Bush for a fluid dynamic bearing and related manufacturing method

Abstract

The present invention relates to a bushing (10), in particular for a hydrodynamic bearing, characterized by providing a polymeric material portion (1) and a support base (2) of metallic material, said support base (2) providing coupling means (3; 6; 7); said polymeric portion (1) being cast on said base (2) so as to also fill said coupling means (3; 6; 7) provided on said base (2), obtaining a firm coupling and a shape complementary to that of the base (2). The present invention also relates to a method for manufacturing a bushing (10).

Description

TECHNICAL FIELD

[0001] The present invention relates to a bushing for a hydrodynamic bearing.

[0002] The present invention also relates to a method for manufacturing said bushing for a bearing.

[0003] More specifically, the present invention relates to a polymer-coated bushing for electric generators, turbines, pumps, transmission components. BACKGROUND

[0004] The currently known polymer-coated bearings of this type are essentially based on a mechanical anchoring between the metal matrix and the coating polymer itself.

[0005] The solution proposed according to the present invention belongs to the field of hydrodynamic generator bearings, such as those described, for example, in patent WO 2004 / 001241 A1.

[0006] WO'241 describes a bearing for a rotor of a rotating machine, in particular a hydroelectric generator, which rotates around a vertical rotation axis. Said bearing is designed as a sliding bearing and comprises axial and radial bearings. Typically, these bearings are coated with white metal, a tin alloy - white metal or "Babbitt".

[0007] However, in many cases, polymer-coated bearings are used.

[0008] In the known type of bushings, sintered bronze or welded metal mesh or a series of micro-grooves machined in the bearing support component are mainly used.

[0009] Typically, in all known types of solutions for bushings, once said intermediate layer is formed, the polymer layer is pressed into it under conditions of high temperature and high pressure.

[0010] This creates a mechanical connection between the metal and the polymer material.

[0011] This technique is characterized by a high degree of complexity, which also means a high cost of the final product.

[0012] In fact, the method for obtaining the known bushings comprises various steps and the use of specialized equipment to manufacture the final product, which also limits the potential suppliers (in addition to the above-mentioned increase in costs).

[0013] Another problem of the known and currently adopted technique is the inevitable presence of limitations on the size that can be processed.

[0014] Furthermore, once the components are connected, said components cannot be disconnected later without destroying the connection.

[0015] Therefore, if the sliding surface is damaged due to wear or seizure of the bearing, the polymer layer cannot be replaced.

[0016] The latest solution that tries to answer the above questions is the one described in EP 3 276 191 A1. In this patent application, it is tried to overcome the above-mentioned drawbacks by proposing a solution for the bushing in which the polymer and metal parts are separated, thus creating a bushing that can also be disassembled later, if necessary, for example due to excessive wear.

[0017] However, the solution according to EP'191 has some drawbacks, such as the need to be machined with very precise tolerances to ensure the coupling between the parts and reduces the possibility of controlling the overall tolerances of the component (the bushings in the bearing have tolerances of about one hundredth of a millimeter).

[0018] Among the known patent literature, particular mention is made of some patent documents that relate to specific solutions proposed according to the present application.

[0019] WO 2013 / 178266 A1 describes a hydrodynamic bearing having a layered structure that is substantially uniform over its circumference and comprises a base, a lead-free sliding layer whose thickness decreases in the edge region than in the central region, and a polymer coating that is thicker in the edge region than in the central region, so that the surface level of the coating is approximately flat, as can be seen in an axial cross-section. This forms a reservoir of coating material in the edge region, which is particularly useful for the initial start-up phase of a rotating machine in which wear occurs, in which phase the bearing and the shaft adapt to each other, thus increasing the resistance to edge seizure and achieving a better alignment of the shaft with the bearing.

[0020] On the other hand, patent US 6,332,716 describes a composite bearing in which a support metal is fixed to a resin layer, in which polytetrafluoroethylene (PTFE) is added to a base resin consisting essentially of polyether ether ketone, so that the proportion of polytetrafluoroethylene is between 0.1 and 50% by weight based on the resin layer. The polytetrafluoroethylene is then dispersed in the base resin in the form of particles.

[0021] U.S. Patent 5,229,198 describes, in turn, a material for low-friction bearings, which comprises a matrix formed by mesh screen wires fused together with a metal support sheet. The polytetrafluoroethylene or other polymer resin fills the voids inside the screen, thus being rigidly blocked together to give the bearing material high strength.

[0022] Patent application US 2005 / 0260431 A1 describes a composite material for use in plain bearings and provides a metal support and at least one reinforcing material having an open structure. The support and the reinforcing material are connected by means of metal connectors.

[0023] Patent application EP 3 276 191 A1 describes a bearing shell for a bearing of a fluid power generator, the bearing shell comprising a polymer portion and a metal base portion, the polymer portion and the metal base portion combining to constitute said bearing shell for the bearing. Thanks to the fact that the polymer portion is separate from the metal portion, the maintenance work in the event of bearing failure is simplified and accelerated.

