WO2012107354A1

WO2012107354A1 - Sealing arrangement

Info

Publication number: WO2012107354A1
Application number: PCT/EP2012/051813
Authority: WO
Inventors: Jürgen Kurth; Frank Sonnenschein
Original assignee: Aktiebolaget Skf
Priority date: 2011-02-08
Filing date: 2012-02-03
Publication date: 2012-08-16
Also published as: DE102011003744A1

Abstract

The invention relates to a sealing arrangement comprising an inelastic substrate (2) and a sealing material (4). An elastic material (6) having a greater elasticity than the sealing material (4) is arranged between the inelastic substrate (2) and the sealing material.

Description

Sealing Arrangement Embodiments of the invention are concerned with sealing arrangements that may be used, for example, to seal a valve.

Seals are used in large numbers in many technical applications. In applications where the material used for sealing is in direct contact with a moving component, a high wear resistance of the sealing material is required. For example, in shaft seals, by means of which a rotating shaft is to be sealed with respect to a housing, the material of the seal must be resistant to wear, as considerable relative velocities between the sealing material and the surface of the shaft or of the movable component can occur. Such wear-resistant sealing materials are relatively hard and inelastic.

In other seals between 2 components there is no relative movement between the sealing material, ie the material from which the seal is made, and the components to be sealed, although the components themselves can move relative to one another. Examples of such seals are bellows, as used for example in motor vehicle steering or -Achs. This sealing materials are used, which have a high elasticity, the wear resistance, however, for example, in view of a possible abrasion, is low. When selecting the materials that make up a seal assembly, the operating conditions in which the seal is to be used must also be considered. These can sometimes be very demanding. For example, in modern cars to reduce emissions of nitrogen oxides (NOx) an exhaust gas recirculation used in which parts of the exhaust gas are supplied to the combustion chamber again to lower the combustion temperature and thus the emission of nitrogen oxides. The recirculated exhaust gas amount is regulated in a designated as exhaust gas recirculation valve arrangement by means of a valve. The actuation of the valve can be done for example via a cam or an electric motor drive. A seal of the valve with respect to the housing of the exhaust gas recirculation valve may be required in modern cars, as they often have sensors that report the current position of the exhaust gas recirculation valve to a central controller, so that this can use this information in the calculation of the operating parameters of the engine. For this reason, no exhaust gas may pass the valve guide, since the exhaust gas, which has a temperature of several 100 ° C or its condensates, would destroy such electronic or sensory components. These are typically located outside of the exhaust-carrying volume, usually in an area on the back of the actual valve, for example when driving the valve. A seal in such an exhaust gas recirculation valve can therefore be exposed to temperatures of -40 ° C during cold start up to +200 ° C during operation.

In seals in which a relative movement of the two components to be sealed to each other can occur, often elastomeric sealing lips are used. In the absence of lubrication and when the two sealed by the seal components perform a relative movement to each other, but often wear this seal quickly, are therefore less stable. Furthermore, such gaskets can not be reliably used over a wide temperature range because elastomers can experience a significant reduction in elasticity even above the glass transition temperature (the temperature at which elastomers lose their elasticity). At lower temperatures, an elastomeric sealing lip can therefore often no longer follow or compensate for the relative movements of the components to be sealed, since the flexibility of the elastomer is already too greatly reduced. The consequence of this is a reduction or loss of the sealing effect.

Wear-resistant sealing materials, which are used in components that perform a relative movement to each other, so that during operation, a relative movement between the sealing material and a component occurs, so have too low flexibility or elasticity, than that they relatively large relative movements or greater Ab- Stand variations between the components to be sealed could follow. Flexible sealing materials are often unusable for reasons of wear.

There is thus the need to provide a sealing arrangement which can be used universally.

Embodiments of sealing arrangements make this possible by arranging in the case of a sealing arrangement between an inelastic support and a sealing material, which can be in contact with a component which is to be sealed relative to the sealing material, an elastic material which has a greater elasticity than the sealing material even.

