Bearing for marine vessel propulsion shaft and bearing restoration method

Abstract

The present invention relates to a barrel-type bearing which uses water lubrication, which supports a propulsion shaft of a marine vessel, and in which a plurality of arc pieces are held and retained at the inner circumferential surface of the bearing. A bearing according to the present invention has, at the inner circumferential surface of a cylindrical shell that supports a propulsion shaft of a marine vessel, a pair of positioning plates which are fixed opposite each other on the horizontal axis of the shell of the shell, a key member which is fixed to the bottom point Pb part of the shell, a bottom arc piece which engages with the key member, arc pieces which are provided to an upper part of the positioning plates, and arc pieces which are provided to a lower part. the horizontal axis is orthogonal to the center-of-gravity line of the propulsion shaft in the transverse section of the shell. this bearing makes it possible to easily hold and retain arc pieces at the inner not worn to easily restore the bearing.

Description

Title of Invention:BEARING FOR MARINE VESSEL PROPULSION SHAFT AND BEARING RESTORATION METHOD Technical Field

[0001] The present invention relates to a bearing using water-lubrication that supports a propulsion shaft of a marine vessel, and more particularly to a barrel-type bearing and a bearing restoration method. Background Art

[0002] In the field of bearings for marine vessel propulsion shafts, water-lubricated bearings that use the water lubrication effect of water, seawater, or the like are attracting attention from the perspective of environmental protection as opposed to oil-lubricated bearings that use oil lubrication.According to Non-Patent Document 1, which summarizes the configuration, characteristics, etc. of such bearings, water-lubricated bearings are being used in place of conventional oil-lubricated bearings for small and medium-sized ships, and it is said that in the future, large ships will also be converted to water-lubricated bearings. Various water-lubricated bearings have also been proposed in patent documents.

[0003] For example, Patent Document 1 proposes a bearing in which a pair of positioning plates and pluralities of closed arc pieces and gap forming arc pieces are arranged on the inner surface of a cylindrical shell that supports a propulsion shaft of a marine vessel. The positioning plates are fixed at opposing positions on the horizontal axis of the shell. The closed arc pieces are arranged below the positioning plates on the lower surface side of the shell and are subjected to the load of the propulsion shaft. The gap forming arc pieces are arranged on the upper surface side of the shell facing the closed arc pieces and have groove forming portions that circulate cooling water on both side edge portions. The closed arc pieces and the gap forming arc pieces each have a three-layer structure of a sliding layer, an intermediate layer composed of an elastic body, and a base that is in close contact with the inner surface of the shell. This bearing has sliding layers composed of a material with a smooth surface and excellent wear resistance and heat resistance, and elastic body layers that can equalize the load from the propulsion shaft, and is said to have low friction, excellent wear resistance, and excellent durability, and is also said to have excellent corrosion resistance because the elastic layers are protected from water or seawater.

[0004] Patent Document 2 proposes a split-type bearing in which the sliding material of bearing members is composed of rubber material to form first bearing members (20a), the sliding material of bearing members provided in the approximately lower half (L) of the shell is composed of fluororesin material to form second bearing members (20b), and stoppers (30, 30a) are provided between the approximately upper and lower halves of the shell to prevent the bearing members from moving in the circumferential direction. This split-type bearing has a smaller sliding resistance against the propulsion shaft than conventional split-type bearings, and is said to improve the fuel efficiency of marine vessels. In recent years, split-type bearings have been used as bearings to support the propulsion shaft of a marine vessel, and it has been reported that split bearings have the advantage of being easy to repair because only the bearing members that are subject to severe wear can be replaced. Prior Art Documents Patent Documents

[0005] Patent Document 1:WO2021 / 260965 Patent document 2: Utility model registration No. 3183964 Non-Patent Document 1:Fumitaka KIKKAWA, Yoshimasa KACHU, "Tribology of Seawater Lubricated Plain Bearings,"Tribologist,2015 Volume 60 Issue 12 Problems to be solved by the Invention

[0006] The water-lubricated bearing disclosed in Patent Document 1 or 2 is not only excellent in the wear resistance, but also has the advantage that the bearing members (arc pieces) that form the bearing can be stored in reserve and only the bearing members that are severely worn can be replaced. However, the range of bearing members that need to be replaced is not necessarily narrow, and the replacement work for the bearing members is not easy. On the other hand, there are cases where an emergency response is required due to unexpected damage to the bearing members caused by poor alignment, unstable whirling motion of the propulsion shaft, sailing with incomplete propeller submersion, or the like, and in such cases, a prompt response is required. In addition, in many cases, the wear of the bearing progresses in the lower portion of the stern side, which supports most of the propeller load. For this reason, those skilled m the art generally set an upper limit of the amount of wear in this portion from the standpoint of safety and propulsion efficiency, and appropriate management of the amount of wear is required.

