JP2017082909A - Foil bearing, foil used in the same and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance supporting force of a foil bearing.SOLUTION: A foil bearing 10 includes a foil 12 having a bearing surface and a foil holder 11 to which the foil 12 is attached. On the bearing surface of the foil 12, a first region S1 in which a film 20 is provided, and a second region S2 in which the film 20 is not provided or in which a thickness of the film 20 is made thinner than that in the first region S1 are alternately provided in a circumferential direction (a rotation direction of a shaft 2).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a foil bearing, a foil used therefor, and a manufacturing method thereof.

  As a bearing for supporting a shaft of a turbo machine such as a gas turbine or a turbocharger, a foil bearing has attracted attention. A foil bearing comprises a bearing surface made of a flexible thin film (foil), and supports a load while allowing the bearing surface to bend. When the shaft rotates, a wedge-shaped bearing gap (fluid film) is formed between the bearing surface of the foil and the shaft, and fluid is pushed into the narrow side of the bearing gap, so that dynamic pressure is generated in the fluid film. Pressure is increased.

  In a foil bearing, it is important to form a wedge-shaped bearing gap in order to effectively generate a dynamic pressure in a fluid film. For example, in Patent Document 1, a plurality of foils are arranged in the circumferential direction on the inner peripheral surface of the foil holder, and the region on the leading side in the axial rotation direction of each foil is run on the underfoil portion of another foil. By doing so, a wedge-shaped radial bearing gap is formed between the bearing surface of the foil and the outer peripheral surface of the shaft.

JP-A-2015-143572

  However, it may not be said that the fluid film pressure can be sufficiently increased only by forming the wedge-shaped bearing gap as described above.

  An object of the present invention is to obtain a higher supporting force by increasing the pressure of a fluid film than that of a conventional foil bearing.

  A foil bearing according to the present invention includes a foil having a bearing surface, and a foil holder to which the foil is attached, and the pressure of a fluid film formed in a bearing gap between the bearing surface of the foil and a rotating member. The rotating member is supported, and a bearing surface of the foil is provided with a first region provided with a coating, and the coating is not provided, or the coating is thinner than the first region. The second region is provided alternately in the rotation direction of the rotating member.

  Thus, on the bearing surface of the foil, the first region in which the coating is provided and the second region in which the coating is not provided (or the film thickness is thin) are set in the rotational direction of the rotating member (hereinafter simply referred to as “ By providing them alternately in the “rotation direction”, irregularities are formed on the bearing surface in the rotation direction. When the rotating member rotates, dynamic pressure is generated in the fluid in the bearing gap that flows along the rotation direction due to the unevenness of the bearing surface. Thereby, the pressure of the fluid film is increased and the supporting force of the foil bearing is increased.

  The first region and the second region provided on the foil are, for example, centered from both ends in the direction orthogonal to the rotational direction (axial direction for radial foil bearings, radial direction for thrust foil bearings) toward one side in the rotational direction. It can be arranged in the shape of a herringbone inclined to the top. In this case, when the rotating member rotates, fluid is collected on the center side of the foil along the herringbone-shaped irregularities formed on the bearing surface, so that dynamic pressure can be generated more effectively in the fluid film. .

  The foil bearing described above includes, for example, an application step of applying a coating material to the bearing surface, a heat treatment step of heating the foil to cure the coating material to form a coating, and fixing the coating to the foil, A cooling process for cooling the foil is sequentially performed.

  The coating is preferably formed of a material that suppresses wear on the bearing surface, specifically, PTFE, DLC, titanium aluminum nitride (TiAlN), or the like. When the foil coated with these coating materials is heated in the heat treatment step, the coating material expands or contracts and is cured in this state to form a coating. In this case, in the subsequent cooling process, the film fixed on the foil may contract or expand, and the foil may be deformed.

  In view of this point, in the present invention, the coating film is not provided with a uniform thickness on the bearing surface, but as described above, the first region where the coating film is provided and the coating film is not provided (or the film thickness). Thin regions) are alternately provided in a predetermined direction (for example, the rotation direction). As a result, the first region where the coating is provided is divided by the second region where the coating is not provided (or where the film thickness is thin), so the stress applied to the foil is reduced by the contraction or expansion of the coating. The deformation of the foil can be prevented.