As a result, a suitable with regard to wear sealing material can be used to ensure a high stability of the seal assembly. At the same time, a possible relative movement between the components to be sealed to one another can be compensated for by utilizing the elasticity of the elastic material, which in turn is supported on the inelastic carrier. Thus, a suitable sealing material can be used for the wear-resistant direct contact with a movable component, whereas due to the additional elastic material it is ensured that the sealing material can follow the movements of the component in contact with the sealing material relative to the inelastic carrier or another component. Embodiments of sealing arrangements can ensure the seal at high wear resistance at any time. In some embodiments, the elastic material is disposed between the sealing material and the inelastic support such that force applied to the sealing material is transferred to the inelastic support via the elastic material. In other words, the elastic material is supported on the inelastic support and, due to its own elasticity, allows a relative movement between the two components to be sealed, which can also take place in a direction perpendicular to the surface of the component to be sealed.

In some embodiments, a material comprising a polysiloxane (silicone) is selected as the elastic material. The elastic material consists in some cases of Examples of more than 50, more than 70, more than 90 or more than 95 weight percent of polysiloxane. This may have the advantage that sealing arrangements whose flexible material has polysiloxane in the scope specified above can be used in a high temperature range, for example of less than -50 ° C to more than 250 ° C, since the material in this Temperature range has a high elasticity.

In some embodiments, a material comprising a polytetrafluoroethylene is used as the sealing material. The sealing material in some embodiments is greater than 50, greater than 70, greater than 90, and greater than 95 weight percent polytetrafluoroethylene. This makes it possible for some embodiments to withstand high relative movements between the sealing material and the component in contact with the sealing material, since polytetrafluoroethylene (PTFE) has an extremely low coefficient of friction. In addition, it is extremely temperature stable. PTFE as a sealing material or PTFE sealing lips have a very good wear behavior with dry friction, i. So even without lubrication and are not least therefore extremely stable.

In some embodiments, the inelastic support is itself formed by a housing or part of a component with respect to which a seal is to be made. This can further increase the manufacturing cost and the usability of the seal assembly.

In some embodiments, a valve in an exhaust gas recirculation valve is sealed relative to the housing of the exhaust gas recirculation valve by means of an embodiment of a seal assembly comprising a sealing material comprising PTFE and an elastic material comprising polysiloxane. By means of this combination of materials, a reliable sealing can be achieved in the embodiments even over a wide temperature range of for example -40 ° C to 200 ° C, since the good emergency running properties of seals made of filled PTFE materials with the good elastic properties of a silicone ring for contact pressure the sealing lip or the sealing material are combined to the shaft. This can ensure a reliable sealing effect, even if a shaft of the valve in the radial direction, that is perpendicular to its surface or to its surface to be sealed, high deviations should show from the nominal position. With exhaust gas recirculation valves, such deviations are frequent, since due to the high temperature range, clearance between the valve stem and the valve guide has to be comparatively large in order to prevent the valve from jamming at all operating temperatures.

In further embodiments, for example, a movable carriage is sealed by means of an embodiment of a sealing arrangement. Thus, in further embodiments, the seal assemblies are linearly expanded in only one dimension and do not completely enclose a subject to be sealed. Embodiments of sealing arrangements are not based on cylin- ders

Seals, which can be used for example for sealing shafts or rods or valve rods, limited.

Some embodiments of the present invention will be explained in more detail below with reference to the attached figures.

FIG. 1 shows a sectional view of an exemplary embodiment of a sealing arrangement;

Figure 2 is an example of a design of the sealing material of the embodiment of Figure 1; Figure 3 is another example of a design of the sealing material of the embodiment of Figure 1; and

Figure 4 shows an embodiment of an exhaust gas recirculation valve. FIG. 1 shows a sectional view of an exemplary embodiment of a sealing arrangement comprising an inelastic carrier 2, a sealing material 4 and an elastic material 6. The elastic material 6 is disposed between and in physical contact with the inelastic support 2 and the sealing material 4, respectively. In the embodiment shown in Figure 1, a valve stem 8 of a valve with respect to a housing or a valve guide is sealed in the housing, wherein the housing itself forms the inelastic support 2 of the seal assembly. The housing or the inelastic support 2 has an annular recess 10, within which the sealing material 4 and the elastic material 6 is arranged. In the rotationally symmetrical arrangement of FIG. 1, the valve stem 8 can move in and counter to an axial direction 12, ie from left to right in the figure.

