arranged in a ring shape.

(21) In FIG. 8, a modified embodiment is illustrated, in which the protective tube is heated locally at a ring-shaped site 12 and there the interior width of the protective tube 6 is reduced to a value which is smaller than the diameter of the thicker section 5a of the glow pin. The ring-shaped site 12 can be heated for example inductively or by radiation and forms an inwardly directed bead.

(22) FIG. 9 shows a detail view of a further embodiment of a glow plug with a securing element 11, which is constructed as a sleeve.

(23) While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

REFERENCE NUMERALS

(24) 1 housing 2 external thread 3 hexagon 4 inner conductor 5 glow pin 5a thicker glow pin section 5b thinner glow pin section 6 protective tube 7 glow tip 8 inner conductor of the glow pin 9 outer conductor of the glow pin 10 insulator layer of the glow pin 11 securing element 12 deformed site of the protective tube