Sealing device

Abstract

The present invention relates to a sealing device (1) for sealing an interior (D) of a machine housing (2) at an exiting shaft (3) or a shaft sleeve against an external environment (A), comprising a shaft sealing disc (5) with its own housing (4) for fixing in a machine housing (2) or a housing cover, and a sealing lip (8) that interacts with a closely adjacent section (9) of a surface (10) of the shaft (3) or the shaft sleeve to produce a sealing effect. In order to create a sealing device suitable for higher pressures and / or speeds for sealing against fluids, which has low losses due to friction in the area of ​​the sealing lip, it is proposed that the sealing function of the sealing lip (6) on the shaft surface (8) be supplemented by a barrier air seal (12).

Description

[0001] The present invention relates to a sealing device which is provided for sealing an interior of a machine housing at an exiting shaft against an external environment.

[0002] Sealing devices are preferably used for sealing between two spaces in the area of ​​shafts, particularly in the case of rotating and / or axially displaceable shafts exiting a machine housing, which must be sealed against an external environment. For the sake of simplicity and without limiting the invention to this specific application, the following will refer only to the contact of a seal with a shaft. These seals are referred to as radial shaft seals and also apply to axial seals. Both types of shaft sealing devices are ready-to-install sealing elements that achieve a sealing effect by radially pressing at least one sealing lip against a shaft or shaft sleeve. The radial pressure required for sealing is determined by the design of the seal, more precisely by the radial pressure of the sealing lip against the shaft as a result of deformation of the sealing disc.For installation in a corresponding recess of a machine housing, a radial shaft sealing disc, for example, is surrounded by its own housing to pre-adjust such a deformation, thus forming a radial shaft seal as a ready-to-install component.

[0003] Various approaches to the design of radial shaft seals of the type mentioned are known from the prior art; see, among others, DE 10 2014 100 577 A1, DE 31 26 716 A1, DE 10 2016 120 219 A1, DE 10 2016 205 057 A1, and DE 10 2018 117 306 A1. Radial shaft seals according to DIN 3760 are widely used in engineering. Radial shaft sealing devices are frequently used to seal a pressurized interior of a machine housing against an exterior at standard pressure. Since the interior of the machine housing is often filled with coolants and / or lubricants, a high degree of tightness in the area of ​​a shaft exit is an essential requirement for a radial shaft sealing device.In the event of any leak, whether caused by material failure of the radial shaft seal or by wear, the affected seal must be replaced immediately to restore the required tightness. Media loss and / or contamination of both external and internal areas must be permanently prevented. Therefore, the operational reliability of a radial shaft seal is of paramount importance. The same applies to axial shaft seals.

[0004] At higher pressures and / or high rotational speeds, there is a significant increase in frictional power between the sealing lip and the shaft surface in contact with it. The resulting increased frictional heat and / or significantly increased wear on the sealing lip leads to rapid failure of the sealing device. When sealing against pressurized liquid media, it has proven effective to reduce frictional power and wear on the sealing lip while maintaining sufficient tightness. For this purpose, DE 10 2011 077 015 A1 provides for the creation of a cavity located beyond a sealing element, which is sealed against a low-pressure area and connected to a high-pressure area. The pressure prevailing in this cavity acts on the sealing element, so that the sealing element is essentially subjected to the high pressure on both sides.Overall, with appropriate design and dimensioning, this approach can be used to reduce the pressure of a sealing lip on a shaft surface to reduce heating and wear.

[0005] Seals have also been successfully used in high-speed shafts where a sealing lip only weakly contacts the shaft surface, or, in the manner of a labyrinth seal, does not contact it at all. These sealing designs are also considered below with regard to their significantly reduced wear due to the relieved sealing lips, which exhibit a pronounced sealing function for sealing against fluids.

[0006] The present invention aims to create a sealing device designed for sealing against fluid substances, even at higher pressures and / or speeds, which exhibits low losses due to friction in the area of ​​the sealing lip.

[0007] This problem is solved according to the invention by the features of claim 1 in that the sealing function of the sealing lip on the shaft surface is supplemented by a barrier air in the sealing area. Fluid tightness places lower demands on a sealing lip than gas tightness, so that the contact force of the sealing lip on a shaft surface is significantly lower or even non-existent. This advantageous reduction in wear on the sealing lip is offset, at low shaft speeds, by the potential for fluid leakage, which spreads under the sealing lip along the shaft and across the shaft surface. Here, particularly at low speeds, a barrier air in the sealing area acts as an additional barrier, which is also wear-free and ensures sufficient fluid tightness.In addition, the sealing air enables cooling by removing heat from the sealing area.

