RU2703873C2 - Method of ignition plug manufacture and ignition plug for internal combustion engine - Google Patents

Abstract

FIELD: machine building.SUBSTANCE: invention relates to method of making ignition plug (1) for internal combustion engine, in particular, internal combustion engine of motor vehicle. Ignition plug (1) comprises main body (2) with head area (8) made with possibility of being installed in combustion chamber of internal combustion engine. Furthermore, the coating formed by at least the following steps is located at least partially in head area (8): head region (8) is made at least partially rough, a suspension is applied on rough area (8) of the head, the applied suspension is dried, the suspension applied on the made rough area (8) of the head is heated to form enamel coating (10).EFFECT: technical result is improvement of exhaust gases, which are formed during operation of internal combustion engine.11 cl, 2 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a method for manufacturing a spark plug for an internal combustion engine, in particular for a motor vehicle according to the independent claim 1. The invention also relates to a spark plug for an internal combustion engine according to independent claim 7.

BACKGROUND

Forced-ignition internal combustion engines require a spark plug to ignite the air-fuel mixture compressed in from the combustion chambers. For this purpose, electric spark plugs are used, which serve for the controlled delivery of the corresponding spark. During this operation, a spark is formed as an open arc between the central electrode and at least one side electrode of the spark plug. Spark plugs usually have a main body with a connecting part, which, for example, may have an external thread. Thus, the spark plug can be screwed into the corresponding hole in the cylinder head of the internal combustion engine.

Through an electrically conductive connection to the connecting part, the side electrode is already in contact with the ground with the vehicle ground when the spark plug is located in the cylinder head. In contrast, the central electrode may be connected, for example, through the ignition wire to the ignition coil. The central electrode may be subjected to the proper ignition voltage through the ignition coil. To this end, the central electrode and the side electrode are electrically isolated from each other by means of a suitable insulator body, since the arcing of the ignition voltage must be carried out exclusively between two electrodes. The distance between the electrodes, in this regard, is a criterion that can be set in advance to obtain the required combustion of the air-fuel mixture.

In the spark plug device, its tip, which has a distance between the electrodes, is facing towards the associated combustion chamber of the internal combustion engine. For purposes of the invention, said tip is referred to as an area of the spark plug head.

During operation of the spark plugs, it is known that possible deposits can form on its head area. Sediments are usually oil soot. These soot deposits may be attributed to the combustion process of the respective fuel. In this case, such deposits concentrate essentially on that part of the insulator body that lies in the region of the head. Depending on the operating time, these deposits can reach a porous structure having a thickness of several millimeters.

The resulting problem can be attributed to the electrical conductivity of the latter. In particular, due to deposits that form between the metal regions of the spark plug, cases of misfire and uncontrolled sparks can occur over time. Moreover, deposits tend to continue to glow in an uncontrolled manner at the end of the combustion cycle; it is like a glow plug. Due to the deteriorated or even incomplete combustion of the air-fuel mixture in this case, this ultimately leads to undesirably high values of volatile organic substances in the exhaust gases (HC emissions).

Various configurations of spark plugs are already known in the art. In addition to functioning purely as a means of ignition, solutions to avoid the deposition discussed have also been disclosed in the prior art.

Thus, EP 1557918 A1 (IPC H01T 13/14, H01T 13/38, published July 27, 2005) describes a spark plug for an internal combustion engine, which is supposed to constantly avoid shunts from electroconductive deposits. For this purpose, a catalytic coating of precious metal is proposed, which is formed on the tip of the foot of the insulator body lying in the region of the spark plug head. The precious metal coating may be platinum (Pt), palladium (Pd) or rhodium (Rh).

The proposed precious metal coating is intended to lower the temperature required for burning out deposits. This, in particular, is of interest in the cold start phase of the internal combustion engine, in which the optimum operating temperature is not yet present. The thus achieved reduction in the burning temperature should ultimately accelerate the oxidation of deposits. As for the position of the coating of precious metal, this is limited by the inner surface of the channel of the insulator, which is facing towards the center electrode of the spark plug. The channel of the insulator is traditionally the opening within the body of the insulator that exposes the central electrode, in other cases, covered by the body of the insulator, so that the specified central electrode can interact with the side electrode.

