WO2008108650A1

WO2008108650A1 - Sealing body with opening for a second body receivable in the opening, and method for manufacture thereof

Info

Publication number: WO2008108650A1
Application number: PCT/NL2008/050132
Authority: WO
Inventors: Cornelis Jan Wagner; Jacobus Salacroup; Ronald Dikken
Original assignee: Hertel Industrial Sealings BV
Current assignee: Eriks Gasket Technology BV
Priority date: 2007-03-07
Filing date: 2008-03-07
Publication date: 2008-09-12
Anticipated expiration: 2009-09-07
Also published as: NL2000525C2

Abstract

The invention relates to a sealing body (1) with opening (2) for a second body (14) receivable in the opening, in particular a sealing ring for an injector (10) of a combustion engine. At least the inner surface (7) of the opening of the sealing body (5) is provided with a graphite-containing surface layer. The sealing body displays a good sealing and corrosion resistance. The sealing body further has a good clamping fit with the second body. The invention also relates to a method for manufacturing the sealing body, and an assembly of a sealing body according to the invention and a second body at least partially received in the opening.

Description

SEALING BODY WITH OPENING FOR A SECOND BODY RECEIVABLE IN THE OPENING, AND METHOD FOR MANUFACTURE THEREOF

The invention relates to a sealing body provided with an opening for a second body receivable in the opening. The invention also relates to a method for manufacturing the sealing body. The invention relates particularly to a sealing body with opening and, received in the opening, an injector part of an injector for a combustion engine.

Sealing bodies are frequently applied in industrial applications, for instance in mechanical engineering. Sealing bodies are thus used for instance in combustion engines. In a combustion engine the fuel is injected into the combustion chamber under high pressure by means of an injector. The injector which injects the fuel is herein arranged through the wall of the combustion chamber. Partly due to the relatively high pressures and temperatures prevailing in the combustion chamber, high demands are made of the seal between the injector and the wall of the combustion chamber.

A sealing body for the injector of a combustion chamber is known from FR 2 851791. The known sealing body is embodied in the form of a copper ring with central opening, in which the injector part of an injector can be received. The copper sealing ring provides for the sealing between the injector and the wall of the combustion chamber of a combustion engine. The ring is raised locally on both sides, whereby the contact surface between injector and wall is reduced. This provides a greatly increased pressure at the position of the raised parts, and therefore evidently a better seal.

A sealing ring of the known type is generally arranged with clamping fit around the injector part of the injector prior to mounting of the injector in the combustion chamber. A clamping fit is necessary in order to avoid leakage between the outer surface of the injector part and the opening, and in order to ensure that the ring remains on the injector part during the mounting. It is therefore of great importance to maintain small tolerances of the dimensioning of injector and sealing body. This imposes high demands on the dimensioning of the injector and of the sealing ring. Red copper is relatively soft material, whereby the above stated clamping fit can be obtained by pushing or pressing the housing, generally of cylindrical form, with great force through the opening of the sealing ring. The seal with the combustion chamber wall is likewise realized in that the copper deforms relatively easily when it is pressed against the wall.

Although the known sealing body seals reasonably well, leakage still occurs, and particularly after some time of use. Because the known sealing body can come into contact with other metals, there is also a danger of corrosion occurring, in particular galvanic corrosion. This is of course undesirable because the lifespan of the injectors is hereby limited. Fouling further occurs easily with the known sealing ring because soot particles are for instance released which then enter the filter and/or the fuel tank. Contamination of the fuel tank is particularly disadvantageous because it is generally not replaced. The contamination is therefore 'permanent'.

The invention has for its object to provide a sealing body with opening for a second body receivable in the opening which does not have, among others, the above stated drawbacks. The sealing body according to the invention has for this purpose the feature that at least the inner surface of the opening of the sealing body is provided with a surface layer of a graphite-containing material comprising expanded graphite flakes. According to the invention the graphite-containing surface layer comes into at least partial contact with the surface for sealing. It has been found that a sealing body according to the invention also results in an excellent seal at the - very high - pressures above 2000 bar usual for combustion engines, wherein the sealing body also retains this function for a long operational use. A further advantage is that the invented sealing ring results in reduced contamination. It has further been found that the sealing body according to the invention can better withstand the additives present in fuel, and in particular diesel fuel. Such additives, such as for instance urea, are mixed into the fuel or added separately, and easily cause chemical deterioration.