If the guide of the valve stem 8, which in the present case is formed by a bore with a diameter 14, has a clearance with respect to the valve stem 8, ie if the diameter 14 of the bore is greater than the diameter of the valve stem 8, the valve stem 8 can move relative to the housing and thus move relative to the inelastic carrier 2 of the seal assembly in a radial direction 16 perpendicular to the axial direction.

Since the elastic material 6 is arranged in the radial direction 14 between the sealing lip or the sealing material 4 and the radial housing wall or the inelastic support 2, the sealing material 4 is pressed elastically against the valve stem 8. This allows the sealing material 4, even if this would otherwise not be possible due to its own elasticity, following an elastic deformation of the formed in the form of an O-ring elastic material 6 of a radial movement of the valve stem 8.

Thus, both high wear resistance and tightness in a wide range of temperature and operating parameters can be ensured. The pressing of the sealing material 4 can, in contrast to, for example, when using steel wire springs on the circumference of the sealing material, take place without high contact pressures would be required, which would increase the wear and the power losses during operation of the valve.

In this sense, an inelastic carrier 2 is to be understood here and in the other embodiments as a carrier made of a material whose elasticity is less than the elasticity of the elastic material 6, so that upon exerting a force on the elastic material 6, the elastic material 6 deformed and not the ine- That is to say that in the radial direction 16 a force acts on the sealing material 4 which is transmitted via the elastic material 6 to the inelastic support 2, only the elastic material 6 deforms. Materials for inelastic supports 2 are used For example, metals or plastics, for example, thermoplastic plastics, into consideration, which apart from their energy elasticity have no further elastic properties.

In the direction of the volume to be sealed, that is to say in the axial direction 12 adjacent to the elastic material 6, in the embodiment shown in FIG. 1, the sealing material 4 itself extends as far as the inelastic support 2, which protects the inelastic material 6 from the inelastic material 6 serve substances contained in the sealed volume. By thus additionally achieved support of the seal assembly in the axial direction 12, a small abdominal cavity can be achieved beyond. Figure 2 shows an embodiment of a geometric shape of the sealing material 4, as it can be used in the embodiment shown in Figure 1. Figure 2 shows a section through a segment of the sealing ring or of the ring of sealing material 4 and of the ring of elastic material 6. In addition to the features shown in Figure 1, the sealing material 4 in Figure 2 has a recess 18 which can receive a lubricant to cause additional lubrication and reduction of friction in the relative movement between the sealing material 4 and the valve stem 8. For this purpose, the recess is arranged on the side of the sealing material 4 facing away from the inelastic carrier 2, that is to say on the side of the sealing material 4 facing the valve stem 8.

Figure 3 shows a further embodiment of a geometric shape of the sealing material 4, in which, in addition to the recess 18, a sealing lip 20 is used, which extends from the surface of the sealing material 4 in the direction of the valve stem 10 to locally hold a grease used for lubrication and to increase the duration of lubrication or to minimize the loss of lubricant. That is, in addition to the recesses 18 in the sealing lip or the sealing material 4 grease is held locally for lubrication, with an additionally attached retaining or sealing lip 20 on the opposite side of the sealing lip of the sealing lip to increase the amount of fat to be introduced even further by adding fat to the chambers on the Valve stem 8 side facing and can be used for an initial lubrication.

