Ship propeller shaft bearing, stern tube bearing device, propulsion device, and method for operating the propulsion device

Abstract

A bearing (1) for radially supporting a propeller shaft (22) of a ship (20) has a plurality of lubrication holes (2a, 2b, 2c, 4a, 4b, 4c) extending from an outer surface of the bearing (1) to an inner surface of the bearing (1) to allow a flow of a lubricating medium between the inner surface and the outer surface, the lubrication holes (2a, 2b, 2c, 4a, 4b, 4c) including a first group of lubrication holes opening into the inner surface of the bearing (1) on a first side of the bearing (1) and a second group of lubrication holes (4) opening into the inner surface of the bearing (1) on a second side of the bearing (1). The bearing (1) further has at least one lubrication inlet (8, 11) opening into the inner surface of the bearing (1) and configured to allow a lubricating medium to be introduced into the inner surface independently of the first and second groups of lubrication holes (2, 4).

Description

[Technical Field]

[0001] The present invention relates to a bearing for radially supporting a propeller shaft of a ship as defined in claim 1. The present invention also relates to a stern tube bearing arrangement for a ship, a propulsion device for a ship and a method for operating a propulsion device. [Background technology]

[0002] A typical propulsion system for a ship has a propeller connected to the crankshaft of the ship's main engine by a propeller shaft. A propeller is attached to the propeller shaft. To allow the propeller shaft to pass through the hull, the ship is equipped with a stern tube. The stern tube is a hollow tube located at the bottom of the ship's stern. A stern tube bearing is located inside the stern tube to radially support the propeller shaft. To avoid direct contact between the surface of the stern tube bearing and the propeller shaft, the stern tube bearing is lubricated. The stern tube bearing can be lubricated with water or oil.

[0003] Lubrication of oil-lubricated stern tube bearings can be based on the rotational motion of the propeller shaft. A typical conventional bearing has lubrication holes extending through the bearing shell. As the propeller shaft rotates, a pumping effect is created, drawing lubricating oil into the bearing and forming an oil film between the propeller shaft and the inner surface of the bearing.

[0004] Although conventional lubrication systems are simple and function adequately under many operating conditions, lubrication is not always optimal. Bearing loads are not uniform and vary with operating conditions. Inadequate lubrication of stern tube bearings can lead to excessive bearing wear or failure. Summary of the Invention

[0005] It is an object of the present invention to provide an improved bearing for radially supporting a marine propeller shaft. It is another object of the present invention to provide an improved marine stern tube bearing arrangement, a marine propulsion device, and a method of operating the propulsion device.

[0006] The bearing according to the present invention is configured to be mounted within a stern tube of a vessel, and when mounted, has a top, a bottom, a first side extending from the top to the bottom in a first circumferential direction of the bearing, and a second side extending from the top to the bottom in a second circumferential direction opposite the first circumferential direction. The bearing has a plurality of lubrication holes extending from an outer surface of the bearing to an inner surface of the bearing to allow a flow of a lubricating medium between the inner surface and the outer surface, the lubrication holes including a first group of lubrication holes opening onto the inner surface of the bearing on the first side of the bearing and a second group of lubrication holes opening onto the inner surface of the bearing on the second side of the bearing. The bearing further has at least one lubrication inlet opening onto the inner surface of the bearing and configured to allow a supply of a lubricating medium to the inner surface independently of the first group of lubrication holes and the second group of lubrication holes.

[0007] The bearing of the present invention provides improved lubrication that can be adjusted as needed. The bearing can be placed in an oil bath, and lubrication holes supply lubricating medium to the inner surface of the bearing as the propeller shaft rotates. Additional lubricating medium can be supplied to areas requiring more lubrication via lubrication inlets. The lubrication inlets also allow for cooling of the lubricating medium and the supply of cooler lubricating medium to specific areas of the bearing. The use of the lubrication inlets can be limited to certain operating conditions to minimize energy consumption of the lubrication system.

[0008] According to one embodiment of the present invention, the at least one lubrication inlet is arranged in the circumferential direction of the bearing at a distance from the lubrication holes of the first and second groups of lubrication holes. By arranging the lubrication inlet at a different height from the lubrication holes, it is easier to provide the lubrication inlet with a separate lubrication channel. However, the lubrication inlet can also be arranged at the same height as the lubrication holes.

[0009] According to one embodiment of the present invention, the at least one lubrication inlet includes a first lubrication inlet located on a first side of the bearing. The propeller shaft places more load on the lower half of the bearing. When the lubrication inlet is located on one side of the bearing, in one direction of rotation of the propeller shaft, the lubrication inlet supplies additional lubricating oil to the lower half of the bearing.

[0010] According to one embodiment of the present invention, the first lubrication inlet opens into a recessed area on the inner surface of the bearing. The recessed area around the lubrication inlet helps to spread the lubricating medium over the inner surface of the bearing. It also reduces the spread of the lubricating medium outside the recessed area in the axial direction of the bearing, thus concentrating more of the lubricating medium in a specific area of ​​the inner surface of the bearing.

[0011] According to one embodiment of the present invention, the length of said recessed area in the axial direction of the bearing is at most 50% of the length of the inner surface of the bearing, which helps to maintain a larger amount of lubricating medium in a specific area of ​​the inner surface of the bearing.

[0012] According to one embodiment of the invention, at least one of the lubrication holes of the first group of lubrication holes opens into the same recess area as the first lubrication inlet, which allows the lubrication hole to function as a pressure relief hole for the lubrication medium supplied via the first lubrication hole, helping to avoid excessive pressure on the inner surface of the bearing.