The invention relates particularly to an assembly of a sealing body with opening and an injector part of an injector for a combustion engine received in the opening. A particular feature of this assembly is that the clamping force of the sealing body with the injector is ensured such that, after being arranged on the injector, the sealing body does in fact form an integral part of the injector. A further unique property of the invented sealing body is that it still has a clamping action after disassembly of the injectors from the cylinders of a combustion engine, while disassembly of the sealing body can however take place in simple manner. This makes it possible to mount new sealing bodies on existing or new injectors. This could for instance be applied in regular servicing of the engines or if the useful life of the injectors has ended and they have to be replaced.

The American patent publication US 2004/118510 Al describes a gasket for connecting pipes. The annular gasket is provided on both sides with a surface layer of a graphite- containing material comprising expanded graphite flakes. The peripheral wall of the opening of the annular gasket described in US 2004/118510 is not provided with the surface layer of the graphite-containing material. The gasket described in US 2004/118510 is not suitable as seal for a second body receivable in the opening of the annular gasket.

DE 33 09 338 Al describes a sealing ring of a metal foil provided with a surface layer of expanded graphite. The annular form is obtained by punching out a central opening, whereby the peripheral wall of the opening is not provided with the surface layer of graphite.

DE 33 20 665 Al describes a sealing ring of a metal substrate provided with grooves, on which is arranged a surface layer of expanded graphite. The peripheral edge of the opening comprises no graphite.

US 2005/0121859 Al describes a sealing ring with a non-round opening. The ring can be provided with a surface layer of expanded graphite, wherein the surface of the metal substrate is profiled. The peripheral edge of the opening comprises no graphite.

EP 0 310 725 Al describes a sealing ring with opening. The sealing ring is provided with a surface layer of expanded graphite, wherein the surface layer is only situated on the flat sides but not on the peripheral surface of the opening. This known sealing ring is thus not suitable either as seal for a second body receivable in the opening of the annular gasket.

Because the sealing body according to the invention is provided with a surface layer of a graphite-containing material comprising expanded graphite flakes, at least in respect of the inner surface of the opening, this results in a guaranteed clamping force on the inner side of the opening of the sealing body and the outer side of the injector. This is particularly important in the sealing of injectors arranged in a combustion engine. None of the above described known sealing bodies can be applied in combination with injectors, among other reasons because they cannot provide this guaranteed clamping force.

Although the advantages of the invention are particularly manifest in the above discussed application in combustion engines, the invention is not limited thereto. In principle the sealing body can advantageously be used for any application in which a seal must be obtained. The sealing body is used particularly advantageously for those applications in which a seal must be obtained which can withstand relatively high pressures and/or temperatures. The sealing body is also used with particularly advantage for those applications in which a seal is obtained by pressing two bodies against each other with a certain clamping force, for instance when a shaft is pushed with force through the opening of an annular sealing body, whereby it is received with clamping fit in the opening.

Because at least the inner surface of the opening is provided with the surface layer, a good seal is obtained between the inner surface and a second body received in the opening. As already indicated above, such a second body is pressed with force through the opening in order to obtain the seal. In order to prevent damage to the relevant surfaces during pressing-on, the dimensional tolerances of the known sealing body and for the outer surface of the injector must be small. By applying a graphite-containing surface layer on the inner surface of the opening as according to the invention, the sealing body is pressed more easily onto the second body, in this case the injector. This has the great advantage that the dimensional tolerances to be applied for the injector need be less stringent than usual. This advantage will generally apply for any second body which must be arranged with clamping fit in the opening of the sealing body. The sealing body according to the invention can thus be arranged on a plurality of second bodies. A further advantage is that deformation of the second body remains relatively limited. If the second body is an injector part of an injector, the risk of injection channels present in the injector part being pressed shut will for instance be reduced. According to the invention the sealing body comprises a graphite-containing surface layer. Graphite is a per se known material. Graphite ore generally has a good chemical resistance, although it is also sensitive to wetting liquids, such as for instance oil, largely as a result of the layered structure of graphite ore. This is because graphite ore comprises layers of carbon atoms which are held together by weak van der Waals forces. These weak forces between the different layers easily result in penetration of foreign material between the layers, resulting in leakage. The application of graphite ore for sealing in an oil-containing environment - such as for instance in combustion engines - is therefore not appropriate. According to the invention the graphite- containing surface layer comprises expanded graphite flakes. Such a graphite- containing material, generally sheet-like, is obtained by exposing graphite ore to an acidic solution, whereby the graphite layers are pressed apart and the graphite ore expands, and by rolling the thus formed flakes of graphite into a foil at a raised temperature and pressure. In principle this per se known method produces a cohesive, sheet-like material without additions to the graphite. Such a material comprising only expanded graphite flakes is recommended. It is however also possible for other compounds to be added to the material. These can be binders for the graphite flakes, such as for instance a fluoropolymer and/or an elastomer, although additives may also be added, such as for instance ceramic particles, rubber particles, fibres, such as for instance carbon or polyaramid fibres.