DE 4222137 B4 (IPC C23C 16/44, C23C 30/00, F02M 61/16, published 04.05.2006) describes a fuel injection nozzle for a diesel internal combustion engine. This includes a nozzle body with injection holes that penetrate said nozzle body, and the walls of which are coated. The coating thickens in the direction of the opening of the holes so that the injection holes narrow to their opening. The coating itself is formed from a solid material, for example, chromium, nickel, nickel-phosphorus, nickel-boron, nickel-cobalt-boron, Al ₂ O ₃ , Cr ₂ O ₃ , TiO ₂ , Cr ₃ C ₂ , SiO ₂ , AlSi, NiCr, WTi or WC.

DE 19951014 A1 (IPC F02M 51/06, F02M 61/16, published 04.01.2001) describes an injection valve for fuel, which, likewise, has a coating at least around the area in which its outlet opening opens. The coating is a catalytically active layer of Co or Ni, or cobalt oxides or nickel oxides, or Co alloys, or Ni alloys, or Ru or Rh, or Pd, or Os, or Ir, or Pt, or alloys of these metals with each other or with other metals.

JP 2007-309167 A (IPC B01D 53/86, B01J 35/02, published 29.11.2007) describes a system for cleaning a combustion chamber for an internal combustion engine. To this end, titanium oxide is applied to the surface of the opening for injecting a nozzle.

JP 2005-155618 A (IPC F02M 51/06, F02M 61/18, published June 16, 2005) describes a method for forming a coating consisting of titanium oxide on a nozzle of an injection valve.

As a result, although the coating of precious metal can accelerate the combustion of deposits that are already present, for example, its properties and local layout, in addition, they can also lead to uncontrolled ignitions and glow afterglow. In general, therefore, today it is the case that neither methods that go back to physical or chemical vapor deposition (PVD / CVD), nor methods that include electroplating, make it possible to create suitable coatings for reliable preventing the formation of deposits and related imperfections.

In light of this observation, spark plugs for internal combustion engines, in particular for internal combustion engines of motor vehicles, also still definitely have room for improvement.

SUMMARY OF THE INVENTION

Based on the problems of the prior art, the invention is based on the goal of further developing a method for manufacturing a spark plug, as well as further developing a spark plug for an internal combustion engine so that a possible cost-effective way of forming a suitable coating is provided that can be integrated into existing manufacturing processes , and which provides reliable operation to improve the performance of the exhaust gases that are formed during operation.

The solution for the part related to the method of the specified goal is the essence of the method, characterized by the features according to paragraph 1 of the claims. The part of the specified goal related to the product is achieved by means of a spark plug, characterized by the features according to paragraph 7 of the claims. In addition, particularly useful improvements to the invention are found in the respective dependent claims.

It is indicated that the measures and features, individually specified in the following description, can be combined with each other in any required technically significant way and reveal additional improvements of the invention.

Accordingly, the method according to the invention includes manufacturing a spark plug for an internal combustion engine. With particular preference, the internal combustion engine may be a motor vehicle engine.

The spark plug, which must be manufactured, has a main body, which contains the area of the head. The coating is applied at least partially to the head area. The head region is configured to face at least one of the combustion chambers of the internal combustion engine when the spark plug is mounted on it. In this regard, the head region may be located at least partially in the associated combustion chamber. In this regard, the head region is adapted to be installed in the combustion chamber of an internal combustion engine.

Preferably, the spark plug itself may have a typical design. It includes a central electrode and at least one side electrode, which is located at a certain distance from the latter and is electrically isolated relative to the central electrode by at least partially incorporating the insulator body.

According to the invention, the coating is applied to the head region of the spark plug by the following steps:

the head region is at least partially roughened,

apply the suspension to a rough region of the head,

dry the applied suspension,

heat the suspension deposited on the rough region of the head to form an enamel coating.