[0007] In response to such conventional problems and demands, objects of the present invention include providing a water-lubricated bearing that is not only excellent in the wear resistance and durability, but also allows the bearing members that form the bearing to be easily and promptly rearranged without using spare parts,and providing a bearing restoration method. Means for solving the Problems

[0008] The bearing according to the present invention comprises:a cylindrical shell having an inner surface and supporting a propulsion shaft of a marine vessel;a pair of positioning plates fixed firmly to the inner surface of the shell so as to face each other on a horizontal axis of the shell;an anchor member fixed firmly to a lowest point Pb portion of the shell; and arc pieces including a bottom arc piece that fits with the anchor member, upper arc pieces that are arranged on an upper portion than the positioning plates, and lower arc pieces arranged on a lower portion than the positioning plates. refers to an axis orthogonal to a center-of-gravity line of the propulsion shaft in a cross section of the shell.

[0009] In the above invention, an arc piece that is in contact witha lower edge of another arc piece that is in contact with a lower edge of each of the positioning plates preferably has a shape that is interchangeable with the bottom arc piece.

[0010] In the above invention,the bottom arc piece can have a groove that fits with the anchor member, and the groove can be provided in a bottom central portion or a bottom side edge portion.

[0011] In the above invention, the upper arc pieces are preferably pressed against each other and held on an upper inner surface of the shell between the positioning plates, and the lower arc pieces are preferably pressed against each other and held on a lower inner surface of the shell between the positioning plates and the bottom arc piece. The positioning plates are preferably each a strip-shaped body in which an upper plate having a shell fixing means and a lower plate held on the inner surface of the shell via the upper plate are engaged with each other to be one body.

[0012] In addition, the lower plate can preferably be pulled out from the shell with a predetermined pulling force when all the arc pieces are arranged on the inner surface of the shell.

[0013] In addition, the upper plate is preferably subjected to a precision surface finishing process against an arc piece that is in contact with the upper plate, and the lower plate is preferably subjected to a precision surface finishing process against an arc piece that is in contact with the lower plate.

[0014] In addition, the number of the upper arc pieces including an arc piece at a shell top portionis preferably an odd number.

[0015] In addition, the upper arc pieces preferably comprise gap forming arc pieces, and the lower arc pieces preferably comprise gap forming arc pieces or closed arc pieces.

[0016] The bearing restoration method according to the present invention is for a bearing comprising:a cylindrical shell having an inner surface and supporting a propulsion shaft of a marine vessel;a pair of positioning plates fixed firmly to the inner surface of the shell so as to face each other on a horizontal axis of the shell; an anchor member fixed firmly to a lowest point Pb portion of the shell; and arc pieces including a bottom arc piece that fits with the anchor member, upper arc pieces that are arranged on an upper portion than the positioning plates, and lower arc pieces arranged on a lower portion than the positioning plates. The bearing restoration method comprises performing a rearrangement of the arc pieces in which when a wear depth of the lowest point Pb portion reaches a predetermined value in a worn portion W occurring on a stern side of the lower arc pieces, the arc piecesl5 that are less worn are rearranged closer to the lowest point Pb of the inner surface of the shell 11, and the arc piecesl5 that are more worn are rearranged farther from the lowest point Pb. Here, the horizontal axis refers to an axis orthogonal to a center-of-gravity line of the propulsion shaft in a cross section of the shell.

[0017] In the above bearing restoration method, the rearrangement of the arc pieces is preferably performed so as to structurally ensure continuity of a wear cross section of the worn portion W.

[0018] In another aspect, the bearing according to the present invention can comprise:a cylindrical shell having an inner surface and supporting a propulsion shaft of a marine vessel;a pair of positioning plates fixed firmlyto the inner surface of the shell so as to face each other on a horizontal axis of the shell, the positioning plates being each a strip-shaped body in which an upper plate having a shell fixing means and a lower plate held on the inner surface of the shell via the upper plate are engaged with each other to be one body; an anchor member fixed firmly to a lowest point Pb portion of the shell; andarc pieces including a bottom arc piece that fits with the anchor member, upper arc pieces that are arranged on an upper portion than the positioning plates, and lower arc piecesarranged on a lower portion than the positioning plates,the lower arc pieces including an arc piece that is in contact with a lower edge of another arc piece that is in contact with a lower edge of each of the positioning plates, the arc piece being a substitute arc piece that is interchangeable with the bottom arc piece. Here, the horizontal axis refers to an axis orthogonal to a center-of-gravity line of the propulsion shaft in a cross section of the shell.