The content of graphite in the surface layer can vary within wide limits. The surface layer of the sealing body according to the invention preferably comprises 80 - 99.95% by weight of graphite relative to the overall weight of the surface layer. The surface layer of the sealing body more preferably comprises 95 - 99.95% by weight of graphite relative to the overall weight of the surface layer, most preferably the surface layer of the sealing body comprises 98 - 99.95% by weight of graphite relative to the overall weight of the surface layer.

As will be discussed hereinbelow with reference to the likewise invented method for manufacturing the sealing body, a further improved seal is obtained if the density of the graphite-containing surface layer is increased relative to the density of the graphite- containing material. This can take place according to the invention by compacting the surface layer under increased pressure after arranging thereof on a body. A preferred embodiment of the sealing body according to the invention has a surface layer with a density between 700 - 2500 kg/ra³. The density of the surface layer more preferably lies between 1000 - 2400 kg/m³, still more preferably between 1600 - 2200 kg/m³, and most preferably between 1750 - 2000 kg/m³.

The surface layer can in principle be connected in any manner to the body on which it is arranged. It is thus possible to obtain adhesion by increasing temperature and pressure. The sealing body according to the invention is preferably characterized in that the sealing body also comprises an adhesive layer for the surface layer. The adhesive layer is preferably substantially chlorine-free. This is understood to mean that the chlorine content in the adhesive layer preferably amounts to no more than 100 ppm, and more preferably no more than 50 ppm. This preferred embodiment results in an improved sealing, but moreover ensures a reduced risk of corrosion. An additional advantage of the present preferred variant is that it results in a further reduced risk of damage to the injector.

In yet another preferred embodiment of the sealing body according to the invention the sealing body is provided with one or more profiling grooves extending below the surface layer. Such a variant ensures a further improved sealing and also improves the adhesion of the surface layer. The sealing is further enhanced when the overall volume of the surface layer is greater than the overall volume of the profiling grooves. If the surface layer is arranged in substantially regular manner on the body and compacted according to the above described method, the surface layer will thus wholly cover the profiling grooves without for instance the uppermost parts hereof protruding through the surface layer.

The sealing body according to the invention can withstand pressures of at least 1000 bar, more preferably at least 1500 bar, and still more preferably at least 2000 bar. The sealing body can further withstand exceptionally low temperatures, of at least -50⁰C, but also exceptionally high temperatures of at least 25O⁰C, preferably at least 35O⁰C, still more preferably at least 55O⁰C. This is understood to mean mat the sealing body fulfills its normal function at the stated pressures and temperatures. The invention also relates to a method for manufacturing a sealing body with opening for a second body movable through the opening. The method comprises the steps of: a) providing a body in the form of the sealing body; b) arranging a material comprising expanded graphite flakes on at least the peripheral surface of the opening of the body, thus forming a surface layer; c) placing the graphite-containing material under pressure until the desired thickness and/or density of the surface layer is obtained.

