Rolling bearing and method for manufacturing same

Abstract

Disclosed is a rolling bearing comprising at least one outer ring (1), at least one inner ring (2) and at least one rolling element (3) arranged between the at least one outer ring (1) and the at least one inner ring (2) wherein an outer surface of the at least one outer ring (1) is configured to fit into a first element and an outer surface of the at least one inner ring (2) is configured to fit into a second element. The inner surface of the inner ring (2) is configured to fit to a second element and the first element and the second element are rotatable relative to each other wherein at least one of the outer surface of the outer ring (1) and the inner surface of the inner ring (2) is provided with a composite coating (5), the composite coating (5) comprises a binder and polytetrafluoroethylene as a solid lubricant, wherein the coating is free of antimony.

Description

Technical Field

[0001] The invention relates to a rolling bearing. In addition, the invention relates to a method for producing a rolling bearing. Background Art

[0002] Many rotating mechanical devices may include rolling bearings that enable relative rotation between a first element and a second element. For example, the first element may be a housing and the second element may be a rotating shaft, wherein the outer ring of the rolling bearing is fitted into the housing and / or the inner ring of the rolling bearing is fitted onto the shaft. Depending on the specific application, it may happen that either due to a load that deforms the ring or due to design, one of these fits is a loose fit, which may cause the ring to creep.

[0003] In some cases, this ring creep may cause so-called ring creep wear damage. For example, if a steel outer ring is loosely fitted into an aluminum alloy housing, the ring creep of the outer ring has the opportunity to cause ring creep wear damage on the aluminum alloy housing due to the relative movement between the outer ring and the housing (ring creep movement). In other words, the outer diameter surface of the outer ring and the inner surface of the housing rub against each other, causing wear on the housing. When the wear of the housing increases, backlash may occur in the rotating support part, resulting in abnormal vibration and out of order of the rotating mechanical equipment. This may further lead to a loss of alignment, which may cause undesirable noise. In addition, creep wear may cause debris and / or contaminants, which may damage components of the bearing and / or mechanical equipment, such as gears, which may shorten the life of the bearing and / or mechanical equipment.

[0004] This ring creep movement can be prevented by interlocking or rubber O-rings. However, in practice, interlocking mechanisms and rubber O-rings are not an ideal solution because it is difficult to implement and / or unreliable. Polymer coatings of the friction surfaces ( / rubbing surfaces) consisting of solid lubricants and a manganese-phosphating (i.e. MnPh) pretreatment are another alternative to reduce creep wear. So far, the coatings consist of antimony (Sb), which is considered a material toxic to human health, and the necessary coating process ( / treatment) is very complicated because the entire bearing needs to be immersed in an acid liquid bath for the manganese-phosphating process ( / treatment) and the thermal curing of the polymer coating.

[0005] Therefore, the object of the present invention is to provide a measure for reducing creep wear damage, overcoming the above-mentioned disadvantages. Summary of the invention

[0006] This object is achieved by a rolling bearing according to claim 1 and a method for producing a rolling bearing according to claim 10 .

[0007] Hereinafter, a rolling bearing is provided, which includes at least one outer ring, at least one inner ring, and at least one rolling element arranged between the at least one outer ring and the at least one inner ring. The outer surface of the at least one outer ring is configured to be assembled into a first element (such as a housing), and the inner surface of the inner ring is configured to be assembled into a second element (such as a shaft), wherein the first element and the second element are rotatable relative to each other.

[0008] The outer surface of the at least one outer ring may be the outer surface of the ring in the radial direction of the bearing, such as the outer circumferential surface of the outer ring. The inner surface of the at least one inner ring may be the inner surface of the ring in the radial direction of the bearing, such as the inner hole of the inner ring. For example, the rolling bearing may be a ball bearing, a cylindrical roller bearing, a tapered roller bearing, etc. In addition, the outer ring and / or the inner ring may be made of a first material. The first material may be steel, in particular bearing steel. The first element and / or the second element may be made of a second material different from bearing steel. In particular, the second material may be softer than the first material. For example, the second material may be aluminum, an aluminum alloy, etc. In addition, the roller bearing may be used in an electric motor, such as an electric vehicle, or a pump.

[0009] To reduce creep wear and exposure to toxic materials, at least one of the outer surface of the outer ring and the inner surface of the inner ring is provided with a composite coating comprising a binder and polytetrafluorethylene as a solid lubricant, wherein the coating is free of antimony.