[0013] According to one embodiment of the invention, a first lubrication inlet opens into a first recessed area on the inner surface of the bearing, a first side of the bearing comprises a second recessed area separated from the first recessed area by a wall, and at least one of the lubrication holes of the first group of lubrication holes opens into the second recessed area. The two separate recessed areas help to maintain a larger amount of lubricating medium in a specific area of ​​the bearing.

[0014] According to one embodiment of the present invention, the first lubrication inlet is arranged above the level of the lubrication holes of the first group of lubrication holes.

[0015] According to one embodiment of the present invention, the bearing has a first lubricant supply hole opening on the end face of the bearing and a first lubricant channel connecting a first lubricant inlet to the first lubricant supply hole. This arrangement allows lubricant to be supplied to the first lubricant inlet via the end face of the bearing. The first lubricant channel can be either a groove on the outer surface of the bearing or an internal channel.

[0016] According to one embodiment of the present invention, the at least one lubrication inlet includes a second lubrication inlet that coincides with the bottom of the bearing. By providing a lubrication inlet at the bottom of the bearing, a lubricating medium can be supplied below the propeller shaft. The lubricating medium supplied through the second lubrication inlet can be pressurized to provide lift to the propeller shaft.

[0017] According to one embodiment of the invention, the second lubrication inlet opens into a recessed area on the inner surface of the bearing, the recessed area around the second lubrication inlet facilitating the spreading of the lubricating medium.

[0018] According to one embodiment of the present invention, the bearing has a second lubricant supply hole opening on the end face of the bearing and a second lubricant channel connecting the second lubricant inlet to the second lubricant supply hole, which allows lubricant to be supplied to the second lubricant inlet via the end face of the bearing.

[0019] According to one embodiment of the present invention, the at least one lubrication inlet is located at a distance of 10-40% of the length of the bearing from one end of the bearing. Often, the most loaded areas of a bearing are close to the end of the bearing, and by locating the lubrication inlet close to the end of the bearing, more lubricating medium can be supplied to this area.

[0020] According to one embodiment of the invention, the lubrication inlet is located close to the aft end of the bearing. The aft end of the bearing is often more heavily loaded than the bow end, and therefore it may be beneficial to provide more lubricating medium at the aft end. However, in some applications and in certain operating conditions, the bow end may be more heavily loaded, and therefore the bearing may have lubrication inlets at the bow end or at both the bow and bow ends.

[0021] According to one embodiment of the present invention, the lubrication holes of the first group are arranged at the same height as each other around the circumference of the bearing, and the lubrication holes of the second group are arranged at the same height as each other around the circumference of the bearing. Thus, the lubrication holes promote uniform lubrication of the bearing, while the lubrication inlets can increase lubrication in specific areas.

[0022] According to one embodiment of the present invention, the lubrication holes of the first group of lubrication holes open into first grooves on the outer surface of the bearing having a longitudinal direction parallel to the axial direction of the bearing, and the lubrication holes of the second group of lubrication holes open into second grooves on the outer surface of the bearing having a longitudinal direction parallel to the axial direction of the bearing.

[0023] A stern tube bearing arrangement according to the present invention comprises a stern tube and a bearing as defined above arranged within the stern tube.

[0024] A propulsion device according to the invention comprises a stern tube device as defined above, a propeller shaft supported on bearings, and a propeller mounted on the propeller shaft.

[0025] According to one embodiment of the invention, the propulsion device comprises means for supplying pressurized lubricating medium to said at least one lubrication inlet.

[0026] According to one embodiment of the present invention, the propulsion device comprises means for controlling the pressure and / or the amount of lubricating medium supplied to said at least one lubrication inlet, which makes it possible to optimize the lubrication of the bearings in different operating conditions.

[0027] According to one embodiment of the present invention, the propulsion device comprises means for cooling the lubricating medium supplied to said at least one lubrication inlet, said cooling means making it possible to control the temperature of the most heavily loaded areas of the bearing.

[0028] According to one embodiment of the present invention, the propulsion device comprises at least one of the following: a temperature sensor for monitoring the temperature of the lubricating medium in the stern tube, a sensor for monitoring the thickness of the lubricating medium film in the bearing, and a rotational speed sensor for monitoring the rotational speed of the propeller shaft. By monitoring different parameters, the lubrication of the bearing can be optimized in different operating conditions. The temperature sensor can be arranged to monitor the temperature of the lubricating medium in the bearing.

[0029] According to an embodiment of the present invention, the propulsion device comprises a control unit configured to control the supply of lubricating medium through the at least one lubrication inlet based on the temperature of the lubricating medium in the stern tube, the thickness of the lubricating medium film in the bearing, and / or the rotational speed of the propeller shaft.

[0030] The vessel of the present invention comprises a propulsion device as defined above.

[0031] A method of operating a propulsion device as defined above includes the step of introducing a lubricating medium to an inner surface of the bearing via said at least one lubrication inlet.

[0032] According to one embodiment of the present invention, the method comprises at least one operating mode in which lubricating medium is introduced to the inner surface of the bearing through both the lubrication holes and the at least one lubrication inlet, and at least one operating mode in which lubricating medium is introduced to the inner surface of the bearing only through the lubrication holes, thereby allowing the lubrication of the bearing to be controlled as needed, with lubricating medium being supplied through the lubrication inlet only when needed.

[0033] According to one embodiment of the present invention, the bearing has a first lubrication inlet and a second lubrication inlet, and the method includes at least one operating mode in which the lubrication medium is supplied through all of the lubrication holes and the first lubrication inlet and the second lubrication inlet, at least one operating mode in which the lubrication medium is supplied only through the lubrication holes and the first lubrication inlet, and at least one operating mode in which the lubrication medium is supplied only through the lubrication holes and the second lubrication inlet.