The essence of the method according to the invention, in this regard, is the formation of an enamel coating in the head region of the main body of the spark plug. Compared to providing a precious metal coating, this gives rise to the advantage that the enamel coating according to the invention already substantially prevents the deposition of oil soot. In this regard, the enamel coating does not serve to lower the temperature required to burn such deposits, but instead prevents or at least reduces their formation right from the start.

The reason for this is the knowledge that in practice, the constituent fuels - for example, in droplet form - cannot precipitate and dry out on an enamel coating. This has been recognized as the main reason for the formation of tar-like linings on spark plugs. Prevention or at least a large reduction of such deposits means that their possible afterglow of incandescent, in this case, is no longer possible.

In addition, the enamel coating according to the invention acts as an additional insulator, and therefore, possible breakdown of the spark plug is reliably prevented. This, in particular, is appropriate if possible deposits would actually form in the head region over time. Since deposits are electrically conductive, an uncontrolled and harmful ignition spark can occur if such a conductive coating of precious metal is provided for, as is known in the art; this can be avoided by the invention.

Due to the enamel coating according to the invention, in fact double protection therefore arises with respect to the reliable operation of the spark plug, as a result of which the performance of the exhaust gases that are formed during operation of the internal combustion engine are improved accordingly. The reason for this is the release and electrical insulating properties according to the invention of the enamel coating, at least in the relevant region of the spark plug head.

The arrangement of the enamel coating according to the invention can advantageously be easily integrated into existing methods for manufacturing spark plugs. Due to the heat-resistant properties of the enamel coating, it turns out to be extremely durable with respect to its place of work and the associated heat load acting on it.

With particular preference, the enamel coating can be an oxide and, moreover, a smooth and catalytically active enamel coating. Alternatively or in addition to this, the enamel coating may also be in the form of “pure enamel”. Enamel coatings of this type, for example, are known for cladding household appliances such as drying ovens. These include the self-cleaning effect if the oven is operated at a higher temperature than normal. This then entails calcination for cleaning, in which any adhering deposits, such as oil coatings, can be destroyed purely catalytically without mechanical action.

For the purposes of the invention, a suspension is intended as an initial base for the enamel coating to be provided. This can preferably be a mass in the form of a mineral mixture, which is present in a liquid, from a pasty to viscous, consistency, and is suitably applied to the rough part (s) of the head region.

A contact method or a non-contact method, for example with respect to the use of a coating agent, is possible for application. Thus, the suspension can be applied, for example, by means of a roller for applying or brush for applying. Moreover, the application can be achieved by immersion or spraying, for example, in particular, airless spray.

The applied slurry is subsequently dried, for example, in ambient air or by an incoming stream of heated air. Subsequent heating of the dried suspension serves to form an enamel coating. For the purposes of the invention, heating is also meant to mean calcination, sintering or calcination.

According to a preferred embodiment of the fundamental concept of the invention, the metal part of the spark plug located in the head region can be at least partially roughened and provided with a suspension before heating. In other words, in this regard, the invention provides that an enamel coating can be formed on the metal parts of the head region.

It is particularly preferred that the finished enamel coating can extend over the inside and outside of the head region. In this regard, the inner part is meant to mean that region that faces in the direction, mostly located in the center, of the central electrode. In contrast, the outer part is the area that is remote from the central electrode. On the inside, the enamel coating has the task, due to its electrical insulating effect, to effectively prevent possible breakdown of the ignition spark through deposits that are already present. The provision of an enamel coating on the outside, in contrast, mainly serves to prevent deposits, which, otherwise, lead to high emissions due to their glow afterglow.

Moreover, it is contemplated that a portion of the insulator body located in the region of the head may be at least partially roughened and provided with a suspension before heating. In other words, the location of the enamel coating may also continue on the area of the insulator body.