[0008] Advantageous further developments are the subject of the dependent claims. Accordingly, a radial groove connected to a bore is provided in the sealing device. This radial groove is designed to supply compressed air at a pressure p, which forms the sealing air seal via an annularly closed surface on the shaft surface.

[0009] In a preferred embodiment of the invention, the sealing air seal is arranged between two sealing lips. In one embodiment, two ready-to-install radial shaft seals are provided as a component of the sealing device in a common annular housing, which in turn has the aforementioned radial groove connected to a bore. In an alternative embodiment, two sealing lips with a sealing air seal arranged between them are provided in a ready-to-install radial shaft seal.

[0010] According to a particularly preferred embodiment of the invention, slots or holes are provided as recesses in an elastic molded part of a sealing device designed according to DE 10 2011 077 015 A1 to create a purge air seal. In a further development, these recesses, designed as slots or holes in the elastic molded part, have a predetermined position, shape, and / or size. These parameters are designed and selected to produce a specific effect of the purge air seal at a predetermined purge air pressure. At a predetermined pressure, the elastic molded part of the sealing device with the recesses thus acts as a throttle for setting a predetermined pressure reduction.

[0011] In a further development of the invention, the sealing device features a sequence of axial bores or recesses and radial grooves extending from a first housing part to a spacer ring within the elastic molded part. Since the intervening radial grooves facilitate the distribution of supplied compressed air, axial alignment of the bores or recesses across the individual components is not required during assembly of the sealing device. Otherwise, achieving precise alignment from the first housing part to the elastic molded part would significantly complicate manufacturing.

[0012] Preferably, the elastic molded part has a nose or a shoulder. This nose or shoulder is designed to secure positioning and orientation relative to the outer housing part.

[0013] In a further development, a second or additional sealing lip is provided on a sealing device based on the disclosure of DE 10 2011 077 015 A1, so that the barrier air seal is now enclosed in a single structural unit, essentially between two sealing lips. This design is significantly smaller and more compact than a seal of the type described above, which consists of two complete sealing devices with a barrier air seal integrated between them.

[0014] Further features and advantages of embodiments of the invention are explained in more detail below with reference to exemplary embodiments and the drawing. The drawing schematically depicts: Fig. 1: an embodiment according to the present invention with a cutaway side view of the rotationally symmetric arrangement; Fig. 2: a further embodiment according to the illustration of Fig. 1; Fig. 3: a further embodiment according to the present invention as a further development of a sealing device of the applicant; Fig. 4a and Fig. 4b: Sectional views of two further embodiments based on the representation of Fig. 3 and Fig. 5: a further embodiment according to the present invention as a further development of a sealing device according to Fig. 3 for use in higher temperature ranges.

[0015] Across the various illustrations and embodiments, the same reference numerals are always used for identical elements. Without limiting the invention to this application, only radial shaft sealing devices are described below.

[0016] Fig. Figure 1 shows a first embodiment of a radial shaft sealing device 1 in a sectional side view of the arrangement, which is rotationally symmetrical about a central axis M. The radial shaft sealing device 1 is designed to seal a machine housing 2 at a shaft 3 exiting from an interior space subjected to high pressure D, with a radius R, against an external environment with an ambient pressure A. In this embodiment, the radial shaft sealing device 1 comprises two identical radial shaft seals 5 in an annular housing 4, which have been pressed into the housing 4 as finished components.

[0017] From DE 10 2016 120 219 A1, to which full reference is hereby made, a radial shaft sealing device 5 of the design shown here is known, in which a sealing lip 6 of a sealing element 7 bears against a surface 8 of the shaft 3 under low contact pressure. By using a metal sealing element 7, this sealing device 5 is also suitable for continuous use in hot environments, particularly at temperatures well above 250°C, e.g., in exhaust gas turbochargers with temperatures up to approximately 500°C and in contact with a high-speed rotating shaft 3. The sealing element 7 is spring-loaded and pre-tensioned against the surface 8 of the shaft 3. A helical surface (not shown) on the shaft surface 8 in contact with the sealing lip 6 is provided to generate a return flow effect on a fluid, in particular a lubricant.This ensures sufficient fluid tightness in an application on a fast-rotating shaft 3, even with a comparatively low sealing effect of the sealing lip 6, due to low contact pressure on the surface 8 of the shaft 3.

