Scroll compressors in training as oil-free compressor units and commercial and / or rail vehicles

Abstract

Scroll compressor in the form of an oil-free compressor unit, wherein at least one spiral wall of a spiral of the scroll compressor is formed from a metal base body with a multi-layered PFAS-free coating system to form a sealing surface against overflow in the circumferential direction, characterized in that that the metal base body is made of aluminum or an aluminum alloy; and that the multi-layer coating system i) has a hard anodized layer of aluminium oxide and ii) has at least one polymer sliding layer or one sol-gel sliding layer.

Description

[0001] The present invention relates to a scroll compressor according to the preamble of claim 1 and a commercial and / or rail vehicle.

[0002] Many pneumatically actuated components are used in commercial and / or rail vehicles. For example, brakes are predominantly pneumatically operated. Various types of compressors have become established in this field for air compression and compressed air supply. These include, among others, so-called piston machines, such as reciprocating piston machines or rotary piston machines.

[0003] WO 2012103043 A2 discloses a piston engine in the form of a reciprocating piston engine for generating compressed air in a commercial and / or rail vehicle. The reciprocating piston is sealed against a cylinder or piston skirt. This is typically achieved by means of sealing elements, e.g., piston rings, lip seals, piston skirt coatings, or other friction-reducing sealing elements. These friction-reducing sealing elements are mostly made of PTFE or other PFAS. However, the sealing materials used are subject to wear due to movement, which inevitably releases persistent microplastics into the environment. Therefore, there is an increased need for PFAS-free friction-reducing sealing elements in the field of piston engines.

[0004] Another type of compressor includes a compressor unit known as a scroll compressor. In this design, an orbiting scroll moves around a rotational axis relative to a stationary scroll. During this orbital movement, air is compressed in the spaces between the two scrolls. Unlike linear piston movements, the orbital motion generates rolling friction as the orbiting scroll rolls against the stationary one. This can lead to leaks at the axial ends of the scrolls and circumferential overflow at the contact points between the scrolls. Sealing materials must be provided to prevent these leaks. Especially when sealing against circumferential overflow, the sealants should also be wear-resistant against rolling forces. PTFE is known to have particularly good tribological properties.Previously, PTFE or other PFAS were used as low-wear sealants in the aforementioned application area. However, these sealing elements cannot be recycled or sustainably disposed of after abrasion and at the end of the compressor's life cycle.

[0005] Based on this preliminary consideration, the object of the present invention is to provide a sealant that is optimized for the intended application and at the same time environmentally friendly.

[0006] The invention solves this problem by means of a scroll compressor with the features of claim 1.

[0007] A scroll compressor according to the invention is designed as an oil-free compressor unit of a compressor. It has at least one spiral wall of a scroll compressor spiral. The spiral wall comprises or consists of a metal base body with a multilayer PFAS-free coating system, which forms a sealing surface to prevent circumferential airflow within the compressor.

[0008] The metal base body is made of aluminum or an aluminum alloy.

[0009] The multi-layer coating system features a hard anodized layer of aluminum oxide. This layer improves the bonding of a subsequently applied sliding layer to the metal substrate and, moreover, exhibits very little or no increase in wall thickness compared to an initially provided metal substrate prior to electrolytic anodizing. The hard anodizing is essentially formed in-situ from the metal substrate.

[0010] In addition, at least one polymer or sol-gel sliding layer is applied to the hard anodized surface.

[0011] The sliding layer reduces abrasion through a tribologically optimized surface of the spiral wall. Furthermore, the sliding layer is mechanically reinforced against deformation by the anodized layer.

[0012] Since the entire coating system is PFAS-free, the sliding layer is also PFAS-free. This makes the entire coating system significantly more environmentally friendly than previous solutions.

[0013] Further advantageous embodiments of the invention are the subject of the dependent claims.

[0014] It is advantageous if the polymer sliding layer or the sol-gel sliding layer comprises a solid lubricant, in particular an inorganic solid lubricant and preferably a bronze alloy, a molybdenum disulfide and / or a carbon, in particular a graphite and / or a fullerene. This can be incorporated particulately into the polymer matrix and released upon abrasion.

