WO2007009830A1

WO2007009830A1 - Sheathed element glow plug

Info

Publication number: WO2007009830A1
Application number: PCT/EP2006/062679
Authority: WO
Inventors: Simon Schmittinger; Jens Schneider
Original assignee: Robert Bosch Gmbh
Priority date: 2005-07-19
Filing date: 2006-05-29
Publication date: 2007-01-25
Also published as: DE102005033936A1; EP1910743A1

Abstract

The invention relates to a ceramic sheathed element glow plug (1) for arrangement in a chamber of an internal combustion engine. Said sheathed element glow plug (1) comprises a ceramic heating element (10) having a glow section (20) and optionally a conducting section (21, 22). The glow section (20) is completely produced from only one ceramic material recipe, thereby rendering the heating element (10) very robust. The invention allows to produce a heating element (10) in a simple and cost-effective manner.

Description

glow plug

State of the art

The invention relates to a ceramic glow plug for arrangement in a chamber of an internal combustion engine. Specifically, the invention relates to a ceramic glow plug for arrangement in a pre-vortex or combustion chamber of an air-compressing, self-igniting internal combustion engine.

From DE 198 44 347 Al a ceramic glow plug is known, which has a consisting of a ceramic layer composite radiator. In this case, two electrically conductive composite ceramic layers are provided which are separated from each other by an insulating composite ceramic layer. At the top of the ceramic heater, the two electrically conductive composite ceramic layers are connected by a thin web of electrically conductive composite ceramic.

The known from DE 198 44 347 Al glow plug has the disadvantage that complicated manufacturing steps are required for the production and the Probability of a fault in the manufactured glow plug is thereby increased. The radiator of the known glow plug is in fact multi-layered, with different in their sintering behavior matched to each other conducting and insulating materials must be used. The use of multiple compounds with different formulations requires complicated manufacturing steps and increases the likelihood of a defect in the manufactured radiator. In addition, due to the different masses and layers constructed radiator lower mechanical strength and increased production costs.

Advantages of the invention

The glow plug according to the invention with the features of claim 1 has the advantage that the thermal and mechanical robustness of the glow element is improved, that the production can be simplified and that a reduction in manufacturing costs is possible. In addition, the probability of the occurrence of a defect in the manufactured radiator is reduced, whereby the proportion of rejects in the manufacturing reduced and the reliability of the manufactured glow plug is improved.

The measures listed in the dependent claims advantageous refinements of the claim 1 glow plug are possible.

Advantageously, the radiator is electrically contacted at a first end by means of a first electrical contact element and at a second end by means of a second electrical contact element, wherein the radiator is acted upon in operation of the glow plug with a voltage applied between the contact elements operating voltage. The radiator is flowed through over its entire cross-section with electric current. It also comes with certain damage to the radiator, for example in the area of its surface, not to significantly affect the heat development, so that the robustness of the radiator is improved. In addition, a simple shape for the ceramic heater can be specified, which can be performed without sharp-edged transitions, whereby cracks or breaks of the ceramic material are prevented from the outset. In particular, the radiator may be rod-shaped and specially cylindrical. Such a radiator is inexpensively manufacturable by extrusion or by transfer molding, wherein an aftertreatment by grinding or the like is required only to a small extent or can be omitted altogether.

It is advantageous that the heating element has one or more electrically conductive guide sections which connect the glow section to the electrical contact elements. Both the annealing section and the guide section can each be made from a mass formulation which results in a highly conductive ceramic body after a corresponding pyrolysis treatment. The adjustment of the required electrical resistance can be done by adjusting the recipe and / or reducing the Leitquerschnitts, for example, by a taper in the incandescent body, which stresses and cracks are avoided by a rounded design of the transitions. It is advantageous that at least one of the contact elements in the region of the electrical contacting is made of a wear-resistant material, in particular of tungsten or nickel, of a platinum group metal or of an alloy with at least one of these metals. The contacting can be done by a direct connection of the ceramic to the metal or via a single or multi-layer metallization of the ceramic surfaces. In the metallization of the contact surfaces and cermet layers can be used to increase the adhesion. Specifically, the contact element may be made of pure platinum or a platinum alloy. Furthermore, an iridium alloy, a Nicroferlegierung, or an Inconelverbindung is possible. A cost-effective solution results from the formation of the contact element made of a steel alloy.