[0018] The arrangement according Fig. Figure 1 shows a serial arrangement of identical and similarly oriented sealing devices 5 of the design described above in the sealing device 1. These devices are fixed in a modular arrangement via their respective housings 9 in the annular housing 4 of the sealing device 1. A radial groove 10 is provided in the housing 9 between the two sealing devices 5, which is connected to a bore 11. This bore 11 is designed to supply compressed air at a pressure p between the two sealing devices 5. The compressed air is distributed evenly around the shaft 3 via the radial groove 10 and exits through the two sealing devices 5 as so-called sealing air. This arrangement forms a sealing air seal 12 in the area outlined with dashed lines.This additional sealing air ensures a reliable seal of the sealing device 1 against a fluid, even with only minimal contact between the sealing lips 6 and the shaft surface 8, using known components in the form of the sealing devices 5. This is achieved even when the shaft 3 is stationary or at such low rotational speeds that no sufficient backflow effect on a fluid can be exerted. Fig. Figure 1 outlines a scenario where the pressure ratio of internal pressure D > sealing air pressure p > external pressure A is such that sealing air can escape from under the sealing lip 6 to the outside. This permanently prevents fluid from penetrating from the outside along the shaft surface 8 through the sealing device 1.

[0019] It is only hinted at in Fig. 1. The radial groove 10 can be supplied with compressed air at a pressure p = D via a bore 11 (shown with a dashed line). In this case, the bore 11 extends from a fluid-free area of ​​an interior space to be sealed to the radial groove 10 and does not need to pass through a machine housing 2.

[0020] In this embodiment, it is advantageously dispensed with using a PFAS material for the disc-shaped sealing elements 7. Instead, the sealing elements 7 are made of metal, e.g., brass or bronze, according to the teachings of DE 10 2016 120 219 A1. In contact with the shaft surface 8 at low pressure, comparatively low losses are generated, with the exhaust air from the sealing air seal 12 serving not only to reduce wear in the sealing area but also to dissipate heat.

[0021] The illustration of Fig. 2 shows a further embodiment according to the illustration of Fig. 1. Here too, two radial shaft sealing devices 5 are joined together via the annular housing 4 to form a sealing device 1, in which a sealing air seal 12 is added between the sealing devices 5. Both sealing devices 5 are constructed according to the teaching of DE 10 2011 077 015 A1, to the content of which reference is hereby made in full. These sealing devices 5 have an elastic molded part 13, which is clamped between an outer first housing part 15 and a profile ring 16 as a second housing part and fixed by a spacer ring 14. In one installation position, the elastic molded part 13 rests against the sealing lip 6 of the sealing element 7, which is pre-tensioned by a forming element 17.Via bores 18 and – as an advantageous innovation for simplifying assembly – radial grooves 19 provided on the first housing part 15, the sealing element 7, and the elastic molded part 13, which distribute the external compressed air, an interior of the elastic molded part 13 is connected to one of the outer surfaces of the sealing device 5, i.e., a side of the higher pressure D. The area of ​​application of the pressure D directly at the sealing lip 6 is significantly smaller than an area of ​​the elastic molded part 13 pressing on the sealing lip 6 from an opposite side. This results in an increased pressure of the sealing lip 6 on the surface 8 of the shaft 3 in response to a high pressure D. For high-speed shafts, a lower pressure is applied to the sealing lip 6 and the elastic molded part 13 via the surface area ratios indicated above to reduce wear, resulting in a reduced sealing function. As described in . Fig. The same applies to the sealing device 5 arranged on the right, as described for the sealing device 5 arranged on the left, except that here the pressure p acts instead of the pressure D.

[0022] To improve the tightness of a sealing device 1 against a fluid at low rotational speeds of the shaft 3 down to standstill, the exemplary embodiment of Fig. 2. Hereafter analogous Fig. 1. Procedure: The air seal 12, which is arranged centrally between the sealing devices 5, is connected to the Fig. The described setup ensures sufficient fluid tightness across the surface 8 of the shaft 3.

[0023] Alternatively to the embodiment of Fig. 2 and, with an otherwise identical design of the sealing device 1, an embodiment according to the teaching of DE 10 2013 122 465 A1 is carried out without further graphical representation, the content of which is hereby also fully incorporated by reference. A pressure change relative to ambient pressure is caused in the area of ​​the bores 18 by means of a fan wheel additionally fixed on the shaft 3. In comparison with a design modification within the above to Fig. In the radial shaft seal 5 described in section 2, which is a more complex finished component, this technical approach with a fan wheel outside the radial shaft seal 5, which is used as a one-piece closed component, allows a pressure difference to be easily adjustable via the fan wheel according to the respective requirements, which is particularly noticeable in the area of ​​high speeds of the shaft 3 as a relief of the pressure on the sealing lip.