[0010] This composite coating can reduce wear on the components assembled to the outer ring and / or the inner ring, so that abnormal vibration and / or noise can be reduced. Due to the solid lubricant mixture, the amount of wear on the outer ring and / or the inner ring surface and / or the first element and / or the second element can be reduced, which can also reduce the amount of debris. This can reduce damage to components of the bearing and / or mechanical equipment (such as gears), which may lead to a longer life of the bearing and / or the mechanical equipment. In addition, due to the lack of antimony in the composite coating, any debris and / or contaminants generated by creep wear may be less toxic.

[0011] In addition, the composite coating can be applied directly to the metal surface of the outer ring and / or the inner ring without providing ( / setting) a bonding layer. This allows the composite coating to be applied to the surface by brushing, spraying and / or dipping, which can reduce manufacturing costs because a complicated application process can be avoided.

[0012] Preferably, the content of polytetrafluoroethylene is up to 30 wt % (i.e. weight percentage, also known as: wt %). This can have the advantage of reducing friction and / or creep wear. However, the content of polytetrafluoroethylene can also be limited to less than 5 wt %, preferably less than 3 wt %, without unduly reducing the performance of the composite coating. Lower contents of PTFE have the following advantages: the amount of per- and polyfluoroalkyl substances (PFAS) can be limited while still having good wear properties, wherein PFAS are organofluorine chemical compounds (organofluorine chemical compounds) with at least one fluorine atom attached to the alkyl chain, such as polytetrafluoroethylene (PTFE), which may be released from the composite coating (e.g. in wear debris).

[0013] The thickness of the composite coating can be between 2 μm and 70 μm, preferably between 10 μm and 30 μm. When the film thickness is less than 2 μm, the composite coating may wear out at an early stage and creep wear resistance cannot be maintained for a long time. In addition, it is difficult to uniformly form a bonded film with a thin film thickness of less than 2 μm. On the other hand, when the film thickness exceeds 70 μm, the strength of the coating may decrease, so that the composite coating may peel off ( / peel off). Therefore, the coating thickness between 2 μm and 70 μm allows to effectively reduce creep wear and reduce the risk of coating peeling ( / peeling off).

[0014] Preferably, the binder is polyamide-imide, epoxy, acrylic and / or polybutyl titanate. This allows the production of a self-lubricating layer that is not composed of antimony and can significantly reduce the wear on the housing, in particular on aluminum alloy housings.

[0015] Preferably, the particle size of the solid lubricant is in the range of 0.1-15 μm, preferably 0.5-5 μm. More specifically, the preferred particle size may be defined by the coating thickness and / or the desired coating strength.

[0016] According to another preferred embodiment, the porosity of the composite coating is in the range of 2 vol% to 50 vol% (i.e., volume percentage, also known as volume %), preferably in the range of 5 vol% to 25 vol%. Preferably, the pore size ( / pore size) is in the range of 2 μm to 50 μm, preferably from 5 μm to 25 μm. Advantageously, the pores can be used as reservoirs for lubricants and / or traps for wear debris, which can reduce abrasive wear on softer materials. Advantageously, the pores can be formed by evaporation of a solvent included in the binder.

[0017] Preferably, before applying the composite coating, the surface roughness of the outer surface of the outer ring and / or the inner surface of the inner ring has a surface roughness Ra of 0.5 to 10 μm, preferably 1 to 3 μm. This allows for improved bonding of the composite coating on the outer surface of the outer ring and / or the inner surface of the inner ring.

[0018] In addition, before applying the composite coating, the outer surface of the outer ring and / or the inner surface of the inner ring may be provided with a phosphate bonding layer, wherein preferably, the thickness of the phosphate bonding layer is 1 μm to 7 μm, preferably 2 μm to 4 μm. This can further improve the bonding of the composite coating on the outer surface of the outer ring and / or the inner surface of the inner ring.

[0019] Preferably, the friction coefficient in dry contact with aluminum alloy is between 0.05 and 0.32. In particular, a lower friction coefficient can indicate a lower amount of creep wear.

[0020] According to another preferred embodiment, the composite coating has a dielectric strength greater than 10 kV / mm and a dielectric constant or relative permittivity lower than 6.

[0021] In the case of rolling bearings used in electric motors (for example in electric vehicles), it may happen that current flows through the bearings and / or voltage is applied to the rolling bearings. Due to the leakage of current through the bearings, the lubricant in the bearings and / or the bearings, in particular the metal surfaces of the bearings, such as the raceways for rolling elements, may be damaged. The damage may include an increase in surface roughness and / or noise, and may impair the bearing function. By providing a composite coating for the outer surface of the outer ring and / or the inner surface of the inner ring, the composite coating may have a dielectric strength greater than 10 kV / mm and a dielectric constant less than 6, the current passing intensity can be significantly reduced, for example greater than 80%, and the service life of the bearing is extended. The relatively high dielectric strength and low dielectric constant of the coating can reduce the current intensity and bearing damage.