Furthermore, it is advantageous that at least one of the contact elements has a copper core. As a result, an increased heat dissipation and thus a lower load on the material in the contact area can be achieved. The copper core can be both flow-pressed and introduced via a Napftiefziehen in the contact element. The connection of the contact element can be done by means of laser, resistance or WIK welding.

It is advantageous that one of the contact elements contacts the heating element on an end face which is provided on the chamber-side end of the heating element. As a result, an additional protection of the radiator is ensured, which prevents damage during operation of the internal combustion engine and also during assembly or disassembly of the glow plug. It is also advantageous that one of the contact elements laterally contacts the heating element at a chamber-side end at least at one point. Preferably, a contacting takes place from several sides. This embodiment also ensures protection for the radiator in the region of its chamber-side end.

In addition, by the contact in the region of the chamber-side end a safeguard against falling into parts of the radiator in the chamber of the

Internal combustion engine can be achieved, which in particular with respect to the combustion chamber damage to the engine is avoided.

It is advantageous that the electrically conductive guide section has a guide element which is embedded in the ceramic material of the radiator, and that the glow section has a heating element which is embedded in the ceramic material of the radiator. In this case, instead of a conductive ceramic, such as SiOxCy or MoSi2, preferably a non-conductive ceramic, such as Si3N4, used with an internal heating element, which is formed for example by a tungsten wire or a tungsten layer. The heating element can then be connected on one or both sides to a guide element, which is formed, for example, from a conductive wire or a conductive layer, wherein the ceramic material of the entire heater can be made of only one mass formulation. The contacting for applying the operating voltage can be done at opposite pin ends, with suitable contact elements can be provided. drawing

Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings. It shows:

1 shows a first embodiment of a glow plug according to the invention in a schematic sectional view;

FIG. 2 shows the section of a glow plug according to a second exemplary embodiment, designated II in FIG. 1; FIG.

FIG. 3 shows the section of a glow plug in accordance with a third exemplary embodiment, designated by II in FIG. 1;

FIG. 4 shows the detail of a glow plug according to a fourth exemplary embodiment, designated by II in FIG. 1; FIG.

FIG. 5 shows the section of a glow plug according to a fifth exemplary embodiment, designated II in FIG. 1; FIG.

6 shows a heating element of a glow plug according to a sixth embodiment of the invention;

Fig. 7 denoted in Fig. 4 with VII section of a glow plug according to a seventh embodiment and

Fig. 8 shows a radiator of a glow plug according to an eighth embodiment of the invention. Description of the embodiments

Fig. 1 shows a first embodiment of a ceramic glow plug 1 in a schematic sectional view. The glow plug 1 can be configured in particular as a glow plug 1 for an air-compressing, self-igniting internal combustion engine. With its chamber-side end 2, the glow plug 1 protrudes in pre-and swirl chamber engines in the chamber of the internal combustion engine and in direct injection engines in a combustion chamber of the engine. However, the glow plug 1 according to the invention is also suitable for other applications.

The glow plug 1 has a metallic housing 3, on which an external thread 4 is formed for screwing the glow plug 1 into a bore of the internal combustion engine. The housing 3 has an inner space 5, which is closed to the chamber-side end 2 with a metallic end plate 6. At a chamber-side end 2 opposite the chamber-distal end 7, a connecting device 8 is provided, which is connected via an electrically insulating sealing element 9 to the housing 3, wherein the sealing element 9 seals the interior 5 on the side of the chamber distal end 7.