[0024] Fig. Figure 3 represents a further embodiment according to the present invention. It is a further development of a sealing device according to the teaching of DE 10 2011 077 015 A1, wherein, in contrast to the preceding descriptions of the Fig. 1 and Fig. 2 with a barrier air seal 12 between two fully assembled and ready-to-install sealing devices 5, a barrier air seal 12 is now described which is additionally provided in only one sealing device 5.

[0025] The air seal 12 is therefore integrated into the sealing device 5. One to Fig. The advantageous sequence of bores or recesses 18 and radial grooves 19 described in section 2, extending from the first housing part 16 to the spacer ring 14 within the elastic molded part 13, is also realized in this embodiment and enables assembly without alignment of the bores or recesses 18 with each other.

[0026] To create a barrier air seal 12, in Fig. 3. Slots or holes of a predetermined shape and size are provided in the elastic molded part 13 as recesses 20. In exemplary embodiments, recesses 20 are provided in the elastic molded part 13 by punching or drilling with diameters of 0.3 to 1 mm. One axis of the recesses 20 can be oriented perpendicular to a surface of the elastic molded part 13. Alternatively, one axis of the recesses 20 is oriented at an angle other than 90° to a surface of the elastic molded part 13 to generate a radially directed flow in the gap or radial groove 19.

[0027] The recesses 20 allow air under defined pressure to escape in a directed and metered manner towards the shaft 3. In one embodiment, these recesses 20 are specifically designed as throttles to create a pressure difference between the high internal pressure D and the sealing air pressure p at the shaft surface 8.

[0028] Opposite the forming element 17 on the sealing element 7, a sheet metal layer 21 is arranged. The sheet metal layer 21 is provided to reinforce the sealing element 7 in the area of ​​the sealing lip 6 and is also in contact with the elastic molded part 13.

[0029] Additionally, the elastic molded part 13 has a nose or shoulder 22 through which it makes contact with the outer housing part 15 and positions itself relative to it. The nose or shoulder 22 ensures the positioning and orientation, in particular of the recesses 20 of the elastic molded part 13, relative to the outer housing part 15 and the sealing lip 6. Otherwise, the slots or holes forming the recesses 20 in the elastic molded part 13 could be covered, blocked, or closed by the sealing lip 6 or the outer housing part 15. This would deactivate the sealing air seal 12. This malfunction could easily occur, for example, during the assembly of the sealing device 1 or when inserting the shaft 3 through the sealing device 1, and would be difficult to rectify.

[0030] Analogous to the embodiment of Fig. 1 is in the embodiment of Fig. 3. It is possible to provide a compressed air supply to the elastic molded part 13 via a radial feed corresponding to the bore 11. A seal can then be inserted in the area of ​​the bores 18 and / or the radial grooves 19. This would seal off any axial connection to the elastic molded part 13.

[0031] Fig. 4a and Fig. Figure 4b shows sectional views of two further embodiments extending the embodiment of Fig. 3. Here, a second or additional sealing lip 23 is provided, so that the barrier air seal 12 is now essentially enclosed between two sealing lips 6 and 23. This reduces the losses occurring due to the pressure difference p > A to a level necessary to prevent fluid leakage. This additional sealing lip 23 is part of a disc-shaped additional sealing element 24, which is clamped between the outer first housing part 15 and the elastic molded part 13 with subsequent spacer ring 14 against the sealing element 7 and the profile or angle ring 16. In contrast to the embodiment according to Fig. 4a is in the one by Fig. 4b only the additional sealing lip 23 is pre-formed in a mirror image orientation towards the radial groove 19 instead of towards the low-pressure side with the external pressure A.

[0032] For applications in higher temperature ranges from approximately 200° to about 500° C, the cross-section shows Fig. 5 a sealing device 1, which is installed, for example, on a hot side of an exhaust gas turbocharger. In modification of the embodiments of the Fig. In sections 3 to 4b, no elastic molded part 13 is provided. The area of ​​a sealing air seal 12 is essentially defined by the spacer ring 14 with the radial groove 19 together with the sealing lip 6; a sheet metal layer 21 is not provided here. This design utilizes existing components from series production, all of which are stable within the specified temperature range. In this embodiment, the sealing lip 6 is part of a sealing element 7 made of a non-ferrous metal alloy, e.g., bronze. With only slight contact with the surface 8 of the shaft 3, the non-ferrous metal alloy sealing element 7 exhibits low wear at the sealing lip 6, ensuring a sufficient service life for the sealing device 1. The sealing lip 6 is manufactured by turning and, in one embodiment of the invention, is also formed by deep drawing.The advantages of a swirl structure for generating a return conveying effect are discussed with regard to the exemplary embodiment of . Fig. 1 referred to. In this embodiment, a comparable helical structure is produced in a simple manner on the sealing lip 6 instead of on the surface 8 of the shaft 3, as shown in the figure of Fig. 5 cannot be represented. A desired tightness of the entire sealing device 1 is achieved analogously to the exemplary embodiment, among other things, by Fig. 3 ensured by the sealing air seal 12.