[0034] According to one embodiment of the present invention, the lubricating medium is supplied through the second lubricating inlet at a higher pressure than the first lubricating inlet. The higher pressure generates a lift force acting on the propeller shaft. The pressure of the lubricating medium supplied through the second lubricating inlet can be, for example, at least 15 bar.

[0035] According to one embodiment of the present invention, the lubricating medium supplied through the first lubrication inlet is cooled before being supplied to the bearing. Cooling the lubricating medium helps maintain the temperature of the lubricating medium within a desired range. By cooling the lubricating medium supplied through the first lubrication inlet, there is no need to cool the high-pressure lubricating medium supplied through the second lubrication inlet, thus avoiding the need for a heat exchanger capable of withstanding high pressure.

[0036] According to one embodiment of the present invention, the method comprises the steps of monitoring at least one of the following parameters: thickness of the lubricating medium film on the inner surface of the bearing, rotational speed of the propeller shaft, and temperature of the lubricating medium; and controlling the flow of lubricating medium through the at least one lubrication inlet based on the value of the one or more monitored parameters. By monitoring the one or more parameters, the lubrication of the bearing can be optimized at all operating conditions. [Brief explanation of the drawings]

[0037] Embodiments of the invention will be described in more detail below with reference to the accompanying drawings.

[0038] [Figure 1] FIG. 2 shows a perspective rear view of a bearing according to one embodiment of the present invention. [Figure 2] FIG. 2 shows a perspective front view of the bearing of FIG. 1. [Figure 3] 1 shows a schematic portion of a vessel and a propulsion device according to an embodiment of the present invention; [Figure 4] 2 shows diagrammatically further details of a propulsion device according to one embodiment of the present invention; [Figure 5] 1 shows a control system for the propulsion device as a block diagram. DETAILED DESCRIPTION OF THE INVENTION

[0039] 1 and 2 show a bearing 1 according to an embodiment of the present invention. The bearing 1 can be used to radially support a propeller shaft of a ship. Here, the term "propeller shaft" refers to a shaft that connects a propeller of the ship to the crankshaft of the ship's main engine. The main engine may be, for example, a two-stroke piston engine that can be driven in two rotational directions to enable the ship to be propelled both forward and backward. The bearing 1 may in particular be a stern tube bearing. A stern tube is a hollow tube located at the bottom of the stern of a ship. The stern tube allows the propeller shaft to pass through the hull of the ship.

[0040] The bearing 1 is configured to be mounted in a specific orientation within the stern tube. One end face of the bearing 1 is configured to face aft, and the other end face of the bearing 1 is configured to face forward. Thus, the bearing 1 has a forward end, or bow end, and an aft end, or rear end, in the axial direction. FIG. 1 shows the aft end of the bearing 1, and FIG. 2 shows the bow end of the bearing 1. The bearing 1 is not rotationally symmetrical and is therefore configured to be mounted in a specific rotational direction. When mounted, the bearing 1 has a top, a bottom, a first side, and a second side. The first side extends from the top to the bottom in a first circumferential direction of the bearing 1, and the second side extends from the top to the bottom in a second circumferential direction opposite the first circumferential direction. In the illustrated embodiment, the first side of the bearing 1 is the port side of the bearing 1, i.e., the side located on the left side when viewing the bearing 1 from the rear of the vessel, and the second side of the bearing 1 is the starboard side of the bearing 1, i.e., the side located on the right side when viewing the bearing 1 from the rear of the vessel. In the illustrated embodiment, the direction of rotation of the propeller shaft is counterclockwise when viewed from the stern as the propeller moves the vessel forward. Therefore, the first circumferential direction of the bearing 1 is the same as the direction of rotation of the propeller shaft as the propeller moves the vessel forward. The direction of rotation of the propeller shaft is from the first side of the bearing 1 through the bottom of the bearing 1 to the second side. Therefore, as the propeller moves the vessel forward, a point on the outer surface of the propeller shaft moves from top to bottom on the first side, and then from bottom to top on the second side.

[0041] The bearing 1 has an outer surface, i.e., an outer peripheral surface, and an inner surface, i.e., an inner circumferential surface. The inner surface is the bearing surface on which the propeller shaft rotates. Although the shaft does not rotate directly against the bearing surface, the bearing 1 is configured to allow a lubricating medium to be supplied to the inner surface of the bearing 1. The lubricating medium can be a lubricating oil. The lubricating oil forms an oil film between the bearing surface and the propeller shaft. This avoids direct contact between the surface of the bearing 1 and the propeller shaft, reducing friction between the surfaces.

[0042] In the illustrated embodiment, bearing 1 is a single piece. However, bearing 1 can also be made of two or more pieces. For example, bearing 1 can be made of two or more pieces having the shape of a portion of a circle.

[0043] The bearing 1 has a plurality of lubrication holes 2a, 2b, 2c, 4a, 4b, and 4c extending from the outer surface of the bearing 1 to the inner surface of the bearing 1. The lubrication holes 2a, 2b, 2c, 4a, 4b, and 4c allow the flow of lubricating medium between the inner and outer surfaces. The lubrication holes include a first group of lubrication holes 2 that open to the inner surface of the bearing 1 on a first side of the bearing 1 and a second group of lubrication holes 4 that open to the inner surface of the bearing 1 on a second side of the bearing 1. In the illustrated embodiment, the lubrication holes 2a, 2b, and 2c on the first side and the lubrication holes 4a, 4b, and 4c on the second side are arranged symmetrically about an imaginary vertical midplane that divides the bearing 1 into the first and second sides. In this way, lubrication of the bearing 1 via the lubrication holes 2a, 2b, 2c, 4a, 4b, and 4c functions substantially similarly regardless of the direction of rotation of the propeller shaft. However, the lubrication holes do not necessarily have to be arranged symmetrically about the midplane.