A useful further refinement of the invention provides that a possible excessive spraying of the applied suspension can be at least partially mechanically removed after the suspension has been dried and before heating. This mainly includes a central electrode and / or at least one side electrode. The goal is the formation of a controlled and sufficient spark, for which purpose, the corresponding electrodes should be present in the most exposed form possible. Depending on the method used to apply the suspension, therefore, it may be necessary to locally remove unwanted applications of the suspension, referred to by the reference as excessive spraying, before it is heated.

The basis for applying the slurry is provided by a suitable method of roughening in the region of the head. To this end, the invention provides that the initially necessary roughening of parts of the head region or the entire head region, for example, can be accomplished by shot peening. It goes without saying that additional roughening methods which enable suitable preparation of the respective surfaces for applying the slurry are also possible. This roughening mainly serves to provide a durable connection between the surface of the head region and the enamel coating. As a result, the latter can be better fixed on the surface of the head region. In addition, the contact surface can be increased by roughening.

The applied suspension may preferably be heated in a temperature range from 800 ° C to 900 ° C. It is particularly preferred that the heating can be carried out using a protective gas medium. By heating in a protective gas environment, the formation of carbon deposits and tarnishing, in particular on the external thread of the spark plug, can be effectively prevented.

The method according to the invention, which is presented below, for the manufacture of a spark plug provides a possible cost-effective method of forming a coating in the form of an enamel coating, which can be easily integrated into existing manufacturing processes. Due to the electrical insulating effect of the heat-resistant enamel coating in combination with the fact that the latter prevents deposits, the reliable operation of the spark plug is generally guaranteed to improve the performance of the exhaust gases that form during operation.

The invention also relates to a spark plug for an internal combustion engine, in particular an internal combustion engine of a motor vehicle. The spark plug could preferably be made by the above method according to the invention.

Here, the spark plug comprises a main body with a head region that is configured to be installed in a combustion chamber of an internal combustion engine. Moreover, the coating is located at least partially on the head area. According to the invention, the coating is an enamel coating. As an alternative to this, the coating can also contain at least enamel.

The resulting advantages have already been explained above together with the method according to the invention for the manufacture of a spark plug and are accordingly applied to the spark plug according to the invention. This, moreover, also applies to additional useful improvements to the spark plugs according to the invention, which are indicated below. For this reason, at the moment, a reference is made to the statements made above.

According to a preferred embodiment of the spark plug of the invention, an enamel coating is formed from the suspension. As for the composition of the suspension, it is envisaged that it may contain at least one glass-forming oxide in addition to at least one additional component of IC, and optionally at least one opacifier.

A possible group of glass forming oxides, for example, may be at least one of the following:

- silicon dioxide (SiO ₂ ),

- boron trioxide (B ₂ O ₃ ),

- sodium oxide (Na ₂ O),

potassium oxide (K ₂ O),

- alumina (Al ₂ O ₃ ).

It goes without saying that this list is not final, and therefore, additional glass-forming oxides are also possible.

With respect to at least one additional component, it, for example, may be one of the following group:

- boron

- feldspar,

- quartz

- fluoride compound

- soda,

- sodium nitrate.

It also takes place here that this list is not final, and therefore, additional components are also possible.

As for the addition, if necessary, of at least one opacifier, this, for example, can be selected from the following group:

- titanium (Ti),

- zirconium (Zr),

- molybdenum (Mo).

This is also not a final list, and therefore, other opacifiers are also possible, for example, such as tin oxide or titanium silicate.

The enamel coating according to this invention is preferably a melt mixture. At enamel temperature, glass-forming oxides melt together to form a glass melt. Base enamels contain approximately 23-34% by weight of boron, 28-52% by weight of feldspar, 5-20% by weight of quartz, approximately 5% by weight of fluoride compounds, the remaining part of soda and sodium nitrate. As already indicated, the oxides Ti, Zr and Mo can serve as a cloud agent.

Moreover, ceramic pigments, for example, such as iron oxides, chromium oxides and spinels, may also be present.

In order to improve adhesion, in particular, on a metal base, the enamel coating according to the invention, in addition, for example, may also contain at least one oxide from the following group:

- cobalt oxide,

- manganese oxide,

- nickel oxide.