  In particular, if the first region is dispersed on the bearing surface and the entire circumference of each first region is surrounded by the second region, the first region is divided by the second region in all directions on the bearing surface. Therefore, deformation of the foil can be reliably prevented. Specifically, for example, the second region can be arranged in a lattice shape, and the first region can be arranged in each region (window portion) partitioned by the second region. Alternatively, the first regions can be arranged in a staggered manner. In this case, unevenness in the rotation direction is formed in the entire region of the film formation region, so that the dynamic pressure effect is enhanced.

  As described above, according to the present invention, since the unevenness in the rotational direction due to the coating is formed on the bearing surface of the foil, the dynamic pressure effect is enhanced and a high supporting force can be obtained.

It is sectional drawing of the foil bearing which concerns on embodiment of this invention. It is the top view of the foil provided in the said foil bearing, and its enlarged view. It is a top view which expand | deploys and shows several connected foil. It is sectional drawing in the XX line of FIG. It is a top view of the shielding member used for formation of a film. It is sectional drawing which shows a mode that film material is apply | coated to foil. It is sectional drawing which shows the other example of foil. It is a top view which shows the other example of a film. It is a top view which shows the other example of a film. It is a top view which shows the other example of a film.

  Hereinafter, as an example of a foil bearing according to the present invention, a radial foil bearing will be described as an example, and a description will be given based on the drawings.

  FIG. 1 shows a radial foil bearing 10 according to an embodiment of the present invention. The radial foil bearing 10 supports the shaft 2 as a rotating member inserted in the inner periphery in the radial direction. The radial foil bearing 10 of the present embodiment is an air dynamic pressure bearing that uses air as a pressure generating fluid. The radial foil bearing 10 includes a foil holder 11 and a plurality (three in the illustrated example) of foils 12 attached to the inner peripheral surface of the foil holder 11. In the following, the rotation direction leading side (the arrow direction leading side in FIG. 1) of the shaft 2 is referred to as “one circumferential direction”, and the rotation direction rear side (the arrow direction rear side in FIG. Side ".

  The foil holder 11 is made of metal or resin. As a metal which forms the foil holder 11, a sintered metal and a smelting material (for example, steel materials) are mentioned, for example. The foil holder 11 has a cylindrical shape, and has a cylindrical inner peripheral surface 11a and an outer peripheral surface 11b in the illustrated example. The outer peripheral surface 11b of the foil holder 11 is fixed to the inner peripheral surface of a housing (not shown). An axial groove 11c is formed as a recess into which the end of the foil 12 is inserted at a plurality of locations (three locations in the illustrated example) spaced apart in the circumferential direction on the inner peripheral surface 11a of the foil holder 11. Both axial ends of each axial groove 11 c are open to the end face of the foil holder 11. In addition, you may provide the latching | locking part which engages with the foil 12 and controls the axial movement of the foil 12 at the axial direction one end or both axial ends of the axial groove 11c. The locking portion can be provided integrally with the foil holder 11 or separately.

  The foil 12 is made of a metal having a high spring property and good workability, and is made of, for example, steel or a copper alloy. The foil 12 is formed by subjecting a metal foil having a thickness of about 20 μm to 200 μm to press working or electric discharge machining. In the air dynamic pressure bearing using air as the pressure generating fluid as in this embodiment, since there is no lubricating oil in the atmosphere, it is preferable to use stainless steel or bronze as the metal foil.

  As shown in FIG. 2, each foil 12 includes a top foil portion 12a, an insertion portion 12b provided on one side in the circumferential direction of the top foil portion 12a (left side in FIG. 2), and a circumferential direction of the top foil portion 12a. And an underfoil portion 12c provided on the other side (right side in FIG. 2).

  The surface on the inner diameter side of the top foil portion 12a functions as a bearing surface (see FIG. 1). In the present embodiment, of the foils 12, the surface that directly faces the outer peripheral surface 2 a of the shaft 2 is all constituted by the top foil portion 12 a. Minute circumferential cuts 12a1 are provided in the vicinity of both ends in the axial direction of the edge on one circumferential side of the top foil portion 12a (see FIG. 2). Note that the cut 12a1 may be omitted unless particularly necessary.