[0044] In the illustrated embodiment, three lubrication holes 2a, 2b, 2c, 4a, 4b, 4c are arranged on each side of the bearing 1. However, the number of lubrication holes may vary. Preferably, at least two lubrication holes 2a, 2b, 2c, 4a, 4b, 4c are arranged on each of the first and second sides to distribute the lubricating medium over the entire bearing surface.

[0045] In the illustrated embodiment, the lubrication holes 2a, 2b, and 2c of the first lubrication hole group 2 are arranged at the same height as one another in the circumferential direction of the bearing 1, and the lubrication holes 4a, 4b, and 4c of the second lubrication hole group 4 are arranged at the same height as one another in the circumferential direction of the bearing 1. However, the lubrication holes may be arranged at different heights. In the illustrated embodiment, the lubrication holes 2a, 2b, 2c, 4a, 4b, and 4c are arranged on both sides of the bearing 1 within a horizontal mid-plane that divides the bearing 1 into a lower half and an upper half. However, the lubrication holes 2a, 2b, 2c, 4a, 4b, and 4c may be arranged above the horizontal mid-plane. The lubrication holes 2a, 2b, 2c, 4a, 4b, and 4c may all be at the same height. Alternatively, the lubrication holes 2a, 2b, and 2c on the first side may be arranged higher than the lubrication holes 4a, 4b, and 4c on the second side.

[0046] The lubrication holes 2a, 2b, 2c, 4a, 4b, 4c open into recessed areas 6a, 6b, 7 on the inner surface of the bearing 1. The recessed areas 6a, 6b, 7 form oil pockets between the bearing surface 1 and the propeller shaft. The oil pockets facilitate the spreading of the lubricating medium across the bearing surface. On the second side of the bearing, all of the lubrication holes 4a, 4b, 4c open into the same recessed area 7. The recessed area 7 on the second side of the bearing 1 extends across the entire bearing surface in the axial direction of the bearing 1. In the circumferential direction of the bearing 1, the recessed area 7 extends over an angle of approximately 30 degrees. The recessed area 7 may extend over an angle of, for example, 15 to 45 degrees. On each side of the circumferential direction of the bearing 1, the recessed area 7 has a transition zone where the depth of the recessed area 7 gradually changes.

[0047] On a first side of the bearing 1, the lubrication holes 2a, 2b, 2c open into two separate recessed areas 6a, 6b. One of the lubrication holes 2a opens into the first recessed area 6a, and two of the lubrication holes 2b, 2c open into the second recessed area 6b. In the circumferential direction, the recessed areas 6a, 6b extend over the same angle as the recessed area 7 on the second side of the bearing 1.

[0048] The lubrication holes 2a, 2b, and 2c of the first lubrication hole group 2 open into a first groove 3 on the outer surface of the bearing 1, the first groove 3 having a longitudinal direction parallel to the axial direction of the bearing 1. Depending on the flow direction, the first groove 3 either supplies or withdraws lubrication medium to or from the first lubrication hole group 2. Similarly, the lubrication holes 4a, 4b, and 4c of the second lubrication hole group 4 open into a second groove 5 on the outer surface of the bearing 1, the second groove 5 having a longitudinal direction parallel to the axial direction of the bearing 1. Both the first groove 3 and the second groove 5 extend to both ends of the bearing 1, thereby enabling the flow of lubrication medium across the entire outer surface of the bearing 1 in the axial direction of the bearing 1. The bearing 1 can be press-fit into a stern tube. The first and second grooves 4 and 5, together with the stern tube, define a lubrication medium channel for the flow of lubrication medium. The outer surface of the bearing 1 includes additional grooves 14, 15, 16, and 17.

[0049] The bearing 1 according to the present invention further comprises at least one lubrication inlet 8, 11 opening onto the inner surface of the bearing 1 and configured to allow the supply of lubricating medium to the inner surface of the bearing 1 independently of the first and second groups of lubrication holes 2, 4. The lubrication inlet 8, 11 thus provides an additional method of introducing lubricating medium to the bearing surface, which allows the amount of lubricating medium to be increased in areas where more lubrication is needed.

[0050] In the illustrated embodiment, the bearing 1 has a first lubrication inlet 8 located on a first side of the bearing 1. The bearing 1 also has a second lubrication inlet 11 located at the bottom of the bearing 1. However, the bearing 1 may also have only the first lubrication inlet 8 or only the second lubrication inlet 11. The bearing 1 may also have additional lubrication inlets. The first and second lubrication inlets 8, 11 are located circumferentially of the bearing 1, away from the lubrication holes 2a, 2b, 2c, 4a, 4b, 4c of the first and second lubrication hole groups 2, 4. The first lubrication inlet 8 is located above the height of the lubrication holes 2a, 2b, 2c of the first lubrication hole group 2. By locating the first lubrication inlet 8 at a different height from the lubrication holes 2a, 2b, 2c, the first lubrication inlet 8 is not in fluid communication with the first groove 3, which supplies the lubricating medium to the first lubrication hole group 2. However, by arranging the supply of lubricating medium to the first lubrication hole group 2 and the first lubrication inlet 8 in a different way, the first lubrication inlet 8 can also be arranged at the same height as the lubrication holes 2a, 2b, 2c of the first lubrication hole group 2. The first lubrication inlet 8 can also be arranged below the height of the lubrication holes 2a, 2b, 2c of the first lubrication hole group 2.