[0015] For reasons of mechanical strength of the coating system, the proportion of solid lubricant in the polymer or sol-gel sliding layer should be minimal. Therefore, the solid lubricant content in the sliding layer is particularly preferably less than 20 wt.%, and preferably less than 10 wt.%.

[0016] The contact surfaces of the spiral walls are usually defined. However, vibrations of the reference system, e.g., of the commercial and / or rail vehicle, can cause a slight displacement of the spirals from their initial positions. In this case, it is advantageous if the coating system is applied across the entire surface of the metal substrate of the spiral wall, so that even with a minor change in the position of the contact surface, the tribologically advantageous material properties of the coating system are maintained.

[0017] The coating system can comprise an arrangement of several PFAS-free sliding layers, with at least one of the sliding layers being a polymer or sol-gel sliding layer. For example, an emergency running layer can be provided after abrasion of the surface sliding layer. This emergency running layer can cause a detectable change in the coefficient of friction.

[0018] Furthermore, it is advantageous if the arrangement of sliding layers and / or the polymer sliding layer or the sol-gel sliding layer has a layer thickness that is at least 50%, preferably at least 100%, and particularly preferably 110–350% greater than the layer thickness of the hard anodized layer. The aforementioned single sliding layer or the arrangement of several sliding layers also serves as a wear layer. To achieve a service life of the scroll compressors comparable to that of PFAS, it is advantageous if the layer thickness of the wear layer is greater than the layer thickness of the hard anodized layer.

[0019] The hard anodized layer can advantageously have an average thickness of more than 9 µm, preferably between 10 and 25 µm. Any variations in layer thickness are negligible. The same applies to the phase boundaries between the layers and between the hard anodized layer and the base material, which in this case are comparatively sharp and clearly visible in the cross-sectional view.

[0020] Furthermore, the polymer sliding layer or the sol-gel sliding layer can be designed as the outermost layer of the coating system in order to directly utilize the tribologically advantageous material properties of the sliding layer.

[0021] Alternatively, the arrangement of several sliding layers can also include a running-in layer, preferably a solid lubricant layer. This layer is worn away during the running-in of the scroll compressor, so that essentially gap-free operation between the spirals is achievable after the wear has occurred.

[0022] The polymer sliding layer can consist of at least 50 wt.%, preferably at least 80 wt.%, of one or more PEEK compounds, a resin-based system, preferably an epoxy resin and / or a polyester resin and / or an organosilicon compound.

[0023] Alternatively, the sol-gel coating can consist of at least 50 wt.%, preferably at least 80 wt.%, of a sol-gel system.

[0024] The other components of the coating can consist in particular of a solid lubricant component.

[0025] Particularly advantageous for significantly reduced friction in the operation of the scroll compressor is that two opposing spiral walls each have a coating system as described above, and preferably an identically designed coating system. This is advantageous from a manufacturing perspective, as otherwise masking of individual surfaces would be necessary. In this context, at least partial masking of the bottom surfaces or base plates of a scroll compressor may be necessary during the application of the PFA-free plastic coating, since hard surfaces are required in the area of ​​the base plates as sliding surfaces for the so-called tip seals.

[0026] Furthermore, according to the invention, a scroll compressor is designed as an oil-free compressor unit, wherein at least one spiral wall of a spiral of the scroll compressor has a metal base body. This scroll compressor can be particularly advantageously designed as a scroll compressor as described above, i.e., with a sealing surface featuring the aforementioned coating system to prevent circumferential flow. However, this is not strictly necessary within the scope of the present invention.

[0027] The spiral has one or more axially terminal sealing elements made of a PFAS-free polymer, preferably strip-shaped sealing elements, which are particularly preferably arranged on a hard anodized layer on the metal base body.

[0028] Both spirals, i.e., the stationary and the orbiting spiral of a scroll compressor, are particularly preferred when designed as described above.

[0029] The axially terminal sealing elements, so-called tip seals, exhibit improved adhesion due to a hard anodized layer applied to the metal base body. This layer can be formed analogously to the aforementioned hard anodized layer on the sealing surface or as a portion of this hard anodized layer.