Figure 4 shows an embodiment of an exhaust gas recirculation valve 22 in a schematic sectional view. Exhaust gas recirculation valve 22 includes a housing 24 within which is arranged a valve 26 which regulates an exhaust gas flow through exhaust gas recirculation valve 22 which can flow between an inlet 28 and an outlet 30 of exhaust gas recirculation valve 22. The valve 26 is sealed by means of an embodiment of a sealing arrangement with respect to a valve seat 32, wherein in the illustrated in Figure 4 embodiment of the inelastic support 2 is formed by a part of the housing 18 of the exhaust gas recirculation valve 22. The sealing material 4 and the elastic material 6 are in the embodiment shown in Fig. 4 within a recess 34 in the inelastic support 2 forming housing 24. In further embodiments, the elastic material 6 may also be supported on the valve stem, which in case of defect Replacement of the seal assembly together with the valve 26 can allow.

In order to ensure good sealing of the valve 26 with respect to the valve seat 32 at all times, despite the large temperature differences that occur during normal operation of an exhaust gas recirculation valve, in the embodiment shown in FIG. 4, a filled PTFE is used as the sealing material Material used. In addition, an O-ring made of a silicone or a polysiloxane is used as the elastic material, so that during all operating conditions and temperatures, that is, e.g. between -40 ° C and 200 ° C, the housing passage of the valve stem can be sealed against passing gas and any condensate occurring in order to avoid disturbances and defective adjacent components, which may be located, for example, on the side facing away from the exhaust chamber 26 of the valve. As an example of such a component, a valve position sensor 36 is shown schematically in FIG.

Although in the previously described embodiments sealing arrangements have been described which seal a housing or a component with respect to a cylindrical shaft, it goes without saying that further embodiments of Sealing arrangements can be used to non-rotationally symmetrical, for example, rectangular components, as well as waves arbitrary, for example, elliptical cross-section, seal. In addition, other embodiments of sealing arrangements can be used which do not completely enclose a component, but for example extend linearly in one direction. In such an embodiment, the sealing material may, for example, rest on one side of a table of a press or similar device from one side to achieve a seal between two linearly movable elements.

LIST OF REFERENCE NUMBERS

2 inelastic carrier

4 sealing material

6 elastic material 8 valve stem

10 annular recess

12 axial direction

14 diameter

16 radial direction

18 recess

20 sealing lip

22 exhaust gas recirculation valve

24 housing

26 valve

28 entrance

30 output

32 valve seat

34 recess

36 Valve position sensor

Claims

P a n t a n s p r e c h e

sealing arrangement

Sealing arrangement comprising the following features:

an inelastic support (2);

a sealing material (4); and

between the inelastic support (2) and the sealing material

(4) arranged elastic material (6), which has a greater elasticity

as the sealing material (4).

Sealing arrangement according to claim 1, wherein the elastic material (6) is arranged between the sealing material (4) and the inelastic support (2) in such a way that a force acting on the sealing material (4) over the elastic material (6) on the inelastic carrier (4) is transmitted.

Sealing arrangement according to one of claims 1 or 2, wherein the sealing mate rial (4) comprises a polytetrafluoroethylene.

Sealing arrangement according to one of claims 1 to 3, wherein the elastic material (6) comprises a polysiloxane (silicone).

Sealing arrangement according to one of claims 1 to 4, wherein the sealing material (4) on one of the inelastic support (2) facing away from one or meh rere recesses (18) for receiving a lubricant.

6. Sealing arrangement according to one of claims 1 to 5, wherein the elastic material (6) directly adjacent to the sealing material (4) and to the inelastic support (2).

7. Sealing arrangement according to one of claims 1 to 6, wherein the inelastic carrier (2), the sealing material (4) and the elastic material (6) on the said inelastic support (2) facing away from the side of the sealing material (4) opening completely enclose.

8. exhaust gas recirculation valve (22) with a sealing arrangement according to one of the preceding claims.

9. exhaust gas recirculation valve (22) according to claim 8, wherein the shaft of an exhaust gas flow regulating valve (26) is sealed by means of the sealing arrangement with respect to a valve guide (32) for the valve.

10. Exhaust gas recirculation valve according to claim 9, wherein the inelastic support (2) of the sealing arrangement of a housing (24) of the exhaust gas recirculation valve (22) or of the shaft of the valve (26) is formed.