DE102022131223A1 - Sealing unit for a shaft - Google Patents

Abstract

The invention relates to a sealing unit (10) for a shaft, comprising a first annular body (11) and a second annular body (12), which are arranged concentrically around a common central axis M, wherein the first annular body (11) is made at least partially from a metal sheet and wherein the second annular body (12) is made at least partially from a polymer, wherein the first annular body (11) and the second annular body (12) are formed separately from one another and contact one another at a contact surface (12a) of the second annular body (12), and wherein the second annular body (12) is impregnated with oil or an oil-containing fluid at least in the region of the contact surface (12a).

Description

The invention relates to a sealing unit for a shaft, in particular for a drive shaft of a motor vehicle.

In the current state of the art, so-called radial shaft seals are used to seal shafts, i.e. elongated machine elements rotating around a longitudinal axis for transmitting torque. These seals are made from a carrier plate with vulcanized sealing lips. In automotive engineering, such shafts are used, for example, to transmit drive torque.

The radial shaft seals are exposed to both mechanical loads (from spring tensions) and thermal stresses. Particularly in the field of electric vehicle drives, particularly high temperatures prevail in the area of these shafts due to the high speeds of the shaft, which makes it necessary to manufacture the sealing lips from particularly temperature-resistant materials such as fluororubber (FKM) or acrylate rubber (ACM).

The disadvantage here is that the materials mentioned are expensive and sometimes difficult to obtain. However, if cheaper materials are used, the seals often fail early.

It is therefore an object of the invention to provide a sealing unit for a shaft, in particular for a drive shaft of a motor vehicle, which is at the same time inexpensive and wear-resistant.

This object is achieved according to the invention by a sealing unit for a shaft according to claim 1. Preferred embodiments are specified in the subclaims.

A sealing unit according to the invention has a first annular body and a second annular body, which are arranged concentrically around a common central axis M, wherein the first annular body is made at least partially from a metal sheet and wherein the second annular body is made at least partially from a polymer. The first annular body and the second annular body are formed separately from one another and contact one another at a contact surface of the second annular body, wherein the second annular body is impregnated with oil or an oil-containing fluid at least in the region of the contact surface.

The first and second annular bodies are arranged concentrically around the central axis M, and when the sealing unit is used to seal a shaft, this central axis M can coincide with a longitudinal axis L of the shaft. It should be noted in general that when directional terms such as "radial", "axial" and the like are used within the scope of the invention, these terms refer to this central axis M unless otherwise stated.

Since the first and second bodies are designed separately from one another, the bodies can slide relative to one another, whereby one body can be attached to the shaft and the other to a stationary housing. Due to the impregnation with oil or an oil-containing fluid, sliding is facilitated while at the same time sufficient sealing is made possible. In the context of the invention, the term "impregnated" means in the broader sense any application of oil or an oil-containing fluid which ensures that the fluid remains on a side of the second body facing the first body even when both bodies perform a rotational movement relative to one another.

Since the two bodies come into contact via a flexible sheet metal, in particular a flexible stainless steel sheet metal, on a plastic counter surface made of polyamide (oil modified), it is possible to use inexpensive materials for the two bodies. Furthermore, materials can be used that are more robust against dirt and contamination than the known materials fluororubber (FKM) or acrylate rubber (ACM), which is why the sealing unit according to the invention is also suitable for use under extreme environmental conditions.

According to a preferred embodiment, the first body is made of stainless steel. This enables a particularly robust and low-wear construction.

In order to enable elastic contact of the second body by the first, the first body is preferably shaped such that in cross section, in a plane which encloses the central axis M holds, has the shape of an open ring, with an opening of approximately 15 to 50% of the circumference of the ring. It should be noted that the ring shape is not necessarily a circular ring.

According to a preferred embodiment, the first annular body has a curved end region with an outer surface that is arcuate in cross section, the curved end region contacting the contact surface of the second annular body at a partial region of the outer surface that is arcuate in cross section. Due to the aforementioned curvature, the sliding properties of the end region are improved and the stability of the end region is increased.

In this context, it is particularly advantageous if the first annular body has a radially outer wall from which an at least partially concave central wall region extends to the curved end region. In other words, this means that in this embodiment the ring shape of the first body, which is open in cross section, is at least partially concavely curved. In this case, the opening of the ring is located between the radially outer wall and the curved end region of the first body.