[0019] In still another aspect, the bearing restoration method for the above bearingis carried out by performing a rearrangement of the arc pieces in which, provided that the arc pieces from a right-side substitute arc piece to the bottom arc piece are grouped into a right arc piece group and the arc pieces from a left-side substitute arc piece to the bottom arc piece are grouped into a left arc piece group,the lower positioning plate is first pulled out from the shell, and the right arc piece group is then pulled out from the shell as a group and rearranged as the group in the shell with axial directions reversed while the left arc piece group is then pulled out from the shell as a group and rearranged as the group in the shell with axial directions reversed. Here, vertical axis refers to an axis opposite to a direction of the center-of-gravity line of the propulsion shaft orthogonal to the horizontal axis, and the right side of the vertical axis is referred to as the right side of the shell

[0020] In yet another aspect, for the above bearing is cross section. the bearing restoration method carried out by performing a rearrangement of the arc pieces in which, provided that the arc pieces from right-side sub s t i tut e arc piece to the bottom arc piece are grouped into a right arc piece group and the arc pieces from a left-side substitute arc piece to an arc piece in contact with the bottom arc piece are grouped into a left arc piece group or the arc pieces from the right-side substitute arc piece to an arc piece in contact with the bottom arc piece are grouped into a right arc piece group and the arc pieces from the left-side substitute arc piece to the bottom arc piece are grouped into a left arc piece group,the lower positioning plate is first pulled out from the shell, andthe right arc piece group is then pulled out from the shell as a group and rearranged as the group in the shell with axial directions reversed while the left arc piece group is then pulled out from the shell as a group and rearranged as the group in the shell with axial directions reversed. Here, a vertical axis refers to an axis opposite to a direction of the center-of-gravity line of the propulsion shaft orthogonal to the horizontal axis, and the right side of the vertical axis is referred to as the right side of the shell cross section. Advantageous Effect of the Invention

[0021] The bearing according to the present invention allows the arc piecesto be easily and promptly rearranged on the inner surface of the shell, and is excellent in the wear resistance and durability. The bearing restoration method according to the present invention replaces the arc pieces with worn or damaged arc pieces as a group with sound arc pieces with little wear or damage, and the bearing can therefore be restored easily and promptly without using spare parts. Brief Description of the Drawings

[0022] [FIG. 1] FIG. 1 is a set of explanatory diagramsfor describing the configurations of bearings according to the present invention, wherein FIG. 1(a) is a set of a front view and a side view of a bearing in which the arc piecesare composed only of gap forming arc pieces, and FIG. 1 (b) is a front view of a bearing in which the arc pieces are composed of gap forming arc pieces and closed arc pieces . [FIG. 2] FIG. 2(a) is a detailed view of part A of FIG. 1(a), and FIG. 2(b) is an enlarged view of a positioning plate portion. [FIG. 3] FIG. 3 is a set of enlarged partial cross-sectional views of anchor member portions, wherein FIG. 3 (a) illustrates the case in which two bottom arc pieces (gap forming arc pieces) on the left and right are fitted with the anchor member, and FIG. 3(b) illustrates the case in which one arc piece (closed arc piece) is fitted with the anchor member. [FIG. 4] FIG. 4 is a set of drawingsillustrating the shapes / configurations of various arc pieces, wherein FIG. 4 (a) is a drawing for describing the configuration of a closed arc piece, FIG. 4(b) is a drawing for describing the configuration of a gap forming arc piece, FIG. 4(c) is a set of explanatory diagrams regarding the arrangement of grooves of bottom arc pieces that fit with the anchor member, and FIG. 4(d) is an explanatory diagram of a notch provided on the side end portion of a closed arc piece that is in contact with the lower edge of a positioning plate. [FIG. 5] FIG. 5 is aset of a schematic diagram of the wear state of a bearing and an explanatory diagram for the bearing restoration method. [FIG. 6] FIG. 6 is a set of explanatory diagramsfor the bearing restoration method. Embodiments for Carrying out the Invention

[0023] Hereinafter, one or more embodiments for carrying out the present invention will be described. Examples of bearings according to the present invention areillustrated in FIG. 1. FIG. 1 illustrates a front view and a side view of the bearing. As illustrated in the side view, the bearing includes two portions of upper and lower portions via a horizontal axis (HA) . The bearing according to the present invention is a barrel-type bearing in which arc pieces are held on the inner surface of a cylindrical shell that supports a propulsion shaft of a marine vessel. As illustrated in FIG. 1, the arc pieces are held on the inner surface of a shell 11 having an axially long main body 110 and a flange 111 provided on an end surface of the main body 110. In the bearing 10 of this example, the flange side is on the stern side. This bearing 10 includes a cylindrical shell 11 having an inner surface and supporting a propulsion shaft of a marine vessel, a pair of positioning plates 12 fixed firmly to the inner surface of the shell so as to face each other on a horizontal axis of the shell 11, an anchor member 13 fixed firmly to a lowest point Pb portion of the shell, andarc pieces 15.The arc pieces 15 include a bottom arc piece 15b that fits with the anchor member 13, upper arc pieces that are arranged on an upper portion than the positioning plates, and lower arc pieces arranged on a lower portion than the positioning plates. Here, the horizontal axis refers to an axis orthogonal to the center-of-gravity line of the propulsion shaft in a cross section of the shell 11.FIG. 1(a) illustrates a bearing composed only of gap forming arc pieces, which will be described below, and FIG. 1(b) illustrates a side view of a bearing in which the upper arc pieces are composed of gap forming arc pieces and the lower arc pieces are composed of closed arc pieces. The bearings 10 of the present examples each have the flange 111 as described above, but there are also bearings without the flange 111. There are also cases in which the mounting direction of the bearing is reversed from that of the bearings 10 of the present examples and the flange side is on the bow side.