[0030] The tip seals rub against the hard-anodized counter surface, the base surface, especially the base plate, of the scroll. The hard anodizing process brings a very hard friction element into contact with a softer friction element, the tip seal, thereby minimizing wear.

[0031] The sealing elements can be made, for example, from a polyetheretherketone-based polymer matrix (PEEK) or a polyimide-based polymer matrix (PI), and the sealing elements can preferably include a solid lubricant, particularly preferably incorporated in the aforementioned polymer matrix.

[0032] The sealing elements can each be arranged on an axial end face of the spiral, and particularly preferably each in a receiving groove located in the end face. The hard anodizing layer can also be arranged in the receiving groove. The receiving groove serves as a stop and as protection against wear of the sealing elements under oblique forces.

[0033] One or more of the sealing elements may have a surface profile. This surface profile can be formed, for example, by cuts and / or slots. Unlike a flat, wide sealing element, the surface profile allows for elastic deformation of the protruding profile elements, such as projections, lugs, flaps, ridges, or the like, under mechanical stress, thus achieving a better seal. At the same time, the tensile forces on the sealing elements are increased. These tensile forces are compensated for by the improved adhesion to the hard-anodized layer. This results in additional interactions.

[0034] To prevent radial gap formation, it is advantageous if the sealing elements do not protrude radially from the spiral wall.

[0035] The invention will now be explained in more detail using an exemplary embodiment and the accompanying figures. These show: Fig. 1. Schematic diagram of the construction of a scroll compressor; Fig. 2. Cutaway top view of a scroll compressor; Fig. 3 several detailed views of a sealing system to prevent axial overflow in a scroll compressor; Fig. 4. Schematic diagram for limiting radial overflow through an annular gap; and Fig. 5 Schematic diagram for a layer structure of a spiral wall of a scroll compressor according to the invention.

[0036] Fig. Figure 1 schematically shows an air compressor unit in the form of a so-called scroll compressor. Air compressor units that operate on the scroll compressor principle consist of a stationary spiral 1 (fixed scroll) and an orbiting spiral 2 (orbiting scroll). Typically, one spiral rotates clockwise and the other counterclockwise. The spirals interlock and, together with their base plates 3, define a volume consisting of several crescent-shaped sections 5. In most designs, the outer starting points of the spirals are offset by 180° from each other. However, other offsets are also possible. When the orbiting spiral 2 is driven, particularly with an eccentric drive, a compression process of a gas within the defined volume is initiated. During this process, a gas, such as...Air is drawn in at the outer diameter and successively conveyed to the scroll center, where the gas, preferably air, is compressed and heated. The compressor outlet is located at the scroll center. The individual compression volumes are crescent-shaped and decrease in volume as they pass from the outside to the inside.

[0037] The overall structure will also consist of Fig. 1 and Fig. 2 is evident. In Fig. Figure 2 shows a circular arc sealing line 4 known from the prior art.

[0038] An important aspect for efficient and low-loss compression is limiting overflow losses or leaks at the transition areas of the crescent-shaped compression volumes. Two areas must be distinguished here: - Radial overflow at the spiral tips (tip-losses) - Overflow in circumferential direction at the vertical edges (engl. leakage from circumferential gap) in the area of ​​the circular arc sealing line 4.

[0039] Besides compressing air, scroll compressors are also frequently used in HVAC systems, where they are typically lubricated by oil contained in the refrigerant being compressed. HVAC stands for Heating, Ventilation and Air Conditioning and refers to a technology for controlling indoor air and temperature in buildings and vehicles.

[0040] In addition to its lubricating effects, the oil also acts as a seal at the transition points of the compression volumes.

[0041] Scroll compressors designed for air compression are typically oil-free. This means that circumferential and radial flow losses must be reduced by other means.

[0042] To prevent radial overflow, so-called tip seals are known in the prior art. These are plastic strips embedded in the end face of the scroll walls and forced into contact with the opposing surface by the pressure in the compression chambers. The opposing surface is the base plate of the opposite spiral. In some cases, six cuts are made into the plastic strips to improve the sealing function (see...). Fig. 3) This is known from the prior art. See: Anest Iwata. (2023) « First developers of oil-free scroll compressors worldwide » From https: / / anestiwata-air.com / company / Press / First%20Development%20in%20the%20world

[0043] The standard materials used to date for these tip seals are compound mixtures with PTFE (polytetrafluoroethylene) as the main component or matrix material. Thus, the tip seals consist of at least 50 wt.%, preferably at least 70 wt.%, and particularly more than 85 wt.%, of PTFE. PTFE is used especially due to its good dry lubrication properties and its stable material properties over a wide temperature range. Furthermore, PTFE's resistance to condensation is an advantage.