Step a) of the method can for instance be performed by giving a body of metal the form of the sealing body by means of a suitable machining process. This can for instance take place by turning the sealing body from a metal plate, for instance in the form of a ring with centra] opening. In a preferred embodiment of the method according to the invention the part of the body on which the graphite-containing material is arranged is thus provided at least partially with a profile. The upper surface and/or the lower surface of the ring can thus preferably be provided with a number of grooves, preferably in the form of a number of concentric rings. Concentric grooves provide for a further improved seal. For the purpose of a good clamping fit the inner surface of the opening in the sealing body is preferably finished, for instance by means of abrasion or another precision-machining technique such as for instance honing. Honing is a form of abrasion with which holes can be cleared with utmost precision. A honing tool generally comprises 2-6 honing stones placed in the longitudinal direction which are pressed against the wall of the opening by means of a hydraulic or mechanical system. Prior to arranging the graphite-containing material an adhesive layer is preferably arranged on at least a part of the body. After the graphite-containing material has been arranged on the surfaces of the body intended for this purpose, the material is brought under pressure in step c) until the desired thickness of the surface layer is obtained.

The dimensions of the opening can for instance here be monitored with random tests until the desired dimensioning enabling the second body to be received is achieved. The dimensions of a produced sealing body are preferably inspected in automatic manner. If the method is performed by means of a robotic device, as further indicated hereinbelow, the robotic device then comprises for this purpose a thickness control means and the inner diameter (graphite) of the sealing body is determined by making use of a special pressure pin in the robotic device. In addition to a visual check, the dimensioning is guaranteed by means of a regulated procedure and documented according to international quality systems.

The invention also relates to a method for manufacturing an assembly of a sealing body with opening and a second body at least partially received with clamping fit in the opening, in particular the injector part of an injector for a combustion engine. The method comprises the steps of: a) providing a body in the form of the sealing body; b) arranging a material comprising expanded graphite flakes on at least the peripheral surface of the opening of the body, thus forming a surface layer; c) pushing or pressing the second body through the opening, wherein the graphite- containing material is brought under pressure until the desired thickness and/or density of the surface layer is obtained.

The sealing body according to the invention preferably has an inner diameter chosen relative to the - usually conical - injector part of the injector such that it will automatically acquire its clamping action during assembly. In this preferred variant the sealing body, for instance in the form of a ring, is as it were further tightened onto the injector part during the pressing-on during step c). By exerting a pressing(-on) force the sealing body is then pressed to the end of the injector (the shoulder of the injector). The graphite layer arranged on the inner side of the sealing body has a low frictional resistance and is compacted to the desired level during the pressing onto the injector part of the injector, and such that a seal is also created here, and in particular the required clamping is obtained. Despite the fact that the graphite layer on the inner side of the opening compacted during assembly has a relatively high mechanical strength it is still possible, owing to the properties of graphite, to remove the sealing body in relatively simple manner after use.

Applying the graphite-containing surface layer in the invented sealing body avoids the injector being easily damaged during mounting of the sealing body thereon.

Furthermore, there is less danger of the injectors becoming blocked during the pressing- on. The particular deformation properties of the surface layer moreover achieve that this layer can be arranged relatively easily on injectors with slightly varying outer dimensions. This makes the sealing body according to the invention "more tolerant" to dimensional variations than the known sealing body.

If desired, the method according to the invention can be performed by means of an at least partially automated device. Such a device comprises at least means for providing a body in the form of the sealing body; means for arranging a graphite-containing material on at least a part of the body; and means for placing the graphite-containing material under pressure until the desired thickness of the surface layer is obtained. The means for providing a body in the form of the sealing body preferably comprise a robot which can transport the body between, from and/or to a number of stations. One of the stations comprises means for arranging a graphite-containing material on at least a part of the body, for instance in the form of a punching and adhesive unit. The punching unit gives the graphite-containing material the desired form, the adhesive unit applies the adhesive layer to the punched-out graphite-containing material and/or to the body. Another station of the device comprises means for placing the graphite-containing material under pressure, for instance in the form of a pressing unit with heating means. If desired, the graphite-containing material punched out in the desired form, optionally provided with an adhesive layer, is carried along a drying belt. A station comprising a packaging machine is optionally also present.

According to the invention at least the inner surface of the opening is provided with the surface layer. In a preferred embodiment of the method the inner surface of the opening is provided here with the surface layer by arranging an excess of the graphite-containing material on at least one side of the body and then folding the excess along the peripheral edge of the opening by means of a punch nose so that the excess is pressed substantially against the inner surface. A further preferred variant is characterized in that an excess of graphite-containing material is arranged on either side of the body and each excess is then folded along the peripheral edge of the opening by means of a punch nose so that these excesses are pressed substantially against the inner surface. It is recommended that the excesses have a size on each side such that they substantially do not overlap when the two excesses are folded along the peripheral edge of the opening.

hi order to further improve the clamping fit between the outer surfaces of the sealing body and the opening, as well as the sealing therebetween, in a first preferred variant of the method at least the excess of graphite-containing material is brought under pressure until the desired thickness and/or density of the surface layer is obtained, and is then folded along the peripheral edge of the opening.