[0024] As illustrated in FIG. 2, each positioning plate 12 is an integral strip-shaped body in which the upper plate 121 and the lower plate 122 are engaged with each other. The upper plate 121 has a shell fixing means, and in this example, is fixed to the shell 11 by means of screws. The upper plate 121 and the lower plate 122 each have an engagement surface 123, and the lower plate 122 is held on the inner surface of the shell 11 via the upper plate 121 so as not to fall off or become loose. The lower plate 122 can be pulled out with a predetermined pulling force from the bearing 10 on which the positioning plates 12 and the arc pieces 15 are disposed. In consideration of functionality and workability, the upper plate 121 and the lower plate 122 are preferably tapered such that the engagement surface 123 becomes thicker (wider) toward the stern side as illustrated in FIG. 2(b). The lower plate 122 can be preferably pulled out with a pulling force of 0.1 to 20.0 tons. This allows the bearing to be easily and promptly restored by the bearing restoration method, which will be described later. The structure of the engagement surfaces 123 of the positioning plates 12 is not limited to this example and may be in other forms. For example, it may be in a form in which a wedge is driven between the upper plate and the lower plate to fix them together.

[0025] As illustrated in FIG. 1 or 3, the anchor member 13 is provided at the lowest point Pb portion of the inner surface of the shell 11 and is fixed so as to extend in the axial direction of the shell 11. In this example, the anchor member 13 is fixed to the shell 11 by means of screws. The anchor member 13 has a function of fixing the bottom arc piece 15b in a predetermined position. The arc 15 are arranged on the inner surface of the shell with reference to the bottom arc piece 15b fitted with the anchor member 13. This allows the arc pieces 15 to be easily and promptly assembled. While the anchor member 13 in this example is strip-shaped, it may be a rod-shaped anchor member.

[0026] It is preferred that the surface pressure acting on the bottom arc piece 15b should be uniform. To this end, the bottom arc piece 15b that fits with the anchor member 13preferably has a short groove 155 portion (FIGS. 1 and 4) . It is also preferred that the groove 155 of the bottom arc piece 15b should not be present at the lowest point Pb portion of the shell on the stern side of the bearing 10, which receives high loads. To ensure uniformity of surface pressure and a certain fitting length, it is preferred that the length of the anchor member 13 should be 50% to 75% of the length of the bottom arc piece 15b (the length of the shell 11). It is also preferred that the anchor member 13 should be disposed so that the bottom arc piece 15b is inserted from the stern side of the bearing 10 and fits. The anchor member 13 of this example is structured to fit into the groove 155 of the bottom arc piece 15b, but another structure is also possible in which the bottom arc piece 15b has a ridge portion and the anchor member 13 has a groove that fits with the ridge portion.

[0027] Each arc piece 15 has a width that has a predetermined arc length or chord length on the inner surface of the shell 11, and a length that extends in the axial direction of the shell 11. Depending on its shape, each arc piece 15 may be a gap forming arc piece 15g or a closed arc piece 15p as illustrated in FIG. 4. The bearing 10 illustrated in FIG. 1(a) is an example in which the inner surface of the shell 11 is formed by gap forming arc pieces 15g. FIG. 1(b) is an example in which the upper side of the inner surface of the shell 11 is formed by gap forming arc pieces 15g and the lower side is formed by closed arc pieces 15p.

[0028] The bottom arc piece 15b is provided at the lowest point PB portion of the shell 11. The bottom arc piece 15b may also be in a gap forming shape (arc piece 15gb) or in a closed shape (arc piece 15pb) . As illustrated in FIG. 3, two bottom arc pieces 15b (15pb) may be symmetrically disposed on the anchor member 13 (FIG. 3(a)) or one bottom arc piece 15b (15pb) may be disposed on the anchor member 13 (FIG. 3(b)).For this reason, as illustrated in FIG. 4(c) the bottom arc piece 15b may have a groove 155 that fits with the anchor member 13 and is provided at a bottom side edge portion or bottom central portion of the bottom arc piece 15b. In the bottom arc pieces 15b with a non penetrating groove 155 at the bottom side edge portion as in this example, there are a left arc piece 15bl and a right arc piece 15br.