The radially outer wall can be a flat wall and can in particular run parallel to the central axis M. The radially outer wall thus forms a cylindrical surface of the annular first body. In this context, it should be noted that the term "annular" in the context of this invention means a hollow cylinder shape with a height, i.e. a dimension in the axial direction with respect to the central axis M, which is smaller than half a diameter of the annular body in the radial direction.

According to a further advantageous embodiment, the at least partially concave central wall region has a weaker curvature than the curved end region of the first annular body. This ensures that the elasticity of the first annular body is determined by the curvature of the concave central wall region thereof and can be adjusted accordingly.

The at least partially concave central wall region can comprise a radial inner wall part which is made of an elastomer. The radial inner wall part can in particular have several parts, preferably of the same shape, which are inserted into recesses in the sheet metal of the first annular body distributed in the circumferential direction around the central axis M. For example, there can be between three and 50 radial inner wall parts which extend at equal intervals on an inner circumference of the concave central wall region. This radial inner wall part or the radial inner wall parts serve to make the first annular body flexible and elastic. The elastomer is preferably made of silicone or contains silicone.

As far as the second annular body is concerned, which is formed separately from the first annular body, it can be inserted, for example, into a receptacle of the shaft and connected to it in a form-fitting and/or force-fitting manner. According to an alternative, however, the second annular body can also rest on an outer wall opposite the contact surface against a radial wall of a third annular body, the third annular body further having an axial wall connected to the radial wall, which delimits the first annular body inwards. The radial wall and the axial wall can enclose an angle of approximately 90° with one another. In particular, the radial wall and the axial wall are formed integrally with one another. In this case, the third annular body forms a receptacle for the first and second annular bodies, so that the three bodies together form a compact ring, which can be easily introduced into a predetermined structure during assembly. The third annular body is preferably also formed from a metal sheet, with stainless steel or aluminum being particularly preferred materials.

The invention will now be explained in more detail using a non-limiting embodiment with reference to the drawing.

• 1 eine Welle mit einer Radialwellendichtung nach dem Stand der Technik;
• 2 einen Querschnitt durch eine erste Ausführungsform einer erfindungsgemäßen Dichtungseinheit;
• 3 einen Querschnitt durch eine zweite Ausführungsform einer erfindungsgemäßen Dichtungseinheit;
• 3a eine perspektivische Ansicht der zweiten Ausführungsform;
• 4 eine perspektivische Ansicht des ersten ringförmigen Körpers einer erfindungsgemäßen Dichtungseinheit;
• 4a einen Querschnitt durch den ersten ringförmigen Körper; und
• 5 ein Diagramm aus jeweiligen Reibungskoeffizienten verschiedener Polymermaterialien gegenüber Stahl sowie jeweiligen Verschleißraten der Polymere.

In the drawing show:

• 1 a shaft with a radial shaft seal according to the state of the art;
• 2 a cross section through a first embodiment of a sealing unit according to the invention;
• 3 a cross section through a second embodiment of a sealing unit according to the invention;
• 3a a perspective view of the second embodiment;
• 4 a perspective view of the first annular body of a sealing unit according to the invention;
• 4a a cross-section through the first annular body; and
• 5 a diagram of the respective friction coefficients of different polymer materials compared to steel as well as the respective wear rates of the polymers.

The figures are merely schematic in nature and serve solely to assist in understanding the invention. Identical elements are provided with the same reference numerals.

Regarding 1 The state of the art will now be explained in more detail. 1 shows a cross-sectional view of a shaft 1, which can in particular be a drive shaft of a motor vehicle, which can rotate about a longitudinal axis L. In 1 only an area above the longitudinal axis L is shown. The shaft 1 is sealed by a conventional radial shaft seal 2, which, as can be seen, is made up of a carrier plate 2a and a sealing lip 3 vulcanized to it. The sealing lip 3 touches the shaft 1 with one end. The sealing lip 3 is usually made of fluororubber (FKM) or acrylate rubber (ACM), whereby a contact surface between the shaft 1 and the sealing lip 3 must be lubricated with grease.

With reference now to 2 a first embodiment of the invention is explained. In the figure, the reference number 10 designates a sealing unit of the first embodiment. The sealing unit 10 here comprises a first annular body 11 and a second annular body 12, which are designed as separate parts. The first annular body 11 has the shape of an open ring in the cross-sectional plane shown, which contains the longitudinal axis L of the shaft 1. The first annular body 11 and the second annular body 12 extend concentrically around a central axis M, which coincides with the longitudinal axis L of the shaft 1 when the sealing unit 10 is used, as shown in the figure. In this context, it should be noted that a distance between the axes L, M and the annular bodies 11, 12 or the shaft 1 is shown shortened for reasons of better representation. This means that the distance of the elements mentioned from the axes L, M is greater in a scaled representation than that shown.

