Sliding layer for fluid-lubricated plain bearings

Abstract

Fluid-lubricated plain bearing (2) with at least one bearing ring (21) which has a sliding surface (24), wherein a sliding layer (10) is formed at least partially on the sliding surface (24), wherein the sliding layer (10) is formed from a fiber composite material which has a matrix (16) in which fibers are embedded.

Description

Technical area

[0001] The present invention relates to a fluid-lubricated plain bearing, in particular a hydrodynamic plain bearing, according to the preamble of patent claim 1. Technical background

[0002] Fluid-lubricated plain bearings are divided into hydrodynamically lubricated and hydrostatically lubricated plain bearings. Hydrostatically lubricated plain bearings operate on the principle of external pressure generation, meaning the necessary lubricant pressure is generated outside the bearing by a pump.

[0003] Hydrodynamically lubricated plain bearings (hydrodynamic plain bearings) are plain bearings in which the lubricating film forms due to the rotational movement of the shaft / axle. Initially, the lubricant rests on the plain bearing. During start-up, mixed friction initially develops between the shaft and bearing. As the rotational movement increases, lubricating oil is supplied to the unloaded upper surface, increasing the pressure around the shaft. This raises the shaft, creating fluid friction and thus reducing friction. In hydrostatic plain bearings, lubricant is supplied to the power-transmitting point using an external pump and at the required pressure.

[0004] This means that hydrodynamic plain bearings can be operated wear-free as long as a continuous lubricating film is present. This depends on the bearing geometry and the operating conditions. The hydrodynamic lubricating film is established automatically or builds up as soon as certain parameters have been reached. The sliding speed, among other things, plays a key role in the build-up of a hydrodynamic lubricating film. However, when a bearing starts up from a standstill or when the bearing is stopped, the sliding speed is too low to build up a hydrodynamic lubricating film. Without a separating lubricating film, both sliding surfaces are in direct contact, i.e. operation takes place under mixed / boundary friction. Due to inadequate lubrication, this phase of operation can lead to significant damage, such as wear on the surfaces of the sliding partners.

[0005] It is therefore the object of the present invention to find a solution to improve the friction and wear properties when starting a bearing from a standstill or when stopping a bearing, i.e. when the sliding speed is too low. Summary of the invention

[0006] This object is achieved by a fluid-lubricated plain bearing according to patent claim 1.

[0007] The following proposes a fluid-lubricated plain bearing comprising at least one bearing ring having a sliding surface. To reduce friction even when the bearing is stationary or starting up, and to ensure that friction on the sliding surface is as low as possible in all operating conditions, it is further proposed that a sliding layer be formed at least partially on the sliding surface. The sliding layer is formed from a fiber composite material having a matrix in which fibers are embedded.

[0008] The sliding layer itself can be attached to at least one surface of the tilting segment, for example by means of an adhesive connection, or can be sprayed onto the surface.

[0009] The sliding layer made of fiber composite material ensures that the sliding surfaces are not in direct contact with each other at low sliding speeds, especially during start-up and stop phases, thus reducing wear on the surfaces of the sliding partners of a plain bearing. Overall, the resilience and thus the wear resistance and service life of the bearing are increased. Furthermore, in fiber composite materials, the embedding of the fibers in a matrix ensures that the fibers are supported and the stiffness, strength, shear strength, and wear resistance are increased, which is particularly advantageous during start-up and deceleration operations of fluid-lubricated plain bearings.

[0010] The weave can be selected depending on the desired properties. For example, an ATLAS weave is advantageous for sliding materials. With this weave type, there are only a few crossings between the warp and weft yarns. This makes the fabric very flexible and smooth, making it suitable for complex geometries and generally low friction values. The weave also influences the component distribution across the fabric thickness. For example, a higher proportion of the sliding component on the upper side and reinforcing fiber on the underside of the fabric is advantageous. This allows wear and friction properties to be controlled or adjusted to a certain extent as wear progresses. Another option is so-called double weaving, in which, for example, an additional weft yarn—i.e., if desired, two identical or different weft yarn materials—can be incorporated.For example, one could generate targeted signals for wear or friction monitoring based on the fabric thickness, e.g., one weft yarn with lower and one with higher friction. As wear increases, upon reaching the fiber with high friction, the drive force or torque required for movement, the bearing temperature, or possibly even the noise level will increase. If these signals are recorded with suitable sensors, bearing damage can be detected before the sliding layer actually fails or wears through, allowing appropriate action to be taken and the bearing replaced.