  The insertion part 12b is extended from the top foil part 12a to the circumferential direction one side. The insertion part 12b is provided in the axial direction edge part (in the example of illustration, axial direction both ends) of each foil 12. As shown in FIG. In this embodiment, each insertion part 12b has comprised the rectangular shape.

  The underfoil portion 12c extends from the top foil portion 12a to the other circumferential side. A cutout portion 12c1 is provided at the edge on the other circumferential side of the underfoil portion 12c. In the illustrated example, the notch 12c1 is formed in a substantially arc shape. In addition, the cutout portion 12c1 may have a substantially V shape in which a straight line is bent at the center in the axial direction. Further, if not particularly necessary, the notch portion 12c1 may be omitted, and the edge of the underfoil portion 12c on the other side of the axial traverse may be a straight line parallel to the axial direction.

  An insertion port 12d into which the insertion portion 12b of the adjacent foil 12 is inserted is provided at the boundary between the top foil portion 12a and the underfoil portion 12c. The insertion port 12d is provided at the same axial position as the insertion portion 12b. In the illustrated example, insertion ports 12 d are provided at both ends in the axial direction of the foil 12, and open at the axial ends of the foil 12, respectively. The axial width of each insertion port 12d is slightly larger than the axial width of the insertion portion 12b inserted therein.

  The insertion portion 12b of each foil 12 is inserted into the insertion port 12d of the foil 12 adjacent to one side in the circumferential direction (see FIG. 3), and further inserted into the axial groove 11c of the inner peripheral surface 11a of the foil holder 11. (See FIG. 1). In FIG. 3, the foils 12 are slightly shifted in the axial direction for easy understanding. On the other hand, the underfoil portion 12 c of each foil 12 is disposed between the top foil portion 12 a of the foil 12 adjacent to the other circumferential side and the inner peripheral surface 11 a of the foil holder 11. Thereby, the area | region of the circumferential direction one side is supported from the back by the underfoil part 12c of the other foil 12 among the top foil parts 12a. Of the top foil portion 12 a, the region on the other circumferential side is not supported by the underfoil portion 12 c of the other foil 12 and is in contact with the inner peripheral surface 11 a of the foil holder 11. An edge on one side in the circumferential direction and an edge on the other side in the circumferential direction of the top foil portions 12a of the adjacent foils 12 are engaged with each other in the circumferential direction and stick to each other. Thereby, the top foil part 12a of each foil 12 protrudes to the outer diameter side, and is curved into a shape along the inner peripheral surface 11a of the foil holder 11.

  A coating 20 is provided on the bearing surface of each foil 12. In the present embodiment, the coating 20 is provided in a predetermined pattern on the entire bearing surface of the top foil portion 12 a of each foil 12. Specifically, as shown in an enlarged view in FIG. 2, a first region S1 where the coating 20 is provided and a second region S2 where the coating 20 is not provided are formed on the bearing surface. The first region S1 and the second region S2 are alternately provided in the circumferential direction, whereby unevenness is formed on the bearing surface in the circumferential direction (see FIG. 4). The first region S1 is provided distributed on the bearing surface, and the entire circumference of each first region S1 is surrounded by the second region S2. In the present embodiment, the second region S2 is provided in a lattice shape, and the first region S1 is provided in each region (window portion) partitioned by the second region S2.

  The coating 20 is made of a material that suppresses wear of the bearing surface of the foil 12. Examples of such materials include materials that reduce the friction coefficient of the bearing surface (PTFE, etc.), materials that increase the hardness of the bearing surface (titanium aluminum nitride, etc.), or materials having both of these properties (DLC, etc.). Can be used.

  In the illustrated example, each first region S1 (coating 20) has a rectangular shape, but each first region S1 may have a rhombus, a circle, an ellipse, or the like. Further, the coating 20 may be provided only on the bearing surface (top foil portion 12a) of each foil 12, or may be provided on the entire surface of the foil 12 including the insertion portion 12b and the underfoil portion 12c. The coating 20 may be provided on the entire bearing surface of each foil 12, or may be provided on a part of the bearing surface (for example, a partial region in the circumferential direction or the axial direction). For example, the coating film 20 may be provided only in the circumferential region of the bearing surface of each foil 12 that rides on the underfoil portion 12c of the other foil 12.