[0029] Arc pieces 15gm or arc pieces 15pm (FIGS. 1 and 2) that are in contact with the positioning plates 12 are preferably subj ected to a precision surface finishing process (which will be referred to as a lapping process, hereinafter) against the positioning plates 12. This allows the arc pieces 15 arranged on the inner surface of the shell 11 to be held on the shell’s inner surface with a predetermined holding force while pressed against each other. In the present bearing 10, since the positioning plates 12 are composed of upper plates 121 and lower plates 122, the arc pieces 15 arranged on the upper side of the inner surface of the shell 11 are subjected to the lapping process against the upper plates 121, and the arc pieces 15 arranged on the lower side of the inner surface of the shell 11 are subjected to the lapping process against the lower plates 122. The lapping process refers to "Hand finishing work to create a highly accurate flat surface. The surface is subjected to the lapping process against a grinding table and finished by scraping with a scraper (Kojien)This is a processing method that is described as "precision surface finishing by burnishing, precision surface finishing; mating by rubbing together (Weblio English-Japanese Dictionary / Japanese-English Dictionary: https : / / ejje.weblio.jp / content / %E6%93%A6%E3%82%8A%E5%90%88% E3%82%8F%E3%81%9B) ." When the arc piece 15 that is in contact witheach positioning plate 12 is the closed arc piece 15pm, it is preferred to provide a notch 156 on the side edge portion that contacts the positioning plate 12 as illustrated in FIG. 4(d). This notch 156 can prevent the end surface portion of a sliding layer 153 from lifting up, and can suppress stress concentration and wear of the sliding layer 153.

[0030] As illustrated in FIG. 4 each arc pisco 15 preferably hasa three-layer structure composed of a sliding layer 153 with excellent abrasion resistance and heat resistance, an intermediate layer 152 made of an elastic material, and a base 151. The base 151 can be made of metal or resin. A copper alloy with good machinability and excellent corrosion resistance can be used as the metal base 151. A fiber-reinforced thermosetting resin, for example, a carbon fiber-reinforced phenolic resin, can be used as the resin base 151.

[0031] The intermediate layer 152 is preferably made of an elastic body with a hardness (Shore A) of 50° to 95°. For example, nitrile rubber (NBR) with a hardness (Shore A) of 50° to 95° can be used.When the intermediate layer is made of rubber, the three-layer structure is preferably formed by vulcanized adhesion. This allows a strong adhesive structure to be formed. The intermediate layer 152 can equalize the load from the propulsion shaft, suppress the heat generation on the sliding surface of the sliding layer 153 of the propulsion shaft, and improve the wear resistance and durability of the arc piece 15. When the closed arc pieces 15p are arranged on the lower side of the inner surface of the shell 11, the elastic deformation of the intermediate layer 152 is limited to the vertical direction as viewed from the rotation axis of the propulsion shaft. Therefore, deformation in the shear direction at the interface between the sliding layer 153 and the intermediate layer 152 is suppressed, and deterioration of the adhesive portion between the sliding layer 153 and the intermediate layer 152 can be reduced.

[0032] The sliding layer 153 is preferably made of a synthetic high polymer compound containing fluorine atoms (F) in the molecule from the viewpoints of low frictional properties, wear resistance, and heat resistance. For example, a fluorine-based resin such as ethylene tetrafluoride (PTFE) resin ethylene tetrafluoride / propylene hexafluoride copolymer (FEP) resin, or ethylene tetrafluoride / perfluoroalkoxy ethylene copolymer (PFA) resin can be used. Alternatively, a polyamide resin or a phenol resin can be used.

[0033] The bearing according to the present invention has are formed of gap forming arc pieces, but the lower arc pieces can be formed of gap forming arc pieces or closed arc pieces. When the cooling of the bearing is more important than the load on the bearing, a configuration is adopted in which the lower arc piece is a gap forming arc piece. On the other hand, when the load on the bearing is more important than cooling, a configuration in which the lower arc piece is a closed arc piece is adopted.In addition, the upper arc pieces of the bearing are preferably formed of an odd number of arc pieces so that the arc pieces are arranged symmetrically on the left and right of the arc piece at the top of the shell. Thus, by controlling the dimension between the arc piece at the top portion of the shell and the bottom arc piece, it is possible to measure and control the wear depth of the sliding surface of the bottom arc piece, which is the most worn of the bearing 10, as described below, and the wear state of the bearing 10 can be measured / controlled with high accuracy.

[0034] FIG. 5 is a schematic diagram illustrating the wear state of the bearing 10 during operation. Wear occurs in the lower arc pieces of the bearing 10, especially around the lowest point Pb portion on the stern side. The planar shape of aworn portion W is triangular, larger on the stern side and gradually smaller toward the bow. The A-A cross-sectional shape of the worn portion W has a smoothly descending slope with the lowest point Pb being the valley, with the most severe wear at the lowest point Pb portion. Thus, the wear of the bearing 10 is partial, and there are portions where almost no wear occurs. Accordingly, when the worn portion W of the bearing 10 reaches a certain wear state, the bearing 10 can be restored by rearranging the worn arc pieces and the arc pieces that have not worn or havealmost not worn. The restoration of the bearing 10 can be performed in the state in which the propulsion shaftis inserted.

[0035] The wear state of the bearing 10 is partial as described above, and has a smoothly inclined surface. It is therefore preferred to rearrange the arc piecesas a group (set) to ensure the continuity of the worn surface, rather than rearranging them individually. If the arc pieces are rearranged to ensure the continuity of the wear surface, it is possible to prevent the occurrence of steps on the sliding surface of the bearing due to a change in the order of the arc pieces. This also prevents abnormal wear of the arc pieces and vibration of the propulsion shaft.