The open ring of the first annular body 11 is formed by a curved end region 11a, a radially outer wall 11b and a central wall region 11c connecting the curved end region 11a and the radially outer wall 11b, wherein the central wall region 11c accommodates a radially inner wall part 11d. As already mentioned, the first annular body 11a is made of a metal sheet, in particular of stainless steel. In contrast, the second annular body 12 is made of a polymer which, at least in a contact region 12a at which the curved end region 11a of the first annular body 11 contacts the second annular body 12, is impregnated or wetted with oil or an oil-containing fluid. More precisely, the curved end region 11a contacts the contact region 12a of the second annular body 12 with an outer surface 11a1. Due to the materials used and in particular the impregnation of the contact area 12a with oil or an oil-containing fluid, greasing in the area of the sealing lip 3 according to the state of the art (see 1 ) can be dispensed with. This eliminates the need for the complex greasing process during production. In addition, since the embodiments according to the invention have the curved end region 11a instead of the sealing lip 3, a labor-intensive process for vulcanizing the sealing lip 3 made of FKM is no longer necessary and there is no risk of the sealing lip 3 being deformed during handling during assembly.

With reference to the representation of 3 A second embodiment of the invention is described below, wherein the same or corresponding components as in the embodiment of the 2 used are provided with the same reference numerals. In the second embodiment of a sealing unit 10 according to the invention, a first annular body 11 and a second annular body 12 are also present, the first annular body 11 comprising a curved end region 11a, a radial outer wall 11b and a central wall region 11c connecting them. The central wall region 11c is penetrated by a radial inner wall part 11d, the insertion and position of which will be explained later with reference to 4 will be explained.

In contrast to the embodiment of 2 includes that of the 3 a third annular body 13 having a radial wall 13a and an axial wall 13b which are approximately perpendicular to This third annular body 13 serves to form, with its radial wall 13a, a contact surface for the second annular body 12, or more precisely for an outer wall 12b of the second annular body 12. This outer wall 12b is opposite the contact surface 12a against which the outer surface 11a1 of the curved end region 11a of the first annular body 11 rests. With this design, a compact ring can be formed from the first annular body 11, the second annular body 12 and the third annular body 13, which is particularly easy to handle during assembly.

Such a ring is shown in perspective view in 3a shown. Thus, 3a a sealing unit 10 of the second embodiment, in which only the radially outer wall 11b of the first annular body 11 can be seen in this illustration. As can be clearly seen in the figure, this forms a cylindrical outer surface concentric to the central axis M. The sealing unit 10 is limited radially inwards by the axial wall 13b of the third annular body 13 and downwards (on the right in the picture) by the radial wall 13a of the third annular body 13. During production, the second annular body 12 is attached to the radial wall 13a of the third annular body 13 so that the two bodies 12, 13 are connected to one another in a rotationally fixed manner.

In 4 the first annular body 11 according to the first or second embodiment is shown in isolation as a blank for production, whereby a detail on the middle wall area 11c of that body 11 can be seen. In the middle wall area 11c, elongated recesses 11e are introduced in the axial direction, in the embodiment shown distributed at equal distances from one another over an inner circumference of the middle wall area 11c. These recesses 11e serve to accommodate the radial inner wall parts 11d, which in the representations of the 2 and 3 can be seen. During production, the radial inner wall parts 11d, which can be made of an elastomer, in particular silicone, are introduced into the respective recesses 11e.

4a shows the first annular body 11 in section, without inserted radial inner wall parts 11d. As can be seen, the recesses 11e as well as the entire middle wall area 11c are concavely curved. It should be noted that in the illustration of 4a the curved end region 11a is not shown for illustration reasons. However, it is obvious to the person skilled in the art that the curved end region 11a is analogous to the illustration of the 2 and 3 adjoins the middle wall area 11c.

Regarding 5 A suitable material selection for the second annular body 12, which forms a counter-running surface for the curved end portion 11a of the first annular body 11, will now be described. As can be seen from the 5 As can be seen in the diagram shown, a wear rate and a friction coefficient for different polymers were plotted against each other in order to select a suitable material.