  When the shaft 2 inserted in the inner periphery of the foil bearing 10 having the above configuration rotates in the direction of the arrow in FIG. 1, the inner diameter surface (bearing surface) of the top foil portion 12 a of each foil 12 of the radial foil bearing 10 and the outer periphery of the shaft 2. A radial bearing gap is formed between the surface 2a. At this time, since the region on the one side in the circumferential direction of the top foil portion 12a rides on the underfoil portion 12c of the adjacent foil, the radial bearing gap is on the one side in the circumferential direction (the axial rotation direction leading side). It has a wedge shape that narrows as you go to. When air is pushed into the narrow side of the wedge-shaped radial bearing gap, the pressure of the air film in the radial bearing gap is increased, and the shaft 2 is supported in a non-contact manner in the radial direction by this pressure.

  In particular, in the present embodiment, on the bearing surface of the foil 12, the first region S1 provided with the coating 20 and the second region S2 provided with no coating 20 are alternately provided in the circumferential direction, whereby the bearing Irregularities in the circumferential direction are formed on the surface. Due to the unevenness in the circumferential direction, dynamic pressure is generated in the air in the radial bearing gap that flows along the circumferential direction, whereby the pressure of the air film in the radial bearing gap is further increased, and the force that supports the shaft 2 (bearing rigidity) ) Is enhanced.

  At this time, due to the flexibility of the foil 12, the bearing surface of each foil 12 is arbitrarily deformed according to the operating conditions such as the load, the rotational speed of the shaft 2, the ambient temperature, etc. It is automatically adjusted to the appropriate width. Therefore, the radial bearing gap can be managed to the optimum width even under severe conditions such as high temperature and high speed rotation, and the shaft 2 can be stably supported. When the shaft 2 is rotating, the foils 12 are pushed to the leading side in the rotational direction due to friction with the fluid (air) that flows along with the rotation of the shaft 2, and the axial grooves 11 c of the foil holder 11. It hits the inner corner.

  Further, in the present embodiment, as shown in FIG. 2, by providing a notch 12c1 at the edge on the other circumferential side of the underfoil 12c, the top foil 12a that rides on the notch 12c1 is provided on the notch 12c1. A step along it is formed. As a result, the fluid flowing along the top foil portion 12a flows along the above steps and is collected on the center side in the axial direction, so that the pressure improvement effect is enhanced (see the arrow in FIG. 3). In particular, by providing minute notches 12a1 in the vicinity of both axial ends of the edge on one circumferential side of the top foil portion 12a, the rigidity of this portion is lowered. Thereby, the top foil part 12a is easily deformed along the notch part 12c1 of the underfoil part 12c arranged behind the top foil part 12a.

  Further, each foil 12 is not completely fixed to the foil holder 11 and can be moved with respect to the foil holder 11. Therefore, during the rotation of the shaft 2, the foil 12 is pressed against the foil holder 11 due to the influence of the air film formed in the radial bearing gap, and accordingly, the foil 12 and the foil holder 11, in particular, the top of each foil 12 are pressed. Minute sliding occurs between the outer diameter surfaces of the foil portion 12 a and the underfoil portion 12 c and the inner peripheral surface 11 a of the foil holder 11. The vibration of the shaft 2 can be attenuated by the frictional energy generated by the minute sliding.

  When the shaft 2 is rotated at a low speed immediately before stopping or immediately after starting, the bearing surface of each foil 12 and the outer peripheral surface of the shaft 2 slide in contact with each other. As described above, the bearing surface has PTFE, DLC, titanium aluminum. By providing the coating 20 made of nitride or the like, the wear of the bearing surface is prevented. Moreover, in order to adjust the frictional force caused by the minute sliding between the foil 12 and the foil holder 11, the above-described coating may be formed on one or both of them. In addition to the above, a tungsten disulfide film or a molybdenum disulfide film may be used as a film provided on the foil 12 or the foil holder 11.

  Hereinafter, a method for forming the coating film 20 on the bearing surface of the foil 12 will be described. The coating film 20 is formed on the bearing surface of the foil 12 through a coating process, a heat treatment process, and a cooling process. Hereinafter, each process will be described in detail.