[0036] The rearrangement of the arc pieces 15 is preferably performed, for example, by dividing the lower arc pieces into two groups with reference to the bottom arc piece 15b and rearranging them into respective groups. In other words it is preferred to rearrange the lower arc pieces so that the right side of the lowest point Pb of the shell 11 is one group and the left side of the lowest point Pb of the shell 11 is another group, with respective axial directions (from the stern side to the bow side or the fore-aft directions) being reversed. In this case, the rearrangement is performed as illustrated by the dashed lines in FIG. 5. The less worn arc pieces 15 are rearranged closer to the lowest point Pb of the inner surface of the shell 11, and the more worn arc pieces 15 are rearranged farther from the lowest point Pb. That is, the bottom arc piece 15b is repositioned to the position farthest from the lowest point Pb of the shell 11.

[0037] As illustrated in FIGS. 1 and 2, considering that the arc piece 15 (15gm, 15pm) that is in contact with each positioning plate 12 (lower plate 122) is subjected to the lapping process against the lower plate 122, it is preferred to perform the rearrangement for a group of arc pieces excluding the arc piece 15 (15gm, 15pm) that is in contact with the lower edge of the positioning plate 12 (lower plate 122) . In this case, the arc piece 15 that is in contact with the lower edge of the arc piece 15 that is in contact with the lower edge of the positioning plate 12 is disposed at the bottom arc piece position after the group of arc pieces is rearranged. That is, the arc piece 15 that is in contact with the lower edge of the arc piece 15 that is in contact with the lower edge of the positioning plate 12 is disposed as an arc piece that is interchangeable with the bottom arc piece 15b. This interchangeable arc piece is a substitute arc piece for the bottom arc piece 15b.

[0038] Bearings for restoration differ depending on the type of bottom arc piece 15b of the bearing. There isa bearing for restoration 10A in which the bottom arc piece 15b has grooves 155 in the bottom side edge portions as illustrated in FIG. 6(a), and a bearing for restoration 10B in which the bottom arc piece 15b has a groove 155 in the bottom central portion as illustrated in FIG. 6(b). In the bearing for restoration 10A, the substitute arc piece 15bl' on the right side has the same shape as the bottom arc piece 15bl, but the arrangement direction is reversed, and the substitute arc piece ISbr' on the left side has the same shape as the bottom arc piece 15br, but the arrangement direction is reversed. In the bearing for restoration 10B, the substitute arc pieces 15b' on the left and right sides have the same shape as the bottom arc piece 15b, but the arrangement direction is reversed. The left and right of the bearing (10, 10A, or 10B) or arc pieces 15 are defined with reference to the vertical axis VA of the cross section of the shell 11. The vertical axis refers to the axis in the opposite direction to the center-of-gravity line of the propulsion shaft that is orthogonal to the horizontal axis, and the right side of the vertical axis is referred to as the right side of the shell cross section.

[0039] In the bearing for restoration lOAillustrated in FIG. 6(a) , the restoration the bearing is performed as follows. First, it is assumed that the arc pieces fromthe right-side substitute arc piece IShl' to the bottom arc piece 15br are grouped into a right arc piece group 15R, and the arc pieces fromthe left-side substitute arc piece 15br' to the bottom arc piece 15bl are grouped into a left arc piece group 15L. Next, the lower plate 122 is pulled out from the shell 11. Then, the right arc piece group 15R is pulled out as a group from the shell 11 and rearranged as the group in the shell 11 with axial directions reversed. The left arc piece group 15L is then pulled out from the shell 11 as a group and rearranged as the group in the shell 11 with axial directions reversed. The axial direction is the direction from the stern to the bow of the bearing.

[0040] In the bearing for restoration 10B illustrated in FIG. 6(b), the restoration of the bearing is performed as follows. First, it is assumed that the arc pieces from the right-side substitute arc piece 15b' to the bottom arc piece 15b are grouped into a right arc piece group 15R, and the arc pieces fromthe left-side substitute arc piece 15b to the arc piece 15 in contact with the bottom arc piecel5b are grouped into a left arc piece groupl5L. Alternatively, the arc pieces from the right-side substitute arc piece 15b'to the arc piece in contact with the bottom arc piece 15b are grouped into a right arc piece groupl5R and the arc pieces from the left-side substitute arc piece 15b'to the bottom arc piecel5b are grouped into a left arc piece group 15L. Note, however, that the bottom arc piece 15b can be included in the right arc piece group 15R or the left arc piece group 15L, and this can be determined based on the state of the worn portion W. Next, the lower plate 122 is pulled out from the shell 11. Then, the right arc piece group 15R is pulled out as a group from the shell 11 and rearranged as the group in the shell 11 with axial directions reversed. The left arc piece group 15L is then pulled out from the shell 11 as a group and rearranged as the group in the shell 11 with axial directions reversed. The axial direction is the direction from the stern to the bow of the bearing. Description of Reference Numerals