[0051] As mentioned above, in the illustrated embodiment, the direction of rotation of the propeller shaft is from the first side of the bearing through the bottom to the second side. This allows the bearing 1 to be effectively lubricated via the first lubrication inlet 8 when the propeller moves the ship forward. In most cases, the ship only moves backward for a short period of time. Therefore, less stringent requirements are placed on lubrication in the reverse direction of the propeller shaft, and the lubrication inlet 8 on the second side of the bearing 1 is not required. However, a similar lubrication inlet 8 can also be provided on the second side.

[0052] In the illustrated embodiment, the first lubrication inlet 8 opens into the inner surface of the bearing 1, into a first recessed region 6a on a first side of the bearing 1. Thus, one of the lubrication holes 2a, 2b, and 2c opens into the same recessed region 6a. The first recessed region 6a and the second recessed region 6b are separated from each other. Between the two recessed regions 6a and 6b is a wall 18 that prevents direct flow between the recessed regions 6a and 6b. This ensures that the lubricating medium supplied through the first lubrication inlet 8 does not immediately spread across the entire bearing surface 1, but rather that most of the lubricating medium remains around the first lubrication inlet 8. In the illustrated embodiment, the axial length of the first recessed region 6a in the bearing 1 is approximately one-third of the length of the inner surface of the bearing 1. The length of the first recessed region 6a is preferably at most 50% of the length of the bearing surface. The lubrication hole 2a, which opens into the same recessed region 6a as the first lubrication inlet 8, functions as a pressure relief hole. The pressure relief holes help to avoid excessive pressure on the inner surface of the bearing 1.

[0053] In the illustrated embodiment, the first lubrication inlet 8 is located closer to the aft end of the bearing 1 than to the bow end. In the illustrated embodiment, the distance from the aft end of the first lubrication inlet 8 is approximately 20% of the length of the bearing 1. The first lubrication inlet 8 can be located 10-40% of the length from the aft end of the bearing 1. The aft end is often subject to higher loads than the bow end, and therefore it is beneficial to locate the first lubrication inlet closer to the aft end. However, in some operating conditions, the bow end may be subject to higher loads, and therefore the first lubrication inlet 8 can be located closer to the bow end. The bearing 1 can also be equipped with lubrication inlets located at both the aft end and the bow end. Preferably, the supply of lubricating medium to the two lubrication inlets can be controlled independently of each other.

[0054] The first recessed region 6a does not extend to the end of the bearing surface, but is formed at its rear end with a wall 19. The wall 19 reduces the escape of lubricating medium from the recessed region 6a via the rear end of the bearing 1.

[0055] The bearing 1 has a first lubricating medium supply hole 9 opening into the end face of the bearing 1 and a first lubricating channel 10 connecting the first lubricating inlet 8 to the first lubricating medium supply hole 9. In the embodiment shown, the first lubricating channel 10 is a groove in the outer surface of the bearing 1 and the first lubricating medium supply hole 9 is located at the bow end of the bearing 1. However, the first lubricating medium channel 10 may also be located in the shell of the bearing 1 and / or the first lubricating medium supply hole 9 may also be located at the aft end of the bearing 1. The lubricating medium may also be supplied to the first lubricating inlet 8 via a different arrangement, for example via a pipe passing radially through the stern tube.

[0056] Additionally, the second lubrication inlet 11 opens into a recess 12 on the inner surface of the bearing 1. The recess 12 does not have any holes other than the second lubrication inlet 11.

[0057] The bearing 1 has a second lubricating medium supply hole 13 opening on the end face of the bearing 1 and a second lubricating channel connecting the second lubricating inlet 11 to the second lubricating medium supply hole 13. Also, the second lubricating medium supply hole 13 is located at the bow end of the bearing 1, but can be located differently.

[0058] The second lubricating medium supply hole 11 is arranged in the axial direction of the bearing 1 at a distance of about 20% of the length of the bearing 1 from the rear end of the bearing 1. This distance may be, for example, in the range of 10-40% of the length of the bearing 1.

[0059] Similar to the first lubrication inlet 8, the second lubrication inlet 11 can be located near the aft end of the bearing 1 to provide additional lubrication in the area that is typically most heavily loaded. The lubricating medium supplied through the second lubrication inlet 11 can be introduced to the bearing surface at higher pressure, thereby providing lift to the propeller shaft.

[0060] FIG. 3 shows a schematic representation of a propulsion device and part of a vessel 20 according to an embodiment of the present invention. FIG. 4 shows further details of the propulsion device. The vessel 20 is equipped with a propeller 21. The propeller 21 is connected to a crankshaft 23 of a main engine 21 of the vessel 20 by a propeller shaft 22. The main engine 21 may be, for example, a two-stroke or four-stroke piston engine. The propeller shaft 22 passes through a hull 24 of the vessel 20 in a stern tube 25. A bearing 1 according to the present invention is arranged at the aft end of the stern tube 25 to support the propeller shaft 22. In the embodiment of FIG. 3, another stern tube bearing 26 is arranged at the bow end of the stern tube 25. The bearing 26 at the bow end of the stern tube 25 can be similar to the bearing 1 at the aft end of the stern tube 25. The bearings 1 and 26 can be attached to the stern tube 25 by press-fitting. A further bearing 27 is arranged between the stern tube 25 and the main engine 21 to support the propeller shaft 22. The number of bearings supporting the propeller shaft 22 may vary. It is also possible that only one bearing is located in the stern tube 25 and the other bearing supporting the propeller shaft is outside the stern tube 25.