The glow plug 1 has a radiator 10 which extends through an opening formed in the end plate 6, wherein the opening is closed with a sealing bushing 11. The bush 11 is designed to be electrically insulating in order to insulate the radiator 10 from the end plate 6. In addition, the radiator 10 circumferentially at least in the region of the bush 11 with a be provided insulating insulation to further improve the insulation.

The glow plug 1 has a first contact element 12, which is connected on the one hand by a weld or the like with the end plate 6. The contact element 12 is L-shaped, wherein it is connected to the radiator 10 at an end face 13 of the radiator 10. The end face 13 is formed on the chamber-side end 2 of the radiator 10. In the region of the interior 5, the radiator 10 is enclosed circumferentially by an annular second contact element 14. Thus, the first contact element 12 contacts the heating element 10 at a first end 15 and the second contact element 14 contacts the heating element 10 in the region of a second end 16. The first contact element 12 is connected via the connection plate 6 and the housing 3 to the internal combustion engine and thus to ground (0 V) connected. The second contact element 14 is connected to the connecting device 8 via an electrical line 17 provided in the inner space 5. The line 17 is shown in simplified form in FIG. 1 and can be formed by further elements arranged in the inner space 5, in particular by a connecting bolt or the like (not shown). By applying an operating voltage to the connecting device 8 with respect to ground, the heating element 10 is acted upon between the electrical contacts formed by the contact elements 12, 14 with this operating voltage.

The radiator 10 has an annealing portion 20 which is made continuously from only a ceramic mass formulation. Further, the radiator 10 has a guide portion 21 extending from the end face 13 up to the glow portion 20 extends. In addition, a guide portion 22 is provided extending from the glow portion

20 extends to the second end 16 of the radiator 10. The glow section 20 has a relatively high resistance with respect to the conductive sections 21, 22, so that the heating element 10 heats up during operation of the glow plug 1 mainly in the region of the glow section 20. The lead section

21 ensures a certain distance between the glow portion 20 and the electrical contact with the first contact element 12 on the end face 13, so that the thermal load of this contact is reduced. Accordingly, by the guide portion 22, an excessive thermal load of the bush 11 and the contact formed with the second contact element 14 is prevented. The guide sections 21, 22 are also made of only one ceramic mass formulation, so that there is a simple construction of the radiator 10. The guide sections 21, 22 and the glow section 20 can also be produced in each case as separate ceramic components, which are joined to one another to form the radiator 10.

By the first contact element 12, which may also be designed hook-shaped, a protection of exposed on the chamber side end 2 radiator 10 is ensured, even with damage to the radiator 10, a break off of parts of the radiator 10 is prevented.

Fig. 2 shows the designated in Fig. 1 with II section of a glow plug 1 according to a second embodiment of the invention. Already described elements are provided in this and in all other figures with matching reference numerals, whereby a repetitive description is unnecessary. In this embodiment, the glow plug 1 has a U-shaped first contact element 12, which surrounds the heater 10 and in particular the glow portion 20 of the radiator 10 from two sides. As a result, an effective protection of the radiator 10 against external influences, in particular against a striking during assembly or disassembly of the glow plug 1, guaranteed. For this purpose, the first contact element 12 has two longitudinal sections 23, 24 which are arranged parallel to the heating element 10 and which pass over in an arc-shaped manner into a head section 25 oriented perpendicular thereto. Alternatively, more than two longitudinal sections 23, 24 may be provided, which are oriented substantially parallel to the heating element 10 and pass into a correspondingly designed head section 25. The head portion 25 may be configured, for example, star-shaped or plate-shaped. The first contact element 12 is thereby configured cage-shaped, wherein the glow portion 20 is preferably arranged approximately in the middle of the first contact element 12.

The first contact element 12 is connected both to the longitudinal section 23 and to the longitudinal section 24 by means of a weld or the like with the end plate 6, so that a robust construction results and a reliable operation of the glow plug 1 is ensured over its lifetime.