In order to further improve the clamping fit and the sealing, in yet another preferred variant of the method at least the surface layer arranged on the inner surface of the opening is compacted by arranging in the opening a punch which can be radially expanded. Such a punch can for instance comprise a number of peripheral bodies arranged around a central feed channel. The peripheral bodies can then be moved outward by means of a medium under pressure carried through the inlet channel, whereby they exert a radial pressure which is directed substantially perpendicularly of the inner surface of the opening. It will be apparent that many options are available here to the skilled person.

The invention will now be further elucidated here on the basis of the non-limitative exemplary embodiment described in the figures. Herein:

- figure l(a) shows a schematic top view of a sealing body according to the invention;

- figure l(b) shows a schematic cross-section of the sealing body of figure l(a);

- figure 2(a) is a schematic top view of a body serving as basis for the sealing body shown in figure 1;

- figure 2(b) shows a schematic cross-section of the body of figure 2(a);

- figure 3(a) is a schematic top view of graphite-containing material serving as surface layer for the sealing body shown in figure 1 ;

- figure 3(b) shows a schematic cross-section of the graphite-containing material of figure 3(a); and

- figure 4 shows a schematic side view of an injector provided with a sealing body according to the invention.

Referring to figures l(a) and l(b), a sealing body 1 is shown, provided with an opening 2 with diameter 4 for receiving a second body 14 of an injector 10 for arranging through opening 2 (see figure 4). Sealing body 1 comprises a body 5 with a surface at least partially provided with profiling grooves 6. Body 5 is provided over practically its whole surface with a graphite-containing surface layer 3. Surface layer 3 comprises a flexible graphite foil, Sigraflex APX₅ available from the company SGL Technologies GmbH in Germany. This foil comprises 80 - 99.95% by weight of graphite and has a thickness of about 0.5 mm. Situated between body 5 and surface layer 3 is an adhesive layer (not shown) for surface layer 3. The adhesive layer preferably comprises a chlorine-free adhesive. By also providing inner surface 7 of opening 2 with surface layer 3 a shaft 14 can be received with clamping fit in opening 2. By applying surface layer 3 according to the invention a practically leakage-tight connection is obtained between the outer surface of shaft 14 and inner surface 7 of opening 2, which also remains leakage-tight at high pressures, preferably at pressures of 2000 bar, and over a wide temperature range, preferably from -5O⁰C to 500⁰C. Such conditions are usual in combustion chambers of combustion engines. Although sealing body 1 according to the invention is widely applicable, it is applied particularly as seal for instance for injectors. Referring to figure 4, such an injector 10 generally comprises a housing in the form of a cylindrical part 11, and an injector part or nozzle 14. Accommodated in the housing is a shaft (not shown) movable in the axial direction of the housing and connected to a nozzle 13. Nozzle 13 comprises a number of openings through which the fuel is injected under pressure into the combustion chamber. Injector 10 is for instance arranged through an opening in the wall of the combustion chamber, wherein the opening is sealed by sealing body 1.