[0024] In particular, EP'191 proposes a stationary bearing shell for a bearing of a fluid power generator, designed in a simplified method compared to the traditional polymer-coated bearing shells for bearings, which allows to reduce the production costs, while increasing its main advantages, such as high thermo-mechanical resistance and low wear in mixed lubrication. It is a bearing shell for a fluid power generator, having a polymer portion and a metal base portion, the polymer portion and the metal base portion combining to form the bearing shell. The shell is characterized in that the polymer portion is a separate polymer plate, the metal base portion is a support plate, and the polymer plate is fixed to the support plate, but is also removable.

[0025] According to EP'191, the polymer plate is fixed in the stationary plate by means of a seat in the stationary plate, said seat perfectly mates with a seat in the polymer plate, said seat in the polymer plate provides a seat and an offset protruding from the perimeter of the plate, thus forming a seal strip of reduced thickness. The polymer plate and the support plate have or can have the same edge profile. Again according to EP'191, the support plate and the polymer plate can be coupled by at least one bolt. Furthermore, in the solution proposed in EP'191, a locking device can be provided at the edge of the polymer plate, which interacts with the side walls of a recess of the stationary plate. In particular, said locking device can comprise a key and a slotted joint extending along the edge of the polymer plate, and a removable fixing plate can be provided on the side on which the bearing is supported, to allow the insertion of the polymer plate from one side by sliding it inward, and then to be able to fix the polymer plate in its sliding position in the recess when closed. The fixing plate can be fixed to the stationary plate by means of fixing screws.

[0026] In one example reported in EP'191, the polymer portion is at least partially composed of polyether ether ketone (PEEK).

[0027] As is known, PEEK is a material with superior properties in terms of strength, which makes it superior to other polymers. The polymer can also be at least partially composed of polytetrafluoroethylene (PT-FE).

[0028] Finally, according to EP'1919, the polymeric portion can be composed of a combination of different polymers and of fillers composed of carbon fibers and / or graphite.

[0029] EP'919 constitutes the main prior art document relevant to the invention described herein. SUMMARY

[0030] The solution proposed according to the present invention is suitable for this case, which proposes a bearing bush composed of a polymeric portion and a metal base coupled in an innovative way that can significantly reduce costs by simplifying the production process.

[0031] In addition, the solution proposed according to the present invention makes it possible to achieve considerable improvements in the operation of the components, such as the addition of components that yield at the maximum load point of the bush or the introduction of sensors below the polymer layer to monitor its behavior.

[0032] These and other results are obtained by a bush for a hydrodynamic bearing comprising the features described in independent claim 1.

[0033] Further features of the bush according to the present invention are described in the dependent claims. BRIEF DESCRIPTION OF DRAWINGS

[0034] The present invention will now be described according to the preferred embodiments of the present invention, by way of non-limiting illustrative examples, with particular reference to the figures of the attached drawings, in which:

[0035] Figure 1 is a perspective view of a bush for a bearing according to the present invention;

[0036] Figure 2 is a close-up sectional view of the bush in Figure 1 ;

[0037] Figure 3 shows a detail of the bush of Figure 1 ;

[0038] Figure 4 shows a perspective view of a second embodiment of a metal base of a bush for a bearing according to the present invention;

[0039] Figure 5 shows a perspective view of a second embodiment of a polymeric portion of a bush for a bearing according to the present invention;

[0040] Figure 6 shows a perspective view of the two elements shown in Figure 4 and Figure 5 ;

[0041] Figure 7 a detail of the bushing in Figure 6 ;

[0042] Figure 8 a detail of the bushing in Figure 5 , Figure 6 and Figure 7 ;

[0043] Figure 9 is an exploded perspective view of a third embodiment of a bushing according to the present application;

[0044] Figure 10 shows a perspective view of a metal base of a fourth embodiment of a bushing according to the present application;

[0045] Figure 11 is a sectional view of the base of Figure 10 ;

[0046] Figure 12 shows a perspective view of a metal base of a fifth embodiment of a bushing according to the present application; and,

[0047] Figure 13 is a sectional view of the base of Figure 12 . DETAILED DESCRIPTION

[0048] Reference will now be made to the drawings, and particularly with reference to the first of them, Figures 1-3 , shows a static bushing for bearings, in particular for fluid power generator bearings, generally indicated by the reference number 10, comprising a polymeric portion 1 and a metal base 2.

[0049] In the embodiment of the bushing 10 according to the present application, the polymeric portion 1 is provided, consisting of a polymeric plate cast / moulded on the metal base 2, said metal base constituting a support plate.

[0050] The solution according to the present application provides for casting, in the preferred embodiment described it means 3D printing, but this technique by no means can be interpreted as limiting the scope of the present application, on the metal base 2 one or more layers of polyether ether ketone (hereinafter also indicated by the acronym PEEK) reinforced with carbon fibres or graphite. The use of PEEK should not be understood as limiting the scope of protection of the present application; for example, the polymeric material can consist of other polymers, such as polyethylene terephthalate PTFE or mixtures thereof. In fact, the polymeric element can also be made of, for example, PTFE or a mixture of PEEK and PTFE, with the addition of carbon fibres or graphite.