[0011] The sliding layer thickness is preferably less than 600µm. This thickness ensures that the sliding layer is still sufficiently hard to withstand the loads of the plain bearing. However, if the thickness is too great, the plastic material, especially the matrix material, e.g., the polymer, becomes too soft and can no longer adequately support the component being supported.

[0012] According to a preferred embodiment, the fibers are designed as sliding fibers and are made of a solid lubricant material and / or comprise a solid lubricant, wherein the fibers are, in particular, PTFE fibers, UHMWPE fibers, pitch-based carbon fibers, coated fibers made of reinforcing fiber materials, and / or bicomponent fibers. By using sliding fibers in the fiber composite material, the sliding layer can be further optimized for friction. The use of PTFE as the sliding fiber is particularly preferred. If fluorine is not to be used, UHMWPE can also be used as an alternative. Both materials have excellent sliding properties and can be easily formed as fibers.

[0013] According to another preferred embodiment, the fiber composite additionally or alternatively comprises reinforcing fibers, in particular continuous reinforcing fibers. This allows the fiber composite material to be reinforced, which in turn can also increase the stiffness, strength, shear strength, and wear resistance of the composite material. In particular, glass fibers, carbon fibers, PEEK fibers, polyester fibers, basalt fibers, PPS fibers, PA fibers, PLA fibers, PAI fibers, cotton fibers, and / or sisal fibers can be used as reinforcing fibers.

[0014] Pitch-based carbon fibers are particularly preferred as sliding and / or reinforcing fibers, as they offer not only mechanical strength but also lubricating properties. Alternatively or additionally, PEEK can be used, which is particularly chemically resistant and does not absorb water, which is particularly important when oil is used as the fluid for hydrodynamic plain bearings. PEEK is also thermally stable, which is advantageous given the temperatures expected during bearing operation. PEEK also has good sliding properties and can be easily formed into fibers.

[0015] It is also advantageous if the fibers, whether gliding fibers or reinforcing fibers, are designed as continuous fibers, preferably forming a sheet-like structure. In a preferred embodiment, the sheet-like structure comprises both continuous reinforcing fibers and continuous gliding fibers, which are preferably arranged in a crossed pattern within the sheet-like fabric. The crossing of the continuous fibers within the sheet-like structure achieves high shear strength of the composite material and a uniform distribution of the solid lubricant, while also preventing excessive wear of the friction-reducing fiber or solid lubricant.

[0016] According to a further advantageous embodiment, the fabric can be a non-crimp, knitted, or woven fabric. A slip-on fabric is particularly preferred. The advantage of a slip-on fabric is that it can be applied very thinly with a smooth surface. This has the advantage of minimal geometric irregularities.

[0017] Furthermore, the continuous fibers can be single- or multifilament yarns. Single-filament yarns are thicker and therefore more wear-resistant. The linear density of the single- or multifilament yarns can range from 20 to 600 dtex. Multifilament yarns preferably have single filaments with a diameter in the range of 10 to 50 µm.

[0018] This allows for the provision of a stiff and strong fabric that can withstand the loads of the sliding bearing.

[0019] In particular, the multifilament yarns can consist of different fiber materials. The individual fibers can also consist of different materials. For example, a coated fiber can also be used as a single fiber. Such fibers can be present as single filaments, but can also be used in multifilament yarns. This offers the advantage of achieving the best possible yarn properties for the respective application. The multifilament yarns can be interlaced or twisted.

[0020] According to another preferred embodiment, a solid lubricant is embedded in the matrix of the fiber composite, wherein the solid lubricant is preferably selected from the group consisting of PTFE, MoS2, graphite, graphene, carbon nanotubes, WS2, h-BN, MgSt-D, or UHMWPE. This allows the friction of the sliding layer to be further reduced.

[0021] It is particularly preferred if the solid lubricant is embedded in the matrix as a powder or particles and / or in the form of fibers, especially short fibers. This leads to a uniform distribution of the solid lubricant throughout the composite material, which in turn stabilizes the composite material. If the solid lubricant is embedded in the matrix in the form of fibers, the fiber composite is simultaneously reinforced.

[0022] According to a further preferred embodiment, the matrix comprises a duromer or a thermoplastic, preferably selected from the group consisting of epoxy resin, phenolic resin, polyurethane, PEEK, PEK, PI, PPS, PEI, POM, PA, PAI or PBI.

[0023] This allows a flexible plastic matrix with high wear resistance to be provided.