[0061] The stern tube 25 is filled with a lubricating medium such as lubricating oil, and when the propeller shaft 22 rotates, the lubricating medium flows through the lubrication holes 2a, 2b, 2c, 4a, 4b, 4c of the bearing 1 to keep the bearing 1 lubricated. Each end of the stern tube 25 is provided with sealing devices 28, 29. The purpose of the sealing devices 28, 29 is to prevent water from entering the stern tube 25 and to prevent the lubricating medium from escaping from the stern tube 25.

[0062] To improve lubrication of the bearings 1, the propulsion unit is provided with a lubrication pump 30. In the embodiment of FIG. 4, two lubrication pumps 30 are provided for redundancy. If redundancy is not required, the propulsion unit can be provided with a single lubrication pump 30. Each of the lubrication pumps 30 is configured to supply lubricating medium to the bearings 1. The lubrication pumps 30 also supply lubricating medium to the sealing devices 28, 29, which lubricating medium functions as seal oil. However, separate pumps can also be provided to supply lubricating medium to the sealing devices 28, 29.

[0063] The propulsion device has a first supply line 31 that supplies lubricating medium from a lubrication pump 30 to the first lubrication inlet 8 of the bearing 1, and a second supply line 32 that supplies lubricating medium to the second lubrication inlet 11 of the bearing 1. A sealing medium supply line 33 is provided to supply lubricating medium to the sealing devices 28, 29. A distribution block 40 and a pressure control block 41 are arranged between the lubrication pump 30 and the stern tube 25. The distribution block 40 functions as a flow control means that controls the amount of lubricating medium supplied to the bearing 1 and the sealing devices 28, 29. The pressure control block 41 functions as a pressure control means that controls the pressure of the lubricating medium supplied to the bearing 1 and the sealing devices 28, 29.

[0064] The two separate supply lines 30, 31 and the flow control means 40 allow independent control of the amount of lubricating medium supplied through the first lubricating inlet 8 and the second lubricating inlet 11. The two separate supply lines 30, 31 and the pressure control means 41 allow independent control of the pressure of the lubricating medium supplied through the first lubricating inlet 8 and the second lubricating inlet 11.

[0065] The arrangement further comprises a return line 39 configured to supply excess lubricating medium from the stern tube 25 back to the lubrication pump 30. A heat exchanger 34 is arranged in the first supply line 31. The heat exchanger 34 is configured to cool the lubricating medium supplied via the first lubrication inlet 8. The heat exchanger 34 makes it possible to control the temperature of the bearing 1 arranged at the aft end of the stern tube 25.

[0066] The pressure control means 41 can be configured to supply the lubricating medium to the second lubricating inlet 11 at a higher pressure than the first lubricating inlet 8. The pressure of the lubricating medium supplied through the first lubricating inlet 8 can be, for example, in the range of 1-5 bar, more preferably 1-3 bar. The pressure of the lubricating medium supplied through the second lubricating inlet 11 can be, for example, in the range of 15-30 bar. However, the pressure of the lubricating medium supplied through the lubricating inlets 8, 11 may exceed the above range for a short period of time. For example, when the supply of the lubricating medium supplied through the second lubricating inlet 11 is started, the impact pressure can be as high as 60-70 bar, and then the pressure quickly drops to the above range of 15-30 bar.

[0067] The propulsion device of Figures 3 and 4 further comprises a rotational speed sensor 37 arranged to monitor the rotational speed of the propeller shaft 22. The device also comprises a temperature sensor 35 arranged to monitor the temperature of the lubricating medium in the bearing 1. The device further comprises an oil film thickness sensor 36 for monitoring the thickness of the lubricating medium film on the bearing surface of the bearing 1.

[0068] The amount and pressure of lubricating medium supplied to bearing 1 can be controlled in many alternative ways. For example, the propulsion device can be provided with separate pumps for supplying lubricating medium to first lubrication inlet 8 and second lubrication inlet 11. Alternatively, the amount and / or pressure of lubricating medium can be controlled by lubrication pump 30, in which case separate flow and / or pressure control means are not required.

[0069] Lubrication of the bearing 1 can be controlled based on the operating conditions of the propulsion device. FIG. 5 shows a block diagram of a control system for the propulsion device. The control system includes a control unit 38 configured to control the operation of the lubrication pump 30. The control unit 38 also controls the operation of the distribution block 40 and the pressure control block 41 to control the flow rate and pressure of the lubricating medium. The control system includes a temperature sensor 35 configured to monitor the temperature of the lubricating medium. The temperature sensor 35 can be located in the bearing 1 or in the stern tube 25. The control system can include two or more temperature sensors located at different positions. Preferably, at least one temperature sensor 35 is located approximately in the center of the bearing 1 in the axial direction of the bearing 1. The control system further includes at least one sensor 36 for monitoring the thickness of the lubricating medium film on the bearing surface of the bearing 1. The oil film thickness sensor 36 can be located at the aft end of the bearing 1. This allows the oil film thickness at the aft end of the bearing 1 to be monitored. This is particularly advantageous when the first lubrication inlet 8 and / or the second lubrication inlet 11 are arranged close to the rear end of the bearing 1, as it allows monitoring of the oil film thickness in the area to which the lubricating medium is supplied via the lubrication inlets 8, 11. The control system further comprises a rotational speed sensor 37 configured to monitor the rotational speed of the propeller shaft 22. The control unit 38 receives measurement data from the temperature sensor 35, the oil film thickness sensor 36 and the rotational speed sensor 37. Instead of the rotational speed sensor 37, the control unit 38 can receive rotational speed data from the engine 21. The functions of the sensors 35, 36, 37 can also be combined into one or more multi-function sensors configured to monitor two or more different parameters.