[0051] The metal base 2 is machined along at least one of the sides that delimit the perimeter of the metal base 2, thus forming an undercut 3 (the geometry of the undercut 3 is described in more detail in the following figures); Figure 3are shown in detail in the following.

[0052] Due to the configuration of the undercut 3, it is not possible to apply the technique described in the technical document EP'191, since the polymer plate cannot slide freely in the undercut 3.

[0053] Furthermore, it is not possible to use the hot-pressing technique inherent in some solutions of the known art.

[0054] The undercut 3 provided in this embodiment of the bush 1 according to the present application for coupling between the polymer portion 1 and the base 2 has a depth of the order of millimetres, so it is not possible to obtain the correct anchoring of the polymer plate pressed on the top by heating.

[0055] The undercut 3 and its distribution are just one example of a coupling mechanism that can be provided in the bush 10 according to the present application, as will also be seen below.

[0056] The solution proposed according to the present application allows the polymer portion 1, anchored to the metal base 2, to be positioned directly on the base itself.

[0057] The process can be performed by using a machine to deposit the molten polymer on the metal surface, which allows the undercut to be filled and then allows the polymer portion 1 to be anchored on the metal base 2.

[0058] The solution proposed according to the present application offers significant advantages over the currently known solutions, in particular:

[0059] - the production costs of polymer-coated guide and thrust bearings are reduced, both due to less material waste and to the significant reduction in the requirement for precise machining of the coupling between polymer and metal, since there is no need for strict tolerances to be performed for the undercut 3, which will be completely filled or partially filled (in any case sufficient) to ensure the anchoring between polymer and metal support;

[0060] - by making the cut along the seat specially formed in the metal support, it is possible to separate the polymer component 1 and the metal base 2. In this way, if the bush 10 is damaged or needs to be replaced, the metal base 2, the metal support can be reused to form a new bush;

[0061] - further machining can be provided inside the metal base 2, which will further facilitate the anchoring of the polymer portion 1 to the base 2 and the operation of the bearing 10 as a whole. In fact, by increasing the thickness of the polymer material in the areas that are subjected to higher pressure during operation, it is possible to exploit the yield of the material itself, in particular of PEEK, to favour a better distribution of the pressure on each single bush 10. This advantage is illustrated in the Figures 4 to 8In which a cavity 4 is provided on the metal base 2, the cavity 4 having a step that decreases towards the centre of the cavity 4. Figure 8 The effect obtained in terms of pressure release is shown for this embodiment;

[0062] - a sensor 5 can be introduced inside the bush 10 between the PEEK portion 1 and the metal base 2 to monitor the operating conditions and the health status of the bush. This type of embodiment is shown in Figure 9 .

[0063] Now observing Figure 10 and Figure 11 , another embodiment of the bush 10 according to the present application is shown, in which a groove 6 is formed on the base element 2, in which, when the polymeric material of the element 1 is cast, a coupling is formed between the elements 1 and 2.

[0064] In Figure 12 and Figure 13 , a groove 7 is formed on the base element 2, in which, when the polymeric material of the element 1 is cast, a coupling is formed between the elements 1 and 2.

[0065] The present application has been described above with reference to its preferred embodiments, but it is understood that experts in the field can make modifications thereto without thereby departing from the scope of protection of the present application as defined by the claims that follow.

Claims

1. A bearing bush (10) for a hydrodynamic bearing, the bearing bush (10) being characterized by providing a polymer material portion (1) and a metal material support base (2). The support base (2) provides a connecting mechanism (3; 6; 7); The polymer material portion (1) is cast onto the support base (2) to also fill the connecting mechanism (3; 6; 7) disposed on the support base (2), thereby obtaining a strong connection and a shape complementary to the shape of the support base (2). in, At least one cavity (4) is provided on the surface of the support base (2) on which the polymer material will be poured. The cavity (4) corresponds to the area of ​​the hydrodynamic bearing that is subjected to higher pressure. The cavity (4) is stepped and has a step that gradually decreases toward the center of the cavity (4).

2. The bearing bush (10) according to claim 1, characterized in that, The connecting mechanism (3; 6; 7) is disposed on the periphery of the support base (2) and / or inside the support base (2).

3. The bearing bush (10) according to claim 1, characterized in that, The connecting mechanism consists of one or more undercuts (3) and / or grooves or hollow sections (6; 7).

4. The bearing bush (10) according to claim 1, characterized in that, The polymer material portion (1) is made of polyetheretherketone (PEEK), PTFE or a mixture thereof, and contains carbon fiber or graphite.

5. The bearing bush (10) according to claim 1, characterized in that, The supporting base (2) is made of steel, aluminum, copper or metal alloy.

6. The bearing bush (10) according to claim 1, characterized in that, One or more sensors (5) are provided between the support base (2) and the polymer material portion (1) for measuring one or more parameters of the bearing bush (10).

7. A method for manufacturing a bearing bush (10) according to any one of claims 1 to 6, characterized in that, The polymer material portion (1) is cast onto the support base (2).

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