[0044] To prevent overflow in the circumferential direction, the prior art involves the use of a very narrow radial gap 8, preferably in the range of a few tens of µm (see Fig. 4)., known. If, for example, wall contact occurs due to an unfavorable tolerance chain in the orbiting kinematics, this can lead to material transfer with weld overgrowth on uncoated scroll walls. These weld overgrowths significantly increase the stress on the scroll walls, so that after a short time the walls break away and thus the scroll compressor suffers total failure. For this reason, surface coatings are usually applied to the scroll walls, which, among other things, are intended to reduce the susceptibility to this specific type of damage. In addition, the surface coatings can further reduce radial overflow losses by reducing the manufacturing-related radial gap through a running-in process. The usual coating material for preventing this type of damage has been PTFE. This is where the present invention comes in.

[0045] In contrast to the previously used PTFE coating, a coating structure according to the invention preferably consists of an aluminum alloy 9 as the base material of a spiral wall and a hard anodizing 10 applied thereto, onto which a PFAS-free polymer sliding layer 11 is subsequently applied (see Fig. 5).

[0046] The use of aluminum alloy 9 as the base material for the spiral walls of a scroll compressor represents a good compromise with regard to thermal expansion, mechanical stability, and weight. A problematic aspect of aluminum alloys is their relatively high tendency to form an undefined oxide layer. Typically, an oxide layer acts as a barrier layer, posing a particular challenge for the adhesion of plastic coatings. For example, powder coating on aluminum is not readily possible, unlike on iron or steel surfaces. In this case, however, an additional hard anodizing process is used as a bonding layer.

[0047] Hard anodizing 10 leads to the electrolytic formation of a defined aluminum oxide layer. Both the density or porosity of the coating and the layer thickness can be adjusted, for example, via the deposition rate and other process parameters. These parameters include the salt concentration of the electrolyte, the pH value of the electrolyte, and the applied current or the proportionally increasing voltage. Overvoltage effects can be reduced, among other things, by increasing mass transport to or from the surface. Thus, the stirring speed is another process parameter for adjusting the layer thickness and / or the density of the formed layer. The electrolytic formation of hard anodizing 10 on an aluminum layer results in a hard anodized layer that is scratch-resistant and highly wear-resistant.

[0048] However, when used as a coating for the spiral wall of a scroll compressor, hard anodizing 10 exhibited similar application-related damage due to material transfer from rolling forces as completely uncoated scroll walls. Nevertheless, hard anodizing can increase the surface area for the adhesion of the polymer sliding layer. This surface area increase can be determined using a so-called BET measurement via gas adsorption. This is a common measurement method in surface chemistry and can be performed with multi-point BET instruments according to the standards DIN ISO 9277 and DIN 66131, both in their current versions from April 2025. After each BET measurement, individual process parameters of the electrolysis can be varied until an optimum is achieved.

[0049] Hard anodizing preferably results in layer hardnesses between 400 HV and 600 HV at 25°C. To determine the Vickers hardness according to ISO 6507 and ASTM E384, a pyramid-shaped indenter (with a face angle of 136°) is pressed into the sample (workpiece) with a defined test load starting at 1 gf. The determination can be carried out, for example, using the "Micro Vickers" hardness testing machine with a test load of 0.025 kg.

[0050] The optimal average layer thickness of the hard anodizing 10 over the entire height of the spiral walls is between 10 µm and 25 µm.