[0024] Epoxy resin is particularly preferred as a matrix because of its low water absorption and high thermal stability. Furthermore, it has good mechanical strength, allowing it to withstand the stresses of the plain bearings.

[0025] According to another preferred embodiment, the sliding layer is attached using a duromer-based adhesive. This ensures a good bond between the plain bearing and the sliding layer, which can withstand the expected operating temperatures and exhibits optimal durability, strength, and curing.

[0026] According to a further advantageous embodiment, the sliding layer can be applied to a raceway of the plain bearing. The plain bearing is preferably a hydrodynamic plain bearing.

[0027] A particularly preferred embodiment is one in which the plain bearing is a tilting-pad bearing, and the sliding layer is formed at least partially on at least one tilting pad. The tilting-pad bearing can be designed as a hydrodynamic tilting-pad bearing, in which the sliding layer is applied to the raceway of the hydrodynamic tilting pad. This allows the plain bearing to be used even for the most demanding applications, such as in wind turbines. The tilting-pad bearing preferably has at least eight tilting pads around its circumference, with the sliding layer formed on each tilting pad.

[0028] Further advantages and advantageous embodiments are set forth in the description, the drawings, and the claims. In particular, the combinations of features set forth in the description and the drawings are purely exemplary, so the features may also be present individually or in other combinations. Short character description

[0029] The invention will be described in more detail below with reference to exemplary embodiments illustrated in the drawings. The exemplary embodiments and the combinations shown in the exemplary embodiments are purely exemplary and are not intended to define the scope of the invention. This scope is defined solely by the appended claims.

[0030] They show: Fig. 1: a schematic representation of a preferred embodiment of a fluid-lubricated plain bearing Fig. 2: a schematic representation of one of the sliding layers on the in Fig. 1 shown plain bearing is applied. Detailed description of the invention

[0031] In the following, identical or functionally equivalent elements are identified by the same reference symbols.

[0032] Fig. Figure 1 schematically shows a fluid-lubricated plain bearing, which in the embodiment shown here is designed as a tilting pad bearing 20. The tilting pad bearing 20 shown is designed for radial bearing of a component 2 and has a bearing ring 21 that carries radially supporting tilting pads 22. The tilting pads 22 have hydrodynamic sliding surfaces 24 (see detail in Fig. 1a), which rest against the component 2 when the bearing is at rest. Furthermore, the tilting pad bearing 20 is designed as a fluid-lubricated, in particular hydrodynamic, plain bearing and has a lubricant supply opening (not shown) through which a fluidic lubricant is delivered to the hydrodynamic sliding surfaces 24. During normal operation, the lubricating film applied to the sliding surfaces 24 by the fluidic lubricant ensures that the component 2 to be supported "floats" on the lubricating film. However, a minimum rotational speed is necessary for this. In order to ensure that as little friction as possible occurs on the sliding surfaces 24 even during start-up or at slow rotations, even if the hydrodynamic lubricating film has not yet been able to build up, Fig. 1a shows the tilting segments 22 having a sliding layer 10 on the sliding surfaces 24. The sliding layer 10 is formed as a coating made of a fiber composite material with a plastic matrix in which fibers are embedded.

[0033] Fig. Figure 2 schematically illustrates such a sliding layer 10, which is applied to the hydrodynamic sliding surface 24 of the tilting segments 22. The Fig.The sliding layer 10 illustrated in Figure 2 comprises a fabric, also called a sliding fabric, made of sliding fibers 12 and reinforcing fibers 14, which is embedded in a plastic matrix 16 made of a matrix material. The sliding fibers 12 and reinforcing fibers 14 are preferably formed as continuous fibers, with the sliding fibers 12 being woven around the reinforcing fibers 14. An ATLAS weave is preferably selected, in which at least two fibers are always covered with a crossing fiber. This creates as few crossings as possible between the fibers to be woven in order to provide the smoothest possible fabric. The crossing of the sliding fibers 12 and reinforcing fibers 14, which are formed here as continuous fibers, in the fabric ensures high shear strength of the sliding layer. The sliding fabric as a whole is very thin and has a very smooth surface.

[0034] In particular, fibers made of a solid lubricant are used as sliding fibers 12, wherein the fibers in particular comprise PTFE fibers, UHMWPE fibers, pitch-based carbon fibers, coated fibers made of reinforcing fiber materials and / or bi-component fibers.