[0041] 10 Bearing 11 Shell 110 Main body 111 Flange 12 Positioning plate 121 Upper plate 122 Lower plate 123 Engagement surface 13 Anchor member 15 Arc piece 151 Base 152 Intermediate layer 153 Sliding layer 154 Groove forming portion 155 Groove 156 Notch

Claims

1. A bearing comprising:a cylindrical shell having an inner surface and supporting a propulsion shaft of a marine vessel;a pair of positioning plates fixed firmly to the inner surface of the shell so as to face each other on a horizontal axis of the shell;an anchor member fixed firmly to a lowest point Pb portion of the shell; andarc pieces including a bottom arc piece that fits with the anchor member, upper arc pieces that are arranged on an upper portion than the positioning plates, and lower arc pieces arranged on a lower portion than the positioning plates, wherein the horizontal axis refers to an axis orthogonal to a center-of-gravity line of the propulsion shaft in a cross section of the shell.

2. The bearing according to claim 1, wherein an arc piece that is in contact with a lower edge of another arc piece that is in contact with a lower edge of each of the positioning plates has a shape that is interchangeable with the bottom arc piece.

3. The bearing according to claim 1 or 2, wherein the bottom arc piece has a groove that fits with the anchor member, and the groove is provided in abottom central portion or a bottom side edge portion.

4. The bearing according to claim 1 or 2, whereintheupper arc piecesare pressed against each otherand held on an upper inner surface of the shell between thepositioning plates, andthe lower arc piecesare pressed against each otherand held on a lower inner surface of the shell between thepositioning plates and the bottom arc piece.

5. The bearing according to claim 1 or 2, wherein thepositioning plates are each a strip-shaped body in which anupper plate having a shell fixing means and a lower plateheld on theinner surface of the shell via theupper plateare engaged with each other to be one body.

6. The bearing according to claim 5, wherein the lower plate can be pulled out from the shell with a predetermined pulling force when all the arc pieces are arranged on the inner surface of the shell.

7. The bearing according to claim 5, wherein the upperplate issubjected toa precisionsurfacefinishing processagainst an arc piece that is in contact with the upperplate, and the lower plate is subjected to a precisionsurface finishing process against an arc piece that is incontact with the lower plate.

8. The bearing according to claim 1 or 2, wherein the number of the upper arc pieces including an arc piece at ashell top portionis an odd number.

9. The bearing according to claim 1 or 2, wherein theupperpiecescomprise gapformingand thelower arc pieces comprise gap forming arc pieces or closedarc pieces.

10. A bearing restoration method for a bearing comprising: a cylindrical shell having an inner surface and supporting a propulsion shaft of a marine vessel;a pair of positioningplates fixed firmly to the inner surface of the shell so as to face each other on a horizontal axis of the shell;an anchor member fixed firmly to a lowest point Pb portion of the shell; and arc pieces including a bottom arc piece that fits with the anchor member, upper arc pieces that are arranged on an upper portion than the positioning plates, and lower arc pieces arranged on a lower portion than the positioning plates,the bearing restoration method comprising performing a rearrangement of the arc pieces in which when a wear depthof the lowest point Pb portion reaches a predeterminedvalue in a worn portion W occurring on a stern side of thelower arc pieces,thearcpiecesare less worn arerearranged closer to the lowest point Pb of the innersurface of the shell, and the arc pieces that are more wornare rearranged farther from the lowest point Pb,wherein the horizontal axis refers to an axisorthogonal to a center-of-gravity line of the propulsionshaft in a cross section of the shell.The bearing restoration method according to claim 10, wherein the rearrangement of the arc pieces is performed so as to ensure continuity of a wear cross section of the worn portion W.

12. A bearing comprising:a cylindrical shell having an inner surface and supporting a propulsion shaft of a marine vessel;a pair of positioning plates fixed firmly to the inner surface of the shell so as to face each other on a horizontal axis of the shell, the positioning plates being each a strip-shaped body in which an upper plate having a shell fixing means and a lower plate held on the inner surface of the shell via the upper plate are engaged with each other to be one body;an anchor member fixed firmly to a lowest point Pb portion of the shell; andarc pieces including a bottom arc piece that fits with the anchor member, upper arc pieces that are arranged on an upper portion than the positioning plates, and lower arc pieces arranged on a lower portion than the positioning plates,the lower arc pieces including an arc piece that is in contact with a lower edge of another arc piece that is in contact with a lower edge of each of the positioning plates, the arc piece being a substitute arc piece that is interchangeable with the bottom arc piece, wherein the horizontal axis refers to an axis orthogonal to a center-of-gravity line of the propulsion shaft in a cross section of the shell.A bearing restoration method for the bearing accordinggrouped into a right arc piece group and the from a left-side substitute arc piece to the piece are grouped into a left arc piece group, the lower plate is first pulled out fromto claim 12, comprising performing a rearrangement of the arc pieces in which, provided that the arc pieces from a right-side substitute arc piece to the bottom arc piece are arc pieces bottom arcthe shell,andthe right arc piece group is then pulled out from the shell as a group and rearranged as the group in the shell with axial directions reversed while the left arc piece group is then pulled out from the shell as a group and rearranged as the group in the shell with axial directions reversed,wherein a vertical axis refers to an axis opposite to a direction of the center-of-gravity line of the propulsion shaft orthogonal to the horizontal axis, and the right side of the vertical axis is referred to as the right side of the shell cross section.