[0070] The control unit 38 is configured to control the operation of the lubrication pump 30 , the flow control means 40 and the pressure control means 41 based on the temperature of the lubricating medium, the thickness of the lubricating medium film and / or the rotational speed of the propeller shaft 22 .

[0071] The propulsion device can operate in different operating modes depending on the values ​​of different control parameters, such as the lubricating medium temperature, the oil film thickness, and the rotational speed of the propeller shaft 22. To select an operating mode, the lubricating medium temperature and / or the lubricating medium film thickness can be compared with respective target ranges or one or more threshold values. Furthermore, the rotational speed of the propeller shaft 22 can be compared with one or more threshold values.

[0072] According to one embodiment of the present invention, the propulsion unit can operate in at least four different operating modes. Since the stern tube 25 is filled with lubricating medium, in all operating modes at least a portion of the lubricating medium flows through the lubrication holes 2a, 2b, 2c, 4a, 4b, 4c of the bearing 1. In the first operating mode, the lubricating medium is additionally supplied through the first lubrication inlet 8. In the second operating mode, the lubricating medium is supplied through the second lubrication inlet 11. In the third operating mode, the lubricating medium is supplied through both the first lubrication inlet 8 and the second lubrication inlet 11. In the fourth operating mode, the lubricating medium is supplied only through the lubrication holes 2a, 2b, 2c, 4a, 4b, 4c.

[0073] The first operating mode is a normal operating mode that can be used in most operating conditions.

[0074] The second operating mode can be used in particular when the rotational speed of the propeller shaft 22 is low, for example below a threshold value. The second operating mode is also beneficial when the temperature of the lubricating medium is low, for example below a target range or below a first threshold value, and the thickness of the lubricating medium film is low, for example below the first threshold value.

[0075] The third operating mode can be used when the lubricating medium temperature is high, e.g. above the target range or above the second threshold, and the lubricating medium film thickness is low, e.g. below the first threshold.

[0076] The fourth operating mode can be used when the lubricating medium temperature is relatively low, e.g., below the second threshold, and the lubricating medium thickness is within a desired range or above the first or second threshold. The fourth operating mode also serves as an emergency mode to be used when the lubricating pump 30 fails and other operating modes are unavailable.

[0077] As an example, a target range is determined for the temperature of the lubricating medium. The lower limit of the target range may be, for example, 20°C. The upper limit of the target range may be, for example, 50°C. Furthermore, a threshold value may be determined for the temperature of the lubricating medium. The threshold value may be within the target range. For example, the threshold value may be 45°C.

[0078] The threshold value may be determined relative to the rotational speed of the propeller shaft 22. The threshold value may be a certain percentage of the maximum continuous speed of the propeller shaft 22, i.e., the nominal rotational speed of the propeller shaft 22. For example, the threshold value may be 25% of the nominal speed.

[0079] A first threshold value can be determined for the thickness of the lubricating medium film. For example, the first threshold value can be 50 μm. A second threshold value can be determined for the thickness of the lubricating medium film. The second threshold value can be greater than the first threshold value and can be, for example, 60 μm.

[0080] The operating mode can be selected by comparing the monitored parameters to respective target ranges or thresholds. A first operating mode provides cooling of the lubricating medium. A second operating mode provides damping and support for the propeller shaft 22. A third operating mode provides both cooling, damping, and support. A fourth operating mode provides energy savings.

[0081] The first operating mode can be used when the rotational speed of the propeller shaft 22 exceeds the respective threshold value, the thickness of the lubricating medium film exceeds the respective first threshold value, and the temperature of the lubricating medium is within or above the respective target range.

[0082] The second operating mode can be used when the rotational speed of the propeller shaft 22 is below the respective threshold value and / or the thickness of the lubricating medium film is below the respective first threshold value and the temperature of the lubricating medium is below the respective target range.

[0083] The third operating mode can be used when the lubricating medium temperature is above the respective target range and the lubricating medium film thickness is below the respective first threshold value.

[0084] The fourth operating mode can be used when the thickness of the lubricating medium film is above the respective second threshold value and the temperature of the lubricating medium is below the respective second threshold value.

[0085] In operating modes that include supplying lubricating medium via the first and / or second lubricating inlets 8, 11, the pressure and / or flow rate of the lubricating medium can be adjusted to more precisely suit the lubrication needs. Also, the temperature of the lubricating medium supplied via the first lubricating inlet 8 can be controlled, for example, by providing a bypass line in the first supply line 31 between the lubricating pump 30 and the bearing 1 that allows bypassing the heat exchanger 34. Alternatively, or additionally, the flow rate and / or temperature of the heat exchange medium flowing through the heat exchanger 34 can be controlled to control the temperature of the lubricating medium.

Claims

1. 1. A bearing for radially supporting a propeller shaft of a marine vessel, the bearing being configured to be mounted within a stern tube of the marine vessel, and when mounted comprising: - top, - bottom, a first side extending from the top to the bottom in a first circumferential direction of the bearing; a second side extending from the top to the bottom in a second circumferential direction opposite the first circumferential direction; and the bearing has a plurality of lubrication holes extending from an outer surface of the bearing to an inner surface of the bearing to allow a flow of a lubricating medium between the inner surface and the outer surface, the lubrication holes having a first group of lubrication holes opening to the inner surface of the bearing on the first side of the bearing and a second group of lubrication holes opening to the inner surface of the bearing on the second side of the bearing; the bearing further comprises at least one lubrication inlet opening into the inner surface of the bearing and configured to allow supply of a lubricating medium to the inner surface independently of the first group of lubrication holes and the second group of lubrication holes. Bearing.