[0051] A particular advantage of hard anodizing is that the layer forms directly from within the aluminum material without requiring any additional material application. The anodized layer forms virtually in situ on the aluminum base material 9. While this reduces the wall thickness of the aluminum base material 9, the formation of the hard anodizing 10 results in little to no increase in the overall wall thickness, thus maintaining the dimensional accuracy of the gap between two scroll walls. Furthermore, it is possible to add friction-reducing materials to the electrolyte during electrolysis, so that these are incorporated into the hard anodizing layer during its formation. These materials can include compounds for dry lubrication, such as molybdenum disulfide (MoS₂), carbon compounds, especially graphite, or even bronze alloys.The hard anodized layer thus has an adhesion-promoting and / or mechanically stabilizing function for the polymer sliding layer 11 compared to the aluminium base material.

[0052] The polymer sliding layer 11 applied to this is a layer of PFAS-free plastic. It is also commonly referred to as a "soft coating." In the context of the present invention, the term "soft" merely distinguishes it from the adjacent anodized layer or hard anodizing. The hard anodizing is significantly harder than the plastic layer. In principle, a variety of PFAS-free plastics are suitable for the polymer sliding layer 11. They serve to protect against wear and, ideally, also against corrosion of the underlying hard anodizing layer. Several sliding layers can also be arranged one above the other. For example,It is also possible to arrange a tribo-emergency running layer, preferably with an increased or decreased content of a solid lubricant such as molybdenum disulfide or graphite, beneath a polymer sliding layer. This layer enables emergency running after the polymer sliding layer wears away and prevents welding of the scroll walls. With a higher content of molybdenum disulfide or graphite, the frictional resistance values ​​of the scroll compressor decrease. However, with increased wear, the compression will decrease due to increased circumferential flow.

[0053] It is also possible to design a multi-layered sliding layer arrangement such that the spiral wall has a so-called running-in layer. This running-in layer is particularly soft and can also be made of a polymer and / or a solid lubricant. The running-in layer is worn away during commissioning or the break-in period of the scroll compressor, so that after the initial wear, essentially gap-free movement of the orbiting spiral relative to the stationary spiral is possible.

[0054] Unlike PTFE, PFAS-free plastics are subject to increased wear due to their higher coefficients of friction, which can be compensated for by a thicker material application. At the same time, the underlying hard anodizing provides significantly greater stabilization of the coating against material loss. Accordingly, the layer thickness of the overall coating system, starting from the aluminum surface, is at least 30 µm, with the soft coating being at least 50%, preferably at least 100%, thicker than the hard anodizing. The polymer-based sliding layer 11 can also be formed only in certain areas.

[0055] Pores along the hard anodized layer allow the soft coating to flow in more effectively before it cross-links or compacts, thus providing better resistance to abrasion. At the same time, the hard anodizing process enables the coating system to withstand temperature changes on the aluminum substrate.

[0056] The polymer-based sliding layer 11 applied to the hard anodized surface can contain additives intended to further improve the friction and wear properties of the layer. Molybdenum disulfide (MoS2) and / or carbon, e.g., as graphite, and / or bronze are preferably used as additives. The sliding layer is specifically PFAS-free.

[0057] Overall, PFAS-free materials are advantageous for oil-free scroll compressors, both for the tip seals (reduction of radial overflow losses) and for the surface coatings of the scroll walls (reduction of circumferential overflow losses).

[0058] Alternative PTFE-free plastic compounds can be used for the tip seals. Possible base materials include polyether ether ketones (PEEK) or polyimides (PI). The compound additives mentioned above (bronze, MoS2, carbon, etc.) can be used depending on the matrix material. Other matrix materials (including mixtures) are also conceivable.

[0059] Examples of materials suitable for the polymer sliding layer, which protects against friction and circumferential flow, include PEEK compounds, resin-based systems (e.g., epoxy or polyester), and / or organosilicon compounds. Sol / gel systems can be used as an alternative or supplement to a polymer sliding layer.

[0060] A tribopolymer can preferably be used for the polymer sliding layer. This includes compounds such as polyethylene (PE), polypropylene (PP), polyacetal (POM), polycarbonate (PC), polyamide (PA, PA6, PA12, PA46, PA66), polyvinyl chloride (PVC), polyketone (PK), phenolic resin and / or acrylonitrile butadiene styrene (ABS).

[0061] Further preferred options include other base polymers as sliding materials. These preferably include polyetherketone (PEK), polyetheretherketone (PEEK), polysulfone (PSU), polyphenylsulfone (PPSU), and polyphenylene sulfide (PPS).