  In the coating step, a liquid or gel film material is applied to the bearing surface of the foil 12. Specifically, first, the foil 12 is placed on a flat surface with the bearing surface facing upward, and a shield having a grid-like wire 31 (for example, a wire mesh) as shown in FIG. The member 30 is disposed. After that, as shown in FIG. 6, the coating material 20 ′ is sprayed from above the shielding member 30 by spraying or the like, so that the coating material 20 ′ is foiled through the holes 32 provided between the wire members 31 of the shielding member 30. Supplied on 12 bearing surfaces.

  In the heat treatment step, the foil 12 coated with the coating material 20 ′ is heated to cure the coating material 20 ′ to form the coating 20 and fix the coating 20 on the bearing surface of the foil 12. In the subsequent cooling step, the foil 12 on which the coating film 20 is formed is cooled to room temperature. As described above, the foil 12 in which the first region S1 where the coating 20 is provided and the second region S2 where the coating 20 is not provided is obtained on the bearing surface.

  Here, when the coating material 20 ′ is PTFE, the coating material 20 ′ expands due to heating in the heat treatment step, and is cured and fixed on the bearing surface in this state. In this case, when the foil 12 is cooled in the subsequent cooling step, the coating 20 fixed on the bearing surface in a expanded state contracts. Due to the contraction (tensile stress) of the coating film 20, stress is applied to the foil 12, and the foil may be deformed (warped, curved, etc.). In the present embodiment, since the first region S1 provided with the coating 20 is divided by the second region S2 where the coating 20 is not provided, the stress applied to the foil 12 due to the contraction of the coating 20 is relieved, and the foil Thus, deformation such as warping can be prevented. In particular, in the illustrated example, since the entire circumference of each first region S1 provided dispersed on the bearing surface is surrounded by the second region S2, the first region S1 provided with the coating 20 is in all directions. Since it is divided at the second region S2, deformation of the foil 12 can be prevented more reliably.

  When the coating material 20 ′ is titanium aluminum nitride, as in PTFE, it expands by heating in heat treatment and is fixed to the bearing surface in this state, so that the same phenomenon as described above occurs. On the other hand, when the coating material 20 ′ is DLC, the coating material 20 ′ is contracted by heating in the heat treatment step, and is fixed to the bearing surface in this state. In this case, stress is generated in the foil 12 due to the expansion of the coating film 20 made of DLC in the subsequent cooling step. Even in this case, the deformation of the foil 12 due to the expansion (compression stress) of the first region S1 can be prevented by dividing the first region S1 by the second region S2.

  The present invention is not limited to the above embodiment. Hereinafter, although other embodiment of this invention is described, description of the point which overlaps with said embodiment is abbreviate | omitted.

  In forming the coating film 20 on the bearing surface of the foil 12, when the liquid or gel-like coating material 20 ′ is supplied to the bearing surface, the coating material 20 ′ droops depending on the viscosity or supply amount of the coating material 20 ′. As shown in FIG. 7, the adjacent coating materials 20 ′ may be connected to each other. When the coating film 20 is formed through the heat treatment process and the cooling process in this state, the coating film 20 having a thickness smaller than that of the first area S1 is provided in the second region S2. Even in this case, since the unevenness in the circumferential direction by the coating 20 is formed on the bearing surface, the same effect as the above embodiment can be obtained.

  In the embodiment shown in FIGS. 8 and 9, the first regions S1 are arranged in a staggered manner. In FIG. 8, each first region S1 has a rectangular shape, and in FIG. 10, each first region S1 has a diamond shape. In these embodiments, the first regions S1 are arranged side by side in the circumferential direction while being shifted by a half pitch in the axial direction. Thereby, since the unevenness | corrugation of the circumferential direction by the coating film 20 is formed in the whole region (for example, whole bearing surface) of the formation area of the coating film 20, the dynamic pressure effect is heightened.

  In the embodiment shown in FIG. 10, the first region S1 and the second region S2 are arranged in a herringbone shape. Specifically, both the regions S1 and S2 are inclined from the axial end portion side toward the axially central side toward the circumferential direction one side (axial rotation direction leading side). In this case, the air flowing along the circumferential direction is collected along the both regions S1 and S2 on the axially central side, whereby the pressure of the air film at the axially central portion is increased. In particular, in the illustrated example, by providing the notch portion 12c1 at the edge on the other circumferential side of the underfoil portion 12c, coupled with the effect of providing a herringbone-shaped step on the bearing surface of the top foil portion 12a that rides on the airfoil, The pressure of the membrane is further increased.