2. the at least one lubrication inlet is positioned in a circumferential direction of the bearing away from the lubrication holes of the first group of lubrication holes and the second group of lubrication holes; 2. The bearing according to claim 1.

3. the at least one lubrication inlet includes a first lubrication inlet disposed on the first side of the bearing; 2. The bearing according to claim 1.

4. the first lubrication inlet opens into a recessed area on the inner surface of the bearing; 4. The bearing according to claim 3.

5. the length of the recessed region in the axial direction of the bearing is at most 50% of the length of the inner surface of the bearing; 5. A bearing according to claim 4.

6. At least one of the lubrication holes of the first group of lubrication holes opens into the same recessed area as the first lubrication inlet.

6. A bearing according to claim 5.

7. the first lubrication inlet opens into a first recessed area on the inner surface of the bearing, the first side of the bearing comprises a second recessed area separated from the first recessed area by a wall, and at least one of the lubrication holes in the first group of lubrication holes opens into the second recessed area; 5. A bearing according to claim 4.

8. the first lubrication inlet is positioned above the height of the lubrication holes of the first group of lubrication holes; 4. The bearing according to claim 3.

9. the bearing has a first lubricating medium supply hole opening at an end surface of the bearing, and a first lubricating channel connecting the first lubricating medium inlet to the first lubricating medium supply hole; 4. The bearing according to claim 3.

10. the at least one lubrication inlet includes a second lubrication inlet coincident with the bottom of the bearing; 4. The bearing according to claim 3.

11. the second lubrication inlet opens into a recessed area on the inner surface of the bearing; 11. A bearing according to claim 10.

12. the bearing has a second lubricant supply hole opening to an end surface of the bearing, and a second lubricant channel connecting the second lubricant inlet to the second lubricant supply hole; 11. A bearing according to claim 10.

13. the at least one lubrication inlet is located at a distance of 10-40% of the length of the bearing from one end of the bearing; 2. The bearing according to claim 1.

14. the lubrication inlet is located adjacent to the rear end of the bearing; 14. A bearing according to claim 13.

15. the lubrication holes of the first lubrication hole group are arranged at the same height as one another in the circumferential direction of the bearing, and the lubrication holes of the second lubrication hole group are arranged at the same height as one another in the circumferential direction of the bearing.

2. The bearing according to claim 1.

16. The lubrication holes of the first group of lubrication holes open into first grooves on the outer surface of the bearing, the first grooves having a longitudinal direction parallel to the axial direction of the bearing, and the lubrication holes of the second group of lubrication holes open into second grooves on the outer surface of the bearing, the second grooves having a longitudinal direction parallel to the axial direction of the bearing.

2. The bearing according to claim 1.

17. The apparatus is a stern tube bearing arrangement for a marine vessel, comprising a stern tube and a bearing according to any one of claims 1 to 16 arranged within the stern tube.

18. 18. A propulsion device for a vessel, the propulsion device comprising: a stern tube bearing arrangement according to claim 17; a propeller shaft supported by the bearing; and a propeller attached to the propeller shaft.

19. the apparatus having means for supplying pressurized lubricating medium to the at least one lubrication inlet; 20. The propulsion device of claim 18.

20. the device having means for controlling the pressure and / or the amount of lubricating medium supplied to the at least one lubrication inlet; 20. The propulsion device of claim 19.

21. the apparatus having means for cooling the lubricating medium supplied to the at least one lubrication inlet; 20. The propulsion device of claim 19.

22. the device having at least one of a temperature sensor for monitoring the temperature of the lubricating medium in the stern tube, a sensor for monitoring the thickness of the lubricating medium film in the bearing, and a rotational speed sensor for monitoring the rotational speed of the propeller shaft; 20. The propulsion device of claim 18.

23. the apparatus having a control unit configured to control the supply of lubricating medium through the at least one lubrication inlet based on the temperature of the lubricating medium in the stern tube, the thickness of the lubricating medium film in the bearing, and / or the rotational speed of the propeller shaft.

23. The propulsion device of claim 22.

24. A watercraft comprising a propulsion device according to claim 18.

25. 23. A method of operating a propulsion device as recited in claim 22, said method including introducing said lubricating medium to said inner surface of said bearing via said at least one lubrication inlet.

26. The method includes at least one operating mode in which the lubricating medium is introduced to the inner surface of the bearing through both the lubrication hole and the at least one lubrication inlet, and at least one operating mode in which the lubricating medium is introduced to the inner surface of the bearing only through the lubrication hole.

26. The method of claim 25.

27. The bearing is the bearing according to claim 3, and the method includes at least one operating mode in which the lubricating medium is supplied through all of the lubrication holes, the first lubrication inlet, and the second lubrication inlet, at least one operating mode in which the lubricating medium is supplied only through the lubrication holes and the first lubrication inlet, and at least one operating mode in which the lubricating medium is supplied only through the lubrication holes and the second lubrication inlet.

26. The method of claim 25.

28. the lubricating medium is supplied through the second lubricating inlet at a higher pressure than the first lubricating inlet; 28. The method of claim 27.

29. the pressure of the lubricating medium supplied through the second lubrication inlet is at least 15 bar; 29. The method of claim 28.

30. the lubricating medium supplied through the first lubrication inlet is cooled before being supplied to the bearing; 28. The method of claim 27.

31. The method includes monitoring at least one parameter of a thickness of the lubricating medium film on the inner surface of the bearing, the rotational speed of the propeller shaft, and the temperature of the lubricating medium; and controlling the flow of the lubricating medium through the at least one lubrication inlet based on values ​​of one or more of the monitored parameters.

26. The method of claim 25.

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