[0062] In the case of tip seals, this means that, for example, a higher tip seal section with a correspondingly deeper tip seal groove can be provided in the scroll wall end face.

[0063] In the case of surface coatings 11, higher coating thicknesses for the soft coatings (e.g. by repeated layer application) can thus compensate for increased wear of the PFAS-free layer.

[0064] Alternatively or additionally, the tolerance chain of the orbiting kinematics can be optimized, which can result in lower contact pressures of the scroll walls and thus lower surface pressures, which are crucial for the wear of the soft coating.

[0065] In summary, the use of PFAS-free coatings in oil-free air compressors based on the scroll compressor principle offers numerous technological advantages over previous scroll compressors.

[0066] It is understood that, for reasons of reducing sliding and rolling friction, the opposing spiral walls of the two spirals of a scroll compressor according to the invention each have a coating system as described above. Particularly preferably, for reasons of simple manufacturing, both spiral walls have an identical coating system. This allows both spirals to undergo the same coating processes. For example, the anodized layer can be formed on both spirals simultaneously in a single electrolysis step.

[0067] When the sliding layers of both spiral walls come into contact with each other, the radial gap is closed and an overflow of compressed air in the circumferential direction is prevented.

[0068] The one or more sliding layers can be designed to be elastically deformable. This allows deformation upon contact of the spiral walls and compensates for surface irregularities.

[0069] The scroll compressor described above is preferably used in commercial vehicles and / or rail vehicles. It can be used to supply compressed air to pneumatically operated components and assemblies associated with the commercial vehicle and / or rail vehicle. For example, a pneumatic assembly is typically provided to actuate the brakes of the commercial vehicle and / or rail vehicle. The compressor generally consists of a drive unit, e.g., an electric motor, and a compressor unit driven by a crankshaft. The crankshaft is driven by the drive unit, which converts the rotary motion of the drive unit into an orbiting motion of the scroll, thereby generating compressed air in conjunction with the stationary scroll.

[0070] The scroll compressor according to the invention is suitable for use in commercial vehicles at ambient temperatures ranging from -40 to +80°C or even beyond. For example, trucks in northern regions such as Canada, Russia, Norway, or Alaska are exposed to such low temperatures and heat up within a short time.

[0071] Conversely, comparatively high temperatures of over 60°C are readily reached in the Sahara and sub-Saharan regions under solar radiation. The compressors and the coating system are therefore subject to a wide operating range with regard to temperature and the associated thermal expansion, and simultaneously require high resistance to temperature fluctuations. The temperature-induced thermal expansion of the curved walls of the two spirals is particularly significant and not comparable to other industrial applications of scroll compressors with more or less constant operating conditions.

[0072] The same applies to rail vehicles, even to an even greater extent. For example, trains in Russia must be designed to withstand temperatures as low as -50°C. This entails the corresponding coefficients of thermal expansion and the brittleness or hardness of the individual coating components at these temperatures. The intermediate layer with hard anodizing, due to its porosity and the compression and expansion of the pores, allows for the equalization of the different thermal expansion behaviors between the metal substrate and the polymer and / or sol-gel sliding layer. This has surprisingly proven to be an advantage for the application described above.

[0073] Therefore, the intended use, with an operating range of less than or equal to -40°C to greater than or equal to +80°C, is not comparable to applications of compressors in factory halls with more or less constant conditions regarding the outside temperature. Reference sign 1 spiral 2 spirals 3 Base plate 4 Sealing line 5 crescent-shaped sub-area 6 plastic strips 7 cuts 8 radial gap 9 Aluminum alloy 10 Hard anodizing 11 PFAS-free sliding layer 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] WO 2012103043 A2

[0003] Cited non-patent literature

[0000] Anest Iwata. (2023) « First developers of oil-free scroll compressors worldwide » Von https: / / anestiwata-air.com / company / Press / First%20Development%20in%20the%20world

[0042] DIN ISO 9277

[0048] DIN 66131

[0048]