[0022] According to another aspect of the present invention, a method for manufacturing a rolling bearing as described above is provided. The method comprises the following steps:

[0023] Providing a composite coating comprising a binder and polytetrafluoroethylene as a solid lubricant, wherein the content of the polytetrafluoroethylene is up to 5 wt %, preferably less than 3 wt %, and wherein the coating is free of antimony, and

[0024] The composite coating is applied on at least one of the outer surface of the outer ring and the inner surface of the inner ring, wherein applying the composite coating includes spraying, brushing and / or dipping the composite coating on at least one of the outer surface of the outer ring and the inner surface of the inner ring.

[0025] Furthermore, before applying the composite coating, the outer surface of the outer ring and / or the inner surface of the inner ring may be provided with a phosphate bond layer, wherein preferably, the thickness of the phosphate bond layer is 1 μm to 7 μm, preferably 2 μm to 4 μm. Advantageously, the addition of the phosphate bond layer may improve the bonding of the coating composition to the steel component.

[0026] Preferably, the method further comprises curing the composite coating at a temperature of 150°C or less, preferably at a temperature between 130°C or less and 22°C or more. Although higher curing temperatures can provide greater strength to the composite coating, curing at lower temperatures has the advantage of saving energy and costs. In particular, the composite coating can be cured at room temperature. In addition, it can also allow problems that may arise from temperatures above 150°C for hardened steel components (such as bearing components) to be avoided. Therefore, it can be advantageous to limit the curing temperature to below 150°C.

[0027] According to another embodiment, the method further comprises, before applying the composite coating, preparing at least one of the outer surface of the outer ring and the inner surface of the inner ring to have a surface roughness Ra of 0.5 to 10 μm, preferably Ra of 1 to 3 μm. This allows improving the bonding of the composite coating on the outer surface of the outer ring and / or the inner surface of the inner ring.

[0028] Further preferred embodiments are defined in the dependent claims as well as in the description and the drawings.Therefore, elements described or shown in combination with other elements may exist alone or in combination with other elements without departing from the scope of protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In the following, preferred embodiments of the present invention are described in conjunction with the accompanying drawings, wherein the accompanying drawings are only exemplary and are not intended to limit the scope of protection. The scope of protection is defined only by the accompanying claims.

[0030] These figures show:

[0031] Figure 1 : depicts a cross-sectional view of an example of a rolling bearing according to an embodiment of the present invention,

[0032] Figure 2 : The graph obtained in the experiment depicts the relationship between aluminum wear depth and different composite coatings.

[0033] Figure 3: Graph obtained from the experiment, depicting the relationship between the average friction coefficient and the different composite coatings, and

[0034] Figure 4 : Graph obtained in the experiment depicting the relationship between coating wear depth and different composite coatings.

[0035] Description of Reference Numerals

[0036] 1 Outer ring

[0037] 1a Outer raceway

[0038] 1b Outer surface

[0039] 2Inner ring

[0040] 2a Inner raceway

[0041] 3 Rolling elements

[0042] 5. Composite coating DETAILED DESCRIPTION

[0043] In the following, identical or similar functional elements are denoted by the same reference numerals.

[0044] In the present invention, the type of rolling bearing 10 is not limited. Figure 1 The ball bearing shown is exemplified. The ball bearing includes: an outer ring 1 having an outer ring raceway 1a, an inner ring 2 having an inner ring raceway 2a, and a plurality of balls 3 arranged between the two raceways 1a, 2a. In addition, the outer diameter surface ( / outer diameter surface) 1b of the outer ring 1 of the ball bearing is assembled to a housing ( / seat) (housing) (not shown), and the inner peripheral surface (inner peripheral surface) of the inner ring 2 is assembled to a shaft member (not shown).

[0045] The outer ring 1 and the inner ring 2 are made of metal, such as bearing steel. In addition, the outer diameter surface 1b of the outer ring 1 is coated with a composite coating 5, which includes a binder and polytetrafluorethylene (PTFE) as a solid lubricant. In many cases, the housing is made of aluminum or an aluminum alloy (e.g., an aluminum die-cast material) to reduce weight. Since the composite coating 5 of the present invention is softer than aluminum or an aluminum alloy (e.g., an aluminum die-cast material), even if the outer diameter surface 1b of the outer ring and the housing can move relative to each other, the housing will not be damaged.

[0046] The adhesive may have high adhesion and wear resistance, so that the wear of the housing is small and the creep resistance wear characteristic is improved. For example, polyamide-imide, epoxy resin, acrylic acid and / or polybutyl titanate may be used as the adhesive.