[0033] The foregoing describes various exemplary embodiments of sealing devices 1, which can also be combined with one another with regard to their features and possess numerous technical properties and advantages. These are based, not least, on the addition of a sealing functionality sufficient even for a high-speed shaft 3, in combination with a specifically applied sealing air. Thus, the described sealing device 1 exhibits sufficient sealing against a pressurized fluid even when the shaft 3 is stationary, and is simultaneously characterized by low wear and therefore long service life. Reference symbol list 1 Sealing device 2 machine housings 3 Shaft exiting through sealing device 1 4 ring-shaped housing of the sealing device 1 5 complete radial shaft seals as part of the sealing device 1 6 Sealing lip 7 Sealing element 8 Surface of the shaft 3 9 Housing of the sealing device 5 10 radial groove 11. Bore in the housing 4 towards the radial groove 10 12. Sealing air gasket 13 elastic molded part 14 Spacer ring 15 outer first housing part 16 Profile ring / angle ring / cover plate as second housing part 17 Shaping element 18 Bore towards the interior of the elastic molded part 13 19 Radial groove for internal pressure distribution without alignment of the bores 18 on the first housing part 15 and the sealing element 7 20 Slot or hole in the elastic molded part 13 21 Sheet metal layer to strengthen the sealing lip 22 Nose / Shoulder 23 Additional sealing lip 24 Additional sealing element External pressure / pressure in the external environment Internal pressure / pressure of the interior M Central axis of shaft 3 and sealing device 1 p Sealing air pressure / Pressure of the sealing air in the radial groove 10 R Radius of the wave 3 QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2014 100 577 A1

[0003] DE 31 26 716 A1

[0003] DE 10 2016 120 219 A1 [0003, 0017, 0020] DE 10 2016 205 057 A1

[0003] DE 10 2018 117 306 A1

[0003] DE 10 2011 077 015 A1 [0004, 0010, 0013, 0021, 0024] DE 10 2013 122 465 A1

[0023] Cited non-patent literature

[0000] DIN 3760

[0003]

Claims

Sealing device (1) for sealing an interior (D) of a machine housing (2) at an exiting shaft (3) or a shaft sleeve against an external environment (A) against the escape of a fluid, wherein the sealing device (1) in a housing (4) has a sealing disc (5) for fixing in the machine housing (2) or a housing cover, and a sealing lip (8) of the sealing disc (5) interacts with an adjacent section (9) of a surface (10) of the shaft (3) as a sealing area under low contact force to produce a sealing effect, characterized in that the sealing function of the sealing lip (6) on the shaft surface (8) is supplemented by a barrier air seal (12). Sealing device (1) according to the preceding claim, characterized in that a radial groove (10) connected to a bore (11) is provided in the sealing device (1), which is designed to supply compressed air at a pressure (p) that forms the sealing air seal (12) on the shaft surface (8). Sealing device (1) according to one of the preceding claims characterized in that the sealing air seal (12) is arranged between two sealing lips (6, 23). Sealing device (1) according to one of the preceding claims, characterized in that slots or holes are provided as recesses (20) in an elastic molded part (13) of a sealing device (1) according to the teaching of DE 10 2011 077 015 A1 to create a barrier air seal (12). Sealing device (1) according to the preceding claim, characterized in that the recesses (20) designed as slots or holes in the elastic molded part (13) have a predetermined position, shape and / or size designed to produce a specific effect of the sealing air seal (12) at a predetermined sealing air pressure (p). Sealing device (1) according to the preceding claim, characterized in that a sequence of bores or recesses (18) and radial grooves (19) is provided from a first housing part (16) to a spacer ring (14) within the elastic molded part (12). Sealing device (1) according to one of the preceding claims, characterized in that the elastic molded part (13) has a nose or shoulder (22) to secure a positioning and location relative to the outer housing part 15. Sealing device (1) according to one of the preceding claims 4 - 6 , characterized in that a second or additional sealing lip (23) is provided, so that the barrier air seal (12) is now virtually enclosed between two sealing lips (6, 23). Sealing device (1) according to one of the preceding claims, characterized in that a spiral structure is provided on the sealing lip (6). Sealing device (1) according to the preceding claim, characterized in that the sealing lip (6) is made as part of a sealing element (7) from a non-ferrous metal alloy, in particular from a bronze.

Images