FIG. 3 shows the detail designated II in FIG. 1 according to a third exemplary embodiment of the glow plug 1 according to the invention. In this exemplary embodiment, the glow portion 20 has an at least approximately spherical surface. The glow section 20 can also be used as a solid ball be educated. The glow portion 20 of the radiator 10 is connected to the rod-shaped guide portion 22. Through the guide section 22, the electrical energy is conducted to the glow portion 20 so that the glow portion 20 heats up during operation of the glow plug 1. The return of the thereby flowing through the guide portion 22 current is carried out via the first contact element 12. In addition, in the illustrated embodiment, the head portion 25 is V-shaped and designed so that it contacts the glow portion 20 from two sides.

Alternatively, instead of or in addition to the glow portion 20, the portion 26 of the radiator 10 may be formed as an annealing portion 26. This can be achieved by the choice of a suitable material and a correspondingly reduced cross section, in particular reduced diameter, of the glow section 26. As a result, the electrical resistance of the glow section 26 per unit length with respect to the guide section 27 can be increased so much that a considerable development of heat occurs in the glow section 26. In this case, the guide portion 27 of normal cross-section preferably extends through the bushing 11 formed in the opening of the end plate 6 to reduce the thermal stress on the bushing 11 and to prevent heat buildup in the interior space 5.

Fig. 4 shows the designated in Fig. 1 with II section of a glow plug 1 according to a fourth

Embodiment. In this embodiment, the first contact element 12 is rod-shaped and connected to the end plate 6 by means of welding or the like, wherein it is additionally inserted into a bore formed in the end plate 6. Corresponding is also formed the second contact element 14 which extends through the bush 11. The contact elements 12, 14 are each formed at its chamber-side end 2 ösenförmig, the eyelets are used to receive the radiator 10. Alternatively, fastening eyes may be formed by a bore or the like. In this case, the radiator 10 is connected at its first end 15 to the first contact element 12 and at its second end 16 to the second contact element 14, wherein the radiator 10 is arranged at least substantially in a plane perpendicular to an axis 28 of the glow plug 1 lies. In this embodiment, the radiator 10 is made of a single ceramic mass formulation, so that the glow portion 20 extends from the first end 15 to the second end 16 of the radiator 10, that is, the radiator is completely formed as an annealing portion 20. The contact elements 12, 14 are at least in the region of the ends 15, 16 made of a suitably resistant material or coated with a suitable material to withstand the thermal load.

Fig. 5 shows the designated in Fig. 1 with II section of a glow plug 1 according to a fifth embodiment of the invention. In this embodiment, the housing 3 is formed as a guide tube, wherein the radiator 10 is framed with its contact end 30 deep in the housing 3 designed as a guide tube. The radiator 10 is made of only one ceramic mass formulation. In the annealing portion 20 of the radiator 10 is formed as a tungsten wire or tungsten layer heating element 31 is embedded. The heating element 31 is on the one hand via a designed as a guide wire or conductive layer guide element 32 with the Connecting device 8 (Fig. 1) connected and on the other hand connected via a formed by a guide wire or a conductive layer guide member 33 with the metallic housing 3 of the glow plug 1. The guide element 32 extends through a formed in the end plate 6 through opening 31, which may also be filled with an electrically insulating material. In addition, the guide element 32 is connected to the line 17. The guide element 33 is connected via connecting elements 34a, 34b and 34c to the housing 3 and the end plate 6, respectively. In this case, only one of the connecting elements 34a, 34b, 34c may be provided. The guide elements 32, 33 are embedded in the guide section 21 of the radiator 10. When the radiator 10 is supplied with the operating voltage, the heating element 31 heats up so that a glow tip 35 of the radiator 10 is heated. A particular advantage of the embodiment shown in FIG. 5 is the small space requirement in the chamber of the internal combustion engine.