The polymers are the following products: Trade name composition TEKAPEEK Polyetheretherketone (PEEK) TEKAPEEK PVX modified PEEK TEKAPEEK CF 30 PEEK material filled with 30% carbon fibres TEKAMID 66 Preparation based on polyamide 66 (polymer of hexamethylenediamine and adipic acid) TEKAMID 66 CF Polyamide 66 with carbon fibres TEKAMID 66 GF Polyamide 66 with glass fibers TEKAMID 66 LA Polyamide 66 with solid lubricant TECAST-L Polyamide 6 modified with oil TEKADUR PBT Polybutylene terephthalate (semi-crystalline thermoplastic in the polyester family) TEKAFORM AH POM-C (Polyoxymethylene (copolymer)) TEKAFINE PES Polyethylene (polycrystalline thermoplastics)

The measured values of the diagram of 5 were determined under the following conditions: load: 1MPa, speed: 0.5 m/s; against steel with Rz 2.5 µm.

It has been found that oil-modified PA 6 C black is a very suitable material for the second ring-shaped body. This cast nylon polyamide is modified with oil to achieve better sliding properties and a better coefficient of friction. It offers excellent wear and abrasion resistance, which leads to a longer service life of the components and lower maintenance costs. Due to its black color, TECAST L black is particularly suitable for outdoor use, where the material is exposed to the weather and UV radiation.

The friction coefficient of TECAST L under the specified measuring conditions is 0.2, whereas the radial shaft seal made of fluororubber that is usually used in the state of the art has a friction coefficient of 0.3-0.45. A sealing unit designed according to the invention results in significantly more favorable friction behavior. By reducing friction losses, significantly lower energy consumption and lower _CO2 emissions can be achieved when using the sealing unit.

List of reference symbols

1

Wave

2

Radial shaft seal

2a

Carrier plate

3

vulcanized sealing lip

10

Sealing unit

11

first ring-shaped body

11a

curved end area

11a1

Exterior surface

11b

radial outer wall

11c

middle wall area

11d

radial inner wall part

11e

Recess

12

second ring-shaped body

12a

Touch surface

12b

Exterior wall

13

third ring-shaped body

13a

radial wall

13b

axial wall

Claims (10)

Sealing unit (10) for a shaft, comprising a first annular body (11) and a second annular body (12), which are arranged concentrically about a common central axis M, wherein the first annular body (11) is made at least partially from a metal sheet and wherein the second annular body (12) is made at least partially from a polymer, characterized in that the first annular body (11) and the second annular body (12) are formed separately from one another and contact one another at a contact surface (12a) of the second annular body (12), and that the second annular body (12) is impregnated with oil or an oil-containing fluid at least in the region of the contact surface (12a). Sealing unit (10) according to Claim 1 , characterized in that the first annular body (11) is made of stainless steel. Sealing unit (10) according to Claim 1 or 2 , characterized in that the first annular body (11) has a curved end region (11a) with an outer surface (11a1) which is arcuate in cross section, wherein the curved end region (11a) contacts the contact surface (12a) of the second annular body (12) at a partial region of the outer surface (11aa) which is arcuate in cross section. Sealing unit (10) according to Claim 3 , characterized in that the first annular body (11) has a radially outer wall (11b) from which an at least partially concave central wall region (11c) extends to the curved end region (11a). Sealing unit (10) according to Claim 4 , characterized in that the radially outer wall (11b) runs parallel to the central axis M. Sealing unit (10) according to Claim 4 or 5 , characterized in that the at least partially concave middle wall region (11c) has a weaker curvature than the curved end region (11a). Sealing unit (10) according to one of the preceding Claims 4 until 6 , characterized in that the at least partially concave central wall region (11c) comprises at least one radial inner wall part (11d) which is formed from an elastomer. Sealing unit (10) according to Claim 7 , characterized in that the elastomer consists of silicone or contains silicone. Sealing unit (10) according to Claim 7 or 8th , characterized in that there are between three and 50 radial inner wall parts (11d) which extend at equal intervals on an inner circumference of the concave central wall region (11c). Sealing unit (10) according to one of the preceding claims, characterized in that the second annular body (12) rests on an outer wall (12b) opposite the contact surface (12a) against a radial wall (13a) of a third annular body (13), wherein the third annular body (13) has an axial wall (13b) connected to the radial wall (13a) which delimits the first annular body (11) inwards.