14. A bearing restoration method for the bearing according to claim 12, comprising performing a rearrangement of the arc pieces in which, provided that the arc pieces from a right-side substitute arc piece to the bottom arc piece are grouped into a right arc piece group and the arc pieces from a left-side substitute arc piece to an arc piece in contact with the bottom arc piece are grouped into a left arc piece group or the arc pieces from the right-side substitute arc piece to an arc piece in contact with the bottom arc piece are grouped into a right arc piece group and the arc pieces from the left-side substitute arc pieceto the bottom arc piece are grouped into a left arc piecegroup,the lower plate is first pulled out from the shell, andtherightgroup is then pulled out from theshell as a group and rearranged as the group in the shell with axial directions reversed while the left arc piece group is then pulled out from the shell as a group and rearranged as the group in the shell with axial directions10 reversed,wherein a vertical axis refers to an axis opposite toa direction of the center-of-gravity line of the propulsionshaft orthogonal to the horizontal axis, and the right sideof the verticalaxisis referred to as theright side of15 the shell cross section.INTERNATIONAL SEARCH REPORT International application No. PCT / JP2022 / 044I67 A. CLASSIFICATION OF SUBJECT MATTER F16C J7 / «2(2006.01)i; F16C J5 / «2(2006.01)i; F16C4J / «2(2006.01)i FI: F16C17 / 02 Z; F16C35 / 02 Z; F16C43 / 02 According to International Patent Classification (IPC) or to both national classification ar id IPC B. FIELDS SEARCHEDMinimum documentation searched (classification system followed by classification symbols)F16C17 / 02; F16C35 / 02; F16C43 / 02Documentation searched other than minimum documentation to the extent that such documents are included in the fields searchedPublished examined utility model applications of Japan 1922-1996Published unexamined utility model applications of Japan 1971-2023Registered utility model specifications of Japan 1996-2023Published registered utility model applications of Japan 1994-2023Electronic data base consulted during the international search (name of data base and, where practicable, search terms used)DOCUMENTS CONSIDERED TO BE RELEVANTCategory* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. A WO 2021 / 260965 Al (MIKASA CORPORATION) 30 December 2021 (2021-12-30) 1-14 A A A JP 2019-113099 A (MITSUBISHI HEAVY IND COMPRESSOR CORP) 11 July 2019 (2019-07-11) JP 57-195919 A (KAGUCHI, Shinsaku) 01 December 1982 (1982-12-01) JP 3183964 U (OHTSU CHEMICAL CO., LTD.) 06 June 2013 (2013-06-06) 1-14 1-14 1-14 A KR 10-2014-0075232 A (HYUNDAI HEAVY INDUSTRIES CO., LTD.) 19 June 2014 (2014-06-19) 1-14| | Further documents are listed in the continuation of Box C. | J | See patent family annex.* Special categories of cited documents:“A” document defining the general state of the art which is not considered“T” later document published after the international filing date or priority“O”“P”to be of particular relevanceearlier application or patent but published on or after the international filing datedocument which may throw doubts on priority claim(s) or which is cited to establish the publication date of another citation or other special reason (as specified)document referring to an oral disclosure, use, exhibition or other meansdocument published prior to the international filing date but later than the priority date claimed‘Y’date and not in conflict with the application but cited to understand the principle or theory underlying the inventiondocument of particular relevance; the claimed invention cannot be considered novel or cannot be considered to involve an inventive step when the document is taken alonedocument of particular relevance; the claimed invention cannot be considered to involve an inventive step when the document is combined with one or more other such documents, such combination being obvious to a person skilled in the aitdocument member of the same patent familyDate of the actual completion of the international searchDate of mailing of the international search report08 February 202321 February 2023Name and mailing address of the ISA / JPJapan Patent Office (ISA / JP)3-4-3 Kasumigaseki, Chiyoda-ku, Tokyo 100-8915JapanAuthorized officerTelephone No.INTERNATIONAL SEARCH REPORT Information on patent family members International application No. PCT / JP2022 / 044I67Patent document cited in search report Publication date (day / month / year) Patent family member)s) Publication date (day / month / year) WO 2021 / 260965 Al 30 December 2021 GB 2604254 A KR 10-2022-0044618 A CN 114630969 A JP 2019-113099 A 11 July 2019 US 2019 / 0195284 Al JP 57-195919 A 01 December 1982 (Family: none) JP 3183964 U 06 June 2013 (Family: none) KR 10-2014-0075232 A 19 June 2014 (Family: none)

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