Fig. 6 shows a radiator 10 of a glow plug 1 according to a sixth embodiment. In this case, the radiator 10 to the first end 15 toward a conical portion 36, to which a cylindrical portion 38 connects, which is the first end 15 of the radiator 10. On the other side, ie towards the second end 16, the radiator 10 has a conical section 37, to which a cylindrical section 39 adjoins, which forms the second end 16 of the radiator 10. The radiator 10 is preferably made over the entire length of only one ceramic mass formulation, so that the annealing portion 20 extends over the entire radiator 10. The radiator 10 shown in Fig. 6 is particularly suitable for attachment to contact elements 12, 14, which are configured according to the illustrated in Fig. 4 fourth embodiment of the glow plug 1 according to the invention.

Fig. 7 shows the designated in Fig. 4 with VII section of a glow plug 1 according to a seventh

Embodiment in a sectional view. In this embodiment, the radiator 10 is made of only one mass formulation, so that the annealing portion 20 extends over the entire length of the radiator 10. In addition, bores 40, 41 are respectively provided at the ends 15, 16 of the radiator 10, in which the contact elements 12, 14 are introduced, so that a reliable attachment of the radiator 10 by means of the contact elements 12, 14 results. The contact elements 12, 14 are made at least in the region of the ends 15, 16 of a temperature-resistant and robust material or coated with a corresponding material.

Fig. 8 shows a heater 10 according to an eighth embodiment of the invention. The radiator 10 has contact surfaces 42a to 42f, two of which can be selected for contacting the radiator 10. FIG. 8 shows another possible form for a simple ceramic body made only from a bulk ceramic formulation. In this case, the corners 43, 44 designed rounded, so that the occurrence of cracks and crumbling of ceramic particles is prevented by the radiator 10.

The invention is not limited to the described embodiments.

Claims

claims

1. glow plug (1) for arrangement in a chamber of an internal combustion engine with a ceramic heater (10), characterized in that the heater (10) has at least one annealing portion (20) which is made continuously from at least substantially only a ceramic mass formulation ,

2. glow plug according to claim 1, characterized in that the radiator (10) at a first end (15) by means of a first electrical contact element (12) is electrically contacted, that the radiator (10) at a second end (16) by means of a second electrical contact element

(14) is electrically contacted and that the heating body (10) during operation of the glow plug (1) with a between the first contact element (12) and the second contact element

(14) applied operating voltage is applied.

3. glow plug according to claim 2, characterized in that the heating element (10) has an electrically conductive guide portion (21) which connects the glow portion (20) on the one hand with the first electrical contact element (12).

4. glow plug according to claim 3, characterized in that the heating element (10) has a further electrically conductive guide portion (22) which connects the glow portion (20) on the other hand with the second electrical contact elements (14).

5. glow plug according to one of claims 2 to 4, characterized in that the first contact element (12) and / or the second contact element (14) has a copper core.

6. glow plug according to one of claims 2 to 5, characterized in that the first contact element (12) and / or the second contact element (14) at least in the region of the electrical contact of a wear-resistant material, tungsten or nickel, a platinum group metal or from an alloy with one of these metals is formed.

7. glow plug according to one of claims 2 to 6, characterized in that the first contact element (12) an end face (13) of the radiator (10) at a chamber-side end (2) contacted.

8. glow plug according to one of claims 2 to 6, characterized in that the first contact element (12) contacts the radiator (10) at a chamber-side end (2) at least at one point laterally.

9. glow plug according to one of claims 1 to 8, characterized in that the heating element (10) is designed as a rod-shaped, in particular cylindrical, radiator (10).

10. glow plug according to claim 9, characterized in that the heating element (10) is arranged at least approximately parallel to an axis (28) of the glow plug (1).

11. glow plug according to claim 9, characterized in that the heating element (10) is arranged at least approximately in one of an axis (28) of the glow plug (1) vertical planes.

12. glow plug according to claim 2, characterized in that the electrically conductive guide portion (21) has at least one guide element (32, 33) which is embedded in the ceramic material of the radiator (10).

13. glow plug according to one of claims 1 to 12, characterized in that the annealing portion (20) has a heating element (31) which is embedded in the ceramic material of the radiator (10).