In a preferred embodiment, said materials are finely ground and melted. The molten mass is cooled, that is, preferably introduced into water, moreover, the granular glassy frit, thus made, is again finely ground in the next step. As an example, from 30% to 40% of water, together with clay and silica powder, are added to the grinding operation. Depending on the nature of the enamel, these opacifiers and coloring oxides are also added.

This forms an enamel suspension, which, for better mixing, should be at rest for a certain time, preferably for several days, before the enamel suspension is to be used again. The use of suitable modifiers ensures that a uniform layer thickness is formed.

For a smooth enamel coating, the latter preferably contains a high proportion of cerium oxide (CeO). Due to its catalytic effect, fuel droplets are collected on the surface of an enamel coating. evaporate. As a result, deposits that could later have negative effects on exhaust emissions cannot form. Moreover, the initial temperature for combustion of the fuel and unburned hydrocarbons (HC), as well as carbon monoxide (CO), thereby, can mainly be reduced. As a result, the emissions of an internal combustion engine can be reduced in a similar manner.

The enamel coating may contain a high proportion of alumina, Al ₂ O ₃ , in order to increase the breakdown strength with respect to the ignition spark.

According to a preferred embodiment, the enamel coating may have a thickness of from 100 μm to 250 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional useful details and results of the invention are explained in more detail below on the basis of exemplary embodiments schematically illustrated in the figures. In the figures:

FIG. 1 shows a part of a spark plug according to the invention in longitudinal section, and

FIG. 2 shows a part of FIG. 1 in a complementary form, otherwise identical in presentation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a longitudinal section through a spark plug 1 according to the invention. For clarity, this longitudinal section is markedly reduced in relation to the connecting part of the main body 2 of the spark plug 1. This essentially shows the area that is intended to form an ignition spark (not shown in more detail) of the spark plug 1.

A longitudinal section shows a typical construction of a spark plug 1 made of a central electrode, which extends in the longitudinal direction x of the spark plug 1, and which is surrounded by an insulator body 4. The insulator body 4 may be a ceramic body. The insulator body 4 has a tubular configuration (not shown in more detail) with a pencil-shaped central electrode 3 located inside the insulator body 4. The insulator body 4 serves to electrically isolate the central electrode 3 with respect to additional metal regions of the main body 2.

In this regard, the insulator body 4 also serves to electrically isolate the central electrode 3 with respect to the side electrode 5, which is located on the main body 2. The side electrode 5 is angular, like a bracket, first extending from the end face 6 of the main body 2 in the longitudinal direction x and then tilting at an angle above the central electrode 3. Thus, the central electrode 3 and the side electrode 5 are located at a certain distance from each other, and a gap is formed ok a between the electrodes.

As can be seen, the outer circumference of the main body 2 has an external thread 7. The external thread 7 serves to connect the spark plug 1 to the opening of the cylinder head (not shown in more detail) of the internal combustion engine. To this end, the hole (not shown) has a corresponding internal thread that can be brought into engagement with the external thread 7 of the main body 2 of the spark plug 1.

The parts of the spark plug 1 that are visible in FIG. 1 include a head region 8, which is intended to be appropriately positioned or aligned with the combustion chamber (not visible) of the internal combustion engine. It can be seen that the main body 2 has a tubular configuration in the head region 8, moreover, a part of the insulator body 4 together with the central electrode 3 located therein is placed inside the main body 2 and is located at a certain distance from it. An annular gap 9, therefore, is formed between the inner side region of the main body 2 and the outer side region of the insulator body 4 together in the central electrode 3.

As can be seen, the coating in the form of an enamel coating 10 is located in the region 8 of the head. Here, the enamel coating 10 continues along the annular gap 9, and therefore, along the corresponding inner side region of the main body 2 and the corresponding outer side region of the insulator body 4. Here, the enamel coating 10 also further covers the side 6 of the main body 2 until the very beginning of the external thread 7 of the main body 2. Moreover, the part of the side electrode 5, which extends in the longitudinal direction x, is also substantially covered by the enamel coating 10.