  Further, as the material of the coating film 20 (coating material 20 '), a material that hardly expands or contracts by heating in the heat treatment step may be used. Even in this case, the effect of enhancing the dynamic pressure effect can be obtained by forming circumferential irregularities on the bearing surface.

  In the above embodiment, the radial foil bearing 10 that supports the shaft 2 in the radial direction is shown as an embodiment of the present invention. However, the present invention is not limited to this, and the present invention is a thrust foil bearing that supports the shaft 2 in the thrust direction. It can also be applied to. The thrust foil bearing includes, for example, a disc-shaped foil holder and a foil attached to an end surface of the foil holder. When the shaft 2 rotates, a thrust bearing gap is formed between the end surface of the thrust collar provided on the shaft 2 and the bearing surface of the foil of the thrust foil bearing. The bearing surface of the foil includes a first region S1 provided with the coating 20 and a second region S2 where the coating 20 is not provided or the coating 20 is thinner than the first region S1 in the circumferential direction. Are provided alternately. In addition, since the function and modification of each structure are the same as that of said radial foil bearing 10, description is abbreviate | omitted.

  The object of application of the foil bearing according to the present invention can be suitably used, for example, as a bearing that supports a turbine shaft of a gas turbine or a bearing that supports a rotor of a turbocharger (supercharger). The foil bearing according to the present invention is not limited to turbomachines such as gas turbines and turbochargers, but can be widely used as vehicle bearings and industrial equipment bearings in which the use of oil is restricted.

  Each of the foil bearings described above is an air dynamic pressure bearing that uses air as a pressure generating fluid. However, the present invention is not limited to this, and other gases can be used as the pressure generating fluid, or water or oil can be used. A liquid such as can also be used.

2 shaft 10 radial foil bearing (foil bearing)
DESCRIPTION OF SYMBOLS 11 Foil holder 12 Foil 12a Top foil part 12b Insert part 12c Underfoil part 12d Insert 20 Coating 20 'Coating material 30 Shielding member S1 1st area | region S2 2nd area | region

Claims (9)

A foil bearing comprising a foil having a bearing surface and a foil holder to which the foil is attached, and supporting the rotating member with a pressure of a fluid film formed in a bearing gap between the bearing surface of the foil and the rotating member. Because
Rotation of the rotating member includes a first region where a coating is provided on the bearing surface of the foil and a second region where the coating is not provided or the thickness of the coating is smaller than the first region. A foil bearing characterized by being alternately provided in the direction.   The first region and the second region provided in the foil are arranged in a herringbone shape inclined from both ends in a direction orthogonal to the rotation direction toward the center side toward the rotation direction leading side. Item 1. A foil bearing according to item 1.   The foil bearing according to claim 1, wherein the coating is made of PTFE, DLC, or titanium aluminum nitride.   The foil bearing according to claim 3, wherein the first region is provided in a distributed manner on the bearing surface, and the entire circumference of each first region is surrounded by the second region.   The foil bearing according to claim 4, wherein the second region is arranged in a lattice pattern.   The foil bearing according to claim 4, wherein the first regions are arranged in a staggered manner. A foil provided with a foil bearing and having a bearing surface that forms a bearing gap with a rotating member,
A first region where a coating is provided on the bearing surface, and a second region where the coating is not provided or the coating is thinner than the first region, in the rotational direction of the rotating member. A foil characterized by being provided alternately. A foil manufacturing method comprising a bearing surface provided on a foil bearing and forming a bearing gap with a rotating member,
A coating process for coating the bearing surface with a coating material; a heating process for heating the foil to cure the coating material to form a coating and fixing the coating to the foil; and cooling the foil The cooling process is performed in order,
In the coating step, on the bearing surface, a first region where the coating material is provided, and a second region where the coating is not provided, or the thickness of the coating is thinner than the first region, The manufacturing method of the foil provided alternately by the rotation direction of the said rotation member. By heating the foil in the heat treatment step, the coating material expands or contracts, and is cured in this state to form the coating,
The foil manufacturing method according to claim 8, wherein the film fixed to the foil contracts or expands by cooling the foil in the cooling step.

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