[0047] In addition, the composite coating 5 has a porosity in the range of 2 to 50 vol%, preferably 5 to 25 vol%, and a pore size in the range of 2 to 50 μm, preferably from 5 to 25 μm, wherein the pores can be used as reservoirs for lubricants and / or traps for wear debris, which can reduce abrasive wear on the composite coating 5.

[0048] In order to form the composite coating 5, a predetermined amount of PTFE is added to the binder, thereby formulating a coating solution. In addition, the content of PTFE in the composite coating is up to 5wt%, preferably less than 3wt%. Before applying the coating 5 to the workpiece, the surface roughness of the workpiece is machined to have a surface roughness Ra of 0.5 to 10μm, preferably 1 to 3μm. This allows for improved bonding of the composite coating 5 on the workpiece surface. Then, the coating solution is applied to the workpiece (e.g., the outer diameter surface 1b of the outer ring 1) by dipping, spraying, brushing, etc. Then, the composite coating 5 can be cured at room temperature or at a temperature below 150 degrees Celsius, preferably below 130 degrees Celsius.

[0049] The film thickness of the composite coating 5 is between 2 and 70 μm. When the film thickness is less than 2 μm, the composite coating 5 wears at an early stage and cannot maintain creep wear resistance for a long time. Moreover, it is difficult to uniformly form a thin bonded film with a film thickness of less than 2 μm. On the other hand, when the film thickness exceeds 70 μm, the strength of the coating is reduced, so that the composite coating 5 may be peeled off. The film thickness is more preferably 10 μm to 30 μm.

[0050] Optionally, as a pretreatment for forming the composite coating 5, a phosphate bond layer may be formed before applying the composite coating 5. The phosphate bond layer may be formed by a phosphoric acid chemical conversion treatment, which can enhance the adhesion between the composite coating 5 and the outer diameter surface of the outer ring 1b. As a phosphate used in the phosphoric acid chemical conversion treatment, manganese phosphate may be used as an example. However, other phosphates may also be cited, such as zinc phosphate, calcium zinc phosphate, iron phosphate, etc. The phosphoric acid chemical conversion coating is formed by a phosphoric acid chemical conversion treatment.

[0051] As another alternative, the composite coating 5 may be formed on the inner surface of the inner ring 2 when creep occurs in the inner ring and the shaft.

[0052] The present invention will be further described with reference to experimental examples. However, it should be noted that the present invention is not limited thereto.

[0053] In this experiment, the desired effect of the bonded film of the present invention was verified.

[0054] As shown in Table 1, an adhesive containing an epoxy resin and polytetrafluoroethylene ("PTFE" in Table 1) are combined in the amounts shown to formulate a coating solution. In addition, the average particle diameter of the raw material of polytetrafluoroethylene is 0.5 to 3 μm. As an undercoating treatment, a chemical conversion coating of manganese phosphate is formed, and the coating solution is applied to the surface of a test specimen made of bearing steel. The coating solution is cured for 30 minutes at the temperature given in Table 1 to form a composite coating. The thickness of the composite coating is given in Table 1.

[0055] For this test, a pin on disk test was performed, in which a pin is moved on a disk for a predetermined amount of time with a defined ( / defined) load and a defined contact pressure. This allows the wear depth as well as the average friction coefficient to be determined. For this test, two groups were performed, in which in the first group a steel pin was moved on an aluminum disk and in the second group an aluminum pin was moved on a steel disk. In both groups, the steel components (i.e. the pins in the first group and the disks in the second group) were provided with a composite coating according to Example 1 and a reference coating containing antimony. In addition, an uncoated reference sample was prepared. The diameter of the steel pin was 82 mm and the diameter of the aluminum pin was 64 mm. The defined load for the steel pin was 20 N and for the aluminum pin was 10 N, with an average contact pressure of 130 MPa for the steel pin and 124 MPa for the aluminum pin. The results of the wear depth and the average friction coefficient of the aluminum (Al) and the composite coating are given in Table 1. Figures 2 to 4 Shown in.

[0056]

[0057] from Figures 2 to 4 It can be seen that both the wear on the aluminum and the wear on the coating can be significantly reduced, and the average friction coefficient of the example coating 1 is significantly ( / significantly) lower than that of the reference coating.