Claims

[1] Scroll compressor in the form of an oil-free compressor unit, wherein at least one spiral wall of a spiral of the scroll compressor is formed from a metal base body with a multi-layered PFAS-free coating system to form a sealing surface against circumferential overflow, characterized by , that the metal base body is made of aluminum or an aluminum alloy; and that the multi-layer coating system i) has a hard anodized layer of aluminium oxide and ii) has at least one polymer sliding layer or one sol-gel sliding layer. [2] Scroll compressor according to claim 1, characterized by that the polymer sliding layer or the sol-gel sliding layer comprises a solid lubricant, preferably a bronze alloy, molybdenum disulfide and / or a carbon compound, in particular a graphite and / or a fullerene. [3] Scroll compressor according to claim 1 or 2, characterized by that the proportion of solid lubricant in the polymer sliding layer or the sol-gel sliding layer is less than 20 wt.%, preferably less than 10 wt.%. [4] Scroll compressor according to any of the preceding claims, characterized by that the coating system is applied across the entire surface of the metal substrate. [5] Scroll compressor according to any of the preceding claims, characterized by that the coating system has an arrangement of several PFAS-free sliding layers, wherein at least one of the sliding layers is the polymer sliding layer or a sol-gel sliding layer. [6] Scroll compressor according to any of the preceding claims, characterized bythat the arrangement of sliding layers and / or the polymer sliding layer or the sol-gel sliding layer has a layer thickness at least 50%, preferably at least 100%, particularly preferably 110-350% greater than the layer thickness of the hard anodizing layer. [7] Scroll compressor according to any of the preceding claims, characterized by that the hard anodizing layer has a layer thickness of more than 9 µm, preferably between 10-25 µm. [8] Scroll compressor according to any of the preceding claims, characterized by that the polymer sliding layer or the sol-gel sliding layer is formed as the outermost layer of the coating system. [9] Scroll compressor according to any one of the preceding claims 1-7, characterized by that the arrangement of several sliding layers has a running-in layer, preferably a solid lubricant layer, as a running-in layer. [10] Scroll compressor according to any of the preceding claims, characterized by that the polymer sliding layer consists of at least 50 wt.%, preferably at least 80 wt.%, of a PEEK compound, a resin-based system, preferably an epoxy resin and / or polyester resin and / or an organosilicon compound. [11] Scroll compressor according to any of the preceding claims, characterized by that the sol-gel coating consists of at least 50 wt.%, preferably at least 80 wt.%, of a sol-gel system. [12] Scroll compressor according to any of the preceding claims, characterized by , that two opposing spiral walls each have a coating system according to one of the preceding claims, and preferably an identically designed coating system. [13] Scroll compressor, preferably according to one of the preceding claims, in the configuration as an oil-free compressor unit, wherein at least one spiral wall of a spiral of the scroll compressor has a metal base body, , characterized by that the spiral has one or more axially terminal sealing elements made of a PFAS-free polymer, preferably strip-shaped sealing elements, which are particularly preferably arranged on a hard anodized layer on the metal base body. [14] Scroll compressor according to claim 13, characterized by that the sealing elements are formed from a polyetheretherketone-based polymer matrix or a polyimide-based polymer matrix and that the sealing elements preferably have a solid lubricant, particularly preferably incorporated into the polymer matrix. [15] Scroll compressor according to any of the preceding claims, characterized by that the sealing element(s) is or are arranged on an axial end face of the spiral and is particularly preferably arranged in a receiving groove arranged in the end face. [16] Scroll compressor according to any of the preceding claims, characterized by that one or more of the sealing elements has a surface profile, in particular cuts and / or slots. [17] Scroll compressor according to any of the preceding claims, characterized by that the sealing elements do not protrude radially from the spiral wall. [18] Rail vehicle comprising a scroll compressor according to one of the preceding claims as an oil-free compressor unit of a compressor, preferably for pneumatic actuation of a brake of the rail vehicle. [19] Commercial vehicle comprising a scroll compressor according to one of the preceding claims as an oil-free compressor unit of a compressor, preferably for pneumatic actuation of a brake of the commercial vehicle. [20] Rail and / or commercial vehicle according to any of the preceding claims, characterized by, that the operating range of the scroll compressor is between a minimum temperature of less than or equal to -40°C and greater than or equal to +80°C.

Images