FIG. 2 shows the head region 8 again in a simplified form. In this regard, the cutouts are not made through the housing 4 of the insulator, and therefore, in this case, the latter covers the central electrode 3 passing in it. In contrast to the illustration in FIG. 1, here the enamel coating 10 ends on the end face 6 of the main body 2. In contrast, the enamel coating 10 extends much further over the side electrode 5, in particular, in addition, three quarters of the corner portion of the side electrode 5, so that the latter is not coated on sites only at its free end. In general, the enamel coating 10 has a sufficient layer thickness to achieve high breakdown strength with respect to the ignition spark. The layer thickness has a value from 100 μm to 250 μm in this case.

LIST OF REFERENCE POSITIONS

1 spark plug

2 The main body of the element 1

3 Central electrode of element 1

4 Case insulator element 1

5 Side electrode of element 1

6 End face of element 2

7 External thread element 2

8 Head area of elements 1 and 2

9 The gap between elements 2 and 4

10 Enamel coating element 1

a The distance between the electrodes between elements 3 and 5

x Longitudinal direction of element 1.

Claims (50)

1. A method of manufacturing a spark plug (1) for an internal combustion engine of a motor vehicle comprising a main body (2) with a head area (8) configured to install an internal combustion engine in the combustion chamber coated with a head in area (8) , which includes stages in which: perform area (8) of the head at least partially rough, apply the suspension to a rough region (8) of the head, dry the applied suspension, the suspension is applied to the rough region (8) of the head to form an enamel coating (10), which extends over the inner and outer parts of the head region. 2. The method according to claim 1, wherein the metal part of the spark plug (1) located in the head region (8) is at least partially roughened and provided with a suspension before heating. 3. The method according to claim 2, wherein the part of the insulator body (4) located in the head region (8) is at least partially roughened and provided with a suspension before heating. 4. The method according to p. 2 or 3, in which excessive spraying of the deposited suspension on the central electrode (3) and / or side electrode (5) is at least partially mechanically removed after the suspension has been dried and before heating. 5. The method according to claim 1, wherein the head area (8) is roughened by shot peening. 6. The method according to p. 1, in which the suspension is heated in the temperature range from 800 ° C to 900 ° C using a protective gas environment. 7. The method according to p. 1, in which the suspension contains at least one glass-forming oxide from the following group - silicon dioxide (SiO ₂ ), - boron trioxide (B ₂ O ₃ ), - sodium oxide (Na ₂ O), potassium oxide (K ₂ O), - alumina (Al ₂ O ₃ ), and also contains at least one component from the following group - boron - feldspar, - quartz - fluoride compound - soda, - sodium nitrate, and contains, if necessary, at least one opacifier from the following group - titanium (Ti), - zirconium (Zr), - molybdenum (Mo). 8. Spark plug for an internal combustion engine manufactured by the method according to any one of paragraphs. 1-7, comprising a main body (2) with a head region (8) configured to be installed in the combustion chamber of the internal combustion engine, coated in the head region (8), the coating being an enamel coating (10) extending over internal and external parts of the head area. 9. The spark plug according to claim 8, in which the enamel coating (10) is formed from a suspension, the suspension containing at least one glass-forming oxide from the following group - silicon dioxide (SiO ₂ ), - boron trioxide (B ₂ O ₃ ), - sodium oxide (Na ₂ O), potassium oxide (K ₂ O), - alumina (Al ₂ O ₃ ), and also contains at least one component from the following group - boron - feldspar, - quartz - fluoride compound - soda, - sodium nitrate, and contains, if necessary, at least one opacifier from the following group - titanium (Ti), - zirconium (Zr), - molybdenum (Mo). 10. The spark plug according to claim 8 or 9, in which the enamel coating (10) contains at least one oxide from the following group - cobalt oxide, - manganese oxide, - nickel oxide. 11. The spark plug according to claim 8, in which the enamel coating (10) has a layer thickness of from 100 μm to 250 μm.

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