[0058] In summary, the described composite coating is able to reduce wear on components (such as aluminum housings ( / aluminum seats)) assembled to the outer ring and / or inner ring, so that abnormal vibrations and / or noise can be reduced. In addition, the wear of the coating itself is reduced, resulting in a longer service life of the coating. The described composite coating has a low coefficient of friction, which can allow the amount of debris to be reduced, resulting in a longer life of the bearing and / or mechanical equipment. In addition, due to the lack of antimony in the composite coating, any debris and / or contaminants that may be generated by residual amounts of creep wear may be less toxic.

[0059] In addition, the composite coating can be applied directly to the metal surface of the outer ring and / or the inner ring without providing a bonding layer. This allows the composite coating to be applied to the surface by brushing, spraying and / or dipping, which can reduce manufacturing costs because complex application processes can be avoided.

Claims

1. A rolling bearing (10), comprising at least one outer ring (1), at least one inner ring (2) and at least one rolling element (3) arranged between the at least one outer ring (1) and the at least one inner ring (2), wherein: The outer surface of at least one outer ring (1) is configured to be assembled into a first element, the inner surface of the inner ring (2) is configured to be assembled into a second element, and the first element and the second element are rotatable relative to each other, wherein at least one of the outer surface of the outer ring (1) and the inner surface of the inner ring (2) is provided with a composite coating (5), the composite coating (5) comprising a binder and polytetrafluoroethylene as a solid lubricant, wherein the coating is free of antimony.

2. The rolling bearing (10) according to claim 1, characterized in that: The content of polytetrafluoroethylene is up to 30 wt%, preferably less than 5 wt%.

3. The rolling bearing (10) according to claim 1 or 2, characterized in that: The thickness of the composite coating (5) is between 2 μm and 70 μm, preferably between 10 μm and 30 μm.

4. The rolling bearing (10) according to any one of the preceding claims, characterized in that The adhesive is polyamide-imide, epoxy, acrylic and / or butyl titanate.

5. Rolling bearing (10) according to any one of the preceding claims, characterized in that The particle size of the polytetrafluoroethylene is in the range of 0.1-15 μm, preferably in the range of 0.5-5 μm.

6. Rolling bearing (10) according to any one of the preceding claims, characterized in that The porosity of the composite coating (5) is in the range of 2 to 50 vol%, preferably in the range of 5 to 25 vol%, wherein preferably the pore size is in the range of 2 to 50 μm, preferably from 5 to 25 μm.

7. Rolling bearing (10) according to any one of the preceding claims, characterized in that Before applying the composite coating (5), the surface roughness of the outer surface of the outer ring (1) and / or the inner surface of the inner ring (2) has a surface roughness Ra of 0.5 to 10 μm, preferably 1 to 3 μm.

8. Rolling bearing (10) according to any one of the preceding claims, characterized in that Before applying the composite coating (5), the outer surface of the outer ring (1) and / or the inner surface of the inner ring (2) is provided with a phosphate bonding layer, wherein preferably, the thickness of the phosphate bonding layer is 1 to 7 μm, preferably 2 to 4 μm.

9. Rolling bearing (10) according to any one of the preceding claims, characterized in that The friction coefficient of the composite coating (5) in dry contact with the aluminum alloy is between 0.05 and 0.

32.

10. Rolling bearing (10) according to any one of the preceding claims, characterized in that The composite coating (5) has a dielectric strength greater than 10 kV / mm and a dielectric constant lower than 6.

11. A method for producing a rolling bearing (10) according to any one of the preceding claims, wherein: The rolling bearing (10) comprises at least one outer ring (1), at least one inner ring (2) and at least one rolling element (3) arranged between the at least one outer ring (1) and the at least one inner ring (2), wherein the outer surface of the at least one outer ring (1) is configured to be fitted into a first element, the inner surface of the inner ring (2) is configured to be fitted into a second element, and the first element and the second element are rotatable relative to each other, wherein the method comprises the following steps: A composite coating (5) is provided, comprising a binder and polytetrafluoroethylene as a solid lubricant, wherein the coating is free of antimony, and The composite coating (5) is applied to at least one of the outer surface of the outer ring (1) and the inner surface of the inner ring (2), wherein applying the composite coating (5) includes spraying, brushing and / or dipping the composite coating on at least one of the outer surface of the outer ring (1) and the inner surface of the inner ring (2).

12. The method for producing a rolling bearing (10) according to claim 11, characterized in that The method further comprises curing the composite coating (5) at a temperature of 150°C or less, preferably at a temperature between 130°C and 22°C or more.

13. The method for producing a rolling bearing (10) according to claim 11 or 12, characterized in that: The method further comprises, before applying the composite coating (5), preparing at least one of the outer surface of the outer ring (1) and the inner surface of the inner ring (2) to have a surface roughness Ra of 0.5 to 10 μm, preferably 1 to 3 μm.

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