The sealing body is obtained by a method comprising the following steps. A body 5 in the form of the sealing body is first provided. Body 5 can for instance consist of a metal, preferably stainless steel, and be manufactured in known manner, for instance by turning. Body 5 is provided with profiling grooves 6. Referring to figures 3(a) and 3(b), two graphite rings 3 are punched out of the above mentioned graphite foil. These rings are then preferably provided with an adhesive layer, for instance by spraying a suitable adhesive, which is preferably chlorine-free. The graphite rings are then preferably dried and both pressed onto either side of body 5. This can take place in one operation by approaching body 5 from both sides. It is however also possible to first arrange a graphite layer on one side of body 5, to then turn it over and subsequently arrange the second graphite layer on the other side. Because opening 9 present in graphite rings 3 has a smaller diameter 8 than the diameter 24 of opening 22 present in body 5, a portion of graphite rings 3 will be bent round while they are being pressed on and will thus cover peripheral surface 27 of opening 22, so creating peripheral surface 7 with diameter 4 (see figure I). In a final step the thus formed surface layer 3 of graphite- containing material is brought under pressure until the desired thickness of surface layer 3 is obtained. Densities of the surface layer are obtained here which preferably lie between 700 - 2500 kg/m\ The thus obtained sealing body 1 is then pressed with relatively great force over injector part 14 of injector 10, which results in a clamping fit between outer surface 14 of the injector part and inner surface 7 of the sealing body. Injector 10 thus provided with sealing body 1 can then be arranged in an opening of a combustion chamber wall, wherein surface 15 (see figure 4) of sealing body 1 comes to lie against the relevant wall part. Use of the sealing body according to the invention not only results in a good seal between surface 15 and the relevant wall part of the combustion chamber, but also between injector part 14 and inner surface 7 of the sealing body. A thus obtained preferred embodiment of an assembly of a sealing body 1 with opening and an injector part 14 of an injector 10 for a combustion engine received in the opening has a pressure resistance of at least 1500 bar and a temperature resistance of at least 250⁰C.

Claims

1. Sealing body with opening for a second body receivable in the opening, characterized in that at least the inner surface of the opening of the sealing body is provided with a surface layer of a graphite-containing material comprising expanded graphite flakes.

2. Sealing body as claimed in claim 1, characterized in that the surface layer comprises 80 - 99.95% by weight of graphite.

3. Sealing body as claimed in claim 2, characterized in that the surface layer comprises 95 - 99.95% by weight of graphite.

4. Sealing body as claimed in claim 3, characterized in that the surface layer comprises 98 - 99.95% by weight of graphite.

5. Sealing body as claimed in any of the foregoing claims, characterized in that the density of the surface layer lies between 700 - 2500 kg/m³.

6. Sealing body as claimed in claim 5, characterized in that the density of the surface layer lies between 1750 - 2000 kg/m³.

7. Sealing body as claimed in any of the foregoing claims, characterized in that the sealing body also comprises an adhesive layer for the surface layer.

8. Sealing body as claimed in claim 7, characterized in that the adhesive layer is substantially chlorine-free.

9. Assembly of a sealing body as claimed in any of the foregoing claims and a second body at least partially received with clamping fit in the opening of the sealing body.

10. Assembly of a sealing body as claimed in any of the foregoing claims and an injector part of an injector for a combustion engine at least partially received with clamping fit in the opening of the sealing body.

11. Method for manufacturing a sealing body with opening for a second body receivable through the opening, comprising the steps of: a) providing a body in the form of the sealing body; b) arranging a material comprising expanded graphite flakes on at least the inner surface of the opening, thus forming a surface layer; c) placing the graphite-containing material under pressure until the desired thickness and/or density of the surface layer is obtained.

12. Method as claimed in claim 11, wherein the inner surface of the opening is provided with the surface layer by arranging an excess of the graphite-containing material on at least one side of the body and then folding the excess along the peripheral edge of the opening by means of a punch nose so that the excess is pressed substantially against the inner surface.

13. Method as claimed in claim 12, wherein an excess of graphite-containing material is arranged on either side of the body and each excess is then folded along the peripheral edge of the opening by means of a punch nose, wherein the excesses have a size on each side such that they substantially do not overlap when the two excesses are folded along the peripheral edge of the opening.

14. Method as claimed in either of the claims 12-13, wherein at least the excess of graphite-containing material is brought under pressure until the desired thickness and/or density of the surface layer is obtained, and is then folded along the peripheral edge of the opening.

15. Method as claimed in any of the claims 11-14, wherein the surface layer arranged on at least the inner surface of the opening is compacted to the desired thickness and/or density thereof by arranging in the opening a punch which can be radially expanded.

16. Method for manufacturing an assembly of a sealing body with opening and a second body at least partially received with clamping fit in the opening, wherein step c) of the method as claimed in any of the claims 11-15 comprises the step of pushing or pressing the second body through the opening, wherein the graphite-containing material is brought under pressure until the desired thickness and/or density of the surface layer is obtained.

17. Assembly of a sealing body with opening and an injector part of an injector for a combustion engine received in the opening, which assembly is obtainable with a method as claimed in claim 16 and has a pressure resistance of at least 1500 bar and a temperature resistance of at least 250⁰C.