[0035] The reinforcing fibers 14 may comprise, for example, glass fibers, carbon fibers, PEEK fibers, polyester fibers, basalt fibers, PPS fibers, PA fibers, PLA fibers, PAI fibers, cotton fibers and / or sisal fibers.

[0036] The plastic matrix 16 is preferably a flexible plastic matrix, which can be made, for example, from a resin that can be a thermoset and / or a thermoplastic from the group consisting of epoxy resin, phenolic resin, polyurethane, PEEK, PEK, PI, PPS, PEI, POM, PA, PAI, or PBI. The plastic matrix 16 can support the fibers and increase the stiffness, strength, shear strength, and wear resistance of the fabric. This creates a high-strength composite material with superior sliding properties.

[0037] Furthermore, solid lubricant particles 18 can be incorporated into the fabric, which further reduce the frictional resistance of the sliding layer. The solid lubricant can comprise molybdenum(IV) sulfide (MoS2), graphite, graphene, carbon nanotubes, tungsten(IV) sulfide (WS2), hexagonal boron nitride (h-BN), and / or magnesium stearate dihydrate (MgSt-D). With the help of the fabric of sliding fibers 12 and reinforcing fibers 14, a uniform distribution of the solid lubricant particles 18 can be achieved, which also prevents excessive wear of the friction-reducing fibers or the solid lubricant. This, in turn, ensures high wear resistance of the sliding layer 10 and thus of the plain bearing 2.

[0038] Overall, the fluid-lubricated plain bearing with a fiber composite sliding layer can increase the durability and thus wear resistance and service life of the fluid-lubricated plain bearing. Furthermore, maintenance intervals can be extended and CO2 emissions reduced. Furthermore, the risk of bearing failure is minimized. List of reference symbols 2 plain bearings 10 Sliding layer 12 gliding fibers 14 reinforcing fibers 16 plastic matrix 18 solid lubricant particles 20 tilting pad bearings 21 Bearing ring 22 tilting segment 24 Sliding surface

Claims

[1] Fluid-lubricated plain bearing (2) with at least one bearing ring (21) having a sliding surface (24), characterized by that a sliding layer (10) is formed at least partially on the sliding surface (24), wherein the sliding layer (10) is formed from a fiber composite material which has a matrix (16) in which fibers are embedded. [2] Fluid-lubricated plain bearing (2) according to claim 1, wherein the fibers are made of a solid lubricant material and / or comprise a solid lubricant (18), wherein in particular the fibers are PTFE fibers, UHMWPE fibers, pitch-based carbon fibers, coated fibers of reinforcing fiber materials and / or bi-component fibers. [3] Fluid-lubricated plain bearing (2) according to claim 1 or 2, wherein the fibers are formed as continuous fibers, which preferably form a sheet-like structure. [4] Fluid-lubricated plain bearing (2) according to one of the preceding claims, wherein the fiber composite material has reinforcing fibers (14), in particular continuous reinforcing fibers, as fibers. [5] Fluid-lubricated plain bearing (2) according to claim 4, wherein the reinforcing fibers (14) comprise glass fibers, carbon fibers, PEEK fibers, polyester fibers, basalt fibers, PPS fibers, PA fibers, PLA fibers, PAI fibers, cotton fibers and / or sisal fibers. [6] Fluid-lubricated plain bearing (2) according to one of the preceding claims, wherein a solid lubricant (18) is embedded in the matrix (16) of the fiber composite material, wherein the solid lubricant (18) is preferably selected from the group consisting of PTFE, MoS2, graphite, graphene, carbon nanotubes, WS2, h-BN, MgSt-D or UHMWPE. [7] Fluid-lubricated plain bearing (2) according to claim 6, wherein the solid lubricant (18) is embedded as a powder or particles in the matrix (16) and / or wherein the solid lubricant (18) is embedded in the matrix (16) in the form of fibers, preferably short fibers. [8] Fluid-lubricated plain bearing (2) according to one of the preceding claims, wherein the matrix (16) comprises a duromer or a thermoplastic, preferably selected from the group consisting of epoxy resin, phenolic resin, polyurethane, PEEK, PEK, PI, PPS, PEI, POM, PA, PAI or PBI. [9] Fluid-lubricated plain bearing (2) according to one of the preceding claims, wherein the sliding layer (10) is attached by means of a duromer-based adhesive bond. [10] Fluid-lubricated plain bearing (2) according to one of the preceding claims, wherein the plain bearing (2) is a tilting pad bearing (20) and the sliding layer (10) is formed at least partially on at least one tilting pad (22).

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